Abdo, P, Huynh, BP, Irga, PJ & Torpy, FR 2019, 'Evaluation of air flow through an active green wall biofilter', Urban Forestry and Urban Greening, vol. 41, pp. 75-84.
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© 2019 Elsevier GmbH Green walls show promise as active bio-filters to improve indoor air quality by removing both gaseous and particulate air pollutants. The current work represents a detailed assessment of airflow through an active green wall module. Airflow distribution through the module, the effect of wetting the substrate, and the effect of introducing a cover to the module's open top face were investigated, with the aim to improve the module's design and achieve more appropriate and effective airflow. Four cases of both planted and unplanted modules under both dry and wet conditions are considered. This work's primary observation is that more air will pass through a typical green wall substrate, and hence become cleansed, when the substrate is saturated wet more than when it is dry. The increase was substantial at approximately 50% more with 14.9 ± 0.2 L/s total air flow rate passing through the wet planted module versus 10 ± 0.2 L/s when dry. Reducing the 15.5 ± 0.75% of airflow passing through the module's open top face was found to be essential to maximize the bio-filtration capacity. Adding a top cover to the module having six 10 mm holes for irrigation decreased the airflow through the top by 6 ± 0.75%, and directed it through the filter increasing the percentage of air flow passing through the front openings from 79 ± 4% to 85 ± 4%.
Acosta, E, Smirnov, V, Szabo, PSB, Buckman, J & Bennett, NS 2019, 'Optimizing Thermoelectric Power Factor in p-Type Hydrogenated Nano-crystalline Silicon Thin Films by Varying Carrier Concentration', JOURNAL OF ELECTRONIC MATERIALS, vol. 48, no. 4, pp. 2085-2094.
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Al-Muhsen, NFO, Huang, Y & Hong, G 2019, 'Effects of direct injection timing associated with spark timing on a small spark ignition engine equipped with ethanol dual-injection', FUEL, vol. 239, pp. 852-861.
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Alzahran, S, Islam, M & Saha, S 2019, 'A thermo-hydraulic characteristics investigation in corrugated plate heat exchanger', Energy Procedia, vol. 160, pp. 597-605.
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© 2019 The Authors. Published by Elsevier Ltd. The amount of heat transfer from plate heat exchanger (PHE) is much higher compared with other types of conventional heat exchangers due to the high surface area of each plate. This study aims to investigate the heat transfer characteristics in a commercial corrugated PHE for sinusoidal corrugation type. A computational fluid dynamics (CFD) has been used to simulate the fluid flow inside the PHE for 1-1 single (water-water) and two (air-water) phase flow, counter arrangement. An advanced meshing technique has been used to generate the mesh for the PHE and a proper grid refinement test has been performed for the generated mesh. The overall investigation has been conducted for 60°/60° chevron angle plate (β) for a wide range of Re (500 ≤ Re ≤3000) and Prandtl number (Pr) (0.72 ≤ Pr ≤ 7.5). The result is validated with the benchmark experimental data. The impact of Reynolds and Pr has been investigated. The CFD results illustrate that the Nusselt number (Nu) increases with increasing of Reynolds number, while f decreasing with increasing of Re. The effect of Pr on Nusselt number and isothermal friction factor is presented. The corresponding correlations of Nu and f are developed from the CFD results.
Al-Zubaydi, AYT & Hong, G 2019, 'Experimental study of a novel water-spraying configuration in indirect evaporative cooling', APPLIED THERMAL ENGINEERING, vol. 151, pp. 283-293.
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Arora, A, Furlong, PM, Fitch, R, Sukkarieh, S & Fong, T 2019, 'Multi-modal active perception for information gathering in science missions', Autonomous Robots.
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© 2019, Springer Science+Business Media, LLC, part of Springer Nature. Robotic science missions in remote environments, such as deep ocean and outer space, can involve studying phenomena that cannot directly be observed using on-board sensors but must be deduced by combining measurements of correlated variables with domain knowledge. Traditionally, in such missions, robots passively gather data along prescribed paths, while inference, path planning, and other high level decision making is largely performed by a supervisory science team located at a different location, often at a great distance. However, communication constraints hinder these processes, and hence the rate of scientific progress. This paper presents an active perception approach that aims to reduce robots’ reliance on human supervision and improve science productivity by encoding scientists’ domain knowledge and decision making process on-board. We present a Bayesian network architecture to compactly model critical aspects of scientific knowledge while remaining robust to observation and modeling uncertainty. We then formulate path planning and sensor scheduling as an information gain maximization problem, and propose a sampling-based solution based on Monte Carlo tree search to plan informative sensing actions which exploit the knowledge encoded in the network. The computational complexity of our framework does not grow with the number of observations taken and allows long horizon planning in an anytime manner, making it highly applicable to field robotics with constrained computing. Simulation results show statistically significant performance improvements over baseline methods, and we validate the practicality of our approach through both hardware experiments and simulated experiments with field data gathered during the NASA Mojave Volatiles Prospector science expedition.
Babayan, M, Mazraeh, AE, Yari, M, Niazi, NA & Saha, SC 2019, 'Hydrogen production with a photovoltaic thermal system enhanced by phase change materials, Shiraz, Iran case study', JOURNAL OF CLEANER PRODUCTION, vol. 215, pp. 1262-1278.
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Barker, RA, Eager, D & Sharwood, LN 2019, 'Ensuring safety in public playgrounds is everybody's business.', The Medical journal of Australia, vol. 210, no. 1, pp. 9-11.e1.
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Barker, RA, Eager, D & Sharwood, LN 2019, 'Ensuring safety in public playgrounds is everybody's business.', The Medical journal of Australia, vol. 210, no. 1, pp. 9-11.
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When an injury occurs in a children’s playground, who is responsible? Media headlines1,2 have highlighted risks associated with a recently opened playground in north-western Sydney. The playground’s giant tube slide was closed following a spate of injuries to both adult and child patrons. With injuries described as “horrific”, the media questioned “how the 30 m long, 14 m tall slide passed safety rules”.1 While playground injuries are fairly common,3 there are specific multilevel responsibilities required to balance the importance of play and physical activity with mitigation of injury risk. In this article, we review the role of standards in industry governance and injury prevention.
Best, G, Cliff, OM, Patten, T, Mettu, RR & Fitch, R 2019, 'Dec-MCTS: Decentralized planning for multi-robot active perception', International Journal of Robotics Research, vol. 38, no. 2-3, pp. 316-337.
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© The Author(s) 2018. We propose a decentralized variant of Monte Carlo tree search (MCTS) that is suitable for a variety of tasks in multi-robot active perception. Our algorithm allows each robot to optimize its own actions by maintaining a probability distribution over plans in the joint-action space. Robots periodically communicate a compressed form of their search trees, which are used to update the joint distribution using a distributed optimization approach inspired by variational methods. Our method admits any objective function defined over robot action sequences, assumes intermittent communication, is anytime, and is suitable for online replanning. Our algorithm features a new MCTS tree expansion policy that is designed for our planning scenario. We extend the theoretical analysis of standard MCTS to provide guarantees for convergence rates to the optimal payoff sequence. We evaluate the performance of our method for generalized team orienteering and online active object recognition using real data, and show that it compares favorably to centralized MCTS even with severely degraded communication. These examples demonstrate the suitability of our algorithm for real-world active perception with multiple robots.
Bhowmick, S, Saha, SC, Qiao, M & Xu, F 2019, 'Transition to a chaotic flow in a V-shaped triangular cavity heated from below', INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol. 128, pp. 76-86.
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Bykerk, L, Quin, P & Liu, D 2019, 'A Method for Selecting the Next Best Angle-of-Approach for Touch-Based Identification of Beam Members in Truss Structures', IEEE SENSORS JOURNAL, vol. 19, no. 10, pp. 3939-3949.
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Chen, B, Huang, J & Ji, JC 2019, 'Control of flexible single-link manipulators having Duffing oscillator dynamics', MECHANICAL SYSTEMS AND SIGNAL PROCESSING, vol. 121, pp. 44-57.
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Chen, Z, Zhang, B, Zhang, N, Du, H & Kong, G 2019, 'Optimal preview position control for shifting actuators of automated manual transmission', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 233, no. 2, pp. 440-452.
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© IMechE 2018. This paper is concerned with the problem of position tracking control for the motor-driven gear-shift actuating mechanism for electro-mechanical automated manual transmissions (AMT). It is well known that torque interruption is an inherent flaw of AMT. As shift duration directly affects the torque interruption interval, shift quality can be improved by minimizing the duration of the shift. To realize rapid and precise gear-shift control, an optimal discrete-time preview position control scheme is proposed. The proposed control scheme consists of state-feedback control, a discrete integrator, and preview feed-forward control. Instead of the traditional difference method, the state transformation method is utilized to construct the augmented error system such that the augmented system can be kept in a simple form. The H∞ performance index is employed to reduce the effect of the shifting load disturbance during the gear-shifting process. The controller gains are obtained by solving a linear matrix inequality (LMI). Simulation and test bench results all show that the proposed preview control algorithm has better dynamic response and adaptability under different loads compared to the optimal linear quadratic regulator (LQR) controller and the standard PID controller.
Cheng, S, Dong, H, Yu, L, Zhang, D & Ji, J 2019, 'Consensus of Second-order Multi-agent Systems with Directed Networks Using Relative Position Measurements Only', INTERNATIONAL JOURNAL OF CONTROL AUTOMATION AND SYSTEMS, vol. 17, no. 1, pp. 85-93.
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Cheng, X, Jiang, Z, Wei, D, Wu, H & Jiang, L 2019, 'Adhesion, friction and wear analysis of a chromium oxide scale on a ferritic stainless steel', WEAR, vol. 426, pp. 1212-1221.
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Cui, H, Xu, F, Saha, SC & Liu, Q 2019, 'Transient free convection heat transfer in a section-triangular prismatic enclosure with different aspect ratios', International Journal of Thermal Sciences, vol. 139, pp. 282-291.
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© 2019 Elsevier Masson SAS Free convection studies in a section-triangular prismatic enclosure with different aspect ratios (depth-width ratios, A) is conducted using three-dimensional numerical modeling approach. The Rayleigh number (Ra) covers a broad range from 10 0 to 10 7 . Transient free convection is characterized under top cooled and bottom heated boundary conditions. The flow structure of transverse rolls and longitudinal rolls is described. The critical Rayleigh numbers for the transition of the flow from driven by the baroclinic to Rayleigh-Bénard instability and from a steady to an unsteady state have been obtained for different aspect ratios. Free convection in the section-triangular prismatic enclosure could be divided into three regimes, which are presented in a Ra-A space. The quantitative relationship between heat transfer and the aspect ratio as well as the Rayleigh number has been obtained numerically.
Cui, Y, Poon, J, Miro, JV, Yamazaki, K, Sugimoto, K & Matsubara, T 2019, 'Environment-adaptive interaction primitives through visual context for human–robot motor skill learning', Autonomous Robots.
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© 2018, The Author(s). In situations where robots need to closely co-operate with human partners, consideration of the task combined with partner observation maintains robustness when partner behavior is erratic or ambiguous. This paper documents our approach to capture human–robot interactive skills by combining their demonstrative data with additional environmental parameters automatically derived from observation of task context without the need for heuristic assignment, as an extension to overcome shortcomings of the interaction primitives framework. These parameters reduce the partner observation period required before suitable robot motion can commence, while also enabling success in cases where partner observation alone was inadequate for planning actions suited to the task. Validation in a collaborative object covering exercise with a humanoid robot demonstrate the robustness of our environment-adaptive interaction primitives, when augmented with parameters directly drawn from visual data of the task scene.
Ding, H, Ji, J & Chen, L-Q 2019, 'Nonlinear vibration isolation for fluid-conveying pipes using quasi-zero stiffness characteristics', MECHANICAL SYSTEMS AND SIGNAL PROCESSING, vol. 121, pp. 675-688.
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Eager, D & Hayati, H 2019, 'Additional injury prevention criteria for impact attenuation surfacing within children’s playgrounds', ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part B: Mechanical Engineering.
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Ernesto Solanes, J, Gracia, L, Muñoz-Benavent, P, Valls Miro, J, Perez-Vidal, C & Tornero, J 2019, 'Robust Hybrid Position-Force Control for Robotic Surface Polishing', Journal of Manufacturing Science and Engineering, Transactions of the ASME, vol. 141, no. 1.
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© 2018 HMP Communications. All rights reserved. This work presents a hybrid position-force control of robots for surface polishing using task priority. The robot force control is designed using sliding mode ideas in order to benefit from its inherent robustness and low computational cost. In order to avoid the chattering drawback typically present in sliding mode control, several chattering-free controllers are evaluated and tested. A distinctive feature of the method is that the sliding mode force task is defined using not only equality constraints but also inequality constraints, which are satisfied using conventional and nonconventional sliding mode control, respectively. Moreover, a lower priority tracking controller is defined to follow the desired reference trajectory on the surface being polished. The applicability and the effectiveness of the proposed approach considering the mentioned chattering-free controllers are substantiated by experimental results using a redundant 7R manipulator.
Gao, J, Gao, L, Luo, Z & Li, P 2019, 'Isogeometric topology optimization for continuum structures using density distribution function', International Journal for Numerical Methods in Engineering.
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© 2019 John Wiley & Sons, Ltd. This paper will propose a more effective and efficient topology optimization method based on isogeometric analysis, termed as isogeometric topology optimization (ITO), for continuum structures using an enhanced density distribution function (DDF). The construction of the DDF involves two steps. (1) Smoothness: the Shepard function is firstly utilized to improve the overall smoothness of nodal densities. Each nodal density is assigned to a control point of the geometry. (2) Continuity: the high-order NURBS basis functions are linearly combined with the smoothed nodal densities to construct the DDF for the design domain. The nonnegativity, partition of unity, and restricted bounds [0, 1] of both the Shepard function and NURBS basis functions can guarantee the physical meaning of material densities in the design. A topology optimization formulation to minimize the structural mean compliance is developed based on the DDF and isogeometric analysis to solve structural responses. An integration of the geometry parameterization and numerical analysis can offer the unique benefits for the optimization. Several 2D and 3D numerical examples are performed to demonstrate the effectiveness and efficiency of the proposed ITO method, and the optimized 3D designs are prototyped using the Selective Laser Sintering technique.
Gao, J, Luo, Z, Li, H & Gao, L 2019, 'Topology optimization for multiscale design of porous composites with multi-domain microstructures', Computer Methods in Applied Mechanics and Engineering, vol. 344, pp. 451-476.
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Gao, J, Luo, Z, Li, H, Li, P & Gao, L 2019, 'Dynamic multiscale topology optimization for multi-regional micro-structured cellular composites', Composite Structures, vol. 211, pp. 401-417.
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In this paper, a new dynamic multiscale topology optimization method for cellular composites with multi-regional material microstructures is proposed to improve the structural performance. Firstly, a free-material distribution optimization method (FMDO) is developed to generate the overall configuration for the discrete element densities distributed within a multi-regional pattern. The macrostructure is divided into several sub regions, and each of them consists of a number of elements but with the same densities. Secondly, a dynamic topology optimization formulation is developed to perform the concurrent design of the macrostructure and material microstructures, subject to the multi-regional distributed element densities. A parametric level set method is employed to optimize the topologies of the macrostructure and material microstructures, with the effective macroscopic properties evaluated by the homogenization. In the numerical implementation, the quasi-static Ritz vector (QSRV) method is incorporated into the finite element analysis so as to reduce the computational cost in numerical analysis, and some kinematical connectors are introduced to make sure the connectivity between adjacent material microstructures. Finally, 2D and 3D numerical examples are tested to demonstrate the effectiveness of the proposed dynamic multiscale topology optimization method for the material-structural composites.
Gao, J, Xue, H, Gao, L & Luo, Z 2019, 'Topology optimization for auxetic metamaterials based on isogeometric analysis', Computer Methods in Applied Mechanics and Engineering, vol. 352, pp. 211-236.
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© 2019 Elsevier B.V. In this paper, an effective and efficient topology optimization method, termed as Isogeometric Topology Optimization (ITO), is proposed for systematic design of both 2D and 3D auxetic metamaterials based on isogeometric analysis (IGA). Firstly, a density distribution function (DDF)with the desired smoothness and continuity, to represent the topological changes of structures, is constructed using the Shepard function and non-uniform rational B-splines (NURBS)basis functions. Secondly, an energy-based homogenization method (EBHM)to evaluate material effective properties is numerically implemented by IGA, with the imposing of the periodic boundary formulation on material microstructure. Thirdly, a topology optimization formulation for 2D and 3D auxetic metamaterials is developed based on the DDF, where the objective function is defined as a combination of the homogenized elastic tensor and the IGA is applied to solve the structural responses. A relaxed optimality criteria (OC)method is used to update the design variables, due to the non-monotonic property of the problem. Finally, several numerical examples are used to demonstrate the effectiveness and efficiency of the proposed method. A series of auxetic microstructures with different deformation mechanisms (e.g. the re-entrant and chiral)can be obtained. The auxetic behavior of material microstructures are numerically validated using ANSYS, and the optimized designs are prototyped using the Selective Laser Sintering (SLS)technique.
Gao, P, Ruan, J, Du, Y, Walker, PD & Zhang, N 2019, 'The prediction of braking noise in regenerative braking system using closed-loop coupling disk brake model', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering.
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© IMechE 2019. Aiming at improving regenerative braking ability in electric vehicles without compromising any safety, two different regenerative braking strategies are proposed in this study. The impact of continuously varying braking force distributions between front/rear wheel and electric/friction corresponding in two different strategies on braking noise are investigated. Based on the closed-loop coupling disk brake model, the relationship between the contact coupling stiffness and the braking force is established by considering the stationary modal test, the nonlinear optimization, and the relationship between brake-line pressure and braking force. The continuously varying braking force is initially transformed to continuously varying contact coupling stiffness, then, the brake noise tendency at each frequency band is calculated in closed-loop coupled model. The predicted result shows good consistency with the result recorded in bench test, verifying the reliability and effectivity of the presented method. The comparison of the two different electric braking strategies shows that the second braking strategy is superior to the first braking strategy in terms of suppressing the brake noise tendency.
Gao, P, Walker, PD, Liu, H, Zhou, S & Xiang, C 2019, 'Application of an adaptive tuned vibration absorber on a dual lay-shaft dual clutch transmission powertrain for vibration reduction', MECHANICAL SYSTEMS AND SIGNAL PROCESSING, vol. 121, pp. 725-744.
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Gao, P, Xiang, C, Liu, H, Walker, P & Zhou, H 2019, 'Vibration reduction performance parameters matching for adaptive tunable vibration absorber', Journal of Intelligent Material Systems and Structures, vol. 30, no. 2, pp. 198-212.
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© The Author(s) 2018. Based on the principle of vibration absorber, an adaptive tunable vibration absorber with the magnetorheological elastomer as the core intelligent component was designed to eliminate variable frequency vibration of the powertrain system. The simulation of the magnetic circuit of the adaptive tunable vibration absorber was carried out to ensure the magnetic field generated by the design with a closed magnetic circuit could meet the requirement. The transient dynamic simulation analysis of the adaptive tunable vibration absorber shows that the natural frequency of the vibration absorber could well follow the external excitation signal. The natural vibration sensitivity analysis of the 4-degree-of-freedom dynamic system of the powertrain system was performed to obtain the key moment of inertia that affects the natural frequencies of each stage and then the installation position of the adaptive tunable vibration absorber corresponding to external excitation near the resonant frequency band could be determined. Subsequently, taking the third natural vibration as an example, an adaptive tunable vibration absorber with corresponding variable-stiffness range was installed on the key moment of inertia affecting the vibration of this order. The transient changes of each natural vibration frequency of the powertrain system with the adaptive tunable vibration absorber were studied and then the best starting and stopping frequencies were determined. According to the optimal frequency tuning scheme, the variation range of the storage modulus required for the magnetorheological elastomer material in the limited magnetic field range was obtained. The relationship between the controllable current and the torsional stiffness of the vibration absorber is established. Aiming at the vibration problem near the third-order natural vibration, the best vibration reduction performance parameters were matched to the adaptive tunable vibration absorber. Finally, a time...
Geekiyanage, NM, Balanant, MA, Sauret, E, Saha, S, Flower, R, Lim, CT & Gu, Y 2019, 'A coarse-grained red blood cell membrane model to study stomatocyte-discocyte-echinocyte morphologies', PLOS ONE, vol. 14, no. 4.
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Ghaffari Jadidi, M, Valls Miro, J & Dissanayake, G 2019, 'Sampling-based incremental information gathering with applications to robotic exploration and environmental monitoring', International Journal of Robotics Research, vol. 38, no. 6, pp. 658-685.
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© The Author(s) 2019. We propose a sampling-based motion-planning algorithm equipped with an information-theoretic convergence criterion for incremental informative motion planning. The proposed approach allows dense map representations and incorporates the full state uncertainty into the planning process. The problem is formulated as a constrained maximization problem. Our approach is built on rapidly exploring information-gathering algorithms and benefits from the advantages of sampling-based optimal motion-planning algorithms. We propose two information functions and their variants for fast and online computations. We prove an information-theoretic convergence for an entire exploration and information-gathering mission based on the least upper bound of the average map entropy. A natural automatic stopping criterion for information-driven motion control results from the convergence analysis. We demonstrate the performance of the proposed algorithms using three scenarios: comparison of the proposed information functions and sensor configuration selection, robotic exploration in unknown environments, and a wireless signal strength monitoring task in a lake from a publicly available dataset collected using an autonomous surface vehicle.
Guertler, M, Sick, N & Kriz, A 2019, 'A Discipline-Spanning Overview of Action Research and Its Implications for Technology and Innovation Management', Technology Innovation Management Review, vol. 9, no. 4, pp. 48-65.
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The iterative and learning character of action research is particularly beneficial for exploring complex socio-technical problems in technology and innovation management (TIM). In this respect, action research allows both rigorous and relevant research due to parallel solving of real-world problems, capability building, and gaining scientific insights. However, the use of action research within TIM research is surprisingly limited. Action research also is not a homogeneous research methodology since each research discipline, such as education and organizational science, has its own action research streams, which are often only loosely linked. A systematic overview of those action research traditions and specific best practices is still missing, which complicates a systematic transfer and use of action research in TIM. This article addresses this essential gap by building a cross-disciplinary overview of action research streams based on a bibliometric analysis using Scopus. The analysis includes relevant disciplines with action research traditions, their development over time, and the most influential journals, authors, institutions, and countries. Along with this discipline-spanning analysis, the article investigates particular TIM benefits and challenges of action research. The two key contributions of this article are: 1) a discipline-spanning overview of action research and its evolution and 2) an analysis of its implications for TIM research. These contributions build the basis for strengthening the use of action research in TIM. In the medium-term, action research has the capacity to link academia and industry more closely and, in doing so, assists important endeavours of translating more of our research outcomes into practice.
Hassan, M, Liu, D & Xu, D 2019, 'A Two-Stage Approach to Collaborative Fiber Placement through Coordination of Multiple Autonomous Industrial Robots', Journal of Intelligent and Robotic Systems.
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Hodges, J, Attia, T, Arukgoda, J, Kang, C, Cowden, M, Doan, L, Ranasinghe, R, Abdelatty, K, Dissanayake, G & Furukawa, T 2019, 'Multistage bayesian autonomy for high-precision operation in a large field', Journal of Field Robotics, vol. 36, no. 1, pp. 183-203.
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© 2018 Wiley Periodicals, Inc. This paper presents a generalized multistage bayesian framework to enable an autonomous robot to complete high-precision operations on a static target in a large field. The proposed framework consists of two multistage approaches, capable of dealing with the complexity of high-precision operation in a large field to detect and localize the target. In the multistage localization, locations of the robot and the target are estimated sequentially when the target is far away from the robot, whereas these locations are estimated simultaneously when the target is close. A level of confidence (LOC) for each detection criterion of a sensor and the associated probability of detection (POD) of the sensor are defined to make the target detectable with different LOCs at varying distances. Differential entropies of the robot and target are used as a precision metric for evaluating the performance of the proposed approach. The proposed multistage observation and localization approaches were applied to scenarios using an unmanned ground vehicle (UGV) and an unmanned aerial vehicle (UAV). Results with the UGV in simulated environments and then real environments show the effectiveness of the proposed approaches to real-world problems. A successful demonstration using the UAV is also presented.
Hu, J, Liang, B & Qiu, X 2019, 'High-efficiency collimation of airborne sound through a single deep-subwavelength aperture in an ultra-thin planar plate', APPLIED PHYSICS EXPRESS, vol. 12, no. 2.
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Huang, S 2019, 'A review of optimisation strategies used in simultaneous localisation and mapping', Journal of Control and Decision, vol. 6, no. 1, pp. 61-74.
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© 2018, © 2018 Northeastern University, China. This paper provides a brief review of the different optimisation strategies used in mobile robot simultaneous localisation and mapping (SLAM) problem. The focus is on the optimisation-based SLAM back end. The strategies are classified based on their purposes such as reducing the computational complexity, improving the convergence and improving the robustness. It is clearly pointed out that some approximations are made in some of the methods and there is always a trade-off between the computational complexity and the accuracy of the solution. The local submap joining is a strategy that has been used to address both the computational complexity and the convergence and is a flexible tool to be used in the SLAM back end. Although more research is needed to further improve the SLAM back end, nowadays there are quite a few relatively mature SLAM back end algorithms that can be used by SLAM researchers and users.
Karimi, M, Croaker, P, Skvortsov, A, Moreau, D & Kessissoglou, N 2019, 'Numerical prediction of turbulent boundary layer noise from a sharp-edged flat plate', International Journal for Numerical Methods in Fluids.
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© 2019 John Wiley & Sons, Ltd. An efficient hybrid uncorrelated wall plane waves–boundary element method (UWPW-BEM) technique is proposed to predict the flow-induced noise from a structure in low Mach number turbulent flow. Reynolds-averaged Navier-Stokes equations are used to estimate the turbulent boundary layer parameters such as convective velocity, boundary layer thickness, and wall shear stress over the surface of the structure. The spectrum of the wall pressure fluctuations is evaluated from the turbulent boundary layer parameters and by using semi-empirical models from literature. The wall pressure field underneath the turbulent boundary layer is synthesized by realizations of uncorrelated wall plane waves (UWPW). An acoustic BEM solver is then employed to compute the acoustic pressure scattered by the structure from the synthesized wall pressure field. Finally, the acoustic response of the structure in turbulent flow is obtained as an ensemble average of the acoustic pressures due to all realizations of uncorrelated plane waves. To demonstrate the hybrid UWPW-BEM approach, the self-noise generated by a flat plate in turbulent flow with Reynolds number based on chord Re c = 4.9 × 10 5 is predicted. The results are compared with those obtained from a large eddy simulation (LES)-BEM technique as well as with experimental data from literature.
Khosoussi, K, Giamou, M, Sukhatme, GS, Huang, S, Dissanayake, G & How, JP 2019, 'Reliable Graphs for SLAM', International Journal of Robotics Research, vol. 38, no. 2-3, pp. 260-298.
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© The Author(s) 2019. Estimation-over-graphs (EoG) is a class of estimation problems that admit a natural graphical representation. Several key problems in robotics and sensor networks, including sensor network localization, synchronization over a group, and simultaneous localization and mapping (SLAM) fall into this category. We pursue two main goals in this work. First, we aim to characterize the impact of the graphical structure of SLAM and related problems on estimation reliability. We draw connections between several notions of graph connectivity and various properties of the underlying estimation problem. In particular, we establish results on the impact of the weighted number of spanning trees on the D-optimality criterion in 2D SLAM. These results enable agents to evaluate estimation reliability based only on the graphical representation of the EoG problem. We then use our findings and study the problem of designing sparse SLAM problems that lead to reliable maximum likelihood estimates through the synthesis of sparse graphs with the maximum weighted tree connectivity. Characterizing graphs with the maximum number of spanning trees is an open problem in general. To tackle this problem, we establish several new theoretical results, including the monotone log-submodularity of the weighted number of spanning trees. We exploit these structures and design a complementary greedy–convex pair of efficient approximation algorithms with provable guarantees. The proposed synthesis framework is applied to various forms of the measurement selection problem in resource-constrained SLAM. Our algorithms and theoretical findings are validated using random graphs, existing and new synthetic SLAM benchmarks, and publicly available real pose-graph SLAM datasets.
Kishore Kumar, D, Hsu, MH, Ivaturi, A, Chen, B, Bennett, N & Upadhyaya, HM 2019, 'Optimizing room temperature binder free TiO 2 paste for high efficiency flexible polymer dye sensitized solar cells', Flexible and Printed Electronics, vol. 4, no. 1.
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© 2019 IOP Publishing Ltd. Binder free TiO 2 paste is prepared using tert-butyl alcohol in dilute acidic conditions at room temperature for flexible polymer dye sensitized solar cells (DSSCs). The present paper reports the detailed studies carried out to elucidate the importance of stirring times during the paste preparation on the final device performance. The maximum conversion efficiency of 4.2% was obtained for flexible DSSCs fabricated on tin doped indium oxide/polyethylene naphthalate substrates using TiO 2 paste prepared with an optimum stirring time of 8 h. The effect of optimum stirring times on the device characteristics has been understood in terms of the detailed morphology and surface area measurements.
Kumar, DK, Suazo-Davila, D, Garcia-Torres, D, Cook, NP, Ivaturi, A, Hsu, M-H, Marti, AA, Cabrera, CR, Chen, B, Bennett, N & Upadhyaya, HM 2019, 'Low-temperature titania-graphene quantum dots paste for flexible dye-sensitised solar cell applications', ELECTROCHIMICA ACTA, vol. 305, pp. 278-284.
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Kumar, DK, Swami, SK, Dutta, V, Chen, B, Bennett, N & Upadhyaya, HM 2019, 'Scalable screen-printing manufacturing process for graphene oxide platinum free alternative counter electrodes in efficient dye sensitized solar cells', FlatChem, vol. 15.
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© 2019 Elsevier B.V. The graphene oxide paste (GO) was prepared by mixing α-terpineol and ethyl cellulose, and GO films was prepared by screen printing on fluorine doped Tin oxide (FTO) glass substrates to validate as an alternative counter electrode material to platinum in dye sensitized solar cells (DSSC). The graphene oxide films were characterised by X-Ray Diffraction, Scanning Electron Microscopy, Raman spectroscopy and the catalytic properties of films were being investigated by cyclic voltammetry and electrochemical Impedance measurements. The DSSC fabricated by coupling TiO 2 films soaked in N719 dye with GO as counter electrode exhibited photoconversion efficiency of 5.58% under standard one Sun illumination, whereas platinum based device showed photoconversion efficiency of 7.57%. The present study suggests that graphene oxide counter electrodes can be considered as a promising alternative to platinum, with further optimisation, which clearly has advantages in terms of its abundance and low cost processing towards industrial prospects.
Kuruneru, STW, Marechal, E, Deligant, M, Khelladi, S, Ravelet, F, Saha, SC, Sauret, E & Gu, Y 2019, 'A Comparative Study of Mixed Resolved–Unresolved CFD-DEM and Unresolved CFD-DEM Methods for the Solution of Particle-Laden Liquid Flows', Archives of Computational Methods in Engineering.
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© 2018, CIMNE, Barcelona, Spain. The exorbitant economic and environmental cost associated with fouling propels the need to develop advanced numerical methods to accurately decipher the underlying phenomena of fouling and multiphase fluid transport in jet-engine fuel systems. Clogging of jet-fuel systems results in the foulants to settle in seconds to form a porous layer which restricts fuel flow. The objective of this research is to numerically examine the transient evolution of particle-laden liquid flow and particle accumulation on an idealized jet-fuel filter. This is achieved by using two numerical approaches: coupled unresolved computational fluid dynamics-discrete element method (CFD-DEM), and coupled mixed resolved–unresolved CFD-DEM method. We assess the efficacy of both numerical methods by comparing the numerical results against experimental data. Results have shown that the particle accumulation and deposition profiles are in good agreement with the experimental results. Moreover, it is found that the particle distribution spread along the length and height of the channel reflects the actual particle spread as observed in the experiments. The unresolved CFD-DEM and mixed resolved–resolved CFD-DEM method could be harnessed to study complex multiphase fluid flow transport in various other applications such as compact heat exchangers and fluidized beds.
Kuruneru, STW, Saha, SC, Sauret, E & Gu, YT 2019, 'Transient heat transfer and non-isothermal particle-laden gas flows through porous metal foams of differing structure', APPLIED THERMAL ENGINEERING, vol. 150, pp. 888-903.
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Le, A, Le, H, Nguyen, L & Phan, M 2019, 'An efficient adaptive hierarchical sliding mode control strategy using neural networks for 3D overhead cranes', International Journal of Automation and Computing.
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In this paper, a new adaptive hierarchical sliding mode control scheme for a 3D overhead crane system is proposed. A controller is first designed by the use of a hierarchical structure of two first-order sliding surfaces represented by two actuated and un-actuated subsystems in the bridge crane. Parameters of the controller are then intelligently estimated, where uncertain parameters due to disturbances in the 3D overhead crane dynamic model are proposed to be represented by radial basis function networks whose weights are derived from a Lyapunov function. The proposed approach allows the crane system to be robust under uncertainty conditions in which some uncertain and unknown parameters are highly difficult to determine. Moreover, stability of the sliding surfaces is proved to be guaranteed. Effectiveness of the proposed approach is then demonstrated by implementing the algorithm in both synthetic and real-life systems, where the results obtained by our method are highly promising.
Le, HX, Le, AV & Nguyen, L 2019, 'Adaptive Fuzzy Observer based Hierarchical Sliding Mode Control for Uncertain 2D Overhead Cranes', Cyber-Physical Systems.
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This paper proposes a new approach to robustly control a 2D under-actuated overhead crane system, where a payload is effectively transported to a destination in real time with small sway angles, given its inherent uncertainties such as actuator nonlinearities and external disturbances. The control law is proposed to be developed by the use of the robust hierarchical sliding mode control (HSMC) structure in which a second-level sliding surface is formulated by two first-level sliding surfaces drawn on both actuated and under-actuated outputs of the crane. The unknown and uncertain parameters of the proposed control scheme are then adaptively estimated by the fuzzy observer, where the adaptation mechanism is derived from the Lyapunov theory. More importantly, stability of the proposed strategy is theoretically proved. Effectiveness of the proposed adaptive fuzzy observer based HSMC (AFHSMC) approach was extensively validated by implementing the algorithm in both synthetic simulations and real-life experiments, where the results obtained by our method are highly promising.
Li, W & Ma, H 2019, 'A novel model order reduction scheme for fast and accurate material nonlinear analyses of large-scale engineering structures', Engineering Structures, vol. 193, pp. 238-257.
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© 2019 Elsevier Ltd A new framework is developed for the fast and accurate analysis of large-scale engineering structures considering material nonlinearity. A fundamental linear model is constructed first by assigning nominal linear material parameters for each of the potentially nonlinear elements, and then, for each nonlinear element, a Nonlinear Deviation Force Vector (NDFV) is defined as the difference between the true nonlinear nodal force vector and the vector calculated using the nominal linear material parameters. In this way, the displacement of the nonlinear model can be expressed as a linear combination of a set of basis solutions of the fundamental linear model. These basis solutions include nodal displacement solutions due to the applied load and all unit components of NDFVs of nonlinear elements. Therefore, the values of these NDFVs, as combination coefficients in the displacement expression are the only unknowns for the whole structure and can be determined by considering a much smaller nonlinear equation system. It is noteworthy that no approximation is introduced in the proposed model order reduction scheme and the new scheme can be applied to the iterative solution process of both static and dynamic problems. Numerical examples are presented to show the effectiveness of the proposed scheme.
Li, W, Ma, H & Gao, W 2019, 'A higher-order shear deformable mixed beam element model for accurate analysis of functionally graded sandwich beams', Composite Structures, vol. 221.
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© 2019 Elsevier Ltd In this paper, a new higher-order shear deformation beam theory is developed by introducing the stress equilibrium condition. On the basis of the new shear deformation theory, novel shear deformable mixed beam elements with independent internal force fields and displacement fields are developed for accurate analysis of the functionally graded sandwich beams. Furthermore, a shear deformable beam element with additional interpolated axial displacement is also constructed in order to get reliable reference solutions. Two examples are presented to investigate the solution accuracy of different beam elements. Numerical results indicate that the present mixed beam elements can accurately predict the stress distributions over the cross section and ultimately give accurate displacement solutions. Moreover, the characteristics of axial displacement distributions and transverse shear strain distributions for functionally graded sandwich beams are discussed and the difficulty of getting accurate solutions by introducing a single form higher-order displacement function is pointed out. In these cases, the equilibrium-based beam theory and the corresponding mixed beam elements are more effective and reliable to obtain accurate solutions. Finally, the numerical stability for different beam elements is investigated and the results indicate the present higher-order shear deformable mixed beam element has excellent numerical stability.
Liang, J, Walker, PD, Ruan, J, Yang, H, Wu, J & Zhang, N 2019, 'Gearshift and brake distribution control for regenerative braking in electric vehicles with dual clutch transmission', MECHANISM AND MACHINE THEORY, vol. 133, pp. 1-22.
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Lin, C, Sun, S, Walker, P & Zhang, N 2019, 'Accelerated adaptive second order super-twisting sliding mode observer', IEEE Access.
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OAPA An accelerated second order super twisting sliding mode observer with an adaptive gain is proposed for a typical nonlinear system. The key contribution of this algorithm is that the rate of convergence of observation error is accelerated remarkably by introducing "system damping". Chattering issue is attenuated with satisfactory performance compared to conventional sliding mode observer. Furthermore adaptive gain can vary with deviation between the trajectory and sliding mode switching manifold dynamically so that overshoot can be reduced. The novel observer is proven mathematically to be convergent in a finite time. Finally, an example of nonlinear system is given to verify the performance.
Lin, C, Sun, S, Yi, J, Walker, P & Zhang, N 2019, 'Accelerated adaptive super twisting sliding mode observer-based drive shaft torque estimation for electric vehicle with automated manual transmission'.
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Lin, Z, Zhou, L & Qiu, X 2019, 'A composite objective measure on subjective evaluation of speech enhancement algorithms', APPLIED ACOUSTICS, vol. 145, pp. 144-148.
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Liu, L, Zhang, T, Leighton, B, Zhao, L, Huang, S & Dissanayake, G 2019, 'Robust Global Structure From Motion Pipeline With Parallax on Manifold Bundle Adjustment and Initialization', IEEE Robotics and Automation Letters, vol. 4, no. 2, pp. 2164-2171.
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© 2016 IEEE. In this letter, we present a novel global structure from motion (SfM) pipeline that is particularly effective in dealing with low-parallax scenes and camera motion collinear with the features that represent the environment structure. It is therefore particularly suitable in Urban SLAM, in which frequent road-facing motion poses many challenges to conventional SLAM algorithms. Our pipeline includes a recently explored bundle adjustment (BA) method that exploits a feature parameterization using Parallax angle between on-Manifold observation rays (PMBA). It is demonstrated that this BA stage has a consistently stable optimization configuration for features with any parallax and therefore low-parallax features can stay in reconstruction without pre-filtering. To allow practical usage of PMBA, we provide a compatible initialization stage in the SfM to initialize all camera poses simultaneously, exhibiting friendliness to collinear motion. This is achieved by simplifying PMBA into a hybrid graph problem of high connectivity yet small node set size, solved using a robust linear programming technique. Using simulations and a series of publicly available real datasets including "KITTI" and "Bundle Adjustment in the Large," we demonstrate the robustness of the position initialization stage in handling collinear motion and outlier matches, superior convergence performance of the BA stage in the presence of low-parallax features, and effectiveness of our pipeline to handle many sequential or out-of-order urban scenes.
Liu, Q, Zhang, N, Feng, F & Zhou, M 2019, 'Handling performance of tractor-semitrailers equipped with hydraulically interconnected suspension', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering.
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© IMechE 2018. This paper focuses on the contribution of a hydraulically interconnected suspension on the handling performance of a tractor-semitrailer. A hydraulically interconnected suspension model is integrated with a traditional tractor-semitrailer suspension for the purpose of study, and the hydraulically interconnected suspension system is first investigated through the bench test simulation to study its nonlinear and damping characteristic. Then a static rollover test, a steady-state circular test, a pulse steer input test, a pulse road input test and a random road input test are simulated in order to fully investigate the performance of a tractor-semitrailer with hydraulically interconnected suspension. The comparison analyses are conducted among two vehicles which are a fully loaded tractor-semitrailer without hydraulically interconnected suspension, an unloaded tractor-semitrailer without hydraulically interconnected suspension, a fully loaded tractor-semitrailer with hydraulically interconnected suspension and an unloaded tractor-semitrailer with hydraulically interconnected suspension. The obtained results show that the fully loaded tractor-semitrailer has enhanced handling performance, an improved steady-state rollover threshold and unchanged ride performance with the assistance of hydraulically interconnected suspension.
Man, X, Luo, Z, Liu, J & Xia, B 2019, 'Hilbert fractal acoustic metamaterials with negative mass density and bulk modulus on subwavelength scale', Materials & Design, vol. 180, pp. 107911-107911.
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Man, X-F, Xia, B-Z, Luo, Z & Liu, J 2019, '3D Hilbert fractal acoustic metamaterials: low-frequency and multi-band sound insulation', Journal of Physics D: Applied Physics, vol. 52, no. 19.
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Miao, Z, Yu, J, Ji, J & Zhou, J 2019, 'Multi-objective region reaching control for a swarm of robots', AUTOMATICA, vol. 103, pp. 81-87.
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Mo, W, Walker, PD & Zhang, N 2019, 'Dynamic analysis and control for an electric vehicle with harpoon-shift synchronizer', MECHANISM AND MACHINE THEORY, vol. 133, pp. 750-766.
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Moss, DL, Park, HW, Mettu, RR & Landry, SJ 2019, 'Deimmunizing substitutions in Pseudomonas exotoxin domain III perturb antigen processing without eliminating T-cell epitopes', Journal of Biological Chemistry, vol. 294, no. 12, pp. 4667-4681.
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© 2019 Moss et al. Effective adaptive immune responses depend on activation of CD4 T cells via the presentation of antigen peptides in the context of major histocompatibility complex (MHC) class II. The structure of an antigen strongly influences its processing within the endolysosome and potentially controls the identity of peptides that are presented to T cells. A recombinant immunotoxin, comprising exotoxin A domain III (PE-III) from Pseudomonas aeruginosa and a cancer-specific antibody fragment, has been developed to manage cancer, but its effectiveness is limited by the induction of neutralizing antibodies. Here, we observed that this immunogenicity is substantially reduced by substituting six residues within PE-III. Although these substitutions targeted T-cell epitopes, we demonstrate that reduced conformational stability and protease resistance were responsible for the reduced antibody titer. Analysis of mouse T-cell responses coupled with biophysical studies on single-substitution versions of PE-III suggested that modest but comprehensible changes in T-cell priming can dramatically perturb antibody production. The most strongly responsive PE-III epitope was well-predicted by a structure-based algorithm. In summary, single-residue substitutions can drastically alter the processing and immunogenicity of PE-III but have only modest effects on CD4 T-cell priming in mice. Our findings highlight the importance of structure-based processing constraints for accurate epitope prediction.
Nguyen, L, Valls Miro, J & Qiu, X 2019, 'Multilevel B-Splines based Learning Approach for Sound Source Localization', IEEE Sensors Journal, vol. 10, no. 10, pp. 3871-3881.
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In this paper, a new learning approach for sound source localization is presented using ad hoc either synchronous or asynchronous distributed microphone networks based on the time differences of arrival (TDOA) estimation. It is first to propose a new concept in which the coordinates of a sound source location are defined as the functions of TDOAs, computing for each pair of microphone signals in the network. Then, given a set of pre-recorded sound measurements and their corresponding source locations, the multilevel B-splines-based learning model is proposed to be trained by the input of the known TDOAs and the output of the known coordinates of the sound source locations. For a new acoustic source, if its sound signals are recorded, the correspondingly computed TDOAs can be fed into the learned model to predict the location of the new source. Superiorities of the proposed method are to incorporate the acoustic characteristics of a targeted environment and even remaining uncertainty of TDOA estimations into the learning model before conducting its prediction and to be applicable for both synchronous or asynchronous distributed microphone sensor networks. The effectiveness of the proposed algorithm in terms of localization accuracy and computational cost in comparisons with the state-of-the-art methods was extensively validated on both synthetic simulation experiments as well as in three real-life environments.
Nguyen, LTN, Eager, D & Nguyen, H 2019, 'The relationship between compression garments and electrocardiogram signals during exercise and recovery phase', BioMedical Engineering Online, vol. 18, no. 1.
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© 2019 The Author(s). Background: The direction of the current research was to investigate whether electrocardiogram (ECG) signals have been impacted by using compression garments during exercise and recovery phase. Each subject is non-athletes, conducted two running tests, wearing either non-compression garments (NCGs) or compression garments (CGs) throughout experiments and 2-h of the recovery phase. Experiment 1 (number of participants (n) = 8; 61.4 ± 13.7 kg, 25.1 ± 3.8 years, 165.9 ± 8.3 cm) focused on the exercising phase while Experiment 2 (n = 14; 60.9 ± 12.0 kg, 24.7 ± 4.5 years, 166.0 ± 7.6 cm) concentrated on the recovery phase. Electrocardiogram (ECG) data were collected through wearable biosensors. Results: The results demonstrated a significant difference between compression garments and non-compression garments at the end of the tests and from 90 min onwards during the recovery phase (p < 0.05). Corrected QT (QTc), ST interval and heart rate (HR) indicated the significant difference between NCGs and CGs. Conclusion: Based on the findings, the utilization of compression garments showed a positive influence in non-athletes based on the quicker recovery in HR, ST, and QTc.
Nguyen, LV, Hu, G & Spanos, CJ 2019, 'Efficient Sensor Deployments for Spatio-Temporal Environmental Monitoring', IEEE Transactions on Systems Man and Cybernetics: Systems.
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This paper addresses the problem of efficiently deploying sensors in spatial environments, e.g., buildings, for the purposes of monitoring spatio-temporal environmental phenomena. By modeling the environmental fields using spatio-temporal Gaussian processes, a new and efficient optimality-cost function of minimizing prediction uncertainties is proposed to find the best sensor locations. Though the environmental processes spatially and temporally vary, the proposed approach of choosing sensor positions is proven not to be affected by time variations, which significantly reduces computational complexity of the optimization problem. The sensor deployment optimization problem is then solved by a practical and feasible polynomial algorithm, where its solutions are theoretically proven to be guaranteed. The proposed method is also theoretically and experimentally compared with the existing works. The effectiveness of the proposed algorithm is demonstrated by implementation in a real tested space in a university building, where the obtained results are highly promising.
Nguyen, T, Thai, N, Pham, H, Phan, T, Le, H, Nguyen, H & Nguyen, L 2019, 'Adaptive neural network based backstepping sliding mode control approach for dual arm robots', Journal of Control, Automation and Electrical Systems.
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The paper introduces an adaptive strategy to effectively control a nonlinear dual arm robot under external disturbances and uncertainties. By the use of the backstepping sliding mode control (BSSMC) method,
the proposed algorithm rst allows the manipulators to be able to robustly track the desired trajectories. Furthermore, due to the nonlinear, uncertain and unmodelled dynamics of the dual arm robot, it is proposed to employ the radial basis function network (RBFN) to adaptively estimate the robot's dynamic model. Though the estimation of the dynamics is approximate, the adaptation law is derived from the Lyapunov theory, which provides the controller with ability to guarantee stability of the whole system in spite of its nonlinearities, parameter uncertainties and external load variations. The effectiveness of the proposed RBFN-BSSMC approach is demonstrated by implementation in a simulation environment with realistic parameters, where the obtained results are highly promising.
Ning, D, Sun, S, Yu, J, Zheng, M, Du, H, Zhang, N & Li, W 2019, 'A rotary variable admittance device and its application in vehicle seat suspension vibration control', Journal of the Franklin Institute.
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© 2019 The Franklin Institute In this paper, a novel semi-active variable admittance (VA) concept is proposed, and a seat suspension prototype with a magnetorheological fluid damper based rotary VA device is designed, manufactured, and experimentally validated. The conventional inerter with a single flywheel has a constant inertance, which can effectively improve the suspension performance by being integrated into a mechanical network with springs and dampers. The proposed rotary VA device comprises a gear reducer, two flywheels and a variable damping (VD) device which is used to connect the two flywheels. With carefully designing, the rotary VA device is compacted and is similar with a VD device in size. The rotary VA device is installed in the centre of a seat suspension's scissors structure to form a VA seat suspension. According to the test results, the equivalent inertance of the seat suspension can vary from 11.3 Kg–76.6 Kg with a 3 Hz frequency and 5 mm amplitude sinusoidal movement by changing the current from 0 A–1 A. By analysing the system characteristics, a hybrid controller with two acceleration feedbacks is proposed. Thereafter, the seat suspension and controller are validated in experiments by comparing the performance with a conventional passive seat suspension. The random vibration test shows the excellent performance of the proposed seat suspension; the frequency weighted root mean square acceleration of the seat is reduced by 43.6%, which indicates a great improvement of the ride comfort. The VA device shows great prospect in the suspension application.
Qin, Y, Wei, C, Tang, X, Zhang, N, Dong, M & Hu, C 2019, 'A novel nonlinear road profile classification approach for controllable suspension system: Simulation and experimental validation', Mechanical Systems and Signal Processing, vol. 125, pp. 79-98.
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© 2018 Elsevier Ltd Driven by the increasing requirement for road conditions in the field of the controllable suspension system, this paper presents a novel nonlinear road-excitation classification procedure for arbitrary suspension control strategy. The proposed procedure includes four steps: the definition of controller parameters, selection of insensitive frequency ranges, calculation of superior features, and generation of the classifier. To better illustrate the proposed procedure, the clipped optimal control strategy is taken as an example in the simulation part. Simulation results reveal that the proposed method can accurately estimate road excitation level for various controller parameters, vehicle speeds, and vehicle models. Three contributions have been made in this paper: (1) A road classification procedure that can be used for road adaptive suspension control with any control algorithm is developed; (2) In order to improve classification accuracy, the concept of insensitive index which is based on the time-frequency analysis is proposed; (3) Experimental validation with a quarter vehicle test rig is performed, which has verified the effectiveness of the proposed method for the adaptive controllable suspension system.
Schleppi, J, Gibbons, J, Groetsch, A, Buckman, J, Cowley, A & Bennett, N 2019, 'Manufacture of glass and mirrors from lunar regolith simulant', JOURNAL OF MATERIALS SCIENCE, vol. 54, no. 5, pp. 3726-3747.
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Shakor, P, Nejadi, S & Paul, G 2019, 'A Study into the Effect of Different Nozzles Shapes and Fibre-Reinforcement in 3D Printed Mortar', Materials, vol. 12, no. 10.
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Recently, 3D printing has become one of themost popular additivemanufacturing technologies.
This technology has been utilised to prototype trial and produced components for various applications,
such as fashion, food, automotive,medical, and construction. In recent years, automation also has become
increasingly prevalent in the construction field. Extrusion printing is the most successful method to print
cementitiousmaterials, but it still faces significant challenges, such as pumpability ofmaterials, buildability,
consistency in the materials, flowability, and workability. This paper investigates the properties of 3D
printed fibre-reinforced cementitious mortar prisms and members in conjunction with automation to
achieve the optimum mechanical strength of printed mortar and to obtain suitable flowability and
consistent workability for the mixed cementitious mortar during the printing process. This study also
considered the necessary trial tests, which are required to check the mechanical properties and behaviour
of the proportions of the cementitious mix. Mechanical strength was measured and shown to increase
when the samples were printed using fibre-reinforced mortar by means of a caulking gun, compared
with the samples that were printed using the same mix delivered by a progressive cavity pump to a
6 degree-of-freedom robot. The flexural strength of the four-printed layer fibre-reinforced mortar was
found to be 3.44 0.11MPa and 5.78 0.02MPa for the one-layer. Moreover, the mortar with different
types of nozzles by means of caulking is printed and compared. Several experimental tests for the fresh
state of the mortar were conducted and are discussed.
Shakor, P, Nejadi, S, Paul, G & Malek, S 2019, 'Review of emerging additive manufacturing technologies in 3D printing of cementitious materials in the construction industry', Frontiers in Built Environment, vol. 4.
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Additive manufacturing is a fabrication technology that is rapidly revolutionizing the manufacturing and construction sectors. In this paper, a review of various prototyping technologies for printing cementitious materials and selected 3D printing techniques are presented in detail. Benchmark examples are provided to compare three well-known printing techniques; inkjet printing (binder jetting), selected laser sintering (SLS), and extrusion printing (extrusion based process). A comprehensive search in the literature was conducted to identify various mix designs that could be employed when printing cementitious materials. Aspects of concrete mix design are described, and some new experiments are conducted to analyse the printability of new mixes by the authors. Future research in the area of the rheology of cementitious materials and its relationship with the structural performance of finished concretes are highlighted.
Shakor, P, Nejadi, S, Paul, G & Malekmohammadi, S 2019, 'Review of emerging additive manufacturing technologies in 3D printing of cementitious materials in the construction industry', Frontiers in Built Environment, vol. 4, pp. 1-17.
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Shakor, P, Nejadi, S, Paul, G, Sanjayan, J & Nazari, A 2019, 'Mechanical Properties of Cement-Based Materials and Effect of Elevated Temperature on Three-Dimensional (3-D) Printed Mortar Specimens in Inkjet 3-D Printing', ACI Materials Journal, vol. 116, no. 2, pp. 55-67.
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Shalby, M, Dorrell, D & Walker, P 2019, 'Multi–chamber oscillating water column wave energyconverters and air turbines: A review', International Journal of Energy Research.
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Shalby, M, Elhanafi, A, Walker, P & Dorrell, DG 2019, 'CFD modelling of a small–scale fixed multi–chamber OWC device', Applied Ocean Research, vol. 88, pp. 37-47.
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Song, R, Clemon, L & Telenko, C 2019, 'Uncertainty and Variability of Energy and Material Use by Fused Deposition Modeling Printers in Makerspaces', Journal of Industrial Ecology.
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© 2018, Yale University. Desktop-grade fused deposition modeling (FDM) printers are popular because of compact sizes and affordable prices. If we are moving toward a future where desktop FDM printers are in every school and office, like conventional printers, then these machines will consume a large amount of energy and material. However, it is very difficult to evaluate the environmental impacts of FDM printers since there are so many different brands and types of printers using different raw materials under different scenarios. This study uses data from two different printing sites to evaluate the scenario and parameter uncertainty and variability in energy and material balances for FDM printers. Data from the two makerspaces provide insight into the material and energy consumption data using polylactic acid and acrylonitrile butadiene styrene (ABS) with four types of printers. The use of actual performance data allowed for the additional study of scrap ratio. Regressions provide insight into predictive factors for energy and material consumption. Monte Carlo simulations show the range of energy life cycle inventory values for the desktop-grade FDM printers. From the regressions, Type A Pro was the most energy-intensive machine. For material waste, an open-access makerspace using ABS was associated with higher scrap ratio. Regression analysis indicates that the rate of material usage is not a strong predictor of waste rates. The amount of waste generated across both sites indicates that more ubiquitous access to FDM printing may create a significant addition to the waste stream.
Stender, M, Oberst, S & Hoffmann, N 2019, 'Recovery of Differential Equations from Impulse Response Time Series Data for Model Identification and Feature Extraction', Vibration, vol. 2, no. 1, pp. 25-46.
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Time recordings of impulse-type oscillation responses are short and highly transient. These characteristics may complicate the usage of classical spectral signal processing techniques for (a) describing the dynamics and (b) deriving discriminative features from the data. However, common model identification and validation techniques mostly rely on steady-state recordings, characteristic spectral properties and non-transient behavior. In this work, a recent method, which allows reconstructing differential equations from time series data, is extended for higher degrees of automation. With special focus on short and strongly damped oscillations, an optimization procedure is proposed that fine-tunes the reconstructed dynamical models with respect to model simplicity and error reduction. This framework is analyzed with particular focus on the amount of information available to the reconstruction, noise contamination and nonlinearities contained in the time series input. Using the example of a mechanical oscillator, we illustrate how the optimized reconstruction method can be used to identify a suitable model and how to extract features from uni-variate and multivariate time series recordings in an engineering-compliant environment. Moreover, the determined minimal models allow for identifying the qualitative nature of the underlying dynamical systems as well as testing for the degree and strength of nonlinearity. The reconstructed differential equations would then be potentially available for classical numerical studies, such as bifurcation analysis. These results represent a physically interpretable enhancement of data-driven modeling approaches in structural dynamics.
Tang, L, Wang, Y, Ding, X, Yin, H, Xiong, R & Huang, S 2019, 'Topological local-metric framework for mobile robots navigation: a long term perspective', Autonomous Robots, vol. 43, no. 1, pp. 197-211.
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© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Long term mapping and localization are the primary components for mobile robots in real world application deployment, of which the crucial challenge is the robustness and stability. In this paper, we introduce a topological local-metric framework (TLF), aiming at dealing with environmental changes, erroneous measurements and achieving constant complexity. TLF organizes the sensor data collected by the robot in a topological graph, of which the geometry is only encoded in the edge, i.e. the relative poses between adjacent nodes, relaxing the global consistency to local consistency. Therefore the TLF is more robust to unavoidable erroneous measurements from sensor information matching since the error is constrained in the local. Based on TLF, as there is no global coordinate, we further propose the localization and navigation algorithms by switching across multiple local metric coordinates. Besides, a lifelong memorizing mechanism is presented to memorize the environmental changes in the TLF with constant complexity, as no global optimization is required. In experiments, the framework and algorithms are evaluated on 21-session data collected by stereo cameras, which are sensitive to illumination, and compared with the state-of-art global consistent framework. The results demonstrate that TLF can achieve similar localization accuracy with that from global consistent framework, but brings higher robustness with lower cost. The localization performance can also be improved from sessions because of the memorizing mechanism. Finally, equipped with TLF, the robot navigates itself in a 1 km session autonomously.
Ulapane, N & Nguyen, L 2019, 'Review of Pulsed Eddy Current Signal Feature Extraction Methods for Conductive Ferromagnetic Material Thickness Quantification', Electronics (Basel).
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Thickness quantification of conductive ferromagnetic materials has become a common necessity in present-day structural health monitoring and infrastructure maintenance. Recent research has found Pulsed Eddy Current (PEC) sensing, especially the detector-coil-based PEC sensor architecture, to effectively serve as a nondestructive sensing technique for this purpose. As a result, several methods of varying complexity have been proposed in recent years to extract PEC signal features, against which conductive ferromagnetic material thickness behaves as a function, in return enabling thickness quantification owing to functional behaviours. It can be seen that almost all features specifically proposed in the literature for the purpose of conductive ferromagnetic material-thickness quantification are in some way related to the diffusion time constant of eddy currents. This paper examines the relevant feature-extraction methods through a controlled experiment in which the methods are applied to a single set of experimentally captured PEC signals, and provides a review by discussing the quality of the extractable features, and their functional behaviours for thickness quantification, along with computational time taken for feature extraction. Along with this paper, the set of PEC signals and some MATLAB codes for feature extraction are provided as supplementary materials for interested readers.
Wang, G, Ji, J & Zhou, J 2019, 'Practical stochastic synchronisation of coupled harmonic oscillators subjected to heterogeneous noises and its applications to electrical systems', IET CONTROL THEORY AND APPLICATIONS, vol. 13, no. 1, pp. 96-105.
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Wang, J, Tang, L, Zhao, L & Zhang, Z 2019, 'Efficiency investigation on energy harvesting from airflows in HVAC system based on galloping of isosceles triangle sectioned bluff bodies', Energy.
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Galloping-based piezoelectric energy harvester (GPEH) has been used in power generation from small-scale airflows for low-power devices such as Micro-Electromechanical Systems (MEMS) and wireless sensing electronics. The bluff body plays an important role for the onset of galloping. Existing literature regarding analytical and numerical analysis of GPEH has focused on designs incorporating bluff bodies with a variety of cross-sections, such as square, D-section and regular triangle. In this work, a GPEH with triangular cross-section bluff bodies with different vertex angles is investigated. The aerodynamic characteristics are determined by Computational Fluid Dynamics (CFD) and verified by experimental data. Subsequently, an aero-electro-mechanical model with piezoelectric coupling is established and numerically solved. Furthermore, a parametric study is performed to investigate the influence of electromechanical coupling on the GPEH's behavior, with a focus on the threshold wind speed, transverse displacement and power output. It is determined that with weak coupling, the obtuse angle β = 130° is the most preferred vertex angle. This is the first documented determination that an obtuse angled isosceles triangle could be used for efficient galloping energy harvesting. The findings provide a guideline for designing efficient GPEHs with triangular bluff bodies.
Wang, K, Wang, P & Qiu, X 2019, 'Increasing speech intelligibility in monaural hearing by adding noise at the other ear', APPLIED ACOUSTICS, vol. 146, pp. 50-55.
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Woolfrey, J, Lu, W & Liu, D 2019, 'A Control Method for Joint Torque Minimization of Redundant Manipulators Handling Large External Forces', Journal of Intelligent and Robotic Systems: Theory and Applications.
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© 2019, The Author(s). In this paper, a control method is developed for minimizing joint torque on a redundant manipulator where an external force acts on the end-effector. Using null space control, the redundant task is designed to minimize the torque required to oppose the external force, and reduce the dynamic torque. Furthermore, the joint motion can be weighted to factor in physical constraints such as joint limits, collision avoidance, etc. Conventional methods for joint torque minimization only consider the internal dynamics of the manipulator. If external forces acting on the end-effector are inadvertently implemented in to these control methods this could lead to joint configurations that amplify the resulting joint torque. The proposed control method is verified through two different case studies. The first case study involves simulation of high-pressure blasting. The second is a simulation of a manipulator lifting and moving a heavy object. The results show that the proposed control method reduces overall joint torque compared to conventional methods. Furthermore, the joint torque is minimized such that there is potential for a manipulator to execute certain tasks beyond its nominal payload capacity.
Wu, H, Walker, P, Wu, J, Liang, J, Ruan, J & Zhang, N 2019, 'Energy management and shifting stability control for a novel dual input clutchless transmission system', MECHANISM AND MACHINE THEORY, vol. 135, pp. 298-321.
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Wu, J, Luo, L, Zhu, B, Zhang, N & Xie, M 2019, 'Dynamic computation for rigid–flexible multibody systems with hybrid uncertainty of randomness and interval', Multibody System Dynamics.
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© 2019, Springer Nature B.V. Considering the unavoidable uncertainty of material properties, geometry, and external loads existing in rigid–flexible multibody systems, a new hybrid uncertain computational method is proposed. Two evaluation indexes, namely interval mean and interval error bar, are presented to quantify the system response. The dynamic model of a rigid–flexible multibody system is built by using the absolute node coordinate formula (ANCF). The geometry size and external loads of rigid components are considered as interval variables, while the Young’s modulus and Poisson’s ratio of flexible components are expressed by a random field. The continuous random field is discretized to Gaussian random variables by using the expansion optimal linear estimation (EOLE) method. This paper proposes an orthogonal series expansion method, termed as improved Polynomial-Chaos-Chebyshev-Interval (PCCI) method, which solves the random and interval uncertainty under one integral framework. The improved PCCI method has some sampling points located on the bounds of interval variables, which lead to a higher accuracy in estimating the bounds of multibody systems’ response compared to the PCCI method. A rigid–flexible slider–crank mechanism is used as a numerical example, which demonstrates that the improved PCCI method has a higher accuracy than the PCCI method.
Wu, J, Ruan, J, Zhang, N & Walker, PD 2019, 'An Optimized Real-Time Energy Management Strategy for the Power-Split Hybrid Electric Vehicles', IEEE Transactions on Control Systems Technology.
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IEEE This paper proposes a new real-time energy management strategy (R-EMS) to improve the fuel economy performance of the power-split hybrid electric vehicles (HEVs). Being different from most conventional optimization-based EMS, the R-EMS does not need priori information of the driving cycle and is used to the online control of HEV. The forward dynamic model of power-split powertrain is built based on the Prius MY10. At each instant, the proposed R-EMS tries to minimize the equivalent consumed power of the HEV, which is the weighted summation of gasoline power and battery output power. The equivalence factor of battery output power has a clear physical meaning that is the efficiency of gasoline energy transferred to battery energy. Another two coefficients are introduced to control the state of charge (SOC) of battery. By considering the engine torque and engine speed as two independent or dependent design variables, respectively, the 2-D R-EMS and 1-D R-EMS are formed. Several typical driving cycles are used to simulate the performance of the R-EMS, and the results show that the proposed R-EMS not only maintains the battery SOC but also saves the fuel consumption compared with the rule-based EMS.
Xu, H & Ji, J 2019, 'Analytical-numerical studies on the stability and bifurcations of periodic motion in the vibro-impact systems with clearances', INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, vol. 109, pp. 155-165.
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Xu, L, Qiu, X, Zhou, J, Li, F, Zhang, H & Wang, Y 2019, 'A 2D dual-mode composite ultrasonic transducer excited by a single piezoceramic stack', SMART MATERIALS AND STRUCTURES, vol. 28, no. 2.
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Yang, H, Zhang, Y, Liang, J, Liu, J, Zhang, N & Walker, PD 2019, 'Robust Deadbeat Predictive Power Control With a Discrete-Time Disturbance Observer for PWM Rectifiers Under Unbalanced Grid Conditions', IEEE TRANSACTIONS ON POWER ELECTRONICS, vol. 34, no. 1, pp. 287-300.
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Yang, W, Liang, J, Yang, J & Zhang, N 2019, 'Optimal control of a novel uninterrupted multi-speed transmission for hybrid electricmining trucks', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering.
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© IMechE 2019. Considering the energy consumption and specific performance requirements of mining trucks, a novel uninterrupted multi-speed transmission is proposed in this paper, which is composed of a power-split device, and a three-speed lay-shaft transmission with a traction motor. The power-split device is adapted to enhance the efficiency of the engine by adjusting the gear ratio continuously. The three-speed lay-shaft transmission is designed based on the efficiency map of traction motor to guarantee the drivability. The combination of the power-split device and three-speed lay-shaft transmission can realize uninterrupted gear shifting with the proposed shift strategy, which benefits from the proposed adjunct function by adequately compensating the torque hole. The detailed dynamic models of the system are built to verify the effectiveness of the proposed shift strategy. To evaluate the maximum fuel efficiency that the proposed uninterrupted multi-speed transmission could achieve, dynamic programming is implemented as the baseline. Due to the “dimension curse” of dynamic programming, a real-time control strategy is designed, which can significantly improve the computing efficiency. The simulation results demonstrate that the proposed uninterrupted multi-speed transmission with dynamic programming and real-time control strategy can improve fuel efficiency by 11.63% and 8.51% compared with conventional automated manual transmission system, respectively.
Yang, W, Yang, J & Zhang, N 2019, 'A novel coaxial multi-mode hybrid transmission system for mining trucks', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering.
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© IMechE 2018. Given that hybrid electric vehicles could significantly reduce fuel consumption, and mining trucks are much more sensitive to energy conversion efficiency, it is essential to develop a hybrid system, which could meet both the specific requirements of the structure of mining trucks and the needs for overall efficiency improvements. In this paper, a novel multi-mode transmission system, which is composed of an engine, two motors, one planetary gear set, and a parallel transmission structure, is proposed. The planetary gear set serves as a power-split device, and the parallel transmission structure can make the engine and motor work in the high-efficiency area both in low-speed and high-speed conditions. Due to the flexibility of the proposed system, five power-flow modes can be implemented, and they are illustrated with a specially designed rule-based energy management strategy. To validate the effectiveness of the multi-mode transmission system, dynamic programming is used to assess the fuel consumption during the given driving cycle without considering drivability. The simulation results reveal that the proposed multi-mode transmission system owns better fuel efficiency for mining trucks compared with highly regarded Toyota Hybrid System and conventional automated manual transmission system.
Yang, W, Yang, J, Liang, J & Zhang, N 2019, 'Implementation of velocity optimisation strategy based on preview road information to trade off transport time and fuel consumption for hybrid mining trucks', IET INTELLIGENT TRANSPORT SYSTEMS, vol. 13, no. 1, pp. 194-200.
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Ye, K & Ji, J 2019, 'Current, wave, wind and interaction induced dynamic response of a 5 MW spar-type offshore direct-drive wind turbine', ENGINEERING STRUCTURES, vol. 178, pp. 395-409.
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Yin, S, Ji, J & Wen, G 2019, 'Complex near-grazing dynamics in impact oscillators', International Journal of Mechanical Sciences, vol. 156, pp. 106-122.
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© 2019 Elsevier Ltd Impact oscillators frequently appear in various physical and engineering systems with non-smooth characteristics and can exhibit different dynamic behavior from the smooth nonlinear systems, including grazing bifurcation in which an impact with zero velocity occurs. This paper investigates the near-grazing dynamics of the multi-degree-of-freedom impact oscillators in the small neighborhood of degenerate grazing points, with a focus on the stability and potential bifurcations of near-grazing period-one impact motions. The high order zero time discontinuity mapping method is applied to perform the prospective analyses of stability and bifurcations. Particularly, this paper shows that the peculiar Neimark-Sacker bifurcations regaining the stability of near-grazing period-one impact motion can be induced by two different ways, either through the interaction between the singular and regular real eigenvalues or via a grazing bifurcation directly. A two degree-of-freedom impact oscillator is taken as an example to present detailed numerical results for the verification of proposed analysis.
Yin, S, Ji, J, Wen, G & Wu, X 2019, 'Use of degeneration to stabilize near grazing periodic motion in impact oscillators', COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION, vol. 66, pp. 20-30.
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Yu, J, Ji, J, Miao, Z & Zhou, J 2019, 'Neural network-based region reaching formation control for multi-robot systems in obstacle environment', NEUROCOMPUTING, vol. 333, pp. 11-21.
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Zhan, J, Ge, XJ, Huang, S, Zhao, L, Wong, JKW & He, SXJ 2019, 'Improvement of the inspection-repair process with building information modelling and image classification', Facilities, vol. 37, no. 7-8, pp. 395-414.
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© 2019, Emerald Publishing Limited. Purpose: Automated technologies have been applied to facility management (FM) practices to address labour demands of, and time consumed by, inputting and processing manual data. Less attention has been focussed on automation of visual information, such as images, when improving timely maintenance decisions. This study aims to develop image classification algorithms to improve information flow in the inspection-repair process through building information modelling (BIM). Design/methodology/approach: To improve and automate the inspection-repair process, image classification algorithms were used to connect images with a corresponding image database in a BIM knowledge repository. Quick response (QR) code decoding and Bag of Words were chosen to classify images in the system. Graphical user interfaces (GUIs) were developed to facilitate activity collaboration and communication. A pilot case study in an inspection-repair process was applied to demonstrate the applications of this system. Findings: The system developed in this study associates the inspection-repair process with a digital three-dimensional (3D) model, GUIs, a BIM knowledge repository and image classification algorithms. By implementing the proposed application in a case study, the authors found that improvement of the inspection-repair process and automated image classification with a BIM knowledge repository (such as the one developed in this study) can enhance FM practices by increasing productivity and reducing time and costs associated with ecision-making. Originality/value: This study introduces an innovative approach that applies image classification and leverages a BIM knowledge repository to enhance the inspection-repair process in FM practice. The system designed provides automated image-classifying data from a smart phone, eliminates time required to input image data manually and improves communication and collaboration between FM personnel for maintenance i...
Zhang, G, Tao, J, Qiu, X & Burnett, I 2019, 'Decentralized Two-Channel Active Noise Control for Single Frequency by Shaping Matrix Eigenvalues', IEEE-ACM TRANSACTIONS ON AUDIO SPEECH AND LANGUAGE PROCESSING, vol. 27, no. 1, pp. 44-52.
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Zhang, J, Ding, F, Zhang, N, Chen, S & Zhang, B 2019, 'A New SSUKF Observer for Sliding Mode Force Tracking H∞ Control of Electrohydraulic Active Suspension', Asian Journal of Control.
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© 2018 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd Compared to passive and semi-active suspensions, active suspensions have the capacity to overcome the tradeoff design of vehicle ride comfort and handling performance. In this paper, a new control system with modified spherical simplex UKF (SSUKF) observer and sliding mode force tracker is proposed for electrohydraulic active suspensions. The estimated states obtained from the SSUKF observer are used to derive the mode energy of body motion and design the target demanded forces for suspension actuators. A sliding mode controller is presented to drive electrohydraulic actuators to track the demanded forces. Based on a robust H∞ control method, a new control strategy depending on body mode energy is proposed to restrict body motion. The performance comparisons between passive and active suspensions under three typical excitations are presented, and the obtained results indicate that the proposed control system can significantly depress body motion and decrease the mode energy to improve ride comfort and also effectively enhance the road hold abilities.
Zhang, M, Qiu, B, Kalhori, H & Qu, X 2019, 'Hybrid reconstruction method for indirect monitoring of an ice load of a steel gate in a cold region', COLD REGIONS SCIENCE AND TECHNOLOGY, vol. 162, pp. 19-34.
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Zhang, Y, Lu, W, Ou, W, Zhang, G, Zhang, X, Cheng, J & Zhang, W 2019, 'Chinese medical question answer selection via hybrid models based on CNN and GRU', Multimedia Tools and Applications.
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© 2019, Springer Science+Business Media, LLC, part of Springer Nature. Question answer selection in the Chinese medical field is very challenging since it requires effective text representations to capture the complex semantic relationships between Chinese questions and answers. Recent approaches on deep learning, e.g., CNN and RNN, have shown their potential in improving the selection quality. However, these existing methods can only capture a part or one-side of semantic relationships while ignoring the other rich and sophisticated ones, leading to limited performance improvement. In this paper, a series of neural network models are proposed to address Chinese medical question answer selection issue. In order to model the complex relationships between questions and answers, we develop both single and hybrid models with CNN and GRU to combine the merits of different neural network architectures. This is different from existing works that can onpy capture partial relationships by utilizing a single network structure. Extensive experimental results on cMedQA dataset demonstrate that the proposed hybrid models, especially BiGRU-CNN, significantly outperform the state-of-the-art methods. The source codes of our models are available in the GitHub (https://github.com/zhangyuteng/MedicalQA-CNN-BiGRU).
Zhang, Z, Oberst, S & Lai, J 2019, 'A non-linear friction work formulation for the analysis of self-excited vibrations', Journal of Sound and Vibration, vol. 443, pp. 328-340.
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Even though much research has been devoted to understand friction-induced vibrations, its root cause is not yet fully understood. Reliable prediction of friction-induced unstable vibrations such as in brake squeal or hip squeak remains a challenge because of nonlinearities involved and because the complex eigenvalue analysis (CEA) widely used in industry is linear. The energy fed back into the system by friction has been shown to be useful for analysis of measurements and numerical simulations. In numerical simulations, the linearised method of feed-in energy, calculated purely based on friction work has provided some insights into the physical mechanism for instabilities. However, the dynamics due to friction-induced instabilities is highly nonlinear and damping may offset some or all of the excess friction energy provided to the system. By using a nonlinear 2-DOF dry friction oscillator, a nonlinear friction work formulation is proposed to demonstrate that in combination with viscous damping the energy budget provides an improved analysis capability over linearised friction work. The results highlight the potential of nonlinear friction work as a reliable tool to study friction-induced instabilities to gain deeper physical insights into squeal triggering mechanisms and to better understand the over- and under-predictive character inherent to linear methods.
Zhao, L, Huang, S & Dissanayake, G 2019, 'Linear SLAM: Linearising the SLAM problems using submap joining', AUTOMATICA, vol. 100, pp. 231-246.
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Zhao, S, Qiu, X, Lacey, J & Maisch, S 2019, 'Configuring fixed-coefficient active control systems for traffic noise reduction', BUILDING AND ENVIRONMENT, vol. 149, pp. 415-427.
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Zheng, J, Luo, Z, Jiang, C & Gao, J 2019, 'Robust topology optimization for concurrent design of dynamic structures under hybrid uncertainties', Mechanical Systems and Signal Processing, vol. 120, pp. 540-559.
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Zheng, J, Luo, Z, Jiang, C & Wu, J 2019, 'Level-set topology optimization for robust design of structures under hybrid uncertainties', International Journal for Numerical Methods in Engineering, pp. 523-542.
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© 2018 John Wiley & Sons, Ltd. This paper will develop a new robust topology optimization (RTO) method based on level sets for structures subject to hybrid uncertainties, with a more efficient Karhunen-Loève hyperbolic Polynomial Chaos–Chebyshev Interval method to conduct the hybrid uncertain analysis. The loadings and material properties are considered hybrid uncertainties in structures. The parameters with sufficient information are regarded as random fields, while the parameters without sufficient information are treated as intervals. The Karhunen-Loève expansion is applied to discretize random fields into a finite number of random variables, and then, the original hybrid uncertainty analysis is transformed into a new process with random and interval parameters, to which the hyperbolic Polynomial Chaos–Chebyshev Interval is employed for the uncertainty analysis. RTO is formulated to minimize a weighted sum of the mean and standard variance of the structural objective function under the worst-case scenario. Several numerical examples are employed to demonstrate the effectiveness of the proposed RTO, and Monte Carlo simulation is used to validate the numerical accuracy of our proposed method.
Zhong, J, Tao, J & Qiu, X 2019, 'Increasing the performance of active noise control systems on ground with a finite size vertical reflecting surface', Applied Acoustics, vol. 154, pp. 193-200.
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© 2019 Elsevier Ltd This paper investigates the feasibility of increasing the noise reduction performance of active noise control systems on ground by introducing a finite size reflecting surface vertical to the ground. By using the image source method and the disk scattering model, the sound radiation power of an active noise control system on ground with an additional finite size semicircular rigid disk vertical to the ground is studied. It is found that the noise reduction of the system can be increased significantly with the infinitely large reflecting surface when the primary and secondary source distance is less than half of the wavelength at the frequency of interest, and the finite size disk can further increase the noise reduction performance at certain bandwidth by up to 2.3 dB. The mechanisms for the performance increase are explored, and the experimental results are presented to validate the analytical and simulation results.
Zhu, Q, Coleman, P, Qiu, X, Wu, M, Yang, J & Burnett, I 2019, 'Robust Personal Audio Geometry Optimization in the SVD-Based Modal Domain', IEEE-ACM TRANSACTIONS ON AUDIO SPEECH AND LANGUAGE PROCESSING, vol. 27, no. 3, pp. 610-620.
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Zou, HS & Qiu, XJ 2019, 'A review of research on active noise control near human ear in complex sound field', Wuli Xuebao/Acta Physica Sinica, vol. 68, no. 5.
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© 2019 Chinese Physical Society. Local control of sound around human ears in complex acoustic environments is important for both active noise control and sound reproduction. Two typical active noise control approaches for this objective are active headrest systems and virtual sound barrier systems. In this paper, the history and the present status for the active headrest systems and virtual sound barrier systems are briefed first, then the theoretical principles, the design methods and the applications of these approaches are reviewed. Their advantages and limitations are discussed, and finally, the currently existing problems and future research directions are presented. The feasibility of these approaches to generating a quiet zone near a human ear has been verified by the theoretical research, numerical simulations and experiments. The active headrest systems require less control sources and are simpler for implementation; however, they suffer the problem of small-sized quiet zones. This results in the restrictions on the head movement since the error sensor needs to be close to the human ear to obtain better noise reduction performance. Based on the virtual sensor technology, a physical error sensor can be placed farther away from the human head, and create the quiet zone at the virtual sensor position near the human ear. Moreover, combined with the virtual sensor technology and the head-tracking technology, an active headrest system can generate a moving zone of quiet following the head movement, and the noise reduction can be achieved in a middle-to-high frequency range. A virtual sound barrier system reduces the sound pressure inside a volume, through controlling the sound pressure and normal gradient on the boundary of the volume. Two main design methods are the expansion method of the primary sound field which is suitable for steady primary sound fields, and the least mean square method which is applicable to time-varying primary sound fields. It can gen...
Abdo, P, Taghipour, R & Huynh, BP 2019, 'THREE DIMENSIONAL SIMULATION OF THE EFFECT OF WINDCATCHER`S INLET SHAPE', Proceedings of The ASME - JSME - KSME Joint Fluids Engineering Conference 2019, The ASME - JSME - KSME Joint Fluids Engineering Conference 2019, San Francisco, CA, USA.
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Abdo, P, Taghipour, R & Huynh, BP 2019, 'THREE DIMENSIONAL SIMULATION OF VENTILATION FLOW THROUGH A SOLAR WINDCATCHER', Proceedings of The ASME - JSME - KSME Joint Fluids Engineering Conference 2019, The ASME - JSME - KSME Joint Fluids Engineering Conference 2019, San Francisco, CA, USA.
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Aldini, S, Akella, A, Singh, A, Wang, Y-K, Carmichael, M, Liu, D & Lin, C-T 2019, 'Effect of Mechanical Resistance on Cognitive Conflict in Physical Human-Robot Collaboration', International Conference on Robotics and Automation, Canada.
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Almeida, F, Brennan, M, Karimi, M, Scussel, O, Paschoalini, A & Kessissoglou, N 2019, 'On the interaction between waves in a buried water pipe and ground vibration due to a leak', Recent Advances in Structural Dynamics (RASD), Lyon, France.
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Leak location in a buried water pipe can be carried out by measuring the vibration of the ground above the pipe. This is possible due to pipe-soil interaction and wave propagation caused by the excitation due to the leak. To measure the vibration due to a leak, sensors are placed on the ground and signals are then acquired. The measured phase between these sensors is used to locate the leak. However, the phase can be affected by the way in which the soil interacts with the buried pipe. Shear and dilatational waves propagate through the soil. The interaction between these waves can be observed as two different phase gradients in different frequency ranges due to the differences in the speeds of these waves. This paper investigates the interaction between the waves using a classical wave model. A numerical model based on the finite element method (FEM) is also used to predict the problem. The phase is evaluated using the FEM and then the model parameters are estimated using an optimization tool. It is shown that although the physical model is complicated, a simple two-wave model can be used to capture the observed behaviour.
Bai, F, Vidal Calleja, T, Huang, S & Xiong, R 2018, 'Predicting Objective Function Change in Pose-Graph Optimization', International Conference on Intelligent Robots and Systems, IEEE, Madrid, pp. 1-8.
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Robust online incremental SLAM applications require metrics to evaluate the impact of current measurements. Despite its prevalence in graph pruning, information-theoretic metrics solely are insufficient to detect outliers. The optimal value of the objective function is a better choice to detect outliers but cannot be computed unless the problem is solved. In this paper, we show how the objective function change can be predicted in an incremental pose-graph optimization scheme, without actually solving the problem. The predicted objective function change can be used to guide online decisions or detect outliers. Experiments validate the accuracy of the predicted objective function, and an application to outlier detection is also provided, showing its advantages over M-estimators.
Bai, F, Vidal-Calleja, T, Huang, S & Xiong, R 2018, 'Predicting Objective Function Change in Pose-Graph Optimization', IEEE International Conference on Intelligent Robots and Systems, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, Madrid, Spain, pp. 145-152.
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© 2018 IEEE. Robust online incremental SLAM applications require metrics to evaluate the impact of current measurements. Despite its prevalence in graph pruning, information-theoretic metrics solely are insufficient to detect outliers. The optimal value of the objective function is a better choice to detect outliers but cannot be computed unless the problem is solved. In this paper, we show how the objective function change can be predicted in an incremental pose-graph optimization scheme, without actually solving the problem. The predicted objective function change can be used to guide online decisions or detect outliers. Experiments validate the accuracy of the predicted objective function, and an application to outlier detection is also provided, showing its advantages over M-estimators.
Brown, T 2018, 'a simple spring-loaded', pittsburgh.
Giovanangeli, N, Piyathilaka, L, Kodagoda, S, Thiyagarajan, K, Barclay, S & Vitanage, D 2019, 'Design and Development of Drill-Resistance Sensor Technology for Accurately Measuring Microbiologically Corroded Concrete Depths', 36 International Symposium on Automation and Robotics in Construction, Canada.
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Gong, S, Oberst, S & Wang, X 2019, 'Dynamic analysis of vibrating flip-flow screens equipped with support and shear rubber springs', Recent Advances in Structural Dynamics, Lyon, France.
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Vibrating flip-flow screens provide an effective means of screening highly viscous or fine materials, and the dynamic characteristics of the main and the floating screen frames are largely responsible for a flip-flow screen’s screen performance and its processing capacity. An accurate dynamic model of the rubber shear springs used within the frame of the screen is critical for its dynamic analysis – to understand deficiencies and improve its performance. In this paper, the Sjöberg model is used to predict the frequency-and amplitude-dependent behaviour of the rubber shear springs. A friction model represents the amplitude dependency of the rubber shear springs. The fractional derivative model is used to describe its frequency dependency with its elasticity being represented by a linear spring. This model is further validated by cyclic tests of the rubber shear springs. Furthermore, dynamic response of the VFFS have been analysed using the Sjöberg model and the Kelvin-Voigt model, respectively. Experimental results indicate that dynamic response of VFFS can be better predict using the Sjöberg model than Kelvin-Voigt model in time region as well as in the frequency domain.
Gong, S, Oberst, S & Xinwen, W 2019, 'A non-linear model of rubber shear springs validated by experiments', Nonlinear Dynamics, Rome, Italy.
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Vibrating flip-flow screens provide an effective solution for screening highly viscous or fine materials. However,
yet, only linear theory has been applied to their design. Yet, to understand deficiencies and to improve performance an
accurate model especially of the rubber shear springs equipped in screen frames is critical for its dynamics to predict e.g.
frequency- and amplitude-dependent behaviour. In this paper, the amplitude dependency of the rubber shear spring is
represented by employing a friction model in which parameters are fitted to an affine function rather constant values used for
the classic Berg’s model; the fractional derivative model is used to describe its frequency dependency and compared to
conventional dashpot and Maxwell models with its elasticity being represented by a nonlinear spring. The experimentally
validated results indicate that the proposed model with a nonlinear spring, friction and fractional derivative model is able to
more accurately describe the dynamic characteristics of a rubber shear spring compared with other models.
Gracia, L, Solanes, JE, Munoz-Benavent, P, Miro, JV, Perez-Vidal, C & Tornero, J 2018, 'A Sliding Mode Control Architecture for Human-Manipulator Cooperative Surface Treatment Tasks', IEEE International Conference on Intelligent Robots and Systems, IEEE/RSJ International Conference on Intelligent Robots and Systems, Madrid, Spain, pp. 1318-1325.
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© 2018 IEEE. This paper presents a control architecture readily suitable for surface treatment tasks such as polishing, grinding, finishing or deburring as carried out by a human operator, with the added benefit of accuracy, recurrence and physical strength as administered by a robotic manipulator partner. The shared strategy effectively couples the human operator propioceptive abilities and fine skills through his interactions with the autonomous physical agent. The novel proposed control scheme is based on task prioritization and a non-conventional sliding mode control, which is considered to benefit from its inherent robustness and low computational cost. The system relies on two force sensors, one located between the last link of the robot and the surface treatment tool, and the other located in some place of the robot end-effector: the former is used to suitably accomplish the conditioning task, while the latter is used by the operator to manually guide the robotic tool. When the operator chooses to cease guiding the tool, the robot motion safely switches back to an automatic reference tracking. The paper presents the theories for the novel collaborative controller, whilst its effectiveness for robotic surface treatment is substantiated by experimental results using a redundant 7R manipulator and a mock-up conditioning tool.
Gunatilake, A, Piyathilaka, L, Kodagoda, S, Barclay, S & Vitanage, D 2019, 'Real-Time 3D Profiling with RGB-D Mapping in Pipelines UsingStereo Camera Vision and Structured IR Laser Ring', The 14th IEEE Conference on Industrial Electronics and Applications 2019, Xi'an, China.
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This paper is focused on delivering a solution that can scan and reconstruct the 3D profile of a pipeline in real-time using a crawler robot. A structured infrared (IR) laser ring projector and a stereo camera system are used to generate the 3D profile of the pipe as the robot moves inside the pipe. The proposed stereo system does not require field calibrations and it is not affected by the lateral movement of the robot, hence capable of producing an accurate 3D map. The wavelength of the IR light source is chosen to be non overlapping with the visible spectrum of the color camera. Hence RGB color values of the depth can be obtained by projecting the 3D map into the color image frame. The proposed system is implemented in Robotic Operating System (ROS) producing real-time RGB-D maps with defects. The defect map exploit differences in ovality enabling real-time identification of structural defects such as surface corrosion in pipe infrastructure. The lab experiments showed the proposed laser profiling system can detect ovality changes of the pipe with millimeter level of accuracy and resolution.
Halkon, B 2019, 'ON THE POSSIBILITY OF UAV-MOUNTED LDVS FOR RESPONSE-ONLY DYNAMIC CHARACTERISATION OF REMOTE INFRASTRUCTURE', Copenhagen.
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Halkon, B, Rauter, A, Oberst, S & Marburg, S 2019, 'Research and development of an air-puff excitation system for lightweight structures', 8th International Operational Modal Analysis Conference 2019, Copenhagen.
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Lightweight, thin-walled structures appear in numerous engineering and natural structures. Due to their sensitivity, vibration excitation by, now traditional, contacting techniques, such as modally-tuned impact hammers or electrodynamic shakers, to investigate their dynamics is challenging since it typically adds substantial mass and/or stiffness at the excitation location. The research presented in this article, therefore, is intended to yield a system for the non-contact excitation of thin-walled structures through small, controlled blasts of air. An air-puff system, consisting of two fast-acting solenoid controlled valves, a small air outlet nozzle and bespoke control software with a programmable valve control sequence, is researched and developed. The excitation impulse characteristics are investigated
experimentally and described in detail for varying input control parameters. Ultimately, suitability of the system for the excitation of thin-walled structures is explored, for both a 3D-printed micro-satellite panel and a natural bee honeycomb, with promising results when compared to that of an impact hammer.
Hassan, M & Liu, D 2018, 'A Deformable Spiral Based Algorithm to Smooth Coverage Path Planning for Marine Growth Removal', 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), International Conference on Intelligent Robots and Systems, IEEE, Madrid, Spain, pp. 1913-1918.
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Marine growths that flourish on the surfaces of underwater structures, such as bridge pylons, make the inspection and maintenance of these structures challenging. A robotic solution, using an Intervention Autonomous Underwater Vehicle (I-AUV), is developed for removing marine growth. This paper presents a Deformable Spiral Coverage Path Planning (DSCPP) algorithm for marine growth removal. DSCPP generates smooth paths to prevent damage to the surfaces of the structures and to avoid frequent or aggressive decelerations and accelerations due to sharp turns. DSCPP generates a spiral path within a circle and analytically maps the path to a minimum bounding rectangle which encompasses an area of a surface with marine growth. It aims to achieve a spiral path with minimal length while preventing missed areas of coverage. Several case studies are presented to validate the algorithm. Comparison results show that DSCPP outperforms the popular boustrophedon-based coverage approach when considering the requirements for the application under consideration.
Le Gentil, C, Vidal Calleja, T & Huang, S 2019, 'IN2LAMA: INertial Lidar Localisation And MApping', International Conference on Robotics and Automation, Montreal.
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Li, Z, Kim, J & Yu, C 2019, 'Control Design and Analysis of an Epidemic SEIV- Model upon Adaptive Network', European Control Conference, Italy.
Li, Z, Kim, J & Yu, C 2019, 'Control Design and Stability Analysis of a Two-Infectious-State Awareness Epidemic Model', Asian Control Conference (ASCC), Japan.
LU, S, Oberst, S, Zhang, G & Luo, Z 2019, 'Period adding bifurcations in dynamic pricing processes', IEEE CIFEr 2019: 2019 IEEE Conference on Computational Intelligence for Financial Engineering and Economics, Shenzhen.
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Price information enables consumers to anticipate
a price and to make purchasing decisions based on their price
expectations, which are critical for agents with pricing decisions
or price regulations. A company with pricing decisions can
aim to optimise the short-term or the long-term revenue, each
of which leads to different pricing strategies thereby different
price expectations. The choices between the two optimisation
objectives consider the maximal revenue and the robustness of
a chosen pricing strategy against market volatility. However
the robustness is rarely identified in a volatile market. Here,
we investigate the robustness of optimal pricing strategies with
the short-term or long-term optimisation objectives through the
analysis of nonlinear dynamics of price expectations. Bifurcation
diagrams and period diagrams are introduced to compare their
change in dynamics. Our results highlight that period adding
bifurcations occur during the dynamic pricing processes studied.
These bifurcations would challenge the robustness of an optimal
pricing strategy. The consideration of the long-term revenue
allows a company to charge a higher price, which in turn
increases the revenue. However, the consideration of the shortterm
revenue can avoid period adding bifurcations, contributing
to a robust pricing strategy. This allows a company to harvest
a good revenue through a robust pricing strategy in a volatile
market and to satisfy regulations of a control in price volatility.
Maleki, B, Alempijevic, A & Vidal Calleja, T 2018, 'Continuous Optimization Framework for Depth Sensor Viewpoint Selection', Workshop on the Algorithmic Foundations of Robotics, Merida, Mexico.
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Distinguishing differences between areas represented with point cloud data is generally approached by choosing a optimal viewpoint. The most informative view of a scene ultimately enables to have the optimal coverage over distinct points both locally and globally while accounting for the distance to the foci of attention. Measures of surface saliency, related to curvature inconsistency, extenuate differences in shape and are coupled with viewpoint selection approaches. As there is no analytical solution for optimal viewpoint selection, candidate viewpoints are generally discretely sampled and evaluated for information and require (near) exhaustive combinatorial searches. We present a consolidated optimization framework for optimal viewpoint selection with a continuous cost function and analytically derived Jacobian that incorporates view angle, vertex normals and measures of task related surface information relative to viewpoint. We provide a mechanism in the cost function to incorporate sensor attributes such as operating range, field of view and angular resolution. The framework is evaluated as competing favorably with the state-of-the-art approaches to viewpoint selection while significantly reducing the number of viewpoints to be evaluated in the process.
Nguyen, L & Valls Miro, J 2019, 'Acoustic Sensor Networks and Mobile Robotics for Sound Source Localization', IEEE International Conference on Control & Automation, Edinburgh, UK.
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Localizing a sound source is a fundamental but
still challenging issue in many applications, where sound information
is gathered by static and local microphone sensors.
Therefore, this work proposes a new system by exploiting
advances in sensor networks and robotics to more accurately
address the problem of sound source localization. By the use of
the network infrastructure, acoustic sensors are more efficient
to spatially monitor acoustical phenomena. Furthermore, a
mobile robot is proposed to carry an extra microphone array
in order to collect more acoustic signals when it travels around
the environment. Driving the robot is guided by the need to
increase the quality of the data gathered by the static acoustic
sensors, which leads to better probabilistic fusion of all the
information gained, so that an increasingly accurate map of
the sound source can be built. The proposed system has been
validated in a real-life environment, where the obtained results
are highly promising.
Niwa, K, Zhang, G & Kleijn, WB 2019, 'Fast Edge-Consensus Computing Based On Bregman Monotone Operator Splitting', ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, IEEE, Brighton, UK.
Sutjipto, S, Tish, D, Paul, G, Vidal Calleja, T & Schork, T 2018, 'Towards Visual Feedback Loops for Robot-Controlled Additive Manufacturing', Robotic Fabrication in Architecture, Art and Design 2018, ROBARCH 2018: Robotic Fabrication in Architecture, Art and Design 2018, Springer, Cham, Zurich, pp. 85-97.
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Robotic additive manufacturing methods have enabled the design and fabrication of novel forms and material systems that represent an important step forward for architectural fabrication. However, a common problem in additive manufacturing is to predict and incorporate the dynamic behavior of the material that is the result of the complex confluence of forces and material properties that occur during fabrication. While there have been some approaches towards verification systems, to date most robotic additive manufacturing processes lack verification to ensure deposition accuracy. Inaccuracies, or in some instances critical errors, can occur due to robot dynamics, material self-deflection, material coiling, or timing shifts in the case of multi-material prints. This paper addresses that gap by presenting an approach that uses vision-based sensing systems to assist robotic additive manufacturing processes. Using online image analysis techniques, occupancy maps can be created and updated during the fabrication process to document the actual position of the previously deposited material. This development is an intermediary step towards closed-loop robotic control systems that combine workspace sensing capabilities with decision-making algorithms to adjust toolpaths to correct for errors or inaccuracies if necessary. The occupancy grid map provides a complete representation of the print that can be analyzed to determine various key aspects, such as, print quality, extrusion diameter, adhesion between printed parts, and intersections within the meshes. This valuable quantitative information regarding system robustness can be used to influence the system’s future actions. This approach will help ensure consistent print quality and sound tectonics in robotic additive manufacturing processes, improving on current techniques and extending the possibilities of robotic fabrication in architecture.
Wang, K, Tao, J & Qiu, X 2019, 'Boundary control of sound transmission into a cavity through its opening', JOURNAL OF SOUND AND VIBRATION, ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, pp. 350-365.
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Wickramanayake, S, Thiyagarajan, K, Kodagoda, S & Piyathilaka, L 2019, 'Frequency Sweep Based Sensing Technology for Non-destructive Electrical Resistivity Measurement of Concrete', 36 International Symposium on Automation and Robotics in Construction, Canada.
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Xiao, T & Qiu, X 2019, 'A COMPARISON OF USING SOUND PRESSURE AND PARTICLE VELOCITY AS ERROR SIGNALS FOR LOCAL ACTIVE NOISE CONTROL', The 26th International Congress on Sound & Vibration, Montreal, Canada.
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Controlling the sound pressure as the error signal is well understood for local active noise control, and controlling both the sound pressure and the sound particle velocity has been proposed to improve the performance of the system. However, the performance of controlling only the sound particle velocity is still not clear, which is investigated in this paper. Two local active noise control systems are considered which use either the sound pressure or the sound particle velocity as the error signal. The primary sound field is assumed to be made of plane waves and the secondary source is a monopole. Simulations are carried out to cancel either the squared sound pressure or the squared sound particle velocity in one direction at the error location. The noise reduction at error microphones and the surrounding spatial distributions indicates that using the sound pressure as the error signal always achieves the best sound pres-sure control at the error sensor, while controlling the sound particle velocity is not favourable in the near field or at the low frequency in terms of sound pressure reduction. Controlling the sound particle velocity may provide larger quiet zone in the far field or at the high frequency. The control performance is also affected by the propagation direction of the primary sound field and the secondary sound field at the error location, and this angle should be less than 90 degrees to avoid noise amplification with control.
Zhang, G, Tao, J & Qiu, X 2019, 'Empirical Study of Decentralized Multi-Channel Active Noise Control Based on the Genetic Algorithm', PROCEEDINGS of the 23rd International Congress on Acoustics, the 23rd International Congress on Acoustics, Aachen, Germany.
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Zhao, L 2019, 'Analytical solutions for a broadband concurrent aeroelastic and base vibratory energy harvester', Active and Passive Smart Structures and Integrated Systems XII, Active and Passive Smart Structures and Integrated Systems XIII, SPIE.
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