Eager, DM 2003, 'How the New Standard Will Impact on Playgrounds', Journal Institute of Public Works Engineering Australia, vol. N/A, no. June/July 2003, pp. 22-27.
Eager, DM 2003, 'Raising the Standard', Journal of the Australian Institute of Landscape Architects, vol. 25(4), no. 100, pp. 70-75.
Eager, DM 2003, 'Understanding The Need For Playground Undersurfacing', Journal Institute of Public Works Engineering Australia, vol. N/A, no. August/September, pp. 36-37.
Eager, DM 2003, 'Undersurfacing - Myths and Facts', Playground News, vol. 11, no. Winter 2003, pp. 1-2.
Halkon, BJ & Rothberg, SJ 2003, 'Vibration measurements using continuous scanning laser Doppler vibrometry: theoretical velocity sensitivity analysis with applications', Measurement Science and Technology, vol. 14, no. 3, pp. 382-393.
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It is readily accepted that a laser vibrometer measures target velocity in the direction of the incident laser beam, but this measured velocity must be considered in terms of the various components of the target velocity. This paper begins with a review of the theoretical description of the velocity sensed by a single laser beam incident in an arbitrary direction on a rotating target undergoing arbitrary vibration. The measured velocity is presented as the sum of six terms, each the product of a combination of geometric parameters, relating to the laser beam orientation, and a combination of motion parameters-the 'vibration sets'. This totally general velocity sensitivity model can be applied to any measurement configuration on any target. The model is also sufficiently versatile to incorporate time-dependent beam orientation and this is described in this paper, with reference to continuous scanning laser Doppler vibrometry. For continuous scanning applications, the velocity sensitivity model is shown formulated in two useful ways. The first is in terms of the laser beam orientation angles, developing the original model to include time dependency in the angles, whilst the second is an entirely new development in which the model is written in terms of the mirror scan angles, since it is these which the operator would seek to control in practice. In the original derivation, the illuminated section of the rotating target was assumed to be of rigid cross section but, since continuous scanning measurements are employed on targets with flexible cross sections, such as beams, panels and thin or bladed discs, the theory is developed in this paper for the first time to include provision for such flexibility.
Halkon, BJ, Frizzel, SR & Rothberg, SJ 2003, 'Vibration measurements using continuous scanning laser vibrometry: velocity sensitivity model experimental validation', Measurement Science and Technology, vol. 14, no. 6, pp. 773-783.
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This paper builds on a previous study in which the theoretical description of the velocity sensed by a single laser beam incident in an arbitrary direction on a rotating target undergoing arbitrary vibration was extended to continuous scanning laser vibrometer measurements on targets with flexible cross sections. The velocity sensitivity model was written in terms of either laser beam orientation angles or deflection mirror scan angles, with the latter found to be the most useful for continuous scanning applications. The model enables the prediction of the laser vibrometer output for any measurement configuration on any target. The experimental validation presented in this paper confirms that additional components appear in rotating target measurements that are associated with both the scanning system configuration and any misalignment between the scanning system and target rotation axes. This paper will show how use of the velocity sensitivity model enables the vibration engineer to make laser Doppler vibrometry measurements with confidence.
Ji, JC 2003, 'Dynamics of a Jeffcott rotor-magnetic bearing system with time delays', INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, vol. 38, no. 9, pp. 1387-1401.
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A Jeffcott rotor with an additional magnetic bearing locating at the disc is employed to investigate the effect of time delays on the non-linear dynamical behavior of the system. The time delays are presented in the proportional and derivative feedback, respectively. For the corresponding autonomous system, a linear stability analysis is performed for the system with two identical time delays in the control loop. The nature of a single Hopf bifurcation is determined by constructing a center manifold. For the non-autonomous system, the primary resonance response is studied for its small non-linear motions using the method of averaging. The effects of time delays and control gains, as well as excitation amplitude, on the amplitude of the steady-state response are investigated. Finally, experiments are carried out to validate the theoretical predictions.
Ji, JC 2003, 'Stability and bifurcation in an electromechanical system with time delays', MECHANICS RESEARCH COMMUNICATIONS, vol. 30, no. 3, pp. 217-225.
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The effect of time delays occurring in a proportional-integral-derivative feedback controller on the linear stability of a simple electromechanical system is investigated by analyzing the characteristic transcendental equation. It is found that the trivial fixed point of the system can lose its stability through Hopf bifurcations when the time delay crosses certain critical values. Codimension two bifurcations, which result from non-resonant and resonant Hopf-Hopf bifurcation interactions, are also found to exist in the system.
Ji, JC 2003, 'Stability and Hopf bifurcation of a magnetic bearing system with time delays', JOURNAL OF SOUND AND VIBRATION, vol. 259, no. 4, pp. 845-856.
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The effect of time delays occurring in the feedback control loop on the linear stability of a simple magnetic bearing system is investigated by analyzing the associated characteristic transcendental equation. It is found that a Hopf bifurcation can take place when time delays pass certain values. The direction and stability of the Hopf bifurcation are determined by constructing a center manifold and by applying the normal form method. It is also found that a codimension two bifurcation can occur through a Hopf and a steady state bifurcation interaction. Finally, numerical simulations are performed to verify the analytical predictions.
Ji, JC & Hansen, CH 2003, 'Local bifurcation control in a rotor-magnetic bearing system', INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS, vol. 13, no. 4, pp. 951-956.
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Linear-plus-nonlinear feedback control is used to stabilize Hopf bifurcation in a rotor-magnetic bearing system, for which the linearized system possesses a double zero eigenvalues. The addition of nonlinear (quadratic) terms to the original linear feedback control formulation is used to modify the coefficients of the nonlinear terms in the reduced normal forms. It is found that feedback control incorporating certain quadratic terms renders the Hopf bifurcation supercritical. Finally, illustrative examples are given to verify the analytical results.
Ji, JC & Leung, AYT 2003, 'Non-linear oscillations of a rotor-magnetic bearing system under superharmonic resonance conditions', INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, vol. 38, no. 6, pp. 829-835.
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The effect of non-linear magnetic forces on the non-linear response of the shaft is examined for the case of superharmonic resonance in this paper. It is shown that the steady-state superharmonic periodic solutions lose their stability by either saddle-node or Hopf bifurcations. The system exhibits many typical characteristics of the behavior of non-linear dynamical systems such as multiple coexisting solutions, jump phenomenon, and sensitive dependence on initial conditions. The effects of the feedback gains and imbalance eccentricity on the non-linear response of the system are studied. Finally, numerical simulations are performed to verify the analytical predictions.
Li, QS, Fang, JQ, Liu, DK & Tang, J 2003, 'Failure probability prediction of concrete components', Cement and Concrete Research, vol. 33, no. 10, pp. 1631-1636.
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In order to predict the probability of failure for brittle fracture of concrete components under multiaxial stress states, the imperfections of concrete components are modeled as cracks with different shapes in this paper. A new probability distribution function for evaluating the failure probability of concrete components is proposed. A simplified measurement method for determining the parameters of the governing Weibull distribution, using the three-point bending test, is presented and discussed. The experimental results of the combined bending/torsion failure tests of concrete components verify that the proposed crack model is more reasonable than the Batdorf's crack model and the proposed prediction formula can evaluate the failure probability of concrete components accurately. © 2003 Elsevier Ltd. All rights reserved.
Liu, DK, Yang, YL & Li, QS 2003, 'Optimum positioning of actuators in tall buildings using genetic algorithm', Computers & Structures, vol. 81, no. 32, pp. 2823-2827.
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An effective method for determining the optimal position of actuators in tall buildings using genetic algorithm is introduced through the formulation of a discrete and non-linear optimization problem. The simulation study is carried out for a 16-story building under 18 different earthquake excitations. The effects of different earthquake excitations on the optimal placement of actuators and on the proposed optimization algorithm are thus examined. © 2003 Elsevier Ltd. All rights reserved.
Luo, Q & Tong, L 2003, 'Exact dynamic solutions to piezoelectric smart beams including peel stresses Part II: Numerical results, comparison and approximate solution', International Journal of Solids and Structures, vol. 40, no. 18, pp. 4813-4836.
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Shoudong Huang & James, MR 2003, 'l/sup ∞/ -bounded robustness for nonlinear systems: analysis and synthesis', IEEE Transactions on Automatic Control, vol. 48, no. 11, pp. 1875-1891.
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The purpose of this paper is to describe systematic analysis and design tools for robust control problems with l∞ criteria. We first generalize the Hill-Moylan-Willems framework for dissipative systems to accommodate l∞ criteria, and then derive state feedback and measurement feedback synthesis procedures for l∞ robust control problems. The information state framework is used for the measurement feedback robust control problem. Necessary and sufficient conditions are proved, and new synthesis procedures using dynamic programming are presented.
Smith, DB & Aubrey, TA 2003, 'Performance degradation of differential space-time modulation in fast frequency flat fading Rayleigh MIMO channels', Electronics Letters, vol. 39, no. 17, pp. 1278-1278.
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Tong, L & Luo, Q 2003, 'Exact dynamic solutions to piezoelectric smart beams including peel stresses I: Theory and application', International Journal of Solids and Structures, vol. 40, no. 18, pp. 4789-4812.
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Williams, SB, Durrant-Whyte, H & Dissanayake, G 2003, 'Constrained initialization of the simultaneous localization and mapping algorithm', INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH, vol. 22, no. 7-8, pp. 541-564.
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In this paper we present a novel feature initialization technique for the Simultaneous Localization and Mapping (SLAM) algorithm. The initialization scheme extends previous approaches for identifying new confirmed features and is shown to improve the steady-state performance of the filter by incorporating tentative features into the filter as soon as they are observed. Constraints are then applied between multiple feature estimates when a feature is confirmed. Observations that are subsequently deemed as spurious are removed from the state vector after an appropriate timeout. It is shown that information that would otherwise be lost can therefore be used consistently in the filter. Results of this algorithm applied to data collected using a submersible vehicle are also shown.
Zhang, N, Crowther, A, Liu, DK & Jeyakumaran, J 2003, 'A Finite Element Method for the Dynamic Analysis of Automatic Transmission Gear Shifting with a Four-Degree-of-Freedom Planetary Gearset Element', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 217, no. 6, pp. 461-473.
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A dynamic model of a passenger car automatic transmission and driveline is developed for simulating transient torsional vibration in gearshifts. A finite element method is proposed for presenting the transient dynamics of the parametric system, element matrices are defined and then global inertial, stiffness and damping matrices are formulated corresponding to the defined global coordinate vectors. A four-degree-of-freedom matrix element is developed that describes the rigid body dynamics of the planetary gear set and is then integrated with the driveline system; this element captures the parametric change while the transmission speed ratios vary over gearshifts. Free vibration analysis and a transient 2-3 upshift simulation are discussed and results presented.
Zhang, YJ, Xue, L, Han, JT & Wei, DB 2003, 'Morphology change during crack healing of impacted sample', Journal of Iron and Steel Research, vol. 15, no. 3, pp. 52-55+65.
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By observation, there are zigzag on the surface of inner crack impacted samples. Healing process used many methods such as integer, division, microscope with heating stage. During healing, the zigzag disappeared and crack boundary passivated. The big curvature result in atom diffusion and microscope with heating stage don t fit observation of inner crack healing in situ. The morphology change during crack healing was analyzed based on diffusion-kinetics and thermodynamics.
Dutta-Roy, T, Zhang, N, Dissanayake, G & Wang, M 1970, 'Free Vibrational Analysis of Vehicle Powertrain Equipped With a Half Toroidal CVT', Proceedings of the 10th Asia-Pacific Vibration Conference, Asia Pacific Vibration Conference, Queensland University of Technology, Gold Coast, Queensland, Australia, pp. 109-114.
Eager, D 1970, 'A Study Into LDPE as an Undersurfacing Material for Injury Prevention and Risk Minimisation in Children’s Playgrounds', Engineering/Technology Management: Safety Engineering and Risk Analysis, Technology and Society, Engineering Business Management, and Homeland Security, ASME 2003 International Mechanical Engineering Congress and Exposition, ASMEDC, Washington DC, USA, pp. 1-9.
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Low Density Polyethylene (LDPE) closed-cell foam is used extensively as an impact absorbing material for injury prevention and risk minimisation in a variety of applications, including children’s playground undersurfacing, padding for trampoline frames, and other fall zones. This paper presents and analyses the data from numerous impact tests performed on samples of LDPE of select different product thicknesses (10, 20, 30 and 40 mm), nominal Relative Densities (30, 45, 60 and 75 kg/m3) and drops or free height of fall (100 mm steps in heights from 300 to 2100 mm). The impact absorption properties of LDPE are characterized using the Australian and New Zealand Standard AS/NZS 4422: Playground Surfacing — Specifications, Requirements and Test Method. The gmax and HIC results are presented both graphically and numerically. This paper also discusses uses and limitations of LDPE with particular emphasis on injury prevention and risk minimisation.
Furukawa, T, Durrant-Whyte, HF, Bourgault, F, Dissanayake, G, IEEE & IEEE 1970, 'Time-optimal coordinated control of the relative formation of multiple vehicles', 2003 IEEE INTERNATIONAL SYMPOSIUM ON COMPUTATIONAL INTELLIGENCE IN ROBOTICS AND AUTOMATION, VOLS I-III, PROCEEDINGS, IEEE International Symposium on Computational Intelligence in Robotics and Automation, IEEE Operations Centre, Kobe, Japan, pp. 259-264.
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This paper presents a solution to the time-optimal control of the relative formation of multiple vehicles. This is a problem in cooperative time-optimal control with a free terminal state constraint. In this paper, a canonical formulation of the problem is first derived. Then, a numerical technique to solve this class of problem is proposed. Numerical results demonstrate the efficacy of the proposed formulation and solution to the problem of expeditiously building and controlling formations of cooperative autonomous vehicles.
Furukawa, T, Durrant-Whyte, HF, Dissanayake, G, Sukkarieh, S, IEEE & IEEE 1970, 'The coordination of multiple UAVs for engaging multiple targets in a time-optimal manner', IROS 2003: PROCEEDINGS OF THE 2003 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE Service Centre, Las Vegas, USA, pp. 36-41.
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This paper presents a solution to the real-time control of cooperative unmanned air vehicles (UAVs) that engage multiple targets in a time-optimal manner. Techniques to dynamically allocate vehicles to targets and to find the time-optimal control actions of vehicles are proposed. The effectiveness of the time-optimal control technique is first demonstrated through numerical examples. The proposed strategy is then applied to a practical battlefield problem where ten vehicles are required to engage four targets, and numerical results show the efficiency of the proposed strategy.
Goktogan, AH, Furukawa, T, Mathews, G, Sukkarieh, S & Dissanayake, G 1970, 'Time-Optimal Cooperation of Multiple UAVs in Real-Time Simulation', Proceedings of the 2nd Computational Intelligence, Robotics and Autonomous Systems (CIRAS 2003), International Conference on Computational Intelligence, Robotics and Autonomous Systems, National University of Singapore, Singapore, pp. 1-6.
Halkon, B & Rothberg, S 1970, 'Continuous Scanning Laser Vibrometry for Measurements on Rotating Structures', Materials Science Forum, 5th International Conference on Modern Practice in Stress and Vibration Analysis, Trans Tech Publications, Ltd., GLASGOW, SCOTLAND, pp. 245-252.
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It is readily accepted that a Laser Vibrometer measures target velocity in the direction of the incident laser beam but it is essential that, for correct measurement interpretation, the target velocity be considered in terms of the various target motion components. This paper begins with a review of the theoretical description of the velocity sensed by a dual mirror scanning Laser Vibrometer incident in an arbitrary direction on a rotating target of flexible cross-section undergoing arbitrary vibration. This comprehensive velocity sensitivity model can be applied to any Laser Vibrometer measurement configuration on any target and is sufficiently versatile to incorporate time dependent beam orientation. This is described in this paper with particular reference to continuous circular scanning Laser Doppler Vibrometry. The velocity sensitivity model allows a detailed analysis of the form of the measurement that is obtained in actual scan configurations. For example, additional components occur in a circular scanning Laser Vibrometer measurement on a rotating target that can be shown to be due to a combination of instrument configuration and target misalignment. In this paper, the measured data obtained from a circular scanning measurement on a rotating target undergoing axial vibration is investigated as a means of demonstrating the usefulness of the comprehensive velocity sensitivity model.
Kwok, N & Dissanayake, G 1970, 'Bearing-only SLAM in Indoor Environments Using a Modified Particle Filter', Proceedings of the Australasian Conference on Robotics & Automation 2003, Australasian Conference on Robotics and Automation, University of Queensland, Brisbane, Australia, pp. 1-8.
Kwok, N & Dissanayake, G 1970, 'Simultaneous Localization and Mapping in Unstructured Indoor Environments', Proceedings for the 2nd International Conference on Computational Intelligence, Robotics and Autonomous Systems (CIRAS 2003), International Conference on Computational Intelligence, Robotics and Autonomous Systems, Centre for Intelligent Control, National University of Singapore, Singapore, pp. 1-6.
Liu, D, Lau, H & Dissanayake, G 1970, 'A Hierachical Approach and A Multilevel Genetic Algorithm For Vehicle Path Plan', Proceedings of International Conference on Computational Intelligence, Robotics and Autonomous Systems, International Conference on Computational Intelligence, Robotics and Autonomous Systems, Centre for Intelligent Control, National University of Singapore, Singapore, pp. 1-6.
Rozyn, MK, Wilson, NJ, Andrews, M, Eager, DM & Clout, RB 1970, 'HOMER - A High Speed Robot For Indoor Exploration', Australian Robotics & Automation Association, Australasian Conference on Robotics and Automation, Australian Robotics & Automation Association, Brisbane, Australia, pp. 1-9.
Samuels, S & Parnell, J 1970, 'A novel technique of allowing for the effects of pavement surface type in the prediction of road traffic noise', Proceedings - Conference of the Australian Road Research Board, pp. 1911-1926.
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The prediction of road traffic noise is an essential component of modern road design. It is also an important process in the assessment of the potential noise impacts of both new road proposals and the upgrading of existing roads. Many factors such as traffic conditions, road alignment and receptor locations are involved in traffic noise prediction, the accuracy of which depends in turn on the accuracy associated with the values of the input parameters that quantify these factors. One critical factor is pavement type, particularly in the case of high-speed roads and freeways. The present paper summarises an extensive body of recent work conducted by the authors, under contract to QDMR, aimed at improving the way in which the effects of pavement type is incorporated into traffic noise prediction procedures. Initially a very large data set of measured vehicle passby noise levels was established. These data were then analysed to produce an array of values of the Statistical Passby Index (SPBI), which is a relatively new index that quantifies the effects of pavement type on traffic noise for varying traffic conditions. From there, the set of SPBI values was analysed to produce pavement type factors that were subsequently incorporated into traffic noise predictions conducted with the US Traffic Noise Model (TNM) on roads and freeways in Queensland. The accuracy of this modified version of TNM was determined by comparing its predictions with measured data by means of a robust statistically based analysis. It was found that the accuracy of the TNM predictions was not affected by this novel technique of allowing for pavement type in the prediction of road traffic noise.
Smith, DB & Aubrey, T 1970, 'Generalized space-time modelling of the MIMO channel applied to analysing and optimising transmit antenna configurations', IEEE International Conference on Communications, 2003. ICC '03., IEEE International Conference on Communications, IEEE, Alaska, USA, pp. 1978-1982.
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For the purposes of macroscopic system design a space-time Rayleigh fading multiple-input multiple-output (MIMO) radio channel is modelled for an arbitrary transmit antenna configuration of three to six transmit antennas. A traditional ring of scatterers model is use to generate the space-time cross correlations and thence flat fading channel distortions. A general trend is demonstrated for a specific non-coherent modulation scheme where the optimality of different transmission frame lengths can be related to the well known autocorrelation functions; based on this trend two frame lengths are chosen for MIMO channel analysis. Several beneficial arbitrary transmit antenna configurations are obtained from this analysis using some typical arbitrary configurations, and some initial optimisation using a genetic algorithm, from which further possible optimisation is proposed.
Takezawa, S & Dissanayake, G 1970, 'Autonomous Robot Control Applied for Slam Problem At Indoor Stereo Artificial Landmarks', Proceedings of the 10th Asia-Pacific Vibration Conference, Asia Pacific Vibration Conference, Queensland University of Technology, Gold Coast, Queensland, Australia, pp. 893-898.
Wijesoma, WS, Kodagoda, KRS, Balasuriya, AP & Challa, S 1970, 'Road curb tracking in an urban environment', Sixth International Conference of Information Fusion, 2003. Proceedings of the, Proceedings of the Sixth International Conference of Information Fusion, IEEE, Cairns, Australia, pp. 261-268.
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Road detection and tracking is very useful in the synthesis of driver assistance and intelligent transportation systems. In this paper a methodology is proposed based on the extended Kalman filer for robust road curb detection and tracking using a combination of onboard active and passive sensors. The problem is formulated as detecting and tracking a maneuvering target in clutter using onboard sensors on a moving platform. The primary sensors utilized are a 2 dimensional SICK laser scanner, five encoders and a gyroscope, together with an image sensor (CCD camera). Compared to the active 20 laser scanner the CCD camera is capable of providing observations over an extended horizon, thus making available much useful information about the curb trend, which is exploited in mainly the laser based tracking algorithm. The advantage of the proposed image enhanced laser detection/tracking method, over laser alone detection/tracking, is illustrated using simulations and its robustness to varied road curvatures, branching, turns and scenarios, is demonstrated through experimental results. © 2003 ISlF.
