DISSANAYAKE, MWMG & GAL, JA 1994, 'Workstation planning for redundant manipulators', International Journal of Production Research, vol. 32, no. 5, pp. 1105-1118.
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Dissanayake, MWMG & Phan‐Thien, N 1994, 'Neural‐network‐based approximations for solving partial differential equations', Communications in Numerical Methods in Engineering, vol. 10, no. 3, pp. 195-201.
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AbstractA numerical method, based on neural‐network‐based functions, for solving partial differential equations is reported in the paper. Using a ‘universal approximator’ based on a neural network and point collocation, the numerical problem of solving the partial differential equation is transformed to an unconstrained minimization problem. The method is extremely easy to implement and is suitable for obtaining an approximate solution in a short period of time. The technique is illustrated with the aid of two numerical examples.
Husain, M & Waldron, KJ 1994, 'Position Kinematics of a Three-Limbed Mixed Mechanism', Journal of Mechanical Design, vol. 116, no. 3, pp. 924-929.
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Although robotics has traditionally focused on the serial chain structures typical of industrial robots, fully parallel structures such as the Stewart Platform have also found considerable industrial use. Actively coordinated mechanisms which have combinations of serial and parallel characteristics have been practically employed, and can be expected to become more important in the future. There has been very little study of the kinematic and static characteristics of these mechanisms which have combinations of the characteristics of fully serial and fully parallel structures. This work addresses the direct and inverse position kinematics of such a hybrid mechanism with combination of serial and parallel structure which has multiple, actively controlled actuators. While not the most general possible configuration, this particular case does include many important features of the general mechanism, and the solution obtained gives useful insight for developing a general theory of forward and inverse kinematics which will be equally applicable to serial, parallel and combination structures. Such a theory is necessary for rational design of hardware and software for such systems.
Nanua, P & Waldron, KJ 1994, 'Instability and Chaos in Quadruped Gallop', Journal of Mechanical Design, vol. 116, no. 4, pp. 1096-1101.
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A dynamic model for the two-dimensional quadruped has been developed. The main body is modelled as a rigid bar and each leg consists of a constant stiffness spring, a viscous damper and a force actuator. Based on symmetry principles, a controller has been devised that will enable the quadruped to gallop at constant speed. The controller consists of two parts: an energy controller which will apply the required amount of force through the legs, and the speed controller that will control the forward speed by appropriately placing the legs. It will be shown that the body pitch need not be explicitly controlled. The stability of this controller will be examined using Poincare maps. Stable systems show either periodic or quasi-periodic response. This system also exhibits chaotic behavior and chaotic response results in instability. The stability of the system with changes in the initial conditions, as well as variations in the system parameters, will also be examined. It will be shown that the system is stable for a range of leg stiffnesses. Outside this range, the system shows chaotic behavior.
Sreenivasan, SV & Waldron, KJ 1994, 'A Drift-Free Navigation System for a Mobile Robot Operating on Unstructured Terrain', Journal of Mechanical Design, vol. 116, no. 3, pp. 894-900.
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The orientation and the angular rates of the body of a robotic vehicle are required for the guidance and control of the vehicle. In the current robotic systems these quantities are obtained by the use of inertial sensing systems. Inertial sensing systems involve drift errors which can be significant even after the vehicle has traversed only short distances on the terrain. A different approach is suggested here which guarantees accurate, drift-free sensing of the angular position and rates of the vehicle body. A camera system consisting of two cameras in fixed relationship to one another is made to continuously track two stationary objects (stars or the sun). The camera system is mounted on the vehicle body through an actuated three-degree-of-freedom joint. The angular positions and rates of these joints can be used to evaluate the angular positions and rates of the vehicle body. An estimate of the absolute position of the vehicle on the terrain can also be obtained from this sensing system. This can serve as the primary system for estimating the position of a vehicle on a planet, or as an inexpensive alternative/backup to a more accurate Global Positioning System (GPS) for estimating the position of a vehicle on earth.
Sreenivasan, SV, Waldron, KJ & Nanua, P 1994, 'Closed-form direct displacement analysis of a 6-6 Stewart platform', Mechanism and Machine Theory, vol. 29, no. 6, pp. 855-864.
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The direct displacement analysis of a class of 6-6 Stewart platforms is considered here. Even though this is not the most general possible configuration, it has many of the advantages of the general configuration, and includes several useful arrangements
