Comparatively little attention has been paid to the kinematic and static characteristics of mixed mechanisms which have combinations of the characteristics of fully serial and fully parallel mechanisms. Such actively coordinated mechanisms having combina
Chin, P.C. & Waldron, K.J. 1993, 'Hybrid velocity/force control of manipulators using PID controller and feedforward compensation', Proceedings of the IEEE Conference on Control Applications, pp. 403-408.
An effort has been made to use PID control technique and feedforward compensation to control robotic manipulators under a combined task of velocity and force. This approach is based on the assumption that the task configuration is homogeneous. However, the proposed scheme is still applicable for a non-homogeneous task configuration with frictional forces being the only non-homogeneous constraints. The proposed controller will control a planar 3R manipulator in this work to demonstrate system responses and simulation results.
Chung, W.Y. & Waldron, K.J. 1993, 'Force distribution by optimizing friction angles for multifinger system', Proceedings - IEEE International Conference on Robotics and Automation, pp. 717-722.
An efficient way of finding the force distribution by optimizing the contact friction angles, which are the angles between the contact forces and contact normals, for multi-finger grasping systems was developed. Three steps, projection, residual wrench equilibrium, and optimization, are proposed to solve the force distribution problem. Examples are presented to show how the proposed method works. The results are also compared to those obtained by using Lagrange multipliers. Furthermore, the proposed method shows sufficient efficiency to be used for real-time control applications.
Chung, W.Y. & Waldron, K.J. 1993, 'Integrated control strategy for multifingered systems', American Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC, pp. 263-270.
A method of force allocation by optimizing the friction angles at finger contacts was combined with the computed torque method to find the torques to be commanded at finger joints for multifingered systems. In this way, slip can be avoided when the object is grasped or manipulated. The proposed method can be efficiently used to find the input torques, and is applicable for real-time application. A history-based method is also proposed to improve the smoothness of the input torque commands. Three dimensional simulation results are given.
Postcrash fires are a frequent cause of death in otherwise survivable automobile and aircraft accidents. The idea of the ICED (Internal Circuit Emergency Disconnect) battery  is to eliminate electrically ignited postcrash fires by means of an inertial interrupt device that will disconnect the active circuit at the battery if an accident should happen. The design of the prototypes that were tested and the analysis of the disengagement performance will be discussed. A ballistic pendulum impact test rig was designed and used to test the prototypes. The test results and analytical values were shown to be satisfactorily close to each other.Copyright © 1993 Society of Automotive Engineers, Inc.
Sreenivasan, S.V., Waldron, K.J. & Nordholt, J.B. 1993, 'Characterization of redundancy in spatial closed kinematic chains', Lecture Notes in Control and Information Sciences, pp. 52-59.
© 1993, Springer Verlag. All Rights Reserved. The force allocation problem in closed kinematic chains is anderdetermined and the available degrees of freedom can be used to extremize a desired objective function. This generally leads to complicated nonlinear optimization problems. The solution of these problems can be greatly simplified if the redundancy is characterized in the simplest possible form. This paper gives strategies that lead to efficient algorithms to evaluate the null space of the linear set of force allocation equations. The approach exploits the geometry and physics in the problem rather than looking at numerical solutions. The general problem of n contact points of a kinematic chain in three dimensions is considered. Further, degenerate situations occurring due to the presence of several points along a line, or on a plane, are also addressed. Numerical examples are considered to illustrate the use of these algorithms.
Venkataraman, S.C. & Waldron, K.J. 1993, 'Performance improvement with active control of steering angles and wheel torques during a combined braking and steering maneuver', American Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC, pp. 39-48.
A four-wheel steered vehicle is considered in which the steering angles and the braking torques at the wheels are assumed to be actively actuated. The driver's steering and braking inputs are interpreted to yield commanded vehicle states during a combined braking and steering maneuver. The front and rear steering angles are coordinated to keep the body side-slip angle near zero. The braking forces are coordinated to equalize and hence minimize the force ratios at the inner and outer wheels while ensuring that they provide a net zero yaw moment. A control law based on a linearised vehicle model is developed which augments the steering and braking inputs to enhance handling performance.