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On modelling and simulation of a manipulator under consideration of a jammed joint

In this paper, the modelling of a jamming process of a joint during the operation of a manipulator is presented. Based on the kinematic property of a jamming process, a motion law of the jammed joint is chosen. By introducing a matrix coressponding to jammed joint, the equation of motion of the system is restructured without re-deriving. Some numerical simulations are carried out to illustrate the proposed algorithm. | Vietnam Journal of Mechanics, VAST, Vol. 32, No. 3 (2010), pp. 191 – 198 ON MODELLING AND SIMULATION OF A MANIPULATOR UNDER CONSIDERATION OF A JAMMED JOINT Nguyen Quang Hoang Hanoi University of Technology Abstract. In this paper, the modelling of a jamming process of a joint during the operation of a manipulator is presented. Based on the kinematic property of a jamming process, a motion law of the jammed joint is chosen. By introducing a matrix coressponding to jammed joint, the equation of motion of the system is restructured without re-deriving. Some numerical simulations are carried out to illustrate the proposed algorithm. 1. INTRODUCTION During the operation of a manipulator or of a mechanical system failures can be occurred. One of these failures is jamming of a joint. The joint can be locked due to a jammed brake, the stuck of gear transmittion,. . . As consequence, there will be no relative motion between the two links that are connected through the jammed joint, i.e., the corresponding links and the joint will be reduced to a single link. The length of the resultant single link can be calculated from the lengths of two original links, and the relative position of these links after jamming occurs. A jammed joint will result in the reduction of a DOF of the manipulators. The issue of fault detection and isolation for serial and parallel manipulators have been investigated recently [2-6, 10,14,15]. However, the modelling of a jamming process for simulation has not been discussed yet. The investigation on kinematics and dynamics of a manipulator in case a joint getting stuck can be carried out by examining of each case of the jammed joint. The approach method requires time and calculating burden. In this paper, the dynamic problem of a manipulator in case of a joint getting stuck is considered. If the jamming time and the jammed joint are known, the equation of motion of a manipulator can be determined by introduction of the so-called structure matrix. .