MODELING AND CONTROL OF A DEFORMABLE-LINK FLEXIBLE-JOINT ROBOT

Present studies on industrial manipulator control either completely neglect structural flexibility or only consider manipulator link flexibility. Ignoring joint flexibility may cause significant errors in gross motion control if the joint elastic effect is predominant. A control scheme that can effectively compensate for the motion disturbances due to simultaneous existence of link and joint flexibility is presented. The manipulator dynamics is first formulated by a superposition of two models. An assumed modes of vibration is proposed to model the flexible links and a linear torsional spring to model the elastic joint. Then, a non-linear feedback rate servo control system is developed that compensates for the gross motion bias introduced by both joint elasticity and link flexibility. Motion simulation results show that the proposed modelling technique can effectively describe the dynamic behaviour of a flexible-link, elastic-joint robot. They also verify that the proposed controller is robust in that it can satisfactorily suppress the disturbances due to both link flexibility and joint elasticity and yield an accurate gross motion.