Effect of Link Flexibility on a Near Minimum Time Controller for a Robot Manipulator

The objective of this paper is to study the effects of flexible links on the near minimum time (NMT) controller for a robot manipulator. In order to obtain the effects of the flexible links on the controller, a rigid-based NMT controller is implemented with a rigid and a flexible dynamic model respectively. The Lagrange-Euler equation is employed to formulate a workable state variable model for both dynamic systems. The link flexibility is incorporated in the flexible dynamic model by using the method of assumed mode. Two different flexural link rigidities are employed in the simulation studies by using two cross-sections of links. The simulation results indicate that effects of small link flexibility could not be ignored. In the worst case, vibrations may even disable the controllers. Results indicate also that higher torque inputs produce larger tip displacements, and reduce execution times.