Initial Experiments on the Control of a Two-Link Manipulator with a Very Flexible Forearm

Understanding how to control the flexibility in mechanical manipulator allows us to increase their performance and to reliably design and control larger, lighter, and more power-efficient manipulators. To date, a number of papers and some experiments have addressed the control of single-link flexible manipulators. In order to understand fully and to control a larger, more useful class of manipulators, we need to extend our knowledge further to the two-link configuration. To this end, this paper addresses the dynamics and control of a two-link manipulator with a very flexible forearm. Further, to verify the theoretical developments, an experimental planar two-link flexible manipulator system has been constructed. A nonlinear model of the experimental manipulator is developed using an assumed-modes description for the deflections in the forearm link. The design of an initial collocated proportional-plus-derivative controller is presented and implemented on the experimental manipulator. For a step command of 10° in each joint, the simulation and experimental responses are found to be in excellent agreement.