A Novel Approach for Robust Control of Single-Link Manipulators with Visco-Elastic Behavior

Overwhelming number of control laws has been studied for control of robot manipulators with rigid links and joints. However, controllers designed under this assumption may not accurately control the manipulator link due to visco-elastic properties that appear in the link behavior. In this study, a novel approach for robust control of a single-link manipulator is presented to force the link to have rigid motions, while it has visco-elastic behavior. In this regard, initially robot dynamics is extracted, followed by the design of four appropriate controllers through the loop-shaping approach. The obtained model is first represented in state space, however later converted to transfer function representation to attain robot characteristic equation. Next, a simple and effective method is applied to reduce the order of the robot manipulator model. The final model is examined in time and frequency domains to show the validation of the order reduction method. In order to locate proper zeros and poles of the controllers, Bode plot is used to change the magnitude curve of the manipulator response as desired. The four special controllers are planned for each of four zones of the frequency response. The results show improvements in five major aspects of the behavior of the manipulator, namely transient response, steady state response, robust stability, command following and noise rejection.