Vibration suppression during input tracking of a flexible manipulator using a hybrid controller

The aim of this paper is to investigate the performance of the hybrid controller for end-point vibration suppression of a flexible manipulator, while it is tracking a desired input profile. Due to large structural vibrations, precise control of flexible manipulators is a challenging task. A hybrid controller is used to track large movements of flexible robotic manipulators, which is a combination of inverse dynamics feedforward control, command shaping and linear state feedback control. The case study of a single-link flexible manipulator is considered, where the manipulator is controlled under open-loop as well as closed-loop control scheme. In the open-loop control scheme, the aim is to test the effectiveness of the command shaper in reducing the vibration levels. Moreover, the effect of payload variations on the performance of command shapers and the importance of more robust shapers is demonstrated in this work. Under the closed-loop control scheme, the control objective is to track the large-hub angle trajectory, while maintaining low vibration levels. In comparison to collocated PD control, being reported in the literature, large reductions in tip acceleration levels as well as input torque magnitudes are observed with the proposed hybrid controller.