Effective vibration suppression of a maneuvering two-link flexible arm via an event-based stiffness controller

Vibration control of a maneuvering flexible robotic arm is a challenging task in the presence of changing structural dynamics which has to deal with measurement inaccuracies and complex modeling efforts. This paper presents an effective and versatile controller for a maneuvering flexible arm. Control is based on the detection of a kinematic event, peak relative displacement, rather than an accurate knowledge of structural dynamics. Hence, although there may not be a claim for the suggested control to be the most effective, it certainly represents significant practical advantage for cases where there may be structural uncertainties. Proposed variable stiffness control (VSC) is a stable controller, due to its being dissipative in nature. The technique is suitable to be implemented as an add-on controller to existing robots, and it requires no additional hardware. In this investigation, structural dynamics is represented using standard finite elements. The control scheme has been tested both numerically and experimentally. Responses of the uncontrolled and controlled cases are compared with desired trajectory profiles.