Wave-Based Control of a Mass-Restricted Robotic Arm for a Planetary Rover

Abstract

Here wave-based control is applied to suppress vibrations during repositioning of a flexible robotic arm on a planetary rover in a Martian environment. Typically, such a robotic arm has very low power and mass budgets, implying significant flexibility, with static and dynamic consequences. Meeting precision performance specifications then becomes challenging and active vibration control is required. The example of the DExtrous LIghtweight Arms for exploratioN (DELIAN) arm is the focus of this paper. DELIAN is a general purpose arm, currently in development by SELEX ES for the European Space Agency (ESA). For active vibration control, a wave-based controller is used: a strategy formulated specifically for flexible mechanical systems. It considers actuator motion as launching and absorbing mechanical waves into and from the system. Absorbing the returning wave provides effective, active vibration damping while simultaneously moving the system to the target displacement. It is robust to both actuator performance and modelling errors, very stable, and easy to implement. The controller was found to perform well in limiting the effect of the flexibility during manoeuvres and also when rejecting vibrations due to impacts.