Robust tip trajectory tracking of a very lightweight single-link flexible arm in presence of large payload changes

This article discusses a robust control scheme for the trajectory tracking of very lightweight single-link flexible arms. Since the payload is one of the most variable parameters in a manipulator, the control is designed to achieve stability during the robot manoeuvres for any value of tip mass, while accurately tracking the desired tip trajectory. The proposed controller additionally guarantees stability for small uncertainties in parameters such as stiffness or motor friction. The effect of spillover on the performance of the controlled system is also analysed, and it is proven that stability is preserved independently of the non-modelled high-order dynamics. The theoretical analysis is supported by an extensive set of numerical simulations which shows controlled system response when variations in the robot parameters, or dynamics neglected in the controller design, are considered. The proposed method is compared to some of the most efficient current robust control strategies for suppressing flexible structure vibrations: Integral Resonant Control, Wave-Based Control, H-infinity control and LQR control. Finally, some experiments have been carried out in order to test the performance of the tip trajectory tracking of the proposed control system.