Adaptive control of mixed rigid/flexible joint robot manipulators based on virtual decomposition

A modular approach, called virtual decomposition, is applied to adaptive control of robot manipulators with mixed rigid/flexible joints. The system is virtually decomposed into the held object, the links, and the rigid/flexible joints. Each subsystem is controlled independently with decentralized parameter adaptation, while the dynamic interactions between the subsystems are completely represented by virtual power flows (VPFs) which are independent of the dynamics of the subsystems. The equivalence between a rigid joint control and a flexible joint control is established, since they dedicate the same dynamic interactions with their connecting links. Each subsystem is assigned a nonnegative accompanying function which takes care of its dynamics. The system Lyapunov function is formed by considering the VPFs without considering the dynamics of the subsystems. Lyapunov asymptotic stability is guaranteed. Finally, simulation results are presented.