Variable structure adaptive cascade control of multi-link robot manipulators with flexible joints: the case of arbitrary uncertain flexibilities

The design of adaptive tracking control of flexible joint manipulators in the general n-link case with arbitrary (possibly large) uncertain flexibility is addressed. Two strategies based on cascade control are presented combining an adaptive scheme for link control with two alternative variable structure control laws for joint control. Global stability or arbitrarily large domain of stability is obtained. Very satisfactory performance is illustrated by a simulation example. The proposed schemes are considerably simpler than those available in the literature