Adaptive and sliding control of flexible joint robots in constrained motion

This paper addresses motion and force control issues of flexible joint robots in constrained motion. A two-stage control scheme consisting of a constrained motion controller and a joint torque controller is established in a systematic way for the general n-link case. To deal with uncertainties in the robotic system, an adaptive and sliding control algorithm is developed assuming that all system parameters including the joint flexibility values are unknown except for some of their bounds. The system stability is analyzed via Lyapunov stability theory. It is shown that with the proposed controller, the motion and force tracking errors will converge asymptotically to zero