Adaptive control of time-varying mechanical systems: Analysis and experiments

Adaptive control of time-varying mechanical systems is considered in this p aper. A new adaptive controller for time-varying mechanical systems is prop osed based on two assumptions. First, the dynamics of time-varying mechanic al systems is derived under the assumption that the generalized constraints on the system do not depend on time but the system parameters such as mass es and payloads are time-varying. Second, the time-varying parameters are g iven by a group of known bounded time functions and unknown constants. It i s shown that the proposed adaptive controller results in a stable closed-lo op system. Further, if the desired trajectory of the system is periodic, a time-scaling technique of mapping one cycle period of the desired trajector y into a unit interval is proposed to provide robustness to the parameter a daptation algorithm. An experimental platform consisting of a two-link robo t with a time-varying payload is developed to test the proposed adaptive co ntroller. The experimental platform mimics robotic pouring and filling oper ations in industry. Comparative experimental results demonstrate the effect iveness of the proposed design.