Real-time implementation of regressor-based sliding mode control algorithm for robotic manipulators

A regressor-based variable structure control scheme has been developed for the trajectory control of robot manipulators in the presence of disturbances, parameter variations, and unmodeled dynamics. The method is based on the regressor structure given by Slotine and Li, 131, without parameter adaptation. This avoids the requirement of persistency of excitation, and the convergence of the overall transient is exponential. The method is robust against a class of state-dependent uncertainties, which may result, for example, from unmodeled dynamics. The problem of chattering is solved by the smoothing control law. It is shown that the closed-loop system is globally ultimately bounded with respect to a set around the origin, which can be made arbitrarily small. To illustrate the feasibility of this controller, it was implemented using a Motorola M68000 microprocessor on a two-link revolute joint manipulator subjected to a variable payload. Experimental results confirm the validity of accurate tracking capability and the robust performance.