A sliding mode controller with bound estimation for robot manipulators

A sliding-mode control algorithm combined with an adaptive scheme, which is used to estimate the unknown parameter bounds, is developed for the trajectory control of robot manipulators. The major contribution of this methodology lies in the use of a special matrix, called the regressor, which makes it possible to isolate the unknown parameters from the robotic dynamics. Based on the upper bounds of those unknown parameters, which are estimated by a simple adaptive law, the proposed VSS (variable-structure-system) controller guarantees the stability of the closed-loop system. The robustness analysis shows that in the presence of the uncertainties, which are assumed to be unbounded and rapidly varying, the closed-loop system can still be stabilized. Chattering is reduced by using the boundary layer technique. Simulation results show the validity of the proposed algorithm.>