Two Adaptive Robust Sliding Mode Controllers for Robot Manipulators

Abstract

Sliding mode controllers are known to be capable of achieving robustness against modeling errors, plant disturbances and plant parameter variations. They, however, require upper-bounds of uncertainties in plant parameters to specify feedback gains that realize robustness. These upper-bounds are often chosen conservatively and, as a result, high feedback gains and oscillations, refered to as chattering, occur. Recently, on-line identification of the upper-bounds of uncertainties have been successfully incorporated into sliding mode regulators to alleviate the chattering. Here, we propose to extend this on-line identification technique to two types of controllers, called adaptive robust sliding mode controllers, for trajectory control of robot manipulators. The stability properties of the proposed controllers are demonstrated using Lyapunov functions and are implemented using a PUMA-type manipulator. The performance of these controllers is compared with that of regular sliding mode controllers. The result of comparison reveals excellent robustness and chattering suppression of the proposed controllers.