Two adaptive robust sliding mode controllers for robot manipulators

Sliding mode controllers are known to be able to achieve 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, called chattering, occur. Recently, online identification of the upper-bounds of uncertainties have been successfully incorporated into sliding mode regulators to alleviate the chattering. We propose to extend this to two types of controllers, named 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 onto a PUMA type manipulator. Performances of those controllers are compared with that of regular sliding mode controllers. The result showed excellent robustness combined with chattering suppressing capability of the proposed controllers