Robust control with exact uncertainties compensation: With or without chattering?

The problem of robust exact output control for linear systems with smooth bounded matched unknown inputs is considered. The higher order sliding mode observers provide both theoretically exact observation and unknown input identification. In this paper, a methodology is proposed to select the most adequate output control strategy for matched perturbations compensation. The aim of this paper is to investigate the possibility for exact uncertainties compensation using signals identified by high order sliding mode observers. Towards this aim, we modify the hierarchical super-twisting observer in order to have the best observation and identification accuracy possible. Then, two controllers are compared. The first one is an integral sliding mode controller based on the observed values of the state variables. The other strategy is based on the direct compensation of matched perturbations using their identified values. The performance of both controllers is estimated in terms of the deterministic noise upper bounds, sampling step and execution time. Based on these estimations, the designer may select the proper controller for the system. Experimental results are given for an inverted rotary pendulum system.