A Robust Tracking Controller Design With Hierarchical Perturbation Compensation

A robust tracking controller for mechanical systems is proposed by combining the robust perturbation compensator which effectively attenuates the perturbation to the plant with the nominal tracking controller designed using the sliding surface. This approach enables a smooth sliding mode in tracking control loop without chattering problem. A unified view is given on a class of perturbation observers. Three kinds of equivalent expressions for the perturbation of a plant is described. In terms of the equivalents, we propose the feedforward perturbation observer (FFPO), the feedback perturbation observer (FBPO), and the sliding mode perturbation observer (SMPO). Successively, by hierarchically adopting these three observers to attenuate the residual perturbation, the hierarchical perturbation compensator (HPC) is constructed with stability analysis. The adaptive and integral property of the HPC greatly enhances the robust performance with minimal control effort. The actuator saturation issue is also considered. Experimental results demonstrate the effectiveness of the proposed controller.