Cascade robust control for a class of MIMO nonlinear systems

In this paper, a decentralized cascade robust control scheme is developed for a class of MIMO nonlinear systems with lower triangular property and unknown nonlinearities. Due to the active compensation of the TC controller, the unknown nonlinearities will be counteracted. The algorithm proposed has no problem of the controller singularity, which may occur in algorithms based on neural networks or fuzzy systems. By choosing proper design parameter values, the tracking errors converge to a small neighborhood around zero. Simulations performed on a two-link robot manipulator illustrate the approach and verify its performance.