Fast tracking nonlinear H∞ control for uncertain flexible joint robots with bounded input control

In this paper the design of an optimal nonlinear H_infin (NL-H_infin) controller for flexible joint robot (FJR) with bounded input control and fast tracking is presented. Moreover, FJR robot link positions are controlled without any undershoot and overshoot. Also, this paper discusses the robust L2-gain performance synthesis problem for uncertain FJRs which have nonlinear dynamic. So, the Hamilton-Jacobi equation approach can be used for this problem. Based on a positive-definite solution of a Hamilton-Jacobi inequality, a sufficient condition is given such that the uncertain FJRs system is robust and by using this condition, state feedback laws which ensure robust L2-gain performance of the closed-loop system are derived. Simulation results show the efficiency and superiority of the proposed method in compare with conventional H_infin.