Combined Direct and Indirect Adaptive Control of Nonlinear Four-bar Linkage Robot Manipulator

In this paper, a combined direct and indirect adaptive control for a nonlinear a robot manipulator is introduced. The combined direct and indirect adaptive control improves accuracy and speed of adaptation, which would lead to increase tracking performance. The adaptive mechanism can be viewed as a modified version of the direct adaptive controller. The parameters are updated based on the information provided by the tracking error and identification error. The closed-loop system stability is proven by the Lyapunov theory of stability. The proposed scheme is applied to a nonlinear four-bar linkage robot manipulator using a FPGA and the simulation results are compared with the direct adaptive method. Although this method is applied to four-bar linkage robot it can be generalized to all types of nonlinear robots.