Motion Control of Manipulator Robots via Two PD-Based Nonlinear Controllers: Design and Comparative Analysis

The motion control or trajectory tracking is a fundamental and benchmark problem while controlling the manipulator robots to move along a predefined trajectory. Extensive research in the literature has addressed the motion control problem for robotic manipulators. To address this challenge effectively, it becomes imperative to design suitable controllers and make adequate choices regarding the appropriate feedback gain values. In this study, we consider and investigate two PD-based nonlinear control laws for controlling the motion of manipulator robots, namely the PD-plus-compensation controller and the augmented one. We establish conditions for determining the feedback gains of these two controllers, ensuring tracking error stability. Moreover, conditions guaranteeing the uniqueness of the zero error of the closed-loop robotic system are developed. Finally, we consider a two-degree-of-freedom manipulator robot to reveal the effectiveness of the two proposed controllers in tracking a desired trajectory and hence evaluating their performance in addressing the motion control problem.