Methods of Trajectory Tracking for Flexible Joint Space Manipulators

This paper presents a comparative study of four control strategies for a flexible joint space manipulator. The considered control strategies consist in the classical Slotine and Li algorithm, a simple proportional derivative controller, a singular perturbation-based controller and a nonlinear backstepping controller. All control methodologies are assessed in numerical simulations for endpoint positioning while tracking a 12.6 × 12.6 m square trajectory by a two-link flexible joint space robot, thus providing a common framework to compare the respective performance of the considered control schemes. Simulation results indicate that controlling both nonlinearities and joint flexibility effects improve the closed-loop behavior of the space robot where the control of nonlinearities is of greater importance in the sense that it provides the most significant improvements. While each control scheme tracks the trajectory with a different degree of accuracy, the best performance for this particular application is obtained with the nonlinear backstepping control strategy.