Robust Control of Space Robots Considering Friction Characteristics

In this chapter, a planar two-bar space robot is taken as the research object, and the dynamics equations of fully rigid and joint flexible space robot systems are derived by using momentum conservation and Lagrange equation of the second kind. Aiming at flexible joint space robot system, the system is decomposed into fast and slow subsystems based on singular perturbation. Considering the friction characteristics of joints, a robust controller based on the friction upper bound was designed to offset the influence of friction torque and improve the flat roof phenomenon in joint trajectory tracking control. For flexible joint space robot system, a fast variable subsystem controller is designed using moment differential to actively suppress flexible vibration. The controller of slow subsystem is designed by robust method and a bounded friction compensation term is introduced to offset the influence of joint friction torque. The effectiveness of the proposed manipulator control scheme is verified by numerical simulation experiments.