Contraction Theory Based Trajectory Tracking Control of Free-Floating Space Manipulator

In the space on-orbit task, achieving precise trajectory tracking for the end-effector is crucial. This necessitates the use of high-precision, fast, and stable controllers. In order to minimize fuel consumption and avoid the impact of the switching the base position and attitude controller on the control accuracy of end-effector, the space robot is in a free-floating state, where the base remains uncontrolled. Considering the nonlinear and coupling characteristics of the free-floating space manipulator, this paper proposes the utilization of the contracting back-stepping method to achieve end-effector trajectory tracking control. This approach is based on the principles of contraction theory and the design concepts of the back-stepping controller. Notably, the contracting back-stepping method offers a significant advantage over the traditional back-stepping method by eliminating the need to design a Lyapunov function at each step. Consequently, this simplifies the controller design process to a great extent. To validate the effectiveness of the proposed method, a simulation experiment was conducted. The contracting back-stepping method was employed to design an end-effector trajectory tracking controller for a free-floating space robot equipped with a 7-degree-of-freedom robotic arm. The simulation results demonstrated that, the controller was able to swiftly, accurately, and consistently track the desired trajectory.