Dynamic modeling and fuzzy adaptive control strategy for space flexible robotic arm considering joint flexibility based on improved sliding mode controller

Abstract

Space flexible robotic arms can be installed on space stations or spacecraft to perform on-orbit tasks such as capturing artificial satellites, removing space debris, and assisting astronauts in overhauling. The space flexible robotic arm is a nonlinear complex dynamic system with disturbance torque and nonlinear factors coupled with joint and load flexibility. Many nonlinear terms and disturbance torque in the dynamic equations constitute the uncertain part of the space flexible robotic arm. The space flexible robotic arm is affected by the uncertain part, which will cause trajectory tracking errors. In this paper, the improved sliding mode control strategy based on fuzzy compensation is proposed to compensate for the uncertain part to enhance the trajectory tracking accuracy. Firstly, the dynamics model of the space flexible robotic arm considering joint flexibility is established. Next, the control law of the control strategy is designed by the tanh function. Then, the adaptive law of fuzzy systems is designed by the Lyapunov stability theorem. Finally, numerical simulation analysis and prototype control experiments show that the control strategy can effectively reduce the speed fluctuation of the space flexible robotic arm. Compared with the classical sliding mode control strategy, the control strategy decreased the means of absolute error by 9.1425%, which reveals that the strategy can enhance the trajectory tracking accuracy of the space flexible robotic arm.