Fast non-singular terminal sliding mode control of the cubesat attitude for on-orbit assembly process

The construction of space assemblies using on-orbit assembly technology is beneficial for supporting various complex space missions, and has broad application prospects and high practical significance. This paper designs a novel terminal sliding mode attitude controller to address the time-varying mass parameters and suppress internal and external disturbances during the on-orbit assembly process of CubeSat. Specifically, the CubeSat attitude dynamics model with a telescopic mechanism is established based on the vector mechanics method. Subsequently, given the expressions for fast, non-singular terminal sliding surfaces and adaptive power-reaching laws, the controller's stability is demonstrated. Then, the variation pattern of the model parameters is determined through dynamic simulations, and finally, extensive simulations verify the attitude control effect of the two CubeSats in the on-orbit assembly process. The simulation results demonstrate that the proposed method is robust to time-varying and jumping CubeSat mass parameters and presents a significant suppression effect on random interference caused by the shaking of the telescopic mechanism and the impact torque at the moment of the docking lock. The proposed method has faster attitude convergence and smoother control torque than traditional sliding mode control methods.