Fixed-time terminal sliding mode control of spinning tether system for artificial gravity environment in high eccentricity orbit

In this paper a new strategy is introduced to produce an artificial gravity environment by spinning tether system (STS) in high eccentricity transfer orbit. Compared with other common artificial gravity environment methods, spinning tether system has simple structure, light weight and suitable spin velocity, which is more favorable for the spacecraft to generate the artificial gravity in the weightless space. The mathematical model of the spinning tether system is established by the second type of Lagrangian equation firstly. Then, the tension control law and the tangential thrust control law of tether system are designed. Through the mutual coordination of both control law, a method of Variable Moment-of-Inertia and Angular Momentum is realized which makes the tether system spin along the expected spinning velocity in most of the processes of uniform velocity development by constant tangential thrust. With the end of development, the artificial gravity environment level on the spacecraft also met the expected requirements, and the nominal trajectory curve of STS under the high-eccentricity transfer orbit was obtained. Finally, considering the rapidity of convergence time, a fixed time terminal sliding mode controller is designed to control the closed-loop trajectory curve of the tether system.