Fractional-Order Nonsingular Terminal SMC for the Deployment of STS

In this chapter, a novel FO nonsingular terminal sliding mode (FONTSM) control scheme is developed, which guarantees the desired deployment performance of STS system. The presented control scheme is to stabilize the underactuated deployment mission with only tension regulation. Based on the underactuated model, a practicable integer-order nonsingular terminal sliding mode (IONTSM) controller is designed to realize the deployment of STS system, with the finite-time stability. Then, to improve the deployment performance, the FO calculus is introduced to raise the FONTSM controller, whose Mittag-Leffler-based uniform ultimate boundedness is proved to ensure the finite-time convergence and steady-state performance. In the FONTSM controller, a FO disturbance observer and a FO adaptive compensation law are proposed, to eliminate the adverse impacts of external disturbances and input saturation respectively. Moreover, compared to the reported FO sliding mode control strategy of STS system, a better deployment performance can be obtained by the IONTSM and FONTSM controllers in this work. Finally, the effectiveness of the proposed controllers is verified by groups of deployment simulations of STS system.