Pure-tension non-linear sliding mode control for deployment of tethered satellite system

This paper presents a sliding mode controller for the deployment of two-body tethered satellite system. A sliding surface design for underactuated system is employed to reconcile pure-tension control scheme with non-linear coupled deployment dynamics. The proposed sliding surface is strictly non-linear. Hence, the control scheme does not require linearization operation of tethered satellite system and can guarantee that all the system states converge to zero with arbitrary small errors. To deal with input constraint of pure-tension control, an adaption is introduced into the controller design to remove the negative effect caused by input constraint in stability analyses and ensures the feasibility of the proposed controller even though command input overtakes the tolerance of tension actuator. To avoid the chattering phenomena, the trivial sign function is removed from the switching input and replaced by the disturbance observer. Numerical results demonstrate the effectiveness of the proposed controller for the deployment of the tethered satellite system.