6-DOF fixed-time adaptive tracking control for spacecraft formation flying with input quantization

This paper addresses fixed-time tracking control problems for spacecraft formation flying (SFF) with model uncertainties, external disturbances, and input quantization. Firstly, a coupled model based on dual quaternions is introduced to describe the six-degrees-of-freedom (6-DOF) relative motion of spacecraft formation flying. Secondly, hysteretic quantized control input is implemented to reduce the required communication rate and to avoid the oscillations caused by the logarithmic quantizer. Thirdly, a fast terminal sliding mode tracking controller with adaptive updating laws is proposed to guarantee that the resulting closed-loop system is fixed-time stable, and that the relative motion tracking errors converge to a neighborhood around the origin in a fixed time, despite the presence of model uncertainties, external disturbances, and input quantization. Finally, a simulation example is presented to show the effectiveness of the proposed control design scheme.