Input constrained preset-trajectory-based adaptive anti-unwinding control of spacecraft with parameter estimation

This paper addresses the anti-unwinding attitude control problem for spacecraft under parameter uncertainties and input constraints. To handle the potential problem that the barrier-function-based anti-unwinding control law may become singular when the scalar part of the error quaternion becomes 0 due to some unexpected factors, a preset-trajectory-based anti-unwinding control approach that still works in this scenario is proposed as a supplement. Specifically, a preset trajectory is elaborately generated according to the initial condition of the attitude system to characterize the desired behavior of the error quaternion, based on which a controller is designed to achieve the anti-unwinding control goal by restricting the error between the error quaternion and the preset trajectory. Besides, a parameter estimation error reconstruction mechanism is incorporated into the controller so that inertia parameter estimates converge to their true values under the weaker interval exciting condition. The input constraint being considered is actuator saturation, whose effect on closed-loop system performance and parameter estimation is compensated by the introduction of an anti-windup compensator and the accompanying modification of the nominal adaptive anti-unwinding controller. The effectiveness and advantages of the proposed control approach are validated by numerical simulations.