Variable structure maneuvering control and vibration suppression for flexible spacecraftsubject to input nonlinearities

Abstract

A new approach integrating the technique of active vibration suppression and the methodof variable structure control is proposed in this paper. In this approach, the technique ofactive vibration suppression utilizing piezoelectric materials is used to design a controller inthe inner feedback loop, which adds damping to the structures in certain critical modes;then an attitude controller is designed by using a variable structure output feedback controlstrategy in the outer feedback loop to slew the spacecraft and satisfy the pointingrequirements. The advantage in this method is that the vibration reduction and attitudepointing are implemented separately in the two separate feedback loops, allowing these twoobjectives to be satisfied independently of one another. The controller developedis achieved through an adaptive version without the limitation of knowing thebounds of the uncertainties and perturbations in advance. In addition, a modifiedadaptation control law is also given for the upper bound on the uncertainty toimprove the adaptive performances such that a new controller is designed whichcan guarantee the bound of the closed-loop system and can be described as acombination of sliding mode control law and modification adaptive law. With thepiezoelectric actuator/sensor, three effectiveness active vibration control techniquesare studied and compared for active vibration suppression. Both analytical andnumerical results are presented to show the theoretical and practical merits of thisapproach.