Adaptive Dynamic Inversion Control with actuator saturation constraints applied to tracking spacecraft maneuvers
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This paper presents an adaptive control methodology for nonlinear plants that prevents the adaptive parameters from drifting due to trajectory errors arising from control saturation. The reference trajectory is modified upon saturation, so that the modified trajectory approximates the original reference closely and can be tracked within saturation limits. The adaptive parameters are updated by the error between the plant trajectory and this modified reference. Asymptotic tracking of the modified reference is guaranteed with the assumption that the modified reference remains bounded and asymptotic convergence of the modified reference to the original reference is guaranteed whenever the control becomes unsaturated. Also, bounded learning of the adaptive parameters is guaranteed. A numerical example of attitude tracking for a rigid spacecraft is presented which shows that, in the presence of persistent excitation, the adaptive parameters converge to the true parameters, even when the actuator saturates.
