Direct Adaptive Control Treatment to Flight Control Input Saturation

What is it about?

Input saturation or “limit riding situation” is the operating condition that is well recognized by the control community for its “side effects” to the baseline system performance. It affects both conventional and adaptive controllers. This paper presents an effective adaptive control treatment to input saturation using direct adaptive control coupled with a baseline PID controller implemented in a control augmentation fashion. The proposed adaptive controller can also perform two simultaneous roles: basic stabilization and input saturation treatment without the need of the PID controller remaining in the loop. Its treatment solution is first characterized using the Lyapunov function approach, and its stability is then interpreted and confirmed by the point-wise simulation based approach. The treatment effectiveness is then demonstrated via a nonlinear spacecraft control environment subject to two types of input saturation violations: (1) actuator authority limits and (2) attitude and rate error limits. Validation of the direct adaptive treatment is substantiated by a high fidelity simulation demonstration.

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