Multi-Frequency-Band Uncertainties Rejection Control of Flexible Gimbal Servo Systems via a Comprehensive Disturbance Observer

Considering the multi-frequency-band uncertainties with distinctive forms and perturbed coefficients faced by flexible gimbal servo systems (GSSs) in control moment gyros (CMGs), a robust high-accuracy speed-regulation controller is proposed in this paper. Firstly, to obtain a more precise uncertainties compensation, a generalized model of flexible GSS with refined classification and description upon various types of uncertainties is accomplished. Then a comprehensive disturbance observer is designed based on this generalized model to accurately estimate compound disturbances in multi-frequency-band simultaneously, and a novel quantitative robustness analysis and method against the frequency deviations of faced periodic disturbance is further conducted. Due to the nominal recovery performance guaranteed by this estimation-based feedforward framework, a resonance cancellation-based composite controller is designed for the speed vibration suppression during the transient processes even in the presence of flexibility coefficients perturbation. Rigorous robust stability analysis for the closed-loop system is established. Experimental results with various uncertainties are provided to fully validate the effectiveness of the proposed scheme.