Stepwise modeling with friction/inertia effects separation and velocity control with dynamic compensation of a reaction wheel

Abstract

Reaction wheels have been largely employed as primary actuators in attitude control systems to perform pointing functions in Earth observation satellites. Their dynamic behavior characterization and proper velocity control are relevant tasks in the scope of attitude control design. In this work, a given reaction wheel is evaluated. Firstly, a stepwise identification procedure is applied to obtain the dynamic model. Separated tests are proposed to highlight the contribution of friction and inertia forces in the underlying dynamics and to estimate their respective parameters. Then, this model is used in a design of a velocity control law for the reaction wheel. A structure with a model-based dynamic compensation, a proportional-integral (PI) feedback loop and a pre-filter is proposed to obtain smoother behavior in velocity reversals and tracking performance in a determined velocity range. A comparison between the proposed controller with the feedback PI control and pre-filter only shows a clear advantage of using the dynamic compensation.