High fidelity mathematical modeling of reaction wheel performance

Accurate mathematical models of components are an essential element of attitude control system design, analysis, and simulation. This paper presents a detailed mathematical model of a reaction wheel, containing relationships for predicting reaction torques and drag torques, power consumption and disturbances. Performance coefficients are included for ITHACO's Type A and Type B reaction wheels. Disturbances from reaction wheels contribute to spacecraft pointing jitter and potentially generate microphonics in payload instruments. Definitions and quantitative examples are provided for the various types of reaction wheel disturbances due to sources such as flywheel imbalance, bearing stiction, bearing torque noise and motor torque ripple and cogging.