Stability and hidden oscillations analysis of the spacecraft attitude control system using reaction wheels

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The paper is devoted to the problem of spacecraft attitude control using reaction wheels. The control system should ensure switching between less accurate to more accurate flight modes, resistance to external environmental influences, and, in some cases, the survival of the spacecraft. In these modes, the reaction wheel drives can reach their maximum performance, which introduces a saturation effect into the control loop. Its appearance can lead to self-excited attitude oscillations and significantly degrade positioning accuracy. In the paper, by the example of the DEMETER satellite, taking into account the flexibility of the appendices, attached to the spacecraft, the hidden oscillations in the PID-controlled spacecraft orientation system under the conditions of an actuator saturation were localized, and their parameters were found. The algorithms for the spacecraft attitude control were derived and a comparative study of their oscillatory attractors areas was given. To ensure asymptotic stability of the spacecraft orientation system the anti-windup correction was introduced, preventing hidden oscillations of the spacecraft attitude in the practically meaningful region of the initial conditions. Special attention is paid to the uncertainty of the satellite model parameters, which are not initially known with good precision and are varying along the satellite's orbit. For ensuring the attitude control system robustness in the face of the parametric uncertainty, in the paper the discrete-time adaptive controller with the Implicit Reference Model and anti-windup correction is proposed, and its efficiency is demonstrated by intensive simulation research.