A clear-box adaptive system for flexible spacecraft identification and disturbance rejection

This paper presents an automatic system for identification and rejection of unknown periodic disturbances applicable to real-time control of flexible spacecraft. The system adaptively performs system identification, monitors and tracks disturbance frequencies if they are present, detects the emergen ce of new disturbance frequencies, predicts the contribution of each distur bance frequency on the system response, determines which disturbance freque ncies should be targeted for cancellation and which should be ignored by ta king into account actuator constraints, and synthesizes the necessary feed- forward control for selective disturbance cancellation No direct measuremen t of the disturbances is required. New system identification results are ex tensively used to bring out detailed information about the system dynamics and the disturbance environment that is normally hidden or left unused in s tandard black-box approaches, hence the descriptive term clear-box is used. Intelligent decision-making logic can be built into this information-rich architecture so that selective cancellation of the disturbance frequencies can be achieved. This paper derives all the relevant recursive expressions for multi-input multi-output clear-box system and disturbance identificatio n and control signal synthesis. A detailed simulation study is used to illu strate the application of the proposed scheme on a high-fidelity 52-state f lexible spacecraft model, followed by an extensive discussion on the lesson s learned.