Momentum exchange feedback control: A new approach to the control of flexible spacecraft and space-tethered systems

This dissertation studies the control methods for the maneuver and vibration control of flexible space structures and the control of space tethered systems. An innovative control concept and technique, so-called momentum exchange feedback control, is introduced to provide a general methodological framework for the control design of the various systems. This new control method is first developed for the two-dimensional maneuver and vibration control of a flexible system. An energy Lyapunov function is used to establish the global stability of the closed-loop system and obtain the stability ranges of the control gains. Both the analytical and numerical results are investigated to show the theoretical and practical merits of the new approach. The implementation of this control technique to the three-dimensional maneuver and vibration control of a flexible spacecraft, the control of an articulated flexible arm, and the retrieval problem of a space tethered system are sequentially investigated. Also, various control techniques such as independent modal control and piezoelectric film actuator control for vibration suppression are discussed. The results of this research demonstrate that the flexible vibrations can be significantly suppressed with the momentum exchange feedback control design for the spacecraft attitude controller. Also, the independent modal control, as well as the piezoelectric film actuator control, can provide further micro-vibration control and fine-tune the system performance. Micro-vibration control at the final stage of a maneuver operation or at a stationkeeping mode is crucial for precision pointing or shape control of advanced spacecraft. As to the control of the tethered antenna/reflector system, the control design based on the concept of the momentum exchange feedback control is shown to be effective for suppression of the tether swing motions during the otherwise unstable retrieval procedure.