Improved satellite attitude control using a disturbance compensator

An attitude control algorithm using a disturbance compensator has been developed for three-axis-controlled satellites with flexible appendages. It consists of a compensator to stabilize the system (e.g., PD control), a filter to prevent excitation of the neglected higher flexible-mode vibration (e.g., a low-pass filter), and a compensator to suppress the effect of disturbances on the satellite attitude. This disturbance compensator can be designed in the frequency-domain in terms of the robust model matching design method, and also, in the time-domain in terms of the observer/estimator approach. The designed compensator can easily be implemented for a conventional attitude control system. Theoretically, the disturbance compensator makes it possible to assure arbitrarily low sensitivity over any frequency range for disturbances due not only to the environment but also to structural flexibility with keeping the control performance for reference inputs. Thus, the control algorithm can improve the control performance of satellites with the flexible structures. It is applied for the attitude control system of the Japanese VLBI satellite, "HALCA", launched on February 12, 1997. (C) 2004 Elsevier Ltd. All rights reserved.