Precision control moment gyroscope spacecraft control with disturbance

Standard feedback control systems subjected to periodic disturbances often cannot avoid sustained oscillatory responses at the disturbance frequency. Periodic disturbance rejection in a feedback control system via the insertion of an oscillator in the controller (internal model principle) is an effective method and well understood. By proper pole-zero placement, stable, steady-slate performance which asymptotically approaches zero is achieved through the application of this type of filter. When the periodic disturbance is variable in frequency, the application of this type of filter is achieved by allowing the oscillator frequency to follow the disturbance. This, however, presents several problems in the actual application. This paper describes two applications of a variable periodic disturbance rejection filter in a spacecraft attitude control system and discusses the problems encountered and areas of further research.