Direct Digital Attitude Control with a Double-Gimballed Momentum Wheel

Summary A direct digital control scheme is proposed for double-gimballed-momen-tum-wheel (DGMW) attitude control systems with stepwise gimbal actuation It is shown that the use of stepper motors leads to some scheme of pulse frequency modulation (PFM). Presuming that an on-board computer is available for realizing state estimation and control, a general design concept for computer-controlled PFM-systems is developed and applied to DGMW-systems. The theoretical scheme providing high precision control is verified by a physical simulation including an air-bearing simulator, a DGMW with stepwise gimbal actuation and a process computer as a controller.