Abstract: The fast-maneuver and high-attitude-stability control problem of agile satellites is addressed by employing the variable speed control moment gyros (VSCMGs) as the actuator. A steering law is proposed by using the Lyapunov approach. The VSCMG can work in two modes, control moment gyro（CMG）or moment wheel（MW）. The singularity problem of each working mode is analyzed. An approach is proposed to avoid the singularity. To improve the control performance, the problem of matching the VSCMGs wheel’s speed with its nominal value is also studied. A method for rapid dumping of wheel’s speed is presented by adjusting the formation of wheels. Numerical simulations illustrate the feasibility and performance of the proposed steering law.

Key words: variable speed control moment gyro(VSCMG), singularity, steering law