Abstract: Spacecraft precise attitude control is easily affected by system parameter errors. Adaptive control can estimate parameters reasonably and make the model based controller design more easily. Adaptive parameters are sorted into three groups includingspacecraft main body inertia, VSCMGs gimbal androtor inertia, and their dynamic friction coefficients. The detailed spacecraft attitude dynamics model considering VSCMGs gimbal and rotor friction was transformed according to the parameter groups. The attitude controller, VSCMGs steering law and parameters adaptive updating law were developed by Lyapunov method. Weight matrix was imported into the steering law to relief the gyroscopes singularity problem. Theory analysis and numerical simulation prove that the closed loop control system is global uniformly and ultimately bounded stable. Parameters adaptive updating can effectively reduce angular velocity tracking errors and make attitude quaternion errors converging faster. Parameter estimates can not accurately converge to their real values, but they are all within acceptable scopes.

Key words: Variable speed control moment gyroscopes, Friction moment, Adaptive control, Attitude control, Spacecraft