Spacecraft Adaptive Robust Attitude Tracking Control with New Actuator

This paper deals with the attitude tracking of spacecraft with single-gimbal Variable-Speed Control Moment Gyro-scopes(VSCMGs) as actuator. The quaternion is used to describe the attitude, the attitude error is expressed by rotation matrix from desired attitude to current one. Considering actuator model parameter uncertainties and external disturbances, the spacecraft equations of motion are fully nonlinear and can be represented as a Multi-Input-Multi-Output(MIMO) system. The adaptive robust controller is derived based on Lyapunov theorem, a smooth projection algorithm is then applied to keep the parameter estimates from singularity. Simulation results show that the proposed law attenuates the attitude error obviously, successfully deals with external disturbances and unknown misalignment of the axis directions of the actuators due to installation error or wearing out of the mechanical parts.