Robust steering law design for single gimbal control moment gyroscopes with parameter uncertainty

Physical parameters of single gimbal control moment gyroscopes (SGCMGs) are often assumed to be known exactly when steering law is designed taking gimbal servo characteristics into account. However, exact physical parameters cannot be achieved due to system complexity. In order to attenuate the effect of parameter uncertainty on steering performance, a robust steering law is presented. This steering law uses only estimate of physical parameters and can calculate the control torque for each SGCMG gimbal directly according to the momentum (or torque) command. Since it has no arithmetic singularity, steering error can be made converge to zero exponentially when system singularities do not appear. Meanwhile, the steering law is guaranteed to have strong robustness to parameter variations through the proper choice of the controller gain. Comparatively, it has a simple form and is easy to be realized. Finally, simulation analysis is conducted for a certain 4-SGCMG system mounted on a rigid spacecraft. Simulation results indicate that the steering law stated above is feasible.