Research on integral sliding mode control with exponential approximation law for magnetically suspended rotor system of CMG

A robust controller for the magnetic bearing system of magnetically suspended control moment gyroscope (MSCMG) is presented in this paper. The controller mainly deals with the problems such as the strong nonlinearity, parameter perturbation and modeling uncertainties in MSCMG. The axial dynamics as well as the linearized electromagnetic-force models of magnetic bearings are developed. Besides, the parameter perturbation and modeling uncertainties are analyzed. Furthermore, a novel nonlinearity integral sliding mode controller is introduced based on the exponential approximation law. An integral sliding mode plane relating to current and position is designed; both exponential approximation law and saturation function are adopted to suppress the chattering phenomenon. Experimental results prove that the new method effectively suppresses SMC's chattering problem and that the new method has good dynamic performance under parameter perturbation. Moreover, the control system possesses strong robustness to restrain multiple disturbances when both rotor and gimbal system work.