High-Precision Control for Magnetically Suspended Rotor of a DGMSCMG Based on Motion Separation

The magnetically suspended rotor (MSR) in a double-gimbal magnetically suspended control moment gyro (DGMSCMG) is a complicated system with multivariable, nonlinearity, and strong coupling. Not only the torsional motion of the MSR is coupled depend on the rotating speed but also its translational and torsional motions at the same axis are coupled due to the asymmetric position stiffness of magnetic bearings. Besides, the MSR also encounters the nonlinear coupling torque due to gimbals' movements. These problems influence the control accuracy of the MSR. To resolve these issues, this work presents a high-precision control strategy. A compensation method for asymmetric position stiffness is proposed to realize separation between the translational and torsional motions. Then the integral sliding mode control based on motion separation (MSISMC) is employed to stabilize the translational and torsional dynamics. To suppress the coupling torque from gimbals' movements, a novel switching function considering the estimation of the coupling torque is designed in torsional controller, and the decoupling control for the torsional motion is implemented by pole assignments. The stability of the closed-loop MSR control system is analyzed by the Lyapunov and state space methods. Comparative simulations and experiments verify the effectiveness and superiority of the proposed control strategy.