Internal-model-principle-based robust optimal nonlinear control for position tracking of permanent-magnet synchronous motor servo system

This paper proposes an internal model principle (IMP)-based robust optimal nonlinear control with observer for position tracking of surface-mounted permanent magnet synchronous motor servo systems. We provide the control method to reject offset errors and load torque for designing field-oriented control (FOC) based on an alternating current (AC) frame. The proposed method consists of a torque generator, a commutation scheme, a electrical controller, and a nonlinear observer. The torque generator consists of a mechanical controller and an IMP controller. The mechanical controller is designed to compensate for the load torque and the offset error and generate the desired torque. The IMP controller is augmented to reject the position ripple. The commutation scheme is proposed to generate the desired currents for the desired torque. The electrical controller is developed to compensate for DC offset error and to guarantee the desired currents. The nonlinear observer is designed to estimate both velocity and load torque. In order to get the robustness to parameter uncertainties and the gain-tuning guideline, the linear quadratic regulator method is embedded in the proposed method. The closed-loop stability is proven using input-to-state stability. The detailed process for FOC design and the analysis of the control method based on an AC frame are presented. The performance of the proposed method was validated via experiments.