Fourth-Order Generalized Integrator-Based Discrete-Time Resonance Observer for NIPMVM Considering Switching Frequency

In this article, an improved discrete-time resonance observer is proposed for a noncontact integrated permanent magnet Vernier motor (NIPMVM) considering switching frequency. First, a brief introduction to the mechanical model and the mathematical model of NIPMVM is provided. Then, a traditional orthogonal principle-based resonance observer (OPRO) and a second-order generalized integral resonance observer (SOGIRO) are introduced, and the influence of harmonics on the resonance identification of both methods is analyzed. Furthermore, to address the issue of poor disturbance rejection capability in these two observers, a fourth-order generalized integral resonance observer (FOGIRO) based on the cascaded structure of second-order generalized integrator (SOGI) is proposed, and its ability to suppress low- and high-order harmonics is theoretically demonstrated. Additionally, considering the discretization, the impact of the switching frequency on the resonance identification precision of traditional backward Euler method-based FOGIRO (BE-FOGIRO) is analyzed. To improve the precision of the FOGIRO, T-FOGIRO and PT-FOGIRO based on Tustin and prewarped Tustin methods with higher discretization accuracy at the center frequency are proposed and analyzed. Finally, the proposed PT-FOGIRO is validated on the NIPMVM platform, demonstrating its ability to achieve fast and accurate online resonance identification unaffected by the switching frequency.