An improved sliding-mode observer for IPM drives with a new phase delay mitigation algorithm based on extended electromotive force model

This paper presents a new sliding-mode observer (SMO) for interior permanent-magnet motors (IPM) to be utilized in sensorless field-oriented control (FOC) algorithms. Due to IPM's rotor saliency, the traditional back electromotive force (back-emf) model for surface-mount permanent motors (SPM) cannot be used in IPM observers directly. In order to address this problem, the extended electromotive force (EEMF) model is adopted for observer design. Unlike many other EEMF model based SMOs, the phase delay mitigation algorithm (PDMA) integrated in the proposed observer significantly reduces steady-state estimation error while maintaining low-pass filter's dynamic performance. The simple structure makes the proposed observer an ideal candidate for cost-sensitive applications which guarantees satisfactory performance and efficiency. Theoretical analysis, simulation and experimental results are provided to validate the fidelity of the proposed SMO.