Jinpeng Liu

This work presents a sensorless control strategy for SynRMs based on dual-band hybrid biaxial high-frequency signal injection (Bi-HFSI) strategy, aiming to enhance torque performance. The proposed approach concurrently mitigates two dominant sources of torque ripple: inherent torque ripple caused by motor tooth-slot structure and high-frequency (HF) components induced by signal injection. To suppress these effects, a compensation signal is designed via nonlinear function fitting, and a hybrid HF voltage waveform is synthesized and injected using biaxial pseudo-random (Bi-PR) excitation. This configuration effectively reduces HF current noise while maintaining accurate rotor position estimation. The proposed strategy is validated through both finite element analysis and experimental testing, exhibiting significant torque ripple reduction under various load conditions, particularly under high-load operation. Although the integration of the compensation signal adds some complexity to the analysis of HF currents, it significantly enhances torque output quality and ensures reliable rotor position tracking. Power spectral density (PSD) and noise analysis confirms that the proposed method achieves lower noise levels than conventional square-wave injection, demonstrating its feasibility for high-performance sensorless SynRM drive applications.

This work proposes a hybrid d-axis high-frequency signal injection (HFSI) technique for low-speed sensorless control of SynRMs, aiming to regulate the high-frequency (HF) current and suppress HF torque ripple and electromagnetic (EM) vibration. The proposed technique employs a hybrid sinusoidal excitation, which, under the same current amplitude, generates lower HF current and HF torque components than the conventional sinusoidal and square-wave HFSI techniques, as validated through power spectral density (PSD) analysis. Benefiting from its intrinsically lower HF injection noise characteristics, the hybrid signal further achieves reduced HF noise when combined with pseudo-random signal injection approach, thereby outperforming sinusoidal and square-wave pseudo-random signal injection methods. Although the injected hybrid HF signal exhibits a complex waveform, this complexity is effectively managed during signal demodulation without increasing the computational burden of the sensorless control algorithm. Experimental tests using both fixed-frequency and pseudo-random d-axis HFSI approaches with sinusoidal, hybrid and square-wave signals on a 5.5 kW SynRM demonstrate that the proposed hybrid signal significantly mitigates HF torque ripple and EM vibrations, thereby enhancing the sensorless control performance of the SynRMs.

This work presents a hybrid biaxial pseudorandom high-frequency signal injection (Bi-PR-HFSI) strategy to suppress high-frequency (HF) torque ripple and electromagnetic (EM) vibration, thereby improving the low-speed sensorless control performance of SynRMs. The proposed method combines hybrid HF excitation with Bi-PR modulation, which helps redistribute spectral energy while suppressing discrete harmonic components in the HF current. Compared with conventional square-wave injection techniques, the injected hybrid voltage contributes to lower current components and minimizes HF torque ripple and EM vibration under injected frequencies. Despite the increased waveform complexity, the hybrid signal remains compatible with demodulation schemes, ensuring no additional computational overhead. Experimental evaluation on a 5.5 kW SynRM under fixed and PR injection conditions confirms that the hybrid voltage effectively smooths HF torque ripple and suppresses EM vibration across the injected frequency range. These results highlight the feasibility and effectiveness of the hybrid Bi-PR-HFSI method in improving motor performance for sensorless SynRM drives.

Due to the inherent assembly errors, rotor eccentricity in motors is an inevitable phenomenon. In the case of the interior permanent magnet synchronous motor (IPMSM), its relatively short air-gap length makes it more susceptible to the effects of eccentricity. Therefore, this study proposes a new analytical model and a rotor vibration calculation model for IPMSM in eccentric scenarios. First, the theoretical feasibility of equivalent transformation for eccentricity is analyzed. A novel equivalent transformation method for rotor eccentricity is presented. The nonuniform air gap resulting from eccentricity can be represented as the superposition of a uniform air gap and a virtual surface permanent magnet (VSPM). By maintaining constant air-gap flux density before and after equivalence, the remanence distribution of the VSPM is determined, thereby achieving the unity of the stator and rotor geometric centers. Second, to consider the complex magnetization patterns and structures of interior permanent magnet (IPM), this article presents an improved subdomain model that combines equivalent current and subdivision while also incorporating the core’s nonlinear saturation. Third, based on the magnetomotive force (MMF)-permeability method, a new analytical equation of the unbalanced electromagnetic force (UEF) considering rotor vibration is derived. Furthermore, an analytical model of rotor vibration is established, which appropriately considers the mutual coupling effect between the UEF and the rotor vibration displacement. Finally, all the proposed methods are verified and analyzed.

While various methods accurately and efficiently address motor thermal and stress analyses separately, effectively solving this dual field problem for complex rotor structures in synchronous reluctance motors (SynRMs) remains challenging. This work presents an improved hybrid method (HM) for comprehensive three-dimensional thermal and rotor stress performance prediction in SynRMs. The proposed improved HM integrates the improved finite difference method (IFDM), subdomain method (SDM), and lumped parameter thermal networks (LPTNs). The key advantages of the proposed improved HM are fourfold: First, incorporating the variable density method into the IFDM eliminates inner boundary conditions, simplifying rotor dual-field computation. Second, integrating the SDM and LPTN significantly enhances the accuracy and efficiency of three-dimensional thermal field calculations, particularly facilitating solutions for axially asymmetric thermal performance. Third, leveraging steady-state temperatures from the improved HM enables rapid prediction of transient temperature characteristics. Fourth, the improved HM uniquely solves coupled dual fields using a unified model, streamlining computational procedures. Finite element analysis and prototype testing validate the accuracy and efficiency of the proposed improved HM, demonstrating over 90% improvement in computational efficiency, especially for transient thermal prediction.

This work proposes an improved analytical model and a novel location method for irreversible demagnetization (ID). The analytical model accounts for the nonlinearities from the demagnetization curve and saturation, and it is suitable for any magnetization orientation; the ID location method is unaffected by saturation, ensuring high accuracy and low detection costs. First, to calculate the local state of the permanent magnet, an improved analytical model involving radial subdomain layering and tangential unit partition is established. Next, the new calculation method for the knee point of the exponential demagnetization curve and the ID iteration calculation method are presented. Additionally, the characteristics of the electromagnetic force density under any ID state are summarized using the magnetomotive force (MMF)-permeability method and verified using the proposed analytical model. It is found that nonuniform ID introduces new spatial and temporal components. Furthermore, a new method for locating ID faults is introduced, deriving the quantitative expression between MMF harmonics and back electromotive force harmonics from the perspective of the location principle. Based on this, an accurate method for determining fault interval parameters is proposed. Finally, all the conclusions are validated through the test results.