Low-Speed Sensorless Control of SynRM Using Hybrid Biaxial Pseudo-Random High-Frequency Signal Injection Strategy for High-Frequency Torque Ripple and Electromagnetic Vibration Suppression

This work presents a hybrid biaxial pseudo-random 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.