A High Precision Initial Position Estimation Method for Low Saliency Ratio Machine Based on Image Tracking

In sensorless control of permanent magnet synchronous motor drives, initial rotor position detection is critical to ensure smooth start-up operation. However, extracting initial position information for machines with ultra-low saliency ratios is challenging. To address this issue, this article proposes an estimation method for rotor position using image tracking based on high-frequency rotating voltage vector injection. Specifically, this article extracts positive- and negative-sequence currents in the stationary reference frame and reconstructs the induced current vector. By utilizing the support vector machine algorithm, the resulting current vector images, which contain amplitude and phase information of the position, are trained to establish the correlation between the current image and rotor position information. Ultimately, the electric position can be obtained from image recognition. Since this method employs image tracking for position estimation, it accounts for cross-saturation and multiple saliencies, leading to the relatively high precision of position estimation. Experimental evaluation shows that the proposed method achieves higher precision compared to conventional observers.