Normalized Current and Adaptive Super-Twisting Observer-Based Motor Parameter-Free Initial Position Detection for PMSM Drives

To determine initial rotor position, permanent magnet synchronous motor drives with incremental encoders typically require motion at startup, which is not acceptable in some practical applications. To address this issue, this article proposes an improved motor parameter-free and fast initial position detection (IPD) strategy with normalized current and adaptive super-twisting sliding-mode observer (ASTO). First, a high-frequency (HF) square-wave voltage is injected to obtain the HF current response in stationary frame. Then, a modified rotor position error extraction method, which does not require information about motor parameters, is applied using the normalized current response. Besides, the ASTO allows the initial rotor position to be rapidly observed. The stability of the observer is analyzed to ensure convergence of the proposed method. Finally, multiple sets of experiments have been carried out to demonstrate the effectiveness and accuracy of the proposed strategy for fast IPD, as well as its robustness against motor parameter uncertainty.