A novel method of estimating an initial magnetic pole position of a PMSM

This paper proposes a novel method of estimating an initial magnetic pole position of a Permanent Magnet Synchronous Motor (PMSM), which has an accurate incremental encoder for servo applications but does not have Hall sensors as a magnetic pole sensor. The proposed estimation method based on the secant method as a numerical procedure finds either of two zero torque positions by successively applying test currents to the estimated d-axis and then finds out the correct d-axis by applying a test current to the estimated q-axis. It requires only a tuned current controller and the relative position information and therefore it can be easily applicable. The experimental results show the validity of the proposed method, which accurately estimates the initial magnetic pole position under both small angular displacement and fast convergence time.