An initial rotor position estimation method is proposed in this study for an interior permanent-magnet synchronous motor without
a resolver or an absolute encoder. This method uses least squares approximation to estimate the initial rotor position. The magnetic
polarity is identified by injection of short pulses. The proposed estimation process is robust because it does not require complex
signal processing that depends on the performance of a digital filter. In addition, it can be applied to various servo systems because
it does not require additional hardware. Experimental results validate the effectiveness of the proposed method using a standard
industrial servomotor with interior-permanent magnets.