This paper presents a method for transitioning between sensorless rotor position estimation methods for an interior permanent magnet synchronous
motor (IPMSM); through the proposed method, rotor position estimation over the entire speed range of the IPMSM is possible. Considering that each
sensorless method governs a different speed range for estimating rotor position and speed with good accuracy, a strategy for transitioning between
two methods is indispensable. In this study, the sensorless method based on extended back electromotive force (EMF) is used for high-speed
operation. In contrast, during low-speed operation, rotor position is estimated using the slope of measured current through the application of the
zero-voltage vector. A weight function is applied to the position and speed information obtained from the two sensorless methods. The combined
information is then used throughout the speed range of the IPMSM. To achieve smooth transition, the weight function is altered based on rotor speed
in the transition region. The effectiveness of the proposed transition method was demonstrated via simulations and experiments.