<p>The accuracy of rotor position estimation is key to achieving high-performance sensorless control of permanent magnet synchronous motors (PMSMs). However, the performance of traditional disturbance observer-based sensorless control methods is deteriorated by the differential calculation of state variables. To address the above problems, this study proposes a disturbance observer based on an intermediate function. By designing an intermediate function to replace the differential calculation of state variables and treating the back electromotive force (back-EMF) in the two-phase coordinate system as the disturbance input of the observer, the back-EMF can be accurately estimated. The strategy enables the estimation of back-EMF without requiring the differential calculation of state variables or the design of filtering components. The rotor information is estimated by a phase-locked loop based on the back EMF estimation results. By compensating for the rotor position at the same time, sensorless control of PMSMs can be achieved using the intermediate function disturbance observer. Finally, the experimental platform was constructed for verification. The analysis of steady-state and dynamic experimental waveforms demonstrates that this method can accurately estimate rotor position information, and the system exhibits excellent dynamic performance.</p>