An Improved Sensorless Hybrid Control Method of Permanent Magnet Synchronous Motor Based on I/F Startup.

Sensorless control of permanent‑magnet synchronous motors (PMSMs) is especially hard at low speeds and during startup because the back‑EMF signal is weak and noisy. This work looks at a hybrid sensorless strategy that starts the motor with a current‑frequency (I/F) method and then switches to an observer‑based controller for higher speeds. The key idea is to choose the switching point between the open‑loop I/F start‑up and the closed‑loop sensorless mode so that current ripple and rotor‑position errors stay small. To do this we: – Model the PMSM dynamics. – Design an I/F start‑up controller that includes a smooth‑transition algorithm. – Add a sliding‑mode observer **or** an extended Kalman filter to

estimate speed and position at medium to high speeds. Simulations test the hybrid controller under different load torques and speed trajectories. The development effort includes: – Writing out the math that defines the transition strategy. – Guiding the tuning of the current loop parameters. – Checking the stability of the combined control system. The framework gives clear steps for evaluating sensorless drive performance, ensuring a smooth handover between start‑up and normal operation, and maintaining reliable speed tracking across the whole speed range.

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