A comparison of different sensorless position acquisition methods at low speeds for a permanent magnet synchronous machine in vehicle applications

In this paper three sensorless position acquisition methods at standstill and low speeds for a permanent magnet synchronous machine based on the evaluation of the phase current step responses are introduced and compared in terms of usability for electric vehicles. Besides the well-known INFORM method a new method is described which uses switching commands as test impulses and therefore does not require any additional test signals which yields to an increase of the system efficiency. All three methods were implemented on a test system and measurements were done to compare their performance.