DSP-based sensorless position estimation in switched reluctance drives

Information on rotor position is essential for controlling the operation of switched reluctance motors (SRMs). Conventional SRM drives utilize optical or electromagnetic rotor position sensors which provide a rotor position reference signal while the rotor is in operation. The fitting of a rotor position transducer on an SRM requires additional electrical connections, additional cost and a potential source of unreliability. Considerable attention has recently been applied to various methods for sensorless rotor position measurement, generally based on measurement of phase current and flux and a preknowledge of the magnetic characteristics. This paper presents two methods which deduce sensorless rotor position information by monitoring the excitation signals of the motor phases whilst the inductance is rising. This is done without the injection of diagnostic current pulses and has the advantages that the measured current is large and mutual effects from other phases are negligible.