Sensorless operation of brushless DC motor drives

The brushless DC motor requires position and speed sensors for control. However, it is desirable to eliminate these sensors from the standpoints of size and cost reduction, maintenance and reliability. The approach to the sensorless operation becomes different, depending on the flux distribution. The paper presents the speed and position sensorless control of the brushless DC motor with a sinusoidal flux distribution, which provides high quality torque control. Two approaches are presented and compared; one is based on the voltage model of the motor and the other is based on the current model. Experimental results using a 1.2 kW, 164 V, 1200 RPM, six-pole motor which is controlled by a TMS320C25 DSP are shown for comparison, which demonstrate desired characteristics both in steady state and starting condition