Adjustable speed control of brushless DC motors without position and speed sensors

A sensorless drive scheme with adaptive gain speed controller for brushless DC motors is proposed in this paper. There are three observers in the control system, they are a disturbance voltage observer, a speed observer, and a disturbance torque observer. These observers are used not only for a position and speed estimator in the sensorless vector control, but also for a current controller. The rotor position and speed estimator are robust for parameter variations, such as the e.m.f. constant. The validity of the sensorless vector control of brushless DC motors is confirmed with computer simulations