Sensorless commutation techniques for brushless permanent-magnet and reluctance motor drives

Rotor position detection is essential for phase commutation in brushless permanent-magnet and reluctance motor drives when they are operating as closed loop servo motors. Traditional methods to obtain the rotor position are based on optical, inductive or Hall effect sensors. These are expensive to install and can be unreliable. Researchers have investigated various sensorless position detection techniques for all types of brushless permanent magnet and reluctance motor drives. The authors discuss the basic principles of sensorless rotor position detection in brushless permanent-magnet and reluctance motor drives. Existing techniques for sensorless rotor position detection from the literature are reviewed. All the methods proposed in the literature extract the rotor position information from measurements on the phase winding circuits. Such techniques therefore eliminate the connections of the sensor to the motor and controller simplifying the system construction. Furthermore, continuous rotor position information can be obtained for optimal control