Novel adjustable micropermanent-magnet synchronous-motor control system without using a rotor-position/speed sensor

The paper proposes a shaft-position/speed-estimating technique for a micropermanent-magnet synchronous motor. Based on the characteristics of the micromotor, the back EMF of the motor can be detected. In addition, the shaft position/speed can be estimated according to the back EMF. Finally, a closed-loop sensorless adjustable speed-control system is implemented. The controlled speed range is from 600 to 36000 rev/min. A DSP is used to estimate the shaft position/speed and to execute the speed-loop control algorithm. In addition, some hardware circuits, including current-controlled circuits, PWM circuits, and an inverter are implemented to control the current of the micromotor. Satisfactory performance, including a wide adjustable speed range, good transient responses, and good load-disturbance responses can be achieved. Experimental results validate the theoretical analysis and show the correctness and feasibility of the proposed estimation technique.