Brushless Motor Rotor Position Detection Method Without Position Sensor

Although there is no rotor position sensor in a brushless motor without position sensor, rotor position information is still needed during operation to control the normal commutation of the windings. Therefore, how to obtain rotor position information is critical to the reliable operation of a brushless motor without a position sensor. The following are the main methods often used to detect the position

1. Counter-electromotive force method
When a brushless motor is running, the counter-electromotive force of each phase winding is closely related to the rotor position, and the counter-electromotive force method is currently the most commonly used method to detect the rotor position. The waveform of the counter-electromotive force is discernible at the end of the winding when each phase winding alternates between conducting and non-conducting states. The rotor position can be determined by using the waveform of the counter-electromotive force in a specific and special place. The over-zero method, the phase-locked loop method and the integration method are the three basic techniques for detecting the counter-electromotive force.

2. Rotor position calculation method
To control the operation of the motor, this method uses the transient voltage and current equations for each phase of the brushless motor to calculate the transition from standstill to normal operation of the motor in real time. The entire process of detecting rotor position information can be accomplished using this method without additional start-up techniques, but because it relies on a mathematical model of the brushless motor body, control accuracy is affected when motor parameters drift due to temperature changes.

3. Continuity diode method
This method indirectly detects the counter-electromotive force above the zero point by detecting the conduction state of the anti-parallel continuity diode on the power tube of the non-conducting phase of the inverter to obtain rotor position information.
The above is the method of brushless motor rotor position detection, I hope it will help you, more related information welcome to consult Vshida micro motor at any time!