Difference between motor driver with and without position sensor

Many applications are controlled by the speed and torque of the motor, and the starting and driving methods of the motor can be roughly divided into two types: ① Driving with position sensor and ② Driving without position sensor.

① Motor driver with position sensor: Motor drive method that requires sensors to detect the rotation speed and position of the motor.

② Motor driver without position sensor: Motor drive mode without the above sensor.

① The motor has the advantage of sensor driving: it can accurately detect the position and rotation of the motor when it is started and driven, and through the motor driver with built-in hardwired logic controller, it can realize smooth motor driving and rotation control from low speed to high speed 2.
Disadvantages: Sensors such as Hall element/Hall IC must be installed in the motor, so it is necessary to consider the installation position accuracy of the sensor and the wiring connecting the sensor and the motor controller.

② Advantages of sensor-less motor driving: it can be used to drive motors that can not be physically equipped with sensors and motors exposed to adverse environments such as high temperature, water and oil.
Disadvantages: Because the speed electromotive force is used to perform poorly at low speed, and the rotation position is estimated by MCU calculation, the overall response performance is poor. In addition, the estimation using motor current, voltage and motor parameters (R, L of motor winding) instead of position and rotation detection sensors will be influenced by individual motor differences.

For sensor-less driving, another method is to use the external forced commutation signal to start through a dedicated hard-wired logic controller other than MCU, and then use the velocity electromotive force as the position signal.

To sum up, both methods have their advantages and disadvantages. Therefore, it is necessary to select a motor driving method suitable for the required characteristics according to the environment in which the motor is used, the degree of demand for reliability and the type of motor load (constant torque, constant output).