Drive Motor Speed Sensor Operation Diagram

Overview

The rotor of the drive motor speed sensor is mounted on the same shaft as the drive motor rotor assembly (see Figure 24). The sensor contains an excitation coil and two output coils arranged in sine and cosine configurations.

The sensor detects the rotational speed and direction of the drive motor (see Figure 25), providing basic information for controlling the three-phase AC supply to the drive motor. The output signals are fed into the drive motor control module, which transmits the rotation information to the vehicle control unit (VCU) via CAN communication.

Operation Principle

1. A constant AC excitation is applied to the excitation coil. By electromagnetic induction, the output coils (Cos and Sin) generate signals at the excitation frequency.
2. When the drive motor rotates, the gap between the output coils and the sensor rotor changes due to surface variations on the rotor. This alters the magnetic flux in the output coils and causes corresponding variations in the peak voltages of the output signals.
3. The drive motor control module processes the peak voltages from the output coils, converts them into virtual waveforms, and derives rotor position, rotation direction, and rotational speed from those waveforms.