When the ring gear rotates with the wheel, an alternating voltage signal is generated in the electromagnetic induction coil on the permanent magnet (this is because the magnetic field strength changes when the tooth peaks and tooth valleys on the ring gear pass), and the frequency of the signal It is proportional to wheel speed and varies with wheel speed. The ABS electronic control unit (ECU) determines the speed of the wheel by identifying the frequency of the alternating voltage signal sent by the sensor. If the electronic control unit finds that the circumferential deceleration of the wheel increases sharply, when the slip rate reaches 20%, it will be 10 times// Calculate the speed of s, and then send a command to the actuator to reduce or stop the braking force of the wheel to prevent the wheel from locking.