What is the working principle of the ABS system?

[SanAmy]

ABS system, also known as the Anti-lock Braking System, works as follows: During braking, the ABS system, based on speed signals from each wheel speed sensor, closes the normally open input solenoid valve for the wheel that is starting to lock up, maintaining the braking force. If the wheel continues to lock, the normally closed output solenoid valve is opened. This keeps the braking state at the optimal point, ensuring the best braking performance and the highest level of driving safety. ABS, short for Anti-lock Braking System, functions to automatically control the braking force during vehicle braking, preventing the wheels from locking up and keeping them in a state of rolling and sliding (with a slip ratio of about 20%). This ensures maximum traction between the wheels and the road surface. The ABS system mainly consists of four components: wheel speed sensors, the electronic control unit (ECU), the hydraulic unit, and the ABS warning light. The wheel speed sensors detect the motion state of the wheels and generate sinusoidal electronic pulse AC signals. These signals are then processed by a modulator, converted into digital signals, and transmitted to the electronic control unit. The electronic central control unit (ECU) receives input signals from the wheel speed sensors and uses these parameters to calculate the wheel speed, vehicle speed, and slip ratio. Based on the slip ratio, it determines the state of the wheels and issues control commands to the hydraulic unit. The hydraulic unit adjusts the pressure in the brake lines according to the control commands. The adjustment process includes maintaining pressure, increasing pressure, and decreasing pressure. The ABS warning light alerts the driver to any system faults. If the ABS warning light is illuminated, it is recommended not to continue driving. This is because the ABS light indicates a fault in the vehicle's anti-lock braking system. During emergency braking, if the wheels lock up, the vehicle may skid uncontrollably, making it difficult for the driver to slow down or adjust the vehicle's trajectory, posing significant safety risks.