The anti-lock braking system limits the pressure created in the hydraulic brake drive so that the amount of slip is optimal. The action of this system must be separate for each wheel. The system must respond immediately to each change in the surface (coefficient of adhesion) and the load on the vehicle.
The anti-lock braking system prevents the wheels from locking during sudden braking, thereby reducing the braking distance. The force of adhesion between the wheels and the road is greater in this case if the wheels continue to rotate during braking. Even with full braking, the car remains controllable. Speed sensors, one on each wheel, measure the speed of rotation of the wheel. Based on the signals from the sensors, the electronic control unit calculates the average speed, which approximately corresponds to the speed of the car. By comparing the speed of rotation of each individual wheel with the average calculated speed, the electronic unit determines the slip state of the individual wheel and thus determines which wheel is in the pre-lock state.
When one of the four wheel speed sensors signals that the corresponding wheel has locked, the electronic control unit immediately issues a closing signal to the corresponding inlet solenoid valve, which shuts off the supply of brake fluid through the line to the wheel brake. The braking force remains constant. If slipping continues, the outlet valve opens and the pressure in the hydraulic system of this brake decreases. The wheel does not brake, and excess brake fluid returns to the reservoir. As soon as the wheel starts to rotate again, the inlet valve opens and the outlet valve closes. The pressure in the circuit increases, and the wheel brakes again.
The change between braking and free wheel rotation cycles occurs very quickly (several times per second) and continues until the vehicle stops or until the brake pedal is released.
The process is repeated under hard braking separately for each wheel until the brake pedal is released.
The emergency system ensures that ABS is switched off in the event of any malfunction or low voltage in the vehicle's on-board network (below 10 V). ABS malfunction does not affect the operation of the brakes.
Content based on information from www.MazBook.ru
The hydraulic drive consists of a hydraulic unit, brake calipers and brake pipes. The hydraulic unit includes an electric pump that creates pressure and electromagnetic valves.