Anti-Lock Braking System
1 - front brake; 2 - rear brake; 3 - front brake disc; 4 - rear brake disc; 5 - vacuum brake booster and main brake cylinder; 6 - brake tube; 7 - front brake tube; 8 - rear brake tube; 9 – brake pedal; 10 – parking brake lever; 11 – parking brake cable; 12 - ABS control unit (HECU); 13 - front wheel speed sensor; 14 - rear wheel speed sensor
Anti-Lock Braking System (ABS) controls the pressure in the hydraulic drive of the brakes of each wheel separately and reduces the fluid pressure in the wheel brake mechanism, the wheel of which begins to block.
ABS performs the following functions:
- Improving driving stability when avoiding obstacles, even during braking.
- Reduced stopping distance during heavy braking while maintaining vehicle stability and control even when cornering.
The anti-lock braking system works based on information from four sensors transmitted to the ABS unit. The system controls each wheel individually and reduces the fluid pressure in the wheel brake mechanism, the wheel of which begins to block.
Under normal conditions, the standard brake system applies the brakes until a wheel lock is detected by the ABS control unit. When the ABS control unit detects a blocked wheel, it controls each valve to increase or decrease the pressure.
The ABS control unit determines the speed and deceleration rate of each wheel based on information from the wheel speed sensors. When braking, the wheel speed decreases and the ABS unit detects the difference between the vehicle speed and the wheel speed. If the deceleration of some wheels exceeds the expected value, the ABS unit detects the start of a blockage and opens the appropriate solenoid valves to reduce the brake fluid pressure. In this case, the wheel speed increases and the pressure relief solenoid valve closes and the brake fluid pressure in the working brake cylinder of the corresponding wheel increases.
EBD (Electronic brake force distribution)
EBD is additionally used in place of a pressure regulator to ideally distribute pressure to the front and rear brakes to prevent rear wheel lockup under heavy braking.