Anti-Lock Brake System System Description

ABS (Anti-lock Brake System)
The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.

1. Operation description
   The skid control ECU detects wheel lock based on speed signals received from the wheel speed sensors. Based on this information, the skid control ECU controls the pump motor and solenoid valves. The pump motor and solenoid valves are used to prevent wheel lock by controlling the hydraulic pressure applied to the brakes at each wheel. The ABS warning light will come on when the system is malfunctioning.
   

EBD (Electronic Brake force Distribution)
The EBD control utilizes the ABS to properly distribute brake force between the front and rear wheels in accordance with driving conditions.
In addition, when braking while cornering, it also controls the brake force distribution between the right and left wheels, helping to maintain vehicle behavior.

1. Operation description
   The skid control ECU receives a speed signal from each wheel speed sensor, and uses these signals to detect locking of the wheels. The ECU uses this information in order to determine appropriate control of the solenoid valves. The solenoid valves control the hydraulic pressure applied to the brake cylinder at each wheel. In this way, the solenoid valves are used to control the brake power split between the front and rear, and left and right wheels. The ABS warning and brake warning lights will come on if there is a malfunction in the EBD system.
   

BA (Brake Assist)
The primary purpose of the brake assist system is to provide auxiliary brake force to assist a driver who cannot generate a large enough brake force during emergency braking, thus helping to maximize the brake performance of the vehicle.

1. Operation description
   The brake assist mechanism installed on the control valve of the brake booster determines an emergency brake application based on the speed and the amount the brake pedal is depressed. This mechanism generates a stronger braking force as needed.
   

Based on the signals received from the 4 wheel speed sensors, the skid control ECU calculates the deceleration and speed of each wheel, while monitoring for wheel lock. If wheel lock is occurring, the ECU controls the solenoid valves in the brake actuator in order to adjust the hydraulic pressure applied to the brakes at each wheel.

When a malfunction occurs in the ABS system, the ABS warning light comes on, and operation is prohibited. In addition, when a malfunction which disables EBD operation occurs, the brake warning light also comes on, and operation is prohibited.

When the vehicle speed first reaches approximately 6 km/h (4 mph) or more after the ignition switch is turned to ON, each solenoid valve and motor of the brake actuator assembly are sequentially activated to perform an electrical check. During the initial check, the operating sound of the solenoid valves and motor can be heard from the engine compartment, but this is not a malfunction.