Vehicle Stability Control System (for BOSCH Made)
BRAKE CONTROL: VEHICLE STABILITY CONTROL SYSTEM (for BOSCH Made): SYSTEM DIAGRAM
(*1): with multi-information display (Combination meter)
BRAKE CONTROL: VEHICLE STABILITY CONTROL SYSTEM (for BOSCH Made): SYSTEM DESCRIPTION
1. SYSTEM DESCRIPTION
HINT
* The skid control ECU is located within the brake actuator assembly.
* The yaw rate sensor and acceleration sensor are combined in a single unit. This unit communicates with the skid control ECU through the CAN communication system.
(a) ABS operation
(1) 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.
2. FUNCTION DESCRIPTION
(a) 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 condition by receiving vehicle speed signals from each speed sensor, and sends control signals to the pump motor and solenoid valves.
The pump motor and solenoid valves avoid wheel lock by controlling the hydraulic pressure of each wheel cylinder.
The ABS warning light comes on when the ABS system is malfunctioning.
(b) EBD (Electronic Brake force Distribution)
The EBD control utilizes ABS, which ensures proper brake force distribution between the front and rear wheels in accordance with driving conditions. In addition, when braking while cornering, it also controls the brake forces of the right and left wheels, helping to maintain vehicle behavior.
(1) Operation description
The skid control ECU receives a speed signal from each 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 BRAKE warning light comes on if there is a malfunction in the EBD system.
(c) 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. This system helps to maximize the brake performance of the vehicle.
(1) Operation description
The skid control ECU receives the speed signal from each speed sensor and the hydraulic pressure signal from the master cylinder pressure sensor to determine whether brake assist is necessary. If brake assist is considered to be necessary, the skid control ECU sends control signals to the pump motor and solenoid valve.
The pump and solenoid valve then control the pressure applied to each wheel cylinder.
The ABS warning light comes on to indicate a malfunction in the BA (brake assist) system.
(d) TRAC (Traction Control)
The TRAC system helps prevent the drive wheel from slipping if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.
(1) Operation description
The skid control ECU detects wheelspin condition by receiving signals from each speed sensor and the ECM via CAN communication.
The skid control ECU controls engine torque with the ECM via CAN communication and brake hydraulic pressure through the pump and solenoid valve.
The SLIP indicator light blinks when the system is operating. When there is a malfunction in the TRAC system, the SLIP indicator light will come on and the DTC will be displayed on the multi-information display (models with multi-information display).
The VSC OFF switch stops traction control operation. If TRAC control is turned off, the TRAC OFF indicator light will come on.
(e) VSC (Vehicle Stability Control)
The VSC system helps prevent the vehicle from slipping sideways as a result of a strong front or rear wheel skid during cornering.
(1) Operation description
The skid control ECU determines the vehicle operating conditions based on signals received from the wheel speed sensors, yaw rate and acceleration sensor, and steering angle sensor. The skid control ECU sends signals via CAN communication to the ECM in order to control engine torque. The skid control ECU controls brake hydraulic pressure using the pump and solenoid valves.
The SLIP indicator light will blink, and the skid control buzzer will sound when the system is operating. If a malfunction occurs in the VSC system, the SLIP indicator light will come on. In addition, the DTC will appear on the multi-information display (models with multi-information display).
The VSC OFF switch stops VSC control operation. If VSC control is turned off, the TRAC OFF indicator and the VSC OFF indicator lights will come on.
3. ABS with EBD, BA, TRAC and VSC OPERATION
(a) The skid control ECU calculates vehicle stability tendency based on the signals from the speed sensor, yaw rate and acceleration sensor, and steering angle sensor. In addition, it evaluates the results of the calculations to determine whether any control actions (control of the engine output torque by electronic throttle control and of the wheel brake pressure by the brake actuator assembly) should be implemented.
(b) The SLIP indicator light blinks and the skid control buzzer sounds to inform the driver that the VSC system is operating. The SLIP indicator light also blinks when traction control is operating, and the operation being performed is displayed.
4. FAIL SAFE
(a) When a failure occurs in the ABS with BA, TRAC and VSC systems, the ABS warning and SLIP indicator lights come on or the DTC will be displayed on the multi information display (models with multi-information display) and ABS with BA, TRAC and VSC operations are prohibited. In addition, when there is a failure that disables the EBD operation, the BRAKE warning light also comes on and the EBD operation is prohibited.
(b) If control is prohibited due to a malfunction during operation, control will be disabled gradually. This is to avoid sudden vehicle instability.
5. INITIAL CHECK
(a) When the vehicle speed first becomes approximately 4 mph (6 km/h) or more after the ignition switch is turned on (IG), each solenoid valve and motor of the brake actuator assembly is sequentially activated to perform an electrical check. During the initial check, the operating sound of solenoid valve and motor can be heard from the engine compartment, but this is not a malfunction.
6. FUNCTION OF COMPONENTS
(*1): w/ multi-information display