Antilock Brakes / Traction Control Systems: Description and Operation

VSC

SYSTEM OUTLINE

1. ABS OPERATION
If the brake pedal is depressed suddenly, the ABS controls the hydraulic pressure of the wheel cylinders for all the four wheels to automatically avoid wheel locking and ensure the directional and steering stability of the vehicle. If the brake pedal is depressed suddenly, the skid control ECU controls the solenoids in the actuators using the signals from the sensors to move the brake fluid to the reservoir in order to release the braking pressure applied to the wheel cylinder. If the skid control ECU detects that the fluid pressure in the wheel cylinder is insufficient, the ECU controls the solenoids in the actuators to increase the braking pressure.

2. TRACTION CONTROL OPERATION
The traction control system controls the engine torque, the hydraulic pressure of the driving wheel cylinders, slipping of the wheels which may occur at start or acceleration of the vehicle, to ensure an optimal driving power and vehicle stability corresponding to the road conditions.

3. VSC OPERATION
Unexpected road conditions, vehicle speed, emergency situation, and any other external factors may cause large under - or over - steering of the vehicle. If this occurs, the VSC system automatically controls the engine power and wheel brakes to reduce the under - or over - steering.

To reduce large over - steering :
If the VSC system determines that the over - steering is large, it activates the brakes for the outer front turning wheels depending on the degree of the over - steering to produce the moment toward the outside of the vehicle and reduce the over - steering.

To reduce large under - steering :
If the VSC system determines that the under - steering is large, it controls the engine power and activates the rear wheel brakes to reduce the under - steering.

VSC indicator light
If an malfunction occurs in the VSC system, the VSC indicator lights up to warn the driver.

4. MUTUAL SYSTEM CONTROL
To efficiently operate the VSC system at its optimal level, the VSC system and other control systems are mutually controlled while the VSC system is being operated.

Engine control
The engine power does not interfere with the VSC brake control by fuel cut controlling and reducing the engine output.
Engine control and electronically controlled transmission control
The strong braking force does not interfere with the braking force control of the VSC system by turning off the accel and reducing changes in the driving torque at shift - down.
VSC system operation indication
The slip indicator light flashes and the buzzer alarm intermittently to warn the driver that the current road is slippery, while the VSC system is being operated.

5. FAIL SAFE FUNCTION
If an malfunction occurs in the skid control ECU, sensor signals, and/or actuators, the skid control ECU inhibits the brake actuator control and inputs the malfunction signal to the engine control module. According to the malfunction signal, the brake actuator turns off the solenoid and the engine control module rejects any electronically controlled request from the VSC system. As a result, the vehicle functions without the ABS, BA, TRAC, and VSC systems.