System Outline

System Outline

1. ABS Operation
If the brake pedal is depressed suddenly, the ABS controls the hydraulic pressure of all the four wheel cylinders to automatically avoid wheel locking and to ensure the directional and steering stability of the vehicle. Under the situation, 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. Electronic Brake-Force Distribution
Skid control ECU distributes appropriate brake-force to front and rear wheels (Control of brake-force distribution to front and rear wheels) corresponding to the vehicle driving conditions. It also makes effective use of rear wheel brake-force to match loading condition and decelerating of the vehicle, resulting to reduce depressing of brake pedal and to ensure effective braking. In braking during making a turn, the ECU controls appropriate brake-force distribution to right and left wheels (Control of brake-force distribution to right and left wheels) to ensure stability and braking of the vehicle.

4. Brake Assist System
Skid control ECU recognizes emergency braking from detecting applying speed of brake pedal and brake travel, and controls braking effectiveness to supply strong brake-force for the emergency braking.

5. VSC Operation
Unexpected road conditions, emergency situation, and any other external factors may cause large under- or over-steering of the vehicle. If they occur, the VSC system automatically controls the driving 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 turning wheels depending on the degrees 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 driving power and activates the front wheel brakes and rear inner side wheel brake to reduce the under-steering. If there is malfunction in the VSC system, the VSC indicator lights up to warn the driver.

6. Mutual System Control
Due to cooperative control with hybrid vehicle control ECU, skid control ECU controls hydraulic brake to collect much electrical energy by making the most use of regenerative brake.
Skid control ECU also improves stability of the vehicle, performing cooperative control with power steering ECU to give steering torque assistance, corresponding to driving conditions.

7. Electric Source Backup Function
Electric charge is stored in brake control power supply assembly. If voltage of vehicle electricity is declined, electric charge is released to cover electric supply to the system.

8. Fail Safe Function
Skid control ECU monitors the system component parts electrically. In case there is abnormality in ECU, sensor signal and actuator, normal parts except parts with abnormality continue braking operation.
Even in case braking is shut off due to malfunction of oil pressure source, braking is secured as master cylinder pressure made by manpower works on wheel cylinder.
In case only regenerative brake is not effective due to abnormality in communication with hybrid vehicle control ECU, control will be changed to have oil pressure brake generate all the braking force