System Outline

If the brake pedal is depressed suddenly, the ABS automatically controls the hydraulic pressure of the brake cylinders on all four wheels to prevent the wheels from locking and to ensure the directional and steer stability of the vehicle. In this situation, the skid control ECU controls the solenoids in the actuators, using the signals from the various sensors to move the brake fluid to the reservoir in order to release the braking pressure applied to the wheel cylinders. If the skid control ECU detects that the fluid pressure in the wheel cylinder is insufficient, the ECU can also control the solenoids in the actuators to increase the braking pressure.

The traction control system controls the engine torque, the hydraulic pressure of the driving wheel cylinders, and any wheel slippage which may occur at take off or when accelerating of the vehicle, to ensure optimal driving power and vehicle stability according to the road conditions.

The skid control ECU distributes appropriate brake-force to the front and rear wheels corresponding to the vehicle driving conditions. It also makes effective use of the rear wheel brake-force to match the load conditions and the vehicle deceleration, resulting in less pressure needing to be applied to the brake pedal while still ensuring effective braking force. When braking during making a turn, the ECU delivers appropriate brake-force distribution to the right and left wheels to ensure stability and braking of the vehicle.

The skid control ECU recognizes emergency braking by detecting the speed at which the brake pedal is depressed and how far it is depressed, and controls the brake application to supply firm brake-force for the emergency braking.

Unexpected road conditions, emergency situations, and other external factors may cause a large under- or over-steer in the vehicle. If they occur, the VSC system automatically controls the driving power and wheel brakes to reduce the under- or over-steer.

To reduce large over-steer :

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

To reduce large under-steer:

If the VSC system determines that the under-steer is large, it controls the driving power and activates the front wheel brakes and rear inner side wheel brake to reduce the under-steer.

If there is malfunction in the VSC system, the VSC indicator lights up to warn the driver.

Due to cooperative control with the hybrid vehicle control ECU, the skid control ECU controls the hydraulic brakes to collect as much electrical energy as possible by making extensive use of the regenerative brake.

The skid control ECU also improves the stability of the vehicle, performing cooperative control with the power steering ECU to give steering torque assistance corresponding to the driving conditions.

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

The skid control ECU monitors the system component parts electrically. In case there is an abnormality in the ECU, sensor signal or actuators, all normal parts except those parts with an abnormality continue the braking operation.

Even in the case that braking is shut off due to a malfunction in the oil pressure source, braking is ensured as the master cylinder pressure generated by the driver continues to be applied to the wheel cylinder.

In the situation that only the regenerative brake is ineffective due to an abnormality in communication with the hybrid vehicle control ECU, control will be changed to have the oil pressure brake generate all the braking force