BRAKE CONTROL SYSTEM GENERAL


  1. OUTLINE


    1. The following brake control functions are provided: Anti-lock Brake System (ABS), Electronic Brake force Distribution (EBD), brake assist, Traction Control (TRC), Vehicle Stability Control (VSC), steering cooperative control and brake hold function.

    2. Vehicle Dynamics Integrated Management (VDIM) is used.

    3. An electronically controlled brake system is used to control the hydraulic pressure at the 4 wheels.

    4. A regenerative braking cooperative control is used.

  2. MAIN FEATURES


    1. Vehicle Dynamics Integrated Management (VDIM)


      1. In contrast to the ABS, TRC and VSC functions that were controlled individually in the conventional brake control system, the VDIM manages these functions in the form of an integrated system.

      2. Furthermore, the VDIM effects cooperative control together with the Electric Power Steering (EPS) system in order to improve the dynamic performance of the vehicle to "run, turn, and stop".

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    2. Electronically Controlled Brake System


      1. In this system, the conventional brake booster portion has been discontinued. Instead, it consists of a power source and hydraulic control portions.

      2. During normal braking, the fluid pressure generated by the master cylinder does not directly actuate the wheel cylinders, but serves as a hydraulic pressure signal. Instead, the actual control pressure is obtained by regulating the fluid pressure of the hydraulic power source in the brake actuator assembly, which actuates the wheel cylinders.

      3. The brake control power supply assembly is used as an auxiliary power source, to supply power to the brake system in a stable manner.

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    3. Regenerative Braking Cooperative Control


      1. Regenerative braking consists of a resistance force that is generated at the rotational axle in the reverse direction of the rotation of the generator (MG2) that is generating electricity. The greater the generated amperage (battery charging amperage), the greater will be the resistance force.

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        Text in Illustration
        *1 Engine *2 MG1
        *3 MG2 *4 Inverter
        *a Rotating Direction to Electricity Generation *b Resistance
        *c Brake Force - -

      2. The drive wheels and MG2 are joined mechanically. When the drive wheels rotate MG2 and cause it to operate as a generator, a regenerative brake force of MG2 is transmitted to the drive wheels. Based on the signals from the skid control ECU assembly, this force is controlled by the hybrid system, which controls the generation of electricity.

      3. The regenerative brake cooperative control does not rely solely on the braking force of the hydraulic brake system to supply the brake force required by the driver. Instead, by effecting cooperative control with the hybrid system, this control provides a joint braking force provided by the regenerative braking and the hydraulic braking. As a result, this control minimizes the loss of the kinetic energy associated with the normal hydraulic braking, and recovers this energy by converting it into electrical energy.

      4. The apportioning of the brake force between the hydraulic braking and the regenerative braking varies by the vehicle speed and time.

      5. The apportioning of the brake force between the hydraulic braking and the regenerative braking is accomplished by controlling the hydraulic braking so that the total brake force of the hydraulic braking and the regenerative braking matches the brake force required by the driver.

      6. If the regenerative braking becomes inoperative due to a malfunction in the hybrid system, the brake system effects control so that the entire brake force required by the driver is supplied with the hydraulic brake system.

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