Regenerative Brake System (RBS)

REGENERATIVE BRAKE SYSTEM (RBS)

The regenerative brake system (RBS) used on the 5.7L hybrid electric vehicle (HEV) incorporates all functions of the electronic stability program (ESP(R)) as well as braking by electric drive motors which is referred to as regenerative braking, and hydraulic braking. Information from the dynamic sensor, brake pedal angle (BPA) sensor as well as information from various other sensors and modules is evaluated to determine which mode of braking is used. There may be regenerative braking, electronic controlled hydraulic braking, standard vacuum assist hydraulic braking, or any combination of these. Under a system fault, the brakes return to standard vacuum assisted braking.

Below is a brief explanation of the different methods of braking.

REGENERATIVE BRAKING
Regenerative braking is accomplished through the electric drive motors inside the transmission during light braking applications. The 300V batteries are also charged through the electric drive motors during this mode of braking. While only the electric drive motors are braking there is no physical connection between the brake pedal and the master cylinder therefore the brake calipers are not operating. A pedal simulator unit (PSU) is used to create normal brake pedal feel during this braking mode. For more information on the PSU Brake and/or Accelerator Pedals - Description and Brake and/or Accelerator Pedals - Operation.

ELECTRONICALLY CONTROLLED HYDRAULIC BRAKING
Brake by wire is accomplished using vacuum from the electric vacuum pump (EVP) to the active brake booster moving the boosters secondary push rod into the master cylinder actuating the brake calipers. For more information on the EVP Description and Operation With electronically controlled hydraulic braking there is no physical connection between the brake pedal and the master cylinder therefore the brake calipers are not operating. The active brake booster does the mechanical brake application under this mode. A pedal simulator unit (PSU) is used to create normal brake pedal feel during this braking mode or combined with regenerative braking. For more information on the active brake booster and its sub-components Power Brake Booster - Description Power Brake Booster - Operation For more information on the PSU Brake and/or Accelerator Pedals - Description and Brake and/or Accelerator Pedals - Operation.

STANDARD VACUUM ASSISTED HYDRAULIC BRAKING
Standard vacuum assisted braking may be used during extreme braking conditions in any combination with regenerative and by wire braking. During specific fault conditions or extreme braking the PSU cut off solenoid may bypass the pedal simulator allowing standard vacuum assisted braking. Bypassing the pedal simulator allows full mechanical braking and the brake pedal may seem somewhat lower than normal.