Electric Servo Brake System Description - Hill Start Assist Control
Overview
The hill start assist control assists drivers by automatically controlling brake pressure when starting a vehicle on a steep hill; this assist prevents the vehicle from rolling on a hill for a few seconds while the driver's foot moves from the brake pedal to the accelerator pedal. The hill start assist control may not be activated when the driver does not press the brake pedal strongly enough upon stopping the vehicle or when the driver releases the brake pedal gradually upon starting the vehicle.
Control
The control unit reads the angle of inclination from the longitudinal acceleration signal and that all four wheels are stopped, then it calculates the amount of fluid pressure required to keep the vehicle from rolling backward. This takes place as the control unit sees the brake pressure decrease when the driver lifts their foot off of the brake pedal and moves it onto the accelerator pedal. After the driver transitions to the accelerator pedal and the drive torque is restored to the predetermined level required to start-up the vehicle, the hill start assist control will release the brake fluid pressure. The hill start assist control will release the brake fluid pressure if the accelerator pedal is not pressed for a certain period of time after the brake pedal has been released.