Electronic Brake Control Feature Descriptions
Antilock Braking System
The ABS system includes one hydraulic modulator that is capable of performing ABS and Electronic Brake force Distribution (EBD) functions. The ABS monitors wheel speeds and other select vehicle parameters. The ABS and EBD operations shall meet the brake balance requirements defined by four regions of friction utilization and Z critical parameter in the base brake SSTS. The EBD shall balance brake forces both longitudinally and laterally at full speed range. This function shall improve vehicle stability during normal braking by means of all corners brake pressure control without the use of a conventional mechanical proportioning valve(s). In addition, the included sub-functions (such as split coefficient yaw control and Cornering Brake Control - CBC) have to reduce unwanted yawing while braking in any condition (straight-line as well as any cornering). When braking on straight line homogeneous road surface the EBD shall provide optimum front and rear brake balance and control the rear brakes with equal pressure. During braking in a turn or steering while braking the EBD shall provide appropriate side-to-side brake proportioning through CBC to optimize vehicle deceleration and meet vehicle stability specified in ABS vehicle performance requirements. The ECU and relays are integral to the hydraulic modulator.
Straight Line Stability (SLS)
SLS is used when vehicles exhibit excess yaw during straight line non-ABS, or threshold, brake applies. Vehicles with short wheelbases often exhibit this behavior. Straight Line Stability control shall have the capability to adjust front and rear brake corner pressures to assist the driver to maintain intended straight line vehicle path.
Enhanced Corner Brake Control (ECBC)
Enhanced Corner Brake Control shall have the ability to detect vehicle path deviation during very slight cornering maneuvers. Corner Brake Control may not engage in these maneuvers because the turn is not big enough. Also, ECBC shall integrate EBD and CBC to control both front and rear inner wheels to maintain vehicle stability.
Panic Brake Assist (PBA)
PBA detects that the driver intent is to stop the vehicle as quickly as possible, but does not apply sufficient brake pressure to do so. The feature will detect this driver intent then actively apply brake pressure to maximum pressure, thus activating the ABS system and stopping the vehicle as quickly as possible.
Hydraulic Fade Compensation (HFC)
The Hydraulic Fade Compensation (HFC) function detects a fading brake condition and activates the ESC modulator to increase the brake pressure above current master cylinder pressure from the driver apply. Once activated, HFC will drive all wheels into ABS. Built on a brake disc/pad temperature model, brake pressure and deceleration rate, brake pressure will be added to the already applied pressure from the driver. This increases the total brake pressure in the system and enhancing stopping distance in fading situations. The driver will experience fading brakes while using low or medium brake pedal force application. The HFC will activate only during high brake pedal force application.
Engine Drag Control (EDC)
This feature is designed to mitigate drop-throttle-oversteer. During maximum cornering while applying throttle, the vehicle could exhibit oversteer when the driver quickly releases the throttle. This feature will slowly reduce the engine torque in order to maintain vehicle stability.
Engine Torque Steer Control
Engine Torque Steer Control uses engine torque reductions to minimize torque steer. This is a pre-emptive engine torque reduction used on vehicles that exhibit excessive torque steer during large accelerator pedal inputs. This feature will also improve the Intersection maneuver (standing launch with 90 deg turn) performance.
Extended Hold Hill Start Assist (EHHSA)
Extended Hold Hill Start Assist is a feature that will hold the vehicle while on a grade, to prevent the vehicle from rolling down the hill. This feature will activate the Electronic Park Brake under driver exist scenarios.
Dynamic Braking with Electronic Park Brake
Dynamic Braking with the Electronic Park Brake (EPB) provides autonomous braking when the EPB switch is pressed when the vehicle is in motion. With the use of this feature, if the EPB switch is pressed while the vehicle is moving, the EBCM will apply braking at all 4 corners until the vehicle is stopped, then the EPB will apply and EBCM will release pressure
Reduced Boost Ratio During ABS (RBR)
On brake by wire systems, it is possible to reduce the amount of pressure applied by the system upstream of the wheel valves to improve ABS wheel control on low mu surfaces. This in essence reduces the amount of driver applied pressure when low mu ABS is detected. The overall goal of this feature is to improve ABS feel.
EV Powerhop and Powertrain Mount Control
Powerhop is defined as an oscillation of the driven wheels due to acceleration on high coefficient surfaces. This wheel oscillation causes the vehicle to bounce resulting in driver discomfort, failure of driveline components and potentially other damage to the vehicle. Powertrain Mount Resonance is also related to wheel oscillation. With the TCS feature "ON", power hop shall be detected using wheel speed sensor signals. With the TCS feature "OFF", the EBCM and ECM shall be required to mitigate power hop. If the vehicle is exhibiting this signature, the traction control system will attenuate powerhop by reducing engine torque and applying brake pressure.