Principle of Operation - Advanced Emergency Brake Assist
The radar sensor detects vehicles ahead that are moving in the same direction as the host vehicle. In the event of a collision risk, and 'Forward Alert' is on, the driver is initially alerted by a visual and audible warning signal. If the risk of collision increases after the warning, advanced EBA maybe activated. The advanced EBA prepares the brake system for rapid braking with the brakes being applied gently. If the brake pedal is depressed quickly then braking is implemented with full brake function, even if the force on the pedal is light.
The forward alert and Advanced EBA system response to an imminent rear-end collision with another moving vehicle reacts in the following order:
- Forward alert
- Collision warning - audible and visual (driver can turn this function off)
- Advanced Emergency Brake Assist
- 1st stage precharge - If a collision is judged to be credible and the driver takes no action then Advanced EBA will prepare the brake system by requesting a fixed precharge brake pressure (approximately 3 bar). Reduction of EBA activation threshold provides a faster entry to the full EBA function.
- 2nd stage precharge
- If a collision is judged to be imminent and the driver shows an intent to respond to the threat, for example; quick release of the throttle, Advanced EBA will request that the brake system applies a fixed brake pressure (approximately 10 bar).NOTE: If the accelerator pedal is already released, precharge 1 and 2 occurs simultaneously (the system moves directly to precharge level 2).
ITEM DESCRIPTION A Host vehicle B Target vehicle 1 Forward alert warning: Visual and audible warning 2 Brake support: 1st stage pre-charge (stop lamps on) Advanced EBA 3 Brake support: 2nd stage pre-charge (throttle release) Advanced EBA
EBA is designed to detect an emergency braking situation giving an automatic increase in vehicle deceleration, up to ABS levels. This quick, increase in braking deceleration assists the 'average' driver to achieve a reduced stopping distance.
Advanced EBA enhances the performance of EBA. When a critical approach to forward vehicles is detected Advanced EBA requests a pre-charge pressure to the brake system and increases the sensitivity for activation of EBA.
The graph below shows a comparison of 'normal' braking, EBA and Advanced EBA brake pressure profiles.
| ITEM | DESCRIPTION |
|---|---|
| A | Percent total brake force |
| B | Time |
| 1 | Conventional brake system without EBA |
| 2 | Conventional brake system with EBA (higher activation threshold based on low level of threat, or normal brake assist sensitivity) |
| 3 | Advanced EBA (lower activation threshold based on high level of threat and higher brake assist sensitivity) |
- The system:
- Only operates at speeds above 5 mph (7 km/h)
- Responds only to vehicles moving in the same direction as the host vehicle
- Is designed to help reduce the crash speed and damage in certain rear-end collisions only
- Is not a collision avoidance system and is not a substitute for safe and attentive driving
- Effectiveness depends on many factors, such as speed, driver input, and road conditions
- DOES NOT WARN FOR STATIONARY OR SLOW MOVING VEHICLES
- The driver should always keep a safe following distance.
- The stop lamps will always be activated on application of the service brakes including all electronic braking interventions (pre-charge, brake assist etc.).