Full Speed Range Forward Collision Warning Plus: Notes

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

1.	Refer to: ANTI-LOCK BRAKE SYSTEM (ABS) MODULE .
2.	Refer to: BODY CONTROL MODULE (BCM) .
3.	Refer to: DISPLAY SCREEN MODULE (DSM) .
4.	Refer to: DRIVER ASSISTANCE SYSTEM MODULE (DASM) .
5.	Refer to: INSTRUMENT PANEL CLUSTER (IPC) .
6.	Refer to: AMPLIFIER (AMP) IF EQUIPPED OR RADIO .

• The FCW system uses a forward looking radar to determine the range and speed of the vehicles and objects in the forward path of the host vehicle and a camera to perform object classification and to determine road lane markings which are integrated into the DASM Electronic Control Unit (ECU).
• The DASM uses the radar and camera fusion data to determine probable collisions with vehicles and objects in the forward path of the host vehicle.
• Based on the sensor fusion algorithm and vehicle dynamic data, the DASM determines a Time To Collision (TTC) between the host vehicle and any target vehicles or objects in its forward path.
• When the TTC becomes too small the FCW system provides the driver with audible and visual warning, brake prefill, a haptic warning in the form of a brake jerk, limited autonomous braking and Advanced Brake Assist (ABA) to attempt to alert the driver and to mitigate a potential frontal collision.
• At low vehicle speeds, in addition to the above mentioned functionality, the FCW system provides full autonomous braking in an attempt to mitigate a frontal collision.

The FCW system uses three levels of warnings:

• A visual warning displayed in the IPC
• An audible warning generated by the radio or amplifier system
• A haptic warning in the form of a brake jerk. A brake jerk is a brake pulse or a momentary application of the brakes

The FCW system has six customer configurations:

• FCW+ Far
• FCW+ Medium
• FCW+ Near
• FCW Far
• FCW Medium
• FCW Near

The FCW system is disabled and enabled via a soft switch located in the radio settings in the safety and driver assistance menu. When the system is disabled by the user or if the system is disabled due to a fault, the FCW OFF  icon will be displayed in the IPC.

OPERATION 

• The FCW system is only active when the status of the ignition position is ON, the transmission is in D  rive and wheel speed sensors indicate that the vehicle is moving in a forward direction.
• The system can be manually disabled and enabled by the vehicle operator using the soft switch in the radio. The default status of FCW is ON. The system state is kept in memory from one key cycle to the next. If the system is turned OFF, it will remain OFF when the vehicle is restarted. The minimum speed for FCW activation is 3 mph (5 km/h).
• The FCW+ system uses the forward looking DASM to determine the range and speed of the vehicle(s) and objects in the forward path of the host vehicle.
• The FCW+ system uses the DASM to perform object classification and to determine lane markings.
• The FCW+ system uses a sensor fusion algorithm to combine the information detected from the object detection and the lane markings to determine probable collisions with vehicles and objects in the forward path of the host vehicle. The internal camera provides the DASM with object information, lane information and the camera status. The sensor fusion algorithm and logic is contained within the DASM.
• Based on the sensor fusion algorithm and vehicle dynamic data the FCW+ System determines a TTC between the host vehicle and any target vehicles or objects in its forward path.
• The system will react on moving objects. A target is considered a moving object if it has a velocity greater than zero while the system is tracking it.
• The system will react on stopped objects. A target is considered a stopped object if it has a velocity greater than zero, then comes to a stop while the system is tracking it.
• The system will react on stationary objects. A target is considered a stationary object if it has zero velocity the entire time the system is tracking it.
• When the TTC becomes too small the FCW system issues visual, audible and haptic warning(s) to alert the driver of a probable collision.
• The first warning provided by the system will be a combined audible/visual warning to the driver. This audible/visual warning may be activated at the same time the brake prefill is performed.
• After the first warning, if the driver has not responded and the collision is still probable, the system provides a second warning. The second warning is a haptic warning in the form of a brake jerk. The DASM will request a brake jerk by transmitting a request to the ABS module. The ABS module will respond and execute the brake jerk request. The audible/visual warnings will be active during the brake jerk warning.
• After the brake jerk, if the driver still has not responded and the collision is still probable the system will activate autonomous braking. The DASM makes the deceleration requests for autonomous braking by transmitting the signals to the ABS module. The ABS module will respond to the deceleration request for autonomous braking. The audible and visual warnings will be active during the autonomous braking.
• If an ABS event is active, the DASM will continuously send an autonomous brake request while the ABS event is active. Under this condition, the ABS module will honor the autonomous brake request based on the arbitration strategy defined for multiple requests to the ABS system. Autonomous braking may be requested after, at the same time as, or without a brake jerk request, and the request must be honored by the ABS in this condition.

BRAKE PREFILL OPERATION 

• Under normal circumstances, there is space between the pads and rotors to prevent the pads from wearing out prematurely. This space between the pads and rotors increases the response time during any situation which may require emergency braking. The brake prefill prepares the system for braking by moving the pads closer to the rotor to improve braking response time.
• The brake prefill is performed by the ABS module.
• The DASM controls the activation and deactivation of the brake prefill.
• The brake prefill should cause no audible brake noise.
• The brake prefill should cause no vehicle deceleration.
• The brake lights will not be activated during a brake prefill.

ADVANCED BRAKE ASSIST OPERATION 

• The ABA feature of FCW will provide additional braking during an emergency braking event if the driver provides insufficient braking for the situation.
• The DASM will make deceleration requests for the advanced brake assist feature by transmitting request signals to the ABS module.
• ABA will be aborted when the driver completely releases the brake pedal.
• If an ABS event is active, the DASM will continuously send an ABA request while the ABS event is active. Under this condition, the ABS module will honor the ABA request based on the arbitration strategy defined for multiple requests to the ABS system.

AUTONOMOUS BRAKE REQUEST OPERATION 

• After the brake jerk, if the driver still has not responded and the collision is still probable the system will activate autonomous braking.
• The DASM will make the deceleration requests for autonomous braking by transmitting the signals to the ABS module.
• The ABS system will send a Controller Area Network-Chassis (CAN C) bus request to the BCM to activate the brake lights.

Since there are multiple modules involved in the operation of the FCW system, all faults or diagnostic trouble codes should be checked during diagnosis. The DASM integrated radar requires proper alignment. Any alignment or configuration issues may cause the system to be inoperative. If the DASM detects incorrect or compromised information, the FCW will function in a limited capacity.