Part 2
GF30.30-P-0006CE DISTRONIC PLUS Incl. BAS PLUS and PRE-SAFE Brake, Function
MODEL 204.0 /2
- with CODE (233) Distronic Plus
- as of model year 2012
/YoM 11 facelift
MODEL 204.3
- with CODE (233) Distronic Plus
Continued -
View of the multifunction display for an activated DISTRONIC PLUS and vehicle immediately ahead
D Speed of vehicle immediately ahead
E Own speed
F Target speed
G Vehicle moving immediately ahead (target object)
H Own vehicle
I Target distance (white line)
If the vehicle driving immediately ahead moves off, the driver can press the accelerator pedal or alternatively actuate the switch "Resume from memory" to confirm the automatic drive off function. The brake pedal must not be pressed during this time.
Operation of the accelerator pedal is registered by the accelerator pedal sensor. The CDI control unit or ME-SFI [ME] control unit directly reads in signals from the accelerator pedal sensor. The CDI control unit or the ME-SFI [ME] control unit transmits these signals via the chassis CAN to the video and radar sensor system control unit. Actuation of the brake pedal is detected by the brake lights switch. The Electronic Stability Program control unit directly reads in the status of the brake lights switch and transmits these via the chassis CAN to the video and radar sensor system control unit.
The vehicle will subsequently start off itself, accelerates and follows the vehicle driving immediately ahead at the programmed distance up to the maximum for the set maximum speed.
The maximum positive acceleration of the automatic distance control is detected by the yaw rate sensor for lateral and longitudinal acceleration sensor and is limited on safety and comfort grounds to about a = 2.5 m/s 2. The yaw rate sensor for lateral and longitudinal acceleration sensor transmits the information for acceleration via the dynamics CAN, Electronic Stability Program control unit and chassis CAN to the video and radar sensor system control unit.
Furthermore the acceleration of the vehicle is detected from the increase in the speed of revolution of the wheels. To do this the Electronic Stability Program control unit directly reads in signals from the following components and transmits these via the chassis CAN to the video and radar sensor system control unit:
- Left front axle rpm sensor
- Right front axle rpm sensor
- Left rear axle rpm sensor
- Right rear axle rpm sensor
The maximum positive acceleration requested for automatic distance control is antiproportional to the vehicle speed which means that limitation of the positive and negative accelerations reduces with increasing speed.
The automatic distance control can only be activated while driving if a vehicle driving immediately ahead was detected by the radar sensor system.
If the vehicle driving immediately ahead brakes, the DISTRONIC PLUS function can instigate the following measures for deceleration of the vehicle:
- Reducing the engine torque
- Shifting down the A/T
- Active braking
Reducing the engine torque
To do this the video and radar sensor system control unit transmits an appropriate request to reduce the engine torque via the chassis CAN to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates this request as well as vehicle dynamic requests internally and passes it on according to its relevance via the chassis CAN to the CDI control unit or ME-SFI [ME] control unit. The CDI control unit or the MESFI [ME] control unit implements this request.
Shifting down the A/T
To do this the video and radar sensor system control unit transmits an appropriate request via chassis CAN to the ESP control unit.
The Electronic Stability Program control unit evaluates this request as well as further driving dynamics requests internally and passes them on according to their relevance via chassis CAN to the CDI control unit or to the ME-SFI [ME] control unit and the drive train CAN to the transmission control unit. This request is, however, to be understood as a switching recommendation.
The shift down of the A/T takes place autonomously by the A/T itself, dependent on the current operating condition.
Active braking
To do this the video and radar sensor system control unit transmits an appropriate request via chassis CAN to the ESP control unit. The Electronic Stability Program control unit reacts by actuating the traction system hydraulic unit directly; the vehicle is braked.
If the driver sees that the instigated measures are not adequate he must press on the brake pedal to avoid any possible collision.
If the vehicle driving immediately ahead accelerates again, the engine torque is increased and the vehicle also accelerates.
The CDI control unit or the ME-SFI [ME] control unit transmits permanent information about the available torque via the chassis CAN to the video and radar sensor system control unit. The video and radar sensor system control unit evaluates this information and transmit an appropriate request to increase the engine torque via the chassis CAN to the Electronic Stability Program control unit.
The Electronic Stability Program control unit evaluates this request as well as vehicle dynamic requests internally and passes it on according to its relevance via the chassis CAN to the CDI control unit or ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit implements this request.
The driver also has the option to accelerate the vehicle manually using the accelerator pedal (e.g. to overtake a vehicle). The automatic acceleration is put out of action for as long a the driver uses the accelerator pedal. This process is visually displayed in the multifunction display with the message "DISTRONIC passive".
If the automatic distance control requires a higher acceleration than the driver prescribes, the driver request is overlaid by the request for automatic distance control
For overtaking above a speed of v = 60 km/h (45 mph) the vehicle is also accelerated automatically. To this the driver must initiate the overtaking maneuver by setting the flasher.
To do this the steering column tube module control unit reads on the status of the combination switch directly and transmits this via the chassis CAN to the video and radar sensor system control
In as far as the automatic distance control is activated, the video and radar sensor system control unit recognizes the intention of the driver to overtake and accelerates the vehicle while taking account of the distance to the vehicle driving immediately ahead.
The vehicle then accelerates up to set maximum speed (automatic speed control) after the overtaking maneuver in as far as there was no vehicle driving immediately ahead detected as a target object.
If a vehicle driving immediately ahead is subsequently detected as a target object the automatic speed control function changes over again into the automatic distance control function.
The overtaking maneuver is broken off in the following situations:
- Risk of collision with the current target object
- Risk of a collision with a vehicle which is in the left blind spot, detected by the Active Blind Spot Assist function
If the vehicle is in active distance control and the vehicle driving immediately ahead accelerates above v = 200 km/h (v = 120 mph) or removes itself from the detection area of the radar sensor system, the automatic distance control function switches over into the automatic speed control function.
If the vehicle driving immediately ahead turns off and there is another vehicle in front, the system only switches over to the new target vehicle if it is moving. The system does not operate for stationary objects unless a preceding vehicle is tracked to a standstill.
If while driving a vehicle turns in front within the safe distance to the vehicle driving immediately ahead, the distance to this new vehicle is regulated.
If the vehicle is in automatic speed control and a vehicle turns onto the lane driven in this vehicle is registered as the vehicle driving immediately ahead.
If the distance to the moving in vehicle is below the value which was programmed, the DISTRONIC PLUS function brakes the vehicle. The negative acceleration (deceleration) over the traction system hydraulic unit is limited to 40% (about a = 4 m/s 2) of the maximum possible brake power. If the requested brake power is not adequate the driver must press the brake pedal.
DISTRONIC PLUS function is thereby deactivated.
This process is signaled to the driver by outputting of a notification tone over the warning buzzer and indication of a message in the multifunction display.
To do this the video and radar sensor system control unit respectively transmits a request for actuation of the warning buzzer and the multifunction display via the chassis CAN to the IC.
The driver can subsequently reactivate the DISTRONIC PLUS function.
For an active DISTRONIC PLUS function the vehicle will follow the vehicle driving immediately ahead to standstill. The service brake is activated if the vehicle is stationary.
The vehicle is therefore secured against rolling away.
Securing the vehicle using the DISTRONIC PLUS function does not replace securing the vehicle for parking.
The following traffic situations show the limits of the DISTRONIC PLUS function.
Obstacles and stationary vehicles
The DISTRONIC PLUS function does not brake for obstacles or stationary vehicles which were not previously detected as the target object.
If, for example, the detected vehicle turns off and there is an obstacle or stationary vehicles behind it, no automatic intervention by the brake system occurs.
Curves, curved entrances and exits:
The DISTRONIC PLUS function can only provides limited detection of vehicles in curves. One's own vehicle can then brake unexpectedly or late.
Vehicles moving across in front of one's own vehicle:
The DISTRONIC PLUS function may detect vehicles in cross traffic by mistake. For an activated distance control the vehicle can start off unintended, (e g. at a traffic light with cross-traffic).
Offset driving style
The DISTRONIC PLUS function may not be able to detect displaced vehicles driving ahead. The distance to the vehicle in front becomes too small.
Lane change of other vehicles :
The DISTRONIC PLUS function does not detect the vehicle moving into the lane in time. The distance to the vehicle moving into the lane becomes too small.
Narrow vehicles:
The DISTRONIC PLUS function does not detect the vehicle in front at the edge of the road in time because it is (too) narrow. The distance to the vehicle in front becomes too small.
Furthermore, the DISTRONIC PLUS function uses navigation data to adapt the system behavior to the following situations:
- Entrance of the vehicle to and passage around a roundabout
- Entrance lane to a T intersection
- Driving on a freeway exit lane
This means that if the vehicle driving immediately ahead leaves the detection area of the radar sensor system in one of the above-mentioned traffic situations then the current speed is maintained:
- about t = 10 s before a roundabout or a T intersection
- about t = 12 s before a freeway exit lane and about t = 4 s after a freeway exit lane
If no vehicle driving immediately ahead is detected afterwards, the vehicle accelerates or decelerates to the set specified speed.
Since traffic situations are subject to alteration, the digital map data has to be regularly updated.
Function sequence for PRE-SAFE brake and BAS PLUS
The PRE-SAFE brake assesses the traffic situation in front of the vehicle.
In hazard situations within the following speed ranges, the vehicle is decelerated automatically by the PRE-SAFE brake or the emergency braking maneuver by the driver is supported by the BAS PLUS system:
- Vehicle speed range for the PRE-SAFE brake: v = 7 to 200 km/h (5 to 120 mph).
- Vehicle speed range for BAS PLUS: v = 7 to 250 km/h (5 to 150 mph).
In the case of stationary obstacles the function PRE-SAFE brake or the function BAS PLUS is only activated if the vehicle's own vehicle speed is a maximum of v = 72 km/h (v = 45 mph).
If a stationary object is detected in the lane by both the short and long range radar sensor systems (the lane is determined, amongst other things, by the steering angle and vehicle speed, etc.), the PRE-SAFE brake function and the BAS PLUS function are activated.
The steering angle is recorded by the steering angle sensor.
The steering column tube module control unit reads in the signals from the steering angle sensor and transmits this via the chassis CAN to the video and radar sensor system control unit
The PRE-SAFE brake function also includes a proximity warning system to warn the driver of moving or stationary obstacles in his lane.
The distance warning takes place in a vehicle speed range of v = 7 up to 250 km/h (v = 5 up to 150 mph).In this case differentiation is made between a static distance warning and a collision critical distance warning.
Static distance warning:
The static distance warning is triggered if the time interval between the system vehicle and vehicle driving immediately ahead is less than t = 0.8 s (e.g. in moving traffic). The DISTRONIC warning lamp lights up in the IC.
To do this the video and radar sensor system control unit transmits an appropriate request for actuation of the DISTRONIC warning lamp via the chassis CAN to the IC.
Collision critical distance warning:
If a moving obstacle within the detection range of the radar sensor system is classified as accident-critical (a collision will occur within t less than 2.6 s), the DISTRONIC warning lamp lights and the warning buzzer issues an intermittent tone.
The warning output is automatically switched off again when the situation is no longer critical and cannot be acknowledged during an active control.
To do this the video and radar sensor system control unit transmits an appropriate request for actuation of the warning buzzer via the chassis CAN to the IC.
The proximity warning system can be separately and independently activated by the automatic distance control in the menu "PRE-SAFE brake" of the instrument cluster
The distance warning is always active for an active DISTRONIC PLUS function. If the function DISTRONIC PLUS is deactivated, actuation of the DISTRONIC warning lamp takes place by the function PRE-SAFE brake
Visual warning message in instrument cluster when a safe distance is not maintained
A1e59 DISTRONIC warning lamp
J Distance warning readiness indicator
If the driver does not react to the warning signals, the DISTRONIC PLUS function initiates partial braking. To do this the video and radar sensor system control unit calculates the required braking torque while taking account of the driving dynamics input factors.
To do this the video and radar sensor system control unit transmits an appropriate request via chassis CAN to the ESP control unit. The Electronic Stability Program control unit reacts by actuating the traction system hydraulic unit directly; the vehicle is braked.
The vehicle is braked according to this request.
If the driver then reacts with an emergency braking maneuver, the BAS PLUS function provides support for optimum utilization of the braking distance to the obstacle The hazard braking is defined over the actuation speed and the actuation strength with which the brake pedal is actuated.
To do this the video and radar sensor system control unit also uses the data from the radar sensor system and also calculates the necessary brake servo assistance while taking account of the distance and the closing speed to the obstacle. At the same time, to do this, the PRE-SAFE function implemented in the Electronic Stability Program control unit evaluates the To do this the video and radar sensor system control unit current requested braking torque.
If there is no actuation or the intensity of actuation of the brake pedal by the driver reduces, the brake servo assistance is reduced to the driver braking level and the BAS PLUS function is deactivated. The function BAS PLUS will also be deactivated if the driver presses on the accelerator pedal. If the driver does not react to the partial braking and if the video and radar sensor system control unit calculates that the collision with the obstacle is unavoidable, the video and radar sensor system control unit instigates emergency braking for t = 1 s and thus reduces the possible consequences of an accident.
Emergency braking is not triggered if the front passenger seat is occupied and the front passenger is not strapped in.
