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DISTRONIC Plus, Function - GF30.30-P-3300RF

Model 205 

up to model year 2019 

with code 239 (Active Distance Assist DISTRONIC) 

Model 253 (except 253.99) 

up to model year 2020 

with code 239 (Active Distance Assist DISTRONIC) 

G14185358Courtesy of MERCEDES-BENZ USA

Function requirements, general 

DISTRONIC PLUS, general 

Depending on the driver's requirements, DISTRONIC PLUS automatically controls the speed and distance to the vehicle directly ahead in a vehicle speed range of v = 0 to 200 km/h and v = 200 to 0 km/h. The control is realized via the DISTRONIC electric controller unit.

The DISTRONIC PLUS is extended by the function Collision Prevention Assist PLUS. It includes the following functions: distance warning, adaptive brake assist and autonomous partial braking (vehicle speed up to v = 200 km/h). If the driver does not react to the warning tones in an accident-critical situation, the DISTRONIC electric controller unit initiates an autonomous partial braking.

IMPORTANT If the DISTRONIC PLUS is switched off, the situation directly in front of the vehicle is still detected and evaluated. In dangerous situations warnings are given, as described above, or there is autonomous braking.

The adaptive Cruise Control electric controller unit actively intervenes in the engine management, the transmission control and controlling of the brake system to implement the DISTRONIC PLUS.

The following subfunctions of DISTRONIC PLUS are described in a separate document:

The following graphic represents the mode of function of the DISTRONIC PLUS:

G14185359Courtesy of MERCEDES-BENZ USA

Detection range of DISTRONIC electric controller unit, shown on model 205.0 

Design of the Cruise Control lever 

G14185360Courtesy of MERCEDES-BENZ USA

If the LED SPEEDTRONIC (except code 494 (USA version)) lights up, the DISTRONIC PLUS is deactivated and the function variable SPEEDTRONIC programmed. The steering column tube module control unit actuates the SPEEDTRONIC LED directly.

IMPORTANT Whenever the Cruise Control lever is operated, the distance to the vehicle driving immediately ahead is displayed in the multifunction display for t = 5 s. Through selection of the operating level "DISTRONIC PLUS" in the menu "Assistance" the distance graphic is shown permanently. Display of the distance graphic can be switched on or off independently of the activity of the automatic distance control.

The distance to the vehicle directly ahead can be set via the DISTRONIC controller in seven increments between approx. t = 1.0 and 2.0 s.

DISTRONIC electric controller unit evaluates the following input factors: 

The DISTRONIC PLUS is switched on over the CC lever:

The steering column tube module control unit reads in the switch position of the CC lever directly and sends it to the DISTRONIC electric controller unit via the chassis FlexRay.

Operating condition for engine/drivetrain:

The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drivetrain operational" signal via the drive train CAN, powertrain control unit and chassis FlexRay to the DISTRONIC electric controller unit.

Parking brake status:

The Electronic Stability Program control unit sends the status of the parking brake (applied or released) over the chassis FlexRay to the DISTRONIC electric controller unit.

Engaged gear range:

Information on the engaged gear range is sent by the fully integrated transmission control unit via the drive train CAN, powertrain control unit and the chassis FlexRay to the DISTRONIC electric controller unit.

Driver request via the Cruise Control lever:

The driver request over the CC lever are directly read in by the steering column tube module control unit. The steering column tube module control unit sends the Cruise Control lever's control signals over the chassis FlexRay to the DISTRONIC electric controller unit.

Vehicle speed/acceleration:

The vehicle speed is calculated from the wheel speed. The acceleration is defined over the increase in rotational speed. The Electronic Stability Program control unit sends the wheel speed signals over the chassis FlexRay to the DISTRONIC electric controller unit.

Object recognition:

The DISTRONIC electric controller unit monitors the traffic area in front of the vehicle up to a distance of s = 200 m in a corridor of ∠ = 12°.

Engine drive torque:

Information about the currently available engine torque is sent by the CDI control unit or the ME-SFI [ME] control unit via the drive train CAN, powertrain control unit and the chassis FlexRay to the Electronic Stability Program control unit which then evaluates this accordingly and sends it over the chassis FlexRay to the DISTRONIC electric controller unit.

Braking torque:

Information on the currently applied braking torque is sent by the Electronic Stability Program control unit over the chassis FlexRay to the DISTRONIC electric controller unit.

Acceleration/yaw rate:

The acceleration/yaw rate is detected by the acceleration sensor integrated into the Supplemental Restraint System control unit. The Supplemental Restraint System control unit sends the corresponding values over the vehicle dynamics CAN, Electronic Stability Program control unit and the chassis FlexRay to the DISTRONIC electric controller unit.

IMPORTANT For reasons of safety and comfort the maximum (positive) acceleration of the automatic distance control is limited to approx. a = 2.5 m/s2. It operates antiproportional to the vehicle speed, which means that the positive and negative accelerations reduce with increasing speed.

Wheel angle

The Electronic Stability Program control unit calculates the wheel angle based on the position of both front wheels and transmits appropriate information via the chassis FlexRay to the DISTRONIC electric controller unit.

Driver request to overtake (sets the turn signals on the combination switch)

The steering column tube module control unit reads in the switch position of the combination switch directly and sends it to the DISTRONIC electric controller unit via the chassis FlexRay.

Brake pedal position:

The Electronic Stability Program control unit sends the status of the brake pedal over the chassis FlexRay to the DISTRONIC electric controller unit.

Accelerator pedal position:

The CDI control unit or the ME-SFI [ME] control unit sends information on the accelerator pedal position over the drive train CAN, powertrain control unit and the chassis FlexRay to the DISTRONIC electric controller unit.

The DISTRONIC electric controller unit issues the following initial 

parameters (requests): 

Raise/reduce engine torque:

The DISTRONIC electric controller unit sends the "Increase engine torque" or "Reduce engine torque" request over the chassis FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit processes this request and further driving dynamics requests and sends them according to their relevance over the chassis FlexRay, powertrain control unit and engine CAN to the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit implements this request.

Engage targeted gear (downshift or upshift):

The DISTRONIC electric controller unit sends the "Engage targeted gear" request over the chassis FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit processes this request as well as further driving dynamics requests and transmits it according to its relevance via the suspension FlexRay, powertrain control unit and drive train CAN to the fully integrated transmission control unit. This request is to be understood as a shift recommendation. Downshifting or upshifting of the A/T takes place autonomously itself by the fully integrated transmission control unit, dependent on the current operating condition.

Object information:

The DISTRONIC electric controller unit transmits object information (e. g. the distance from and speed differential to the target vehicle and the movement status of the target vehicle) via the suspension FlexRay, powertrain control unit and engine CAN to the CDI control unit or the ME-SFI [ME] control unit.

Raise/reduce braking torque:

The DISTRONIC electric controller unit sends the "Increase braking torque" or "Reduce braking torque" request over the chassis FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit reacts by directly actuating the traction system hydraulic unit, which reacts by increasing or decreasing the braking torque according to the brake torque.

IMPORTANT

Model 205.012/047/147/212/247 up to model year 2019 with code 239 (Active Distance Assist DISTRONIC)

Model 253.354/954 up to model year 2020 with code 239 (Active Distance Assist DISTRONIC)

The Electronic Stability Program control unit decides in relation to additional variables such as the current charge level of the high voltage on-board electrical system whether and to what intensity the deceleration occurs through regenerative braking or through the service brake.

Emit warning tones, system or warning messages

The DISTRONIC electric controller unit sends the requests to output acoustic warnings, display system or warning messages request via the chassis FlexRay, the electronic ignition lock control unit and user interface CAN to the instrument cluster. The respective system or warning message is issued over the multifunction display and the actuates the IC speaker directly.

Function sequence for DISTRONIC PLUS 

The description of the DISTRONIC PLUS function takes place, as an example, in the following chronological sequence:

The sequence can vary depending on the driver requests and the current traffic situation.

Activate DISTRONIC PLUS and drive off automatically 

The following options are available for activating DISTRONIC PLUS:

The vehicle moves off and adapts its speed to the maximum speed of the vehicle immediately ahead up to the selected target speed. If there is no vehicle immediately ahead, the DISTRONIC PLUS functions like the CC.

IMPORTANT For vehicles at a standstill a specified distance limit exists beyond which a stationary vehicle is no longer displayed.

Technical implementation 

The DISTRONIC electric controller unit receives or sends the following information or requests for this:

Input factors:

Initial parameters:

Automatic distance control 

The automatic distance control can be activated while driving (v < 20 km/h) only if a vehicle directly ahead has been detected. If the vehicle driving immediately ahead brakes or accelerates, the DISTRONIC PLUS can initiate the following measures for deceleration or acceleration of the vehicle:

The brake application takes place by means of hydraulic pressure controlling in the wheel brake cylinder by the traction system hydraulic unit according to the current vehicle status. To do this the Electronic Stability Program control unit assesses various variables such as the required braking torque.

IMPORTANT

Model 205.012/047/147/212/247 up to model year 2019 with code 239 (Active Distance Assist DISTRONIC)

Model 253.354/954 up to model year 2020 with code 239 (Active Distance Assist DISTRONIC)

The kinetic energy is converted within defined limits into electrical energy (regenerative braking). If the requested braking torque exceeds the deceleration through recuperation (for example in a case of a emergency braking), the Electronic Stability Program control unit additionally actuates the traction system hydraulic unit and therefore the service brake.

In order to prevent a possible collision, the driver must fully depress the brake pedal if it is apparent to him that the initiated measures are insufficient.

If the vehicle driving immediately ahead accelerates again, the engine torque is increased and the vehicle also accelerates. The increase in engine torque is dependent on the ascent or the descent involved, among other things.

The driver furthermore has the option of operating the accelerator pedal to accelerate the vehicle (e. g. when overtaking). The multifunction display shows the "DISTRONIC passive" message. 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 and the "DISTRONIC passive" message goes off.

IMPORTANT The automatic distance control is also active if the acceleration request from the driver is lower than the automatic distance control request.

IMPORTANT If the vehicle driving directly ahead leaves the detection range of the DISTRONIC electric controller unit, the automatic distance control is deactivated at v < 20 km/h.

Technical implementation 

The DISTRONIC electric controller unit receives or sends the following information or requests for this:

Input factors:

Initial parameters:

Change of driving lane (overtaking) 

For an overtaking maneuver above a speed of v = 60 km/h, the vehicle is also automatically accelerated. To do this the driver must initiate the overtaking maneuver by setting the turn signal. If automatic distance control is activated, the DISTRONIC electric controller unit detects that the driver intends to overtake and accelerates the vehicle, taking into account the distance to the vehicle in front.

When approaching a slowly moving vehicle and therefore an active automatic intervention by the brake system, this is then canceled insofar as the driver initiates the overtaking procedure by operating the turn signal. If required, the vehicle is additionally accelerated.

After the overtaking maneuver the vehicle accelerates to the set speed (automatic speed control), insofar as no other vehicle driving in front was 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:

Technical implementation 

The DISTRONIC electric controller unit receives or sends the following information or requests for this:

Input factors:

Initial parameters:

Automatic speed control 

If the vehicle is in active distance control and the vehicle driving immediately ahead accelerates above v = 200 km/h or removes itself from the detection area of the DISTRONIC electric controller unit, the automatic distance control switches over into the automatic speed control.

Technical implementation 

The DISTRONIC electric controller unit receives or sends the following information or requests for this:

Input factors:

Initial parameters:

Going back into a lane/person in the front regulation 

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 tuns onto the lane driven in this vehicle is registered as the vehicle driving immediately ahead. If the distance to the vehicle that is merging into the lane is below the preselected value, the DISTRONIC PLUS functions brakes the vehicle. If the requested braking power is not sufficient, a visual warning and warning tones are output and the driver must press the brake pedal.

DISTRONIC PLUS is thereby deactivated. The driver is signaled concerning this process through output of a message "DISTRONIC PLUS OFF" in the multifunction display of the IC. The driver can subsequently reactivate the DISTRONIC PLUS.

Technical implementation 

The DISTRONIC electric controller unit receives or sends the following information or requests for this:

Input factors:

Initial parameters:

Distance warning 

The DISTRONIC PLUS warns the driver visually and acoustically in the vehicle speed range of v = 7 to 250 km/h or the maximum design speed about moving obstacles in their lane. DISTRONIC PLUS differentiates here between a static (except CODE 494 (USA version)) and a collision-critical distance warning.

Static distance warning (except code 494 (USA version)):

Output of the static distance warning takes place purely optically.

If the distance to the vehicle ahead in moving traffic falls below t = 0.8 s and remains for t > 3 s at this critical distance (e. g. at a speed of v = 100 km/h, distance approx. s = 22.2 m), the DISTRONIC electric controller unit transmits a request to issue a warning to the instrument cluster via the suspension FlexRay, electronic ignition lock control unit and user interface CAN. The instrument cluster reacts by actuating the DISTRONIC warning lamp.

Collision critical distance warning:

Output of the collision-critical distance warning takes place optically and acoustically.

If an obstacle in the detection range of the DISTRONIC electric controller unit is classified as accident-critical (collision within t < 2.6 s), the DISTRONIC electric controller unit transmits a request to issue a warning via the suspension FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster, which then activates the DISTRONIC warning light and directly actuates the instrument cluster speaker (intermittent tone).

Take-back of the warning only occurs if the situation has been defused.

In the case of stationary obstacles, a warning is only output in the vehicle speed range between v > 7 to approx. 70 km/h.

Optical warning messages in instrument cluster 

G14185361Courtesy of MERCEDES-BENZ USA

This is shown inversely on the multifunction display, i. e. the distance warning readiness indicator is hidden when the distance warning function is active. If the distance warning function is deactivated, the distance warning readiness indicator and the "OFF" lettering are shown.

IMPORTANT The distance warning is basically active for an active DISTRONIC PLUS. If DISTRONIC PLUS is deactivated, Collision Prevention Assist Plus, which also contains a distance warning system, can be separately activated in the "Collision Prevention Assist Plus" menu on the instrument cluster.

Adaptive Brake Assist 

If the driver reacts in a critical situation with emergency braking, he is supported by the Adaptive BAS. The DISTRONIC electric controller unit calculates the necessary brake force boosting in order to avoid any collision or to at least mitigate its consequences. Adaptive Brake Assist supports the driver in a vehicle speed range between v = 7 to 250 km/h for a maximum full-stop braking to vehicles in front and in a vehicle speed range between v = 7 to approx. 70 km/h to stationary obstacles.

IMPORTANT The emergency braking is defined over the actuation speed and the actuation strength with which the brake pedal is actuated.

The DISTRONIC electric controller unit takes the current distance and the closing speed to the obstacle into account to permanently calculate the required brake force. If there is no actuation or the intensity of actuation of the brake pedal by the driver considerably decreases, the brake boost on the driver braking is reduced and the Adaptive Brake Assist System is also deactivated. The Brake Assist System will also be deactivated if the driver presses the accelerator pedal.

Additional function requirements for autonomous partial braking 

Autonomous partial braking 

If the driver fails to react in an accident-critical situation to the warning, the DISTRONIC electric controller unit initiates autonomous partial braking and reduction in engine torque. The DISTRONIC electric controller unit calculates the braking torque required (maximum deceleration approx. a = 6 m/s2) under consideration of the following variables:

The DISTRONIC electric controller unit sends the appropriate request to increase the braking torque and it reduce the engine torque via the chassis FlexRay to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates the incoming requests, actuates the traction system hydraulic unit directly, and sends the request to reduce engine torque via the chassis FlexRay, powertrain control unit and the drive train CAN to the CDI control unit or the ME-SFI [ME] control unit.

To make the best possible use of the braking distance to the obstacle, the driver is supported by the adaptive Brake Assist if he reacts to the autonomous partial braking and brakes.

IMPORTANT If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system.

Automated Stop Vehicle 

For an active DISTRONIC PLUS the vehicle will follow the vehicle driving immediately ahead to standstill. Deceleration here takes place through regenerative braking (model 205.012/047/147/212/247, 253.954) or through the service brake. The service brake also secures a stationary vehicle against rolling away.

After a defined time period the electric parking brake is also activated (standstill control safety strategy).

IMPORTANT Securing the vehicle using the DISTRONIC PLUS function (standstill control) does not replace securing the vehicle for parking.

Technical implementation 

The DISTRONIC electric controller unit receives or sends the following information or requests for this:

Input factors:

Initial parameters:

The following traffic situations show the limits of DISTRONIC PLUS:

Obstacles and stationary vehicles 

G14185362Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS does not brake for obstacles or stationary vehicles which were not previously registered 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 

G14185363Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS 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 

G14185364Courtesy of MERCEDES-BENZ USA

DISTRONIC PLUS 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 

G14185365Courtesy of MERCEDES-BENZ USA

DISTRONIC PLUS may not be able to detect vehicles driving displaced to one side. The distance to the vehicle in front becomes too small.

Lane change by other vehicles 

G14185366Courtesy of MERCEDES-BENZ USA

The DISTRONIC PLUS does not yet detect the vehicle moving into the lane. The distance to the vehicle moving into the lane becomes too small.

Narrow vehicles 

G14185367Courtesy of MERCEDES-BENZ USA

DISTRONIC PLUS does not detect the vehicle in front at the edge of the carriageway because of its narrow width. The distance to the vehicle in front becomes too small.

  Electrical function schematic for DISTRONIC PLUS   PE30.30-P-2053-97FBA 
  Overview of system components for driver assistance systems   GF54.00-P-9998RF
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