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DISTRONIC, function - GF30.30-P-3200GV

MODEL 164.1/8, 251.0/1 as of model year 2009 with CODE 219 (Distronic (DTR)) 

Fig 1: DISTRONIC - Function Diagram
G10116094Courtesy of MERCEDES-BENZ USA

Function requirements, general 

DISTRONIC in general 

The DISTRONIC regulates the target speed and the specified distance to the vehicle immediately ahead, according to specification by the driver, in the range 30 to 180 km/h (up to 30.06.09) or from v = 0 to 200 km/h (as of 1.7.09).

Furthermore there is an AWF contained which advises the driver about a clearance which is too small to the vehicle immediately ahead and warns against possible collisions with vehicles (for example collision) or stationary obstacles on is driving lane, optically and acoustic.

If the driver reacts to the acoustic warning and brakes, he will be assisted in this by the Brake Assist. The required brake servo assistance for this will be calculated according to the situation. A possible collision can be prevented or at least its consequences can be mitigated. The DTR controller unit actively intervenes in the engine timing to implement the DISTRONIC, in the transmission control and control of the brake system.

The following subfunctions in the DISTRONIC are described in the separate partial function "Cruise control (CC) Function" description:

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

Fig 2: Identifying DISTRONIC Radar Beam Patterns
G10116095Courtesy of MERCEDES-BENZ USA

DISTRONIC in operation (as of YoM 09 facelift) 

CC [TPM] push button, vehicles without code (494) USA version 

Fig 3: Identifying Adjustment Position Of CC(TPM) Push Button On Vehicles Without Code (494)
G10116096Courtesy of MERCEDES-BENZ USA

CC [TPM] push button, vehicles with code (494) USA version 

Fig 4: Identifying Adjustment Position Of CC(TPM) Push Button On Vehicles With Code (494)
G10116097Courtesy of MERCEDES-BENZ USA

IMPORTANT If the SPEEDTRONIC LED (without code (494) USA version) lights up, DISTRONIC is deactivated and the SPEEDTRONIC variable function (without Code (494) USA version) is preselected. The steering column tube module actuates the yellow LED, variable speed limiter directly.

IMPORTANT For every operation of the CC push button, the distance to the vehicle immediately ahead is displayed for t = 5 s in the multifunction display. Through selection of the operating level "DISTRONIC" 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 driving immediately ahead can be set over the DTR distance potentiometer in seven stages between about. t = 1.0 and 2.0 s. If a distance of t = 2.0 s is set for example, the vehicle driving immediately ahead will be followed at a temporal distance of t = 2.0 s. This physical gap increases with increasing speed.

The DTR controller unit evaluates the following input factors: 

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 engine compartment CAN, ESP control unit and vehicle dynamics CAN to the DTR controller unit.

Parking brake status

The SAM control unit at the front detects the status of the parking brake indicator switch directly and transmits the status of the parking brake via the engine compartment CAN, ESP control unit and vehicle dynamics CAN to the DTR controller unit.

Engaged gear range/stage:

Information on the engaged gear range and the stage is sent by the fully integrated transmission control unit via the engine compartment CAN, ESP control unit and vehicle dynamics CAN to the DTR controller unit. Driver request over the CC [TPM] push button

The steering column tube module reads in the driver's request directly over the TPM push button. The steering column tube module transmits the control signals of the TPM push button via the engine compartment CAN, ESP control unit and vehicle dynamics CAN to the DTR controller unit.

Vehicle speed/acceleration:

The vehicle speed is calculated on the basis of the wheel speeds. The acceleration is defined over the increase in rotational speed. The ESP control unit transmits the wheel speed signals via the vehicle dynamics CAN to the DTR controller unit.

Object recognition:

The DTR controller unit monitors the traffic in front of the vehicle up to a distance of s = 200 m in a corridor of ∠ = 18°.

Engine drive torque:

The CDI control unit or the ME-SFI control unit sends information about the currently available engine torque via the engine compartment CAN to the ESP control unit, which evaluates these appropriately and transmits this via the dynamics CAN to the DTR controller unit.

Braking torque:

Information about the currently applied braking torque transmits the ESP control unit via the dynamics CAN to the DTR controller unit.

Acceleration/yaw rate:

The acceleration/yaw rate is detected by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration transmit appropriate values via the dynamics CAN to the DTR controller unit.

IMPORTANT On safety and comfort grounds the maximum (positive) acceleration of the automatic distance control is limited to about a = 1 m/s2 (up to 30.6.09) or to about. a = 2.5 m/s2 (as of 1.7.09). It is dependent on the selected transmission mode and it responds anti-proportional to the vehicle speed. This means that smaller accelerations are permitted for an increasing vehicle speed.

Steering wheel angle:

The steering wheel angle is recorded by the steering angle sensor. The steering column tube module directly reads the signals of the steering angle sensor and transmits information about the steering wheel angle via the engine compartment CAN, ESP control unit and vehicle dynamics CAN to the DTR controller unit.

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

The steering column tube module control unit directly reads in the switch position of the combination switch and sends it via the engine compartment CAN, ESP control unit and dynamics CAN to the DISTRONIC controller unit.

Brake pedal position:

The ESP control unit transmits the status of the brake pedal via the dynamics CAN to the DTR controller unit.

Accelerator pedal position:

The CDI control unit or the ME-SFI [ME] control unit sends information on the accelerator pedal position via the engine conmpartment CAN, ESP control unit and dynamics CAN to the DTR controller unit.

The DTR controller unit outputs the following initial parameters (requests): 

Raise/reduce engine torque:

The DTR controller unit transmits the request "Raise engine torque" or "Reduce the engine torque" via the dynamics CAN to the ESP control unit. The Electronic Stability Program control unit processes this request as well as further driving dynamic requests and transmits them, according to the relevance, via the engine compartment-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 DTR controller unit transmits the request "Engage targeted gear" via the dynamics CAN to the ESP control unit. The Electronic Stability Program control unit processes this request as well as further driving dynamic requests and transmits them, according to their relevance, via the engine compartment CAN to the fully integrated transmission control unit (VGS). This request is to be understood as a shift recommendation.

Downshifting or upshifting of the A/T takes place autonomously by the fully integrated transmission control unit, dependent on the current operating condition.

Raise/reduce braking torque:

The DTR controller unit transmits the request "Raise braking torque" or "Reduce the braking torque" via the dynamics CAN to the ESP control unit. The Electronic Stability Program control unit reacts by directly controlling the traction system hydraulic unit which increases or decreases actuation of the braking torque.

Emit warning tones, system or warning messages

The DISTRONIC controller unit sends the requests to issue warning tones, system or warning messages via the dynamics CAN, ESP control unit and engine compartment CAN to the instrument cluster, which then issues the corresponding system or warning messages over the multifunction display and which actuates the warning buzzer directly.

Distronic function sequence 

The description of the DISTRONIC 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 and drive off automatically 

The DISTRONIC can be activated for a speed from v = 30 up to 180 km/h (up to 30.6.09) or v = 0 up to 260 km/h (as of 1.7.09). However, at speeds from v <30 km/h, it can only be activated if a vehicle driving immediately ahead is detected.

If there is a vehicle recognized immediately ahead for the activated DISTRONIC the segments between the measured speed of the vehicle immediately ahead and the set specified speed is lit up in the IC. The vehicle immediately ahead is shown in the multifunction display of the instrument cluster with the current distance from it in meters.

Technical implementation 

The DISTRONIC controller unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

View of IC, DISTRONIC activated 

Fig 5: Screen Display - DISTRONIC Activated
G10116098Courtesy of MERCEDES-BENZ USA

Automatic distance control 

The automatic distance control can only be activated while driving (v < 30 km/h (mph)) if a vehicle driving immediately ahead was detected. If the vehicle driving immediately ahead brakes or accelerates, the DISTRONIC 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.

The driver must press on the brake pedal is sees that the instigated measures are not adequate to avoid any possible collision.

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 automatic acceleration is put out of action for as long a the driver uses the accelerator pedal. 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.

IMPORTANT If the vehicle driving immediately in front leaves the detection range of the DISTRONIC controller unit, the automatic distance control is deactivated at v < 10 km/h.

Technical implementation 

The DISTRONIC controller unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

View of IC, automatic distance control 

Fig 6: Screen Display - Automatic Distance Control
G10116099Courtesy of MERCEDES-BENZ USA

Change of driving lane (overtaking) 

When overtaking above a speed of v = 70 km/h the vehicle is also automatically accelerated. To this the driver must initiate the overtaking maneuver by setting the flasher. In as far as the automatic distance control is activated, the DISTRONIC controller 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.

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 controller unit receives or transmits the following information or requests:

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 DTR controller unit, the automatic distance control switches over into automatic speed control.

IMPORTANT Detailed information on automatic speed control is available in the separate "Cruise Control (TPM) function" subfunction.

Technical implementation 

The DISTRONIC controller unit receives or transmits the following information or requests:

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 moving in vehicle is below the value which was programmed, the DISTRONIC function brakes the vehicle. If the requested brake power is not sufficient, a visual and an acoustic warning is issued, and the driver has to press the brake pedal.

IMPORTANT The negative acceleration (deceleration) about the traction system hydraulic unit is limited to 20% (about. a = 2 m/s2 ) (up to YoM 09 facelift) or to 40% (about a = 4 m/s2 ) (as of YoM 09 facelift) of the maximum possible brake power.

DISTRONIC is thereby deactivated. The driver is notified of this by the sounding of an intermittent tone over the warning buzzer and lighting up of the DTR DTR warning lamp. The driver can subsequently reactivate the DISTRONIC.

Technical implementation 

The DISTRONIC controller unit receives or transmits the following information or requests:

Input factors:

Initial parameters:

Proximity warning system 

The DISTRONIC warns the driver in the speed range of v = 30 up to 250 km/h about moving or stationary obstacles on its lane, optically and acoustically.

The driver can activate or deactivate the distance warning system of the DISTRONIC separately via a menu "Additional functions", submenu "Proximity warning device" in the instrument cluster. Thus the proximity warning system is dependent here on the function (function requirements) of the radar sensor system.

If the distance warning is activated the symbol for the distance warning lights up in the lower multifunction display of the instrument cluster. In the upper multifunction display of the instrument cluster, the driver's vehicle, the set target distance and the vehicle ahead, with its current distance, are all displayed.

If the distance from the vehicle directly ahead goes below t = 0.8 s in flowing traffic and this critical distance is maintained for t > 3 s (e.g. at a speed of v = 100 km/h, distance about s = 22.2 m), the DISTRONIC controller unit sends the request to issue the warning via the vehicle dynamics CAN, ESP control unit and engine compartment CAN to the instrument cluster. The instrument cluster reacts by actuating the DTR warning lamp and an intermittent signal.

The distance warning is triggered whenever a deceleration > a =6 m/s2 of one's own vehicle is necessary in order to avoid a collision. Distance warnings are indicated by the DTR warning lamp and an intermittent signal. The DTR controller unit transmits the request to output the warning via the vehicle dynamics CAN, ESP control unit and engine compartment CAN to the IC, which activates the DTR warning lamp and directly actuates the warning buzzer (intermittent tone).

IMPORTANT The proximity warning system does not automatically perform any control functions, such as braking the vehicle.

The target distance in the distance indicator matches the current vehicle speed without the driver having to adjust the DTR distance potentiometer.

Vehicles without code (494) USA version

As an additional function, the driver is alerted if he/she remains within a distance <0.9 s driving time from the vehicle immediately ahead for longer than 3 seconds. The DTR warning lamp remains lit until the correct distance has been reestablished. This gives the driver the opportunity of avoiding a fine (for leaving insufficient minimum distance to the vehicle in front).

View of instrument cluster, distance warning active (distance display switched on) 

Fig 7: Screen Display - Distance Warning Active (Distance Display Switched On)
G10116100Courtesy of MERCEDES-BENZ USA

Adaptive Brake Assist 

If the driver reacts in a critical situation with emergency braking, he is supported by the Adaptive BAS. The DISTRONIC controller unit calculates the necessary brake servo assistance in order to avoid any collision or at least to mitigate its consequences. The Adaptive BAS supports the driver in a vehicle speed range of v = 30 up to 250 km/h for emergency braking of the vehicles immediately ahead.

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

The DISTRONIC 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 servo assistance on the driver braking is reduced and the Adaptive Brake Assist System is deactivated. The Brake Assist System will also be deactivated if the driver presses the accelerator pedal.

Automated Stop Vehicle (as of 1.7.09) 

In a situation where the target vehicle stops, regulation continues up to a standstill and is then switched off. The driver is informed through fading out of the segment ring in the speedometer and a subsequently sounding signal tone through the DISTRONIC switching off. The set braking torque at the point in time of switching off is slowly reduced after the switching off tone.

The DISTRONIC is already deactivated in the following situations before reaching a standstill:

Deactivate DISTRONIC 

DISTRONIC is deactivated when:

The following traffic situations show the limits of the DISTRONIC:

Curves, curved entrances and exits:

The DISTRONIC can only provides limited detection of vehicles in curves. One's own vehicle can then brake unexpectedly or late.

Fig 8: Overview Of Activated Distance Control
G07300325Courtesy of MERCEDES-BENZ USA

Displaced driving style:

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

Fig 9: Overview Of Displaced Driving Style
G10050075Courtesy of MERCEDES-BENZ USA
Fig 10: Overview Of Lane Change By Other Vehicles
G10050076Courtesy of MERCEDES-BENZ USA

Lane change by other vehicles:

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

Fig 11: Overview Of Narrow Vehicles
G10050077Courtesy of MERCEDES-BENZ USA

Narrow vehicles:

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 (DTR) MODEL 164.1/8 as of model year 2009 with CODE 219 (Distronic (DTR)) PE30.30-P-2050-97MAB 
MODEL 251.0/1 as of model year 2009 with CODE 219 (Distronic (DTR)) PE30.30-P-2050-97RAB
Overview of system components for driver assistance systems   GF54.00-P-9998GV
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