Active Distance Assist DISTRONIC, Function - GF30.30-D-3315TSA

Model 907 

with code ET4 (Active Distance Assist DISTRONIC) 

Shown on model 907 

Function requirements, general 

• No undervoltage or overvoltage
• Active Distance Assist DISTRONIC must be coded correctly.
• Engine running or drive train operational.
• Parking brake not operated
• Vehicle is not in backward movement
• Electronic Stability Program (ESP®) not switched to passive mode
• No active ESP® intervention recognized (vehicle not in sliding movement)
• Active Distance Assist DISTRONIC, switched on
• Soiling and function test of DISTRONIC distance pilot control unit successfully completed:

  The DISTRONIC Distance-Pilot controller unit performs a soiling and function test to ensure proper operation after each engine start. This assumes an object is in the detection range which can be used as a reference value. If a malfunction is detected or there is no object present in the detection range of the Distance Pilot DISTRONIC controller unit, the Active Distance Assist DISTRONIC cannot be activated.

• Standstill control, enable issued (driver's door/driver belt buckle, and front passenger door closed).

Active Distance Assist DISTRONIC function in general 

The Active Distance Assist DISTRONIC regulates the speed and the distance to the vehicle immediately ahead automatically according to the specification of the driver in that it brakes when necessary accelerates again where possible. Distance and speed control is performed by the DISTRONIC distance pilot control unit. To do so, the DISTRONIC distance pilot control unit actively intervenes in engine management/the brake system. The handling characteristics of the Active Distance Assist DISTRONIC adapt automatically to the selected drive program.

In stop-and-go traffic, the Active Distance Assist DISTRONIC decelerates the vehicle automatically (up to a standstill if necessary).

Once the traffic situation allows it again, the Active Distance Assist DISTRONIC accelerates the vehicle automatically to the set specified speed and thus frees the driver from these tiring routine tasks, e.g. frequent starting off and braking in stop-and-go traffic.

If the Active Distance Assist DISTRONIC recognizes that braking is necessary (e.g. weaving in traffic, a stationary obstacle), the DISTRONIC warning lamp in the instrument cluster lights up and an intermittent warning tone sounds. Both require the driver to proceed with increased caution and to possibly also brake himself. If the driver responds to the warning tone and brakes, he will be supported in this by the Active Brake Assist. This calculates the required brake force amplification according to the situation. A threatening accident can be prevented under certain circumstances or at least one can mitigate its consequences. However, if the driver fails to respond to the warning tone, the Active Brake Assist initiates (in addition to the visual warnings and warning tones) firstly, automated partial braking and, later, maximum full-stop braking.

If the Active Distance Assist DISTRONIC is switched off, the situation in front of the vehicle continues to be monitored and evaluated. In dangerous situations warnings are given, as described above, or there is autonomous braking.

Operation 

The operation of the Active Distance Assist DISTRONIC occurs via the instrument cluster multifunction steering wheel button group. During this process, the following settings can be made:

• Activate/deactivate the Active Distance Assist DISTRONIC
• Increase or reduce speed.
• Increase or reduce specified distance to the vehicle in front.

The steering wheel electronics read in the operation signals of the instrument cluster multifunction steering wheel button group and send them to the Distance Pilot DISTRONIC controller unit via the steering wheel CAN, steering column tube module (MRM) control unit, and suspension FlexRay. In addition, the signals are sent to the instrument cluster via the EZS control unit and user interface CAN.

Automatic distance control 

If the preceding vehicle brakes or accelerates, the Active Distance

Assist DISTRONIC can initiate the following measures to decelerate or accelerate the vehicle:

• Increase/reduce engine torque.
• Increase/reduce braking torque.

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 ESP® control unit evaluates several variables, such as the required braking torque.

The driver must press on the brake pedal if he sees that the initiated measures are not sufficient to avoid a possible collision.

If the driver does not intervene, an additional brake application occurs via the Active Brake Assist.

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 maximum (positive) acceleration is dependent on the selected transmission mode. The driver can influence the acceleration behavior of the vehicle by selecting the drive program.

The driver furthermore has the option of operating the accelerator pedal to accelerate the vehicle (e. g. when overtaking). As soon as the driver actuates the accelerator pedal, no distance control occurs.

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 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 swinging-in vehicle is below the value that was preselected, the Active Distance Assist DISTRONIC decelerates 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. If the driver fails to respond, the Active Brake Assist initiates (in addition to the visual warnings and warning tones) firstly, automated partial braking, and, later, maximum full-stop braking.

The Active Distance Assist DISTRONIC is deactivated in the process.

This process is indicated to the driver through the output of an intermittent warning tone via the warning buzzer and a warning in the instrument cluster. The driver can then activate the Active Distance Assist DISTRONIC again.

Location 

The DISTRONIC Distance-Pilot controller unit is located in the middle in front of the cooler.

Task 

The DISTRONIC Distance-Pilot controller unit assesses the traffic situation ahead of the vehicle through evaluation of the data from the integral long range radar. The detected data serve to implement the following functions:

• Cruise control
• Variable limiter
• Permanent limiter
• Active Distance Assist DISTRONIC
• Distance warning
• Active Brake Assist

The DISTRONIC Distance-Pilot controller unit compares the permanent target and actual values with each other and evaluates the respective driver requirements. For the implementation of the automatic distance and speed control, the Distance Pilot DISTRONIC control unit transmits corresponding acceleration, deceleration and gearshift requests via the suspension FlexRay after the evaluation of all input factors.

This means that the DISTRONIC Distance-Pilot controller unit has the following tasks:

• Reading in input factors
• Evaluation of input factors
• Actuation of components
• Transmission of initial parameters

Reading in input factors 

The DISTRONIC Distance-Pilot controller unit receives the following input signals via chassis FlexRay, among other things:

• Operating condition for engine/drivetrain
• No undervoltage or overvoltage
• Driving stage engaged
• Parking brake status
• Engine drive torque
• Brake torque
• Acceleration/yaw rate
• Driver request via TEMPOMAT
• Driver request to overtake through setting the turn signal
• Vehicle speed/acceleration
• Steering wheel angle
• Brake pedal position
• Accelerator pedal position

Evaluation of input factors 

The input factors are evaluated by the microprocessor and the corresponding assembly parts are actuated.

Transmission of initial parameters 

The DISTRONIC Distance-Pilot controller unit sends the following initial parameters via the chassis FlexRay, among other things:

• Active Distance Assist DISTRONIC system status
• Object information
• Increase/reduce engine torque request.
• Increase/limit drive range request.
• Increase/reduce braking torque request.
• Request to emit warning tones and system or warning messages.

Structure 

The DISTRONIC Distance-Pilot controller unit contains the following assembly parts:

• Long range radar
• Control unit

Properties of the long range radar:

• Detection range:
  • s > 45 m for a detection angle of a = 45°
  • s = 45 to 200 m for a detection angle of a = 9°
• Carrier frequency: 77 GHz (in accordance with the "Pulse Doppler Principle" for independent measurement of distance and speed)

The Distance Pilot DISTRONIC controller unit must be newly adjusted after exchange (e.g. after an accident repair) using the integrated "service adjustment mode".

Electrical function schematic for Active Distance Assist DISTRONIC	PE30.30-D-2074-97TSA
Overview of system components for driver assistance systems	GF54.00-D-9998TSA