DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE brake, function - GF30.30-P-0006CE
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
Function requirements, general
- No undervoltage or overvoltage
- Circuit 61 ON or "PT_Rdy" (drivetrain ready) signal set
- ""ADTR_AVL" (Advanced DISTRONIC PLUS) coded in the front SAM control unit
- Navigation module plugged in (with code (508) Navigation box preinstallation or code (509) Navigation box)
- Radar sensor system not switched off (manual or automatic)
- Long range radar soiling and function test completed successfully
- Electronic Stability Program (ESP) not passively switched (without model 204.077/277/375)
- ESP not switched into "SPORT HANDLING MODE" (for model 204.077/277/375.)
- Active ESP intervention not recognized
- Vehicle is not in backward movement
- Gear range "D" engaged
- Parking brake not operated
The status of circuit 61 or the "PT_Rdy" signal is sent by the CDI control unit or the ME-SFI [ME] control unit via the chassis CAN.
The gear range status is sent by electronic transmission control unit (for transmission 722.6) or the fully integrated transmission control unit (for transmission 722.9) via the drive train CAN to the CDI control unit or the ME-SFI [ME] control unit which transmits the gear range status via the chassis CAN.
The status of the parking brake is registered via the parking brake indicator switch. This is read directly by the front SAM control unit and provided on the chassis CAN.
The status of the ESP is transmitted by the ESP control unit via the chassis CAN.
Apart from the listed function requirements there is constant checking on safety grounds whether the driver is present in the vehicle.
Driver recognition takes place by the standstill coordinator which is implemented in the electronic stability program control unit.
The following vehicle components are monitored to do this:
- Driver door and driver belt lock (closed)
- Front passenger door (closed)
- Engine hood (closed)
The function of the standstill coordinator described in detail can be taken from the separate description "Adaptive Brake (ABR)".
DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE brake, general points
Speed data:
The units and values for the speed given in the following text should be assigned according to the tachometer scale in the IC:
- Display in "Kilometer": km/h
- Display in "Miles": (mph)
The driving assist system DISTRONIC PLUS regulates the speed automatically according to the driver's specification and also the clearance to the vehicle driving immediately ahead within a vehicle speed range of v = 0 to 200 km/h and from v = 200 up to 0 km/h (v = 0 to 120 mph and from v = 120 to 0 mph).
The DISTRONIC PLUS system also contains an AWS which warns the driver of the systems vehicle about an excessively low clearance to the vehicle driving immediately ahead as well as of any possible collisions with vehicles (e.g. danger of a head-on collision) or stationary obstacles on its lane, both optically and acoustically.
If the driver reacts to the collision critical warning with an emergency braking maneuver, the BAS PLUS feature provides support.
The brake support offered by the function BAS PLUS takes place by means of a situation-related, targeted brake force calculation. This means that the brakes remain applied automatically and as intensively as required (max. approx. a = 10 m/s2 ).
This innovation allows one to prevent an imminent collision or at least to reduce the consequences of an accident.
If the driver does not react to the collision critical warning, the PRE-SAFE feature decelerates the vehicle within the physical limits by automatically actuating the brakes to prevent a possible collision or to reduce the possible consequences.
For this purpose, the PRE-SAFE brake permanently determines the potential danger of a head-to-tail crash occurring and initiates appropriate measures to warn of an impending collision and possibly to mitigate the effects of a collision in critical situations.
The PRE-SAFE brake feature also supports the PRE-SAFE safety concept.
Detailed information about the PRE-SAFE safety concept is given in the separate "PRE-SAFE function" description.
The functions DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE brake use close range radar sensors integrated in the bumper as well as the long range radar integrated in the radiator grille to recognize vehicles or obstacles driving immediately ahead.
The executed functions are controlled by the video and radar sensor system control unit. To do this the video and radar sensor system control unit intervenes actively in the engine timing as well as the brake system and actuates the IC to issue optical and acoustic warning messages.
The from SAM control unit is the central interface for data exchange between the different CAN bus systems (Gateway).
The use of the DISTRONIC PLUS driving assistance system including BAS PLUS and PRE-SAFE brake significantly increases the convenience and driving safety without fatiguing the driver.
The following presentation should be taken from the detection area of the radar sensor system on which the system DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE brake is based.
Illustration of the principle "Detection range of the radar sensor system"
Operation of the DISTRONIC PLUS system takes place over the CC lever whose design and function is as follows:
Design of the CC lever
Schematic function diagram of the cruise control lever for vehicles without code (494) USA version
Schematic function diagram of the cruise control lever for vehicles with code (494) USA version
The following functions are part of the distance regulation and warning system DISTRONIC PLUS and are described in a separate document:
- Cruise control Variable SPEEDTRONIC (without code (494) USA version)
- Permanent limiter
Function sequence for DISTRONIC PLUS
The DISTRONIC PLUS system requires the following input factors to implement the distance regulating system as well the AWS:
- Object recognition in the short range
- Object recognition in the long range
Object recognition in the short range by means of the short range radar sensors (24 GHz short range radar):
The short range radar sensors work in the 24 GHz frequency range for a maximum range of s = 30 m and is integrated in the following components:
- DISTRONIC sensor (DTR)/left front bumper
- DISTRONIC sensor (DTR)/right front bumper
The recording angle of the short range radar sensors is a maximum of ∠ = 130°. Within a detection angle of ∠ = 60° the angle is determined precisely and objects are still detected up to an angle of ∠ = 130°.
The radar sensors communicate via an autarchic sensor CAN with the video and radar sensor system control unit.
Due to legal requirements on the 24 GHz radar system (short range radar), the short range radar sensor system is automatically switched off in certain protected areas around radio astronomy stations.
The short range radar sensor system is not required in countries in which no approval exists for the 24-GHz radar system.
The protected areas of the radio astronomy stations are stored in the form of Global Positioning System (GPS) coordinates in the video and radar sensor system control unit.
The NAV for the COMAND controller unit or the radio in combination with navigation module adapted via the telematics CAN permanently transmits the current global positioning system coordinates via the interior CAN to the front SAM control unit.
The front SAM control unit forwards the GPS coordinates via the chassis CAN to the video and radar sensor system control unit which then switches off the short range radar sensors. When DISTRONIC PLUS is active, the message "Radar sensor system automatically switched off, see operator's manual" is shown on the multifunction display (A1p13) of the instrument cluster.
When the vehicle leaves the protected area, the short range radar sensor system is switched on again automatically. For an activated DISTRONIC PLUS the message "DISTRONIC PLUS available again" is issued.
The driver has the option to switch the short range radar sensor system off and on manually using the "Vehicle settings" menu in the instrument cluster. If one seeks to manually switch on the short range radar sensors within a protected area, the message "Radar sensor system switched off automatically" is displayed in the multifunction display.
Schematic display of automatic radar sensor system shutoff
Object recognition in the long range by means of the long range radar sensors (77 GHz long range radar):
The long range radar operating in the 77 GHz frequency range is integrated in the DISTRONIC electric controller unit (A89) and covers the front area of the vehicle for a length of s = 60 m up to s = 200 m for a detection angle of ∠ = 18°. The range s = 0 m to s = 60 m in front of the vehicle is detected for an angle of ∠ = 60°. The DISTRONIC control unit performs a soiling and function test to secure its perfect functioning after each engine start.
The function test requires an object in the detection range of the long range radar which is used as a reference value for the function test by the DISTRONIC control unit. The DISTRONIC PLUS cannot be activated if a malfunction is established or if there are no objects (for the function test) in the detection range of the long range radar. The DISTRONIC PLUS controller unit communicates via the vehicle dynamics CAN with the video and radar sensor system control unit.
The long range radar operates according to the pulse-duplicator principle which allows the distances and speeds of individual objects (e.g. vehicles) to be measured independently of each other.
Apart from information from the radar sensor system, the following additional information is needed in order to realize the automatic distance regulating system:
- Intensity of the acceleration in the longitudinal direction
- Direction of travel
- Vehicle speed
- Steering angle
Intensity of the acceleration in the longitudinal direction
The maximum positive acceleration requested by the system for automatic distance control is limited on safety and comfort grounds to about g = 2.5 m/s 2 while the negative acceleration is limited to about 40% (ca. a = 4 m/s 2 ) of the maximum possible brake power.
The maximum positive acceleration requested by the system for automatic distance control is antiproportional to the vehicle speed which means that limitation of the positive and negative acceleration reduces with increasing speed.
The positive and negative acceleration of the vehicle is registered by the yaw rate sensor for lateral and longitudinal acceleration and transmitted via the vehicle dynamics CAN.
Direction of travel and vehicle speed:
In order to determine the direction of travel and speed of the vehicle, the Electronic Stability Program Premium control unit directly reads in signals from the following components:
- Left front axle speed sensor
- Right front axle speed sensor
- Left rear axle speed sensor
- Right rear axle speed sensor
The wheel rotation direction is determined dependent on the drive variants.
The electronic stability program control unit sends the information on the wheel speeds and wheel rotation direction via the chassis CAN to the video and radar sensor system control unit.
The video and radar sensor system control unit uses the information from the rpm sensors to internally calculate the vehicle speed and direction of travel.
Rotation angle:
The current rotation angle is detected by the steering angle sensor which is read in directly by the steering column tube module control unit. The steering column tube module reads in the steering angle sensor data and sends the data via the chassis CAN to the video and radar sensor system control unit.
The functions of the DISTRONIC PLUS system including BAS PLUS and PRE-SAFE brake can be subdivided into the following subfunctions:
- Function sequence for automatic speed control
- Function sequence for automatic distance control
- Function sequence for PRE-SAFE brake and BAS PLUS
Function sequence for automatic speed control
The automatic speed control (CC) allows the driver to establish a speed within the vehicle speed range of v = 30 to v = 200 km/h (v = 20 mph to v = 120 mph) which the vehicle is then automatically regulated to stay at.
The driver has the option here to activate the automatic speed control over the cruise control lever and for vehicles without code (494) USA version to set the desired speed in v = 1 km/h or 10 km/h steps.
For vehicles with code (494) USA version the setting is in steps of v = 1 mph or 5 mph.
1 km/h or 1 mph steps:
The accelerate and set switch must be actuated upwards to the actuation point or the decelerate and set switch must be actuated downwards to the actuation point.
10 km/h or 5 mph steps:
The accelerate and set switch must be actuated upwards beyond the actuation point or the decelerate and set switch must be actuated downwards beyond the actuation point.
If the respective switch is held at or beyond the actuation point then the set speed increases automatically by an interval of t = 0.6 s.
Activity of the CC function is signalized to the driver through deactivation of the SPEEDTRONIC LED (without code (494) USA version) and the selected vehicle speed range is displayed through lighting up of the segment ring around the speedometer (A1p8).
If the CC function is activated, the vehicle accelerates automatically to the prescribed speed value.
Actuation of the SPEEDTRONIC LED (without code (494) USA version) takes place by means of the integrated switching logic in the cruise control lever.
The status of the SPEEDTRONIC LED (without code (494) USA version) is read in directly by the steering column tube module control unit which then transmits it via the chassis CAN to the video and radar sensor system control unit.
When driving on slopes there is also active intervention in the brake system in order to maintain the speed within the selected vehicle speed range.
If the automatic distance control is active and the selected target vehicle accelerates to above v = 200 km/h (v = 120 mph) or the selected target vehicle removes itself from the detection range of the radar sensor system, the function of the automatic distance control changes over into the function of the automatic speed control.
The vehicle reacts by being regulated at the speed set by the driver.
Additional automatic distance control function requirements
- Cruise control lever in DISTRONIC PLUS position (SPEEDTRONIC LED Off)
- Target object (vehicle driving immediately ahead) detected by the radar sensor system
Function sequence for automatic distance control
If the target object is detected by the radar sensor system, the interval selected over the DISTRONIC control is realized. The distance to the vehicle driving immediately ahead can be set in seven stages ranging between about t = 1.0 and 2.0 s.
View of the instrument cluster for an activated DISTRONIC PLUS and vehicle immediately ahead
Fig 7: Identifying View Of Instrument Cluster For Activated Distronic Plus And Vehicle Immediately AheadCourtesy of MERCEDES-BENZ USA
The partial function automatic distance control takes place within the system limits depending on the input factors and is subdivided into the following subfunctions:
- Function sequence for automatic acceleration and braking
- Automatic start-off function sequence (with Stop-and-Go traffic)
At speeds of v < 30 km/h (v = 20 mph) the automatic distance control can only be activated if a vehicle driving immediately ahead has already been detected by the radar sensor system and was displayed in the multifunction display. If the automatic distance control is active, the video and radar sensor system control unit recognizes the vehicle driving immediately above over input factors from the long range or short range radar sensor system, which is then registered as a target object. Activation of the automatic distance control function is confirmed to the driver by activation of the SPEEDTRONIC LED (without code (494) USA version). The distance to the target object in the multifunction display is also displayed graphically, which is like the following illustration, for t = 5 s.
Function sequence for automatic acceleration and braking
The video and radar sensor system control unit reads in the following input factors from the respective components to regulate the self-sufficient acceleration:
- Intensity of acceleration of deceleration in longitudinal direction
- Motion/speed of target object
If the target object, which accelerates or decelerates, is detected by the radar sensor, the DISTRONIC control unit evaluates the target data, processes this internally and transmits the respective information via the vehicle dynamics CAN to the video and radar sensor system control unit.
The video and radar sensor system control unit processes the input factors internally and transmits a request to increase or reduce the engine torque via the chassis CAN to the ESP control unit.
The electronic stability program control unit evaluates this information as well as vehicle dynamic requests internally and sends them according to their 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, according to the concept of an assist system, to intervene manually in acceleration of the vehicle over the accelerator pedal (e.g. to perform an overtaking maneuver).
To do this the CDI control unit or the ME-SFI [ME] control unit directly reads in the signals from the accelerator pedal sensor and transmits this via the chassis CAN to the video and radar sensor system control unit.
automatic acceleration is put out of action for as long a the driver accelerates the vehicle using the accelerator pedal.
This process is passively displayed in the multifunction display with the message "DISTRONIC passive".
If reduction of the engine torque is not sufficient to achieve the required distance, the video and radar sensor system control unit sends a request to apply the brakes to the electronic stability program control unit via the chassis CAN.
This implements the request to brake through modulated actuation of the traction system hydraulic unit.
Automatic start-off function sequence
(with Stop-and-Go traffic)
Self-initiated starting off initiated by DISTRONIC PLUS allows the vehicle to move with the traffic in stop-and-go traffic.
This function is executed only after acknowledgment by the driver. To do this the "resume from memory switch" must be actuated.
The status of the resume from memory switch is transmitted by the steering column tube module control unit via the chassis CAN.
The video and radar sensor system control unit receives the input values listed via the chassis CAN and processes them internally.
The video and radar sensor system control unit then sends a request to increase the engine torque to the electronic stability program control unit.
The electronic stability program control unit evaluates this information as well as vehicle dynamic requests internally and sends them according to their relevance via the chassis 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 appropriately and the vehicle starts off automatically.
Important function notes in special driving situations:
- The system does not operate for stationary objects (e.g. vehicles) unless a preceding vehicle is tracked to a standstill.
- If a vehicle cuts in between the host vehicle and the vehicle ahead (target vehicle), the system switches over to the new target vehicle.
- If the preceding vehicle turns off and there is another vehicle in front, the system only switches over to the new target vehicle if it is moving. In the event that a stationary obstruction is encountered, a signal tone and the DISTRONIC warning lamp (A1e59) warn the driver about the impending collision.
The special considerations arising from the following traffic situations should also be observed:
Obstacles and stationary vehicles
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:
The DISTRONIC PLUS can only provides limited detection of vehicles in curves.
The systems vehicle can then brake unexpectedly or late.
Vehicles moving across in front of one's own vehicle:
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).
Courtesy of MERCEDES-BENZ USA
Function sequence for BAS PLUS and PRE-SAFE brake
The PRE-SAFE brake evaluates the situation of the traffic in the area in front of the vehicle.
In a dangerous situation in the following vehicle speed range the vehicle is autonomously braked by the PRE-SAFE brake or an emergency braking by the driver is supported by BAS PLUS:
- vehicle speed range for PRE-SAFE brake: v = 7 to 200 km/h (v = 5 to 120 mph)
- Vehicle speed range for BAS PLUS: v = 7 to 250 km/h (v = 5 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 by the video and radar sensor system control unit when the time interval between the system vehicle and vehicle in front is less than t = 0.8 s (e.g. in moving traffic). The video and radar sensor system control unit sends a request to the visual warning device in the instrument cluster via the chassis CAN which then actuates the DISTRONIC warning lamp.
Collision critical distance warning:
If a moving obstacle within the detection range of the radar sensor system is recognized as accident-critical (a collision will occur within
t < 2.6 s) the video and radar sensor system control unit transmits a request for an optical and acoustic warning to the IC via the chassis CAN which reacts by actuating the DISTRONIC warning lamp and the warning buzzer (A1h1) (intermittent tone).
The request present as a warning is switched off automatically when the situation is defused and cannot be deactivated during active regulation.
Visual warning message in instrument cluster when a safe distance is not maintained
Courtesy of MERCEDES-BENZ USA
The video and radar sensor system control unit will initiate a partial braking if the driver does not react to the acoustic and optical warning signals.
To do this the video and radar sensor system control unit calculates a braking torque while taking account of the driving dynamics input factors, which is transmitted via the chassis CAN to the ESP control unit.
The electronic stability program control unit implements the request over the traction system hydraulic unit and brakes the vehicle according requirements.
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 object.
The distance warning is basically active for an active DISTRONIC PLUS. If the function DISTRONIC PLUS is deactivated, actuation of the DISTRONIC warning lamp takes place by the function PRE-SAFF break.
To do this the video and radar sensor system control unit uses data from the radar sensor system and also calculates the necessary brake servo assistance both permanently and according to the situation while taking account of the current clearance and the closing speed to the obstacle.
To do this, the video and radar sensor system control unit transmits the appropriate requests via chassis CAN to the electronic stability program control unit which actuates the hydraulic brake pressure over the traction system hydraulic unit. If there is no actuation or the intensity of actuation of the brake pedal by the driver reduces, the brake servo assistance on the driver braking is reduces and the function BAS PLUS deactivated. The function BAS PLUS will also be deactivated if the driver presses on the accelerator pedal. Operation of the accelerator pedal is registered by the accelerator pedal sensor.
The CDI control unit or the ME-SFI [ME] control unit directly reads in the accelerator pedal sensor and transmits this via the chassis CAN to the video and radar sensor system control unit.
If the driver does not react to the partial braking and if the calculation is made by the video and radar sensor system control unit that a collision with the obstacle is unavoidable, the video and radar sensor system control unit instigates emergency braking for t = 1 s and thereby reduces the possible consequences of the accident.
Electrical function schematic for DISTRONIC PLUS incl. BAS PLUS and PRE-SAFE brake PE30.30-P-2055-97FAA Overview of system components for driver assistance systems GF54.00-P-9998CE