GF30.30-P-0008LE Adaptive Cruise Control, Function
GF30.30-P-0008LE Adaptive cruise control, function
- MODEL 221.0 /1 (except 221.095 /195)
- with CODE (239) Autonomous intelligent cruise control Plus Light as of model year 2011 / YoM 10
Function requirements for adaptive cruise control, general
- No undervoltage or overvoltage
- Autonomous intelligent cruise control Plus Light coded in central gateway control unit (N93)
- Circuit 61 On (n greater than 300 rpm)
- Gear range "D" engaged
- Long range radar soiling and function test completed successfully
- Vehicle is not in backward movement
- Electronic Stability Program (ESP) not switched passively (without model and 221.074/174)
- ESP not switched into "SPORT HANDLING MODE" (for model 221.074/174)
- No active intervention recognized by the Electronic Stability Program (ESP)
- Parking brake not operated
The attached function requirements are determined as follows: The circuit 61 status is sent by the CDI control unit (N3/9) (for a diesel engine) or the ME-SFI [ME] control unit (N3/10) (for a gasoline engine) via the chassis CAN (CAN E).
The gear range status is sent by the EGS control unit (N15/3) (transmission 722.6) or the fully integrated transmission control unit (VGS) (Y3/8n4) via the drive train CAN (CAN C) to the CDI control unit or the ME-SFI [ME] control unit, which sends the gear range status via the chassis CAN.
The electric parking brake controller unit (A13) transmits the status of the parking brake via the front end CAN (CAN G).
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 ESP control unit (N47-5).
The following vehicle components are monitored to do this:
- Driver door and driver belt lock (closed)
- Front passenger door (closed)
- Rear doors (closed)
- Engine hood (closed)
The detailed function of the standstill coordinator should be taken from the separate description "Adaptive Brake (ABR)".
Adaptive cruise control, general
The driver assist system adaptive cruise control automatically regulates the speed in the vehicle speed range from v = 0 up to 200 km/h and from v = 200 to 0 km/h according to the driver's request and also the distance to the vehicle immediately ahead.
For vehicles with code (494) USA version regulation takes place in the vehicle speed range from v = 0 up to 120 mph and from v = 120 to 0 mph.
The driver assistant system ART also includes an AWS which warns the driver about possible collisions (e.g. danger of a collision) with vehicles on its lane, optically and acoustically.
The System ART system is also supplemented by the function BAS PLUS. BAS PLUS is an additional function of the Brake Assist System (BAS), which assists the driver during emergency braking by means of a situation-related, targeted brake force calculation.
The ART system uses a long range radar integrated in the radiator grille for recognition of the vehicles or obstacles driving immediately ahead.
The radar sensors control unit (SGR) (N62/1) is the master control unit for the ART system. It intervenes actively in the engine timing as well as in the brake system and actuates the IC to issue an optical and acoustic warning messages.
The central gateway control unit is the central interface for data exchange between the different CAN bus systems (Gateway).
The driver assist system ART actively increases the driving safety. In this way the incidence of accidents is reduced or the consequences of an accident are reduced. There is also a significant comfort advantage obtained.
From the following presentation it is possible to establish the detection range of the radar sensor system on which the ART system.
Illustration of the principle Detection range of the radar sensor system
1 Systems vehicle, equipped with the ART
2 The target vehicle (target object) moving directly ahead is detected by the long range radar sensors
3 The vehicle immediately ahead in the traffic is detected by the medium detection range of the long range radar sensors
A Long range radar
(up to s = 200 m, for a detection angle of about Angular = 18°)
B Medium detection area of the radar sensor system
(up to s = 60 m, for a detection angle of about Angular = 60°)
Operation of the ART system takes place via the CC push button (S40/4), the design of which and function are described in the following.
Design of the CC push button
S40/4 CC [TPM] switch
S40/4r1 DTR distance potentiometer
S40/4s1 Resume from memory
S40/4s2 Decelerate and set
S40/4s3 Accelerate and set
S40/4s4 Switching off
S40/4s6 Variable speed (without code (494) USA version)
S40/4v1 Yellow LED, variable speed limiter (without code (494) USA version)
Schematic function diagram of the CC push button for vehicles without code (494) USA version
5a Accelerate and set in 1 km/h increments
5b Accelerate and set in 10 km/h increments
6a Decelerate and set in 1 km/h increments
6b Decelerate and set in 10 km/h increments
7 Switching off of the ART (acknowledgment for automatic driving off) or Variable SPEEDTRONIC (if no target speed is stored, the current speed is set as the target speed)
8 Increasing the specified distance for the ART
9 Decreasing the specified distance for the ART
10 Selection option between the ART and variable SPEEDTRONIC
11 Yellow LED, variable speed limiter (lights up in the position variable SPEEDTRONIC)
12 Switching off the ART or variable SPEEDTRONIC
Schematic function diagram for vehicles with code (494) USA version
13 A Accelerate and set in 1 mph/h increments
13b Accelerate and set in 5 mph/h increments
14a Decelerate and set in 1 mph/h increments
14b Decelerate and set in 5 mph/h increments
15 Switching off of the ART (acknowledgment for automatic driving off) or switching on the CC (if no target speed is stored, the current speed is set as the target speed)
16 Increasing the specified distance for the ART
17 Decreasing the specified distance for the ART
18 Switching off the ART
Additional function requirements of the ART
- CC push button in the position ART (yellow LED, variable speed limiter off) (without code (494) USA version)
Function sequence for ART
The ART System requires object recognition in the front area of the vehicle to implement the automatic distance regulating system as well as the AWS.
The object recognition takes place over the DTR radar sensor (A89b1) which operates in the 77 GHz frequency range. The DTR radar sensor is integrated in the DTR controller unit (A89) and covers the front area of the vehicle for a length of s = 60 m for s = 200 m for a detection angle of Angular = 18°.
The range s = 0 m to s = 60 m in front of the vehicle is detected for an angle of Angular = 60°.
The DTR controller 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 DTR radar sensor which is used as a reference value for the function test by the DTR controller unit.
The intelligent cruise control 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.
To do this the DTR controller unit communicates via the vehicle dynamics CAN (CAN H) with the video and radar sensor system control unit.
The DTR radar sensor 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 information is also needed:
- Intensity of the acceleration in the longitudinal direction
- Direction of travel
- Vehicle speed
- Steering angle
Intensity of the acceleration in the longitudinal direction
The automatic maximum positive acceleration of the automatic distance control is limited on safety and comfort grounds to about g = 2.5 m/s2 while the negative acceleration is limited to about 40% (ca. g = 4 m/s2) of the maximum possible brake power.
The automatic maximum positive and negative acceleration of the automatic distance control is antiproportional compared 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 (B24/15) and transmitted via the vehicle dynamics CAN.
Direction of travel and vehicle speed:
In order to determine the direction of travel of the vehicle, the ESP control unit reads in the wheel speeds over the following components:
- Left front rpm sensor (L6/1)
- Right front rpm sensor (L6/2)
- Left rear rpm sensor (L6/3)
- Right rear rpm sensor (L6/4)
Evaluation of the wheel rotation direction takes place over the front rpm sensor.
The ESP control unit transmits information from the wheel speeds and wheel rotation direction via the chassis CAN to the radar sensors control unit. The radar sensors control unit calculates the vehicle speed on the basis of information from the rpm sensors.
Rotation angle:
The current rotation angle is detected by the steering wheel angle sensor (N49) which is read in directly by the steering column tube module (N80). The steering column tube module control unit transmits data from the steering angle sensor via the chassis CAN to the radar sensors control unit.
The ART system subdivides itself into the following partial functions:
- Function sequence for automatic speed control
- Function sequence for automatic distance control
- Function sequence for AWS and Brake Assist Plus (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 for code (494) USA version) which the vehicle automatically regulates itself to.
The driver has the option here to activate the automatic speed control over the CC push button and for vehicles without code (494) USA version to set the desired speed in 1 km/h or 10 km/h steps. For vehicles with code (494) USA version the setting is in steps of 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.
The activity of the cruise control function is signaled to the driver through deactivation of the LED, variable speed limiter (without code (494) USA version). The selected vehicle speed range is displayed through lighting up of the segment ring around the electronic speedometer (A1p8). Actuation of the LED, variable speed limiter (without code (494) USA version) takes place by the switchover electronics integrated in the CC push button.
The status of the LED, variable speed limiter (without code (494) USA version) is read in directly by the steering column tube module control unit which then transmits it via the radar sensors control units.
If the CC function is activated, the vehicle accelerates automatically to the prescribed speed value.
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 is accelerated to above v = 200 km/h (v = 120 mph for code (494) USA version) or the selected target vehicle removes itself from the detection range of the radar sensor system, then the function of the automatic distance control passes over to the function of the automatic speed control. The vehicle reacts by being regulated at the speed regulated by the driver. If the LED, variable speed limiter without code (494) USA version) lights up the automatic distance control and the variable SPEEDTRONIC (without code (494) USA version) is programmed.
A detailed description of the CC function can be taken from the separate description.
Additional function requirements for automatic distance control
- 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 is realized over the DTR distance potentiometer. The distance to the vehicle driving immediately ahead can be set in six stages between about. t = 1.0 and 2.0 s.
The temporal information about the specified distance is related to the distance the vehicle travels at a certain speed. The distance to the vehicle driving immediately ahead is displayed in the multifunction display (A1p13) and should be at least 50% of the displayed speed value.
At speeds v less than 30 km/h (v = 20 mph for code (494) USA version) the automated distance control can only be activated if a vehicle driving immediately ahead has already been detected by the radar sensor system and this was displayed in the multifunction display. If the automatic distance control is active, the radar sensors control unit recognizes the vehicle driving immediately above over input factors from the long range or short range radar sensor system, which is registered as a target object.
Activation of the automatic distance control is acknowledged to the driver through activation of the LED, variable speed limiter. The distance to the target object in the multifunction display is also displayed graphically, which is like the following illustration, for t = 5 s.
Through selection of the operating level "ART" in the menu "Assistant" in the IC (A1) the distance graphic is shown permanently. Display of the distance graphic can be activated or deactivated independently of the activity of the automatic distance control.
View of the instrument cluster for an activated ART and the vehicle immediately ahead
D Speed of vehicle ahead
E Own speed
F Target speed
G Vehicle moving immediately ahead (target object)
H Own vehicle
I Target distance (white line)
In the electronic speedometer of the IC, for an activated ART, the segments between the measured speed of the vehicle moving immediately ahead and the set target speed are activated to represent the distance.
The function automatic distance control takes place within the system limits depending on the following input factors, which the radar sensors control unit receive to regulate the automatic acceleration via the vehicle dynamics CAN by the respective components:
- Intensity of the acceleration or deceleration in the longitudinal direction (yaw rate sensor for lateral and longitudinal acceleration)
- Movement/speed of the target object (DTR controller unit)
If the target object, which accelerates or decelerates, is detected by the DISTRONIC radar sensor, the DTR electric controller unit evaluates the target data, processes this internally and transmits the respective information via the vehicle dynamics CAN to the radar sensors control unit.
The radar sensors control unit processes the input factors internally and transmits a request to increase or decrease the engine torque to the ESP control unit which evaluates this request as well as further driving dynamic requests internally and passes on their relevance appropriately to the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or evaluates this request as well as further driving dynamic requests internally and passes on their relevance appropriately to the CDI control unit or the ME-SFI [ME] control unit implements these requests appropriately.
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 signals from the accelerator pedal sensor (B37) and transmits these via the chassis CAN to the radar sensors control unit, which processes the signals internally.
Automatic acceleration is put out of action in response for as long a the driver accelerates the vehicle using the accelerator pedal.
This process is optically acknowledged in the multifunction display by the message "ART passive".
If the automatic distance control requires a higher acceleration than the driver prescribes, the driver request is overlayed by the request for automatic distance control.
If the radar sensors control unit recognizes a deceleration on speed of the vehicle directly ahead a request is sent to brake to the ESP control unit, which reacts by actuating the traction system hydraulic unit (A7/3).
For longer drives over slopes one should switch manually from the gear range "D" to "2", for example, to avoid unnecessary wear on the brake system.
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 switching off tone over switching off of the intelligent cruise control. The IC actuates the warning buzzer (A1h1) to issue the switching-off tone. The set braking torque at the point in time of switching off is slowly reduced after the switching off tone.
The intelligent cruise control is already deactivated in the following situations before reaching a standstill:
- Loss of the target vehicle at a speed of less than 25 km/h
- For slopes greater than 4% the intelligent cruise control C is turned off dependent on the slope for a higher speed (e.g. a 4% slope at 7 km/h and a 30% slope at v = 25 km/h)
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.
The special considerations arising from the following traffic situations should also be observed:
Obstacles and stationary vehicles
The ART 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 ART can only recognize vehicles in the range of curve in a limited way. The systems vehicle can then brake unexpectedly or late.
Function sequence for AWS and BAS PLUS
The function ART also includes an AWS which warns the driver in the vehicle speed range of v = 30 to v = 250 km/h (v = 20 mph up to v = 150 mph for code (494) USA version) optically and acoustically about moving obstacles on its lane. To do this the radar sensors control unit evaluates input factors from the following components:
- DTR control unit
- Steering angle sensor
If a moving obstacle is recognized in the detection range of the radar sensor system suggesting an accident (collision within t less than 2.6 s), the radar sensors control unit transmit a request via the chassis CAN for an optical and acoustic warning to the IC, which reacts by actuating the DTR warning lamp (A1e59) and the warning buzzer (intermittent tone).
The request present as a warning is switched off automatically when the situation is defused and cannot be deactivated during active regulation.
A warning will only be given about stationary obstacles if they were previously registered as moving and the vehicles own speed is a maximum of v = 70 km/h (v = 45 mph for code (494) USA version).
The AWS can be separately and independently activated by the automatic distance control in the menu "AWS" of the IC.
View of the IC for an active AWS and currently present warning
A1e59 DTR warning lamp
J Distance warning readiness indicator
The distance warning is basically active for an active adaptive cruise control.
The function BAS supports the driver to optimally evaluate the braking distance to the obstacle within the physical limits existing. To do this the radar sensors control unit uses data from the radar sensor system and 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.
The radar sensors control unit transmits the appropriate requests via chassis CAN to the ESP 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 deactivated. Actuation of the brake pedal will be registered by the brake light switch (S9/1) and is directly read in by the ESP control unit. The function BAS will also be deactivated if the driver presses on the accelerator pedal.
To do this the accelerator pedal sensor registers the activity of the accelerator pedal. 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 radar sensors system control unit.
