Parking System, Function - GF54.65-P-0006RDM
Model 172.4 as of model year 2017
with code 230 (Advanced Parking Guidance)
Illustration shows model 172.4
Function requirements, general
- Terminal 15 ON
The status of circuit 15 is sent by the electronic ignition lock control unit via the interior CAN, front SAM control unit with fuse and relay module and chassis CAN 2 to the parking system control unit.
The engaged reverse gear is recognized via the manual transmission main shifter shaft position sensor. The ME-SFI control unit reads in the signals from the manual transmission main shifter shaft position sensor directly and sends the "reverse gear engaged" signal via chassis CAN 1 to the front SAM control unit.
Parking system, general
The parking system uses an ultrasonic measuring system to detect the distance between the vehicle and an obstacle.
During a journey at speeds of v lt 36 km/h longitudinal parking spaces on both sides of the vehicle in the direction of travel are measured and stored. The driver is assisted when parking by means of corresponding steering and driving instructions. The distance between the vehicle and the obstacle is indicated to the driver visually and acoustically.
In certain situations warnings from the parking system are suppressed, e.g. when reversing through narrow passages (driveway). There is an obstacle within the detection range but, based on the current steering wheel position, a collision will not take place. Parking system operation is dependent on speed and direction of travel, and therefore the following input factors have to be determined:
- Direction of travel and vehicle speed
- Status of reverse gear
- Status of parking brake
Direction of travel and vehicle speed:
The direction of travel is defined using the wheel rotation direction. The vehicle speed is calculated from the wheel speed. The wheel rotation direction and the wheel speeds are recorded by the RPM sensors for each wheel.
The Electronic Stability Program control unit reads in the signals from the RPM sensors directly and sends them via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the instrument cluster and the parking system control unit. The parking system control unit calculates the vehicle speed and defines the direction of travel.
At the same time, the instrument cluster calculates the speed to be displayed and additionally sends it to the parking system control unit via chassis CAN 2.
Reverse gear status:
Vehicles with transmission 711.6 (manual transmission):
Engagement of reverse gear is defined via the status of the backup lamp switch, which is read in directly by the front SAM control unit. Vehicles with transmission 716.7 (manual transmission):
Vehicles with transmission 725.0 (automatic transmission):
The request to "Engage gear range R" is defined by the corresponding selector lever position.
The DIRECT SELECT INTERFACE control unit (transmission 725.0) sends the selector lever position via the drive train CAN, CDI control unit or ME-SFI control unit and chassis CAN 1 to the front SAM control unit.
In addition, the fully integrated transmission control unit (transmission 725.0) sends information on the engaged gear range via the drive train CAN, the CDI control unit or ME-SFI control unit, and chassis CAN 1, front SAM control unit and chassis CAN 2 to the parking system control unit.
Two microprocessors are installed in the front SAM control unit, one for control of basic functions, e.g. the exterior lights, and the second for control of the central gateway functions. Both processors communicate with each other internally via interior CAN.
Using all incoming information, the microprocessor which controls the central gateway functions generates the "reverse gear engaged" signal (irrespective of the transmission variant) and sends this signal via chassis CAN 2 to the parking system control unit.
Parking brake status:
The status of the parking brake is transmitted by the electric parking brake control unit via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the parking system control unit.
The parking system includes the following subfunctions:
- Measuring procedure function sequence
- Self-test function sequence
- Behavior in the event of overvoltage and undervoltage function sequence
- Activate and deactivate function sequence
- Function sequence for monitoring reverse travel
- Function sequence for monitoring forward travel
- Parking space recognition function sequence
- Display of potential parking spaces function sequence
- Function sequence for issuing steering and driving instructions
Illustration of the principle for measuring procedure
Measuring procedure function sequence
The distance measurement is based on the ultrasound measurement system. The parking system control unit actuates the parking system distance sensor directly to do this. As a result of this these emit an ultrasonic signal. The signal reflected by an obstacle is received and evaluated. The distance of the vehicle to each object is notified to the driver through the parking system warning indicators.
In principle a distinction is made between two measurements. On the one hand the direct measurement, resulting from a direct echo and on the other hand the indirect distance measurement which is achieved via a cross echo. Generally, reflected echoes can also be received from adjacent distance sensors due to the large distance sensor detection angles; these are known as cross echoes. These occur at the obstacle due to scattered reflection.
With the help of the triangulation method, the distance from the vehicle to an obstacle can be calculated from two echo signals. The propagation times of the signals from the direct measurement and from the cross measurement are required for this method.
The parking system may not work correctly in some cases because of the functional principal (sending and receiving of ultrasound waves). So for example, when approaching a strong sound absorbent obstacle (e.g. a vehicle covered in snow) it is possible that false data may be displayed.
Monitoring ranges of distance sensors
The distance sensors are activated according to the direction of travel. The appropriate distance sensors are activated with forward travel for monitoring the front area (A) and the corner protection area (B).
The appropriate distance sensors are activated with reverse travel for monitoring the front area, the corner protection area and the rear area (C).
The monitored front area amounts to a maximum of s = 100 cm (c) and the monitored rear area amounts to a maximum of s = 120 cm (e). If the distance of the vehicle to an obstacle is less than s = 20 cm (a1, c1), the parking system will not obtain any more defined data for technical reasons.
Below a speed of v = 36 km/h the parking space detection range (D) at the right and left of the vehicle is measured up to a distance of s = 400 to 450 cm (d), and stored for s = 15 m in the parking system control unit.
Self-test function sequence
During the self-test the following components are checked for proper operation:
- Parking system control unit
- Distance sensors
- Parking system warning indicator
- Parking assist electrical lines
Parking system control unit self-test:
The parking system control unit performs a self test after the ignition is switched on (circuit 15 ON). The hardware of the parking system control unit is checked here for faults.
The status of the parking brake and the status of the reverse gear do not exert any influence on the parking system control unit's self-test.
Distance sensor self-test:
A self-test of the distance sensors (e.g. for connection) is only performed when a distance sensor is "pulsed" (ultrasonic transmitting).
This is dependent on the status of the parking brake, the status of the reverse gear and the speed.
Distance sensor test for subsequent vibrations:
A distance sensor test for subsequent vibrations (acoustic-physical function of distance sensor) is only conducted when the speed v = 60 km/h is exceeded or dropped below.
After the self-test, the parking system control unit fully actuates all the LEDs for the parking system warning indicators for approx. t = 1 s. If there are no malfunctions or errors, the two yellow horizontal standby bars light up on both parking system warning indicators with reduced brightness.
The background illumination of the parking system warning indicators is automatically adjusted to the ambient brightness.
The parking system control unit carries out further self-tests at regular intervals.
The following states can be recorded here:
- Operational problem
- System error(s)
With a malfunction or a system error, the parking system is deactivated and the display element in the parking system button in the upper control panel lights up. The parking system control unit sends a request for this via chassis CAN 2, the front SAM control unit and instrument panel LIN to the upper control panel control unit. The upper control panel control unit directly actuates the display element in the parking system button.
Malfunction:
A malfunction can be caused by a temporary external disturbance (e.g. a jackhammer on a construction site, a steam jet or by driving through an automatic car wash). If a malfunction occurs during operation, this is indicated by illumination of the red LEDs of the parking system warning indicator which is directly actuated by the parking system control unit.
If the malfunction persists for a longer period of time, a self-test is run while driving to identify the cause. If the malfunction is still present, this is interpreted as a system error.
A warning sound is not emitted.
System error:
A system error can have the following causes:
- Defective component
- Error in communication
- Overvoltage or undervoltage
If a system error is detected, the red LEDs light up on the parking system warning indicator which is directly actuated by the parking system control unit. An acoustic warning is also emitted for t = 2 s. After another t = 18 s, the parking system switches off and a fault is entered in the fault memory of the parking system control unit.
The size of the license plate bracket attached to the bumper varies depending on the national version. Due to the different dimensions and shapes the parking system must be adapted to the particular circumstances. The diagnosis tester can be used to code the national version to avoid any malfunctions caused by the license plate bracket.
Behavior in the event of overvoltage and undervoltage function sequence
The parking system behavior in the event of overvoltage or undervoltage is described in the following table.
| On-board power supply voltage U lt 9.0 V | On-board power supply voltage U gt 16.0 V | Undervoltage with reset | Undervoltage without reset (start pulse) |
|---|---|---|---|
| Parking system nonfunctional | Parking system nonfunctional | The function is activated again after a reset | Display of distance |
| Parking system warning indicators, dark | Parking system warning indicators, dark | No checking up of parking system warning indicators | Start pulse has no influence on parking system |
| No checking up if voltage is normal again | No checking up if voltage is normal again | - | No checking up of parking system warning indicators |
| LED in parking system ON button | LED in parking system ON button | - | - |
Additional function requirements for activation and deactivation
- Self-test completed successfully
- Gear range "D" or "R" engaged (transmission 725.0)
If the parking brake is activated and gear range "N" is engaged, the parking system is active for t = 2 s before it is automatically switched off.
Activate and deactivate function sequence
The parking system can be manually deactivated or activated by pressing the parking system button in the upper control panel. The parking system button status is sent by the upper control panel control unit over the instrument panel LIN to the front SAM control unit. This sends the status to the parking system control unit via the chassis CAN 2.
If the parking system function is manually switched off using the parking system button, then this is automatically switched on when circuit 15 is activated again.
The intensity of the warning indicator illumination for an activated parking system changes to match the ambient brightness. To this end, the light sensor or the rain/light sensor detects the ambient brightness. The data from the light sensor or rain/light sensor is read in by the front SAM control unit via the wiper/inside rear view mirror LIN and forwarded to the parking system control unit via chassis CAN 2. If the light sensor or rain/light sensor determines that it is "Night", then the parking system warning indicators are actuated at 60 % brightness. If the light sensor or rain/light sensor determines that it is "Day", then the parking system warning indicators are actuated at 100 % brightness. When the parking system is deactivated, only the light-emitting diode in the parking system button lights up. In driving operation, the parking system switches into "Standby mode" between v = 60 and 16 km/h, i.e. the parking system control unit, parking system warning indicators and the distance sensors are supplied with power but the parking system warning indicators are however switched to a dim setting. The respective system states are available on a transmission-specific basis in the following table:
| Condition (transmission 711.6, 716.7) | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Parking system button | OFF | ON | ON | ON | ON | ON |
| LED in parking system button | ON | OFF | OFF | OFF | OFF | OFF |
| Gearshift lever position | x | x | x | x | All reverse gear | Reverse gear |
| v in km/h | x | ≥ 60 | 0 | Deceleration of gt 60 down to less than 60 | ≥ vu | ≥VU |
| Parking brake activated | x | x | Yes | x | No | No |
| Wheel speed signal | x | x | 0 (t ≥ 2 s) | x | x | x |
| Front distance sensors 1 | Inactive | Inactive | Inactive | active for test, then inactive | Active | Active |
| Rear distance sensors 1 | Inactive | Inactive | Inactive | active for test, then inactive | Inactive | Active |
| Instrument panel parking system warning indicator 1 | Dim 2 | OFF | Dim | active for test, then dark | ON | ON |
| Rear parking system warning indicator 1 | Dim | OFF | Dim | active for test, then dark | Dim | ON |
| Condition (transmission 725.0) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | |||
|---|---|---|---|---|---|---|---|---|---|---|
| 4.1 | 4.2 | 4.3 | 4.4 | |||||||
| Parking system button | OFF | ON | ON | ON | ON | ON | ON | ON | ON | ON |
| LED in parking system button | ON | OFF | OFF | OFF | OFF | OFF | OFF | OFF | OFF | OFF |
| Drive position | x | D, R or N | P | P | R | D | N | D, R or N | D | R or N |
| v (in km/h) | x | ≥ 60 | x | x | x | x | x | Deceleration of gt 60 down to less than 60 | ≤VU | ≤ VU |
| Parking brake activated | x | x | x | Yes | Yes | Yes | Yes | x | No | No |
| Wheel pulse counter signal | x | x | x | 0 (t ≥ 2 s) | 0 (t ≥ 2 s) | 0 (t ≥ 2 s) | 0 (t ≥ 2 s) | x | x | x |
| Front distance sensors1 | Inactive | Inactive | Inactive | Active | Inactive | Active | Active | active for test, then inactive | Active | Active |
| Rear distance sensors1 | Inactive | Inactive | Inactive | Active | Active | Inactive | Active | active for test, then inactive | Inactive | Active |
| Front instrument panel parking system warning indicator! | Dim2 | OFF | Dim | Dim | Inactive | Active | active for t = 2 s, then inactive | active for test, then dark | ON | ON |
| Rear parking system warning indicator1 | Dim | OFF | Dim | Dim | Active | Inactive | active for t = 2 s, then inactive | active for test, then dark | Dim | ON |
D: "Drive"
R: "Reverse"
N: "Neutral"
P: "Park position"
v: Current speed
vu : Lower limit speed (v = 16 km/h)
V0 : upper Limit speed (v = 18 km/h)
OFF: Supply voltage switched off
Active: Supply voltage applied and in operation
Dim: Power supplied, but parking system warning indicator switched off
Inactive: Distance sensors supplied with power, but not emitting any ultrasound
x: Optional condition/value
1 : The specified operating conditions are valid only under the following conditions:
- Bus not asleep
- No system components malfunctioning
2 : Standby:
The distance sensors and the parking system warning indicator are being supplied with power. The distance sensors are not transmitting an ultrasound signal and the parking system warning indicator is dark.
Additional function requirements for monitoring reverse travel
- Vehicle speed v = 0 to 18 km/h or vehicle speed v = 16 to 0 km/h
- Backward movement of vehicle
Function sequence for monitoring reverse travel
During reverse travel the areas in front of and behind the vehicle are monitored.
When the lower limit speed of v = 16 km/h is dropped below, the parking system changes to measuring mode.
When obstacles are detected in front of or behind the vehicle, the driver is initially visually warned by the appropriate light-emitting diodes lighting up in the parking system warning indicators. When a distance of s = 30 cm is dropped below, the warning is intensified by an intermittent tone and subsequently by a continuous signal (see following tables). When the upper speed limit of v = 18 km/h is exceeded, the parking system goes over into stand by mode again.
| Warning messages in front monitoring range | ||||
|---|---|---|---|---|
| Instrument panel parking system warning indicator display element | Warning signal | Distance (cm) | ||
| Distance sensor (B8/1, B8/6) | Distance sensor (B8/2, B8/3, B8/4, B8/5) | |||
| Visual | 1 (yellow) | - | - | lt 100 |
| 2 (yellow) | - | - | lt 80 | |
| 3 (yellow) | - | lt 60 | lt 65 | |
| 4 (yellow) | - | lt 50 | lt 50 | |
| 5 (yellow) | - | lt 40 | lt 40 | |
| Visual and acoustic | 6 (red) | Intermittent tone with f = 6 Hz | lt30 | lt30 |
| 7 (red) | Continuous signal | lt 15 | lt 20 | |
| Warning message in rear monitoring range | ||||
|---|---|---|---|---|
| Rear parking system warning indicator display element | Warning signal | Distance (cm) | ||
| Distance sensor (B8/7, B8/10) | Distance sensor (B8/8, B8/9) | |||
| Visual | 1 (yellow) | - | - | lt 120 |
| 2 (yellow) | - | - | lt 95 | |
| 3 (yellow) | - | lt 80 | lt 75 | |
| 4 (yellow) | - | lt55 | lt55 | |
| 5 (yellow) | - | lt 40 | lt 40 | |
| Visual and acoustic | 6 (red) | Intermittent tone with f = 6 Hz | lt30 | lt30 |
| 7 (red) | Continuous signal | lt 20 | lt 20 | |
Additional function requirements for monitoring forward travel
- Vehicle speed v = 0 to 18 km/h or vehicle speed v = 16 to 0 km/h
- Forward movement of vehicle
Function sequence for monitoring forward travel
When driving forwards the area in front of the vehicle is monitored. When the lower limit speed of v = 16 km/h is dropped below, the parking system changes to measuring mode.
When obstacles are detected in front of the vehicle the driver is initially visually warned by the lighting up of corresponding light-emitting diodes in the parking system warning indicators. When a distance of s = 30 cm is dropped below, the warning is intensified by an intermittent tone and subsequently by a continuous signal (see preceding tables). When the upper speed limit of v = 18 km/h is exceeded, the parking system goes over into stand by mode again.
Additional function requirements, parking space recognition
- Antilock braking system (ABS) and Electronic Stability Program
(ESP®) have not intervened for t = 5 s
Parking space recognition function sequence The parking space detection function is used for simple locating of suitable parallel parking spaces. The parking space detection function is implemented via the outer front distance sensors. These monitor the area left and right of the vehicle and therefore have a larger range than the rest of the distance sensors.
At a speed of v = 0 to 18 km/h the parking system operates in mixed mode between obstacle and parking space detection. As of v gt 18 km/h the parking system changes to the parking space detection function and is activated up to v = 36 km/h.
The maximum range of the outer front distance sensors is between s = 400 and 450 cm depending on environmental influences (e.g. rain, snowfall, air humidity, extreme temperature (T = -40 to 85°C), air pressure, hot engine air).
The data from the outer front distance sensors is read in and evaluated by the parking system control unit.
It is calculated whether the parking space is suitable for the vehicle from the stored vehicle dimensions and deviations of the recorded parking space.
For a parking space to be recorded by the parking system, it must be:
- Parallel to the direction of travel
- At least s = 150 cm wide
- At least s = 130 cm longer than the vehicle
As soon as a parking space is detected an "Activate Park Assist?" message appears in the instrument cluster's multifunction display.
Next to the "Note surrounding area" warning message, the lower part of the multifunction display also enables the Park Assist to be activated.
The symbols shown in the multifunction display correspond to the OK button for "Yes" (activate) or the "Back" and voice control system OFF button for "No" (do not activate) in the left multifunction steering wheel button group.
The steering column tube module control unit reads in the control signals from the left multifunction steering wheel button group via the steering LIN and steering wheel electronics and sends these signals via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the instrument cluster. Depending on the response to the message, the instrument cluster sends the status of the Active Park Assist to the parking system control unit via chassis CAN 2.
Parking space recognition only recognizes a free space which is geometrically suitable for parking, not whether this free space actually also represents a parking space.
Monitoring ranges of distance sensors basic diagram for parking space detection
The trajectory, which consists of two arcs, forms the path to be taken into the parking space.
Display of potential parking spaces
Additional function requirements for displaying possible parking spaces
- Gear range "D" engaged
- Vehicle speed v = 0 to 30 km/h
Display of potential parking spaces function sequence
If the parking system is searching for a parking space, an indication in the form of a P symbol (6) is shown in the instrument cluster. As soon as an appropriate parking space is detected by the parking system, a left directional arrow (8) or a right directional arrow (7) also appears, that indicates the side of the vehicle on which the parking space is located.
Parking spaces are always looked for on both sides of the vehicle. However, only parking spaces on the passenger side are pointed out by default. To also allow parking spaces on the driver side to be displayed, the driver must actuate the turn signal in the appropriate direction. The signal to activate the display in the instrument cluster is transmitted by the parking system control unit over the chassis CAN 2 to the instrument cluster.
The switch position of the combination switch is read in by the steering column tube module control unit and sent via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the parking system control unit.
Changes to the parking situation after parking space detection are not considered by the parking system.
Additional function sequences for issuing steering and driving instructions
- Parking space detected
- Reverse gear engaged
- Activation information confirmed
Function sequence for issuing steering and driving instructions
If the parking system has detected a parking space and the parking procedure is to be commenced, appropriate steering and driving instructions are issued through the multifunction display in the instrument cluster.
The displayed arrow symbol fills or empties according to the steering angle or the distance traveled.
The steering angle is recorded by the steering wheel angle sensor. The steering column tube module control unit reads in the data from the steering wheel angle sensor directly and sends information about the steering wheel angle via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the parking system control unit. This calculates the required steering angle from the values read in and the calculated trajectory.
The distance traveled is calculated from the RPM sensor signals. The signals from the RPM sensors are read in by the Electronic Stability Program control unit and sent via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the parking system control unit. The parking system is active during the parking procedure.
If an obstacle is detected in the trajectory during the parking procedure, the instrument cluster issues a warning message over the multifunction display and actuates the internal warning hazard. The warning mode is abandoned if the obstacle is removed or the obstacle position is passed.
The following displays are possible with steering and driving instructions:
Driving instruction "Please drive to the right"
Driving instruction "Please reverse"
Driving instruction "Please drive to the left"
In the event of any "oversteer", a "Please correct left/right" message is displayed in the multifunction display. The steering wheel image remains the same, only the arrow changes direction.
target position in the parking space is reached.
| Electrical function schematic of parking system | PE54.65-P-2054-97TAB | ||
| Overview of system components of parking assistance systems | GF54.00-P-9997RDM |