Parking system, function - GF54.65-P-0006GN

MODEL 166 as of model year 2016 with CODE 235 (Active Parking Assist)

MODEL 292 with CODE 235 (Active Parking Assist)

Fig 1: Parking System Block Diagram

Courtesy of MERCEDES-BENZ USA

Block diagram

Function requirements, general

Circuit 15 ON

The circuit 15 status is sent by the electronic ignition lock control unit via the chassis CAN 2 to the parking system control unit.

Parking system, general

The parking system uses an ultrasonic measuring system to detect the distance between the vehicle and an obstacle. While driving at speeds of v < 36 km/h, parallel or perpendicular parking spaces on both sides of the vehicle in the direction of travel are measured, stored and the vehicle is moved in and out of a parking space semi-automatically upon the request of the driver.

Using the parking system warning indicator, the driver is visually informed of the respective distance between the vehicle and the obstacle. An acoustic warning is also issued via the warning buzzer in the instrument cluster.

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:

Vehicle speed and direction of travel
Driving stage engaged

Vehicle speed and direction of travel:

The vehicle speed is calculated on the basis of the wheel speeds. The direction of travel is determined using the wheel rotation direction of the front wheels. The Electronic Stability Program control unit sends this information via chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the parking system control unit and to the instrument cluster. The parking system control unit calculates the vehicle speed and defines the direction of travel. At the same time the instrument cluster also calculates the speed to be displayed and sends it over the chassis CAN 2 to the parking system control unit.

Engaged drive position:

The fully integrated transmission control unit transmits the current gear range via drive train CAN, CDI control unit or ME-SFI [ME] control unit, chassis CAN 1, electronic ignition lock 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
Deactivate and activate function sequence
Function sequence for reverse travel
Forward travel function sequence
Parking space recognition function sequence
Function sequence for display of possible parking spaces on instrument cluster
Function sequence for semiautomatic parking
Function sequence for semi-automatic parking space exit

Illustration of the principle for measuring procedure

Fig 2: Principle For Parking System Measuring Procedure

Courtesy of MERCEDES-BENZ USA

Measuring procedure function sequence

The parking system is based on the ultrasonic measuring procedure. In the process, the parking system distance sensors are actuated by the parking system control unit.

As a result of this these emit an ultrasonic signal. The ultrasonic waves reflected by an obstacle are received again by the distance sensors. The parking system control unit directly reads in the signals of the distance sensors and evaluates them. 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. Echoes can usually 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. The distance between the vehicle and obstacle can be calculated from two echo signals using the triangulation method. The propagation times of the signals from the direct measurement and from the cross measurement are required for this method. A long signal runtime thus equals a long distance between the vehicle and the obstacle, a short signal runtime equals a short distance between the vehicle and the obstacle.

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.

Fig 3: Measuring Parking Distance Procedure

Courtesy of MERCEDES-BENZ USA

Shown on model 292

The distance sensors are activated according to the direction of travel.

The distance sensors responsible for monitoring the front area (A) and the front corner protection area (B) are activated when the vehicle is moving forward.

The distance sensors responsible for monitoring the rear corner protection area (C) and the rear area (D) are also activated when the vehicle is moving backward.

The monitored range at the front (A) measures max. s = 100 cm and the monitored range at the rear (B) measures max. s = 120 cm. If the distance between the vehicle and an obstacle is less than s = 20 cm (c, e), the parking system will for technical reasons no longer receive any defined data.

Below a speed of v = 36 km/h the parking space detection range 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). In the process, the hardware of the parking system control unit is tested.

The gear range that is engaged does not influence the parking system control unit 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).

The self-test of the distance sensors depends on the engaged gear range.

Distance sensor test for subsequent vibrations:

A distance sensor test for subsequent vibrations (acoustic/physical function of the distance sensor) is performed cyclically.

Function test on parking system warning indicators:

If the parking system control unit receives the "Circuit 15 ON" status, all display elements of the parking system warning indicators are fully actuated for approx. t = 1 s.

If there are no malfunctions or faults, the two yellow horizontal "standby" bars light up in the parking system warning indicator. 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)

If there is a malfunction or system error, the parking system is deactivated and the LED in the parking system button lights up.

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 display elements of the currently actuated parking system warning indicator. They are directly actuated by the parking system control unit for t = 5 s.

If a malfunction exists any longer, identification of the cause takes place during driving operation via a self test. 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 display elements of the rear parking system warning indicator or those of the front parking system warning indicator light up, depending on the engaged gear range. An acoustic warning is also emitted for t = 2 s.

For this purpose, the parking system control unit sends a corresponding request via chassis CAN 2 to the instrument cluster. The instrument cluster then actuates the warning buzzer directly to issue the acoustic warning. After a further t = 3 s, the parking system switches off. A fault is entered in the fault memory of the parking system control unit, and the LED in the parking system button lights up. If the system error occurs again after a driving cycle, the described scenario is repeated.

Behavior in the event of overvoltage and undervoltage function sequence

The behavior of the parking system in the event of overvoltage or undervoltage is shown in the following table.

On-board electrical system voltage U < 9.0 V	On-board electrical system voltage U > 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 function test of parking system warning indicator	Start pulse has no influence on parking system
No function test, if voltage returns to normal	No function test, if voltage returns to normal	-	No function test of parking system warning indicator
LED in parking system ON button	LED in parking system ON button	-	-

Additional function requirements for activation and deactivation

Self-test completed successfully
Drive position "D" or "R" is engaged

Deactivate and activate function sequence

The parking system can be manually deactivated or activated by pressing the parking system button in the upper control panel.

The SAM control unit reads in the status of the parking system button via battery sensor LIN and transmits this via interior CAN, electronic ignition lock control unit and chassis CAN 2 to the parking system control unit.

If the parking system function is manually switched off using the parking system button, the function is automatically switched on when circuit 15 is activated again.

The intensity of the parking system warning indicator illumination for an activated parking system changes to match the ambient brightness. The ambient brightness is sensed by the rain/light sensor with additional functions. The SAM control unit reads in the data from the rain/light sensor with additional functions via the roof LIN and sends it via the interior CAN, electronic ignition lock control unit, and chassis CAN 2 to the parking system control unit. If the rain/light sensor with additional functions detects "night", the parking system warning indications are actuated at 60 % brightness. If the rain/light sensor with additional functions detects "day", the parking system warning indications are actuated at 100 % brightness.

When the parking system is deactivated, only the light-emitting diode in the parking system button lights up. The parking system control unit sends a corresponding request via chassis CAN 2, electronic ignition lock control unit, interior CAN, SAM control unit and battery sensor LIN to the upper control panel control unit. When driving, the parking system switches to standby mode between v = 60 and 16 km/h. In other words, the parking system control unit, the parking system warning indicators and the distance sensors are still supplied with power but the parking system warning indicators are switched to "dark".

Additional function requirements for reverse travel

Vehicle speed v = 0 to 18 km/h or vehicle speed v = 16 to 0 km/h
Backward movement of vehicle
No trailer recognized (with CODE 550 (Trailer hitch))

The "Trailer detected" status is transmitted by the trailer recognition control unit to the parking system control unit over the interior CAN, electronic ignition lock control unit and chassis CAN 2.

Function sequence for 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 warning segments of the parking system warning indication lighting up.

When dropping below a distance of s = 30 cm, the warning is then intensified by an intermittent tone and subsequently by a continuous signal. When the upper speed limit of v = 18 km/h is exceeded, the parking system goes over into stand by mode again.

If gear range "R" is engaged immediately after the engine is started, no acoustic warning is issued even if an obstacle is located immediately in front of the vehicle (only a visual warning is given).

Additional function requirements for forward travel

Vehicle speed v = 0 to 18 km/h or vehicle speed v = 16 to 0 km/h

Forward travel function sequence

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 first warned visually by the appropriate warning segments in the parking system warning indication lighting up.

Additional function requirements, parking space recognition

Antilock braking system (ABS) and Electronic Stability Program (ESP®) have not intervened for t = 5 s
Vehicle speed v < 36 km/h

Parking space recognition function sequence

The parking space detection function is used for simple locating of suitable parallel or perpendicular 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 > 18 km/h the parking system changes to the parking space detection function and is activated up to v = 36 km/h.

Shown on model 292

Fig 4: Measuring Maximum Range Of Outer Front Distance Sensors For Parking Space Detection

Courtesy of MERCEDES-BENZ USA

The range of the outer front distance sensors amounts to a maximum of between s = 400 to 450 cm depending on environmental influences (e.g. rain, snowfall, air humidity, extreme temperatures of e.g. T = -40 or +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.

Minimum size of a parallel parking space (parallel to the direction of travel):

At least s = 150 cm wide
At least s = 100 cm longer than the vehicle

Minimum size of a perpendicular parking space:

At least vehicle width + s = 100 cm
At most vehicle width + s = 250 cm

A boundary point is always required for longitudinal and transverse parking.

After the driver has engaged gear range "R", the "Activate Park Assist?" query appears in the multifunction display of the instrument cluster. Alongside the warning message to pay attention to the surrounding area, the option to activate the Active Parking Assist is also shown in the lower part of the multifunction display. The semi-automatic parking space entry function is activated using the OK button. The procedure is aborted by pressing the "Back" button. The buttons are in the left multifunction steering wheel button group.

The steering wheel electronics reads in the signals of the multifunction steering wheel button group directly and sends these via steering LIN, steering column tube module control unit, chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the parking system control unit.

The parking system detects an empty space which is geometrically suitable for parking. It does not recognize whether the empty space is actually suitable as a parking space.

Parking space detection, illustration of the principle

Fig 5: Principle For Parking Space Measuring Procedure

Courtesy of MERCEDES-BENZ USA

The trajectory, which consists of two arcs, forms the path to be taken into the parking space.

Additional function requirements for display of possible parking spaces on instrument cluster

Gear range "D" engaged
Vehicle speed v = 0 to 30 km/h

View of parking symbol in multifunction display

Fig 6: View Of Parking Symbol In Multifunction Display

Courtesy of MERCEDES-BENZ USA

Function sequence for display of possible parking spaces on instrument cluster

When the parking system is searching for a parking space, a P symbol (6) appears in the multifunction display of the instrument cluster. As soon as an appropriate parking space is detected by the parking system, a left directional arrow (7) or a right directional arrow (8) also appears in addition to this symbol 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 multifunction display is sent by the parking system control unit over the chassis CAN 2 to the instrument cluster.

The position of the combination switch is read in by the steering column tube module control unit and sent via the chassis CAN 1, electronic ignition lock 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 requirements for semi-automatic parking

Speed v < 10 km/h (except CODE 498 (Japan version))
Speed v < 7 km/h (with CODE 498 (Japan version))

Function sequence for semiautomatic parking

If the Active Park Assist has been activated, appropriate driving instructions appear on the multifunction display in the instrument cluster. The driver can now take the hands off the steering wheel.

The parking system control unit calculates the corresponding steering angle based on the size of the detected parking space as well as the data from the steering wheel angle sensor. The steering column tube module control unit directly reads in the data of the steering wheel angle sensor and sends it over chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 to the parking system control unit. The parking system control unit then sends corresponding steering commands over chassis CAN 2 to the electrical power steering control unit. The electrical power steering control unit actuates the electric power steering actuator motor correspondingly. The steering gear is used to mechanically convert the electric power steering actuator motor actuation into steering movements.

At the same time, the request to engage the required gear range is shown in the multifunction display.

The parking system control unit monitors the gear rack travel on the steering gear. The electrical power steering control unit then sends the corresponding information over chassis CAN 2 to the parking system control unit.

After the respective gear range or gear has been changed, the driver must move the vehicle until the end position has been reached and the vehicle brakes automatically.

As of a speed of v = 7 km/h, the multifunction display shows the "Park Assist only up to 10 km/h" message (except CODE 498 (Japan version))
As of a speed of v = 5 km/h, the multifunction display shows the "Park Assist only up to 7 km/h" message (with CODE 498 (Japan version))

If the vehicle reaches (forward or backward) a distance of s < 30 cm to the parking space boundary, this is signaled to the driver by illumination of the first red display element in the corresponding parking system warning indicator.

At the same time, the parking system control unit sends information about the current remaining distance to the obstacle via chassis CAN 2, electronic ignition lock control unit and chassis CAN 1 to the Electronic Stability Program control unit.

The Electronic Stability Program control unit calculates the required braking torque and actuates the traction system hydraulic unit directly. The vehicle is braked. The vehicle is braked to stop at the required maneuvering points as well as an in the target parking position.

Any changes to the remaining distance to the obstacle that occur at short notice are also taken into account (e.g. a person walking into the path of the vehicle). Depending on the current driving situation, however, it is not always possible to prevent a collision in such cases. Delimitation at the side of the parking space is defined by a recognized obstacle (e.g. a curb or pole). If an obstacle is not detected at the side, the vehicle is aligned flush to the front or rear obstacle.

The inclined position of the vehicle in the parking space is corrected by the parking system by means of corresponding maneuvering movements. The wheels are straightened once the parking procedure has been completed. As soon as the vehicle is secured, the message "Park Assist complete - Take over vehicle" appears for t = 5 s on the multifunction display in the instrument cluster.

The vehicle is secured by the driver engaging the gear range "P" or operating the parking brake.

Additionally, the warning buzzer issues a warning tone.

The target position of the vehicle is generally as far into the parking space as possible.

The following situations lead to deactivation of the parking system and therefore to cancellation of the Active Parking Assist:

Exceeding the permissible speed of v = 10 km/h (except CODE 498 (Japan version)) or v = 7 km/h (with CODE 498 (Japan version))
Turning the steering wheel ("hands-on detection").
To do this, the electrical power steering control unit directly reads in the torque values of the electric power steering torque sensor and recognizes that the steering wheel is actively turned based on the torque difference. In this case, the electrical power steering control unit sends a corresponding status information to the parking system control unit over the chassis CAN 2.
Defect on an electrical component in the power steering
Defect on an electric or hydraulic component of the brake system
Faulty CAN signals
Driver's door and driver seat-belt buckle open at same time
Deactivating the parking system by pressing the parking system button

In the event of a deactivation of the parking system because of the listed circumstances, a reactivation requires a change of gear range. If the vehicle is out of the previously calculated trajectory, then the vehicle must be manually returned to the starting position, from which a new trajectory can then be calculated.

The following messages are additionally shown on the multifunction display in the instrument cluster:

"Park Assist Active - Please engage gear range D"
"Park Assist Active - Please engage gear range R"
"Park Assist terminated - Please take over"
"Park Assist terminated"
"Park Assist nonfunctional"
"Park Assist only up to 10 km/h" (except CODE 498 (Japan version))
"Park Assist only up to 7 km/h" (with CODE 498 (Japan version))

Additional function requirements for semi-automatic parking space exiting

Vehicle was parked semi-automatically
Semi-automatic parking space exit function activated in "Park Assist" menu
Gear range not equivalent to "P"
Obstacle detected in front of and behind vehicle
Turn signal indicator set (in exit parking space direction)

Function sequence for semi-automatic parking space exit

The semi-automatic parking space exit function must be preceded by the semi-automatic parking space entry function and can only be executed on the side of the road on which the vehicle was parked. This ensures that the vehicle is positioned parallel to the curb, if applicable. This information is required as the Active Parking Assist first requests "straight to the rear" vehicle movement to exit the parking space.

If the vehicle was positioned in the parking space at an angle, the rims could be damaged by the curb. The semi-automatic parking space exit function is activated by actuating the turn signal indicator in the direction (left or right) in which the parking space is to be exited. The steering column tube module control unit directly reads in the position of the combination switch and sends it via the chassis CAN 1, electronic ignition lock control unit, and chassis CAN 2 to the parking system control unit.

The parking system control unit also evaluates the gear range status here. If the gear range is not "P", the parking system control unit transmits the request "Start Parking Assist?" over chassis CAN 2 to the instrument cluster.

The driver can then activate the semiautomatic parking function using the left multifunction steering wheel button group to match the driver request (exit parking space at left or right). The semi-automatic exiting of a parking space is activated via the OK button. The procedure is aborted by pressing the "Back" button.

The parking system control unit sends corresponding steering commands to the electrical power steering control unit via chassis CAN 2.

The electrical power steering control unit actuates the electric power steering actuator motor correspondingly (full steering angle). The steering gear is used to mechanically convert the electric power steering actuator motor actuation into corresponding steering movements.

According to the necessary maneuvering movements, the parking system control unit sends the request for visual output of the corresponding driving instructions via chassis CAN 2 to the instrument cluster.

If the vehicle reaches (forward or backward) a distance of s < 30 cm to the parking space boundary (maneuvering point), this is signaled to the driver by illumination of the first red display element in the corresponding parking system warning indicator.

The vehicle is braked automatically at the corresponding maneuvering points.

The Electronic Stability Program control unit calculates the required braking torque and actuates the traction system hydraulic unit directly. The vehicle is braked.

Once the Active Parking Assist has positioned the vehicle so that the driver can drive directly out of the parking space, the parking system control unit sends the message "Parking assistance completed - Take over vehicle" via chassis CAN 2 to the instrument cluster.

The following circumstances lead to deactivation of the parking system and therefore to cancellation of the Active Parking Assist:

Exceeding the permissible speed of v = 10 km/h (except CODE 498 (Japan version)) or v = 7 km/h (with CODE 498 (Japan version))
Turning the steering wheel ("hands-on detection").
To do this, the electrical power steering control unit directly reads in the torque values of the electric power steering torque sensor and recognizes that the steering wheel is actively turned based on the torque difference. In this case, the electrical power steering control unit sends a corresponding status information to the parking system control unit over the chassis CAN 2.
Defect on an electrical component in the power steering
Defect on an electric or hydraulic component of the brake system
Faulty CAN signals
Driver's door and driver seat-belt buckle open at same time
Deactivating the parking system by pressing the parking system button

The following messages are also displayed on the instrument cluster:

"Park Assist Active - Please engage gear range D"
"Park Assist Active - Please engage gear range R"
"Park Assist terminated - Please take over"
"Park Assist terminated"
"Park Assist nonfunctional"

Electrical function schematic of parking system		PE54.65-P-2054-97NBA
Overview of system components of parking assistance systems	MODEL 166 as of model year 2016 with CODE 218 (Rear view camera) with CODE 235 (Active Parking Assist) with CODE 501 (360° camera) MODEL 292 with CODE 218 (Rear view camera) with CODE 235 (Active Parking Assist) with CODE 501 (360° camera)	GF54.00-P-9997GN