PARK DISTANCE CONTROL (PDC)
Model: E65 - 745i
Production Date: 11/2001 - Start of Production
Objectives
After completing this article you should be able to
- Recognize the changes made to the E65 PDC system over the previous model.
PDC Control Unit
The PDC Control Unit is located in the right rear corner of the luggage compartment.
Its main tasks are
Scheme 40
- Activation of sensors and reception of echo signals.
- Evaluation of the received echo signals.
- Activation of the function indicator (LED in the switch).
- Sending messages via K-CAN-S to ASK and the CD.
- Monitoring the inputs and outputs.
- Management of the diagnosis and test functions.
PDC uses the echo sounding principle to calculate the distances between each of the 4 sensors in the front and rear bumpers and any obstacle that might be present.
In addition, a three-way calculation can be used to calculate the effective distance to the bumper in the case of an obstacle between two sensors.
This three-way calculation is enabled by co-sensing of the neighboring sensors.
An active sensor system in the converter processes the received echo signals, performs the evaluation and communicates across a bi-directional data line with the control unit.
Sensors
The PDC system of the E65 uses 8 sensors in total, 4 in the front bumper and 4 in the rear.
The control unit sends a digital signal to set the ultrasonic sensor either in a combined transmit and receive mode or in a receive only mode.
Combined Mode
The sensor first transmits a packet of ultrasonic impulses and then receives the echoes reflected by the obstacle within its sensing range.
Scheme 41
On the basis of the time span between transmission and reception, the control unit calculates the distance to the obstacle.
Receive Only Mode
The sensor receives the impulses deflected by the neighboring sensors. The evaluation of these signals in the control unit improves the certainty of detection of the system.
Previous Sensor
Scheme 42
E60 PDC Sensor
Scheme 43
The design of the sensor varies from that used until now in that the outer membranes are completely round instead of oval.
The advantages of this new round membrane shape are the greater detection range and lower sensitivity in wet conditions. The sensors are always painted in body color.
The PDC button is to the left of the start/stop button and it consists of the following components
Scheme 44
- Button
- Function indicator (LED)
- Location light
The button can be used to activate or deactivate PDC manually. The locating light is connected to terminal 58g. The function indicator LED is connected to the control unit.
When the PDC is activated, the LED turns on permanently. In the event of an error message, it flashes at a frequency of 2 Hz.
Interfaces
The communication with the vehicle electronics takes place across the K-CAN S.
Scheme 45
Audio System Controller (ASK)
The acoustic distance warning is output through the front midrange speaker of the audio system in the doors and in the rear shelf. The signal tones for all 4 loudspeakers as well as their intervals are processed in the ASK and mixed with the current audio output.
The dedicated speakers used until now are no longer used in the E65.
Control Display (CD)
If the "PDC Pic" option is enabled from the "Settings" menu, the visual distance warning is displayed in the CD and the graphic is generated in the CD.
Instrument Cluster
The instrument cluster is used by the PDC as a display unit for Check Control (CC) messages. The PDC control unit also receives the outside temperature as well as the mileage reading from the instrument cluster.
Ice and dew can lead to false activations of the ultrasonic sensors. In order to reduce the effect of this phenomenon, the response characteristics are adapted via software as of +6°C and colder.
In the case of a fault code entry in the fault memory, the km reading and the outside temperature are also stored.
Dynamic Stability Control DSC
The DSC control unit provides the speed signal.
Adaptive Gearbox Control (AGS)
The AGS provides the reverse gear signal for automatic activation of the PDC.
CAR Access System (CAS)
The CAS reports the terminal status (KLR, KL15, KL50).
Power Module (PM)
The PM telegrams the vehicle battery voltage.
Activation Of The PDC
The system is activated automatically with a delay of approximately one second when the ignition is on and the selector lever is moved reverse.
After a driving distance of 50 m or a speed of 30 km/h is exceeded, the system switches off. The indicator LED in the button goes out when the system is no longer active.
The PDC can also be manually activated or deactivated by using the PDC button.
PDC Acoustic Warning
The distance to an obstacle is indicated by an intermittent tone according to its distance from the sensor. If, for example, an obstacle is detected to the left front of the vehicle, the sound signal is issued at the left front speaker.
Scheme 46
The closer the vehicle comes to the object, the shorter the frequency of the signal becomes. If the distance to a detected object is smaller than approximately 30 cm (11 in.), a continuous tone is issued.
The sound signal is interrupted after approximately 3 seconds if the vehicle is driven parallel to a wall.
This interruption does not occur in the continuous tone mode (distance smaller than 30 cm).
PDC Visual Warning
The distance to an obstacle can also be displayed visually in the Control Display.
To enable the visual display Select "settings" in the CD and then select the "other vehicle functions" page which is displayed as the silhouette of a car. Activate it by pressing "PDC pic."
Once the visual display is enabled it will always display whenever the PDC becomes active.
The display takes priority over any item that is currently being displayed on the Control Display. It can be temporarily switched off by pressing down on the Controller.
To disable the visual display completely requires returning to the settings menu and deselecting it.
Scheme 47
Maximum Visual Detection Range Displayed In The CD
The visual display uses color to distinguish how close an object is, the following colors are used
- Green: over 100 cm (39 inches)
- Yellow: 100 to 50 cm (38 to 19 inches)
- Red: less than 50 cm (less than 19 inches)
Check Control Message
If there is a fault in the PDC system, no acoustic and visual warning is issued. The indicator LED in the PDC button flashes.
The following Check Control Message is issued
Scheme 48
Review Questions
- What control unit is responsible for generating the acoustic output of the PDC? How does it receive the request?
- How is the visual display of the PDC enabled? Does it have to be turned on this way every time the driver wishes to have the visual display?