2398715 - 5580H parking obstacle detection device
The parking sensors provide the
driver with information relating to distance when approaching obstacles
either in front of or behind the vehicle. This aids parking manoeuvres
by identifying obstacles outside the driver's field of view.The information that there is an obstacle
and its distance is transmitted to the driver by means of acoustic
signals whose frequency depends on the distance from the obstacle.
COMPOSITION
The parking assistance system
on the vehicle comprises the following components:1 - electronic control unit
2 - ultrasound sensors
3 - trailer connection
4 - connection to CAN. (Body Computer)
5 - connection to CAN. (Instrument Panel)
COMPOSITION
On this version the acoustic
signal is located inside the instrument panel.
PARKING SENSOR CONTROL UNIT (CPA)
The CPA is an electronic component
which carries out functions helping the driver during manoeuvres
with reverse gear engaged by detecting any obstacles behind the
vehicle.The electronic control unit performs
the following functions:
- Activating the sensors
- Processing the signals received from the sensors
- Checking the operation of the sensors
- Activating the instrument panel buzzer
- Managing the diagnostics and test functions
The electronic control unit has a device
that provides protection against voltage fluctuations and short
circuits
CONTROL UNIT PIN OUT
The diagram below shows the control
unit and Pin Out1 - Electronic control unit
A - CONNECTOR A
B - CONNECTOR B
CONTROL UNIT PIN OUT
CONNECTOR A| Pin | Signal |
|---|
| 1 | Supply controlled by the ignition |
| 5 | Negative deactivating signal with tow hook
fitted |
| 7 | B-CAN A |
| 8 | Earth |
| 14 | B-CAN B |
CONNECTOR B| Pin | Signal |
|---|
| 1 | Sensor earth |
| 2 | Right rear interior sensor signal |
| 3 | Left rear interior sensor signal |
| 4 | Right rear exterior sensor signal |
| 5 | Left rear exterior sensor signal |
| 6 | Sensor positive |
SENSORS
The sensors are incorporated
in the bumper by means of special adaptors. The ultrasound technology
sensors act as intelligent transmitters/receivers through a triangulation
technique: this allows improved detection in critical situations
or in the presence of small obstacles. The impulses emitted are
reflected by any obstacles; the transducer therefore receives an
echo which is converted into a digital signal and sent to the electronic
control unit
SENSORS
Tow hooks, bicycle carriers or
similar accessories should not interfer with the operating range
of the sensors.The system covers the middle and side areas
of the rear of the vehicle with the performance depending on the
programmable detection area. If an obstacle is located in the middle
area, it is detected at a distance of between a minimum of 120 cm ± 10 cm
and a maximum of 150 cm ± 10 cm along the entire width of the
vehicle (door mirrors excluded). If the obstacle is loated in the side area,
it is detected at a distance of less than 0.6 m.
Operation
The sensors are ultrasoud transducers
working like intelligent transmitters and receivers of ultrasound
impulses. Both the impulse frequency and voltage is generated in
the transducer.The impulses emitted are reflected by any
obstacles; the transducer therefore receives an echo which is amplified
and converted into a digital signal and sent to the electronic control
unit via the same line used for the transmission request.Each sensor can also be operated as a receiver
only, in oder to carry out a triangular measurement between two
sensors. This technique allows for improved detection of small obstacles
and in situations featuring critical reflections.The sensors all have the same electrical
and mechanical properties: the maximum detection distance for each
sensor can be adapted using software depending on the location of
the actual sensor.
SENSOR PINOUT
| Pin | Signal |
|---|
| 1 | Sensor signal |
| 2 | Earth |
| 3 | Sensor supply |
OPERATION
The operation is illustrated
schematically
MEASURING THE DISTANCE OF OBSTACLES
The electronic control unit operates
the senors which convert the control unit electrical signals into
ultrasound impulse trains, with a cadence that varies from 3 to
10 measuring processes per second.The signal, reflected by any obstacles,
is received by the sensor and amplified, converted into a digital
signal and sent, in this format, to the electronic control unit.The control unit compares the signal emitted
with the one received and, using suitable algorithms, calculates
the time that elapses between the emission of the signal and the
receipt of the echo. This information is translated into distance
and communicated to the driver by means of acoustic warnings.  | The reflection from the ground
is ignored unless it has the properties of an obstacle. |
SELF-DIAGNOSIS
The control unit carries out
an autodiagnostic test when it is switched on. The sensors are diagnosed
each time they are activated.
RECOVERY STRATEGIES
The sensors and the wiring are
continuously diagnosed during the operation of the system. A fault
in even only one sensor will inhibit the operation of the entire
system.
ACTIVATION AND DEACTIVATION OF THE SYSTEM
When the control unit is switched
on (key-on and reverse gear engaged), an autodiagnostic test and
a test on all the surrounding components is carried out. The system
is ready to use in less than 0.5 seconds.The distance measurements only take place
when the system is activated.The system is activated when the
following two conditions occur:
- Key ON
- Reverse gear engaged
When the system is activated the buzzer
in the instrument panel gives off a signalIf obstacles are present, it emits the obstacle
distance signals whose frequency increase as the obstacle gets closer.If a fault occurs, the system emits a warning
signal.
OBSTACLE DISTANCE SIGNAL
The buzzer warns the driver that
the vehicle is approaching an obstacle. The tone lasts 75 ms, whilst
the interval between the tones is directly proportional to the distance
of the obstacle: impulses in rapid succession indicate that the
obstacle is very close. A continuous tone indicates that the obstacle
is less than 30 cm away. The tone cycle remains constant if the distance
measured by the centre sensors remains unchanged.
ERROR SIGNAL
Any faults/errors are signalled
acoustically.The acoustic signalling stops after 3 seconds.Errors/faults are signalled immediately
whilst the system is activated.
