Object Detection Description and Operation (UD7)
The ultrasonic parking assist system is designed to identify and
notify the driver of an object in the vehicle's path when reversing
at speeds of less than 8 km/h (5 MPH). The distance and location of
the object is determined by 4 object sensors located in the rear
bumper. The parking assist system will notify the driver using an
audible beep signal through the radio.
The parking assist system is made up of the following
components:
| • |
Parking assist control
module |
| • |
Rear object alarm
sensors |
| • |
Parking assist switch
indicator |
Parking Assist Control Module
The parking assist control module provides an 8 V reference and a
low reference to the four object alarm sensors. The parking assist
control module receives individual signals from each of the four
sensors and determines the location and distance of an object based
on these inputs. When an object is detected, the parking assist
control module will send a data message via CAN-Bus to the radio
requesting an audible alert.
Rear Object Alarm Sensors
The object alarm sensors are located in the rear bumper of the
vehicle. The sensors are used to determine the distance between an
object and the bumper. Each sensor emits an ultrasonic frequency
which is reflected off any object located behind the vehicle. These
reflections are received by the sensors. The time difference
between the emission of the frequency and when the reflection is
received is known as sensor echo time, it is used to determine the
distance to the object. The sensors report this information to the
parking assist control module.
Parking Assist Switch
The parking assist can be activated and deactivated by pressing the
parking assist switch. By engaging the reverse gear the parking
assist can also be activated. By subsequently pressing the parking
assist switch the parking assist can be disabled again.
Parking Assist Switch Indicator
The indicator in the parking assist switch shows the status of the
parking assist. If the lamp is ON, the parking assist is activated.
Rear Parking Assist Operation
When an object is within the measuring range of the sensor, the
ultrasonic pulse is reflected and is received by the sending or a
neighboring sensor. The sensor converts this signal into a voltage
signal and sends this signal to the parking assist control module.
The parking assist control module evaluates the received sensor
signals. As soon as an object is within the measuring range, the
parking assist control module sends a message to the radio in order
to give out the acoustic distance signal. If an object is detected
within 2.5 m (8 ft) away from the rear bumper, there will be an
audible beep out of the speakers. As the vehicle gets closer to an
object, the time between the beeps becomes shorter. If the vehicle
stops and there is an object within 2.5 m (8 ft) away from the rear
bumper the beeping will stop after 5 s. When the distance between
the object and the vehicle starts to decrease again the beeping
will start again. From a distance less than 30 cm (9.84 in), the
sound becomes continuous.
The rear parking assist system can detect objects greater than
7.6 cm (3 in) wide and 25.4 cm (10 in) tall. The system cannot
detect objects below the bumper, underneath the vehicle.
The parking assist can be activated and deactivated by pressing
the parking assist switch. By engaging the reverse gear the parking
assist can also be activated. By subsequently pressing the parking
assist switch the parking assist can be disabled again.
The parking assist control module carries out a self test and
monitors the sensors for electrical and mechanical faults.
Monitored is the power supply of each sensor and the sensor
signals, which need to alter when the vehicle moves. If this is not
the case, the sensor is acoustically blocked or faulty. Mud, ice
and snow may cause obstruction of the function of the sensors.
Besides that the parking assist control module checks whether the
correct type of sensor is installed. If any of these tests fails, a
DTC with corresponding symptom is set, the parking assist is
deactivated and the parking assist control module will send a
serial data message to display the SERVICE PARK ASSIST message on
the driver information center
Rear Parking Assist System Driver Information Center
Messages
SERVICE PARK ASSIST
The driver information center displays SERVICE PARK ASSIST when the
parking assist control module detects a malfunction in the rear
parking assist system and the system is disabled. The driver
information center also displays SERVICE PARK ASSIST when a loss of
communication occurs with the parking assist control module.
PARK ASSIST OFF
The PARK ASSIST OFF message is displayed in the driver information
center when the parking assist system is disabled due to conditions
that disable or inhibit the system. The parking assist control
module requests the driver information center display PARK ASSIST
OFF when it detects that one of the following conditions:
| • |
The rear parking assist system
is manually disabled by the vehicle operator through the parking
assist switch or audio system personalization menu. |
| • |
An object is attached to the
rear of the vehicle, such as a trailer, bicycle rack, trailer hitch
receiver, or tow bar. Also, an object extending beyond a lowered
tailgate will disable the system. |
| • |
The parking assist sensors are
covered by snow, mud, dirt, slush, or ice. |
| • |
The vehicle bumper is
damaged. |
| • |
Excessive paint thickness on a
replacement parking assist sensor. |
| • |
The parking assist sensors are
disrupted by vibrations, like those caused by a large nearby
vehicle or from heavy equipment such as a jackhammer. |
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