Description and Operation

System Overview

RPAS (Rear Parking Assist System) is an electronic driving aid that warns the driver to be careful when parking or moving at low speed. After detecting an object at the side and rear of the vehicle using ultrasonic waves, it alerts the driver. RPAS consists of four RPS sensors that detect obstacles and transmit the result divided into three warning levels: first, second and third, to the BCM via the communication line. The BCM determines the warning level from the communication message transmitted by the slave sensors, then activates the buzzer or transmits data for display.

System Block Diagram

System Operation Specification

1. 1
   INITIAL Mode

   1. The system initialization time is 500 ms after IGN1 + R gear.
   2. RPAS recognizes the LID and sets the sensor identifier during initialization.
   3. The RPAS activates each sensor and then performs diagnostics after the BCM initialization is completed.
   4. The R-PAS starting buzzer operates normally when the sensor does not send an error message and after error diagnosis is completed.
   5. If any sensor failure is received, the R-PAS starting buzzer does not operate, but the warning buzzer operates momentarily. If a display option is fitted, a warning indicator is also shown on it.
   6. The buzzer sounds once when a sensor fails, but the display is shown continuously until the system is fully repaired.
2. 2
   Normal Mode

   1. LIN communication starts and maintains the procedure after IGN1 ON + R gear.
   2. BCM sends a request message once to each sensor to check the initial system status and to operate the four sensors in time. At this time, if there are no problems, the alarm starts after 500 ms of shifting into R, at 300 ms intervals.
   3. After initialization, normal mode starts 100 ms after completion. Warning output.
   4. The obstacle warning is divided into 3 levels. The first and second levels are intermittent sounds, and the third level is a continuous alarm. (Front sensors have second and third level warnings.)
   5. The effective vehicle speed for RPAS operation is less than 10 km/h.
   6. For details, refer to the section "Digital PAS Project LIN Communication" for the detailed communication specification.
3. 3
   Measurement conditions – PVC pole (diameter 75 mm, length 3 m), normal temperature
4. 4
   Distance to detected objects (measured directly in front of the sensor)

   Position	Level	Distance Range
   		cm	inch
   Rear	1st	61 ~120 (±15)	24,0 ~ 47,2 (±5,9)
   	2nd	31 ~ 60 (±15)	12,2 ~ 23,6 (±5,9)
   	3rd	Less than 30 (±10)	Less than 11.8 (±3.9)

   

   

Detection Zone / Horizontal Detection Zone / Vertical Detection Zone / Distance Measurement

Direct measurement

Transmission and reception are performed by one sensor (RL, RCL, RCR, RR for each sensor configuration).

Indirect measurement

(RCL → RL, RCL → RCR, RCR → RCL, RCR → RR, performed in order) With two or three sensors, one of them transmits and the others receive.

Direct and indirect measurement at one time

With two or three sensors, one sensor performs both transmission and reception, and the others perform reception only.

PAS Warning System When the RPAS sensor detects an obstacle, the warning is given by an audible alarm. The device acts as a buzzer. The RPAS sensor sends data to the BCM via the LIN bus, and the BCM outputs the audible warning for each RPAS sensor according to priority. The BCM acts as a gateway only when it sends a visual warning device, such as the cluster.

• Sensor Buzzer / Information Processing Method in BCM Display In the case of RL / RR sensor information, the BCM processes each sensor's information directly for the display and buzzer function. For the CL/CR sensor buzzer output, the BCM processes the central combination information according to the priority of both sensors.

System Operation Specification When power is supplied to the system (after IGN ON and R gear is selected), the MICOM checks all sensor channels. If no faults are detected, the buzzer sounds for 300 ms, 500 ms later. If any fault is found, even in a sensor, the corresponding buzzer sounds as a sensor fault instead of the initial start signal. Normal mode entry function is shown below.

With R gear, the system function is as follows:

When the R gear is released, the system functions as shown below.

※ Permissible signal error range: ±10% Warning output characteristics classified by distance between sensors. The status logic according to warning level priority is as follows. (Identical sensor)

* Determination of α value

1. 1
   Low priority sensor off: α = 0 ms
2. 2
   Low priority sensor - 1st level warning: α < 340 ms
3. 3
   Low priority sensor - 2nd level warning: α < 170 ms
4. 4
   Low priority sensor - 1st level warning: β = 1700 ms
5. 5
   Low priority sensor - 2nd level warning: β = 1700 ms
6. 6
   Low priority sensor - 3rd level warning: β = 700 ms
7. 7
   First warning zone (61 cm ~ 120 cm)

   

8. 8
   Second warning zone (31 cm to 60 cm)

   

9. 9
   Third warning zone (less than 30 cm)

   

10. 10
    Alarm period

    1. With visible display

       

    2. Without Visual Display When the system has a channel error at the initial moment, the system informs the location of the sensor channel error through the audible buzzer (three times for each sensor).

       

*Determination of β value Warning control by distance determination is as shown below. Error Handling

LIN BUS Off Error Case

Section	Fault recognition condition	Fault release condition
Initial routine	LIN BUS OFF detected once	Fault is not reset in the initial mode.
Normal routine	LIN BUS OFF detected several times in succession	The fault is cleared when the BCM or LIN master module determines four times in a row, in normal mode, that the LIN bus is on.

※ Note:

1. 1
   When counting faults, the output message or signal must be transmitted as the last valid value.
2. 2
   Fault in initial mode, fault buzzer operates (BCM).

Sensor error (LIN message: 0x08)

Section	Fault recognition condition	Fault release condition
Initial routine	Single detection of the message	Fault is not reset in the initial mode.
Normal routine	Sensor malfunction. The message is recorded four times in succession.	The fault is cleared when the BCM or LIN master module determines four times in a row, in normal mode, that the LIN bus is on.

※ Note:

1. 1
   When counting faults, the output message or signal must be transmitted as the last valid value.
2. 2
   Fault in initial mode, fault buzzer operates (BCM).
3. 3
   When a fault occurs in the direct state, the sensors send the same fault status for the indirect condition.

Communication Standard This section defines the communication between the RPAS and the BCM. The RPAS sends the obstacle detection result and the sensor diagnosis result to the BCM in accordance with this document, and the BCM takes on the role of the alarm. The indicator shows the transmitted position and alarm data; in case of an alarm, it finds the nearest DATA and gives the signal for the nearest DATA first. (Example: If RL is the first-level warning and RR is the third level, the RR warning has priority.)