System Overview

RPAS (Rear Parking Assist System) is an electronic driver assistance system that warns the driver to exercise caution when parking or at low speed. The sensors use ultrasonic waves to detect objects in the immediate vicinity of the vehicle. RPAS consists of four sensors that detect obstacles and transmit the result, divided into three warning levels, to the IPM (BCM) via the communication line. The IPM (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. R-PAS activates each sensor and then performs diagnosis after BCM initialization is complete.
   4. R-PAS start buzzer operates normally when the sensor does not send a malfunction message and after the fault diagnosis is complete.
   5. If any malfunction is received from any sensor, the R-PAS start buzzer does not sound, but the warning alarm sounds for a moment. If the vehicle has a display option, the warning symbol is also shown in the cluster.
   6. When a sensor malfunction occurs, the buzzer sounds once, but the display remains on until the malfunction is fully repaired.
2. 2
   Normal Mode

   1. Line communication starts and maintains the procedure after IGN1 ON+P transmission.
   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 the alarm output is completed.
   4. The obstacle warning is divided into 3 levels. The first and second are intermittent sounds, and the third alarm is continuous.
   5. The effective vehicle speed for R-PAS operation is below 10 km/h.
   6. Refer to the "Digital PAS Project LIN Communication" section for more detailed communication specifications.
3. 3
   Measurement conditions – PVC pole (diameter 75 mm, length 3 m), normal temperature
4. 4
   Detection distance range (measured directly in front of the sensor) 61 cm (24.0 in) ~ 120 cm (47.2 in): ± 15 cm (5.9 in) 31 cm (12.2 in) ~ 60 cm (23.6 in): ± 15 cm (5.9 in) Less than 30 cm (11.8 in): ± 10 cm (3.9 in)

   

   

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, in sequence) 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.

RPAS Warning System: When an RPAS sensor detects an object, the warning is output through an audible warning device such 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. It also acts as a gateway only when sending the visual warning device signal, such as the cluster.

• Sensor buzzer/display information processing method in BCM. In case of RL/RR sensor information, BCM processes the information of each sensor directly for the display and buzzer function. Buzzer output for CL/CR sensors: BCM processes the center combination information by giving priority to both sensors.

System Operation Specification: When the system is powered (after IGN ON and shift to R), the MICOM checks each sensor channel. If any error is detected, the buzzer sounds for 300 ms, then 500 ms. However, if any error is found, including a sensor error, the corresponding buzzer sounds for the sensor malfunction instead of the initial start signal. Normal mode entry function is as shown below.

With R gear, the system function is as follows:

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

※Allowable signal error range ±10%. Alarm output characteristics are classified by distance between sensors. The state logic according to alarm level priority is as follows. (Same 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 (61–120 cm / 24–47.2 in)

   

8. 8
   Second warning zone (31–60 cm / 12.2–23.6 in)

   

9. 9
   Third warning zone (less than 30 cm / 11.8 in)

   

   

*Determination of β value. Alarm control by distance determination is as shown below. Visual Alarm Indicator Specification: When the transmission is in the R position, the indicator on the instrument cluster illuminates as shown in the illustration below. When the system detects an object, the indicator illuminates immediately. During object detection, if no object is present, the indicator that is not in alarm status illuminates for two seconds, then turns off after object detection. (However, when changing from the third-step alarm to the "No Alarm" state, the third-step alarm indicator illuminates for two seconds and then turns off.)

• It only indicates the obstacle detection position.
• At the third warning level, the indicator flashes at one-second intervals.
• When the normal alarm level is displayed, the RCR/RCL indicators are combined by priority.

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