Description and Operation

System Overview

RPAS (Rear Parking Assist System) is an electronic driver assistance system that warns the driver to be careful when parking or in low-speed environments. The sensors use ultrasonic waves to detect objects within the proximity of the vehicle. The 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 over the communication line. The BCM determines the warning level from the communication message transmitted by the slave sensors, and 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. RPAS activates each sensor and then performs diagnosis after BCM initialization is completed.
   4. The R-PAS start buzzer operates normally when the sensor does not send an error message and after the error diagnosis is completed.
   5. If any sensor failure is received, the R-PAS start buzzer does not operate, but the warning signal operates momentarily. If the vehicle has a display option, a warning symbol is also displayed on it.
   6. The sensor failure buzzer sounds once, but the display remains continuously illuminated until the fault is fully rectified.
2. 2
   Normal Mode

   1. LIN communication starts and continues the procedure after IGN1 ON+R.
   2. The BCM sends a operation request message once to each sensor to check the initial system status, and the four sensors are activated simultaneously. 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 levels sound intermittently, and the third level sounds continuously.
   5. The effective vehicle speed for RPAS operation is less than 10 km/h.
   6. Refer to "Digital PAS LIN Communication" for more detailed communication specifications.
3. 3
   Measurement conditions: PVC pole (diameter 75 mm, length 3 m), normal temperature
4. 4
   Distance to detected object (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, performed in order) With two or three sensors, one of them transmits and the others receive.

Direct and indirect measurement at the same 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, a warning is issued through an audible warning device such as a buzzer. The RPAS sensor sends data to the BCM via LIN communication, and the BCM implements the audible warning for each RPAS sensor by priority. It also acts as a gateway only when sending to a visual warning device such as the cluster.

• Buzzer and display processing method of BCM. In case of RL/RR sensor information, BCM processes each sensor information directly for the display and buzzer output function. For CL/CR sensor output, BCM processes the information as a center combination, with priority given to both sensors.

System Operation Specification: When the system has power (after IGN ON and R gear transmission), the MICOM checks each sensor channel. If any error is detected, the buzzer sounds at 300 ms and 500 ms intervals. If an error is found in a sensor, the buzzer of the corresponding faulty sensor sounds instead of the initial startup alarm. The 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 are classified by sensor distance. The state logic according to warning 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 (31–80 cm / 12.2–23.6 in)

   

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

   

   

*Determining the value of β. Alarm control using distance detection is as shown below. Visual Alarm Indicator Specification. When the transmission is in R, the indicator on the instrument cluster illuminates as shown in the figure below. When the system detects an object, the indicator illuminates immediately. During object detection, if there is no object, the indicator illuminates for two seconds, which is not an alarm, and then turns off after the object is detected. (However, when it changes the third-step alarm to the "No Alarm" state, it illuminates for two seconds and 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 RPAS and BCM. RPAS sends the object detection result and sensor diagnosis result to the BCM in accordance with this document, and the BCM performs the alarm function. The indicator displays the transmitted position and alarm data. In the event of an alarm, it finds the nearest DATA and first issues an alarm for the nearest DATA. (Example: If RL is a first-step alarm and RR is a third-step alarm, the RR alarm takes priority.)