Hyundai Creta: Rear Parking Assist System / Description and operation

System Overview
RPAS(Rear Parking Assist System) is an electronic driving aid device warning driver to be cautious when they park or speed low after detecting an object on side and behind of vehicle by using the feature of ultrasonic waves.
RPAS consists of four RPS sensors which are detecting the obstacles and transmit the result separated into three warning levels, the first, second and third to BCM by Lin communication. BCM decides the alarm level by the transmitted communication message from the slave sensors, then operate the buzzer or transmits the data for display.

System Block Diagram

System Operation Specification.
INIT mode
System initializing time is 500ms after IGN1+ R Gear.
RPAS recognizes LID and sets the sensor ID up during initialization.
RPAS activates each sensor and then executes the diagnosis after finishing initialization of BCM
R-PAS Starting buzzer" is normally worked, when sensor does not send an error message and after finishing error diagnosis.
If any failure is received from the any sensors, R-PAS Starting Buzzer" does not work but the failure alarm is operated for a moment.
If you have display option, warning sign is also shown on it.
Buzzer for sensor failure is operated once, but display is shown continuously until it is repaired completely.
Lin communication starts and keeps the routine after IGN1 ON+R gear
BCM send a message once to each sensor for operating request to check the initial status of the system and four sensors response at a time. At this time, if there is no problem, the alarm starts after 500ms of R gear shifting at 300ms intervals.
After initialization, normal mode starts 100ms later after finishing alarm output.
Alarm for obstacles is divided into 3 levels.
The first and second are intermittent sound, and the third alarms continuously
The efficient vehicle speed of RPAS operation is under 10Km/h.
Refer to ‘Digital PAS Project LIN communication’ for the more detailed communication specification.
Sensing Area
Measurement condition – PVC pole (diameter 75mm, length 3m), normal temperature
Distance range detected objects (Measured directly in front of sensor)
61cm(24.0in) ~ 120cm(47.2in) : ± 15cm(5.9in)
31cm(12.2in) ~ 60cm(23.6in): ± 15cm(5.9in)
Less than 30cm(11.8in) : ± 10cm(3.9in)
Horizontal Sensing Area

Vertical Sensing Area

Distance Measurement
Direct Measurement
Transmission and Reception are executed with one sensor
(RL, RCL, RCR, RR each sensor execution)

Indirect Measurement
(RCL → RL, RCL → RCR, RCR → RCL, RCR → RR Execution in order)
With two or three sensors, one of them sends the transmission and the others get the reception.

Direct and Indirect Measurement at once
With two or three sensors, the one sensor performs both transmission and reception, and the others perform only reception.

RPAS Alarm System
When the RPAS sensor detects the object, warning is operated by audible alarm device as like buzzer. RPAS sensor sends data to BCM with LIN communication and BCM implements audible warning for each RPAS SENSOR by priority. And it performs a role of gateway only when it sends visible alarm device such as Cluster.
Sensor buzzer/display information processing method of BCM In case of RL/RR sensor information, the BCM handles each sensor information directly about Display and buzzer output function. Buzzer output of CL/CR sensor, BCM handles center combination information by priority both sensor.
System Operation Spec
When the system has the power (after IGN ON and R gear), MICOM checks every sensor channel. In case it is not find any error, it sounds 300ms buzzer 500ms afterward. But it finds any error even a sensor, it sounds buzzer corresponding fault sensor instead of initial starting alarm. Function for normal mode entrance is as below

With R Gear, system function is as below

With R gear releasing, system function is as below

※acceptable error range on waveform ±10%
Alarm Output Specification Classified by Distance Between Sensors
Condition logic according to priority of alarm level is as below. (the identical sensor)

*α value definition
low priority sensor off : α = 0ms
low priority sensor is 1st warning level : α < 340ms
low priority sensor is 2nd warning level : α < 170ms
*β value definition
low priority sensor is 1st warning level : β = 1700ms
low priority sensor is 2nd warning level : β = 1700ms
low priority sensor is 3rd warning level : β = 700ms
Alarm control by sensing distance is as below
First warning area (61cm ~ 120cm)

Second warning area (31cm ~ 80cm)

Third warning area (less than 30cm)

Visible Alarm Indicator Specification
When the gear is applied to R, cluster lights the indicator as below figure.
When the system finds an object, it lights indicator immediately. During sensing an object, if there is no object, it lights indicator that is no alarm status for two seconds and then turns out afterward detecting an object.
(But when it turns third step alarm to No alarm status, it lights third step alarm for two second and turns out.)

It shows only the detecting position of obstacles.
In third level alarm, indicator flickers at intervals of a second.
In normal alarm level display, RCR/RCL indicator is combinated by priority.
Communication Standard
This section defines the communication between RPAS and BCM.
RPAS send a detecting result of object and sensor diagnosis result to BCM according to this document, and BCM takes a role to alarm.
Indicator shows the transmitted position and alarm data, in alarm case, it finds the nearest DATA and alarms the nearest DATA first.
(Ex. In case, RL is first step alarm and RR is third step, RR alarm has priority.)
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