Continental Automotive 5WK4291 Child Seat Presence and Orientation Detection/Pass User Manual Inst Manual

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Document ID	61173
Application ID	imqT2FIn+yv8AKgjGnAxbA==
Document Description	Inst Manual
Short Term Confidential	No
Permanent Confidential	No
Supercede	No
Document Type	User Manual
Display Format	Adobe Acrobat PDF - pdf
Filesize	22.29kB (278679 bits)
Date Submitted	1999-09-30 00:00:00
Date Available	1999-12-23 00:00:00
Creation Date	1999-09-30 11:14:51
Producing Software	Photoshop PDF Plug-in 1.0
Document Lastmod	1999-09-30 11:15:13
Document Title	Inst Manual
Document Creator	Photoshop PDF Plug-in 1.0

(r;
SI EM ENS Automotive Systems
AT SE 801 CA13
Operating Manual/Functional Description
for
Siemens
Child seat Presence and Orientation Detection!
Passenger Presence Detection
(CPOD/PPD)
FCC ID: KR55WK4291
This device complies with part 15 of the FCC Rules. Operation is subject to the following two
conditions: (1) This device may not cause harmful interference, and (2) this device must
accept any interference received, including interference that may cause undesired operation.
CPOD Technical Description
I. Technical description CPOD
The Child Seat Presence and Occupant Detection (CPOD) is a transponder principle based
sensing device that provides information on the passenger and child seat presence in order
to adapt the airbag deployment in regard to the occupant situation The system is
comprised of a Force Sensitive Resistor (FSRTM) that has both a sending and receiving
antenna and an Electronic Controi Unit (ECU), both are permanently connected and built
into the passenger seat, along with two resonators that are permanently built into the child
seat.
The ECU generates a 130kHz-band inductive field which charges up the resonators. After
capturing the transmitted signal, the resonators modulate the phase shift of the carrier
signal by periodically switching of the resonance frequency. The phase modulated signal is
captured by the receiving antenna and re-transformed by way of a demodulator circuit, The
CPOD-ECU sends the child seat status to the Central Airbag ECU by way of an interface
line, In addition, the passenger presence status is also evaluated by way of a resistance
measurement through force sensors on the FSR mat. This information is also entered to the
Central Airbag ECU.
ll. Power Supply
The CPOD-ECU operates on the passenger vehicle power supply. an internal voltage
regulator unit delivers a steady operating voltage of 5 volts to supply the controller and
peripheral components. if the operating voltage falls below a defined threshold due to the
loss of input voltage, a signal is sent to reset the microcontroller.
lll. Transmitting Frequency Generator
The transmitting frequency generator produces a signal in the 125 to 135kHz band which
drives the transmitting antenna. The micro controller can modify the transmitting frequency
in ZkHz steps. This ensures that the resonance frequency in a specific child seat is
optimized.
IV. Micra'cpntrolier
A microcontroller is used to control the entire process. The controller includes an analog to
digital converter for the evaluation of the demodulated signals. for passenger seat
occupancy status detection, and an EEPROM for storing system parameters, part
identification and system failures.
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V. Process
To detect an infant seat, a carrier field in the 130kHz band is transmitted via the transmitting
antenna. The respective receiving antennae on the left and right side of the passenger seat
are scanned sequentially for the response of the resonators in the child seat, by variation of
the carrier frequency the optimum response of each resonator is determined Based on the
signal strength (phase modulation), detected via the receiving antenna, the presence and
orientation of the child seat is detected. Also, complementary information on the
manufacturer I type of the child seat can be read.
Having detected a correctly positioned child seat (forward- or rear-facing), its position is
verified every 4.8 seconds and the child seat type every 40 seconds.
With an incorrectly positioned child seat (out-of-position), the position as well as the
resonator messages are checked every 4.8 seconds,
The transmitting antenna is stimulated sequentially every 2.4 seconds or 38.4 seconds,
depending on the occupant status of the PPD sensor. The transmitting signal strength is
programmed in the EEPROM, In case that no auxiliary frequency should be detected, a test
signal is sent to test for the system functionality.
The occupancy status of the passenger seat is determined by measurement of the
resistance of the FSF!w sensor mat implemented in the seat. The presence of a passenger
on the seat and the resulting pressure on the sensor spots leads to a reduction of the
resulting FSRm sensor resistance which falls under a fixed threshold.
The occupancy status is determined periodically with a defined cycle time.
in order to check the conductor FSRWI sensor tracks for interruptions or disconnections, the
resistance of these parallel PPD conductortraces is measured. For this purpose, a diode is
connected in series with the traces and in parallel to the sensing elements and is driven in
forward direction. Thereby, a disconnection can properly be distinguished from a non
occupied seat. In the normal functioning mode, when measuring the resistance of the
FSR sensor elements for seat occupancy detection, the diode is driven in a blocking
direction and thus does not influence the resistance measurement.
I . .
VI. Communication Interface
The communication between the PPD/CPOD interface electronics and the airbag ECU is
based on a serial single wire unidirectional interface This serial link shall be connected to
the K-line of the airbag ECU. The data transmission rate is either 20 or 1000 Baud,
depending on the and customer.
After "ignition on", the PPD/CPOD interface electronics periodically sends a status message
to the airbag ECU. In this standard operational mode, the communication with the airbag
ECU is unidirectional. For mat purpose an "open collector" output IS provided by the
interface electronics which must be connected via a pull-up-resistor to Uh,“ in the airbag
ECU.
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Vll. Mechanical
Either Action Pins TM or soldered pins are used for both the connection between interface
electronics and the conductors of the PPD sensor mat as well as for the connection
between interface electronics and transmitting/receiving antennae,
The connection between the PPD/CPOD ECU and the airbag ECU is by a cable link with
the customer specified three pin connector attached. The interface electronics is designed
for automotive use in the interior of the vehicle seat, the over molded ECU conforms to the
lP54 standard. '
Vlll. Block Diagram
Key for diagram:
Control unit - Steuergerat
Voltage supply / reset - Spannungsversorgung / Reset
Serial interface - Senelle Schnittstelle
Evaluation logic - Auswertungslogik
Microprocessor - Mikroprozessor
Transmitting frequency generator - Sendefrequenzgenerator
Output stage 1 of low pass - Endstufe 1 des Tiefpafifilters
Amplifier with demodulator 2 - Verstarker mit Demodulator 2
Transmitting antenna < Sendeantenne
Receiving antennae - Empfangsantennen
FSR-Sensor - FSR-Sensor

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