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Crash Sensor Development Issues in Automotive Electronic Airbag Systems for Passenger Protection. International Solid-State Circuits Conference 2008. Young-Ho Cho. Digital Nanolocomotion Center NanoSentuating Systems Laboratory BioEngineering and Mechanical Engineering, KAIST.

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Crash sensor development issues in automotive electronic airbag systems for passenger protection
Crash Sensor Development Issuesin Automotive Electronic Airbag Systems for Passenger Protection

International Solid-State Circuits Conference 2008

Young-Ho Cho

Digital Nanolocomotion Center

NanoSentuating Systems Laboratory

BioEngineering and Mechanical Engineering, KAIST

(Phn) +82-42-869-8699 • (E-mail) [email protected] • (Web) http://mems.kaist.ac.kr


Outline

Outline

  • Electronic Airbag Systems

    - Safety Issues

    2. Automotive Crash Sensors

    - Reliability Issues

    3. Summary and Discussion



Automotive innovation
Automotive Innovation

  • Value

  • Safety

  • Comfort

  • Convenience

  • Performance


Automotive electronics systems
Automotive Electronics Systems

Innovation and Safety Value

Automotive Electronic Systems

Value

Passenger Restraint System (Airbags, Active Seatbelts)

Tracking Control System (TCS/ABS)

Collusion Avoidance System (Night Vision, Obstacle Detection)

Safety

Suspension Control System

Climate Control System

Noise Control System

Comfort

Steering Enhancement System

Navigation System (Autopilot)

Information & Communication System (Phone, Network)

Convenience

Environment: Engine/Emission Control System (Anti-knock)

Energy: Hybrid Engine System (Fuel cells)

Performance


Electronic airbag systems
Electronic Airbag Systems

Safety : Passenger Protection

SPR (Supplementary Passenger Restraint)

Front Protection

Side Protection


Electronic airbag systems1
Electronic Airbag Systems

Car Structure

Seat,Seat belt

Airbag System

Knee bolster

Instrument Panel

Steering System

Accelerometer

Safety Sensor

Diagnostics

Firing Logic

Circuit Board

Contact coil

Wiring

Electronics

Bags

Harness

Module Sub-ass’y

Cover

Bag

Plate

Inflator

Squib

Booster

Propellant

Filter

Case


Electronic airbag systems2
Electronic Airbag Systems

Physical Realms

Automotive Electronic Systems

Crash

Monitoring

and

Triggering

(Processor

and Logic)

Crash

Detection

(Sensors)

Vehicle

Passenger

Environments

Airbag

Deployment

(Inflators)


Sensors
Sensors

  • Vehicle : Crash detection

  • Passenger: Presence, Position, Weight

  • Seatbelt: Type, Tension


Inflators
Inflators

Electronic airbag deployment systems for passenger protection


Inflators1
Inflators

Driver Airbag

Passenger Airbag

Side Airbag

Reference : Hyundai MOBIS



Electronic airbag systems3
Electronic Airbag Systems

Collision

Detection

Inflation

Contact

Reference : Hyundai MOBIS


Crash sensors
Crash Sensors

Collision and Direction Detection

  • Accelerometers (Acceleration)

  • Pressure Sensors

  • Gyroscopes (Yaw-rate)

  • Position/Tension Sensors


Accelerometers
Accelerometers

Electrical detection of

Mechanical structure

motion

a

Acceleration (F=ma)

Mass Movement (F=kx)

Output Signal (x, a)


Capacitive Accelerometers

Measured Total Noise : 5.5 [µg/Hz] @ 19V


Piezoresistive accelerometers
Piezoresistive Accelerometers

Fabricated accelerometer

Frequency response

Sensitivity

Natural frequency :

2.15 kHz

Sensitivity :

176 mV/g


Mems sensors
MEMS Sensors

Miniaturization: 3P

- Performance

- Price

- Power

[Analog Devices]


MEMS Accelerometers

Navigation

Earth Gravity

Ref.: B.E. Boser, “Capacitive Interfaces for Monolithic Integrated Sensors,”

Workshop on Advanced in Analog Circuit Design, Como, 1997(slides)


Mems sensor issues
MEMS Sensor Issues

Reliability Issues:

Function vs. Malfunction

Fire vs. No-fire

  • Small vs. Precision (Fabrication Uncertainty)

  • Sensitive vs. Stable (Noise Disturbance)

  • Thin vs. Uniform (Material Behavior)

Garbage-in Garbage-out


Analog Devices ADXL 50

  • Measurement Range: ±50 g

  • Sensitivity : 19 mV/g

  • Frequency Response: DC to 10 kHz

  • Voltage Supply : +5V

  • Shock Survival: >2,000 g Unpowered

  • Self-Test on digital demand

  • Adjustable Zero-g Level

Function

Reliability


Airbag accelerometer specification
Airbag Accelerometer Specification

Function

Reliability

(Environmental

malfunction)

Reliability

(Operational

malfunction)

Source : MANDO Corporation


Malfunction: Sensor Failure

  • Safety and Self-diagnosis capability

  • Collusion and Rough Roads:

  • High cross-axis sensitivity or multi-axis sensors

  • Mechanical stoppers:

  • Barriers to shock or out-of-range protection

  • Force or zero balancing:

  • Null positioning of proof mass

  • Self test and calibration:

  • Response to known electrostatic actuation

  • Mechanical failure detection:

  • Electrical lines or resistors along beams


Malfunction: Logic Failure

Velocity Domain

Malfunction:

Banging (door, hood)

Road (rough, bump)

Energy Domain

G ≥ Gthreshold

Predicted Displacement Domain

Safety Sensor:

A latch switch for

threshold acceleration

(~5g)


Malfunction: Sensor + Logic + a

  • Calibration, Tuning or Adaptation for

  • Collusion Directions:

  • front/back, oblique, side

  • Vehicle Models:

  • structures, dynamic behavior

  • Passengers:

  • presence, position, weight

  • Seatbelts:

  • type, tension

0 ms

30 ms

65 ms

  • Watchdogs for

  • Circuit failure / warning

  • Power failure / back-up

100 ms


Airbag Sensors (Supplement)

Multiple Sensors for

Adaptable, Reliable and Functional Systems

1. Safety Sensors

2. Passenger Sensor

3. Seatbelt Sensor

4. Front Collision Sensor

5. Side Collision Sensor

6. Seat Position Sensor

Reference : Hyundai MOBIS


Federal Motor Vehicle Safety Standard

Reliability Issues:

Fire or not, Safe or not

  • FMVSS 208 : Occupant Crash Protection

    • Performance requirements for

    • the protection of vehicle occupants in crashes.

  • ※ For 30 mile/h (48 km/h) crash into a fixed barrier

    • - Head injury criterion(HIC) ≤ 1000

    • Chest G’s ≤ 60G for 3msec

    • Femur Loads ≤ 10 kN

a : acceleration of head

t2-t1 ≤ 36ms for max HIC


Automotive electronic systems
Automotive Electronic Systems

Passenger

(Behavior & Response)

Environment

(Status & Conditions)

Vehicle

(Behavior & Response)

Sensor: Types, Numbers & Locations

Automotive

Electronic

Systems

Reference

Storage:

Criteria, Data,

Look-up Tables

Processor: Processing & Conditioning

Logic: Interpretation & Confirmation

Inflator: Reaction & Verification

Control or inform

Adaptive, Reliable, Functional Cross-linked Sensor Network



Electronic airbag systems4
Electronic Airbag Systems

Physical Realms

Automotive Electronic Systems

Crash

Monitoring

and

Triggering

(Processor

and Logic)

Crash

Detection

(Sensors)

Vehicle

Passenger

Environments

Airbag

Deployment

(Inflators)


Sensor issues
Sensor Issues

Miniaturization: 3P

- Performance

- Price

- Power

[Analog Devices]


Mems sensor issues1
MEMS Sensor Issues

Reliability Issues:

Function vs. Malfunction

Fire vs. No-fire

  • Small vs. Precision (Fabrication Uncertainty)

  • Sensitive vs. Stable (Noise Disturbance)

  • Thin vs. Uniform (Material Behavior)

Garbage-in Garbage-out


Automotive electronic systems1
Automotive Electronic Systems

Passenger

(Behavior & Response)

Environment

(Status & Conditions)

Vehicle

(Behavior & Response)

Sensor: Types, Numbers & Locations

Automotive

Electronic

Systems

Reference

Storage:

Criteria, Data,

Look-up Tables

Processor: Processing & Conditioning

Logic: Interpretation & Confirmation

Inflator: Reaction & Verification

Control or inform

Adaptive, Reliable, Functional Cross-linked Sensor Network

for Safety


System design issues

Innovation

Safety

Adaptation

Comfort

Convenience

Perfor

mance

Reliability

Function

Logic

Sensor

Inflator

Market Values

Vehicle, Passenger, Environment

System Design Issues

Adaptive, Reliable, Functional System


Acknowledgements

Dr. Johannes Solhusvik, SE5 Session Organizer

Dr. Tim Denison, SE5 Session Chair

at ISSCC 2008

Researchers and sponsors of

NanoSentuating Systems Laboratory &

Digital Nanolocomotion Center

at KAIST

Thank you


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