Crash sensor development issues in automotive electronic airbag systems for passenger protection
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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


Se0501update

1. Electronic Airbag Systems


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


Se0501update

3. Automotive Crash Sensors


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)


Se0501update

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]


Se0501update

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


Se0501update

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


Se0501update

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


Se0501update

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)


Se0501update

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


Se0501update

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


Se0501update

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


Se0501update

3. Summary and Discussion


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


Se0501update

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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