Crash Sensor Development Issues in Automotive Electronic Airbag Systems for Passenger Protection

1. 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) mems@kaist.ac.kr • (Web) http://mems.kaist.ac.kr

2. Outline • Electronic Airbag Systems - Safety Issues 2. Automotive Crash Sensors - Reliability Issues 3. Summary and Discussion

3. 1. Electronic Airbag Systems

4. Automotive Innovation • Value • Safety • Comfort • Convenience • Performance

5. 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

6. Electronic Airbag Systems Safety : Passenger Protection SPR (Supplementary Passenger Restraint) Front Protection Side Protection

7. 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

8. Electronic Airbag Systems Physical Realms Automotive Electronic Systems Crash Monitoring and Triggering (Processor and Logic) Crash Detection (Sensors) Vehicle Passenger Environments Airbag Deployment (Inflators)

9. Sensors • Vehicle : Crash detection • Passenger: Presence, Position, Weight • Seatbelt: Type, Tension

10. Inflators Electronic airbag deployment systems for passenger protection

11. Inflators Driver Airbag Passenger Airbag Side Airbag Reference : Hyundai MOBIS

12. 3. Automotive Crash Sensors

13. Electronic Airbag Systems Collision Detection Inflation Contact Reference : Hyundai MOBIS

14. Crash Sensors Collision and Direction Detection • Accelerometers (Acceleration) • Pressure Sensors • Gyroscopes (Yaw-rate) • Position/Tension Sensors

15. Accelerometers Electrical detection of Mechanical structure motion a Acceleration (F=ma) Mass Movement (F=kx) Output Signal (x, a)

16. Capacitive Accelerometers Measured Total Noise : 5.5 [µg/Hz] @ 19V

17. Piezoresistive Accelerometers Fabricated accelerometer Frequency response Sensitivity Natural frequency : 2.15 kHz Sensitivity : 176 mV/g

18. MEMS Sensors Miniaturization: 3P - Performance - Price - Power [Analog Devices]

19. 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)

20. 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

21. 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

22. Airbag Accelerometer Specification Function Reliability (Environmental malfunction) Reliability (Operational malfunction) Source : MANDO Corporation

23. 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

24. 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)

25. 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

26. 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

27. 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

28. 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

29. 3. Summary and Discussion

30. Electronic Airbag Systems Physical Realms Automotive Electronic Systems Crash Monitoring and Triggering (Processor and Logic) Crash Detection (Sensors) Vehicle Passenger Environments Airbag Deployment (Inflators)

31. Sensor Issues Miniaturization: 3P - Performance - Price - Power [Analog Devices]

32. 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

33. 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

34. Innovation Safety Adaptation Comfort Convenience Perfor mance Reliability Function Logic Sensor Inflator Market Values Vehicle, Passenger, Environment System Design Issues Adaptive, Reliable, Functional System

35. 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