S Ahmad Central Electronics Engineering Research Institute, Pilani

1. Automotive MEMS Microsensors S Ahmad Central Electronics Engineering Research Institute, Pilani Workshop onEmbedded System in Automobile Industry Indian Institute of Technology, Mumbai 1st December, 2003

2. Introduction • Automotive Industry Quest Passenger Car -Performance Improvement, Reduced Cost, Enhanced Reliability • Conventional Sensor - MEMS Replacement • Newer Possible Applications • Earliest Use - Manifold Absolute Pressure Sensor - MAP - 1979 • Silicon Accelerometer - Airbag - 1990s • Warranty Period - 10Years/ 150,000 Miles 24 April, 2003

3. Introduction • Improved Fuel Efficiency, Emission and Safety - Federal Standards • Higher Expectations - Performance, Comfort • Greater Availability - Micro-controller, Memory, Display and Enhanced Diagnostics • Very Harsh Under the Hood Environment High Temperature, Shock, Vibration, Humidity, Corrosive Media, EMC and RFI • Military Grade at Lowest Consumer Price 24 April, 2003

4. Automotive Sensor Global Market Growth 24 April, 2003

5. Automotive Sensor Usage Early Estimate - 1997 24 April, 2003

6. Automotive Industry MEMS Sensors 24 April, 2003

7. Product Evolution Time Schedule 24 April, 2003

8. Top Ten MEMS Markets • Micro-fluidic Biochip • Glucose Monitoring MEMS Sensor • Tire Pressure Sensors • Hard Disc Drive Heads • Inkjet Print Head • Medical Condition Detection Device • Large Format Print Head • Automotive Function Enabling Device • ABS Accelerometer and Gyroscope • Automobile Mass Airflow SensorVenture Development Corporation 24 April, 2003

9. Basic Auto MEMS Requirements • Crash Sensing - Air Bag Deployment • Vehicle Dynamic Control • Rollover Detection System • Antitheft System • Electronic Parking Brake System • Vehicle Navigation System • Seat Occupancy / Passenger Position • Climate Control • Digital Engine Control • Road Conditions 24 April, 2003

10. Major Growth Areas • Accelerometer– VDC and Airbags • Pressure Sensor– Transmission, Brakes, Diesel Fuel Rails, Refrigeration, Tires, Fuel Evaporation,Yaw Rates, GPS Backup • Position Sensor– Wheel Speed, Camshaft, Crankshaft, Pedal Positions • Humidity Sensor– Cabin Comfort • Distance Sensor – Collision Avoidance 24 April, 2003

11. Airbag Deployment • Acceleration - Continuously Measured • Acceleration Exceeds Some Threshold • Measured Acceleration Curve Integrated • Large Velocity Change - Airbag Fired • Steering Wheel and Side Airbag Firing • Earlier Sensors - Distributed g Switch • Insufficient Information – On/Off Type • More Expensive , Less Reliable • MEMS Accelerometer - Far Better • Gyroscope - ANALOG Devices - Introduced 24 April, 2003

12. Vehicle Dynamic Control • VDC - Vehicle Skid Control • Contains : Gyroscope, Low g Accelerometer, Wheel Speed Sensor • Yaw Rate Prediction - Speed Measurement • Gyroscope Measurement - Compared • Larger Difference - Single Wheel Brake or Torque Reduction Applied, Airbag Fired • Shock / Vibration Tolerant Gyroscopes - Need • ANALO Devices - iMEMS Gyro Better Device 24 April, 2003

13. Vehicle Rollover Detection • More Appropriate - Vans, Trucks, Sport Vehicle • Roll Angle and Rate Measurement - Tripping • Gyroscope - Roll Rate, Integration - Angle • Z - Axis Acceleration – Additional Accelerometer • Sideways Sliding Cause Rollover - Curb/Object • Dual Axes Low g Accelerometer – Ideal Solution • Shock/Vibration Resistant Gyros - Necessary • Fast Response Time Gyroscope - Essential 24 April, 2003

14. Security - Antitheft • Vehicle Towing - Popular Type Theft • Tilt Detection System - Effective Sensor • Pan European Specification - 30 Tilt over 3 minute period - i.e. 0.016o tilt per second • Fluid Tilt Sensor - Possible Use - Limited Tilt Range, Parked Car @ Large Tilt Angle - Sensor Ineffective Harsh Environment - Temperature Change, Sensor Performance Heavily Impaired • Low g Accelerometers – Ideal Tilt Sensor 24 April, 2003

15. Parking Brake System • Manual Parking Brake Activation Robust Push or Pull Type Operation • Braking Force Magnitude - No Concern • Electronic Parking Brake - Button Activation • Sensor Measures Vehicle InclinationBraking Force Requirement DeterminedBrake Applied - Easy Operation • Low g Accelerometers - Ideal Tilt Detection Sensor Sometimes – Single Sensor Used Both Antitheft and Parking Brake Systems 24 April, 2003

16. Vehicle Navigation System • Standard Feature – Luxury Cars • Global Positioning System– Fundamental Part • GPS - Position and Altitude but No Direction • Magnetometer – Early Direction SensorLarge Ferrous Metal Object - Confused Magnetometer Performance - Not Reliable • Compass and GPS – Initial StartTravel Direction Match - Map Data - DirectionGyroscope - When and How Much Car Turned, Directional Data Match - Map Data • Gyroscope - Heading Information, Low g Accelerometer – Position Data , Integration 24 April, 2003

17. Electronic Engine Control • Intake Manifold Pressure - Air to Fuel Ratio • Mass Air Flow Devices - MEMS Version • Barometric Pressure - Altitude Information Rich to Lean Fuel to Air Mixture Decision • Cylinder Pressure Measurement - PerformanceOptimization - Piezoelectric/ Fiber Optic Sensor • Exhaust Gas Re-circulation - Capacitive Pressure Sensor – Better Solution • Hydraulic Fluid Pressure - Isolated Diaphragm Type Configuration, Sensor – ASIC Integration • Fuel Injection - Silicon Fuel Injection Nozzle 24 April, 2003

18. Sensor Cluster System • Same Sensor Family - Variety of Measurements • Accelerometer/Gyros - Sometimes15 Sensors • Difficult Integration, Unsafe Operation Fear • Inertial Measurement Unit - Six Axes Inertial Measurements, Proper location Signal Routing • Additional Stand Alone Sensors - Still Required • Sensor Cluster Configuration - MoreEconomical Solution, Better Micro-controller Utilization 24 April, 2003

19. Commercial Off-the-Shelf MEMS Pressure Sensor 24 April, 2003

20. 6H-SiC High g Piezo-resistive Accelerometer 24 April, 2003

21. 24 April, 2003

22. ARIES Airbag Deployment Test System 24 April, 2003

23. Three Axes MEMS Accelerometer Sandia Laboratories 24 April, 2003

24. Delphi Automotive System Air Bag 24 April, 2003

25. CEERI Developed Sensors 24 April, 2003

26. Piezo-resistive Pressure Sensor - CEERI 24 April, 2003

27. ZnO Piezoelectric Acoustic Sensor - CEERI 24 April, 2003

28. Polysilicon Load Cell - CEERI 24 April, 2003

29. Three Axes Bulk Micro-machined Accelerometer Test Structure - CEERI 24 April, 2003

30. Sensor Interface ASIC - Schematic 24 April, 2003

31. Sensor Output – Without Conditioning 24 April, 2003

32. Corrected Sensor Output 24 April, 2003

33. Universal Signal Conditioner – Resistive Bridge 24 April, 2003

34. Intelligent Pressure Sensor Chip 24 April, 2003

35. Capacitive Sensor Interface ASIC 24 April, 2003

36. Conclusions • Automobile MEMS Sensor - Fast Growing • Multi Billion Dollar Industry Growth • Intelligent Sensor Development - Needed • Interface and Signal Conditioning - Essential • Hybrid Approach - Initial Stage • ASICs Use - Commercial ASICS Available • Sensor Cluster Approach – Better Solution • Already Late Start – Sooner Starting Better 24 April, 2003

37. Thank You 24 April, 2003