S AhmadCentral Electronics Engineering

Research Institute, Pilani

Workshop onEmbedded System in Automobile Industry

Indian Institute of Technology, Mumbai

1st December, 2003

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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

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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

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Automotive Sensor Global Market Growth

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Automotive Sensor Usage Early Estimate - 1997

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Automotive Industry MEMS Sensors

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Product Evolution Time Schedule

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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 Sensor

Venture Development Corporation

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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

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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

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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

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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

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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

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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

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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 Inclination

Braking Force Requirement DeterminedBrake Applied - Easy Operation

Low g Accelerometers - Ideal Tilt Detection Sensor Sometimes – Single Sensor Used Both Antitheft and Parking Brake Systems

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Vehicle Navigation System

Standard Feature – Luxury Cars Global Positioning System– Fundamental Part GPS - Position and Altitude but No Direction Magnetometer – Early Direction Sensor

Large 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

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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 - Performance

Optimization - 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

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Sensor Cluster System

Same Sensor Family - Variety of Measurements Accelerometer/Gyros - Sometimes 15 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 - More Economical

Solution, Better Micro-controller Utilization

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Commercial Off-the-Shelf MEMS Pressure Sensor

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6H-SiC High g Piezo-resistive Accelerometer

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ARIES Airbag Deployment Test System

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Three Axes MEMS Accelerometer Sandia

Laboratories

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Delphi Automotive System Air Bag

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Piezo-resistive Pressure Sensor - CEERI

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ZnO Piezoelectric Acoustic Sensor - CEERI

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Polysilicon Load Cell - CEERI

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Three Axes Bulk Micro-machined Accelerometer Test Structure - CEERI

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Sensor Interface ASIC - Schematic

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Sensor Output – Without Conditioning

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Corrected Sensor Output

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Universal Signal Conditioner – Resistive Bridge

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Intelligent Pressure Sensor Chip

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Capacitive Sensor Interface ASIC

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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

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