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MEMS Inertial Sensors Monitor

Vehicles in Motion

Automotive Electronics & Electrical Systems Forum

Stuttgart6 May 2008

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Presentation Outline

Automotive Safety System Mandates and StandardsChallenges for Inertial SensorsMerging Safety SystemsSafety System Architectures and TrendsSafety Sensor IntegrationAutomotive Electronics and Sensor ImplicationsSummary

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ADI In Automotive Safety NHTSA ESC Mandate

Passenger VehiclesUnder 10,000 lbs by

September 1 2008All Vehicles by

September 1 2011

Z

6-DOF IMU

Z

6-DOF IMU

Z

6-DOF IMU

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Safety Integrity Level Requirements

Emerging EU trend for automotive safety systems to achieve Safety Integrity Level 3 (SIL3) requirements

IEC 61508Functional safety of electrical/electronic/programmable electronic safety-related systems (E/E/PES)

SIL 1 through SIL 4ISO 26262

ISO TC22 SC3 WG16 adapting IEC 61508 for automotive functional safetyASIL A through D

IEC 61508 SIL3 requirementsSafe Failure Fraction (SFF) > 99%Probability of dangerous failure fraction per hour (PFH) < 10-7

Achieving ASIL C compliance requires a holistic approach to system and product design

Requirements flow from OEMs to Tier 1’s to component suppliersClose collaboration between Tier 1’s and critical component suppliers required for success

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Challenges for Inertial Sensors

Tough safety standardsFMVSS210FMVSS214European NCAPAllianz Center for Technology

Harsh Operating EnvironmentTemperature Effects On SensorOverload

Determining Between Crash vs. Misuse EventsHigh-Voltage

Demand for Increased IntegrationMore Robust Self-Test ConceptsMore Discriminate Crash DetectionCompatible with multiple busses

Low System Cost

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Active/Passive Safety System Integration Key Enablers

Collision Warning and Preparation Pre-Crash Emergency Braking Lane Departure Warning Park Assist Rollover Prevention and Mitigation Adaptive Restraints Side Impact Integration System Electronic Stability ControlSeatbelt Pre-tensioning Source: Continental

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Merging SafetySystemsAccidentAvoidance &Mitigation

Adaptive Cruise ControlLane Departure WarningBlind Spot DetectionLane Keeping SystemParking Assist

Adaptive Cruise ControlLane Departure WarningBlind Spot DetectionLane Keeping SystemParking Assist

Airbags and SeatbeltsOccupant ProtectionPedestrian Protection

Airbags and SeatbeltsOccupant ProtectionPedestrian Protection

Navigation SystemsVisual/Audible WarningInter-vehicleCommunications

Navigation SystemsVisual/Audible WarningInter-vehicleCommunications

Electronic Stability ControlAdaptive SuspensionYaw / Roll Control

Electronic Stability ControlAdaptive SuspensionYaw / Roll Control

Communication

The Intelligent Vehicle

Collision AvoidanceAccident PreventionSeverity Reduction

ActiveSafety

PassiveSafety

Driver Assistance

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Future Systems Will Employ Inertial Measurement Units That Support Multiple Systems

Z

6-DOF IMU

Central IMU featuring measurements with 6 degrees of freedom supports multiple

systems

Crash Detection System Satellite Sensor Airbag

Vehicle Dynamic Control System SeatbeltPretensioner

Dual-axis airbag sensorNavigation/Driver Information System

Body/Chassis Control SystemLow g chassis control sensor Gyroscopes

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Modular Solutions Enable Scalability

Variety of safety and assistance functions can be incorporated into module

Active Rollover ProtectionTrailer Stability AssistHill Start AssistAdaptive Cruise Control

Braking system is monitored by electronics which detect and configure components which have been exchanged

Eliminates time-consuming calibration procedures

Integrating sensor cluster (yaw-rate and acceleration sensors) into brake control unit reduces components and interfaces

Reduces weight, size and co$t

Source: Continental

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Existing Safety System ArchitecturesAirbag Control Unit

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Crash SensorsContinuous Improvement in Performance At “First Contact”

Crash sensing (passive safety) strives for two main objectives:

More accurate crash discriminationSafer and more effective deployment

Expanding awareness of vehicle environment

More sensors per vehicleIncreased mechanical informationNew kinds of sensors beyond accelerometersOccupant size, out-of-position classificationPedestrian safety

Mounting sensors closer to edge of the vehicle (frame rails)

Earlier detection of collisionKnow location of crashMutual safing

Links to other systems EDR (Electronic Data Recorder)Telematics (eCall)

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Existing Safety System ArchitecturesElectronic Stability Control Unit

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Integrated Safety Module: Crash + ESCEmerging System Architecture

FMVSS126 expands low-g sensor fit-rate in stability control applications

NHTSA estimates ESC will reduce single-vehicle crashes of passenger cars by 34% and single-vehicle crashes of SUV’s by 59%, with a much greater reduction of rollover crashesBy 2012, 98% of new vehicles in Europe and 100% of new vehicles in the US will have ESC systems

OEMs will integrate both Airbag and ESC in airbag control unit

Reduce two packages into single package able to cover both ESC and restraint accelerometer needsSavings $30/vehicle

All systems will haveMid-g (20 g - 100 g) crashLow-g (< 5 g) ESC

Source: Autoliv

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Evolution in Automotive NetworksApplication-Specific vs. Networked Sensors

FlexRay

Chassis Gateway

Safety Steer-by-Wire Brake-by-Wire

Present direction to decrease number of ECU’sPossible decentralization of data processing to individual deviceIndividual ECU’s and semiconductor content will need greater functionality and speedSystem reliability depends upon that of individual ECU’sSpecifications of semiconductors in resulting networks may change dramatically

Vehicle Sensors are networked to provide motion data to various safety systems

Star (e.g., BMW 7-Series Airbag using ByteFlight), Ring or IMU configurationFlexRay becoming standard for more advanced control applications

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Future of MEMS Inertial Sensors in Vehicles

System designers are re-thinking current stand-alone sensor architectures in favor of integrating additional functionality of, e.g., an Airbag Control Unit into one single ASIC/ASSP:

Receiver (for sensor satellites)SPI output for communication with µCSquib driverWatchdogPower management for entire ACUClock NVM for diagnostics/calibrationPSI5CAN or FlexRay interface

This sensor ASIC/ASSP model is being evaluated by automotive OEMs and will become crucial to cost control as well as to conserve electronics real estate without compromising performance

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Active/Passive Safety Sensor IntegrationESC and Crash Acceleration Sensing in Single Package

Crash high-g and VSC low-g in a single packageFacilitate integration of active and passive safetyReduce total system costIncrease usage of digital signal path to enhance sensor performanceDigital SPI communicationsEnhance performance via communication with other sensorsContinuous self-test/status pinLow power consumptionSmall plastic packaging

PDM

ASIC

2-Axis Accelerometer

Sen

sor C

ross

-Che

ckin

g

ToECUµC

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Active/Passive Safety Sensor Integration ESC Angular Rate and Acceleration Sensing in Single Package

Gyro

Low-g

MEMSSensor

2- and 3-Axislinear rate sensing

Single axisangular rate sensing

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Automotive Electronics Trends

Increasing System ComplexityIncreasing functionality

Comfort, Entertainment, SafetyProliferation of safety-critical functions

ABS, ESP, EPSNetworking between subsystems

Electrical System RobustnessMore stringent EMI and ESD requirementsQuality and reliability

New Technologies and RequirementsVehicle-to-Vehicle and Vehicle-to-Road CommunicationCollision avoidance

Increasing Cost PressureElectronics contribute significantly to vehicle manufacturing costs

Source: Continental

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Safety Sensor Integration and NetworkingEmerging Requirements

SizeSmall form factor necessary for flexible placement and integration of multiple sensorsReduced hardware complexity

OrientationX-Y-Z Accelerometers and Roll-Yaw Gyros needed to cover full array of implementations

FeaturesModular partitioning to merge active and passive safetyDigital functionality and features3.3 V and lower operationMore digital signal processingSupport new communications and networking standards

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Safety Sensor Integration and NetworkingEmerging Requirements

Quality and ReliabilityZero Incident TargetHigher Device YieldsEnhanced Self-Test and FMEA characteristics

RobustnessOperation in harsh environments with intense vibration and high temperature

Ease of ManufacturingEliminate module-level calibrationIncreased configurability, e.g. filter and g-ranges

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MEMS Automotive Inertial Sensor IntegrationSummary

Automotive customers are expressing strong interest in combined sensors and IMUs

Primarily interested in gyros and low-g accelerometersReduced sensor packaging volumePerceived cost saving based on reduce package cost

Numerous approaches to combined sensors/IMUsModule level

Packaged sensorsSensor Die

Component levelSingle packageFunctional equivalent to a single packageAngular Rate and Acceleration from a single sensor structure

Packaging volume reduction dependent on sensor technology and integration strategyFuture automotive safety systems will require close collaboration between OEMS, Tier 1s and critical component suppliers

Fail-safe and ASIL C compliance strategies and IPSystem-level trade-offs to optimize system performance and cost

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Presented By:Kristen Manon McNair Hopper

European Automotive Customer Marketing Manager

Analog Devices, Inc.Micromachined Products Division21 Osborn StreetCambridge, MA 02139-3556+1 617 761 7645kristen.mcnair@analog.com