Optical Sensors in Automotive Applications
“Solving Sensing Problems with Photonics”
Photonex 2010, 3rd November 2010
Roger Hazelden
Technology Leader, Sensors & Optoelectronics
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Agenda
• Introduction to Conekt
• Automotive applications of optical sensors:
– Optical Torque and Angle Sensor for Electric Power Steering
– Rain / Light Sensor
– Video Camera for Lane Guidance Systems
– In-cylinder Instrumentation
• Summary
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This copyrighted document is the property of TRW Limited. No license is granted by TRW to anyone to use, reproduce or exploit any content. Any authorized copies made by any method must also include this legend. Copyright TRW Limited 2010.
Introduction to Conekt
•Conekt is the technology andengineering consultancy business ofTRW Automotive
•The origins of Conekt date back tothe mid 1950s as the former LucasResearch Centre
•Conekt provides specialistengineering consultancy and testing/ validation services to customers inaerospace, automotive, defence andother markets
Consultancy in Engineering, Knowledge and Technology
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This copyrighted document is the property of TRW Limited. No license is granted by TRW to anyone to use, reproduce or exploit any content. Any authorized copies made by any method must also include this legend. Copyright TRW Limited 2010.
•Automotive sensors must operate in harshenvironmental conditions – high temperature,vibration, corrosive fluids, etc.
•Achieving the required performance at the right(low !) cost is always paramount
•Fibre-optic sensors (still) cost too much for mass-market automotive use: data links for“infotainment” are the only current automotivemarket for fibre-optics
•But there are some optical sensors in volumeproduction, and fibre-optic sensors are very usefulfor instrumentation
Automotive Applications for Optical Sensors
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Optical Torque and Angle Sensor for Electric Power Steering
A power steering system is a torque servo system. The system determines how much torque isbeing applied to the steering wheel by the driver, and adds an appropriate amount of torqueassistance to keep the applied torque to the required value.
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Steering wheel
Torque sensor
I-shaft to steering rack
Motor
Vehicle speed signal
ECU
Gearbox
At the heart of the TRW EPS system is an optical torque and rotation angle sensor, whichdetects the driver’s applied torque and transmits torque data to the system Electronic ControlUnit (ECU). The sensor was originally conceived and developed at Conekt, and is now in fullvolume production (more than 10 million produced so far)
Optical Torque and Angle Sensor for Electric Power Steering
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Light from an LED shines through spokes on discs attached to the shaftonto a 128-pixel photodiode array.
Measurement of the disc spoke edge image positions on the receiver
array enables relative disc movement - and hence applied torque -
to be determined with very high accuracy.
Shaft rotation speed and rotation angle can also be determinedwith the same sensor.
Optical Torque and Angle Sensor for Electric Power Steering
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Automatic Headlight / Windscreen Wiper System
Rain and Light Sensor
Rain / light sensors attach to the front windscreenand automatically the windscreen wipers andheadlights turn on and off depending on pre-determined external conditions
The rain sensor technology is based on an IRsystem that measures differences due torefraction in the optical path (see following slide)
The light sensor consists of independent forwardand horizontal looking receivers to determinetunnels, bridges and specific ambient conditions(eg dawn) for automated headlight control
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Automatic Headlight / Windscreen Wiper System
Rain and Light Sensor (continued)
• To detect the presence of rain onthe windscreen, an IR beam isreflected from the outer windscreensurface back to a IR sensor array
• When a rain drop strikes thewindscreen, some IR energy istransmitted out through the droplet:the system detects the change inreflected IR energy
• Advanced analogue and
digital signal processing determinesthe intensity of the rain. The sensorcommunicates to the wiper controlmodule, which automatically controlsthe wipers to achieve optimumvision for the driver
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This copyrighted document is the property of TRW Limited. No license is granted by TRW to anyone to use, reproduce or exploit any content. Any authorized copies made by any method must also include this legend. Copyright TRW Limited 2010.
Lane Guidance Systems
Forward-looking Video Camera
Lane Departure Warning
Video camera technology enables a range ofsafety systems which are supported by aforward-looking monocular camera mounted atthe windscreen in the rear-view mirror mount:
• Lane Departure Warning (LDW):
detects lane markings in front of the vehicle andprovides a warning if the driver unintentionallyleaves the driving lane
• Lane Keeping Assistance (LKAS): combineslane detection with an electric steering system toprovide a torque overlay on steering, automaticallydirecting the vehicle back into the correct lane
• Other possible functions: auto lane guidance,
obstacle / pedestrian detection, traffic sign
recognition, forward collision warning…
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Lane Guidance Systems
Forward-looking Video Camera (continued)
Steering
Vehicle Dynamics
Driver Input
Video Camera
HapticControl
Example System: Lane Keeping Assistance
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Using fibre-optic probes, in-cylinder combustion processescan be monitored by detecting and analysing the lightemitted during combustion
• A “Window” into the combustion chamber enables direct
monitoring of the light emitted during combustionprocesses in petrol and diesel engines
• Remote optical sensor head connected via fibre-optic
cable to electronics unit
• Intensity sensor:
– start / end of combustion
– engine knock detection
• Colour (wavelength) sensor:
– combustion “quality”
– in-cylinder temperature measurement
In-cylinder Instrumentation
Fibre-optic Combustion Sensors
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Fibre-optic Combustion Sensors (continued)
Fibre-optic
Combustion Probe
Combustion
Signal
IncipientKnockDetection
Misfire Detection
In-cylinder Instrumentation
Summary
•Fibre-optic and optical sensors can solve many measurementproblems in the harsh environment presented by road vehicles
•Several examples of high-volume exploitation of optical sensors inautomotive applications have been presented, including optical torquesensors, rain / light sensors, and in-vehicle video cameras
•Except for data-bus applications, fibre-optic technology still costs toomuch for mass-market automotive use: but the industry does use fibre-optic sensors for instrumentation purposes
•Contact us at Conekt to discuss how we can help you with yourmeasurement and sensing problems
TRW Conekt
Technical CentreTel: +44 (0)121 627 4242
B90 4GW
UK