Optical Sensors in Automotive Applications “Solving Sensing Problems with Photonics” Photonex 2010, 3 rd November 2010 Roger Hazelden Technology Leader, Sensors & Optoelectronics
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 2 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 Consultancy in Engineering, Knowledge and Technology • Conekt is the technology and engineering consultancy business of TRW Automotive • The origins of Conekt date back to the mid 1950 s as the former Lucas Research Centre • Conekt provides specialist engineering consultancy and testing / validation services to customers in aerospace, automotive, defence and other markets 3 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 Applications for Optical Sensors • Automotive sensors must operate in harsh environmental 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 massmarket automotive use: data links for “infotainment” are the only current automotive market for fibre-optics • But there are some optical sensors in volume production, and fibre-optic sensors are very useful for instrumentation 4 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.
Optical Torque and Angle Sensor for Electric Power Steering A power steering system is a torque servo system. The system determines how much torque is being applied to the steering wheel by the driver, and adds an appropriate amount of torque assistance to keep the applied torque to the required value. 5 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.
Optical Torque and Angle Sensor for Electric Power Steering At the heart of the TRW EPS system is an optical torque and rotation angle sensor, which detects the driver’s applied torque and transmits torque data to the system Electronic Control Unit (ECU). The sensor was originally conceived and developed at Conekt, and is now in full volume production (more than 10 million produced so far) Steering wheel Vehicle speed signal ECU Torque sensor Gearbox Motor I-shaft to steering rack 6 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.
Optical Torque and Angle Sensor for Electric Power Steering Light from an LED shines through spokes on discs attached to the shaft onto a 128 -pixel photodiode array. LED 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 determined with the same sensor. Input shaft from steering wheel LED Wide Spoke (Input) Disc Narrow Spoke (Output) Disc Receiver Lens/Diffuser Resultant Illumination Pattern on Receiver Resultant Waveform Generated by Receiver (128 pixels) Input shaft disc Output shaft to motor and rack Pixel 128 Output shaft disc 7 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.
Automatic Headlight / Windscreen Wiper System Rain and Light Sensor Rain / light sensors attach to the front windscreen and automatically the windscreen wipers and headlights turn on and off depending on predetermined external conditions The rain sensor technology is based on an IR system that measures differences due to refraction in the optical path (see following slide) The light sensor consists of independent forward and horizontal looking receivers to determine tunnels, bridges and specific ambient conditions (eg dawn) for automated headlight control 8 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.
Automatic Headlight / Windscreen Wiper System Rain and Light Sensor (continued) • To detect the presence of rain on the windscreen, an IR beam is reflected from the outer windscreen surface back to a IR sensor array • When a rain drop strikes the windscreen, some IR energy is transmitted out through the droplet: the system detects the change in reflected IR energy • Advanced analogue and digital signal processing determines the intensity of the rain. The sensor communicates to the wiper control module, which automatically controls the wipers to achieve optimum vision for the driver 9 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 Video camera technology enables a range of safety systems which are supported by a forward-looking monocular camera mounted at the windscreen in the rear-view mirror mount: • Lane Departure Warning (LDW): detects lane markings in front of the vehicle and provides a warning if the driver unintentionally leaves the driving lane Lane Departure Warning • Lane Keeping Assistance (LKAS): combines lane detection with an electric steering system to provide a torque overlay on steering, automatically directing the vehicle back into the correct lane • Other possible functions: auto lane guidance, obstacle / pedestrian detection, traffic sign recognition, forward collision warning… 10 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 (continued) Example System: Lane Keeping Assistance Driver Input Steering Vehicle Dynamics Video Camera Haptic Control 11 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.
In-cylinder Instrumentation Fibre-optic Combustion Sensors Using fibre-optic probes, in-cylinder combustion processes can be monitored by detecting and analysing the light emitted during combustion • A “Window” into the combustion chamber enables direct monitoring of the light emitted during combustion processes 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 12 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.
In-cylinder Instrumentation Fibre-optic Combustion Sensors (continued) Combustion Signal Fibre-optic Combustion Probe Incipient Knock Detection Misfire Detection 13 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.
Summary • Fibre-optic and optical sensors can solve many measurement problems in the harsh environment presented by road vehicles • Several examples of high-volume exploitation of optical sensors in automotive applications have been presented, including optical torque sensors, rain / light sensors, and in-vehicle video cameras • Except for data-bus applications, fibre-optic technology still costs too much for mass-market automotive use: but the industry does use fibreoptic sensors for instrumentation purposes • Contact us at Conekt to discuss how we can help you with your measurement and sensing problems TRW Conekt Technical Centre Stratford Road Solihull B 90 4 GW UK Tel: +44 (0)121 627 4242 Email: conekt-enquiries@trw. com Web: www. conekt. co. uk 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 2008. This
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