the state of soot sensor technology
TRANSCRIPT
The State of Soot Sensor Technology EMA OBD Certification Workshop, April 25, 2013 Presenter: Patrick Thompson, CEO, EmiSense Technologies
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Agenda
• Background • Overview of OBD Sensing Technologies • Technical Challenges • Recent Progress with Real Time Sensors • Paths Forward for OBD Implementation
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Background • This audience is aware of PM sensor regulatory drivers,
challenges, etc. • The perspective presented here is that of a venture-backed startup
doing applied research, trying to solve technical challenges, and understand practical OEM problems
• PM is very hard to measure (further complicated in situ) • Mass, #, Volume? • Particle Size, Charge & Morphology can impact
• Sources include Southwest Research PSPD Consortium, UCR CERT, ACEA/Ricardo Study, OEM and Internal testing.
• There are essentially 2 classes of viable direct PM OBD sensors: 1. Accumulator sensors (resistive, capacitive, etc.) 2. Real-time sensors (natural charge, induced charge, contact
charge, etc.)
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Accumulator Sensors • Many suppliers are developing accumulators:
• Denso • Bosch • Delphi • NGK Insulators • NGK Spark Plugs / NTK Technical Ceramics • Continental • Electricfil • Stoneridge
• Some suppliers appear to have hit development walls, but much work is ongoing to improve/address accumulator weaknesses.
• On production vehicles starting MY2103
All Trademarks are the property of their respective owners.
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Accumulator Sensors
Source: Public presentations by suppliers. All copyrights are the property of their respective owners.
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Accumulator Sensors • Can exhibit good correlation with integrated/cumulative plot of MSS
• Weaknesses:
1. High variability 2. Response time 3. Drift as a result of accumulation of conductive contamination
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Soot Conductivity & Ash • Even small amounts of
inorganic impurities found in real diesel soot samples can create significant signal drift over time.
• Exact composition of fuel and ash is unpredictable (Silica, Calcium, Zinc, Magnesium, etc.)
Source: Grob, B.; Schmid, J.; Ivleva, N.; Niessner, R; “Conductivity for Soot Sensing: Possibilities & Limitations” American Chemical Society 2012; 3586-3592
Conductivity as a function of mass fraction of graphite.
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Real Time Sensors • Honeywell
• Natural Charge • Requiring very sensitive,
expensive electrometers (pA) • Development may have stalled
• Pegasor • Active/Induced Charge • Good performance • Requiring very sensitive,
expensive electrometers (pA) • Requiring relatively large and
complicated apparatus, challenging to cost-effectively reduce.
• EmiSense • See next slide
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PMTrac® Real Time Sensor • Exhaust gas directed over steel HV electrode • Field-directed assembly of soot provides amplification
(2-3 orders of magnitude), enables use of low-cost insulators and amplifiers
• Field-induced disassembly maintains equilibrium • Charge loss is proportional to soot concentration • Tolerant of contaminants on the sensing electrode over
the lifetime of the sensor • Real time response (200-500 millisecond range) • Full model-based transfer function now developed
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Heavy Duty Urban Drive Cycle at UCR
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200 250 300 350 400 450 500 550 600time (sec)
PM C
once
ntra
tion
(mg/
m^3
)
Sensor aSensor bSensor cSensor dSensor eSensor fSensor gTSI Dusttrak
PMTrac® Sensor • SwRI 155 Tests, 6 sensors, Model-based Transfer Function R2 = .975 • Drive cycle transient testing at both UCR and SwRI
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PMTrac® Summary and Next Steps • Fundamentals becoming understood (see UCR PEMS presentation) • Inherent durability advantage (extended validation in process) • No cost disadvantage to resistive • Weaknesses:
• Not ready for 2014 applications • 2013 fundamentals and principle durability • 2014 production-intent samples (with Tier-1 partner) • 2015 Path to PPAP • 2016 SOP (for MY 2017+)
• Particle size and charge dependencies • Finite errors (+/- 35% range), requiring engine-family
characterization (feasible for OBD) • Long term drift of PSD or PCD highly unlikely
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ACEA Perspective
Source: Savage, Scott; Ricardo; SAE Symposium ACEA HDD Soot Sensor Technology Survey and Performance; 2012
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Soot Sensor Technology Comparison
Sensor Cost Resolution Durability
Resistive Accumulators
2012-2017?
2017+
Field-Directed Equilibrium
Active Charger
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Conclusions
• Commercially-available accumulators: • Include risk of warranty issues (false + and -) • Questionable if they meet present requirements • Unlikely to meet requirements beyond 2016 • But only option for near term
• Real time PMTrac® sensors show promise in simplicity, resolution, and durability
• If the author formed enforcement policy, OBD DPF-failure detection via direct measurement of PM would not be mandated until reliability of sensors was proven
