Radio Frequency Antenna for Direct SCR Load Measurement

Abstract

Radio Frequency Antenna for Direct SCR Load Measurement
High potential of RF antenna for SCR load determination

Full text

Radio Frequency Antenna
for Direct SCR Load Measurement
Marco Moser (IAV), Dr. Markus Dietrich (Continental), November 2018

Motivation
Correct SCR Load Determination
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High potential of RF antenna for SCR load determination
DOC SCR
DPF
SCR model
Engine
NOX
NH3
NH3load
Current Situation:
NH3load modelled
complex miscalculation 
emissions
New RF (Microwave) Sensor:
NH3load measured
direct measurement
NH3load
Diesel

Content
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•Sensor Concept
•Simulative Assessment
•Signal Modelling
•SCR Load Control
zettberlin/photocase.de

Sensor Concept
RF Antenna
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•Resonator
•Catalyst canning as radio frequency cavity resonator
•Exciting standing electromagnetic waves (resonances)
by incoupling with coaxial antennas
•Resonance behavior depending on dielectric properties
of catalyst material
Sensitivity of RF antenna depends on electric field strength
RF antennas
Catalyst
Metal canning
•Resonance Type Influence
•Canning shape dependent
•Different electric field distributions
Electric Field: low high
Basic Principle
|S
11
|, |S
21
| / dB
f / GHz
reflection
transmission

Sensor Concept
RF Antenna
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Current NH3load mirrored in RF antenna signal
Resonance Peak Analysis
0
1
2
mNH3 / g/lKat
resonance frequency
catalyst state / mass balance
3
1
0
4
2
RF response
time
Material Effects
•NH3storage on SCR
catalyst
•Change of dielectric
properties of catalyst
•Cross sensitivity on
temperature and humidity
Analyzable RF Signals
•Resonance frequency
•RF losses / peak damping
RF Response to NH3Storage
resonance frequency /
peak amplitude

Sensor Concept
RF Measurements in SCR-Catalyst
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NH3load measurable through antenna signals: “Amplitude” (resonance damping) and “Frequency Shift”
No sensitivity
Emitter Receiver
Transmission
No sensitivity Highest sensitivity
High sensitivity
in all bricks
Exhaust System
Underfloor SCR
system
Electric Field Strength of Different Resonances
Possible antenna
positions
Application to geometry of each catalyst required
•Antenna positions and length related on coupling
strength and space
•Analyze resonance with best sensitivity at all catalyst
bricks and on catalyst front
•Frequency of analyzed resonance specifies
requirements electronic analyzer unit
Antennas located
in cones

Simulative Assessment
Challenge for New Sensor Concepts
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Automobile
Manufacturer
Legislative
Change
Sensor
Manufacturer
Request
(without
specs)
Prototype New Request
(with specs)
New
sensor
necessary
First Development
(specifications based on
assumptions )
Pre-Prototype
Second Development
(changed specification
based on experiences)
Testing
(too expensive and/or
inaccurate)
Delayed development

Simulative Assessment
Workflow for New Sensor Concepts
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Automobile
Manufacturer
Legislative
Change
Sensor
Manufacturer
New
sensor
necessary
Request
Series
Production
Simulative
Analysis
•Sensor valuation
•Specification
Shared understanding of requirements
Development
(based on specifications)
Pre-Prototype
Cost / Benefit

Simulative Assessment
Simulation Environment
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Simulative valuation of benefit for functions: ‘NH3dosing’ and ‘Adaption’
Release conditions
min
max
const.
Temp.
λ
dm
const.
Tolerance
RF sensor signal based
RF antenna
NOx
conversion
NOx-
sensor
RF signal based difference
detection
Conventional adaption
(NOxconversion rate based)
axisuite
NOx-
sensor
RF signal utilization
Output: NH3load
Conventional
(characteristic map based)
Adaption NH3dosing
DOC
DPF
vs.
vs.

Simulative Assessment
Simulation Environment
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Compiled source code of MATLAB simulation environment
Automated parameter variation
Source: http://www.cbcity.de/wp-
content/uploads/2013/07/Matlab-Simulink.png
Simulation
Environment
<
=…
Inca-FLOW
Wait
Parameter
variation
Sim...
IAV MiL-Desk
Gain on NH
3
-dosing [%]
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Tolerance of HF-sensor [%]
±90 ±80 ±70 ±60 ±50 ±40 ±30 ±20 ±10 ±0
Difference in time (HF-based Adaption vs. NO
x
-based)
-120
-80
-40
-20
-10
-5
0
5
10
20
40
80
120
Compiled
Source Code
Parameter
Variation
Accuracy/Benefit
Specification
‘.exe’

Simulative Assessment
Simulation: AdBlue Dilution
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mNH3 [g]
0
1
2
3
ECU model
SCR model ("real")
NH3-load demand
SCR efficiency
0.0
0.5
1.0
Time [s ]
0
1000
2000
3000
ECU model
SCR model ("real")
V [km/h]
0
50
100
Current situation: Efficiency drop mandatory for dosing adaption
2xFTP (low temperature)
High NH3load level
Demand: NH3load level min. 1g
Lower „real“ NH3load level through
AdBlue dilution
0g
„Real“ NH3load leads to efficiency
drop

Simulative Assessment
Simulation: AdBlue Dilution with RF Input
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V [km/h]
0
50
100
mNH3 [g]
0
1
2
3
HF-antenna tolerance
HF-signal
SCR model ("real")
NH3-load demand
SCR efficiency
0.0
0.5
1.0
Time [s ]
0
1000
2000
3000
ECU model
SCR model ("real")
HF sensor status
Despite the rare measurement events and inaccuracy of RF antenna: no increase in emission
Rare release of RF antenna: stat.
lambda, stat. T, stat. mass flow
„Real“ SCR load at higher level through
RF rectified ECU model
Virtual sensor with gain, offset, white-
noise…. measures too high load in
average
No efficiency drop

Signal Modelling
Test Vehicle
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Pre-Prototype Measurements (with UNI Bayreuth)
RF Antenna
Vector Network Analyzer
Development State RF Electronic (dyno and test car)
•Internal resonance peak analysis
•CAN interface analyzed RF parameters
Prototype sensor and support for further investigation

Signal Modelling
Measurements
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Main cross-influences of RF signal: temperature and exhaust gas humidity (indirectly measured by lambda)
Other
sensors
CAN
distributor
Measurement
recorder
RF signal
interpreter
VNA
SCR
Humidity
Road Measurement with Empty SCR (0g NH3):
Temperature
RF signal

Signal Modelling
Measurements RTB
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RF Signal proportional to axisuite SCR model
Dynamometer
Measurements:
1. Stationary operation
mode
2. Stable overdosing till
constant NH3slip
(sensor)
3. Dosing-Off till empty
NH
3
Load [g]
0
5
10
15
220° C - Axisuite
220° C - RF Signal
350° C - Axisuite
350° C - RF Signal
NH
3
Slip
0
200
400
600
Zeit [s]
0
1000
2000
3000
4000
220° C
350° C

Signal Modelling
Model Development
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Influences:
•Temperature
•Lambda
Same procedure for static
defined NH3load within SCR
catalyst
Infinite variable representation of amplitude damping in relation to temperature, lambda and NH3load
Empty
SCR-catalyst

 ,
=0+1�  +2�  +3� 2+4�  �  +5� 2

Signal Modelling
Testing
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•Road Measurement:
•Sensor signal vs. model
•Temperature and lambda correlated
Good correlation between RF signal and RF model for relevant operation modes (lambda 1-5)
Road Measurement

SCR Load Control
Real Drive Control with INCA-Flow
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INCA Flow allows in situ monitoring and manipulation of all signals transported in the CAN BUS
ECU
VNA
INCA-Flow:
1. Input:
•RF antenna signal (through VNA)
•ECU calculated NH3load
Modified
NH3load
ECU
NH3load
Measured
amplitude
2. Calculation
• RF amplitude damping NH3load
•ECU vs measured NH3load
3. Output:
•Modified NH3load

SCR Load Control
Simple Control Approaches
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Different approaches –have to be combined for optimisation
1. Correction of Calculated NH3Load 2. Adaption of NH3Dosing 3. Ammonia Loading Logic
SCR
NH3dosing RF antenna(s)
INCA-Flow
SCR
NH3dosing RF antenna(s)
INCA-Flow
SCR
NH3dosing RF antenna(s)
INCA-Flow
ECU
Calculated
NH3load [g]
NH3dosing
adaption
ECU
Calculated
NH3load [g]
ECU
Calculated
NH3load [g]
NH3load
offset

SCR Load Control
ECU Manipulation
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Implemented closed-loop control capable to compensate different errors without causing additional emission
Example Road Measurement
Correction of calculated NH3
load
Continuous errors are
corrected visibly (saw teeth)
•Complex/ time consuming
analysis of sensor signal
within VNA
•Release conditions of RF
sensor
NH3 balance through RF
controls fits ECU target

SCR Load Control
Prospects
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Advantages for combination of closed-loop control with RF antenna input
Additional
Input
Antenna
Calibration

Evaluation and Conclusion
OBD Prospects
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Pros:
•SCR ageing (fail part detection)
•SCR empty can detection
•ASC detection
•Dosing error
•NOx-sensor error
•Dew point reached detection
•Clogging detection (AdBlue)
High potential expected

Evaluation and Conclusion
Pros/Cons
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Pros:
•No release conditions necessary
•SCR removal detection simple
•Alternative for additional NH3/NOxsensor in complex SCR
systems
•Aging detection possible
•Sensor-OBD simple because of evaluable cross influences
•Simple construction robust and reliable
•Detection of NH3slip if applied beside a conventional NOx
sensor
Cons
•Earliest expected availability 2021
• Calibration of RF sensor for SCR layout is necessary
•NH3sensible only in SCR catalyst without additional
functions (DPF…)
•Additional costs for RF sensor
High potential expected

Summary
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•Sensor model of SCR NH3load based on polynomial functions realised
•Usable working range defined
•Closed loop control with ECU manipulation implemented
•Concept for OBD diagnostics
Superior system behaviour
Control of SCR load without emissions through emptied or
overfilled SCR
Main challenges for SCR systems (controlling of NH3load and OBD pinpointing) could be resolved with this sensor

Contact
Marco Moser
IAV GmbH
www.iav.com
Dr. Markus Dietrich
Continental Automotive GmbH
www.continental-corporation.com