1. Evaluation of PEMS tests Veh 01 & Veh 02 with the CLEAR Method
Meeting Brussels,
Stefan Hausberger, Silke Lipp

2. CONTENT
Short reminder: Explanation of the CLEAR method + options for detailed evaluation and explanation of CO2-based CLEAR method
Analysis for Vehicle#1
Vehicle data
Difficulties
Measured data
Evaluation results vehicle#1
Analysis for Vehicle#2

3. “CLEAR” method x Pdrive
De-normalise the generic Target Power Pattern (multiply with vehicle specific Pdrive)
2) Average measured instantaneous (1Hz) signals from PEMS test over 3s
Bin the modal measured emissions into corresponding power class
Check minimum number of valid emissions in each bin
4) Average emission value per power bin
5) Multiply avg. emission value with the corresponding time share of power class
 weighted Emission value [g/h] for urban, road motorway and total trip
Target Power Pattern
x Pdrive
Pnorm

4. “CLEAR” method
Actual engine power of each vehicle is normalised by division by driving power demand of the vehicle to get representative power distribution for all cars.
Pdrive = vref * [mref * aref + R0 + R1 * vref + R2 * vref²]
With R0, R1, R2 ……road load mref……...kurb weight of the vehicle [kg]
aref………reference acceleration [0.45 m/s²]
vref………reference vehicle velocity [70 km/h = 19.4 m/s]
Evaluation of WLTP data on 49 different cars
 Generic Target Power Pattern for urban, road, motorway

5. “CLEAR” method using CO2 instead of Pe (1/2)
Principal illustration char. Gas pedal
The Problem
Power signals from veh#1 and veh#2 were gained from gas pedal position which typically overestimates real propulsion power due to its characteristic line (> 50% over-estimation of real power, see later slides).
This made the application of an alternative method necessary.
Possible solution:
Vehicle specific Willans lines are applied in WLTC correction functions, in MAC test procedure, in WLTC-NEDC correlation study,..
Logical to use them also in RDE
From WLTC (or any other reasonable hot start test) a linear equation between power and CO2 emissions can be established

6. “CLEAR” method using CO2 instead of Pe (2/2)
Additional steps in application of CLEAR:
1) Willans function of the vehicle test results in WLTC is produced
CO2 [g/h] = D + k x Power [kW]
2) power is calculated from CO2 measured in PEMS trip as input for CLEAR. Go ahead like usual (details on results shown later).
Willans-Coefficients:
(CO2(t)– d) k
P(t) =
Etc.
Additional condition:
If v=0  P = 0
P_Willans

7. Results vehicle #1 Vehicle data: Kerb mass [kg] 1470 F0 [N] 79.19
F1 [N/(km/h)]
0.73
F2 [N//km/h)²]
0.03
Prated [kW]
109
Model year
2013
Emission Standard
EURO 6
Engine type
DIESEL

8. Test data available for vehicle #1
9 trips measured with vehicle no. 1

9. Difficulties with vehicle #1
As example details on power signals versus calculated power for Trip: ROM_01
Test time: 6780 s → chart shows power values between 900 s an 1100 s
Calculated power by using the Willans-Coefficients is in the middle of measured and wheel power calculated from velocity and reference mass and road load data (no road gradients available).
P_wheel = v*(m*a+R0+R1*v+R2*v²)

10. Difficulties with vehicle #1
Difficulties encountered with the test data
1st run: all trips were identified to be invalid by CLEAR due to too much deviation between measured and calculated power signal .
Integral of measured power (from gas pedal position), lower value with motoring values added manually
ca kNm
ca kNm
ca kNm
ca kNm
Example integral of power
Trip: ROM_01
Calculated from measured 1Hz CO2 and Willans equation
Calculated from measured 1Hz velocity with reference mass and road load

11. Difficulties with vehicle #1
Similar problems detected also for chassis dyno tests received for veh#1
After the detection of the inconsistencies discussion with JRC on data sources, road load settings etc. started.
Many thanks to Theodoros Vlachos and Pierre Bonnel for the support in explaining contents and sources of data and especially for the extensive and good work in data collection!
Conclusions TUG:
Power signal calculated from measured gas pedal position are too inaccurate without knowing its characteristic line. Interpolation of power from existing fuel map of veh#1 failed due to missing data in low load areas
Results from power signal shown only for information but are no valid evaluations!
Option for CO2 based CLEAR evaluation was applied. Willans line had to be gained from chassis dyno test of same vehicle model at TUG!
In second version of data provided by JRC emissions during cold start, DPF regeneration phases etc. have been set to zero by JRC if at test start. We excluded these “virtual zero emission phases” from evaluation. We assume there are no virtual zero emission events somewhere in the middle of test data (to be validated).

12. Vehicle no. 1 Willans-Line
Creation of the Willans-Line from vehicle no.1:
Dataset of a measured CADC-drive cycle for the determination of the Willans-Line:
=Average values of positive wheel power
Classification of different phases
=Average values of the measured CO2
Vehicle no. 1 Willans-Line
Coefficients of the Willans-Line for the vehicle no. 1 for calculation of the power in the next step (source: CADC measurement at TUG!)
Trend line
Average CO2 [g/h]
Average positive wheel power [kW]

13. Results for vehicle #1 P_Willans
Share of power for the different trips:
Visualization of the different power values over time share.
For CO2-based method the separation between idle and motoring needs to be improved
„larger than“

14. Results for vehicle #1 P_Willans
Note: Valid trips marked with dots, others miss measured emissions in one ore more power bins (only power bins with > 0.1% target time share tested for this criterion yet, otherwise more invalid trips)
Lowest emission value from valid trip = 280 mg NOx/km
 Vehicle#1 would fail, if CF< 3.5

15. Results for vehicle #1 P_Willans
Note: Valid trips marked with dots, others miss measured emissions in one ore more poser bins
Overview Vehicle#1 NOx emission results:

16. Area includes ~94% of NOx for this car
P_Willans
Some details for vehicle #1
Results per power bin for total trip show high variability of NOx at medium and high power areas
Share in weighted NOx
Fluctuation of the NOx-values from the different trips at higher power bins.
Area includes ~94% of NOx for this car
Examples for further details next slide
„larger than“

17. Weighted engine speed gradient Weighted power gradient
P_Willans
Weighted NOx
Weighted engine speed
„larger than“
Weighted engine speed gradient
Weighted power gradient

18. Some details for vehicle #1
P_Willans
Some details for vehicle #1
Reasons for high and low NOx emissions in single power bins can be analysed based on power and rpm data, e.g.:
Low engine speed level in “Eco” leads to full load phases where veh#1 obviously has no sufficient NOx control  high specific NOx (power bin 8 and 9 are empty -> trip avg. reduced)
Higher engine speeds in “Agg” seem to have better NOx control. However, high derivates of P and rpm also lead to rather high specific NOx (in addition power bin 8 and 9 are filled)
Route1 Eco “Power bin 6”
Route1 Agg “Power bin 6”
Route1 Eco “Power bin 7”
Route1 Agg “Power bin 9”

19. Total weighted NOx [g/km] based on ~50% overestimated power!
Results CLEAR with measured power signal
P from gas pedal
When power value gained from gas pedal position is used for the evaluation, power signals seem to be on average 50% too high.
 If CLEAR still is applied, all trips are treated as if they have more than normal power distribution what results in a reduction of emissions:
Total weighted NOx [g/km] based on ~50% overestimated power!
Only validated power signals shall be allowed (e.g. +/- 3% accuracy)
“Power at wheel hub” may be used as reference: measurable at chassis dyno; can be calculated with reasonable accuracy from Willans line; can be measured accurately with torque meter rim (in case of eventual disagreements between OEM and TA).
OEM may use CAN signals for their tests (cost efficient, accurate) while TA, TS and anyone else can use the CO2 based CLEAR method.
In case of doubts reference method could be power based method (distribution of driving resistances should be valid for all cars, “distribution of CO2” not necessarily)

20. Results vehicle #2 Vehicle data: Test mass [kg] 1700 R0 [N] 121
R1 [N/(km/h)]
0.8
R2 [N//km/h)²]
0.03
Prated [kW]
103
Vehicle data:
Model year
2012
Emission Standard
EURO 6 *
Engine type
DIESEL
* in vehicle description it is noted as “EURO 5”, in file names EURO 6

21. Test data available for vehicle #2
17 trips where measured with vehicle no. 2

22. Difficulties with vehicle #2
Similar problems as for veh#1:
Nor reliable power signal available.
All evaluations based on “measured power” invalid due to too high deviations in measured and calculated cycle work
Additionally Willans Lines gained from chassis dyno tests at JRC suffers also from not validated wheel power data.  power in WLTC calculated by TUG from mass and road load Eventually road load and mass was different in WLTC test than in NEDC? Results should be validated between TUG and JRC! With this task TUG is delayed due to the complications for veh#1
 Willans line uncertain for veh#2  only preliminary results for internal discussion!

23. Willans line computed for vehicle #2
v… velocity
m… test mass
a… acceleration
R0… road load coefficient
R1… road load coefficient
R2… road load coefficient
Using calculated wheel power: Pwheel = v * (m*a + R0+R1*v+R2*v²)
TUG-Willans Version seems to be too high (maybe the car was tested in WLTC with different mass and road load?)
Other too low

24. Power-Data:
Three different calculated data where considered for the calculation with CLEAR:
P_Mean_corr
P_Willans_JRC
P_Willans_TU
P_Mean_corr:
The measured power values for each trip where taken with an addition for detecting drag power. Drag power was set on a value of -10 kW, when the acceleration a < 0 and the CO2 < CO2idle.
Shown only for illustration!
P_Willans_JRC:
Willans-Coefficients where calculated by using the WLTC-data from JRC
P_Willans_TU:
Willans-Coefficients where calculated by using the wheel power

25. Comparison of the different Power-Data:
Example for Trip: BS_2013_03_04
Time: s
Result: Different power values over time for each calculation.

26. Power-Data: Seems to be too high
Result: Summation of power data results very different work values over trip time.

27. Results for vehicle #2 Total trip results evaluated based on measured power and “TUG-Willans power”
P_Willans
P_measured
Correct results should be between these 2 evaluation results (TUG-Willans delivers rather too low power values, measured power seems to be too high)  further analysis after clarifications with JRC
Note: Valid trips marked with dots, others miss measured emissions in one ore more power bins

28. Thank you very much for the attention!

29. Backup slides

30. Schematic picture „Option A“
“CLEAR” method using CO2 instead of Pe (1/2)
Additional steps in application of CLEAR:
1) Willans function of the vehicle test results in WLTC are produced
CO2 [g/h] = D + k x Power [kW]
2) calculate power from CO2 measured over PEMS trip as input for CLEAR. Go ahead like usual = actual option (details shown later)
Options for a next CLEAR release:
Convert x-axis in target power pattern from P [kW] to CO2 [g/h] (+ “if v=0  idling bin”) Bin emissions over CO2 instead of binning over power
Calculate Power in CLEAR from CO2 measured with PEMS and allow binning for “Willans Power” as well as for directly measured power.
Schematic picture „Option A“
x Pdrive 
x (D + k x P) 