1. WLTP drive trace normalization
WLTP-08-46e
BMW,
Christoph Lueginger
WLTP drive trace normalization
Comments on Tug proposal of drive trace correction

2. WLTP normalization of drive trace Analysis on drive trace correction
TUG proposal for correcting possible deviations to target speed:
property of correction
fulfilled?
tolerance > measurement tolerance 
significant influence
measureable
physical meaning of correction func.
improves result
Fact box check for correction function.
Correction of driven speed vs. target speed and distance respectively seems to be a feasible approach whilst considering some important additional conditions and requirements.
Possible difficulties not addressed, e.g.:  handling of gear shifting (drive trace will always deviate during shifting).  handling of 10 Hz data (dyno as well as drive trace interpolation).  handling of poor driving style, that cannot be corrected.  additional criteria needed.  handling of electrified or hybrid vehicles.
WLTP normalization drive trace, BMW,

3. WLTP normalization of drive trace Drive trace correction – 10Hz issue
Interpolation method
WLTC 1Hz  WLTC 10Hz
linear
spline
another?
EER value [%]
- 1.9 %
- 2.2 % ?
With an example from correlation measurements the following problem occurred:
If the interpolation of the cycle is done in a different way, the correction will be different as well (which of course is logical, but not addressed at the moment).
As the time-interval is fundamental for the correction:  It should be fixed (e.g. 10Hz) and not a minimum or range.
As the cycle is obviously fundamental as well:  The interpolation – which is a kind of a new definition of a cycle – should be clarified.  The interpolation should not change the a/v distribution and other parameters of the WLTC, in order to keep the properties of the cycle.
Additional activity necessary regarding this issue!
WLTP normalization drive trace, BMW,

4. example for a 50km/h NEDC plateau
WLTP normalization of drive trace
drive trace correction – Filtering issue
example for a 50km/h NEDC plateau
The proposed filter T4253H was tested for some use cases:
It shall not be used for smaller data sampling (e.g. 1 Hz), but works well for 10Hz data.
WLTP normalization drive trace, BMW,

5. WLTP normalization of drive trace road load setting
Two methods for dyno setting are allowed: "fixed run method" (no tolerances!) and "iterative method", but checking of chassis dyno setting is only possible for the "iterative method".
As the number of coast downs for the "iterative method" is not fixed, even with this method a check might not be possible.
The force measurement has a tolerance of 10 N, as also the chassis dyno setting. Therefore only corrections in the magnitude of the tolerance would be applied, which results in correcting measurement errors instead of real existing deviations.
No improvement of the CO2-result possible!
Same procedure would results in same (temperature-) conditions, but only for the "iterative method" and only, if it had luckily the same number of coast downs
CD: Set: Test:
Warm-up:
Coast down:
Warm-up:
Dyno setting:
Test:
"Quickcheck"
gearbox
temperature:
17°
45°
45°
43°
23°
47°
47°
48° - 52°
23°
47°
47°
49°
WLTP normalization drive trace, BMW,

6. WLTP normalization of drive trace
road load setting, analysis and proposal
TUG proposal for correcting possible deviations of road load setting:
property of correction
fulfilled?
tolerance > measurement tolerance 
significant influence
()
measureable
physical meaning of correction func. 
improves result
Fact box check for correction function.
Address dyno setting issue by clarifying GTR is more appropriate.  First proposals already existing, e.g. limit number of cost downs for dyno load setting.
Correction in the order of measurement tolerance makes no sense, additionally it possibly corrects something that should not be corrected (fixed run method, see input from Japan during LabProcICE on that issue).
The effort of a road load check by coast downs after each test is in the magnitude of 20min, which significantly increases the time and therefore costs for a tests.
Effort is unnecessarily increased!
WLTP normalization drive trace, BMW,

7. WLTP normalization of drive trace Summary
Several issues for drive trace correction not solved:  electrified vehicles, 10Hz interpolation, gear shifting, etc.
Additional quality criteria are needed (to define tests as invalid at a certain point).  Poor driving cannot be corrected at a certain point but should be addressed as well.
There is no precise and clear proposal on the normalization functions, which would be needed to have progress on that issue. The report is ok as report, but sometimes confusing and too general to use it as a proposal.
Road load correction would tremendously increase testing effort by not improving the result and is therefore clearly rejected.
There is a political statement, that normalization should be included and the proposed corrections are illustrated as they are finished and only details are in discussion:  This is wrong and the wrong sequence. First it should be discussed and solved technically. Only the remaining and technically correct parts should then be proposed and included.  All proposed corrections are far away from being mature enough to be included, only rare technical discussion took place until now.
WLTP normalization drive trace, BMW,