working paper no. wltp-07-06e 1 agenda item 5: status report on downscaling / gearshifting (oil...

H.S.H.S.Working Paper No. WLTP-07-06e

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Agenda item 5: Status report onDownscaling / Gearshifting (OIL #4-9)

Points that are resolved in the TFs are written in green colour.Points that still need further considerations are written in red colour.

by H. Steven

21.05.2014

7th WLTP IWG meeting, 04. June 2014

H.S.H.S.Downscaling, issues to be treated

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The downscaling procedure is specified in paragraph 7 of annex 1.

• One point that needs clarification is related to paragraph 7.4 of annex 1 “Additional requirements”.

• The text, that specifies the drive instructions in case the vehicle cannot follow the trace of the downscaled cycle does not exclude the activation of a “kick-down” for automatic transmission vehicles.

• It is proposed by the TF chairman to add the following sentence, which was copied from ECE R51:

External downshifting (for example kickdown) shall be excluded.

This proposal needs to be discussed within the TF.


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• In addition to that an error in formula 6 of paragraph 7.2.2 of annex 1 needs to be corrected. It should read “with i = 1520 to 1724” instead of “with i =

1520 to 1725”.

Done!


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• The downscaling method as such is agreed, but paragraph 7.3 “Determination of the downscaling factor” needs to be amended.

• India requests modifications of the calculation parameter/coefficients r0, a1 and b1 and made already a proposal for amendments (see WLTP-DHC-18-05). This issue is related to # 5 of WLTP-05-04.

• Calculations based on the Indian amendment proposal were performed for a series of class 3 vehicles.

• In addition to that the database used for the development of the downscaling method was re-analysed in order to assess this proposal.

H.S.H.S.Downscaling, work done so far

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The following approach was chosen and applied to class 3 vehicles.

• The downscaling method uses the ratio between the maximum required power of the cycle phases where the downscaling is to be applied and the rated power of the vehicle.

• This ratio is independent of the transmission design, which is necessary in order to make the method applicable for any kind of transmission.

• But in order to better consider the influence of the transmission design, the necessary downscaling factor was related to the power available in second 1566 of the WLTC instead of rated power.


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• Second 1566 is the time, at which the maximum power is required within the cycle for class 3 vehicles.

• The calculation was performed for 81 vehicles of the development database. The rated power to kerb mass ratio of these vehicles varies between 34,1 kW/t to 52 kW/t and includes different transmission designs.

• As expected, the correlation is much better than for rated power.

• The correlation between Preq/Pavailable and Preq/Prated was used in order to re-establish the relationship with Preq/Prated.


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• A significant number of vehicles (14 of 81) have ratios that are further away from the regression curve.

• For these vehicles it can be expected, that f_DSC based on the regression line will not be sufficient, especially, when the wot percentage is considered as additional requirement.

• Therefore the average between the regression curve and the upper envelope curve is proposed by the chairman as compromise.

• This results in a f_DSC curve, that is close to the Indian proposal, but starts at a 3% higher Preq/Prated values (87% instead of 84%).


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• The same approach was applied to 105 class 2 vehicles and to 34 class 1 vehicles in the gearshift prescription development database.

• The results are shown in figure 1.

H.S.H.S.

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Preq, max, i / Prated

DSC India 3DSC new proposal, class 3new proposal, class 2new proposal, class 1average class 2 & 3current GTR, class 3current GTR, class 2current GTR, class 1

f_DSC vs Preq/Prated, all classes

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H.S.H.S.Proposal for new r0, a1 and b1 values

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The calculation parameter/coefficients r0, a1 and b1 are determined as follows:

• Class 1: r0 = 0.978, a1 = 0.680, b1 = -0.665

• Class 2: for vehicles with v_max> 105 km/h, r0 = 0.866, a1 = 0.606, b1 = -0.525. No downscaling shall be applied for vehicles with v_max≤ 105 km/h

• Class 3: for vehicles with v_max> 112 km/h, r0 = 0.867, a1 = 0.588, b1 = -0.51; for vehicles with v_max ≤ 112 km/h, r0 = 1.3, a1 = 0.65, b1 = -0.65.

• A more simplified proposal, valid for all classes, is r0 = 0.867, a1 = 0.597, b1 = -0.5175 (yellow curve in figure 11)

H.S.H.S.Downscaling, next steps

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• This proposal was sent to the Indian colleagues at 19.05.2014 for comments and assessment.

• After the consultations with the Indian colleagues, the proposal will be sent to other stakeholders within the WLTP IG for further consultations.

• The final proposal will be sent to the WLTP IG in due time prior to meeting 8 for decision.

H.S.H.S.Downscaling using torque meter

method results

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Another point on the issues list is related to the use of road load coefficients in the downscaling factor calculation formulas.

• # 4 of WLTP-05-04 (Calculation parameter/coefficients for torque meter method):

The problem was clarified between Japan and HS (coast down method delivers f0, f1 and f2, torque meter method delivers C0, C1 and C2).

The discussions with test bench and calculation experts are still ongoing. A deadline for a solution cannot be fixed yet.

H.S.H.S.Gearshifting, current status

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• The gearshift prescriptions for manual transmission vehicles are specified in annex 2 of the GTR.

• The following issues are listed in WLTP-05-04 for further amendments:

1. Special gearboxes or auxiliary gearboxes (e.g. exclusion of “crawler” gears), see OIL # 6 in WLTP-05-04.

2. Addition of formulas based on the torque meter method, see OIL # 7 in WLTP-05-04.

3. Skipping of gears, see OIL # 8 in WLTP-05-04.

• To point 3 the skipping of the 3 s rule for acceleration phases, the modification of the safety margin for the full load power curve and related issues were added.

H.S.H.S.Gearshifting, issues list

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• The actual issue list contains the following points:

1. Corrections in the current text (paragraph 3.2),

a. n_max (should be 90% for all gears except highest gear instead of 120%),

b. Correction of requirements for n_min for 2. gear, (the current text is insufficient),

c. Point (d) of the additional requirements for corrections and/or modifications of gear use (see para 4 of annex 2 of the GTR) is unnecessary and can be skipped, because it is covered by point (e). The rank order of the other points in the calculation tool is: (b), (c), (e), (f), (g), (a). The text in the GTR should be rearranged accordingly.

H.S.H.S.Gearshifting, issues list

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2. Specification of rated engine speed in case of a Prated plateau,

3. Amendment of the definition of n_min_drive,

4. Review 3 s rule for acceleration phases,

5.

a. Review gear use at a transition from an acceleration phase to a cruise phase,

b. Assess the possibility of skipping of gears during acceleration phases.

6. Additional speed depending safety margin,

7. Assess the exclusion of auxiliary gears (crawler gears)

H.S.H.S.Gearshifting, current status, next steps

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• The task force had a web/telco at 20.03.2014 and a face to face meeting at 08.05.2014 in Brussels with the participation of the Japanese colleagues via web/telco.

• JRC and the Indian colleagues were informed about the results of the discussions by the meeting minutes.

• Ad 1) Corrections in the current text (paragraph 3.2) n_max (should be 90% for all gears except highest gear

instead of 120%) was agreed and accepted;

remaining open point: Engine speed limit for gear ngmax – 1, if gear ngmax is an overdrive.

Correction of requirements for n_min for 2. gear, (the current text is insufficient). The chairman will prepare an amendment till end of June 2014.


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• Ad 1) Corrections in the current text (continued) Point (d) of the additional requirements for corrections

and/or modifications of gear use (see para 4 of annex 2 of the GTR) is unnecessary and can be skipped, because it is covered by point (e). The rank order of the other points in the calculation tool is: (b), (c), (e), (f), (g), (a). The text in the GTR should be rearranged accordingly.

The chairman will prepare an amendment till end of June 2014.


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Ad 2), 3) Specification of nrated in case of a Prated plateau,

Amendment of the definition of n_min_drive Since this issue is mainly related to the specification of

n_min_drive and n_max, top 3 and top 4 were discussed together.

Some group members proposed to find better solutions for both parameters independent of rated engine speed (e.g. k*nidle for n_min_drive, k >= 1,2).

In this case point 2) becomes unnecessary.

The group agreed that further investigations and more time would be necessary in order to find a robust solution. One member of the group volunteered to prepare a proposal by end of June 2014 as basis for further considerations in the group.


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Ad 2), 3) continued In this context the chairman reminded the group that

this new proposal should lead to engine speeds for high powered vehicles that are still in line with practical use.

One member mentioned that the maximum torque and the maximum power of an engine is certified, but not the full load power curve and expressed the concern that a certification procedure would be required for the GTR.

The chairman recommended the consideration of ECE R 85 for the needed requirements.


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• Ad 4) Review 3 s rule for acceleration phases The Japanese colleagues argued, that a time period > 1

s in a specific gear is necessary from the view points of repeatability and reproducibility and because the time tolerance for a gearshift is +/- 1 s (Annex 6, 1.2.6.5.1.2).

Therefore they recommended to replace the 3 s rule by a 2 s rule, as originally proposed by Japan (WLTP-DHC-09-03).

One colleague expressed some concerns with respect to the 1. Gear and Ford’s in-use driving behaviour data, but agreed to go ahead with this proposal.

The other group members supported the Japanese proposal.


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• Ad 5 a) Review gear use at a transition from an acceleration phase to a cruise phase

Already in the web/telco was the possibility, to allow upshifts by two gears at the transition from an acceleration phase to a cruise phase required, if the available power would be high enough to ensure driveability.

This request was supported and adopted by the group.

The Japanese colleagues mentioned that it would be good if this proposal could be supported by actual in-use driving behaviour data and that situations should be avoided where a downshift would follow within a short time period after an upshift with a skipped gear.


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• Ad 5 a) Review gear use at a transition from an acceleration phase to a cruise phase (continued)

The chairman argued, that this possibility will be prohibited by the other additional requirements, but promised to check his database results with respect to this point and deliver the results prior to the next face to face meeting.


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• Ad 5 b) Assess the possibility of skipping of gears during acceleration phases

The Japanese colleagues questioned that the possibility to skip a gear during an acceleration phase would be necessary with the 2 s rule.

This issue is also linked to the definition of n_min_drive. Upshifts by two gears would be avoided, if the n_min_drive values would be high enough.

In addition to that some members argued that phase indicators for acceleration, cruise and deceleration would be necessary for clear and robust gear skipping prescriptions.


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• Ad 5 b) Assess the possibility of skipping of gears during acceleration phases (continued)

The chairman argued that he does not see this need but proposed to use the same criteria for these phases as were used during the cycle development, if they would be needed.

The chairman promised to perform calculations with his database applying the 2 s rule and the possibility to skip gears and to deliver the results for further discussions prior to the next face to face meeting.


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• Ad 6) Additional speed depending safety margin This request was raised by vehicle manufacturers from

India and Europe with regard to downsized, high pressure turbocharged engines.

In the current tool such measure is already foreseen with the additional margin fully applied at idling speed and linearly reduced to 0 at rated speed.

One group member presented his contribution to this agenda point and stated that

- The current gear shift tool has a 10% margin to full load and an estimation of inertia for rotating parts of 10%.

- The full load margin is based on stationary max torque/power and cannot account for any transient response beyond the 10%.


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• Ad 6) Additional speed depending safety margin (continued)

- The inertia estimation compensates to some extent but not in lower gears.

- This means that full load, caused by dynamic limitations, occurs in the cycle particularly for engines with turbochargers.

- The target is to find a general method to characterize dynamically available torque for turbocharged engines.

The colleague presented alternatives in order to solve the problem and illustrated and discussed these alternatives based on his further slides.


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• Ad 6) Additional speed depending safety margin (continued) The conclusion of the group was that engine type

specific solutions would be required, if the problem would be solved by an approximation of the dynamic torque response and that more general solutions (like an additional safety margin for low engine speeds) bare the risk, that their effectiveness for different engine designs is different.

After intensive discussions the group agreed on the following proposal as basis for further considerations:

- The manufacturer can require and define an additional safety margin, which is fully applied at idling speed and linearly reduced to 0 at rated speed. This extra margin needs to be documented.


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• Ad 6) Additional speed depending safety margin (continued) Some members required the possibility to propose

alternative solutions till the end of June 2014.

It needs to be checked whether there could be a goal conflict with OBD requirements.

Also possible interactions with n_min_drive need to be checked.

This point might require more time, so that it could be necessary to extend the deadline for a proposal till WLTP IG 09.


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• Ad 7) Assess the exclusion of auxiliary gears The proposal from Ford was used as basis for the

discussion.

It consists of six different criteria. Three of them are technical requirements, the other three supportive.

The technical requirements are:

a. The vehicle can pull away in 1st gear at 50% GTM at 20% incline within 4.0 s.

b. The vehicle cannot pull away in 1st gear at GTM on 20% incline within 4.0 s.

c. The vehicle when in crawler gear has maximum speed of 12.5mph or 20km/h at 75% of rated speed whether with petrol or diesel engine.


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• Ad 7) (continued) This proposal was discussed and the group at first

agreed that the supportive requirements should be disregarded.

The requirement c. was adversatively discussed. Therefore the group focussed in the further discussion on modifications of requirements a and b.

The following proposal was made, which shall be used for further considerations:

The first gear is a crawler gear and disregarded for the gear use calculation, if the vehicle can pull away in second gear at 20% incline within 4.0 s with test mass high but not with gross vehicle mass.

The Japanese colleagues agreed but required the possibility to work on a counter proposal.


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• Ad 7) (continued) The rest of the group shall consider, whether this

proposal could be misused by very high powered vehicles.

In the context of this agenda point it needs to be checked, whether the current GTR text excludes the low transmission range for vehicles with low and high range transmissions, where the high range is dedicated to on road operation and the low range is dedicated to off road operation.

If not, the GTR needs to be amended accordingly. The group supported this proposal.

The discussion will be continued at the next face to face meeting based on further proposals from the group.

H.S.H.S.Gearshift prescriptions using torque

meter method results

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Another point on the issues list is related to the use of road load coefficients in the gearshift calculation formulas.

• Add calculation formulas based on road load values from the torque meter method

The problem was clarified between Japan and HS (coast down method delivers f0, f1 and f2, torque meter method delivers C0, C1 and C2).

The discussions with test bench and calculation experts are still ongoing. A deadline for a solution cannot be fixed yet.

H.S.H.S.Gear shift family criteria

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A further point is listed in WLTP-05-04, which should be added to the gearshift prescriptions:

• Development of gear shift family criteria, see OIL # 9 in WLTP-05-04.

• For this point the GP TF will be co-chaired by Japan and HS.

• The necessary steps for this issue will be drafted after preparatory discussions with Japan.

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