Transcript WLTP-DHC-16-03e

WLTP-DHC-16-03
WLTP
H.S.
Comments on the Ste 3 gearshift calculation tool
from validation 2 participants
Heinz Steven
08.01.2013
1
Background
H.S.
• In order to take into account the technical progress and the
increased variety of transmission design (e.g. 4-speed up to 7speed gearboxes) shift points at fixed vehicle speeds are no
longer appropriate.
• In order to reflect practical use as well as fuel efficient driving
behaviour as much as possible, the prescriptions are based
on the balance between the power required for driving
resistance and acceleration and the power provided by the
engine in all possible gears at a specific cycle phase.
• In order to cover the wide range of rated engine speeds (e.g.
3200 to 8000 min-1) depending of the engine technology, a
calculation tool was developed which is based on normalised
engine speeds (normalised to the span between idling speed
and rated engine speed) and normalised full load power
curves (normalised to rated power) versus normalised engine
speed.
2
H.S.
Input data
parameter
Prated
unit
kW
s
min-1
nidle
min-1
-1
nmin_drive
min
mt
kg
ngmax
Idling speed, the engine speed when the gear lever is in neutral and the vehicle is not
in motion.
minimum engine speed for gear numbers ≥ 3 when the vehicle is in motion. The
minimum value is determined by n idle + 0,125×(s - nidle). Higher values can be required
by the manufacturer.
test mass of the vehicle
number of foreward gears
ndvi
min-1/(km/h)
f0
N
f1
N/(km/h)
f2
N/(km/h)2
Pwot(nnorm)/Prated
definition/description
The maximum power of the engine as declared by the manufacturer.
Rated engine speed, the engine speed at which an engine develops its maximum
power. If the maximum power is developed over an engine speed range, s is
determined by the mean of this range.
ratio of engine speed and vehicle speed for gear i, i = 1 to ng max
driving resistance coefficients as defined in Annex 4
Normalised full load power curve as function of normalised engine speed
nnorm = (n - nidle)/(s - nidle)
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Interim feedback from validation 2
participants
H.S.
• This calculation tool was used during validation 2 of the WLTP
project.
• Some participants wanted to get the opportunity to choose
n_min_drive values below the current limit, which is not
possible in the current version.
• Another comment: Downshift to 1. gear should be avoided or
minimised. This downshift is most probably caused by the
definition of n_min for the 2. gear: n_min = 1,25*n_idle,
which might be too high.
• A comment from one party: upshifts are too early, engine
speeds are too low, shift behaviour not in line with practical
use,
• A comment from another party tended into the opposite
direction and requested also the use of n_min_drive values
below the current limit curve.
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Modifications performed during
validation 2
H.S.
• The author concluded that the following modifications should
be made in conjunction with the implementation of the
modified cycle versions for low powered vehicles.
 options for the choice of lower n_min_drive values (for
gears >= 3),
 Add an option for the choice of n_min values for the 2.
gear.
 A 3rd modification is related to the choice of the safety
margin for the full load power curve.
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Modifications
H.S.
Modific. 0: Implementation of modified cycle versions for low
powered vehicles (class 1 and 2),
Modific. 1: n_min_2 was added as input parameter.
n_min_2 is the minimum engine speed in gear 2.
n_min_2 was defined as 1,25*idling_speed.
It is now recommended to set n_min_2 to
1,15*idling_speed.
The minimum value that can be used for the
calculation is 1,1*idling_speed.
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Modifications
H.S.
Modific. 2: n_min_drive, the minimum engine speed for short
trips in gears > 2, was limited to
0,125*(rated_speed - idling_speed) + idling_speed.
The use of this value is still recommended, but lower
values down to n_min_2 can be used for the
calculation.
Modific. 3: The safety margin accounting for the difference
between stationary wot power curve and the power
available during transient conditions could be chosen
as input parameter in the previous version.
The choice of 90% was recommended.
The safety margin is now set to 90% and cannot be
changed any more.
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Further comments
H.S.
•
These modifications were implemented in an updated
version of the tool (reference date 09.07.2012) which was
then distributed and used for validation 2.
•
Further comments on the calculation tool were made by the
following participants:

ACEA members

Daimler,

Delphi,

PSA

India,

Japan
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Comments from Daimler
H.S.
•
prevent backshifting, because a scenario with reduced
downshifting/backshifting points is closer to real driving
behaviour,
•
It increases driveability during test procedure,
•
Backshift to „Gear 1“ often not necessary as long as vehicle
is in motion,
•
Average engine speed is only slightly reduced by the
modification,
•
Suggestion for improvement of Gearshift Calculation
Approach “Steven”：

Possibility to define „n_min_drive“ for single gears
individually.
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Comments from Delphi
•
The Delphi comments were also delivered as presentation
and can be summarised as follows:
•
Downshifting to 1st gear:

•
H.S.
We observe that the speed decrease sharply during the
downshifting with the risk of missing the target speed.
Feedback from drivers who had tested the cycle:

It’s hard to follow the cycle in 1st gear

Downshifting frequently to 1st gear isn’t totally
representative of a real drive on the road
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Comments from Delphi
•
•
H.S.
Proposal for improvement:

Not engage the 1st gear when the vehicle is still moving,

Let the 2nd gear engaged,

At the time when the 1st gear is engaged, disengage the
clutch,

Re-engage the clutch when the vehicle speed will
increase again
Benefits:

The vehicle speed is closer to the target than before

The risk of driver violation is decreased
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Comments from Delphi
•
•
H.S.
Feedback from drivers:

The cycle is easier to follow

The time spent on the slip point is decrease because the
the downshifting to 1st gear requires more time on this
point than the re-engagement of the 2nd gear
Other effects:

Time spent without a gear engage is increased
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Comments from PSA
•
The approach is too much aiming at economic driving,
•
The number of shift points is too high,
•
The current proposal disadvantages gasoline engines.
H.S.
13
Comments from India
•
•
H.S.
No. of Gear Shifts (Stevens) vs PMR

Gear shifts are higher than proposed by Japan,

With reduction of Safety Margin from 90% to 80% the
cycle is expected to become stringent on the lower PMR
Range,

Use of Moderated Cycle 5.1 will compensate for this
effect as shown in the chart in WLTP-DHC-15-03.
Safety Margin on Full Load Power Curve

Steven’s Gear Shift is based on the assumption of 90%
Safety Margin of Power Available.

The actual power available at Wheel is 80%. Hence for
actual safety margin, the criteria should be modified to
80%. (20% margin),
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Comments from India

H.S.
For new vehicles tested for COP will have lesser Power
Availability due to Higher Engine Friction Losses. The
proposed criteria of 80% barely meets requirements of
new vehicles.
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Comments from Japan
H.S.
•
The Japanese colleagues sent analysis results for 8 different
vehicles including low powered N1 vehicles.
•
The results are summarised in the following table.
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H.S.
Comments from Japan
No Categories
Current
Proposal
input interval data,
then automatic data deviation
(proportional)
reference doc.
comments Steven
NA
agreed, was not yet foreseen
due to lack of time
1
General
Specific power curve
input each 1/100 data (total 120 data is required)
2
General
Default power curve
seems to be diesel engine curve
separate "default" curve for diesel and
petrol
NA
3
General
grouping
input each vehicle specification/each road-load value
for each test
tbd
NA
4
logic
power curve margin
exceed 10% margin (exceed 100% power In some
area)
should be less than margin in all area
JAMA_1
5
logic
bug ?
exist mysterious shift
JAMA_1
6
logic
improve gear shift point, but don't know why/how
JAMA_2
WLTP_Steven3 shift
JAMA_2.ppt POINT1&2
7
logic
busy shift operation at low vehicle speed
WLTP_Steven3 shift JAMA_2.ppt POINT3
need hysteresis for minimum engine
speed
JAMA_2
8
↑
class2
the interval of gear shifting is very tight.
Most of acceleration portions
need more hold duration ?
JAMA_3_A
needs to be discussed
9
↑
↑
many down shifting during deceleration.
HS Shift_JAMA_3_A.xls CIRCLE area
JAMA_3_A
should be discussed
10
↑
↑
11
↑
all phases
too many gear shifting, especially down shifting
JAMA_3_B
12
↑
Ex-H
same gear, but vehicle speed is relatively different
(red box)
JAMA_3_B
13
↑
all phases
14
↑
all phases
it is impossible to accelerate from under 30km/h in
JAMA_3_A
5th gear (176sec ~ , 530sec ~)
P_available_lower_P_requested (but within 1 or 2
seconds)
Clutch_disengaged occur faster than expected
just comments, no action is requested
JAMA_4_A~D
remove "n_min_drive" lower limit
JAMA_4_B
default value was only provided
for validation 2 and should be
deleted for future use
I agree, should be related to
representative for vehicle family
margin will be increased to 80%
or will be made engine speed
dependent
cannot be reproduced on my
computer
is this statement related to
Steven 3, version 1 or version 2
(0907)?
This effect is due to the
n_min_drive limitation which is
necessary to achieve realistic
results for high powered
vehicles. Needs to be
discussed!!!
But the necessary power is
delivered in that gear, needs to
be discussed.
see no 7 and 9
this is because the
accelerations are significantly
different
needs to be
explained/discussed
see no 7
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Summary of discussion points
H.S.
• Input data:
 Default values for the full load power curve and for driving
resistance coefficients should not be provided in a final
version.
 The safety margin for the full load power curve needs to be
updated/improved, the input data for the curve need to be
simplified.
 Uniform input data for a vehicle family.
• Downshifts:
 Downshift to 1. gear: Although the number of downshifts
to the 1. gear within a short trip were reduced with version
2 compared to version 1, there is still a need for further
improvement.
 Downshifts by more than 2 gears.
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Summary of discussion points
H.S.
• Approach
 The current approach aimes at a compromise between
economic driving and representativity with respect to inuse data,
 The current n_min_drive concept is a bit more favourable
for Diesel engines compared to Petrol engines
• As a consequence the number of shift points is higher
compared to a vehicle speed based system.
• It should be assessed, how the number of shift points
correlates with the in-use data and whether or to what extent it
could be reduced by an increase of engine speeds.
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