Appendix 7a F1
United Kingdom
Verification of trip dynamics
1.
INTRODUCTION
This Appendix describes the calculation procedures to verify the trip dynamics by determining the excess or absence of dynamics during urban, rural and motorway driving.
2.
SYMBOLS, PARAMETERS AND UNITS
RPA
Relative Positive Acceleration
difference
larger
larger or equal
per cent
smaller
smaller or equal
acceleration [m/s2]
acceleration in time step i [m/s2]
positive acceleration greater than 0,1 m/s2 [m/s2]
positive acceleration greater than 0,1 m/s2 in time step i considering the urban, rural and motorway shares [m/s2]
acceleration resolution [m/s2]
distance covered in time step i [m]
distance covered in time step i considering the urban, rural and motorway shares [m]
discrete time step
discrete time step of positive acceleration datasets
refers to the respective category (t=total, u=urban, r=rural, m=motorway)
number of samples for urban, rural and motorway shares with positive acceleration greater than 0,1 m/s2
total number of samples for the urban, rural and motorway shares and the complete trip
relative positive acceleration for urban, rural and motorway shares [m/s2 or kWs/(kg*km)]
duration of the urban, rural and motorway shares and the complete trip [s]
compound data smoother
vehicle speed [km/h]
actual vehicle speed in time step i [km/h]
actual vehicle speed in time step i considering the urban, rural and motorway shares [km/h]
actual vehicle speed per acceleration in time step i [m2/s3 or W/kg]
actual vehicle speed per positive acceleration greater than 0,1 m/s2 in time step j considering the urban, rural and motorway shares [m2/s3 or W/kg].
95th percentile of the product of vehicle speed per positive acceleration greater than 0,1 m/s2 for urban, rural and motorway shares [m2/s3 or W/kg]
average vehicle speed for urban, rural and motorway shares [km/h]
3.
TRIP INDICATORS
3.1.
Calculations
3.1.1.
Data pre-processing
Dynamic parameters like acceleration, (v · apos) or RPA shall be determined with a speed signal of an accuracy of 0,1 % for all speed values above 3 km/h and a sampling frequency of 1 Hz. This accuracy requirement is generally fulfilled by distance calibrated signals obtained from a wheel (rotational) speed sensor. Otherwise, acceleration shall be determined with an accuracy of 0,01 m/s2 and a sampling frequency of 1 Hz. In this case the separate speed signal, in (v · apos), shall have an accuracy of at least 0,1 km/h.
The correct speed trace builds the basis for further calculations and binning as described in paragraph 3.1.2 and 3.1.3.
3.1.2.
Calculation of distance, acceleration and
The following calculations shall be performed over the whole time based speed trace (1 Hz resolution) from second 1 to second tt (last second).
The distance increment per data sample shall be calculated as follows:
where:
is the distance covered in time step i [m]
is the actual vehicle speed in time step i [km/h]
is the total number of samples
The acceleration shall be calculated as follows:
where:
is the acceleration in time step i [m/s2]. For i = 1: , for : .
The product of vehicle speed per acceleration shall be calculated as follows:
where:
is the product of the actual vehicle speed per acceleration in time step i [m2/s3 or W/kg].
3.1.3.
Binning of the results
After the calculation of ai and (v · a)i, the values vi, di, ai and (v · a)i shall be ranked in ascending order of the vehicle speed.
All datasets with vi ≤ 60 km/h belong to the ‘urban’ speed bin, all datasets with 60 km/h < vi ≤ 90 km/h belong to the ‘rural’ speed bin and all datasets with vi > 90 km/h belong to the ‘motorway’ speed bin.
For N2 category vehicles that are equipped with a device limiting vehicle speed to 90 km/h, all datasets with vi ≤ 60 km/h belong to the ‘urban’ speed bin, all datasets with 60 km/h < vi ≤ 80 km/h belong to the ‘rural’ speed bin and all datasets with vi > 80 km/h belong to the ‘motorway’ speed bin.
The number of datasets with acceleration values ai > 0,1 m/s2 shall be greater or equal to 100 in each speed bin.
For each speed bin the average vehicle speed shall be calculated as follows:
, i = 1 to Nk, k= u, r, m
Where:
Nk is the total number of samples of the urban, rural, and motorway shares.
3.1.4.
Calculation of per speed bin
The 95th percentile of the values shall be calculated as follows:
The values in each speed bin shall be ranked in ascending order for all datasets with and the total number of these samples Mk shall be determined.
Percentile values are then assigned to the values with as follows:
The lowest value gets the percentile 1/Mk, the second lowest 2/Mk, the third lowest 3/Mk and the highest value
is the value, with If cannot be met, shall be calculated by linear interpolation between consecutive samples j and j+1 with and .
The relative positive acceleration per speed bin shall be calculated as follows:
where:
is the relative positive acceleration for urban, rural and motorway shares in [m/s2 or kWs/(kg*km)]
is a time difference equal to 1 second
is the sample number for urban, rural and motorway shares with positive acceleration
is the total sample number for urban, rural and motorway shares
4.
VERIFICATION OF TRIP VALIDITY
4.1.1.
Verification of per speed bin (with v in [km/h])
If
and
is fulfilled, the trip is invalid.
If and is fulfilled, the trip is invalid.
F2Upon the request of the manufacturer, and only for those N1 or N2 vehicles where the vehicle power-to-mass ratio is less than or equal to 44 W/kg then:
If
and
is fulfilled, the trip is invalid.
If
and
is fulfilled, the trip is invalid.
To calculate the power-to-mass ratio, the following values shall be used:
the mass which corresponds to the actual test mass of the vehicle including the drivers and the PEMS equipment (kg);
the maximum rated engine power as declared by the manufacturer (W).
4.1.2.
Verification of RPA per speed bin
If and is fulfilled, the trip is invalid.
If and RPAk < 0,025 is fulfilled, the trip is invalid.
Annotations
Textual amendments
- F1
- F2