FAQ.md

@@ -149,10 +149,171 @@ and fuel-consumption maps as provided in the input data are not extrapolated. In
 engineering mode, VECTO can be operated like any other vehicle simulation tool. All
 simulation parameters can be set and/or edited by the user.
 
-# 15. Can I run VECTO Simulator in batch mode/from the command line?
+# 15. Which vehicles are currently supported in declaration mode?
+
+Currently only rigid trucks and tractors are supported in declaration mode. According to the
+upcoming Commission Regulation on the determination of CO<sub>2</sub> emissions and fuel
+consumption of HDVs, Annex I, Table 1 vehicles are allocated to certain groups according to
+gross vehicle mass rated, axle configuration, and vehicle type (tractor, rigid truck). Supported
+vehicle groups actually are 1, 2, 3, 4, 5, 9, 10, 11, 12, and 16. All-wheel drive vehicles (4x4,
+6x6, and 8x8) are excluded from CO<sub>2</sub> declaration at the moment.
+
+# 16. Why are vehicles simulated on different cycles? What are the criteria for selecting the cycles?
+
+Depending on the vehicle group, a vehicle is typically used for certain purposes and the
+cycles (“mission profiles”) also represent different usage profiles. Thus, the vehicle group
+determines which cycles are simulated. The allocation of vehicle groups to mission profiles is
+defined in the upcoming Commission Regulation on the determination of CO<sub>2</sub> emissions and
+fuel consumption of HDVs Annex I, Table 1. Certain vehicle groups may be used also in EMS
+vehicle configurations (European Modular System, gross combination mass of 60.000 kg and
+a maximum length of 25.25 m) if the engine power is sufficient. In this case the long-haul
+and the regional delivery mission are simulated with an additional trailer.
+
+# 17. What is the vehicle's total mass for the simulation?
+
+The vehicle's total mass for the simulation is the sum of 'corrected actual curb mass', 'body
+mass', mass of the trailer(s), and 'payload'. In the VECTO declaration mode all of those
+parameters, except the 'corrected actual curb mass' are generic (depending on the vehicle
+group). The definition of 'corrected actual curb mass' is specified in Annex III of the
+upcoming Commission Regulation on the determination of CO<sub>2</sub> emissions and fuel
+consumption of HDVs.
+
+# 18. Why is the fuel consumption for group 2 vehicles on the long-haul cycle significantly higher than on the other cycles?
+Group 2 vehicles are simulated on the long-haul driving cycle with an additional trailer which
+increases the fuel consumption significantly.
+
+# 19. What is the meaning of the VECTO messages “FC-Map too small” or “Loss-map too small”?
+
+In declaration mode, VECTO does not extrapolate the fuel consumption map, transmission or
+axle loss map as provided in the input data. If an error occurs, indicating that a loss-map is
+too small, either the component data does not contain the full map, or the gearbox/axle
+gear does not match the engine's maximum torque (positive torque range) and engines'
+drag torque (negative torque range).
+
+# 20. Why are the cycles defined as target speed over distance instead of actual speed over time?
+
+Driving behaviour of HDV to a very large extend is determined by the power to mass ratio of
+the vehicle. This parameter varies significantly between different vehicles and is additionally
+highly dependent on the payload conditions. Hence, a general valid definition of typical HDV
+driving behaviour is not possible via vehicle speed over time cycles.
+In VECTO driving cycles are defined as target speed over distance. The VECTO model
+operates the vehicle according to its full-load capabilities applying a driver model with
+underlying definitions for maximum desired acceleration, vehicle coasting and decelerations
+during braking events. This approach provides a good representation of typical driving
+behaviour for all HDV types in all loading conditions.
+
+# 21. The component tools (VECTO Engine and VECTO Air Drag) produce an XML file that cannot be used in the VECTO Graphical User Interface (GUI). Why?
+
+The VECTO process as foreseen in the official certification for HDV is based on handling and
+compiling of data in XML structure. This process is actually not supported via the VECTO GUI.
+For a VECTO simulation in using the XML files from VECTO Engine, VECTO Air Drag a job file
+needs to be compiled that contains data on all vehicle components. For this purpose the
+`Engine`, or `Airdrag` XML block need to be copied to the correct position in the job file
+describing the complete vehicle. This XML file than can be loaded to the VECTO GUI job list
+and the simulation can be started.
+
+# 22. Why is the fuel consumption simulated in version `x` different from version `y`?
+
+Although VECTO is already quite mature, it is still under development. Models may be
+refined, strategies may be adjusted, etc. Some of those changes have no (or a negligible)
+impact on the fuel consumption, other changes might have more effect. In any case the
+changes are typically due to a more accurate simulation. Other cases are that certain generic
+values are adapted in a new version. Details can be found in the VECTO changelog.
+
+# 23. The values computed in the `.vmod` file do not accumulate to the results in the `.vsum` file.
+
+VECTO uses variable time steps in the simulation. In order to calculate the accumulated
+results for the total cycle the instantaneous data for the single time steps need to be
+weighted with the simulation interval `dt`.
+
+# 24. What is the impact of the vehicle's 'Gross Vehicle Mass Rated'?
+
+In the declaration mode the vehicle's 'gross vehicle mass rated' is used for selecting the
+according vehicle group to allocate the generic model parameters. The 'gross vehicle mass
+rated' is furthermore used to limit the payload such that the simulated vehicle mass does
+not exceed the gross vehicle mass rated. For vehicles of type 'tractor' the 'gross vehicle mass
+rated' model parameter is only the GVMR of the tractor, without the trailer. VECTO adds the
+GVMR of the trailer internally (and limits the total GVMR to 40t or 60t for EMS
+configurations).
+
+# 25. Why is it required to specify the engine idling speed in the vehicle configuration?
+
+According to Annex V of the upcoming Commission Regulation on the determination of CO<sub>2</sub>
+emissions and fuel consumption of HDVs an engine is certified with the lowest possible idling
+speed. The vehicle manufacturer, however, can decide that in a particular vehicle
+configuration the engine idling speed is set to a higher value. After the certification it is not
+possible to modify the engine component file because this would void the integrity
+measures. Therefore, the engine idling speed has to be specified additionally in the vehicle
+input data. This value must not be lower than the idling speed in the engine component
+(otherwise this input is ignored).
+
+# 26. How are the shift polygons computed in declaration mode? What happens if no shift polygons are specified in engineering mode?
+
+The shift polygons depend on the gear ratios, the wheel dimension, the axle ratio, and the
+engine full-load curve. Based on all those parameters the shift polygons are computed based
+on the rules described in the user manual.
+Currently an update of the AMT and AT gear shift models is under elaboration which will be
+based on more complex decision criteria (gear selection mainly driven by optimisation of
+overall powertrain efficiency).
+
+# 27. We tried to reproduce the cross-wind correction in declaration mode. How is the Cd scaling factor computed?
+
+In declaration mode, an ambient wind of 3m/s in 4m height blowing from uniformly
+distributed from all directions is assumed. The dependency of C d xA on the yaw angle is
+described by a generic 3<sup>rd</sup> order polynomial depending on the vehicle configuration in the
+particular mission profile. The final C d xA scaling factor for a certain vehicle velocity is
+calculated considering boundary layer effects of the ambient wind speed. The user manual
+contains the detailed equations and provides an Excel spreadsheet to calculate the C d xA
+scaling factor as applied in the declaration mode.
+
+# 28. The airdrag losses in the `.vmod` file do not match the manually re-computed values using the average velocity for a certain time step.
+
+A basic definition in VECTO is that the acceleration is constant within a simulation time step.
+Consequently, forces and torques from vehicle inertia are constant and vehicle speed and
+rotational speeds evolve linear within a certain simulation interval. The air drag resistance,
+however, depends on the vehicle's velocity squared and hence does not evolve linear within
+a time step. To consider this influence correctly, for each time step VECTO computes a
+power-equivalent average airdrag resistance force. For a single simulation step, VECTO
+analytically computes the energy losses due airdrag and then computes a constant airdrag
+resistance force that results in the same energy losses. This air resistance force does not
+match with the value re-computed values using the average velocity for a certain time step if
+the vehicle speed is not constant.
+
+# 29. What are the properties of the trailer used for the simulation (wheels dimension, rolling resistance, wheels inertia, mass, volume, …)?
+
+Depending on the vehicle group either a T1, T2 or ST1 trailer is used in the simulation. The
+simulation parameters can be found in the file “Body_Trailer_Weights.csv” in the
+Declaration folder. The rolling resistance is 5.5 N/kN with an FzISO of 37.5kN for all tires at
+all trailers.
+
+# 30. How is the total rolling resistance coefficient computed?
+
+The total rolling resistance is the sum of the rolling resistance for every axle (truck and
+trailer), whereas the tyre's rolling resistance coefficient is scaled according to the actual tyre
+load. The actual tyre load is the total vehicle mass multiplied by the relative axle load share
+(generic value) and divided by the number of wheels on the axle.
+
+# 31. Does VECTO support any advanced driver assistant systems?
+
+From the early 2019 version on VECTO will include generic CO<sub>2</sub> reduction rates for the ADAS
+systems:
+  - Engine stop-start during vehicle stops
+  - Eco-roll without engine stop-start
+  - Eco-roll with engine stop-start
+  - Predictive cruise control (PCC)
+in all its reasonable combinations.
+
+# 32. How to handle aftersales changes in engine mapping which, for example, are performed for customer specific optimisation of fuel consumption?
+
+The “engine system” as defined in the family concept of Annex V of Regulation (EU)
+2017/2400 includes the engine control system. Hence, any changes not in agreement with
+the approval authority are illegal. In general, a new engine certification is needed in such
+cases.
+
+# 33. Can I run VECTO Simulator in batch mode/from the command line?
 
 This can be accomplished by using the command line version of VECTO: `vectocmd.exe`. This executable file comes with the normal VECTO package. Check the corresponding section of the manual:
 - Navigate to the _User manual_ folder, the file is named `help.html`.
 - Open it with a browser and then look for the section _Command Line Arguments_.
 
-# 16. How to cite VECTO?
+# 34. How to cite VECTO?