To widen the evaluation methods beyond traditional chassis dynamometer and on-road measurement programs, simulation tools and simulations were included in the work program of Annex 57. Especially considering future technologies simulation tools provide an important way for analyses for new possible technologies.
Annex 57 includes two types of simulation (carried out by AMF participants):
1. Simulation tool developed by VTT for the assessment of fuel consumption and CO2 emissions for High Capacity Transport (HCT) combined vehicles with varying axle configurations and masses 2. Simulation tool (Heavy-duty vehicle Emission Simulator, HES)
generated by the Government of Korea for the estimation of fuel consumption of heavy-duty vehicles
Thus the main objectives in simulation activities are:
1. Investigate the potential of HCT combinations for fuel consumption and CO2 emission reductions
2. To present a method developed in Korea for fuel consumption evaluation of heavy-duty vehicles of various configurations as a part of the type approval process
In addition, simulation activities are carried out in cooperation with HEV TCP, as mentioned previously. This joint exercise will be presented in a separate Chapter.
Finland
In the Finnish part of the simulation activities, computer simulation is used to study the effects of gross vehicle weight on fuel consumption.
The studied vehicle combination is a high capacity transport unit (Figure 3026), which consists of a three-axle tandem driven tractor, a three-axle semitrailer, and a five- axle full trailer. The trailers are equipped with twin tires, except the last axle of the semitrailer and the last axle of the full trailer, which are steering axles with single tires. The total length of the vehicle combination is 32 meters, the maximum gross weight 88 tons and the curb weight around 37 tons. The height of the trailers is 4.4 meters, and the volume of the box body over 200 m3.
The simulation model consists of model blocks for the diesel engine, gearbox and the drivetrain, and a longitudinal dynamic model of the heavy-duty truck and trailer combination. The input to the simulation model is the reference speed of the vehicle and the slope of the road.
The simulation model has a controller to model the driver’s actions on
26Eero Sjögren Oy
Figure 30: Studied vehicle combination (picture from Eero Sjögren/Veho).
the accelerator pedal position and brake pedal position in order to meet the requested vehicle speed. Another controller is defined to control the gearbox model. As an output, the simulation model defines the momentary engine torque, speed, and fuel rate based on the engine fuel consumption map for each time step. The driving resistances are based on a coast-down measurement done with a vehicle combination, which has a similar tractor unit and the same general configuration of the vehicle combination, but different dimensions for the trailers. The coast-down tests are done with loaded vehicle combination on dry asphalt.
The simulation model is validated using measured data gathered from the actual vehicle in operation. Data collected from the vehicle CAN bus and the GPS device. Figure 31 shows a validation plot for the simulation.
Figure 31: Measured and simulated values for the simulation model validation: vehicle speed, engine speed and fuel rate.
The first plot shows the measured vehicle speed, which is used as a reference in the simulation model, the simulated vehicle speed, and the slope of the road taken from the map data. The second plot shows measured and simulated engine load, and the third plot measured and simulated fuel rate.
Korea
Korea contributed with information on development and deployment of the Heavy-duty vehicle Emission Simulator (HES). The HES tool has been developed in the C# language as an executable file, and was developed by the National Institute of Environmental Research in Ministry of Environment Korea. During the development process, HES has been issued four times, with the latest version (v 1.09, 4th) launched in September of 2020. Figure 32 shows the development schedule of the HES tool.
HES is based on longitudinal vehicle dynamics and composed of five components as follows:
Pre-processor module: reading input data (vehicle specifications and velocity profile)
Chassis module: calculating total resistance force acting on vehicle
Transmission module: predicting gear position at each time step based on engine operating condition
Engine module: determining engine torque & speed at each time step
CO2 emission module: predicting CO2 emission based on fuel map &
CO2 emission factor of fuel
Figure 32: Development schedule of HES tool.
Figure 33 shows calculation flow and the main blocks of the model.
Specific calculation methods for each model blocks and loading elements can be found in Appendix A.
In 2019, the HES graphical user interface allowing the user to run HES without any installation process after downloading was launched. Figure 34 shows an example of the user interface, allowing adjustment of vehicle data. Figure 35 shows an example of simulation results.
Chassis (prediction of total resistance F)
Transmission (gear shifting)
Engine (engine speed, engine torque)
CO₂ emission (FC map) Calculation flow
Pre-processor 1. Test cycle (K-WHVC mode) 2. Vehicle spec.
(input data)
Figure 33: Calculation flow of HES model.
Figure 34: Example of HES user interface for adding the corresponding vehicle data.
Figure 35: Example of HES simulation result.