Virtual Test Bed, real Results

Virtual and HiL Test Beds as Solutions for RDE Cycles

15. August 2016 | Software & Testing Solutions

D2T, a Member of the FEV Group, has developed a unique simulation-based solution that allows the performance of a significant portion (up to 30 percent) of Engine Control Unit (ECU) calibration on virtual and Hardware in the Loop (HiL) test beds, without the need for an engine test bed. In the demanding context of new transient cycles (Worldwide harmonized Light vehicles Test Procedures (WLTP)) and environmental cycles (Real Driving Emissions (RDE) linked to new temperature and altitude conditions), this is a most welcome solution.
Calibrating the ECU by simulating the engine and its environment has often been envisaged and even tried. However, traditionally, the process has encountered major technical problems. Within the framework of a 0D/1D physical or numerical simulation with various software systems available in the market, it is possible to simulate the impact of engine design on pollutant emissions and fuel consumption and thus define the most suitable concept to achieve the desired performance. The level of accuracy is nevertheless low and not sufficient for ECU calibration. 

On the other hand, Design of Experiments (DoE) allows the creation of reliable statistical models with a limited and reasonable number of experimental data. As a result, global DoEs allow for modelling and predicting pollutant emissions and fuel consumption over the entire engine map, considering specific steady-state operating points as well as the air path and injection parameters. The accuracy for these operating points (5% to 10% on NOX) is at the requested level for calibration tasks. However, the development of more dynamic cycles with Euro 6/7, such as WLTP and RDE, reveals the limits of this method: Since the acceleration phases are much more prevalent than in the previous NEDC cycle, air loop control errors become more significant. These air loop differences can result in an accuracy degradation in the prediction of pollutant emissions of up to 25% of NOX emissions on cycle.

A Powerful Combination of Technologies

To overcome these challenges, the FEV Group proposed an innovative and simple solution based on FEV products in combination with well-known third-party products: ICE²*DoE model for combustion and pollutant emissions and third-party products for physical modelling of the air path. These tools have been coupled and integrated into the xMOD/MORPHEE integration and automation platforms to optimize CPU performances, easily set-up automated procedures, and even connect a real ECU (HiL). This innovative solution allows the attainment of good accuracy levels (for instance 10% for NOX Emissions on a WLTC cycle), as a result of the good behaviour of the complete air path, thus making verifying an efficient and reliable virtual calibration platform.

Reliable Results for All Kinds of Cycles

With these virtual test beds, engine settings are tested in simulations and quick results for emissions and fuel consumption can easily be obtained on RDE and WLTC cycles for a wide range of applications. With respect to On Board Diagnostics (OBD), it is also possible and straight-forward to test different types of engine failures, sensors, actuators or injectors (production dispersion) and directly assess their impacts on the engine outputs. Finally, virtual beds enable testing non-standard conditions, such as changing altitudes and ambient temperatures, as they can occur in RDE cycles.
This allows the transfer of a large part of testing traditionally completed on physical test beds – both on the engine test bed and on the chassis dynamometer – to a virtual test bed and/or to a HiL test bed. In such a scenario, physical test beds will be used more for validation than for development, in the future. As the calibration teams work within the same, MORPHEE-based graphical user environment on the Virtual/HiL test beds and on the physical test, team efficiency is also improved. The optimizations of the calibration process reduce both time and the cost of development, while improving final quality.

*ICE²: developed by IFPEN, sold by FEV Software and Testing Solutions

*ICE²: developed by IFPEN, sold by FEV Software and Testing Solutions