Mr. Osaki presented JASIC’s comments on the WHDHC approach proposed by TU Graz. The comments are related to the Excel tool provided by TU Graz to elaborate their proposal. The comments focus on five items: negative work, gear shifting, vehicle mass (for post-transmission simulation – option B), power patterns (option B) and option B HILS simulation.

The negative work, which is essential for energy recuperation, is considered being underestimated when only taking the engine cycle as basis (see page 7). Therefore, it should be vehicle based. Gear shifting needs some smoothing procedure for option B. In general, engine speeds will be different with options A and B resulting in different emission results. As regards power patterns, the introduction of road gradients is considered necessary for option
B. In a second evaluation, JASIC examined the possibility of using HILS for the WHDHC approach. In summary, only post-transmission approach is considered to be applicable for the HILS method, but in order to match with the WHVC approach, it is necessary to set gradients on the WHVC approach. The gradients turned out to be so big as to cause a hybrid ECU error in the simulation.

Mr. Silberholz responded that some of the issues raised by JASIC are on the to-do-list for the next weeks. The negative work proposed by TU Graz is based on European vehicle classes and might need to be adapted for vehicles outside Europe. Work on how to deal with gear shifting is also underway.

In general, it was agreed that the option B approach is closer to the original HILS approach than option A. It was agreed that the gradients with the WHVC approach would need to be limited to realistic values. The secretary reminded the group that the ToR are based on the WHVC (whole vehicle) approach. So, any alternative such as the WHDHC approach (options A and B) would need to be validated against the WHVC approach during the validation test program.