4.2.1 Calculation of slopes on WHVC

Mr. Morita (JARI) presented working paper HDH-13-08e on methods for matching integrated power values of WHTC and WHVC. At the 11th HDH meeting, it was shown that calculation of instantaneous slopes resulted in very steep slopes of up to 40% and could therefore not be used for the HILS simulation. When applying a 3 second moving average for curve smoothing, slopes could be reduced, but slopes of approx. 30 % were still present (page 7). Only by applying a 30 second moving average, slopes could be reduced to realistic levels of max. 10 % (page 8). Another approach is the calculation of a constant slope, which resulted in this example as 1.13 %. However, a constant positive slope is neither realistic nor favorable for hybrid vehicles. It was concluded that a 30 second moving average would be the best approach.

Mr. Osaki (JASIC) presented working paper HDH-13-06e. This presentation also deals with the calculation of slopes for the WHVC, but used a slightly different method than JARI. The method is described on pages 3 to 5, and was tested for two different vehicles (26 t / 317 kW and 5 t, 96 kW). Like with JARI, a constant slope approach was compared to a 30 second moving average approach. The constant slope was 0.35 %, while the 30 second moving average resulted in slopes between – 1.9 % and + 3.9 % for the heavy vehicle and + 6.5 % for the light vehicle, respectively. The correlation between power patterns and torque patterns on the traction side is slightly better with the 30 second moving average, while the traction and braking cycle work is slightly better with the constant slope (pages 6, 7). Overall, JASIC considers the 30 second moving average as the more favorable approach.

The difference between the constant slopes of 1.13 % vs. 0.35 % was considered to be due to the different calculation methods. From the test results it became clear that the slopes vary depending on the vehicle. It was therefore discussed whether the slope should be fixed in the gtr or calculated for the individual vehicle. No conclusion could be reached on this topic, but the IWG members agreed that slopes need to be added to the WHVC.