Test Technologies Contributing to Electrification - 4. Virtual–Real, Simulator–Test Technology for Optimizing Electric Powertrain Performance Without Using an Actual VehicleFig. 6 Concept of FDVFig. 7 Result of the real-time accuracy validation of the model3. Results of vehicle driving simulation testFig. 8 Temperature comparison between actual vehicle and VRS3.2 Results of temperature distribution obtained by 53vehicle driving simulation2.4 Overview of NVH evaluation test using FDV-RNoise, vibration, and harshness (NVH) were evaluated in addition to the driving performance using the PT-VRS test system for the powertrain. The test system was linked to FDV-R, which runs a vehicle model called a functional digital vehicle (FDV) in real time. Fig. 6 illustrates the concept of the FDV. The FDV is a full-vehicle behavior analysis model that comprises all mechanical elements of an actual vehicle to reproduce its characteristics. Coupled plant and control models predict the behavior of the vehicle running in transient and steady states. However, the FDV is not suitable for use with actual components on the bench because the FDV simulation consumes more time than the real one. Therefore, we developed an FDV-R that performs computations in real time. With FDV-R, we evaluated the driving performance and NVH on the PT-VRS test system. 3.1 Results of real-time test using modelsThe vehicle simulation model must be computed in real time in a VRS test system. Fig. 7 shows the results of a chassis dynamometer (C/D) test run in NEDC mode driving and a VRS test simulating the NEDC mode. The VRS test demonstrated the feasibility of the test model. The system shown in Section 2.1 shows the same vehicle and engine speeds as those of the actual vehicle running with C/D.The measurements in the test with C/D must be reproduced in the VRS test to develop powertrains with engine exhaust emissions below the regulatory limits. The test system shown in Section 2.3 is used to compare the internal engine and ambient temperatures with those obtained in the test with C/D. Fig. 8 shows a comparison of the exhaust after-treatment catalyst temperature. In the initial VRS test, the measurements were performed with a constant-rate wind blowing around the aftertreatment catalyst (red line). In this method, the temperature of the aftertreatment catalyst did not reproduce that obtained by the test with C/D, which resulted in a discrepancy in the amount of hydrocarbons (HC) emitted. The temperature of the aftertreatment catalyst became close to that obtained in the test with C/D when a fan with variable air volume was used to match the airflow around the aftertreatment catalyst with that used in the test with C/D (blue line). Therefore, the HC emissions matched well with those observed in the C/D test.The ENG-VRS test system shown in Figs. 2 and 3 is used along with the techniques used in the tests, as shown in Fig. 8; the amount of modal emissions is measured using a test bench. Fig. 9 shows the unburned HC emissions obtained for the entire test mode. In Fig. 8, the colored lines represent the results obtained by these tests Similar to the behavior of HC emissions shown in Fig. 8, the unburned HC emissions observed over the entire mode reproduced the behavior observed in the test with C/D. The VRS benchtop test system enabled emission compliance tests.Fig. 10 shows the effect of work-hour reduction in the compliance evaluation of the control constants related to exhaust emissions, and it compares the results obtained by the VRS and vehicle bench-top tests. The VRS test saves 65% workhours by reducing the time required to prepare vehicles and conduct tests.
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