To achieve global market and brand specific drivability characteristics as unique selling proposition for the increasing number of passenger car derivatives, an objectified evaluation approach for the drivability capabilities of the various cars is required. Thereto, it is necessary to evaluate the influence of different engine concepts in various complex and interlinked powertrain topologies during engine load change maneuvers based on physical criteria. Such an objectification approach enables frontloading of drivability related engineering tasks by the execution of drivability development and calibration work within vehicle subcomponent-specific closed-loop real-time co-simulation environments in early phases of a vehicle development program. So far, drivability functionalities could be developed and calibrated only towards the end of a vehicle development program, when test vehicles with a sufficient level of product maturity became available. The resulting compaction and parallelization of the calibration work to meet the emissions, on-board diagnostics as well as the drivability requirements drastically reduces development costs and time.
This article presents an objectified drivability evaluation and classification approach for passenger cars, which is based on physical criteria, developed at the RWTH Aachen University in cooperation with FEV Europe GmbH. At the beginning of this work, the derived physical criteria for the objectification of longitudinal drivability load change maneuver results are presented and their subjective significance is explained. The calculation and variation of these criteria are discussed against the background of reproducibility and vehicle-spanning sensitivity. In addition, the automated method for determining and recording of the drivability measurements is explained. Furthermore, the results of sensitivity tests, which are based on calibration changes with regard to the longitudinal vehicle drivability behavior, are examined in detail. Individual disturbances and their influence on the results and physical criteria are also discussed. Finally, by presenting and discussing the results of a multitude of driving tests with a variety of vehicles using different characteristic diagrams (e.g. scatter bands), the reliability, maturity and validity of the holistic method is demonstrated.