Model Exchange for Virtual SIL/MIL Verification of Passenger Cars with Electric Axles

Abstract

In the present day, stiff competition in the automotive industry and shorter timelines for introduction of new passenger vehicles has forced vehicle manufacturers and component suppliers to cut down on development time. Virtual simulations help in bringing down this time drastically and are a critical phase in the design and development of new vehicles. Multiple subsystems make up a vehicle and these subsystems need to be tested before being used in production. In the case of system development in electric vehicles, virtual verification of subsystems early in the project phase is important given the platform modularity of the driveline in such a scenario. It also helps if the simulation models are modular, since model exchange between vehicle manufacturer and subsystem suppliers have to take place to build virtual prototypes. This report explores the modelling and simulation of such type of modular drivetrain for electric passenger vehicles. The modelling of drive axle as a subsystem is a key aspect in this project. Three types of drive axles, i.e., Torque Vectoring Dual Clutch (TVDC), Electric Torque Vectoring (e-TV) and an Open Differential axles are considered. Modelling the powertrain, specifically the motor, is done to determine the energy consumption of this driveline. Modellica language uses an equation-based modelling approach which has a higher flexibility when compared to the library-based modelling. For this reason, the open-differential model was modelled in Modellica and was exported as a Functional Mockup Unit (FMU). The TVDC model and the e-TV model is given as inputs by the concerned stakeholders from the project. Further, these models were integrated with a control model and a vehicle model in a VVE, namely, IPG CarMaker. To establish a comparison between these different models, vehicle performance and energy consumption of these drivelines were studied. Validation and verification of the developed models were carried out as a precursor to simulation in the project. Sanity check of the model was done to make sure that the given vehicle does not run off the desired path. This ticks off the basic physics involved in the models. This was an iterative process based on the validation results of the models. Further, to draw a comparison between the different powertrains, the models were simulated with an open diff at the rear wheel (RWD) as a reference. Plots for dynamic variables and energy were used to analyze the results and compute measures like vehicle performance and energy consumption. AWD, as expected, performed the best in terms of vehicle stability. However, the interesting comparison was between e-TV and the TVDC models. To establish a comparison for the RWD configurations, the open differential at the rear axle is taken as a reference. Apart from the deduced results, the most relevant aspect of the project, i.e., the modularity of the subsystems (specifically, the drive axles) was achieved. i