Virtual 48 V Mild Hybridization: Efficient Validation by Engine-in-the-Loop 2018-01-0410

New 12 V/48 V power net architectures are potential solutions to close the gap between customer needs and legislative requirements. In order to exploit their potential, an increased effort is needed for functional implementation and hardware integration. Shifting of development tasks to earlier phases (frontloading) is a promising solution to streamline the development process and to increase the maturity level at early stages.

This study shows the potential of the frontloading of development tasks by implementing a virtual 48 V mild hybridization in an engine-in-the-loop (EiL) setup. Advanced simulation technics like functional mock-up interface- (FMI) based co-simulation are utilized for the seamless integration of the real-time (RT) simulation models and allow a modular simulation framework as well as a decrease in development time. As baseline, an existing and validated co-simulation consisting of a GT-POWER engine model, a SimulationX transmission model, and a dSPACE Automotive Simulation Models (ASM) vehicle dynamics model is used. A Simulink-based dual 12 V/48 V power net model is developed to extend the base model. The 48 V side is mainly composed of a belt-driven starter generator (BSG) that is directly connected to the combustion engine (P0 layout) and a 48 V lithium-ion (Li-ion) battery. The 48 V side is coupled via a bidirectional DC/DC to the 12 V absorbent glass mat (AGM) battery and the 12 V loads.

In the next step, an engine test bench is coupled with the RT simulation by replacing the simulated combustion engine. Extensive tests are carried out on the EiL test bench, considering new legislative test requirements like WLTC (Worldwide harmonized Light vehicles Test Cycle) and RDE (real drive emission). The results show the great emission reduction potential of 48 V mild hybrids and proof that the frontloading-based EiL methodology is a promising solution to validate the system behavior with a heterogeneous cyber-physical test setup.