Virtual Vehicle


Independent Co-Simulation

Example: Design and Validation of a Hybrid Electrical Vehicle

The complexity in the design of serial hybrid electrical vehicles with a Lithium-Ion battery clearly demonstrates the need for a cross-domain co-simulation. The development process starts (after fixation of the serial architecture) from the topological view (Fig. 1).



Figure 1: Topological schematics of a serial hybrid electrical vehicle.
Source: Area Vehicle Electrics/Electronics & Software, ViF


The main task is the validation of the powertrain concept for different driving cycles and styles as well as for various complex battery models by means of a coupled co-simulation. Together the individual models (powertrain, rolling resistance, aerodynamics, inertia, losses, etc.) together depict the entire vehicle, the combustion engine, and the electric components (power electronics, electrical motor, energy storage, vehicle electrical system) etc. Fig. 2 shows an example for such a coupling based on ICOS.


Figure 2: ICOS co-simulation example: Different models are concurrently simulated under various driving conditions.
Source: Area Vehicle Electrics/Electronics & Software, ViF


The importance of an overall simulation for the system optimization is evident: Starting from the overall simulation the battery model is augmented with the temperature behavior as a function of the charging/discharging current and time. The battery condition (“state-of-health”) is monitored through the voltage, internal resistance, capacity and temperature. In order to avoid an accelerated aging of the battery (when the temperature exceeds 40° C) a SuperCap is added to the energy storage system. The energy management is realized by means of a cascaded controller (the vehicle electrical system controller is based on an underlying temperature control).


Fig. 3 shows the result of the co-simulation for a real driving cycle. Based on the inter-disciplinary modeling it is possible to optimize the controller in a way that the temperature always stays below 40° C. Additionally, the Supercap offers the possibility to provide high power for short-term stress; i.e. it delivers “Boost”-functionality.


Figure 3: Co-simulation result for a real driving cycle: By introducing a SuperCap and an optimized controller design the battery temperature stays below 40° C for all driving conditions.
Source: Area Vehicle Electrics/Electronics & Software, ViF


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