58 “A few years back there was a limitation on the compute performance as it was expensive. Now you can have a full, multi-body system with hundreds of degrees of freedom for the chassis, suspension brackets, and still run in real-time using multicore, multi-CPU technologies. “What is really limiting right now is that the full digital twin is not at the model level but at the HIL with the ECU. These are developed by the tier one suppliers and they want to hold onto this technology, and that part is really timeconsuming. There is a trend from OEMs for in-house development for software, leading that development and not just modifying what comes from the tier one supplier. “That’s why the customers, OEMs and tier ones want the complete ECU with a complete replica of the ECU, and then you start to look at the functionality, but that’s too late and expensive. Instead, there is a unified protocol for exchanging data between the ECUs. The problem is that most of the ECUs are black boxes.” This can be a challenge. For example a black box ECU for the powertrain provides the inputs and outputs for the ECU, but the system also needs the inverter model and the battery management system (BMS) for more data for virtual development. “If you don’t simulate the rest of the bus connected to the battery pack, the BMS will go into safe mode and will not work,” he says. Custom hardware Typhoon HIL is extending its simulation and emulation to model chargers and battery management. The company has developed an emulation system for power electronics testing, including powertrain development, based around an array of field-programmable gate arrays (FPGAs). “We specialise in HIL for power electronics, with a focus on motor drives and chargers in e-mobility applications. While we can model ECUs for motor drives, onboard chargers and BMS, our HIL system is specifically designed to test real ECUs, ensuring reliable and high-fidelity validation,” says Petar Gartner, director of HIL Solutions at Typhoon HIL. “When we talk about HIL, we believe the value is at the signal level, so you have a controller ECU exchanging signals. While we do support signallevel interfaces, BMS hardware requires higher current than our base devices can provide. However, since there’s no real power transfer involved in this approach, it remains both safe and flexible.” The hardware interface emulates the physical signals of the battery cells with the voltages and currents. A parameterisable model running in the simulator replicates different discharge characteristics and thermal behaviour, generating signals that pass through the signal-conditioning unit before reaching the BMS. “This gives us full control, as besides the hardware, we make the software tools, the models’ vertical integration, and we are quicker to adapt to the customer, so we don’t need to make sure we are fully compatible with third-party vendors. “Typically, we see voltage ranges from 350-850 V and, depending on how the customer arranges the cells in series or parallel, we choose the appropriate number,” Gartner says. Each card emulates up to four cells from 1.5 V to 3.5 V. There are six cards in a rack, and up to 16 racks in a unit. This approach allows for physical fault insertion. “What you can do is disconnect a line, reverse the voltage. And, also from the model, you can insert disturbances, electrical noise and that noise would propagate to the output,” says Gartner. There is a controller area network flexible data-rate (CAN FD) link from the central processing unit to the cell emulators as different nodes. The parameterisable model supports a range of chemistries and different models from Simulink or other tools. This uses the Functional Mock-up Interface standard for simulation model exchange, or developers can port C-code to the tool and compile to processor and import the compiled code. The software environment for modelling includes drive models and converter models to build a system using a drag-and-drop interface, and Deep insight | HIL testing March/April 2025 | E-Mobility Engineering A BMS emulation system (Image courtesy of Typhoon HIL)
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