E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

72 May/June 2023 | E-Mobility Engineering superseded by 700-850 VDC systems, largely to meet the need for faster charging. “We expect this voltage level to remain the ceiling for the mainstream automotive market for a reasonable period of time; however, motorsport and special off-road applications will continue to push the boundaries,” the expert at the test and validation services provider says. Beyond system voltage, the expert does not expect further major changes in powertrain technologies in the short term, as the industry is in an era of rapidly increasing production volumes. He anticipates incremental improvements in batteries, electricmachines and inverters, such as the shift to SiC devices, but does not expect them to drive significant changes in the testing required. The engineering consultancy and services provider points to the growing importance of fuel cells in EV powertrains as the economy for future fuels such as hydrogen develops, leading to a greater need for testing them. “We have invested in fuel cell test systems and are focusing future facilities to allow testing of integrated hydrogen and EV systems,” it says. The rotating machinery testing services provider regards the development of autonomous driving as the big challenge ahead, to which testing organisations will have to rise. “This represents a game-changer in the way we use our cars and the driving sensations we expect,” says its expert. “Comfort, quietness and driving dynamics will be perceived in a completely different way. This will require a new way of thinking about the e-motor integration and the global sense of being driven rather than driving a vehicle.” notes. “For example, it is possible to test a single physical e-drive system in combination with multiple virtual vehicles in different driving scenarios.” The real and the virtual come together in a piece of equipment the company calls an executable digital twin bench, which the expert describes as a real-time simulation rig. It uses closed-loop automation that relies on physical sensor measurements from the system under test (SUT) and variables from the real-time simulation environment. The rig control loop includes a real-time platform that replicates the physical boundaries of the SUT using software models of the rest of the vehicle. The company’s engineers develop high-fidelity variants of thesemodels to operate the SUT in all possible environments, he says. “The rig enables our customers to accelerate the development of their subsystems and control logics, and supports adaptive retrofit studies.” Preparing for test Given the complexity of the testing, it might be assumed that vehicle developers have to make elaborate preparations for any test campaign, but that is not necessarily the case. For example, the engineering consultancy and services provider prepares one- off prototypes for initial r&d as well as testing production-level drive units. The vehicle test and validation services provider emphasises the importance of flexibility in this respect, because different customers often want to engage with them in different ways. Some, he says, like to supply all the fixturing along with the system they want tested, while others want to deliver the SUT only, relying on the testing provider to design andmake all the fixturing. “We will typically look to the customer to supply a CAN database file along with their hardware,” the expert says. “Other than that, no special preparation is needed to test at our facilities.” Voltage trends Looking to the future, an increase in both current and voltage is expected in EV powertrain systems, the engineering consultancy and services provider notes. It explains that although the passenger car market seems to have settled on 400 or 800 V systems at the moment, that is likely to change, as much higher voltages are already in use in other industries, such as rail. This view of voltage trends is not universal, however. The variable-speed drives and controls manufacturer for example does not expect voltages to go much above 800 for passenger vehicles. The vehicle test and validation services provider agrees, adding that the 350-450 V DC systems that were common a few years ago are being Focus | Powertrain testing Acknowledgements The author would like to thank Tim Bassett at Ricardo, Andy Gardner at Unico (UK), and Brian Donohoe, Phil Robertson and Peter Miller at UTAC for their help with researching this article. Modal analysis on e-drive hardware is essential, because laminated stator housings with windings for example are highly non-linear in their vibration responses, so modelling requires test-based calibration (Courtesy of Siemens)