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

66 May/June 2023 | E-Mobility Engineering they say. “Test systems include electromechanical shakers for impact and vibration testing, coolant and air- to-air thermal shock rigs, dust and water ingress as well as salt spray.” The rotating machinery testing provider says it is important for data acquisition systems to be able to handle parameters including current, voltage, temperature, pressure, vibration and torque. Measuring very high torque at low rpm can be difficult because, for example, vehicle driveshafts can deform plastically, while typical torque measurement systems based on strain sensors assume that shaft deformation will remain in the material’s elastic zone, the company’s expert says, so there is a need to adapt the instrumentation. “Analysis systems should also have enough flexibility to handlemulti-attribute balancing,” he adds. “Noise and vibration analysis is completely redefined with electric powertrains, so advanced sound quality analysis tools with interactive audio analysis, jury testing and a sound designer to craft a unique sound signature for the brand are required. Issues surrounding the integration of the powertrain and the battery pack are also critical, both froma durability and NVH perspective, he stresses, so accuratemodal analysis and noise/ vibration prediction starting early in the design stage is essential. The ability to interface a typical NVH systemwith power analyser data is becoming increasingly important for studying the impact of EDU control strategies on the occupants’ perception of comfort, he adds. He says test benches need to adapt to modern EVs in a number of ways, including mechanically. “Typical sedan [saloon] cars these days are heavier than in the past, and have the same torque levels as trucks from not so long ago, and this from the lowest rpm,” he says. “Test systems should not be seen as standalone entities, but should be closely interfaced with simulation systems. We should be able to test physical prototypes of subsystems in combination with multiple virtual vehicles, and by doing so avoid late surprises on the final vehicle prototype. This requires dedicated innovative test benches that combine test and simulation technologies.” For the safety of thoseworking on the test bench, he adds, proper cabling, sensors and operator training are essential. The company uses simulation to optimise system performance from the early design stage, applying 3D simulation to predict mechanical performance across disciplines including noise and vibration analysis and acoustics, along with fatigue analysis, multi-body dynamics and crash safety. Assessing the thermal behaviour of electric powertrains is crucial, the expert says, so the company uses CFD to analyse highly complex behaviours in liquids and gases, and has comparable capabilities in electromagnetic simulation to analyse the performance of electromechanical systems. The company brings the test and simulation worlds together, he says, in a model-based testing capability that includes model-based virtual sensors and system-in-the-loop testing. Need to know When EV developers approach testing organisations, they can have one or several of a variety of goals in mind – performance mapping, efficiency characterisation, durability and responses to environmental stressors for example. However, battery and motor efficiency seems to be the top priority, closely followed by performance, durability and NVH. The same rigs might be used to test for these attributes can also be used for validation and/or certification, according to the consultancy and services provider. The different test system architectures available allow customers to benchmark against competitors and develop improved EDUs for future products, its expert says. The rotating machinery testing provider notes that its customers’ requests focus on two main subjects: multi-attribute balancing in an NVH context and energy flow analysis. In the first, they are looking for help with identifying noise sources and analysis of the contribution of each source, and the company provides either the required tool or a complete set of analysis services. Problems addressed range from the mechanical, such as structural integration issues, to Focus | Powertrain testing Designed specifically for testing EV powertrains including batteries, Unico’s Quantum Drive Platform supports cell, module and pack-level tests in the same systemwith isolation between all the channels (Courtesy of Unico)