Lee Sykes, commercial director at Drive System Design, believes there is an opportunity for the automotive industry to fast-track future e-powertrains to market, but only through collaboration
The pace of electrification in automotive powertrain engineering is creating many challenges. The most obvious are in product planning and design, but there are equally difficult issues to address in powertrain testing. It has taken the industry decades to refine the testing of IC engine powertrains to the point where validation timescales can be radically compressed without sacrificing robustness. How are we to achieve the same efficacy in the development and validation of the new generation of electrified powertrains?
Unlike the predominantly mechanical systems used in previous powertrains, we are now faced with a diverse mixture of increasingly integrated technologies: a high-voltage battery pack with its management system; an inverter; power electronics; the e-machine itself; a transmission and the mechanical driveline to the road. Each element has particular characteristics that determine its durability and fitness for purpose in its intended application. Failure to fully understand these differences can result in a test program that is inappropriate, leading either to an expensively over-specified product or one whose performance is uncompetitive, constrained by the weakest links in the chain.
An obvious example would be the durability testing of an integrated 3-in-1 EDU (electric drive unit). This could take up to 25 weeks to complete, compared with four weeks for a typical transmission durability test, demonstrating the sizeable challenge facing the industry. Typically, accelerated testing of the geartrain requires cycling at high torque under both intermittent and sustained conditions. For an electric driveline, this might introduce unrealistically high motor temperatures or unrepresentative levels of thermal cycling, leading to failures that do not correlate with real-world use. Similar risks can be identified throughout an electrified powertrain.
Before we can accelerate e-powertrain testing to meet the shorter timelines dictated by increasingly challenging government legislation, we as an industry must fill in the gaps in understanding of the interactions between various subsystems. Only then can we optimize the process by which the overall powertrain is brought to market.
No single organization has all the required information; collaboration is critical. OEMs have potentially rich seams of real-world data on user habits, based on their experience with customers. Tier 1 and 2 suppliers have unrivaled knowledge of their specific product characteristics. Independent engineering consultancies can bring analytical clarity and systems integration expertise, coupled with an impartial perspective.
What will stimulate the necessary collaboration? In the UK, government bodies have the necessary reach and funding to incubate such an initiative and create a framework within which the different contributors could cooperate. Because the primary focus is on process, rather than product, even market competitors should be able to participate without risking their hard-won intellectual property. There are precedents for such cooperation, as seen from notable OEM collaborations in EDU hardware.
Successful collaboration would generate optimized test regimes that capture the full system failure modes experienced during real-world operation. This would enable better informed planning of test programs, increasing efficiency and reducing overall cost and timing. Downstream, we could all deliver more robust, better optimized products within shorter timescales.