Optimized for the Fleet, Customizable for Every Model

The future belongs to electric drives. Automobile manuacturers today want solutions which are, on the one hand, optimized for an entire fleet but, on the other, can also be customized for individual models without major input, for example in terms of performance, number of speeds or special comfort functions. IAV has developed a modular, scalable and highly integrated electric drive unit that meets these demands while also permitting short development cycles.

In order to meet their customers’ wishes, engineers need to reconcile different aspects when developing an electric powertrain. What is called for here are low development costs and shorter development times with product costs kept to a minimum. In-house development work at IAV has shown that, for all intents and purposes, these different and challenging demands can be met with a smart design.

Modular Systems for Sustainable Electrified Powertrains

The electric drive unit from IAV reduces complexity by using modular design and identical interfaces to all subsystems. At the same time, it is possible to customize drives for a particular vehicle class, for example in respect of gear speed number and transmission ratios. It can also be adapted to suit the various market segments and the costs that are acceptable in these segments by using different technologies. Parameters, such as engine power and torque, can also be varied for the same layout of electric motor.

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Depending on customer requirements, additional functions, such as a parking lock system or a shutdown system, can be provided, with the latter deactivating the electric motor if speed from the combustion engine is too high while the axle is being used in a P4 application. Although the number of speeds can be varied, higher efficiency and better performance are more likely to benefit relatively heavy vehicles. For lightweight models, one gear speed is usually sufficient. “Depending on comfort demands, for example, we can shift gear with or without traction interruption,” reports René Kockisch, Team Manager for Transmission Mechanics at IAV. “Optional torque vectoring for sporty vehicles is also planned.” Shifting torque between the wheels enhances driving dynamics and improves safety when cornering.

High performance with high efficiency

The electric drive unit has a power output of between 100 kW/250 Nm and 180 kW/300 Nm. Attainable output torque is between 2150 Nm and 4150 Nm. The electric drive unit’s sophisticated thermal management system and demand-controlled transmission lubrication provide a high level of efficiency. An agreeable background noise is also guaranteed: “We optimized the casing in terms of NVH right from the outset,” Kockisch says. “This began as early as the simulation model and continued through to optimizing topology for low weight and maximum strength.

By using many shared components and subsystems, IAV’s developers were able to keep the costs of the modular electric drive unit low. In terms of the transmission alone, they are five to ten percent lower than for other solutions. The electric motor and power electronics allow further potential savings to be realized. Substantial additional savings can be achieved by reducing the number of drive units that need to be developed for the vehicle fleet.

Layout with proven IAV tools

The point of departure for the developers was IAV’s Powertrain Synthesis tool which was used to match the modular electric drive unit to the requirements of an example fleet in respect of fuel consumption, performance, cruising range and costs. “In this initial step, we defined the framework for the modular system,” Kockisch says. “IAV’s Powertrain Synthesis then gave us suggestions for the key parameters needed for the drive unit, including the number of speeds and transmission ratios for the particular vehicle segment. Then we used IAV’s E-Motor Synthesis and IAV Actuation Synthesis tools. They assisted the developers in finalizing the drive unit’s detailed layout.

“With our modular electric drive unit, we have demonstrated that our customers’ various demands can be met with tried and tested development tools and a smart design.”

René Kockisch — Team Manager for Transmission Mechanics at IAV

“We benefited from our expertise and experience. They provided the key to overcoming all of the technical challenges and achieving a short development time.” The modular IAV solution can be easily adapted to the requirements of other vehicle fleets and quickly turned into a production-ready solution.

The article was published in automotion 03/2019, the automotive engineering magazine of IAV. Here you can order the automotion free of charge.