23. July 2015

Engineers from Aachen established real-time connection between test benches for increased efficiency

Real-time connected test benches speed up development: The virtual shaft of FEV and VKA controls the dynamometers in two separated test benches in a way that achieves the equivalent system behavior of a real mechanical shaft (Source: FEV GmbH).

In order to achieve significant time and cost reduction in the development process, FEV and the Institute for Combustion Engines of the RWTH Aachen University (VKA) have implemented a virtual connection between two test benches. The test environment consists of spatially separated test benches, which are connected by a real-time deterministic EtherCAT connection. “The dynamometers in both test benches are controlled in a way that achieves the equivalent system behavior of a real mechanical shaft,” explains Professor Stefan Pischinger, President and CEO of FEV Group and Director of the Institute for Combustion Engines of the RWTH Aachen University. „With this an interaction – for example between engine and transmission – is achieved during the prototype phase before both components are able to be adapted, thus saving important development time.“

The test effort of modern hybrid drives is significantly higher when compared to conventional powertrains. The main reason for this lies in the higher number and more complex interaction of the components. At the same time, current trends in powertrain development – for example, ”road to rig“ approaches – result in the movement of significant portions of the development process from the vehicle to the test bench and, thus, into earlier project phases. New solutions must be found to manage this increasing test complexity and to accelerate development cycles. Against this background, an important new tool called the “virtual shaft” was developed in collaboration between FEV and VKA.

From component testing to system testing
Networking the test cells with the virtual shaft offers some significant advantages: In addition to saving time, these mainly include the provision of a protected test environment and high number of monitoring options for the individual test objects. With this scenario, damage to prototypes can be effectively prevented. In addition, the virtual shaft allows the combination of hybrid powertrains that are not yet mechanically compatible and would otherwise have to be extensively adapted. “In conventional development processes complexity increases step-wise as we move from a single component up to system testing in the vehicle,“ Dr. Albert Haas, Group Vice President test systems at FEV, explains. “First the e-motor, the engine and the transmission are tested separately in single test cells. The real interactions between the different components, though, cannot be evaluated until composite system testing can be accomplished on a full powertrain test bench.” This step requires not only a change in the test environment, but also mechanical modifications and software changes. Therefore, this is usually performed in a later development phase, where either a vehicle or a complete powertrain is needed. “The virtual shaft makes a valuable contribution to handling the increasing complexity of modern hybrid drives and provides the opportunity to make the development process more efficient,” Haas concludes.

About FEV
The FEV Group with headquarters in Aachen, Germany, is an internationally recognized development service provider for drive and vehicle technologies. The company offers its global transport industry customers a complete range of engineering services, providing support in the design, analysis and prototyping for powertrain and transmission development, as well as vehicle integration, calibration and homologation for advanced internal combustion gasoline-, diesel-, and alternative-fuelled powertrains. FEV's competencies also include design, development and prototyping of innovative vehicle concepts, powertrain electronic control systems and hybrid-electric engine concepts that address future emission and fuel economy standards. The Test Systems division is a global supplier of advanced test cell, instrumentation and test equipment. The FEV Group employs a staff of over 4,000 highly skilled specialists at advanced technical centers on three continents.

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