Fieldbus-based Measurement Technology for Digital Transmission of Torque and Rotational Speed in Test Benches

Energy efficiency is a hot topic in the automotive industry. The focus is increasingly on engines and rolling resistance. Optimizing these two parameters requires new, more efficient vehicle designs, which demand the use of increasingly accurate measurements. Consequently, the demands being placed on test benches and test and measurement equipment used to determine torque and rotational speed are increasing steadily. Digital torque transducers have been standard for a long time. Not surprisingly, the number of modern Fieldbus-based systems has also grown due to their application flexibility, precision results, and real-time measurement capabilities.

Controlling increasingly efficient and complex engines from a growing number of test bench engine management functions is more demanding than ever, particularly in terms of flexibility, data throughput, and speed. The EtherCAT real-time environment allows highly dynamic, top-quality test bench control, thanks to the low message transmission latency and very low jitter of the system. In addition, the powerful TIM-EC interface module supports update rates/bus cycle times of up to ≤20 kHz. Direct digital processing and output of the torque signal via the TMC signal on the stator, in combination with optimized hardware and signal conditioning in the TIM-EC interface module, make possible group delays of just 100 µs. Therefore, TIM-EC makes it possible to enhance the quality and stability of the test bench-based control loop.

In addition to comprehensive diagnostics data via EtherCAT, TIM-EC has an Ethernet TCP/IP service interface. The integrated web server allows visualizing diagnostics data for the interface module and the connected torque transducer (“traffic light” presentation). Plain-text diagnostics and status information allows for further analyses. For example, users can retrieve on-site diagnostics data conveniently. The entire measuring chain or the TIM-EC can be tested quickly and easily.

The modern integrated web server simplifies visualizing TIM-EC functions. The interface module can be conveniently connected, tested, analyzed, and parameterized with a standard PC with Ethernet card. No complex software installation is required.

The measurement system is well suited for use in test benches and offers an ideal solution for applications such as testing dual-mass flywheels. In this application scenario, torque (angle) can be determined quickly and reliably using the angular signal.