For a long clutch life

Unplanned breakdowns of commercial vehicles cost money – a problem especially for transport companies, which usually operate with low sales margins. One effective method of optimizing machine running times is predictive maintenance. To this end, IAV has developed an algorithm that determines the “state of health” of dry vehicle clutches in automated manual transmissions.

The clutch is the central link between the engine and the transmission – if it fails, trouble-free starting and gear changes are no longer possible. This makes it all the more important to surveil its condition continuously and precisely. To do this, an algorithm developed by IAV uses the standard speed sensors on the engine and transmission input side as well as the torque estimated by the engine control unit.

“With this information, we can determine the friction power per start-up process, which allows us to estimate the material removal and the change in the friction coefficient of the start-up clutch,” explains Dr René Knoblich, Technical Consultant in the Transmission and Hybrid Systems department at IAV. “This allows us to predict when the vehicle needs to go to the workshop for maintenance, thus avoiding unexpected breakdowns.”


And not only that: Because the current condition of the clutch is known, another algorithm developed by IAV can influence the starting behavior and in this way ensure that the component reaches a specified minimum service life. “Depending on driving style or payload, the clutch is subjected to different loads,” says Dr Jörg Beilharz, Head of Department for Transmission and Hybrid Systems at IAV. “Our algorithm prevents particularly wear-intensive starting processes, for example. This reduces negative effects on the coefficient of friction and avoids increased material removal.”

The method is particularly suitable for small commercial vehicles that handle logistics on the “last mile” and where a particularly large number of start-up processes occur. An extension of the approach to wet start-up systems is planned.

Ready for series development

The physical model behind the new algorithm describes the wear processes and is based on numerous test bench measurements of different clutches that IAV has carried out together with TU Berlin. In the meantime, IAV’s solution is so precise that nothing stands in the way of series development. The developers are also helped by the fact that the computing power of modern control units is now sufficient to permanently determine the condition of the clutch while the vehicle is in operation.

“At the moment, the estimation and control algorithms are still running on a prototype ECU,” says Knoblich. “In the next step, we want to make the software fit for a production ECU.”

«Downtime and operating costs are important issues in the commercial vehicle sector. We are sure that demand for our new algorithm will increase strongly in the foreseeable future.»

Dr René Knoblich — Technical Consultant in the Transmission and Hybrid Systems department at IAV

The article was published in automotion 01/2021, the automotive engineering magazine of IAV. Here you can order the automotion free of charge.

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