On Self-adjusting Contacts in Pin-On-Disk Testers

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The Automated Universal Tribotester (AUT) represents a fully automated reduced scale brake dynamometer. The setup is based on the pin-on-disc principle, where the specifically designed load unit on the one hand guides the pin and on the other hand applies the necessary normal load on the friction contact.

Even with highly developed tribometers such as the AUT at IDS, long bedding processes after load changes are necessary for a valid evaluation of wear and emissions. The applied loads in combination with the limited material stiffness of machines result in an inevitable tilting of the pin, which influences the surface dynamics in the friction layer. Only an intelligent adaptive compensation system is capable of measuring and adjusting the specimens alignment towards the disc during measurements in a way, that a full surface contact can be assured.

This paper presents the adaptive system, which is added to the load unit of our fully automated tribometer. It presents the observer model to monitor the specimens angle in the friction interface, including its application in the overall control loop. Furthermore, the kinematic principle with its self-locking features and the drive concept is presented. Finally, this paper demonstrates the adjustment range and speed performance of the complete adaptive system. The impact of the compensation on characteristic values of friction such as the coefficient of friction, wear and emissions will be presented elsewhere.

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