Abstract
Fluid-driven actuators are not only well-established in automation, but also a promising drive technology for collaborative robots. Their inherent compliance due to the compressibility of suitable fluids such as air, as well as their direct drive properties are advantageous safety features for human-machine collaboration. In this work, we provide an overview of different fluid-driven manipulators, namely fluidic muscle actuated ones, continuum manipulators, and those with rotary joints. For the latter, we introduce the mathematical model including mechanics and pressure dynamics and describe its properties such as strong nonlinearities, which make trajectory tracking control challenging. A model-based nonlinear cascaded controller is presented. Experimental results on a 6 degrees of freedom (DOF) prototype demonstrate the resulting trajectory tracking performance.
Zusammenfassung
Fluidisch angetriebene Aktuatoren sind nicht nur in der Automatisierungstechnik etabliert, sondern auch eine vielversprechende Antriebs-Technologie für kollaborative Roboter. Ihre inhärente Nachgiebigkeit aufgrund der Kompressibilität geeigneter Fluide, wie z. B. Luft, sowie ihre Eigenschaften als Direktantriebe sind vorteilhafte Sicherheitsmerkmale für die Mensch-Maschine-Kollaboration. In dieser Arbeit geben wir einen Überblick über verschiedene fluidisch angetriebene Manipulatoren, nämlich durch fluidische Muskeln angetriebene, Kontinuumsmanipulatoren und solche mit Drehgelenken. Für letztere stellen wir das mathematische Modell inklusive Mechanik und Druckdynamik vor und beschreiben seine Eigenschaften, wie z. B. starke Nichtlinearitäten, die die Trajektorienfolgeregelung herausfordernd machen. Ein modellbasierter nichtlinearer kaskadierter Regler wird präsentiert. Experimentelle Ergebnisse an einem Prototypen mit 6 Freiheitsgraden zeigen das resultierende Trajektorienfolgeverhalten.
Dedicated to Prof. Dr.-Ing. Peter Neumann on his 80th birthday.
About the authors
Kathrin Hoffmann received the M. S. degree in Engineering Science and Mechanics from the Georgia Institute of Technology, Atlanta, USA in 2018, and the M. Sc. degree in Engineering Cybernetics from the University of Stuttgart, Stuttgart, Germany in 2019. She is currently a Research Assistant with the Institute for System Dynamics, University of Stuttgart. Her research interests include the modeling and nonlinear control of fluid-driven actuators and manipulators.
Daniel Müller received the M. Sc. degree in Engineering Cybernetics from the University of Stuttgart, Germany, in 2018. Since spring 2018, he has been a Research Assistant with the Institute for System Dynamics, University of Stuttgart, Germany. His research interests include continuum manipulators, machine learning and optimization.
René Simon received a Dipl.-Ing. degree in automation from the Technical University “Otto von Guericke” Magdeburg in 1991 and a doctor of engineering from the Otto-von-Guericke-University Magdeburg in 2001. He is Professor of Control Systems at the Faculty of Automation & Computer Sciences, Harz University of Applied Sciences, Wernigerode, Germany. His major research fields include engineering of automation systems, especially industrial controllers. He is chairman of PLCopen and convenor of IEC TC65 SC65B WG7.
Oliver Sawodny received the Dipl.-Ing. degree in electrical engineering from the University of Karlsruhe, Karlsruhe, Germany, in 1991, and the Ph. D. degree from the Ulm University, Ulm, Germany, in 1996. In 2002, he became a Full Professor with the Technical University of Ilmenau, Ilmenau, Germany. Since 2005, he has been the Director of the Institute for System Dynamics, University of Stuttgart, Stuttgart, Germany. His current research interests include methods of differential geometry, trajectory generation, and applications to mechatronic systems.
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