Dr.-Ing.  Ulrich Römer

Dr.-Ing. Ulrich Römer

  • Postanschrift:
    Karlsruher Institut für Technologie
    Institut für Technische Mechanik
    Teilinstitut Dynamik/Mechatronik
    Postfach 6980
    76049 Karlsruhe

    Haus- und Lieferanschrift:
    KIT-Campus Süd
    Institut für Technische Mechanik
    Teilinstitut Dynamik/Mechatronik
    Geb. 10.23 R 205.2
    Kaiserstraße 10
    76131 Karlsruhe


Design of bipedal robots with optimized energy efficiency in varying environments

five link bipedal robot
mean energy consumption per distance over different climbing inclination angles
energy consumption per distance over different walking speeds

In the development of biped robots, energy efficient locomotion via walking or running is a major research priority. Due to the limited energy storage (battery), energy efficiency significantly determines the walking distance that can be covered. Energy efficiency depends not only on the controller used for stabilizing the motion, but also on the structural design and its mechanical model parameters. Hence, the purpose of this research is to develop and apply a method to systematically optimize the structure of a bipedal robot to maximize energy efficiency in different environments.

In the first step we consider an underactuated robot model which consists of five segments. Its rigid segments are additionally connected by elastic couplings such as torsion springs. Knowing that the robot’s periodic walking or running gaits can be analyzed as limit cycles of the controlled mechanical system, its resonance frequency can be adjusted to match the current step frequency by modifying the elastic couplings. A systematic approach to achieve this matching consists in the simultaneous optimization of the elastic couplings and the controlled motion. Consequently, the robot exploits the mechanical system's natural dynamics instead of wasting energy on its suppression.

Since the optimization of the parameters essentially depends on the conditions of the environment and the gait, the focus is on how the adaptation of the robot to the current operating state can be realized. Unlike the motion, which can be continuously updated by the controller based on the measured state variables, the elastic couplings need to be optimized to achieve the best characteristics by using "compliant smart mechanics" (COSM). Between the stance and swing phases of the robot’s legs, and especially during switching processes of the movement, an optimal (force-displacement and/or force-velocity) characteristic of COSM leads to an overall high energy efficiency for a wide range of walking scenarios.

This project is being carried out jointly by two research groups: The Compliant Systems Group (FG NSYS) from the Ilmenau University of Technology (TU Ilmenau) and the Institute of Engineering Mechanics (ITM) from the Karlsruhe Institute of Technology (KIT). While the team at TU Ilmenau investigates the compliant mechanical systems and their design and implementation, the team at KIT simulates and optimizes bipedal robots with those COSM mechanisms in different environments. It is financially supported by the German Research Foundation (DFG), grant FI 1761/4-1 | ZE 714/16-1.


Project partner: Prof. L. Zentner, M. Zirkel.

Contact: Prof. A. Fidlin, Dr. U. Römer, Y. Luo


Veröffentlichungen in Zeitschriften und Tagungsbänden

Improving energy efficiency of bipedal walking using nonlinear compliant mechanisms.
Luo, Y.; Zirkel, M.; Römer, U. J.; Zentner, L.; Fidlin, A.
2021. Proceedings in applied mathematics and mechanics, 21 (1). doi:10.1002/pamm.202100197VolltextVolltext der Publikation als PDF-Dokument
The Influence of ground inclination on the energy efficiency of a bipedal walking robot.
Luo, Y.; Römer, U. J.; Fidlin, A.
2021. Proceedings in applied mathematics and mechanics, 20 (1), e202000142. doi:10.1002/pamm.202000142VolltextVolltext der Publikation als PDF-Dokument
Parameter Study of Compliant Elements for a Bipedal Robot to Increase Its Walking Efficiency.
Zirkel, M.; Luo, Y.; Römer, U. J.; Fidlin, A.; Zentner, L.
2021. Microactuators, Microsensors and Micromechanisms : MAMM 2020. Ed.: L. Zentner, 58–75, Springer International Publishing. doi:10.1007/978-3-030-61652-6_6
A Brief Survey on Non-standard Constraints: Simulation and Optimal Control.
Kern, D.; Römer, U. J.
2019. Proceedings of 8th GACM Colloquium on Computational Mechanics, 211–214, kassel university press GmbH
Simultaneous optimization of gait and design parameters for bipedal robots.
Römer, U. J.; Kuhs, C.; Krause, M. J.; Fidlin, A.
2016. Proceedings of the 2016 IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden 16-21 May 2016, 1374–1381, Institute of Electrical and Electronics Engineers (IEEE). doi:10.1109/ICRA.2016.7487271
Investigation of optimal bipedal walking gaits subject to different energy-based objective functions.
Römer, U.; Fidlin, A.; Seemann, W.
2015. Proceedings in applied mathematics and mechanics, 15 (1), 69–70. doi:10.1002/pamm.201510025
Energy-optimized bipedal running of a simple humanoid robot.
Römer, U.; Fidlin, A.
2014. Proceedings in applied mathematics and mechanics, 14 (1), 81–82. doi:10.1002/pamm.201410028
Transition from walking to running of a bipedal robot to optimize energy efficiency.
Römer, U.; Bauer, F.; Fidlin, A.
2014. 17th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2014, Poznan, Poland; 21 - 23 July, 2014, 409–416, World Scientific Publishing. doi:10.1142/9789814623353_0048

Vorträge bei Tagungen und Kolloquien

Collision detection for rigid superellipsoids using the normal parameterization.
Römer, U. J.
2021, August 24. 25th International Congress of Theoretical and Applied Mechanics (ICTAM 2021), Online, 22.–27. August 2021 VolltextVolltext der Publikation als PDF-Dokument
Kontaktdetektion zwischen konvexen Objekten auf Basis der Normalenparameterisierung.
Römer, U. J.; Seemann, W.; Fidlin, A.
2020. 6. IFToMM D-A-CH Konferenz 2020 : 27./28. Februar 2020, Campus Technik Lienz. doi:10.17185/duepublico/71212VolltextVolltext der Publikation als PDF-Dokument
Two-dimensional contact problems revisited – explicit analytical solutions for contact detection with straight and circular counterparts.
Römer, U. J.; Fidlin, A.; Seemann, W.
2018. 89. Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2018), München, Deutschland, 19.–23. März 2018
Dance-like motions in optimal walking.
Römer, U. J.; Fidlin, A.
2017. 9th European Nonlinear Dynamics Conference (ENOC 2017), Budapest, Ungarn, 25.–30. Juni 2017 VolltextVolltext der Publikation als PDF-Dokument
Design and optimization of hybrid zero dynamics for a bipedal walking robot with series elastic actuators.
Römer, U. J.; Fidlin, A.; Seemann, W.
2016. 87. Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2016), Braunschweig, Deutschland, 7.–11. März 2016
A novel analytical foot rollover model for planar walking.
Römer, U. J.; Fidlin, A.
2016. Dynamic Walking (2016), Holly, MI, USA, 4.–7. Juni 2016 VolltextVolltext der Publikation als PDF-Dokument
Energy optimization of bipedal walking through parallel springs.
Römer, U.; Bauer, F.; Seemann, W.; Fidlin, A.
2014, Mai 14. 4th French-German-Japanese Conference on Humanoid and Legged Robots (2014), Heidelberg, Deutschland, 12.–14. Mai 2014


Angebotene studentische Arbeiten
Titel Typ Datum
Abschlussarbeit (B.Sc. oder M.Sc.) ab sofort
Abschlussarbeit (B.Sc. oder M.Sc.) ab sofort
Abgeschlossene oder vergebene studentische Arbeiten
Titel Typ Bearbeiter

Amira Khelifi


Alexander Michael Dyck


Yonzhou Zhang


Daniel Debertin


Franziska Krebs


Jimmy Alberto Aramendiz Fuentes


Jan-Hendrik Witt


Shreyas Vivek Joshi


Simon Lüdke


Cornelius Kuhs 


Timo Fetzer 


Jan Wachter 


Sonja Marahrens


Simeon Braun


Philipp König


Christian Pihuave


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