Gait Stability

Leg design and control for stable locomotion

Walking and running are the natural gaits of human. Since human use just two legs for locomotion the moving system is naturally unstable, we could stumble and fall over. To feel free in locomotion, stability is absolutely necessary.

In this project we focus on strategies required for stability in bipedal gaits. One part of the project is to apply a leg control during swing phase in order to compensate perturbations. A single leg strategy, e.g. swing-leg retraction, seems to be not unique in human gait. Therefore, we combine two or more strategies, e.g. retraction and leg stiffening, which is more naturala and can be veryfied in human experiments.

In the second part of this project we investigate on how parts of the leg influence stability in locomotion. Herefore, we increase the complexity of a model and implement e.g. elastic joints. This bottom up process allows for a sharp view on single design elements and to identify their influence on leg dynamics and gait stability.

Involved People: Yvonne Blum, Jürgen Rummel, Daniel Maykranz, André Seyfarth

Previous people: Fumiya Iida, Hartmut Geyer, Elmar Dittrich, Heidi Knuesel

Subjects

The fundamental model for investigating bipedal gaits is the spring-mass model. In this template the legs are represented as massless springs and the body is reduced to a point mass. The spring-mass model is able to show the leg dynamics in both, walking and running.


Based on the spring-mass model a template was created with an additional massless rigid foot element attached to the ankle. Between the foot element and the leg spring an elastic element was placed. In this model the resulting forces in periodic gait patterns as well as stability can be investigated.

The two-segment leg has massless bones and the the elastic structure is located at joint level. This model allows to identify on how leg segmentation influences running stability. Basically, the transmission from joint torque to leg force is highly nonlinear and is the reason for stable low speed running and hopping.



JenaHopper with an elastic two-Segment leg is the first robot of the Lauflabor. This robot shows stable hopping motion just by swinging the leg back and forth. JenaHopper was the inspiration for some research topics in the Lauflabor, e.g. the investigation of leg design and hip control.

PogoHopper is the robot most related to the spring-mass model. The PogoHopper has a telescoping leg and linear spring. This robot is used to prove swing-leg strategies previously identified with the spring-mass model. Additionally, PogoHopper helps to investigate hip torques during stance phase.



Numerous biomechanical variables are supplied by a number of experiments on human walking and running. These include ground reaction forces, motion analysis, and surface EMG, which are basis for a broad variety of analysis.

Jena Hopper

JenaHopper is a monopedal robot designed for investigating the role of leg segmentation in compliant legs. Experiments on JenaHopper have shown that the leg design enables for highly simplified control strategies to stabilize hopping.














The robot JenaHopper was recently described in a review article in Science Magazine. Here, the stabilizing behaviour of BioLegI is shown for emphasizing the importance of compliant legs in locomotion.

Literature
Pfeifer et. al., Self-Organization, Embodiment, and Biologically Inspired Robotics,
Science vol. 318, no. 5853, pp. 1088-1093, 2007

Seyfarth et al., Running and Walking with Compliant Legs, Springer Berlin Heidelberg, pp. 383-402, 2006

Simulation of Models













Publications

  • Rummel J, Blum Y, Seyfarth A. From Walking to Running, Autonome Mobile Systeme 2009, Dillmann R, Beyerer J, Stiller C, Zöllner JM, Gindele T (Eds.) Springer: 89-96, 2009.
  • Maykranz D, Grimmer S, Lipfert SW, Seyfarth A. Foot function in spring mass running, Autonome Mobile Systeme 2009, Dillmann R, Beyerer J, Stiller C, Zöllner JM, Gindele T (Eds.) Springer: 81-88, 2009.
  • Blum Y, Lipfert S, Rummel J, Seyfarth A. Swing Leg Control in Human Running, Journal of the Royal Society Interface, (submitted)
  • Blum Y, Lipfert S, Seyfarth A. Effective Leg Stiffness in Running, Journal of Biomechanics, 42(16): 2400-2405, 2009.
  • Rummel J, Blum Y, Seyfarth A. From walking to running, Autonome Mobile Systeme 2009, Beyerer J, Stiller C, Zöllner JM, Gindele T (Eds.) Springer: 89-96, 2009.
  • Rummel J, Seyfarth A. Stable running with segmented legs, International Journal of Robotics Research, 27(8): 919-934, 2008.
  • Rummel J, Iida F, Smith JA, Seyfarth A. Enlarging Regions of Stable Running with Segmented Legs, IEEE International Conference on Robotics and Automation (ICRA), May 19-23, Pasadena, California, 367-372, 2008.
  • Blum Y, Rummel J, Seyfarth A. Advanced swing leg control for stable locomotion, Autonome Mobile Systeme 2007, Berns K, Luksch T (Eds.), Springer: 301-307, 2007.
  • Seyfarth A, Geyer H, Blickhan, R, Lipfert S, Rummel J, Minekawa Y, Iida F. Running and walking with compliant legs, Fast Motions in Biomechanics and Robotics - Optimization and Feedback Control, Diehl M, Mombaur K (eds.). Springer Verlag, Berlin Heidelberg: 383-402. 2006.
  • Dittrich E, Geyer H, Karguth A, Seyfarth A. Obstacle avoidance in a simple hopping robot, Climbing and Walking Robots, Brussels, Belgium, 2006.
  • Rummel J, Iida F, Seyfarth A. One-legged locomotion with a compliant passive joint, Intelligent Autonomous Systems 9, Arai T, Pfeifer R, Balch T, Yokoi H (eds.). IOS Press: 566-573, 2006.
  • Knuesel H, Geyer H, Seyfarth A. Influence of swing leg movement on running stability, Human Movement Science, 24: 532-543, 2005.
  • Dittrich E. Kontrollstrategien für den Gangartwechsel zwischen Gehen und Laufen am Beispiel des Masse-Feder Templates, Diploma thesis, TU Ilmenau, Germany, 2005.
  • Knuesel H. Influence of swing leg movement on stability of running, Diploma thesis, ETH Zurich, Switzerland, 2004.


Conference Contributions

  • Blum Y, Lipfert SW, Seyfarth A. Stiffness Estimation in Human Running. XXII Congress of the International Society of Biomechanics, July 05-09, Cape Town, South Africa, 2009.
  • Blum Y, Lipfert SW, Seyfarth A. Leg Parameter Adaptation for Stable Running. Annual Main Meeting of the Society for Experimental Biology 2009, June 28 - July 01, Glasgow, Scotland, 2009.
  • Gross M, Rummel J. Swing-leg strategies for stable dog trotting. Annual Main Meeting of the Society for Experimental Biology 2009, June 28 - July 01, Glasgow, Scotland, 2009.
  • Blum Y, Lipfert SW, Seyfarth A. Can Impacts Be Avoided in Stable Running? Dynamic Walking 2009, June 06-11, Vancouver, Canada, 2009.
  • Gross M, Rummel J, Seyfarth A. How to achieve stable trotting? Dynamic Walking 2009, June 06-11, Vancouver, Canada, 2009.
  • Blum Y. Leg Parameter Adaptation for Stable Running. Bionik-Kongress 2008, Bremen, Germany, 2008.
  • Blum Y. Movement Control by Leg Parameter Adaptation. Neuro-Robotics Symposium 2008, Freiburg, Germany, 2008.
  • Rummel J, Iida F, Smith JA, Seyfarth A. Enlarging regions of stable running with segmented legs. Dynamic Walking 2008, Delft, Netherlands, 2008.
  • Blum Y, Lipfert S, Rummel J, Seyfarth A. Advanced Swing Leg Control. Dynamic Walking 2008, Delft, Netherlands, 2008.
  • Rummel J, Seyfarth A. Self-stable running with segmented legs. XXIth Congress of the International Society of Biomechanics, July 1-5 Taipei, Taiwan, 2007, In: Journal of Biomechanics 40 (Suppl. 2), S384, 2007.
  • Rummel J, Lipfert S, Seyfarth A. Knee joint stiffness for self-stable running. XXIth Congress of the International Society of Biomechanics, July 1-5 Taipei, Taiwan, 2007, In: Journal of Biomechanics 40 (Suppl. 2), S590, 2007.
  • Seyfarth A, Iida F, Rummel J, Geyer H. Leg design for stable walking and running. 5th World Congress of Biomechanics, July 29 - August 4, Munich, Germany. In: Journal of Biomechanics 39 (Suppl. 1), 114, 2006.
  • Rummel J, Iida F, Dittrich E, Seyfarth A. Adaptive mechanics: compliant legged locomotion. 50th Anniversary Summit of Artificial Intelligence, July 9-15, Ascona, Switzerland, 2006.
  • Lipfert S, Blum Y, Seyfarth A. Estimation of Leg Stiffness in Human Locomotion. Dynamic Walking 2006, Ann Arbor, Michigan, USA, 2006.
  • Rummel J, Seyfarth A, Iida F. Adjustment of mass and stiffness in a two-segmented leg. 3rd International Symposium on Adaptive Motion in Animals and Machines, September 25-30 Ilmenau, Germany, 2005.
  • Seyfarth A, Lipfert S, Rummel J. Hip control in locomotion. XXth Congress of the International Society of Biomechanics, July 31 - August 5 Cleveland, USA, 2005.
  • Rummel J, Seyfarth A, Iida F. Stable locomotion of feedforward controlled one-legged robot. XXth Congress of the International Society of Biomechanics, July 31 - August 5 Cleveland, USA, 2005.
  • Seyfarth A, Rummel J, Guenther M, Geyer H. Segment orientation and direction of locomotion. Society for Experimental Biology, July 11-15 Barcelona, Spain, 2005.