ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Emergence of Gait in Legged Systems André Seyfarth ISB conference Cleveland, 2005

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Emergence of Gait in Legged Systems André Seyfarth Locomotion Laboratory Friedrich-Schiller University, Jena

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Arrival at Cleveland JürgenSuziHartmut

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Models Springs Joints Segments Muscles Robots Springs Screws Metal parts Servos Rubber simple, fast, easy to understand

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Central questions What are the common design and control principles of legged locomotion? Internal Leg Function Global Leg Function

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Central questions What are the common design and control principles of legged locomotion? MECHANICS STABILITY CONTROL What are the movement primitives of legged locomotion?

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Outline Jumping for distance Stable operation of a segmented leg Generation of muscle activity Stable running with elastic legs From running to walking Exploration of simple legged robots Conclusions

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de 1 Jumping for distance

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Seyfarth et al. (1999) J. Biomech. Dynamics of the long jump k m1m1 m2m2 Nonlinear spring-damper element time (ms) Ground reaction force (N) Energetic losses may increase performance!

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Seyfarth et al. (1999) J. Biomech. Dynamics of the long jump k m1m1 m2m2 Nonlinear spring-damper element Is this model able to predict jumping distance? Is this model able to predict maximum jumping distance?

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Muscle operation in long jump eccentric operation Tendon compliance (SE) shifts eccentric muscle operation (CE) into midstance Seyfarth et al. (2000) J. Exp. Biol.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take home message (long jump) The dynamics of long jump can well be described by a simple two-mass model Energetic losses due to impacts and eccentric muscle operation can improve jumping distance Tendon compliance shifts eccentric muscle operation into midstance

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de 2 Stable operation of a segmented leg

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Control of a segmented leg Idea Global Leg Function Local Leg Function

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Control of a segmented leg Idea

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Control of a segmented leg Idea

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Control of a segmented leg b3a

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Control of a segmented leg Solutions Seyfarth et al. (2001) Biol. Cybern. Biarticular Structures (e.g. Muscles) Geometric Constraints (e.g. Heel pad) +

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take home message (internal leg stability) With three or more leg segments, internal stability becomes important At certain leg length, symmetric joint flexion becomes unstable Different safety strategies do exist to resolve the intrinsic stability problem

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de 3 Generation of muscle activity

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Geyer et al. (2003) Proc.Roy.Soc.B. Generation of muscle activity Positive Force Feedback

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Generation of muscle activity

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take home message (positive force feedback) In hopping or running tasks, the generation of extensor muscle activity could be facilitated by positive force feedback This control regime imitates spring-like leg behavior and is robust with respect to environmental changes

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de 4 Stable Running with elastic legs

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Spring Mass Running fixed angle of attack fixed leg stiffness Seyfarth et al. (2002) J. Biomechanics PERIODICITY SYMMETRY ELASTICITY

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Spring Mass Running RETRACTION Seyfarth et al. (2003) J. Exp. Biol.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Spring Mass Running Seyfarth & Geyer (2002) CLAWAR Meeting, Paris.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take home message (spring mass running) For a given leg stiffness and angle of attack, self-stable running can be found. The stability of running is largely increased, if leg retraction is applied.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de 5 From Running to Walking

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Spring Mass Walking Geyer et al. (2005) ISB Conference

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de RUNNING Spring Mass Running &Walking stiffness kstiffness 0stiffness kstiffness 0 WALKING stiffness kstiffness 2kstiffness kstiffness 2k mass mmass m/2mass mmass m/2  Y COM FYFY FYFY SS DS POSTER #197

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Spring Mass Walking Stable solutions E k 00

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de ABC Ground Reaction Forces Spring Mass Walking E=const.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Walking and Running with Elastic Legs Running Walking stiffness k Speed v X angle of attack  0 GAP

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take home message (spring mass walking) In bipedal spring-mass model, self-stable walking can be found. The model predicts the experimentally observed force pattern. Running and walking are behaviors of one and the same system.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de 6 Exploration of simple legged robots

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Our Approach Experiments Theory Simulations Robotics

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Experiments

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Robotics

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Hip Control

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Experimental Robotics CPG

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Comparison with Biology robothuman

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Human Walking & Running walkingrunning

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take-home message (hip control) Sinusoidal hip oscillations applied to an elastic leg may result in stable hopping patterns Elastic joints are important to master impacts and to keep control simple.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Movement Direction ?

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Hopping direction? High Speed 200Hz Rummel et al. (2005) ISB Conference

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de ? Frequency Bias Angle

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Hopping direction? v CPG

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Influence of Hip Retraction v CPG M = c (  0 –  ) F LEG

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take-home message (movement direction) Leg segmentation and motor frequency defines preferred locomotion direction. Leg compliance supported by the hip action Leg stiffness supported by the hip action

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Leg Segmentation & Gait

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Leg Segmentation and Gait Is walking just running with double support phases?

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Leg Segmentation and Gait WALKRUN

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Leg Segmentation and Gait GAS

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Leg Segmentation and Gait (corresponds to GAS length)

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Passive Walking? 1 2 Cornell ankle-powered biped walking on a level surface 1 2 straight leg during stance curved foot Collins et al. Science 18 Feb 2005; 307:

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Compliant Walking

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Compliant Walking HUMANROBOT Iida (2005) AMAM Conference

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Running & Walking LEG FUNCTIONRUNNINGWALKING KNEE AND ANKLE JOINT ↑ ↑ ↓ ELASTIC ENERGY HIGHLOW LEG COMPRESSION FASTSLOW LEG ROTATION FASTSLOW BI-ARTICULAR MUSCLE SLOWFAST KNEE STANCE ↓ + ↑↓ + ↑ + ↓

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Take-home message (leg segmentation and gait) Walking and running can be observed in passive elastic legs with harmonic oscillations at the hip. In the three-segmented leg, ankle and knee joint symmetry is switched between running and walking.

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Conclusions Simple models and robots can help to better understand legged locomotion Selfstability is an effective tool to identify movement patterns with cheap control Walking and running can be described as two behaviors of the same mechanical system

ISB conference 2005 Seyfarth: Emergence of gaitwww.lauflabor.de Thank you! Locomotion Lab Jena Hartmut Geyer · Heidi Knüsel Fumiya Iida · Susanne Lipfert Jürgen Rummel · Jan Michel Elmar Dittrich Research Partners Prof. Reinhard Blickhan · Motion Science, Jena Prof. Volker Dietz · ParaLab, Zurich Prof. Hugh Herr · Biomechatronics Lab, MIT Prof. Karl Th. Kalveram· University Düsseldorf Supported by German Research Foundation (DFG grant SE1042) Jena