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ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Emergence of Gait in Legged Systems
André SeyfarthAndré Seyfarth
ISB conference Cleveland, 2005ISB conference Cleveland, 2005
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Emergence of Gait in Legged Systems
André SeyfarthLocomotion Laboratory
Friedrich-Schiller University, Jena
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Arrival at Cleveland
Jürgen
Suzi Hartmut
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Models
• Springs• Joints• Segments• Muscles
Robots
• Springs• Screws• Metal parts• Servos • Rubber
simple, fast, easy to understand
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Central questionsWhat are the common design and
control principles of legged locomotion?
Internal Leg
Function
Global Leg Function
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Central questionsWhat 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 gait www.lauflabor.de
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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
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ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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1Jumping for distance
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Seyfarth et al. (1999) J. Biomech.
Dynamics of the long jump
k
m1
m2
Nonlinear spring-damper element
time (ms)
Gro
und
reac
tion
for
ce (
N)
Energetic losses may
increase performance!
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Seyfarth et al. (1999) J. Biomech.
Dynamics of the long jump
k
m1
m2
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 gait www.lauflabor.de
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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
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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 gait www.lauflabor.de
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2 Stable operation of a
segmented leg
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Control of a segmented leg
Idea
Global Leg Function
Local Leg Function
ISB conference 2005
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Control of a segmented leg
Idea
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Control of a segmented leg
Idea
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Control of a segmented leg
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3b3a
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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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
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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 gait www.lauflabor.de
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3 Generation of muscle activity
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Geyer et al. (2003) Proc.Roy.Soc.B.
Generation of muscle activity
Positive Force
Feedback
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Generation of muscle activity
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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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 gait www.lauflabor.de
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4 Stable Running with
elastic legs
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Spring Mass Running
fixed angle of attack
fixed leg stiffness
Seyfarth et al. (2002) J. Biomechanics
PERIODICITY
SYMMETRY
ELASTICITY
ISB conference 2005
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Spring Mass Running
RETRACTION
Seyfarth et al. (2003) J. Exp. Biol.
ISB conference 2005
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Spring Mass Running
Seyfarth & Geyer (2002) CLAWAR Meeting, Paris.
ISB conference 2005
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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
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5 From Running
to Walking
ISB conference 2005
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Spring Mass Walking
Geyer et al. (2005) ISB Conference
ISB conference 2005
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RUNNING
Spring Mass Running &Walking
stiffness k stiffness 0
stiffness k stiffness 0
WALKING
stiffness k stiffness 2k
stiffness k stiffness 2k
mass m mass m/2 mass m mass m/2
YCOM
FY
YCOM
FY SS DS
POSTER #197
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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Spring Mass Walking
Stable solutions
E
k 0
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
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A B C
Ground Reaction Forces
Spring Mass Walking
E=const.
ISB conference 2005
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Running
Walking
stiffness k
Speed vX
angle of attack 0
GAP
ISB conference 2005
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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 gait www.lauflabor.de
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6 Exploration of simple
legged robots
ISB conference 2005
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Our Approach
• Experiments• Theory• Simulations• Robotics
ISB conference 2005
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Experiments
ISB conference 2005
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Robotics
ISB conference 2005
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Hip Control
ISB conference 2005
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Experimental Robotics
CPG
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Comparison with Biology
robot human
ISB conference 2005
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Human Walking & Running
walking
running
ISB conference 2005
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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
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Movement Direction
?
ISB conference 2005
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Hopping direction?
High Speed200Hz
Rummel et al. (2005) ISB Conference
ISB conference 2005
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?
FrequencyBias Angle
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
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AL
-0.2
0
0 0
00
0.1
0.1
0.1
0.1
0.1
0.1
0.3
0.3
0.3
0.3
0.3
0.3
0
oscillation frequency [Hz]
bias
ang
le [
deg]
horizontal velocity [m/s]
2 4 6 8
-20
-10
0
10
20
-0.6
-0.4
-0.2
0
0.2
Hopping direction?
v
CPG
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Influence of Hip Retraction
v CPG
M = c (0 – )FLEG
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
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 gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Leg Segmentation & Gait
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Leg Segmentation and Gait
Is walking just running with double support phases?
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Leg Segmentation and GaitWALK RUN
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Leg Segmentation and Gait
GASGAS
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Leg Segmentation and Gait
(corresponds to GAS length)
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
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: 1082-1085
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Compliant Walking
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Compliant Walking
HUMAN ROBOT
Iida (2005) AMAM Conference
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Running & Walking
LEG FUNCTION
RUNNING
WALKING
KNEE AND ANKLE JOINT
↑ ↑ ↑ ↓
ELASTIC ENERGY HIGH LOWLEG COMPRESSION FAST SLOW
LEG ROTATION FAST SLOWBI-ARTICULAR
MUSCLESLOW FAST
KNEE JOINT @ STANCE
↓ + ↑ ↓ + ↑ + ↓
ISB conference 2005
Seyfarth: Emergence of gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
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 gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
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 gait www.lauflabor.de
F
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
ALF
U
A
L
U
N
I J E
N
A
R
O
B
AL
Thank you!Locomotion Lab JenaHartmut Geyer · Heidi KnüselFumiya Iida · Susanne LipfertJürgen Rummel · Jan MichelElmar DittrichResearch PartnersProf. Reinhard Blickhan · Motion Science, Jena Prof. Volker Dietz · ParaLab, ZurichProf. Hugh Herr · Biomechatronics Lab, MITProf. Karl Th. Kalveram· University Düsseldorf
Supported by German Research Foundation (DFG grant SE1042) Jena
