“Ecological foundations of human motion model

Faculty of Human Kinetics
Technical University of Lisbon
Neuromechanics Research Group
Wangdo Kim1,*, Antonio Veloso1, Duarte Araújo3, Maria Machado1,
Veronica Vleck2, Liliana Aguiar1, Silvia Cabral1 and Filomena Vieira1
1 Biomechanics Laboratory
2 CIPER (Center for the Interdisciplinary Study of Human Performance)
3Sports Expertise Laboratory
Faculty of Human Kinetics
Technical University of Lisbon
Ecological foundations of human
motion model

Movements and postures are controlled and
coordinated to realize functionally specific acts
based on the perception of affordances (that
is, possibilities for action (Gibson 1979)
James Jerome Gibson (January 27, 1904–
December 11, 1979), was an American
psychologist
Edward S. Reed (November 20, 1954 -
February 14, 1997) was a philosopher of
science and an ecological psychologist in the
vein of James J. Gibson.
Eleanor J. Gibson (December 7,
1910 – December 30, 2002) was an
American psychologist

Don Norman: Designing For People
PERCEIVED AFFORDANCE
" The designer cares more about what actions the user perceives to be
possible than what is true "
"The Psychology of Everyday
Things" (POET: Norman, 1988)

BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
Aims
 To present experimental evidence to
support the idea that invariants are, in fact,
used by the golfer’s perceptual system.
 Golfer’s pickup of invariants can explain
the totality of golf swing.
 The performer and its environment are co-
participants.

The Niches of the environment
 Animals: their movements are animate.
 They are not governed by the law of
mechanics
 A niche referes to how an animal lives
 The niche implies a kind of animal
 The animal implies a kind of niche
 Note the complementarity of the two

J.J. Gibson’s Perception
 Invariants
 Constraint manifolds
 Direct Perception
 Affordances
 Experimental Evidence

As shown in Figure 6, a thin rectangular plate is
supported on a frictionless horizontal plane (z = 0) with
four circular shaped pegs arranged in configuration (a),
(b) and (c). The contact between the plate and the peg
is assumed frictionless point contact.Determine the wrench (force/torque) exerted on the plate by the four pegs respectively and
write the four wrenches in a 6 x 4 matrix for configuration (a), (b) and (c) respectively.
(6 marks)
The plate is allowed to move only on the horizontal plane. Based on the configurations of the
pegs, determine the directions of the unconstrained instantaneous motion (the directions of the
twist motion) of the plate for configuration (a), (b), and (c) respectively, if there is any.
x
y
o
1
2
3
4
x
y
o
a
a
b
b
1
2
3
4
(a)

For case (a), 4 wrenches can only constrain the plate in X- and Y-
direction.
It cannot constrain the rotation in Z-direction, i.e., the reciprocal twist
motion is in [0,0,0,0,0,1].
For case (b), the 4 wrenches can partially constrain the plate in all 3
directions. However, as the peg are arranged in such a way that a twist
motion in the CW Z-direction rotation cannot be constrained. This can be
reflected in the linear combination of the 4 wrenches that the torque in
Z-direction is always positive.
For case (c ), the 4 wrenches can fully constrain the plate in 3 directions.
Hence, there is no unconstrained twist motion.

MORPHOLOGY LABORATORYDOF Analysis Example
 Individual feature
screw representation
 Algorithms
 Resultant
Twistmatrix and
Wrenchmatrix
 Interpretation
2
2
4
X
Y
Z
x
x
x
y
yy
zz
f2
f1
Taken From [Adams and Whitney 2001]

MORPHOLOGY LABORATORYExample (Cont.)
2
2
4
X
Y
Z
x
x
x
y
yy
zz
f2
f1
 Assembly DOF and Constraint
Solution
F1
1 0 0 2
0 1 0 2
0 0 1 0
0 0 0 1













F2
0 1 0 2
1 0 0 6
0 0 1 0
0 0 0 1














 TResultant  0 0 1 2 2 0
WResultant 












0 1 0 0 0 2
0 0 1 0 0 0
0 0 0 1 0 0
0 0 0 0 1 0Taken From [Adams and Whitney 2001]

Singular configuration for the 2D parallel manipulator
a linear variety of the set of lines
Jean-Pierre Merlet. Singular Configurations of Parallel Manipulators and Grassmann
Geometry. The International Journal of Robotics Research 1989; 8; 45
a pair of skew lines : a flat pencil of lines

The generalized problem of degrees of
freedom
“How can a neuromuscular system with an
exorbitant number of degrees of freedom be made
to act if it had but one degree of freedom?”
Bernstein (1935)
(Turvey, 1990)
Perception controls behavior by detecting
informational constraints specific to goal-paths
(Gibson, 1979)−in the nature of laws at the
ecological sense.

A reciprocal connection
LCL
6$
A reciprocal connection scenario compatible with a single DOF of
the right knee joint about $. Here the vectors associated with the
five constraints $i´ intersect the axis of $. The five intersections are
indicated by the markers. In this model, for simplicity, the LCL as
indicated is not included. (Kim and Kohles, 2011)
The Plenitute hypothesis:
Biology makes extra degrees of
freedom that may be used to
modulate external force by
internal forces. (Shaw 1999)
are cast in terms of
efference
be cast in terms of afference

The knee joint provides the instantaneous screw which is
reciprocal to the impulsive ground reaction force . No combination
of angular velocity at the will cause instantaneous translational
movement, and any force at the ground contact will cause no
rotation at . The reaction forces (and torques) of the GRF will then
be taken by the structures of the limbs (i.e. the femur is the largest
bone) than they would have been taken by joint constraints.


Under the law of
mutability, structures are
slow function.

-10
-8
-6
-4
-2
0
2
4
6
8
10
-60
-40
-20
0
20
40
60
-40
-20
0
20
40
-40
-20
0
20
40
60
-60
-40
-20
0
20
40
60
-100
0
100
ISA screws are shown to regularly intersect the GRF wrenches as indicated with
the colored lines progressing in time and space (X-direction).
Progression of Gait
-100
-50
0
50
100
150
200
250
300
350
180
200
220
240
260
280
300
320
340
-500
-400
-300
-200
-100
0
100
200
300
400
X
-Y (mm)
Z
$
$´
X
-Y
Z
Wangdo Kim et al., Measuring Knee Constraints Through Mechanical Reciprocity, Submitted to Medical
Engineering & Physics
Shank Thigh
Relative

Some Affordances of the terrestrial
environment
 Locomotion, movement through the
environment, is the behavior that most
dictates the morphology and physiology of
animals
 The perception of the ground that is
literally the basis of the behavior of land
animals

a simple spring-mass system
Claire T. Farley
Leg stiffness is not directly related to hopping
mechanics, but, rather, to the hopping
environment.

• In a verification purpose for positioning IAK tracking in time-sequence of
motion data, the knee ISA screws are shown to nearly coincide with a
reciprocal screw of the GRF as indicated in the zoom up pan. This
representative analysis indicates a reciprocal connection (close to a
special configuration that can exert a wrench of substantial intensity on
the corresponding reciprocal screw in the GRF without overloading the
knee joint torque).

The one-degree-of-freedom
inverted pendulum model
K C
y
m
L
K = spring constant of the foot/ground interface
C = damping coefficient of the foot/ground interface
The “extended Kalman filter (EKF)” approach
used here for the first time to directly apply
measured ground forces
Kim, W., Tan, J., Veloso, A., Vleck, V., & Voloshin, A. S. (2011). The natural
frequency of the foot-surface cushion during the stance phase of running.
Journal of Biomechanics, 44(4), 774-779

55
identification process of combined
estimation of both unknown physiological
state and mechanical characteristics of
the environment in an inverse dynamic
model

Y
Z
O
MC
A
Y
Z
O
MC
A
A pure
force
A pure
translation
at A
A pure
rotation in
a principal
direction of
inertia
A pure
couple in a
principal
direction of
inertia

Y
X
Z
X
Y
Z
O
MC
C
f
Cτ
α
aC
A
T
m1 H
H I
 
  
 
OM
0.788 0 0 0 29.241 1.001
0 0.788 0 29.241 0 1.108
0 0 0.788 1.001 1.108 0
0 29.241 1.001 2855.908 5.206 123.719
29.241 0 1.108 5.206 2859.116 111.823
1.001 1.108 0 123.719 111.823 20.966
  
 
 
 
 
 
   
 
 
 
Due to its special 6×6 form, the screw inertial tensor at ‘O’
=

The eigenvalue problem provides
a unique decomposition of as
m1 H 0 0 0
0H J
T
f
T O
f m f
M
m
   
     
       
         

Detached club (Physical physics)

An astonishing behavior to animals with hands
Invariants , taken with reference to the golfers
(exteroception)

X
Y
Z

 : A special line complex is the linear line complex defined by a single twist .
Every marker point of the segment has its velocity vector tangential to the helix
that passes through it. The pattern of this velocity vector is a helicoidal velocity
field. Each marker point that does not coincide with the twist axis of is referred
to as a pole. Associated with each pole is its corresponding polar plane. Shown
are a polar plane and its corresponding pole as defined by the instantaneous
screw axis .
 The ISA used to transform the marker set to must be determined form
cylindroids . and are two twists of zero pitch on the cylindroid .
$ISA
pole
(marker)
polar plane

Perception and Action as
Functional Relationsas
:dispositional properties
 ‘Perceiving is an achievement of the individual, not an
appearance in the theatre of his consciousness. It is a
keeping-in-touch with the world, an experiencing of
things rather than a having of experiences’ (Gibson,
1979, p. 239).
 And we aimed to share in the social world this
information as a “genuine” tool for performance
variables.
 A functional system can manifest itself in different ways,
through different assemblages of anatomical substrates.

:
-100 0
100 200 300
0
50
100
150
-100
-50
0
50
100
150
200
250
300
350
1
Ant
Pos
Z (cm)
Y (cm)
X (cm)
C
Y (cm)
X (cm)

1
Ant
Pos
Y (cm)
Z (cm)
X (cm)
D
Y (cm)
X (cm)
the goal-directedness of behavior is captured

Equally a fact of environment and a fact of behavior
Attached club (Ecological physics)
D
Y (cm)
X (cm)
Radius of
gyration
Club initial
position

Environment (neighborhood) in
swing?
Niches not yet occupied
C
Y (cm)
X (cm)

Conclusion
 This perception-action coupling manifold,
which utilizes correlating alignments of
both the generating lines of ISA and e3,
can be directly applied to investigate how
the novices can perceive the affordances
about an effective swing, without an
excessive amount of learning (Gibson
1979). "You think too much."

The difficulties are of a different kind
 James J. Gibson (1979 The ecological approach to visual
perception. Boston: Houghton Mifflin) asks us mainly to do
is to unlearn.
 Our entire education has been geared to
making us distrust our sense and slightly
to look down on those who confuse their
subjective experiences with objective
facts.

Thank you!
The world is a meaningful environment of an animal.

“Ecological foundations of human motion model

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