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Faculty of Human KineticsTechnical 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 Laboratory2 CIPER (Center for the Interdisciplinary Study of Human Performance)3Sports Expertise LaboratoryFaculty 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 Americanpsychologist
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 PeoplePERCEIVED 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.
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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
o1
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.
"You think too much."
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY DOF Analysis Example
Individual feature screw representation
Algorithms
Resultant Twistmatrix and Wrenchmatrix
Interpretation
2
2
4
X
Y
Z
x
x
x
y
yy
zz
f2f1
Taken From [Adams and Whitney 2001]
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY Example (Cont.)
2
2
4
X
Y
Z
x
x
x
y
yy
zz
f2f1
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]
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
Singular configuration for the 2D parallel manipulatora linear variety of the set of lines
Jean-Pierre Merlet. Singular Configurations of Parallel Manipulators and GrassmannGeometry. The International Journal of Robotics Research 1989; 8; 45
a pair of skew lines : a flat pencil of lines
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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.
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
A reciprocal connection
LCL6
$
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
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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.
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
-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
050
100150
200250
300350
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
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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 forcesKim, 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
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
Y
XZ
X
Y
Z
O
MC
C
f
Cτ
α
a C
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’
=
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
The eigenvalue problem provides a unique decomposition of as
m1 H 0 0 0
0H J
T
f
T O
f m fM
m
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
Detached club (Physical physics)
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
An astonishing behavior to animals with hands
Invariants , taken with reference to the golfers
(exteroception)
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
X
Y
Z
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
: 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 .
$ISApole
(marker)polar plane
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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.
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
:
-100 0100 200 300
050
100150
-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
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
Environment (neighborhood) in swing?
Niches not yet occupied
C
Y (cm)
X (cm)
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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."
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
BIOMECHANICS AND FUNCTIONAL
MORPHOLOGY LABORATORY
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.