“Ecological foundations of human motion model

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

http://en.wikipedia.org/wiki/United_States

http://en.wikipedia.org/wiki/Psychologist

http://en.wikipedia.org/wiki/Philosophy_of_science

http://en.wikipedia.org/wiki/Ecological_psychology

http://en.wikipedia.org/wiki/James_J._Gibson

http://en.wikipedia.org/wiki/United_States

http://en.wikipedia.org/wiki/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.



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

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."


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]


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]



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



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

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



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

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



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



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’

=



The eigenvalue problem provides a unique decomposition of as

m1 H 0 0 0

0H J

T

f

T O

f m fM

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 .

$ISApole

(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 0100 200 300

050

100150

-100

-50

0

50

100

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200

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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

Sports

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