36 a joint force position measurement system for accessibility quantification

11-12/01/2010 Kick-off meeting Brussels, Belgium

A JOINT FORCE-POSITION MEASUREMENT SYSTEM FOR ACCESSIBILITY QUANTIFICATION M. Kirchner, M. Confalonieri, A. Paludet, F. Degasperi, M. Da Lio, M. De Cecco University of Trento, DIMS - Department of Mechanical and Structural Engineering – via Mesiano 77, 38100 Trento, Italy. [email protected], [email protected]

Matteo Kirchner

Michele Confalonieri

Alberto Paludet

Filippo Degasperi

Mauro Da Lio

Mariolino De Cecco

AEGIS Conference Brussels 28-30 November 2011

INTRODUCTION

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A large variety of motor disabilities have

neuromuscular or cardiovascular cause. These

ultimately happen as reduced ability to control

movements.

From the functional point of view, several limitations

can be observed, ranging from muscle tone

functions to control of voluntary movements

(such as bradikinesia, akinesia, apraxia, etc.), to

involuntary movements (such as tremors, tics, etc.),

to loss of sensations related to muscles and

movements.


INTRODUCTION

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These ultimately cause problems in

interacting with products, services and

environments encountered in all aspects of

daily life.

Those systems, intended for the consumer

market and the workplace, should be

designed to be accessible for all people

including those with special requirements,

such as older persons and persons with

disabilities.


INTRODUCTION – Clinical scales

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To assess human functions, a large number of clinical

scales exist, specific for each disease: the Unified

Parkinson’s Disease Rating Scale, or the Gross Motion

Function Measure for Cerebral Palsy, etc.

However, clinical scales rely on the expertise of

examiners, are disease related. For these reasons,

several attempts have been made to use objective

indicators that can be derived from measurements.

Computerized assessment tools have been

proposed in several types of motor disabilities.


INTRODUCTION – Computerized tests

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We may classify basically four types of tests,

depending on the type of task that is measured:

1) Point-to-point aiming tests, which assess movement

time, reaction, time, dwelling time and accuracy of

target achievement;

2) Continuous tracking tests, which assess motion

jerkiness and tracking errors (both lateral and

longitudinal deviations);

3) Hold tests, in which the ability to reject perturbance

forces is assessed;

4) Force control tests, which measure the ability to

achieve and control forces.


INTRODUCTION - Standards

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On the side of standards, ISO/IEC Guide 71 introduces the

concept that taking care of the needs of older persons and

persons with disabilities is fundamental in developing

relevant International Standards for products and services

design.

Technical report ISO/TR 22411:2008 presents ergonomics

data and guidelines for applying ISO/IEC Guide 71.

It provides ergonomics data and knowledge about human

abilities like sensory, physical and cognitive, as well as

guidance on the accessible design of products, services and

environments.


INTRODUCTION - Standards

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In this framework it is possible to find data about

hand/finger dexterity. Two subcategories that

regard the interaction with a 2D interface are listed.

One is “Data on hand steadiness”, the other “Grip

strength”.

Data about hand steadiness is defined as the

minimum hole diameter of a plate through which a

person can pass a pencil or needle without touching

the edge.

Grip strength data are given only for maximal-effort

contraction in clench grip that uses all fingers

wrapped around the controlled object.


TOUCH INTERACTION

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Touch sensing interfaces have rapidly grown in the

last decade and several new features have been

added and are going to appear

The 3M MicroTouch™ Capacitive

TouchSense® System (MCT

System) provides tactile feedback

effects for on-screen, video

buttons so users actually "feel"

like they are depressing

mechanical buttons.


TOUCH INTERACTION

Magic Trackpad form Apple is aMulti-Touch trackpad designed

to work with the Mac Desktop computers

click scroll swipe rotate

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TOUCH INTERACTION

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Korea - Advanced Institute of Science and Technology

Similar sliding gestures may have different meanings when

they are performed with changing force intensity. Touch

screens, however, fail to properly distinguish those

intensities due to their inability to sense variable pressures.

For the above reason they developed a touch screen

enabled by distinguishing normal and tangential forces

that allows new possibilities for gesture recognition on a

touch screen.


Standards – deficiencies in providing

indications for interaction dexterity

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At least data about the following are lacking:

- path/trajectory following (with finger, mouse, etc)

- the ability to achieve and control different level of

forces

- position/force coordination issues

Furthermore hand steadiness is covered only for a

very peculiar task

The above are addressed by the “Force Panel”

and the specific tests developed


FORCE PANEL – The instrument

The instrument is composed of the following:

an LCD

a resistive touch panel

three force transducers

an embedded control system

an interface with a PC

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Point to point motion task

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Measures the following:

• Reaction time

• Movement time

• Path deviation in point to point motion

• Dwelling Percentage Time in Target


Subject 1: mild hemiparesis

[mm]

[mm

]

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[mm]

[mm

]

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Subject 3: severe hemiparesis

not enough force


Subject 1

Time outside

target [ms]

Movement

Time [ms]

Reaction

Time [ms]

Path dev iation

[mm]

target 1 0 1375 327 2.8

target 2 0 1484 405 6.3

target 3 0 1343 406 4.9

target 4 0 1405 312 8.9

target 5 250 1202 297 2.3

target 6 0 1375 343 4.1

target 7 0 1266 280 4.3

Subject 3

Time outside

target [ms]

Movement

Time [ms]

Reaction

Time [ms]

Path dev iation

[mm]

target 1 983 1546 31 2.6

target 2 0 2638 31 2.5

target 3 0 2185 546 7.0

target 4 452 2295 515 5.8

target 5 110 2466 343 5.1

target 6 31 3496 63 5.9

target 7 702 2373 874 17.1

Subject 1: mild hemiparesis

Subject 3: severe hemiparesis

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Continuous tracking tasks

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• Percentage time in target

• Deviation to path

• Deviation to trajectory


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Subject 1: mild

hemiparesis

Subject 3: severe

hemiparesis

Subject

RMS deviation to

path [mm]

Mean target to finger

(trajectory) deviation

[mm]

Percentage of

time outside

the target [%]

1 10.9 2.2 9

3 26.0 4.2 36


FORCE PANEL –

HUMAN’S TRANSFER FUNCTION

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Transfer functions have been used to model how

human beings control several types of plants, for

example the lane keeping task in automobiles

(Kondo-like models) or route keeping in aircraft.

The transfer function used is the following:

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H 1 i Z1 i P

1

1 2i /N iN

2 eD i

Vertical line

horizontal trajectory

Finger horizontal

position

H


Measured quantities:

tau: delay, corresponding to the reaction time

H(w): frequency transfer function in trajectory

following

rms: root mean square error of the steady state

reached with respect to the reference (an estimate

of the reached accuracy)

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Example of an estimated transfer function

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Some shots of real and simulated data with the

estimated model

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To simulate the lane following for a bike rider game

(in this way the game accessibility can be evaluated)

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Position-Force tracking tasks

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• Position MSE

• Force MSE


Example of measurements

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Thanks for your attention!