36 a joint force position measurement system for accessibility quantification

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.
mauro.dalio@unitn.it, mariolino.dececco@unitn.it

Matteo Kirchner
Michele Confalonieri
Alberto Paludet
Filippo Degasperi
Mauro Da Lio
Mariolino De Cecco

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

INTRODUCTION
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.),
2
to loss of sensations related to muscles and
movements.

AEGIS Conference Brussels 28-30 November 2011

INTRODUCTION

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,
3
such as older persons and persons with
disabilities.


INTRODUCTION – Clinical scales
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
4 proposed in several types of motor disabilities.


INTRODUCTION – Computerized tests
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;
5 4) Force control tests, which measure the ability to
achieve and control forces.


INTRODUCTION - Standards
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
6 guidance on the accessible design of products, services and
environments.


INTRODUCTION - Standards
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
7
contraction in clench grip that uses all fingers
wrapped around the controlled object.


TOUCH INTERACTION
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"
8 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

9


TOUCH INTERACTION

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
10 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

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

11
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

12


Point to point motion task

Measures the following:
• Reaction time
• Movement time
• Path deviation in point to point motion
• Dwelling Percentage Time in Target

13


Subject 1: mild hemiparesis

[mm]

14

[mm]

Subject 3: severe hemiparesis

[mm]

not enough force

15

[mm]


Subject 1: mild hemiparesis
Subject 3: severe hemiparesis

Time outside M ov e me nt Re action Path de v iation
Subject 1 targe t [ms] Time [ms] Time [ms] [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

Time outside M ov e me nt Re action Path de v iation
Subject 3 targe t [ms] Time [ms] Time [ms] [mm]
target 1 983 1546 31 2.6
target 2 0 2638 31 2.5
16 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


Continuous tracking tasks

• Percentage time in target
• Deviation to path
• Deviation to trajectory

17


Subject 1: mild
hemiparesis

Subject 3: severe
hemiparesis

Mean target to finger Percentage of
RMS deviation to (trajectory) deviation time outside
18 Subject path [mm] [mm] the target [%]
1 10.9 2.2 9
3 26.0 4.2 36


FORCE PANEL –
HUMAN’S TRANSFER FUNCTION

19


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:

1 i   Z 1
H      e D  i
1 i   P   
i
2
1 2i / N    
 N 

Vertical line Finger horizontal

H  
20 horizontal trajectory position



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
21
of the reached accuracy)


Example of an estimated transfer function

22


Some shots of real and simulated data with the
estimated model

23


To simulate the lane following for a bike rider game
(in this way the game accessibility can be evaluated)

24


Position-Force tracking tasks

• Position MSE
• Force MSE

25


Example of measurements

26


Thanks for your attention!


36 a joint force position measurement system for accessibility quantification

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