ISWC2002

The Comfort Assessment of Wearable Computers

James F. Knight, Chris Baber,

Anthony Schwirtz and Huw W. Bristow

ISWC2002

Ergonomics

• Interest in human aspects of wearing technology

• How does the technology affect the human?• Aspects of the technology to assess

• Size• Weight• Positioning

• Need a dependant variable

ISWC2002

Previous work

• Measured responses to musculoskeletal loading

• Body posture and movement

• Problems• Use of specialised

expensive equipment• Need for specialist

knowledge• Time consuming

• Need for quick method of assessment

ISWC2002

Subjective assessment

• Comfort• Discomfort one of the main causes for non-use of

personal protective equipment (Abeysekera & Shahnavaz, 1990; Akbar-Khanzadeh & Biesi,

1995)

• Usually assessed as unidimensional• Wearing something can affect the wearer in

numerous ways• Need a multidimensional tool

ISWC2002

Comfort Descriptors

• Generate terms that describe different elements of comfort based on:

• The concept of wearing something

• Wearing some electrical or mechanical device

• Wearing something that has the ability to measure, record or determine some aspect of the wearer

• 92 terms generated• Need to reduce number of terms

ISWC2002

Comfort Descriptor Matrix

• Eight participants given cards with terms and definitions written on them.

• Participants asked to group the terms based on self selected criteria.

• Term by term association matrix developed.

Accurate data

Aching Adaptation Alignment Amount Annoying Appearance Awkwardness BalanceBlood flow

Blunt hitting

BruisingBumping

intoChafing Change Clamminess

Accurate data - - - - - - - - - - - - - - - -Aching 0 - - - - - - - - - - - - - - -Adaptation 0 0 - - - - - - - - - - - - - -Alignment 2 0 0 - - - - - - - - - - - - -Amount 1 1 1 2 - - - - - - - - - - - -Annoying 0 2 0 0 1 - - - - - - - - - - -Appearance 1 1 0 1 1 3 - - - - - - - - - -Awkwardness 0 0 2 0 0 0 1 - - - - - - - - -Balance 0 0 2 1 0 0 0 5 - - - - - - - -Blood flow 0 4 0 0 0 1 0 0 0 - - - - - - -Blunt hitting 0 3 0 0 0 1 0 0 0 5 - - - - - -Bruising 0 4 0 0 0 1 0 0 0 4 5 - - - - -Bumping into 0 2 1 1 0 2 0 2 2 2 2 2 - - - -Chafing 0 5 0 0 0 1 0 0 0 4 3 6 2 - - -Change 0 1 3 0 0 1 0 4 4 1 1 1 3 1 - -Clamminess 0 6 0 0 0 1 0 1 1 5 3 5 2 4 2 -Clowning 1 1 0 1 1 4 7 1 0 0 0 0 0 0 0 0Cold 0 1 0 1 1 1 0 0 0 3 3 2 1 2 1 1Compensation 1 0 3 1 0 0 1 2 2 0 0 0 1 0 5 0Conscious 1 1 1 1 2 2 3 0 2 0 0 0 0 0 0 0Constricting blood 1 3 0 1 0 0 1 1 1 6 3 2 1 2 1 5Constricting movement 0 1 2 0 1 1 0 1 1 2 2 1 0 1 0 1Cool (fashionable) 0 1 1 0 1 4 6 2 1 0 0 0 0 0 0 0Counteraction 1 0 2 2 0 0 1 1 1 0 0 0 0 0 4 1Cramped 0 0 1 1 1 3 1 2 3 0 0 0 1 0 1 1Damage 4 0 0 2 0 0 1 0 0 0 0 0 0 0 0 0Dangerous 4 0 0 2 0 1 2 0 0 0 0 0 0 0 0 0Difficult 0 0 3 0 0 1 0 6 5 0 0 0 4 0 4 1Digging in 0 3 0 0 0 1 0 0 0 6 6 3 2 3 1 4Dropping 0 0 2 2 1 0 0 1 3 0 1 0 0 0 0 0Embarrassing 1 1 0 1 1 4 7 1 0 0 0 0 0 0 0 0Explosion 4 0 0 2 0 0 1 0 0 0 0 0 0 0 0 0Falling over 2 1 0 1 0 1 2 1 2 1 1 1 3 1 1 1Fit 1 1 0 4 1 1 0 1 2 1 2 1 1 1 2 2Flapping 0 0 1 3 1 0 0 1 2 1 2 0 1 0 0 0Friction 0 1 0 1 0 1 0 0 0 3 3 3 1 3 1 1General fatigue 0 3 0 0 0 2 0 2 1 2 1 2 3 2 2 3Hot 0 1 0 1 1 1 0 0 0 3 3 2 1 2 1 1Impeding activity 0 1 0 0 0 2 0 2 2 1 1 1 3 1 3 2Impeding movement 0 2 0 0 0 2 0 2 2 2 2 1 2 1 4 3Impeding sensation 0 2 1 0 1 1 0 3 3 2 2 1 3 1 4 3Inertia 0 0 1 3 1 0 0 1 2 0 0 0 1 0 0 0Inhibited movement 0 1 0 0 0 1 0 3 2 1 1 1 3 1 3 2Intrusive 1 0 1 0 1 3 1 1 3 0 0 0 0 0 0 0Irritating 0 1 0 0 0 6 2 1 2 1 1 1 1 1 2 2Jerky 0 1 1 0 0 2 0 4 2 1 1 1 4 1 3 1Knocking 0 3 0 1 0 1 0 0 0 5 7 5 2 3 1 3Location 0 1 1 2 1 1 0 1 2 1 1 1 2 1 2 1Loose 1 0 0 3 1 0 1 1 2 0 1 0 1 0 1 1Mental work rate 0 1 2 0 3 2 1 1 2 0 0 0 0 0 0 0Modified movement 0 0 4 0 0 0 0 3 2 0 0 0 1 0 3 0Muscular fatigue 0 5 0 0 1 2 1 2 1 3 3 2 4 2 2 3Obstruction 0 2 1 0 0 1 0 2 2 2 2 1 2 1 3 3Over heating 4 0 0 2 0 0 1 0 0 0 0 0 0 0 0 0

ISWC2002

Multidimensional Scaling• Multidimensional scaling finds

the structure in a set of distance measures between objects or cases.

• Accomplished by assigning observations to specific locations in a conceptual space.

• Distances between points in space match the given dissimilarities.

• By applying the association matrix to MDS 6 groups of comfort terms derived.

ISWC2002

Comfort Groups• Emotion

• Concerns about appearance, embarrassment, conspicuousness

• Attachment• Physical feel of the device on the body

• Harm• Physical affect on the body, damage to the body

• Perceived change• The wearer feels physically different, upset

• Movement• The device affects movement

• Anxiety• Worry about the device, safety and reliability (white coat syndrome)

ISWC2002

Comfort Rating ScalesTitle Endpoints Description

Emotion Low/High I am worried about how I look when I wear this device. I feel tense or on edge because I am wearing the device.

Attachment Low/High I can feel the device on my body. I can feel the device moving.

Harm Low/High The device is causing me some harm. The device is painful to wear.

Perceived change Low/High Wearing the device makes me feel physically different. I feel strange wearing the device.

Movement Low/High The device affects the way I move. The device inhibits or restricts my movement.

Anxiety Low/High I do not feel secure wearing the device.

Emotion

Low High

Attachment

Low High

Harm

Low High

Perceived change

Low High

Movement

Low High

Anxiety

Low High

ISWC2002

SensVest

• Part of the Lab of Tomorrow project.

• Designed to house components that measure and transmit physiological data

• heart rate• temperature• acceleration

• Used as a teaching tool to record aspects of every day activities.

ISWC2002

SensVest Comfort Assessment• Comfort assessment is being

used to evaluate the SensVest

• Comfort measured after carrying out self selected activities

• eg. Walking, sitting, bending, raising and rotating arms

• 10 postgraduate students (age: 252)

ISWC2002

SensVest Comfort Assessment• Comfort measured after

wearing SensVest in accelerometry data collection sessions

• Wrist acceleration during throwing

• Body acceleration during whole body activities

• 14 undergraduates took part in both sessions (age: 19 1)

Wrist acceleration when throwing

-1

0

1

2

3

4

5

0 1 2 3 4 5 6 7 8 9 10

Time (s)

Acc

eler

ati

on

(g

)

Dynamic body acceleration

-2

-1

0

1

2

3

4

0 20 40 60 80 100 120

Time (s)

Acc

eler

ati

on

(g

)

Stand

SitWalk Run

Jump

ISWC2002

SensVest Comfort

• General pattern• Attachment, Perceived

change and Movement scored highest

• Harm and Anxiety scored lowest

• Between conditions• Dynamic condition

scored highest

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101214161820

Emotion Attachment Harm PerceivedChange

Movement Anxiety

Comfort Dimension

CR

S S

core

General Throwing Dynamic

ISWC2002

SensVest Comfort• Emotion

• Aesthetics, size and bulk, feel conspicuous

• Attachment• Size, weight, pulls shirt out of shape, move during dynamic activity

• Harm• Not painful, increased during dynamic activity – components collide with the

body

• Perceived change• Size, bulk, due to attachment issues

• Movement• Size, components around shoulder affect arm movement

• Anxiety• Low in general condition (no data collected) increased in accelerometry studies

(data collected)• Dynamic activity – damage to the device

ISWC2002

Redesigned SensVest

• Vest design• Smaller, lighter• Cooler• Can be worn over or

under own shirt• Adjustable size

ISWC2002

Comfort of new SensVest

• Comfort scored when carrying out self selected activities

• CRS scores lowered for new design

• New design improved comfort

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Emotion Attachment Harm Perceivedchange

Movement Anxiety

Comfort Dimension

CR

S S

core

SensVest Redesigned SensVest

ISWC2002

WECA PC

• Wearable PC that displays different web pages depending on your location.

• Worn in side bag over the shoulder

• Measures 17x4x10cm• Weighs 600g• See Bristow et al.

ISWC2002

WECA PC Comfort

• Comfort assessed under two conditions

• General condition • After carrying out self selected activities

(as used in SensVest study)

• After User trials• Using the WECA PC while walking around the

University of Birmingham campus

• See Bristow et al.

ISWC2002

WECA PC Comfort

• General pattern• Attachment, Perceived

change and movement scored highest

• Harm scored lowest

• Between conditions• Comfort scores

increased in field studies

• Greatest increase in Emotion and Anxiety

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Emotion Attachment Harm PerceivedChange

Movement Anxiety

Comfort Dimension

CR

S S

core

Laboratory Field

ISWC2002

WECA PC Comfort• Emotion

• Size and bulk, feel conspicuous, increased in social environment

• Attachment• Size and bulk, loose fitting, moves during movement

• Harm• Not painful

• Perceived change• Size, bulk, due to attachment issues

• Movement• Size, position, inhibits arm swing when walking

• Anxiety• Low in general condition (not interacting with device) • High in field study (interacting with device)

ISWC2002

Implications

• Studies show comfort should be measured over a range of dimensions

• Cognitive factors of comfort should be measured

• Comfort should be measured in the field when carrying out a number of activities

• Knowledge of context and situations of use are important

ISWC2002

Conclusions

• CRS provide a tool to assess comfort over a range of dimensions for wearable technology

• CRS can be used to measure comfort specific for device or dimension

• CRS may assist designers decide what aspect of devise needs alteration to improve comfort and make more wearable

• Used pre and post CRS can be used to determine the effectiveness of any modification made to design