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Rosén, B-G., Eriksson, L., Bergman, M. (2016)Kansei, surfaces and perception engineering.Surface Topography: Metrology and Properties, 4(3): 033001https://doi.org/10.1088/2051-672X/4/3/033001

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Kansei, surfaces and perception engineering

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Surf. Topogr.:Metrol. Prop. 4 (2016) 033001 doi:10.1088/2051-672X/4/3/033001

TOPICAL REVIEW

Kansei, surfaces and perception engineering

B-GRosen1,2, L Eriksson1,2 andMBergman1

1 Functional Surfaces ResearchGroup,HalmstadUniversity, Halmstad, Sweden2 Industrial DesignDepartment, JönköpingUniversity, Jönköping, Sweden

E-mail: bg.rosen@hh.se

Keywords: surface texture, affective engineering, softmetrology, industrial design, Kansei, surface, perception

AbstractThe aesthetic and pleasing properties of a product are important and add significantly to themeaningand relevance of a product. Customer sensation andperception are largely about psychological factors.There has been a strong industrial and academic need and interest formethods and tools to quantify andlink product properties to thehuman response but a lack of studies of the impact of surfaces. In thisstudy, affective surface engineering is used to illustrate andmodel the link between customerexpectations andperception to controllable product surface properties. The results highlight the use ofthe softmetrology concept for linking physical andhuman factors contributing to the perception ofproducts. Examples of surface applications of theKanseimethodology are presented fromsaunabath,health care, architectural andhygiene tissue application areas to illustrate, discuss and confirm thestrengthof themethodology. In the conclusions of the study, future research in softmetrology is proposedto allowunderstanding andmodelling of product perception and sensations in combinationwith adevelopment of theKansei surface engineeringmethodology and software tools.

1. Introduction

Consumer decisions when choosing a product com-prise a complexity of aspects including experiencecontrolled by our five senses, fulfilling of functionalrequirements, and gestalt, describing the sum of theproduct properties.

The widely implemented ISO 9001 series is basedon seven quality management principles whereof thefirst is customer focus. ′′Sustained success is achievedwhen an organization attracts and retains the con-fidence of customers and other interested parties onwhom it depends. Every aspect of customer interac-tion provides an opportunity to create more value forthe customer. Understanding current and futureneeds of customers and other interested parties con-tributes to sustained success of an organization’’. [1]

Organizations depend on their customers andtherefore should understand current and future custo-mer needs, should meet customer requirements andstrive to exceed customer expectations. Here, tools andmethods to measure customer satisfaction and link it tophysical properties of products are of great interest.

Form, colour, gloss, material and texture selectionare examples of critical product properties; and convey amessage from the industrial and engineering design

departments to the customer. Well-polished metal sur-faces and finely woven clothes may be examples of pro-duct properties specially designed to be appealing to thehuman sense of visual feedback and touch from pro-ducts aiming at an exclusive highqualitymarket [2].

Material and manufacturing selection of a car, forexample, is not only about ensuring safety in a con-struction, ensuring low cost production or optimizingthe weight. Zoom into the material beyond what wecan see with the naked eye and the microstructure willexpose a landscape in the submillimetre scale affectingus as customers and users in a subtle way.

The aim of the paper is to present the importanceand context of ‘affective engineering’ and to give exam-ple of the application for engineering surfaces to supportthe discussion of continued research in the field—addressing the problem of the absence of a current jointapproach to affective surface engineering in general.

2. Emotions and product experience

2.1. From stimuli to sensationThe combined sensation of a products’ surface gloss,colour, haptic properties like ‘friction’, ‘elasticity’, ‘hard-ness’ and ‘temperature’ create an intended message to

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the customer received as stimuli (R) by the human fivesenses, transformed to psychological sensation (S).Psychological sensation (S) was expressed in Fechner’slaw as

= ( )S k Rlog 1

where k is a constant and the sensation S follows alogarithmic function where small differences in sti-muli create a larger variation of sensation than forchanges of stimuli at higher values [3].

Later S S Stevens at Harvard developed a similarmodel—Stevens’ power law—sensitive to the fact thatdifferent types of stimuli follow different curve shapesto psychological sensation:

= ( )S Ia , 2b

where a is a constant, b is a stimuli exponent varyingwith the type of stimulation (visual, haptic, smell, taste,or audio) and I is the stimulus energy related to stimuli(R), Fechener’s law in equation (1) above [4]. So toconvey a ‘message’ strong enough to the customer,thresholds for the lowest detection level of changes instimuli and the function relating the stimuli topsychological sensation are important to understand.

Questions that need to be answered related to surfaceengineering are the minimum roughness of a handle thecustomer can sense and the differences of texture rough-ness allowing a handle with two textured parts to be per-ceived as having the samehaptic roughness sensation, i.e.defining thresholds for texture sensation and tolerancein relation to customer expectations and satisfaction.

2.2. Aesthetics and semantic scales to rate attitudeAesthetics can be explained as the human perceptionof beauty, including sight, sound, smell, touch, tasteand movement—not just visual appeal. Hidden fac-tors controlling appreciation of beauty have beendiscussed by philosophers since the Ancients and wereestablished as a subject of science when Osgood et alintroduced the semantical differential method used toquantify people’s perception of a product [5]. Here, asemantic scale composed of polar opposite adjectivepairs separated by a five to seven point rating scale isused. For example, a customer could rate the attitudeto a product by grading adjective pairs (rough tosmooth, cold to warm, dark to bright) on seven gradescales. Semantic scales could then be evaluated usinge.g. principal component analysis (PCA), to drawgeneral conclusions of attitudes.

2.3.Motivation andneedHowever, one important component affecting theaesthetics and attitude to the products is the customers’need or motivation. Motivation and need of a customerwere discussed by Maslow [6]. Here, five levels ofmotivation (biological and psychological needs, safetyneeds, belonging and love needs, esteem needs and selfactualization) were accentuated. If the psychologicalsensation (S) triggered by the physical stimuli matches

the customers’ expectation at the present motivation‘level’, the attitude to the product would be positive, i.e.themessage of the product designwould create a positiveperception of the product and its properties to thespecific customer, including both the psychologicalsensation e.g. from surface roughness level and thecustomers’ current ‘level’ of motivation from a positionof wanting to satisfy basic biological needs, e.g. havingsimple eye glass frames without requirements of expen-sive, exclusive and luxury signalling high gloss polishedroughness.

3. The intended productmessage

3.1.Designing the customermotivationSchutte [7] added to the discussion of needs of thecustomer the pleasures ofmotivation by Jordan’s ‘fourpleasures’ [8]: physio—to do with the body and thesenses; psycho—to dowith themind and the emotions;socio—to do with relationships and status; and Ideo—to do with tastes and values. Jordan’s four groupscomplete Maslow’s five steps and their fulfilment atthe different motivation levels is of importance whendesigning customermotivation into the product.

3.2.Design parameters and intention—the affectiveengineering equalizerOur motivation for and how we perceive a product arestrongly linked to the customers’ ‘buy’ decision. Indus-trial designmethodology aims at creating thismotivationand pleasurable product experience including meaningandmessage for the customer [9–11].

The aesthetic and pleasing properties of a productare of major importance in order to create motivation,interest, meaning and relevance of a specific productfor the customer. Since there almost always exist alter-native competitive products that fulfil basic requiredfunctionalities, the intended design of product prop-erties towards increased customer motivation is oneway of ‘making a difference’ and standing out from thecompetition. The ‘equalizer’ introduced by Bergmanet al [12] in figure 1 below, is a tool to visualize the rela-tive importance of design element properties (form,material, colour and surface); how they are used andtuned for a given product to create the intendedmotivation, meaning and message, i.e. the aestheticsand core values, intended by the industrial designer.

In the example from figure 1 above, the 13 corevalues are adjectives decided by the industrial design-ers to define the product message of a roof-mountedbicycle carrier for the automotive industry [13]. Thedesign element surface is decided to have its highestimportance on ‘user friendliness’, ‘aesthetics’, ‘well-thought out’, ‘quality’, ’prestige’ and ‘professional’,and consequently surface properties like gloss, averageroughness and texture on the final product needed tobe verified towards those core values for a successfulproduct.

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3.3. Ideaesthesia and semantics—connecting designelements and product experienceIdeaesthesia can be defined as the phenomenon inwhichactivations of concepts results in a perception-likeexperience [14] To objectively and transparently judgeand measure how the specification of physical designelements create the expected subjective customerpercep-tion, i.e. creating ideaesthesia, is a complex task involvingboth physical metrology and perceptual evaluations. Anexample of ideaesthesia is the experiment made by thepsychologist Wolfgang Köhler in 1929 [14], showing thestrong correlation between the visual shape of an objectand the speech sound (see below figure 2, top andmiddle) named the ‘bouba/kiki’ effect. The wordlumumba is normally connected to the top and middleright ‘soft-large radii contour shape’ image and the wordtakete with the top and middle left ‘sharp angle, straightline contour shape’ image. Today, a strong belief in theindustrial designers’ expertise and intuitive ability tomake judgements exists and is regarded as ‘tacit’ knowl-edge based on skills, ideas and experiences hard toformalize for anorganization.

A tool used frequently within the discipline of indus-trial design and strongly related to ideaestathesia, toexplain and formalize former tacit knowledge is ‘seman-tics’, the study of meaning and the relation between sig-nifiers, likewords and symbols, andwhat they stand for.

An example of industrial design semantics connect-ing design elements to core values, adjectives, is the ‘soft-ening’ of the perceived visual sensation in figure 2 from asheetmetal surface bymimicking a ‘soft’natural hair tex-ture (bottom left)with the Angel Hair™ texturing3 (bot-tom middle), compared to the more traditional ‘hard’‘Taketeish’brushed steel texture (bottomright).

The bouba/kiki effect, which later became thelumumba/takete effect, can be explained as a case ofideasthesia [15], In the example above, the design ele-ments form and surface were possible to correlate to

both the sensoric visual and sound experience of theadjective pair ‘takete’ (hard) and ‘lumumba’ (soft).

3.4. Perceptual product experience,modelling theproducts’ intendedmessagePerceptions involve any or all of the five senses. Under-standing the structureofhowthisworks cancreate amorerobust and controlled process when industrial designerscreatenewconcepts for apredicteduser experience.

The framework of perceptual product experience(PPE framework) [9, 16] considers perceptual productexperience as composedof three coremodes: the sensorialmode including perceptions of stimuli experienced withany of the receiver senses; the cognitive mode, where weunderstand, organize, and interpret and make sense ofwhat we perceive; and finally the affective mode concernsitself with experiences that are affective: feelings, emo-tions andmood states, as a result of product perceptions.

The PPE model in figure 3 illustrates a model forthe intended product communication between theproducer and the consumer, i.e. how the industrialdesigners’ intended product message, semantics, isexpressed as core values, adjectives and converted intodesign elements with controlled properties creatingconsumer sensations, and ideally results in ideaesthe-sia, a pleasurable experience of the product at the cus-tomersmotivation level.

4. A ‘softmetrology’ framework tomeasuretotal appearance

4.1. Softmetrology—themeasurement of customersatisfactionSoft metrology is defined as ‘‘the set of techniques andmodels that allow the objective quantification ofcertain properties of perception, in the domain of allfive senses.’’ [17]

Soft metrology addresses a broad range of mea-surement outside of the traditional field of physicalmetrology [17]:

Figure 1.The equalizer with the design elements (horizontal scale) and the product intended core values or ’productmessage’ (verticalscale) and how the ‘tuning’ of the ‘equalizer’ setting creates the total perception and aesthetics of a product. Reproducedwithpermission from [12].

3AZahner Company, Kansas City,MO,USA;www.azahner.com.

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• psychometric measurement or perceived feeling(colour, taste, odour, touch),

• qualitative measurements (perceived quality, satis-faction, comfort, usability),

• econometrics and market research (image, stock ex-changenotation), sociometry (audience andopinion),

• measurements related to the human sciences: bio-metrics, typology, behaviour and intelligence.

Figure 2. Lumumba/takete or bouba/kiki words (top andmiddle) and themeaning of formwhich has a strong connection to productexperience. Takete to the left and Lumumba to the right. Below is a typical soft hair texture (left) and the AngelHair™ (middle) steeltexture,mimicking hair and a brushed unidirectional steel texture (right).

Figure 3.Amodel for intended product communication linked to the PPE framework.

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The ideal would be to perform physical measure-ment using sensors applied to a subject placed in a testsituation and thus to establish usefulmeasurement scalescorrelating human subjective responses and physicalobjective metrology, i.e. combining traditional physical‘hard metrology’ (geometry, colour, gloss, taste, smell,nois and tactile properties) to enable increased under-standing of the influence of physical product propertiesonhuman responses andperception, seefigure 4.

Here, the humanwould be considered as ameasure-ment systemdefining sensitivity, repeatability and repro-ducibility, and comparing the resultswith those obtainedbymethods from traditional ‘hard’physicalmetrology.

The notion of subjectivism can of course be dis-cussed further, related to figure 4. Parts of what aredescribed as subjective human responses in the figurecan actually be described as general perception, thoughsubjective. For instance, the bouba/kiki effect, in whichsubjective perceptions are shared by all respondents,and therefore can be seen as a general perception, andnot notified as a personal opinion ofwhat is perceived.

The area of soft metrology has got a lot of attentionand departments were formed both at the standardsinstitutes NIST in the US and NPL in the UK [17–19];and a European project—Measuring the Impossible(MINET) 2007–2010—with 22 partners from Europeand Israel including industries and academia as well asthe national standards institutes NPL, UK, and SP,Sweden [20]. In addition, in 2013 L Rossi publishedher doctoral thesis ‘Principle of soft metrology andmeasurement procedures in humans’ stating theimportance of thefield [21].

4.2. Total appearanceAppearance is, according to the American Society forTesting and Materials (ASTM) [22], defined as ‘the

aspect of visual perception by which objects arerecognized’.

The visual appearance of an object is a result of theinteraction between the object and the light fallingupon it. Colour appearance is a result of the lightreflection and adsorption by the pigments.Gloss is cre-ated by the reflection of light from the surface, andtranslucency is a result of light scattering while the lightpasses through the object (figure 5). The describedcomplexity of the object’s appearance causes differentmeasurement technologies and instruments to beemployedwhen attempting to quantify it [17]. Textureis a complementary component of the visual appear-ance and also needs to be considered.

The concept of total appearance has been intro-duced to extend the concept of the appearance of anobject. The total appearance, however, would require adescription of the shape, size, texture, gloss and anyother object properties possible to detect by our fivesenses (visual, haptic, smell, sound and taste) andinterpreted by the brain as a ‘total appearance’ of anobject [17, 23].

The total appearance (figure 6) could also bedescribed as a combination of three aspects ofappearance:

Physical: object properties physically detectable byour senses, modified by the surrounding, properties ofthe illumination, individual factors like ageing, handi-cap, etc, affecting our sensibility.

Physiological: the neural effect when human recep-tors are subjected to physical stimuli and convey sig-nals to the cerebral cortex, creating a sensation

Psychological: created when sensations are inter-preted by the cortex, recognized as an object, andcombined with inherited and taught response modi-fiers (memory, culture, fashion, preferences). Figure 8

Figure 4. Softmetrology, correlating the objective physicalmeasurements to human subjective perceptions. Reproducedwithpermission from [17].

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summarizes the factors affecting the total appearance,resulting in two appearance images: the impact imageand the sensory image. The impact image is the initialrecognition of the object or scene (the gestalt), plus aninitial opinion or judgement. For the sensory appear-ance image, three viewpoints are used to create thetotal appearance: sensory, emotional and intellectual.The sensory viewpoint describes thoughts associatedwith the colours, gloss, etc, of the object. The emo-tional viewpoint associates the emotions connected

with colours, gloss, etc, while the intellectual view-point covers other aspects associated to the object andsituation rather than sensory or emotional associa-tions [24, 25].

Total appearance is closely related to themodels ofIntended product communication and the PPE frame-work, and could be used when quantifying customerperception and satisfaction using soft metrology tocorrelate physical and human factors contributing toproduct appearance images.

Figure 5.Visual appearance is one aspect of the total appearance. Here, the four basic optical properties (colour, gloss, texture andtranslucency) of visual appearance are grouped together.

Figure 6.The concept of total appearance. Reproducedwith permission from [17].

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5. Affective engineering—tomeasure totalappearance and control customersatisfaction

5.1.Quality function deployment andKano tounderstand psychological sensationAfter Osgood’s publications [5] more methodologies,e.g. quality function deployment (QFD) and the Kanomodel were developed with similar motivation[26, 27]. Those methods are very capable of dealingwith psychological sensation but not as capable whenit comes to translating the subjective sensation intodesign parameters, i.e. real product features influen-cing the perceived sensation.

5.2. Kansei engineering—from subjectivesensations to design parameters and totalappearanceNagamachi developed the method ‘affective’ or ‘Kan-sei‘ engineering (KE) in the 1970swhich has its roots inthe Japanese concept of Kansei: ‘intuitive mentalaction of the person who feels some sort of impressionfrom an external stimulus’ [28–31]. By using theframework of KE as an approach and focusing onfinding correlations between the functions, customerrequirements, function requirements, design require-ments and process requirements, a higher level of userquality and a methodology for soft metrology asdiscussed above could be obtained.

According to Nagamachi, the Kansei conceptincludes ‘a feeling about a certain something that likelywill improve one’s quality of life’. KE can also bedefined as a customer-oriented approach to productdevelopment. The basic idea is that the client’s feelingsshall be observed at the phase of idea generation in theproduct development process, which then facilitatesthe project later on when a concept reaches the pro-duction stage.

Kansei engineering handles six different phases/steps [12, 28–31], starting with the definition of theproducts’ domain and context, seefigure 7.

The six phases range from a pilot study where theproduct or service is defined, including specification ofthe product and market, to synthesis and modellingthe result of the given study.

1. Pilot study: defining the product domain, marketand users, i.e. what, who, where, why, when andhow; e.g. Interior surface textures for small urbanfour-wheel drive cars.

2. Describe the experience (span the semantic space):collect adequate adjectives, expected by the customerfrom the domain to define the physiological require-ments, e.g. organic, innovative, stimulating, robust.

3. Define key product properties (span the space ofproperties): in this phase it is important to findphysical product properties that affect the users’view of the total appearance and experience, e.g.surface texture anisotropy, surface texture ampl-itude and number of cavities in a surface.

4. Connect the experience to product properties: byusing qualitative and/or quantitative studies onfocus groups, connections between customeradjectives (phase 2) and design elements (phase 3)can be made, e.g. organic surfaces possess hightexture amplitude and isotropic texture patterns.

5. Validity check point: when the qualitative correla-tion in step 4 is established, it is important to verifythe results quantitatively by verifying experimentsor virtual simulations, e.g. physical tests on surfacespassing the acceptance level of cleanability instep 4 all possess a texture mean amplitude lessthan 0.8 μm.

6. Modelling the domain: design and validation of a‘prediction model’, e.g. surfaces passing the accep-tance level of cleanability and hygiene in step 4 allpossess a texturemean amplitude lesser than 0.8 μmand the cleanability increases linearly for meanamplitudes from 0.8 μm to 0.03 μm in the domainof steam sterilizers formedical applications.

Figure 7.TheKansei based research approach and six different phases.

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A full project ranging over all the six phases of KEwill result in a model or prediction of the total appear-ance or a limited sector of the total appearance, e.g.visual appearance or total appearance of the texture of aproduct within the domain selected in phase 1 of theproject. Visual appearance is limited to optical factorsof the product appearance while the total appearanceof the texture of a product includes visual, haptic andother sensory aspects of the total appearance of themicro- or nanometre texture experience.

Below in the following sections, the Kansei metho-dology briefly described generally in the sections abovewill be detailed and exemplified with results from cur-rent and past cases and studies to illustrate the poten-tial of an application of affective engineering conceptson product surfaces.

5.3. Phase 1, the pilot study, defining the domain

In this phase, it is important to defineproduct domain and users; define andanalyze what, who, where, why, when andhow. In the pilot study, see figure 8, there

are a lot of questions to be answered and it is crucial tonavigate efficiently in the right direction from thebeginning in a development project. Product designersin general have good internal navigation and relationto the design process, however sometimes the lack ofcommunication in a project can result in endlessdiscussions of what the aim is for whom. The ‘DesignCompass’ and persona studies as well as mood boardsare useful Kansei tools and work as external stimuliand guidelines in the process of affective engineeringto facilitate the workflow in order to focus on theprimary questions (what, who, why, where, when andhow) in the pilot study.

5.4. Phase 2, describe the experience

In this phase it is important to find

psychological emotions and expectedtotal appearance and perception related

to a product expressed as adjectives, ‘Kansei words’,and grouped in logical clusters (seefigure 9).

The idea of describing the product experienceusing adjectives is about framing the emotional func-tions, i.e. defining the expected perception and totalappearance. To be able to do that there is a need to‘span the semantic space’, collect the expressed ‘emo-tions’, by collecting adequate describing words, whichthe user expresses when interacting within the productdomain. By using describing words it is possible tofind appropriate expressions and clusters of Kanseiwords expected to be associated with (and not!) a pro-duct designed to evoke an intended perception orideaesthesia.

Today, the collection phase is optimized to be ableto offer amore cost-efficient process and service with ahigher quality. The ‘word game’ [12], see figure 10, wasdeveloped to serve as a physical tool for designers to be

able to set high quality core values for a product or ser-vice in a structural way, and faster than before. Insteadof implementing questionnaires, a focus group is par-ticipating in a physical word game.

The ‘word game’ is implemented, sorting outambiguous words which do not fit in the domain andcontext, and grouping words which are considered assynonyms among the describing words, or words thatcould be directly connected to each other, e.g. thewords ‘organic’ and ‘natural’ could be clustered witheach other even though they are not synonyms. Theamount of words is reduced during this part of theproject and clusters of belonging words are created.Figure 10 illustrates the last implementation step ofthis phase and an example of word clusters from astudy of building exteriors representing the core valuesandKansei words for the building exteriors [32].

5.5. Phase 3, define key product properties

In this phase it is important to findphysical product properties that affectthe user; analyze the properties of thedomain; define properties that affect; and

isolate significant properties.When the identification of the core values and Kan-

sei words is made, the next step is to identify propertiesof the existing product that can be controlled and affectthe product towards those core values, i.e. design ele-ments. In product design the primary design elementsare form (geometry/shape), colour (hue, saturation,whiteness and blackness),material (chemical substanceor raw material, isotropic or anisotropic, structure andstrength) and surface (texture ratio, fractal dimensionand directionality, texture amplitude, texture spatialproperties and texture geometrical feature), in accor-dancewith ISO25178-2:2012, seefigure 11.

The design elements should be appropriately mea-surable using standardized methods and parameterslike the surface texture field, stratified and featureparameters in accordance with acknowledged ISO25178 series of standards.

Now, the correlations between the experience and‘feeling’ (psychological requirements) and the func-tional requirements (physical requirements) have tobe established as well. For instance, the adjectives cleanand hygienic, expressing customer psychologicalrequirements for a surface in a medical environment,are connected to demands on: cleanability thus relatedto chemical resistance against stains and cleaningagents; and scratch proofness to withstand negativewear and cleaning effects on the surface [33, 34].ASME standard [35] connect today’s requirements ofhygienic surfaces to texture average arithmetic ampl-itude (Ra) according to ISO 4287:1997 and it is con-sidered sufficiently smooth when the Ra value for agiven surface is<0.8 μm [33, 34].

Here the ASME standard defines the surfaces’ tex-ture mean amplitude as the design element controlling

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the feeling and psychological requirements on cleanand hygienic. Figure 12 is an example of four surfacevariants exhibiting different areal texture averagearithmetic amplitudes possessing different levels ofcleanability and hygienic properties [33, 34].

All surfaces are well below the ASME level on thesurface design element mean amplitude defining theupper threshold for a hygienic surface from 2009 butthe influence of other recently standardized surfacetexture properties like anisotropy, fractal dimension,etc, not included in the standard could supply futuremore detailed information more sensitive to therequirements than the mean amplitude averagingother texture details of the surfaces infigure 12.

5.6. Phase 4, connect the experience andproductproperties By using qualitative studies on focus

groups, connections between Kanseiwords and design elements can bemade.An important tool to visualize the con-

nection between Kansei words and design elementscontributing to the total appearance is the ‘equalizer’.

For a given domain identified in step 1, the key pro-duct properties (design elements fromphase 3) are con-nected to theKansei words fromphase 2, in this 4th stepby, for example, using focus groups (figure 13).

In the example below from a study made on thedomain architectural external building panels [32], thevaluation of the Kansei words was made by 20 people

Figure 8.The ‘DesignCompass’ is a tool to help the design team to focus on the primary questions (what, who, why, where, when andhow) defining targets for the pilot study.

Figure 9.A focus group in action using the ‘word game’ (left). The right part of the image show thementalfiltering of the collectedadjectives into an amount of core values during a ‘word game’ session.

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on a semantic scale 1–10 for each of the four differentsurface textures infigure 14 (left).

A useful tool to visualize the correlation between sur-faces’ appearance with the design elements is the equal-izer infigure15, alsodescribed in section3.2 above [12].

The equalizer is a dynamic tool owing to the possi-bility to visualize the total influence and total appear-ance of the combination of design elements (the form,material, colour and surface) on the selected Kanseiwords developed in step 2 above.

5.7. Phase 5, validity checkpointWhen the correlation in thesynthesis instep 4 is established, it is important toverify the results by statistical tests,experiments or virtual simulations.

The validity checkpoint is about an overall valida-tion of the concept’s total appearance, verifying quan-titatively the Kansei words from phase 2 and theirconnection to the design elements obtained in phase 4.Practical testing of concepts ismade and quantitativelyevaluated by the correlation of ‘soft’ judgements ofKansei words to ‘hard measurements’ of design ele-ment properties.

In affective surface engineering, a connectionbetween Kansei words and surface texture parametersdescribing the micro- and nanotopography is made.In a study made by the authors on wall panels for hotbath sauna interiors [32], three test panels of 10 peoplewith experience from general product development,specific sauna product development and general saunabathing, graded the 11 surface textures on a sevengrade scale against the eight emotional Kansei wordsand three design element-related surface areal textureproperty parameters from the ISO 25178-2:2006 (seetable 1).

The Sq, Str and Sdq parameters (texture averageamplitude, texture ratio and texture slope) had a sig-nificant correlation with the Kansei words beautiful,stylish, and attractive. Here the soft metrology adjec-tives are demonstrated to correlate to ‘hard’metrology

measurable surface texture parameters, i.e. the exam-ple validates the principle that Kansei adjectives can belinked to ISO standardized measurable parameters,thus defining geometrical features controllable bymanufacturing engineering and possibly to use to spe-cify product requirements.

5.8. Phase 6—synthesis andmodelling the domainThe final step is intended to create amodel that combines, refines anddescribes the results from the previousfive phases in the Kansei methodology.

Hence, to assemble a model bridging the emotionalsemantic and product properties’ space.

In the project with a sauna manufacturer, a designmanual was made on request of the company. Thedesign manual basically linked surface geometricalproperties (the significant design elements and prop-erties) to the Kansei words according to the resultsdemonstrated in step 5 above. In practice this resultedin designer rules collected in a physical booklet for thecontext of saunawall panels, establishing that:

• A low average roughness (Sa) and low surface slope(Sdq) increase the stylish and attractive emotions of asaunawall texture,

• Thesamesurface combinations togetherwith increasedtexture anisotropy, e.g. a directional pattern, will alsoaffect thebeautifulnessof the surface.

This realizes a product development tool for thesauna company to facilitate the material and surfacedesign of their products connecting to the needs andexpectations of the customer.

In many cases it is desirable to formulate modelsdescribing quantitatively the relation between designelements and the desired soft metrology Kansei wordsas a complement to the design manuals with qualita-tive designer rules. In a study [36, 37] in the context oftissue paper haptic appearance a complex model was

Figure 10.A focus group in action using the ‘word game’ (left) [12]. To the right, the ten selectedKansei words highlightedwithin eachof the seven clusters with similar words [32].

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Figure 12.Coherence scanning interferometermeasurements of 0.1×0.1 mmareas of three candidatematerials for replacingstainless steel (left) for hot-steam sterilizer units. Areal arithmeticmean height amplitude (the Sa parameter) of the surfaces variesfrom 10 nm to about 0.7 μm—a factor of 70. Reproducedwith permission from [34].

Figure 13. Left: the hot-steam sterilizer in a typical hospital environment domain, reproducedwith permission from [34]. Right: afocus group consisting of company experts grading the influence of 12 selected surface textures on the individual Kansei words,reproducedwith permission from [36].

Figure 14. Left: themicrotopography of four surface textures. Right: a graphical valuation of the Kansei words for each of the foursurfaces. Reproducedwith permission from [32].

Figure 11.Pictogram illustrating design elements affecting the function and emotions of a product. The surface element is expandedwith textural properties according to the ISO 25178-2:2012 areal surface texture standard.

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Surf. Topogr.:Metrol. Prop. 4 (2016) 033001 B-GRosen et al

synthesized using eight constants (A–H), three mat-erial properties (layer type (DL), stiffness, elasticity(stretch)) and four areal ISO 25178 surface textureproperties (peak material volume (Vmp), core height(Sk ), maximum height (amplitude, Sz), autocorrela-tion length (repeatingwave length, Sal)).

= -+ + ++ - -

*

* * *

* * *

A B DL

Vmp D Sal Sk

G H Sz

‘perceived haptic roughness’

C E

F stiffness stretch .

In the equation above, the product design proper-tiesDL, Sz, and stretch have a negative regression coeffi-cient sign, showing that an increase in the parametervalue results in a decrease in ‘perceived haptic rough-ness’. The coefficients for Vmp, Sk and Sal were posi-tive, hence positively correlated with increased(improved) perceived haptic ‘roughness’, i.e. increasedtexture peakmaterial volume, core height, autocorrela-tion length and decreased maximum texture heightimprove the customers’ haptic perception of tissue pro-ductswithin the context of theperformed study.

The designer rules and the equation above areexamples where affective engineering and soft metrol-ogy results are synthesized into tools able to predictcustomer perception and aspects of total experiencesupporting organizations’ possibilities to maintaincustomer focus and competitive advantage.

6. Conclusions and future

The aesthetic and pleasing properties of products areone of themajor design dimensions in order to create ameaning and relevance of a product.

The correlation of objective characterization ofmat-erial properties in relation to human response is themain component in soft metrology, a concept previouslyintroduced and known, naming the methodology withthe power of enabling affective surface engineering.

• Total experience can be used when quantifyingcustomer satisfaction using soft metrology

correlating physical and human factors contributingto products’ appearance images.

• Soft metrology allows the objective quantification ofcertain properties of perception, in the domain of allfive senses, i.e. a quantification method for measur-ing total appearance.

• Affective surface engineering using theKanseimethod iseffective to connect the expected sensation, using softmetrologymethods, to validateddesignparameters.

• Appearance and perception of a product surface’svisual, haptic and other functional requirements likevisual requirements on external buildings and saunapanels andperceived haptic roughness of tissue paperas well as cleanability of surfaces for the medicalindustry can be taken into account using the Kansei‘six phase’ engineering approach.

• The affective, Kansei surface engineeringmethodol-ogy has great potential to help organizations tomaintain customer focus by allowing industrialdesigners to understand and model a desiredperception and total appearance of a product.

The results from the paper discuss a current direc-tion in product development and industrial designwhere surface engineering and the concepts of softmetrology, total appearance and affective, Kanseiengineering are combined and exemplified.

Future possibilities to increase the generality andapplicability lies firstly in the development of softmetrology to enable detailed understanding andmodel-ling of the customerperception and total appearance.

Secondly, the development of software tools sup-porting and optimizing the six phases of affective, Kan-sei surface engineering will increase the accessibility ofand interest in the method, and increase the number ofperformed case studies, thus increasing knowledge inthis emerging research area.

Thirdly, there exist a possibility and need of furtherresearch into the development of theword ‘metrology’ insoftmetrology,wheremultisensorial physical datawill be

Figure 15. Left: the equalizer is a designer tool to visualize the importance of design elements on the Kansei words. The equalizer to theright with the design elements (horizontal) and the 13Kansei words (vertical) visualizes a possible importance profile for a givenproduct, i.e. the product’s intended perception. Reproducedwith permission from [12].

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Surf. Topogr.:Metrol. Prop. 4 (2016) 033001 B-GRosen et al

Table 1.Correlation table between the saunaKansei words and surface texture areal parameters according to ISO 25178-2:2006 (significant parameters in bold) defining three design elements associated to the surfaces. Reproducedwithpermission from [32].

10,7

0,7

0,90,0

0,80,8

0,9

0,9

0,90,9

0,7

0,5

0,5

0,50,5

0,50,2

0,2

0,2

0,4

0,40,4

0,4

1

0,60,4

0,3

0,3

11

0,1

0,8 0,8

0,8

0,90,90,8 0,8

0,8

0,7

0,1

0,50,7

0.00,3

0,3

11

11

11

1

0,9

0,80,50,9

1,0

0,7

0,60,70,9

0,70,30,6

Kansei words

Kan

sei w

ords

InnovativeInnovative

Practical

Practical

Beutiful

Beutiful

Stylish

Stylish

Exiting

Exiting

Reliable

Reliable

Attractive

Attractive

Fresh

Fresh

Sq

Sq

Str

Str

Sdq

Sdq

Surface texture

Surf

ace

text

ure

Average amplitude

Average

Texture

Texture

Average slope

Average slope

amplitude

––

––

–

–––

–

–

–

–––

––

–––

––

––

––– –

––

13

Surf.Topogr.:M

etrol.Prop.4

(2016)033001B-G

Rosen

etal

linked to human multisensorial perceptual data. Finally,the question of ‘how and to what level can we qualityassure soft metrology data, and in turn assure the qualityof affective, Kansei engineering approaches’ needs to beaddressed in future studies.

Acknowledgments

The authors wish to thank the companies A.ZahnerCompany MO USA, Tylö AB Sweden and GetingeSterilization Sweden, for financial support as well asexpert input. We would also like to thank Digital SurfFrance for the support with the Mountain Mapsoftware. The conducted research is financed and partof the Vinnova, The Swedish Governmental Agencyfor Innovation Systems, project ‘Robust injectionmoulding of automotive components with desiredsurface properties (SW: Robust formsprutning avfordonskomponentermed önskade ytegenskaper).

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