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

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Kansei, surfaces and perception engineering

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TOPICAL REVIEW Kansei, surfaces and perception engineering OPEN ACCESS B-G Rosen1,2, L Eriksson1,2 and M Bergman1 RECEIVED 1 Functional Surfaces Research Group, Halmstad University, Halmstad, Sweden 7 April 2016 2 Industrial Design Department, Jönköping University, Jönköping, Sweden REVISED 29 June 2016 E-mail: [email protected]

ACCEPTED FOR PUBLICATION Keywords: surface texture, affective engineering, soft metrology, industrial design, Kansei, surface, perception 18 July 2016

PUBLISHED 19 September 2016 Abstract Original content from this The aesthetic and pleasing properties of a product are important and add significantly to the meaning work may be used under the terms of the Creative and relevance of a product. Customer sensation and perception are largely about psychological factors. Commons Attribution 3.0 There has been a strong industrial and academic need and interest for methods and tools to quantify and licence. Any further distribution of link product properties to the human response but a lack of studies of the impact of surfaces. In this this work must maintain study, affective surface engineering is used to illustrate and model the link between customer attribution to the author(s) and the title of expectations and perception to controllable product surface properties. The results highlight the use of the work, journal citation and DOI. the soft metrology for linking physical and human factors contributing to the perception of products. Examples of surface applications of the Kansei methodology are presented from sauna bath, health care, architectural and hygiene tissue application areas to illustrate, discuss and confirm the strength of the methodology. In the conclusions of the study, future research in soft metrology is proposed to allow and modelling of product perception and sensations in combination with a development of the Kansei surface engineering methodology and software tools.

1. Introduction departments to the customer. Well-polished metal sur- faces and finely woven clothes may be examples of pro- Consumer decisions when choosing a product com- duct properties specially designed to be appealing to the prise a complexity of aspects including human of visual feedback and touch from pro- controlled by our five , fulfilling of functional ducts aiming at an exclusive high quality market [2]. requirements, and gestalt, describing the sum of the Material and manufacturing selection of a car, for product properties. example, is not only about ensuring safety in a con- The widely implemented ISO 9001 series is based struction, ensuring low cost production or optimizing on seven quality management principles whereof the the weight. Zoom into the material beyond what we first is customer focus. ′′Sustained success is achieved can see with the naked eye and the microstructure will when an organization attracts and retains the con- expose a landscape in the sub millimetre scale affecting fidence of customers and other interested parties on us as customers and users in a subtle way. whom it depends. Every aspect of customer interac- The aim of the paper is to present the importance tion provides an opportunity to create more value for and context of ‘affective engineering’ and to give exam- the customer. Understanding current and future ple of the application for engineering surfaces to support needs of customers and other interested parties con- the discussion of continued research in the field— tributes to sustained success of an organization’’. [1] addressing the problem of the absence of a current joint Organizations depend on their customers and approach to affective surface engineering in general. therefore should understand current and future custo- mer needs, should meet customer requirements and strive to exceed customer expectations. Here, tools and 2. Emotions and product experience methods to measure customer satisfaction and link it to physical properties of products are of great interest. 2.1. From stimuli to sensation Form, colour, gloss, material and texture selection The combined sensation of a products’ surface gloss, are examples of critical product properties; and convey a colour, haptic properties like ‘friction’, ‘elasticity’, ‘hard- message from the industrial and engineering design ness’ and ‘temperature’ create an intended message to

© 2016 IOP Publishing Ltd Surf. Topogr.: Metrol. Prop. 4 (2016) 033001 B-G Rosen et al the customer received as stimuli (R) by the human five the customers’ expectationatthepresentmotivation senses, transformed to psychological sensation (S). ‘level’, the attitude to the product would be positive, i.e. Psychological sensation (S) was expressed in Fechner’s themessageoftheproductdesign would create a positive law as perception of the product and its properties to the specific customer, including both the psychological Sk= log R () 1 sensation e.g. from surface roughness level and the where k is a constant and the sensation S follows a customers’ current ‘level’ of motivation from a position logarithmic function where small differences in sti- of wanting to satisfy basic biological needs, e.g. having muli create a larger variation of sensation than for simple eye glass frames without requirements of expen- changes of stimuli at higher values [3]. sive, exclusive and luxury signalling high gloss polished Later S S Stevens at Harvard developed a similar roughness. model—Stevens’ power law—sensitive to the fact that different types of stimuli follow different curve shapes to psychological sensation: 3. The intended product message

SI= a,b () 2 3.1. Designing the customer motivation Schutte [7] added to the discussion of needs of the where a is a constant, b is a stimuli exponent varying ’ ‘ ( customer the pleasures of motivation by Jordan s four with the type of stimulation visual, haptic, smell, taste, ’ [ ] — ) pleasures 8 : physio to do with the body and the or audio and I is the stimulus energy related to stimuli — ( ) ’ ( ) [ ] senses; psycho to do with the and the emotions; R , Fechener s law in equation 1 above 4 .Soto — — convey a ‘message’ strong enough to the customer, socio to do with relationships and status; and Ideo ’ thresholds for the lowest detection level of changes in to do with tastes and values. Jordan s four groups ’ fi fi stimuli and the function relating the stimuli to complete Maslow s ve steps and their ful lment at psychological sensation are important to understand. the different motivation levels is of importance when Questions that need to be answered related to surface designing customer motivation into the product. engineering are the minimum roughness of a handle the customer can sense and the differences of texture rough- 3.2. Design parameters and intention—the affective ness allowing a handle with two textured parts to be per- engineering equalizer ceived as having the same haptic roughness sensation, i.e. Our motivation for and how we perceive a product are defining thresholds for texture sensation and tolerance strongly linked to the customers’‘buy’ decision. Indus- in relation to customer expectations and satisfaction. trial design methodology aims at creating this motivation and pleasurable product experience including meaning 2.2. and semantic scales to rate attitude and message for the customer [9–11]. Aesthetics can be explained as the human perception The aesthetic and pleasing properties of a product of beauty, including sight, sound, smell, touch, taste are of major importance in order to create motivation, and movement—not just visual appeal. Hidden fac- interest, meaning and relevance of a specific product tors controlling appreciation of beauty have been for the customer. Since there almost always exist alter- discussed by philosophers since the Ancients and were native competitive products that fulfil basic required established as a subject of science when Osgood et al functionalities, the intended design of product prop- introduced the semantical differential method used to erties towards increased customer motivation is one quantify people’s perception of a product [5]. Here, a way of ‘making a difference’ and standing out from the semantic scale composed of polar opposite adjective competition. The ‘equalizer’ introduced by Bergman pairs separated by a five to seven point rating scale is et al [12] in figure 1 below, is a tool to visualize the rela- used. For example, a customer could rate the attitude tive importance of design element properties (form, to a product by grading adjective pairs (rough to material, colour and surface); how they are used and smooth, cold to warm, dark to bright) on seven grade tuned for a given product to create the intended scales. Semantic scales could then be evaluated using motivation, meaning and message, i.e. the aesthetics e.g. principal component analysis (PCA), to draw and core values, intended by the industrial designer. general conclusions of attitudes. In the example from figure 1 above, the 13 core values are adjectives decided by the industrial design- 2.3. Motivation and need ers to define the product message of a roof-mounted However, one important component affecting the bicycle carrier for the automotive industry [13]. The aesthetics and attitude to the products is the customers’ design element surface is decided to have its highest need or motivation. Motivation and need of a customer importance on ‘user friendliness’, ‘aesthetics’, ‘well- were discussed by Maslow [6].Here,five levels of thought out’, ‘quality’, ’prestige’ and ‘professional’, motivation (biological and psychological needs, safety and consequently surface properties like gloss, average needs, belonging and love needs, esteem needs and self roughness and texture on the final product needed to actualization) were accentuated. If the psychological be verified towards those core values for a successful sensation (S) triggered by the physical stimuli matches product.

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

3.3. Ideaesthesia and —connecting design both the sensoric visual and sound experience of the elements and product experience adjective pair ‘takete’ (hard) and ‘lumumba’ (soft). Ideaesthesia can be defined as the phenomenon in which activations of results in a perception-like 3.4. Perceptual product experience, modelling the experience [14] To objectively and transparently judge products’ intended message fi and measure how the speci cation of physical design involve any or all of the five senses. Under- elements create the expected subjective customer percep- standing the structure of how this works can create a more tion,i.e.creatingideaesthesia, is a complex task involving robust and controlled process when industrial designers both physical metrology and perceptual evaluations. An create new concepts for a predicted user experience. example of ideaesthesia is the experiment made by the The framework of perceptual product experience [ ] psychologist Wolfgang Köhler in 1929 14 ,showingthe (PPE framework) [9, 16] considers perceptual product strong correlation between the visual shape of an object experience as composed of three core modes: the sensorial and the speech sound (see below figure 2,topand mode including perceptions of stimuli experienced with middle) named the ‘bouba/kiki’ effect. The word any of the receiver senses; the cognitive mode,wherewe lumumba is normally connected to the top and middle understand, organize, and interpret and make sense of right ‘soft-large radii contour shape’ imageandtheword what we perceive; and finally theaffectivemodeconcerns takete with the top and middle left ‘sharp angle, straight itself with that are affective: feelings, emo- line contour shape’ image. Today, a strong belief in the tions and mood states, as a result of product perceptions. industrial designers’ expertise and intuitive ability to The PPE model in figure 3 illustrates a model for make judgements exists and is regarded as ‘tacit’ knowl- the intended product communication between the edge based on skills, and experiences hard to producer and the consumer, i.e. how the industrial formalize for an organization. designers’ intended product message, semantics,is A tool used frequently within the discipline of indus- expressed as core values, adjectives and converted into trial design and strongly related to ideaestathesia, to design elements with controlled properties creating explain and formalize former tacit knowledge is ‘seman- consumer sensations, and ideally results in ideaesthe- tics’, the study of meaning and the relation between sig- sia, a pleasurable experience of the product at the cus- nifiers, like words and symbols, and what they stand for. tomers motivation level. 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 a 4. A soft metrology framework to measure sheet metal surface by mimicking a ‘soft’ natural hair tex- total appearance ture (bottom left) with the Angel Hair™ texturing3 (bot- 4.1. Soft metrology—the measurement of customer tom middle), compared to the more traditional ‘hard’ satisfaction ‘Taketeish’ brushed steel texture (bottom right). Soft metrology is defined as ‘‘the set of techniques and The bouba/kiki effect, which later became the models that allow the objective quantification of lumumba/takete effect, can be explained as a case of certain properties of perception, in the domain of all ideasthesia [15], In the example above, the design ele- five senses.’’ [17] ments form and surface were possible to correlate to Soft metrology addresses a broad range of mea- surement outside of the traditional field of physical 3 A Zahner Company, Kansas City, MO, USA; www.azahner.com. metrology [17]:

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Figure 2. Lumumba/takete or bouba/kiki words (top and middle) and the meaning of form which has a strong connection to product experience. Takete to the left and Lumumba to the right. Below is a typical soft hair texture (left) and the Angel Hair™ (middle) steel texture, mimicking hair and a brushed unidirectional steel texture (right).

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

• psychometric measurement or perceived feeling • econometrics and market research (image, stock ex- (colour, taste, odour, touch), change notation),sociometry(audience and opinion), • qualitative measurements (perceived quality, satis- • measurements related to the human sciences: bio- faction, comfort, usability), metrics, typology, behaviour and .

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Figure 4. Soft metrology, correlating the objective physical measurements to human subjective perceptions. Reproduced with permission from [17].

Theidealwouldbetoperformphysicalmeasure- aspect of visual perception by which objects are ment using sensors applied to a subject placed in a test recognized’. situation and thus to establish useful measurement scales The visual appearance of an object is a result of the correlating human subjective responses and physical interaction between the object and the light falling objective metrology, i.e. combining traditional physical upon it. Colour appearance is a result of the light ‘hard metrology’ (geometry, colour, gloss, taste, smell, reflection and adsorption by the pigments. Gloss is cre- nois and tactile properties) to enable increased under- ated by the reflection of light from the surface, and standing of the influence of physical product properties translucency is a result of light scattering while the light on human responses and perception, see figure 4. passes through the object (figure 5). The described Here, the human would be considered as a measure- complexity of the object’s appearance causes different ment system defining sensitivity, repeatability and repro- measurement technologies and instruments to be ducibility, and comparing the results with those obtained employed when attempting to quantify it [17]. Texture by methods from traditional ‘hard’ physical metrology. is a complementary component of the visual appear- The notion of subjectivism can of course be dis- ance and also needs to be considered. cussed further, related to figure 4. Parts of what are The concept of total appearance has been intro- described as subjective human responses in the figure duced to extend the concept of the appearance of an can actually be described as general perception, though object. The total appearance, however, would require a subjective. For instance, the bouba/kiki effect, in which description of the shape, size, texture, gloss and any subjective perceptions are shared by all respondents, other object properties possible to detect by our five and therefore can be seen as a general perception, and senses (visual, haptic, smell, sound and taste) and not notified as a personal opinion of what is perceived. interpreted by the brain as a ‘total appearance’ of an The area of soft metrology has got a lot of attention object [17, 23]. and departments were formed both at the standards The total appearance (figure 6) could also be institutes NIST in the US and NPL in the UK [17–19]; described as a combination of three aspects of and a European project—Measuring the Impossible appearance: (MINET) 2007–2010—with 22 partners from Europe Physical: object properties physically detectable by and Israel including industries and academia as well as our senses, modified by the surrounding, properties of the national standards institutes NPL, UK, and SP, the illumination, individual factors like ageing, handi- Sweden [20]. In addition, in 2013 L Rossi published cap, etc, affecting our sensibility. her doctoral thesis ‘Principle of soft metrology and Physiological: the neural effect when human recep- measurement procedures in humans’ stating the tors are subjected to physical stimuli and convey sig- importance of the field [21]. nals to the cerebral cortex, creating a sensation Psychological: created when sensations are inter- 4.2. Total appearance preted by the cortex, recognized as an object, and Appearance is, according to the American Society for combined with inherited and taught response modi- Testing and Materials (ASTM) [22],defined as ‘the fiers (memory, culture, fashion, preferences). Figure 8

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

Figure 6. The concept of total appearance. Reproduced with permission from [17]. summarizes the factors affecting the total appearance, with colours, gloss, etc, while the intellectual view- resulting in two appearance images: the impact image point covers other aspects associated to the object and and the sensory image. The impact image is the initial situation rather than sensory or emotional associa- recognition of the object or scene (the gestalt), plus an tions [24, 25]. initial opinion or judgement. For the sensory appear- Total appearance is closely related to the models of ance image, three viewpoints are used to create the Intended product communication and the PPE frame- total appearance: sensory, emotional and intellectual. work, and could be used when quantifying customer The sensory viewpoint describes thoughts associated perception and satisfaction using soft metrology to with the colours, gloss, etc, of the object. The emo- correlate physical and human factors contributing to tional viewpoint associates the emotions connected product appearance images.

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Figure 7. The Kansei based research approach and six different phases.

5. Affective engineering—to measure total The six phases range from a pilot study where the appearance and control customer product or service is defined, including specification of satisfaction the product and market, to synthesis and modelling the result of the given study. 5.1. Quality function deployment and Kano to understand psychological sensation 1. Pilot study:defining the product domain, market After Osgood’s publications [5] more methodologies, and users, i.e. what, who, where, why, when and e.g. quality function deployment (QFD) and the Kano how; e.g. Interior surface textures for small urban model were developed with similar motivation four-wheel drive cars. [26, 27]. Those methods are very capable of dealing 2. Describetheexperience(spanthesemanticspace): with psychological sensation but not as capable when collect adequate adjectives, expected by the customer it comes to translating the subjective sensation into from the domain to define the physiological require- design parameters, i.e. real product features influen- ments, e.g. organic, innovative, stimulating, robust. cing the perceived sensation. 3. Define key product properties (span the space of ) fi 5.2. Kansei engineering—from subjective properties : in this phase it is important to nd ’ sensations to design parameters and total physical product properties that affect the users appearance view of the total appearance and experience, e.g. Nagamachi developed the method ‘affective’ or ‘Kan- surface texture anisotropy, surface texture ampl- sei‘ engineering (KE) in the 1970s which has its roots in itude and number of cavities in a surface. the Japanese concept of Kansei: ‘intuitive mental 4. Connect the experience to product properties: by action of the person who feels some sort of impression using qualitative and/or quantitative studies on from an external stimulus’ [28–31]. By using the focus groups, connections between customer framework of KE as an approach and focusing on adjectives (phase 2) and design elements (phase 3) finding correlations between the functions, customer can be made, e.g. organic surfaces possess high requirements, function requirements, design require- texture amplitude and isotropic texture patterns. ments and process requirements, a higher level of user quality and a methodology for soft metrology as 5. Validity check point: when the qualitative correla- tion in step 4 is established, it is important to verify discussed above could be obtained. the results quantitatively by verifying experiments According to Nagamachi, the Kansei concept or virtual simulations, e.g. physical tests on surfaces includes ‘a feeling about a certain something that likely passing the acceptance level of cleanability in will improve one’s quality of life’. KE can also be step 4 all possess a texture mean amplitude less defined as a customer-oriented approach to product than 0.8 μm. development. The basic is that the client’s feelings shall be observed at the phase of idea generation in the 6. Modelling the domain: design and validation of a product development process, which then facilitates ‘prediction model’, e.g. surfaces passing the accep- the project later on when a concept reaches the pro- tance level of cleanability and hygiene in step 4 all duction stage. possess a texture mean amplitude lesser than 0.8 μm Kansei engineering handles six different phases/ and the cleanability increases linearly for mean steps [12, 28–31], starting with the definition of the amplitudes from 0.8 μm to 0.03 μminthedomain products’ domain and context, see figure 7. of steam sterilizers for medical applications.

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A full project ranging over all the six phases of KE able to set high quality core values for a product or ser- will result in a model or prediction of the total appear- vice in a structural way, and faster than before. Instead ance or a limited sector of the total appearance, e.g. of implementing questionnaires, a focus group is par- visual appearance or total appearance of the texture of a ticipating in a physical word game. product within the domain selected in phase 1 of the The ‘word game’ is implemented, sorting out project. Visual appearance is limited to optical factors ambiguous words which do not fit in the domain and of the product appearance while the total appearance context, and grouping words which are considered as of the texture of a product includes visual, haptic and synonyms among the describing words, or words that other sensory aspects of the total appearance of the could be directly connected to each other, e.g. the micro- or nanometre texture experience. words ‘organic’ and ‘natural’ could be clustered with Below in the following sections, the Kansei metho- each other even though they are not synonyms. The dology briefly described generally in the sections above amount of words is reduced during this part of the will be detailed and exemplified with results from cur- project and clusters of belonging words are created. rent and past cases and studies to illustrate the poten- Figure 10 illustrates the last implementation step of tial of an application of affective engineering concepts this phase and an example of word clusters from a on product surfaces. study of building exteriors representing the core values and Kansei words for the building exteriors [32]. 5.3. Phase 1, the pilot study, defining the domain In this phase, it is important to define 5.5. Phase 3, define key product properties product domain and users; define and In this phase it is important to find analyze what, who, where, why, when and physical product properties that affect fi how. In the pilot study, see gure 8, there the user; analyze the properties of the are a lot of questions to be answered and it is crucial to domain; define properties that affect; and fi navigate ef ciently in the right direction from the isolate significant properties. beginning in a development project. Product designers When the identification of the core values and Kan- in general have good internal navigation and relation sei words is made, the next step is to identify properties to the design process, however sometimes the lack of of the existing product that can be controlled and affect communication in a project can result in endless the product towards those core values, i.e. design ele- ‘ discussions of what the aim is for whom. The Design ments. In product design the primary design elements ’ Compass and persona studies as well as mood boards are form (geometry/shape), colour (hue, saturation, are useful Kansei tools and work as external stimuli whiteness and blackness), material (chemical substance and guidelines in the process of affective engineering or raw material, isotropic or anisotropic, structure and fl to facilitate the work ow in order to focus on the strength) and surface (texture ratio, fractal dimension ( primary questions what, who, why, where, when and and directionality, texture amplitude, texture spatial ) how in the pilot study. properties and texture geometrical feature), in accor- dance with ISO 25178-2:2012, see figure 11. 5.4. Phase 2, describe the experience The design elements should be appropriately mea- In this phase it is important to find surable using standardized methods and parameters psychological emotions and expected like the surface texture field, stratified and feature total appearance and perception related parameters in accordance with acknowledged ISO to a product expressed as adjectives, ‘Kansei words’, 25178 series of standards. and grouped in logical clusters (see figure 9). Now, the correlations between the experience and The idea of describing the product experience ‘feeling’ (psychological requirements) and the func- using adjectives is about framing the emotional func- tional requirements (physical requirements) have to tions, i.e. defining the expected perception and total be established as well. For instance, the adjectives clean appearance. To be able to do that there is a need to and hygienic, expressing customer psychological ‘span the semantic space’, collect the expressed ‘emo- requirements for a surface in a medical environment, tions’, by collecting adequate describing words, which are connected to demands on: cleanability thus related the user expresses when interacting within the product to chemical resistance against stains and cleaning domain. By using describing words it is possible to agents; and scratch proofness to withstand negative find appropriate expressions and clusters of Kansei wear and cleaning effects on the surface [33, 34]. words expected to be associated with (and not!) a pro- ASME standard [35] connect today’s requirements of duct designed to evoke an intended perception or hygienic surfaces to texture average arithmetic ampl- ideaesthesia. itude (Ra) according to ISO 4287:1997 and it is con- Today, the collection phase is optimized to be able sidered sufficiently smooth when the Ra value for a to offer a more cost-efficient process and service with a given surface is <0.8 μm [33, 34]. higher quality. The ‘word game’ [12], see figure 10, was Here the ASME standard defines the surfaces’ tex- developed to serve as a physical tool for designers to be ture mean amplitude as the design element controlling

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Figure 8. The ‘Design Compass’ is a tool to help the design team to focus on the primary questions (what, who, why, where, when and how) 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 the mental filtering of the collected adjectives into an amount of core values during a ‘word game’ session. the feeling and psychological requirements on clean 5.6. Phase 4, connect the experience and product and hygienic. Figure 12 is an example of four surface properties By using qualitative studies on focus variants exhibiting different areal texture average groups, connections between Kansei arithmetic amplitudes possessing different levels of words and design elements can be made. cleanability and hygienic properties [33, 34]. An important tool to visualize the con- All surfaces are well below the ASME level on the nection between Kansei words and design elements surface design element mean amplitude defining the contributing to the total appearance is the ‘equalizer’. upper threshold for a hygienic surface from 2009 but For a given domain identified in step 1, the key pro- the influence of other recently standardized surface duct properties (design elements from phase 3) are con- texture properties like anisotropy, fractal dimension, nected to the Kansei words from phase 2, in this 4th step etc, not included in the standard could supply future by, for example, using focus groups (figure 13). more detailed information more sensitive to the In the example below from a study made on the requirements than the mean amplitude averaging domain architectural external building panels [32], the other texture details of the surfaces in figure 12. valuation of the Kansei words was made by 20 people

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Figure 10. A focus group in action using the ‘word game’ (left) [12]. To the right, the ten selected Kansei words highlighted within each of the seven clusters with similar words [32]. on a semantic scale 1–10 for each of the four different measurable surface texture parameters, i.e. the exam- surface textures in figure 14 (left). ple validates the principle that Kansei adjectives can be A useful tool to visualize the correlation between sur- linked to ISO standardized measurable parameters, faces’ appearance with the design elements is the equal- thus defining geometrical features controllable by izer in figure 15, also described in section 3.2 above [12]. manufacturing engineering and possibly to use to spe- The equalizer is a dynamic tool owing to the possi- cify product requirements. bility to visualize the total influence and total appear- ( ance of the combination of design elements the form, 5.8. Phase 6—synthesis and modelling the domain ) material, colour and surface on the selected Kansei The final step is intended to create a words developed in step 2 above. model that combines, refines and describes the results from the previous 5.7. Phase 5, validity checkpoint five phases in the Kansei methodology. When the correlation in thesynthesis in Hence, to assemble a model bridging the emotional step 4 is established, it is important to semantic and product properties’ space. verify the results by statistical tests, In the project with a sauna manufacturer, a design experiments or virtual simulations. manual was made on request of the company. The The validity checkpoint is about an overall valida- design manual basically linked surface geometrical tion of the concept’s total appearance, verifying quan- properties (the significant design elements and prop- titatively the Kansei words from phase 2 and their erties) to the Kansei words according to the results connection to the design elements obtained in phase 4. demonstrated in step 5 above. In practice this resulted Practical testing of concepts is made and quantitatively in designer rules collected in a physical booklet for the evaluated by the correlation of ‘soft’ judgements of context of sauna wall panels, establishing that: Kansei words to ‘hard measurements’ of design ele- ment properties. • A low average roughness (Sa) and low surface slope In affective surface engineering, a connection (Sdq) increase the stylish and attractive emotions of a between Kansei words and surface texture parameters sauna wall texture, describing the micro- and nanotopography is made. • In a study made by the authors on wall panels for hot The same surface combinations together with increased bath sauna interiors [32], three test panels of 10 people texture anisotropy, e.g. a directional pattern, will also with experience from general product development, affect the beautifulness of the surface. specific sauna product development and general sauna bathing, graded the 11 surface textures on a seven This realizes a product development tool for the grade scale against the eight emotional Kansei words sauna company to facilitate the material and surface and three design element-related surface areal texture design of their products connecting to the needs and property parameters from the ISO 25178-2:2006 (see expectations of the customer. table 1). In many cases it is desirable to formulate models The Sq, Str and Sdq parameters (texture average describing quantitatively the relation between design amplitude, texture ratio and texture slope) had a sig- elements and the desired soft metrology Kansei words nificant correlation with the Kansei words beautiful, as a complement to the design manuals with qualita- stylish, and attractive. Here the soft metrology adjec- tive designer rules. In a study [36, 37] in the context of tives are demonstrated to correlate to ‘hard’ metrology tissue paper haptic appearance a complex model was

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

Figure 12. Coherence scanning interferometer measurements of 0.1×0.1 mm areas of three candidate materials for replacing stainless steel (left) for hot-steam sterilizer units. Areal arithmetic mean height amplitude (the Sa parameter) of the surfaces varies from 10 nm to about 0.7 μm—a factor of 70. Reproduced with permission from [34].

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

Figure 14. Left: the microtopography of four surface textures. Right: a graphical valuation of the Kansei words for each of the four surfaces. Reproduced with permission from [32].

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Figure 15. Left: the equalizer is a designer tool to visualize the importance of design elements on the Kansei words. The equalizer to the right with the design elements (horizontal) and the 13 Kansei words (vertical) visualizes a possible importance profile for a given product, i.e. the product’s intended perception. Reproduced with permission from [12]. synthesized using eight constants (A–H), three mat- correlating physical and human factors contributing erial properties (layer type (DL), stiffness, elasticity to products’ appearance images. (stretch)) and four areal ISO 25178 surface texture • Soft metrology allows the objective quantification of properties (peak material volume (Vmp), core height certain properties of perception, in the domain of all (Sk ), maximum height (amplitude, Sz), autocorrela- five senses, i.e. a quantification method for measur- tion length (repeating wave length, Sal)). ing total appearance. ‘perceived haptic roughness’ =-ABDL* • Affective surface engineering using the Kansei method is +++CE***Vmp D Sal Sk effective to connect the expected sensation, using soft +--F*** stiffnessGHSz stretch . metrology methods, to validated design parameters. • Appearance and perception of a product surface’s In the equation above, the product design proper- ties DL, Sz, and stretch have a negative regression coeffi- visual, haptic and other functional requirements like  cient sign, showing that an increase in the parameter visual requirements on external buildings and sauna value results in a decrease in ‘perceived haptic rough- panels and perceived haptic roughness of tissue paper ness’.Thecoefficients for Vmp, Sk and Sal were posi- as well as cleanability of surfaces for the medical tive, hence positively correlated with increased industry can be taken into account using the Kansei ‘ ’ (improved) perceived haptic ‘roughness’,i.e.increased six phase engineering approach. texture peak material volume, core height, autocorrela- • The affective, Kansei surface engineering methodol- tion length and decreased maximum texture height ogy has great potential to help organizations to ’ improve the customers haptic perception of tissue pro- maintain customer focus by allowing industrial ducts within the context of the performed study. designers to understand and model a desired The designer rules and the equation above are perception and total appearance of a product. examples where affective engineering and soft metrol- ogy results are synthesized into tools able to predict The results from the paper discuss a current direc- customer perception and aspects of total experience tion in product development and industrial design ’ supporting organizations possibilities to maintain where surface engineering and the concepts of soft customer focus and competitive advantage. metrology, total appearance and affective, Kansei engineering are combined and exemplified. 6. Conclusions and future Future possibilities to increase the generality and applicability lies firstly in the development of soft The aesthetic and pleasing properties of products are metrology to enable detailed understanding and model- one of the major design dimensions in order to create a ling of the customer perception and total appearance. meaning and relevance of a product. Secondly, the development of software tools sup- The correlation of objective characterization of mat- porting and optimizing the six phases of affective, Kan- erial properties in relation to human response is the sei surface engineering will increase the accessibility of main component in soft metrology, a concept previously and interest in the method, and increase the number of introduced and known, naming the methodology with performed case studies, thus increasing knowledge in the power of enabling affective surface engineering. this emerging research area. Thirdly, there exist a possibility and need of further • Total experience can be used when quantifying research into the development of the word ‘metrology’ in customer satisfaction using soft metrology soft metrology, where multisensorial physical data will be

12 uf oor:Mto.Prop. Metrol. Topogr.: Surf. 4 ( 2016 ) 301BGRosen B-G 033001 Table 1. Correlation table between the sauna Kansei words and surface texture areal parameters according to ISO 25178-2:2006 (significant parameters in bold) defining three design elements associated to the surfaces. Reproduced with permission from [32].

Surface texture Kansei words Average Texture Average slope amplitude 13 Innovative Practical Beutiful Stylish Exiting Reliable Attractive Fresh Sq Str Sdq Innovative 1 Practical –0,7 1 Beutiful 0,0 –0,2 1 Stylish –0,9 0,8 0,4 1 Exiting 0,8 –0,6 0,1 –0,7 1 Reliable 0,9 –0,4 –0,3 –0,8 0,8 1 Kansei words Kansei Attractive –0,7 0,4 0,7 0,9 –0,5 –0,8 1 Fresh –0,9 0,5 0,4 0,9 –0,7 –1,0 0,9 1 Average amplitude Sq 0,5 –0,2 –0,8– 0,8 0,5 0,7 –0,8 –0,7 1 Texture Str –0,2 0,5 –0,9 –0,1 0.0 0,3 –0,5 –0,3 0,7 1 Surface Surface texture Average slope Sdq 0,4 –0,3 –0,9 –0,8 0,3 0,5 –0,9 –0,6 0,9 0,6 1 tal et Surf. Topogr.: Metrol. Prop. 4 (2016) 033001 B-G Rosen et al

linked to human multisensorial perceptual data. Finally, Conf. Design & Emotion (Hong Kong: Hong Kong Polytechnic the question of ‘how and to what level can we quality University, 6–9 October) [ ] ) — assure soft metrology data, and in turn assure the quality 17 Pointer M R 2003 New directions soft metrology ’ requirements for support from mathematics, statistics and of affective, Kansei engineering approaches needs to be software: recommendations for the software support for addressed in future studies. metrology programme 2004–2007 NPL Report CMSC 20/03 (Teddington: National Physical Laboratory) [18] Krynicki J C 2006 Introduction to ‘soft’ metrology: a CIE Acknowledgments challenge of soft metrology 18’th IMEKO World Congress Metrology for a Sustainable Development (Rio de Janeiro, Brazil, 17–22 September) The authors wish to thank the companies A.Zahner [19] Eugéne C 2008 Measurement of ‘total visual appearance’: a cie Company MO USA, Tylö AB Sweden and Getinge challenge of soft metrology 12th IMEKO TC1 & TC7 Joint Sterilization Sweden, for financial support as well as Symp. on Man, Science & Measurement (Annecy, France, 3–5 expert input. 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