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The Use of Interactive Virtual Prototypes for Products Specification in the Concept Design Phase Monica Bordegoni Dipartimento di Meccanica Politecnico di Milano Via La Masa 1, Milano Francesco Ferrise Dipartimento di Meccanica Politecnico di Milano Via La Masa 1, Milano Joseba Lizaranzu Dipartimento di Meccanica Politecnico di Milano Via La Masa 1, Milano ABSTRACT The paper describes the use of interactive Virtual Prototypes (iVP) for the specification of consumer products and for the evaluation of the perceived quality of the product already in its conceptual form. iVPs are based on multimodal interaction including force-feedback and sound in addition to 3D stereoscopic visualization. The fidelity of the prototypes has been evaluated in comparison with the corre- sponding real products, when used for performing the same tests. Differently from the traditional use of Virtual Prototypes, which aims at evaluating the product design, we have used iVPs for the interaction design of a new product, i.e. it has been used as a means to define the design parameters used for the specification of a new product. Index Terms: J.6 [Computer Applications]: COMPUTER- AIDED ENGINEERING—Computer-aided design (CAD); I.3.6 [Computing Methodologies]: Methodology and Techniques— Interaction techniques 1 I NTRODUCTION Product design processes are typically based on cycles including the specification, the design and the evaluation phases. In fact, it is typical that the result of the design phase is tested and analyzed be- fore its approval [5], and this can lead to modifications of the design specification. This process, which may take long time, is crucial to guarantee that the final product is optimal, and consequently that it will have a long and profitable commercial life. The current practice used to evaluate the product design consists of building one physical prototype that is the result of some design choices defined on the basis of market analysis, and performing some tests to evaluate users acceptance and appreciation. The use of Virtual Prototypes (VP) and the exploitation of their flexible dig- ital nature allow us to reverse the process: we can ask a group of users to define their favorite behavior and features, their preferred interaction for a product, through the direct use and test of an early developed virtual prototype, and pass this information to the de- signer, who considers this for the product specification. We are interested in building VPs of consumer products like household appliances, which are interaction in their nature. We name them interactive Virtual Prototypes (iVPs), and can be used as tools for the interaction design of new products. The iVPs do not necessarily have to exactly replicate the physical behavior of the corresponding real products. In fact, it is sufficient that they ap- proximate the behavior of the products-to-be, i.e., they do not have to contain all the components that a real product has, and each com- ponent does not necessarily have to perform in the same way of the real one. What is important instead is that the overall experience of e-mail: [email protected] e-mail:[email protected] e-mail:[email protected] the user concerning the perception of the product main features is realistic and comparable to the real one. It is also important to have flexibility so that users can choose their favorite product features, and also that they can evaluate them by comparing variants. Several research activities have proposed the use of Virtual Pro- totyping for performing studies and analyses on product design [7]. For example, in [4] Santos et al. explore the possibility of using an immersive visualization system for creating a collaborative design review environment. This application, like several other similar [6], shows examples of tasks concerning product evaluation that can be performed when visualization is the unique available communica- tion channel. An effective and more flexible approach for the rep- resentation of the physical interaction with the virtual prototype is provided by the haptic interfaces. The maturity of the haptic tech- nology is not such that a realistic full bare hand interaction with the virtual prototype is already possible, but the technology is indeed evolving quite rapidly, and some satisfactory results have been ob- tained [1, 2]. Another interesting contribution to the use of iVPs is given in the field of sound. Sonic Interaction Design [3] concerns the use of tangible interfaces and interactive sound simulations in the complex activity of sketching and prototyping the sound effects produced during object manipulation. 2 CASE STUDY The case study consists of a commercial washing machine provided by Whirlpool company (www.whirlpool.com). According to the manufactures, customers are used to judge the quality of a product through a direct interaction with some elements like the knob, the drawer and the door. In front of two products with similar prices and technical specifications, and produced by two different man- ufacturers, customers decide to buy a product rather than another on the basis of the perceived quality. Therefore, it is important to understand which features define the perceived quality of a product. We have developed an interactive Virtual Prototype of a specific washing machine, consisting of a 3D stereoscopic representation of the aesthetic appearance, haptic feedback of some interactive elements like door, drawer, knob and buttons implemented using a general purpose 6 DOFs force-feedback device, and sound pro- duced by these elements during use. Figure 1 shows the elements of the washing machine that the user can interact with. 2.1 Implementation The hardware set-up used for the implementation of the virtual pro- totypes is based on commercial VR technologies and is illustrated in Figure 2. The visual environment includes the digital model of the wash- ing machine and of its interactive components. Then it contains an additional element that is the visual avatar of a human hand that changes its shape according to the component the user is touching or grasping, and visually reproduces the posture that a human hand usually takes during the interaction with that specific real element (Figure 1). The haptic effects are obtained as the combination of a limited number of low level force controls. For example, we have included 197 IEEE Virtual Reality 2011 19 - 23 March, Singapore 978-1-4577-0038-5/11/$26.00 ©2011 IEEE

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Page 1: [IEEE 2011 IEEE Virtual Reality (VR) - Singapore, Singapore (2011.03.19-2011.03.23)] 2011 IEEE Virtual Reality Conference - The use of interactive Virtual Prototypes for products specification

The Use of Interactive Virtual Prototypes for Products Specification in theConcept Design Phase

Monica Bordegoni∗Dipartimento di Meccanica

Politecnico di MilanoVia La Masa 1, Milano

Francesco Ferrise†

Dipartimento di MeccanicaPolitecnico di Milano

Via La Masa 1, Milano

Joseba Lizaranzu‡

Dipartimento di MeccanicaPolitecnico di Milano

Via La Masa 1, Milano

ABSTRACT

The paper describes the use of interactive Virtual Prototypes (iVP)for the specification of consumer products and for the evaluation ofthe perceived quality of the product already in its conceptual form.iVPs are based on multimodal interaction including force-feedbackand sound in addition to 3D stereoscopic visualization. The fidelityof the prototypes has been evaluated in comparison with the corre-sponding real products, when used for performing the same tests.Differently from the traditional use of Virtual Prototypes, whichaims at evaluating the product design, we have used iVPs for theinteraction design of a new product, i.e. it has been used as a meansto define the design parameters used for the specification of a newproduct.

Index Terms: J.6 [Computer Applications]: COMPUTER-AIDED ENGINEERING—Computer-aided design (CAD); I.3.6[Computing Methodologies]: Methodology and Techniques—Interaction techniques

1 INTRODUCTION

Product design processes are typically based on cycles includingthe specification, the design and the evaluation phases. In fact, it istypical that the result of the design phase is tested and analyzed be-fore its approval [5], and this can lead to modifications of the designspecification. This process, which may take long time, is crucial toguarantee that the final product is optimal, and consequently that itwill have a long and profitable commercial life.

The current practice used to evaluate the product design consistsof building one physical prototype that is the result of some designchoices defined on the basis of market analysis, and performingsome tests to evaluate users acceptance and appreciation. The useof Virtual Prototypes (VP) and the exploitation of their flexible dig-ital nature allow us to reverse the process: we can ask a group ofusers to define their favorite behavior and features, their preferredinteraction for a product, through the direct use and test of an earlydeveloped virtual prototype, and pass this information to the de-signer, who considers this for the product specification.

We are interested in building VPs of consumer products likehousehold appliances, which are interaction in their nature. Wename them interactive Virtual Prototypes (iVPs), and can be usedas tools for the interaction design of new products. The iVPs donot necessarily have to exactly replicate the physical behavior ofthe corresponding real products. In fact, it is sufficient that they ap-proximate the behavior of the products-to-be, i.e., they do not haveto contain all the components that a real product has, and each com-ponent does not necessarily have to perform in the same way of thereal one. What is important instead is that the overall experience of

∗e-mail: [email protected]†e-mail:[email protected]‡e-mail:[email protected]

the user concerning the perception of the product main features isrealistic and comparable to the real one. It is also important to haveflexibility so that users can choose their favorite product features,and also that they can evaluate them by comparing variants.

Several research activities have proposed the use of Virtual Pro-totyping for performing studies and analyses on product design [7].For example, in [4] Santos et al. explore the possibility of using animmersive visualization system for creating a collaborative designreview environment. This application, like several other similar [6],shows examples of tasks concerning product evaluation that can beperformed when visualization is the unique available communica-tion channel. An effective and more flexible approach for the rep-resentation of the physical interaction with the virtual prototype isprovided by the haptic interfaces. The maturity of the haptic tech-nology is not such that a realistic full bare hand interaction with thevirtual prototype is already possible, but the technology is indeedevolving quite rapidly, and some satisfactory results have been ob-tained [1, 2]. Another interesting contribution to the use of iVPs isgiven in the field of sound. Sonic Interaction Design [3] concernsthe use of tangible interfaces and interactive sound simulations inthe complex activity of sketching and prototyping the sound effectsproduced during object manipulation.

2 CASE STUDY

The case study consists of a commercial washing machine providedby Whirlpool company (www.whirlpool.com). According to themanufactures, customers are used to judge the quality of a productthrough a direct interaction with some elements like the knob, thedrawer and the door. In front of two products with similar pricesand technical specifications, and produced by two different man-ufacturers, customers decide to buy a product rather than anotheron the basis of the perceived quality. Therefore, it is important tounderstand which features define the perceived quality of a product.

We have developed an interactive Virtual Prototype of a specificwashing machine, consisting of a 3D stereoscopic representationof the aesthetic appearance, haptic feedback of some interactiveelements like door, drawer, knob and buttons implemented usinga general purpose 6 DOFs force-feedback device, and sound pro-duced by these elements during use. Figure 1 shows the elementsof the washing machine that the user can interact with.

2.1 ImplementationThe hardware set-up used for the implementation of the virtual pro-totypes is based on commercial VR technologies and is illustratedin Figure 2.

The visual environment includes the digital model of the wash-ing machine and of its interactive components. Then it contains anadditional element that is the visual avatar of a human hand thatchanges its shape according to the component the user is touchingor grasping, and visually reproduces the posture that a human handusually takes during the interaction with that specific real element(Figure 1).

The haptic effects are obtained as the combination of a limitednumber of low level force controls. For example, we have included

197

IEEE Virtual Reality 2011

19 - 23 March, Singapore

978-1-4577-0038-5/11/$26.00 ©2011 IEEE

Page 2: [IEEE 2011 IEEE Virtual Reality (VR) - Singapore, Singapore (2011.03.19-2011.03.23)] 2011 IEEE Virtual Reality Conference - The use of interactive Virtual Prototypes for products specification

(d)(c)

(a) (b)

Figure 1: Interaction components of a washing machine: a) thedrawer b) the knob c) the buttons d) the door.

Visualization

Sound

Haptic

Tracking

Figure 2: Hardware setup composed by: a rear-projected wall dis-play Cyviz, a six DOF haptic device by Haption, a wireless headsetsystem and an optical tracking system by ARTracking

two small blocks, that are not visually rendered, in order to simulatethe rotational limits of the door hinge in the doors of the washingmachine, and the translational limits of the drawer by returning acollision. In order to reproduce the clicks of the door opening andclosing, we have used some local effort gradients. Regarding theknob the force effect that is returned to the user’s hand is the sumof a continuous torque, that replicates the real dynamic friction onthe hinge, and some forces that are in an opposite direction withrespect to the motion that replicates the clicks.

Sound effects have been added to the simulation of the washingmachine. In order to simplify the interaction with the interactivecomponents, we have introduced the snapping effect. The idea is toautomatically attach the virtual hand to a physicalized object whenthe user is very close to it.

2.2 Test of the fidelity of the Virtual Prototype

After implementing the iVP, we have considered the necessity ofevaluating its fidelity in terms of interaction effects, in compari-son with the corresponding real product. Therefore, we have per-formed a test involving ten persons (8 male and 2 female, of age20-35). The participants were asked to compare the following ef-fects between the ones performed by the real and the virtual wash-ing machine in terms of realism: 1) haptic response of buttons; 2)knob click-effect; 3) knob torque; 4) door weight; 5) door click-effect when closing; 6) drawer weight; 7) drawer click when clos-ing. They filled in a questionnaire, by using scores from 1(bad) to6(good) to evaluate the various aspects.

Table 1 reports the results of the test. The effect that appears tobe less realistic is the one related to the buttons, while those relatedto the door and the drawer have reported high scores. Regarding theknob, the click-effect is perceived as being similar to the real one,while it does not happen for the torque.

2.3 Design of the interaction haptic effects

The iVPs do not only allow us to test different product design solu-tions, but they also allow users to directly set and modify interactioneffects that can be then mapped into specification for the design. Sothey allow us to design the interaction haptic effects of the product.

Table 1: Comparison of real and virtual perceived effects on the iVP

Element Average Median Min Max Standard

Deviation

Buttons 3.1 3 2 5 0.85

Knob Clicks 4.4 4.5 3 5 0.70

Knob Torque 3.6 3.5 2 5 0.97

Door Weight 4.0 4 3 5 0.67

Door Clicks 4.6 5 4 5 0.52

Drawer Weight 4.3 4 3 5 0.67

Drawer Clicks 4.6 5 3 6 0.84

For example, the interaction effects of the knob are obtained asa continuous torque, some localized force effects that return to theuser the click-like effect, plus a sound connected to the click. Thetorque and the clicks, as well as the sound connected, are actu-ally the result of a dynamic friction and of some collisions in thereal physical object. In the example of the knob, the user can askto change the effects using simple expressions like, ”I would likestronger reaction when turning the knob”, or ”I would like lessclicks for the knob when selecting the washing programs with theknob, and with a louder click-sound”.

3 CONCLUSIONS

The paper has presented the development and use of interactive Vir-tual Prototypes for the specification of consumer products. Duringthe tests with users, the force feedback effects of the product com-ponents can be easily modified according to users’ requests andpreferences. We have performed two kinds of tests: the first hasbeen used to check the fidelity of the virtual prototype, i.e. theeffects of the moving components when operated by the user aresimilar to the real ones; in the second test the iVP has been used tocollect the effects preferred by the users, which have been used todefine the specification of the optimal product.

During the experimental tests we have noticed that the intrusive-ness of the haptic device affects the quality and the naturalness ofthe interaction. This problem will be solved in the future by pro-ducing a rapid prototype of the exact shape of the component (forexample the drawer), and by mounting it on the haptic system asend effector.

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