Ziwen Jiang

Monojit Bag

Lawrence A Renna

Seung Pyo Jeong

Vincent M Rotello

D Venkataraman

Aqueous-Processed Perovskite Solar Cells Based on Reactive Inkjet Printing

We report a one-step method for aqueous-processed perovskite active layer via reactive inkjet printing (RIJ) technique. The perovskite was successfully applied to fabricate solar cell devices. This is to the best of our knowledge, the first time that the RIJ technique is demonstrated in the fabrication of perovskite solar cells.

I. INTRODUCTION Perovskite solar cells have been extensively

developed in the recent five years due to their high efficiency, solution processability and low-cost [1][2][3][4][5]. Notably, the rapid progress of perovskite solar cells in terms of power conversion efficiencies (PCEs) has already approached a comparable level of traditional polycrystalline silicon solar cells [6]. Hence, there is a need for manufacturing techniques to bring this academic frontier to industrial applications. The fabrication of such highly efficient solar cells typically contains a mesoporous metal oxide (e.g., TiO 2 or ZrO 2 ) layer to facilitate the electron transport [7]. However, the mesoporous layer requires high a temperature sintering process, slowing down the production and increasing the manufacturing cost. Recently, planar heterojunction (PHJ) perovskite solar cells have shown high PCEs without the need for a metal oxide layer [8,9]. These PHJ devices have a similar layout as organic photovoltaics and inherently feature high flexibility and low-temperature processability [10,11]. Such devices demonstrate the possibility of roll-to-roll (R2R) fabrication of perovskite solar cells. Inkjet printing is a R2R compatible technology and has been applied mainly as a deposition tool in organic electronics [12][13][14][15]. Currently, spin coating [16], drop casting [17], and dip coating [18] are the dominant approaches for active layer fabrication of perovskite solar cells on laboratory scale. However, these methods are not compatible with large-scale manufacture. Inkjet printing offers a low-cost approach where functional materials are deposited only on desired areas [19]. Besides direct patterning capability, the scalability and reproducibility features of inkjet printing have made the technique an attractive scaffold to develop the manufacturing process of solar cells [20]. Very recently, inkjet printing was introduced to the fabrication of perovskite solar cells. In one example, Song and coworkers used inkjet printing to deposit the perovskite precursor mixture (CH 3 NH 3 I and PbI 2 ) on a mesoscopic TiO 2 film to prepare the perovskite layer [21]. A PHJ perovskite solar cell was also demonstrated on spin-coated PbI 2 surfaces by inkjet printing, employing CH 3 NH 3 I and carbon black mixture as the ink material [22]. There are still lingering issues with inkjet printing of perovskite solar cells. A common problem is the clogging of the nozzle [23] arising from the poor solubility of the materials in solvents suitable for inkjet printing. Moreover precursor materials for fabricating perovskites have a good solubility in limited choice of solvents such as typically N,Ndimethylformamide (DMF)], while are not preferred solvents for large scale manufacturing process [24,25]. To overcome these drawbacks, we chose to combine water-soluble perovskite precursors with reactive inkjet printing (RIJ) technique [26]. RIJ has been previously applied to prepare metallic materials [27], polymers [28] and nanoparticles [29]. The technique allows the in situ synthesis of functional materials at specific locations on the substrates, simplifying the fabrication process [30]. During the RIJ process, reactive inks (reactants) are separately deposited on the same spot. Thus the reaction between the precursors proceed after the inkject printing and not within the nozzle, thus avoiding any nozzle clogging issues if the product precipitates [31]. Herein, we report a one-step method for aqueousprocessed perovskite active layer via reactive inkjet printing technique. In this strategy, we used a multichannel inkjet printer to separately deposit lead(II) acetate trihydrate [Pb(OAc) 2 •3H 2 O] and methylamonium iodide (CH 3 NH 3 I) on the same spot of solid substrates (Figure 1a). Pb(OAc) 2 and CH 3 NH 3 I aqueous solutions were used as reactive inks to form the perovskite layer. The perovskite formation was further confirmed by structural characterizations and successfully applied to perovskite solar cell devices. This is to the best of our knowledge, the first time that the RIJ technique is demonstrated in the fabrication of perovskite solar cells.

II. METHOD

Lead(II) acetate was purchased from Sigma-Aldrich Co. LLC. Methylammonium iodide was purchased from 1-Material Inc. Isopropanol (99.9%) was purchased from Fisher Scientific. All the materials were used without further purification. Water was obtained from Mili-Q system.

For our studies, we used an Epson Artisan 50 Inkjet Printer as the multichannel printer model. The printer has been demonstrated with a precise CMYK-based control in previous reports [32,33]. Pb(OAc) 2 ink was prepared at a concentration of 60 mg•mL -1 and loaded into the magenta channel as the lead source. CH 3 NH 3 I ink was prepared at a concentration of 90 mg•mL -1 and loaded into the yellow channel as the organic cation source. The solvent for both of the reactive inks was a mixture of water and isopropanol (v/v = 1:1). Other channels were loaded with blank solution (water or isopropanol). The color combination was set at a 1 to 1 mixture of magenta and yellow so that the molar ratio of two precursors were approximately kept at 1:3 [Pb(OAc) 2 to CH 3 NH 3 I] [34,35]. The reactive RIJ was carried out at ambient conditions with a five-minute annealing at 100 °C after the printing process. The printed patterns are shown in Figure 2. The perovskite layer was characterized using scanning electron microscopy (SEM), powder Xray diffraction (PXRD) and atomic force microscopy (AFM). The SEM was operated on a Magellan 400L XHR-SEM with an accelerating voltage of 2.0 kV and currents of 13-25 pA. The inkjet-printed Pb(OAc) 2 film was pretreated with 40-s gold coating to get focused images. PXRD were measured using a PANalytic X'Pert 3 X-ray diffractometer having a Ni filter, 1/2 in. diverging slit, vertical goniometer, and X'Celerator detector. Samples on glass slides were scanned from 2θ = 5°-60° under Cu Kα (1.542 Å). AFM was carried out using an Asylum Research MFP-3D-SA AFM with samples printed on silicon wafers. Pre-cleaned ITO substrates were treated with UV/O 3 (UVO Cleaner, Model 342, Jelight Company, Inc.) for 15 minutes. Subsequently, a layer of PEDOT:PSS was spin-coated at 3000 rpm for 60 seconds (G3P-8 Spin Coater, SCS) after filtering through a 0.45-µm PVDF filter (Millex, EMD Milipore) under ambient conditions. The resulting substrates were then annealed in air for 30 min at 150 °C and cooled down to room temperature. The annealed coated substrates were then applied to UV/O 3 treatment for 3 minutes. The RIJ of reactive inks was carried out afterwards. Next, a solution of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was prepared in chlorobenzene at a concentration of 20 mg•mL -1 and then spin coated on the as-printed substrates at 1000 rpm for 60 seconds. Afterwards, Ca and Al was thermally deposited at a pressure of 1×10 -6 mbar (Figure 1b).

III. RESULTS

From the optical images (Figure 3), a distinct color change from yellow to brown was observed after the 5-min thermal annealing of RIJ film, indicating perovskite formation. From the SEM images (Figure 4), we can clearly observe the crystallization resulted from the RIJ process compared to the individually printed inks. The perovskite crystals ranged from 1 to 2 µm. AFM results revealed a wire-like morphology of the RIJ-perovskites. (Figure 5). Further structural analysis on the RIJ-processed perovskite layer was obtained from PXRD results. A complete conversion of Pb(OAc) 2 was observed, however there has presence of iodoplumbate complexes [36] observed (2θ = 11.4°) in the blue trace in Figure 6. There is a large peak at 2θ = 13.9° which is attributable to the (101) tetragonal CH 3 NH 3 PbI 3 (I4cm) phase. Figure 6. Powder XRD spectra of reactive inkjet printing-processed perovskite and inkjet-printed precursors.

Finally, we measured the device efficiency containing the RIJ-processed perovskite material as the active layer. The measurement was done under AM1.5G solar simulator at 100 mW•cm -2 light intensity with a scan rate of 250 mV•s -1 . A high reproducibility was observed from the device performance. The best device with a RIJ-processed perovskite layer showed V oc = 0.50 V, J sc = 4.28 mA•cm -2 , FF = 44.4% and PCE = 0.94% (Figure 7a), showing a successful fabrication approach to perovskite solar cells based on RIJ technique. Relatively low efficiency was observed due to very thin and non-uniform perovskite layer with wirelike morphology on PEDOT:PSS coated ITO substrate. Further, PEDOT:PSS is partially soluble in aqueous medium and could be effected during RIJ process. Therefore, further optimization such as precursor ink-formulation, ink concentration, substrate properties, surface treatment and substrate temperature is required to improve the uniformity and thickness of the film to get desired solar cell efficiency from this environmental friendly aqueous processing of RIJ technique. To compare with the conventional inkjet printing of perovskite solar cells from organic solvent, we have also fabricated perovskite active layers from N,Ndimethylformamide (DMF) solvent having maximum efficiency of 3.73% (Figure 7b) but with very low reproducibility. The major challenge faced during organic solvent based inkjet printing other than toxicity issue is the printer head clogging and damage even at room temperature. Choice of hole or electron transport layer (it should not get dissolved in aqueous medium but is compatible to solution processing such as NiO x [37] or CuO [38]) would therefore be very important to fabricate uniform pin-hole free perovskite active layer from RIJ technique. It is also compatible to combinatorial screening of organic cations during film formation [33].

IV. CONCLUSION

We have successfully demonstrated a simple and environmental friendly reactive inkjet printing approach to fabricate highly reproducible perovskite solar cells. The perovskite material was processed using aqueous solutions of perovskite precursors from multi-channel commercial ink-jet printer at ambient condition. This method is potentially useful to facilitate a rapid screening for the optimal stoichiometry between lead source and organic cation. Moreover, it provides a R2R compatible way to fabricate perovskite solar cells.

Figure 1 .

 1 Figure 1. (a) Schematic illustration of the fabrication of perovskite material using reactive inkjet printing technique. (b) Schematic illustration of the solar cell structure.

Figure 2 :

 2 Figure 2: Screenshot of designed pattern for fabricating RIJ-processed perovskite layers.

Figure 3 .

 3 Figure 3. Optical images of as-printed film and the perovskite conversion after thermal annealing. The white scale bar is 5 mm.

Figure 4 .

 4 Figure 4. Scanning electron microscope images of (a), (b) RIJ-processed film; (c), (d) inkjet-printed Pb(OAc) 2 film; (e), (f) inkjet-printed CH 3 NH 3 I film. The white scale bar is 1 µm.

Figure 5 .

 5 Figure 5. 3-D Tapping mode AFM image of RIJperovskite film revealing a wire-like morphology.

Figure 7 .

 7 Figure 7. Current-voltage curve of a perovskite solar cell containing perovskite layer fabricated by (a) reactive inkjet printing; (b) sequential inkjet printing of lead(II) iodide in DMF and methylammonium iodide/formamidinium iodide in isopropanol.

ACKNOWLEDGEMENTS

This work was supported as part of Polymer-Based Materials for Harvesting Solar Energy, an Energy Frontier Research Centre funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0001087. V.M.R. acknowledges support from the NSF (CHE-1307021).


Andreas Fischer

Sara Grimm

Valentine Bernasconi

Angelika Garz

Pascal Buchs

Maurizio Caon

Omar Abou Khaled

Elena Mugellini

Franziska Meyer

Claudia Wagner

Nautilus: Real-Time Interaction Between Dancers and Augmented Reality with Pixel-Cloud Avatars

Keywords: Dance Performance, Augmented Reality, Human Machine Interaction, Kinect, Unity Danse, Réalité Augmentée, Interaction Homme-Machine, Kinect, Unity

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

A dance performance can be easily considered as a multidisciplinary project. Beyond the well known combination between movements and music, a dance performance can involve a variety of audio-visual elements such as sound effects, light effects, and visual projections. These technological elements used in the production of the dance performance allow to create a specific environment, corresponding to an artistic vision, and their use is the foundation of a great interdisciplinary collaboration: a collaboration between art and technology.

A prominent example of such collaborations is the dance performance Variations V (1965) by John Cage and Merce Cunningham. It featured twelve 5-foot-high antennas equipped with photocells that reacted on the proximity and the shadows of the dancers to trigger sound effects based on dozens of mixed tape recorders and radios [START_REF] Miller | Cage, Cunningham, and Collaborators: The Odyssey of Variations V[END_REF]. Thus, the dancers created their own sound by moving on the stage. Visual el-ements of the show included distorted television images by Nam June Paik and films of the dancers shot by Stan VanDerBeek during rehearsal that were projected onto a large screen in the back. This visionary performance from the 1960s can be seen as an example for interactive augmented reality, in a broad sense. The live dance was augmented with virtual elements, viz. the electronic sounds triggered by the sensors and the visual projection.

The mutual benefits arising from a partnership between art and technology can best be described in the words of Swedish research scientist Billy Klüver from Bell Labs, who designed the photocells for Variations V. He was one of the co-founders of the organization Experiments in Art and Technology (E.A.T.) that facilitated an encounter between the two disciplines. In 1995, Klüver explained in an interview that the "goal from the beginning was to provide new materials for artists in the form of technology" [1, p. 8], highlighting the fundamental benefit for artists to engage in such collaborative efforts. Regarding the scientists, he states that the "engineer expands his vision and gets involved with problems which are not the kind of rational problems that come up in his daily routine. And the engineer becomes committed because it becomes a fascinating technological problem that nobody else would have raised" [1, p. 9].

The past decades have brought us many great dance performances that were created in similar spirit, integrating new technology as it emerged. For a survey, we refer the reader to [START_REF] Dixon | Digital Performance: A History of New Media in Theater, Dance, Performance Art, and Installation[END_REF]. One of the most profound changes has been the digital revolution that has facilitated processing sensor data as well as audio-visual media by means of computers, thereby often creating digital works of art in their own right.

Real-Time Interaction: A New Material

Nowadays, with increasing computational power, it is possible to conduct a live analysis of sensor data and to create real-time computer graphics and audio based on commodity hardware. Also, most of the technological equipment can be hidden during shows when employing remote sensing or wearable sensors together with offstage computers. An example from the recent past is the dance performance Hakanaï (2015) by Adrien Mondot and Claire Bardainne.

A dancer is surrounded by a transparent cube, on which real-time computer graphics are projected that interact with the dancer. The visualization follows physical principles and artfully combines real and virtual elements on stage.

The real-time connection between the physical and the digital world is a relatively new material for artists to work with. It differs fundamentally from a synchronization between dancers and pre-recorded media. Instead of focusing on a perfect synchronization between dance and music, or dance and visualization, it allows the dancers to improvise, to affect their environment, and to react again on the change in environment. This principle of closed-loop feedback is illustrated in Figure 1. Note that other senses of the dancers could be stimulated as well. An interface to virtual reality could also convey touch and smell, which would allow the dancer to react more intuitively on a virtual environment. But this kind of technology is still in its beginnings.

The Nautilus Project

In this paper, we present an explorative study on real-time interaction with augmented reality for dance performances.

The project extended over one year and resulted in the performance Nautilus in 2016. Our aim was to explore this new material with a strong focus on the artistic point of view with the help of scientists who built prototypes based on currently available technology.

The system we have developed is based on digital avatars of the dancers in form of pixel clouds that are embedded in a virtual reality. The avatars correspond to a real-time 3D scan of the dancers with a depth sensor and are projected in exact scale on a transparent tulle (a mesh fabric) between the dancers and the spectators (cf. Figure 2). Both the dancers and their life-size avatars are cast in an underwater world, where they interact with plankton in the water. By changing the intensity of the stage light, we create a transition between the real and the virtual world for the spectator, thus exploring the whole spectrum of mixed reality [START_REF] Milgram | A Taxonomy of Mixed Reality Visual Displays[END_REF].

In the following, we discuss the multidisciplinary collaboration that led to this performance, present the technical solution in more detail, describe the performance and its reception, and conclude the paper with lessons learned and an outlook to future work.

A Collaboration Between Art and Technology

An encounter between artists and scientists means to bring together two cultures that differ in language but are closely connected in the spirit of creating new things. Our experience was that this kind of collaboration has radiated a special fascination in both fields and has quickly attracted the interest of over a dozen students and professors from three universities in Switzerland, namely the University of Applied Sciences and Arts Western Switzerland (HES-SO) in Fribourg, the University of Fribourg (UniFR), and the Bern University of Arts (HKB).

From the outset, the project was guided by the artistic vision, that is science provided a service to art in form of new technology. Following this procedure, we hoped to avoid a situation where the dance performance would only be a vehicle to show off the technology.

Work Process

We developed the performance in two phases. At the beginning, the general theme of an underwater world was defined such that all teams could get started. Over a period of several months, we investigated suitable sensor technologies and designed the visualization. At the same time, the choreographer explored the theme of an underwater world with her dancers by developing cells of movement. She was repeatedly invited to the scientists' lab, where prototypes were presented to her. Finally, she selected a promising approach that was installed at the dance school.

In the second phase, which encompassed a few weeks, the prototype was explored in practice together with the dancers. The dancers played with the virtual world and developed dance sequences, which in turn resulted in new requirements for the augmented reality. It was intriguing to observe how the virtual world was transformed into some-thing completely new during these trials. The pixel-cloud avatars, for example, were not planned but discovered by accident. Their original purpose was to serve as invisible proxies of the dancers in the virtual world to facilitate the interaction. But when we saw the avatars displayed in lifesize during a trial, we were amazed by their physicality and expressive power. Eventually, they became a central part of the Nautilus performance.

Aligning the work processes of artists and scientists was rather demanding. As the augmented reality and the choreography are strongly linked together, they have to be changed together. Sometimes even a small change in the software creates completely new artistic possibilities. Therefore, it was important to ensure that, at some point, the augmented reality converges towards a stable design, which the artists can rely on and work with.

Towards Real-Time Interaction

One of the most crucial aspects of real-time interaction is the appropriate choice of sensors and interaction methods. At the beginning of the project, the scientists focused on real-time tracking of the dancers' skeleton, that is identifying their head, hands, feet, etc. for interacting with a virtual world, which is the standard approach. However, the choreographer rejected this solution as too restrictive. When attempted with a camera, 1 the dancers had to be in a nearly frontal position for the camera tracking to work properly; it became unstable as soon as they began to move and turn freely on stage, especially when dancing close to the floor. We have also investigated wearable sensors, 2 yet -despite being small -they felt too invasive for the dancers. Further- more, they were not well suited to track the exact position on stage, which at that time was already an important part of our virtual world.

To provide the dancers with the desired artistic freedom, the request of the choreographer was to take into account the entire bodies of the dancers for the augmented reality, instead of reducing them to their skeleton. It is thanks to these kind of challenges set by the artistic expectations that the scientists had to explore new approaches, which is an example for the great benefits art can have on technology. The suggested solution is an interaction based on a depth sensor and pixel-cloud avatars as illustrated in Figure 2.

Avatars Based on Pixel Clouds

It shows a dark room with a tulle between the dancer and the spectator, on which a violet avatar of the dancer is pro-jected in life-size with a projector facing the spectator. The avatar consists of thousands of 3D pixels captured with the infrared-based depth sensor of a Kinect camera, which is positioned on the floor facing the dancer.

The avatars are embedded in a virtual environment that has been created with the Unity game development platform. They are cast in a virtual underwater world, where they are surrounded by moving plankton (see Figure 3) following physical buoyancy effects. Synchronised in real-time with the dancers, the whole body of the avatar collides with the plankton, which is the principal interaction in the Nautilus performance.

Technically, it has not been trivial to achieve real-time performance based on thousands of colliding pixels. In order to speed up the process, the space is tessellated with small cubes, which are activated when accumulating enough pixels. Upper and lower thresholds are considered to avoid flickering effects. When activated, point force effectors are triggered to repel the plankton, which is moving in a 2D plane. Based on the same principle of counting the number of pixels in virtual cubes, we have also defined larger areas on the stage to trigger certain effects, such as sound effects or changing the stream direction of the plankton. The runtime performance of the system was about 25 frames per second, which led to fluid movements of the avatars in close synchronization with the dancers.

Artistically, the solution based on avatars has provided the dancers with full freedom of movement. They can interact with the plankton and the virtual areas using their whole body in any pose. Even objects become part of the avatar representation when brought on stage. In order to react on their audio-visual environment, the dancers receive auditive feedback when triggering sounds and visual feedback projected on the tulle. Clearly, the auditive feedback is easier Although individual dancers are not explicitly distinguished in the tracking, their identity is clearly visible. The pixel cloud is dense enough such that even fingertip movements are observable in the virtual world. Therefore, the dance movements are also well observable when the stage lights are off and only the avatars are shown in the virtual underwater world. By adding stage light, the virtual reality disappears gradually and makes room for the real dancers.

Stage Setting

In Figure 4, our stage setting is illustrated with the tulle separating dancers and spectators. A stage of about 5m x 6m can be covered in large parts with a single Kinect camera 3accepting occasional occlusion when one dancer is moving in front of the other. The Unity application is running on a commodity laptop offstage. 4 A wide-angle projector is facing the spectators. There is a sporadic blinding effect when a plankton moves between beamer and eye, yet this setup has the advantage that the plankton is also projected into the room of the spectators, on their clothes, the floor, and the walls, which may increase the effect of immersion. Blue stage lights are used to match the colors of the real world to the virtual world.

Although the virtual reality could have been integrated fully automatically, we decided to let someone activate the different phases of the performance manually. One of the main reasons was to let the dancers know that there is a human in control who can help if there are problems.

The Performance

Named after the submarine from Jules Verne's novels, the Nautilus performance aims to immerse the spectators in a world deep under the sea. It explores the borders and transitions between reality and virtuality, merging them together at times to create something in-between.

The different phases of the eight-minute performance can briefly be described as follows. The show starts in a dark room. Diffuse water sounds are played without discernible rhythm and the plankton appears one by one slowly on the tulle. After some time, the dancers enter the stage from the back and their avatars perform an improvised dance amidst the plankton. The lack of meter in the music emphasizes the real-time interaction with the plankton. Gradually, the stage light is turned on and the avatars fade out, leaving the real dancers surrounded by virtual plankton. A stream begins to move the plankton and the dancers perform a 55 55 alt.IHM 25-28 oct. 2016, Fribourg, Suisse synchronized dance to the composition Mad Rush by Philip Glass. Afterwards, the water sounds recommence and the avatars fade in again, mirrored. For a while, the dancers swim against their virtual selves. Finally, the light is gradually turned off and the avatars disappear one by one to the side, alongside with the plankton.

After the performance, the spectators have the chance to explore the Nautilus environment themselves. As soon as they go behind the tulle, their own avatar appears and allows them to interact and play with the plankton.

Reception

Nautilus was performed in the context of the HKB music and movement summer festival 2016 in Biel. We have distributed questionnaires after the show to obtain feedback from the spectators. 34 spectators (18 women, 16 men) with an age between 18 and 66 years returned the questionnaires. Several brief questions were answered with scores between 1 (not agree at all) and 5 (fully agree).

There was also the possibility to provide general feedback, which was for the most part very positive and encouraging.

In the following, numbers in brackets indicate median scores over all answers. When asked if the virtual world or the real world were too intrusive, the answer was in both cases a clear no [START_REF] Candy | Explorations in Art and Technology[END_REF]. The spectators felt that the real and the virtual world complemented each other (4). The quality of the dance movements was well visible in the virtual world (5) and the interaction between the dancers and the virtual world was understandable (4). However, the elements of the virtual reality were not convincingly similar to reality (3). This last point was also criticized in two general comments.

Although the plankton moved according to physical principles, it seems that it could not fully convince as plankton movement underwater.

Conclusions

The collaboration between art and technology has been highly rewarding both for the artists, who could work with a new material on stage, and for the scientists, who were challenged by the artistic expectations. The suggested interaction method based on pixel-cloud avatars was quite successful and has proven to be very reliable even when multiple dancers were moving freely on stage. The spectators could become performers as well when testing the system after the show. Without the need for training, they could interact with the system using their whole body and created, among others, a sort of multiplayer game.

An important lesson learned from our multidisciplinary collaboration is that the practical work with the artists is crucial for the design of the virtual world. Some of the main elements of the Nautilus environment, including the pixel-cloud avatars, were not created in the scientists' lab but instead during the practical trials together with the dancers. Another lesson learned is that even small changes in the software can lead to completely new artistic possibilities. Therefore it is important to fix ideas at some point and let the artists work with a relatively stable environment.

Future work includes the development of other dance performances based on Nautilus by creating new virtual worlds for the avatars. Clearly, there is a wide range of artistic visions that can be developed around this technology. One of the main constraints of the current approach is the dancers' difficulty of registering their own interaction with the virtual world when they are concentrated on the dance movements and cannot watch the visualization. Therefore, we plan to add a stronger focus on auditive feedback for the dancers in future projects. With future technology, it might even become possible to feel virtual sand under one's feet and smell a virtual ocean breeze.

Figure 1 :

 1 Figure 1: Real-time interaction; dancers and their audio-visual environment are in a closed feedback loop.

Figure 2 :

 2 Figure 2: Avatar (magenta) with plankton (white) in the Nautilus environment; projected onto a tulle that separates the dancers from the audience.

Figure 3 :

 3 Figure 3: Drawing of a plankton.

  oct. 2016, Fribourg, Suisse to process for the dancers, as they get only glimpses of the visualization while moving. Therefore, an external observation and guidance has been crucial for the development of the performance.

Figure 4 :

 4 Figure 4: Stage setting.

Figure 5 :

 5 Figure 5: Two avatars catching plankton together; spectators experimenting with the Nautilus environment after the show.

We tested Microsoft Kinect cameras, versions 1 and

2, with infraredbased depth sensor.2 Perception Neuron units with integrated gyroscope, accelerometer, and magnetometer.

To cover such a large stage, we needed to use Kinect version 2.

We used a laptop with 2.16 GHz CPU and 8 GB RAM.


Ricardo Codinhoto
email: r.codinhoto@salford.ac.uk

Arto Kiviniemi
email: a.kiviniemi@liverpool.ac.uk

BIM for FM: A Case Support for Business Life Cycle

Keywords: BIM, FM, Building Information Modelling, Facilities Management, Lifecycle Information Management

Relatively little information exists about the use of BIM in the operation and maintenance of buildings. Reported cases of BIM adoption to support facilities management and lifecycle management reveals that the implementation of BIM for FM processes is, in general, limited to an experimental scale. Even large public owners who have been using BIM for managing their construction projects have not implemented it into their FM activities. Therefore, there is little evidence of the benefits of BIM in the operational phase. In addition, the challenges involved in shifting from traditional FM processes to new BIM-based processes are not well known. In this paper we document some of the issues involved in the adoption of BIM in FM and identify some applications, metrics and benefits related to its adoption. The findings are based on a case study carried out within a major re-development project in Manchester, UK. Results indicate a step rise in the level of awareness regarding potential benefits of BIM in FM activities and lifecycle information management.

FM and Product and Service Life Cycle

Modern Facilities Management (FM) conceptualisation recognises the importance of FM within the business life cycle. Traditionally, the FM function was widely described as involving clients, real estate and AEC teams, all planned around a cost factor to be spent on non-value adding activities such as the maintenance and cleaning of a building, and the provision of support services such as reprographics, reception, stationery [START_REF] Thomson | The essence of facilities management[END_REF], [START_REF] Tay | Facilities management: a 'Jack of all trades[END_REF]. This view has changed considerably. For example, for the British Standards Institute (BSi) FM refers to "the integration of processes within an organisation to maintain and develop the agreed services that support and improve the effectiveness of its primary activities" [START_REF]Facility Management -Part 1: Terms and definitions: BS EN[END_REF]. The Institute of Asset Management (IAM) PAS 55-1:2008 also emphasises the importance of FM to the life cycle of products and services.

The effectiveness of many organisations is certainly dependent on the way its facilities are managed. Effectiveness can be measured in different ways that maintain strong links with the mission, goals and objectives of the organisation, the influence of its stakeholders [START_REF] Alexander | Facilities Management : Theory and Practice[END_REF] and the profit in its operations. To succeed, businesses must recognise that the rising cost of occupying buildings, providing services to support operations and improving working conditions are fundamental factors impacting the business life cycle. As such, business pressures to improve quality, reduce cost and minimize risks continue to drive FM decisions [START_REF] Alexander | Facilities Management : Theory and Practice[END_REF]. If profitability is to be achieved, business owners must make strategic choices related to managing facilities.

It is argued that effectively planned facilities and supporting services can create significant business returns [START_REF] Alexander | Facilities Management : Theory and Practice[END_REF]. This can be seen through introducing professional FM methods to support increased efficiency [START_REF] Amaratunga | Assessment of facilities management process capability: A NHS facilities case study[END_REF], [START_REF] Lennerts | Reducing health care costs through optimised facility management-related processes[END_REF], on-going responsibility for the continuous operation of services [START_REF] Atkin | Total Facilities Management[END_REF] and a holistic view of the dynamics of the workplace amongst the product design and production of the physical workspace, and also between people and processes, and people and their environment [START_REF] Alexander | Facilities Management : Theory and Practice[END_REF].

Despite evidence existing to demonstrate the link between FM and an organisation's success, in practice FM is often seen as a 'fire fighter' service. It is not uncommon to see facilities managers taking a reactive approach in their activities, waiting for instructions before any action is taken. As a result, constantly emerging issues have to be remediated quickly without planned assessment of the best long-term solution [START_REF] Barrett | Facilities Management: Towards Best Practice, Facilities Management[END_REF]. This approach, in general, leads to poor service delivery, dissatisfied customers and loss of value to the organisation that does not operate efficiently. Generally, poor FM delivery is seen in organisations where the business strategy is not effectively aligned with building/asset/service management [START_REF] Amaratunga | A conceptual framework to measure facilities management performance[END_REF].

In this respect, the sought alignment between business and FM has been continuously evolving as a reflection of, amongst other things, the effectiveness of the information technology and communication systems within organisations [START_REF] Abel | A Standard Database Model for Computer Aided Facility Management in Hospitals[END_REF], [START_REF] Atkin | Total Facilities Management[END_REF]. Effective information management forms a critical aspect in the ability of FM teams to coordinate processes so as to achieve the required output, [START_REF] Alexander | Facilities Management : Theory and Practice[END_REF] whilst providing valuable information to planners, designers and corporate decision makers [START_REF] Atkin | Total Facilities Management[END_REF].

However, the efficient utilisation of information, its management and its supporting technology in FM has been somewhat problematic [START_REF] Barrett | Facilities Management: Towards Best Practice, Facilities Management[END_REF], [START_REF] Abel | A Standard Database Model for Computer Aided Facility Management in Hospitals[END_REF], [START_REF] Bainbridge | Getting the attention the facilities manager deserves[END_REF]. Facilities managers can have access to a variety of data sources but the opportunities to utilise or manipulate data are frequently unexploited [START_REF] Barrett | Facilities Management: Towards Best Practice, Facilities Management[END_REF]. Often, systems designed to generate the necessary information required by senior executives to make decisions are lacking [START_REF] Alexander | Facilities Management : Theory and Practice[END_REF] with current solutions relying on the duplication of data leading to the over-processing of this data and information overload [START_REF] Barrett | Facilities Management: Towards Best Practice, Facilities Management[END_REF].

A way of resolving this challenge is to invest in appropriate information management resources. This investment should aim at making information processing easier [START_REF] Barrett | Facilities Management: Towards Best Practice, Facilities Management[END_REF] and it is important that facilities managers evaluate alternative simple and appropriate systems to ensure that they meet the organisation's needs [START_REF]BIFM: The Good Practice Guide to Selecting FM Software, The Good Practice Guide[END_REF]. By easing information overload, the FM team has a greater chance of knowing exactly what is expected of them, thus procedures such as work programmes, service level agreements, maintenance schedules, meeting schedules can be instituted [START_REF] Barrett | Facilities Management: Towards Best Practice, Facilities Management[END_REF].

In this respect, the use of building information modelling (BIM) has been investigated as a way to support the reduction of unnecessary processes through better integration of information in FM [START_REF] Ballesty | Adopting BIM for facilities management: Solutions for managing the Sydney Opera House[END_REF], [START_REF] Eastman | BIM Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers, and Contractors[END_REF]. However, whilst its use within the design and construction phase is well studied [START_REF] Eastman | BIM Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers, and Contractors[END_REF], its adoption for FM purposes is still embryonic, in general, due to a lack of skills in the sector [START_REF] Cracknell | Sector BIM Strategy: Improving BIM Education & Training[END_REF]. An often-introduced claim is that BIM can be a powerful tool for facility managers to improve buildings' performance and manage operations more efficiently throughout their life cycle. Although this claim has been common since the early introduction of BIM, there is relatively little information about the real use of BIM in the operation and maintenance of buildings. Even most large public owners who have been early adopters of BIM, such as GSA, USACE or Senate Properties, have used BIM more in managing their construction projects than into their FM activities.

Indeed, the literature shows that very little has been implemented extensively in FM and even less has been measured in terms of improvements made due to BIM. In the following, twenty BIM FM related articles reporting on case studies were analysed to identify BIM capabilities implemented in case studies and also to identify the measures of success used that can be related to Return on Investment. As shown in Table 1, the application of BIM to FM has been focused on Hard FM to a great extent and in particular on the accuracy of 3D as-built models and the link to digital statutory/maintenance/supplier information available through online services.

Table 1. FM related BIM capabilities explored and implemented in the literature

In regards to measures of success, 'a facility manager is responsible for making critical strategic, tactical, and operational facilities-planning decisions that affect the organization's business performance' [START_REF] Lavy | Computer-Aided Healthcare Facility Management[END_REF]. In this respect, a taxonomy of in-

Capabilities / Cases

[16 [17 [18 [19 [20 [21 [22 [23 [24 [25 [26 [27 [28 [29 [30 [31 [32 [33 [34 [35 [36 Elimination of duplicated and inaccurate data through 3D modelling

! !

Analyse and simulate design to support preventive and reactive maintenance

! ! ! !

Life cycle costs and environmental analysis

! !

4D as-built model containing construction process information dicators of success in the implementation of BIM for FM purposes composed of a) financial indicators related to costs and expenditures associated with operation and maintenance, energy, building functions, real estate, plant, etc.; b) Physical indicators associated with the physical shape and conditions of the facility, buildings, systems, and components; c) functional indicators related to the way the facility and the buildings function and which express building appropriateness through space adequacy, parking, etc.; and d) survey-based indicators, which are based solely on respondents' opinion to surveys that are primarily qualitative in nature [START_REF] Lavy | Establishment of KPIs for facility performance measurement: review of literature[END_REF]. In this respect, Table 2 shows metrics used to identify benefits from adopting BIM for FM purposes across many case studies. To a large extent, most of the results obtained in the studies are based of the testimony of managers rather than from a systematic collection of information. Thus, despite progress being made in terms of advancing the knowledge regarding the adoption of BIM for FM, very little hard evidence is reported in the literature regarding how effective or ineffective BIM based FM processes are in relation to solving FM problems so to justify BIM implementation. Despite the existence of positive testimony that BIM improves FM, a lack of diagnostics for FM problems and baseline measures, BIM in FM is still a solution looking for a problem. carried out to investigate the use of BIM FM in the Manchester City Council Town Hall Complex (MCC THC) project and followed a previous investigation during the design and construction phase of the same project in 2011 [START_REF] Codinhoto | BIM Implementation: Manchester Town Hall Complex[END_REF], [START_REF] Kiviniemi | Challenges in the Implementation of BIM for FM: Case Manchester Town Hall Complex[END_REF].

! 3D as-built model ! ! ! ! ! ! ! 3D
The tools and methods used for data collection included a literature review on FM and ICT related topics, and interviews with project team members and FM team members. It also involved the use of the NBIMS Capability Maturity Matrix [START_REF]US National Building Information Modelling Standard, Version 1 -Part 1: Overview, Principles and Methodologies[END_REF], archival analysis of documentation and a workshop for data validation. The sources of evidence utilised included information extracted from the BIM alongside verbal and written explanations describing integrated processes as provided by six members of the FM team. THC FM Structure: The FM services are organised in a distinctive way. At the macro level, services are divided between front and back-office activities. Within back-office services there are two categories, namely FM Support and Building Support. FM support refers to secondary activities that are directly linked to the provision of primary services. Building support, on the other hand is related to the overall maintenance of the fabric. In this category, there are three levels of 'maintenance': planned preventive maintenance, reactive maintenance and capital projects (i.e. major redevelopments of the facility). In relation to front-office services, there are two categories: housekeeping and customer support. Housekeeping, in general, refers to activities that are performed regularly such as cleaning and waste collection, whilst customer support refers to activities dealing directly with visitors and suppliers to the THC. A BIM was developed to aid building support activities in the main. ICT (hardware, software and systems management) is not managed in coordination with FM. According to the FM interviewees, this disconnection between FM and ICT is an extremely relevant barrier to the adoption of BIM for FM.

With regards to BIM, its depiction for the FM team consists of four systems: C-PAD, ArtrA, eDocuments and UE. C-PAD is the current system used for logging issues raised by end users and non-compliant technical audits. ArtrA, the software which serves as a user friendly interface to access 3D building information on BIM and a cloud-based repository of information (eDocuments), supports this process by making available electronic versions of documents such as statutory requirements and building data, maintenance reports, etc. In this respect, data structure (including building geometry) within ArtrA is hyperlinked to relevant documentation in eDocuments and vice-versa. The maintenance service provider uses the UE as their accounting system and discussions have started regarding the possibilities of increasing UE interoperability.

FM Problems: when the FM team was prompted to identify the benefits of BIM adoption during the initial stages of the research, quite often the answers were related to design and construction benefits such as automated clash detection, support for decision-making, automated costing. Even though these benefits were important for the project, their direct relationship with business core activities or FM was limited or nonexistent. As BIM awareness increased within the FM team the focus shifted to the identification of opportunities for FM service improvement (Table 3).

BIM FM Maturity:

The results presented here (Table 4) highlight the perspective of the FM team within MCC THC on the level of maturity of BIM as applied to the reactive maintenance process. Overall, these results show that high levels of maturity have been attributed to the areas directly related to graphical information development, whilst lower scores have been attributed to areas related to business functions. As argued by the FM team, business functions are not yet linked with FM results. The process for assessment used also revealed that the FM team still face a degree of uncertainty related to their understanding of the actual level of BIM maturity.

Data richness: interviewees agreed that BIM was established, but with only very basic data loaded. Their perception is that additional data has gradually been made available and that data is beginning to be accepted as an authoritative primary source.

Life-cycle view: data was gathered as it was made available throughout the project, however no single phase (design, construction and use) was totally authoritative or complete. One participant indicated that a fourth phase of the facilities lifecycle has been added and some information is flowing.

Table 4. Cumulative assessment of maturity from the FM team (reactive maintenance)

Roles or discipline: roles apply to people's jobs at this level but no roles are fully supported through BIM. Contradicting this conclusion, two members of the FM team believe that the Service Resident Engineer uses BIM for entering data and via building geometry can access related documentation; for them his role is fully supported through BIM.

Business process: business processes are not completely defined and therefore cannot be used to store information in the BIM. However, to a limited extent, cross-departmental integration has begun, as a few business processes are being Problems Data entry procedure was repeated in triplicate for reactive maintenance Errors due to manual input of information within different system Incompletion of planned maintenance due to delays in reactive maintenance Time spent on finding correct information to support building maintenance Lack of information regarding FM performance Lack on links between back and front offices services Errors in the statutory maintenance record due to symmetrical characteristic of the facility

! ! ! ! ! ! ! ! ! ! ! ! 1 ! ! ! ! ! ! ! ! ! ! ! 2 ! ! ! ! ! ! ! ! ! ! ! 3 ! ! ! ! ! ! ! ! ! ! ! 4 ! ! ! ! ! ! ! ! ! ! ! 5 ! ! ! ! ! ! ! ! ! ! ! 6 ! ! ! ! ! ! ! ! ! ! ! 7 ! ! ! ! ! ! ! ! ! ! ! 8 ! ! ! ! ! ! ! ! ! ! ! 9 ! ! ! ! ! ! ! ! ! ! ! 10 ! ! ! ! ! ! ! ! ! ! ! ! FMT1! FMT2! FMT3! FMT4! FMT5! FMT6 -FMT Facilities Management Team!
designed to collect information to maintain the BIM in the organization. Delivery method: despite the BIM being accessible, it is not on a network and there is control over who can access it. This is to be kept this way until the FM team develops enough confidence to operate the BIM.

Timelines / response: the information is stored and managed only on the "room data sheet" through an external database in ArtrA Software. Currently, the system is not designed to reply to a set of pre-determined enquires. The model is under development and as such it is not completed or automated. However, reports can be generated from the service order request logs in C-Pad, and building geometry (in ArtrA) is linked to building documentation (in eDocuments), thus indicating some level of timeliness / response.

Change management: awareness exists that there is change management process for BIM in place at project level, however there is lack of clarity regarding to whether this will be extended to the organisation.

Graphical information: drawings are 3D object based and have intelligence. The MCC FM team has achieved this by using the software solution ArtrA (Figure 1). Within ArtrA, each asset, such as the MEP asset, has a location based asset identifier and a unique webpage reference generated by eDocuments. Currently, information provided via eDocuments is in non-intelligent PDF format. Visualisation of the model is possible in different packages; however, loss of intelligent information happens if functional model manipulation is needed.

Spatial capability: the facility is in a worldview spatially and the common coordinate system was inherited from the architectural model. Despite the space not being spatially located in the real world according to a GPS/GIS system (as indicated in the CMM) the current system adopted constitutes a BIM capability.

Information accuracy: to date, electronic validation of information for internal spaces is available to a limited extent. This is due to limited interoperability, where in some instances data from information structure in one model is lost during exchange, thus leading to gaps and duplication in the information model where data has to be re-entered manually (Figure 1). Interoperability / Exchange support: some interoperability exists that is not yet automatic or seamless. Interoperability was achieved by using COBie for exchanging information from ArtrA (portable 3D intelligent data set), C-Pad (management) and eDocuments (archival register). These applications form a system linked via relationships that enables automatic updating of data and information. Data and information entry can be done from existing models, manually from archival documentation or survey. Key stakeholders within the facilities management team are tasked to author and review the information.

Overview: As expected, the overall results achieved by MCC Reactive Maintenance Services are low analysed independently. That does not mean that MCC is not performing well in the implementation of BIM. Comparatively with the industry in general, the efforts put forward in the implementation are quite remarkable, considering that technology is not ready for full adoption, thus imposing a constraint in higher scores.

Barriers: the research identified many barriers that hindered the implementation of BIM in the THC project. Examples of the identified barriers include the necessary technical expertise to generate and operate BIM, readiness for a fast implementation, the completion of the model before completion of construction to assist hand-over activities, lack of organisational buy in and most importantly the separation of MCC ICT from FM. Table 5 shows the barriers to implementation identified during the research.

Benefits and returns from BIM FM: several benefits were identified for all phases of the project (i.e. design, construction and use). With regards to the benefits for the design and construction phase, these were related to support to decision-making and the reduction of errors and risks on site. A series of simulations revealed that many potential gains in terms of time, human resources and finance can be achieved (Table 6). Above all, faster maintenance process will lead to shorter service disruption, thus enhancing the support to business core activities and customer satisfaction.

Discussion and Conclusions

A great deal of effort has been made in the UK towards the adoption of BIM within the construction sector. However, once construction is finished, the use of the large and rich amount of information generated within project phases has not been explored to the same extent. The literature in this area shows that, despite many attempts to BIM FM implementation exists, these are still piecemeal and FM cases showing extensive use of BIM are lacking. The identified challenge faced by facilities managers relates to the lack of integration and transparency across organisational functions. Integration seems to be discussed as the way forward for the sector and BIM has been considered as a facilitator of this process. However, the lack of evidence demonstrating its benefits generates scepticism within managers. Also, the lack of FM "terminology" and understanding about how it applies to FM (being most of the discussions around design and construction) also contributes to the promotion of misunderstood perspectives of how BIM supports FM, whilst paradoxically also generating inflated expectations. As identified through this research, the ownership of the implementation process is not yet in the hands of FM teams. Much effort is still made by design and construction teams to provide information modelling services to assist FM teams. In this regard, the clarification that roles and responsibilities do not automatically change with BIM implementation is crucial. However, an adequate system must be in place to support authoring of information at all instances. The maintenance of a performance baseline and a history of critical services that can support the prioritization of services are also fundamental.

Conversely to the FM sector in general, the initial findings indicate that MCC despite being at early stages of BIM implementation has progressed rapidly, positively pushing the boundaries of BIM adoption for FM purposes. It is clear from the research that the willingness of MCC to implement BIM and their vision in using BIM to improve FM has been paramount to this fast development. One of the most relevant changes is in the attitude of the FM team that became more process oriented and is seeking to identify process inefficiencies that could be mitigated by the adoption of BIM. In other words, the MCC FM team is not just following a trend, rather the team is focused on promoting continuous improvement by setting new standards for the management of facilities making use of BIM whenever appropriate. This approach is creating an MCC construction knowledge asset base - information assets that improve the future management of this and other projects. With the support of this research, the FM team became aware of their advanced position in relation to traditional FM practices as well as of the path for redefining the process model for FM in public building projects and further BIM implementation and development.

  as-built model linked to estatutory/maintenance information

Fig. 1 .

 1 Fig. 1. ArtrA graphical information displays rich contextual information in a 3D model

Table 2 . Metrics used to identify benefits from adopting BIM for FM Case Manchester Town Hall Complex This

 2 research was done in the context of the UK Government's BIM initiative. Further understanding of the key issues in migrating to BIM-FM is crucial to the development of general guidance. The research strategy was Case Study Research,

	Baseline Measure	[16]	[17]	[18]	[19]	[20]	[21]	[22]	[23]	[24]	[25]	[26]	[27]	[28]	[29]	[30]	[31]	[32]	[33]	[34]	[35]	[36]
	Better customer service	!
	Better decision-making	! !						!		! !						! !			!
	Better cost forescast		!					!								!
	Improved data consistency			!		!		! !				!				! !		! !
	Better access to information				!								!							! !
	Reduced response time					!
	Increased process efficiency						!								!
	Better planning							!								! !
	Better AEC-FM Integration									!
	Reduction of maintenance failure											!
	Strealined processes											!						!		! ! !
	Improved tracking of inventory													!		! !
	Reduction of reactive maintenance															!
	Reduced cost of operations															! !
	Reduced time of operations																!		!
	Reduce effort of operations																					!
	Implemented
	Simulated

Table 3 . FM problems potentially benefiting from BIM FM implementation

 3

Table 5 . Barriers to the implementation of BIM FM within the THC Barriers Technical

 5 expertise needed for the maintenance and updating of the BIM Number of process changes made simultaneously Risk of underperform whilst changing from current to BIM enabled process Limited software interoperability Lack of guidance, protocols and standards for BIM FM Unclear BIM FM requirements at early project stages Model incompletion at project hand over stage Lack of clarity regarding model assembly and its relationship with FM processes Lack of clarity regarding overall management system, KPIs and bechmark figures lack of cross functional buy in wihtin the organisation

Table 6 . Benefits and returns from BIM FM (Adapted from MCC, 2013)

 6

Acknowledgments Our special thanks to the BIS for funding this research, and to Mark Bew (Chairman of the UK Government BIM Implementation Group) and Liam Brady (Town Hall Complex Client Programme Manager) for their support to the research collaboration between the University of Salford and Manchester City Council.


Masato Inoue
email: 1m_inoue@meiji.ac.jp

Shuho Yamada

Tetsuo Yamada

Stefan Bracke

A Design method for product upgradability with different customer demands

Keywords: Product upgradability, sustainability, customer demands, set-based design

A sustainable society requires changes in the traditional paradigm of mass production and consumption. Products such as personal computers and smartphones are discarded even though they are fully functional. This paper proposes a design method for product upgradability which satisfies various different customer demands to increase the product value and extend the value lifespan by exchanging components closely related to its deterioration in value. In addition, this paper also proposes a method that can specify future product performances, effective upgradable product components, and the side effects of upgrade on other product components. Finally, this paper discusses the applicability of our proposed design method by considering a vacuum cleaner and various different customer demands.

Introduction

The change of traditional paradigm of mass production and consumption is required for a sustainable society. Companies and nations are required to reduce their environmental loads [START_REF]Ministry of the Environment in Japan: Kyoto Protocol Target Achievement Plan[END_REF]. Therefore, environmentally conscious product design is essential. Some of these design methods such as 3R including reuse, reduce and recycle, and upgradable product design method have been studied [START_REF] Kobayashi | Product Lifecycle Planning[END_REF]. The upgradable product design method is intrinsically executed prior to the disposal of products. Shimomura et al. [START_REF] Shimomura | Proposal of an Upgrade Planning Method for Upgradeable Product Design[END_REF] proposed a method for upgrade planning based on the prediction of customer demands. Fukushige et al. [START_REF] Fukushige | Computer-Aided Design for Product Upgradability under Geometric Constraints[END_REF] developed a prototype system for product upgradability based on 3D-CAD. However, the method nearly addresses only physical product performance without quantitative considerations of requirements such as cost and environmental load. Thus, this paper focuses on an upgradable product design method, which can treat concurrently physical product performance, environmental loads, and product cost. This method also considers uncertain product requirements and design information needed in the future at the time of upgrade. The authors assume that customers discard their products when the perceived value of their present product has deteriorated with time below a certain level relative to the perceived value of new products in the market. In addition, this paper also proposes a method that can specify future product performance and functions, effective upgradable product components, and the side effects of upgrade on other product components. Finally, this paper discusses the applicability of our proposed design method by applying to a design problem of a vacuum cleaner design problem with different customer demands.

2

A Design Method for Product Upgradability

Purpose and procedure of the method

A design method for product upgradability seeks to design products that are capable of being adapted to future enhancements of product performance and functions at the early phase of design by predicting those product performance and functions that will be required at the time of upgrade. There are two basic classes of this method as follows:

(a) Upgrade by exchanging components (b) Upgrade by adding components or modifying the structure of the product This study focuses on the former class of the method (a). Because future enhancements of product performance and functions eligible for upgrade are to be predicted, the proposed method must include uncertain design information. Here, the uncertain design information is represented as a range value, and a preference setbased design (PSD) method [START_REF] Inoue | Design Support System by Combination of 3D-CAD and CAE with Preference Set-based Design Method[END_REF][START_REF] Inoue | Collaborative Engineering among Designers with Different Preferences: Application of the Preference Set-Based Design to the Design Problem of an Automotive Front-Side Frame[END_REF] is applied to estimate future enhancements of product performance and features eligible for upgrade. The PSD method can obtain a ranged set of design solutions. Figure 1 shows the procedure of the proposed method.

This paper defines two product lifetimes: durable life and value life [START_REF] Murakami | An Upgrade Design Method for Environmental Issues Based on the Concept of Set-Based Design[END_REF]. The durable life is a measure of the duration over which the failure rate of a product or component remains below a defined threshold. Conversely, the value life is a measure of the duration that the product value perceived by the consumer remains above a defined threshold. Products such as personal computers and smartphones are usually discarded even though they are fully functioning. This situation derives from the condition where the value life is shorter than the durable life. Therefore, the primary purpose of our method is to reduce the extent of product disposal and the resulting environmental load by increasing the value life of products by exchanging components that have a relatively short value life or by adding new components in accordance with the description.

Upgrade planning

Here, the authors establish the criterion of the upgrade time. Definition of the upgrade time is based upon several factors such as product upgrade cycle, disposal cycle, or administrative strategy. In addition, the product and component databases are created. These databases contain manufacturers, model numbers, launch times, and product and component performance and/or design variables such as capacity of storage, weight, and dimension. Based on these databases, the authors create product and component roadmaps that evaluate the temporal distributions of performance criteria and/or design variable values. The upgrade time and the product and component roadmaps are used for configuring the performance requirements of the products and components. Under conditions where a product has not yet been launched, roadmaps of similar products can be used for market prediction and for configuring performance requirements.

Developing the function network

A function network diagram illustrates the input and output relationships between performance criteria and product components. This diagram is used for the analysis of upgrade components. Figure 2 provides an example of a function network diagram for a vacuum cleaner. In this diagram, performance criteria and product components are represented by the individual graphics. The positive parameters are indicative of a condition where a higher or larger value represents better performance. Conversely, negative parameters are indicative of a condition where lower or smaller values represent better performance. The input-output relations between performance criteria and product components are connected by straight lines, and relevant design variables are described on these lines. Therefore, designers can easily search for components that are related to upgrade performance by following the input-output lines.

In case of a vacuum cleaner (cf. Figure 2), for example, the suction power is the chosen target for upgrade performance. The pertinent components affecting that performance are motor, turbine fan, body, or power unit. They represent candidates with regard to an upgrade possibility.

Consideration of upgradable performance criteria and components

Upgradable performance criteria are defined as a product performance upon which consumer emphasis is placed, as evaluated by application of quality function deployment (QFD) or, alternatively, those performance criteria, which have a short value life. Using the function network diagram, a designer searches for components that have close relationships with the chosen upgrade performance criterion and defines those as potential upgradable components. When a plurality of upgradable components are identified, the candidates should be narrowed down by considering the balance between upgrade performance criteria and possible upgrade affected performance criteria and components as described below.

Consideration of upgrade affected performance criteria and components

Upgrade affected performance criteria indicate that the value of performance is changed by exchanging upgrade components. In addition, the authors define a component that has a close relationship with an upgrade affected performance criterion as an upgrade affected component. Upgrade affected performance criteria and components are identified in the same way as upgrade components by using the function network diagram. For example, a designer defines the performance of the suction power as the upgrade performance criterion and the turbine fan component as the upgrade component for the vacuum cleaner described in Figure 2. In this case, the waste heat and operation noise are defined as upgrade affected performance criteria because the upgrade of the turbine fan causes the diameter of turbine fan Dt and the coefficient of noise of the turbine Cf to increase. Therefore, the power unit and the motor emerge as upgrade affected components. Possible approaches for mitigating this condition can be developed such as building low-level waste heat and low-noise motor into the 1st generation vacuum cleaner, or developing and upgrading a motor that has high suction power, low-level waste heat and a low noise, simultaneously upgrading and changing the motor with the turbine fan. These approaches are narrowed down in the same way as that of the upgrade components.

Application of the PSD method and the evaluation of the solution set

This study applies the PSD method to the proposed method in order to obtain the range of required product performance and functions, and the range of the component design variables that can realize this performance and function range. To obtain these ranged design solutions, the equations and the range of the required product performance and functions and the design variables of the components are needed.

The equations show the relationships between product performance and functions and component design variables. In the absence of equations, the designer should define approximate equations based on the performance parameters and design variables in the product and component databases. Range of the required product performance and functions and the designer configurable range of design variables are configured in accordance with the distributions in the product and component roadmaps. A conclusive point-based design proposal is selected from the ranged set of design solutions and a preference number. Under conditions where the design proposal must be modified, the designer should search for the design proposal that satisfies the modified requirements from the ranged set of design solutions. However, in the absence of a design proposal in the ranged set of design solutions, the designer should define the required performance and design variables again and apply them to the PSD

3

Case Study: Application to the Design of a Vacuum Cleaner

Setting the design problem

This paper shows an application of the proposed method to a vacuum cleaner.

According to the cycle of trade up to a new model, the authors hypothesize an upgrade time equivalent to approximately five years (for a consumer trade up proportion of 60%) from launch time of the 1st generation product. To understand the trend of performance requirements and design variables, the authors create databases for launched products and components. The product databases include the vacuum cleaners manufactured by three companies (Company A, B, and C) from 2005 to 2013. The component database includes motors manufactured by a single company in 2013 because there is no data for motors manufactured before 2012. Figure 2 shows the function network diagram of the vacuum cleaner. Using the result of QFD as shown in Figure 3, this study defines the suction power F [W] as an upgrade performance that has a high level of value degradation. Using the information in Figure 2, the motor is configured as an upgrade component. In addition, the operation noise S [dB], the amount of CO2 emission D [g], the energy consumption E [W], and total production cost as the performance criteria affected by the upgrade are defined. The product performance requirements and the range of design variables based on the product database and roadmap are configured. Finally, the ranged set of design solutions is calculated using the equations between product performance and design variables from the PSD system.

The range of the design variables can increase and decrease relative to the reference values that are assumed to be the design variables of the 1st generation product. The total production cost for the upgraded product has multiple relations with the costs for the upgrade components and the affected components (i.e., the motor and the turbine fan). The assumption is that the cost for the components increases relative to the difference between the design variables of the 1st generation (reference value) and those of the 2nd generation. Therefore, the cost for components (not including the motor and the turbine fan) is higher than components without the upgrade. This study assumes that if the range of the design variables decreases, then total production cost increases moderately than is the case for an increase in the range of the design variables. Figure 4 shows the relationship of the production cost for the product with and without the upgrade.

In this application, the authors assume that the product performance and design variables of the components of the 2nd generation product without an upgrade are equal to the upgraded product's parameter. In addition, authors assume that the cost of the 2nd generation without a product upgrade is equal to the 1st generation without a product upgrade.

This study classifies the customer demands into 3 types as follows: (1) Performance preferable customer: the customer requires a high suction power (2) Silence preferable customer: the customer requires a low noise (3) Energy-saving preferable customer: the customer requires a low energy consumption

Discussions

With respect to the relation between the suction power and the power consumption, and the operation noise, Figure 5 compares the performance-oriented solutions (performance preferable customer), silence-oriented solutions (silence preferable customer), and ecology-oriented solutions (energy-saving preferable customer). Figure 5 indicates that ecology-oriented solutions satisfy the required performance for the silence preferable customer. The result indicates the designer can define the customer demands as the demands for the performance preferable customer and the energy-saving preferable customer.

In this study, a ranged set of product design solutions that include various performance criteria, cost, and environmental loads in use concurrently with the consideration of future uncertain design information are obtained.

Figure 6 shows the comparison of the cost for each customer demand. The results suggest that the total production cost of the upgraded product is reduced by about 25% compared with that of the product without upgrade, and that suction power satisfies the required range. Therefore, this study concludes that the proposed method can obtain a ranged set of product design solutions in consideration of performance criteria, cost, and environmental load for various customer demands. However, the designers should define the increasing rate of 1st generation production costs of the upgraded product that customers allow to consume because the 1st generation production cost of the upgraded product increases from 22.4% to 27.6%. Also the application of this increasing rate to the requirements of the upgraded product should be done.

Fig. 1 .

 1 Fig. 1. Procedure of the proposed upgradable design method.

Fig. 2 .

 2 Fig. 2. Function network diagram of a vacuum cleaner and graphical representation of performance criteria (positive and negative) and product components.

Fig. 5 .Fig. 6 .

 56 Fig. 5. Comparison of the solution areas of each customer demands.

  Yokohama, Japan, 7 th -9 th July 2014 Solution sets for performance preferable customer Solution sets for silence preferable customer Solution sets for energy-saving preferable customer Required performance for performance preferable customer Required performance for silence preferable customer Required performance for energy-saving preferable customer

		1200							67
	Power consumption E (W)	800 900 1000 1100						Operation noise S (dB)	57 59 65 61 63
		700							55
		590	610	630	650	670	690	710	590	610	630	650	670	690	710
				Suction Power F (W)					Suction Power F (W)

Acknowledgments. This work was partially supported by Research Project Grant by Institute of Science and Technology, Meiji University.

Conclusions

This paper proposed a design method that can obtain a ranged set of solutions that satisfies multiple product performance criteria, cost, and environmental load by considering uncertain design information for various customer demands. To obtain the ranged set of solutions, PSD method is applied to the proposed method that proposes to increase product value and extend product life by exchanging components whose value has diminished below a threshold value. In addition, the authors proposed the function network diagram to define the product performance criteria and components that possess a short value life. This paper showed the usefulness of this diagram by application. In this paper, the ranged set of requirements that include future uncertainty is predicted arbitrarily based on the distribution of the product roadmap. Moreover, this prediction needs the designer's knowledge and experience. Therefore, predicting the ranged set of requirements logically is one of the subjects of future study. In addition, the authors also need to indicate the business model for familiarizing the concept of the product upgradability.