Ralf Schmidt
email: ralf.schmidt@uni-due.de

Mirco Zick
email: mirco.zick@uni-due.de

Burkhard Schmidt²
email: b.schmidt@himh.de

Maic Masuch
email: maic.masuch@uni-due.de

Success Factors for Applied Game Projects -An Exploratory Framework for Practitioners

Keywords: Applied Games, Gamification, Serious Games, Game-Based Learning, Success Factors, Best Practices, Organizational Learning

Applied games are an increasingly utilized approach to develop applications and concepts of organizational learning. However, which factors support the successful planning and execution of such projects within the organizational landscape remains unclear. This study initiates explorative research towards a success-factor model for applied games. The data is based on nine expert interviews within the DACH-region as well as a thorough literature review. The resulting factors are organized in a two-dimensional model, presenting the process of developing applied game projects and major organizational abstraction layers. The model aims to support the development of research and industry applied-games productions in organizational context. Next steps are further validation factors as well as the development of a maturity model.

Introduction

Organizations continuously need to adapt to economic, technical and social changes that challenge established structures and its individuals alike [START_REF]Grünbuch -Arbeit weiter denken[END_REF]. Organizational development (OD) describes attempts of guided changes in organizations, which enable the personnel to cope with such environmental-based changes [START_REF] Nerdinger | Organisationsentwicklung[END_REF]. Typical goals are increases in performances, satisfaction or problem-solving [START_REF] Cummings | Organization development & change[END_REF]. Establishing organizational learning cultures is considered a constant contribution to OD and potential mechanism to achieve these goals [START_REF] Reichwald | Innovative Arbeitsgestaltung im Unternehmen der Zukunft[END_REF].

Applied games [START_REF] Schmidt | Applied Games -In search of a new definition[END_REF] are still relatively new in organizational development and organizational learning. The original idea of using electronic and digital games for purposes other than entertainment roots in the 70s. The early 2000s then mark the beginning of the new generation of technically and educationally advanced, and heavily diversifying forms of applied games. Gameful applications [START_REF] Deterding | From Game Design Elements to Gamefulness. Defining "Gamification[END_REF] mark but the latest branch. A prominent European example was the serious game "Airline Company". The game transports the business model of Lufthansa AG to its employees. "Module X" is a gamification learning platform incorporating applied gaming and web-based trainings at Bayer AG.

Multisensory stimulation, experiences of continual improvement and perceived proficiency are but a few of the many attributes applied games potentially inherit from their entertainment counterparts [START_REF] Whitton | Digital games and learning[END_REF], which can be utilized in OD. Most research focuses on positive characteristics of games [START_REF] Whitton | Digital games and learning[END_REF], best practices [START_REF] Prensky | Digital game based learning[END_REF], frameworks guiding a successful design [START_REF] Freitas | Serious Games: A New Paradigm for Education?[END_REF][START_REF] Oprescu | I play at work -ten principles for transforming work processes through gamification[END_REF] and questions of evaluation end effect [START_REF]Serious games. Mechanisms and effects[END_REF]. Literature on how to successfully set up and conduct applied games projects is comparatively scarce. Therefore the aim of this study was to explore success factors described by experts in the field and to condense those into a model for practitioners.

Methodology

This study is based on an exploratory, qualitative approach. First experts with experience in conducting applied game projects needed to be identified. The search radius was narrowed to persons with a recent history (approximately 2010) of 10+ projects within an organizational context in the DACH-region (Germany, Austria, and Switzerland) to reflect probable cultural specialties. The search criteria resulted in a total of nine experts between 30 and 61 years with a history of 10 to 50 projects within search radius. Four held an academic title (4S). Backgrounds ranged from an explicit vitae in game design and development (2S), media and arts (1S) over economics and informatics (2S), to pedagogy (1S) and management (3S).

To solidify and ground previous findings an extensive literature research for success factors was conducted as a second step. It included relevant databases such as ACM DL, IEEE Xplore, ScienceDirect or SpringerLink. A first iteration concentrated on literature on applied games, such as gamification, game-based learning and serious games developed for organizational contexts. As the results were not extensive, a second iteration was conducted, to see what could be learned from other recent professions that share attributes with applied games. Those were: Relatively novel and innovative to organizations; a potential to contribute to organizational challenges mentioned above; a focus on the design of experiences; respecting the end user's needs. The selection resulted in the professions of user experience design [START_REF] Hassenzahl | Experience design. Technology for all the right reasons[END_REF] and design thinking [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF].

Third a half-standardized interview questionnaire was developed based on the literature research and the underlying structure of a six-phase procedure model [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF]. The questionnaire was assembled by all authors of the study.

Two types of interviews were conducted. The first series of seven interviews resulted in a wide range of statements that was processed according to the qualitative content analysis of Mayring [START_REF] Mayring | Qualitative Inhaltsanalyse. Grundlagen und Techniken[END_REF]. The results were clustered distinctively to the phases of the process model as a horizontal structure. Next a type-structuring was conducted, clustering and counting similar expressions which resulted in a first iteration of the success-factors. A second series of four interviews, including two interviewees from the first series, aimed to revise and enhance the model. The interviewees were asked to comment on the success-factors found so far which resulted in some rearrangements, condensation and changes in wording of the factors.

Last the factors were classified along organizational abstraction layers, as defined below. The layers represent the second, vertical dimension concluding the twodimensional success-factor model.

Abbreviations. Throughout the further paper following abbreviations are used: "AG" = Applied Games; "SP" = Service Provider; User Experience = UX; Design Thinking = DT. A number followed by the letter "S" (e.g. 5S) highlights the collated number of subjects associated with a statement.

Two-dimensional Framework

The horizontal dimension follows a six-phases procedure model [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF]. It consists distinct and sequentially organized phases typical for applied game projects. For each phase input, throughput and output definitions are given. Iterations within each phase are strongly encouraged and common. Each end of a phase marks a possible exit of the procedure if results so far are not convincing or reasons demand ending the project. The idea of having closed phases while still iterating increases the plannability of an AG project. The model encourages a strict user-centered approach to AGs. It further aims at reducing known complexity regarding the solution and costs, with a close-to-100% predictability at the end of the design phase. The vertical organization of the success factors follows three self-defined abstraction layers with an ascending level of influence by a SP. First the organizational layer summarized factors, which are related to the culture, structure and external influences of an organization. The properties of these factors are rather consistent and hard to grasp, such as culture. Organizational factors exert an implicit influence on the AG project. Second the operational layer describes factors that frame the AG project, such as organizational goals, decrees, processes and workflows, teams and responsibilities. These factors follow mostly fixed rules and are usually well documented. Third the project layer refers directly to the AG-project and is about processes, human factors, methods, etc.

3

Literature Review

Applied Games

Michael & Chen [START_REF] Michael | Serious games. Games that educate, train, and inform[END_REF] cite Quinn's most important preconditions for a project: A specific need for training, the perception and believe that a game approach could help and financial resources. Prensky, among other things argues for an openness and acceptance of the younger generation's play attitude towards serious contexts, such as work and learning [START_REF] Prensky | Digital game based learning[END_REF]. Usually an organization needs to be convinced of a gamebased solution and need to discuss an exit strategy for players who successfully finished a game [START_REF] Herger | Enterprise Gamification[END_REF]. Nicholson suggests to start a project with the desired outcome and a set of open questions to get there [START_REF] Nicholson | A RECIPE for Meaningful Gamification[END_REF]. He and others also argue for a user-centered approach that addresses the target-user's needs and goals [START_REF] Oprescu | I play at work -ten principles for transforming work processes through gamification[END_REF]. Other factors are facili-tating a common ground among stakeholders about audiovisual quality and costs [START_REF] Michael | Serious games. Games that educate, train, and inform[END_REF]. Academics again stress the necessity but also complexity of an early planning and implementations of evaluations [START_REF] Michael | Serious games. Games that educate, train, and inform[END_REF][START_REF] Stokes | Impact with Games: A Fragmented Field[END_REF][START_REF] Hamari | Does Gamification Work. A Literature Review of Empirical Studies on Gamification[END_REF] as the overall evidence of successful applied games remains rare [START_REF] Whitton | Digital games and learning[END_REF][START_REF] Kapp | The gamification of learning and instruction. Game based methods and strategies for training and education[END_REF]. There is much more literature on the actual design of games for learning [START_REF] Whitton | Digital games and learning[END_REF][START_REF] Michael | Serious games. Games that educate, train, and inform[END_REF], but that is outside scope of this paper.

User Experience

Likewise applied games, convincing customers is an important first step [START_REF] Schubert | User Experierence and User-Centered Design at DATEV eG[END_REF] in UXprojects [START_REF] Hassenzahl | Experience design. Technology for all the right reasons[END_REF]. Both is often new to organizations. A transparent and clear communication throughout the project avoids mistrust and gains the crucial management support [START_REF] Gulliksen | Making a difference[END_REF]. Scholz and Wallach propose a five-step process for user-centered design [START_REF] Wallach | User Centered Design: Why and How to Put Users First in Software Development[END_REF]. It includes a thorough scoping, analysis of users and products, iterative design, evaluation and delivery of the product. Abele et al. focus on a systemic approach and a strict user-focus and propose communication of successful projects within the organization to advertise and establish the approach [START_REF] Abele | Usability Management bei SAP-Projekten. Grundlagen Vorgehen Methoden[END_REF].

Design Thinking

Design Thinking is more a philosophy than an exact process [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF][START_REF] Uebernickel | Design Thinking[END_REF]. It describes a shift in one's attitude and thinking to approach a problem, likewise Schmidt et al. [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF]. However, there are a number of rules, resources and methods such as ways for organizing information, working in small, mixed teams, well defined project scopes and a structured, time-bound and moderated process [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF]. Flexibility, tangibility of ideas and prototypes and putting people first are other, very important constants of DT [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF].

Others authors stress the importance of management commitment and clear communication to guide stakeholders through the probably unaccustomed way of thinking [START_REF] Uebernickel | Design Thinking[END_REF]. That includes the possibility of failure [START_REF] Kolko | Design Thinking Comes of Age[END_REF]. The idea of design thinking will feel less uncomfortable if an organization already established and innovative culture [START_REF] Hilbrecht | Design Thinking im Unternehmen -Herausforderung mit Mehrwert[END_REF].

General Project Characteristics

All projects were declared innovation-projects and took place across industries (9S). Mid-to large-size organizations dominate the customers, presumably because of an earlier perception of the idea and larger personal and financial resources (9S). The experts did not disclose exact information on budgets but from the information given, ranges are between lower four-figure to mid six-figure amounts with a presumable typical range between 30.000-50.000 € and a project duration between three to six months. Interestingly, gamification budgets were rated 10-20% cheaper in comparison to serious games projects (2S), probably because of smaller expected costs for audiovisual content. The most typical project-goal seems to be the increase of the overall performance and efficiency regarding learning goals. The designs therefore address motivation and behaviour of the learners to increase their engagement in the learning activity (8S). Most projects address younger people and are offered on top existing learning settings. Only rarely the organizations aim to replace a classic setting, such as seminars, completely. Six experts mentioned the additional political use of applied game projects, to support the company's public image (6S).

Success Factors

Overall Success Factors

Organizational layer -A culture of Innovation and Learning (9S). Similar to Prensky [START_REF] Prensky | Digital game based learning[END_REF] for game-based learning and Hilbrecht and Kempkens for DT [START_REF] Hilbrecht | Design Thinking im Unternehmen -Herausforderung mit Mehrwert[END_REF], all interviewees noted that a culture of innovation and learning in a customer's organization is advantageous (9S) on several levels. There seems to be a greater openness towards new ideas and ways to tackle problems and present learning scenarios frequently integrate new media. Most importantly those organizations follow an established innovation process that provides guidance to plan and conduct the project.

Operational layer -Managerial Support (9S). All interviewees and most literature stress the importance of managerial support of department and company heads to ensure the allocation of resources for the project (9S) [START_REF] Herger | Enterprise Gamification[END_REF][START_REF] Uebernickel | Design Thinking[END_REF]. SPs must be aware that in a number of cases the contact person only explores the possibility of applied games and needs a business case before addressing superiors. Managerial support for AG projects cannot be taken for a fact within the organization and usually SPs are to earn and keep that support. Showstoppers, apart from missing managerial support, are a loss of interest in the topic or changes within organizational strategy and focus (3P).

Operational layer -Flexibility of Resources (4S). Fixed budgets are quite common with smaller organizations (2S) while bigger companies tend to allow flexibility (2S).

There is a preference towards flexible budgets and other resources among the SPs while especially enterprises naturally prefer predictability. Two SPs (2S) try to negotiate each phase of the project separately and sequentially as suggested by Schmidt et al. [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF]. Such practice may also foster the trust-building process but will sometimes be prohibited by organizational policy.

Operational layer -Transparency and Trust (5).

Building and keeping up trust towards the idea of AGs and a SPs ability is indispensable across hierarchies. AGs are usually cooperative projects and therefore need a common sense among stakeholders, developed by the SPs. The overall project flow and next steps should be transparent at all times and invite customers to take part. Similar suggestions are found in [START_REF] Uebernickel | Design Thinking[END_REF][START_REF] Wilke | Innovation als Voraussetzung für Erfolg[END_REF].

Operational layer -Moral and Ethics (2S).

AGs are often criticized because of their manipulative nature [START_REF] Ferrara | Games for Persuasion: Argumentation, Procedurality, and the Lie of Gamification[END_REF]. Despite only explicitly mentioned by two interviewees, it was decided to include this factor as everyone working with persuasive designs should know about its advantages and downsides and therefore develop a clear position regarding project goals and morality.

Fig. 1. Success-factor model

Phase 1: Exploration

Both partners aim for a common understanding of the problem, project goals and success criteria. They discuss the motivation and chances for AGs as a possible solution to the problem and agree on milestones and financial parameters. A vision statement is a recommended outcome of this phase and foundation to a contract [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Organizational layer -Communication and Persuasion (5S).

Quite often SPs must argue for AGs as a possible solution for learning and change in organizations. Interviewees stressed the sensibility of the word "game" and suggested to use other terms, such as motivational design or else (3S). Games and play are strongly connected with leisure time and work is attributed with seriousness and effectiveness in Germany (and elsewhere) (2S). Citing positive and competitor examples as well as stressing the idea of pleasure being a good precursor of job satisfaction and work performance, are common among SPs to argue for AGs (e.g. Schubert et al. [START_REF] Schubert | User Experierence and User-Centered Design at DATEV eG[END_REF]). However, some inevitable uncertainties about conventional problem solutions and cost pressure will naturally support the SPs argumentation (2S).

Phase 1 Exploration

Phase 2 Analysis

Phase 3 Ideation

Phase 4 Design

Phase 5 Production

Phase 6 Go-Live and M. Operational layer -Consulting and Expectation Management (4S/6S). Consultancy is needed regarding chances, challenges and risks of a project and its coherence to company culture (4S) [START_REF] Hilbrecht | Design Thinking im Unternehmen -Herausforderung mit Mehrwert[END_REF]. Moreover, most interviewees notice misleading thoughts about the complexity of game design and the expectable audiovisual quality of a product in the light of the budget ranges outlined above (6S). At last, two interviewees also discuss the necessity of an iterative process that accepts unconventional ideas and failing of ideas, likewise design thinking [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF][START_REF] Kolko | Design Thinking Comes of Age[END_REF] (2S).

Project layer -Definition of Scope and Goals (5S).

Most interviewees discussed the relative vagueness of goals in the early stages of a project. The definition of distinct and measurable goals [START_REF] Michael | Serious games. Games that educate, train, and inform[END_REF] within a specific project scope is accordingly part of the consulting and expectation management and will often differ from original ideas. For example, the project lifetime has an important influence on the design of AGs (1S).

Then again, goals need to be readjusted when new information is available (5S). Specifically referring to gamification, two SPs do not believe in cross-departmental projects (2S). Overall interviewees report a certain realism regarding goals and expectations towards behavior change and performance goals.

Phase 2: Analysis

A thorough context and target user-group analysis is conducted using qualitative and sometimes quantitative methods. The overall goal is to outline multiple perspectives from different stakeholders towards the problem and current solution and document the results with suitable artifacts such as user-journeys, use-case descriptions or technical specifications [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Project layer -Accurate User and Case-Analysis (9S).

All SPs ensured to follow a user-centered approach. However, in most cases budgets and logistics do not allow for a thorough user-research process. Instead domain experts such as department managers provide contextual facts and information about users (9S). One interviewee explicitly highlighted the risk of inaccuracy of second-hand information for the success of the project (1S). Another mentioned the importance of choosing efficient methods, such as contextual inquiry and job shadowing, if given the chance (1S). First hand context and user information is a key factor in user-centered design and design thinking, too [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF][START_REF] Wallach | User Centered Design: Why and How to Put Users First in Software Development[END_REF][START_REF] Abele | Usability Management bei SAP-Projekten. Grundlagen Vorgehen Methoden[END_REF]. Standardized quantitative methods on the other hand appear not existent as these are thought to be less efficient.

Phase 3: Ideation (Idea + Creation)

The ideation uses the information of exploration and analysis to review and probably adjust the projects goals. A creative team incorporating multiple professions and domain experts aims to create a number of gameful solutions to the problem in workshop and creative sessions. Ideas are mixed, further elaborated and documented in a structured and comparable format, such as a canvas or exposé sheet, including visuals and first hand low-fi prototypes [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Organizational layer -Understanding of Culture and Law (4S). SPs need a thorough understanding of culture and law, both rural and organizational wise and a sensibility for the context and codes of conduct (4S). For example, in Germany strict data security rules mostly forbid ideas with a competitive nature. The following, nonextensive list of legal-fields is relevant to AGs in enterprises: i.) The Right to informational self-determination concerning the survey and use of personal data and questions of data ownership; ii.) Workplace-related rights usually enforced by employeeorganizations and unions, such as rights of co-determination; iii.) IT-regulations and employee-agreements on ownership and use of outcomes conducted with a software; and iv.) Usage agreements and contractual rights between organization and SP.

Operational layer -Incorporation and Competence (4S).

Besides finding a common ground like discussed above, SPs seek to raise competence levels regarding AGs on the customer side (4S). They do so to incorporate and partner up with the customer during the following project phases for purposes of easier mutual agreements on decisions and their consequences, likewise suggested by Wilke et al. [START_REF] Wilke | Innovation als Voraussetzung für Erfolg[END_REF]. Interviewees preferred to have at least one domain expert on their team who also may represent the target group. Workshops during which both parties ideate together are common. Some SPs are more cautious about incorporating customers, especially during the creativity processes, for effectiveness reasons (2S). DT likewise [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF] argues for variety on the team and domain experts are requested in user experience projects [START_REF] Abele | Usability Management bei SAP-Projekten. Grundlagen Vorgehen Methoden[END_REF].

Project layer -Creativity and Tools (5S).

Interviewees suggested workshops as a primary format to iterate and ideate. These follow common rules for creativity sessions, such as no early critic, time-boxing and early visualization (5S). However, crazy ideas too early in the process could create doubts within conservative organizations. Warm ups exercises and discussing personal game experiences may help to start the activity and build a gameful attitude, which is important. (1S) [START_REF] Prensky | Digital game based learning[END_REF][START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF][START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Phase 4: Design

The design phase starts with a decision for one or more ideation results. The ideas are further elaborated and tested in a number of prototypes to test function, effectiveness, affective reactions of users and the overall experience they provide with respect to the projects goals. This phase includes feedback with target users and aims for a fully documented design concept, prototypes, content plan and technical specification that lays ground for a viable production planning [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Operational layer -Incorporation of Specialists (5S).

When going further with one or more selected ideas, specialists should be added to the design team. On an adminis-trative level the conformity of an idea to rules and regulations is required (employee organizations, stakeholders from IT, compliance and legal) (5S). Domain experts and pedagogical experts consult the team on a content level (4S).

Project layer -Iteration and Prototyping (4S). Likewise ideation the team should plan for a number of iterations during the design phase. Early low-fi and later hi-fi prototypes ensure the communication of functionality and emotionality of an idea (4S). It is important to regularly review the vision and goals of the project and respect common guidelines for usability and accessibility (1S). Other than suggested by literature, but coherent with the critic of phase two, target-users are only introduced late or not at all until the design is fixed (2S) [START_REF] Brown | Change by design. How design thinking transforms organizations and inspires innovation[END_REF][START_REF] Herger | Enterprise Gamification[END_REF][START_REF] Nicholson | A RECIPE for Meaningful Gamification[END_REF][START_REF] Abele | Usability Management bei SAP-Projekten. Grundlagen Vorgehen Methoden[END_REF].

Phase 5: Production

The production is separated from the former creation phases. It is a predictive phase in terms of time and necessary resources where the product is actually implemented. Parallel to production the product's launch is being prepared [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Organizational layer -Communication and Advertisement (6S).

Starting early to advertise the project across the target group and organization is a crucial factor for its later success [START_REF] Abele | Usability Management bei SAP-Projekten. Grundlagen Vorgehen Methoden[END_REF] (4S), but regularly neglected from the experience of the SPs (2S). It is suggested to address management and set up a core communication team. Despite the importance of this aspect SPs usually are not incorporated (2S).

Project layer -Feasibility and Extensibility (3S).

Overall the interviewees did not consider technical feasibility as a problem or risk (3S). A careful decision for a specific technology is of course important (2S). Requests for mobile or cross-platform development increase (1S). Three SPs stressed the need for a solid IT-architecture that allows for easy extension of features and contents after launch (3S).

Phase 6: Go-Live and Maintenance

The launch of the product concludes the project and should be accompanied by strong communication within the organization. An evaluation is conducted to control and review goals the contractors agreed on during project exploration and ideation. Probably maintenance and update conditions are negotiated [START_REF] Schmidt | Ein Vorgehensmodell für angewandte Spielformen[END_REF].

Operational layer -Communication and Lead by Example (4S).

Most AG projects are an additional offer above standard procedures, such as e-learning or seminars. When going live, department managers and core users are important multiplicators for project advertisement and role models (4S).

Project layer -Test and Review (5S). The majority of interviewees report tests of direct measurable data only, such as attendance or test results (5S). Other measures on soft factors, such as motivation or satisfaction are usually not applied. Academic methods, especially quantitative ones, can become costly. Organizations rather rely on informal indicators such as sensed satisfaction, which was criticized (3S).

Project layer -Update and Maintenance (4S).

A periodically data collection and processing is common in the games world. The information suggests improvements and updates necessary to keep a product alive. The same would count for an AG that also wears of over time, like all technical products. Because of the nature of innovative projects unfortunately no budget is planned for maintaining the product (4S).

Discussion

The success-factor model reflects first hand practical experiences of conducting an AG project across a wide range of organizations and budgets. The findings show that project goals mostly seem concerned with organizational learning, probably followed by product marketing and issues of human resources [START_REF] Herger | Enterprise Gamification[END_REF]. However, AGs are far from established yet in the DACH-region and SPs mostly offer such services complementary to others, such as UX or e-learning. All projects were declared as innovation projects and show some typical characteristics accordingly [START_REF] Wilke | Innovation als Voraussetzung für Erfolg[END_REF]. Managerial support, communications and clear goal definitions are preconditions to a project in general. But SPs for applied games should take transparency and communications even more serious to gain trust and understanding towards the process and the only gradually revealing outcome of an AG project. It is suggested to educate customers towards the unfamiliar game-perspective and to incorporate them in creation and decision making. Times and budgets are relatively small and often do not allow for a thorough analysis on case and users. Without, it is difficult to design meaningful experiences and motivate on a deeper psychological level which fosters shallow designs as rightfully criticized [START_REF] Ferrara | Games for Persuasion: Argumentation, Procedurality, and the Lie of Gamification[END_REF]. Applied Games tend to process user data. Legal issues and company specific rules and culture therefore can have serious implications and might interfere with design ideas. Overall most of the qualitative factors presented could be backed up with literature, supporting the notion of a high-level comparability of UX, DT, and AG projects as presumed. However, the complexity of AG-projects suggests experience to be an additional important success-factor.

Since this is an exploratory study some limitations need to be addressed. First this kind of study is not able to and was not planned to infer causality. Second the number of expert interviewees (n=9) is relatively small. This can partly be explained by the relative novelty of applied games and consequently a rare number of projects and partly by the narrow search radius of highly experienced experts. Therefore, we are confident to have identified a relevant sample for the DACH-region. Clearly, an international search would yield more representative results. Third no objective success criteria were mentioned as these differ widely across the projects. Standardized, practicable methods are not available apart from individual and indirect indicators, such as attendance. Fourth interviewees of the second series generally agreed on the twodimensional framework but mentioned individual differences in the definition of the ideation and design phases.

AG projects remain a promising endeavor to organizational development, potentially improving the attractiveness and effectiveness of applications and processes of organizational learning, guided changes and enterprise software. Expectations regarding their quality and power to foster motivation and create meaningful experiences and outcome [START_REF] Whitton | Digital games and learning[END_REF][START_REF] Nicholson | A RECIPE for Meaningful Gamification[END_REF] are high. When conducting such projects, much can already be learned from experts and other disciplines as referenced here. But budgets and circumstances need further adaption in some projects to actually transfer game-like experiences to the enterprise context. To contribute the further success of AGs, the results of this explorative research need further empirical and practical validation. A prioritization of the validated factors then eventually would allow for the design of a maturity model that helps enterprises and service providers to identify risks and areas of development of future projects. Cross-country studies would further help to differentiate general from rural and cultural depended aspects. Outside scope, this study suggests further research on design practices and standardized evaluation methods [START_REF]Serious games. Mechanisms and effects[END_REF][START_REF] Hamari | Does Gamification Work. A Literature Review of Empirical Studies on Gamification[END_REF] as well as on reasons and counterstrategies of weary effects.

Acknowledgements. We thank all interviewees for their time and valuable information and Thannos Rammos for the extensive background on legal aspects. We also thank the German Federal Ministry of Economic Affairs and Energy (BMWi) and DLR Project Management Agency for supporting this research.


Nobumitsu Shikine

Yuki Hayashi
email: yuki-hayashi@entcomp.esys.tsukuba.ac.jpt.akiba

Takeshi Akiba

Mami Tanasaki
email: m.tanasaki@sic-tky.com

Junichi Hoshino
email: jhoshino@esys.tsukuba.ac.jp

Game System of Coordination Skills Training for Elderly People

Keywords: elderly people, coordinated movement, upper-limb-grasp motion, training, game system

In this paper, we propose upper-limb-grasp motion as coordinated movement of five fingers and upper limbs. This coordination skill is important of daily living and we use unconscious. We divide upper-limb-grasp motion into 6 motion elements game system analysis and visualize with upper-limb-grasp motion measurement controller and game contents. We compared elderly and younger people and consider the result. As the result, we research exercise menu and game contents, technique of visualization.

Introduction

In our daily lives, actions such as holding objects, opening doors, reaching for things from high places, cooking, driving a car, and other various activities are carried out by moving the upper-limbs and fingers based on visual information. However, it is known that our faculty to carry out these cooperative motions decreases with age [START_REF] Seidler | Motor control and aging: links to age-related brain structural, functional, and bichemical effects[END_REF]. Therefore, there is a need for older people to train the cooperative motions between the arms and fingers. This has become a particularly important issue as the populations of Japan, and other developed nations, begin to age [START_REF] 文部科学省 | 生涯にわたる心身の健康の保持増進のための今後の健康に関する教育及びス ポ ーツの振興の在り方について保健体育審議会 答申[END_REF]. In the scope of cooperative motion between the arms and fingers, it is has been found after measurements were carried out that focussed on the adjustment of strength in the fingers, there is a decrease in function with age [START_REF] Kun | Age-related changes in finger coordination in static prehension tasks[END_REF], and training is carried out to focus on dexterity [4]. There are also limitations on arm movements, and a measurement of physical function using an actuator and training are performed [START_REF] Vinoth | Skilled Finger Movement Exercise Improves Hand Function[END_REF]. The motion algorithm of hand-eye coordination is also being researched [6].Furthermore, it has been made clear that training carried out through a game designed to improve cognitive function can also help improve the multitasking capabilities necessary for cooperative motion even in the elderly [START_REF] Albert | Robot-Assisted Therapy for Long-Term Upper-Limb Impairment after Stroke, The 8[END_REF]. However, while there is a need to break down and investigate each aspect of physical movement for the arms and fingers so that the cooperative motion between the two can be trained, as well as for an analysis of how they move cooperatively, this is no easy task. Therefore, it's very difficult to develop a system that trains for cooperation between them. This paper defines the cooperative motion of the upper-limbs and fingers based on visual information as upper-limb grasp motion. And propose a game system to support training with a dumbbell-shaped controller, which is easy to grasp with both hands and game contents. We examined the movements that make up the cooperative motions between the upper-limbs and fingers, did an analysis and visualization for elderly people. And through it we support the implementation of healthy exercise and the selfawareness of motion characteristics for upper-limb grasp motion training. By breaking down the elements that make up upper-limb grasp motions into 6 items; the pressure and balance of the fingers, the exercise capabilities of each finger, the smoothness of upper-limb movement, mobility range of the shoulders, cooperation between the upper-limbs and fingers, and the coordination of both hands, changes in the physical capabilities are analyzed. In order to evaluate the effectiveness of this system, the upper-limb grasp motion of the elderly will be measured, and by comparing the analyzed results with a younger age range, the change in physical capabilities with age will be investigated, and the performance indicators and visualization method examined.Furthermore, the giving of visual feedback either to the user or care manager about their motion characteristics and how they stand physically compared to other users is useful in the promotion of healthy exercise, an increase in attentiveness to their daily activities, and the creation of a longterm training care plan.

2

Previous studies

Decline in physical capabilities with age

Through the results of the Jebsen-Taylor hand function test, which investigates the correlation between finger function and ageing, it is known that finger function begins to decline from the age of 60 [8]. In the research that focuses on function in the fingertips, such as pinch strength and accuracy, it was suggested that pinch strength declines with age and it becomes more difficult to keep hands still due to a loss of feeling in the fingertips [START_REF] Crawford | Spatial Transformations for Eye-Hand Coordination[END_REF], which leads to a drop in accuracy [10][11].

Though it is a recognized fact that motor function declines with age, it's also reported that there are individual and crosswise differences [START_REF] Ketcham | Age-Related Kinematic Differences as Influenced by Task Difficulty, Target Size, and Movement Amplitude[END_REF], and that as there are also differences in the tendency towards this decline, it is important to take precautions to prevent it [START_REF] Vinoth | MSE: Effects of Aging on Hand Function[END_REF]. In addition to this, upon suggesting that motor function declines with age, it was also stated that there is also a scope for improvement [START_REF] Bernhardt | Accuracy of Observational Kinematic Assessment of Upper-Limb Movements[END_REF].

Research concerning upper-limb and finger coordination

In hand-eye coordination research, the movement of the eye and the upper-limbs when pointing to a dot was analyzed [6]. The result of this research was that it showed that the method of pointing is powered by feed-forward control. Hand and upper-limb rehabilitation is effective in stroke rehabilitation and attempts are being made to restore physical faculties [START_REF] Desrosiersa | Age-related changes in upper extremity performance of elderly people: A longitudinal study[END_REF]. Many methods are proposed, including both-side training, one-sided training, and rhythm training.

Game systems that improve physical and cognitive function

In the game Neuro Racer [START_REF] Albert | Robot-Assisted Therapy for Long-Term Upper-Limb Impairment after Stroke, The 8[END_REF], cognitive function is shown to improve as the user has to push buttons at the correct time while racing, forcing them to do multiple actions at once. However, as this game only focuses on multitasking, the amount of motor function that the user is using is limited. Games are also now being brought out onto the market that have been developed specifically to improve physical faculties and cognitive function. The standing up game "Rehabilium Kiritsukun", which is often used in stroke treatment, and is based on everyday movements, has also made its way onto the market [START_REF] Poston | Movement structure in young and elderly adults during goal-directed movements of the left and right arm[END_REF]. As the user goes through the game making standing movements they can observe their form on the screen and carry out training of this function. In addition to this, there is a piece of equipment called the "digital mirror" that allows them to see their own physical functionality as they make certain movements. Through imitating the instructors movements while checking their form in a screen that forms a half-mirror and a set of balance scales on the floor, effective rehabilitation can be carried out.

Analysis of movements and cognitive function in the elderly

In research that studies the reaching movements of hemiplegia patients, a chronological data analysis is carried out, as well as an RMS and autocorrelation linear study, and a non-linear analysis that assumes dimensionality reduction through minimizing nearest-neighbor error [START_REF] Voelcker-Rehage | Motor-skill learning in older adults-a review of studies on age-related differences[END_REF]. A significant correlation with the clinical rating scale can be seen and as a rating scale it shows useful things. Furthermore, muscle potential is also used to analyze arm movement. In research that measured muscle potential by asking participants to perform simple movements, such as rotating a rod that they were grasping by 90°, there was a scattering in results [START_REF] Peter G Levine | Stronger After Stroke[END_REF]. As a performance indicator for the smoothness of movement, a minimum-jerk model is proposed to work as a rating scale for the sum total of the multiplication of jerks [19]. This model proved useful for evaluating stability in an experiment that looked at the stability of the walk of an elderly person to examine the smoothness of movement [20]. In regards to simple rotation of the arm, in research that looked in detail at the greatest angle the arm could reach, its speed, and its acceleration, it was found that there was little difference between elderly and young people when they were asked to rotate their arms at a slow speed of their choice, but the difference got much greater as they were asked to speed up. Furthermore, when the dual-tasking ability of posture and attentiveness was investigated over 4 poses, it was found that the older someone was, the more difficult it was for them to hold their attentiveness as they held complicated poses. Cognitive function is also analyzed, and analyses concerning fingertip movement and the relationship between motor capabilities and cognitive function were carried out by using fMRI and EEG. Although research that aims to improve physical and cognitive function in the elderly like that above, which has been conducted from a variety of viewpoints, is being carried out, there is still no analysis or visualization that focuses on the cooperative motions between the fingers and upper-limbs or support for long-term training. This document proposes a system that covers these functions.

System summary

Upper-limb grasp motion

In this document, even within the scope of visiomotor coordination, upper-limb grasp motion refers to the coordinated movements between vision and the fingers and upperlimbs. We have sorted the physical elements of upper-limb grasp motion into 6 types, the details of which are explained below: 1. Balance of finger pressure This is the deviation of the maximum grip strength in each finger when gripping an object using all fingers on both hands. It's known that when elderly people put force on various parts of an object at the same time, that force is less then when they put that force on a more restricted area. A bilateral deficit is also reported. In this paper, because the pressure sensor of the controller has constant area, the physical quantity we measured by fingers is force [N].

Finger exercise capacity

This is related to the ability to join together and move all of the fingers on both hands. It is the ability to move the intended finger at the intended timing, in the intended way. In everyday life people don't only grasp things, sometimes they often need to power 2 fingers to make a pinching motion, or a specific fingers to cook, or even specific fingers in order to operate machines. It's reported that the strength and accuracy of the fingers declines with age [START_REF] Crawford | Spatial Transformations for Eye-Hand Coordination[END_REF][10] [START_REF] Hackel | Changes in hand function in the aging adult as determined by the Jebsen Test of Hand Function[END_REF].

Upper-limb exercise smoothness

This is when an upper-limb is moved at a fixed speed, and concerns the fragmentation that occurs if this movement is not smooth. It's reported that for elderly people, if it's very difficult for them to demonstrate a constant speed which reduces the smoothness of their exercise.Acceleration and jerks [19] are often used as performance indicators for smoothness.

Shoulder movement scope

This is an element of movement that focuses on the shoulder and the scope in which it can be rotated up, down, left, or right. It's said that the range in which the shoulder can be moved upwards decreases with age. Movable region measurement is carried out in physiotherapy, and the exercise direction that will be examined in this research is the bend of the shoulders (and shoulder girdle) as well as their inner and outer rotations.

Upper-limb and finger coordination

This is an essential element of movement when moving the fingers and an upperlimb at the same time, and is related to the movement of gripping something as it is moved. It is the ability of how accurately and how far the hand can go as it grips an object and is moved by joints such as the elbow and shoulder. When a person ages, their movements become slow, and accuracy also decreases. This element of movement is usually examined using the pegboard test.

Hand-eye coordination

This relates to the movement carried out by confirming the position of an object through sight and moving hand accurately and at the intended timing to grasp it, and also to grasp objects that are in motion. Adjustment of the position of the hands encompasses both feed-forward control and feed-back control. Feed-forward control is required for actions such as catching a ball that is flying towards you, while feed-back control is required when adjusting the angle of the hand to prevent a glass of water from spilling as it is carried.

Exercise support system summary

The images of the game system that measures, analyzes, and visualizes the upperlimb grasp motion of elderly people in use are shown in Fig. 1. The user sits in a chair, grasps the controller that will measure the upper-limb grasp motion, and proceeds through the game content that is displayed on the screen. The exercise process is explained by a character in the game who acts as an instructor. The game analyzes the characteristics of each user's upper-limb grasp motion, and gives feedback to either the user or their care manager.

The upper-limb grasp motion is analyzed and visualized and supports the comprehension of the gap in capabilities in the upper-limb grasp motion of the elderly and the young. It measures the motion characteristics found in upper-limb grasp motion in all users, including the young, and by updating the performance indicators, can check the user's motion type, as well as make clear its relation to the state of their health.

A controller that measures upper-limb grasp motion

In order to be able to measure finger pressure, upper-limb movement, or upper-limb grasp motion, which is a combination of the two, it's necessary to be able to measure each finger's pressure and the movement of the arm. In this document, we have developed a controller like that in Fig. 2 together with System Instruments Ltd. The area where the controller is grasped has a rubber cover, and it's shaped to fit all 5 fingers. The pressure sensors buried into the area where the controller is gripped measures finger pressure[N], and upper-limb movement is calculated by 3-axis internal sensors that measure acceleration[m/s 2 ], angular velocity[rad/s], and geomagnetism. Using the body as a center point, the position of the user's up, down, left, and right arm rotations is calculated by information from the acceleration and angular velocity sensors. The data from each sensor is sent to computer via Bluetooth, where it is stored, calculated, and reflected on the screen (Fig. 3).

The values from the sensors are converted by this formula (1)(2)(3)(4)in to the rotational angle (roll, pitch, yaw) [deg] of the arm using the shoulder as center point. The roll and pitch directions use the acceleration value. For the yaw direction, the value of the angular velocity sensor is integrated to estimate the current position, and for this reason the game needs to be calibrated before the game content starts.

𝜃 " ≒ c " 𝑎 & (1) 𝜃 ' ≒ c ' 𝑎 ( | 𝑐 ' > 𝑎 ( (2) 𝜃 ' ≒ c ' 𝑎 -| 𝑐 ' ≤ 𝑎 ( (3

Game unit overview

A game unit is created to measure upper-limb grasp motion, and each game unit is used to acquire data concerning each element of movement related to upper-limb grasp motion. Each game unit features a character who acts as an instructor, re-enacting all of the movements that the user performs, and encourages the appropriate exercise via voice instruction. Furthermore, the user can see the state of their movements through the controller and interface displayed within the game (Fig. 4). The controller is displayed on screen in relation to its actual location. Finger pressure is displayed by lighting up the area around the name of the respondent finger in red.6 types of game content come with the unit, each corresponding to one of the 6 elements of movement or a combination thereof. Since the movements of the user can be analyzed in each section, a performance value can be calculated for each element of movement.

Content and traits of each game unit (a)(b)(c)(d)(e)(f)

(a) Movement imitation game (Fig. 4.a)

The upper-limbs are moved to imitate the movements directed by the instructor. The aim of the game is to move the arm up, down, left, right, and in a diagonal direction using the shoulder as a center point (Fig. 5). The game last for 5 minutes and examines upper-limb exercise smoothness, shoulder movement scope, and flexibility. (b) Simultaneous maximum finger pressure game (Fig. 4

.b)

The controller is grasped using all 5 fingers on each hand, and the maximum finger pressure for each is calculated. The measurement is taken twice to imitate a real finger pressure examination. This examines the balance of finger pressure.

(c) Finger reaction game (Fig. 4.c)

The screen indicates one finger from both of the users hands, which they must then press down as fast as they can. The time between the direction being given and the finger being pressed is then measured. This game examines finger exercise capacity. (d) Object moving game (Fig. 4.d)

This game compels the user to pick up an object in the game and move it to the specified location. The main element of movement that is examined here is upper-limb and finger coordination. The in-game catcher is moved by either rotating the arm in a pitch or yaw direction and closing in upon the object. When the catcher is close to the object, it can be grasped by applying pressure that totals a value greater than that already fixed. The movement to transfer the object to the designated area is performed 3 times from left to right, and 3 times from right to left. The amount of time taken to complete the task and the number of times the object has been dropped are then calculated. (e) Catch ball game (Fig. 4.e)

The user catches the ball that is flying towards them 3 times within the game. The position of where the ball will land is fixed, and it always comes towards the user in the game. This game examines hand-eye coordination and feed-forward control capability is necessary for getting the grasp timing right. The amount of time between the users catch timing and an accurate timing is measured. (f) Ball rolling game (Fig. 4.f)

The controller is tilted backward and forwards and from left to right to cause the ingame ball to roll towards the target area. This game is repeated 3 times, and the ball starts at a different position each turn. This game examines hand-eye coordination as it requires the user to use the visual information in front of them to alter the direction of the ball and the ability of feed-forward control so the user knows when to tilt the controller. The game measures how long it takes the user to get the ball to the target area.

Motion analysis

An analysis is carried out on the data measured by the games and the performance values for the elements of movement calculated. To visualize the parameters for each element of movement, they are put into 5 levels of evaluation. The method for the analysis is shown below:

1. Balance of finger pressure Studies the scattering in maximum pressure from each finger when the user puts pressure on all fingers in the simultaneous maximum pressure finger examination game (b), and standard deviation is calculated from the average pressure of each finger [START_REF] Vinoth | Skilled Finger Movement Exercise Improves Hand Function[END_REF]. The value of the standard deviation is then evaluated into one of 5 levels.

σ = # #$ % & -( ) #$ &*# (5)
σ : Standard deviation ! " ~!"$ : each finger pressure (! " is right thumb,! "# is left pinkie) [N] ! : The mean value of each fingers' maximum pressure [N]

Finger exercise capacity

In order to investigate whether the user can move each finger as instructed in the finger reaction game (c), the amount of time taken between the direction being given and the maximum finger pressure for the relevant finger being exerted is evaluated into one of 5 levels.

Upper-limb exercise smoothness

In order to study the smoothness of the arm movements when the shoulder is centered during the movement imitation game (a), the minimum jerk model is calculated from the value of the 3-axis acceleration sensor. The evaluation function value is then evaluated into one of 5 levels.

Shoulder movement scope

To study the flexibility and range of movement when the arm is rotated with the shoulder centered during the movement imitation game (a),the amount that the controller was moved either up, down, left, right, or at a slant from its place on the knees is evaluated. The evaluation is based on the reference angle of the outer rotation of the joint movement region measurement, and evaluated into one of 5 levels. A value is calculated from the average of each direction.

Upper-limb and finger coordination

To study hand-eye coordination in the object moving game (d), the amount of time taken to move the ball and the number of times that it is dropped is evaluated. The time required is evaluated into one of 5 levels, and a level is dropped for each time the ball was dropped.

Hand-eye coordination

In order to study feed-back control capabilities within the scope of hand-eye coordination during the ball rolling game (f), the time taken to roll the ball to the target area is evaluated into one of 5 levels.

Supporting training by visualization

So that each user can easily comprehend the characteristics of their elements of movement, their data is made into an easy-to-understand spider chart (Fig. 5). The average data for each generation and for young people can also be displayed, making it easier for the user to see where they stand when compared to others.

Experiment

To test the effectiveness of the measurement of upper-limb grasp motion, analysis, and visualization of results using the created system, a comparison was carried out between the elderly and the young.

Target group

The research content was explained orally and through literature to the target group, and 12 healthy young and elderly people who gave their consent were selected. The elderly group was made up of 6 people (3 men and 3 women with an average age of 79.3±5.7) who weren't prevented from exercising by their doctors, and the younger group was also made up of 6 people (3 men and 3 women with an average age of 24.3±2.7) who were healthy university students.

Method

The content of the game was displayed on a large screen via PC, and the target group took part in the experiment by taking the controller and sitting in a chair 2m away from the display. (Fig. 6) The way to use the controller was explained. The games played were the 6 that were described in Chapter 4. The elements of movement of both the younger and older group were measured using the controller and game content, and an evaluation was calculated relating to each of the 6 types of motion characteristics.

Results

The evaluation value of each of the 6 types of motion characteristics were calculated, and the average values of the men and women from the older group, and the men and women of the younger group are shown in Fig. 7.

In all characteristics with the exception of the upper-limb exercise smoothness, the averages of both the men and women in the younger group yielded better results than the averages of the men and women in the older group. However, in the inspection analysis, it was found that the only trait that showed a significant gap was the finger exercise capacity (p<0.05) (Table 1). It was found that when the reaction time was compared for each finger(Fig. 8), the younger group had better results in every finger than the older group.

Furthermore, when each trait was analyzed in detail, a significant difference (p<0.05) between the older and younger group was found in the flexibility and movement scope of the shoulder in the up and down direction only.

Investigations

We analyzed by quantifying 6 motion elements composing upper-limb movement.

Although every subject's result was different from each other, elderly people group's result was more varied than younger group. So that we found, even they are same generation, elderly people's exercise capability and characteristic are not the same for each person. The only trait which showed a significant difference was the finger exercise capability component, it's thought that this is because there is a big scattering in the capabilities of those in the older group. Furthermore, in relation to the finger exercise capability characteristic, which showed a significant difference, although it's thought that the older group's delay in reaction speed is also part of the cause, it's also thought that due to the larger disparity of results when compared to the younger group, the older group find it difficult to move their finger by their reflexes (Fig. 8). In fact, during the experiment itself, it was observed that the older group would move their fingers after vocalizing the direction, or move the wrong finger by mistake. It could be thought that the older group need to comprehend which finger to move and then move the finger after thinking about it. Therefore, there's a possibility that it's difficult for them to move their fingers intuitively in their private lives. (e.g. using a remote control, chop stick, scissors) Though in this paper we didn't impression evaluation, elderly who use our system said "Interesting" "I want to continue to use" "I want to buy". It seems that we can urge to do training by giving a game system entertainment.

Conclusion

This paper has focused on the cooperative motion between the fingers and upperlimbs, a movement important to everyday life, and defined it as the upper-limb grasp motion. The components of this motion were broken down into 6 elements, and a game controller and contents that could measure each element of movement created, as well as a games system that evaluated and comparatively analyzed this data before visualizing it. To evaluate this system, the upper-limb grasp motion of a group of older people and a group of younger people was measured, analyzed, a comparison performed, and visualized before an examination of the performance indicators was also undertaken.

As for the results, we found elderly people's exercise capability and characteristic are not the same for each person compared from younger people. As significant differences could not be found in all of the elements of motion that comprise the upperlimb grasp motion between the older and younger groups, the experiment did not progress to the visualization stage or the examination of the performance indicators. However, from the larger disparity found in the measured values in each element of movement in the older group when compared to the younger group, it was found that there is an individual gap between upper-limb grasp motion capabilities that bears no relation to age. Furthermore, it was also found that in the finger exercise capability tests, the difference in movement when compared to the young people, as well as the measurement results themselves, was significant. But considering that elderly people's exercise capability and characteristic are not the same for each person, it is still difficult to examine generally exercise characteristic of elderly. It is necessary to collect more data from subjects. And to define more suitable performance index which divides elderly from younger by that is our future work.

In the future it will have found, elderly people and care managers can make it easier to see their characteristic or where they stand when compared to others by using this system. Furthermore, it can be expected that this system will be useful for the people who makes long-term care plan.

Fig. 1 .Fig. 2 .Fig. 3 .

 123 Fig. 1. System Image

  Fig.4.Game contents base vision

  ! $ , ! % :triaxial acceleration[m/s 2 ]

Fig. 5 .

 5 Fig.5. Upper-limb-grasp motion cobweb chart Fig.6. Experimental situation

Fig. 7 .

 7 Fig.7. The comparison of upper-limb coordination EM(elderly male), EF(elderly female), YM(young male), YF(young female)

Fig. 8 .Fig. 9 .

 89 Fig.8. finger exercise capacity

)

  𝜃 " ≒ c / 𝑔 & 𝑡 cos 𝜃 " -𝑔 ( 𝑡 sin 𝜃 ' cos 𝜃 " -𝑔 -𝑡 cos 𝜃 ' cos 𝜃 " 𝑑𝑡 (4) 𝑎 & , 𝑎 ( , 𝑎 -: triaxial acceleration [m/s 2 ], 𝑔 & , 𝑔 ( , 𝑔 -: triaxial angular velocity[rad/s] 𝜃 " , 𝜃 ' , 𝜃 / : posture (roll, pitch, yaw) [deg], c " , c ' , c

/ : proportionality constant 4 Configuration of the game unit

Table 1

 1 The comparison of the mean value of each parameter of upper-limb coordination

	elderly	young	P value


Nadia Boufares
email: nedya.boufares@ensi-uma.tn

Pascale Minet
email: pascale.minet@inria.fr

Ines Khoufi
email: ines.khoufi@inria.fr

Leila Saidane
email: leila.saidane@ensi-uma.tn

Covering a 3D

published or not. The documents may come   L'archive ouverte pluridisciplinaire

I. CONTEXT AND MOTIVATION

Recent advanced researches on industrial and commercial applications have enabled the emergence of a new cutting-edge network of small and low-power devices which is the Wireless Sensor Network (WSN). Sensor nodes are scattered in the field of interest in order to monitor environmental and physical phenomena such as temperature, pressure, vibrations... and to track moving targets such as enemy vehicles, intruders, animals...Hence, WSNs are solicited in several applications including underwater acoustic monitoring, weather and environment disaster forecasting, military battlefields, home automation... To do so, node deployment is considered as the main issue in WSNs, since it affects the lifetime and Quality of Service (QoS) for WSNs. To provide an optimized deployment, two key requirements should be taken into consideration: the area coverage and network connectivity. The area to be supervised is said fully covered if each event occurring in this area will be detected by at least one sensor node. If there exists at least one path between each node and a central node collect sink then the network connectivity is said maintained so that any encountered event will be reported to the sink. The requirements that must be met by a network deployment depend mostly on the application supported. Some applications need a full coverage and a permanent connectivity such as in military battlefields. For other applications, partial coverage and temporary connectivity are enough. In order to meet all these requirements, a deployment algorithm is needed to determine the appropriate sensor node positions. The deployment algorithm can be centralized, where the sink node is the entity that collects different nodes positions and then computes the new positions of nodes in the new deployment. Later, a human or a mobile robot will be in charge of moving nodes to their new positions. Otherwise, if sensor nodes are mobile and autonmous, then, the algorithm is distributed and nodes will collaborate and exchange data to determine their new positions and achieve a new deployment. Extensive previous researches on coverage and connectvity issues focused mainly on terrestrial applications but recently it seems that the elevation of nodes plays a very significant role in the WSN deployment. Most of these works took into consideration a 3D space where nodes are located freely within the whole field of interest as shown in Figure 1a. However, in many real world applications, this area is neither horizontal flat 2D nor 3D space. Instead, it is a sequence (continuation) of sloping surfaces (i.e, inclined planes) as depicted in Figure 1b or complex 3D surface as shown in Figure 1c. Volcanos monitoring (e.g mountains) and snow tracking are the most relevant 3D surface covering applications.

In this paper, we are interested in scattering mobile nodes over a 3D flat surface. We started by fixing the parameters of the deployment algorithm considering a horizontal 2D plane. Then, we extend the results to cope with 3D inclined plane. We study several shapes of 3D-flat-surfaces. Nodes must move to cover the surface of the given shape. That is why we propose to design a 3D distributed deployment algorithm that aims to deploy sensor nodes over the 3D surface area in order to ensure full are coverage and network connectivity. This algorithm is based on the virtual forces approach [START_REF] Zou | Sensor deployment and target localization based on virtual forces[END_REF]. This paper is organized as follows: In Section II, we give an overview of the state of the art. Section III describes our 3D distributed virtual forces algorithm in details. Section IV deals with the performance evaluation of our algorithm. Finally, we conclude and discuss future work in Section V.

II. RELATED WORK

In the literature, several strategies are proposed to determine optimal nodes positions in order to provide high coverage rate. Extensive studies were interested in terrestrial deployments. These strategies focused mainly on 2D applications. Recent studies [START_REF] Zhao | Surface coverage in wireless sensor networks[END_REF] showed that 3D surface deployment is completely different from deployments in a 2D plane or a 3D a .3D volume b .3D flat surface c .3D complex surface Fig. 1: 3D area volume. Existing 2D and 3D solutions could not be directly extended to 3D surface covering schemes otherwise coverage holes will arise. Figure 2 shows that if the deployment of the 2D sensor nodes on the horizontal plane depicted in blue is used to build by projection in the deployment on the sloping plane depicted in red, coverage holes appear in both cases of projection. If d the distance between two blue neighboring nodes is increased by projection (d > d on Figure 2a), these nodes projected in the red plane are no longer neighbors. If on the contrary, the distance is decreaed (see Figure 2b Hence, 3D surfaces, whether 3D flat surfaces or 3D complex surfaces, come out with new challenges such as how to handle variations in the shape of the 3D surface. There are different ways to classify existing research on the coverage-connectivity problem. We distinguish two main deployment strategies: static strategies and dynamic strategies. In static approaches, we can adopt the grid-based strategy [START_REF] Khoufi | Survey of deployment algorithms in wireless sensor networks: coverage and connectivity issues and challenges[END_REF]. With the grid-based strategy, if the area is considered regular, then, nodes must be placed either at cell centers or at cell vertices. However, if the region has irregular borders, in order to avoid coverage holes, extra positions are added out of the grid. Many researches were held to determine the best space-filling polyhedron that tessellates a 3D space with the highest volumetric quotient. In fact, a polyhedron is a three-dimensional shape that consists of a finite number of polygonal faces such as the triangular prism, the hexagonal prism, the cube, the truncated octahedron... The authors in [START_REF] Alam | Coverage and connectivity in three-dimensional networks[END_REF] showed that the trucated octahedron tessellation is the best tessellation for ensuring a 3D volume coverage using the minimum number of sensor nodes. Nodes will be placed at the centers of trunacted octahedron cells. They demonstrated, then, that the communication range R must be at least 1.7889 times the sensing range r to maintain the network connectivity.

On the other hand, many studies focused on dynamic deployments where nodes are considered as mobile nodes. Authors, in [START_REF] Li | Autonomous deployment for load balancing-surface coverage in sensor networks[END_REF], used Voronoi cells to ensure 2D or 3D kcoverage (i.e. an area is said k-covered if each each unit of the space considered is covered by at least k sensor nodes). They illustrated APOLLO deployment, an autonomous deployment to provide k-surface coverage. With this approach, nodes are able to move with the intention of achieving k-coverage while minimizing the maximum sensing range required by the nodes. If the computational geometry strategy is adopted, then, nodes positions are computed using the Voronoi diagram or the Delaunay triangulation. This approach has a high cost of computation. The authors in [START_REF] Jin | Optimal surface deployment problem in wireless sensor networks[END_REF] tried to find the optimal deployment on different 3D surfaces that will achieve a high sensing quality. They proved that the Centroidal Voronoi tessellation leads to the required optimal deployment. However, this approach is not scalable since nodes positions are computed by the sink.

The virtual forces paradigm is a distributed algorithm which is based on attractive and repulsive forces. Sensor nodes move to their new positions according to a predefined threshold distance D th that should be maintained between neighbors during the network lifetimne. If the distance between two sensor nodes is less than D th , then, the neighbor node will exert a repulsive node. If this distance is greater than D th , an attractive force is exerted. Otherwise, the force is null. Each node computes its resultant force autonomously and then, determines its new position depending on that force. 2D virtual forces algorithm has been extended to the 3D version and used in both [START_REF] Li | Deploying three-dimensional mobile sensor networks based on virtual forces algorithm[END_REF], [START_REF] Miao | 3d self-deployment algorithm in mobile wireless sensor networks[END_REF] and [START_REF] Boufares | Three dimensional mobile wireless sensor networks redeployment based on virtual forces[END_REF], aiming to ensure 3D space full coverage of 3D area and maintain network connectivity. The virtue of this approach consists in its simplicity: sensor nodes are able to spread and move in the whole area so that they can meet rapidly the coverage and connectivity requirements. In this paper, we focus on 3D flat surface coverage. We assume that the 3D surface may be unknown or hostile and sensor nodes are mobile and autonomous. We adopt the virtual forces strategy to allow nodes spreading over the whole 3D surface (e.g. mountains). The goal is to ensure full 3D surface coverage and maintain network connectivity.

III. OUR CONTRIBUTION : 3D-DVFA-FSC

To deploy sensor nodes in a 3D-surface, we propose 3D-DVFA-FSC algorithm: 3D Distributed Virtual Forces Algorithm for Flat Surface Covering. 3D-DVFA-FSC is a distributed algorithm based on the virtual forces strategy to allow nodes spreading on the 3D-surface to achieve full coverage and connectivity. The main goal of the virtual forces paradigm is to maintain the same target distance between neighboring nodes. This target distance is called D th , the Distance threshold.

A. Models and Assumptions

In this paper, we adopt the following assumptions in order to cover the whole 3D surface:

• Each node in the sensor network can determine its own position from global positioning system (GPS).

• The binary sensing model will be adopted as the sensing model, which means the probability of detecting the target is 1 if this one is within the sensor's sensing range, and 0 otherwise. • The communication model is also binary.

• The sensing range and communication range are modeled by two spheres of radius r and R respectively. • The entity to monitor is a sequence of sloping surfaces.

B. Principles of 3D-DVFA-FSC

The 3D-DVFA-FSC algorithm proceeds in iterations. At each iteration, each node broadcasts a Hello message. In the Hello message, each node sends its position and listens to incoming Hello messages in order to perform the neighborhood discovery. Then, each sensor node s i is able to determine its 1-hop neighbors and 2-hop neighbors. These neighbors will exert either attractive or repulsive force, according to their distance to node s i that will be able to compute its new position depending on the resultant force.

Let d ij denote the euclidean distance between the sensor nodes s i and s j . d ij is given by (x j -x i ) 2 + (y j -y i ) 2 . The force exerted by sensor s j on sensor s i is

• an attractive force if d ij > D th and is given by:

F ij = K a • (d ij -D th ) • (x j -x i , y j -y i ) d ij
• a repulsive force, if d ij < D th and is equal to

F ij = K r • (D th -d ij ) • (x i -x j , y i -y j ) d ij
• null otherwise, (d ij = D th ) Hence, the resultant force F i on s i is computed as the sum of these forces exerted by its 1-hop and 2-hop neighbors:

F i = j F ij
The sensor nodes should move on the given 3D surface depending on the resultant force. Notice that K a and K r are the attractive coefficient and the repulsive coefficient of the virtual forces strategy, respectively. To favor the convergence of the algorithm, K r should be much higher than K a . To improve the efficiency of the algorithm, the distance traveled by each sensor node at each iteration is limited by Dist max , a parameter of the 3D-DVFA-FSC algorithm.

Initially, nodes are scattered at the bottom of the 3D flat surface, except for the fourth configuration 4, where nodes are scattered at the top of the surface. As the resultant force is computed as a 2D planar vector, then to determine accurately the new position onto the 3D sloping surface, sensor nodes should travel on the three dimensional surface the same distance that would be traveled in 2D horizontal surface (without taking into account the height) as illustrated in Figure 3. In case of continous 3D flat surfaces as illustrated in configuration 3 and configuration 4, sensor nodes move to an intermediate position which represents the edge between the two flat areas then moves towards the next flat area. The sum of the traveled distances should not exceed the computed 2D distance (without taking into account the height) as depicted in Figure 4. The distributed algorithm proceeds as follows. Each sensor node computes the resultant of the virtual forces according to the principle given previously, taking into account only the dimensions x and y. Then it moves according to the direction of the resultant force while following the shape of the surface.

C. Simulation Parameters

In real applications, when dealing with 3D surfaces (e.g, mountains), nodes are scattered randomly, by an aircraft, for instance. Hence, we evaluate 3D-DVFA-FSC using an initial configuration where nodes are placed randomly at the bottom of the 3D flat surface. To evaluate performances of our 3D-DVFA-FSC algorithm, we implemented it in the Network Simulator NS3 version 3.25. Table I illustrates the simulation parameters used to evaluate the 3D-DVFA-FSC algorithm. The values of K a and K r are tuned by series of simulations. The value of D th is computed according to the triangular lattice deployment. D th is given by Equations 1 and 2 where the value of the sensing range is equal to 25m and the value of the communication range is equal to 50m. To evaluate the effeciency of our solution, we studied different shapes of flat surfaces inclined at various angles and having an area of 250000m 2 . The height of the surface will be calculated according to the planar equation z = x * tan(α), where α denotes the angle of the surface with the horizontal plane. Nodes are scattered initially at the bottom of the mountain. In the first configuration, the 3D flat surface considered is depicted in Figure 5a. Its equation is given by: z = x * tan(α1), with α1 = 30 • . In the second configuration, the 3D flat surface considered is depicted in Figure 5b. Its equation is given by:z = x * tan(α2), with α2 = 60 • . In the third configuration, the flat 3D surface considered is depicted in Figure 6a. Its equation is given by: We evaluate the coverage rate as a function of time. To do so, we considered a virtual 2D grid of unit cells on the 3D surface. If there exists at least one node whose distance to the cell center is less than or equal to the sensing range, then, the cell is covered. The coverage rate is equal to the number of covered cells over the total number of cells. Figures 7 and8 show the coverage rate obtained as an average of 20 simulations. Full coverage (i.e 100% coverage rate) is reached for all the given configurations as shown in the following figures. Simulations showed that the virtual forces paradigm is still adopted for 3D flat surface coverage as it was for 2D plane area and for 3D volume if we adapt its parameters (K r , K a ,D th ...). The 3D-DVFA-FSC algorithm enables sensor nodes to heal coverage holes during the deployment iterations. In this paper, we also evaluate the total distance traveled by nodes as a function of time. Figures 13,14 show the cumulative distance traveled by nodes as a function of time for the different 3D surface scenarios. We can observe that this distance increases as a function of time. This is due to nthe node oscillations problem, the main drawback of the virtual forces strategy. Then, sensor nodes are still oscillating even if the full coverage is ensured. We observe that a higher slope needs more time to ensure coverage but a smalle cumulative traveled distance. For the same number of sensor nodes and the same surface, the deployment seems more regular and optimized with a higher surface slope. In this paper, we proposed 3D-DVFA-FSC, a distributed deployment algorithm based on virtual forces in order to ensure full 3D-surface coverage and maintain network connectivity. We evaluated 3D-DVFA-FSC using different 3D flat surface shapes. Initially, nodes were randomly deployed. Full coverage was reached in the given configurations and maintain that rate to the end of simulation. We also evaluated the total distance traveled by nodes. Simulation results show that sensor nodes still move even when full 3D-surface coverage is reached. This is due to the node oscillations problem. This problem will be tackled in our future work. We will also focus on how to stop nodes when full coverage is reached and consider 3D surface complex shapes where the challenges of coverage and connectivity are more complicated.

Rc >= √ 3 * Rs (1)
Rs = √ 3 * D th (2)

2 Fig. 2 :

 22 Fig. 2: Planar coverage holes

Fig. 3 :

 3 Fig. 3: 3D-flat-surface Virtual force iteration

zFig. 6 :

 6 Fig. 5: 3D flat surfaces

Fig. 7 :Fig. 8 :

 78 Fig. 7: Coverage rate for configuration 1 and 2

Fig. 9 :Fig. 10 :

 910 Fig. 9: First configuration connectivity

Fig. 13 :

 13 Fig. 13: Distance traveled for configuration 1 and 2

TABLE I :

 I Simulation parameters

	Topology
	Number of nodes	250
	Speed	5m/s
	MAC Layer
	Protocol	IEEE 802.11b
	Throughput	2 Mb/s
	Transmission range R	50m
	Sensing range r	25m
	Simulation
	Result	average of 20 simulation runs
	Simulation time	3000s
	3D-DVFA
	Ka	0.007
	Kr	0.3
	Hello period	2s
	Dth	43.3m
	Distmax	Dth/6