Available online at www.sciencedirect.com
2212-8271 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the International Scientific Committee of the 7th Industrial Product-Service Systems Conference - PSS,
industry transformation for sustainability and business
doi: 10.1016/j.procir.2015.02.092
Procedia CIRP 30 ( 2015 ) 96 – 101
ScienceDirect
7th Industrial Product-Service Systems Conference - PSS, industry transformation for sustainability and
business
Validation of Product-Service Systems in Virtual Reality
Konrad Exnera,*, Rainer Starka,b
aTechnische Universität Berlin, Pascalstraße 8-9, 10587 Berlin, Germany
bFraunhofer Institute for Production Systems and Design Technology, Pascalstraße 8-9, 10587 Berlin, Germany
* Corresponding author. Tel.: +49-30-39006247; fax: +49-30-39006246. E-mail address: konrad.exner@tu-berlin.de
Abstract
Research in the area of the integrated development of products and services, designated as Product-Service Systems (PSS), is maturing and a
transition in industrial practices is noticeable. Nevertheless, PSS development methodologies lack consistent approaches regarding the
integrated validation of different PSS elements rather than a separate development and validation. To prevent an expensive roll-out and testing
in late development stages new methodologies and techniques need to be developed and applied. The challenge is the enablement of
experiencing and thus testing of PSS in early stages, like planning and concept phase. In order to address these challenges for an integrated
validation of PSS a prototyping approach named SHP4PSS has been introduced on a conceptual level [1], integrating virtual and physical
prototypes in a Virtual Reality (VR). To complete the methodology a matrix is presented to derive test cases out of early PSS concepts.
Furthermore, the evaluation matrix regarding the test phase and the current version of the demonstrator is introduced.
© 2015 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the International Scientific Committee of the Conference is co-chaired by Prof. Daniel Brissaud & Prof.
Xavier BOUCHER.
Keywords: Product-Service Systems; validation; evaluation; Virtual Reality; experiencing
1. Introduction
Product-Service Systems (PSS) have to be researched
under many perspectives due to the complexity of PSS and
their interdependent elements, e.g. products, services,
business models and software. The definition and emphasis
regarding PSS are manifold and differ in many ways [3].
Nevertheless, a basic statement is shared widely; PSS have to
be developed in an integrated manner. In realizing this, a
company will transform from a product manufacturer with
additional services to an Original Service Provider (OSP) [4].
The transition to a PSS provider has to be supported by a
PSS development methodology and an implementation
strategy including methods and tools [5]. Research regarding
the development methodologies of PSS has been matured
since 2000 as well as introduced and tested in industry by
different researchers [6]. The main focuses of these
approaches are generic development processes including
methods and tools regarding concept development, business
models, life-cycle perspective etc. However, a validation of
PSS is inherent in these approaches due to following a
methodology, but not specifically integrated regarding the
validation of PSS. In conclusion, a validation methodology
for PSS is a crucial factor for a successful development of
PSS.
In order to cope with the lack of validation methods for
PSS widely disseminated prototyping approaches for the
classical product or service development have been analyzed
and a concept for prototyping of PSS has been introduced as
SHP4PSS [2]. In this paper, further research results regarding
the SHP4PSS method will be discussed.
2. Relation to existing theories and work
In this chapter research with a reference and importance to
the development and validation of PSS will be introduced and
analyzed. This comprises previous results regarding SHP4PSS
as well as new insights for validation dimensions and
validation perspectives for PSS.
© 2015 The Authors. Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the International Scientifi c Committee of the 7th Industrial Product-Service Systems Conference - PSS,
industry transformation for sustainability and business
97
Konrad Exner and Rainer Stark / Procedia CIRP 30 ( 2015 ) 96 – 101
2.1. Development and validation of PSS
The validation of PSS has not been in focus of PSS
researchers [2] due to the emphasis on PSS development
methodologies. Different concepts have been introduced,
whereby the most common methodologies are: Lifecycle
oriented PSS approach of Matzen and Tan [7, 8, 9],
Methodology for PSS (MEPSS) of Halen, Vezzoli and
Wimmer [10], IPS² concept modelling of Sadek [11], Layer-
based Development Methodology for PSS of Müller [3],
Service Engineering of Sakao, Shimomura and Tomiyama [12,
13, 14, 15, 16] and PSS design approach of Lindahl [17]. In
summary, these methodologies do not focus on the validation
of PSS, but on the development of complex PSS in general.
Nevertheless, some methods and tools for the validation of
PSS have been presented, e.g. the requirement checklist [18]
for requirement definition, the PSS-Inspector [19] for design
reviews and the adaption of the Service Self Checklist
SSC4IPS² [20] for evaluation and improvement of existing
PSS. Müller developed a comprehensive PSS development
methodology, which includes also aspects of the validation of
PSS. Based on this research further aspects regarding the
validation of PSS by prototyping will be considered.
2.2. Previous work regarding SHP4PSS
The development of a method for the validation of PSS
with an emphasis on prototyping started in a research project
2012. Since then, an approach for an integrated validation of
PSS, named SHP4PSS, has been introduced on a conceptual
level [1]. The main idea is to use the Smart Hybrid Prototype
(SHP) approach to integrate physical prototypes, digital
models and software in Virtual Reality (VR) to enable an
experiencing of PSS for an urban mobility use case [2]. The
main objective is to realize a realistic experiencing of
different lifecycle phases in VR. Fig. 1 symbolizes the idea of
this concept:
Fig. 1. Pedelec and user in Virtual Reality.
Besides the virtualization of the product (see Fig. 1) a
hybrid prototype will enable interaction with physical and
virtual elements as well as the environment. Furthermore, the
classical product centered perspective will be enhanced with
additional elements to ensure an integrated PSS perspective of
products and services:
x Digital city model
x Smartphone application to rent the pedelec and integrate
further services
x Pedelec station to park and rent pedelec
The actual development and test results will be discussed
in chapter 4.
2.3. Validation dimensions and perspectives of PSS
Regarding the validation of PSS two questions need to be
analyzed: 1. Which properties or dimensions of a PSS can be
validated and how is this different to the classical validation
of products and services? 2. What perspectives regarding the
validation of PSS need to be considered?
Burger et al. [21] derived in a study ten clusters which
should be considered for providers of technical services.
Furthermore, Stark et al. [22] determined three critical
perspectives regarding the validation of mechatronic systems.
These findings can be transferred to the validation of PSS. As
a result of an evaluation Table 1 provides an overview for the
relevance of the dimensions for the different perspectives.
Table 1. Relevance of validation dimensions for perspectives of PSS.
Dimensions
Perspectives
Customer
Developer
Decider
1. Process
ۛ
●
ۗ
2. Concept
ۛ
ۛ
●
3. Resources technology
ۚ
ۛ
ۗ
4. Resources employee
○
ۛ
ۛ
5. Contact to customers
ۗ
ۗ
ۗ
6. Customer acceptance
ۛ
ۗ
●
7. Interaction
ۛ
●
ۗ
8. Customer reaction and emotion
ۗ
ۗ
●
9. Technical requirements
ۗ
●
ۗ
10. Variables service environment
ۗ
ۛ
ۗ
Nomenclature
○ no importance
ۚ minor importance
ۗ medium importance
ۛ high importance
● very high importance
The results of this evaluation need to be verified in a
further step. Therefore, a workshop will be conducted to
ensure an empirical backing of these findings. Nevertheless,
qualitative statements are already possible and Table 1
indicates that the concept (2) is equally important for all
perspectives. In addition process (1) and interaction (7) are
very relevant for all perspectives. Due to these insights a
validation method should focus on these dimensions and has
been the main emphasis for SHP4PSS.
98 Konrad Exner and Rainer Stark / Procedia CIRP 30 ( 2015 ) 96 – 101
3. Research approach
To ensure a holistic view regarding the validation of PSS
with SHP4PSS the research approach will be illustrated and
missing elements will be discussed. Therefore, different
aspects need to be considered to ensure a consistent
methodology, see Fig. 2:
Fig. 2. Development of the SHP4PSS methodology.
Milestones in a PSS development process, e.g. the PSS V-
Model [3], need to be analyzed regarding properties which
have to be validated to these milestones. A consistent analysis
in this matter is not conducted sufficiently so far.
Nevertheless, the SHP4PSS approach will refer to the end of
the concept phase (see Fig. 3) following the system concept
design with PSS Layer Method [3]. The Layer Method
supports the development of PSS concepts by defining PSS
elements on horizontal levels and by linking them vertically.
Fig. 3. Inclusion of the milestone for SHP4PSS in an excerpt of the PSS V-
Model [3].
In order to define the particular objectives for SHP4PSS at
this milestone an analysis has been conducted (see chapter
2.3) to identify and cluster generic dimensions regarding the
integrated validation of PSS. Furthermore, the perspectives of
different stakeholders (developer, customer and manager) in
the validation process of PSS have been reflected.
Subsequently, methods and tools to validate the properties of
products and services have been analyzed and evaluated
regarding their value for a transfer in the PSS domain [2].
Afterwards, a comprehensive set of methods and tools to
enable a validation with SHP4PSS need to be developed. For
this reason, a matrix (see chapter 4) is introduced to derive
test cases out of early PSS concepts developed with the PSS
Layer Method [3]. This approach ensures the availability of
test cases already in the concept phase. Furthermore, a method
to develop Smart Hybrid Prototypes for PSS [2] to provide
interactive devices for experiencing PSS has been developed
[23]. Finally, an evaluation method is introduced (see chapter
4) taking into account the conditions of the first two
objectives. In conjunction with the mentioned test
environment of SHP4PSS a comprehensive methodology
regarding the validation of PSS has been developed. The
introduced methods will be tested according to a use case for
urban mobility as well as a comparative empirical study.
4. Findings
The actual findings include a new method to extract test
cases out of PSS concepts as well as the evaluation process of
the PSS including the evaluation matrix. Additionally, the
current status of the demonstrator is presented.
4.1. Test cases for SHP4PSS out of early concepts
A new method is required in order to ensure a systematic
approach and enable a complete and thorough derivation of
test cases from rough PSS concepts. Therefore, a matrix (see
Table 2) has been developed to transfer the results of concepts
by the PSS Layer Method [3].
Table 2. Excerpt of matrix to derive test cases from PSS Layer Method.
Process
(customer
view)
Services
and
software
Product,
periphery and
infrastructure
Validation
dimensions
Validation
perspectives
[…]
2.4 Go to
pedelec
Smartphone
app,
navigation
(app)
GPS
transmitter
Human-
machine
interaction,
precision of
navigation,
[…]
Usability of
the app with
navigation
(customer/
developer)
2.5
Examine
for
damages
Checklist
(app)
Pedelec,
smartphone
holder, GPS
transmitter
Usability of
the app,
functionality
and design of
the pedelec,
[…]
Usability of
the checklist
(customer/
developer)
[…]
2.9
Remove
pedelec of
charging
station
Guidelines
(app)
Pedelec,
charging
stations,
smartphone
holder
Usability of
the app
Usability of
the
guidelines
[…]
3.1 Defect
while
usage
Guidelines
(app),
provide
help/
alternatives
(phone)
smartphone
holder , repair
and transport
infrastructure,
customer
service center
Usability of
the app,
driving
properties,
[…]
Support by
unknown
events
(customer),
process
(developer)
[…]
5. Testing of the concept and empirical evaluation of SHP4PSS
approach.
4. Development of the methods and tools for PSS prototyping
with SHP4PSS.
3. Analysis of exisiting or feasible validation methods for PSS and
elicitation of gaps for the validation of PSS.
2. Determination of relevant perspectives and dimensions
regarding the validation at milestones.
1. Analyzis of a PSS development process regarding validation at
milestones.
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Konrad Exner and Rainer Stark / Procedia CIRP 30 ( 2015 ) 96 – 101
The main thought is to transfer and enhance the process of
the PSS concepts and use the vertical links in the PSS Layer
Method to integrate the connected PSS elements in the matrix.
Additionally, the validation dimensions and perspectives (see
chapter 2.3) are defined for each process step. The
development of the prototyping device is described in a
further paper [23] and therefore excluded in this matrix.
Otherwise an inclusion of the needed prototypes and the test
environment would be seen in this matrix, but is out of scope
in this paper. Table 2 presents the matrix for an excerpt of one
of the use cases which is described more explicitly in Exner et
al [2], thus the matrix is shortened to enhance the clarity. The
method enables the developer to choose relevant test cases
which should be tested with SHP4PSS. A decision-making
process is not integrated. The main focus is to summarize
possible test cases and provide an overview without missing
important process steps and their linking to the PSS elements.
4.2. Evaluation with SHP4PSS
The evaluation with SHP4PSS needs to be considered for
two objectives. Firstly, the feasibility of the method as well as
the test procedure itself needs to be surveyed. Secondly, the
method needs to be compared with another validation method
for PSS to enable valid statements for the cost-benefit
consideration due to the considerable effort in developing and
providing the test environment for SHP4PSS. The second
aspect is especially challenging regarding the lack of
validation methods for PSS. In adapting the utility analyses
for PSS [24] a low fidelity method to evaluate PSS concept
has been introduced and tested in a case study. In order to
cope with both perspectives an evaluation approach has been
developed. The hypothesis for the evaluation is: By using
SHP4PSS the inter-reliability will be increased. The
composition of the evaluation procedure is shown in Table 3:
Table 3. Framework of the evaluation for SHP4PSS.
Validation of test case with
SHP4PSS
Validation of test case with utility
analysis for PSS [24]
Test group: min. 12 probands
Procedure:
x Welcome and explanation of the
objectives
x Introduction to the VR with an
exercise
x Explanation of the test case
x Experiencing of the test case in
VR
Procedure:
x Welcome and explanation of the
objectives
x Introduction to the utility
analysis with an exercise
x Explanation and hand out of the
visual and textual explanation of
the test case
Evaluation of the test scenario due to given matrix and criteria
Questionnaire regarding the method and standard data regarding the probands
Standardized questionnaires
regarding immersion and presence
due to SHP4PSS
-
Empirical analysis and interpretation of the results
Impact analysis of immersion and
presence regarding the test results
Comparison with the results of the
first study [24]
The evaluation matrix is based on the results of the utility
analysis for PSS [24] and has been adapted for the described
evaluation (see Table 4).
Table 4. Evaluation matrix.
Process phase
Criteria
effort
safety
[…]
1. Reservation of the pedelec
e.g. 10
e.g. -3
[…]
2. Go to the pedelec
3. Examination of damages
4. Open lock at the station
5. Remove pedelec of charging station
6. Usage of the pedelec
7. Defect while usage
8. Return the pedelec
Nomenclature
10 The criterion has a strong positive characteristic in this phase.
6 The criterion has a positive characteristic in this phase.
3 The criterion has a slight positive characteristic in this phase.
0 The criterion has no effect characteristic in this phase.
-3 The criterion has a slight negative characteristic in this phase.
-6 The criterion has a negative characteristic in this phase.
-10 The criterion has a strong negative characteristic in this phase.
The main source of input is the test case matrix (see Table
2) regarding the processes. The criteria originate of both, PSS
Layer Method and test case matrix. This method will also
work with other PSS concept development methods as long as
a process is included. In order to assure the comparability, the
evaluation matrix for the test with SHP4PSS as well as the
utility analysis for PSS will be identical.
4.3. Preliminary test phase of SHP4PSS
The process phases (see Table 4) for the preliminary test
require an elaborate test environment. The main elements (see
chapter 2.2) have been developed and implemented. In
addition to the virtual model of the pedelec, the hybrid
prototype which will realize the interaction with VR has been
constructed. The prototype includes pneumatic hexapods and
an electric motor to enable a realistic experience during the
use phase, see Figure 4:
Fig. 4. Digital Model of the SHP4PSS Prototype.
100 Konrad Exner and Rainer Stark / Procedia CIRP 30 ( 2015 ) 96 – 101
Furthermore, a digital city model of Berlin (Fig. 5) and a
digital charging station for the pedelecs (Fig. 6) has been
developed and integrated in Unity software.
Fig. 5. Digital city model of Berlin.
Fig. 6. Digital Charging station for the pedelecs.
The most complex part is the integration of digital and
physical elements. The driving simulation needs to respond
realistically to the input of the user. Furthermore, additional
input of other devices, e.g. the smartphone, has to cause a
correspondent effect in the simulation. Due to these
constraints an extensive testing is indispensable. The
smartphone app and the prototype are shown in Figure 7 and
8:
Fig. 7. Smartphone App for infrastructure and services for the PSS.
Fig. 8. SHP4PSS Prototype with Oculus Rift as Virtual Reality environment.
The existing implementation is realized with Oculus Rift as
VR which is sufficient for the preliminary test phase. Finally,
a transfer into the Digital Cube Test Center (DCTC), a 4-side
360° visualization cube, regarding the evaluation with the
study group will be realized. Nevertheless, first qualitative
results with Oculus Rift and the current version of the
prototype can be stated. The implementation of SHP4PSS
enables a realistic experiencing of the test case. The
interaction of Oculus Rift and prototype is limited due to a
restricted field of vision (only virtual). Furthermore, the
immersion with Oculus Rift as well as the freedom of
movement is improvable. The integration into the DCTC
should solve these issues by merging virtual and real
environment.
5. Conclusion
So far, an analysis of existing methods for the validation of
PSS has been conducted and due to these results a new
method based on prototyping approaches has been developed
[2]. The main focus of this paper is to complete the validation
methodology of SHP4PSS. In order to achieve this objective a
comprehensive methodology, taking into account the generic
PSS development process – PSS V-Model – has been
introduced. Therefore, a method to extract test cases for
SHP4PSS as well as an evaluation matrix has been introduced
and implemented in a test environment according to the
SHP4PSS approach (see chapter 4). The feasibility of this
demonstrator has been tested in a preliminary phase. First
quantitative results indicate a realistic experiencing of the test
case. In order to verify the results a comprehensive
comparative evaluation will be conducted to provide
quantitative and qualitative data. The methodology has to be
assessed regarding the cost-benefit ration in comparison with
further validation methods for PSS eventually.
Therefore, further research regarding the validation and
prototyping of PSS for different degrees of fidelity need to be
conducted and integrated in this PSS validation methodology.
101
Konrad Exner and Rainer Stark / Procedia CIRP 30 ( 2015 ) 96 – 101
A first step has been successfully achieved by introducing a
utility analysis for PSS [24]. The analysis of the statistical
parameters of the first study with the utility analysis for PSS
indicated good results. Nevertheless, some measured values
differed widely due to a lack in the description of the process
phase. In experiencing the process phase with SHP4PSS the
research teams expect a considerable improvement regarding
the reliability and dispersion of the measurement values.
Finally, two crucial steps have been identified. Firstly, the
evaluation with a group of probands to assess the method is
the most important aspect due to the focus of this method on
the customer perspective. Secondly, the dissemination in
industry, including workshops and interviews to determine the
acceptance of managers and developers regarding SHP4PSS,
is important for the implementation in industrial practice.
These two aspects ensure a continuously improvement and
adaption of SHP4PSS.
Acknowledgements
We sincerely thank the Einstein Stiftung Berlin in funding
the research project Rethinking Prototyping and the Hybrid
Plattform in coordinating and supporting this project. Without
this support a research project in this transdisciplinary
constellation would not be possible.
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