A rough set approach for evaluating vague customer requirement of industrial product-service system_Wenyan Songa

International Journal of Production Research 6691
4.2.3 Calculate rough weights of IPS 2 requirement
Calculate rough weights of each IPS 2 requirement gRW i in different hierarchy with the following equation.
gRW i ¼½RW L
i
; RW U
i
Š (15)
RW L
i
¼ n
sffiffiffiffiffiffiffiffiffiffiffiffi
Y n
i¼1
r L ij;
RW U
i
¼ n
sffiffiffiffiffiffiffiffiffiffiffiffi
Y n
i¼1
r U ij
(16)
i =1, 2, …, n.
In the same way, rough weights of IPS 2 requirement can be got in any other hierarchies.
Finally, each requirement’s overall priority is calculated using multiplication synthesis method from top level to
bottom level.
4.2.4 IPS 2 requirement prioritisation
To covert the rough IPS 2 requirement weight into crisp value, here the authors introduce the optimistic indicator λ
(0 6 λ 6 1); to transform the rough weight gRW i into crisp value RW i . If decision-makers are more optimistic about their
judgements, then λ can select a bigger value (λ > 0.5). If decision-makers are more pessimistic about their evaluations, λ
should select a smaller value (λ < 0.5). If decision-makers keep a moderate attitude, in other words, neither more
optimistic nor more pessimistic, λ selects a certain value 0.5. The transformation calculation is as follows:
RW i ¼ (1
k)RW L
i
þ kRW U
i
(17)
According to the weights from the above steps, all the requirements of IPS 2 can be prioritised, and the important
value-based requirements can also be focused.
5. Case study
In this section, IPS 2 requirement evaluation of a rotary oil-free air compressor is taken as an example to demonstrate
the application of the proposed approach in the real world. In this case, the rotary oil-free air compressor is mainly
designed and sold to pharmaceutical plants that need clean compressed air for washing bottles and starting pneumatic
valves. Company H is a Fortune 500 manufacturer who is specialised in providing different air compressors and related
services for industry: pharmaceutical industry, metallurgical industry, shipbuilding, and mining. The company H now is
more and more concerned with the selling industrial services associated to their air compressors throughout the customer
activity lifecycle, such as air compressor selection consulting, installation and debugging, MRO, and energy saving solutions,
etc. The objective of the IPS 2 requirement evaluation in this case study is to identify key points that the customer
(pharmaceutical plant) is concerned for further IPS 2 design, and therefore, enhance the customer satisfaction and loyalty.
To reveal the advantages of the rough requirement evaluation method, the authors also make comparisons between the
proposed approach and the fuzzy group evaluation method.
5.1 Implementation of the proposed requirement evaluation method
5.1.1 IPS 2 requirement elicitation
First, a survey based on I-CAC is used to analyse main activities of the customer. The activities are pre-sales consulting,
procurement, installation, debugging and commissioning of air compressor, operation and use, MRO, etc. The disposal
of air compressor is not considered here as the pharmaceutical plant has its own special channel to recycle the scrapped
compressor.
Second, the related stakeholders around customer activities are identified. Interactions between stakeholders and the
nature of their relationships such as exchanging information, products or instructions are also identified. For example,
the stakeholders and their relationships in the MRO activity are captured in the Figure 5. There are three main stakeholders,
i.e. air user, IPS 2 provider and operator. The air user proposes the air demand, the operator meet this demand
with the air compressor operation and the IPS 2 provider is mainly responsible for reliable air supply with professional
MRO and spare parts supply in this phase. Similarly, the stakeholders and their relationships in other customer activities
can be acquired, which are not listed here due to the limited space.