Scholarly article on topic 'Flexible Implementation of IPS2 through a Service-based Automation Approach'

Flexible Implementation of IPS2 through a Service-based Automation Approach Academic research paper on "Economics and business"

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Abstract of research paper on Economics and business, author of scientific article — Eckart Uhlmann, Niels Raue, Christian Gabriel

Abstract Industrial Product-Service Systems (IPS2) are characterized through the customer individual configuration of product and service shares to fulfill customer needs. Thus, the ability to react on changing customer requirements is mandatory. There are common approaches which focus on the early stage of the IPS2 development, thereby the implementation phase appears untended. In this article an approach for the flexible implementation of IPS2 is presented, which considers the research of service-oriented architecture (SOA). Furthermore the prototypical realization in the area of micro production is described. The results described in this paper allow IPS2 providers to react on changing requirements by flexible arranging of functionality in terms of services and IPS2 network partners.

Academic research paper on topic "Flexible Implementation of IPS2 through a Service-based Automation Approach"

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Procedía CIRP 11 (2013) 108 - 113

2nd International Through-life Engineering Services Conference

Flexible Implementation of IPS2 through a Service-based Automation

Approach

Eckart Uhlmann, Niels Raue*, Christian Gabriel

Department of Machine Tools and Factory Management, Chair for Manufacturing Technology, Technische Universität Berlin, Pascalstraße 8-9, 10587 Berlin, Germany

* Corresponding author. Tel.: +49 30 39006-419; fax: +49 30 314-21237. E-mail address: raue@iwf.tu-berlin.de

Abstract

Industrial Product-Service Systems (IPS2) are characterized through the customer individual configuration of product and service shares to fulfill customer needs. Thus, the ability to react on changing customer requirements is mandatory. There are common approaches which focus on the early stage of the IPS2 development, thereby the implementation phase appears untended. In this article an approach for the flexible implementation of IPS2 is presented, which considers the research of service-oriented architecture (SOA). Furthermore the prototypical realization in the area of micro production is described. The results described in this paper allow IPS2 providers to react on changing requirements by flexible arranging of functionality in terms of services and IPS2 network partners.

© 2013 TheAuthors.Published by ElsevierB.V.

Selectionandpeer-review underresponsibility ofthelnternationalScientificCommitteeofthe "2ndInternational Through-life Engineering ServicesConference" andtheProgrammeChair-Ashutosh Tiwari

Keywords: Industrial Product-Service System, micro production, agent-based control system, service-oriented architecture

1. Introduction

In order to strengthen the relationship between customer and provider, Industrial Product-Service Systems (IPS2) provide means of combining product and service shares in order to fulfill customer requirements in a most suitable and flexible manner.

The integration of service shares into the automated operation of IPS2, and thus, the resulting interaction of product and service shares is a central challenge for IPS2 providers.

The term service will be stressed in this context to introduce an approach for automating IPS2 operation and enable the provider company to achieve transparency through describing its offerings as modular entities. With exact description of the goals of each service as well as the impact on the customer benefit, services become the building blocks of IPS2 delivery.

An introduction to IPS2 and the particular importance of IPS2 on micro production is presented in section 2. A proposed concept of modularizing functions specific to IPS2 during

operation in terms of services is described subsequently. An example of implementing such services in a micro production environment through software agents is given. The article concludes with a summary and an outlook on future progress and potential applications.

2. Challenges in micro production technology

The ever increasing trend of integrating more functionality into limited space leads to a steadily rising demand of micro-scale systems. In a current study, it is estimated that the industry of micro system technology will experience an average annual growth in terms of turnover of 10.5 % [1]. Micro system technology can be considered as a key technology of the 21st century [2].

Micro production technology is an advancement of the conventional production technology in order to manufacture micro systems, parts or structures with dimensions ranging from one micron to one millimeter and a precision between 0.1 ^m and 10 ^m.

2212-8271 © 2013 The Authors. Published by Elsevier B.V.

Selection and peer-review under responsibility of the International Scientific Committee of the "2nd International Through-life

Engineering Services Conference" and the Programme Chair - Ashutosh Tiwari

doi:10.1016/j.procir.2013.07.060

Typical applications for micro production technology are the production of medical products as well as sensors for space and aviation or automotive industry. Most applications in these industries require a fault-free production.

A majority of advancements in the micro production industry therefore aim at increasing process capability. They are reached through innovations in tools, machine tools and processes. This development results in an increased demand for services which can enable the customer to make use of the evolving technology.

Product-oriented: O Product-related O Advice and consultancy Use-oriented: O Product lease O Product renting or sharing O Product pooling Result-oriented:

O Activity management/outsourcing O Pay per unit O Functional result

Optical

measurement

Micro milling machine tool

Robots

EDM machine tool

Fig. 1. Setup of the machine tool demonstrator

Entrance barriers to micro production exist for customers in terms of a lack of technological experience. An example is tool breakage, which is a key reason for process deficiency in micro milling [3]. Other examples are proper handling systems that meet the precision requirements, automated inline quality inspection, and the assurance of temperature stability. All these requirements lead to a significant financial risk for customers planning to enter the micro production field. Therefore, the micro production industry is a very suitable field for application of IPS2.

3. Customer benefit by IPS2

An IPS2 is characterized by a combination of tangible product and intangible service shares including the immanent software throughout the complete lifecycle to fulfill the customer as well as the IPS2 provider requirements [4], [5], [6], [7]. The IPS2 provider offers a customized solution in terms of an IPS2 business model to the customer [8].

For costumers, IPS2 imply a shift to receiving system solutions which lead to an efficient application of production equipment. For providers, IPS2 lead to a higher degree of responsibility for the product's entire life cycle [9].

The IPS2 business models range from product-oriented over use-oriented to result-oriented [8]. According to TUKKER there are eight possible types of IPS2 [10]:

Adapting this classification to the micro milling area there is a broad range of tasks an IPS2 provider has to take responsibility for to fulfill the specific customer needs. The necessary tasks have been modeled within the IPS2 factory management and are allocated in a process map [11].

Considering the development of IPS2, the integrated development of product and service shares in order to fulfill customer requirements has been a focus in previous research. As a result of such a method, IPS2 are developed by the design or the configuration of IPS2 modules. Between the development and the operation phase, the implementation has to be considered. In order to close the gap between a specification of the IPS2 modules and an operable IPS2, the approach of service-oriented architectures (SOA) was investigated and adapted to the challenges of IPS2.

In order to allow the physical separation of IPS2 modules, technical interfaces as well as roles and parties in IPS2 operation, a software agent system was deployed with single agents acting as providers as well as consumers of services.

The interaction of an agent-based control system with services concerning the approach of the service-oriented architecture will support the implementation of IPS2 following the development phase. A prototypical application has already been developed within a machine tool demonstrator (see Fig. 1)

4. Modularization of IPS2 functions by means of services

4.1. Service-oriented Architectures

Services can be considered as self-contained, atomic units of computation [12]. Through the encapsulation and description of certain functionality in terms of a service, high modularity and reusability can be achieved. In the context of business process management, the goal of a service-oriented architecture is the separation between business application and technical implementation [13].

Deriving from a definition of web services [12], a service can be considered as a function with an input (e.g., product and credit card information)., an output (e.g., purchase confirmation) and, if applicable, side effects (e.g., credit card is charged with the price of the product). Services ensure a transparent description of functionality between requester and provider (see Fig. 2).

Fig. 2. Web service usage process [12]

Besides web services and business process management, SOA approaches have been examined regarding their applicability in manufacturing applications [14]. Author [15] proposed a step-by-step procedure for migrating legacy industrial control systems into SOA-based architectures, aiming at enhancing interoperability through the decoupling of functionality and its implementation. [16] introduced service-based field devices that offer their functionality either directly to an Enterprise Resource Planning (ERP) system or indirectly via a middleware used for service orchestration.

4.2. Adoption of the service paradigm to IPS2

By means of services, the provider is able to separate the description and the implementation of all required IPS2 functions. The services paradigm thus enables the provider to flexibly react to customer demands by the adaption of IPS2 modules. Also transparency of the offering can be achieved through explicitly describing the services by defining attributes that quantify the impact on certain customer requirements.

Considering services as building blocks of IPS2 operation, they can be deployed for automating IPS2 delivery processes. Due to the nature of IPS2 delivery processes, services can represent and implement IPS2 functions that are either fulfilled by service or by product shares.

In this approach, the automation of the concrete IPS2 is realized by an agent-based control system [17], [18]. As a middleware, the Java Agent Development Framework (JADE) was used [19], which allows for cross-platform compatibility and thus can be deployed on different computer systems in the IPS2 scenario.

Aim of the control system is the automation of IPS2 modules by means of software agents. According to the business model, specific functions can be enabled through the software agents. The functionality that each agent makes available to others is offered by services. These services are registered in a special agent called Directory Facilitator, which serves, despite the decentralized character of the agent system, as a central registry for all available services.

The clustering of agent roles of an IPS2 organization was conducted following the principles introduced in [20] and [21]. Three different types of agent roles can be distinguished: IPS2 contractual party agents, IPS2 role agents and interface agents.

• IPS2 contractual party agents represent the main parties of an IPS2 contract relationship, namely IPS2 provider, customer, and external IPS2 network partners.

• IPS2 role agents represent actors that are ensuring the contractually defined performance. Actors can be humans such as machine operators, service technicians and machine tools.

• Interface agents enable the integration of external systems into the IPS2 control system and thus serve as connectors to legacy systems. Examples are the machine tool control (Programmable Logic Controller - PLC), sensor systems, databases, resource planning (IPS2 execution system [22]) and service technician support.

Interface agents offer elementary services to other agents. Such services are atomic functions:

• PLC agent:

O Spindle start, O Spindle stop,

O Move axes to reference position, O Online monitoring [23], O Processing of Numerical Control (NC) files, O Manual Direct Input (MDI) mode.

• Sensor bus agent:

O Temperature stability, O Acquire self-test data, O Feature extraction and classification [24].

• Database agent:

O perform SQL query: read, O perform SQL query: write.

• Toolbox agent:

O read out torque meter, O read out digital caliper, O read RFID tag, O write RFID tag, O display instructions (via GUI), O process manual data input (via GUI).

IPS2 role agents on the other hand utilize elementary services to realize more complex functions. These functions again can be offered as services, so-called composed services.

• Machine Tool Agent:

O Online Condition Monitoring O Component self-test O Tool Setting

O Handling Automation (Transport of work pieces) O Machining (NC file processing)

PS2 planning

IPS2 \\ IPS2 development // implementation

1 IPS2 operation

IPS2 closure

Legend

• Composed Service

• Elementary Service

O Software Agent

-------

/ Machine Tool Agent | ^

Sensor bus Toolbox*

Fig. 3. Schematic illustration of the service-based IPS2 operation (*Toolbox refers to a specially equipped mobile toolbox for service technician support [25])

• Service Technician Agent

O Service Technician Support (Workflow-based support system that guides service technician through maintenance processes in a step-chain manner [25])

• Production Equipment Manager Agent

O Tool management

O CAD/CAM programming

O Quality assurance (Part Measurement)

O Machine acceptance

4.3. Prototypical Implementation

The proposed service-based IPS2 operation was prototypically implemented for operating the machine tool demonstrator (see Fig. 1). In the following, an example is given based on a spindle self-test. Several interface agents participate in delivering the composed service by contributing functions in terms of elementary services (see Fig. 3).

Initially, the service SELFTEST is requested by the IPS2 provider agent (see Fig. 4). A cyclical behavior of this IPS2 contractual party agent ensures the periodical execution of the service. The Machine Tool Agent, who offers the service, then checks at the Directory Facilitator Agent if all necessary elementary services are available. First, an elementary service REFERENCEPOSITION is requested from the PLC Agent,

which moves the spindle to a defined position to ensure repeatability during the self-test. Subsequently, the service SPINDLESTART initiates the rotational spindle movement according to the input argument of the service (e.g. n = 20.000 RPM). As the next step, the service TEMPERATURESTABILITY of the Sensor Bus Agent is requested and initiated. This service calculates a temperature gradient from a time series of measurement values and sends an inform message once the rate of temperature increase has reached a sufficiently small level. After this step, the service SELFTESTDATA is requested and executed.

This service includes the acquisition and processing of acceleration sensor data. The acceleration sensors are monitoring the roller bearings as critical components of the spindle. During processing, the sensor signal is filtered and features are extracted. Subsequently, the results can be classified in a feature space and affiliations to specific damage classes can be determined (see Fig. 5).

As the last step of the composed service, the service SPINDLESTOP stops the rotational spindle movement after the sensor data was acquired.

Depending on the results of the self-test, measures to ensure the availability can be initiated, for example requesting a service call to replace the spindle or even single subcomponents of the spindle. The resource planning is

performed by an external system [26] which is connected to the IPS2 Control System via a particular interface agent. The service process itself can be considered as a sequence of elementary service invocations which are controlled by the service technician agent (see Fig. 3).

IPS2 provider Agent MachineToolAgent

PLCAgent SensorBusAgent

request(SELFTEST)

request(REFERENCEPOSITION) i

inform-done(inform)

request(SPINDLESTART)

inform-done(inform)

request(TEMPERATURESTABILITY)

inform-done(inform)

request(SELFTESTDATA)

agree j

inform-result(SensorResult)

request(SPINDLESTOP)

inform-done(inform)

¡nform-result(SELFTESTRESULT)j^-

Fig. 4. UML interaction diagram of the Agent communication during the composed service "Self-test"

.1 4015

i 20-o

* No damage + Rolling element damage Small damage on outer ring Heavy damage on outer ring Damage on inner ring

Heavy damage on outer ring

No damage

x 10J 7.5

Mean value (vibration [V]) ®

1.0 - x10': Variance (vibration [V])

Fig. 5. Example of the component self-test classification results [24]: Assessment of roller bearing damage through a feature space

Via a Graphical User Interface, the service technician can trigger the service invocation for automatable process steps and receives instructions for tasks that have to be performed manually (see Fig. 6).

Fig. 6. Example of the composed service "Service Technician Support"

5. Summary and conclusion

The service-based approach of IPS2 automation aims at ensuring modularity and transparency when offering and delivering IPS2.

Modularity is achieved by developing, operating and assessing automatable units (services) that fulfill IPS2-specific functions. Each service can be utilized in different contexts and reused thanks due to a uniform service description. The elementary service "temperature stability" for example can be used in the abovementioned scenario, but is also required before the machining of parts to ensure the required precision by preventing a thermal offset.

Transparency is reached by the service-based approach through the creation of system borders. Services can be assessed regarding cost and quality impact as well as the degree to which certain customer requirements are fulfilled. A composed service such as the presented self-test can be offered to a customer and constitutes a positive influence on the contractually defined availability. Furthermore, possible available service offers can be detected by analyzing the elementary services that are realized by existing interface agents and thus could be offered to the customer.

6. Outlook

Further research work will include the development of new services as well as the service descriptions. Especially a more exact characterization of a service's functionality will improve the reusability and assessability of each service. Such service descriptions will enable the IPS2 provider to tailor an IPS2 that precisely fits customer requirements as well as technical boundary conditions. The development of a proper IPS2 service description standard should take into consideration existing standardization efforts such as the Web Services Modeling Language or the OPC Unified Architecture [27].

Furthermore, with such a universal description of services it is possible to offer and search for IPS2 modules in terms of services in a central registry. Such IPS2 marketplace could be an attractive way for a provider to utilize available resources by offering their functions as IPS2 modules in a precise

manner (e.g. precision machining of certain material or measurements of parts with special metrology equipment).

Acknowledgements

We express our sincere thanks to the Deutsche Forschungsgemeinschaft (DFG) for funding this research within the Collaborative Research Project SFB/TR 29 on Industrial Product-Service Systems - dynamic interdependency of products and services in the production area.

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