APPLICATIONS OF RFID TECHNOLOGY IN MAINTENANCE SYSTEMS Adam Adgar Dale Addison Chi-Yung (Alan) Yau University of Sunderland, School of Computing & Technology Edinburgh Building, Chester Road Sunderland, SR1 3SD, U.K.
[email protected] [email protected] [email protected]
ABSTRACT Recent trends observed in modern industrial systems indicate an increasing demand for improved machinery reliability, efficiency and safety [1, 2]. Technological developments in maintenance systems have addressed these issues to some extent but an overall solution with the flexibility to satisfy the demands of a wide range of users is still sometime away. An ongoing project, DYNAMITE (Dynamic Decisions in Maintenance) intends to address this problem by developing and applying a blend of leading-edge communications and sensor technology, combined with state-of-the-art diagnostic and prognostic techniques. The strategy involves the extensive use of stored and transmitted electronic data in order to ensure instant access to up-todate, accurate and detailed information. It provides a great advantage in terms of human and machine-based decision making capabilities. Current efforts are focused on developing systems and templates in which pertinent maintenance data are stored and accessed by both mobile and static computing devices. This article will present: a review of RFID technology; its current applications to maintenance systems; and an outlines of the proposed framework in which the RFID systems reside within the project under consideration.
KEYWORDS: RFID, maintenance strategy, condition monitoring, diagnostics, reliability INTRODUCTION Many industries today face the challenge of managing their maintenance resources as efficiently and cost effectively as possible. The opportunely coordination of different resources like personnel, spare parts, equipments, tools is the key factor to success. A web-based online computerized maintenance management system (CMMS) is a good option to allow field engineers accessing CMMS via local network and internet. However, the time-consuming for entering data, the problem in identifying items and the human mistake are not yet been solved. Barcode are one option for dealing with these problems, but they are easy-to-destroy, especially in an industrial environment, and usually related to the print quality. Hence, radio-frequency identification (RFID) is rapidly emerging as the replacement for the barcode. It can be combined with CMMS to establish a high speed, accurate and reliable wireless maintenance environment. Additionally, RFID contains embedded memory and supports updating of storage information. Based on that, field engineers can immediately and accurately identify items, manipulate storage information, such as machinery data, sensor identification, audit trails of maintenance activities, spare part information and use of maintenance tools. Under the new wireless maintenance
environment, engineers can remotely perform identification of problems and standardization of decision making in a high efficient and convenient way. The Dynamic Decisions in Maintenance (DYNAMITE) project addresses this problem by developing and applying a blend of leading-edge communications and sensor technologies, and combining them with state-of-the-art diagnostic and prognostic techniques. The objective of the project is to deliver a prototype maintenance system to enable the monitoring of machines and processes for predictive maintenance and control. An infrastructure for mobile monitoring technology is to be developed along with devices incorporating sensors and algorithms to improve capability for decision support systems. Some key features include wireless communications, intelligent data analysis, local data history stored in smart tags, and on-line instrumentation. Our research has focused on integrating RFID and CMMS. The main strategy involves the extensive use of stored and transmitted electronic information in order to ensure instant access to up-to-date, accurate and detailed information. The aim of this paper is to report the new maintenance information flow and a design of RFID tags template in order to effectively store maintenance information in passive RFID tags and embed them into a web service based CMMS infrastructure. Ultimately, by taking the advantage of current mobile wireless internet technology, engineers can access to internet at any time any location via RFID and internet equipped mobile computers and PDA for retrieving information from RFID tags and querying CMMS.
REVIEW OF RFID TECHNOLOGY RFID is a wireless identification technology and there are three key components of RFID. Namely; RFID tags, RFID readers and RFID middleware. RFID is often considered a wireless barcode technology, but it not really true because RFID not only can act as a barcode for identification, but also store the information about the item for tracking and maintenance purpose. In practical, RFID tags can be attached inside or outside of any packages or objects. Relying on RFID readers, not like a traditional scanner, people can read the information from multiple tags at the same time, contact-less and hidden. Moreover, tags information can be dispatched to different modules for further processing via RFID middleware. Typically, several frequencies are used in applications: 125KHz, 13.56MHz and 860-930MHz for passive RFID; 433MHz and 2.45GHz for active RFID. A RFID tag, also called smart tag and transponder, is a compact and small silicon-chip that containing memory, modulator and antenna. In the future, it can also be a plastic electronics chip [3]. Reviewing all RFID tags in the world, the smallest and thinnest one is just 0.15 x 0.15 mm, 7.5µm thick [4]. Based on the read methods, there are two conventional classes of tags either passive or active. Respectively, there are powered by reader’s magnetic field and selfpowered by internal on-board supply (e.g. battery). Currently, passive tags are most widely used because they are low tag cost, no batteries replacement cost, long tag life, small and thin comparing with active tags. Toll applications and inventory applications are two instances. However, for some applications specific requiring high-speed identification, long distance area monitoring or continuous sensor monitoring, active tags is more recommended to be used [5]. Container and manifest tracking applications is an example of using active tags. Recently, the global standardisation of RFID is an important milestone. It implies that the end of the complicated RFID protocols generation is anticipated. In the past, different supplies developed their own RFID products. The huge amount of individual specifications became an obstruction of technology development. Alongside the growth of RFID systems, the interoperation between systems was required. It motivated the creation of a common
specification [6]. Until now, the two most well accepted standards are: ISO international standards and EPC Global industrial standards [7, 8, 9]. For a simple overview, ISO standards define RFID in a generic way and it is driven by manufacturers. It does not concern with data rather focus on data access. Reflecting global requirements is the aim. Thus, it covers entire range of air interface frequencies. In contrast, EPC standards are industry specific, where lots of retailers and suppliers are included. It does not cover all range of frequencies rather the interested and needed frequencies only (860–960MHz). The aim at fast addresses what RFID is need for specific industry and allow devices could incorporate more security [10]. Originally, they are totally separated standards, until the middle of last year, ISO 18000-6c and EPC Gen 2 Class 1 UHF standard operating in the 860-960MHz are approved to be compatible [11]. The following table lists the detail of EPC Global RFID class structure and ISO air-frequency standard. Table 1: RPC Global RFID Class and ISO Air-Frequency Standard
EPC Global RFID Class Structure Class 1: a simple, passive and read only non-volatile memory Passive identity tag Class 2: extension of class 1 tag with up to 65KB of read-write memory Passive functional tag Class 3: extension of class 2 tag with a built-in battery power to increase the read range Semi-Passive tag Class 4: a built-in battery power to activate the circuit and power the transmitter for Active Ad-hoc tag broadcasts a signal to reader Class 5: a built-in power, able to communicate with other class 5 tags and devices Reader tag ISO 18000 Air Frequency Standards 18000-1 Generic Parameters for the Air Interface for Globally Accepted Frequencies 18000-2 Parameters for Air Interface Communications below 135 kHz 18000-3 Parameters for Air Interface Communications at 13.56 MHz 18000-4 Parameters for Air Interface Communications at 2.45 GHz 18000-6 Parameters for Air Interface Communications at 860 to 960 18000-7 Parameters for Air Interface Communications at 433 MHz
The second key component is RFID reader. These emit low-powered RF signal to activate passive tags; identifying tags; and transferring information to and from a tag. There are a variety of RFID readers available on the market. USB and serial port type readers are usually used in PC system; otherwise, CF, SDIO and Bluetooth are selected for PDA’s or mobile computers. Besides, RFID readers trend to be embedded into laptops, PDA’s, cell phones and other embedded devices [12]. In addition, an appreciable development direction of RFID readers are toward supporting multi tag standards and acting as gateways to exchange data between tags and other wireless networks such as Bluetooth [13]. On the other hands, there are some other readers designed specific for long-range applications, for example a non-movable RFID crib readers for ports access control and gate-type RFID readers for library access control. The last key components is RFID middleware, which is computing software to merge RFID readers drivers, software components, networks, database and other distributed systems. It establishes bidirectional intermediate information exchange architecture through connecting a reader library to drive a reader to collect and amend tags data; then dispatching the data to other upper-level software modules for data processing; and then linking with network service connecting to database servers or other distributed systems via web services and XML technologies [14]. Reviewing to the evolution of RFID technology, a trend of using RFID technology in a “machine-to-machine” short range communication has been seen. It combines with other medium range and long range communication network to establish a large and global
communication infrastructure. In contrast with other short range protocols (such as Bluetooth), RFID is not designed to transmit signal or data; rather it is designed to store and keep information for communication. Similarity, it also cannot be consider as a sensory network like Zigbee and Wi-Fi; rather it should be consider as an information network allowing information transmission like locations, status and parameters between devices and networks. The main contribution of RFID is act as a gateway to link different physical items (like goods and sensors) and networks (internet) together. By extending the concept to industrial maintenance domain, the integration of RFID with current mobile, wireless and internet technologies can effectively facilitate maintenance operations.
RFID FOR MAINTENANCE MANAGEMENT Maintenance management can be explained as two sections: assets maintenance and assets management. In terms of systems, condition-based maintenance (CBM) system and computerized maintenance management system (CMMS) are referred [15, 16]. The role of CBM is to use the stored historical data like sensory data to determine machine/equipment health. CMMS is high-level management system involving elementary assets management, preventive maintenance, work management, inventory management and so on. RFID technology is particularly suited for assets management, assets tracking and keeping maintenance information because it allows operators identifying tools, machine and spare parts accurately, easily and rapidly [17]. Indeed, RFID is not only applied as the replacement of barcode, but also acting as a distributed memories storage device for keeping up-to-date maintenance information in RFID tags. During maintenance, tags information can be retrieved and providing all the information required for online querying of CMMS, certainly, it can also reduce data entry mistakes thus saving time. However, it is not a perfect because RFID contains a deficiency that it will not function in difficult environments such as high electromagnetic interference, high/low temperature and presence of liquids and metal surfaces. Under these environmental conditions, the performance of the RFID is influenced, in a serious case, it will cause malfunction. Thus, recently there are some new hybrid RFID and multi-standard operable devices can be found with the aim to combine usage of different standards, active or passive tags together appropriately in order to allow RFID working effectively in poor environmental conditions. Additionally, the cost of RFID tags and readers is continuous decreasing. A low price wireless RFID based on-line CMMS can be foreseen in the not too distant future. On the other hands, RFID can be combined with GPS technology to provide auto global position tracking application that achieves the idea of 'anywhere, any time' monitoring. The first all-inone tag product in the market has been announced by Fujitsu Software Technologies [18]; for a solution, an integrated system has been announced by Imation Corporation [19]. In factory maintenance applications for example, the concern of reliability, security and privacy are three most significant factors in designing a factory zone access control; alternatively, fast read speed and multiple read are extremely important for smart tools and spare parts inventory control. Again, if an application requires point-to-point tracking like tracking of containers vehicles, active RFID is recommended. If an application is implemented in a high temperature and wet environment, the material of tags and penetrating capability are critically considered. In here, it is impossible to lists all situations; so, there are some major technical characteristics and features are usually concerned in order to select an appropriate RFID system.
Table 2: Concerned major characteristics and features
Major Technical Characteristics
RFID System Air-interface frequency Global standard Tagging mode Optimum read range* Data transfer rate Penetrating capability Read/write capability Security & Privacy
Specific for RFID tags Memory capacity Effective read range Size/Shape Material
Specific for RFID readers Protocols compatibility Effective read range Host connection interface Software interface Anti-collision features
* Optimum read range is highly depended to both tags and reader’s effective read range. Table 3: RFID Characteristics
Air-interface frequency
Tagging mode
LF (125-135kHz)
Passive
HF (13.56MHz)
Passive
UHF (860-930MHz)*
Passive
UHF (433MHz)
Active
Microware (2.45GHz)
Active
Effective read range short read range (less than 0.5m) medium read range (up to 1.5m) medium read range (up to 5m) ultra long read range (up to 100m) long read range (up to 10m)
Transfer rate
Penetrating capability
Low
can read through liquid but not metal
Moderate
can read through liquid but not metal
Moderate to High
cannot read through liquid or metal
High
cannot read through liquid or metal
Very high
cannot read through liquid or metal
* Due to the national difference of air frequency usage regulation, RFID in 868MHz is generally used in European countries and 915MHz is used for non-European countries.
MAINTENANCE SCENARIOS In this paper, several scenarios, focusing on assets maintenance and management, are considered including the issuance, return and calibration of tools within an inventory system and the basic identification procedures within an access control system. The reason is that this is an important area of maintenance activity and it may be used as a case study to demonstrate many of the features relevant to other scenarios. In addition RFID tags are considered from a machine maintenance perspective, and issues relating to the security of data being collected from RFID tags and transmitted to other locations are discussed. Since the memory size of RFID tags is continually increasing (in line with many other hardware devices) the ability to store information such as the maintenance history of a particular machine is now a realistic possibility. A briefly outline a selection of potential data templates which could be applied to such scenarios as found in the maintenance domain. In contrast with the conventional web-based maintenance strategy, this strategy allows engineers effectively reduce the time for data entering; increase the reliability of data entry processes; and collect basic information from the RFID tags without connecting to CMMS. In this scenario, retrieval of the complete details of the asset (whether it be a machine, a spare part, a tool, a person or some other asset important to a company) is carried out via a database query web service. The query uses the tag’s unique identifying number to retrieve details of the asset from a database server. An important aspect of this project is to consider methods for incorporating more pertinent data onto a single RFID tag. This is particularly important if the tags are required to record details of, for example, a machine’s state.
RFID Template In order to efficiently set up the RFID template, the consideration will be concentrated on some characteristics such as read range, memory capacity, cost, penetrating capability, security and
privacy. In here, a new three layers scheme is suggested to categorise the current RFID tag templates. The first layer is designed for providing primary information, so a large memory capacity is not required. Alternatively, allowing users a convenient access procedure is more important than the others. The second layer focuses on keeping information and securing data. The last layer is designed for forecasting the future RFID tags, which contain large memory capacity and high transfer rate. It is ideal for storing the documentation and specification file directly. It may be required to indicate that, in the scheme described, RFID air-frequency is temporarily ignored because a multi frequency RFID system is anticipated. In fact, airfrequency is not really a matter to be considered as far as the tag template design is concerned. The following table has been proposed to specify the new RFID tag classification scheme for setting up the tag template. During reading table 4, it must be remembered that each tag represents only the current “state of the art”, and therefore may be superseded by later technological developments. Indeed, reviewing most recent RFID products, their designs trend to embed RFID in mobile computing devices, support multi-protocols RFID and combine both active and passive RFID. Table 4: The three layers RFID tag classification scheme used in template design
Type
Memory
Level 1 (Low)
8K bit
Description - Public no data encryption required - Short read range, low data transfer rate - Target to some current low price RFID tags - Ideally for keeping general information for identification purpose - Prefix and numeric representation of storing data is preferred - Private, Protected with data encryption - Medium read range, reasonable data transfer rate - Target to some current larger memory low price RFID tags - Ideally for keeping certification information and configuration data - Limited length description and message are supported - Private, Protected with data encryption and password - Long read range, high data transfer rate - Additional battery/bus power supply may require - Target to future large memory RFID tags - Ideally for storing documentation and file - Long description and message are supported
In Figure 1, a tree structure layout is presented representing six scenarios in which tags may be utilised. The examples chosen, as a representative cross-section of maintenance objects, include locations, facilities, machines, spare parts, tools and personnel. Operators of the system can read the location description from the location tag and access to the location (factory zone 1 in the example) by their personnel tag. In the zone, there are one or more than one facilities like potable water system. Again, operators require using their personnel tag to login to the system in order to contain different levels of permission. Once login succeeds, users can browse the structure of system and change the internal configuration. Certainly, it depends on users’ access permission. Similarly, they can also read the information relating to, for example, machines, tools, spare parts. The information may be read directly from the tags and this information may be then used to manage the asset concerned.
Location Tag (Factory zone 1) Facilities Tag (Potable Water System)
Personnel Tag
Facilities Tag (Power Generation System)
Machine Tag (AC Induction Motor) Spares Parts Tag (Temperature Sensors)
Spares Parts Tag (Bearing)
Tools Tag (Rotation speed tester)
Figure 1: The example hierarchical tree structure layout representing six scenarios of tags
CMMS and Database A CMMS usually consists of two parts. A database (usually relational) and a front end which allows operators to store and retrieve information about an organization’s maintenance operations. This information is intended to help maintenance engineers do their jobs more effectively (which storerooms contain the spare parts they need) and to help management make informed decisions (calculating the cost of maintenance for each piece of equipment used by the organisation). A CMMS packages may be used by any organization that must perform maintenance on equipment and property. There is a typical package dealing with some or all of the following: •
Work orders: Scheduling jobs, assigning personnel, reserving materials, recording costs, and tracking relevant information such as the cause of the problem (if any), downtime involved (if any), and recommendations for future action.
•
Preventive maintenance (PM): Keeping track of PM inspections and jobs, including step-bystep instructions or check-lists, lists of materials required, and other pertinent details. Typically, the CMMS schedules PM jobs automatically based on schedules and/or meter readings. Different software packages use different techniques for reporting when a job should be performed.
•
Asset management: Recording data about equipment and property including specifications, warranty information, service contracts, spare parts, purchase date, expected lifetime.
•
Inventory control: Management of spare parts, tools, and other materials including the reservation of materials for particular jobs, recording where materials are stored, determining when more materials should be purchased, tracking shipment receipts, and taking inventory.
Automatic identification technology based on RFID technology offers inventory tracking and management systems two advantages. First, an accurate knowledge of the inventory level can be maintained by eliminating discrepancies between inventory records and actual inventory levels. Secondly RFID technology can prevent or reduce sources of errors. In addition RFID can reduce labour costs, simplify business processes and reduce inventory inaccuracies. In the project, a CMMS ACCESS database is used. The database is mounted on a web server, along with a series of web services which are designed to process the information gathered by the RFID read operations and update the CMMS database accordingly.
Web Services Web services are a series of software modules that can be accessed over a network, such as the Internet, and executed on a remote system hosting the requested services which are usually
always modular. There are always certain key features inherent within web services defined as follows. •
SOAP: (Simple Object Access Protocol) An XML-based, extensible message envelope format, with "bindings" to underlying protocols. The primary protocols are HTTP and HTTPS, although bindings for others, including SMTP and XMPP, have been written.
•
WSDL: An XML format that allows service interfaces to be described, along with binding details to specific protocols. WSDL is typically used to generate server and client software.
•
UDDI: A protocol used to obtain metadata about Web services, enabling applications to find Web services, either at design time or runtime.
The term refers to clients and servers that communicate XML messages that follow the SOAPstandard. Both SOAP and XML rely upon a machine readable description of the operations supported by the server, a description in the WSDL. The latter is not a requirement of SOAP endpoint, but is required for automated client-side code generation in the mainstream Java and .NET SOAP frameworks. Some industry organizations, such as the WS-I, mandate both SOAP and WSDL in their definition of a Web service.
IMPLEMENTATION In this section, we discuss how web services and RFID can be implemented in a CMMS environment, and describe how each of the aspects discussed above have been integrated in the demonstrator system. The scenario described here concerns the inventory and asset management tracking aspect of the project, focusing on the movement of tools used on a shop floor and their monitoring throughout a typical working day. In the project, both online based web services and offline based client services are used. The web service includes different procedures for login, query and updating information to database. For the interface, ASP.NET mobile web forms and windows based application written in C# language are used in the demonstrator. There are the screenshots for the web service page; the PC-based client tools inventory program at service desk; and the ASP mobile form for PDA.
Figure 2: The screenshot of the Web Service Page and the PC-based tools inventory program at service desk
RFID Tag
RFID Reader
Login
Logout
Mobile ASP Entry Form
Member Form Browse Asset Detail
Mobile ASP Entry Form
Go Back
Result Display Form
Figure 3: The screenshot of PDA and the tools query mobile form
FUTURE WORK In this paper, the basic link between RFID, wireless mobile technologies and CMMS has been developed. From the database manipulation point of view, this demonstrator is successfully implemented; but in terms of system diagnostic, it is not covered yet. So the extension works will concentrate on how to utilise RFID tags information and CMMS database information together for system fault detection and prevention. Besides, this link can also facilitate the implementation of some extensive functions such as dynamic map generation for locating sensor and equipments; data plotting; and global position assets tracking by using GPS and active RFID.
CONCLUSIONS This paper provides the detail of a new RFID embedded CMMS demonstrator system with discussion of relevant background information. The demonstrator system has been developed with the focus on prototyping those tasks typically performed in maintenance scenarios such as spare part tracking and asset location. By cooperating with current wireless and mobile technologies, the demonstrator can be performed via both stationary (PC) and mobile (PDA) computing devices. Finally, it is worthwhile to recall the overall goal of this project is to strive to provide accurate, up-to-date and integrated data so that truly dynamic decisions may be made in the maintenance field.
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