- Email: [email protected]
RFID-based building maintenance system
Automation in Construction 18 (2009) 275–284
Contents lists available at ScienceDirect
Automation in Construction j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / a u t c o n
RFID-based building maintenance system Chien-Ho Ko ⁎ Department of Civil Engineering, National Pingtung University of Science and Technology, 1, Shuefu Rd., Neipu, Pingtung 91201, Taiwan, ROC
a r t i c l e
i n f o
Article history: Accepted 2 September 2008 Keywords: Facilities management Maintenance Radio Frequency Identification (RFID) technology Web-based management information system Scheduling
a b s t r a c t Information technology applications have proven effective in the maintenance of constructed facilities. The objective of the study is to enhance building maintenance using Radio Frequency Identification (RFID) technology. A data management module is first developed to collect building usage and maintenance data. A statistical module is then established to graphically display the collected data. To ensure that building functions perform normally, maintenance activities are arranged using a scheduling module. These three modules are integrated into a web-based RFID building maintenance system. System performance is validated using a real building. Experimental results show that integrating RFID technology with a webbased system, database, and scheduling theory can improve facility and equipment maintenance efficiency. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Deconstructing old buildings requires tremendous cost. One of the ways to extend the life of constructed facilities is to maintain them with corresponding maintenance systems [1,5]. Radio Frequency Identification (RFID) technology is one of the most important technologies developed in the last century, characterizing repetitive read/ rewrite, non-contact, and the ability to access multiple tags simultaneously [9]. This has been regarded as a promising method to improve maintenance efficiency [8]. RFID has been widely used in various kinds of applications [6,11,14]. A few studies can be found in facility and equipment management. Strassner and Chang [17] applied RFID technology to collect data on oil drilling pipes. They monitored pipe usage and provided the collected information for inventory control. These researchers found that applying RFID in drill pipe management greatly reduced oil drilling operating costs. Cardellino and Finch [3] examined innovations in facilities management. They pinpointed that RFID is a promising information technology (IT) in the field. Wing [19] investigated RFID technology applications in construction and facilities management. A case study discussed in the paper collected data using RFID tags and passed information through the Internet. Equipment in the building was controlled according to the status identified by RFID tags. Legner and Thiesse [12] applied the same technology to maintenance at Frankfurt Airport. They integrated RFID and a mobile application with its asset management systems. The benefits induced by this approach included better planning, control, and technical work documentation as well as improved process quality. Ergen et al. [7] overcame dif-
⁎ Corresponding author. Tel.: +886 8 770 3202; fax: +886 8 774 0122. E-mail address: [email protected]. 0926-5805/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.autcon.2008.09.001
ficulties encountered in traditional facility maintenance using RFID. The limitations in data transfer between maintenance workers, lower data quality, longer service process times, and ineffective maintenance history capture were improved by this work. Although previous studies explored the promising of applying RFID in facilities maintenance, their solutions were fractional and incomplete. In addition, complicated maintenance jobs cannot be effectively achieved without a plan. Arranging rational maintenance sequences has never been discussed in the literature RFID applications. The objective of this study is to develop a web-based RFID building maintenance system to enhance maintenance efficiency. To achieve this goal, RFID technology is investigated first. The RFID and bar code system properties are discussed. Three modules, namely data management, statistical, and scheduling modules are established according to the building maintenance needs. The efficiency of the proposed system is examined using a real case. Application results and conclusions are documented in this paper. 2. Radio Frequency Identification (RFID) technology RFID technology is a wireless sensor technology based on electromagnetic signal detection [13]. One of the earliest papers exploring RFID was written by Harry Stockman “Communication by Means of Reflected Power” published in 1948 [16]. This came after radio research undertaken during the Second World War. Today RFID is a generic term for technologies that use radio waves to automatically identify people or objects. A typical RFID system, as shown in Fig. 1, is comprised of three components: an antenna, a transceiver, and a transponder. Fig. 1 shows that the transponder (RF tag) is electronically programmed with unique information. Radio signals are emitted by the transceiver through the antenna. Antennas establish communication between the
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C.-H. Ko / Automation in Construction 18 (2009) 275–284
Fig. 1. Typical RFID system.
tag and transceiver. The RF tag is activated and data on it are read and written by the requested signals sent from the antenna. The RF tag transfers data according to a specific request. The transceiver is responsible for data acquisition. The data can then be transferred to any computer system for processing [6]. The antenna can be packaged with the transceiver into a reader/writer unit. The reader/writer can be implemented either as a handheld or fixed-mount device. The radio wave ranges emitted from the device depends on the power output and radio frequency. Bar codes have been the most frequently used system for facilities management [2,18]. In a bar code system, labels must be so positioned that they can be detected and identified by a laser scanner. Objects that obstruct the optical communication between the label and scanner interrupt barcode scanning. Besides the physical limitations, bar code labels usually have generous dimensions. Unlike bar codes, RFID technology can dynamically transmit and receive information to help identify objects without “line-of-sight.” Information stored in the tag can be modified, which provides flexibility for managerial modification. Information Technology (IT) in the form of RFID is thus regarded as a resource that can be applied in overcoming the problems associated with traditional solutions (alphanumerical codes and bar code labels) [15]. 3. System development 3.1. Application scenario and requirements RFID technology is employed to improve the efficiency of traditional building maintenance solutions. The first step in system development is the scenario design. The maintenance staff carries a tablet PC while executing maintenance activities. A portable RFID reader/writer is attached to the tablet PC. The staff can implement maintenance jobs using a web-based application through an Internet
Fig. 2. Development process of RFID building maintenance system.
browser. Using the web-based software, staff can read/write information from/into tags. Information related to maintenance jobs is accessed from a single database through the Internet in real-time. As a result, multiple users can maintain various kinds of objects at the same time. To further improve working efficiency, staff can setup maintenance periods for each item. The software can remind users about which items require attention and automatically arrange maintenance sequences. Maintenance preparation and effort can therefore be reduced. Three modules i.e. management, statistical, and scheduling are obtained according to this scenario. 3.2. System development process The web-based RFID building management system development process is illustrated in Fig. 2. Each activity is explained as follows. 1. Determine hardware and software: System hardware and software that conform to application requirements are investigated in the first step. ASP.NET is chosen as the development platform to establish the web-based application. ASP.NET is a new technology developed by Microsoft. It supports browsers that execute on various kinds of platforms including personal computer, cell phone, personal digital assistant (PDA) etc. A portable RFID reader/writer, namely UHFBlock, manufactured by Ensyc Technology is selected. This device is compatible with the GEN2 protocol and can be connected using USB interface are the primary reasons for adoption. Fig. 3 represents devices for the staff to implement maintenance work. The system hardware and software used for system development are summarized as follows: • Web and database server: Dell enterprise personal computer • Integrated development environment: Visual Studio.NET (C#.NET) • Operation system: Windows XP professional
Fig. 3. Maintenance kit.
C.-H. Ko / Automation in Construction 18 (2009) 275–284
• • • •
277
tenance jobs through the system using a tablet PC with an attached portable RFID reader/writer (as shown in Fig. 3).
Database format: Microsoft Access Tablet PC: HP 2710P RFID device: UHF-Block RFID tag: UHF G2
3.4. Data management module
2. Establish database schema: Building maintenance induces numerous records. For managerial convenience, information is stored in a single database. The database is designed using third normal form of the relational model [4]. The simplified database schema is represented using class diagram depicted in Fig. 4. 3.3. System architecture The web-based system is application software that can be executed through browsers. The RFID maintenance system is developed as a web-based system to provide users with an application that can be run at anytime, anyplace, any platform with Ethernet cable or wireless network. The system concept, shown in Fig. 5, has three tiers. The storage tier is used for storing system data, such as basic information, maintenance history, seller information, etc. The application logic involves system modules and database connections. The presentation tier is the user interface, which enables users to interact with the application logic layer. Fig. 6 shows that the computational efficiency is driven by web and database servers. The web-system functions are programmed using C#.NET and transferred through Http/Https protocols. System inputs and outputs are stored in the database. Users can implement main-
The data management module is designed to allow manipulating the data stored in the system database. Functions provided by this module are summarized in Table 1. A maintenance object contains the following information: category, item, name, safety degree, durability, frequency of use, purchasing cost, purchasing date, part list, warranty period, seller, holder, location, etc. Users can fill out the information by entering values or selecting a proper description from a list. Each object is identified using RFID code that is a unique identification number written onto the RFID tag. The RFID code structure is shown in Fig. 7. The codification is designed for building maintenance using four sections. The first section, category, is used to store equipment or facility. The second item stores types of equipment or facility, such as universal test machine and electron microscope. Third part involving four cells is used to store serial number. The final area is designed for future extension. RFID code is automatically generated by the module and can be written onto a tag using the RFID device. For searching for information about a specific maintenance object, users can query by its category, name, RFID code, or identify it using RFID device. Information flow in data management module is illustrated using equipment information query displayed in Fig. 8. In the figure, information flow is initiated by user requests. The main form of data management module is shown in Fig. 9.
Fig. 4. Database schema.
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C.-H. Ko / Automation in Construction 18 (2009) 275–284 Table 1 Functions of data management module Function
Explanation
Login
Users enter username and password to log onto the web-based system. Two kinds of authorization are provided in the system: manager and administrator. Manage user Only administrative users can add/edit/remove system users. Manage category Users can add/edit/remove categories that are served as the highest level of maintenance object classification. Manage item Users can add/edit/remove items that are served as the second level of maintenance object classification. Manage parts Users can add/edit/remove parts for each maintenance item. Manage object Users can add/edit/remove a maintenance object and generate its RFID code. Manage space Users can add/edit/remove a space for maintenance object. View history Users can view maintenance record history for each object. Object can be identified using a RFID reader. Manage seller Users can add/edit/remove the seller information for maintenance objects.
jects involve various kinds of parts, which increase the maintenance complexity. A proper maintenance schedule is thus needed to effectively accomplish jobs. The scheduling module developed in this study focuses on arranging maintenance sequences. Two strategies are proposed to enhance maintenance efficiency:
Fig. 5. System concept.
3.5. Statistical module This study collected numerous data while implementing maintenance jobs stored in the system database. However, this data row is meaningless to users. The objective of the module is to represent the system database using statistical charts allowing users to understand the data distribution and properties. This module provides four charts for users to observe the data, i.e. circle graph, ogive, bar chart and line chart. Statistical graphs can help users understand maintenance status. A recommendation table is proposed to assist users making decisions according to the graphs, as explained in Table 2. An example of demonstrating purchasing costs using line chart is depicted in Fig. 10. 3.6. Scheduling module Scheduling involves tasks of making decisions regarding the allocation of available capacity or resources to jobs, activities, tasks, or customers over time. It thus results what is to be done, when, by whom, and with what equipment [10]. Building functions rely on periodic maintenance. Parts wearing out can induce malfunctions. Worn out parts can be identified and replaced by regular maintenance. However, diverse maintenance ob-
• Centralize maintenance time: The first strategy enhances maintenance efficiency by reducing preparation time. This strategy avoids frequent maintenance with small batch jobs. It schedules the time for carrying out maintenance activities, such as once a week, once every two weeks, once a month, or even daily maintenance. This schedule can be assigned by users. The logic for determining which object should be added to the maintenance list is expressed in Eq. (1). If Li z−T; add i in the list:
ð1Þ
Li: Time difference (Di − Ci) between the time point the object i should be maintained (Ci) and when it is planned to be maintained (Di). T: Extended maintenance period, which can be an arbitrary time. The value is determined according to managerial requirements such as national holidays, man power, complexity of maintenance work, etc. • Minimize the required maintenance hours: To accomplish maintenance activities using the most effective way, the module minimizes the total maintenance time. Scheduling methods can be divided into three categories. Mathematical programming is primarily used to solve certain problems. If the problem is difficult to solve, dispatching rules can be considered. However, dispatching rules arrange sequences using certain principles
Fig. 6. System application architecture.
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Fig. 7. RFID codification structure.
acceptable time period. Maintenance scheduling is regarded as a job shop sequencing problem that can be solved using a mathematical programming method. The objective function of the scheduling module, shown in Eq. (2), is to minimize total maintenance time t.
m
Min t ¼ ∑ j¼1
αi βi γj
Fig. 8. Equipment information query sequence diagram.
that cannot obtain an optimum solution for complex problems. Heuristic algorithms are adopted for difficult, complex, and uncertain problems. Although heuristic methods cannot guarantee obtaining the optimum solution, they provide satisfactory results within an
n
∑ ðα i þ βi Þ þ γ j
ð2Þ
i¼1
maintenance time for object i. transportation time from object (i − 1) to i. The βi = 0 when i = 1. transportation time from space (j − 1) to j. The γj = 0 when j = 1.
The RFID building management software developed in the study is a web-based system connecting with a single database. Therefore, the system is running in real-time and the information provided by the system is up-to-date. This advantage also enables multiple users to implement maintenance jobs at the same time. The maintenance direction suggested by this study is depicted in Fig. 11. A single staff member can implement maintenance work using a top-down or bottom-up approach (as shown in Fig. 11(a)). For two staff members, one can implement in the top-down direction and the other bottom-
Fig. 9. Main form of data management module.
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C.-H. Ko / Automation in Construction 18 (2009) 275–284
Table 2 Decision support for statistical graph Statistical group
Decision support
Maintenance object Number of objects located in an individual space can be amount identified. Therefore, users can understand the status of maintenance objects such as missing and broken. Repair frequency According to the graphs, users can recognize the durability of maintenance objects. The information can be fed back to the procumbent department, repair partners, and property holder for preventive analysis. Repair cost The information can be used to determine whether the maintenance objects should be replaced or not. The procumbent department can also use the information as purchasing reference. Object life time Maintenance efficiency effects life time of property. It can also be used as another index for property durability. Breakdown causes Graphs about breakdown causes are ideal for breakdown causes analysis. The information can be used for troubleshooting.
up (as shown in Fig. 11(b)). For more than two staff members, the two staff member case is carried out and the additional staff members implement maintenance work from intermediate positions (as instance in Fig. 11(c)). The module reminds users to take cautious attention to the work if the job is related to safety considerations. The scheduling module setup form is shown in Fig. 12. 4. System validation 4.1. Case study RFID building maintenance system performance was examined using a material test center located in Taipei City, Taiwan. This center, built in 2007, is a five story building that includes more than 12 kinds of laboratories. These laboratories have valuable experimental instruments such as a universal testing machine, electron microscope,
e-beam, spin coater, differential thermal analyzer, rapid thermal annealing machine, etc., requiring periodical maintenance to ensure their functions. In addition, laboratory spaces such as rain and wind laboratories, fireproof laboratory, wind tunnel laboratory, etc. must be kept functional to perform tests. The management objects are therefore divided into two categories: equipment and facility. Equipment is defined as a tool or device necessary for a specific type of work. Facility is defined as a building or place that provides a particular service. 4.2. System implementation Maintenance jobs were carried out by two staff members at the test center. User name, password, and authority were identified first in the system. RFID codes were automatically generated by the data management module according to codification grammar. Staff members then enter equipment and facility information with corresponding RFID codes. When staff members complete the web form, the generated RFID code is written onto the RFID tag (as shown in Fig. 13). The system automatically confirms the writing success. Facility and equipment are available in the system once the data passes confirmation. Staff members can then begin manipulating object data. The scheduling module was launched to automatically arrange maintenance sequences. Analyzed results with minimum maintenance time are displayed in Fig. 14. Staff members then select items and fill in the maintenance records in the form (as shown in Fig. 15). The two staff mode, shown in Fig. 11(b), was adopted when executing maintenance jobs. For this case study, one staff member selected the top-down sequence and the other chose the bottom-up maintenance direction. Items disappeared from the form once they were completed. Incomplete tasks remained on the form for further scheduling. Because the system accesses the database in real-time, members have up-to-date information shown on the form. Maintenance records and
Fig. 10. Line chart of purchasing costs.
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may take another half an hour. The maintenance sequences are automatically arranged by the RFID building maintenance system. The developed RFID system is connected to a single database to enable multiple users to implement maintenance work at the same time. The proposed system updates the database in real-time, which avoids data re-typing, duplicate maintenance, and missing maintenance. Therefore, personnel costs and maintenance makespan can be handled. The data stored in the database can be analyzed using statistical graphs from anywhere at any time with up-to-date distributions. The proposed system is developed based on Internet architecture. Wireless signals should therefore cover the comprehensive area. Before installing the system, the reliability of the wireless signal should be confirmed. Places such as basements and machine rooms frequently lack signal integrity. Another challenge occurs when management objects are located next to each other. Because RFID devices retrieve tag information within a given effective range, more than one object may be identified. Staff members need to recognize the proper equipment item. 5. Conclusions
Fig. 11. Maintenance direction.
equipment/facility information can be queried using the statistical module. 4.3. Discussion Maintenance jobs are executed by laboratory staff members that carry tablet PCs with portable RFID devices (reader/writer). Facility and equipment identifications are automatically identified through RFID devices. The communication (reading/writing) success rate is 100% within 50 cm using an enhanced antenna. Communication between tablet PCs and the system database could be completed within 3 s in this case study. The processes required for managerial purposes can be completed using the developed system. Compared to traditional management methods, document preparation may take 5 to 10 min before maintenance. Paper documents may be lost and require additional effort after maintenance. Moreover, staff members can simply approach targets within the effective range to identify object identifications using the proposed system. Traditional methods, such as bar code systems, need to adjust poses to access alphanumerical codes or bar code labels. The proposed web-based system allows single or multiple users to manipulate the system, providing flexible personal arrangements. The current practice that arranges maintenance sequences by hand is time-consuming, which generally took 20 min in this case study to verify which item required maintenance. In addition, the identified sequence may be subject to an additional optimization effort, which
This paper presented a web-based RFID building maintenance system. Three modules were included, i.e., data management, statistical, and scheduling. Users implement maintenance work using tablet PCs attached with portable RFID devices. The proposed system performance was examined using a material test center. The following benefits of applying RFID technology in building maintenance are drawn from real applications: 1) automatically identifying equipment and facility ID avoids typos and saves operational time, 2) data stored in RFID tags can be easily modified, 3) non-contact and non-line-of-sight RFID technology enhances maintenance convenience, 4) RFID tags can be used under practical challenging conditions such as paint, grime, and dust, and 5) RFID technology cooperates extensively with other information technologies. The developed web-based system can be implemented from anywhere, at any time, for any platform with wired or wireless Internet connections, which enhances managerial efficiency. The proposed system enables multiple users to implement maintenance work directly through the web system at the same time. It highlights the flexibility in personnel arrangement for the required maintenance time. The statistical module established in this study provides users with the opportunity to monitor equipment and facility status using graphs. The scheduling module automatically arranges maintenance sequences based on scheduling theories. The derived results minimize total maintenance time preventing missing or duplicate maintenance activities or records. These characteristics improve convenience and efficiency for building maintenance personnel including: maintenance sequence arrangement, data transfer between maintenance workers, data quality, service process times, maintenance preparation, and effectively capturing maintenance history. However, the system operates depending on Internet communication. Further deployment may improve this system using an offline web application. The developed web-based RFID system is one of the first researches integrating RFID technology, database, Internet technology, and scheduling theory in building maintenance. The proposed scheduling module is also one of the pioneering works applying scheduling theory in RFID applications. Acknowledgements This research was funded by the Architecture and Building Research Institute (Taiwan), whose support is gratefully acknowledged. Any opinions, findings, conclusions, or recommendations expressed in this paper are those of the author and do not reflect the views of the Architecture and Building Research Institute. The writer would also like to thank the investigated laboratory for
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Fig. 12. Scheduling module.
Fig. 13. Writing information onto RFID tag.
C.-H. Ko / Automation in Construction 18 (2009) 275–284
Fig. 14. Scheduling results.
Fig. 15. Maintenance implementation.
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supporting this study. Special thanks to students who helped: Yu-Xian Lin, Guan-Jie Wang, Yi-He Lai, Wei-Jie Chang, Shi-Hong Wang, and Qing-Yuan Ko. References [1] A.L. Barco, Budgeting for facility repair and maintenance, Journal of Management in Engineering 10 (4) (1994) 28–34. [2] R. Bravman, Using bar codes improves management control, Electronic Packaging and Production 27 (2) (1987) 153–154. [3] P. Cardellino, E. Finch, Mapping IT innovation in facilities management, Electronic Journal of Information Technology in Construction 11 (2006) 673–684. [4] E.F. Codd, The Relational Model for Database Management, Second edition, Addison Wesley, New York. [5] M. Djerdjouri, Assessing and benchmarking maintenance performance in a manufacturing facility: a data envelopment analysis approach, INFOR 43 (2) (2005) 121–133. [6] K. Domdouzis, B. Kumar, C. Anumba, Radio-Frequency Identification (RFID) applications: a brief introduction, Advanced Engineering Informatics 21 (4) (2007) 350–355. [7] E. Ergen, B. Akinci, B. East, F. Kirby, Tracking components and maintenance history within a facility utilizing radio frequency identification technology, Journal of Computing in Civil Engineering, ASCE 21 (1) (2007) 11–20. [8] J. Fontelera, RFID exploration, Converting Magazine 23 (9) (2005) 28–32.
[9] V.D. Hunt, A. Puglia, M. Puglia, RFID—A Guide to Radio Frequency Identification, Wiley-Interscience, 2007. [10] C.H. Ko, S.F. Wang, Overcoming difficulties in weekly work planning, Research Journal of Applied Sciences 2 (7) (2007) 823–827. [11] B. Kumar, Special section on RFID applications in engineering, Advanced Engineering Informatics 21 (4) (2007) 349. [12] C. Legner, F. Thiesse, RFID-based maintenance at Frankfurt airport, IEEE Pervasive Computing 5 (1) (2006) 34–39. [13] J.F. McCarthy, D.H. Nguyen, A.M. Rashid, S. Soroczak, Proactive displays & the experience UbiComp Project, Proceedings of the Fifth International Conference on Ubiquitous Computing, 2003, pp. 78–81. [14] E. Ngai, F. Riggins, RFID: technology, applications, and impact on business operations, International Journal of Production Economics 112 (2) (2008) 507–509. [15] A. Regattieri, M. Gamberi, R. Manzini, Traceability of food products: general framework and experimental evidence, Journal of Food Engineering 81 (2007) 347–356. [16] H. Stockman, Communication by means of reflected power, Proceedings of the Institute of Radio Engineers, vol. 36, 10, 1948, pp. 1196–1204. [17] B. Strassner, K. Chang, Integrated antenna system for wireless RFID tag in monitoring oil drill pipe, Proceedings of the International Symposium on Antennas and Propagation Society, vol. 1, IEEE, 2003, pp. 208–211. [18] T.J. Terez, Bar codes move into maintenance management, Hydraulics & Pneumatics 45 (4) (1992) 36. [19] R. Wing, RFID applications in construction and facilities management, Electronic Journal of Information Technology in Construction 11 (2006) 711–721.
Contents lists available at ScienceDirect
Automation in Construction j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / a u t c o n
RFID-based building maintenance system Chien-Ho Ko ⁎ Department of Civil Engineering, National Pingtung University of Science and Technology, 1, Shuefu Rd., Neipu, Pingtung 91201, Taiwan, ROC
a r t i c l e
i n f o
Article history: Accepted 2 September 2008 Keywords: Facilities management Maintenance Radio Frequency Identification (RFID) technology Web-based management information system Scheduling
a b s t r a c t Information technology applications have proven effective in the maintenance of constructed facilities. The objective of the study is to enhance building maintenance using Radio Frequency Identification (RFID) technology. A data management module is first developed to collect building usage and maintenance data. A statistical module is then established to graphically display the collected data. To ensure that building functions perform normally, maintenance activities are arranged using a scheduling module. These three modules are integrated into a web-based RFID building maintenance system. System performance is validated using a real building. Experimental results show that integrating RFID technology with a webbased system, database, and scheduling theory can improve facility and equipment maintenance efficiency. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Deconstructing old buildings requires tremendous cost. One of the ways to extend the life of constructed facilities is to maintain them with corresponding maintenance systems [1,5]. Radio Frequency Identification (RFID) technology is one of the most important technologies developed in the last century, characterizing repetitive read/ rewrite, non-contact, and the ability to access multiple tags simultaneously [9]. This has been regarded as a promising method to improve maintenance efficiency [8]. RFID has been widely used in various kinds of applications [6,11,14]. A few studies can be found in facility and equipment management. Strassner and Chang [17] applied RFID technology to collect data on oil drilling pipes. They monitored pipe usage and provided the collected information for inventory control. These researchers found that applying RFID in drill pipe management greatly reduced oil drilling operating costs. Cardellino and Finch [3] examined innovations in facilities management. They pinpointed that RFID is a promising information technology (IT) in the field. Wing [19] investigated RFID technology applications in construction and facilities management. A case study discussed in the paper collected data using RFID tags and passed information through the Internet. Equipment in the building was controlled according to the status identified by RFID tags. Legner and Thiesse [12] applied the same technology to maintenance at Frankfurt Airport. They integrated RFID and a mobile application with its asset management systems. The benefits induced by this approach included better planning, control, and technical work documentation as well as improved process quality. Ergen et al. [7] overcame dif-
⁎ Corresponding author. Tel.: +886 8 770 3202; fax: +886 8 774 0122. E-mail address: [email protected]. 0926-5805/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.autcon.2008.09.001
ficulties encountered in traditional facility maintenance using RFID. The limitations in data transfer between maintenance workers, lower data quality, longer service process times, and ineffective maintenance history capture were improved by this work. Although previous studies explored the promising of applying RFID in facilities maintenance, their solutions were fractional and incomplete. In addition, complicated maintenance jobs cannot be effectively achieved without a plan. Arranging rational maintenance sequences has never been discussed in the literature RFID applications. The objective of this study is to develop a web-based RFID building maintenance system to enhance maintenance efficiency. To achieve this goal, RFID technology is investigated first. The RFID and bar code system properties are discussed. Three modules, namely data management, statistical, and scheduling modules are established according to the building maintenance needs. The efficiency of the proposed system is examined using a real case. Application results and conclusions are documented in this paper. 2. Radio Frequency Identification (RFID) technology RFID technology is a wireless sensor technology based on electromagnetic signal detection [13]. One of the earliest papers exploring RFID was written by Harry Stockman “Communication by Means of Reflected Power” published in 1948 [16]. This came after radio research undertaken during the Second World War. Today RFID is a generic term for technologies that use radio waves to automatically identify people or objects. A typical RFID system, as shown in Fig. 1, is comprised of three components: an antenna, a transceiver, and a transponder. Fig. 1 shows that the transponder (RF tag) is electronically programmed with unique information. Radio signals are emitted by the transceiver through the antenna. Antennas establish communication between the
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C.-H. Ko / Automation in Construction 18 (2009) 275–284
Fig. 1. Typical RFID system.
tag and transceiver. The RF tag is activated and data on it are read and written by the requested signals sent from the antenna. The RF tag transfers data according to a specific request. The transceiver is responsible for data acquisition. The data can then be transferred to any computer system for processing [6]. The antenna can be packaged with the transceiver into a reader/writer unit. The reader/writer can be implemented either as a handheld or fixed-mount device. The radio wave ranges emitted from the device depends on the power output and radio frequency. Bar codes have been the most frequently used system for facilities management [2,18]. In a bar code system, labels must be so positioned that they can be detected and identified by a laser scanner. Objects that obstruct the optical communication between the label and scanner interrupt barcode scanning. Besides the physical limitations, bar code labels usually have generous dimensions. Unlike bar codes, RFID technology can dynamically transmit and receive information to help identify objects without “line-of-sight.” Information stored in the tag can be modified, which provides flexibility for managerial modification. Information Technology (IT) in the form of RFID is thus regarded as a resource that can be applied in overcoming the problems associated with traditional solutions (alphanumerical codes and bar code labels) [15]. 3. System development 3.1. Application scenario and requirements RFID technology is employed to improve the efficiency of traditional building maintenance solutions. The first step in system development is the scenario design. The maintenance staff carries a tablet PC while executing maintenance activities. A portable RFID reader/writer is attached to the tablet PC. The staff can implement maintenance jobs using a web-based application through an Internet
Fig. 2. Development process of RFID building maintenance system.
browser. Using the web-based software, staff can read/write information from/into tags. Information related to maintenance jobs is accessed from a single database through the Internet in real-time. As a result, multiple users can maintain various kinds of objects at the same time. To further improve working efficiency, staff can setup maintenance periods for each item. The software can remind users about which items require attention and automatically arrange maintenance sequences. Maintenance preparation and effort can therefore be reduced. Three modules i.e. management, statistical, and scheduling are obtained according to this scenario. 3.2. System development process The web-based RFID building management system development process is illustrated in Fig. 2. Each activity is explained as follows. 1. Determine hardware and software: System hardware and software that conform to application requirements are investigated in the first step. ASP.NET is chosen as the development platform to establish the web-based application. ASP.NET is a new technology developed by Microsoft. It supports browsers that execute on various kinds of platforms including personal computer, cell phone, personal digital assistant (PDA) etc. A portable RFID reader/writer, namely UHFBlock, manufactured by Ensyc Technology is selected. This device is compatible with the GEN2 protocol and can be connected using USB interface are the primary reasons for adoption. Fig. 3 represents devices for the staff to implement maintenance work. The system hardware and software used for system development are summarized as follows: • Web and database server: Dell enterprise personal computer • Integrated development environment: Visual Studio.NET (C#.NET) • Operation system: Windows XP professional
Fig. 3. Maintenance kit.
C.-H. Ko / Automation in Construction 18 (2009) 275–284
• • • •
277
tenance jobs through the system using a tablet PC with an attached portable RFID reader/writer (as shown in Fig. 3).
Database format: Microsoft Access Tablet PC: HP 2710P RFID device: UHF-Block RFID tag: UHF G2
3.4. Data management module
2. Establish database schema: Building maintenance induces numerous records. For managerial convenience, information is stored in a single database. The database is designed using third normal form of the relational model [4]. The simplified database schema is represented using class diagram depicted in Fig. 4. 3.3. System architecture The web-based system is application software that can be executed through browsers. The RFID maintenance system is developed as a web-based system to provide users with an application that can be run at anytime, anyplace, any platform with Ethernet cable or wireless network. The system concept, shown in Fig. 5, has three tiers. The storage tier is used for storing system data, such as basic information, maintenance history, seller information, etc. The application logic involves system modules and database connections. The presentation tier is the user interface, which enables users to interact with the application logic layer. Fig. 6 shows that the computational efficiency is driven by web and database servers. The web-system functions are programmed using C#.NET and transferred through Http/Https protocols. System inputs and outputs are stored in the database. Users can implement main-
The data management module is designed to allow manipulating the data stored in the system database. Functions provided by this module are summarized in Table 1. A maintenance object contains the following information: category, item, name, safety degree, durability, frequency of use, purchasing cost, purchasing date, part list, warranty period, seller, holder, location, etc. Users can fill out the information by entering values or selecting a proper description from a list. Each object is identified using RFID code that is a unique identification number written onto the RFID tag. The RFID code structure is shown in Fig. 7. The codification is designed for building maintenance using four sections. The first section, category, is used to store equipment or facility. The second item stores types of equipment or facility, such as universal test machine and electron microscope. Third part involving four cells is used to store serial number. The final area is designed for future extension. RFID code is automatically generated by the module and can be written onto a tag using the RFID device. For searching for information about a specific maintenance object, users can query by its category, name, RFID code, or identify it using RFID device. Information flow in data management module is illustrated using equipment information query displayed in Fig. 8. In the figure, information flow is initiated by user requests. The main form of data management module is shown in Fig. 9.
Fig. 4. Database schema.
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C.-H. Ko / Automation in Construction 18 (2009) 275–284 Table 1 Functions of data management module Function
Explanation
Login
Users enter username and password to log onto the web-based system. Two kinds of authorization are provided in the system: manager and administrator. Manage user Only administrative users can add/edit/remove system users. Manage category Users can add/edit/remove categories that are served as the highest level of maintenance object classification. Manage item Users can add/edit/remove items that are served as the second level of maintenance object classification. Manage parts Users can add/edit/remove parts for each maintenance item. Manage object Users can add/edit/remove a maintenance object and generate its RFID code. Manage space Users can add/edit/remove a space for maintenance object. View history Users can view maintenance record history for each object. Object can be identified using a RFID reader. Manage seller Users can add/edit/remove the seller information for maintenance objects.
jects involve various kinds of parts, which increase the maintenance complexity. A proper maintenance schedule is thus needed to effectively accomplish jobs. The scheduling module developed in this study focuses on arranging maintenance sequences. Two strategies are proposed to enhance maintenance efficiency:
Fig. 5. System concept.
3.5. Statistical module This study collected numerous data while implementing maintenance jobs stored in the system database. However, this data row is meaningless to users. The objective of the module is to represent the system database using statistical charts allowing users to understand the data distribution and properties. This module provides four charts for users to observe the data, i.e. circle graph, ogive, bar chart and line chart. Statistical graphs can help users understand maintenance status. A recommendation table is proposed to assist users making decisions according to the graphs, as explained in Table 2. An example of demonstrating purchasing costs using line chart is depicted in Fig. 10. 3.6. Scheduling module Scheduling involves tasks of making decisions regarding the allocation of available capacity or resources to jobs, activities, tasks, or customers over time. It thus results what is to be done, when, by whom, and with what equipment [10]. Building functions rely on periodic maintenance. Parts wearing out can induce malfunctions. Worn out parts can be identified and replaced by regular maintenance. However, diverse maintenance ob-
• Centralize maintenance time: The first strategy enhances maintenance efficiency by reducing preparation time. This strategy avoids frequent maintenance with small batch jobs. It schedules the time for carrying out maintenance activities, such as once a week, once every two weeks, once a month, or even daily maintenance. This schedule can be assigned by users. The logic for determining which object should be added to the maintenance list is expressed in Eq. (1). If Li z−T; add i in the list:
ð1Þ
Li: Time difference (Di − Ci) between the time point the object i should be maintained (Ci) and when it is planned to be maintained (Di). T: Extended maintenance period, which can be an arbitrary time. The value is determined according to managerial requirements such as national holidays, man power, complexity of maintenance work, etc. • Minimize the required maintenance hours: To accomplish maintenance activities using the most effective way, the module minimizes the total maintenance time. Scheduling methods can be divided into three categories. Mathematical programming is primarily used to solve certain problems. If the problem is difficult to solve, dispatching rules can be considered. However, dispatching rules arrange sequences using certain principles
Fig. 6. System application architecture.
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Fig. 7. RFID codification structure.
acceptable time period. Maintenance scheduling is regarded as a job shop sequencing problem that can be solved using a mathematical programming method. The objective function of the scheduling module, shown in Eq. (2), is to minimize total maintenance time t.
m
Min t ¼ ∑ j¼1
αi βi γj
Fig. 8. Equipment information query sequence diagram.
that cannot obtain an optimum solution for complex problems. Heuristic algorithms are adopted for difficult, complex, and uncertain problems. Although heuristic methods cannot guarantee obtaining the optimum solution, they provide satisfactory results within an
n
∑ ðα i þ βi Þ þ γ j
ð2Þ
i¼1
maintenance time for object i. transportation time from object (i − 1) to i. The βi = 0 when i = 1. transportation time from space (j − 1) to j. The γj = 0 when j = 1.
The RFID building management software developed in the study is a web-based system connecting with a single database. Therefore, the system is running in real-time and the information provided by the system is up-to-date. This advantage also enables multiple users to implement maintenance jobs at the same time. The maintenance direction suggested by this study is depicted in Fig. 11. A single staff member can implement maintenance work using a top-down or bottom-up approach (as shown in Fig. 11(a)). For two staff members, one can implement in the top-down direction and the other bottom-
Fig. 9. Main form of data management module.
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Table 2 Decision support for statistical graph Statistical group
Decision support
Maintenance object Number of objects located in an individual space can be amount identified. Therefore, users can understand the status of maintenance objects such as missing and broken. Repair frequency According to the graphs, users can recognize the durability of maintenance objects. The information can be fed back to the procumbent department, repair partners, and property holder for preventive analysis. Repair cost The information can be used to determine whether the maintenance objects should be replaced or not. The procumbent department can also use the information as purchasing reference. Object life time Maintenance efficiency effects life time of property. It can also be used as another index for property durability. Breakdown causes Graphs about breakdown causes are ideal for breakdown causes analysis. The information can be used for troubleshooting.
up (as shown in Fig. 11(b)). For more than two staff members, the two staff member case is carried out and the additional staff members implement maintenance work from intermediate positions (as instance in Fig. 11(c)). The module reminds users to take cautious attention to the work if the job is related to safety considerations. The scheduling module setup form is shown in Fig. 12. 4. System validation 4.1. Case study RFID building maintenance system performance was examined using a material test center located in Taipei City, Taiwan. This center, built in 2007, is a five story building that includes more than 12 kinds of laboratories. These laboratories have valuable experimental instruments such as a universal testing machine, electron microscope,
e-beam, spin coater, differential thermal analyzer, rapid thermal annealing machine, etc., requiring periodical maintenance to ensure their functions. In addition, laboratory spaces such as rain and wind laboratories, fireproof laboratory, wind tunnel laboratory, etc. must be kept functional to perform tests. The management objects are therefore divided into two categories: equipment and facility. Equipment is defined as a tool or device necessary for a specific type of work. Facility is defined as a building or place that provides a particular service. 4.2. System implementation Maintenance jobs were carried out by two staff members at the test center. User name, password, and authority were identified first in the system. RFID codes were automatically generated by the data management module according to codification grammar. Staff members then enter equipment and facility information with corresponding RFID codes. When staff members complete the web form, the generated RFID code is written onto the RFID tag (as shown in Fig. 13). The system automatically confirms the writing success. Facility and equipment are available in the system once the data passes confirmation. Staff members can then begin manipulating object data. The scheduling module was launched to automatically arrange maintenance sequences. Analyzed results with minimum maintenance time are displayed in Fig. 14. Staff members then select items and fill in the maintenance records in the form (as shown in Fig. 15). The two staff mode, shown in Fig. 11(b), was adopted when executing maintenance jobs. For this case study, one staff member selected the top-down sequence and the other chose the bottom-up maintenance direction. Items disappeared from the form once they were completed. Incomplete tasks remained on the form for further scheduling. Because the system accesses the database in real-time, members have up-to-date information shown on the form. Maintenance records and
Fig. 10. Line chart of purchasing costs.
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may take another half an hour. The maintenance sequences are automatically arranged by the RFID building maintenance system. The developed RFID system is connected to a single database to enable multiple users to implement maintenance work at the same time. The proposed system updates the database in real-time, which avoids data re-typing, duplicate maintenance, and missing maintenance. Therefore, personnel costs and maintenance makespan can be handled. The data stored in the database can be analyzed using statistical graphs from anywhere at any time with up-to-date distributions. The proposed system is developed based on Internet architecture. Wireless signals should therefore cover the comprehensive area. Before installing the system, the reliability of the wireless signal should be confirmed. Places such as basements and machine rooms frequently lack signal integrity. Another challenge occurs when management objects are located next to each other. Because RFID devices retrieve tag information within a given effective range, more than one object may be identified. Staff members need to recognize the proper equipment item. 5. Conclusions
Fig. 11. Maintenance direction.
equipment/facility information can be queried using the statistical module. 4.3. Discussion Maintenance jobs are executed by laboratory staff members that carry tablet PCs with portable RFID devices (reader/writer). Facility and equipment identifications are automatically identified through RFID devices. The communication (reading/writing) success rate is 100% within 50 cm using an enhanced antenna. Communication between tablet PCs and the system database could be completed within 3 s in this case study. The processes required for managerial purposes can be completed using the developed system. Compared to traditional management methods, document preparation may take 5 to 10 min before maintenance. Paper documents may be lost and require additional effort after maintenance. Moreover, staff members can simply approach targets within the effective range to identify object identifications using the proposed system. Traditional methods, such as bar code systems, need to adjust poses to access alphanumerical codes or bar code labels. The proposed web-based system allows single or multiple users to manipulate the system, providing flexible personal arrangements. The current practice that arranges maintenance sequences by hand is time-consuming, which generally took 20 min in this case study to verify which item required maintenance. In addition, the identified sequence may be subject to an additional optimization effort, which
This paper presented a web-based RFID building maintenance system. Three modules were included, i.e., data management, statistical, and scheduling. Users implement maintenance work using tablet PCs attached with portable RFID devices. The proposed system performance was examined using a material test center. The following benefits of applying RFID technology in building maintenance are drawn from real applications: 1) automatically identifying equipment and facility ID avoids typos and saves operational time, 2) data stored in RFID tags can be easily modified, 3) non-contact and non-line-of-sight RFID technology enhances maintenance convenience, 4) RFID tags can be used under practical challenging conditions such as paint, grime, and dust, and 5) RFID technology cooperates extensively with other information technologies. The developed web-based system can be implemented from anywhere, at any time, for any platform with wired or wireless Internet connections, which enhances managerial efficiency. The proposed system enables multiple users to implement maintenance work directly through the web system at the same time. It highlights the flexibility in personnel arrangement for the required maintenance time. The statistical module established in this study provides users with the opportunity to monitor equipment and facility status using graphs. The scheduling module automatically arranges maintenance sequences based on scheduling theories. The derived results minimize total maintenance time preventing missing or duplicate maintenance activities or records. These characteristics improve convenience and efficiency for building maintenance personnel including: maintenance sequence arrangement, data transfer between maintenance workers, data quality, service process times, maintenance preparation, and effectively capturing maintenance history. However, the system operates depending on Internet communication. Further deployment may improve this system using an offline web application. The developed web-based RFID system is one of the first researches integrating RFID technology, database, Internet technology, and scheduling theory in building maintenance. The proposed scheduling module is also one of the pioneering works applying scheduling theory in RFID applications. Acknowledgements This research was funded by the Architecture and Building Research Institute (Taiwan), whose support is gratefully acknowledged. Any opinions, findings, conclusions, or recommendations expressed in this paper are those of the author and do not reflect the views of the Architecture and Building Research Institute. The writer would also like to thank the investigated laboratory for
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Fig. 12. Scheduling module.
Fig. 13. Writing information onto RFID tag.
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Fig. 14. Scheduling results.
Fig. 15. Maintenance implementation.
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