Remote machine maintenance system through Internet and mobile communication

Int J Adv Manuf Technol (2007) 31: 783 789 DOI 10.1007/s00170-005-0236-1 ORIGINAL ARTICLE Wanbin Wang. Peter W. Tse. Jay Lee Remote machine maintenance system through Internet and mobile communication Received: 13 June 2005 / Accepted: 1 August 2005 / Published online: 9 March 2006 # Springer-Verlag London Limited 2006 Abstract Machine condition monitoring is important to factory efficiency and safety of workers. A variety of vibration signals analysis techniques have long been used to diagnosis machine status. Based on the newest Internet and mobile communication technology we developed a remote fault diagnostic system with many merits. This remote monitoring system takes XML as a core and uses it to encode diagnostic data. The utilization of XML gives this system many advantages including minimum research work on the client side, and simplicity to expand the system. This system publishes the diagnosis data not only by WEB, but also by WAP. Then users can check the machine status including data, image and video, through the Internet and mobile terminals. The automatic alarm part, which is developed based on Microsoft 's Smartphone 2003 operating system, can actively send alerting messages to the engineers mobile phones and call these phones to make sure they get an alert when the machine 's status is abnormal. Keywords Web-based maintenance. XML. Mobile phone. PDA. Machine fault diagnosis. Short message service 1 Introduction Failure of machines may not only lead to a loss of production, but also, in some serious situations, may cause W. Wang (*). P. W. Tse Smart Asset Management Laboratory, Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong, Tat Chee Ave., Hong Kong, People s Republic of China e-mail: walter.wang@student.cityu.edu.hk Tel.: +852-278-88431 Fax: +852-278-88423 J. Lee Department of Mechanical, Industrial and Nuclear Engineering, University of Cincinnati, Cincinnati, OH, USA human casualties. Hence, a fault diagnostic system is employed in the processes of identifying a machine 's operating condition and investigating its possible source of fault. These processes can help companies to reduce their overall production costs, improve the production reliability, minimize machine downtime, and increase operational efficiency. A variety of vibration signal analysis techniques, such as Fourier transform and wavelet transform, have long been used to diagnosis machine status through analyzing the vibration spectrum. The current trend of manufacturing is moving toward regionalisation. Hence, the factory for production may be in one place due to cheaper resources, whilst the main office may be in another location for better sales networking. The production machines, which need to be monitored, are perhaps far away from the managers and fault diagnosis experts. Thanks to the techniques based on the Internet and mobile communication, remote machine condition monitoring and fault diagnosis become feasible. Consequently, just-in-time managerial decisions can be made remotely. Contingency plans can be provided to compensate the loss of production due to unexpected breakdown of production machines. Remote machine monitoring and control become vital to companies that are involved in competition, or even worse, to those fighting for survival. As soon as the Web became a more stable avenue for ideas exchange, researchers began to explore web-based machine diagnosis systems. Caldwell et al. [2] used the Internet for diagnosing a scanning electron microscope. Today, GSM (global system for mobile communication) and CDMA (code division multiple access) have already been widely deployed. Wireless application protocol (WAP) has also been developed for mobile devices, such as mobile phones and personal digital assistants (PDAs), to access the Internet. The development of these technologies makes it possible to maintain machines from anywhere at anytime. At the same time, the development of XML provides a new tool for a remote diagnosis system. XML is an acronym for extensible markup language and has been developed by W3C (the World Wide Web Consortium). It provides a

784 general format for expressing both data structures and content. XMLs format is ready for storing structured data that are intended to be published or exchanged between different applications. The advantages of XML are simplicity, openness, extensibility, and self-description. It contains machine-readable context information, allows content to be separable from presentation, facilitates comparison, and provides aggregation of data from multiple types of data. For remote machine monitoring, XML can help different applications share their data, make the data easier to be published for remote users, and enable future expansion for new diagnostic functions. In this paper, we describe how to develop a remote machine fault diagnostic system which monitors machine status through Internet and mobile communication. This system uses XML to encode monitoring and diagnosis related data. The paper is laid out in five sections with this section as the introduction. Section 2 describes the problems of facing remote machine monitoring systems and the need for improvements. Section 3 presents the architecture and layout of the system. Detailed descriptions of how to develop this system are given in Section 4. The diagnosis data publishing aspect makes the users check the machine status through the Internet and mobile terminals. Due to limited capability of mobile communication, the results have been tailor-made so that only the current health condition of the inspected machine will be displayed on the mobile phone or PDA. Detailed machine health data can be reviewed through the Web. Moreover, according to the needs from different viewers, the content of the results will be presented differently to either an engineer or a manager. The automatic alarm part, which is developed based on Microsoft 's Smartphone 2003 smart-phone operating system, can actively send alerting messages to the engineers mobile phones and call these phones to make sure the engineers get the short messages when the machine s status is abnormal. Finally, Section 5 provides the concluding remarks and future work. 2 Problems facing the remote machine monitoring systems Web-based maintenance systems can provide remote sensing, monitoring, and on-line fault diagnosis for equipment. The establishment of such a system can provide manufacturers and users greater flexibility in controlling costs and maximizing the efficiency of production. Over the past decade, Internet and mobile communication have evolved considerably, making rapid progress in remote machine monitoring and diagnosis. For example, Caldwell et al. [2] described a system which used the Internet for diagnosing a scanning electron microscope. Ong et al. [7] presented a Web- and knowledge-based fault diagnostic and learning system which used multi-agent technology. Yuan et al. [11] described the architecture of a Web-based remote operation and monitoring system for open NC devices. Wang et al. [9] employed virtual instruments to provide remote sensing, monitoring and on-line fault diagnosis for equipment, together with a collaborative maintenance platform for international experts to interactively share their experiences in maintenance. Although these systems all provide remote monitoring and diagnosing abilities, we can only check the machine status by a computer connected to the Internet. It is not convenient for the engineers, and especially for the managers, who only want to know whether the machine works well. There is no automatic alarm part, and the engineers have to check the machine through remote machine monitoring regularly. The other problem is that because architectures of different machine diagnosis systems are different, the compatibility of data with different remote systems is lacking, making it difficult to share data between systems. Moreover, for Web-based remote machine monitoring, there are many different types of data requiring transmittal. These types of data include sensory signals, such as running speed, force, vibration, temperature, voltage, pressure, and multimedia related data, such as audio and video data, and contents of a database. How to efficiently publish or broadcast data is a problem which should be considered in a web-based system. On the other hand, communication between the server and clients is a conundrum for existing remote monitoring systems. The systems require the servers to assign a special port for sending data from a server to clients. Nowadays, almost all client owners are reluctant to open a special port for such designated communication due to the risk presented by hackers or virus attacks. Hence, it is increasingly difficult to request system administrators to open such a special port for remote monitoring. Using XML will make the system overcome these problems. Since the XML file is a structured document, it is easier to transmit data from server to browsers and pass the data from one application to another or from one system to another. Moreover, sending and receiving XML files will not require a special port, and can use the same port that is used for http protocol. This port is always open at most companies. Besides, there is a requirement from managers and engineers who hope that the maintenance system can tell them promptly when the status of a machine is abnormal. An automatic alarm can send an SMS and call the user 's phone to satisfy this requirement. 3 Architecture of this remote monitoring system The architecture of our machine maintenance system is sketched in Fig. 1. The system consists of three parts: (1) data acquisition and processing, (2) diagnosis data publishing, and (3) the client side. Data acquisition and processing are as in other conventional remote monitoring systems. They include software which analyzes the data along with necessary remote monitoring devices, such as sensors, Web- or video-cameras, microphones, signal amplifiers or conditioners, data acquisition (DAQ) cards, etc. The sensors collect the machine running signals from the monitored machine and then transmit the collected signals to

785 Data Acquisition and Processing Diagnosis Data Publish Client Computer MIC Internet Acquisition Web Server Sensors Server Database Server Web/Wap Server PDA Machine Camera Video card Mobile Send SMS /Call phone Mobile Fig. 1 The architecture of our remote monitoring and diagnosis system the amplifiers. The amplifiers condition the signals into acceptable formats so that the DAQ cards can convert them to digital signals for further fault analysis. The diagnostic software which is called SAMS (smart asset maintenance systems) in the server will analyze the digital signals and then determine the health conditions of the inspected machine. Faults occurring in the machine parts generate a series of impact vibrations. Then it is possible to use a variety of signal processing techniques to judge the machine status. In our system, SAMS uses a number of signal processing techniques in machine fault diagnosis, such as the fast Fourier transform (FFT), continuous wavelet transform (CWT), exact wavelet analysis (EXA) [8], orbit analysis, etc. When the SAMS finds the machine s status to be abnormal, the Java program running in the server will send short messages and call the engineers phone through the mobile connected to the server. After the diagnosis data have been generated, the XML will encode the data into fixed XML structure. The diagnostic results will be either stored in the database or processed by the server to a format which is ready to be published to the remote browsers via Internet or mobile communication, as required by the authorized browsers. From the browsers, they can review the machine status remotely via a computer that is connected to the Internet, or a mobile phone/pda that has access to a subscribed network. If required, they can also obtain detailed diagnostic results or collect machine signals for further analysis, and either save the data to the database or publish the data via the Internet. The flow of the XML communication process is showninfig.2. The browser/server (B/S) mode is used in our XMLbased system. The B/S mode is different from the common client/server (C/S) mode. The establishment of the C/S mode usually requires intensive programming for clients to perform tasks, such as data interface, data managing, processing programs, etc. However, for the B/S mode, the design is simpler and does not require installation of intensive programs on the client side. We can use any common WWW browser that is already built-in on the computer. For mobile communication, we can also use the WAP browser that is already available in current mobile phones and PDAs. An authorized browser can simply send a request to the server. Once authorization is granted, the server will send the requested diagnosis results and/or machine running data to the browser through Internet or mobile communication. Thus, using the B/S mode in our XML remote system, there is no need to install any software or program on the client side. Such simplicity allows our system to be maintained or updated for any new function. Accordingly, the flexibility of our remote machine monitoring system has been significantly enhanced. Moreover, because the diagnosis results have been formatted in XML structures, the browser can import the results and data to other Web-enabled software for further processing, or transmit to other Web-based systems. 4 System development The software architecture of this machine maintenance system is shown in Fig. 3. SAMS (smart asset maintenance systems) is coded by LabVIEW and provides a graphical user interface (GUI) that allows the user to choose different

786 processing software Diagnosis data Processing software XML Database WEB/WAP server Internet Browser Fig. 2 The use of XML in the communication process virtual instruments, which include fast Fourier transform (FFT), continuous wavelet transform (CWT), active noise cancellation (ANC), orbit analysis, and vibration trend analysis [5]. The automatic alarm module has two parts. One is the Java program running in the server; and the other is the C# program running in the Smartphone which is connected with the server. When SAMS detects an abnormal situation, the Java program will run the C# program which can send SMS messages and call phones. After the diagnosis data have been generated, the data are encoded into fixed XML structure. The generate publishing files ' module will generate publishing files which can be published in the WEB/WAP server. The sections below give detailed information about how to develop these modules through introducing the features of this system. 4.1 Send short message and call phone automatically when the machine status is abnormal Using SMS in industry is not a new idea. There are some researches such as Wu [10] who proposed a home network system integrated with wireless application protocol and short message service to support the connectivity between home and Internet system for mobile communication networks. Al-Ali [1] presented a system which allows the homeowner to monitor and control his home appliances via his mobile phone set by sending commands in the form of SMS messages and receiving the appliance status ' as well. These systems use the SMS AT command to send an SMS through a GSM modem. The AT command is easily understood and implemented, but the function of the SMS AT command is limited because it can only send and receive short messages. Our research is based on Microsoft 's Smartphone 2003 smart-phone operating system. It is a revolutionary mobile phone software platform that allows for more than just talking on the phone. And it empowers developers to build rich and innovative mobile applications by providing a powerful and flexible development tool. Developers can target Windows Mobile natively with Visual C++, or they can target the.net Compact Framework with managed code by using C# or Visual Basic.NET. In our system, the diagnostic software in the server will analyze the digital signals and then determine the health condition of the inspected machine and send the results to the Java program running in the server. When detecting an abnormal situation or a warning signal, the Java program will run the programs in a Motorola MPX 220 mobile phone connected to the server. There are two programs in the mobile phone. One sends message to a mobile phone and one calls a phone. These two programs are coded by Visual C#. The first program needs mobile phone numbers and message content which are sent by the Java program. The second program needs phone numbers. Below is the part of a Java program whose aim is to call the users ' phone. cmdstring1="rapistart \\Storage\\callphone"+" "+Call Phonenum; Process proc2 = Runtime.getRuntime().exec(cmdString1); Rapistart is a command line tool to remotely start an application on Pocket PC or Smartphone from the computer. It is a part of the Windows Mobile Developer Power Toys which can be downloaded from Microsoft s website. Callphone is an exe program which has been installed to the Motorola MPX 220. Storage is a directory where the Callphone program is saved. Callphone is coded by Visual C# and uses Smartphone 2003 API to make a call. CallPhonenum is the phone number from the text file saved in the computer. Runtime.getRuntime().exec() is a Fig. 3 Software architecture of this system SAMS Capture image Generate publishing files Automatic alarm module Get live video

787 Fig. 4 Message content about machine abnormal status Java method to execute the specified string command. Here, it executes rapistart to run the program in the MPX200 to call the specified phone. The Java program runs the program in the mobile to send short messages with the machine s status information to engineers and managers. Figure 4 gives a sample of the message content about machine abnormal status. It includes the company or the factory name, the machine identification, the component, the time when the data were produced, and the machine s status. 4.2 Using XML to provide different machine health information according to needs XML offers open standards to Web-based applications. There has been much research in recent years about XML application, including work from Fong [3], Gutleber [4], and Menten [6]. The program written in XML can be transferred similarly to an HTTP platform. Browsers, such as the Internet Explorer, Opera, and Mozilla, can display a XML file without difficulties. On the other hand, unlike HTML, a XML document does not contain formatting information. Styling information is generally stored outside the XML document. Browsers may view the data in many different ways without concern about how the data could be stored. A machine monitoring system should give users information related to the current machine health condition. The information may include company profile, machine identification, current machine running status, and sensory signals, etc. Different persons need different information to fulfill their job specifications. Machine operators may require a great deal of machine information. Managers may only need to know the current machine running status so that they can make appropriate decisions. In other webbased remote diagnosis systems, developers should design different web pages for these different requirements. Now, using XML, developers only need to consider the integrality and specification of diagnosis data and results. In order to maintain high efficiency in maintenance, a scheme for providing different information of the machine health condition to different persons according to their job duties is worth to employ. Here, we used external styling tools to design the display of diagnosis data with XML format so that different machine information would be sent to the operators or managers based on their needs. External styling tools for formatting XML documents can be the cascading style sheets (CSS) or the extensible style-sheet language (XSL). CSS use selectors, which in their simplest form correspond to element names in order to c <testdata> <COMPANY-NAME>CityU</COMPANY-NAME> <CONTACT-PERSON>JOHN</CONTACT-PERSON> <CONTACT-PERSON-PHONE>852-27878598</CONTACT-PERSON-PHONE> <CONTACT-PERSON-EMAIL>JOHN@cityu.edu.hk</CONTACT-PERSON-EMAIL> </testdata> Fig. 5 a The kind of machine information that will be provided to machine operators. b Shortened machine information that will be provided to maintenance managers. c Part of the XML file

788 identify targets for formatting. XSL takes a much more dramatic approach. It will transform the original document into a new document tree that may be composed of formatting objects, by which an application can then be displayed on a Web page. Figure 5a shows an example of the kind of display that the operators may receive. The XML file includes all necessary machine information that the operators should possess. The information includes the name of the company (or factory), the responsible person and his contact methods, the name of the inspected machine and its associated components, the time and date the diagnosis was made, the current machine health status and its reference, the type of sensory signal, its sampling rate and unit, and finally the collected signal and its unit. Figure 5b shows the machine information that a manger would need to know. Only the names of the company, the machine and its inspected components, the time, and the current machine health status and reference, are shown on the web page. Other information will not be displayed or transmitted unless the manger has requested it. Such information is sufficient for a manger to take appropriate action. Note that parts a and b of Fig. 3 are generated by the same XML document but formatted by a different XSL file for displaying different content. Figure 5c gives a part of this XML document. 4.3 Transmitting machine health information via mobile communication Nowadays, mobile communication is very popular. Messages, voices, even video clips can be sent remotely via mobile communication and received by mobile phone or PDA. In 1997, several wireless-phone manufacturers organized an industry group to formalize the WAP standards. The standards are used to define communication protocol and implementation for wireless-network applications. WAP allows cell phones, PDAs, and other lowcomputational-power devices access to the Internet. WML (wireless markup language) is designed for creating WAP applications. It is user-interface independent. It supports text, images, user input, variables, navigation mechanisms, multiple languages, and management server requests. WML has been designed to adapt the highlatency and narrow-band of the wireless network. When a user accesses a WAP site, it will send contents in a deck of cards through which the user can browse. WML is supported by almost every new mobile phone browser around the world. In our system, we write important machine health information by WML and publish the information via the WAP server. The managers and engineers can obtain the machine diagnosis results from their mobile phones or PDAs anywhere. Figure 6 gives an example of how the important machine health status can be displayed on a Motorola MPX-220 phone, whose operating systems is Microsoft 's Smartphone 2003. Figure 6a shows a menu for displaying the current health conditions of a machine in our laboratory. The cursor can be scrolled up or down to select a particular point to view its health status, to get the real time image of the machine, or to get the live video and audio of the machine. One aspect of note is that the point s health data and machine s image are available to almost every model mobile phone/pda, but the real audio and video can only be played by Windows Media Player in a mobile phone/pda whose operating systems is Microsoft 's Smartphone 2003 or above. Fig. 6 a Enquiring different machine health status via mobile phone equipped with WAP. b Enquiring the detailed health status. c Enquiring real time image of the machine. d Enquiring live video and audio of the machine

789 The menu WML page, by which we can get the machine 's data, image and stream media, seems very simple. But in fact, different new technologies are implemented to get this page. The system receives the new data from the SAMS every 20 s (this time can be configured in the system) and generates the WML file. The WML file includes the menu page and the details of the selected point. The menu page tells the company or the factory name, the machine identification, the component, and the time when the data is produced. Choosing the measured point, we can get more detailed information including data source, value, the point s status, and the reference used to determine the health status of the measured point. The machine health status can be classified as good, satisfactory, unsatisfactory, and unacceptable. The reference (REF) in Fig. 6b shows that the RMS (root-mean-square value of the vibration energy) is LT (less than) 0.2 mm/s (vibration in velocity unit). Hence, the machine health status is good. If the RMS is greater than 0.8 mm/s, then the monitoring machine may be unacceptable. In the menu page, by clicking the Machine Picture link, the WAP browser downloads the picture in the WAP server. The Java program running in the server uses JMStudio to capture the image of machine every 30 s (the time can be configured in the program) through a web camera. JMStudio is a Java application that uses the JMF (Java Media Framework) 2.0 API to play, capture, transcode, and write media data. VI program sends this JPEG file to the web server and then the web server publishes it in the Internet. Moreover, in the menu page, by clicking the video link, the WAP browser sends the address of the stream media to Windows Media Player which is already built-in to some types of smartphones. Then, live video and audio of the running machine can be seen on the mobile phone as shown in Fig. 6d. The free software, Windows Media Encoder, which is running in the server, encodes the audio and video of the machine as the stream media. This stream media only can be played by Windows Media Player in a mobile phone/pda whose operating system is Microsoft s Smartphone 2003 or above. Normally, the bandwidth available to a GPRS user is 20 40 Kbps. Although we use 20 Kbps to encode the data, the delay time to get the stream media is about 20 30 s. 5 Conclusions With the development of a remote machine maintenance system, there is a higher requirement for expandability and facilitation of the system. In this paper, we introduce our remote machine maintenance system. Using XML gives this system many advantages, such as minimal research work on the client side, and simplicity of expansion. In this system, users can not only get the diagnosis data by computer, but also the data, image, and video of the machine by mobile phone. The automatic alarm part of this system will send messages and call the users ' phone when the machine status is abnormal. The trend of business is towards using digital and mobile technologies to increase competitiveness. Today, the development of smartphone and PDA makes the mobile terminal a mini computer, and it is possible to process data in the mobile phone/pda. Our future work will research analyzing a machine 's fault data by smartphone and PDA. Acknowledgement The work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 1100/02E). References 1. Al-Ali AR, Al Rousan M, Mohandes M (2004) GSM-based wireless home appliances monitoring and control system. Proceedings 2004 international conference on information and communication technologies: from theory to applications, Damascus, Syria, pp 237 238 2. 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