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Monitoring networked resources within local manufacturing systems.

Abstract: In this paper we present a monitoring method, which allows the ability to obtain information on the status of selected resources within networked manufacturing systems. We present the method of data acquisition and transformation to final format, available for logging and visualization using universal front-end software, accessible via regular web browsers. The presented method uses software modules and sets of UNIX operating system commands as well as selected software tools available via the Internet on GNU license, making the combination a useful and easy-to-implement flexible monitoring system, capable of being utilized in small, medium and large sized manufacturing systems.

Key words: Manufacturing systems, production systems, monitoring, machine tools

1. INTRODUCTION

Modern manufacturing systems are composed of a collection of different manufacturing devices, like: machine tools, work centers, robots, manipulators, measurement devices, measurement stations and other technological and production devices with many different types of numeric control units.

Manufacturing machines and production devices have a built-in network interface, which allows the exchange of data with control units of those devices using a local area network. Some older manufacturing machines, equipped with a previous generation of Computer Numerical Control (CNC) or Direct Numerical Control (DNC) control units with communication interfaces, like serial RS-232C interface or other vendor specific interfaces, can be connected to the local area network with an intermediary of work cell computers.

Each such networked manufacturing device or work cell computer has its own ethernet interface with an assigned specific IP address, being monitored via the network using standard TCP/IP protocol. Besides the above mentioned networked manufacturing devices, there are also regular network devices present in the maufacturing network, such as: workstations, servers, routers, which use standard network protocols to provide data exchange for networked resources.

Communication between resources within manufacturing systems is realized through the use of local area networks. Wide use of "ethernet enabled" devices in the manufacturing environment allows not only the same data acquisition methods and tools for monitoring of manufacturing resources, but also for: Computer Aided Design (CAD) systems, Computer Aided Manufacturing (CAM) systems, Computer Aided Production Planning (CAPP) and other management systems, like: Manufacturing/ Enterprice Resource Planning MRPII/ ERP as well as for the monitoring of external resources.

There is also external data exchange present in networked manufacturing systems, for instance: file transfers, sending and receiving emails, web browsing or direct 'peer-to-peer' data transfer between cooperating systems, Virtual Private Networks (VPN) realized via interconnection to the Internet using public Internet Service Providers (ISPs). Here constant monitoring of selected parameters and resources is also required.

Monitoring of networked resources within manufacturing systems must be done in the secure mode: access to results of monitoring must be restricted to authorized staff only, as well as monitoring systems must operate in a secure environment, thsi means: secure network, secure operating systems and secure application environment.

2. SOFTWARE TOOLS USED FOR MONITORING

The presented monitoring method can be applied to those resources of manufacturing systems, where the data exchange is realized using standard ethernet interfaces and local area networks based on TCP/IP protocol.

The basis for the presented monitoring method is the use of software tools: commands and software modules available by UNIX operating systems (commands, scripts or software routines, which are already built into the UNIX systems) and selected, additional software modules, available for download via the network for licensed use.

The presented method use selected set of software tools for:

* acquisition of data representing the status of selected resources in manufacturing network

* transformation of acquired data to the form readable by front-end software

* presentation of results using front-end software

* secure access to the monitoring system

For acquisition of data representing the status of selected resources within networked manufacturing system, the presented method uses:

* "nmap"--Stealth Port Scanner for Network Exploration and Security Audits, which allows periodical audits of local manufacturing network and devices, especially the scanning of selected parts of the network, with the aim to map the actual status of devices, as well as to obtain information on active (and/ or inactive) resources.

* a set of regular UNIX regular programs/ daemons (like: cron, which allows the execution of commands or scripts at a specified date and time) and selected UNIX commands, useful for obtaining specific information from the operating system or network (like: ping, netstat, ps, cat, etc.)

For transformation of data acquired by the mentioned software tools, especially to prepare results ready for processing by front-end software--the presented method uses a set of UNIX operating systems built-in resources like: system daemons (for example: cron), as well as a set of regular operating systems commands (like: grep).

For presentation of results--as "front-end" interface--the presented method uses Multi Route Traffic Grapher (MRTG), useful software available via the Interrnet on GNU license, which registers the final results of monitoring and displays them in graphical form

For control of access to monitoring system--the presented method use access control based on htaccess file. This feature is built into Apache web servers.

3. FRONT-END SOFTWARE

There are a number of software tools available today for the monitoring of local networks. The presented method use GNU-licensed software: Multi Route Traffic Grapher (MRTG), which can be used in manufacturing systems for the monitoring of selected events and the graphic presentation of results.

The MRTG is a software tool, primary designed to monitor the traffic load on routers and network interfaces. The MRTG can be installed anywhere in the local manufacturing network, however the most reasonable location for MRTG is the router on enter/exit of the local manufacturing network. MRTG generates (in 5 minute intervals) web pages containing graphs: graphical images in portable network graphics (png) format, which provide a live, visual representation of the monitored traffic load. Graphical results produced by mrtg can be reviewed using regular web browser.

The primary aim for MRTG is to monitor the incoming and outgoing traffic, however--if monitored interfaces are: input and output interfaces of the manufacturing network--then we can monitor traffic load from/to manufacturing systems (sample: see Fig. 1) or also traffic load on ethernet interfaces or routers anywhere inside the local manufacturing network.

[FIGURE 1 OMITTED]

The MRTG is especially useful for monitoring selected resources in manufacturing systems, because (in addition to the ability to monitor traffic load on network interfaces) it also provides:

* ability to log and and display periodical changes of events represented by integer variables: if selected event can be described using integer data, then it can be also presented using mrtg

* universal graphic presentation in Hyper Text Markup Language (HTML) web pages, easily accessible via the Hyper Text Transfer Protocol (HTTP) using any modern type of web browser

* is available under the terms of the GNU (General Public License), free of charge for licensed noncommercial or commercial use

* is scalable: can be used for small, medium and large systems

4. SAMPLE RESULTS

Using the presented software tools: selected UNIX operating system commands and the Scanner for Network Exploration and Stealth Port Scanner (nmap), it was possible to make periodical audits of manufacturing networks with the aim to obtain requested information on the status of selected manufacturing resources.

After logging the results of these audits to the Multi Router Traffic Grapher (MRTG), the status of selected resources is presented as daily, weekly, monthly and yearly graphs.

Sample results of monitoring (Fig. 2 and Fig. 3) show daily and weekly graphs generated by MRTG.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Also, for more complex monitoring of resources in manufacturing systems, a new software tool: Round Robin Database (RRD) can be used.

5. CONCLUSIONS

The presented method gives an effective method for audits and monitoring selected resources in manufacturing systems. In this paper we have presented sample monotoring results only. However, many other variables, specific to each manufacturing system can be monitored using this method.

6. REFERENCES

Apache Software Foundation, Configuration files, 2005: httpd.apache.org/docs-2.0/configuring.html

The Free Stealth Port Scanner for Network Exploration and Security Audits, 2005, www.insecure.org/nmap

The GNU: General Public License: http://www.gnu.org and the GNU Polish translation: Powszechna Licencja Publiczna, http://gnu.org.pl/text/licencja-gnu.html

Tobias Oetiker, Dave Rand: The Multi Router Traffic Grapher, 2005, www.mrtg.org

Tobias Oetiker: RRDtool 1.2 (Round Robin Database), 2005 http://rrdtool.eu.org
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Article Details
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Author:Fabisiak, B.; Zasada, M.
Publication:Annals of DAAAM & Proceedings
Article Type:Report
Geographic Code:4EXPO
Date:Jan 1, 2005
Words:1378
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