Remote Ethernet PLC Networking and Control
Contents
1. a local LAN or WAN con nection In Fig the PLC is connected directly to the Ethernet network using the FX3U Enet module This module allows the PLC and the host computer to communicate via a TCP IP or UDP IP connections using the MELSEC network connec tion witch is a dedicated comunication protocol for the Mit subishi Melsec family The hearth of this project is the Mel sec FX3U Enet ethernet module and the FX3U PLC The FX3U PLC is equipped with 8 input ports and 8 output ports witch cand be transistor or relay based The FX3U Enet Ethernet module suports 8 simultaneous connections using different protocols The Ethernet module can handle different type of network architecture like star bus ring and mesh In Fig2 it is presented how the FX3U Enet module uses different communication protocols such as TCP and UDP transfer protocols related to the OSI model Transmission Control Protocol TCP is a slower protocol but it is a relia ble transmission which uses sequence number to identify each byte of data It has flow control and error detection The UDP User Datagram Protocol is a much faster protocol but it lacks the flow control and the error detection which are incorporated in the TCP protocol This means that if an error has occurred there is no knowledge of the error and at the end of the transmission the original data must be sent again The Ethernet modules support the TCP IP and UDPIP protocols OSI reference model o2. unfriendly conditions and frequent main tenance problems will jeopardize the projects The solution is to find new ways new computer architectures and new tech nologies to overcome these problems In this paper it is presented one kind of architecture which can serve as a platform for many remote applications that need wireless networking This platform encapsulates some industrial very task specific equipment like the FX3U industrial programmable logic controller PLC and the FX3U Enet Ethernet module 2 3 This PLC as any other PLC is a very resilient industrial computer with no moving parts except some rough duty relays consumes less power than a PC of any kind so it is perfect for unsupervised operation The FX3U Enet module is a dedicated Ethernet module for the FX3U PLC allowing remote connection to the PLC from any other location via internet and satellite connection This paper has the following structure section 2 provides an overview of the platform section 3 describes the labora tory implementation and section 4 proposes two case studies The conclusions are presented in section 5 759 II THE STRUCTURE OF THE TEST SYSTEM The used system structure was built from a FX3U program mable logic controller PLC FX3U Enet Ethernet module one router one WIFI accesspoint and two laptops 1 Figurel Test architecture This structure can perform a real time on line high speed comunication with the PLC using
3. 17th Telecommunications forum TELFOR 2009 Serbia Belgrade November 24 26 2009 Remote Ethernet PLC Networking and Control Norbert Gal PhD Student Politehnica University of Timisoara Department of Automation and Applied Informatics Faculty of Automation and Computers 2 V Parvan blvd Timisoara Romania Abstract Nowadays in our highly automated high tech society programmable logic controllers PLC are as common as our personal computers or laptops They are more resilient and more compact than conventional computers they can be programmed to be very specific tasks and they can be used in all kind of environments The paper presents one of the built in technologies that stand behind the remote operation capability of PLCs namely the Ethernet module A low cost flexible platform is build around this module Two case studies are provided a remote monitoring and control system for passive greenhouses and a PLC matrix for industrial applications Keywords Programmable logic controllers Ethernet net work wireless communication platform remote operation pas sive greenhouse PLC matrix I INTRODUCTION The industrial controllers are more and more present in our life Mankind will always be on the mission to conquer new territories Sometimes those territories are unfriendly not only too humans but also to the technological objects In this case most of the state of the art personal computers servers will fail due to the
4. 4 M M Balas V E Balas Smart Control for Passive Greenhouses 2th International Conf IPMU 08 Informa tion Processing and Management of Uncertainty in Know ledge Based Systems L Magdalena M Ojeda Aciego J L Verdegay eds June 22 27 2008 Malaga pp 826 831 762
5. b the communication proto cols are set these protocols can be set too TCP or UDP For TCP communication we have Active Un Passive FullPassive an Melsoft connection Melsoft connection is an auto negotiating auto sensing comunication protocol betwen Melsec products At the other comunication methods the user needs to set the communication buffer type the pairing options host station port number the targeted IP address and the target device port number e Router relay parameters here is told to the module the router IP address and the subnet mask pattern e E mail settings consists of the password and email address the SMTP server name or IP address POP server name or IP address After confirming the settings the FX3U Enet module res tarts itself automatically To test the arhitecture a program was created in GT De signer 2 for a remote LCD touchscreen panel The panel was simulated in Soft GOT1000 a simulation program for the Mitshubishi GOT display family To make the comunication possible before the compilation some settings were to be made the choice of the PLC the IP address of the PLC the port number the communication type the network number and the PLC number The actual testing took place in our laboratory where we maneged to communicate simultanoiusly with the GX Devel oper s monitoring program and the simulation running under Soft GOT 1000 The reprogramming of the PLC was done using the algo rithm prese
6. in mind that such devic es PLCs and their extension modules for instance are much stable and use far less energy comparing to normal comput ers they become ideal candidates for remote monitoring or control applications The paper presents a remote monitoring and control platform based on a widely used PLC and its communication module The system is cheap using few components easy to develop and extremely flexible Thanks to the today s satellite network coverage the system is ready to support the development of an extended passive greenhouses network as well as any usual remote control application Combining the two proposed architectures the limit for a communication engineer which is working in this domain is only his own imagination ACKNOWLEDGMENT This paper is an adaptation of my Romanian language grad uation work given at the Aurel Vlaicu University of Arad The work was achieved under the coordination of Assoc Prof Marius M Balas Senior Member IEEE I thank Takata Petri SRL of Arad and the Romanian branch of Mitsubishi Electric Corporation for their essential support VI REFERENCES 1 N Gal Comanda si monitorizarea de la distanta a auto matului programabil diploma work Aurel Vlaicu Uni versity of Arad Romania 2009 2 FX Configurator EN Operation Manual Mitsubishi Electric Corporation 3 FX3U Enet User s Manual Model FX3U Enet Mitsu bishi Electric Corporation
7. mes Personal cOMpUtETWOTK Station 242M PIG au annn unnn anmenn nnua p eaen nannan nanan nan sn senmn a l PLE From To instruction Buffer memory System call Conmunkaton using the MC protocol Socket Ethemet module TCPIUDP Ethemet NOOBASE TX 10BA3E 7 Ethernet TOOBASE TX 10BASE Lom Figure 2 Comunication Protocols for the FX3U Enet To establish a connection on the Physical layer layer 1 on the OSI model it was used o twisted pair utp cat 5 cable On the wifi side the antenna was a rubber ducky antenna on the acces point side and an internal antenna of the laptop on the remote computer side The software tools used in this project are GX Developer V 8 25B or later FX Configurator EN GT Designer 2 Soft GOT1000 Internet Public dial up line E mail sending receiving Intemet serice eee 2occe opoopo y Extemal device Figure 3 Set up for email sending recieving For even more flexibility we can set the Ethernet module to send email messages using the local mail server as shown in fig3 The data can be sent as an 2K Word atachment or 256 words plain text 760 The SoftGot 1000 program is a Melsec Got Display simu lator We used this program to test the remote monitoring and command functions when we do not dispose of GX Developer II SETTING UP AND TESTING THE PLATFORM The proposed platform was tested using the PLC mounted on a test bench which was eq
8. nted in Fig 4 tart Setup the guest PC Stop PLC program execution s PLO executing program Write new program in PLC Start PLE program execution Verity the new program execution Is the program executed correctly t Ives Disconnect or keep monitorning Stop Figure 4 Flowchart for rewriting the PLC from a guest computer As shown in Fig4 before we can send or read programs from the PLC the GX Develper on the guest computer needs to be configured for Ethernet commnication When the communication is active the currently running program in the PLC must be stoped so that the new version of the cur rent program or a completly new program to be instaled on the PLC After the modifications are completed the execu tion of the program must be resumed If after a verification cycle no errors are detected the connection can be stoped in order for a new connection too be made from another guest equipment if all the 8 connections are curently occupied 761 IV Based on the platform presented above in this paper there are proposed some architectures that use remote operation of the FX3U PLC and the FX3U Enet module PROPOSED ARCHITECTURES a Running and monitoring a passive greenhouse using satellite connection Milas ISP or HQ Aciuators Figure 5 A remote passive greenhouse In this architecture the Ethernet module enables the PLC and the users to communica
9. te from large distances using satellite connections The main components of the architec ture are the 2 high gain directional antennas which can be at either 2 4 GHz or 5 GHz and the Ethernet module The Passive Greenhouses are using exclusively renewable energies geothermal cold water heat pumps wind wind turbines and sun photovoltaic panels and they are indepen dent of any conventional energetic infrastructures Thanks to their energetic independence if we provide them with a re mote communication platform with global satellite coverage in the future the passive greenhouses could be installed vir tually anywhere 4 b Building a PLC matrix for large scale industrial applications PLC Figure 6 A PLC matrix In the nowadays industry almost every machine or terminal is connected to a central server and processing unit These connections are almost all the time made by PCs witch act as media converters between the industrial unit and main server computers that command the involved systems With this module several PLC s can be interconnected and they can communicate with each other using the Ether net network or using a closed circuit Local Area Network Using this architecture large scale industrial applications can be achieved where the use of several programmable logic controllers is required V CONCLUSIONS Nowadays the demand for remote operations and for sturdy hardy systems is increasing Having
10. uipped with 5 input and 5 out put relay ports one timer and one analog input output port On the same bench we mounted the FX3U Enet module To simulate the internet we used a two closed circuit LANs separated by a router On one side of the router was the re mote laptop and a wifi accespoint and on the other side there was the PLC the Ethernet module and the computer which initialized the PLC for the first time The Ethernet settings for the system were the following e The IP address of the router were 192 168 2 1 and 192 168 1 1 and so we separated the 2 networks simulating an internet connection e The IP address of the FX3U Enet module was 192 168 2 4 e The IP address of the remote computer was 192 168 1 1 To make the necessary settings for the Ethernet module we use the FX Configurator EN software lunched for the GX Developer At this fase the PLC is connected to the PC with a programming cable To make the settings the following steps needs to be completed e The operational settings are the main settings where we set the IP address of the PLC the communica tion data code initial timing to alow remote stop and run for the PLC send frame settings TCP Existence confirmation settings using Ping or Keep Alive At the initial settings we can add the response time of the module and we can introduce DNS addresses If there are no need to change these values the de fault values are preset e At the open settings ta
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