Tele-Diagnosis at Networked Automation Systems

Transcription

1 Tele-Diagnosis at Networked Automation Systems Klaus Kabitzsch, Volodymyr Vasyutynskyy Dresden University of Technology, Faculty of Computer Science, D Dresden Kurzfassung. Dieses Papier beschreibt ein Teleservice-Werkzeug, das zur Ferndiagnose von SPS an Maschinen benutzt wird. Es zeichnet die Abläufe im Inneren der SPS auf. Dabei werden alle Echtzeit-Details gemessen. Um die gemessenen Variablen flexibel auswählen zu können, wird ein mobiler Agent im fernen Rechner konstruiert. Dieser Agent wird mit Hilfe des Netzwerks in die SPS übertragen und beginnt dort zu arbeiten. Die Beobachtungen an der Software werden von Video- und Audio-Messungen an der Maschine unterstützt. Abstract. This paper describes a teleservice - tool, which is used for the remote diagnosis of PLCS at machines. It records the operations in the interior of the PLCS. Thereby all real time - details are measured. To be able to select the measured variables flexibly, a mobile agent is constructed in the far computer. This agent will transfer into the PLCS with the help of the network and begins to work there. The observations at the software are supported by video - and audio - measurements at the machine. 1 Introduction Complex machines and equipment are not faultless after their commissioning. Even if all tests were successful, many disturbances and real - time problems remain. Many errors appear only rarely and mostly then, if the maintenance persons has left the construction site already. If errors appear first to a later point in time, it gives large problems particularly at exported machines. While the specialists returned to their office for example in Germany, the machine at the customer is many thousands of kilometers remote. Debugging and repair require high expense and bring following problems: The journey of the specialists to the customer requires long time. The machine can not work during this time and this causes high costs. Often the specialists find only trivial error causes. Some error effects exist only occasionally and disappear then again for long time (transient errors). In most cases the customer turns on these machines again and has

2 they worked further. If the troubleshooter arrives at the machine, all tracks are effaced then. Nobody can find then error causes. The specialists must bring along many resources, gauges and tools. Often they have forgotten an important tool. Then they must wait, until it is supplied later. The journey of the troubleshooters and the transport of the tools cause high costs. 2 Teleservice It would be a better solution, if the specialists remain first of all in their office. For this reason the computers and PLCS at the remote machine are joined by the telecommunication with the specialists. The troubleshooters can manipulate now at the PLCS and observe their function. All maintenance works are executed over a large distance. But their access to the PLCS still remains not complete: The troubleshooters can not see into the interior of the PLCS (hardware, software). They can observe the faulty operations no more with bare eyes, because they are too fast. If an error appears only rarely, the attention is missing to the right point in time. If the cause of an error lasts long time, they lose the overview. video camera machine PLC near PC long distance internet, ISDN, telephone far PC video window monitor window microphone Fig. 1. Principle of the teleservice

3 3 Monitor - Tools The teleservice - tool "AutoSPy" solves these problems with the monitor - technology. This tool observes, records and stores all processes in the interior of the PLCS over long time. The stored time course of all program - variables and input - output - connections is marked also as "history". Figure 2 shows the measurement at the transport system of the high shelf warehouse of a CIM - factory. Sensors measure the position of the sled and send this information to the input - variables E0.1 to E0.6. If the sensor E0.4 refuses in rare cases, this error is recognizable only with the help of a long-time - recording. The duration of the impulses to the input - connection E0.4 is about similarly the cycle time of the PLCS. Therefore the tool must record all variables with high temporal precision. The resolution must be identical with the cycle time. Error: missed impulse E0.4 Fig. 2. Measurement with the tool AutoSPy at the transport system of a CIM - factory It is often necessary, that the contents of variables are recorded with all real time - details. Then all variables may be observed however no more simultaneously, which are founded in a PLC - program. The tool would have to read, store and transfer a mass of data in this case. Instead the user must select now some few variables, whose time course he would like to observe precise.

4 Fig. 3. Selection windows of the tool AutoSPy. In the left window the user chooses names from the symbol - table and data types of the variables. The right window shows the selected variables. For the selection of the variables the teleservice - tool AutoSPy has important properties: All variables of the PLCS - software and the input - output - connectors stand at the disposal for this selection. The uncoded names used in the source code of the PLCS are offered the user actively to the selection. Therefore the far computer shows for example a list with the names of the symbol - table. The user selects the names with the mouse. The new observation - instruction will transfer from the far computer by the near computer into the PLCS. To load the new observation - instruction in the PLCS, the user must not switch off the machine or the PLCS. Also a reduction of the work speed, one-step operation etc. is not desired. The new observation - instruction is loaded in the PLCS, while these runs in the real time - operation.

5 4 Mobile software - agents To fulfill the demands shown in chapter 3, the technology of the mobile agents is used. If the selection of the variables (figure 3) is terminated in the far computer, the work of a code generator begins there. control flow (every cycle of the operating system) data flow (from the PLC - variables) program code reads PLC - variables scratchpad storage data flow (to the network) Fig. 4. Elements of a mobile agent This code - generator creates independently a software object (figure 4). The object contains program code, which should read the selected variables in the PLCS. The object contains also an empty memory, which should store the registered history in the PLCS. The object contains also communication - components, which transfer the history to the near computer.

6 If the agent is created, it will transfer from the far computer to the near computer with the help of the telecommunication (figure 5). The near computer transmits the agent to the PLC. There the agent is installed by the operating system and is integrated in the processing cycle. As soon as the far computer gives the start - command, the agent begins to work in the PLC. The operating system of the PLC processes the agent at the beginning of each cycle now. The agent observes the variables and puts their values into the scratchpad storage. Subsequently it transfers the history to the near computer. To improve the effectiveness of this transmission, a block-by-block transfer was implemented. In the near computer the history is stored on the hard disk agent-1 machine-1 machine-2 PLC-1 PLC-2 near PC-1 long distance agent-2 internet, ISDN, telephone far PC video window monitor window machine-3 PLC-3 near PC-2 agent-3 Fig. 5. Mobile agents are transported from the far computer to their target - places: the PLCS 5 Support of video and audio The preparation of the measurement and the recording of the history require often many hours. Thereby the far computer is remote possibly many thousand kilometers from the machine. The user can not see and hear therefore the PLCS, the machine and their environment. But many users wish an observation of the machine during the measurement. There are different reasons for it: Security: The user wants to avoid dangers for persons, who stand nearby the machine. Diagnosis: The user is interested not only in the history, which he has recorded in the interior of the PLCS. He wants to observe also the outer performance of the machine during this measurement. Subsequently he can compare both observations.

7 Therefore AutoSPy is complemented by a video camera and a microphone. Both are connected to the near computer and transfer images and clays to the far computer. There the images can be observed in a separate window of the tool. Also the noises of the machine are returned by the loudspeaker (figure 1). References 1. Ribbecke, H.-D.: Fehlerlokalisierung in Automatisierungssystemen. SPS-Magazin (1998) H , S Kabitzsch, K.; Hartenstein, D.: Fehlersuche in Automatisierungssystemen mit Feldbus-Vernetzung. e&i Elektrotechnik und Informationstechnik 114(1997) H.5, S , Springer Verlag Wien Dauphin, P.; Hartleb, F.; Kienow, M.; Mertsiotakis, V.; Quick, A.: PEPP: Performance Evaluation of Parallel Programs. Technical Report 5/92, Universität Erlangen-Nürnberg, IMMD VII, Kabitzsch, K.; Hartenstein, D.: Mit Excel gegen Fehler - Fehlern in LON- Netzwerken auf der Spur. Elektronik (1997) H. 19, S Myers, G.J.: The art of software testing. John Wiley & Sons Inc Kabitzsch, K.; Hartenstein, D.: Diagnose bei der Inbetriebnahme komplexer Automatisierungssysteme. VDI-Berichte Nr. 1397, S , VDI-Verlag Düsseldorf Ribbecke, H.-D.; Wittig, E.; Kabitzsch, K.: Fehlern in SPS-Systemen auf der Spur. Elektronik (1998) H. 12, S TU Dresden, Fakultät Informatik, Institut Informationssysteme,