It always must think both of its two sub-systems, e.g., the PLC control system and the physical system being controlled, which are connected by wiring diagrams when diagnosing a PLC controlled manufacturing system. These diagrams of wiring are maintained individually from the program of PLC and the circuit diagrams of pneumatic and hydraulic those characteristically comprise the documentation for the system of physical. Typically in order to know the manufacturing system behavior, you need to recognize how both of its two sub-systems perform and how they interrelate with each other. That is to tell, you need to enclose knowledge about their connection, the diagrams of wiring, which as stated above, comprise the program of PLC and the circuit diagrams of pneumatic and hydraulic.
The manufacturing systems of PLC controlled have monitoring of automatic available for errors described by separate state signals in their memory of PLC. These separate state signals specify the manufacturing systems operating states, by which more diagnosis can be performed. These signals can be attained straightforwardly using a RS232 series interface between the diagnostic system computer and the PLC I/O board. This can also be performed through some technical information levels using LAN, which are the main substances of the database of diagnostic system.
It can be observed that, a PLC controlled manufacturing systems automatic diagnosis is to use particular reasoning algorithms to look for all the potential error causes under the relevant help diagnostic knowledge as well as real-time data. Thus, a system scheme of knowledge-based is appropriate for the complex PLC diagnosis controlled manufacturing systems. The acquisition task of knowledge involved in the such a system development is very time-consuming, therefore more discouragement. If all the knowledge of diagnostic is obtained artificially from a huge amount documentation for the physical systems, they will frequently be not consistent and unfinished, and thus guide to wrong diagnosis or imprecise diagnosis. The acquisition mechanisms of model-based knowledge can assist to resolve this issue, which will result in the knowledge acquisition improvement and efficiency of diagnosis.
The universal structure of a knowledge-based real-time diagnostic system for manufacturing systems of PLC controlled. It is the expansion of an obtainable diagnostic system that developed for a FMS (Flexible Manufacturing System). The system can constantly get data from the recognizing possible faults, PLC, recommend corrective actions and look for their causes. The knowledge related with circuit diagrams of pneumatic and hydraulic is obtained synthetically by knowledgeable engineers, while the knowledge related with the program of PLC is obtained from the running source code the PLC half automatically or automatically by techniques model-based.