PLC program content and quality evaluation indicators - Database & Sql Blog Articles

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1. The content of the plc program PLC application should satisfy the control requirements of the controlled object to the utmost extent. After conceiving the framework of the main body of the program, it should be used as the main line to write the programs for implementing each control function or sub-task one by one. After constant adjustment and improvement. Enables the program to perform the required control functions. In addition, the PLC application should usually include the following aspects: (1) Initialization program After the PLC is powered on, generally some initialization operations are required. Its role is to make the necessary preparations for start-up and to avoid system malfunctions. The main contents of the initialization program are: clear some data areas and counters; restore some data areas to the required data; set or reset some output; display some initial status, and so on. (2) Detection, fault diagnosis, and display program applications generally have detection, fault diagnosis, and display programs. This content can be added when the programming is almost complete. They can also be relatively independent blocks. (3) Protection, chain program In various applications, protection and chain are indispensable parts. It can prevent control logic confusion caused by illegal operation and ensure the system is safer and more reliable. Therefore, we must seriously consider the issue of protection and chain. Chain and protection measures are usually also set up outside the PLC. 2. The quality of the PLC program has the same control requirements. Even if the PLC of the same model is selected, the program written by different design methods may have different structures. Although several programs can implement the same control function, the quality of the program can vary greatly. (http:// Copyright) The quality of the program can be measured by the following aspects: (1) The correctness of the program The quality of the application is the correct one. The so-called correct procedure must be able to withstand the test of system operation practice. It is meaningless to leave this article to evaluate the program. (2) The program with good reliability can ensure that the system can be safely and reliably under normal and abnormal conditions (short-time power failure and re-power, some controlled quantities are exceeded, some links are faulty, etc.) Operation can also ensure that system control errors do not occur in the event of illegal operation (such as pressing or accidentally touching a button that should not be acted upon). (3) Easy adjustment of parameters. One of the advantages of PLC control is flexibility. It is easy to change some functions of the system by modifying programs or parameters. For example, some systems need to change certain control parameters (such as timers or counter settings) under certain circumstances. When designing a program, you must consider how to write it to be easy to modify. (4) The program to be concisely written should be as concise as possible, reduce the statement of the program, generally reduce the program scan time and improve the response speed of the PLC to the input signal. Of course, if you use too many instructions that take a long time to execute, sometimes the program has fewer statements, but its execution time is not necessarily short. (5) The readability of the program is not only for the designer to see, but also for the maintenance personnel of the system. In addition, in order to facilitate communication, the program is also required to be readable.