This paper introduces the design principles and steps of the programmable controller system, and explains the problems that should be considered in the design of the system. The principle of the design of PLC control system is to make up the electrical control system with PLC as the core to realize the automatic control of production equipment and industrial process, so as to improve production efficiency and product quality. In designing the PLC control system, the following basic principles should be followed. Fully exerting the function of PLC and satisfying the control requirements of controlled objects to the greatest extent is the most basic and important requirement for designing PLC control system, and also the most important principle in design.
This requires designers to conduct in-depth field investigation and research before design, collect and control site information and relevant advanced information at home and abroad. At the same time, we should pay close attention to cooperate with the engineering managers, engineers and technicians, and field operators, draw up control plans, and solve the key and difficult problems in the design together. It is an important principle of designing control system to ensure the long-term safe, reliable and stable operation of PLC control system. This requires the designer to consider the system design, component selection and software programming comprehensively to ensure the safety and reliability of the control system. Especially in order to improve the quantity and quality of products and ensure the safety of production, reliability must be put in the first place.
On the premise of satisfying control requirements and ensuring reliable operation, the structure of stress control system is simple. Only the simple control system has the characteristics of economy and practicability, can it be used conveniently and maintained easily. This requires the designer not only to make the control system simple and economical, but also to make the use and maintenance of the control system convenient, low cost, not blind. The debugging of PLC system is divided into hardware debugging and program debugging. Usually these two parts are interrelated and closely related.
Hardware debugging is mainly to test whether the connection of the PLC control system is correct, thermostatic element whether the external connection of the PLC controller and its module is working properly must be correct, especially pay attention to the short circuit of the power supply, because the short circuit of the power supply will burn down the components of the system, or even the PLC. If the connection is correct, you can check the operation of the PLC system by electricity. This mainly depends on the error indicator lamp of the PLC itself. The light of the error indicator lamp indicates that the system is wrong. Of course, this may be the error of the PLC program and configuration parameters, or the hardware error of the PLC itself. It can be judged according to the actual situation of the system, and find out the fault. Repair in time. The debugging of PLC program can be divided into simulation debugging and field debugging.
Connect. According to the function chart, the switch or button can be used to simulate the actual feedback signal at the appropriate time. For example, the connection and disconnection of the limit switch contacts should be fully considered in debugging. All kinds of different working modes and possible progress routes of the system should be checked one by one, and can not be omitted. When problems are found, the ladder diagram and the program in PLC should be modified in time until the relationship between input and output is in full conformity with the requirements under all possible circumstances. After the field debugging of the program, the PLC is installed in the control site for on-line general debugging. During the debugging process, the problems of sensors, actuators and wiring in the system, as well as the problems in the external wiring diagram and ladder diagram programming of the PLC, should be solved in time. Definitely. If the debugging can not meet the requirements of the indicators, the corresponding hardware and software parts should be adjusted appropriately. Usually, the purpose of the adjustment can be achieved by modifying the program. After all debugging, after a period of testing, the system can be put into actual operation. Choose the same type of PLC to achieve the same control requirements. Programs written with different control methods have different structures. Although the program can achieve the same control function, the quality of the program may vary greatly. The quality of a program can be measured from the following aspects: First, the correctness of the program. The so-called correct procedure must be able to withstand the reliability of the practical procedure. The application program should ensure that the system can work normally under normal and abnormal working conditions. Although the program can achieve the same control function, the quality of the program can be measured by the following aspects: First, the correctness of the program. The so-called correct procedure must be able to withstand the test of system operation practice. The second is the reliability of the program.
The application program should ensure that the system can run safely and reliably under normal and abnormal working conditions. It should also ensure that there are no system control errors in the case of illegal operation (such as pressing or touching the button that should not be acted by mistake). Third, the adjustment of parameters. It is easy to change some functions of the system by modifying programs or parameters. Fourth, the procedure should be concise. The program is concise and the program statement is reduced. It can generally reduce the scanning time of the program and improve the response speed of the PLC to the input signal. Fifth, the readability of the program. The program is not only for the designer himself, but also for the maintainer of the system. Zhao Jianwei, male, senior engineer, is engaged in teaching and scientific research of Mechatronics technology.