In recent years, with the rapid development of science and technology, PLC programmable controller has also made rapid progress under the development of computer technology, and its performance indicators and functions have been further improved and enriched, so it has been widely used in many industries and become the core of control systems in various fields. In the field of electrical control, the scope of development is becoming wider and wider.
Compared with relay contactor system, the number of contacts in the control system composed of PLC external circuit is greatly reduced, so the failure rate is effectively reduced. And the PLC itself also has the function of hardware fault self-detection, so once the fault is found, it may alarm in the first time. With the development of PLC function unit, it has been effectively penetrated in the field of industrial control, not only the communication ability has been enhanced, but also the man-machine interface technology has been developed rapidly.
So in many fields, the control system of PLC is the core. As an industrial control computer, PLC is not only easy to interface, but also easy to be accepted and understood by engineers and technicians as a programming language of industrial control equipment directly facing enterprises. Only a small amount of switch logic control instructions of PLC can be skillfully used in electrical control. Even if you are not familiar with electronic circuits, you can use PLC.
Low energy consumption Take miniature PLC as an example. The bottom size of newly produced varieties is less than 100 mm, the quality is less than 150 g, and the power consumption is only a few watts.
Therefore, PLC is the ideal control equipment to realize mechatronics. Because PLC adopts modern large-scale integrated circuit technology, advanced anti-interference processing technology is adopted in internal circuit and production process, which has high reliability. The design principle of PLC and related peripheral equipment is to study and collect data on the actual work site, and to achieve close cooperation between designers and operators, to analyze and solve potential problems together. And ensure the safety and stability of electrical control. Input of information: Under the control of system software, the input points are scanned in sequence and the state of the input points is read. The execution of the program: Scanning the instructions in the user program in sequence, thermostatic element and performing logical operations according to the input state and instructions.
Output of control signal: According to the results of the above logic operation, the output state register sends corresponding signals to each output point at the same time to realize the required logic control function.
After the above process is completed, it is restarted and executed repeatedly, each time a scanning cycle is completed. Instead of traditional relay circuit, logic control and sequential control can be realized, which can be used not only for single equipment control, but also for multi-computer cluster control and automation pipeline.
Such as injection moulding machine, printing machine, bookbinding machine, modular machine tool, grinder, packaging production line, plating line, etc.
In the actual industrial production process, there will be many continuous changes in physical quantities, such as temperature, speed, flow, liquid level, pressure and other analog quantities. These analog quantities can be realized by D/A conversion and A/D conversion between digital quantities to ensure that the programmer can process the analog quantities. In the process of data processing, PLC has the functions of data transmission, data conversion, mathematical operation, table lookup, sorting and operation, and completes data acquisition, analysis and processing. These data can have reference value as well as the data stored in the memory, and complete the control operation.
In addition, these data can also be transmitted to intelligent devices through the realization of communication functions, or printed into tables. At present, data processing is mostly applied to large scale control systems, such as process control system, flexible manufacturing system and so on. PLC communication includes communication between PLC and communication between PLC and other intelligent devices.
With the development of factory automation network, PLC now has communication interface, and communication is very convenient. PLC can control circular motion or linear motion. In the configuration of control mechanism, in the past, special motion control module can be used to directly apply to sensors and actuators.
It can be seen from the above that within the specified range, programmable logic controller (PLC) wins with its high performance and price, and is widely used in the field of automation control with its outstanding characteristics of strong adaptability, high reliability and convenient use.
In addition, the continuous decline of the manufacturing cost of PLC and the continuous enhancement of its functions have become the preferred equipment for industrial enterprises.