
In the era of industry 4.0, the digitalization transformation and intelligent manufacturing of enterprises have become a general trend. The increasing level of automation and the rapid development of industrial Internet are intertwined with the accelerated integration of it (Information Technology), OT (operation technology) and CT (Communication Technology). Programmable logic controller (PLC), as the key equipment of OT and industrial automation and an important component of the bottom of industrial Internet, has also made great progress. At the same time, as equipment, machines and factories become "more intelligent", industrial field control puts forward higher requirements for PLC, DCS and other equipment. It is well known that PLC is a new generation of industrial control device formed by introducing microelectronics technology, computer technology, automatic control technology and communication technology on the basis of traditional sequential controller. Its purpose is to replace the sequential control functions such as relay, executive logic, timing and counting, and establish a flexible programming control system. At present, on the basis of traditional functions, PLC adds analog calculation, PID function, communication function and more reliable industrial anti-interference technology, which are widely used in various fields of industrial production. Therefore, PLC can be simply understood as a computer used in a specific industrial environment, and has a variety of excellent performance. Its hardware structure is basically the same as that of the computer. It has CPU, i/o module, power module, backplane, peripherals and communication networking equipment. Programmable memory is used to store logic operations, sequence control, timing and counting and arithmetic operations, and through digital Analog input and output instructions control various types of industrial production processes. Compared with general-purpose computers, PLC has many application scenarios and wide adaptability in the industrial field, and has the advantages of high reliability, strong anti-interference ability and simple programming.