At home and abroad, PLC has been widely used in metallurgy, petroleum, chemical industry, building materials, machinery manufacturing, electric power, automobile, light industry, environmental protection, culture and entertainment and other industries. From the application type, the application of PLC can be roughly classified into the following aspects:
Switch logic control
Using the most basic logic operation, timing, counting and other functions of PLC to realize logic control, it can replace traditional relay control and be used for single-machine control, multi-machine group control, automatic production line control, etc., such as: machine tools, injection molding machines, printing machinery, assembly production lines , Electroplating assembly line and elevator control. This is the most basic application of PLC and the most extensive application field of PLC.
Motion Control
Most PLCs have single-axis or multi-axis position control modules that drive stepper motors or servo motors. This function is widely used in various mechanical equipment, such as motion control for various machine tools, assembly machinery, robots, etc.
Process control
Both large and medium-sized PLCs have multi-channel analog I/O modules and PID control functions, and some small PLCs also have analog input and output. Therefore, PLC can realize analog quantity control, and PLC with PID control function can form closed-loop control for process control. This function has been widely used in boilers, reactors, water treatment, brewing and closed loop position control and speed control.
Data processing
Modern PLCs have functions such as mathematical operations, data transmission, conversion, sorting and table lookup, which can collect, analyze and process data, and can transmit these data to other intelligent devices through communication interfaces, such as computer numerical control (CNC) ) device for processing.
Communication networking
The communication of PLC includes the communication between PLC and PLC, PLC and upper computer, PLC and other intelligent devices. PLC system and general computer can be connected directly or through communication processing unit and communication conversion unit to form a network to realize the exchange of information. It can form a multi-level distributed control system of “centralized management and decentralized control” to meet the needs of the development of factory automation (FA) systems.
