中文版
Description
PLC application and use should pay attention to the problem
I. Introduction
Over the years, programmable controller (hereinafter referred to as PLC) from its generation to the present, the realization of wiring logic to storage logic leap; Its function from weak to strong, realized the progress of logic control to digital control; Its application field has grown from small to large, realizing the simple control of single equipment to competent motion control, process control and distributed control and other tasks. Today’s PLC in the processing of analog, digital computing, man-machine interface and network of all aspects of the ability has been greatly improved, become the mainstream control equipment in the field of industrial control, in all walks of life is playing a more and more important role.
Two, the application field of PLC
At present, PLC has been widely used in steel, petroleum, chemical industry, electric power, building materials, machinery manufacturing, automobile, textile, transportation, environmental protection and cultural entertainment and other industries at home and abroad. The use is mainly divided into the following categories:
1. Switching quantity logic control
Replace the traditional relay circuit, realize logic control, sequence control, can be used for single equipment control, can also be used for multi-machine group control and automatic assembly line. Such as injection molding machine, printing press, stapler machine, combination machine tools, grinding machine, packaging production line, electroplating line, etc.
2. Industrial process control
In the process of industrial production, there are some such as temperature, pressure, flow, liquid level and speed and other continuous changes of the amount (that is, the analog amount), PLC uses the corresponding A/D and D/A conversion module and a variety of control algorithms to deal with the analog amount, complete the closed-loop control. PID adjustment is a kind of adjustment method commonly used in general closed-loop control system. Process control is widely used in metallurgy, chemical industry, heat treatment, boiler control and so on.
3. Control of motion
PLC can be used to control circular motion or linear motion. General use of special motion control module, such as single-axis or multi-axis position control module can drive stepper motor or servo motor, widely used in a variety of machinery, machine tools, robots, elevators and other occasions.
4. Processing of data
PLC has mathematical operation (including matrix operation, function operation, logic operation), data transmission, data conversion, sorting, table lookup, bit operation and other functions, can complete the data collection, analysis and processing. Data processing is generally used in some large control systems in the paper, metallurgy and food industries.
5. Communication and Networking
PLC communication includes communication among PLC and communication between PLC and other intelligent equipment. With the development of factory automation network, PLC now has a communication interface, communication is very convenient.
Three, the application characteristics of PLC
1. High reliability, strong anti-interference ability
High reliability is the key performance of electrical control equipment. PLC due to the use of modern large-scale integrated circuit technology, the use of strict production process manufacturing, internal circuit adopts advanced anti-interference technology, has high reliability. The use of PLC control system, and the equivalent scale of the relay contactor system, electrical wiring and switch contacts have been reduced to hundreds or even thousands of one, the fault is greatly reduced. In addition, PLC with hardware fault self-detection function, failure can send alarm information in time. In the application software, the user can also program the fault self-diagnosis program of peripheral devices, so that the circuit and equipment in the system except PLC also obtain fault self-diagnosis protection. In this way, the whole system reliability.
2. Complete set, perfect function, strong applicability
PLC development to today, has formed a variety of scale of serialized products, can be used in various scale of industrial control occasions. In addition to logic processing function, PLC mostly has perfect data operation ability, can be used in a variety of digital control fields. A large number of various functional units emerge, so that PLC has penetrated into the position control, temperature control, CNC and other industrial control. With the enhancement of PLC communication ability and the development of human-machine interface technology, it becomes very easy to use PLC to compose various control systems.
3. Easy to learn and easy to use, welcomed by engineers and technicians
PLC is the industrial control equipment for industrial and mining enterprises. Its interface is easy and the programming language is easy for engineers to accept. The graphic symbol of ladder diagram language is quite close to the expression mode and relay circuit diagram, which opens a convenient door for people who are not familiar with electronic circuit, do not understand the computer principle and assembly language to engage in industrial control.
4. System design, workload is small, easy to maintain, easy to transform
PLC storage logic instead of wiring logic, greatly reduce the control equipment external wiring, the control system design and construction cycle is greatly shortened, at the same time, the daily maintenance has become easier, more important is to make the same equipment through the change program and change the production process is possible. This is especially suitable for multi-variety, small batch production occasions.
Four, PLC application needs to pay attention to the problem
PLC is a kind of equipment for industrial production automation control, generally do not need to take any measures, can be directly used in the industrial environment. However, despite the high reliability and strong anti-interference ability as described above, but when the production environment is too bad, electromagnetic interference is particularly strong, or improper installation and use, it may cause program errors or calculation errors, resulting in misinput and misoutput, which will cause the equipment out of control and misaction, so as not to ensure the normal operation of PLC, To improve the reliability of PLC control system, on the one hand, PLC manufacturers are required to improve the anti-interference ability of equipment; On the other hand, the design, installation and use of maintenance requires high attention, multi-party cooperation in order to improve the problem, effectively enhance the anti-interference performance of the system.
PPC380AE01
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