1、第页 附录 On the application and development of PLC 1. PLC definition Programmable logic controller, or PLC (Programmable logic Controller), refers to computer technology as the basis for the new industrial control devices. In 1987 the International Electrotechnical Commission (International Electrical
2、Committee) standards promulgated by the PLC in the draft of the PLC made the following definition: PLC is a specialist in industrial environments for the application of digital design and operation of electronic computing devices. It can be used in the preparation process memory, used in the impleme
3、ntation of its internal storage logical, sequential computing, timing, counting and arithmetic operations such as Operation The directive, and through digital or analog input and output, control various types of machinery or production process. PLC and its related peripheral equipment should be in a
4、ccordance with the industrial control system easy to form a whole, easy to expand its functions to the principle and design. 2. PLC characteristics 2.1 high reliability, strong anti-interference capability High reliability of electrical control equipment is the key to performance. PLC due to the int
5、roduction of modern large-scale integrated circuit technology, rigorous production process, the internal circuitry to take an advanced anti-jamming technology, high reliability. For example, Mitsubishi has produced an average of the F-Series PLC trouble-free time as much as 300,000 hours. Some use t
6、he redundant CPU PLC, the average working hours of trouble-free longer. PLC from the machine outside the circuit, the use of a PLC control system, and equal access for the scale of the relay systems, electrical wiring and switch contact has been reduced to hundreds or even 0.1 percent, fault also gr
7、eatly reduced.In addition, PLC with self-detection hardware failure, a failure to timely warning information. In the application software, applications can also peripheral devices into the fault diagnosis procedures, in addition to the system PLC and equipment outside the circuit fault diagnosis als
8、o be protected. In this way, the whole system is extremely high reliability is also not strange. 2.2 equipped, with perfect functions, the applicability 第页 PLC to develop today, has formed a large, medium and small size of the serialization of various products. Can be used for various industrial con
9、trol the scale of occasions. Apart from the logic processing functions, most of the modern PLC has a complete data computing power and can be used for a variety of digital control of the area. In recent years PLC emergence of a large number of functional units so that the PLC to infiltrate into a po
10、sition of control, temperature control, CNC, and other industrial control. PLC communication capabilities coupled with the strengthening of human-computer interface technology and the development and use of various PLC control system very easily. 2.3 easy to learn and use, welcomed by the engineerin
11、g and technical personnel PLC as the general industrial computer, industrial and mining enterprises are facing the industrial equipment. It easy interface, easy programming language for engineering and technical staff. Ladder language and graphic symbols and expressions of the relay circuit very clo
12、se, only a small number of switches of the PLC logic control orders can easily achieve the functions of the relay circuit. Is not familiar with the electronic circuits, computers do not understand the principles and compilation of language people use computers to carry out industrial control opened
13、the door. 2.4 system design, construction workload of small, maintenance-friendly, easy to transform PLC logic with memory instead of wiring logic, greatly reducing the wiring outside the control equipment, control systems design and construction of the much shorter cycle, while maintaining it has b
14、ecome easier. What is more important is to make the same equipment have been changes in procedures to change the production process possible. This is very suitable for many species, the small batch production of occasions. 3.PLC applications 3.1 switch to the logic of control This is the most basic
15、PLC, the most extensive areas of application, which replaced the traditional relay circuits, and logic control, sequence control, can be used single-control device, can also be used for more automation and control aircraft assembly line. 3.2 analog control In the course of industrial production, man
16、y of the continuous changes, such as temperature, pressure, flow, level and speed are all analog. In order to deal with programmable analog controller, the need to achieve analog (Analog) and digital (Digital) between the A / D converter and D / A converter. PLC manufacturers are supporting the production of A / D and D / A converter module so that the programmable logic controller for analog control.
