With the progress and development of society, automation system has played an increasingly important role in the industrial production process. It is not only the product of social development, but also the objective embodiment of the rapid development of information technology. As the core component of automation system, it has also developed from the early simple PLC (programmable logic controller) to the present PLC system. Programmable Controller is a member of the computer family.
It is specially designed and manufactured for the control role in industry. Programmable Logic Controller (PLC), thermostatic element also known as Programmable Logic Controller (PLC), appeared in the early days. It was originally designed to replace relays to achieve logical control.
With the improvement and development of technology, the functions of this kind of equipment have been greatly complemented and improved, not only limited to logical control, but also expanded in other aspects. Initially this device was called programmable controller, PC for short, but in order to avoid confusion with the abbreviation of personal computer, so the programmable controller is called PLC. Programmable Controller Controller (PLC) is essentially a computer dedicated to industrial control. Its hardware structure is basically the same as that of a microcomputer. It can control machinery or corresponding production process through digital or analog input and output. Because of its small size, light weight, high reliability and strong anti-interference ability, programmable controller controller has been widely used in machinery manufacturing, electric power, chemical industry, building materials, steel, petroleum, textile, automobile, transportation and other industries. But in the early application of programmable controllers, most domestic manufacturers, such as copier plant, thermal power plant and so on, used imported equipment. Mitsubishi’s PLC controller, ABB’s frequency converter, Schneider’s soft starter and so on, because they have mastered the high-end core technology, their equipment has a good performance in stability and accuracy, but such equipment in technology. Technically, it is totally closed for users.
The purchaser can only operate the corresponding equipment by learning how to use it by technicians. But once the equipment breaks down, he must turn to the manufacturer to realize the technological monopoly of the foreign manufacturer, which is not only expensive, but also inconvenient in the process of using the equipment. Since the 1970s, due to the rapid development of computer chip technology in accordance with the law of Moore’s Law, its speed and performance have been improved rapidly. Often when a number of chips have just been popularized, a new batch of high-speed and high-performance chips have been produced. But it is difficult for manufacturers and integrators of automation system equipment to keep up with the development of computer hardware technology. As a result, the equipment of automation system used in industrial production often lags behind the development of computer technology. More importantly, because the development tools and software for purchasing and using all kinds of programmable controller devices are bundled with the manufacturer’s hardware system, that is to say, if you purchase the development tools and software for a manufacturer’s PLC, you can only limit the use of the corresponding supporting hardware provided by that manufacturer. If an industrial enterprise purchases PLC software from different manufacturers, it requires your technicians to be familiar with and master the hardware and software of different manufacturers, so that the enterprise not only invests a lot of financial resources, but also wastes a lot of manpower. If the third party’s LC is replaced by the third party’s LC with high speed, low price and high performance-price ratio, it is necessary to retrain technicians, which greatly wastes human resources. At the same time, some high-tech development tools and software can not be well promoted and used because of the restriction of hardware equipment. In order to make the PLC software have good specification and avoid wasting economy and manpower, in recent years, the international community has provided unified software development guidelines for all PLC manufacturers.
The promulgation and implementation of IEC61131-3 international standard has brought good news for industrial enterprises. Because of the unified interface and standardized programming language of PLC, technicians can easily master and use it and save money.
Gold and human resources have improved efficiency. In terms of hardware, the development of open and high-performance single-chip computer technology provides an effective material basis for the development of hardware. In this context, the development of an open PLC system has a positive practical significance for both scientific research and the promotion of the development of the PLC industry. The integration of PLC, DCS and computer functions into a three-Electronic DCS system has become the trend of industrial process automation in the future. Today, with the development of open industrial computer system becoming more and more mature, some PLC developers put forward the concept of “soft PLC” and “soft DCS” in order to ensure their advantages in developing tool software of PLC and improve their competitiveness in the market. The general idea of this idea is to develop a kind of equipment which can separate the software system and hardware system of PLC and DCS. It can be installed on the software and hardware platforms of various open industrial automation systems, which not only facilitates users, but also breaks away from the dependence and restriction of hardware equipment on manufacturer’s software. In this way, the open industrial control system will gradually become the main control system of industrial process automation in China, and will be widely used unprecedentedly. The future of PLC programmable controller will have greater development prospects. From the technical point of view, the rapid development of computers directly affects the development of programmable controllers. The advantages of faster operation speed, larger storage capacity and stronger intelligence of chips will be more applied to the production of programmable controllers. From the development scale, its specifications will develop towards the direction of super-small and super-large. From the product types, the products will have more types and more complete models. The standard is more unified, the performance is more perfect, the appearance is more comfortable, the function is more complete, and it is suitable for the requirements of various industrial occasions. From the application of computer network, the way that the programmable controller will connect with the intelligent equipment in industrial production directly is the development direction of the future programmable controller technology, and will play an increasingly important role.
In modern industrial production, a lot of programmable control systems have been adopted. Because programmable controllers can work normally in harsh working environment, but the real-time requirement of the course control system composed of programmable controllers is very high, so many factors should be considered in its design.
For example, in the process of monitoring, if we suddenly lose the signal how to solve, the network can have the function of continuous transmission of breakpoints, but once the industrial equipment loses the signal, the consequences can not be estimated. Whether there is a clear distinction between the control function and the management function of the equipment, the program should be concise and easy to understand, whether the hardware interface should be standardized as far as possible in production, and how to effectively the nodes should not be too many. Solving problems in industry, such as problems, still requires us to make more efforts.