With the development of technology, industrial environment tends to be more and more automated. Programmable controllers (PLCs) are widely used in industrial production because of their strong functions, high reliability, flexible and convenient use. Although programmable controllers are in good use at this stage, they have not yet been simulated. In this paper, the characteristics of the programmable controller and the requirements of the current environment are studied, and the way to realize the simulation of the programmable controller application program is explored. The improvement of production automation requires that the programmable controller can not only ensure the stability and reliability of equipment operation, but also be able to respond to emergencies and give timely and accurate response. This requires that the programmable controller can simulate the application program, simulate the running environment, judge the correctness of the program design, and simulate the operation. The function is to verify the integrity and accuracy of the programmable controller program design through off-line simulation, to help designers improve the programmable controller application program, and to ensure the safe transmission of data and information. The development of programmable controller technology is very rapid. As an integrated system, programmable controller has penetrated into the field of artificial intelligence control. Its input and output functions are more perfect and its performance is more reliable. It can be applied to the input and output of switching and analog signals of various forms and properties.
Its application features are as follows: (1) It can resist electromagnetic interference and voltage shock in harsh environment, and has stronger adaptability. (2) The simulation program of the application program of the programmable controller is simpler and simpler, and no high-level language is needed in the programming process. (3) Strong reliability, the time interval of failure can reach 20,000 hours. (4) The simulation system of this program is small in size, low in cost, high in systematization and very standard in window module. (5) The communication function is very strong. In the expansion of the basic system, it can also be configured with other systems to support the connection of various devices. (6) When one site is not needed, it can still be used in another site. In the process of simulation of programmable controller application program system, the main factors of its function are reliability, applicability, maintainability and economy of the product. Reliability, as the most important factor, is an important factor to determine the effect of the system. Only high reliability can guarantee the stability of the market, establish a complete quality assurance system, implement strict quality management system, and ensure the simulation effect of the application system of programmable controller. Applicability refers to the expansion of products and their coverage. At this stage, programmable controllers have many kinds of applications, full functions and more aspects of use. One programmable controller can control many single-machine equipment, and also can control a complex equipment jointly. Maintainability is the advantage of programmable controller. It is modular in structure, easy to replace and good in service.
Users can use it safely. Realizing the simulation of programmable controller application program is an important way to ensure the interests of users. Economy is the focus of customers’attention. The price of our products is only about 60% of that of imported products. Replacing imported products with domestic products can save about 2 million yuan. The quality can also be guaranteed and the long-term operation of equipment can be guaranteed.
When constructing the simulation system of programmable controller application program, three modules should be built, including the internal expression of computer stored programmable controller program, simulation strategy and user interface.
The interface of simulation system is shown in the following figure. When the simulation system runs, the programmable controller program designed by the user is read into the system, and then it is transformed into the expression form in the computer memory. Then the data files of the input contacts are read into the system, the ladder diagram is started, the subroutine is deduced, its logic is solved sequentially, and the state diagram is output. The simulation method includes internal expression and logical deduction. To realize the simulation of the programmable controller, the information of the internal components of the programmable controller needs to be stored by a carrier. In order to facilitate the access of information, the related information of the ladder diagram is described by a data table in order to record the detailed information of each component. For logic deduction, the programmable controller application system mostly uses ladder diagram to compile control program. The basic components are contacts and loads.
The way of composing is to combine contacts in series or in parallel, and then connect with loads to form ladder diagram. The relationship between trapezoids is explained by the programming language of programmable controller. The programming language needs strict format. The programming should be programmed in the order of a cascade from top to bottom, and the running process should follow the direction from top to bottom and from left to right.
The load state of each cascade is determined by the contact state. This process also needs some logical deduction, but the input contact does not need deduction, and it is directly determined by the user’s state. After realizing the simulation of the application program of the programmable controller, the following functions need to be realized: (1) Common programmable controller instruction table programming, ladder diagram programming and their mutual conversion can be realized. (2) It can provide more vivid toolbars. Users can draw trapezoidal program intuitively by mouse. The topological relationship expressed in the diagram can be correctly transformed into instruction list. User programs of editable controllers in various ways can be correctly checked to facilitate users to query and process data. (3) The internal components of the programmable controller can be simulated, the instruction interpreter can be simulated, thermostatic element and the running process can be simulated.
In a word, the simulation of the application program of the programmable controller should basically realize the simulation of hardware and software, which can provide the interface of Chinese characters and help immediately, and print the instruction sheet and ladder diagram. At the present stage, the rapid development and wide application of computer technology have brought the industrial development into a new growth stage. The programmable controller is the most widely used device. Making full use of its advantages to achieve high-efficiency production is the focus of major enterprises at this stage. On the basis of familiarity with its basic principles, the application program is realized. The following points can be achieved in the simulation, which can realize the simulation of most logic elements.
Using database and array as data carriers, the related parameters and data of the whole program can be recorded, the data can be analyzed, the simulation process and results can be described from different angles, and the logical operation blocks and data can also be realized. The information transfer between simulation modules makes the simulation system of programmable controller application more flexible and efficient.