1 Introduction In the PLC in a variety of programming languages, such as ladder diagram language, Boolean mnemonic language, menu plan language, functional block diagram of the structure of language and description language statement. Ladder language and Boolean mnemonic language is the basic programming language, it is usually composed of a series of instructions, use these instructions to complete the majority of simple control functions, for example, instead of relays, counters, timers and logic to complete sequence control control. By expanding or strengthening instruction set, they can also perform other basic operations. Menu map description language is the language and statements advanced programming language, it may need to perform according to more efficient operations, such as analog of control, data manipulation, reports the newspaper, India and other basic programming language can not be done function. Function block diagram language with functional block diagram form, connected by flexible manner required by the control, not only in the PLC, has been widely applied in the distributed control system programming and configuration, also often used. Because of its connection and easy operation, easy to grasp the characteristics of engineering design and application of the general staff favorite. 2 commonly used PLC programming language classification based application, programming language can be used in combination, commonly used programming language of the following:
(1) ladder (Ladder Diagram) programming language
Ladder programming language features:
B7 and the corresponding schematic electrical operation, with intuitive and correspondence;
B7 and the original relay logic control technology is consistent and easy to grip and support learning;
B7 and the original relay logic control technology is different: ladder of energy flow (Power FLow) than the actual meaning of the current, the internal relay of the relay is not real, so take with the original application relay logic control techniques have the concept of discrimination;
B7 and Boolean mnemonic programming languages have one relationship, mutual conversion, and procedures to facilitate inspection.
(2) Boolean mnemonic (Boolean Mnemonic) programming language programming language is Boolean mnemonicBoolean mnemonics to describe the process of a programming language. Boolean mnemonic programming languages and computer assembly language is very similar to that used Boolean operators mnemonic functions.
Boolean mnemonic programming language has the following characteristics:
B7 using mnemonics to represent the operating functions, with easy to remember, easy to grasp the characteristics of support;
B7 in the programmer s keyboard using mnemonics that have the characteristics of easy operation, no computer can be the occasion of Programming;
B7 have one relationship with the ladder, the ladder language features and basic similar.
(3) menu plan (Sepuential Function Chart) programming language programming language menu map menu is used to describe the process diagram of a programming language. It is developed in recent years as a programming language. Map using the menu description, the control system is divided into several sub-systems, starting from the function, the system s operation has a clear meaning, easy to designers and operators of communication design, ease of design and inspection division of the program debugging. Function Charts Programming language features:
B7 to function as the main line, clear, easy understanding of the program operation and communication;
B7 on the large-scale procedures, division of design, a more flexible program structure can save programming and debugging time;
B7 commonly used in the school system, a large-scale, more complex situations procedural relationship;
Menu map from Petri (Petri) nets, because of its graphical expression, can clearly describe the complicated simple and complex system of all phenomena, and can exist in the system such as deadlock, insecurity and other abnormal for the analysis and modeling, on the basis of the model can be directly programmed, so has been widely used. Introduced in recent years, programmable controllers and distributed control systems for small also provides menu map description language used to program the software.
(4) functional block diagram (Function Block) Programming Language function block diagram programming language is used to represent the module function module has the function, different modules have different functions. It has several inputs and outputs, connected by flexible means, are connected to other terminals required to complete the necessary control algorithms or control functions. Modules can be divided into different types, in the same type may also be due to functional parameters of different Ershi be different function or application, for example, the number of inputs, input signals of different types such as the use of it different. As a result of the way the soft connection between the function modules and function modules and the external terminal connection, so the control scheme changes, the signal connection and other operations can easily replace realNow. Function block diagram programming language features:
B7 functional module as a unit, starting from the control function, so that the analysis and understanding of the control scheme easy;
B7 function module is a graphical way to describe the features, it greatly facilitates visual designers of programming and configuration, better ease;
B7 on the control of larger, more complex control relationships recorded in the system, because control of the relationship can be expressed more clearly, therefore, programming and configuration time can be shortened to reduce debugging time;
As each function module B7 certain procedures need to take up the memory, the implementation of the function module implementation will take some time, therefore, this design language in large and medium-PLC and distributed control system programming and configuration has been introduced only.
(5) structured statements (Structured Text) describe a structured programming language programming language statement describing is structured description statement to describe the process of a programming language. It is a similar high-level language programming language. In the medium and large programmable logic controller system, often described using a structured programming language statements to describe the control system of the relationship between the variables. It is also used for distributed control system programming and configuration.
Structured programming language statement describing the description of statements by the computer system of variables to describe the operation relations between the completion of the required functions or operations. Most manufacturers use the statement describedBASIC programming language and the language, PASCAL language or C language and other high-level language similar to, but easy to apply, in the statement of the types of expressions and statements have been simplified so.
Structured programming language has the following characteristics:
B7 by high-level language programming, you can complete more complex control algorithms;
B7 need to have some computer knowledge of advanced programming languages and programming skills, the skills of programmers demanding, difficult to complete general electrical personnel.
B7 intuitive and easy to operate and so poor;
B7 is often used by function modules, and other languages more difficult to achieve the implementation of some control functions.
Part of the PLC, the manufacturer provides the user with a simple structured programming language with mnemonic programming language similar to the steps of the procedure has some limitations. At the same time, providing the interface with the PLC or the communication link between the process of presentation, the user application provides room for expansion. 3 PLC programming languages Application Temperature control is important in many machine components. Its function is to control the temperature within the required temperature, then the processing and handling the workpiece. PID control system is widely used to control one of the methods described in more detail below PID temperature control of the PLC program design.
(1) system components