But the programming language of 5 kinds of levels of program controller

The user program of PLC is the technology control requirement that designs personnel basis to control a system, design through the work out of PLC programming language. The industry that makes according to international Electrotechnical Committee controls programming language standard (IEC1131-3) . The programming language of PLC includes the following 5 kinds: Echelon graph language (LD) , instruction predicative character (IL) , language of functional module graph (FBD) , language of ordinal function flow chart (SFC) reach structured text language (ST) . 1, echelon graph language (LD) echelon graph language is the most commonly used programming language in PLC programming. It is with relay a kind of programming language with similar line. To relay as a result of electric design personnel control is familiar with relatively, accordingly, echelon pursues programming language received extensive welcome and application. Echelon pursues the characteristic of programming language is: Pursue corresponding with electric operation principle, have intuitionistic sex and corresponding sex; With original relay control agrees, electric design personnel masters easily. Echelon pursues programming language and original relay pilot differentia is, echelon pursues medium the electric current that can flowing is not real significance, in-house relay also is not subsistent relay, when application, pilot concept distinction treats need and original relay. Graph the 1 communication asynchronous electromotor that is a model starts control circuit plan directly. Graph 2 it is to adopt plan of echelon of PLC pilot program. Graph electromotor of 1 communication asynchronous starts echelon of 2PLC of circuit plan plan to pursue directly 2, instruction predicative character (IL) the instruction expresses programming language is programming language of as similar as assembly language a kind of mnemonic, count composition by command code and operation with assembly language. Below the circumstance that does not have the computer, suit to use PLC to hold process designing implement have an authorized strength to user program. In the meantime, the instruction expresses programming language and echelon intention programming language graph is one to one correspondence, OK and mutual transition finishs in software of PLC process designing. Graph the 3 instructions that pursue corresponding with graph 2PLC echelon namely are expressed. Graph the characteristic that 3 instructions express an instruction to express programming language is: Use mnemonic to express to handle a function, have easy memory, facilitate master; In hold process designing implement mnemonic is used to express on clavier, facilitating operation, can undertake in the circumstance that does not have the computer process designing is designed; With echelon the graph has one to one correspondence relation. Its characteristic and echelon graph language agree basically. 3, language of functional module graph (FBD) language of functional module graph is the programming language of a kind of PLC with as logistic as the number similar circuit. The form that adopts functional module plan will state module place provides some functions, different functional module has different function. Graph 4 it is corresponding figure the functional module that electromotor of 1 communication asynchronous starts directly pursues the expressive means of programming language. Graph module of function of graph of 4 functions module pursues the characteristic of programming language: Functional module pursues programming the characteristic of the language is: It is an unit with functional module, program of analytic understanding control is simple and easy; Functional module is the formal expression function that uses a figure, intuitionistic sex is strong, the process designing that the design personnel of foundation of logistic to having a number circuit masters very easily; Big to dimensions, control concerns to control a system complexly logically, because functional module graph can be clear that expressive function concerns, make process designing debugs time to decrease greatly. 4, language of ordinal function flow chart (SFC) language of ordinal function flow chart is to satisfy the programming language that ordinal logic is controlled and designs. The process of movement of will ordinal flow when process designing is divided into pace and changeover condition, the functional flow order that controls a system according to transferring a condition to be opposite undertakes allocation, of one pace according to ordinal movement. Each pace controls functional job on behalf of, express with pane. The echelon that is used at finishing job of corresponding control function is contained to pursue logistic inside pane. This kind of programming language makes program structure clear, read easily reach safeguard, reduce the workload of process designing greatly, shorten process designing and debug time. The dimensions officer that is used at the system is big, the circumstance with order more complex concern. Graph the 5 sketch map that are a simple functional flow programming language. Graph the characteristic of the programming language of flow chart of function of sketch map order of a 5 simple functional flow programming language: Give priority to a line with the function, allocate according to the order of functional flow, method is fair, facilitate to the user the program understands; Avoid echelon graph or other language cannot the blemish of ordinal movement, also avoided to use echelon graph language to be opposite at the same time when ordinal movement process designing, because lock of mechanical each other creates user program structure the complex, defect that understands hard; User program sweep time also shortens greatly. 5, structured text language (ST) structured text language is a kind of programming language that the descriptive text version that uses structuralization will come to to describe a process. It is a kind of programming language that is similar to advanced language. In large and medium-sized PLC system, often use structured text to describe each variable relationships in controlling a system. The user to program that basically is used at other programming language to come true harder. Structured text programming language uses the descriptive means of the computer to describe all sorts of operation between all sorts of variable in the system to concern, complete needs function or operation. The advanced language photograph such as the structured text programming language that most PLC manufacturer uses and BASIC language, PASCAL language or C language is similar, but go to the lavatory for application, in the expression of the statement the respect such as the sort of method and statement undertook simplifying. The characteristic of structured text programming language: Use advanced language to undertake process designing, can complete more complex control operation; Need has certain computer the knowledge of advanced language and process designing skill, taller to requirement of engineering design personnel. Intuitionistic sex and operation sex are poorer. The software of PLC process designing of different type to above the supportive sort of 5 kinds of programming language is different, inchoate PLC supports echelon to pursue merely programming language and instruction express programming language. Current PLC pursues to echelon (LD) , the instruction is expressed (STL) , functional module pursues (FBD) programming language in order to support. For instance, SIMATICSTEP7MicroWINV3.

2. In design of PLC control system, the requirement designs staff not only outside understanding the hardware function of PLC, also want to understand the sort that PLC supports programming language. CNC Milling