文献翻译-PLC与组态王6.53

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PLC and kingview 6.53

Programmable controller (PLC) is based on microprocessor, a combination of computer technology, semiconductor integration technology, automatic control technology, digital technology and communication network technology developed a kind of general industrial automatic control device. Its control process and the user, to adapt to the industrial environment, convenient operation, high reliability, formed the three pillars of modern industrial control, robotics, CAD/CAM technology and PC). PLC technology represents the advanced level of process control, PLC device has become a basic unit of the automation system.

Programmable logic controller is a specialized in industrial control computer, its hardware structure is basically the same with a microcomputer, basic structure as follows:

1. The power supply

The power of the programmable logic controller plays a very important role in the whole system. Without a good, reliable power supply system is not work properly, therefore, programmable logic controller manufacturers also attaches great importance to power supply design and manufacturing. General ac voltage fluctuation within + 10% (+ 15%), can not take other measures to PLC communicate directly connected to the grid

2. The central processing unit (CPU)

The central processing unit (CPU) is the control center of the programmable logic controller. It according to the function of the programmable logic controller system program to receive and storage from programmer type in the user program and data; Check that the power supply, memory, I/O and warn the timer state, and diagnose the

grammatical errors in the user program. When programmable logic controller is put into operation, the first it receives in the form of scanning field state of each input device and data, and deposited in the I/O image area respectively, and then passes from the user program memory read the user program, after command interpretation shall be governed by the provisions of the directive arithmetic or logical operation into the I/O image area or the result of the data register. After all of the user program is performed, the last I/O image area of each output state or output register data sent to the corresponding output device, so cycle run, until stop running.

3. The memory

Memory storage system software called system program memory.

4. Input/output interface circuit

(1) the input interface circuit and microcomputer by optical coupling circuit of the input interface circuit, the function is programmable logic controller and the control interface interface input channel.

(2) the output interface circuit and the output data registers, called the road, interrupt request circuit integration, the role of programmable logic controller through the output interface circuit to perform component output corresponding control signals on site.

5. Function module

Such as counting, positioning function module.

6. Communication module

Programmable logic controller has the following distinctive features:

1. Easy to use, simple programming

2. The function is strong, high cost performance

3. The hardware is complete, the user use convenient, strong adaptability

4. High reliability, strong anti-jamming capability

The working process of the PLC is divided into internal processing, communication, program input processing operation, program execution, output stages. The time needed for the whole process of scanning a called scan cycle. Internal processing stage, PLC check the CPU module of hardware is normal, reset monitoring timer, etc. In communication operation service stage, PLC and intelligent communication module, programmer type in the command response, update programmer display content, etc., when the PLC is in a state of stopped (STOP), only for internal processing and communication service operation, etc. In the PLC is in a state of running (RUN), from the internal processing, communication, program input operation, program execution, output, working cycle scan.

1. Input processing

Input processing is also called the input samples. At this stage, the sequence reads all the input terminal of the on-off state, and will read the information stored in memory of the image to register. Be refreshed in the input image register then entered into the phase of program execution. When the program execution, the input image register isolation with the outside world, even if the input signal changes, the image is not changed, the contents of a register only the next scan cycle can be read in information input processing phase.

2. The program execution

According to the ladder diagram procedure of PLC scanning principle, according to the first left after the right after the first step in the sequence, every scan, execute a program. But met jump instruction program, according to the jump condition meets decided to jump the address of the program. From the user program involves the input and output state, PLC from the input image register readout on mining into the state of the corresponding input terminal of a stage, from the output image register read out the current state of the corresponding image register, according to the user program logic operation, operation results stored in the device registers, for each device, device image register register in content, will change with the process of program execution.

3. The process

After finishing the program execution, the output image registers, the device image states of the Y register in the register, transferred to the output latch in the output stage of processing, through isolating circuit, drive power amplification circuit, the output terminal output control signal to the world and the external load.

The response time is when the design of PLC control system is an important parameter to know

(1) filtering time input circuit, it is determined by the RC filter circuit and time constant. Change the time constant of cocoa adjust input lag time.

(2) the output circuit of the time lag, it is associated with the output of the output circuit way;

(3) PLC cycle scanning works;

(4) the PLC to focus on ways of input sampling, output refresh;

A short response time

If in a scan cycle has just received before the end of an input signal, the next scan cycle into the input sampling stage, the input signal is sampled, make the input and update, then the shortest response time.

The shortest response time = input lag time + + a scan cycle output delay time

The long response time

If you receive an input signal after input lag, just missed the I/O refresh time, the input signal is invalid in the scan cycle, until the next scan cycle to be read in input sampling stage, make the input, the longest response time.

The longest response time = input lag time + + output two scanning time delay time Above is the general working principle of PLC, but in the modern emergence of more advanced PLC input image refresh cycle, the program execution cycle and output image refresh cycle has been independent work, improve the execution efficiency of PLC. In practical engineering application, the programmer should know