Based on the PLC to realize sequence control sc - four programming way Industrial control -

1 introduction

simple programmable controller PLC controller wiring, it is mainly the design of the program, the control of preparation of ladder diagram is the most commonly used programming way, generally experienced in using design method, the logical design method, grafting relay control circuit and the sequential control design method, in which the sequential control design method is also called the function chart design method, the function chart is the control process of a control system is used to describe the functions and features of graphics, it mainly by the step, transition, transition conditions, arrow lines and movements. This is an advanced design method for complex systems, you can save 60% ~ 90% of the design time. In our country in 1986 issued a function chart of national standard ( gb6988. 6 - 86). 。 After a function chart, we can prepare the ladder diagram in four ways, they respectively are: the stop programming way, step by step ladder instruction programming mode, shift register programming mode and setting reset programmatically. Based on the mitsubishi f1 series PLC controller as an example, illustrates four programming method to realize sequence control.

for example, a rotary table control of PLC control of the drilling process is: when the rotary table does not turn and bit rotation, if the sensor will detect the workpiece in place, the bit to came into y430 work when the drill bit to a certain depth sleeve x401 under pressure to close to switch, timer t450 timing, 4 s, quick y431 x402 close to switch to the back, get back to the in situ. Function chart shown in figure 1:

2 use the maintenance outage road programming way

the bartender blackout road just use is associated with contact and coil's instructions, no programming components make the intermediate links, various models of PLC instruction system has related instructions, with the circuit USES the remained, which has the memory function, and basic is similar with the traditional relay control circuit, therefore has been widely used. This method of programming a universality, programming easy to learn, generally in the original relay control system of the application of PLC controller in the process of transformation. As shown in figure 2 to use the maintenance outage path programmatically, compiled and figure 1 sequence function diagram of ladder diagram, figure 2 only normally open contacts of the output, the normally closed contact and coil.

3 USES step ladder instruction programming way

step ladder instructions is specially designed for sequence control, which step can only use status register s, status register with power function, in the sequence control program should be used with step by step instructions, and setting status register must use instruction set setting, like this only then has the control function, status register s can offer STL contact, otherwise the status register with general intermediate relay s m. In the step ladder diagram of different step section allows for dual output, allowing a double booked the load on the output, at the end of the step into contact with a ret instruction to the back of the program to return to the original bus. The 0 - in figure 1 3 use status register s600 - S603 instead, instead of using the step ladder instruction after programming, the corresponding ladder diagram as shown in figure 3. This method is easy to be accepted by the beginner programming and master, for experienced engineers, can also improve the efficiency of design, program debug, modify, and is also easy to read, easy to use, also is shorter, priority should be given in the sequential control design, the method is applied in the industrial automation control.

4 using the programming of the shift register

can be seen from the function table figure, at 0 3 each step is only one step at a time through and other steps are disconnected, the each step with intermediate relay m200 - M203 grenade launcher in place of, it is easy to shift register is used to implement control. Figure 4 in the ladder diagram of the shift register when programming, the shift register m200 - M217's top four m200 - M203 grenade launcher on behalf of the four steps to form a circular shift register. With the shift register is mainly for data, shift and reset three input signal processing. The method design of ladder diagram looks simple, detailed instructions are less, but for more complex control system design is not convenient, on-line modification ability is poor, in use process used in industrial control is less, most used in lights sequence control circuit.

5 use setting programmatically reset instructions

as shown in figure 5 for the use of setting reset programmatically compiled with figure 1 sequence function diagram of the ladder diagram. In setting reset instruction programming way, using a conversion step before all level corresponding auxiliary relay normally open contacts and transformation of the corresponding contact or circuit in series, used for all subsequent steps corresponding auxiliary relay setting step and make all the former corresponding auxiliary relay reset condition. For simple sequence control system may also directly to the output relay setting or reset. Clear the method sequence transformation relations, programming is easy to understand, more commonly used in the automatic control system programming manual control procedures.

the above four kinds of sequence control programming methods have their own characteristics, can choose according to actual condition to prepare the ladder diagram, which is compared commonly see table. Teaching practice shows that these programming easily accepted by beginners and master, can use them appropriately to arbitrarily complex sequence control program design. 6 conclusion

using the function table figure four ways to prepare the ladder diagram, can be adapted to different occasions, for engineering and technical personnel as technical requirements. It is an advanced design method for complex systems, you can save ( 60 ~ 90) % of the time.

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