Dear Everybody!

Now, I would like control system with 4 analog input and 4 analog output base on S7-300 PLC. That mean I want establish 4 single control loop by using S7 - 300 PLC and Analog In/Out module and programming for PLC execute control follow PID rule. After studied through document of PLC and functions It seem to be okay (I am not sure). I would like to ask you if follow is Okay?

Each single PID call via FB40/41 with different DB (data block). And using cyclic interrupt (system interrupt) to call sequently FB40.

For example in interrupt routine:
call FB40, DB1 // For control loop 1
call FB40, DB2 // For control loop 2
call FB40, DB3 // For control loop 3
call FB40, DB4 // For control loop 4

Of course, DBx is different. for each control loop.

I really know how to use FB40/41 for multi loop control as description above. And if anybody have any ideal, or suggestion, pls send me via [email protected]. And if anybody have any interesting link website, also send to me via above address.

Thank you in advances.
Nguyen Van Hong

 

You can just call PID FBs 4 times. The instance DBs will be different. You do not need to call them in an interrupt routine, since sampling time can be adjusted on the FB by a parameter.

 

Dear it's really simple.....

Just call FBs as a normal FB and that's all for cycle time you should see the parameters of FB40/41. at the moment i don't have in mind that what that parameter was. Also you can tune up these PID with auto tuner. I think it must be in your package of Step7. This tuner really works with systems of small cycle time. For any further information or sample programme

[email protected]