PID value calculation

[Alwynb]

Hi there,
Is it mathematically possible to calculate the corrrect PID values from history performance data of a not optimally tuned control valve. We have a PLC which does not have autotuning facilities.
Regards
Alwyn

 

[xnuke]

Yes, it is mathematically possible. Do a search on Google for PID tuning. You'll find a ton of information available. Since so many others have put this kind of information on the Web, I'm not going to repeat any tuning methods here.

xnuke

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[garycav]

I always use the %incomplete method. You open the control loop and give the biggest step response that the valve (process) can cope with and record your step input and the process variable. From these value you can get the dead time, system time constants and work out the PID settings. As per the other reply you should be able to get the procedure off the net. If not, let me know and I will send you something.