APPS: PID Feedforward Loop

[The AList]

==> Automation List post by Ritika...
To view or reply to this thread: http://www.control.com/thread/1239272188


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APPS:  PID Feedforward Loop
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I have a question to the experts of this forum.

I wish to know how is error calculated in PIDFF algorithms. In a general PID algorithm error e = PV-SP. The PID algorithm acts on this error. 

But in a PIDFF control algorithm, is error E = PV-SP+FF? Will the PID algorithm act on this E (i.e., PV-SP+FF) OR E is still PV-SP and FF gets added later to the PID output of PV-SP?

thanks and regards
Ritika
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