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PD3(PID)Z Math Control Modelling

Discussed so far has been Math Model PD3(PI) control. E.g. a known 3rd order process transfer function could be controlled best using PD3 feedforward when the set point has been moved by steps. Disturbances have been controlled by feedback PI action.

It is also easily possible to compensate feedforward the disturbances if the process is known. Let's call it PD3(PID)Z. PID will just do the fine work and adjust the system if necessary, e.g. for nonlinearities to be settled.

See Math Control Modelling:

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Diagrams Page 1 PD3(PID) Page 2 (t = 0.25 disturbance) PD3(PID)Z Pade 3 (t = 0.25 disturbance can't be recognized!)

This is in compliance with the Control Theory. The accuracy of control depends on the accuracy of the process transfer function!

Reply to
JCH
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Your feed forward coefficients are wrong. You should be able to control an ideal system with just the feed forwards and the plant transfer function. The product of the feed forwards and the plant should be 1. That way the target is equal to the actual. This isn't the case with your feed forwards values.

Peter Nachtwey

Reply to
pnachtwey

Peter:

Your feed forward coefficients are wrong. You should be able to control an ideal system with just the feed forwards and the plant transfer function.

Jan:

Read again:

PID [feedback] will just do the fine work and adjust the system if necessary, e.g. for nonlinearities to be settled.

IF NECESSAIRY!

It would be NECESSAIRY in any real plant. That's for sure. The controller is prepared for controlling real plants.

Then you can adjust K_PID, T_I and T_D: Page 1

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Reply to
JCH

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