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4.7 Simple Two-degree-of-freedom
This is the simplified control form of the two-degree-of-freedom PID control. In this form of PID control, the Q64TCN
controls the target subject using not only PID constants but also the control response parameter. The response speed
toward the change of the set value (SV) can be selected from three levels.
General PID control is called one-degree-of freedom PID control. In the one-degree-of freedom PID control, when PID
constants to improve "response to the change of the set value (SV)" are set, "response to the disturbance" degrades.
Conversely, when PID constants to improve "response to the disturbance" are set, "response to the change of the set
value (SV)" degrades.
On the other hand, in the two-degree-of-freedom PID control, "response to the change of the set value (SV)" and
"response to the disturbance" can be compatible with each other.
Note that required parameter settings increase and PID constants can hardly be auto-set by the auto tuning function
for complete two-degree-of-freedom PID control. Therefore, the Q64TCN operates in the simple two-degree-of-
freedom PID control for which parameters are simplified.
The level of "response to the change of the set value (SV)" can be selected from the following, maintaining the PID
constants that improve "response to the disturbance".
•Fast
• Normal
•Slow
(1) Setting method
Set a value in CH Control response parameter (Un\G49, Un\G81, Un\G113, Un\G145). ( Page 116,
Section 3.4.2 (25))
Common
Time
Temperature process value (PV)
Set value (SV) 2
Set value (SV) 1
Change
Set value (SV) change point
Fast
Normal
Slow