Appendix 5 Pid; Pid Operations - Mitsubishi Electric MELSEC iQ-F FX5 User Manual

Appendix 5
This section describes PID.

PID operations

The temperature control module can implement the process-value inexact differential PID control.
Operation method and operational expression
The process-value inexact differential PID control is an operation method in which a primary delay filter has been put on the
input of a derivative action and high-frequency noise has been eliminated to execute PID operations on the deviation (E).
■Algorithm of the process-value inexact differential PID control
The following figure shows the algorithm of the process-value inexact differential PID control.
Set value
(SV)
K : Proportional gain
P
T : Integral time
I
T : Derivative time
D
■Operational expression
The following figure shows the operational expression of the temperature control module.

MV = K E + E + I
n P n n
T
I
E: Deviation (SV-PV)
:
Sampling cycle
MV: PID control in process-value incomplete derivation output
PV: Process value
K : Proportional gain
P
T : Integral time
I
T : Derivative time
D
:
Derivative
I: Integral value
D: Derivative value
The PID control in process-value derivation is an operation method in which the temperature process value
(PV) is used as a derivative term in a PID operation. No deviation is used for the derivative term, drastic output
changes due to a derivative action can be reduced when the deviation varies along with a set value change.
APPX
166

Appendix 5 PID

PID
Temperature control module
Control response parameter
Slow
Normal
Fast
η: Derivative
s: Laplace transform
E: Deviation
T
T
D D
+ D -
n-1
n-1
 + T  + T
D D
+
1
K (1 +
P
T · s
- E
I
PV - PV
n n-1
Disturbance D
Control target
+
) G(s)
-
Manipulated value
(MV)
K · T · s
P D
1 + η · T · s
D
Temperature
process value (PV)