User`s manual

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MELSEC-Q
13 AUTO TUNING
(b) Equivalent dead time
1) The segment (b) made by the Y axis and the equivalent dead time (L) provided when the
tangent line is drawn at the response speed for calculation (R') are calculated with the
following expression.
b (maximum slope-time PV) R' (maximum slope counter) AT1ST
L
R'
(Auto tuning start-time PV0)-b
2) If L 0, the following processing is performed and the S. AT1 instruction is terminated.
The identification alarm (BB8) is turned to 1.
The auto tuning completed (BB16) is turned to 1.
When the stepped manipulated value preset flag is 1, the following processing is
performed.
MV MV AT1STEPMV
(11) PID constant calculation processing
The response speed (R), equivalent dead time (L) and AT1 stepped manipulated value
(AT1STEPMV) are assigned to the adjustment rule to calculate the PID constants.
(a) Control system
The control system is selected according to the integral constant T
I
(I) and derivative
constant T
D
(D).
Integral constant T
I
(I) Derivative constant T
D
(D) Control method
T
I
0
Proportional control (P operation)
only
T
D
0 PI control (PI operation)
T
I
0
T
D
0 PID control (PID operation)
(b) Adjustment rule
The ZN process: adjustment rule based on the stepped response of Ziegler and Nichols is
used.
Control
method
Rate example gain Kp (P) Integral constant T
I
(I) Derivative constant T
D
(D)
P
1
R L 100
|AT1STEPMV|
00
PI
0.9
R L 100
|AT1STEPMV|
3.33 L0
PID
1.2
R L 100
|AT1STEPMV|
2 L 0.5 L