Mitsubishi Electric MELSEC iQ-R Series - PID Control Instructions (Inexact Differential)

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10 PID CONTROL INSTRUCTIONS
10.2 PID Control Instructions (Inexact Differential)
10.2 PID Control Instructions (Inexact Differential)
Inexact differential is PID control that applies a primary delay filter to the input of a differentiation term. Inexact differential is
effective in the following cases:
• For control susceptible to high-frequency noise
• When energy effective to actuate an operation end is not provided when a step change occurs in an exact differential
system
The following table summarizes the performance specifications of PID control instructions for inexact differential.
The following are the block diagram and operational expressions of PID operation.
• Block diagram of PID operation (inexact differential)
Item When the PID limit is restricted When the PID limit is not restricted
Number of PID control loops  32 maximum
Sampling period T
S
0.01 to 60.00s
PID operation method  Process value differentiation type (inexact differential) (direct action/reverse action)
PID constants setting
range
Proportional constant K
P
0.01 to 100.00
Integral constant T
I
0.1 to 3000.0s
Derivative constant T
D
0.00 to 300.00s
Derivative gain K
D
0.00 to 300.00
Set value setting range SV 0 to 2000 -32768 to 32767
Process value setting range PV -50 to 2050 -32768 to 32767
Manipulated value output range MV
K
P
: Gain
W: Disturbance
P: Controlled system
V: Detected noise
PV
t
t
T
D
 s
1 + ηT
D
s
PV × 1/η
1/η =
Input
Inexact differential
Primary delay
filter
Derivative term
Derivative gain
(K
D
)
1+(T
D
/K
D
)s
1+
SV
T
I
s
(P)
(I)
(D)
T
D
×s
-
W
-
Kp
MV +++
P
PV
V
1
+
++