Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 270

• SPI operations are conducted as follows.
Output variation (ΔMV)
+ΔMV
-ΔMV
ST_
STHT
ST_: Operating time, STHT: Sample period, HT: Hold time (STHT-ST_)
Item
Deviation (DVn)
Output variation MV during operating time (ST_)
Output variation MV during hold time (HT = STHT -
ST_)
Kp: Gain
Ti: Integral time
DVn: Deviation
DVn-1: Last deviation value
PVn: Process variable
SVn: Engineering value conversion processing result
T: Execution cycle
ST_: Operating time
STHT: Sample period
HT: Hold time (STHT - ST_)
The integral term is as follows under the following conditions.
Condition
When Ti = 0
When either of MH or ML error has occurred, MVP > MH and the following
expression is satisfied
ΔT
×DVn>0
Ti
When either of MH or ML error has occurred, MVP < ML and the following
expression is satisfied
ΔT
×DVn<0
Ti
Ti: Integral time
T: Execution cycle
DVn: Deviation
MH: Output high limit value
ML: Output low limit value
MVP: MV Internal operation value
In the following case, the hold time (HT) is handled as 0 and the PI control is continuously performed.
STHT ST_
≤
ΔT ΔT
■Engineering value conversion
This function block converts the setting value (%) from the primary loop in the CAS or CSV mode into an engineering value.
RH-RL
× Setting value (%) from the primary loop + RL
SV=
100
RH: Engineering value high limit, RL: Engineering value low limit, SV: Setting value
10 LOOP CONTROL OPERATION
268
10.14 Sample PI Control (Disable Tracking for primary loop) (M+P_SPI)
HT ST_ HT ST_
STHT
Direct action
DVn = PVn - SVn
MV = 0
HT ST_ HT
STHT STHT
ΔT
ΔMV = Kp × { (DV - DV ) +
n n-1
Ti
Gain Proportional
Processing
ΔT
×DV =0
n
Ti
t
ST_ HT
STHT
Reverse action
DVn = SVn - PVn
× DV }
n
Integral