Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 234

• PIDP operations are conducted as follows.
Item
Deviation (DVn)
Output variation (MV)
In
Bn
Kp: Gain
Ti: Integral time
Td: Derivative time
Md: Derivative gain
CT: Control cycle
DVn: Deviation
DVn-1: Last deviation value
PVn: Process variable
PVn-1: Last process variable
SVn: Engineering value conversion processing result
The integral term and derivative term are as follows under the following conditions.
Item Condition
Derivative When Td = 0
term
When the control mode is MAN
When the control mode is CMV
Integral When Ti = 0
term
When an MH error has occurred and the following expression is
satisfied
CT
×DVn>0
Ti
When an ML error has occurred and the following expression is
satisfied
CT
×DVn<0
Ti
Ti: Integral time
CT: Control cycle
DVn: Deviation
MH: Output high limit value
ML: Output low limit value
Set an integral multiple of the execution cycle (T) as a control cycle (CT).
Set 0.0 or a value equal to or larger than the control cycle (CT) as an integral constant.
PIDP operations of this tag access FB are performed every control cycle (CT) (MV output).
In other execution cycles (T), the last manipulated value is held.
■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
232
10.9 Position Type PID Control (Enable Tracking for primary loop/Disable Tracking from secondary loop) (M+P_PIDP_T)
Direct action
DVn = PVn - SVn
MV = Kp × { DV + I + B }
n n n
Derivative
Integral
Proportional
Gain
CT
I =I + ×DV
n n-1 n
Ti
Md×Td
B =B + ×
n n-1
Md×CT+Td
CT×B
n-1
{(PV -PV )-
n n-1
Td
Reverse action
DVn = SVn - PVn
Md×Td
B =B +
n n-1
Md×CT+Td
{-(PV
}
Processing
Bn = 0
CT
×DV =0
n
Ti
×
CT×B
n-1
-PV )-
}
n n-1
Td