Delta AS Series Manual page 231

PID Block Diagram (Dependent)
+
SV +
-
PV
PID-I
Ti_Ki
PID-D
Td_Kd, Tf
ERR_DBW
When the PV (present value) is in the range of ERR_DBW, at the beginning, the present error is brought
into the PID algorithm according to the normal processing, and then the CPU module checks whether the
present error meets the cross status condition: PV (present value) goes beyond the SV (target value).
Once the condition is met, the present error is counted as 0 when applying the PID algorithm. After the PV
(present value) is out of the ERR_DBW range, the present error is brought into the PID algorithm again. If
PID_DE is true, that means it uses the variations in the PV to calculate the control value of the derivative,
and after the cross status condition is met, the PLC treats Δ PV as 0 to apply the PID algorithm. (Δ PV=
current PV – previous PV). In the following example, the present error is brought into the PID algorithm
according to the normal processing in section A ,and the present error or Δ PV is counted as 0 to apply
the PID algorithm in the section B.
Ch a pt er 7 Tem per at u r e M eas ur em ent M o d u le A S 0 4/ 0 8T C
PID_D IR
1
DEAD BAND
REVERSE
0
X(-1)
Kc_Kp
>0
<=0
0
BIAS
Ti_Ki
>0
<=0
0
Td_Kd
>0
<=0
0
E
PID-P
Kc_Kp
ERR_DBW
PID_MAN
+
0
+
+
MV_LIMIT
1
MV_MAX, M V_MIN
MOUT_AUTO
MOUT
0
MOUT
PID_MAN
1
MV
0
1
MOUT
7 - 3 5
7_