Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 228

■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 (target)
■Inverse engineering value conversion
This function block converts SVC of an engineering value into SVC in percentage (%).
100
SVC(%)= ×(SVC-RL)
RH-RL
RH: Engineering value high limit, RL: Engineering value low limit, SVC: Setting value (current)
■Disable alarm detection
This function sets whether to detect alarms (ALM) or not in the deviation check and SV variation rate & high/low limiter
processing.
Item
Disable alarm detection by setting tag data
Disable alarm detection by control mode selection
Disable alarm detection by loop stop processing
■Auto tuning (AT1, AT2)
This function block detects dynamic characteristics and automatically calculates a proportional gain (Kp), integral time (Ti),
and derivative time (Td) for PID operations.
Select the step response method or the limit cycle method for auto tuning.
• AT1 (Step response method)
Auto tuning is for setting initial values of the proportional gain (Kp), integral time (Ti), and derivative time (Td) for PID
operations. The ZN method: Ziegler-Nichols' step response method is used for calculating the values. ( Page 595 Step
response method)
This method can be used in the MAN or CMV mode.
• AT2 (Limit cycle method)
In this method, a proportional gain (Kp), an integral time (Ti), and a derivative time (Td) for PID operations are calculated from
the variation amplitude and variation cycle of a process variable obtained by repeatedly outputting the high and low limit
values of a manipulated value. ( Page 598 Limit cycle method)
This method can be used in the MAN, AUT, CAS, CMV, or CSV mode.
■PV tracking function
To avoid sudden changes of the manipulated value at mode switching (from MAN to AUT), this function block matches the
setting value (target) with the process variable when the control mode is MAN or CMV and keeps the value.
Condition
When PVTRK_EN is TRUE and the control mode is "MAN (CMV)"
When PVTRK_EN is FALSE and the control mode is other than "MAN (CMV)"
10 LOOP CONTROL OPERATION
226
10.8 2-degree-of-freedom Advanced PID Control (Disable Tracking for primary loop) (M+P_2PIDH_)
Disable alarm detection processing
If the following bits in the disable alarm detection (INH) and the disable alarm
detection 2 (INH2) are TRUE, DVLA of the alarm (ALM), or DSVLA, SVHA, or
SVLA of the alarm 2 (ALM2) will not be detected.
• ERRI
• DVLI
• DSVLI
• SVHI
• SVLI
No alarm will be detected when the control mode is CASDR.
Page 228 Loop stop processing
PV tracking processing
Setting value (target) = Process variable
Setting value (current) = Process variable
Non-processing