Function For Transfer To The Sv Storage Device For The Pv In Manual Mode - Mitsubishi QCPU Programming Manual

4. FUNCTIONS OF PID CONTROL

4.3.4 Function for transfer to the SV storage device for the PV in manual mode

PID Bumpless Processing Flag
SM794
(Incomplete derivative)
OFF
ON
When using the PID control instruction to perform PID control, execute the PID
operation instruction also in the manual mode.
In the manual mode, it is possible to select whether the PV imported from the A/D
converter module is transferred to the SV storage device or not when the PID
operation instruction is executed, depending on the ON/OFF status of the PID
bumpless processing flag (SM774, SM794).
SM774
(Complete derivative)
• The PV is transferred to the SV storage device when the PID operation
• When the manual mode is switched to the automatic mode, the MV
• When the SV is changed after switching to the automatic mode,
• The PV is not transferred to the SV storage device when the PID
• When the manual mode is switched to the automatic mode, control is
• Before switching to the automatic mode, store the SV into the SV
POINT
Depending on whether SM774/SM794 is ON or OFF, there are the following
differences in control when the manual mode is switched to the automatic mode.
• When SM774/SM794 is OFF, the PV is transferred to the SV storage device.
Therefore, there is no difference between the PV and SV when the manual mode
is switched to the automatic mode.
Hence, an abrupt change does not occur in MV at the time of mode switching.
Instead, since the SV after mode switching differs from the target value in the
automatic mode, the user should change the SV to the target value step by step
in the sequence program.
• When SM774/SM794 is ON, the PV is not transferred to the SV storage device.
Therefore, there is a difference between the PV and SV when the manual mode
is switched to the automatic mode.
If the difference is large at the time of mode switching, an abrupt change may
occur in MV.
Use this method in a system where the mode is switched when the PV has fully
neared the SV.
PID control in the automatic mode can be executed immediately without the SV
being changed step by step in the sequence program.
REMARK
The SV and PV are stored into the devices specified in the I/O data area with the
PID operation instruction.
instruction is executed.
output in the manual mode is continued.
control is performed to achieve the SV, starting from the MV output in
the manual mode.
operation instruction is executed.
performed to achieve the SV, starting from the MV output in the
manual mode.
storage device.
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MELSEC-Q/QnA
Operation