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MELSEC-Q/QnA
4. FUNCTIONS OF PID CONTROL
4.3 Other Functions
During PID control using the PID control instructions, MV upper/lower limit control is
automatically executed by the bumpless changeover function explained below.
4.3.1 Bumpless changeover function
(1) This function controls the MV (manipulated value) continuously when the control
mode is changed between manual and automatic.
(2) When the mode is changed (between manual and automatic), data is transferred
between the "MV area for automatic mode (automatic MV)" and "MV area for
manual mode (manual MV)" as described below.
The control mode is changed in the I/O data area (see Section 5.2).
(a) Changing from the manual ...........
mode to the automatic mode
The MV in the manual mode is transmitted to
the MV area for the automatic mode.
(b) Changing from the automatic .......
mode to the manual mode
The MV in the automatic mode is transmitted
to the MV area for the manual mode.
POINT
(1) Manual and automatic modes of PID control:
1) Automatic mode
PID operation is executed with a PID control instruction.
The control object is controlled according to the calculated MV.
2) Manual mode
PID operation is not executed. The MV is calculated by the user and the
control object is controlled according to the user-calculated MV.
(2) The loop set in the manual mode stores the PV (process value) in the set value
area every sampling cycle.
Содержание Q Mode
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