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10 PID CONTROL INSTRUCTIONS
10.1 Overview
Helpful functions
During PID operation by using PID control instructions, bumpless transfer and manipulated value upper/lower limit control are
automatically executed.
Bumpless transfer
This function controls the manipulated value (MV) continuously when the control mode is switched from manual to automatic,
or vice-versa. When the mode is switched, data are transferred between the MV storage areas for manual mode and
automatic mode.
• From manual to automatic: MV in manual mode is transferred to the MV storage area for automatic mode.
• From automatic to manual: MV in automatic mode is transferred to the MV storage area for manual mode.
Switch the mode in I/O data. ( Page 1155 I/O data)
PID control is performed in each mode as described below.
• Automatic mode: The CPU module controls the target with the MV calculated by PID operation using the
PID control instructions.
• Manual mode: The CPU module controls the target with the MV calculated without performing PID
operation using the PID control instructions. Loops set in manual mode stores the process value (PV) in the
set value storage area every sampling cycle.
Manipulated value upper/lower limits control
This function controls the upper or lower limit of the manipulated value (MV) calculated by PID operation. The function is only
enabled in automatic mode and is not executed in manual mode.
The manipulated value (MV) calculated by PID operation can be limited within the range set by the manipulated value upper
limit (MVHL) and manipulated value lower limit (MVLL). The following figure shows the operation of the function.
The manipulated value upper limit (MVHL) and manipulated value lower limit (MVLL) can be set to each loop within the range
of -50 to 2050 or within any desired range. The following values are set by default.
• Manipulated value upper limit: 2000
• Manipulated value lower limit: 0
An error occurs if the MVHL is smaller than the MVLL.
(1) MV
AUTO
without limit control
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