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9 PID OPERATION INSTRUCTION
9.1 Overview
9 PID OPERATION INSTRUCTION
PID operation instruction and PID control instruction
There are two types of instructions for PID control.
The following table lists the specifications comparison between PID operation instruction and PID control instruction.
9.1 Overview
This section describes an overview of PID control using the PID operation instruction.
PID operation instruction
The PID operation instruction calculates the manipulated value (MV) from the process value (PV) by combining the P action
(proposal action), I action (integral action), and D action (derivative action) to get closer to the set value (SV).
■Alarm output function
This function turns on the alarm output for the variations of input (process value) and output (manipulated value).
■Output upper/lower limit value setting
This function suppresses the increase of integral terms in PID control by setting the output upper/lower limit values.
■Auto tuning function
This function automatically sets the proportional gain (K
P
), integral time (T
I
), and derivative time (T
D
). The auto tuning is
performed in two methods: limit cycle method and step response method.
■Operation method of the PID operation instruction
The instruction performs PID operation in the velocity type or the process value derivative type.
Type Application Reference (Overview) Reference (Details)
PID operation
instruction
This instruction is used to perform PID control using auto
tuning.
Page 1134 Overview Page 1145 PID Operation Instruction
PID control
instruction
This instruction is used to perform PID control equal to that of
the MELSEC-Q series and MELSEC-L series.
Page 1149 Overview Page 1158 PID Control Instructions
(Inexact Differential),Page 1170 PID
Control Instructions (Exact Differential)
Item PID operation instruction PID control instruction
PID operation method Inexact differential Inexact differential/exact differential
Sampling period/sampling time 1 to 32767ms 10 to 60000ms
Number of control loops 1 loop per instruction 32 loops maximum
Auto tuning Enabled (limit cycle method and step response
method)
Disabled
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