Auto Tuning - Mitsubishi Electric MELSEC iQ-R Series Programming Manual

Auto tuning

To obtain satisfactory results in PID control, it is required to determine the optimum values of each constant (control data)
appropriate for the control target. The auto tuning function automatically sets the important constants for PID control,
proportional gain, integral time, and derivative time.
The auto tuning function is performed in two methods: limit cycle method and step response method.
Start auto tuning after the system becomes stable. If not, auto tuning may not be performed correctly.
Limit cycle method
For an overview of the limit cycle method, refer to the following.
Page 2056 Overview of limit cycle method
■Control data set by auto tuning (limit cycle method)
• Proportional gain (K ): (s3)+3
P
• Integral time (T ): (s3)+4
I
• Derivative time (T ): (s3)+6
D
■Procedure
1.
Set the action of PID operation.
Set the action (direct action or reverse action) with the bit 0 of (s3)+1 (Action setting (ACT)).
2.
Select the limit cycle method.
Turn on the bit 6 of (s3)+1 (Action setting (ACT)).
(When the bit is off, the step response method is selected.)
3.
Turn on the auto tuning execution flag.
Turn on the bit 4 of (s3)+1 (Action setting (ACT)).
4.
Set an input filter constant.
Set a value in (s3)+2 (Input filter ()).
5.
Set a sampling time.
Set a value in (s3)+0 (Sampling time (T
6.
Set the output upper limit value (ULV).
Set the upper limit of the manipulated value (MV) in (s3)+26 (Output upper limit value (ULV)).
7.
Set the output lower limit value (LLV).
Set the lower limit of the manipulated value (MV) in (s3)+27 (Output lower limit value (LLV)).
8.
Set the PV value threshold (hysteresis) width (SHPV).
Set a value in (s3)+25 (PV value threshold (hysteresis) width (SHPV)).
9.
Set a set value (SV).
Set a set value (SV) in (s1) of the PID operation instruction.
10.
Start auto tuning.
Auto tuning starts based on the process value (PV) when the start contact device of the PID operation instruction turns on.
The auto tuning related flags (bit 4 and bit 6) of (s3)+1 (Action setting (ACT)) turn off upon completion of auto tuning.
)).
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9 PID OPERATION INSTRUCTION
9.1 Overview
9
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