Mitsubishi Electric MELSEC iQ-R Series, Programming Manual

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9 PID OPERATION INSTRUCTION
9.1 Overview
Step response method
For an overview of the step response method, refer to the following.

Page 2057 Overview of step response method
■
Control data set by auto tuning (step response method)
• Direction (direct action/reverse action): Bit 0 of (s3)+1
• Proportional gain (K
P
): (s3)+3
• Integral time (T
I
): (s3)+4
• Derivative time (T
D
): (s3)+6
■ Procedure
1.
Set the output value for auto tuning.
Transfer the output value for auto tuning to the manipulated value (MV).
Set the output value for auto tuning to the "maximum allowable output value of the external device

0.5 to 1".
2.
Set the data that is not set by auto tuning.
Set the following items, which are not set by auto tuning, depending on the system.
*1 Difference between the set value (SV) and the process value (PV)
To perform auto tuning correctly, the difference between the process value (PV) and the set value (SV) must be 150 or more at the time
of auto tuning start. If the difference is less than 150, set a set value (SV) for auto tuning.
After completion of auto tuning, set the SV back to the original value.
*2 Sampling time (T
S
) setting
To perform auto tuning, set the sampling time (T
S
) to 1000 ms or longer.
The sampling time should also be sufficiently longer than the output change period.
3.
Start auto tuning.
Turn on the bit 4 of (s3)+1 (Action setting (ACT)) to start auto tuning.
When the amount of variation from the process value (PV) at start of auto tuning to the set value (SV) becomes 1/3 or more,
auto tuning is completed and the bit 4 of (s3)+1 (Action setting (ACT)) turns off automatically.
Precautions
• Measures to be taken when the process value (PV) does not change
If the process value (PV) does not change properly due to an analog input disconnection or any other problems, auto tuning
does not end. Detect and avoid such problems by creating a program that monitors the input value and the elapsed time from
the start of auto tuning.
Setting item Remarks
(s1) Set value (SV) Set a value so that the difference from the process value (PV) becomes 150 or more.
*1
(s3) Sampling time (T
S
) Set a cycle to 1000ms or longer.
*2
(s3)+2 Input filter (

)

(s3)+5 Derivative gain (K
D
) When the input filter is used, set the derivative gain to 0.
Others Set other control data as needed.