Auto Tuning - Mitsubishi Electric MELSEC-Q/L Programming Manual

Auto tuning

This section explains the auto tuning function of the PID operation instruction.
The auto tuning function automatically sets the proportional gain and integral time that are important constants in order to
optimize PID control. The auto tuning function can be implemented in two methods: limit cycle method and step response
method.
Limit cycle method
■Parameters set by auto tuning (limit cycle method)
• (S3)+3 (proportional gain (K
• (S3)+4 (integral time (T ))
I
• (S3)+6 (derivative time (T
D
■Auto tuning procedure
No. Procedure
1 Set the direct action or reverse action.
2 Select the auto tuning method. (Limit cycle method)
3 Set the auto tuning flag to ON.
4 Set the input filter.
5 Set the sampling time.
6 Set the maximum output value (ULV).
7 Set the minimum output value (LLV).
8 Set the threshold value (hysteresis) (SH
9 Set the set value (SV).
10 Set the command input of the PID operation instruction to ON
to start auto tuning.
When tuning is completed, the the auto tuning flags (bits 4 and 6) of (S3)+1 (action setting (ACT)) are set to OFF.
))
P
))
).
PV
Description
Set the direct action or reverse action flag (bit 0) of (S3)+1 (action setting
(ACT)).
Set the auto tuning method (bit 6) of (S3)+1 (action setting (ACT)) to ON. (If it is
set to OFF, auto tuning is performed in Page 745 Step response method.)
Set bit 4 of (S3)+1 (action setting (ACT)) to ON.
Set (S3)+2 (input filter constant ()).
Set (S3) (sampling time (T )).
S
Set the maximum output value (ULV) in (S3)+26 (upper limit of output value
(ULV)).
Set the minimum output value (LLV) in (S3)+27 (lower limit of output value
(LLV)).
Set (S3)+25 (PV value threshold (hysteresis) width (SH
Set the set value (SV) in (S1) of the PID operation instruction.
Auto tuning is performed according to the process value (PV).
7 APPLICATION INSTRUCTIONS
).
PV
743
7.18 PID Instruction
7