Limit Cycle Method - Mitsubishi FX3U-4AD User Manual

FX /FX /FX PLC User's Manual - Analog Control Edition
3G 3U 3UC
PID Instruction (FNC 88)
Error
code
<Step response method>
6752
Improper auto-tuning operation
<Limit cycle method>
6753
Abnormal output set value for auto-tuning
[ULV (upper limit) ≤ LLV (lower limit)]
<Limit cycle method>
6754
Abnormal PV threshold (hysteresis) set value for auto-
tuning (SH < 0)
PV
<Limit cycle method>
Abnormal auto-tuning transfer status
6755
(Data of device controlling transfer status is abnormally
overwritten.)
<Limit cycle method>
6756
Abnormal result due to excessive auto-tuning
measurement time (τon > τ, τon < 0, τ < 0)
<Limit cycle method>
6757 Auto-tuning result exceeds proportional gain. (K
of range from 0 to 32767)
<Limit cycle method>
6758
Auto-tuning result exceeds integral time.
(T = Out of range from 0 to 32767)
I
<Limit cycle method>
6759
Auto-tuning result exceeds derivative time.
(T = Out of range from 0 to 32767)
D
Caution
With regard to the measured value (PV) in PID, normal measurement data should be read before PID
operation begins.
Especially when the PID operation is executed to the input value in an analog input block, pay attention to the
conversion time.
Error description
= Out
P
Action
<Auto-tuning is finished. → PID operation is not started.>
Because the set value fluctuated during auto-tuning, auto-
tuning was not executed correctly.
Set the sampling time to a value larger than the output change
cycle, or set a larger value to the input filter constant.
After changing the setting, execute auto-tuning again.
<Auto-tuning is forcibly finished. → PID operation is not
started.>
Check whether the target settings are correct.
<Auto-tuning is forcibly finished. → PID operation is not
started.>
Verify that devices occupied by PID instruction are not
overwritten in the program.
<Auto-tuning is forcibly finished. → PID operation is not
started.>
The auto-tuning time is too long.
Increase the difference (ULV - LLV) between the upper limit and
the lower limit of the output value for auto-tuning, set a smaller
value to the input filter constant (α), or set a smaller value to the
PV threshold (SH ) for auto-tuning, and then check whether
PV
the result is improved.
= 32767). → PID operation is
<Auto-tuning is finished (K
P
started.>
The variation of the measured value (PV) is small compared
with the output value. Multiply the measured value (PV) by "10"
so that the variation of the measured value will increase during
auto-tuning.
= 32767). → PID operation is
<Auto-tuning is finished (K
P
started.>
The auto-tuning time is too long.
Increase the difference (ULV - LLV) between the upper limit and
the lower limit of the output value for auto-tuning, set a smaller
value to the input filter constant (α), or set a smaller value to the
PV threshold (SH ) for auto-tuning, and then check whether
PV
the result is improved.
6 Troubleshooting
6.1 Error Codes
K
L
L-29