Self-Tuning Function - Mitsubishi Electric MELSEC iQ-R Series User Manual

1.12

Self-tuning Function

The temperature control module constantly monitors the control state. When the control system is oscillatory just after the
control start, owing to the set value (SV) change or fluctuation of characteristics of a controlled object, this function allows PID
constants to be automatically changed. Unlike the auto tuning function, a response waveform observation is monitored and
PID constants are automatically calculated and set. This function facilitates an object to be controlled with the most suitable
PID constants all the time without disturbance.
Differences between auto tuning and self-tuning
The following table lists the differences between auto tuning and self-tuning.
Item Auto tuning
Calculation of PID constants The manipulated value (MV) is turned ON or OFF and PID
constants are calculated based on the hunting cycle and
amplitude of the temperature process value (PV) to the set
value (SV).
Execution method Turning from OFF to ON 'CH1 Auto tuning command' (Y4)
starts the auto tuning and changes PID constants upon
completion.
Control response PID constants are calculated based on the control response
of when the manipulated value (MV) is turned ON or OFF.
Therefore, the control may become unstable.
Calculation result The optimum PID constants are calculated by one tuning.
In the standard control, the loop disconnection detection
judgment time is also calculated.
PID constants setting when Users need to execute the auto tuning again to change PID
characteristics of a controlled constants.
object change
Available control mode Standard control, heating-cooling control, or
positionproportional control
Starting ST and vibration ST
Depending on the control system status, the following two types of self-tuning (ST) can be used: Starting ST and vibration ST
• Starting ST: Self-tuning is executed immediately after the control is started or when the set value (SV) is changed.
• Vibration ST: Self-tuning is executed when the control system in a stable state has become oscillatory due to some causes
such as disturbance.
Temperature process value (PV)
Starting ST
■How to set starting ST
Set one of the following values for "Self-tuning setting" in "Application Setting." (The default value is "0:Do Not Run the ST.")
• 1: Starting ST (PID constant only)
• 2: Starting ST (Simultaneous temperature rise parameter only)
• 3: Starting ST (PID Constant and simultaneous temperature rise parameter)
• 4: Starting ST plus Vibration (PID Constant Only)
Vibration ST
Time
Self-tuning
PID constants are calculated based on the oscillation that
occurred in some situations such as after the control has just
started, the set value (SV) has been changed, and when a
control response is oscillatory.
The temperature control module constantly monitors the
control response. PID constants are calculated and changed
when the control response is slow.
PID constants are calculated based on the control response
of the temperature control in execution. Therefore, the control
is stable.
The optimum PID constants may not be obtained by one
tuning. The loop disconnection detection judgment time is not
calculated.
The temperature control module automatically changes the
PID constants.
Standard control only
1.12 Self-tuning Function
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1 FUNCTIONS
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