Mitsubishi Electric FR-F820-04750 Instruction Manual page 530

(A) Application parameters
Step response method
● In the step response method, the manipulated amount is changed step by step for the real system.
From the change in the measured values, the maximum slope (R) and the equivalent waste time
(L) are calculated to determine each constant.
Measured value
waste time L (s)
PID gain tuning start
Fig. 5-175:
● The step manipulated amount (Pr. 1212 – 1000) is added to the present manipulated amount.
● The measured value is taken for every sampling cycle of step response (Pr. 1213). From the
variation between the measured values (Y) and the time (t), the maximum slope (R) is calculated.
● The measurement ends when the timeout time after the maximum slope (Pr.1214) elapsed after
the maximum slope is obtained.
● After the integral term is cleared, PID control is performed with the constant to which the change
has been applied (the constant used before PID gain tuning when a fault occurs).
Limit cycle method
● In the limit cycle method, the two-position ON/OFF operation is performed three times for output
of the manipulated amount for the real system. From the vibration waveform data of the measured
values, the vibration amplitude (Xc) and the vibration cycle (Tc) are measured. Based on the
measured values, each constant is determined.
● In the limit cycle method, less influence of the noise of the measured values is given as compared
in the step response method, and a stable tuning result can be obtained.
5 - 368
Manipulated
amount [%]
[%]
Maximum Maximum
Maximum
slope R slope R
slope R
(R = Y/T) (R=Y/T) (R=Y/T)
Equivalent
STF
PID
PGT
Timing diagram of step response method
Step manipulated amount
(Pr. 1212 – 1000)
PID gain tuning end
Measured value
variation range Y
Equivalent time constant T (s)
Timeout time after the maximum slope (s)
(Pr.1214)
Parameters
Time
Time
I003044E