4-148
PID tuning method
Use the following procedures to start PID control,
(1) Enable PID control (set 10-03 greater than "xxx0b").
(2) Increase the gain (10-05) as high as possible until the maximum value before
oscillation occurs.
(3) Decrease the integral time (10-06) as low as possible until the maximum value
before oscillation occurs.
(4) Increase the differential time (10-07) as high as possible until the maximum
value before oscillation occurs.
. Proportional (P), integral (I) and differential (D) function provide a usable
closed-loop control for system procedure, or adjustment (pressure, temperature,
etc.). The adjustment is based on the comparison error signal between the target
value and the feedback value.
.PID output polarity can be selected by the 10-03 (setting = xx0xb: PID output
forward, setting = xx1xb: PID output reversal). When the PID output is selected as
the reversal and if the PID target value increases, the inverter will output low
frequency.
. PID feedback value can be adjusted by parameter 10-04 (PID feedback gain), and
the feedback analog input gain as well as bias terminal (AI1 or AI2) proportion, gain
and bias. In PID control, 10-14 (PID integral limit) is used to avoid the integral value
exceeding expectation. When the rapid load change occurs, the machine may be
damaged or the motor may be stalled. For these cases, you can reduce the set
value of 10-14 to increase the inverter response.
. 10-23 (PID limit) is used to prevent the over value calculated by PID control. The
maximum output frequency is in line with 100%.
. 10-10 (low-pass filter time constant of PID control output) is used to avoid the event
of the load resonant and rigidness insufficient due to high load resistance. In these
cases, you can adjust the time constant greater than the resonance frequency cycle
and reduce this set value so as to increase the inverter response. 10-09 (PID bias) is
used to adjust the PID control compensation, increasing by the unit of 0.1%.
. If the PID control output is added to the frequency reference as compensation,
10-24 (PID output gain) is used to adjust the amount of compensation.
. When the PID control output is negative, parameter 10-25 (PID reversal output
selection) can be used to reverse the inverter. In any event, when the reversal
prohibition function is selected, the PID control output limit is 0.
. 10-26 (PID target SFS) sets the PID output increasing and decreasing time
to increase or decrease PID target value. The inverter acceleration / deceleration
are set by 00-14 ~ 17 to 00-21 ~24. Based on the settings from 00-14 ~ 17 to
00-21 ~24, the PID control will be used in the cases of load resonance or
instability occurrence. If these cases occur, you can reduce the acceleration /
deceleration time (00-14 ~17 to 00-21 ~ 24) until the system is stable and
maintain the necessary acceleration / deceleration time. This function can be
disabled by setting the parameter of multi-function digital inputs 03-00 ~ 03-07 to
36 (PID target SFS is off).
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