Danfoss VLT AutomationDrive FC 360 Programming Manual page 77

Parameter Descriptions
7-06 Speed PID Lowpass Filter Time
Range: Function:
NOTICE
10 [1 -
ms 6000
*
Severe filtering can be detrimental to
ms]
dynamic performance.
Set a time constant for the speed control low-
pass filter. The low-pass filter improves steady-
state performance and dampens oscillations on
the feedback signal. This parameter is used
with parameter 1-00 Configuration Mode [1]
Speed closed loop or [2] Torque closed loop. This
parameter is useful if there is a great amount
of noise in the system, see Illustration 4.23. For
example, if a time constant (τ) of 100 ms is
programmed, the cutoff frequency for the low-
pass filter is 1/0.1=10 RAD/s., corresponding to
(10/2 x π)=1.6 Hz. The PID regulator only
regulates a feedback signal that varies by a
frequency of less than 1.6 Hz. If the feedback
signal varies by a higher frequency than 1.6 Hz,
the PID regulator does not react.
Practical settings of parameter 7-06 Speed PID
Lowpass Filter Time taken from the number of
pulses per revolutions from encoder:
Encoder PPR
512
1024
2048
4096
MG06C702
Programming Guide
7-06 Speed PID Lowpass Filter Time
Range:
Parameter 7-06 Speed
7-07 Speed PID Feedback Gear Ratio
PID Lowpass Filter
Range:
Time
1
10 ms
*
5 ms
2 ms
1 ms
7-08 Speed PID Feed Forward Factor
Range:
0 %
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Function:
Feedback
Disturbed feedback signal
Lowpass lter
Feedback
Filtered feedback signal
Illustration 4.23 Feedback Signal
Function:
[0.0001 - 32 ]
Par 7-07=1.00
Illustration 4.24 Speed PID Feedback Gear
Ratio
Function:
[0 - 500 %] The reference signal bypasses the speed
*
controller by the amount specified. This
feature increases the dynamic performance
of the speed control loop.
4
0.6 t (Sec.)
f = 10 Hz
g
0.6 t (Sec.)
n1 n2
Motor
Par 7-07=n1/n2
75
4