B2: Acceleration
4.2 Functions
Basic Functions
244
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Mode: Sliding mean value generation
Where minimal contour deviations are required, filter time constants within the range of 20-40 ms can be set
using the "sliding mean value generation" filter mode. The smoothing effect is largely symmetrical.
The display of the calculated servo gain factor (KV factor), e.g. in the HMI Advanced "Axis" service screen,
shows smaller values than would normally be expected for the filter. The contour accuracy is in fact higher than
the displayed KV filter appears to suggest.
When changing from "2nd-order filter" to "sliding mean value generation" filter mode, the displayed KV factor
may, therefore, drop (with identical filter time constant), even though there is an improvement in contour
accuracy.
Mode: Bandstop filter
The bandstop filter is a 2nd-order filter in terms of numerator and denominator:
where:
Since a vibration-capable filter setting is not expected to yield useful results in any case, as with the jerk filter's
"2nd-order filter" (PT2) low-pass filter (PT2) mode there is no setting option for the denominator damping D
N
. The
denominator damping D
N
is permanently set to 1.
The bandstop filter can be parameterized in 2 different ways:
• Real bandstop filter
• Bandstop filter with additional amplitude response increase/decrease at high frequencies
Real bandstop filter
The real bandstop filter is applied when identical numerator and denominator natural frequencies are selected:
• f
Z
= f
N
= f
block
(blocking frequency)
If numerator damping setting = 0 is selected, the blocking frequency is equivalent to complete attenuation. In this
case the 3 dB bandwidth is calculated as follows:
• f
3 dB bandwidth
= 2 * f
block
If instead of complete attenuation, a reduction by a factor of k is all that is required, then numerator damping
should be selected in accordance with k. In this case the above formula for calculating the 3 dB bandwidth no
longer applies.
f
Z
:
Numerator natural freq.
f
N
:
Denominator natural freq.
D
Z
:
Numerator damping
D
N
:
Denominator damping
+V
V
V
˭I
˭I
=
=
˭I
1
V'
=
˭I
1
V'
1
