Danfoss MCO 305 Design Manual page 226

MCO 305 Design Guide
NB!:
Master velocity filtering par. 33-26
Velocity Filter is given in 1/1000 ms for a
better resolution, but the marker filtering
(SYNCMFTIME) is given in units of 1 ms.
Example:
SET SYNCVFTIME –50000
SET SYNCMFTIME 2000
This means, that the master velocity is filtered over
a period of 50 ms. A marker error is corrected
within a period of 2000 ms.
The actual filtered marker distance can be read out
with SYSVAR 4238 indices if this filter is activated
by setting SYNCMFTIME.
The Filter Time for Marker Correction and parame-
ters 33-27 Offset Filter Time and 33-28 Marker
Filter Configuration are used to influence the beha-
vior of Marker Filtering (see below).
Filtering Description
Filtering is handled as follows:
Calculation of Marker Filter only if
SYNCMFTIME > 0
If SYNCMFPAR = 1,
Every time when a real master marker is found,
the Marker Filter constant can be calculated as
SYNCMFTIME/300,
if SYNCMFPAR = 0
Every time when a real master marker is found,
the Marker Filter constant can be calculated as the
Filtered Old Master Velocity * SYNCMFTIME /
(SYNCMPULSM * 3)
which means, that the Marker Filter constant is
used as time constant for filtering. Then the time
which is needed to get an output corresponding to
a steady input should be nearly SYNCMFTIME.
The calculation is necessary, because the filter is
executed every marker and not every ms.
This Marker Filter constant is now used when
filtering the marker distance. The result is then
used to calculate the necessary gear correction.
The Gear Correction can be calculated as follow:
Gear correction = (SYNCMPULSM – Filtered marker
distance) / Filtered marker distance
Filtering master velocity and gear correction
Every sample time when the filtered
master_velocity (difference of actual and last
master position) is calculated
IF (SYNCVFTIME < 0)
default setting
226
__ Parameter Reference __
[ ] value for use in communication via serial communication port
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then Filtered Old Master Velocity is calculated with
a filter time constant equal SYNCVFTIME / 1000
Else the Filtered Old master velocity is set equal to
the actual master velocity.
In case where
SYNCMFTIME > 0 and
SYNCMFPAR = 2
the gear correction is made by taking the current
gear ratio and add the master velocity multiplied
by the Gear correction.
Start correction only if SYNCMFTIME > 0
Start correction is the correction which must be
realized after start condition is fulfilled. That means
either the first two markers (par. 33-23
SYNCMSTART 1,6) were observed or the master
velocity is reached and the first two markers
(SYNCMSTART 2,3,4,5) has been observed.
This start correction is split in such a way, that it
will be eliminated after par. 33-27 SYNCOFFTIME.
(Actually it is divided by the amount of markers,
which will be passed in SYNCOFFTIME at the actual
master velocity and that value is added to the
normal marker correction.)
If SYNCOFFTIME == 0,
Start correction will be eliminated at once, which
means that the correction will be done in between
two markers.
Marker correction SYNCMFTIME > 0
First the remaining start correction is subtracted
from the marker error. Then correction filtering
time corresponding to the par. 33-27
SYNCOFFTIME (master velocity dependant see start
correction number of markers) is set.
Now the sum of all marker distance errors is used
for a marker filter to calculate the filtered sum.
Then the filtered error sum is subtracted from the
unfiltered one. This result is then used to correct
the marker correction.
This corrected correction is then given into the
correction filter. The result of this correction filter is
then stored (plus start correction part if
necessary).
Then this correction is spread over one marker
distance. This is done by dividing the correction by
the number of samples which will be necessary to
pass one marker distance at actual master speed.
This value is stored and will be used every sample
time to correct the calculated slave position.
Following par. 33-28 SYNCMFPAR settings modify
behavior: