Programmable SyncPos motion controller
MG.10.J8.02 – VLT is a registered Danfoss trade mark
180
18
SYNCMFTI ME
Content
Defines the filter time for marker correction
Application example
Newspaper manufacturing needed this sort of filte-
ring to synchronizing a chain to the newspaper
stream coming from a printing machine. Because
the newspaper stream is not quite constant, the
problem is that if synchronized without filter the
movements of the chain are very hard and dynamic.
With all other sort of filters the system starts swinging
in sinusoidal waves.
When using this complex filter the synchronizing
work very well and solve the problem.
Description
SYNCMFTIME is given in ms and is used as follows:
NB!
Master velocity filtering SYNCVFTIME (65) is
given in 1/1000 ms for a better resolution, but
the marker filtering (SYNCMFTIME) is given in units
of 1ms.
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. To achieve the filter value, we
internally calculate how much markers will pass by,
if we run at maximum allowed speed over a period
of SYNCMFTIME.
The SYNCMFTIME and Parameter SYNCOFFTIME
(16) and parameter SYNCMFPAR (17) are used to
influence the behavior of Marker Filtering (see
below).
Portability
If SYNCMFTIME is 0, the behavior is same as up to
Option Card version 5.04, that means the filter time
for marker correction depends on the parameter
value of SYNCVFTIME (65).
Filtering is handled as follows:
Calculation of Marker Filter
only if SYNCMFTIME > 0
if SYNCMFPAR = 1,
Every time we find a real master marker, we can
calculate the Marker Filter constant as
SYNCMFTIME/300,
if SYNCMFPAR = 0
Every time we find a real master marker, we calcu-
late the Marker Filter constant as the Filtered Old
master velocity * SYNCMFTIME / (SYNCMPULS * 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 we calculate the filtered master
velocity (difference of actual and last master
position).
If (SYNCVFTIME < 0) then we calculate Filtered Old
master velocity 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.
Parameter Reference
