User`s manual

Follower Motion
GFK-1742A Chapter 8 Follower Motion 8-5
8
Example 4: Changing the A:B Ratio
One example of variable A:B ratios is to use one ratio while moving positive, and another when
moving negative.
Note that determination of positive and negative velocity and update of the
A:B ratio must be done in the PLC or the DSM314 Local Logic program
. In the profile
below, the following axis uses a 2:1 ratio when moving positive and a 1:2 ratio when moving
negative.
Figure 8-4.
Changing the A:B Ratio
Velocity Clamping
Velocity clamping is available using the
Velocity Limit
set in the Configuration software.
When
the master velocity exceeds the configured limit, the following axis will continue to move at
the limit velocity multiplied by the A:B ratio.
The
Velocity Limit
%I bit is set and a status error
is generated to indicate that the slave axis is no longer locked to the master input positioning.
The slave axis has essentially
fallen behind
the master input.
Example 5: Velocity Clamping
The
Velocity Limit
is set to 100,000 in this example. Thus the slave axis velocity is clamped at
100,000 user units/sec in either direction. When the master axis peaks greater than the limits, the
following axis stays at the limit. After the master slows to under the limit, the following axis
continues tracking the master axis velocity. Counts generated in excess of the
Velocity Limit
are
lost to the follower. The horizontal dashed lines indicate the velocity limits. The shaded area
indicates the times when the
In Velocity Limit
bit is ON and the following axis is falling behind
the master.
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v
t
v
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M
aster Source
F
ollowing Axis
R
atio 2:1
Ratio 1:2