National Instruments NI-Motion User Manual page 125

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For example, if you have a gearing ratio of 2:1 (slave:master), the slave
moves 20 counts when the master device moves 10 counts.
Master Position at Enable
Master Position
Slave Position at Enable
Slave Position
Figure 10-2. Relative Gearing at Enable
Absolute gearing behaves similarly to relative gearing in that when gearing
is enabled, the slave axis follows the master axis movement as it is defined
by the gear ratio. The difference between relative and absolute gearing is
that the reference position calculated for the master axis is updated only
when gearing is enabled. This difference is apparent when the gear ratio is
updated on-the-fly.
For example, if the gear ratio is 2:1, the current master position is 1010, the
current slave position is 3020, and the gear ratio is changed to 3:1, the slave
axis jumps from 3020 to 3030 but the master position remains the same.
Master Position
at Enable
Master Position
Slave Position
at Enable
Slave Position
Figure 10-3. Absolute Gearing at Gear Ratio Change
Chapter 10
Move
1000 1010
Move
1000 1010
3000 3020
Slave Position
After Move
10-3
Electronic Gearing and Camming
Master Position
After Move
Slave Position
After Move
Move
3000 3020
Master Position
After Move
Slave Position
After Gear Change
Jump
3030
NI-Motion User Manual