Galil Motion Control CDS-3310, User Manual

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Chapter 6 Programming Motion CDS-3310
Electronic Gearing
This mode allows the axis to be electronically geared to the auxiliary encoder. The masters may rotate
in both directions and the geared axis will follow at the specified gear ratio. The gear ratio may be
changed during motion.
The command GA DA specifies the master axes. GR a specifies the gear ratio for the slave where the
ratio may be a number b/-127.9999 with a fractional resolution of 0.0001. GR 0 turns off
gearing. A limit switch or ST command disables gearing. GR causes the axis to be geared to the
actual position of the master.
Electronic gearing allows the geared motor to perform a second independent or coordinated move in
addition to the gearing. For example, when a geared motor follows a master at a ratio of 1:1, it may be
advanced an additional distance with PR, or JG.
Ramped Gearing
In some applications, especially when the master is traveling at high speeds, it is desirable to have the
gear ratio ramp gradually to minimize large changes in velocity on the slave axis when the gearing is
engaged. For example if the master axis is already traveling at 1,000,000 cts/sec and the slave will be
geared at a ratio of 1:1 when the gearing is engaged, the slave will instantly develop following error,
and command maximum current to the motor. This can be a large shock to the system. For many
applications it is acceptable to slowly ramp the engagement of gearing over a greater time frame. Galil
allows the user to specify an interval of the master axis over which the gearing will be engaged. For
example, the same master X axis in this case travels at 1,000,000 counts/sec, and the gear ratio is 1:1,
but the gearing is slowly engaged over 30,000 cts of the master axis, greatly diminishing the initial
shock to the slave axis. Figure 1 below shows the velocity vs. time profile for instantaneous gearing.
Figure 2 shows the velocity vs. time profile for the gradual gearing engagement.
Figure 1 Velocity cts/sec vs. Time (msec) Instantaneous Gearing Engagement