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DMC-1700/1800 Chapter 6 Programming Motion • 105
An alternative gearing method is to synchronize the slave motor to the commanded vector motion of several axes
performed by GAS. For example, if the X and Y motor form a circular motion, the Z axis may move in proportion
to the vector move. Similarly, if X,Y and Z perform a linear interpolation move, W can be geared to the vector
move.
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, commands, or VP, or LI.
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