Electronic Gearing
This mode allows up to 8 axes to be electronically geared to some master axes. The masters may rotate in both
directions and the geared axes will follow at the specified gear ratio. The gear ratio may be different for each axis
and changed during motion.
The command GAX yzw or GA ABCDEFGH specifies the master axes. GR x,y,z,w specifies the gear ratios for the
slaves where the ratio may be a number between ±127.9999 with a fractional resolution of .0001. There are two
modes: standard gearing and gantry mode. The gantry mode (enabled with the command GM) allows the gearing
to stay enabled even if a limit is hit or an ST command is issued. GR 0,0,0,0 turns off gearing in both modes.
The command GM x,y,z,w select the axes to be controlled under the gantry mode. The parameter 1 enables gantry
mode, and 0 disables it.
GR causes the specified axes to be geared to the actual position of the master. The master axis is commanded with
motion commands such as PR, PA or JG.
When the master axis is driven by the controller in the jog mode or an independent motion mode, it is possible to
define the master as the command position of that axis, rather than the actual position. The designation of the
commanded position master is by the letter, C. For example, GACX indicates that the gearing is the commanded
position of X.
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 500,000 counts/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 500,000 counts/sec, and the
gear ratio is 1:1, but the gearing is slowly engaged over 30,000 counts of the master axis, greatly diminishing the
initial shock to the slave axis. Figure 6.Error: Reference source not found below shows the velocity vs. time profile
for instantaneous gearing. Figure 6.14 shows the velocity vs. time profile for the gradual gearing engagement.
Chapter 6 Programming Motion ▫ 89
DMC-40x0 User Manual