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48 • Chapter 6 Programming Motion DMC-2X00
The slave axis for each figure is shown in the bottom portion of the figure; the master axis is shown in
the top portion. The shock to the slave axis will be significantly less in figure 2 than in figure1. The
ramped gearing does have one consequence. There isn’t a true synchronization of the two axes, until
the gearing ramp is complete. The slave will lag behind the true ratio during the ramp period. If exact
position synchronization is required from the point gearing is initiated, then the position must be
commanded in addition to the gearing. The controller keeps track of this position phase lag with the
_GP operand. The following example will demonstrate how the command is used.
Example
Electronic Gearing Over a Specified Interval
Objective Run two geared motors at speeds of 1.132 and -.045 times the speed of an external master.
Because the master is traveling at high speeds, it is desirable for the speeds to change slowly.
Solution: Use a DMC-1730 or DMC-1830 controller where the Z-axis is the master and X and Y are
the geared axes. We will implement the gearing change over 6000 counts (3 revolutions) of the master
axis.
MO Z Turn Z off, for external master
GA Z, Z Specify Z as the master axis for both X and Y.
GD6000,6000 Specify ramped gearing over 6000 counts of the master axis.
GR 1.132,-.045 Specify gear ratios
Question: What is the effect of the ramped gearing?
Answer: Below, in the example titled Electronic Gearing, gearing would take effect immediately.
From the start of gearing if the master traveled 6000 counts, the slaves would travel 6792 counts and
270 counts.
Using the ramped gearing, the slave will engage gearing gradually. Since the gearing is engaged over
the interval of 6000 counts of the master, the slave will only travel ~3396 counts and ~135 counts
respectively. The difference between these two values is stored in the _GPn operand. If exact position
synchronization is required, the IP command is used to adjust for the difference.
Command Summary - Electronic Gearing
COMMAND DESCRIPTION
GA n Specifies master axes for gearing where:
n = X,Y,Z or W or A,B,C,D,E,F,G,H for main encoder as master
n = CX,CY,CZ, CW or CA, CB,CC,CD,CE,CF,CG,CH for commanded position.
n = DX,DY,DZ or DW or DA, DB, DC, DD, DE, DF,DG,DH for auxiliary encoders
n = S or T for gearing to coordinated motion.
GD a,b,c,d,e,f,g,h Sets the distance the master will travel for the gearing change to take full effect.
_GPn
This operand keeps track of the difference between the theoretical distance traveled if
gearing changes took effect immediately, and the distance traveled since gearing
changes take effect over a specified interval.