M O T I O N C O N T R O L P R O G R A M M I N G
PROPORTIONAL MOTION &
ELECTRONIC GEARING
Motion Control Programming
111
Another useful feature of motion controllers is their ability
to generate additional controlled motion in proportion to
the vector speed. This feature is useful with the generation of
helical motion whereby two axes form circular motion and a
third axis moves at a proportional velocity in the vertical
direction. Proportional velocity is also useful in applications
such as dispensing glue. Suppose that the motion in the XY
plane is performed at variable speed; in order to produce
uniform amounts of glue per unit of length, it is necessary to
drive the glue pump at a rate that is proportional to the vec-
tor speed in the XY plane.
Consider an XYZ system where the resolution is 100
count/mm for all axes. The objective is to generate a heli-
cal motion with 10 full turns of 5 mm radius in the XY
plane, and a height of 20 mm in the Z direction. The vec-
tor speed in the XY plane is 40 mm/sec, and both the vec-
tor acceleration and deceleration equal 1000 mm/sec
2
.
The motion parameters can be expressed in units of reso-
lution by the parameters
radius = 5 mm = 500 counts
vector speed = 20 mm/sec = 2000 count/sec
accel/decel = 1000 mm/sec
2
= 100,000 count/sec
2
To determine the gear ratio, note that the path in the XY
plane consists of 10 circles with a radius of 5 mm resulting in
a total length of 314 mm. Also note that the motion in the Z
direction is 20 mm. The ratio between the two motions is
20
ratio = ____ = 0.0637
314
The required motion is generated by the following program.
Instruction
Interpretation
#HELICAL
Label
VMXY
Define XY plane
GAS
Select master motion
GR,,0.0637
Set Z as follower
CR 500,0,3600 Define 10 circles
VE
End of path
VS 2000
Vector speed
VA 100000
Vector acceleration
VD 100000
Vector deceleration
BGS
Start the motion
EN
End program
Electronic Gearing
Many applications require motion between axes to be syn-
chronized or geared. Electronic gearing allows up to seven
axes to be geared electronically to one master axis which
may or may not be a motor controlled by the DMC. The
master axis (GA) can rotate in both directions and the
geared axes will follow at the specified ratios (GR). The
gear ratio can be changed during motion. An axis can be
geared and perform an independent or vector move simul-
taneously, which is useful for the precise synchronization
required in flying-shear applications. The electronic gear-
ing mode eliminates mechanical gears and is also useful
for gantry applications.
The following example generates the motion illustrated
on page 112.
Electronic gearing. Example:
Instruction
Interpretation
GAY
Y is master
GR 5,,-2.5
X ratio=5, Z ratio=-2.5
PR,10000
Specify Y distance
SP,100000
Specify Y speed
AC,250000
Specify Y acceleration
DC,250000
Specify Y deceleration
BG Y
Begin motion
Proportional Motion
