Galil Motion Control tut2 Page 11
TECHNICAL REFERENCE
MOTION PROGRAMMING
PROPORTIONAL MOTION, ELECTRONIC GEARING
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 ver-
tical direction. Proportional velocity is also useful in applica-
tions such as dispensing glue. Suppose that the motion in
the XY plane is performed at variable speed; in order to pro-
duce uniform amounts of glue per unit of length, it is neces-
sary to drive the glue pump at a rate that is proportional to
the vector speed in the XY plane.
Many applications require motion between axes to be
synchronized 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. A
geared axis can also simultaneously perform an indepen-
dent or vector move for the precise synchronization
required in flying-shear applications. The electronic gear-
ing mode eliminates mechanical gears and is useful for
gantry applications. The following example generates the
motion illustrated below.
PROPORTIONAL MOTION
ELECTRONIC GEARING
Consider an XYZ system where the resolution is 100
count/mm for all axes. The objective is to generate a
helical motion with 10 full turns of 5 mm radius in the
XY plane and a height of 20 mm in the Z direction. The
vector speed in the XY plane is 40 mm/sec. and both
the vector acceleration and deceleration equal 1000
mm/sec2. The motion parameters can be expressed in
units of resolution by the parameters:
radius = 5 mm = 500 counts
vector speed = 20 mm/sec = 2000 count/sec
accel/decel = 1000 mm/sec2 = 100,000 count/sec2
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
GA,, S
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
Example--Proportional Motion
90
·
Galil Motion Control, Inc.
·
www.galilmc.com
