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*

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*Galil Motion Control, Inc.*

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*www.galilmc.com*