Technical Reference
Motion Programming
www.galilmc.com
/
Galil Motion Control, Inc.
13
Coordinated Motion
Motion controllers can generate various types of motion. One of
the most common types is coordinated motion between two
axes. In this mode, the controller generates motion of both
motors in a manner that results in straight lines and circular arcs.
This motion is quite common in computer numeric control (CNC)
and other industrial applications.
Coordinated motion is defined by the path and by the velocity
profile along the path.The first step is to select the two axes that
define the motion plane using the VM instruction. For example,
VMXY defines the plane of coordinated motion as the XY plane.
The second step defines the motion path which consists of a
collection of straight lines and circular arcs. Straight lines are
defined with the instruction VP m,n where (m,n) are the coordi-
nates of the endpoint with respect to the start of the move
sequence. Circular arcs are defined with the instruction CR r,
,
where r indicates the radius,
defines the starting angle,
and
defines the length of the arc.
The complete path may consist of many such motion seg-
ments as illustrated by the following example.There is no limit to
the number of segments that can be specified and additional
segments can be sent during motion.This allows the DMC to con-
trol motion along very long paths without stopping.
In addition to the motion path, the user can specify the vec-
tor speed (feedrate). In most applications the feedrate is set to a
constant value. However, the velocity can be reduced around cor-
ners. A specific feedrate may be prescribed for an individual seg-
ment. For example: VP 1000,2000<5000 sets the vector speed
to 5000 counts/sec for the segment VP 1000,2000.
Similarly, the acceleration and deceleration rates along the
motion can be specified.The instructions for the vector velocity,
acceleration, and deceleration are VS,VA, and VD respectively.
C (6000,2000)
D (-6000,2000)
B (6000,0)
E (-6000,0)
A (0,0)
The generation of a coordinated move is illustrated by the following
example. Consider the motion path described by the figure below
and write a program to generate it.The motion is in the XY plane, the
radius of the corners is 1000 counts, the vector speed is 20,000
count/sec, and the vector acceleration and deceleration rates are
both 100,000 ct/sec
2
.
The instructions and their interpretations are shown below.
INSTRUCTION
INTERPRETATION
#M
Label
VM XY
Specify XY plane
VP 6000,0
Move to Point B
CR 1000,270,180
Move to Point C
VP -6000,2000
Move to Point D
CR 1000,90,180
Move to Point E
VP 0,0
Return to Point A
VE
End of path
VS 20000
Vector speed
VA 100000
Vector acceleration
VD 100000
Vector deceleration
BGS
Start motion
EN
End program
Example--Motion Path for XY
