Technical Reference
Motion Programming
www.galilmc.com
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Galil Motion Control, Inc.
17
Contouring
The contour mode bypasses the DMC motion profiler and pre-
scribes an arbitrary position trajectory. Position increments (CD)
over a time interval (DT) are specified for each axis.The contour
mode is useful when complex and computer-generated trajecto-
ries must be followed. An automatic data recording feature allows
the DMC to "learn" a path then follow it in the contour mode.
Dual Loop
The dual-loop encoder feature enables the DMC to compensate for
backlash.There are two compensation methods: continuous dual
loop which performs the correction along the move; and sampled
dual loop which performs the correction at the final point.
In both cases, two encoders are used for each axis: one mount-
ed on the motor and the other on the load.The continuous dual
loop, which is activated with the instruction DV1, closes the posi-
tion loop with the load encoder and derives the damping terms
from the motor encoder.This method provides backlash compensa-
tion along the motion path.
INSTRUCTION
INTERPRETATION
#RECORD
Begin program to record
DM XPOS[501]
Dimension array
RA XPOS[]
Specify automatic data record
RD_TPX
Specify X position for capture
MOX
Turn motor off for teach
RC2
Begin recording every 4 msec
#A;JP#A,_RC=1
Wait until done recording
#COMPUTE
Compute program
DM DX[500]
Define new array
C=0
Initialize array counter
#L
Loop label
DX [C] = XPOS [C+1] -XPOS [C] Compute difference and store in array
C=C+1
Increment counter
JP #L,C<500
Loop until done
#PLAYBK
Playback program
SHX
Turn motor on
CMX
Contour mode on X
DT2
Specify time interval
I=0
Initialize array counter
#B
Loop label
CD DX[I];WC
Specify contour distance
I=I+1
Increment counter
JP #B,I<500
Loop until done
EN
End program
Example--Contouring
The sampled dual loop performs the correction at the end of the move,
as illustrated by the example. Consider a linear slide driven by a lead-
screw.The slide is equipped with a linear encoder having a resolution of
1 micron and a rotary encoder which provides 4 counts per micron.The
control method is to close the loop with the rotary encoder and monitor
the linear encoder by the auxiliary encoder input.To perform a move of
10,000 microns, the motor is driven 40,000 counts. Once the motion is
complete, the linear encoder is observed with the TD command and the
position error of the load is monitored.The motor is then required to per-
form a correction move.
INSTRUCTION
INTERPRETATION
#DUAL
Label
DE 0
Set load position to zero
PR 40000
Distance
BGX
Start first move
AMX
Wait for completion
WT 20
Wait for settling if necessary
PR 4*(10000-_TDX)
Correction move
BGX
Start correction
EN
End program
Example--Dual Loop
