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DMC-1700/1800 Chapter 6 Programming Motion • 127
PR 40000 Main move
BGX Start motion
#Correct Correction loop
AMX Wait for motion completion
V1=10000-_DEX Find linear encoder error
V2=-_TEX/4+V1 Compensate for motor error
JP#END,@ABS[V2]<2 Exit if error is small
PR V2*4 Correction move
BGX Start correction
JP#CORRECT Repeat
#END
EN
Motion Smoothing
The DMC-1700/1800 controller allows the smoothing of the velocity profile to reduce the mechanical vibration of
the system.
Trapezoidal velocity profiles have acceleration rates which change abruptly from zero to maximum value. The
discontinuous acceleration results in jerk which causes vibration. The smoothing of the acceleration profile leads to
a continuous acceleration profile and reduces the mechanical shock and vibration.
Using the IT and VT Commands:
When operating with servo motors, motion smoothing can be accomplished with the IT and VT
command. These commands filter the acceleration and deceleration functions to produce a smooth
velocity profile. The resulting velocity profile, has continuous acceleration and results in reduced
mechanical vibrations.
The smoothing function is specified by the following commands
:
IT x,y,z,w Independent time constant
VT n Vector time constant
The command, IT, is used for smoothing independent moves of the type JG, PR, PA and the command, VT, is used
to smooth vector moves of the type VM and LM.
The smoothing parameters, x,y,z,w and n are numbers between 0 and 1 and determine the degree of filtering. The
maximum value of 1 implies no filtering, resulting in trapezoidal velocity profiles. Smaller values of the smoothing
parameters imply heavier filtering and smoother moves.
The following example illustrates the effect of smoothing. Fig. 6.7 shows the trapezoidal velocity profile and the
modified acceleration and velocity.
Note that the smoothing process results in longer motion time.
Example - Smoothing
PR 20000 Position
AC 100000 Acceleration
DC 100000 Deceleration
SP 5000 Speed
IT .5 Filter for smoothing
BG X Begin