Motion Smoothing; Using The It And Vt Commands (S Curve Profiling) - Galil Motion Control DMC-18 2 Series User Manual

spx=_SPX
#LOOP;
SP2048;
WT100;
JP#END,@ABS[_QSX]<10;'END CORRECTION IF ERROR IS WITHIN DEFINED
YRX=_QSX;
MCX
WT100;
JP#LOOP;
#END;
SPX=spx
EN

Motion Smoothing

The DMC-18x2 controller allows the smoothing of the velocity profile to reduce mechanical vibrations
in 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 (S curve profiling):

When operating with servo motors, motion smoothing can be accomplished with the IT and VT
commands. These commands filter the acceleration and deceleration functions to produce a smooth
velocity profile. The resulting velocity profile, known as S curve, has continuous acceleration and
results in reduced mechanical vibrations.
The smoothing function is specified by the following commands:
IT x,y,z,w
VT n
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
DMC-18x2
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'SAVE SPEED VALUE
'SET A NEW SLOW CORRECTION SPEED
'STABILIZE
'TOLERANCE
'CORRECTION MOVE
'STABILIZE
'KEEP CORRECTING UNTIL ERROR IS WITHIN 'TOLERANCE
'END #CORRECT SUBROUTINE, RETURNING TO CODE
Independent time constant
Vector time constant
Chapter 6 Programming Motion • 101