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70 • Chapter 6 Programming Motion DMC-2X00
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 a,b,c,d 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, a,b,c,d 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. 6.9 shows the trapezoidal velocity
profile and the modified acceleration and velocity.
Note that the smoothing process results in longer motion time.
Example
Instruction Interpretation
PR 20000 Position
AC 100000 Acceleration
DC 100000 Deceleration
SP 5000 Speed
IT .5 Filter for smoothing
BG A Begin