76 • Chapter 6 Programming Motion DMC-1000
GR Set gear ratio for gearing - the auxiliary encoder input can be used for gearing
TD Tell dual (auxiliary) encoder input position.
Operand Summary - Using the Auxiliary Encoder
OPERAND DESCRIPTION
_CEx Contains the encoder configuration for the specified axis
_DEx Contains the current position of the specified auxiliary encoder
_DVx Contains a '1' or '0' if the specified axis is in continuous dual loop operation.
_GRx Contains the value of the gear ratio for the specified axis
_TDx Contains the position of the specified auxiliary encoder.
Motion Smoothing
The DMC-1000 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 (S curve profiling):
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, 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 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. 6.6 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
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