Aerotech UNIDEX 600 Series, User Manual

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Parameters U600 User’s Guide
C-10
Aerotech, Inc.
Version 1.4
The gantry mode utilizes the AuxVelCmd axis parameter for commanding motion on
the slave axis, so it should not be used while the gantry mode is active.
This parameter does not change the velocity command; it integrates the auxiliary
velocity command into the position command.
The AUXVELCMD can be useful, for example, when tracing an X-Y pattern on a part
that is moving on a conveyor belt, when the X-Y stages are not moving with the conveyor
belt.
C.2.14. AVGVEL
The controller maintains a read-only parameter called AVGVEL that reports the average
velocity for a given axis. This average has no effect on the operation of the controller, but
is maintained for the benefit of the application program. The AVGVELTIME parameter
specifies the time period to average the velocity over. The units for this parameter are
counts per millisecond.
C.2.15. AVGVELTIME
The AVGVELTIME axis parameter specifies the time period over which to average the
velocity when calculating the value of the AVGVEL axis parameter and the AvgVelUnits
machine parameter. It is in units of milliseconds. However, this parameter is only used to
the next lowest multiple of 10 milliseconds. For example, a value of 12 or 19 is
equivalent to a value of 10. See the AVGVEL axis parameter for more details.
C.2.16. B0/B1/B2/A1/A2
These axis parameters may be used to eliminate instabilities within the servo loop due to
electrical or mechanical oscillations. These instabilities must first be identified. These
axis parameters implement a generic second order digital filter to the torque command in
the following form:
Y(Z) / X(Z) = ((B0 + B1 * Z
-1
+ B2 *Z
-2
) * 8192) / ((A0 + A1 * Z
-1
+ A2 * Z
-2
) * 8192)
Where Z
-1
is the delay operator, A0 is always 1, and the sampling frequency is the current
servo loop update rate (typically 4 kHz). Since A0 is always assumed to be 1, there is no
corresponding axis parameter. These parameters are only used in torque loop configured
axes. Setting B0=B1=4,096 will provide the minimal amount of filtering.
You must disable the axis before entering the filter constants.
If this filter is used in conjunction with the GANTRYMODE, it must be applied to
the master and slave axes.