Xenus Plus User Guide
16-01344 Rev 06
Copley Controls
24
Velocity Loop Gains
The velocity loop uses these gains:
Gain
Description
Vp - Velocity loop proportional
The velocity error (the difference between the actual and the limited commanded
velocity) is multiplied by this gain. The primary effect of this gain is to increase
bandwidth (or decrease the step-response time) as the gain is increased.
Vi - Velocity loop integral
The integral of the velocity error is multiplied by this value. Integral gain reduces
the velocity error to zero over time. It controls the DC accuracy of the loop, or the
flatness of the top of a square wave signal. The error integral is the accumulated
sum of the velocity error value over time.
Velocity Gains Shift
The Velocity Gains Shift feature adjusts the resolution of the units used to express Vp and Vi,
providing more precise tuning. If the non-scaled value of Vp or Vi is 64 or less, the Low Gains Shift
option is available to increase the gains adjustment resolution. (Such low values are likely to be
called for when tuning a linear motor with an encoder resolution finer than a micrometer.) If the non-
scaled value of Vp or Vi is 24001 or higher, the High Gains Shift option is available to decrease the
gains adjustment resolution.
Velocity Loop Command and Output Filters
The velocity loop contains two programmable digital filters. The input filter should be used to reduce
the effects of a noisy velocity command signal. The output filter can be used to reduce the excitation
of any resonance in the motion system.
Two filter classes can be programmed: the Low-Pass and the Custom Bi-Quadratic. The Low-Pass
filter class includes the Single-Pole and the Two-Pole Butterworth filter types. The Custom Bi-
Quadratic filter allows advanced users to define their own filters incorporating two poles and two
zeros. For more information on the velocity loop filters, see the
CME User Guide
.
Velocity Loop Outputs
The output of the velocity loop is a current command used as the input to the current loop.
Summary of Contents for XEL-230-18
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