Appendix A
BA Intellidrive User’s Manual
A-4
Aerotech, Inc.
Version 1.4
position error - Position error is the difference between the commanded position of an
axis and the feedback position (i.e., the difference between the desired position and the
actual position). A position error fault occurs if the current position error exceeds a
programmable maximum position error. Position error is measured in machine steps.
proportional gain - Proportional gain is a dimensionless motor tuning parameter that
produces an output which is related to the Velocity Error in the servo loop.
pull-down menu - A pull-down menu is a vertical list of commands. When the menu is
closed (or “rolled up”), only the menu name is visible on the menu bar. When the menu
name is selected, the menu “unrolls” and the list of commands is displayed. Some options
in pull-down menus are the names of other menus (called cascading menus).
quadrature - Quadrature is the state of two signals that are displaced 90 degrees with
respect to each other. In most rotary incremental optical encoders, light (from an LED,
for example) is measured after it is passed through slits in a grating disk (which is
attached to the axis being measured). Typically, two tracks on the disk have their gratings
displaced 90 degrees with respect to each other (that is, the tracks are said to be in
quadrature).
resolver - A resolver is a two-phase, rotary, electromagnetic transducer in which
inductive coupling (between the rotor and stator windings) and trigonometric principles
are employed to provide absolute position information over one electrical cycle (which is
one revolution for "single-step" resolvers)
RMS current trap - RMS current trap is an error that occurs if the current being
commanded to a motor exceeds a programmable limit (see parameters x48 and x49).
RMS current trap is analogous to a software “fuse”. Essentially, this fault functions the
same as a physical fuse, but is done through software. One obvious advantage is that a
“software fuse” does not have to be replaced like a physical fuse.
software - The term software refers to a computer program. Contrast software with
hardware, the physical machinery, components and support peripherals through which the
software runs.
traps -See faults.
tuning - Tuning is the process of optimizing the operation of a servo system.
velocity error - Velocity error is the difference between the commanded velocity and the
velocity derived from the feedback position (i.e., the difference between the desired
velocity and the actual velocity). Velocity error is measured in machine steps per quarter
millisecond (machine steps/qms). A velocity error fault occurs if, at any time, the
velocity error of the system exceeds a programmable velocity error.
velocity feed forward - Velocity feed forward is a control strategy (represented as a
dimensionless gain value that is sometimes used during the motor tuning process) in
which current velocity disturbances are converted into corrective actions now in order to
minimize the future effects of the disturbances.
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