Aerotech BM Series, Hardware Manual

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BM/BMS Series Hardware Manual Appendix A
www.aerotech.com A-1
APPENDIX A: GLOSSARY OF TERMS
Abbe Error
The positioning error resulting from angular motion and an offset
between the measuring device and the point of interest.
Abbe Offset
The value of the offset between the measuring device and the
point of interest.
Absolute Move
A move referenced to a known point or datum.
Absolute Programming
A positioning coordinate reference where all positions are
specified relative to a reference or “home” position.
AC Brushless Servo
A servomotor with stationary windings in the stator assembly
and permanent magnet rotor. AC brushless generally refers to a
sinusoidally wound motor (such as BM series) to be commutated
via sinusoidal current waveform. (see DC brushless servo)
Acceleration
The change in velocity as a function of time.
Accuracy
An absolute measurement defining the difference between
actual and commanded position.
Accuracy Grade
In reference to an encoder grating, accuracy grade is the
tolerance of the placement of the graduations on the encoder
scale.
ASCII
American Standard Code for Information Interchange. This code
assigns a number to each numeral and letter of the alphabet.
Information can then be transmitted between machines as a
series of binary numbers.
Axial Runout
Positioning error of the rotary stage in the vertical direction when
the tabletop is oriented in the horizontal plane. Axial runout is
defined as the total indicator reading on a spherical ball
positioned 50 mm above the tabletop and centered on the axis
of rotation.
Axis of Rotation
A centerline about which rotation occurs.
Back emf, Kemf
The voltage generated when a permanent magnet motor is
rotated. This voltage is proportional to motor speed and is
present whether or not the motor windings are energized.
Backlash
A component of bidirectional repeatability, it is the non-
responsiveness of the system load to reversal of input
command.
Ball Screw
A precision device for translating rotary motion into linear
motion. A lead screw is a low-cost lower performance device
performing the same function. Unit consists of an externally
threaded screw and an internally threaded ball nut.
Ball Screw Lead
The linear distance a carriage will travel for one revolution of the
ball screw (lead screw).
Bandwidth
A measurement, expressed in frequency (hertz), of the range
which an amplifier or motor can respond to an input command
from DC to -3dB on a frequency sweep.
Baud Rate
The number of bits transmitted per second on a serial
communication channel such as RS-232 or modem.
BCD
Binary Coded Decimal - A number system using four bits to
represent 0-F (15).