Aerotech SOLOIST Hardware Manual page 99

Soloist Hardware Manual
Commutation, 6-Step
Commutation,
Modified 6-Step
Commutation, Sinusoidal
Coordinated Motion
Critical Speed
Current Command
Current, Peak
Current, rms
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Also referred to as trapezoidal commutation. The process
of switching motor phase current based on three Hall
effect signals spaced 120 electrical degrees beginning 30
degrees into the electrical cycle. This method is the
easiest for commutation of brushless motors.
Also referred to as modified sine commutation. The
process of switching motor phase current based on three
Hall effect signals spaced 120 electrical degrees
beginning at 0 electrical degrees. This method is slightly
more difficult to implement than standard 6-step, but
more closely approximates the motor's back emf. The
result is smoother control and less ripple. Aerotech's BA
series self-commutate using this method.
The process of switching motor phase current based on
motor position information, usually from an encoder. In
this method, the three phase currents are switched in very
small increments that closely resemble the motor's back
emf. Sinusoidal commutation requires digital signal
processing to convert position information into three-
phase current values and, consequently, is most
expensive to implement. The result, however, is the best
possible control. All Aerotech controllers, as well as the
BAS series amplifiers, commutate using this method.
Multi-axis motion where the position of each axis is
dependent on the other axis, such that the path and
velocity of a move can be accurately controlled. Drawing
a circle requires coordinated motion.
A term used in the specification of a lead screw or ball
screw indicating the maximum rotation speed before
resonance occurs. This speed limit is a function of the
screw diameter, distance between support bearings, and
bearing rigidity.
Motor driver or amplifier configuration where the input
signal is commanding motor current directly, which
translates to motor torque/force at the motor output.
Brushless motors can be commutated directly from a
controller that can output current phase A and B
commands.
An allowable current to run a motor above its rated load,
usually during starting conditions. Peak current listed on
a data sheet is usually the highest current safely allowed
to the motor.
Root Mean Square. Average of effective currents over an
amount of time. This current is calculated based on the
load and duty cycle of the application.
Glossary of Terms
A-3