PI M-403 2S Series, Руководство пользователя

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8 Glossary of Terms
ActiveDrive™ DC Motor
Some of the advantages of DC-motor drives are good dynamic performance,
fast response, high torque at low rpm, low heat dissipation and low vibration.
The cost of a high-performance amplifier, however, is generally higher than
that for a stepper motor.
The ActiveDrive™ system reduces this cost considerably, by integrating a
PWM (pulse width modulation) driver and amplifier in the motor case. This
design provides several advantages:
■
Increased efficiency, by eliminating power losses between the
amplifier and motor
■
Reduced cost, more-compact system, and improved reliability,
because no external driver and cabling are required
■
Elimination of PWM amplifier noise radiation by mounting the amplifier
and motor together in a single electrically shielded case
Positioning accuracy is assured with either rotary or optical linear encoders.
Backlash
Position error that appears upon reversing direction. Backlash is caused by
play in the drive train components coming after the encoder, such as
gearheads or bearings, and by friction in the guiding system. Unlike
hysteresis, it can lead to instability in closed-loop setups because it causes a
deadband in the servo-loop. Some manufacturers promote controllers with
automatic backlash compensation that add the estimated amount of lost
motion upon each reversal. This solution is very limited in practice, as
backlash is not constant but varies with temperature, deceleration,
acceleration, load, leadscrew position, direction, wear, etc.
Bidirectional Repeatability
The accuracy of returning to a position from any position, regardless of
direction. Effects such as hysteresis and backlash affect bidirectional
repeatability. See also "Unidirectional Repeatability".