GTX Series Actuator Installation & Maintenance Instructions |
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2.0 SYSTEM CONFIGURATION
2.1 GTX SERIES ACTUATOR
GTX Series actuators provide a robust solution for long-life,
continuous-duty applications even when environmental con-
taminants are an issue. In most rotary-to-linear devices, critical
mechanisms are exposed to the environment and must be
frequently inspected, cleaned and lubricated. In contrast, GTX
Series actuators are designed with all converting components
mounted within sealed motor housings. With a simple bushing
and seal on the smooth extending rod, abrasive particles or
other contaminants are prevented from reaching the actuator’s
critical mechanisms. As a result, actuator life can exceed that of
a ball screw actuator by 15 times, even in high-speed, high-
force applications.
2.2 OPTIONS
2.2.1 Servomotor Amplifiers
GTX Series actuators function in the same manner as a brush-
less servomotor. A brushless servo motor amplifier is used to
rotate the motor for a controlled number of revolutions and
move times at controlled speed and torque. This rotary motion
is translated into linear motion by the GTX Series actuator’s
internal planetary roller screw mechanism.
2.2.2 Feedback Devices
Feedback device selection is dictated by the amplifier used to
operate the actuator. Each amplifier has specific requirements
for motor feedback. Standard GTX Series actuators use either
a 2-pole resolver or quadrature incremental encoder as their
primary feedback device.
2.2.3 Resolvers
A resolver is a non-electronic device that functions similarly to
a small transformer. When rotated, the resolver generates two
sine waves that are out of phase with one another. By decoding
these two sine waves, the amplifier can monitor the motor direc
-
tion, revolutions traveled, and speed of rotation. Each sine wave
typically represents one revolution of the motor. The amplifier
uses these signals to identify where the motor is within that
revolution and properly time the supply of current and voltage
to the motor for it to rotate. This process is known as “com-
mutation”. For the amplifier to properly commutate the motor, it
must have a reference (or “zero”) point from which to track the
motor’s rotation.
IMPORTANT!
The zero point is critical and is provided to the
amplifier through the proper alignment of the resolver to the
phases of the motor during the actuator assembly.
NOTE
: Not
all resolver-based amplifiers can use the same resolver, resolver
alignment, or relative direction of resolver rotation.
2.2.4 Encoders
An incremental encoder is an electronic rotary device that
transmits a string of electrical pulses when rotated to measure
position. A quadrature encoder (or “incremental rotary encoder”)
measures the speed and direction of a rotating shaft. Most
brushless motor or servo systems with incremental encoders
use a quadrature encoder.
NOTE:
Not all encoder-based am-
plifiers can use the same encoder, encoder alignment or relative
direction of encoder rotation.
2.2.5 Internal Holding Brake
Many applications require the addition of a holding brake. The
Exlar internal holding brake is engaged by a permanent-magnet.
The mechanical advantage of the roller screw allows the holding
brake to prevent the output rod from back-driving the load. The
holding capacity of the brake is sufficient to hold the rated force
of the actuator.
2.2.6 Anti-Rotation Assembly
The unique design of GTX Series actuators helps simplify ac-
tuator setup by allowing the user to rotate the extending rod and
thread it in and out of the actuator for mechanical attachment
or system testing. In most applications, the load is coupled to
linear bearings or some other support device, preventing rota-
tion during operation. To ensure proper linear motion in applica-
tions in which the rod is free to rotate, an Anti-Rotate Assembly
is required to prevent the rod from rotating.
2.2.7 External Limit Switch
A GTX Series actuator equipped with the anti-rotate and limit
switch options can accommodate multiple limit switches for use
as end-of-travel limit switches or home position sensors posi-
tioned outside the low-profile extruded channel housing.
