 Airex has experience in magnetic bearing development
in both Lorenz and Maxwell actuators. These
technologies have
been combined with toothless motor technology in rotary configuration and
inside or outside positioned rotors to meet varying customer requirements. We
continue to develop our innovative applications of Lorenz actuators to linear
systems and our goal is to remain at the forefront of this technology.
Applications are becoming more common for cost effective, magnetic bearing
platforms in both DoD and commercial environments.
 Among
the magnetic bearing designs we have demonstrated is the test rig assembly
shown below consisting of a single, vertical, motor-bearing. This bearing
supports an optical table upon which is mounted a receiving telescope. The
sending source (mounted on a one meter radius arc) has the capability to move
or oscillate on the arc. The receiving telescope will track the laser source at
a tracking rate target of 28.6 degrees per second and a slew rate of 100
revolutions per minute. Six microradian pointing accuracy is obtained by virtue
of the Lorentz motor-bearing design, which provides extremely low cogging
rotation and 0.018 inch (operational) radial clearance. The thrust bearing has
0.020" axial movement. These clearances facilitate three axes precision
movement control and vibration isolation. Fault tolerance is accomplished in
the Lorentz design through coil redundancy and control algorithms.
 Airex constructed and tested the first spherical
motor-bearing system in the United States. This four-band, electromagnetic
gimbal provides two rotational and three translational degrees of freedom
positioning for a payload of 300 lb/ft2, azimuth and elevation excursions of
+/-10°, a slew rate of 0.40°/ sec. and positioning error of less than
0.008°. Leading a team of national research laboratories and world-renowned
universities, the combination motor-bearing system is the first in the nation
to demonstrate capabilities for toothless, integrated motor-bearing operation.
The proof-of-concept rig built by Airex demonstrates high accuracy pointing for
space-based inter-satellite cross-links used in laser communications. The rig
provides for measurement of bearing function dynamic and static stiffness,
loaded and unloaded static torque, loaded and unloaded pointing accuracy and
slew rate.
This experimental rig also allows testing of fault
tolerant and vibration isolation algorithms developed by Louisiana State
University. Fault tolerance describes the ability of the device to provide
continuous functionality in spite of multiple coil or amplifier failures
through the use of sophisticated digital control algorithms. Vibration
isolation describes the ability of the rig to alter the dynamic compliance of
the payload relative to the platform. The ability to control vibration provides
an inherent advantage to magnetic suspension systems over the more conventional
mechanical approach. This research and development provides the perfect model
for design and test of integrated linear or rotary systems.
Airex has tested the first complete integrated, toothless
rotary motor-bearing for an acquisition sensor in a precise angular positioning
requirement. The illustration shows the proof-of-concept rig developed by Airex
and the University of Kentucky. It features a full 60° pointing range about
the major axis and micro-angular positioning about the transverse axis using an
Airex toothless motor and two radial magnetic bearings. The rig can be run in
varied configurations to demonstrate key technologies. These technologies
include electronic alignment, toothless self-bearing motor function and fault
tolerance. Although separate radial bearings are provided on the test rig, the
toothless motor is designed for demonstration of integrated bearing features.
Low power consumption is established from the results of this testing.
The
commercial benefit
of our work in magnetic bearings includes the innovative development of a fully
integrated gimbal system with integral motor-bearing functions to replace
mechanical gimbals. This technology is considered useful in DoD or commercial
satellite tracking, antenna pointing and inter-satellite cross-links. In space
applications, this electromagnetic design provides inherent vibration
isolation, eliminates the need for lubricants (that can fog delicate on-board
sensors or reduce operational life) and provides exceptional pointing accuracy.
It is also useful in ground-based systems such as portable communication up
links, shipboard systems or satellite tracking.
With increasing
potential for future applications, the development of gimbal design and
manufacturing capabilities has substantially impacted several programs as
discussed below. |
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