Magnetic Bearings

Magnetic Bearing Sphere ShotAirex has experience in Magnetic Bearing Development for both Lorenz and Maxwell Actuators. These technologies have been combined with Motor Technology inin rotary configuration withinside or outside positioned rotors to meet varying customer requirements. We continue to develop our innovative application 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 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 micro-radian 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.

1. Advances in control and drive electronics have led to new levels of commercial potential for this technology. Wear and maintenance free bearings that include vibration isolation, enormous speed ranges and a wide range of load handling capabilities have potential in applications such as:

  • High End Machine Tools
  • Diamond Turning
  • High Speed Grinding
  • Mfg Process Equipment
  • Film and Web Handling Rolls
  • High Resolution Scanning/Imaging
  • Energy Storage (flywheels)
  • Power Generation

2. Space applications requiring vibration isolated, large payload capacities and extended maintenance-free life spans. The lack of friction and gravity in space results in endless vibrations that are easily radiated throughout the frame of the spacecraft. Higher efficiency components can reduce launch costs by lowering mass while increasing useful life and vibration resistance.

3. Satellite surveillance cameras on reconnaissance aircraft must be vibration isolated or compensated to secure clear pictures of target subjects. Airex has developed magnetic bearings for optical stabilization systems designed for use in aerospace applications where high reliability is required with maximum efficiency.

4. Missile guidance systems require very high levels of reliability and performance. Higher efficiency components minimize power requirements and increase the percentage of hits on target. Airex provides electromagnetic system components to major suppliers of Aerospace guidance systems.

Airex is designing systems similar to those described above and continuing development in this critical technology to further enhance the applicability and commercial potential of this technology. These projects combined with associated development activities provide a baseline for the technology and an exceptional opportunity to advance the state-of-the-art. This work exemplifies the importance of technology development in small business.