SEARCH · Search NASA

Results for “MAGNETIC BEARINGS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9

All sources NASA NTRS DOE OSTI

NASA NTRS1996

Development of Y-Ba-Cu-O Superconductors for Magnetic Bearings

The material requirements, material manufacturing and magnetic properties that are relevant to fabrication of High Temperature Superconductor (HTS) magnetic bearings have been discussed. It is found that the seeded-melt-texturing method can be used to fabricate the single domain material that is required to achieve the best magnetic properties. Trapped-field mapping has been used as a non-destructive tool to determine the single-domain nature of the HTS material and quantity of the HTS disks. Both the trapped field and the levitation force of the Y-Ba-Cu-O disks are found to be strongly sensitive to the oxygen content.

Selvamanickam, V.↗

NASA NTRS1992

Stiffness of magnetic bearings subjected to combined static and dynamic loads

This paper investigates the stiffness of a magnetic bearing that is subjected to the combined action of static and dynamic loads. Since their sum cannot exceed the saturation load, a large static load will imply that the bearing can carry only a small dynamic load. This smaller dynamic load together with the practical vibration amplitude define a practical upper bound to the dynamic stiffness. This paper also presents approximate design formulas and curves for this stiffness capacity as a function of the ratio of dynamic and static loads. In addition, it indicates that vibrations larger than a certain gap fraction can destabilize the magnetic bearing. This gap fraction, called the critical gap fraction, depends on the dynamic and static load ratio. For example, if the dynamic load is half of the static load, the use of more than 25 percent of gap can destabilize the bearing.

Rao, D. K.↗

NASA NTRS1992

Force analysis of magnetic bearings with power-saving controls

Most magnetic bearing control schemes use a bias current with a superimposed control current to linearize the relationship between the control current and the force it delivers. For most operating conditions, the existence of the bias current requires more power than alternative methods that do not use conventional bias. Two such methods are examined which diminish or eliminate bias current. In the typical bias control scheme it is found that for a harmonic control force command into a voltage limited transconductance amplifier, the desired force output is obtained only up to certain combinations of force amplitude and frequency. Above these values, the force amplitude is reduced and a phase lag occurs. The power saving alternative control schemes typically exhibit such deficiencies at even lower command frequencies and amplitudes. To assess the severity of these effects, a time history analysis of the force output is performed for the bias method and the alternative methods. Results of the analysis show that the alternative approaches may be viable. The various control methods examined were mathematically modeled using nondimensionalized variables to facilitate comparison of the various methods.

Johnson, Dexter↗

DOE OSTI2019

Halbach-array levitating passive magnetic bearing configuration

Novel configurations of levitating passive magnetic bearing configurations are described. Such configurations can be used for the precise control of the magnitude and sign of the bearing stiffness, thereby facilitating the overall design of the system in ways that are not possible with conventional attractive or repelling bearing elements.

42 ENGINEERING↗

DOE OSTI2020

Halbach-array levitating passive magnetic bearing configuration

Post, Richard F.↗

NASA NTRS2002

A Comparison Study of Magnetic Bearing Controllers for a Fully Suspended Dynamic Spin Rig

NASA Glenn Research Center (GRC) has developed a fully suspended magnetic bearing system for the Dynamic Spin Rig (DSR) that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteropolar radial magnetic bearings and a thrust bearing and the associated control system were integrated into the DSR to provide noncontact magnetic suspension and mechanical excitation of the 35 lb vertical rotor with blades to induce turbomachinery blade vibration. A simple proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked very well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, and energy savings for the system. The test results of a variety of controllers we demonstrated up to the rig's maximum allowable speed of 10,000 rpm are shown.

Choi, Benjamin↗

NASA NTRS1990

Digital control of magnetic bearings in a cryogenic cooler

This paper describes the design of a digital control system for control of magnetic bearings used in a spaceborne cryogenic cooler. The cooler was developed by Philips Laboratories for the NASA Goddard Space Flight Center. Six magnetic bearing assemblies are used to levitate the piston, displacer, and counter-balance of the cooler. The piston and displacer are driven by linear motors in accordance with Stirling cycle thermodynamic principles to produce the desired cooling effect. The counter-balance is driven by a third linear motor to cancel motion induced forces that would otherwise be transmitted to the spacecraft. An analog control system is currently used for bearing control. The purpose of this project is to investigate the possibilities for improved performance using digital control. Areas for potential improvement include transient and steady state control characteristics, robustness, reliability, adaptability, alternate control modes, size, weight, and cost. The present control system is targeted for the Intel 80196 microcontroller family. The eventual introduction of application specific integrated circuit (ASIC) technology to this problem may produce a unique and elegant solution both here and in related industrial problems.

Feeley, J.↗

NASA NTRS1981

A microprocessor-based table lookup approach for magnetic bearing linearization

An approach for producing a linear transfer characteristic between force command and force output of a magnetic bearing actuator without flux biasing is presented. The approach is microprocessor based and uses a table lookup to generate drive signals for the magnetic bearing power driver. An experimental test setup used to demonstrate the feasibility of the approach is described, and test results are presented. The test setup contains bearing elements similar to those used in a laboratory model annular momentum control device.

Groom, N. J.↗

NASA NTRS1996

Approach to Synchronization Control of Magnetic Bearings Using Fuzzy Logic

This paper presents a fuzzy-logic approach to the synthesis of synchronization control for magnetically suspended rotor system. The synchronization control enables a whirling rotor to undergo synchronous motion along the magnetic bearing axes; thereby avoiding the gyroscopic effect that degrade the stability of rotor systems when spinning at high speed. The control system features a fuzzy controller acting on the magnetic bearing device, in which the fuzzy inference system trained through fuzzy rules to minimize the differential errors between four bearing axes so that an error along one bearing axis can affect the overall control loop for the motion synchronization. Numerical simulations of synchronization control for the magnetically suspended rotor system are presented to show the effectiveness of the present approach.

Yang, Li-Farn↗

DOE OSTI2016

Study on fault diagnosis system of active magnetic bearing - 18549

The three main mechanical faults of the active magnetic bearing (AMB) system are put forward and distinguished from the electrical faults. Their mechanism is elaborately investigated and the quantitative relationship between failures and consequent extra forces acting on the rotors is identified. The principles for fault recognition are determined on the basis of the fault mechanism and operating experience in conventional rotating machinery. Fault features extraction methods including Poincare Map and Fast Fourier Transformation and other algorithm are adopted. A practical fault diagnosis system based on the LabVIEW platform is realized. The test result demonstrates the effectiveness of the fault diagnosis system in on-line detection and identification of mechanical faults in AMB systems. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

NASA NTRS1992

Wide gap, permanent magnet biased magnetic bearing system

The unique features and applications of the presented electrical permanent magnetic bearing system essentially result from three facts: (1) the only bearing rotor components are nonlaminated ferromagnetic steel collars or cylinders; (2) all radial and axial forces are transmitted via radial gaps; and (3) large radial bearing gaps can be provided with minimum electric power consumption. The large gaps allow for effective encapsulation and shielding of the rotors at elevated or low temperatures, corrosive or ultra clean atmosphere or vacuum or high pressure environment. Two significant applications are described: (1) a magnetically suspended x ray rotary anode was operated under high vacuum conditions at 100 KV anode potential, 600 C temperature at the rotor collars and speed 18000 rpm with 13 mm radial bearing gap; and (2) an improved Czochralski type crystal growth apparatus using the hot wall method for pulling GaAs single crystals of low dislocation density. Both crystal and crucible are carried and transported by magnetically suspended shafts inside a hermetically sealed housing at 800 C shaft and wall temperature. The radial magnetic bearing gap measures 24 mm.

Boden, Karl↗

NASA NTRS1988

Magnetic bearings for an optical disk read/write head

A program is described whose aim is to establish the technical feasibility of developing magnetic bearings for an optical disk buffer for use in a spacecraft environment. The approach taken was to develop the specifications for the magnetic bearings and define the hardware configuration, controller characteristics, position sensors, and electronic functions required.

Hockney, Richard↗

NASA NTRS1990

Improved operation of magnetic bearings for flywheel energy storage system

Analysis and operation of prototype 500-Wh flywheel at low speeds have shown that many factors affect the correct functioning of the magnetic bearings. An examination is made of a number of these, including magnetic bearing control system nonlinearities and displacement transducer positioning, and their effects upon the successful operation of the suspension system. It is observed that the bearing control system is extremely sensitive to actuator parameters such as coil inductance. As a consequence of the analysis of bearing relaxation oscillations, the bearing actuator design methodology which has previously been used, where coil parameter selection is based upon static considerations, has been revised. Displacement transducer sensors which overcome the collocation problem are discussed.

Zmood, R. B.↗

NASA NTRS1985

Active magnetic bearings for optimum turbomachinery design

The design and shop test results are given for a high speed eight stage centrifugal compressor supported by active magnetic bearings. A brief summary of the rotor dynamics analysis is presented with specific attention given to design considerations for optimum rotor stability. The concerns for retrofit of magnetic bearings in existing machinery are discussed with supporting analysis of a four stage centrifugal compressor. Recommendations are given on design and analysis requirements for successful machinery operation of either retrofit or new design turbomachinery.

Hustak, J.↗

NASA NTRS1973

Design and development of a momentum wheel with magnetic bearings

An engineering model momentum wheel with radial magnetic bearings has been designed and developed and successfully operated to a speed of approximately 500 rad/sec. This speed corresponds to a maximum angular momentum of 83 Nm-sec which is 83% of the design value. The maximum momentum achieved was limited by the suspension servo bandwidth and this, in turn, was limited by the lowest structural resonance of the rotor.

Veillette, L. J.↗

NASA NTRS1978

Magnetic bearings for instruments in the space environment

A magnetic bearing development is documented, which has been successfully applied to support a 0.9 kg - 19 cm diameter rotor in 5 degrees of freedom, with fully controlled drive capability to plus or minus 200 rad/s in the other axis. The construction details are described and illustrated. Performance data on five design variations are presented which extend the load capacity to 8 kilograms at which point the bearing element on the rotor is less than one-half of 1 percent of the total load capacity.

Studer, P. A.↗

NASA NTRS1989

Magnetic bearing stiffness control using frequency band filtering

Active magnetic bearings can be implemented with frequency band-reject filtering that decreases the bearing stiffness and damping at a small bandwidth around a chosen frequency. The control scheme was used for reducing a rotor dynamic force, such as an imbalance force, transmitted to the bearing stator. The scheme creates additional system vibration modes at the same frequency. It also shows that the amount of force reduction is limited by the stability requirement of these modes.

Chen, H. Ming↗

NASA NTRS1987

Magnetic bearings for inertial energy storage

Advanced flywheels utilizing high strength fibers must operate at high rotational speeds and as such must operate in vacuum to reduce windage losses. The utilization of magnetic bearings in the flywheels overcome lubrication and seal problems, resulting in an energy storage system offering potential improvements over conventional electrochemical energy storage. Magnetic bearings evolved in the 1950s from the simple application of permanent magnets positioned to exert repulsive forces to the present where permanent magnets and electromagnets have been combined to provide axial and radial suspension. Further development of magnetic suspension has led to the design of a shaftless flywheel system for aerospace application. Despite the lack of proof of concept, integrated magnetic suspension in inertial storage systems can provide significant performance improvements to warrant development and tests.

Rodriguez, G. Ernest↗