Force Measurements in Magnetic Bearings Using Fiber Optic Strain Gauges

2001 ◽  
Author(s):  
Stephen G. Raymer ◽  
Dara W. Childs
Keyword(s):  
Fiber Optic ◽  
Reaction Force ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Strain Gauges ◽  
Rotordynamic Coefficients ◽  
Precise Knowledge ◽  
Accuracy And Precision ◽  
Force Components ◽  
And Performance

A new method for measuring forces in magnetic bearings is presented. Fiber-optic strain gauges (FOSGs) mounted to the side of the magnet poles are used to detect the small levels of strain that the metal experiences as the bearing exerts a force. These strains can be converted into force components, providing measurements with a previously unattainable level of accuracy and precision. Tests were done using the Magnetic Bearing Test Rig at the Texas A&M University Turbomachinery Laboratory. Two FOSGs were placed approximately 90° apart on two separate poles of one of the bearings, and the strain levels for different load magnitudes and directions were measured. The raw signal has several undesirable attributes that prevent an accurate static measurement. However, dynamic measurements proved to be very effective in the frequency domain, as most of the noise in the signal is confined to frequencies below 1 Hz. Due to the raw signal characteristics, new techniques for load application and calibration were developed. By using these new approaches, an equation relating reaction force components and strain was generated. This equation provides precise knowledge of any force vector in the bearing. An uncertainty analysis was performed on the resulting equation, providing a measure of resolution and a reduction in error several times more precise than any previous result. As a result of these findings, magnetic bearings can now be used to perform precise diagnostic analysis, determine rotordynamic coefficients, and improve magnetic bearing design and performance.

Fiber-Optic Strain Gauge Calibration and Dynamic Flexibility Transfer Function Identification in Magnetic Bearings

2005 ◽  
Author(s):  
Zachary S. Zutavern ◽  
Dara W. Childs
Keyword(s):  
Finite Element ◽  
Strain Gauge ◽  
Electromagnetic Interference ◽  
Fiber Optic ◽  
Transfer Functions ◽  
Magnetic Bearings ◽  
Strain Gauges ◽  
Force Measurements ◽  
Limited Success ◽  
Gyroscopic Coupling

Historical attempts to measure forces in magnetic bearings (MBs) have experienced limited success as a result of relatively high uncertainties. Recent advances in strain-gauge technology have provided a new method for measuring MB forces. Fiberoptic strain gauges (FOSGs) are roughly 100 times more sensitive than conventional strain gauges and are not affected by electromagnetic interference. At the Texas A&M University (TAMU) Turbomachinery Laboratory, installing FOSGs in MBs has produced force measurements with low uncertainties. Dynamic flexibility transfer functions (DFTFs) exhibiting noticeable gyroscopic coupling have been identified and compared with finite element predictions. Comparison has verified the effectiveness of using MBs as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.

scholarly journals Gain-Scheduled Control of Asymmetric Thrust Magnetic Bearing

Actuators ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 329
Author(s):  
Shuyue Zhang ◽  
Jihao Wu
Keyword(s):  
Control Method ◽  
Magnetic Levitation ◽  
Structural Parameters ◽  
Response Speed ◽  
Magnetic Bearing ◽  
Structure Design ◽  
Magnetic Bearings ◽  
And Performance ◽  
The Cost ◽  
Gain Scheduled

The thrust position of the magnetic levitation rotor can be changed, bringing convenience to the practical application of cold compressors. This paper derives the mathematical model of asymmetric thrust magnetic bearings for a cold compressor and analyzes the changes in the system characteristics with the equilibrium position. By constructing PID controllers associated with the structural parameters of the magnetic bearing, the adaptive adjustment of the control parameters under different balanced position commands is realized. The simulation and experimental results prove that the gain-scheduled control method proposed in this paper can achieve a robust stability of the rotor in the range of 50 to 350 μm, and not at the cost of the response speed, adjustment time, and overshoot. The research results have reference significance for the structure design of asymmetric thrust magnetic bearings and play an important role in the commissioning and performance improvement of cold compressors.

On the evolution of passive magnetic bearings

2021 ◽  
pp. 1-50
Author(s):  
Pranab Samanta ◽  
Harish Hirani
Keyword(s):  
Bearing Capacity ◽  
Dynamic Behavior ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Reliable Operation ◽  
Load Bearing Capacity ◽  
Performance Characterization ◽  
Load Bearing ◽  
And Performance ◽  
Stiffness And Damping

Abstract The present work portrays the latest review of the progressive advances in passive magnetic bearing technology. Passive magnetic bearings are an old technology with many encouraging properties. However, there are a number of inherent issues with design, analysis, and performance characterization that must be considered for reliable operation. Finally, it examines in detail the geometrical configurations, load-bearing capacity, dynamic behavior and stability connected with stiffness and damping

Hybrid gas-magnetic bearings: An overview

2021 ◽  
pp. 1-26
Author(s):  
Qing Liu ◽  
Shiping Zhang ◽  
Yuanyuan Li ◽  
Gang Lei ◽  
Li Wang
Keyword(s):  
Numerical Simulations ◽  
Control Systems ◽  
State Of The Art ◽  
Rotor Dynamics ◽  
Magnetic Bearing ◽  
Performance Characteristics ◽  
Magnetic Bearings ◽  
Reliable Operation ◽  
Future Developments ◽  
And Performance

This paper presents a state-of-the-art survey on the development of the hybrid gas-magnetic bearing (HGMB) technology. HGMBs are proposed to complement the advantages of gas bearings and magnetic bearings for enhanced bearing performance. Nevertheless, there are a number of inherent challenges in their designs, analyses, and performance characteristics that must be taken into account for proper functionality and reliable operation. For this purpose, substantial results in theory, numerical simulations, and experiments concerning rotor dynamics, mechanical structures, control systems, and operation modes are discussed to help further investigation and implementation of HGMBs. In addition, future developments of HGMBs in industries and remaining challenges are discussed.

scholarly journals A Vibration Sensor-Based Method for Generating the Precise Rotor Orbit Shape with General Notch Filter Method for New Rotor Seal Design Testing and Diagnostics

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5249
Author(s):  
Karel Kalista ◽  
Jindrich Liska ◽  
Jan Jakl
Keyword(s):  
Notch Filter ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Harmonic Vibration ◽  
Filter Method ◽  
Vibration Exciter ◽  
Active Magnetic Bearings ◽  
Rotor Vibration ◽  
Seal Design ◽  
Exact Shape

Verification of the behaviour of new designs of rotor seals is a crucial phase necessary for their use in rotary machines. Therefore, experimental equipment for the verification of properties that have an effect on rotor dynamics is being developed in the test laboratories of the manufacturers of these components all over the world. In order to be able to compare the analytically derived and experimentally identified values of the seal parameters, specific requirements for the rotor vibration pattern during experiments are usually set. The rotor vibration signal must contain the specified dominant components, while the others, usually caused by unbalance, must be attenuated. Technological advances have made it possible to use magnetic bearings in test equipment to support the rotor and as a rotor vibration exciter. Active magnetic bearings allow control of the vibrations of the rotor and generate the desired shape of the rotor orbit. This article presents a solution developed for a real test rig equipped with active magnetic bearings and rotor vibration sensors, which is to be used for testing a new design of rotor seals. Generating the exact shape of the orbit is challenging. The exact shape of the rotor orbit is necessary to compare the experimentally and numerically identified properties of the seal. The generalized notch filter method is used to compensate for the undesired harmonic vibrations. In addition, a novel modified generalized notch filter is introduced, which is used for harmonic vibration generation. The excitation of harmonic vibration of the rotor in an AMB system is generally done by injecting the harmonic current into the control loop of each AMB axis. The motion of the rotor in the AMB axis is coupled, therefore adjustment of the amplitudes and phases of the injected signals may be tedious. The novel general notch filter algorithm achieves the desired harmonic vibration of the rotor automatically. At first, the general notch filter algorithm is simulated and the functionality is confirmed. Finally, an experimental test device with an active magnetic bearing is used for verification of the algorithm. The measured data are presented to demonstrate that this approach can be used for precise rotor orbit shape generation by active magnetic bearings.

Description and performance of a highly versatile, low‐cost fiber‐optic confocal Raman microscope

1996 ◽  
Vol 67 (1) ◽  
pp. 79-84 ◽  
Author(s):  
C. M. Stellman ◽  
K. S. Booksh ◽  
J. E. Reddic ◽  
M. L. Myrick
Keyword(s):  
Fiber Optic ◽  
Low Cost ◽  
Confocal Raman ◽  
And Performance

The closed-subpopulation method and estimation of population size from mark-recapture and ancillary data

2000 ◽  
Vol 78 (2) ◽  
pp. 320-326 ◽  
Author(s):  
Frank AM Tuyttens
Keyword(s):  
Population Size ◽  
Ancillary Data ◽  
Mark Recapture ◽  
Animal Populations ◽  
Accuracy And Precision ◽  
Population Size Estimates ◽  
Minimum Number ◽  
Flexible Framework ◽  
And Performance ◽  
Better Than

The algebraic relationships, underlying assumptions, and performance of the recently proposed closed-subpopulation method are compared with those of other commonly used methods for estimating the size of animal populations from mark-recapture records. In its basic format the closed-subpopulation method is similar to the Manly-Parr method and less restrictive than the Jolly-Seber method. Computer simulations indicate that the accuracy and precision of the population estimators generated by the basic closed-subpopulation method are almost comparable to those generated by the Jolly-Seber method, and generally better than those of the minimum-number-alive method. The performance of all these methods depends on the capture probability, the number of previous and subsequent trapping occasions, and whether the population is demographically closed or open. Violation of the assumption of equal catchability causes a negative bias that is more pronounced for the closed-subpopulation and Jolly-Seber estimators than for the minimum-number-alive. The closed-subpopulation method provides a simple and flexible framework for illustrating that the precision and accuracy of population-size estimates can be improved by incorporating evidence, other than mark-recapture data, of the presence of recognisable individuals in the population (from radiotelemetry, mortality records, or sightings, for example) and by exploiting specific characteristics of the population concerned.

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