Dynamic Analysis and Control of High Speed and High Precision Active Magnetic Bearings

1992 ◽  
Vol 114 (4) ◽  
pp. 623-633 ◽  
Author(s):  
K. Youcef-Toumi ◽  
S. Reddy
Keyword(s):  
Time Delay ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Successful Operation ◽  
Highly Nonlinear ◽  
Wide Range ◽  
And Control ◽  
Digital Time

The successful operation of actively controlled magnetic bearings depends greatly on the electromechanical design and control system design. The function of the controller is to maintain bearing performance in the face of system dynamic variations and unpredictable disturbances. The plant considered here is the rotor and magnetic bearing assembly of a test apparatus. The plant dynamics consisting of actuator dynamics, rigid rotor dynamics and flexibility effects are described. Various components of the system are identified and their corresponding linearized theoretical models are validated experimentally. Tests are also run to identify the coupling effects and flexibility modes. The highly nonlinear behavior of the magnetic bearings in addition to the inherent instability of such a system makes the controller design complex. A digital Time Delay Controller is designed and its effectiveness evaluated using several simulations based on linear and nonlinear models for the bearing including bending mode effects. This controller is implemented as an alternative to an existing linear analog compensator. Several experiments are conducted with each controller for spinning and nonspinning conditions. These include time responses, closed loop frequency responses and disturbance rejection responses. The experimental results and comparisons between those of a digital Time Delay Controller and an analog compensator indicate that the Time Delay Controller has impressive static and dynamic stiffness characteristics for the prototype considered. The Time Delay Controller also maintains almost the same dynamic behavior over a significantly wide range of rotor speeds.

Simultaneous Time-Frequency Control of Active Magnetic Bearing

2013 ◽  
Author(s):  
Meng-Kun Liu ◽  
C. Steve Suh
Keyword(s):  
Control Theory ◽  
High Speed ◽  
Frequency Control ◽  
Dynamic Stiffness ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Time Frequency ◽  
Highly Nonlinear ◽  
Nonlinear Character ◽  
On Line

Active magnetic bearings enable greater spindle dynamic stiffness through higher attainable bearing surface speeds. However, the active magnetic bearing system is highly nonlinear due to the interaction between electromagnetic field and rotor dynamics. Its nonlinear character becomes prominent when rotating in high speed. The operation undergoes route-to-chaos and is vulnerable to external excitation, which eventually leads to detrimental failure. A novel simultaneous time-frequency control theory is developed for controlling the active magnetic bearing at high speed. The control theory is able to tolerate the uncertainties in the system due to on-line identification and the deterioration in both time and frequency domain can be restrained.

Effects of the Magnetic Damper Locations on Dynamic Characteristics of the Active Magnetic Bearing System in Manufacturing Engineering

2012 ◽  
Vol 252 ◽  
pp. 51-55
Author(s):  
Zhen Yu Xie ◽  
Hong Kai Zhou ◽  
Xiao Wang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Active Magnetic Bearings ◽  
Actual Operation ◽  
And Control ◽  
System Operating ◽  
Bearing System

The magnetic damper was introduced into the high speed rotating machinery to restrain the vibration of the rotor supported by active magnetic bearings. The experimental setup, which was made up of one rotor, two radial active magnetic bearings, one axial active magnetic bearing, one magnetic damper and control system, was built to investigate the effects of the magnetic damper locations on dynamic characteristics of the system by theoretical analysis, experimental modal analysis and actual operation of the system. The results show that the vibration of the active magnetic bearing system operating at the modal frequency can be reduced more effectively if the magnetic damper is located far from the nodes of the corresponding mode shape.

scholarly journals Tip Clearance Actuation With Magnetic Bearings for High-Speed Compressor Stall Control

2000 ◽  
Vol 123 (3) ◽  
pp. 464-472 ◽  
Author(s):  
Z. S. Spakovszky ◽  
J. D. Paduano ◽  
R. Larsonneur ◽  
A. Traxler ◽  
M. M. Bright
Keyword(s):  
High Speed ◽  
Design Procedure ◽  
Magnetic Bearing ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Magnetic Bearings ◽  
Test Facility ◽  
Control Analysis ◽  
Servo Actuator ◽  
Stall Control

Magnetic bearings are widely used as active suspension devices in rotating machinery, mainly for active vibration control purposes. The concept of active tip-clearance control suggests a new application of magnetic bearings as servo-actuators to stabilize rotating stall in axial compressors. This paper presents a first-of-a-kind feasibility study of an active stall control experiment with a magnetic bearing servo-actuator in the NASA Glenn high-speed single-stage compressor test facility. Together with CFD and experimental data a two-dimensional, incompressible compressor stability model was used in a stochastic estimation and control analysis to determine the required magnetic bearing performance for compressor stall control. The resulting requirements introduced new challenges to the magnetic bearing actuator design. A magnetic bearing servo-actuator was designed that fulfilled the performance specifications. Control laws were then developed to stabilize the compressor shaft. In a second control loop, a constant gain controller was implemented to stabilize rotating stall. A detailed closed loop simulation at 100 percent corrected design speed resulted in a 2.3 percent reduction of stalling mass flow, which is comparable to results obtained in the same compressor by Weigl et al. (1998. ASME J. Turbomach. 120, 625–636) using unsteady air injection. The design and simulation results presented here establish the viability of magnetic bearings for stall control in aero-engine high-speed compressors. Furthermore, the paper outlines a general design procedure to develop magnetic bearing servo-actuators for high-speed turbomachinery.

Theory Versus Experiment for the Effects of Pressure Ratio on the Performance of an Orifice-Compensated Hybrid Bearing

1998 ◽  
Vol 120 (4) ◽  
pp. 930-936 ◽  
Author(s):  
P. Mosher ◽  
D. W. Childs
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Pressure Ratio ◽  
Navier Stokes ◽  
Rotordynamic Coefficients ◽  
Wide Range ◽  
Bearing Load ◽  
Hybrid Bearing

This research investigates the effect of varying the concentric recess pressure ratio of hybrid (combination hydrostatic and hydrodynamic) bearings to be used in high-speed, high-pressure applications. Bearing flowrate, load capacity, torque, rotordynamic coefficients, and whirl frequency ratio are examined to determine the concentric, recess-pressure ratio which yields optimum bearing load capacity and dynamic stiffness. An analytical model, using two-dimensional bulk-flow Navier-Stokes equations and anchored by experimental test results, is used to examine bearing performance over a wide range of concentric recess pressure ratios. Typically, a concentric recess pressure ratio of 0.50 is used to obtain maximum bearing load capacity. This analysis reveals that theoretical optimum bearing performance occurs for a pressure ratio near 0.40, while experimental results indicate the optimum value to he somewhat higher than 0.45. This research demonstrates the ability to analytically investigate hybrid bearings and shows the need for more hybrid-bearing experimental data.

Study of Flow Characteristics and Control Circuit on High-Speed Solenoid Valve

2012 ◽  
Vol 619 ◽  
pp. 107-110 ◽  
Author(s):  
Wen Hua Li ◽  
Wen Lin Shao
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Pulse Signal ◽  
Solenoid Valve ◽  
Control Circuit ◽  
Duty Ratio ◽  
Time Sharing ◽  
Small Current ◽  
Wide Range ◽  
And Control

Through the analysis of the flow characteristics of the high-speed solenoid valve, the conclusions that the PWM signal duty ratio is the main factor affecting the solenoid valve flow is obtained, a new available any PWM pulse signal and control circuit are proposed. Further, circuit schematic is simulated by means of SIMULINK tools in MATLAB environment and Verify its stability. A time-sharing drive circuit is design based on the PWM drive mode. The driver circuit have function which is high-current open, small current maintain. Open current and maintain current of Solenoid valve can be adjusted through this circuit. Therefore, the circuit can adapt to different parameters of the solenoid valve. A wide range of applications.

High-Speed Rotor Losses in a Radial Eight-Pole Magnetic Bearing: Part 1—Experimental Measurement

1998 ◽  
Vol 120 (1) ◽  
pp. 105-109 ◽  
Author(s):  
M. E. F. Kasarda ◽  
P. E. Allaire ◽  
E. H. Maslen ◽  
G. R. Brown ◽  
G. T. Gillies
Keyword(s):  
Power Loss ◽  
High Speed ◽  
Large Scale ◽  
Eddy Currents ◽  
Magnetic Bearing ◽  
Rate Of Change ◽  
Magnetic Bearings ◽  
Power Losses ◽  
Loss Mechanism ◽  
Pole Configuration

The continual increase in the use of magnetic bearings in various capacities, including high-speed aerospace applications such as jet engine prototypes, dictates the need to quantify power losses in this type of bearing. The goal of this study is to present experimentally measured power losses during the high-speed operation of a pair of magnetic bearings. A large-scale test rotor has been designed and built to obtain unambiguous power loss measurements while varying a variety of test parameters. The test apparatus consists of a shaft supported in two radial magnetic bearings and driven by two electric motors also mounted on the shaft. The power losses of the spinning rotor are determined from the time rate of change of the kinetic energy of the rotor as its angular speed decays during free rotation. Measured results for the first set of magnetic bearings, a pair of eight-pole planar radial bearings, are presented here. Data from three different parameter studies including the effect of the bias flux density, the effect of the bearing pole configuration, and the effect of the motor stator on the power loss are presented. Rundown plots of the test with the bearings in the paired pole (NNSS) versus the alternating (NSNS) pole configuration show only small differences, with losses only slightly higher when the poles are in the alternating pole (NSNS) configuration. Loss data were also taken with the motor stators axially removed from the motor rotors for comparison with the case where the motor stators are kept in place. No measurable difference was observed between the two cases, indicating negligible windage and residual magnetic effects. Throughout most of the speed range, the dominant loss mechanism appears to be eddy currents.

The Dynamic Analysis of an Energy Storage Flywheel System With Hybrid Bearing Support

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Hongchang Wang ◽  
Shuyun Jiang ◽  
Zupei Shen
Keyword(s):  
Control System ◽  
Energy Storage ◽  
Active Control ◽  
High Speed ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Squeeze Film ◽  
Transmitted Force ◽  
Hybrid Bearing ◽  
Active Control System

Active magnetic bearings and superconducting magnetic bearings were used on a high-speed flywheel energy storage system; however, their wide industrial acceptance is still a challenging task because of the complexity in designing the elaborate active control system and the difficulty in satisfying the cryogenic condition. A hybrid bearing consisting of a permanent magnetic bearing and a pivot jewel bearing is used as the support for the rotor of the energy storage flywheel system. It is simple and has a long working life without requiring maintenance or an active control system. The two squeeze film dampers are employed in the flywheel system to suppress the lateral vibration, to enhance the rotor leaning stability, and to reduce the transmitted forces. The dynamic equation of the flywheel with four degrees of complex freedom is built by means of the Lagrange equation. In order to improve accuracy, the finite element method is utilized to solve the Reynolds equation for the dynamic characteristics of the squeeze film damper. When the calculated unbalance responses are compared with the test responses, they indicate that the dynamics model is correct. Finally, the effect of the squeeze film gap on the transmitted force is analyzed, and the appropriate gap should be selected to cut the energy loss and to control vibration of the flywheel system.

Neural Network Emulation of a Magnetically Suspended Rotor

2004 ◽  
Vol 126 (2) ◽  
pp. 373-384 ◽  
Author(s):  
A. Escalante ◽  
V. Guzma´n ◽  
M. Parada ◽  
L. Medina ◽  
S. E. Diaz
Keyword(s):  
Neural Network ◽  
Virtual Instrument ◽  
High Speed ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
System Response ◽  
The Neural Network ◽  
Artificial Neurons ◽  
Position Data ◽  
System 2

The use of magnetic bearings in high speed/low friction applications is increasing in industry. Magnetic bearings are sophisticated electromechanical systems, and modeling magnetic bearings using standard techniques is complex and time consuming. In this work a neural network is designed and trained to emulate the operation of a complete system (magnetic bearing, PID controller, and power amplifiers). The neural network is simulated and integrated into a virtual instrument that will be used in the laboratory both as a teaching and a research tool. The main aims in this work are: (1) determining the minimum amount of artificial neurons required in the neural network to emulate the magnetic bearing system, (2) determining the more appropriate ANN training method for this application, and (3) determining the errors produced when a neural network trained to emulate system operation with a balanced rotor is used to predict system response when operating with an unbalanced rotor. The neural network is trained using as input the position data from the proximity sensors; neural network outputs are the control signals to the coil amplifiers.

scholarly journals Tip-Clearance Actuation With Magnetic Bearings for High-Speed Compressor Stall Control

2000 ◽  
Author(s):  
Z. S. Spakovszky ◽  
J. D. Paduano ◽  
R. Larsonneur ◽  
A. Traxler ◽  
M. M. Bright
Keyword(s):  
High Speed ◽  
Design Procedure ◽  
Magnetic Bearing ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Magnetic Bearings ◽  
Test Facility ◽  
Control Analysis ◽  
Servo Actuator ◽  
Stall Control

Magnetic bearings are widely used as active suspension devices in rotating machinery, mainly for active vibration control purposes. The concept of active tip clearance control suggests a new application of magnetic bearings as servo-actuators to stabilize rotating stall in axial compressors. This paper presents a first-of-a-kind feasibility study of an active stall control experiment with a magnetic bearing servo-actuator in the NASA Glenn high-speed single-stage compressor test facility. Together with CFD and experimental data a two-dimensional, incompressible compressor stability model was used in a stochastic estimation and control analysis to determine the required magnetic bearing performance for compressor stall control. The resulting requirements introduced new challenges to the magnetic bearing actuator design. A magnetic bearing servo-actuator was designed which fulfilled the performance specifications. Control laws were then developed to stabilize the compressor shaft. In a second control loop, a constant gain controller was implemented to stabilize rotating stall. A detailed closed loop simulation at 100% corrected design speed resulted in a 2.3% reduction of stalling mass flow which is comparable to results obtained in the same compressor by Weigl et al. (1998) using unsteady air injection. The design and simulation results presented here establish the viability of magnetic bearings for stall control in aero-engine high-speed compressors. Furthermore the paper outlines a general design procedure to develop magnetic bearing servo-actuators for high-speed turbomachinery.

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