Levitation Of Rotor Research Articles

Experimental Evaluation of a Surge Controller for an AMB Supported Compressor in the Presence of Piping Acoustics

This brief studies the active control of compressor surge using the thrust active magnetic bearing (AMB) in centrifugal compressors and it presents experimental test data to demonstrate the effectiveness of the control solution in industrial size equipment. A detailed step-by-step description is provided from the derivation of the surge model, to the implementation and experimental testing of the surge controller. To accurately represent the configurations found in industrial systems, the proposed surge suppression method is implemented integrally using common off-the-shelf components. During the design of the surge controller, special attention is paid to a possible conflict between the surge controller and the AMB's internal rotor levitation controller. Observations from the experimental surge testing demonstrate that the presented method is able to stabilize the compression system when operating in the unstable surge region, extending the stable flow range by over 21%. In practice, this allows the compressor to operate at the peak pressure/efficiency point, while maintaining a healthy surge margin as commonly prescribed in industrial compressors.

Research on Neural Network PID Quadratic Optimal Controller in Active Magnetic Levitation

In response to the uncertainty, nonlinearity and open-loop instability of active magnetic levitation control system, a neural network PID quadratic optimal controller has been designed using optimum control theory. By introducing supervised Hebb learning rule, constraint control for positioning errors and control increment weighting are realized by adjusting weighting coefficients, using weighed sum-squares of the control increment and the deviation between actual position and equilibrium position of the rotor in active magnetic levitation system as objective function. The simulation results show that neural network PID quadratic optimal controller can maintain the stable levitation of rotor by effectively improving static and dynamic performances of the system, so as to maintain the stable levitation of rotor in active magnetic levitation system which has stronger anti-jamming capacity and robustness.

An Synergistic Dynamic 2D FEM Model of an Active Magnetic Bearing with Three Electromagnets

This elaboration presents a dynamic model of an Active Magnetic Bearing (AMB) developed in COMSOL Multiphysics. The electromagnetic field is calculated on the basis of Partial Differential Equations (PDEs). The calculated electromagnetic force is applied to the rotor, which is free to move. The Arbitrary Lagrangian-Eulerian (ALE) method for mesh deformation is applied to achieve rotor motion on the bearing plane. The planar rotor motion is described by a set of Ordinary Differential Equations (ODEs) solved in parallel to the electromagnetic field calculations. To enable rotor levitation, three local PD controllers are applied. The mathematical formulas of the control action are coded in the form of COMSOL equations and embedded into the rotor motion ODEs.

3A24 Levitation of a Flexible Rotor Supported by Hybrid Magnetic Bearings(The 12th International Conference on Motion and Vibration Control)

3A24 Levitation of a Flexible Rotor Supported by Hybrid Magnetic Bearings(The 12th International Conference on Motion and Vibration Control)

Progress on electrodynamic passive magnetic bearings for rotor levitation

Electrodynamic suspension exploits repulsive forces due to eddy currents to produce positive stiffness by passive means, without violating the Earnshaw stability criterion. Systems employing this principle to levitate a rotor radial and/or axial degrees of freedom are called electrodynamic bearings (EDBs). Since the eddy currents can be induced either by using alternating current supplied electromagnets or by the relative motion between a conductor and a constant magnetic field, the research on EDBs has developed many different configurations. The present paper reviews the literature on electrodynamic passive magnetic bearings to analyze the evolution of this technology toward completely passive, stable, rotor levitation, and to compare the EDBs performance with other common magnetic bearing technologies. Radial and axial EDB technologies are reviewed attempting to create an organized connection between the works and to discuss some critical issues that still preclude the use of EDBs in industrial applications.

Passive Magnetic Levitation of Rotors on Axial Electrodynamic Bearings

The present paper presents a new modeling approach for null flux axial electrodynamic bearings. Such approach allows defining stability bounds for rotors supported with this type of passive magnetic suspension. The linearized models are developed using the bond graph methodology to better understand the multiphysics nature of the magnetic suspension. The adoption of complex variables together with the bond graph formalism is introduced in order to reduce the complexity of the system's equations. Rules for the use of this approach are established and demonstrated.

Maximum Bearing Force Control for 6 Salient-Pole Active Magnetic Bearings

This paper addresses novel control strategy for 6 salient-pole active magnetic bearings (AMBs). Since 6 salient-pole type AMB has less number of poles as compared with usual 8 salient-pole type AMB, it becomes advantageous to a miniaturization and a low cost. However, since the magnetic circuit has not been independent in x and y direction, bearing forces for coil currents become complicated. Previous research introduced a minimum energy control method which makes the copper loss in coils the minimum. However in the minimum energy control method, the maximum bearing force of specific directions is less than that of the other directions. In order to solve this problem, the maximum bearing force control method is proposed in this paper. Analysis and experiments confirm that the proposed method provides stable rotor levitation and larger bearing force than that of minimum energy control method.

Analysis and Control of Maglev Flywheel Rotor in the Wind Generator

The application of maglev flywheel in wind generator is investigated. The dynamics analysis of maglev flywheel rotor has been performed including the critical speed analysis and unbalance response analysis, which took into account the gyroscopic effect by using of finite element analysis method. Based on the model reduction method, the modeling and LQR control of maglev flywheel rotor is presented, the simulation results show stable levitation and good levitated rotation.

Development of magnetic levitation synchronous motor with high-Tc superconducting bearing

In this study, we propose a new magnetic levitation synchronous motor with a high-Tc superconducting bearing. The levitation rotor obtains the levitation force by the magnetic attraction and the restoring force (axially and radially to the shaft) from a superconducting bearing. The levitation rotor to which the magnetic flux concentration method is applied has a large magnetic field outside of the rotor. Because the superconducting bearing constrains this concentrated magnetic flux, the rotor obtains a large restoring force. In addition, a superconducting bearing with a small bulk can be realized. We stabilized the rotor using this method and confirmed that this motor passed the resonance and that its speed increased to approximately 3500 [rpm] without control.

530 整流コイルを用いたベアリングレスモータのロータ浮上

530 整流コイルを用いたベアリングレスモータのロータ浮上

534 6突極型磁気軸受の最大軸受力制御

This paper addresses novel control strategy for 6 salient-pole active magnetic bearings (AMBs). Since 6 salient-pole type AMB has less number of poles as compared with usual 8 salient-pole type AMB, it becomes advantageous to a miniaturization and a low cost. However, since the magnetic circuit has not been independent in x and y direction, bearing forces for coil currents become complicated. Previous research introduced a minimum energy control method which makes the copper loss in coils the minimum. However in the minimum energy control method, the maximum bearing force of specific directions is less than that of the other directions. In order to solve this problem, the maximum bearing force control method is proposed in this paper. Analysis and experiments confirm that the proposed method provides stable rotor levitation and larger bearing force than that of minimum energy control method.

Electromagnetic Actuator Implementation and Control for Resonance Vibration Reduction in Miniature Magnetically Levitated Rotating Machines

In miniature magnetically levitated rotating machines, permanent magnet bearings are generally used for rotor levitation in the radial directions, while electromagnetic actuators are used for stabilization in the axial direction. Rotor radial oscillations are inevitable in this configuration because no controllable force is applicable in these directions. The oscillations become excessively large as the rotor is running at speeds near the rotor's resonant frequency. This paper presents an implementation and control scheme for an electromagnetic actuator for these machines. The proposed actuator can produce axial as well as radial forces on the rotor. The axial force is used for rotor axial direction control, while the radial force is used to assist in rotor resonance-related oscillation suppression. Theoretical analysis and experimental investigations of the proposed actuator control are performed.

142 永久磁束バイアス型三極小型磁気軸受の浮上回転機構の提案と設計

Recently, many magnetic machine elements are developed for industrial use. Magnetic bearing, which enabled rotation machines to support a rotor without contact, is also developed and applied. For such a practical use, miniaturization can be necessary for magnetic bearings. In this paper, we designed 3-pole magnetic bearing with permanent magnet to shorten both bearing length and bearing outside diameter. With this bearing, we experimented and succeeded in perfect levitation and rotation at 7200rpm. Then, we designed 3-pole self-bearing motor in order to further miniaturize bearing length. This self-bearing motor can rotate a levitated rotor in itself without exterior motor unit.

Vibration control of the high-TC superconducting levitation synchronous motor

In this research, we propose the high-TC superconducting levitation synchronous motor that the levitation, the drive, and the vibration suppression are possible with the single disk type rotor composed by some permanent magnets. The center of gravity position is low because this rotor is the single disk structure, and the pitching doesn't occur easily. The displ acement of the horizontal direction when the levitation rotor rotat es is measured with the laser displacement meter. And, the vibration is controlled by feeding back this whirling speed to an damper. The High-TC Superconducting Levitation synchronous motor with such a vibration suppression mechanism is developed, and utility is verified by the experiment. Motion analysis and the numerical analysis of the force of an damper were done.

High Efficiency Radial Passive Magnetic Bearing

Passive magnetic bearing with Halbach array is presented in this paper. The array uses permanent magnets with radial and axial magnetization to augment the magnetic field on one side of the array and cancel it on the other side. The design of the bearing consists of ring-shaped magnets of 60x70 mm and 75x85 mm with different orientation of magnetization. The designed passive magnetic bearing has air gap of 2.5 mm, stiffness 129297 N/m and maximal value of load 200 N. The bearing ensures magnetic levitation and stabilization of rotor in a work point. The paper presents the design of the passive magnetic bearing as well as the experimental setup together with investigation results.

A Hall Sensor-Based Three-Dimensional Displacement Measurement System for Miniature Magnetically Levitated Rotor

This paper presents a novel scheme for measuring the axial and radial displacements of a miniature magnetically levitated rotor based on linear Hall-effect sensors. The measurement system consists of six single-axis Hall-effect sensors attached to the stator with a ring shaped permanent magnet (PM) mounted on the rotor as the magnetic flux source. The system is configured such that the directions of the magnetic flux into the sensors for each axis are monitored. Consequently, the errors caused by uneven magnetization and the temperature dependence of the PM are minimized. The experimental results demonstrate measurement system satisfactory performance. Since only single-axis Hall sensors are used in the measurement system, this scheme provides a low-cost compact size solution for three-dimensional displacement measurement of miniature magnetically levitated rotors.

Design of a New Electromagnetic Actuator Which Can Produce Three-Dimensional Forces

In miniature magnetically levitated rotating machines, permanent magnet bearings are generally used for rotor levitation in the radial directions, while and electromagnetic actuators are used for rotor stabilization in the axial direction. In this configuration, radial rotor oscillations are unavoidable because no controllable force is applicable in these directions. Consequently, rotor damping relies entirely on the media in the air gap. This paper presents a novel electromagnetic actuator for miniature magnetically levitated rotating machines. The actuator stator core consists of four poles for flux passage. The currents on these poles are independently controlled so that axial and radial forces are produced. The axial force is used for rotor levitation control, while the radial force is used to assist in radial oscillation suppression. Theoretical analysis and experimental verification for the radial force production are provided.

Levitation and Vibration Control of a Flexible Rotor by Using Active Magnetic Bearing

This paper presents a new modeling method and a control system design procedure for a flexible rotor with many elastic modes by using active magnetic bearings. The purpose of our research is to rotate the rotor for passing through critical speeds caused by flexible modes. To achieve this, it is necessary to control motion and vibration of the flexible rotor simultaneously. The new modeling method named as Extended Reduced Order Physical Model is presented to express its motion and vibration uniformly. By using this model, a PID controller to levitate the rotor and a LQ controller to suppress its vibration are designed.

Model-Free Control of Touchdowns Involving Circular Whirl in Rotor-Magnetic Bearing Systems

In this paper, the dynamics associated with rotor-stator touchdowns involving full circular rub are considered. The expected range of phase shifts occurring in various measurable signals are examined from a theoretical standpoint, with the aim of developing model-free control algorithms that can limit contact force magnitudes during touchdown with auxiliary bearings and ensure contact-free rotor levitation can be restored following persistent contact. Two different strategies are proposed according to whether touchdown planes can be considered collocated with the magnetic bearings or not. Requirements for successful operation, in terms of available sub-models and measurement information are explained and verified through experimental tests on a multi-mode flexible rotor test rig.

A model-based flexural rotor vibration control in cage induction electrical machines by a built-in force actuator

In this paper active control of flexural rotor vibration in electrical machines is examined. We consider attenuation of discrete low-frequency range forced vibration components by means of an adaptive harmonic control strategy. A built-in force actuator for actively generating force on the machine rotor is investigated. Previously, such an actuator has mainly been used in bearingless machine design for rotor levitation. The action of the actuator is based on electromechanical interaction between the rotor and the stator of the machine. A low-order linear parametric state-space model is derived for the actuator–rotor system. Parameter estimation is carried out using simulation data obtained from a detailed two-dimensional time-stepping finite element field-circuit model of the machine. Hence, model-based control design is performed using the identified model. The controller is verified by embedding it into the finite element analysis. As a result we present a virtual plant of the machine with vibration control. The virtual plant is introduced as a means of vibration control design prior to implementing the control algorithms in a real machine. Simulation results using real machine data and finite element time-stepping method are presented.