Adaptive Virtual Autobalancing for a Rigid Rotor With Unknown Mass Imbalance Supported by Magnetic Bearings

1998 ◽  
Vol 120 (2) ◽  
pp. 557-570 ◽  
Author(s):  
Kai-Yew Lum ◽  
Vincent T. Coppola ◽  
Dennis S. Bernstein
Keyword(s):  
Physical Model ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Rigid Rotor ◽  
Compensation Scheme ◽  
Elastic Suspension ◽  
Single Plane ◽  
Rotor Imbalance ◽  
Line Identification ◽  
On Line

The objective of this paper is to describe an imbalance compensation scheme for a rigid rotor supported by magnetic bearings that performs on-line identification of rotor imbalance and allows imbalance cancellation under varying speed of rotation. The proposed approach supplements existing magnetic bearing controls which are assumed to achieve elastic suspension of the rotor. By adopting a physical model of imbalance and utilizing measurements of the spin rate, the proposed algorithm allows the computation of the necessary corrective forces regardless of variations in the spin rate. Convergence of the algorithm is analyzed for single-plane balancing, and is supported by simulation in single- and two-plane balancing, as well as by experimental results in single-plane implementation.

scholarly journals Sliding Mode Output Feedback Control of a Flexible Rotor via Magnetic Bearings

1998 ◽  
Author(s):  
A. S. Lewis ◽  
A. Sinha ◽  
K. W. Wang
Keyword(s):  
Differential Equations ◽  
Sliding Mode ◽  
Output Feedback Control ◽  
Angular Speed ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Control Parameters ◽  
Flexible Rotor ◽  
Rotor Imbalance ◽  
Feedback Algorithm

A sliding mode feedback algorithm is proposed to control the vibration of a flexible rotor supported by magnetic bearings. It is assumed that the number of states is greater than the number of sensors. A mathematical model of the rotor/magnetic bearing system is presented in terms of partial differential equations. These equations are then discretized into a finite number of ordinary differential equations through Galerkin’s method. The sliding mode control law is designed to be robust to rotor imbalance and transient disturbances. A boundary layer is introduced around each sliding hyperplane to eliminate the chattering phenomenon. The results from numerical simulations are presented which not only corroborate the validity of the proposed controller, but also show the effects of various control parameters as a function of the angular speed of the rotor. In addition, results are presented that indicate how the current required by the magnetic bearings is affected by control parameters and the angular speed of the rotor.

Adaptive Compensation of Sensor Runout for Magnetic Bearings With Uncertain Parameters: Theory and Experiments

1999 ◽  
Vol 123 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Joga D. Setiawan ◽  
Ranjan Mukherjee ◽  
Eric H. Maslen
Keyword(s):  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Parameter Uncertainties ◽  
Persistent Excitation ◽  
Electrical And Magnetic Properties ◽  
Periodic Disturbances ◽  
Mass Unbalance ◽  
On Line ◽  
The Stability ◽  
Rotor Balancing

The problem of sensor runout in magnetic bearing systems has been largely overlooked due to similarities with mass unbalance in creating periodic disturbances. While the effect of mass unbalance can be significantly reduced, if not eliminated, through rotor balancing, sensor runout disturbance is unavoidable since it originates from physical nonconcentricity between rotor and stator. Sensor runout is also caused by nonuniform electrical and magnetic properties around the sensing surface. To improve performance of magnetic bearings, we present an adaptive algorithm for sensor runout compensation. It guarantees asymptotic stability of the rotor geometric center and on-line feedforward cancellation of runout disturbances using persistent excitation. Some of the advantages of our algorithm include simplicity of design and implementation, stability, and robustness to plant parameter uncertainties. The stability and robustness properties are derived from passivity of the closed-loop system. Numerical simulations are presented to demonstrate efficacy of the algorithm and experimental results confirm stability and robustness for large variation in plant parameters.

Unbalance response of a magnetic suspended dual-rotor system

2019 ◽  
Vol 233 (15) ◽  
pp. 5758-5772
Author(s):  
Dongxiong Wang ◽  
Nianxian Wang ◽  
Kuisheng Chen
Keyword(s):  
Magnetic Bearing ◽  
Rotor System ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Active Magnetic Bearings ◽  
Maximum Displacement ◽  
Critical Speeds ◽  
Unbalance Response ◽  
Rotor Imbalance ◽  
Aero Engine

The magnetic suspended dual-rotor system applied in more electric aero-engine can eliminate the wear and lubrication system of mechanical bearings and solve the vibration control issue of system effectively, which provides the possibility to improve the performance of aero-engine significantly. This research focuses on the unbalance response of the magnetic suspended dual-rotor system. First, a structure of dual-rotor system supported by two active magnetic bearings and two permanent magnetic bearings is presented. With proportional derivative (PD) control adopted, the bearing characteristics of active magnetic bearings are modeled as the equivalent stiffness and equivalent damping, and the permanent magnetic bearings are modeled as elastic support. Then, the Riccati transfer matrix method with good numerical stability is used to establish the model of the magnetic suspended dual-rotor system unbalance response. Subsequently, the validity of the present formulation has been tested against some known results available in literature and the simulation results obtained by finite element method (FEM). Finally, the dynamic characteristics of the unbalance response are investigated. The results reveal that the influence of the inner rotor imbalance excitation on the magnetic suspended dual-rotor system unbalance response is much larger than that of the outer rotor imbalance excitation. In addition, the critical speeds increase with the proportional coefficient, and the derivative coefficient can affect the amplitudes of the unbalance response, but not critical speeds. From the perspectives of the maximum bearing capacity and maximum displacement of active magnetic bearing-rotor system, the possibility of the magnetic suspended dual-rotor system safely crossing the critical speeds of the first three orders is investigated.

Single Plane Radial, Magnetic Bearings Biased With Poles Containing Permanent Magnets

2003 ◽  
Vol 125 (1) ◽  
pp. 178-185 ◽  
Author(s):  
Andrew Kenny ◽  
Alan B. Palazzolo
Keyword(s):  
Power Loss ◽  
Permanent Magnets ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Single Plane ◽  
Side Load ◽  
Coil Inductance ◽  
Coil Resistance ◽  
Radial Magnetic Bearing

Magnetic bearings biased with permanent magnets have lower coil resistance power losses, and the magnets can also be used to help support a constant side load. In this paper, the performance of a single plane radial magnetic bearing biased with permanent magnets in several poles is presented. Although it has less load capacity and stiffness than a similarly sized electrically biased single plane heteropolar bearing, it does not require bias current, and its ratio of load capacity to coil resistance power loss is significantly better. This type of permanent magnet bearing has only a single plane of poles. It can be distinguished from the homopolar bearing type which has two planes and which can also be biased with permanent magnets. Magnetic circuit models for the novel single plane bearing are presented along with verification by finite element models. Equations for the key performance parameters of load capacity, stiffness, coil inductance and resistive power loss are also presented.

Measured and Predicted Force and Stiffness Characteristics of Industrial Magnetic Bearings

1991 ◽  
Vol 113 (4) ◽  
pp. 784-788 ◽  
Author(s):  
J. Imlach ◽  
B. J. Blair ◽  
P. E. Allaire
Keyword(s):  
Critical Speed ◽  
Closed Loop ◽  
Load Capacity ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Dynamic Loadings ◽  
On Line ◽  
Stiffness Characteristics ◽  
Canned Motor ◽  
Displacement Information

Closed-loop stiffness and load capacity (force) equations have been developed for industrial magnetic bearings. Two sets of magnetic bearings have been constructed using these equations as a design basis. These bearings have been installed in two canned motor pumps. The predicted force and stiffness values from the equations are compared to experimental measurements to determine their validity. When obvious sources of error were eliminated, agreement within 10 percent was obtained for development pump’s magnetic bearings. Agreement was generally better for this pump than for the demonstration pump. By employing these equations, along with easily measured current and displacement information from magnetic bearing equipped machinery, actual stiffness’ and bearing loadings can be determined for operating equipment. Thus, the range of information available from magnetic bearings is extended to include static and dynamic loadings as well as shaft orbits and critical speed and damping information (Humphris et al., 1989). This enhances their use as diagnostic and preventative maintenance tools which are built into machinery and can be used on line.

scholarly journals A Magnetic Bearing Suspension System for High Temperature Gas Turbine Applications: Control System Design

1997 ◽  
Author(s):  
James R. Scholten
Keyword(s):  
Control System ◽  
Processing System ◽  
Control Design ◽  
Digital Signal ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Critical Event ◽  
Signal Processing System ◽  
Rotor Imbalance ◽  
External Loads

A practical magnetic-bearing control system has been designed based upon modeling and simulation of the dynamics of a jet engine turbine shaft and bearing system. Simulations include models for flexible rotor dynamics, magnetic actuators, auxiliary touchdown bearings, ordinary and extraordinary external loads, and disturbances from rotor imbalance, stator vibration, and noise. The shaft model includes a motor-generator which acts as an uncontrolled negative stiffness. The control system is decentralized, running independently for each of the five physical axes of control (1 axial, 4 radial). The fundamental algorithm is classical PID: proportional for broadband stiffness, integrator (with anti-windup) for high load-carrying capacity, and derivative to dampen disturbances. Additional phase lead is provided via a first-order pole-zero pair. The vibration due to rotor imbalance is eliminated by an autobalancing algorithm. Compensation for magnetic actuator non-linearity and varying rotor-stator gap is provided by feedback of sensed magnetic flux, using sensor coils built into the actuator. The control design can be readily implemented using a commercial Digital Signal Processing system. The magnetic bearing actuators will be driven with commercial power amplifiers via customized front-end electronics. Based upon simulations, the design goal has been achieved of keeping the shaft within two mils of its desired location at the magnetic bearings, under all normal loads. Under extreme external loads, the capacity of the magnetic bearings will be exceeded and touchdown will occur upon backup mechanical bearings. Simulation shows that the control design handles this critical event, which determines the force slew rate required from the actuators.

Testbed for a Wind Turbine with Magnetic Bearing

2012 ◽  
Vol 512-515 ◽  
pp. 657-660
Author(s):  
M. Ryan Vorwaller ◽  
Kuo Chi Lin ◽  
Ji Hua Gou ◽  
Chan Ham ◽  
Young Hoon Joo
Keyword(s):  
Rare Earth ◽  
Wind Turbine ◽  
World Wide ◽  
Past Research ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Rotor Imbalance ◽  
Turbine Performance ◽  
Efficiency Data ◽  
Bearing System

World-wide demands for sustainable energy have brought increased attention to the improvement of wind turbine technology. Magnetic bearings promise to improve wind turbine performance by reducing frictional losses and mitigating vibration due to rotor imbalance and wind disturbances. However, testing must be performed to validate and quantify these advantages if magnetic bearings are to be used efficiently. Therefore, a practical testbed for a wind turbine with a magnetic bearing system has been developed, including the design of a passive rare earth magnetic bearing and fixture. This testbed will provide experimental vibration and efficiency data needed to extend past research in wind turbine modeling and design to include recent advances in magnetic bearing technology.

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