scholarly journals Active Magnetic Bearings Stiffness and Damping Identification from Frequency Characteristics of Control System

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Chaowu Jin ◽  
Yuanping Xu ◽  
Jin Zhou ◽  
Changli Cheng
Keyword(s):  
Control System ◽  
Theoretical Analysis ◽  
Frequency Characteristics ◽  
Operating Conditions ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Rotating Speed ◽  
Verification Methods ◽  
Stiffness And Damping Identification ◽  
Stiffness And Damping

At present, the stiffness and damping identification for active magnetic bearings (AMBs) are still in the stage of theoretical analysis. The theoretical analysis indicates that if the mechanical structure and system parameters are determined, AMBs stiffness and damping are only related to frequency characteristic of control system, ignoring operating condition. More importantly, few verification methods are proposed. Considering the shortcomings of the theoretical identification, this paper obtains these coefficients from the experiment by using the magnetic bearing as a sine exciter. The identification results show that AMBs stiffness and damping have a great relationship with the control system and rotating speed. Specifically, at low rotating speed, the stiffness and damping can be obtained from the rotor static suspension by adding the same excitation frequency. However, at high speed, different from the static suspension situation, the AMBs supporting coefficients are not only related to the frequency characteristics of control system, but also related to the system operating conditions.

Modeling and Vibration Control of a Flexible Rotor by Using Magnetic Bearings

2011 ◽  
Author(s):  
Takuya Nomoto ◽  
Daisuke Hunakoshi ◽  
Toru Watanabe ◽  
Kazuto Seto
Keyword(s):  
Control System ◽  
Control Method ◽  
Design Procedure ◽  
Modeling Method ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Flexible Rotor ◽  
Modeling And Control ◽  
Elastic Modes ◽  
And Control

This paper presents a new modeling method and a control system design procedure for a flexible rotor with many elastic modes using active magnetic bearings. The purpose of our research is to let the rotor rotate passing over the 1st and the 2nd 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 transfer function of flexible rotor-Active Magnetic Bearings system, we designed a Local Jerk Feedback Control system and conducted stability discrimination with root locus. In order to evaluate this modeling and control method, levitation experimentation is conducted.

Two-Level Control Structure of Magnetic Bearings

1993 ◽  
Vol 5 (5) ◽  
pp. 438-442 ◽  
Author(s):  
Nobuyoshi Taguchi ◽  
◽  
Takakazu Ishimatsu ◽  
Takashi Shimomachi ◽  
◽  
...  
Keyword(s):  
Control System ◽  
Vibration Control ◽  
Control Structure ◽  
Active Vibration Control ◽  
Experimental Results ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Level Control ◽  
Whirling Motion ◽  
Active Vibration

Active magnetic bearings have several advantages over conventional mechanical and fluid bearings. However, when the magnetic bearings are used at high rotational speeds, whirling motions and vibrations synchronized with the rotation of the rotor should be considered. In order to suppress these unfavorable vibrations of rotor which is supported by magnetic bearings, we have developed an active vibration control system with a two-level control structure. Experimental results show that our active bearings system effectively suppresses the whirling motion.

Design Considerations for High Pressure Turbo Expanders Supported by Active Magnetic Bearings

2019 ◽  
Author(s):  
Alice Innocenti ◽  
Francesco Cangioli ◽  
Giuseppe Iurisci ◽  
Davide Biliotti
Keyword(s):  
High Pressure ◽  
Control System ◽  
High Density ◽  
Magnetic Bearings ◽  
Process Efficiency ◽  
Main Process ◽  
Cfd Analysis ◽  
Active Magnetic Bearings ◽  
Turbo Expander ◽  
Force Signal

Abstract Nowadays industrial processes are going toward high power density solutions. This can be read as a general increase in pressure (more than 200 barA) and fluid density indicating Turbo Expander (TEX) as a worthwhile solution to boost main process compressors and increasing process efficiency. On the other hand, inlet high pressure and high density fluids could lead to strong pressure pulsations on the impeller with consequences on the rotordynamic behavior, rotor stability and bearing integrity. For this purpose, a full annulus unsteady CFD analysis of the flow path through the inlet plenum, nozzles and impeller has been performed and analyzed in terms of resulting force FFT on the impeller. The force signal is used as an input of the rotor model supported by Active magnetic bearings (AMB), including their control system and transfer function. The aim of the study is the investigation of the influence of high density gas in TEX applications, coupling the results of unsteady CFD analysis with the dynamic response of the mechanical system. The control system parameters of magnetic bearings are included into the analysis and a sensitivity to different inlet nozzles numbers and inlet pressure levels is performed verifying the feasibility of the rotor.

scholarly journals Permanent magnet thrust bearings for flywheel energy storage systems: Analytical, numerical, and experimental comparisons

2019 ◽  
Vol 233 (15) ◽  
pp. 5280-5293
Author(s):  
Nikolaj A Dagnaes-Hansen ◽  
Ilmar F Santos
Keyword(s):  
Energy Storage ◽  
Permanent Magnet ◽  
Storage Systems ◽  
Magnetic Suspension ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Flywheel Energy Storage ◽  
Energy Storage Systems ◽  
Thrust Bearings ◽  
Stiffness And Damping

A new type of flywheel energy storage system uses a magnetic suspension where the axial load is provided solely by permanent magnets, whereas active magnetic bearings are only used for radial stabilization. This means that the permanent magnet bearing must provide all the axial damping. Furthermore, it must have as low a negative radial stiffness as possible to reduce the workload on the radial active magnetic bearings. Many different mathematical models for determining force, stiffness, and damping of permanent magnet bearings are available in the literature. This work will further develop the most applicable analytical and numerical methods in order to make them directly implementable for designing permanent magnet thrust bearings for flywheel energy storage systems. The outcome is a fast and efficient method for determining force, stiffness, and damping when the bearing setup contains magnetic materials with relative permeability higher than one as well as when it does not. The developed method is validated against numerical and experimental results with good agreement.

Multiharmonic Adaptive Vibration Control of Misaligned Driveline via Active Magnetic Bearings

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Hans A. DeSmidt ◽  
K. W. Wang ◽  
Edward C. Smith
Keyword(s):  
Vibration Control ◽  
Closed Loop ◽  
Explicit Knowledge ◽  
Operating Conditions ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Load Torque ◽  
Stability Robustness ◽  
Adaptive Vibration Control ◽  
Loop Stability

Active magnetic bearings (AMBs) have been proposed by many researchers and engineers as an alternative to replace traditional contact bearings in rotor and driveshaft systems. Such active, noncontact bearings do not have frictional wear and can be used to suppress vibration in sub- and supercritical rotor-dynamic applications. One important issue that has not yet been addressed by previous AMB-driveline control studies is the effect of driveline misalignment. Previous research has shown that misalignment causes periodic parametric and forcing actions, which greatly impact both driveline stability and vibration levels. Therefore, in order to ensure closed-loop stability and acceptable performance of any AMB controlled driveline subjected to misalignment, these effects must be accounted for in the control system design. In this paper, a hybrid proportional derivative (PD) feedback/multiharmonic adaptive vibration control (MHAVC) feedforward law is developed for an AMB/U-joint-driveline system, which is subjected to parallel-offset misalignments, imbalance, and load-torque operating conditions. Conceptually, the PD feedback ensures closed-loop stability while the MHAVC feedforward suppresses steady-state vibration. It is found that there is a range of P and D feedback gains that ensures both MHAVC convergence and closed-loop stability robustness with respect to shaft internal damping induced whirl and misalignment effects. Finally, it is analytically and experimentally demonstrated that the hybrid PD-MHAVC law effectively adapts to and suppresses multiharmonic vibration induced by imbalance, misalignment, and load-torque effects at multiple operating speeds without explicit knowledge of the disturbance conditions.

Control System Design of Frequency-Feedback Magnetic Bearings

1997 ◽  
Author(s):  
Takeshi Mizuno ◽  
Kenji Araki ◽  
Hirotaka Namiki
Keyword(s):  
Control System ◽  
Digital Signal ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Digital Control System ◽  
Load Impedance ◽  
Displacement Sensors ◽  
Digital Format ◽  
Converted Signal ◽  
Counter Circuit

Abstract The structures and features of control system are discussed for active magnetic bearings (AMBs) with frequency type of displacement sensors. The control systems are classified according to the signal conversions performed there. One of them uses a counter circuit for converting the frequency to a digital format, and the converted signal for digital signal processing. It is also pointed out that self-sensing operation can be realized by using hysteresis amplifiers because their switching rates are sensitive to load impedance. A digital self-sensing AMB, which uses a counter circuit for interface and hysteresis amplifiers for energizing the electromagnets, is manufactured for experimental study. The experimental results show that accurate suspension can be achieved with the proposed digital control system.

Effects of Impeller Tip Clearance on Centrifugal Compressor Efficiency

2007 ◽  
Author(s):  
Jari L. H. Backman ◽  
Arttu Reunanen ◽  
Juha Saari ◽  
Teemu Turunen-Saaresti ◽  
Petri Sallinen ◽  
...  
Keyword(s):  
Control System ◽  
Steady State ◽  
Mach Number ◽  
Centrifugal Compressor ◽  
Tip Clearance ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Centrifugal Compressors ◽  
Compressor Efficiency

The paper describes the results of tip clearance variation experiments in centrifugal compressors. The compressors work at different peripheral Mach number speeds either with vaneless or vaned diffusers. In the experiments, the compressors were operated in a thermally steady state after which the axial positions of the shafts were changed. The changes in the performance of the compressors were recorded and analyzed. The clearance between the impeller and its housing affects the efficiency of the centrifugal compressor. The clearance is optimized to adapt to various phenomena: thermal expansions, impeller tip deflections, shaft bending and gyroscopic motions. The compressors of this study are equipped with active magnetic bearings. They contain a control system, which constantly measures and controls the position of the shaft. This gives useful information about impeller clearance variation, and the measured results are precise within 1/100 millimeters.

A New Modeling Technique and Control System Design of a Flexible Rotor Supported by Active Magnetic Bearings for Motion and Vibration Control

2003 ◽  
Author(s):  
Mitsuhiro Ichihara ◽  
Hideo Shida ◽  
Takahito Sagane ◽  
Hiroshi Tajima ◽  
Muneharu Saigou ◽  
...  
Keyword(s):  
Control System ◽  
Vibration Control ◽  
System Design ◽  
Physical Model ◽  
Magnetic Bearings ◽  
Control System Design ◽  
Active Magnetic Bearings ◽  
Flexible Rotor ◽  
Reduced Order ◽  
And Control

This paper proposed a new modeling technique and control system design of a flexible rotor using active magnetic bearings (AMB) for motion and vibration control. The purpose of the research was to pass through a critical speed and achieve high-speed rotation. To achieve this, it is necessary to control both vibration and motion. Even though reduced order physical model [1] that we used before is available technique in expressing vibration, this technique cannot express motion. Thus we propose an extended reduced order physical model [2] that can simultaneously express motion and vibration. Further, by using the model we apply the design of a new controller that combined proportional integral derivative (PID) with linear quadratic (LQ) control to a flexible rotor. The procedure we propose is verified by simulations as being effective for a flexible rotor.

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