Effecting Critical Frequency Shift in Rotors Using Active Magnetic Bearings
01 Jan 2021-pp 527-538
TL;DR: In this paper, the stiffness of the bearing is changed online during operation by using an active magnetic bearing instead of a conventional constant stiffness rolling element bearing, which is shown for a rigid rotor using both simulation and experimental techniques.
Abstract: Low stiffness bearings are useful to reduce the force transmitted from the vibrating rotor to the surrounding support structure. However, having low stiffness requires us to cross the low rigid body critical frequency while accelerating to operating rpm. In this work the stiffness of the bearing is changed online during operation by using an active magnetic bearing instead of a conventional constant stiffness rolling element bearing. This methodology is shown for a rigid rotor using both simulation and experimental techniques. During acceleration phase, a high stiffness is maintained, which gives us high critical frequency. After acceleration to operating rpm, the stiffness of the bearing is reduced at run time so that the bearing again becomes a soft support. In this work, a thrust magnetic bearing of variable stiffness is used to show that by changing the stiffness at run time, we can avoid crossing the rigid body critical frequency and hence reduce the amplitude of resonant vibrations.
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TL;DR: In this paper , the authors used a successive integration-based algebraic technique to obtain parameters of the force model of an active magnetic bearing (AMB) from closed-loop control signals and air gap signals.
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01 Jul 2009
TL;DR: In this paper, the authors survey the principle of active magnetic suspension, hardware components, actuators, and losses in magnetic bearing motors, and design criteria and limiting characteristics for fault tolerance.
Abstract: and Survey.- Principle of Active Magnetic Suspension.- Hardware Components.- Actuators.- Losses in Magnetic Bearings.- Design Criteria and Limiting Characteristics.- Dynamics of the Rigid Rotor.- Control of the Rigid Rotor in AMBs.- Digital Control.- Dynamics of Flexible Rotors.- Identification.- Control of Flexible Rotors.- Touch-down Bearings.- Dynamics and Control Issues for Fault Tolerance.- Self#x2013 Sensing Magnetic Bearings.- Self#x2013 Bearing Motors.- Micro Magnetic Bearings.- Safety and Reliability Aspects.
1,036 citations
TL;DR: In this article, a nonlinear two-dimensional finite element method (FEM) was used to predict the performance of radial magnetic bearings and the load capacity of AMB systems.
Abstract: Load capacity is a primary performance criterion of an active magnetic bearing (AMB) system. The load capacity depends on the size and geometry of the bearings as well as on the performance of the control system. In this paper, we use a nonlinear two-dimensional (2-D) finite element method (FEM) to predict the performance of radial magnetic bearings. The force calculations based on the finite element method are verified by measurements with two machines equipped with active magnetic bearings. The parameters of a linearized model of radial bearings are also calculated at different operation points. With this information, the load capacity can be estimated.
68 citations
Dissertation•
08 Aug 2011
TL;DR: Wadhvani et al. as discussed by the authors developed a permanent magnet biased magnetic bearing system using high temperature (HT) permanent magnets (PM) developed by EEC and the entire system consisted of two radial bearings, two catcher bearings, one axial thrust bearing and a motor.
Abstract: Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System. (May 2011) Vishal Ashok Wadhvani, B.E., University of Pune Chair of Advisory Committee: Dr. Alan B. Palazzolo Magnetic bearings are increasingly being used in a wide variety of applications in the industry such as compressors, turbines, motors, generators etc. Also, there are different types available depending upon their construction. The research presented here investigates a high temperature permanent magnet biased magnetic bearing system which is jointly being researched by National Aeronautics and Space Administration (NASA) and Electron Energy Corporation (EEC). The purpose of this research was to develop a permanent magnet biased magnetic bearing system using high temperature (HT) permanent magnets (PM) developed by EEC. This system was designed for high performance, high temperature (1000F) and high speed applications. The entire system consisted of two radial bearings, two catcher bearings, one axial thrust bearing and a motor. The central rotor shaft is powered by a high temperature permanent magnet motor to be able to run at the designed conditions of 20,000 rpm. This thesis documents the design of a feedback control law that stabilizes this HTPM biased AMB levitated system and summarizes efforts to build a test rig for the HT tests of the machine. A decentralized PD control law is used to achieve successful levitation.
5 citations