A System Identification Technique Using Bias Current Perturbation for Determining the Effective Rotor Origin of Active Magnetic Bearings

2006 ◽  
Vol 129 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Robert J. Prins ◽  
Mary E. F. Kasarda ◽  
Samantha C. Bates Prins
Keyword(s):  
System Identification ◽  
Magnetic Circuit ◽  
Force Measurement ◽  
Measurement Techniques ◽  
Magnetic Bearing ◽  
Bias Current ◽  
Active Magnetic Bearing ◽  
Force Model ◽  
Air Gaps ◽  
Identification Technique

Locating the effective rotor origin of an active magnetic bearing (AMB) is an important step toward accurate characterization of the bearing air gaps for field tuning, performance analyses, and some shaft force measurement techniques. Specifically, application of current-based force measurement techniques to AMBs requires accurate modeling of air gaps in order to predict dynamic forces with accuracy. This paper discusses the application of a system identification technique that employs perturbation of the bias current and allows the user to establish the location of the effective rotor origin, an important step in characterizing the actual bearing gap. The technique analyzes the AMB system’s response to the perturbation of bias currents in conjunction with a magnetic circuit model to infer the center position. The effective rotor origin identification technique developed here does not require additional hardware and is suitable for use in the general class of AMBs in field applications. For our purposes, the effective rotor origin of an electro-magnet biased magnetic bearing is defined as the unique rotor location for which a magnetic circuit based force model of the bearing is satisfied for zero position offset of the rotor along each control axis. Note that the effective rotor origin referred to here is the radial origin.

scholarly journals A System Identification Technique Using Bias Current Perturbation for the Determination of the Magnetic Axes of an Active Magnetic Bearing

2017 ◽  
Author(s):  
Dewey Spangler Jr. ◽  
Robert Prins ◽  
Mary Kasarda
Keyword(s):  
Force Measurement ◽  
Measurement Techniques ◽  
Magnetic Bearing ◽  
Bias Current ◽  
Active Magnetic Bearing ◽  
Mechanical Assembly ◽  
Identification Technique ◽  
Potential Improvement

Inherent in every Active Magnetic Bearing (AMB) are differences between the expected geometric axes and the actual magnetic axes due to a combination of discrepancies, including physical variation from manufacturing tolerances and misalignment from mechanical assembly, fringing and leakage effects, as well as variations in magnetic material properties within a single AMB. A method is presented here for locating the magnetic axes of an AMB that will facilitate the accurate characterization of the bearing air gaps for potential improvement in field tuning, performance analyses and certain shaft force measurement techniques. This paper presents an extension of the application of the bias current perturbation method for the determination of the magnetic center [4] to the determination of magnetic axes for the further development of accurate current-based force measurement techniques [1].

scholarly journals System Identification and Robust Control of Multi-Input Multi-Output Active Magnetic Bearing Systems

2016 ◽  
Vol 24 (4) ◽  
pp. 1227-1239 ◽  
Author(s):  
Amin Noshadi ◽  
Juan Shi ◽  
Wee Sit Lee ◽  
Peng Shi ◽  
Akhtar Kalam
Keyword(s):  
Robust Control ◽  
System Identification ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing

NON-PARAMETRIC IDENTIFICATION TECHNIQUES FOR INTELLIGENT PNEUMATIC ACTUATOR

2015 ◽  
Vol 77 (20) ◽  
Author(s):  
Abdulrahman A. A. Emhemed ◽  
Rosbi Mamat ◽  
Ahmad ‘Athif Mohd Faudzi
Keyword(s):  
System Identification ◽  
Parametric Identification ◽  
Pneumatic Actuator ◽  
Step Response ◽  
Model Parameters ◽  
Force Model ◽  
Force System ◽  
Identification Technique ◽  
Identification Techniques ◽  
Non Parametric

The aim of this paper is to present experimental, empirical and analytic identification techniques, known as non-parametric techniques. Poor dynamics and high nonlinearities are parts of the difficulties in the control of pneumatic actuator functions, which make the identification technique very challenging. Firstly, the step response experimental data is collected to obtain real-time force model of the intelligent pneumatic actuator (IPA). The IPA plant and Personal Computer (PC) communicate through Data Acquisition (DAQ) card over MATLAB software. The second method is approximating the process by curve reaction of a first-order plus delay process, and the third method uses the equivalent n order process with PTn model parameters. The obtained results have been compared with the previous study, achieved based on force system identification of IPA obtained by the (Auto-Regressive model with eXogenous) ARX model. The models developed using non-parameters identification techniques have good responses and their responses are close to the model identified using the ARX system identification model. The controller approved the success of the identification technique with good performance. This means the Non-Parametric techniques are strongly recommended, suitable, and feasible to use to analyze and design the force controller of IPA system. The techniques are thus very suitable to identify the real IPA plant and achieve widespread industrial acceptance.

Influence of Retainer Bearing Misalignment on the Performance of Active Magnetic Bearing

2012 ◽  
Vol 588-589 ◽  
pp. 141-146 ◽  
Author(s):  
Hong Wei Li ◽  
Wen Tao Yu ◽  
You Peng Fan ◽  
Shu Qin Liu
Keyword(s):  
Pid Controller ◽  
Damping Ratio ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
System Structure ◽  
Design System ◽  
Force Model ◽  
Low Pass ◽  
And Performance ◽  
Low Pass Filters

The retainer bearing will be misaligned for mechanical errors, which leads to the uneven air gap of AMB and affects the performance of AMB. To study this problem, the electric-magnetic force model was built first with the misalignment of retainer bearing. With this model, the influences of the misalignment on the system stiffness, damping and damping ratio of AMB were studied through theory analysis and simulation based on the PID controller with low-pass filters. The study indicates that the system stiffness and damping ratio of AMB employing PID controller will increase with the increase of retainer bearing misalignment. The results provide certain references for the system structure optimum design, system debugging and fault diagnosis and performance improvement of AMB-rotor system.

scholarly journals Modelling and system identification of active magnetic bearing systems

2007 ◽  
Vol 13 (2) ◽  
pp. 125-142 ◽  
Author(s):  
Young Man Cho ◽  
Sriram Srinavasan ◽  
Jae-Hyuk Oh ◽  
Hwa Soo Kim
Keyword(s):  
System Identification ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing

Development of Experimental Active Magnetic Bearing Device for Measurement of Mechanical Seal Reaction Force Acting on Rotor

2018 ◽  
Author(s):  
Hiroki Manabe ◽  
Shota Yabui ◽  
Hideyuki Inoue ◽  
Tsuyoshi Inoue
Keyword(s):  
Force Measurement ◽  
Reaction Force ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Mechanical Seal ◽  
Rotating Shaft ◽  
Fluid Force ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Measurement And Evaluation

In turbomachinery, seals are used to prevent fluid leakage. At seal part, rotordynamic fluid force (RD fluid force), which causes whirling motion of rotor, is generated. Under certain conditions, the RD fluid force may contribute to instability of the machine. There are several cases that the whirling is accompanied by eccentricity due to the influence of gravity, or the whirling orbit becomes elliptical due to the influence of the bearing support anisotropy. In these cases, mathematical modeling of the RD fluid forces becomes increasingly complex. As a result, the RD fluid force measurement is more preferable. To improve the measurement and evaluation technology of the RD fluid force, a method to arbitrarily control whirling of the orbit is required. In this paper, RD fluid force measurement by controlling the shape of the orbit using an active magnetic bearing (AMB) is proposed. A contact type mechanical seal is used as a test specimen. When the rotating shaft is whirling, the RD fluid force due to hydrodynamics lubrication and the frictional force due to contact occur on the sliding surface. The resultant force of these forces is taken as the reaction force of mechanical seal and the measurement is performed. The measured reaction force of the mechanical seal is compared with simulation results and the validity of the proposed measurement method is confirmed.

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