Robust control of magnetic bearings in subcritical machines
No Thumbnail Available
URL
Journal Title
Journal ISSN
Volume Title
Doctoral thesis (monograph)
Checking the digitized thesis and permission for publishing
Instructions for the author
Instructions for the author
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
1999-02-05
Major/Subject
Mcode
Degree programme
Language
en
Pages
143
Series
Acta polytechnica Scandinavica. El, Electrical engineering series, 94
Abstract
This publication deals with the robust control of active magnetic bearings (AMB). Methods are developed for the control system synthesis and analysis for subcritical machines. A new synthesis method is developed for the position control loop. In the method, linearization is achieved using two rotation matrices, and two controllers are designed using SISO (single-input, single-output) methods. The controller structure is based on the H∞-optimal controller, which is the best solution with respect to the stated physical performance limits. A generalized Nyquist diagram, based on the numerical range, is used to analyze the system. This diagram gives highly nonconservative stability robustness estimates and is mathematically elegant. The effect of the most important nonlinearity, i.e. power amplifier saturation, is carefully analyzed. For unbalance compensation a simple algorithm is proposed which has only one tuning parameter. By using the generalized Nyquist diagram, it is shown that this simple algorithm generally works in the case of subcritical machines, also at the rigid-body resonance speeds. The single feedback coefficient and robustness can be easily determined using the generalized Nyquist diagram. Finally, AMB is used in mechanical balancing of an elastic rotor.Description
Keywords
active magnetic bearings, robust control, unbalance compensation, generalized Nyquist diagram, numerical range