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Research Papers: Gas Turbines: Structures and Dynamics

A Multiobjective Adaptive Controller for Magnetic Bearing Systems

[+] Author and Article Information
M. Necip Sahinkaya1

 University of Bath, Bath BA2 7AY, U.K.ensmns@bath.ac.uk

Abdul-Hadi G. Abulrub

Warwick Manufacturing Group, University of Warwick, Coventry CV4 7AL, U.K.

Clifford R. Burrows, Patrick S. Keogh

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, U.K.

1

Corresponding author.

J. Eng. Gas Turbines Power 132(12), 122503 (Aug 27, 2010) (7 pages) doi:10.1115/1.4001060 History: Received August 12, 2009; Revised August 13, 2009; Published August 27, 2010; Online August 27, 2010

The paper considers three issues in flexible rotor and magnetic bearing systems, namely, the control of rotor vibration, control of transmitted forces, and prevention of rotor contact with auxiliary bearings. An adaptive multiobjective optimization method is developed to tackle these issues simultaneously using a modified recursive adaptive controller. The proposed method involves automatic tuning of the weighting parameters in accordance with performance specifications. A two-stage weighting strategy is implemented, involving base weightings, calculated from a singular value decomposition of the system’s receptance matrices, and two adjustable weighting parameters to shift the balance between the three objective functions. The receptance matrices are functions of rotational speed and they are estimated in situ. The whole process does not require prior knowledge of the system parameters. Real-time implementation of the proposed controller is explained and tested by using an experimental flexible rotor magnetic bearing system. The rotor displacements were measured relative to the base frame using four pairs of eddy current displacement transducers. System stability is ensured through local PID controllers. The proposed adaptive controller is implemented in parallel, and the effectiveness of the weighting parameters in changing the balance between the transmitted forces and rotor vibrations is demonstrated experimentally.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Photograph of the experimental system

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Figure 2

A view of the experimental rotor/bearing system showing the eight sensor and two magnetic bearing positions

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Figure 3

Implementation of OLAC. The figure represents the situation at a particular running speed ω. An encoder on the output shaft provides the once per revolution synchronization signal as a phase reference for the FFT and the signal generator.

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Figure 4

Effect of β on the normalized rotor vibration (JY) and normalized transmitted forces (JF) at Ω=22 Hz. (Simulation results from Ref. 25.)

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Figure 5

Real-time implementation of MO-ROLAC

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Figure 6

Experimental results showing the effect of ROLAC

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Figure 7

Experimental results showing the effect of β on the system performance (γ=1)

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Figure 8

Synchronous amplitudes of the total control action (MO-ROLAC+PID) as a function of β(γ=1)

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Figure 9

Experimental results showing the effect of γ on the system performance (β=1)

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Figure 10

Synchronous amplitudes of the total control action (MO-ROLAC+PID) as a function of γ(β=1)

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