Suppression of Base Excitation of Rotors on Magnetic Bearings

Abstract

This paper deals with rotor systems that suffer harmonic base excitation when supported on magnetic bearings. Magnetic bearings using conventional control techniques perform poorly in such situations mainly due to their highly nonlinear characteristics. The compensation method presented here is a novel optimal control procedure with a combination of conventional, proportional, and differential feedback control. A four-degree-of-freedom model is used for the rotor system, and the bearings are modeled by nonlinear expressions. Each disturbance frequency is expected to produce a multiharmonic system response, a characteristic of nonlinear systems. We apply optimal control choosing to minimize a performance index, which leads to the optimization of the trigonometric coefficients in the correction current function. Results show that the control technique suppresses rotor vibration to amplitudes that were significantly smaller than the disturbance amplitudes for the entire range of disturbance frequencies applied. The control technique explored in this paper is a promising step towards the successful application of magnetic bearings to systems mounted on moving platforms.

The effect of time-periodic base angular motions upon dynamic response of asymmetric rotor systems

“…As the base motions would induce severe vibrations to rotor system under certain conditions, several researchers also presented the active control method using the electromagnetic actuators. [31][32][33] From the above literature, one can see that both linear and angular base motions not only cause external force excitations but also internal excitations to the rotor-bearing system. It is well known that the rotor asymmetry results in parametric excitations to the system.…”

Numerical investigation on the dynamic behavior of an onboard rotor system by using the FEM approach

“…The experimental validation of the proposed methodology was presented. Marx and Nataraj [12] showed a novel optimal control procedure with a combination of conventional, proportional, and differential feedback control, to attenuate base excitations applied in a rotating shaft supported by magnetic bearings. Das et al [5] used an electromagnetic actuator to control the lateral vibrations of an onboard rotating machine.…”

Parametric instability of flexible rotor-bearing system under time-periodic base angular motions

“…The moving base not only causes external force excitations but also gyroscopic and stiffness excitations to the rotor-bearing system. Over the past ten years, a number of studies [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] have been carried out on the dynamic characteristics of base excited rotor systems, which differ distinctly from that of the fixed supported rotor systems.…”

“…Hou et al [16] focused on the nonlinear vibration phenomenon caused by aircraft hovering flight in a rub-impact rotor system supported by two general supports with cubic stiffness. Moreover, several researchers also concerned about the active vibration control of base excited rotor-bearing system utilizing the electromagnetic actuators [17][18][19].…”