Model and Control System Development for a Distributed Actuation Magnetic Bearing and Thin-Walled Rotor Subject to Noncircularity

Abstract

This paper considers the problem of controlling the vibration of a lightweight thin-walled rotor with a distributed actuation magnetic bearing (DAMB). A theoretical flexible rotor model is developed that shows how multiharmonic vibration arises due to small noncircularity of the rotor cross section. This model predicts a series of resonance conditions that occur when the rotational frequency matches a subharmonic of a system natural frequency. Rotor noncircularity can be measured offline, and the measurement data used to cancel its effect on the position sensor signals used for feedback control. A drawback of this approach is that noncircularity is difficult to measure exactly and may vary over time due to changing thermal or elastic state of the rotor. Moreover, any additional multiharmonic excitation effects will not be compensated. To overcome these issues, a harmonic vibration control algorithm is applied that adaptively modifies the harmonic components of the actuator control currents to match a target vibration control performance, but without affecting the stabilizing feedback control loops. Experimental results for a short thin-walled rotor with a single DAMB are presented, which show the effectiveness of the techniques in preventing resonance during operation. By combining sensor-based noncircularity compensation with harmonic vibration control, a reduction in vibration levels can be achieved without precise knowledge of the rotor shape and with minimal bearing forces.

Linearizing Control of a Distributed Actuation Magnetic Bearing for Thin-Walled Rotor Systems

“…A harmonic vibration control (HVC) algorithm is applied in parallel with the PD controller to eliminate multi-harmonic vibration of the rotor when rotating. Previously, it has been shown that multi-harmonic vibration of a thin-walled rotor is prone to arise due to a combination of mass-unbalance and non-circularity of the rotor wall [6]. In the present study, the HVC is used to eliminate rotor vibration so that the required vibration control forces can be evaluated and compared.…”

“…Significant vibration of the rotor involving higher harmonics of the rotational frequency occurred for this case. This vibration is caused by noncircularity of the rotor cross-section, as well as nonlinear effects from the bearing (see Reference [6]). The effectiveness of the control implementations can be further compared from Figure 15, where Fourier transform data for the rotor vibration signals and coils currents are presented.…”

“…Feedback control of actuator coil currents based on measured rotor displacements is used to stabilize the rotor positioning within the bearing and prevent excessive vibration [1,2]. Although AMBs have been widely applied with solid-shaft rotors, there has been recent research interest in the design and application of AMBs with hollow and ring-like rotors [3][4][5][6]. In the case of thin-walled rotors, a larger number of smaller actuators may be incorporated within the bearing to support the rotor around its periphery [5].…”

Piezo-based flexural vibration suppression for an annular rotor via rotating-frame H2 control optimization

“…Excitation by massunbalance does not occur for these modes. However, excitation can still arise due to interaction of the rotor structure with external components/forces (Chamroon et al, 2019;Cole and Fakkaew, 2018;Cooley and Parker, 2014;Endo et al, 1984). This paper addresses a main challenge in achieving optimal vibration control, which is that these aspects must be correctly accounted for in the system modeling, control configuration, and controller design.…”