Practical Limits to the Performance of Magnetic Bearings: Peak Force, Slew Rate, and Displacement Sensitivity

Maslen, Eric H.; Hermann, P; Scott, Maricia; Humphris, R. R.

doi:10.1115/1.3261918

Cited by 65 publications

(20 citation statements)

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“…9(a). Specifically, the current of either the full-performance or the economy driving configuration for the adjacent electromagnets has slightly smaller peaks than that of the full-bridge configuration, which leads to a small degradation of the dynamic performance [12,13].…”

Section: Voltage and Current Profilesmentioning

confidence: 99%

Driving an AMB system using a 2D space vector modulation of three-leg voltage source converters

Ahn

Jeong

2011

J Mech Sci Technol

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This paper presents new methodologies for driving an active magnetic bearing (AMB) system using a two-dimensional (2D) space vector modulation of three-leg voltage source converters. Two types of driving configurations are proposed: full-performance and economy. The economy configuration is proven to be more cost-effective than the conventional driving configurations. For both driving configurations, conversion rules are developed to calculate the three-leg voltage references from two-coil voltage references of an AMB system. In addition, the potential performance limit of the proposed driving configurations is analyzed. Experimental results are presented using a single degree of freedom (DOF) AMB system to verify the analytical results.

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Section: Voltage and Current Profilesmentioning

confidence: 99%

Driving an AMB system using a 2D space vector modulation of three-leg voltage source converters

Ahn

Jeong

2011

J Mech Sci Technol

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“…Because each gap displacement for the x-direction and y-direction can be controlled individually [21], we focus our analysis strictly on the x-direction motion without loss of generality. As in [21] and [30], we can express the bearing force, which is proportional to the square of the air gap displacement, as follows:…”

Section: Magnetic Bearing Systems Ant Its Fuzzy Modelingmentioning

confidence: 99%

Robust H ∞ control for uncertain nonlinear active magnetic bearing systems via Takagi-Sugeno fuzzy models

Lee

Park

Joo

et al. 2010

Int. J. Control Autom. Syst.

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In this paper, a systematic procedure to design the robust ∞ H fuzzy controller for a nonlinear active magnetic bearing (AMB) system affected by time-varying parametric uncertainties is presented. First, the continuous-time Takagi-Sugeno (T-S) fuzzy model is employed to represent the nonlinear AMB system. Next, based on the obtained fuzzy model, sufficient conditions are derived in terms of linear matrix inequalities (LMIs) for robust stability and ∞ H performance of the control system. The main feature of this paper is that some drawbacks existing in the previous approaches such as truncation errors and nonconvex bilinear matrix inequality (BMI) problem are eliminated by utilizing the homogeneous fuzzy model which includes no bias terms in the local state space models rather than the affine one which includes bias terms. Hence, the design method presented here will prove to be more tractable and accessible than the previous ones. Finally, numerical simulations demonstrate the effectiveness of the proposed approach.

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“…The actuator has several unique force output limitations arising from electromagnetic effects as well as requirements for accurate sensor feedback of the rotor position (Schweitzer, 2002). These limiting effects are particularly important as their onset is accompanied by deterioration of the expected actuator stiffness and damping properties regardless of the type of control algorithm used (Maslen et al, 1988).…”

Section: Unique Limitations Of Ambsmentioning

confidence: 99%

“…Displacement sensitivity is characterized by the reduction of bearing effective spring rate during large amplitude vibrations approaching bearing clearance (Maslen et al, 1988). (Schweitzer, 2002).…”

Section: Unique Limitations Of Ambsmentioning

confidence: 99%

Robust Control of Rotordynamic Instability in Rotating Machinery Supported by Active Magnetic Bearings

Mushi

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This dissertation addresses the control challenges for a practical mechatronic system subject to self-excited instability modeled as a parametric uncertainty. Achieving a balance between the conflicting requirements of performance and robustness in the face of system uncertainty is the primary objective of feedback control. Practical issues such as unstable open-loop plant dynamics, finite actuator capacity, the presence structural flexibility and suboptimal sensor/actuator placement limit the achievable performance through the use of feedback.The ROMAC Magnetic Bearing Test Rig for Rotordynamic Instability (MBTRI) is a state-of-the-art experiment designed to investigate algorithms that may affect the region of stability of a rotor-bearing system with respect to rotordynamic instability as a result of aerodynamic cross-coupled stiffness. The onset of rotordynamic instability is a significant challenge to successful design and operation of high speed rotating machinery particularly gas compressors. The unique design of the test rig includes several features of an industrial centrifugal gas compressor with a flexible rotor designed to operate above its first bending critical speed. The impellers and gas seals within compressors are the primary source of load-dependent aerodynamic cross-coupled stiffness forces which can lead to self-excited instability and serious machine damage in the absence of sufficient support damping. During the design phase of rotating machines the accurate prediction of the onset of instability is made difficult by reliance on semi-empirical dynamic models with significant uncertainty. Literature on the rotordynamic instability mechanism reveals that in the presence of optimum support damping, a maximum achievable stability threshold can be derived as a function of physical parameters of the rotor-bearing system. This presents an ideal opportunity for the exploration of optimal robust active vibration control algorithms using active ii magnetic bearings (AMBs). A notable advantage of AMBs is their ability to generate optimal support stiffness and damping characteristics. Unlike passive mechanical bearings, the support characteristics of AMBs may be modified over the operating life of the system without any major hardware changes.A general framework is presented whereby properties of the rotor-AMB system that impose fundamental limitations on achievable performance of the closed-loop system are evaluated as a nominal model of the MBTRI plant dynamic is constructed. This model was validated using system identification techniques, and augmented with uncertainty models representing the effects of variation in parameters such operating speed and the magnitude of the destabilizing stiffness. Using µ-synthesis several robust controllers were designed and implemented on the MBTRI hardware to investigate their effect on the stability threshold. The best controller established a thirty-six percent increase in the stability threshold over an existing benchmark controller. This represented an ...

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Practical Limits to the Performance of Magnetic Bearings: Peak Force, Slew Rate, and Displacement Sensitivity

Cited by 65 publications

References 0 publications

Driving an AMB system using a 2D space vector modulation of three-leg voltage source converters

Driving an AMB system using a 2D space vector modulation of three-leg voltage source converters

Robust H ∞ control for uncertain nonlinear active magnetic bearing systems via Takagi-Sugeno fuzzy models

Robust Control of Rotordynamic Instability in Rotating Machinery Supported by Active Magnetic Bearings

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