Damping Ratio Estimation Techniques for Rotordynamic Stability Measurements

Cloud, C. Hunter; Maslen, Eric H.; Barrett, Lloyd

doi:10.1115/gt2008-50691

Cited by 3 publications

(3 citation statements)

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“…Multiple output backward autoregression (MOBAR) method was proposed by C. Hunter Cloud [2] for estimating the damping ratio of complex systems. When stability measurements were performed by the Dresser-Rand [3], Sulzer Turbo Ltd [4,5] and Hitachi Plant Technologies Ltd [6] , a magnetic bearing exciter was used.…”

Section: Introductionmentioning

confidence: 99%

Identification of Damping Ratio for a Rotor-Bearing System Using a Magnetic Bearing Exciter

Zhu

Zhang

Wang

et al. 2011

AEF

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A magnetic bearing exciter is attached to the rotor-bearing system, to exert an asynchronously rotating force on the rotor to excite the first forward mode. And the half-power point method is developed on the basis of displacement response function, where displacement response data is needed only to identify the frequency and damping. The simulation results show that the method can effectively identify the damping with speed and white noise interference. The experiment results show that the damping radio decreases with increasing rotational speed. It has a good engineering application prospects.

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Section: Introductionmentioning

confidence: 99%

Identification of Damping Ratio for a Rotor-Bearing System Using a Magnetic Bearing Exciter

Zhu

Zhang

Wang

et al. 2011

AEF

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“…，開ループ特性の位相余裕からロータの減衰比を求める手法(藤原他，2008) ，加振後の減衰振動からシステムの減衰比を求める手法 (Cloud et al, 2009) ，周波数応答からシステムの複素固有値を求める手法 (Takahashi et al, 2012)…”

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Stability diagnosis of rotor-oil film bearing system by utilizing magnetic bearing

Tsunoda

Hijikata

Shinshi

et al. 2016

Transactions of the JSME (In Japanese)

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Oil film bearings are applied for large rotational machineries owing to their large load capacity and damping effect. However, a swirling flow of the lubricant induces self-excitation at high rotational speed. The stability margin changes during many years due to the mechanical wear and fatigue. Thus, stability diagnosis of the rotor-oil film bearing systems is required. In this paper, we focus on the onset rotational speed of self-excitation as a stability index. Firstly, a 2-DOF rotor-oil film bearing model is constructed using the mode synthesis method and Bently/Muszynska model for oil film bearings. Then, an estimation method of the onset rotational speed using frequency responses measured at lower rotational speeds than the onset one is derived from the model. Finally, a test rig consisting of a rotor supported with two oil film bearings and a radial magnetic bearing is fabricated and frequency response functions with forward circular excitation are measured by utilizing the magnetic bearing. The experimental result shows that the predicted onset rotational speed using the frequency responses at 30, 40 and 50 rps is 60.4 rps, and the error between the estimated and measured onset rotational speeds is less than 4 rps (6%).

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“…The angle of impact was either ver- ward or backward) was varied so as to target the precise frequency of Nc1. This is known as blocking (Cloud et al, 2009). The free decay of the rotor vibrations following either the hammer impact, or termination of the blocking excitation was recorded from multiple position sensors using a separate data acquisition system from the DSP controller (see Appendix C).…”

Section: Stability Thresholdmentioning

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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Damping Ratio Estimation Techniques for Rotordynamic Stability Measurements

Cited by 3 publications

References 0 publications

Identification of Damping Ratio for a Rotor-Bearing System Using a Magnetic Bearing Exciter

Identification of Damping Ratio for a Rotor-Bearing System Using a Magnetic Bearing Exciter

Stability diagnosis of rotor-oil film bearing system by utilizing magnetic bearing

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

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