Identification of damping and complex modes in structural vibrations

Bajrić, Anela; Høgsberg, Jan Becker

doi:10.1016/j.jsv.2018.05.048

Cited by 32 publications

(7 citation statements)

References 35 publications

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“…But practically a lot of natural frequencies will be missing, and only several apparent frequencies can be measured and identified. How many and which frequencies can be identified from the testing data depend mainly on the properties of excitation, position of sensors, and so on [14][15][16][17]. For measuring the overall low-frequency vibration of the excavator boom, the excitation of initial displacement must be exerted on the whole boom rather than local part.…”

Section: Test Methodsmentioning

confidence: 99%

Low‐Frequency Vibration Testing of Huge Bucket Wheel Excavator Based on Step‐Decay Signals

Jiang

Liu

et al. 2018

Shock and Vibration

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The low-frequency vibration of the bucket wheel excavator has an important impact on the fatigue life of the structures. For conventional vibration testing methods, it is difficult and expensive to excite the overall low-frequency vibration of the whole machine. Hence, in this paper, the excitation method that uses the belt-supporting rollers on the boom as an exciter is tried to excite the low-frequency vibration, so that the low natural frequencies can be identified by Fourier transforming the free decay signals caused by the sudden power off. By this method, the first five natural frequencies are obtained, and the results are verified through corresponding computational numerical model of the bucket wheel excavator. It can be concluded that the proposed testing method can achieve the same accuracy but is much more convenient and costs less than existing methods.

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Section: Test Methodsmentioning

confidence: 99%

Low‐Frequency Vibration Testing of Huge Bucket Wheel Excavator Based on Step‐Decay Signals

Jiang

Liu

et al. 2018

Shock and Vibration

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“…Quadratic regression is necessary because multiple parameters of the structure change as more mass is added. Changing mode shapes increase or decrease attenuation at specific frequencies [3] while material compression shifts the resonant frequencies of the structure. When a resonant peak shifts into one of the considered frequency bands, its magnitude response increases, but then drops as the peak shifts away.…”

Section: Actuated Mass Measurementmentioning

confidence: 99%

“…MassHog uses the principle of induced vibrations, with near-resonance frequency bands instead of ultrasonic frequencies. These frequencies have been used for occupant detection in past work [8] and enable better sensitivity to mass changes through mode shape and frequency response analysis [3].…”

Section: Related Workmentioning

confidence: 99%

MassHog: Weight-Sensitive Occupant Monitoring for Pig Pens using Actuated Structural Vibrations

Codling

Bonde

Dong

et al. 2021

Adjunct Proceedings of the 2021 ACM International Joint Conference on Pervasive and Ubiquitous Computing and Proceedings of The

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In the swine livestock industry, weight tracking is commonly used to track health and growth of pigs. This is especially crucial during the farrowing period, where mother sows and their newborn piglets are housed together to facilitate nursing. Existing weight measurement methods, however, either provide only sporadic snapshots or have scalability and reliability issues in the harsh environment of industrial farms. This paper presents MassHog, a multi-layered system for ubiquitous weight measurement in harsh environments, such as pig pens, using structural vibrations. MassHog combines an existing sensor concept with actuated vibrations to weigh both piglets and adult hogs together. We evaluate the components of this system through testing deployments, including at real-world operating pig farms. Preliminary results show less than 2 kg mean absolute error for adult hogs. CCS CONCEPTS• Applied computing → Agriculture; • Computer systems organization → Sensor networks.

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“…Hilbert–Huang transform obtains the responses with one single mode through empirical mode decomposition, and then modal parameters are also calculated by Hilbert transform (N. E. Huang et al., 1998). For the complex modal identification, Bajrić and Høgsberg (2018) gave the damping matrix expression, which is formed by the complex eigenvectors and eigenvalues of a nonclassically damped structure. Puthanpurayil et al.…”

Section: Introductionmentioning

confidence: 99%

Complex frequency identification using real modal shapes for a structure with proportional damping

Yao

et al. 2021

Computer aided Civil Eng

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Modal identification is based on modal superposition theory. For structures with proportional damping, the structural responses are recognized as real modal shapes multiplied by real modal coordinates. However, it is not true because the actual modal shapes should be complex even though they can be normalized to real ones. If the modal shapes are recognized as real ones, the modal superposition theory cannot reflect the actual modal parameters. This paper proposes an innovative method to identify complex frequencies for a structure with proportional damping using the identified real modal shapes, where the complex modal shapes are considered. The proportional damping is ideal but always assumed in practical engineering. The characteristic of the proposed method is that the complex property of frequencies is considered along with modal identification process. First, the reason why the complex modal shapes are hidden is revealed. When the real modal shapes are obtained, the Hilbert transform of analytical responses is used to estimate complex coordinates. Then, formulas to identify the complex frequencies are derived. The k‐means clustering method is employed. Finally, the proposed method is used in a numerical example and a practical bridge example. The results show that the proposed method can estimate the complex frequencies effectively, and can be used in practical engineering.

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Identification of damping and complex modes in structural vibrations

Cited by 32 publications

References 35 publications

Low‐Frequency Vibration Testing of Huge Bucket Wheel Excavator Based on Step‐Decay Signals

Low‐Frequency Vibration Testing of Huge Bucket Wheel Excavator Based on Step‐Decay Signals

MassHog: Weight-Sensitive Occupant Monitoring for Pig Pens using Actuated Structural Vibrations

Complex frequency identification using real modal shapes for a structure with proportional damping

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