Fault diagnosis of bolt loosening in structures with a novel second-order output spectrum–based method

2019 ◽  
Vol 19 (1) ◽  
pp. 123-141 ◽  
Author(s):  
Quankun Li ◽  
Xingjian Jing
Keyword(s):  
Estimation Algorithm ◽  
Second Order ◽  
New Method ◽  
Spectrum Estimation ◽  
Output Spectrum ◽  
Damage Indicator ◽  
Restoring Forces ◽  
Bolt Loosening ◽  
A Chain ◽  
Detection And Localization

This article presents a novel second-order output spectrum–based method for detecting and localizing multiple bolt loosening faults in complex structures with a sensor chain. This new method is developed based on a recently developed nth-order output spectrum estimation algorithm using only proper data obtained from a chain of sensors. The properties of the second-order output spectrum transmissibility of the sensor chain along physical structures with bolts are studied systematically. In the new method, the noise effect on accuracy of the estimation of fault indicators is investigated as well. The new method also considers more general nonlinear restoring forces not only due to faults but also due to inherent nonlinearity in structure when deriving the properties of the second-order output spectrum transmissibility. Extensive simulation and experimental results demonstrate that the second-order output spectrum of the studied structure can be estimated efficiently, and the second-order output spectrum transmissibility can be used as an effective and reliable damage indicator for the detection and localization of multiple bolt loosening faults in complex bolted structures.

A second-order output spectrum based method for detecting bolt-loosening fault in a satellite-like structure

2019 ◽  
Vol 26 (4) ◽  
pp. 157-165
Author(s):  
Quankun Li ◽  
Xingjian Jing
Keyword(s):  
Second Order ◽  
Bolted Joint ◽  
Output Spectrum ◽  
Engineering Structures ◽  
Local Tuning ◽  
Damage Indicator ◽  
Non Linear ◽  
Linear Behaviour ◽  
Novel Method ◽  
Bolt Loosening

Bolt-loosening faults frequently exist in industrial engineering structures since these bolted structures are often subjected to vibrations or the like in their service process. In this paper, a novel method based on the second-order output spectrum (SOOS) is proposed to detect potential bolt-loosening faults in a complex satellite-like structure. In this method, a general multi-degree-of-freedom (MDOF) model simulating bolt-loosening faults induced non-linearities and inherent boundary or material non-linearities by non-linear forces is built to describe the non-linear behaviour of the structure, and then a local damage indicator is derived for bolt-loosening fault detection through a local tuning approach (LTA) which tunes local structural properties. Results of experimental cases demonstrate that the state of bolted joint in the satellite-like structure with inherent non-linearities can be estimated by this novel SOOS based method effectively and reliably.

A New Method for Detection and Localization of Urinary Infection: the Fluorescence Antibody Test

1976 ◽  
Vol 2 (3) ◽  
pp. 145-148 ◽  
Author(s):  
A. Pujol ◽  
F. Linares ◽  
J. Muñoz ◽  
A. Rusconi ◽  
V. Orejas ◽  
...  
Keyword(s):  
Urinary Infection ◽  
Antibody Test ◽  
New Method ◽  
Fluorescence Antibody ◽  
Detection And Localization

scholarly journals Barycentric prolate interpolation and pseudospectral differentiation

2021 ◽  
Author(s):  
Yan Tian
Keyword(s):  
Boundary Value Problem ◽  
Convergence Rates ◽  
Boundary Value ◽  
High Accuracy ◽  
Second Order ◽  
New Method ◽  
Numerical Examples ◽  
Helmholtz Problem ◽  
Collocation Scheme

AbstractIn this paper, we provide further illustrations of prolate interpolation and pseudospectral differentiation based on the barycentric perspectives. The convergence rates of the barycentric prolate interpolation and pseudospectral differentiation are derived. Furthermore, we propose the new preconditioner, which leads to the well-conditioned prolate collocation scheme. Numerical examples are included to show the high accuracy of the new method. We apply this approach to solve the second-order boundary value problem and Helmholtz problem.

scholarly journals Position Estimation of a PMSM in an Electric Propulsion Ship System Based on High-Frequency Injection

Electronics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 276 ◽  
Author(s):  
Hongfen Bai
Keyword(s):  
Permanent Magnet ◽  
High Frequency ◽  
Electric Propulsion ◽  
Permanent Magnet Synchronous Motor ◽  
Estimation Algorithm ◽  
Synchronous Motor ◽  
Position Estimation ◽  
Second Order ◽  
Application Range ◽  
Rotor Position

To improve the operating performance of electric propulsion ships, the permanent magnet synchronous motor is commonly used as the propulsion motor. Additionally, position estimation without sensors can further improve the application range of the propulsion motor and the estimated results can represent the redundancy of measured values from mechanical sensors. In this paper, the high-frequency (HF) injection algorithm combined with the second-order generalized integrator (SOGI) is presented on the basis of analyzing the structure of the electric propulsion ship and the vector control of the motors. The position and rotor speed were estimated accurately by the approximate calculation of q-axis currents directly related to the rotor position. Moreover, the harmonics in the estimated position were effectively reduced by the introduction of the second-order generalized integrator. Then, the rotor position estimation algorithm was verified in MATLAB/Simulink by choosing different low speeds including speed reversal, increasing speed, and increasing load torque. Finally, the correctness of the proposed improved high-frequency injection algorithm based on the second-order generalized integrator was verified by the experimental propulsion permanent magnet synchronous motor (PMSM) system at low speed.

scholarly journals A New Online Dynamic Testing Method for Noise of Broadcast Transmitter

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Shan-Shan Li ◽  
Jian Zhou ◽  
Xuan Wang
Keyword(s):  
Real Time ◽  
Data Storage ◽  
Dynamic Testing ◽  
Noise Figure ◽  
Estimation Algorithm ◽  
Test Method ◽  
Noise Estimation ◽  
Experimental Simulation ◽  
Spectrum Estimation ◽  
Low Efficiency

Aiming at the shortcomings of traditional broadcast transmitter noise test methods, such as low efficiency, inconvenient data storage, and high requirements for testers, a dynamic online test method for transmitter noise is proposed. The principle of system composition and test method is given. The transmitter noise is real-time changing. The Voice Active Detection (VAD) noise estimation algorithm cannot track the transmitter noise change in real time. This paper proposes a combined noise estimation algorithm for VAD and dynamic estimation. By setting the threshold of the double-threshold VAD detection to be low, it can accurately detect the silent segment. The silent segment is used as a noise signal for noise estimation. For the nonsilent segment detected by the VAD, a minimum value search dynamic spectrum estimation algorithm based on the existence probability of the speech (IMCRA) is used for noise estimation. Transmitter noise is measured by calculating the noise figure (NF).The test method collects the input and output data of the transmitter in real time, which has better accuracy and real-time performance, and the feasibility of the method is verified by experimental simulation.

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