Wyniki wyszukiwania - BazTech

1

Diagnosis of inter-turn short circuit fault in IPMSMs based on the combined use of greedy tracking and random forest

Wang Jianping, Ma Jian, Meng Dean, Zhao Xuan, Zhang Kai, Liu Qiquan, Xu Kejie

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2024

|

Vol. 72, nr 2

art. no. e148943

EN

Inter-turn short circuit (ITSC) is a frequent fault of interior permanent magnet synchronous motors (IPMSM). If ITSC faults are not promptly monitored, it may result in secondary faults or even cause extensive damage to the entire motor. To enhance the reliability of IPMSMs, this paper introduces a fault diagnosis method specifically designed for identifying ITSC faults in IPMSMs. The sparse coefficients of phase current and torque are solved by clustering shrinkage stage orthogonal matching tracking (CcStOMP) in the greedy tracking algorithm.The CcStOMP algorithm can extract multiple target atoms at one time, which greatly improves the iterative efficiency. The multiple features are utilized as input parameters for constructing the random forest classifier. The constructed random forest model is used to diagnose ITSC faults with the results showing that the random forest model has a diagnostic accuracy of 98.61% using all features, and the diagnostic accuracy of selecting three of the most important features is still as high as 97.91%. The random forest classification model has excellent robustness that maintains high classification accuracy despite the reduction of feature vectors, which is a great advantage compared to other classification algorithms. The combination of greedy tracing and the random forest is not only a fast diagnostic model but also a model with good generalisation and anti-interference capability. This non-invasive method is applicable to monitoring and detecting failures in industrial PMSMs.

2

Electrowetting-based beam scanner with controllable field of view

Zhao Rui, Zhang Kai, Kou Songfeng, Wei Xian, Liang Zhongcheng

Optica Applicata

|

2023

|

Vol. 53, nr 4

655--665

EN

A beam scanner based on electrowetting with controllable field of view is designed. Depending on the first-order paraxial approximation, the scanning path and scanning radius of the beam scanner are derived. Its physical model and properties are established and analyzed with the help of by using the COMSOL and MATLAB. The results show that the scanning beam emitting from the beam scanner realizes 360° scanning freely, and its controllable field of view varies from 0 to 65.3 m successfully under the action of working voltage. The two liquid interfaces in the beam scanner can rotate clockwise or counterclockwise independently, and their inclination angle ranges from 0° to 45°. When the two liquid interfaces turn in the same direction, the scanning effect of edge field is better than that of the central zone. While the scanning effect of the central area is greatly improved and better than that of the edge field when the two liquid interfaces turn in the different direction. In addition, the rotation frequencies of the two interfaces affect the performance of the beam scanner.

3

Wavefield-reconstructed least-squares reverse time migration with dynamic constraint factor

Ding Yi, Li Zhenchun, Zhang Kai, Lin Yuzhao

Acta Geophysica

|

2023

|

Vol. 71, no. 2

671--680

EN

Least-squares reverse time migration is a high-precision migration method, the objective function of this method appears as a strong nonlinear function which is likely to plunge into local minimization, and the whole migration process requires massive calculation. Wavefield reconstruction is an optimized inversion theory proposed in recent years, and has achieved good results in full waveform inversion. In this method, the objective function introduces the wave equation as its penalty term to expand the search space of the solution and weaken the influence of the local minimization. In this paper, the idea of wavefield-reconstructed inversion is introduced into the least-squares reverse time migration. The scattering wavefield reconstruction algorithm under Born approximation is used to constrain the migration process, and the dynamic constraint factor in time–space domain is introduced to suppress the high-order scattering artifacts and improve the signal-to-noise ratio of the migration results. Generally, the method can ensure the accuracy of the update gradient. The experimental results show that this method can effectively suppress the artifacts caused by high-order scattering wave when there are large-scale high-velocity anomalies in the velocity field. In addition, the method has also achieved good results in the test of field datasets.

4

Elastic full waveform inversion in VTI media using logging data constraints and gradient precondition

Xu Yipeng, Zhang Kai, Li Zhenchun, He Zilin, Gao Jinfeng, Zhao Xianyang

Acta Geophysica

|

2022

|

Vol. 70, no 4

1665--1676

EN

Elastic full waveform inversion (EFWI) in VTI media using velocity model-based parameterization (PARM-VTIEFWI) can improve the sensitivity of anisotropic parameters, but there are still the problems of gradient’s interference and Nonunique. Research has shown that logging data can constrain the Non-unique of FWI. Therefore, in this paper, we use the logging data as a constraint to limit the Non-unique of the PARM-VTIEFWI. We derive the objective function and gradient equation for the PARM-VTIEFWI based on the constraint of logging information. In addition, to reduce the interference between the gradients of parameters in VTI media, we incorporate a pseudo-Hessian matrix to precondition the gradients and derive a gradient preconditioning formula based on the pseudo-Hessian matrix in this paper. In summary, we propose a new PARM-VTIEFWI method based on logging information constraint and gradient precondition, which reduces the interference between the parameter gradients and constrains the Non-unique of the inversion. The correctness and validity of the method were demonstrated by examples.

5

Autothermal Reforming of Diesel Oil for PdCeCrFeCu/Al2O3-Catalyzed Hydrogen Production

Lin Lin, Zhang Kai, Sun Chiyu, Zhang Ying

Polish Journal of Chemical Technology

|

2021

|

Vol. 23, nr 2

12--19

EN

To make clear the feasibility and influence factors of diesel fuel autothermal reforming to hydrogen, PdCeCr-FeCu/Al2O3 catalyst was prepared by equivalent-volume impregnation method. Experimental facility based on an adiabatic tubular reactor with preheating section was designed and set up, the behaviors of diesel reforming to hydrogen with straight-run diesel as a raw material according to the analysis of the components were studied. Diesel oil reforming over a catalyst for hydrogen production was analyzed using an adiabatic tubular reactor with a preheating section that was designed and built in-house. The operating conditions were optimized. Under the suitable operating conditions, viz., catalyst bed inlet temperature of 700°C, diesel liquid space velocity of 0.24 h–1, water-carbon ratio of 20, and oxygen-carbon ratio of 0.6, the hydrogen yield reached 28.3 (mol/mol).

6

Effects of initial damage on time-dependent behavior of sandstone in uniaxial compressive creep test

Hou Rongbin, Zhang Kai, Tao Jing

Archives of Mining Sciences

|

2019

|

Vol. 64, no. 4

687--707

EN

Time-dependent behavior of rock mass is important for long-term stability analysis in rock engineering. Extensive studies have been carried out on the creep properties and rheological models for variable kinds of rocks, however, the effects of initial damage state on the time-dependent behavior of rock has not yet been taken into consideration. In the present study, the authors proposed a creep test scheme with controlled initial damage to investigate the influence of initial damage on the time-dependent behavior of sandstone. In the test scheme, the initial states of damage were first determined via unloading the specimen from various stresses. Then, the creep test was conducted under different stress levels with specific initial damage. The experimental results show that there is a stress threshold for the initial damage to influence the behavior of the rock in the uniaxial compressive creep tests, which is the stress threshold of dilatancy of rock. When the creep stress is less than the stress threshold, the effect of the initial damage seems to be insignificant. However, if the creep stress is higher than the stress threshold, the initial damage has an important influence on the time-dependent deformation, especially the lateral and volumetric deformation. Moreover, the initial damage also has great influence on the creep failure stress and long-term strength, i.e., higher initial damage leading to lower creep failure stress and long-term strength. The experimental results can provide valuable data for the construction of a creep damage model and long-term stability analysis for rock engineering.

PL

Przebieg czasowy zachowania górotworu jest zagadnieniem kluczowym w analizie stabilności systemu w ujęciu długoterminowym. Przeprowadzono szerokie badania modeli reologicznych i właściwości procesów pełzania dla rozmaitych typów skał; jednakże w badaniach nie uwzględniano wpływu uszkodzeń początkowych na zachowanie górotworu i jego przebieg czasowy. W artykule autorzy zaproponowali nowy sposób przeprowadzania próby pełzania, z uwzględnieniem kontrolowanych uszkodzeń początkowych, tak by wpływ obecności uszkodzeń początkowych na przebieg czasowy zmian zachowania piaskowca mógł zostać uwzględniony. W metodzie tej w pierwszej fazie określono zakres początkowych uszkodzeń poprzez odprężenie próbki w celu wyeliminowania rożnego rodzaju naprężeń. Następnie przeprowadzono próbę pełzania w warunkach zmiennych obciążeń przykładanych do próbki o określonym poziomie uszkodzeń początkowych. Wyniki eksperymentu wskazują na istnienie pewnej wartości progowej naprężenia powyżej której obecność uszkodzeń początkowych będzie mieć wpływ na zachowanie próbki skalnej w trakcie próby jednoosiowego pełzania; jest to poziom progowy dla powstawania dylatacji. Gdy naprężenie pełzania ma wartość niższą od wartości progowej, wpływ uszkodzeń początkowych wydaje się nieznaczny. Jednakże, dla naprężeń pełzania powyżej wartości progowej, wpływ uszkodzeń początkowych na przebieg odkształceń jest znaczący, zwłaszcza w odniesieniu do odkształceń poprzecznych i objętościowych. Ponadto, istnie-nie uszkodzeń początkowych ma także wpływ na poziom naprężeń rozrywających przy próbie pełzania i wytrzymałość próbki w ujęciu długoterminowym. Wykazano, że im większe uszkodzenia początkowe, tym niższa wartość naprężenia zrywającego przy próbie pełzania i niższa wytrzymałość długoterminowa. Wyniki eksperymentu dostarczyć mogą cennych danych niezbędnych do skonstruowania modelu uszkodzeń skał wskutek pełzania oraz do analiz stabilności konstrukcji inżynierskich w ujęciu długoterminowym.