Stochastic resonance can use noise to enhance weak signals,effectively reducing the effect of noise signals on feature extraction.In order to improve the early fault recognition rate of rolling bearings,and to overcom...Stochastic resonance can use noise to enhance weak signals,effectively reducing the effect of noise signals on feature extraction.In order to improve the early fault recognition rate of rolling bearings,and to overcome the shortcomings of lack of interaction in the selection of SR(Stochastic Resonance)method parameters and the lack of validation of the extracted features,an adaptive genetic random resonance early fault diagnosis method for rolling bearings was proposed.compared with the existing methods,the AGSR(Adaptive Genetic Stochastic Resonance)method uses genetic algorithms to optimize the system parameters,and further optimizes the parameters while considering the interaction between the parameters.This method can effectively extract the weak fault features of the bearing.In order to verify the effect of feature extraction,the feature signal extracted by AGSR method was input into the Fully connected neural network for fault diagnosis.the practicality of the algorithm is verified by simulation data and rolling bearing experimental data.the results show that the proposed method can effectively detect the early weak features of rolling bearings,and the fault diagnosis effect is better than the existing methods.展开更多
Aiming at the fact that the rotor winding inter-turn weak faults can hardly be detected due to the strong electromagnetic coupling effect in the excitation system,an interval observer based on current residual is desi...Aiming at the fact that the rotor winding inter-turn weak faults can hardly be detected due to the strong electromagnetic coupling effect in the excitation system,an interval observer based on current residual is designed.Firstly,the mechanism of the inter-turn short circuit of the rotor winding in the excitation system is modeled under the premise of stable working conditions,and electromagnetic decoupling and system simplification are carried out through Park Transform.An interval observer is designed based on the current residual in the two-phase coordinate system,and the sensitive and stable conditions of the observer is preset.The fault diagnosis process based on the interval observer is formulated,and the observer gain matrix is convexly optimized by linear matrix inequality.The numerical simulation and experimental results show that the inter-turn short circuit weak fault is hardly detected directly through the current signal,but the fault is quickly and accurately diagnosed through the residual internal observer.Compared with the traditional fault diagnosis method based on excitation current,the diagnosis speed and accuracy are greatly improved,and the probability of misdiagnosis also decreases.This method provides a theoretical basis for weak fault identification of excitation systems,and is of great significance for the operation and maintenance of excitation systems.展开更多
When the bi-stable stochastic resonance method was applied to enhance weak thruster fault for autonomous underwater vehicle(AUV), the enhancement performance could not satisfy the detection requirement of weak thruste...When the bi-stable stochastic resonance method was applied to enhance weak thruster fault for autonomous underwater vehicle(AUV), the enhancement performance could not satisfy the detection requirement of weak thruster fault. As for this problem, a fault feature enhancement method based on mono-stable stochastic resonance was proposed. In the method, in order to improve the enhancement performance of weak thruster fault feature, the conventional bi-stable potential function was changed to mono-stable potential function which was more suitable for aperiodic signals. Furthermore, when particle swarm optimization was adopted to adjust the parameters of mono-stable stochastic resonance system, the global convergent time would be long. An improved particle swarm optimization method was developed by changing the linear inertial weighted function as nonlinear function with cosine function, so as to reduce the global convergent time. In addition, when the conventional wavelet reconstruction method was adopted to detect the weak thruster fault, undetected fault or false alarm may occur. In order to successfully detect the weak thruster fault, a weak thruster detection method was proposed based on the integration of stochastic resonance and wavelet reconstruction. In the method, the optimal reconstruction scale was determined by comparing wavelet entropies corresponding to each decomposition scale. Finally, pool-experiments were performed on AUV with thruster fault. The effectiveness of the proposed mono-stable stochastic resonance method in enhancing fault feature and reducing the global convergent time was demonstrated in comparison with particle swarm optimization based bi-stochastic resonance method. Furthermore, the effectiveness of the proposed fault detection method was illustrated in comparison with the conventional wavelet reconstruction.展开更多
On the basis of the Xining active urban fault survey, we studied the relationship between the active urban fault and fold deformation. The result of this research shows that the Huangshuihe fault and the NW-striking f...On the basis of the Xining active urban fault survey, we studied the relationship between the active urban fault and fold deformation. The result of this research shows that the Huangshuihe fault and the NW-striking fault on the northern bank of the Huangshulbe River are tensional faults on top of an anticline, the Nanchuanhe fault is a transverse tear fault resulting from differential folding on two sides of the fault, the east bank of the Beichuanhe River fault is a compressional fault developed on the core or climb of a syncline. By balance profile analysis of fold deformation and inversion of gravity anomaly data, we obtained the depth of the detachment plane and established the seismotectonic model of the ）fining urban area. Based on the seismotectonic model, we analyzed the earthquake potential of the active urban fault.展开更多
Fault formation and evolution in the presence of multiple pre-existing weaknesses has not been investigated extensively in rift basins. The fault systems of Weixinan Sag, Beibuwan Basin of China, which is fully covere...Fault formation and evolution in the presence of multiple pre-existing weaknesses has not been investigated extensively in rift basins. The fault systems of Weixinan Sag, Beibuwan Basin of China, which is fully covered with high-precision 3-D seismic data and is rich in oil-gas resources, have been successfully reproduced by sandbox modeling in this study with inclusion of multiple pre-existing weaknesses in the experimental model. The basic characteristics of fault formation and evolution revealed by sandbox modeling are as follows. 1） Weakness-reactivation faults and weakness-related faults are formed much earlier than the distant-weakness faults （faults far away from and with little or no relationship to the weakness）. 2） Weakness-reactivation faults and weakness-related faults develop mainly along or parallel to a pre-existing weakness, while distant-weakness faults develop nearly perpendicular to the extension direction. A complicated fault system can be formed in a fixed direction of extension with the existence of multiple pre-existing weaknesses, and the complicated fault system in the Weixinan Sag formed gradually in a nearly N-S direction with multiple pre-existing weaknesses. 3） The increase in the length and number of faults is closely tied to the nature of pre-existing weaknesses. The sandbox model may provide a new clue to detailed fault system research for oil and gas exploration in rift basins.展开更多
In this paper, the well-known Duffing equation and the nonlinear equation describing vibration of the human eardrum are introduced from elastic nonlinear system theory. According to the fact that the human ear can dis...In this paper, the well-known Duffing equation and the nonlinear equation describing vibration of the human eardrum are introduced from elastic nonlinear system theory. According to the fact that the human ear can distinguish weak sound with small difference, the idea that the Duffing oscillator can be used to detect a weak signal and diagnose early fault of machinery is proposed. In order to obtain a model for weak signal detection via the Duffing oscillator, the first step is to seek all forms of solutions of the Duffing equation. The second step is to study global bifurcations of the Duffing equation using qualitative analysis theory of a dynamic system. That is to say, a series of bifurcations thresholds of the Duffing equation can be analyzed by the Melnikov function and a subharmonics Melnikov function. Then the three types of bifurcations thresholds varying with damping and external exciting amplitude are discussed. The analysis concludes that the bifurcation threshold corresponding to the maximum orbit of solutions outside the homo-clinic orbit of the Duffing equation can be used to detect a weak signal. Finally, the implementing model of the Duffing oscillator for weak signal detection is given.展开更多
为了提高二维随机共振的信号增强能力,提出一种基于外加信号和高斯函数的二维非对称随机共振系统(novel two-dimensional asymmetric bistable potential system based on external signal and Gaussian function,NTABPS-EG).首先,以输...为了提高二维随机共振的信号增强能力,提出一种基于外加信号和高斯函数的二维非对称随机共振系统(novel two-dimensional asymmetric bistable potential system based on external signal and Gaussian function,NTABPS-EG).首先,以输出信噪比为衡量指标,研究了3种非对称势的系统性能,根据分析结果选取阱深阱宽非对称势进行后续研究,并探究了不同参数下系统输出信噪比随噪声强度的变化趋势.其次,采用四阶龙格库塔算法进行数值模拟,并采用遗传算法求解最佳参数,使系统得到最佳输出响应.通过与二维指数势双稳系统(two-dimensional exponential potential bi-stable potential system,TEPBPS)的对比,发现NTABPS-EG系统更能有效地驱动粒子跃迁,对微弱信号的恢复效果较好.最后,将NTABPS-EG系统应用于轴承故障检测,实验结果表明系统可以有效诊断出轴承的内外圈故障,且诊断能力优于TEPBPS,证明了系统的实用性和先进性.展开更多
该文针对极弱电网、严重故障场景研究传统故障穿越策略对虚拟同步发电机(virtual synchronous generator,VSG)型构网变流器大干扰稳定性的影响。首先,通过理论推导并建立传统故障穿越策略下VSG构网特性表征模型,用以表征电网故障阶段VS...该文针对极弱电网、严重故障场景研究传统故障穿越策略对虚拟同步发电机(virtual synchronous generator,VSG)型构网变流器大干扰稳定性的影响。首先,通过理论推导并建立传统故障穿越策略下VSG构网特性表征模型,用以表征电网故障阶段VSG构网同步特性与电压支撑特性;在此基础上,结合故障成功穿越所需具备的条件,进一步提出故障穿越可行域的概念以及故障严重程度的界定原则,明确传统VSG故障穿越策略对于不同程度故障、不同限流幅值的适用范围;并且,针对传统故障穿越无法覆盖全故障场景的问题,提出一种名为动态限幅电压控制的新型控制方式(dynamic limiting voltage control,DLVC),并在其基础上进一步提出一种增强型VSG故障穿越策略(dynamic limiting voltage control fault ride through,DLVC-FRT),其具有近区无功、远区电压控制的灵活控制特性,在限制短路电流的同时可有效提升VSG在极弱电网场景下对电网电压的支撑能力;最后,在PSCAD/EMTDC中构建仿真,并验证所提策略的有效性。展开更多
基金The authors would like to acknowledge the financial support from the National Science Foundation of China(Grant Nos.51505234,51575283,51405241).
文摘Stochastic resonance can use noise to enhance weak signals,effectively reducing the effect of noise signals on feature extraction.In order to improve the early fault recognition rate of rolling bearings,and to overcome the shortcomings of lack of interaction in the selection of SR(Stochastic Resonance)method parameters and the lack of validation of the extracted features,an adaptive genetic random resonance early fault diagnosis method for rolling bearings was proposed.compared with the existing methods,the AGSR(Adaptive Genetic Stochastic Resonance)method uses genetic algorithms to optimize the system parameters,and further optimizes the parameters while considering the interaction between the parameters.This method can effectively extract the weak fault features of the bearing.In order to verify the effect of feature extraction,the feature signal extracted by AGSR method was input into the Fully connected neural network for fault diagnosis.the practicality of the algorithm is verified by simulation data and rolling bearing experimental data.the results show that the proposed method can effectively detect the early weak features of rolling bearings,and the fault diagnosis effect is better than the existing methods.
基金supports from National Science Foundation of China(Grant No.51777121).
文摘Aiming at the fact that the rotor winding inter-turn weak faults can hardly be detected due to the strong electromagnetic coupling effect in the excitation system,an interval observer based on current residual is designed.Firstly,the mechanism of the inter-turn short circuit of the rotor winding in the excitation system is modeled under the premise of stable working conditions,and electromagnetic decoupling and system simplification are carried out through Park Transform.An interval observer is designed based on the current residual in the two-phase coordinate system,and the sensitive and stable conditions of the observer is preset.The fault diagnosis process based on the interval observer is formulated,and the observer gain matrix is convexly optimized by linear matrix inequality.The numerical simulation and experimental results show that the inter-turn short circuit weak fault is hardly detected directly through the current signal,but the fault is quickly and accurately diagnosed through the residual internal observer.Compared with the traditional fault diagnosis method based on excitation current,the diagnosis speed and accuracy are greatly improved,and the probability of misdiagnosis also decreases.This method provides a theoretical basis for weak fault identification of excitation systems,and is of great significance for the operation and maintenance of excitation systems.
基金Project(51279040)supported by the National Natural Science Foundation of China
文摘When the bi-stable stochastic resonance method was applied to enhance weak thruster fault for autonomous underwater vehicle(AUV), the enhancement performance could not satisfy the detection requirement of weak thruster fault. As for this problem, a fault feature enhancement method based on mono-stable stochastic resonance was proposed. In the method, in order to improve the enhancement performance of weak thruster fault feature, the conventional bi-stable potential function was changed to mono-stable potential function which was more suitable for aperiodic signals. Furthermore, when particle swarm optimization was adopted to adjust the parameters of mono-stable stochastic resonance system, the global convergent time would be long. An improved particle swarm optimization method was developed by changing the linear inertial weighted function as nonlinear function with cosine function, so as to reduce the global convergent time. In addition, when the conventional wavelet reconstruction method was adopted to detect the weak thruster fault, undetected fault or false alarm may occur. In order to successfully detect the weak thruster fault, a weak thruster detection method was proposed based on the integration of stochastic resonance and wavelet reconstruction. In the method, the optimal reconstruction scale was determined by comparing wavelet entropies corresponding to each decomposition scale. Finally, pool-experiments were performed on AUV with thruster fault. The effectiveness of the proposed mono-stable stochastic resonance method in enhancing fault feature and reducing the global convergent time was demonstrated in comparison with particle swarm optimization based bi-stochastic resonance method. Furthermore, the effectiveness of the proposed fault detection method was illustrated in comparison with the conventional wavelet reconstruction.
基金This project was sponsored by National Development and Reform Commission (NDRC) on studies of experimental exploration of active fault in urban area(20041138)
文摘On the basis of the Xining active urban fault survey, we studied the relationship between the active urban fault and fold deformation. The result of this research shows that the Huangshuihe fault and the NW-striking fault on the northern bank of the Huangshulbe River are tensional faults on top of an anticline, the Nanchuanhe fault is a transverse tear fault resulting from differential folding on two sides of the fault, the east bank of the Beichuanhe River fault is a compressional fault developed on the core or climb of a syncline. By balance profile analysis of fold deformation and inversion of gravity anomaly data, we obtained the depth of the detachment plane and established the seismotectonic model of the ）fining urban area. Based on the seismotectonic model, we analyzed the earthquake potential of the active urban fault.
基金supported by China National Major Project of Oil and Gas (2011ZX05023-004-012, 2011ZX05006-006-02-01)China Natural Science Foundation (Grant No. 40772086)
文摘Fault formation and evolution in the presence of multiple pre-existing weaknesses has not been investigated extensively in rift basins. The fault systems of Weixinan Sag, Beibuwan Basin of China, which is fully covered with high-precision 3-D seismic data and is rich in oil-gas resources, have been successfully reproduced by sandbox modeling in this study with inclusion of multiple pre-existing weaknesses in the experimental model. The basic characteristics of fault formation and evolution revealed by sandbox modeling are as follows. 1） Weakness-reactivation faults and weakness-related faults are formed much earlier than the distant-weakness faults （faults far away from and with little or no relationship to the weakness）. 2） Weakness-reactivation faults and weakness-related faults develop mainly along or parallel to a pre-existing weakness, while distant-weakness faults develop nearly perpendicular to the extension direction. A complicated fault system can be formed in a fixed direction of extension with the existence of multiple pre-existing weaknesses, and the complicated fault system in the Weixinan Sag formed gradually in a nearly N-S direction with multiple pre-existing weaknesses. 3） The increase in the length and number of faults is closely tied to the nature of pre-existing weaknesses. The sandbox model may provide a new clue to detailed fault system research for oil and gas exploration in rift basins.
文摘In this paper, the well-known Duffing equation and the nonlinear equation describing vibration of the human eardrum are introduced from elastic nonlinear system theory. According to the fact that the human ear can distinguish weak sound with small difference, the idea that the Duffing oscillator can be used to detect a weak signal and diagnose early fault of machinery is proposed. In order to obtain a model for weak signal detection via the Duffing oscillator, the first step is to seek all forms of solutions of the Duffing equation. The second step is to study global bifurcations of the Duffing equation using qualitative analysis theory of a dynamic system. That is to say, a series of bifurcations thresholds of the Duffing equation can be analyzed by the Melnikov function and a subharmonics Melnikov function. Then the three types of bifurcations thresholds varying with damping and external exciting amplitude are discussed. The analysis concludes that the bifurcation threshold corresponding to the maximum orbit of solutions outside the homo-clinic orbit of the Duffing equation can be used to detect a weak signal. Finally, the implementing model of the Duffing oscillator for weak signal detection is given.
文摘为了提高二维随机共振的信号增强能力,提出一种基于外加信号和高斯函数的二维非对称随机共振系统(novel two-dimensional asymmetric bistable potential system based on external signal and Gaussian function,NTABPS-EG).首先,以输出信噪比为衡量指标,研究了3种非对称势的系统性能,根据分析结果选取阱深阱宽非对称势进行后续研究,并探究了不同参数下系统输出信噪比随噪声强度的变化趋势.其次,采用四阶龙格库塔算法进行数值模拟,并采用遗传算法求解最佳参数,使系统得到最佳输出响应.通过与二维指数势双稳系统(two-dimensional exponential potential bi-stable potential system,TEPBPS)的对比,发现NTABPS-EG系统更能有效地驱动粒子跃迁,对微弱信号的恢复效果较好.最后,将NTABPS-EG系统应用于轴承故障检测,实验结果表明系统可以有效诊断出轴承的内外圈故障,且诊断能力优于TEPBPS,证明了系统的实用性和先进性.
文摘该文针对极弱电网、严重故障场景研究传统故障穿越策略对虚拟同步发电机(virtual synchronous generator,VSG)型构网变流器大干扰稳定性的影响。首先,通过理论推导并建立传统故障穿越策略下VSG构网特性表征模型,用以表征电网故障阶段VSG构网同步特性与电压支撑特性;在此基础上,结合故障成功穿越所需具备的条件,进一步提出故障穿越可行域的概念以及故障严重程度的界定原则,明确传统VSG故障穿越策略对于不同程度故障、不同限流幅值的适用范围;并且,针对传统故障穿越无法覆盖全故障场景的问题,提出一种名为动态限幅电压控制的新型控制方式(dynamic limiting voltage control,DLVC),并在其基础上进一步提出一种增强型VSG故障穿越策略(dynamic limiting voltage control fault ride through,DLVC-FRT),其具有近区无功、远区电压控制的灵活控制特性,在限制短路电流的同时可有效提升VSG在极弱电网场景下对电网电压的支撑能力;最后,在PSCAD/EMTDC中构建仿真,并验证所提策略的有效性。
