This paper presents an automatic system for failure detection in hydro-power generators. The main idea of this system is to detect failure using current and voltage signals acquired without any type of internal interf...This paper presents an automatic system for failure detection in hydro-power generators. The main idea of this system is to detect failure using current and voltage signals acquired without any type of internal interference in the generator operation. The detected failures could be mechanical or electrical origins, such as: problems in bearings, unwanted vibrations, partial discharges, misalignment, unbalancing, among others. It is possible because the generator acts as a transducer for mechanical problems, and they appear in current and voltage signals. This automatic system based on electric signature analysis has been installed in Itapebi Power Plant generators since 2012. Some results are presented in this paper.展开更多
Blades are one of the important components on aircraft engines.If they break due to vibration failure,the normal operation of the entire engine will be offected.Therefore,it is necessary to measure their natural frequ...Blades are one of the important components on aircraft engines.If they break due to vibration failure,the normal operation of the entire engine will be offected.Therefore,it is necessary to measure their natural frequency before installing them on the engine to avoid resonance.At present,most blade vibration testing systems require manual operation by operators,which has high requirements for operators and the testing process is also very cumbersome.Therefore,the testing efficiency is low and cannot meet the needs of efficient testing.To solve the current problems of low testing efficiency and high operational requirements,a high-precision and high-efficiency automatic test system is designed.The testing accuracy of this system can reach ±1%,and the testing efficiency is improved by 37% compared to manual testing.Firstly,the influence of compression force and vibration exciter position on natural frequency test is analyzed by amplitude-frequency curve,so as to calibrate servo cylinder and fourdimensional motion platform.Secondly,the sine wave signal is used as the excitation to sweep the blade linearly,and the natural frequency is determined by the amplitude peak in the frequency domain.Finally,the accuracy experiment and efficiency experiment are carried out on the developed test system,whose results verify its high efficiency and high precision.展开更多
For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmissi...For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmission power loss and the hydraulic system leakage. Based on this model, a flow-based control strategy is developed for EOP to satisfy the system flow requirement. This control strategy is verified through the forward driving simulation. The results indicate that there is a best combination for the size of mechanical oil pump(MOP) and EOP in terms of minimum energy consumption. In order to get a quick and smooth starting process, control strategies of the EOP and the on-coming clutch are proposed. The test environment on a prototype vehicle is built to verify the feasibility of the integrated EOP and its control strategies. The results show that the selected EOP can satisfy the flow requirement and a quick and smooth starting performance is achieved in the start–stop function. This research has a high value for the forward design of EOP in automatic transmissions with respect to efficiency improvement and start–stop function.展开更多
Multiple failure modes tend to be identified in the reliability analysis of a redundant truss structure.This identification process involves updating the model for identifying the next potential failure members.Herein...Multiple failure modes tend to be identified in the reliability analysis of a redundant truss structure.This identification process involves updating the model for identifying the next potential failure members.Herein we intend to update the finite element model automatically in the identification process of failure modes and further perform the system reliability analysis efficiently.This study presents a framework that is implemented through the joint simulation of MATLAB and APDL and consists of three parts:reliability index of a single member,identification of dominant failure modes,and system-level reliability analysis for system reliability analysis of truss structures.Firstly,RSM(response surface method)combines with a constrained optimization model to calculate the reliability indices ofmembers.Then theβ-unzipping method is adopted to identify the dominant failuremodes,and the system function in MATLAB,as well as the EKILL command in APDL,is used to facilitate the automatic update of the finite element model and realize load-redistribution.Besides,the differential equivalence recursion algorithmis performed to approximate the reliability indices of failuremodes efficiently and accurately.Eventually,the PNET(probabilistic network evaluation technique)is used to calculate the joint failure probability as well as the system reliability index.Two illustrative examples demonstrate the accuracy and efficiency of the proposed system reliability analysis framework through comparison with corresponding references.展开更多
目的探讨四维自动右室定量(4D Auto RVQ)技术评价不同程度慢性心力衰竭(CHF)患者右室功能的临床价值。方法前瞻性选取在我院住院部确诊的CHF患者99例,依据6 min步行距离(6MWD)将其分为轻度CHF组(6MWD>450 m)、中度CHF组(150 m≤6MWD...目的探讨四维自动右室定量(4D Auto RVQ)技术评价不同程度慢性心力衰竭(CHF)患者右室功能的临床价值。方法前瞻性选取在我院住院部确诊的CHF患者99例,依据6 min步行距离(6MWD)将其分为轻度CHF组(6MWD>450 m)、中度CHF组(150 m≤6MWD≤450 m)、重度CHF组(6MWD<150 m),每组各33例。应用二维斑点追踪技术获取右室整体纵向应变(RVGLS)及右室游离壁纵向应变(RVFWLS),4D Auto RVQ技术获取四维右室射血分数(4D-RVEF)、右室舒张末期容积指数(4D-RVEDVI)、四维右室收缩末期容积指数(4D-RVESVI)、四维右室每搏量指数(4D-RVSVI)、四维三尖瓣环收缩期位移(4D-TAPSE)、四维右室面积变化分数(4D-RVFAC),比较各组上述参数的差异。采用有序Logistic回归分析4D Atuo RVQ参数及应变参数与患者CHF程度的关系。结果轻度CHF组、中度CHF组及重度CHF组4D-RVEF、4D-RVSVI、4D-TAPSE、4D-RVFAC、RVGLS及RVFWLS均依次降低,组间两两比较差异均有统计学意义(均P<0.05)。重度CHF组4D-RVEDVI、4D-RVESVI均增大,与轻度CHF组和中度CHF组比较差异均有统计学意义(均P<0.05)。有序Logistic回归分析显示,4D-RVEF对患者CHF程度具有显著负向影响(β=-1.302,P<0.001)。结论4D Auto RVQ技术可以定量评价不同程度CHF患者右室功能,具有一定的临床应用价值。展开更多
文摘This paper presents an automatic system for failure detection in hydro-power generators. The main idea of this system is to detect failure using current and voltage signals acquired without any type of internal interference in the generator operation. The detected failures could be mechanical or electrical origins, such as: problems in bearings, unwanted vibrations, partial discharges, misalignment, unbalancing, among others. It is possible because the generator acts as a transducer for mechanical problems, and they appear in current and voltage signals. This automatic system based on electric signature analysis has been installed in Itapebi Power Plant generators since 2012. Some results are presented in this paper.
基金supported by the National Natural Science Foundation of China (No.51975293)Aeronautical Science Foundation of China (No.2019ZD052010)Postgraduate Research & Practice Innovation Program of NUAA (No.xcxjh20230502)。
文摘Blades are one of the important components on aircraft engines.If they break due to vibration failure,the normal operation of the entire engine will be offected.Therefore,it is necessary to measure their natural frequency before installing them on the engine to avoid resonance.At present,most blade vibration testing systems require manual operation by operators,which has high requirements for operators and the testing process is also very cumbersome.Therefore,the testing efficiency is low and cannot meet the needs of efficient testing.To solve the current problems of low testing efficiency and high operational requirements,a high-precision and high-efficiency automatic test system is designed.The testing accuracy of this system can reach ±1%,and the testing efficiency is improved by 37% compared to manual testing.Firstly,the influence of compression force and vibration exciter position on natural frequency test is analyzed by amplitude-frequency curve,so as to calibrate servo cylinder and fourdimensional motion platform.Secondly,the sine wave signal is used as the excitation to sweep the blade linearly,and the natural frequency is determined by the amplitude peak in the frequency domain.Finally,the accuracy experiment and efficiency experiment are carried out on the developed test system,whose results verify its high efficiency and high precision.
基金Project(51405010)supported by the National Natural Science Foundation of ChinaProject(2011BAG09B00)supported by the National Science and Technology Support Program of China
文摘For the purpose of improving efficiency and realizing start–stop function, an electric oil pump(EOP) is integrated into an 8-speed automatic transmission(AT). A mathematical model is built to calculate the transmission power loss and the hydraulic system leakage. Based on this model, a flow-based control strategy is developed for EOP to satisfy the system flow requirement. This control strategy is verified through the forward driving simulation. The results indicate that there is a best combination for the size of mechanical oil pump(MOP) and EOP in terms of minimum energy consumption. In order to get a quick and smooth starting process, control strategies of the EOP and the on-coming clutch are proposed. The test environment on a prototype vehicle is built to verify the feasibility of the integrated EOP and its control strategies. The results show that the selected EOP can satisfy the flow requirement and a quick and smooth starting performance is achieved in the start–stop function. This research has a high value for the forward design of EOP in automatic transmissions with respect to efficiency improvement and start–stop function.
基金support from the National Key R&D Program of China(Grant Nos.2021YFB2600605,2021YFB2600600)the Overseas Scholar Program in the Hebei Province(C20190514)+1 种基金from the State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Project(ZZ2020-20)from the Youth Foundation of Hebei Science and Technology Research Project(QN2018108).
文摘Multiple failure modes tend to be identified in the reliability analysis of a redundant truss structure.This identification process involves updating the model for identifying the next potential failure members.Herein we intend to update the finite element model automatically in the identification process of failure modes and further perform the system reliability analysis efficiently.This study presents a framework that is implemented through the joint simulation of MATLAB and APDL and consists of three parts:reliability index of a single member,identification of dominant failure modes,and system-level reliability analysis for system reliability analysis of truss structures.Firstly,RSM(response surface method)combines with a constrained optimization model to calculate the reliability indices ofmembers.Then theβ-unzipping method is adopted to identify the dominant failuremodes,and the system function in MATLAB,as well as the EKILL command in APDL,is used to facilitate the automatic update of the finite element model and realize load-redistribution.Besides,the differential equivalence recursion algorithmis performed to approximate the reliability indices of failuremodes efficiently and accurately.Eventually,the PNET(probabilistic network evaluation technique)is used to calculate the joint failure probability as well as the system reliability index.Two illustrative examples demonstrate the accuracy and efficiency of the proposed system reliability analysis framework through comparison with corresponding references.
文摘目的探讨四维自动右室定量(4D Auto RVQ)技术评价不同程度慢性心力衰竭(CHF)患者右室功能的临床价值。方法前瞻性选取在我院住院部确诊的CHF患者99例,依据6 min步行距离(6MWD)将其分为轻度CHF组(6MWD>450 m)、中度CHF组(150 m≤6MWD≤450 m)、重度CHF组(6MWD<150 m),每组各33例。应用二维斑点追踪技术获取右室整体纵向应变(RVGLS)及右室游离壁纵向应变(RVFWLS),4D Auto RVQ技术获取四维右室射血分数(4D-RVEF)、右室舒张末期容积指数(4D-RVEDVI)、四维右室收缩末期容积指数(4D-RVESVI)、四维右室每搏量指数(4D-RVSVI)、四维三尖瓣环收缩期位移(4D-TAPSE)、四维右室面积变化分数(4D-RVFAC),比较各组上述参数的差异。采用有序Logistic回归分析4D Atuo RVQ参数及应变参数与患者CHF程度的关系。结果轻度CHF组、中度CHF组及重度CHF组4D-RVEF、4D-RVSVI、4D-TAPSE、4D-RVFAC、RVGLS及RVFWLS均依次降低,组间两两比较差异均有统计学意义(均P<0.05)。重度CHF组4D-RVEDVI、4D-RVESVI均增大,与轻度CHF组和中度CHF组比较差异均有统计学意义(均P<0.05)。有序Logistic回归分析显示,4D-RVEF对患者CHF程度具有显著负向影响(β=-1.302,P<0.001)。结论4D Auto RVQ技术可以定量评价不同程度CHF患者右室功能,具有一定的临床应用价值。
