Tandem gas metal arc welding （ T-GMAW） process shows a high deposition rate that up to three times o f the single electrode GMAW, so the welding speed could be significantly increased in this process. H...Tandem gas metal arc welding （ T-GMAW） process shows a high deposition rate that up to three times o f the single electrode GMAW, so the welding speed could be significantly increased in this process. However, the majority o f this process applications are based on the pre-programmed robotic welding, which does not allow them to track the seam real-time during welding. Rotating arc sensor, sensing the seam position by detecting the changing of welding currents, has been widely adopted in the automatic robot welding process. It is proposed in this paper to integrate the rotating arc sensor with a trailing torch to develop a new approach of rotating arc lead tandem gas metal arc welding （RLT-GMAW） process. The characteristics of the welding currents in the proposed new welding process were firstly studied, and then a self-turning fuzzy control seam tracking strategy was developed for the mobile robot automatic welding. The experimental results showed that the proposed RLT-GMAW process had an excellent seam tracking performance and high welding deposition rate. Even if there were some electromagnetic interactions between the two arcs, the deviation of the welding seam could also be reflected by the fluctuation of the welding currents on the leading arc once the correct welding parameters were selected. Based on the detected deviation, the welding tracking experiments showed that the proposed self-turning fuzzy controller had a good performance for the RLT-GMAW process seam tracking.展开更多
The basic"current"statistical model and adaptive Kalman filter algorithm can not track a weakly maneuvering target precisely,though it has good estimate accuracy for strongly maneuvering target.In order to s...The basic"current"statistical model and adaptive Kalman filter algorithm can not track a weakly maneuvering target precisely,though it has good estimate accuracy for strongly maneuvering target.In order to solve this problem,a novel nonlinear fuzzy membership function was presented to adjust the upper and lower limit of target acceleration adaptively,and then the validity of the new algorithm for feeblish maneuvering target was proved in theory.At last,the computer simulation experiments indicated that the new algorithm has a great advantage over the basic"current"statistical model and adaptive algorithm.展开更多
In the present work, tracking phenomenon in Silicone rubber material has beenstudied under AC and DC voltage, with ammonium chloride as a contaminant. It is observed that thetracking is more severe under the DC voltag...In the present work, tracking phenomenon in Silicone rubber material has beenstudied under AC and DC voltage, with ammonium chloride as a contaminant. It is observed that thetracking is more severe under the DC voltages. The tracking time is less under negative DC comparedto the positive DC voltage. The tracking mechanism is explained in detail. The leakage currentduring the tracking studies was as measured and the moving average technique was adopted tounderstand the trend in current flow. The leakage current magnitude is high with thermally agedspecimens compared to the virgin specimen, irrespective of the type of applied voltage. It isrealized that the tracking time and the leakage current magnitude shows an inverse relationship.展开更多
Because variations of ultra-capacitor voltage and battery voltage generate subharmonic and chaotic behaviors in hybrid energy storage system (HESS) application when a DC-DC converter is under the peak current control,...Because variations of ultra-capacitor voltage and battery voltage generate subharmonic and chaotic behaviors in hybrid energy storage system (HESS) application when a DC-DC converter is under the peak current control, a novel digital control strategy, i.e., peak current control with extended-state tracking compensator, is introduced to deal with the stability. The gains of the control algorithm are selected based on pole locations formulated from the Bessel filter. The simulation results validate that under the peak current control strategy with compensator, the DC-DC converter does not have the subharmonic and chaotic behaviors. The response time under the peak current control with compensator is the same as that under the peak current control. The ripple voltage and ripple current of battery are less. The tracking error of inductor current tends to zero.展开更多
Bearing-only passive tracking is regarded as a nonlinear hard tracking problem. There are still no completely good solutions to this problem until now. Based on current statistical model, the novel solution to this pr...Bearing-only passive tracking is regarded as a nonlinear hard tracking problem. There are still no completely good solutions to this problem until now. Based on current statistical model, the novel solution to this problem utilizing particle filter (PF) and the unscented Kalman filter (UKF) is proposed. The new solution adopts data fusion from two observers to increase the observability of passive tracking. It applies the residual resampling step to reduce the degeneracy of PF and it introduces the Markov Chain Monte Carlo methods (MCMC) to reduce the effect of the “sample impoverish”. Based on current statistical model, the EKF, the UKF and particle filter with various proposal distributions are compared in the passive tracking experiments with two observers. The simulation results demonstrate the good performance of the proposed new filtering methods with the novel techniques.展开更多
Low dark current photocathode guns are highly desired for high-brightness continuous-wave operations.Direct-current superconducting radio-frequency(DC-SRF)gun,a hybrid photocathode gun combining a DC gap and an SRF ca...Low dark current photocathode guns are highly desired for high-brightness continuous-wave operations.Direct-current superconducting radio-frequency(DC-SRF)gun,a hybrid photocathode gun combining a DC gap and an SRF cavity,effectively isolates the photocathode from the SRF cavity and offers significant advantages in terms of minimizing dark current levels.This paper presents an in-depth analysis of the dark current of a newly developed high-brightness DC-SRF photocathode gun(DC-SRF-Ⅱ gun).Particularly,a systematic experimental investigation of the dark current was conducted,and a comprehensive understanding of its formation was achieved through compliant simulations and measurements.Additionally,measures for attaining sub-nanoampere dark currents in the DC-SRF-Ⅱ gun are presented,including design considerations,cavity processing,assembly,and conditioning.The findings of this study establish a strong foundation for achieving high-performance operation of the DC-SRF-Ⅱ gun and provide a valuable reference for other photocathode guns.展开更多
The coastal ocean west of Guangdong Province(refers to Yuexi)is characterized as wide and shallow continental shelf,and connected to the Beibu Gulf through the Qiongzhou Strait(as shown in Fig.1).The circulation patte...The coastal ocean west of Guangdong Province(refers to Yuexi)is characterized as wide and shallow continental shelf,and connected to the Beibu Gulf through the Qiongzhou Strait(as shown in Fig.1).The circulation pattern is complicated,controlled by the East Asian monsoon,tides,buoyancy forcing,and topography.In general,the mean cur-rent on the shelf flows southwestward in winter and northeastward in summer,while the coastal current flows always southwestward in summer(Yang et al.,2003;Shu et al.,2018).展开更多
The muhiyear averaged surface current field and seasonal variability in the Kuroshio and adjacent regions are studied. The data used are trajectories and （1/4） ° latitude by （1/4） ° longitude mean curren...The muhiyear averaged surface current field and seasonal variability in the Kuroshio and adjacent regions are studied. The data used are trajectories and （1/4） ° latitude by （1/4） ° longitude mean currents derived from 323 Argos drifters deployed by Chinese institutions and world ocean circulation experiment from 1979 to 2003. The results show that the Kuroshio surface path adapts well to the western boundary topography and exhibits six great turnings. The branching occurs frequently near anticyclonic turnings rather than near cyclonic ones. In the Luzon Strait, the surface water intrusion into the South China Sea occurs only in fall and winter. The Kuroshio surface path east of Taiwan, China appears nearly as straight lines in summer, fall, and winter, when anticyclonic eddies coexist on its right side; while the path may cyclonically turning in spring when no eddy exists. The Kuroshio intrusion northeast of Taiwan often occurs in fall and winter, but not in summer. The running direction, width and velocity of the middle segment of the Kuroshio surface currents in the East China Sea vary seasonally. The northward intrusion of the Kuroshio surface water southwest of Kyushu occurs in spring and fall, but not in summer. The northmost position of the Kuroshio surface path southwest of Kyushu occurs in fall, but never goes beyond 31 °N. The northward surface current east of the Ryukyu Islands exists only along Okinawa-Amami Islands from spring to fall. In particular, it appears as an arm of an anti- cyclonic eddy in fall.展开更多
The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling syst...The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.展开更多
In recent times, silicone rubber insulating material is used for power transmission line and substation insulation applications. In the present work, tracking and erosion resistance of the micro size filled and nano s...In recent times, silicone rubber insulating material is used for power transmission line and substation insulation applications. In the present work, tracking and erosion resistance of the micro size filled and nano size filled silicone rubber material has been studied under the AC voltage, with ammonium chloride as a contaminant, as per IEC 60587 test procedures. The characteristic changes in the tracking resistance of the micro size and nano size filled specimens are analyzed through leakage current measurement. Comparative Tracking Index （CTI） is also evaluated in order to understand the relative behavior of solid electrical insulating material with regard to their susceptibility to surface tracking. Trend followed by the fundamental, third harmonic and fifth harmonic components of the leakage current during the tracking study are analyzed using moving average current technique. It is observed that the harmonic components of leakage current show good correlation with the tracking and erosion resistance of the material. It is noticed that 5 % wt ofnano size filler gives similar performance to that of 30 % wt of micro size filler in silicone composites.展开更多
在光储孤岛直流微电网中,需要最大化利用光伏发电,通常对光伏系统采用最大功率点跟踪(maximum power point tracking, MPPT)技术。但传统的MPPT控制速度慢、精度低,特别是在局部阴影情形下极易陷入局部最优解。基于此,首先提出一种将布...在光储孤岛直流微电网中,需要最大化利用光伏发电,通常对光伏系统采用最大功率点跟踪(maximum power point tracking, MPPT)技术。但传统的MPPT控制速度慢、精度低,特别是在局部阴影情形下极易陷入局部最优解。基于此,首先提出一种将布谷鸟搜索算法与电导增量法相结合的混合MPPT控制。利用布谷鸟搜索算法快速全局寻优,再使用电导增量法精确定位,实现快速而准确地跟踪最大功率点。储能单元是光储直流微电网的重要组成部分,其输出电流均分、荷电状态(stateof charge, SoC)均衡和直流母线电压稳定是主要控制目标。但电流均分受线路电阻差异的影响,进而影响SoC均衡和直流母线电压稳定,于是设计一种新的电压电流双环控制策略以实现上述目标。该策略在电压外环采用母线电压作为反馈值,在电流内环中设计了基于一致性算法的控制策略,将SoC与指数函数结合并引入加速因子,使得在充放电过程中实现SoC的快速均衡。所提控制策略既不需要下垂控制,也无需二次补偿控制,减轻了通信负担。最后在Matlab/Simulink中搭建直流微电网系统模型,验证所设计新的混合MPPT控制和电压电流双环控制策略的有效性。展开更多
为提高电网频率波动条件下并联型有源电力滤波器(shunt active power filters,SAPF)的补偿电流跟踪控制精度,有效抑制电网的谐波污染,提出一种具有变频适应性的重复控制策略。采用可调整采样频率的选择性重复控制器构建多采样率重复控...为提高电网频率波动条件下并联型有源电力滤波器(shunt active power filters,SAPF)的补偿电流跟踪控制精度,有效抑制电网的谐波污染,提出一种具有变频适应性的重复控制策略。采用可调整采样频率的选择性重复控制器构建多采样率重复控制系统,利用基于拉格朗日线性插值法的有限脉冲响应(FIR)滤波器将多采样率重复控制系统转换成具有统一采样频率的重复控制系统(frequency-adaptive uniform-rate selective repetitive control system,FUSRCS),通过跟随电网频率调整重复控制器延迟环节近似表达式系数的方法使FUSRCS能适应电网频率波动,设计了FUSRCS的补偿器,分析了FUSRCS的稳定性、收敛性和稳态误差,建立了三相SAPF的数学模型,依据实际数据设计了基于FUSRCS的补偿电流复合重复控制系统。仿真和实验结果表明:基于FUSRCS的SAPF能够在电网频率存在稳态偏差、电网频率动态变化和负载切换等情况下,保持较高的补偿电流跟踪精度和较好的补偿效果。与经典重复控制相比,FUSRCS在具有变频适应性的同时,减少了控制系统的计算负担,提高了系统的动态响应速度,解决了多采样率重复控制系统带来的问题。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51465043)
文摘Tandem gas metal arc welding （ T-GMAW） process shows a high deposition rate that up to three times o f the single electrode GMAW, so the welding speed could be significantly increased in this process. However, the majority o f this process applications are based on the pre-programmed robotic welding, which does not allow them to track the seam real-time during welding. Rotating arc sensor, sensing the seam position by detecting the changing of welding currents, has been widely adopted in the automatic robot welding process. It is proposed in this paper to integrate the rotating arc sensor with a trailing torch to develop a new approach of rotating arc lead tandem gas metal arc welding （RLT-GMAW） process. The characteristics of the welding currents in the proposed new welding process were firstly studied, and then a self-turning fuzzy control seam tracking strategy was developed for the mobile robot automatic welding. The experimental results showed that the proposed RLT-GMAW process had an excellent seam tracking performance and high welding deposition rate. Even if there were some electromagnetic interactions between the two arcs, the deviation of the welding seam could also be reflected by the fluctuation of the welding currents on the leading arc once the correct welding parameters were selected. Based on the detected deviation, the welding tracking experiments showed that the proposed self-turning fuzzy controller had a good performance for the RLT-GMAW process seam tracking.
文摘The basic"current"statistical model and adaptive Kalman filter algorithm can not track a weakly maneuvering target precisely,though it has good estimate accuracy for strongly maneuvering target.In order to solve this problem,a novel nonlinear fuzzy membership function was presented to adjust the upper and lower limit of target acceleration adaptively,and then the validity of the new algorithm for feeblish maneuvering target was proved in theory.At last,the computer simulation experiments indicated that the new algorithm has a great advantage over the basic"current"statistical model and adaptive algorithm.
文摘In the present work, tracking phenomenon in Silicone rubber material has beenstudied under AC and DC voltage, with ammonium chloride as a contaminant. It is observed that thetracking is more severe under the DC voltages. The tracking time is less under negative DC comparedto the positive DC voltage. The tracking mechanism is explained in detail. The leakage currentduring the tracking studies was as measured and the moving average technique was adopted tounderstand the trend in current flow. The leakage current magnitude is high with thermally agedspecimens compared to the virgin specimen, irrespective of the type of applied voltage. It isrealized that the tracking time and the leakage current magnitude shows an inverse relationship.
基金Research Fund on the Cutting-Edge Technology of Electrical Vehicles towards the Sino-US clean Energy Cooperation
文摘Because variations of ultra-capacitor voltage and battery voltage generate subharmonic and chaotic behaviors in hybrid energy storage system (HESS) application when a DC-DC converter is under the peak current control, a novel digital control strategy, i.e., peak current control with extended-state tracking compensator, is introduced to deal with the stability. The gains of the control algorithm are selected based on pole locations formulated from the Bessel filter. The simulation results validate that under the peak current control strategy with compensator, the DC-DC converter does not have the subharmonic and chaotic behaviors. The response time under the peak current control with compensator is the same as that under the peak current control. The ripple voltage and ripple current of battery are less. The tracking error of inductor current tends to zero.
基金This workis supported by national863project :No.2001AA422420 02
文摘Bearing-only passive tracking is regarded as a nonlinear hard tracking problem. There are still no completely good solutions to this problem until now. Based on current statistical model, the novel solution to this problem utilizing particle filter (PF) and the unscented Kalman filter (UKF) is proposed. The new solution adopts data fusion from two observers to increase the observability of passive tracking. It applies the residual resampling step to reduce the degeneracy of PF and it introduces the Markov Chain Monte Carlo methods (MCMC) to reduce the effect of the “sample impoverish”. Based on current statistical model, the EKF, the UKF and particle filter with various proposal distributions are compared in the passive tracking experiments with two observers. The simulation results demonstrate the good performance of the proposed new filtering methods with the novel techniques.
基金partially supported by the National Key Research and Development Program of China(Nos.2016YFA0401904 and 2017YFA0701001)the State Key Laboratory of Nuclear Physics and Technology,Peking University(Nos.NPT2022ZZ01).
文摘Low dark current photocathode guns are highly desired for high-brightness continuous-wave operations.Direct-current superconducting radio-frequency(DC-SRF)gun,a hybrid photocathode gun combining a DC gap and an SRF cavity,effectively isolates the photocathode from the SRF cavity and offers significant advantages in terms of minimizing dark current levels.This paper presents an in-depth analysis of the dark current of a newly developed high-brightness DC-SRF photocathode gun(DC-SRF-Ⅱ gun).Particularly,a systematic experimental investigation of the dark current was conducted,and a comprehensive understanding of its formation was achieved through compliant simulations and measurements.Additionally,measures for attaining sub-nanoampere dark currents in the DC-SRF-Ⅱ gun are presented,including design considerations,cavity processing,assembly,and conditioning.The findings of this study establish a strong foundation for achieving high-performance operation of the DC-SRF-Ⅱ gun and provide a valuable reference for other photocathode guns.
基金The National Key Research and Development Program of China under contract No.2022YFC3104805the National Natural Science Foundation of China under contract Nos 42276019,42176184,and 42476027+3 种基金the Guangdong Basic and Applied Basic Research Foundation under contract Nos 2024A1515012572 and 2025A1515010741the Innovation Team Plan for Universities in Guangdong Province under contract No.2023KCXTD015the Tropical Ocean Environment in Western Coastal Waters Observation and Research Station of Guangdong Province under contract No.2024B1212040008the Undergraduate Innovation Team Project under contract No.CXTD2019001.
文摘The coastal ocean west of Guangdong Province(refers to Yuexi)is characterized as wide and shallow continental shelf,and connected to the Beibu Gulf through the Qiongzhou Strait(as shown in Fig.1).The circulation pattern is complicated,controlled by the East Asian monsoon,tides,buoyancy forcing,and topography.In general,the mean cur-rent on the shelf flows southwestward in winter and northeastward in summer,while the coastal current flows always southwestward in summer(Yang et al.,2003;Shu et al.,2018).
基金The National Natural Science Foundations of China under contract Nos40406009,40333030and40706013
文摘The muhiyear averaged surface current field and seasonal variability in the Kuroshio and adjacent regions are studied. The data used are trajectories and （1/4） ° latitude by （1/4） ° longitude mean currents derived from 323 Argos drifters deployed by Chinese institutions and world ocean circulation experiment from 1979 to 2003. The results show that the Kuroshio surface path adapts well to the western boundary topography and exhibits six great turnings. The branching occurs frequently near anticyclonic turnings rather than near cyclonic ones. In the Luzon Strait, the surface water intrusion into the South China Sea occurs only in fall and winter. The Kuroshio surface path east of Taiwan, China appears nearly as straight lines in summer, fall, and winter, when anticyclonic eddies coexist on its right side; while the path may cyclonically turning in spring when no eddy exists. The Kuroshio intrusion northeast of Taiwan often occurs in fall and winter, but not in summer. The running direction, width and velocity of the middle segment of the Kuroshio surface currents in the East China Sea vary seasonally. The northward intrusion of the Kuroshio surface water southwest of Kyushu occurs in spring and fall, but not in summer. The northmost position of the Kuroshio surface path southwest of Kyushu occurs in fall, but never goes beyond 31 °N. The northward surface current east of the Ryukyu Islands exists only along Okinawa-Amami Islands from spring to fall. In particular, it appears as an arm of an anti- cyclonic eddy in fall.
文摘The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.
文摘In recent times, silicone rubber insulating material is used for power transmission line and substation insulation applications. In the present work, tracking and erosion resistance of the micro size filled and nano size filled silicone rubber material has been studied under the AC voltage, with ammonium chloride as a contaminant, as per IEC 60587 test procedures. The characteristic changes in the tracking resistance of the micro size and nano size filled specimens are analyzed through leakage current measurement. Comparative Tracking Index （CTI） is also evaluated in order to understand the relative behavior of solid electrical insulating material with regard to their susceptibility to surface tracking. Trend followed by the fundamental, third harmonic and fifth harmonic components of the leakage current during the tracking study are analyzed using moving average current technique. It is observed that the harmonic components of leakage current show good correlation with the tracking and erosion resistance of the material. It is noticed that 5 % wt ofnano size filler gives similar performance to that of 30 % wt of micro size filler in silicone composites.
文摘在光储孤岛直流微电网中,需要最大化利用光伏发电,通常对光伏系统采用最大功率点跟踪(maximum power point tracking, MPPT)技术。但传统的MPPT控制速度慢、精度低,特别是在局部阴影情形下极易陷入局部最优解。基于此,首先提出一种将布谷鸟搜索算法与电导增量法相结合的混合MPPT控制。利用布谷鸟搜索算法快速全局寻优,再使用电导增量法精确定位,实现快速而准确地跟踪最大功率点。储能单元是光储直流微电网的重要组成部分,其输出电流均分、荷电状态(stateof charge, SoC)均衡和直流母线电压稳定是主要控制目标。但电流均分受线路电阻差异的影响,进而影响SoC均衡和直流母线电压稳定,于是设计一种新的电压电流双环控制策略以实现上述目标。该策略在电压外环采用母线电压作为反馈值,在电流内环中设计了基于一致性算法的控制策略,将SoC与指数函数结合并引入加速因子,使得在充放电过程中实现SoC的快速均衡。所提控制策略既不需要下垂控制,也无需二次补偿控制,减轻了通信负担。最后在Matlab/Simulink中搭建直流微电网系统模型,验证所设计新的混合MPPT控制和电压电流双环控制策略的有效性。
文摘为提高电网频率波动条件下并联型有源电力滤波器(shunt active power filters,SAPF)的补偿电流跟踪控制精度,有效抑制电网的谐波污染,提出一种具有变频适应性的重复控制策略。采用可调整采样频率的选择性重复控制器构建多采样率重复控制系统,利用基于拉格朗日线性插值法的有限脉冲响应(FIR)滤波器将多采样率重复控制系统转换成具有统一采样频率的重复控制系统(frequency-adaptive uniform-rate selective repetitive control system,FUSRCS),通过跟随电网频率调整重复控制器延迟环节近似表达式系数的方法使FUSRCS能适应电网频率波动,设计了FUSRCS的补偿器,分析了FUSRCS的稳定性、收敛性和稳态误差,建立了三相SAPF的数学模型,依据实际数据设计了基于FUSRCS的补偿电流复合重复控制系统。仿真和实验结果表明:基于FUSRCS的SAPF能够在电网频率存在稳态偏差、电网频率动态变化和负载切换等情况下,保持较高的补偿电流跟踪精度和较好的补偿效果。与经典重复控制相比,FUSRCS在具有变频适应性的同时,减少了控制系统的计算负担,提高了系统的动态响应速度,解决了多采样率重复控制系统带来的问题。
