Blade vibration monitoring can ensure the safe operation of aeroengine rotor blades.Among the methods of blade vibration monitoring,Blade Tip Timing(BTT)method has attracted more and more attention because of its adva...Blade vibration monitoring can ensure the safe operation of aeroengine rotor blades.Among the methods of blade vibration monitoring,Blade Tip Timing(BTT)method has attracted more and more attention because of its advantages of non-contact measurement.However,it is difficult to install the Once-Per-Revolution(OPR)probe in the confined space of aeroengine,and the failure and instability of the OPR signal will reduce the reliability of the blade vibration analysis results,which directly affects the accuracy of the blade vibration parameters identification.The Multi-Probe linear fitting and Time of Arrival(ToA)Linear Correction method based on the BTT(MP-LC-BTT)without OPR is proposed to reduce the errors of single probe linear fitting method for blade vibration displacement analysis.The proposed method can also correct the calculation error of blade vibration displacement due to the nonlinear change of rotation speed,which can improve the analysis accuracy of the blade vibration displacement.A new blade vibration model conforming to the actual vibration characteristics is established,and the effectiveness of the proposed method is verified by numerical simulation.Finally,the reliability and accuracy of the MP-LC-BTT method have been verified by the experiments which include two high-speed blade test-benches and an industrial axial fan.This method can be used in the actual aero-engine monitoring instead of the BTT method with OPR.展开更多
We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its ...We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its optical absorption contrast and high spatial resolution with great imaging depth.OR-PAM allows label-free and noninvasive imaging by maximizing the optical absorption of endogenous biomolecules.However,given the inadequate absoption of some biomolcules,detection sensitivity at the same incident intensity requires improvement.In this study,a modulated continuous wave with power density less than 3mW/cm^(2)(1/4 of the ANSI safety limit)excited the weak photoacoustic(PA)signals of biological cells.A microcavity traneducer is developed based on the bulk modulus of gas five orders of magnitude lower than that of solid;air pressure variation is inversely proportional to cavity volume at the same temperature increase.Considering that a PA wave expands in various directions,detecting PA signals from different positions and adding them together can increase detection sensitivity and signal-to-noise ratio.Therefore,we employ four detectors to acquire tiny PA signals simul-taneously.Experimental results show that the developed OR-PAM system allows the label-free imaging of cells with weak optical absorption.展开更多
With the development of new materials and ultra-precision processing technology, the sizes of mea- sured objects increase, and the requirements for machining accuracy and surface quality become more exacting. The trad...With the development of new materials and ultra-precision processing technology, the sizes of mea- sured objects increase, and the requirements for machining accuracy and surface quality become more exacting. The traditional measurement method based on reference datum is inadequate for measuring a high-precision object when the quality of the reference datum is approximately within the same order as that of the object. Self-referenced measurement techniques provide an effective means when the direct reference-based method cannot satisfy the required measurement or calibration accuracy. This paper discusses the reconstruction algorithms for self-referenced measurement and connects lateral shearing interferometry and multi-probe error separation. In lateral shearing interferometry, the reconstruction algorithms are generally categorized into modal or zonal methods. The multi-probe error separation techniques for straightness measurement are broadly divided into two-point and three-point methods. The common features of the lateral sheafing interferometry method and the multi-probe error separation method are identified. We conclude that the reconstruction principle in lateral shearing interferometry is similar to the two-point method in error separation on the condition that no yaw error exists. This similarity may provide a basis or inspiration for the development of both classes of methods.展开更多
In this paper, channel spatial characteristics which mainly depend on the spatial correlation are selected as the significant factors in over-the-air （OTA） testing for multiple input multiple output （MIMO） devices...In this paper, channel spatial characteristics which mainly depend on the spatial correlation are selected as the significant factors in over-the-air （OTA） testing for multiple input multiple output （MIMO） devices. The multi-probe anechoic chamber method, a promising candidate of the MIMO OTA testing methods, can reproduce the multipath environments in a controllable manner. A novel physical configuration based on the variation of relative positions of probes in a MIMO OTA setup is put forward to obtain better spatial characteristics. Two physical configurations are presented to make a comparison with the typical configuration in this paper. The simulation results show that by making a proper probe configuration, good channel simulation accuracy can be achieved. Meanwhile, in order to get better performance of emulating channel spatial characteristics, probes in the first and the last probe rings should be placed symmetrically in three dimensional （3D） physical probe configuration.展开更多
针对光学元件研磨阶段传统单测头检测方法对机床导轨运动误差敏感,难以同时兼顾检测精度与在位测量效率的问题,提出一种适用于普通机床集成条件下的多测头非接触式面形检测方法,以实现光学元件研磨阶段的高精度在位检测。阐述由3个激光...针对光学元件研磨阶段传统单测头检测方法对机床导轨运动误差敏感,难以同时兼顾检测精度与在位测量效率的问题,提出一种适用于普通机床集成条件下的多测头非接触式面形检测方法,以实现光学元件研磨阶段的高精度在位检测。阐述由3个激光位移传感器组成的多测头系统的差分检测原理,通过三测头两两差分抑制机床导轨运动误差,并将位移差分量转换为被测面局部斜率信息,再基于Zernike多项式的斜率拟合与面形重建原理,利用最小二乘拟合由斜率场反演得到全口径面形。建立系统的几何仿真模型,采用蒙特卡罗法分析测头位置误差和姿态误差对面形重构结果的影响,进一步引入Sobol全局敏感度系数量化各误差源对均方根(Root Mean Square,RMS)误差的贡献,为系统装调公差分配和误差控制策略提供依据。最后,对一片口径为Φ400 mm、材料为单晶硅的研磨阶段平面反射镜进行实验验证,将本研究的检测结果与三坐标测量机(Coordinate Measuring Machine,CMM)的检测结果进行对比。实验结果表明,两种方法得到的峰谷值(Peak to Valley,PV)值绝对偏差为0.21μm,相对偏差为2.22%;RMS值绝对偏差为0.14μm,相对偏差为7.78%。所提方法可保持良好的测量一致性和稳定性,为光学元件研磨阶段的高精度面形检测提供了一种易于工程实现的解决方案。展开更多
基金supports of the National Science and Technology Major Project,China(No.2017-Ⅲ-0009-0035)the Major Program of National Natural Science Foundation of China(No.51790513).
文摘Blade vibration monitoring can ensure the safe operation of aeroengine rotor blades.Among the methods of blade vibration monitoring,Blade Tip Timing(BTT)method has attracted more and more attention because of its advantages of non-contact measurement.However,it is difficult to install the Once-Per-Revolution(OPR)probe in the confined space of aeroengine,and the failure and instability of the OPR signal will reduce the reliability of the blade vibration analysis results,which directly affects the accuracy of the blade vibration parameters identification.The Multi-Probe linear fitting and Time of Arrival(ToA)Linear Correction method based on the BTT(MP-LC-BTT)without OPR is proposed to reduce the errors of single probe linear fitting method for blade vibration displacement analysis.The proposed method can also correct the calculation error of blade vibration displacement due to the nonlinear change of rotation speed,which can improve the analysis accuracy of the blade vibration displacement.A new blade vibration model conforming to the actual vibration characteristics is established,and the effectiveness of the proposed method is verified by numerical simulation.Finally,the reliability and accuracy of the MP-LC-BTT method have been verified by the experiments which include two high-speed blade test-benches and an industrial axial fan.This method can be used in the actual aero-engine monitoring instead of the BTT method with OPR.
基金supported by the National Natural Science Foundation of China(Grant No.61178086)Science and Technology Program of Guangzhou,China(Grant No.2012J4300138)Foundation for Distinguished Young Talents in South China Normal University,China.(Grant No.2012KJ010).
文摘We demonstrate the feasibility of simultancous multi-probe detection for an optcal-resolution photoacoustic microscopy(OR-PAM)system.OR-P AM has elicited the attention of biomedical imaging researchers because of its optical absorption contrast and high spatial resolution with great imaging depth.OR-PAM allows label-free and noninvasive imaging by maximizing the optical absorption of endogenous biomolecules.However,given the inadequate absoption of some biomolcules,detection sensitivity at the same incident intensity requires improvement.In this study,a modulated continuous wave with power density less than 3mW/cm^(2)(1/4 of the ANSI safety limit)excited the weak photoacoustic(PA)signals of biological cells.A microcavity traneducer is developed based on the bulk modulus of gas five orders of magnitude lower than that of solid;air pressure variation is inversely proportional to cavity volume at the same temperature increase.Considering that a PA wave expands in various directions,detecting PA signals from different positions and adding them together can increase detection sensitivity and signal-to-noise ratio.Therefore,we employ four detectors to acquire tiny PA signals simul-taneously.Experimental results show that the developed OR-PAM system allows the label-free imaging of cells with weak optical absorption.
文摘With the development of new materials and ultra-precision processing technology, the sizes of mea- sured objects increase, and the requirements for machining accuracy and surface quality become more exacting. The traditional measurement method based on reference datum is inadequate for measuring a high-precision object when the quality of the reference datum is approximately within the same order as that of the object. Self-referenced measurement techniques provide an effective means when the direct reference-based method cannot satisfy the required measurement or calibration accuracy. This paper discusses the reconstruction algorithms for self-referenced measurement and connects lateral shearing interferometry and multi-probe error separation. In lateral shearing interferometry, the reconstruction algorithms are generally categorized into modal or zonal methods. The multi-probe error separation techniques for straightness measurement are broadly divided into two-point and three-point methods. The common features of the lateral sheafing interferometry method and the multi-probe error separation method are identified. We conclude that the reconstruction principle in lateral shearing interferometry is similar to the two-point method in error separation on the condition that no yaw error exists. This similarity may provide a basis or inspiration for the development of both classes of methods.
基金supported by the National Natural Science Foundation of China(61327806)the Youth Foundation of Beijing University of Posts and Telecommunications(2016RC14)The Corresponding Patent(CN 106209284 A)is pending
文摘In this paper, channel spatial characteristics which mainly depend on the spatial correlation are selected as the significant factors in over-the-air （OTA） testing for multiple input multiple output （MIMO） devices. The multi-probe anechoic chamber method, a promising candidate of the MIMO OTA testing methods, can reproduce the multipath environments in a controllable manner. A novel physical configuration based on the variation of relative positions of probes in a MIMO OTA setup is put forward to obtain better spatial characteristics. Two physical configurations are presented to make a comparison with the typical configuration in this paper. The simulation results show that by making a proper probe configuration, good channel simulation accuracy can be achieved. Meanwhile, in order to get better performance of emulating channel spatial characteristics, probes in the first and the last probe rings should be placed symmetrically in three dimensional （3D） physical probe configuration.
文摘针对光学元件研磨阶段传统单测头检测方法对机床导轨运动误差敏感,难以同时兼顾检测精度与在位测量效率的问题,提出一种适用于普通机床集成条件下的多测头非接触式面形检测方法,以实现光学元件研磨阶段的高精度在位检测。阐述由3个激光位移传感器组成的多测头系统的差分检测原理,通过三测头两两差分抑制机床导轨运动误差,并将位移差分量转换为被测面局部斜率信息,再基于Zernike多项式的斜率拟合与面形重建原理,利用最小二乘拟合由斜率场反演得到全口径面形。建立系统的几何仿真模型,采用蒙特卡罗法分析测头位置误差和姿态误差对面形重构结果的影响,进一步引入Sobol全局敏感度系数量化各误差源对均方根(Root Mean Square,RMS)误差的贡献,为系统装调公差分配和误差控制策略提供依据。最后,对一片口径为Φ400 mm、材料为单晶硅的研磨阶段平面反射镜进行实验验证,将本研究的检测结果与三坐标测量机(Coordinate Measuring Machine,CMM)的检测结果进行对比。实验结果表明,两种方法得到的峰谷值(Peak to Valley,PV)值绝对偏差为0.21μm,相对偏差为2.22%;RMS值绝对偏差为0.14μm,相对偏差为7.78%。所提方法可保持良好的测量一致性和稳定性,为光学元件研磨阶段的高精度面形检测提供了一种易于工程实现的解决方案。
