High-precision automatic measurement of two-dimensional geometric features based on machine vision

To realize high-precision automatic measurement of two-dimensional geometric features on parts, a cooperative measurement system based on machine vision is constructed. Its hardware structure, functional composition and working principle are introduced. The mapping relationship between the feature image coordinates and the measuring space coordinates is established. The method of measuring path planning of small field of view （FOV） images is proposed. With the cooperation of the panoramic image of the object to be measured, the small FOV images with high object plane resolution are acquired automatically. Then, the auxiliary measuring characteristics are constructed and the parameters of the features to be measured are automatically extracted. Experimental results show that the absolute value of relative error is less than 0. 03% when applying the cooperative measurement system to gauge the hole distance of 100 mm nominal size. When the object plane resolving power of the small FOV images is 16 times that of the large FOV image, the measurement accuracy of small FOV images is improved by 14 times compared with the large FOV image. It is suitable for high-precision automatic measurement of two-dimensional complex geometric features distributed on large scale parts.

Measurement of Angular and Linear Accelerations Using Linear Accelerometers

In order to solve the problem, which may be encountered by those former schemes, such as six accelerometer, nine accelerometer configuration, under specific conditions, a ten accelerometer configuration was presented to compute the rotational and translational accelerations of a rigid body, based on well known kinematics principles. The theoretical analysis shows that the configuration can meet the requirement. The simulation results of this scheme show promise for measuring a rigid body's rotational and translational accelerations.

Simultaneous estimation of aerosol optical constants and size distribution from angular light-scattering measurement signals

The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneously. Meanwhile, an optimized selection principle of the ALSM signals based on the sensitivity analysis and principle component analysis（PCA）is proposed to improve the accuracy of the retrieval results. The sensitivity analysis of the ALSM signals to the optical constants or characteristic parameters in the ASD is studied first to find the optimized selection region of measurement angles. Then, the PCA is adopted to select the optimized measurement angles within the optimized selection region obtained by sensitivity analysis. The investigation reveals that, compared with random selection measurement angles, the optimized selection measurement angles can provide more useful measurement information to ensure the retrieval accuracy. Finally,the aerosol optical constants and the ASDs are reconstructed simultaneously. The results show that the retrieval accuracy of refractive indices is better than that of absorption indices, while the characteristic parameters in ASDs have similar retrieval accuracy. Moreover, the retrieval accuracy in studying L-N distribution is a little better than that in studying Gamma distribution for the difference of corresponding correlation coefficient matrixes of the ALSM signals. All the results confirm that the proposed technique is an effective and reliable technique in estimating the aerosol optical constants and ASD simultaneously.

Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum

In this paper, we propose a measurement-device-independent quantum-key-distribution（MDI-QKD） protocol using orbital angular momentum（OAM） in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol,the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie＇s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover,the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence（AT） and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source.

An angular blinking jamming method based on electronically controlled corner reflectors

Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.

Measurement Device Independent Quantum Key Distribution Based on Orbital Angular Momentum under Parametric Light Source

On the one hand,existing measurement device independent quantum key distribution(MDI-QKD)protocols have usually adopted single photon source(SPS)and weak coherent photon(WCP),however,these protocols have suffered from multi-photon problem brought from photon splitter number attacks.On the other hand,the orbital angular momentum(OAM)-MDI-QKD protocol does not need to compare and adjust the reference frame,solving the dependency of the base in the MDI-QKD protocol.Given that,we propose the OAM-MDI-QKD protocol based on the parametric light sources which mainly include single-photon-added-coherent(SPACS)and heralded single-photon sources(HSPS).Due to the stability of OAM and the participation of parametric light sources,the performance of MDI-QKD protocol gradually approaches the ideal situation.Numerical simulation shows that compared with WCP scheme,HSPS and SPACS schemes have increased the maximum secure transmission distance by 30 km and 40 km respectively.

Direct evidence of high temperature superconductivity in one-unit-cell FeSe films on SrTiO_3 substrate by transport and magnetization measurements

Zero resistance and Meissner effect are two crucial experimental evidences of superconductivity in determining a new kind of superconductor, which can be detected by transport and diamagnetic measurements. In this paper, we briefly review the main transport and magnetization results on the one unit cell （1-UC） FeSe films grown on SrTiO3 （STO） substrates from our team in recent years, which identify the high temperature superconductivity in 1-UC FeSe films.

Nodeless superconductivity in a quasi-two-dimensional superconductor AuTe2Se(4/3)

We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor Au Te2Se（4/3）, which has a superconducting transition temperature Tc = 2.70 K. A negligible residual linear term κ0/T in zero magnetic field is observed, which suggests fully gapped superconducting state.Furthermore, the field dependence of κ0/T is similar to that of the multi-band s-wave superconductor Ba Fe1.9 Ni0.1 As2 at low field. These results reveal multiple nodeless superconducting gaps in this interesting quasi-two-dimensional superconductor with Berezinsky–Kosterlitz–Thouless topological transition.

Application of wavelet analysis to fault diagnosis of angular measuring system

For fault diagnosis, signal singularity and irregularity discontinuity fraction are very significant characteristics of signal. The discontinuity of output signal represents a system fault . In an angular measuring system, function transformer uses two D/A convertors, output circuit fault of a D/A convertor brings about discontinuity of one phase input voltage amplitude of inductosyn, results in a system error exceeding the allowable error and reduces the system accuracy. This is the reason why discontinuity is detected. Fourier transform has no resolution ability in angular domain, but wavelet can analyse signal in angular and frequency domains. So we decompose the error signal of angular measuring system by wavelet, detect the signal singularity at high frequency layer and find out the accurate position of it.

Dynamic error research and application of an angular measuring system belonging to a high precision excursion test turntable

Angular measuring system is the most important component of a servo turntable in inertial test apparatus. Its function and precision determine the turntable＇ s function and precision. It attaches importance to research on inertial test equipment. This paper introduces the principle of the angular measuring system using amplitude discrimination mode. The dynamic errors axe analyzed from the aspects of inductosyn, amplitude and function error of double-phase voltage and wavefonn distortion. Through detailed calculation, theory is provided for practical application; system errors are allocated and the angular measuring system meets the accuracy requirement. As a result, the schedule of the angular measuring system can be used in practice.

Energy and flux measurements of laser-induced silver plasma ions by using Faraday cup

Silver(Ag)plasma has been generated by employing Nd:YAG laser(532 nm,6 ns)laser irradiation.The energy and flux of ions have been evaluated by using Faraday cup(FC)using time of flight(TOF)measurements.The dual peak signals of fast and slow Ag plasma ions have been identified.Both energy and flux of fast and slow ions tend to increase with increasing irradiance from 7 GW cm-2 to 17.9 GW cm-2 at all distances of FC from the target surface.Similarly a decreasing trend of energies and flux of ions has been observed with increasing distance of FC from the target.The maximum value of flux of the fast component is21.2×10^(10) cm^(-2),whereas for slow ions the maximum energy and flux values are 8.8 keV,8.2×10^(10) cm^(-2) respectively.For the analysis of plume expansion dynamics,the angular distribution of ion flux measurement has also been performed.The overall analysis of both spatial and angular distributions of Ag ions revealed that the maximum flux of Ag plasma ions has been observed at an optimal angle of~15°.In order to confirm the ion acceleration by ambipolar field,the self-generated electric field(SGEF)measurements have also been performed by electric probe;these SGEF measurements tend to increase by increasing laser irradiance.The maximum value of 232 V m^(-1) has been obtained at a maximum laser irradiance of 17.9 GW cm^(-2).

基于光学编码成像的新型角位移传感器

传统光学角位移测量方法存在光路复杂、抗干扰能力弱等问题。为此,提出一种基于光学编码成像的新型角位移测量方法。首先,该方法借鉴格雷码转换成二进制的原理,在直径为50 mm的圆周面上均匀分布两圈红色、绿色、蓝色(Red、Green、Blue,RGB)色块,通过检测外圈目标点周围的颜色信息将其转换为与绝对位置对应的二进制数;然后,为降低噪声,利用高斯滤波与中值滤波对图像进行预处理,并使用霍夫圆算法定位跟踪目标点以获得其始末位置,从而计算出粗角度;最后,利用视频最后一帧目标点所处位置与最终位置之间的角度对粗角度进行补偿,实现角度测量。通过搭建实验平台与制作实物传感器,在光圈整周360°测量范围内,对实验装置进行精度测量与稳定性实验,实验结果表明,分辨力达到16位,测量均方差为0.23°。提出的新型角位移测量方法为角位移测量领域提供了新的思路。

基于自适应小波回声神经网络的光纤陀螺测角仪温度误差补偿技术

基于光纤陀螺的测角仪可以实现对各项角运动参数的一体化动态精密测量,但在实际应用中,光纤陀螺测角仪受到温度变化的影响,导致测量精度下降。针对这一问题,本文提出了一种基于自适应小波回声神经网络的光纤陀螺测角仪温度误差补偿技术。为了提高温度误差建模的进度,提高传统神经网络的逼近能力,通过自适应前向线性预测滤波器对建模用测角仪温度漂移数据进行预处理,并采用自适应小波回声神经网络建立温度漂移模型,能够避免传统神经网络结构设计的盲目性和局部最优等问题,增强了网络学习能力和泛化能力,并利用自适应律代替神经网络梯度进行网络训练,提升神经网络的逼近精度和收敛速度。实验结果表明,该模型可以提高光纤陀螺测角仪的测量精度和环境适应性,为光纤陀螺测角仪的性能优化和实际应用提供了可靠的技术支撑。

转台负载工况下角位置误差补偿方法研究

负载会影响转台回转轴的运动状态,进一步影响转台角位置误差的大小。通过分析负载工况下转台角位置误差傅里叶阶次的变化情况,提出一种基于谐波补偿的误差补偿方法。首先,分析负载对转台回转轴的影响,建立回转轴误差运动与角位置误差之间的数学模型,并进行数值仿真;其次,通过负载变化影响回转轴误差运动的大小,获取转台不同负载下的自校准曲线,采用傅里叶法分析对负载变化敏感的傅里叶阶次;最后,选取对负载变化敏感的傅里叶阶次拟合谐波补偿函数对转台角位置误差进行补偿。误差补偿后转台在不同负载工况下的角位置误差最大为±0.25″,与补偿后空载工况下角位置误差相差±0.03″,有效减小了负载对转台角位置误差的影响。

电磁炮轨道间距高精度测量技术研究

电磁轨道炮内膛尺寸精度与发射过程中枢轨高速滑动电接触状态密切相关,准确获取内膛尺寸可有效指导其电枢设计、枢轨匹配性研究等工作。根据轨道炮异形炮膛截面及其形貌特征,并结合内膛间距变化形态,提出一种基于角平分线特性的内膛尺寸高精度测量方法,通过将局部长度范围内两条轨道空间位置关系等效成一定角度张开的两条线段,以角平分线为测量基准,在其上任取一测量点,过该点分别做两条轨道的垂线,定义两垂足的连线即为该测量点处的轨道间距值。通过开展样机设计、全系统误差分析及对比校核,对某口径轨道炮轨道间距进行工程实测。结果表明测量误差≤0.05 mm,满足精度要求。通过获取轨道间距准确数据,可对后期电磁发射装置数值建模、装配工艺及性能检测提供不可或缺的测量手段,进而促进轨道炮武器的工程化应用。

基于ACFM单传感器的裂纹角度识别与重构

交变电磁场测量(ACFM)技术广泛应用于海洋装备和制造业等领域中金属结构物的缺陷检测。针对单传感器检测过程中存在的角度偏转和裂纹定位等问题展开了研究。首先,通过COMSOL Multi-physics仿真结果可知B_(x)和B_(y)在多角度偏转的过程中存在互补的规律;然后,通过建立比例因子,实现高精度的数值拟合。此外,通过多梯度偏转仿真实现了偏转裂纹的重构。最终通过搭建实验平台和信号特征提取等工作验证了拟合规律的合理性;通过优化拟合公式,提高了检测精度;通过所测角度,进而解决了非平行检测过程中裂纹重构图像的偏转问题。

多功能旋转靶装置研究

针对D-D中子发生器采用静态水冷靶时中子产额不稳定、中子产额持续下降等主要问题,研制了一套多功能紧凑型旋转靶装置。装置采用一体化设计,结构紧凑、尺寸小,具备靶体高速旋转和水冷、靶点可视化监测、靶面温度实时测量、中子产额实时监测等功能。本文介绍了该装置的主体结构、功能设计和性能测试,以及靶结构对中子散射影响的模拟计算。性能测试结果表明,该装置真空度满足加速器运行要求,相比静态水冷靶,束流靶点中心最高温度明显降低,中子产额稳定度明显提高。模拟计算结果显示中子能谱峰展宽范围为0~0.0577 MeV,散射中子占比为10.53%~26.75%。本文还针对模拟计算结果和测量结果中存在的问题进行了分析,提出了改进和优化方案。

一种仅用单相绕组的新型绝对式角位移传感器

绕组结构是影响旋转变压器精度的关键因素之一,而VR旋转变压器的感应绕组和励磁绕组之间存在寄生电容,容易干扰信号。针对上述问题,在VR旋转变压器的基础上,设计了一种仅有单相绕组的定子和叶片形转子,结合电桥测量及自感原理的新型绝对式角位移传感器。通过切换电路改变绕线方式,实现精机和粗机绕线的切换,进而实现传感器的绝对测量。采用有限元仿真验证了分析的可行性,得到传感器精机和粗机结构仿真误差峰峰值分别为55.8″和5291″。搭建实验平台,设计传感器样机并进行测试,验证了所提出的传感器结构设计的有效性,在0~360°的采样范围内误差峰峰值约为0.104°。

被动探测视场角约束下的深度强化学习制导方法

针对红外制导导弹拦截机动目标的导引律设计问题,提出了一种纯角度量测下考虑视场角约束的深度强化学习制导方法。首先,将拦截制导问题转化为一个马尔可夫决策过程,建立了基于双延迟深度确定性策略梯度算法的深度强化学习制导模型,并充分考虑了导弹一阶自动驾驶仪特性;其次,设计了一种满足导引头视场角约束,同时又能权衡能量消耗和制导精度的综合奖励函数,并在典型场景下进行了深度强化学习制导律训练。在目标采用不同机动形式的条件下进行了对比仿真与蒙特卡洛仿真。仿真结果表明,该方法采用红外导引头探测到的纯角度信息,能够在满足视场角约束、过载指令饱和约束的前提下以较高精度命中目标,同时对目标的不同机动方式具有较强的鲁棒性。

Research and test of the measurement sensing device for the downforce of no-till planter row unit gauge wheels

To effectively obtain the downforce of the gauge wheels in real time,mechanical models of the interaction among the ground,gauge wheels,gauge wheel arms,and depth adjustment lever were constructed.A measuring method was proposed for monitoring the downforce through a two-dimensional radial sensing device,and a corresponding prototype was designed.Through simulation analysis of the sensing device with ANSYS,a 45°angle was determined to exist between the strain gauge axis and the sensing device axis,and the Wheatstone bridging circuit of R1+R3−R5−R7(R stands for resistance strain gauge,different figures represent the strain gauge number)and R2+R4−R6−R8 was adopted.According to performance and calibration tests for the sensing device,the maximum interaction effect between the X and Y axes was 2.52%,and the output signal was stable and consistent.The standard error of the slope of the fitting equation of the downforce calculation model is 0.008.According to the field test,the average downforce of the gauge wheels was 1148,1017,843,and 713 N,at different sowing speeds of 6,8,10,and 12 km/h,respectively.The coefficients of variation were 0.40,0.41,0.62,and 0.71,respectively.The results indicate that the downforce fluctuation of the gauge wheels became more severe with increasing planting speed.Both the strain simulation analysis and field test verified that the measurement method is accurate and reliable,the performance of the sensing device is stable,the measurement method and sensing device meet the application requirements and lay a foundation for the research of accurate and stable control of downforce of no-till planter.