基于光纤陀螺的捷联寻北仪误差分析

光纤陀螺寻北仪的静态误差包括陀螺误差、倾斜角测量误差、安装误差、转位控制误差、物理量(纬度、地球重力加速度)误差等.分析各种误差对四位置寻北精度的影响机理,重点详细推导误差模型,并进行仿真验证.仿真结果表明:陀螺精度对寻北精度的影响最大;转位误差和安装误差的影响大于倾斜角测量误差影响,纬度误差影响最小;同时,除安装误差...     

基于环形激光陀螺调制输出的寻北系统

利用环形激光陀螺对角速度输入量具有较高灵敏度的特点,提出了一种新型的激光陀螺寻北系统,将一环形激光陀螺垂直安3 水平的恒速转台上,使输入轴与台面平行,通过测量地球自转角速度的向向分量,实现寻北过程,通过与其对称放的加速度计可以测量出由于轴系安装和系统调平引起的台面倾斜误差,从而对激光陀螺的数据出量进行补偿,同时采用单周期多位置采集技术和多周期重复测量的方法,有效地抑制了激光陀螺的测量噪声,最大限度地减少了随机误差和系统误差的影响,提出了系统的寻北精度,适合多种领域的需要。     

趋势预测1/8周期快速寻北法

保证陀螺经纬仪寻北精度的同时,缩短寻北时间实现快速寻北具有重要意义.从陀螺仪寻北原理出发,建立陀螺运动轨迹的数学模型.基于数字化测量光路建立了非线性回归模型,通过欠周期的采集数据,预测整周期函数信息,研究1/8周期快速寻北方法,实现陀螺开始寻北1 min以内高精度快速寻北,开辟快速寻北的新途径.以改进型JT-15陀螺仪为样机的寻北试验表明,在陀螺开始寻北56 s内,仪器寻北测量精度优于0.831 1’.     

自抗扰控制在捷联寻北仪速度稳定回路中应用

在捷联寻北仪工作过程中,摩擦非线性造成转台伺服系统低速不平稳性,导致陀螺输出漂移变大,影响寻北精度.为了提高伺服转台速度平稳性,设计了自抗扰控制器,实现转台的稳速控制,保证转台快速、平稳定位,以便减少陀螺漂移.仿真结果表明,与采用PID控制相比,速度稳定回路获得较好的动态性能,快速性、平稳性和抗干扰能力都得到提高;实验结果表明,动力调谐陀螺输出更加平稳,减小了陀螺输出的随机漂移,寻北误差从34.4″减小到27.7″,有效地提高了系统的寻北精度.     

光纤陀螺静态寻北算法的误差分析

以光纤陀螺静态寻北原理为基础,建立了3种常用寻北算法的误差模型,并定量计算算法中参数对寻北误差的影响。对3种模型的分析仿真结果表明,四位置寻北算法的寻北精度高,算法比较稳定,对纬度等寻北参数的敏感度小。     

陀螺电机转速稳定性对寻北影响及其稳速控制

针对交流陀螺电机转速不稳,影响陀螺寻北精度的问题,选择两相无刷直流电机作为陀螺电机.通过分析陀螺运动规律和寻北算法,以中天法为例定量分析了转速稳定性对寻北精度的影响,得到电机转速稳定性优于1×10-5的控制要求;通过分析两相无刷直流电机的运动方程,建立了电机的数学模型,提出了直接占空比电压矢量调制的方法,对电机进行稳速控制,该方法结构简单、响应速度快、精度高.最后通过仿真和实验验证了该方法的可行性.     

基于sym8小波寻北系统去噪研究

针对寻北系统在实际运用中因受周围环境影响而导致寻北精度下降的问题,提出了基于小波变换的去噪方法.该方法选用sym8小波基,采用高次逼近法和改进的小波阈值对含有阵风噪声的原始陀螺信号进行小波去噪.结果表明sym8小波基为含阵风噪声陀螺信号进行小波去噪的最优小波基.调整其分解尺度进行仿真,发现分解尺度为4时达到了最佳去噪效果且提高了寻北精度,证明了方法的有效性与可靠性.     

实时中天寻北算法

中天法是机械陀螺仪精密寻北中最常用的测量方法之一,但是传统中天法测量一般需要1-1．5个以上中天周期才能得到测量结果,严重影响到测量速度．文中介绍了中天法寻北理论,并根据陀螺仪运动规律,提出了实时中天法寻北测量方法．该方法不需要等到光标穿过零刻线,在任意位置时即可以开始寻北测量,从而可以最大程度地避免陀螺下放后因光标远离零刻线而占用的测量时间．实验结果表明,该方法在保证寻北测量精度的同时,可以有效缩短寻北测量时间,达到了快速寻北的目的．     

基于动调陀螺的多位置寻北仪的转位误差分析

针对实验过程中转台在每个转位处存在的转位误差对系统寻北精度的影响,介绍了动调陀螺多位置寻北仪的工作过程及真北解算原理,进行了转位误差对寻北精度影响的误差分析。运用误差理论和偏导数原理,推导出转位误差与寻北误差二者之间的关系模型。理论分析及实验结果表明,在相同寻北位置数的情况下,转位误差越小寻北精度越高;同时在一定的转位误差时,寻北位置数越多则寻北精度越高。根据理论分析,提出了两种不同的误差补偿方法。     

光纤陀螺温度漂移的多变量模型

针对光纤陀螺温度漂移的补偿问题,本文提出一种线性多变量光纤陀螺温度漂移建模方法.建立的模型由两部分组成:陀螺输出的自回归项和温度梯度的多项式分布滞后项(PDL).自回归项描述光纤陀螺历史输出对当前输出的影响,PDL项描述由温度变化引起的陀螺漂移.根据模型的线性特性,采用最小二乘法确定模型参数.用实测的光纤陀螺温度漂移数据进行了模型的有效性验证.实验结果表明,提出的线性多变量模型能有效补偿光纤陀螺的温度漂移,补偿后光纤陀螺的精度提高50%以上.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.