Prediction of diameter errors compensation in bars turning

On the basis of analyzing the machine-workpiece-tool system, the main factors affecting diameter errors in bars turning are considered, and the mathematic models of the actual workpiece diameter at the cutting point are established according to the three usual methods of mounting workpieces on a turning machine. Further a predictionsystem for diameter errors is developed; a new method, called discrete nodes output, is presented and applied to expressing workpiece diameter errors at given points along the part axis, then off-line compensation is implemented according to the prediction values to diminish machining errors. The results indicate that the method can diminish diameter errors more than 70%, greatly improve the machining accuracy of bars.     

基于最小化测量误差的被动定位算法

借助传感器各自的坐标位置及其三角函数关系,推导出了各个传感器之间测量值的约束关系式．然后将传感器测量误差作为变量构造目标函数,通过拉格朗日-牛顿最优化方法最小化测量误差．使用这些误差修正测量值,取得了较好的目标定位结果．该算法不需要设置目标位置初值,定位结果不会发散,并且具有较高的定位精度．仿真实验结果验证了该算法的有效性．     

Prediction of diameter errors compensation in bars turning

On the basis of analyzing the machine-workpiece-tool system, the main factors affecting diameter errors in bars turning are considered, and the mathematic models of the actual workpiece diameter at the cutting point are established according to the three usual methods of mounting workpieces on a turning machine. Further a prediction system for diameter errors is developed; a new method, called discrete nodes output, is presented and applied to expressing workpiece diameter errors at given points along the part axis, then off-line compensation is implemented according to the prediction values to diminish machining errors. The results indicate that the method can diminish diameter errors more than 70%, greatly improve the machining accuracy of bars. Foundation item: Projects (50175081 and 50475117) supported by the National Natural Science Foundation of China; project (033181611) supported by the Tianjin Municipal Science and Technology Commission     

提高滚轮法测量大直径精度的研究

滚轮法用于大型工件的直径测量时,由于滚轮和被测工件之间产生的滑失现象造成测量误差较大。在采用空气轴承,减小滚轮轴摩擦力,调整微调机构使滚轮轴与工件轴平行的正确方法之后,滑失现象减小,测量精度有所提高。同时还详细介绍了数据采集系统的硬件和软件。     

A Multi-Vehicle Cooperative Localization Method Based on Belief Propagation in Satellite Denied Environment

The global navigation satellite system (GNSS) is currently being used extensively in the navigation system of vehicles. However, the GNSS signal will be faded or blocked in complex road environments, which will lead to a decrease in positioning accuracy. Owing to the higher-precision synchronization provided in the sixth generation (6G) network, the errors of ranging-based positioning technologies can be effectively reduced. At the same time, the use of terahertz in 6G allows excellent resolution of range and angle, which offers unique opportunities for multi-vehicle cooperative localization in a GNSS denied environment. This paper introduces a multi-vehicle cooperative localization method. In the proposed method, the location estimations of vehicles are derived by utilizing inertial measurement and then corrected by exchanging the beliefs with adjacent vehicles and roadside units. The multi-vehicle cooperative localization problem is represented using a factor graph. An iterative algorithm based on belief propagation is applied to perform the inference over the factor graph. The results demonstrate that our proposed method can offer a considerable capability enhancement on localization accuracy.     

基于RSSI的四边测距改进加权质心定位算法

该文根据接收信号强度指示的测距特性,改进四边测距,并提出一种改进的加权质心定位算法。首先引入统计中值加权的方法,有效地降低了采集RSSI信号时的测量误差。然后运用Euclidean节点定位算法,改进四边测距算法。为进一步提高精度,对WSN定位技术中关于未知节点近似位置的算法做了修正,并对加权质心定位算法中的加权因子进行了优化,使未知节点的定位精度更加精确。相比之前的许多加权质心定位算法,仿真结果表明,改进的质心定位算法在定位精度方面有很大的提高,鲁棒性也较高。     

稳健的虹膜定位算法

虹膜定位是虹膜识别的第一步,同时也是最为关键的一步,它将直接影响整个虹膜识别系统的效率和准确率。针对目前已有虹膜定位算法的局限性,该文提出了一种新的基于多分辨率理论的虹膜定位算法。该算法首先在某一分辨率下搜索虹膜内外缘的边界点,然后针对这些边界点进行椭圆曲线拟合。通过大量的实验表明,该算法快速、准确,并能够在一定程度上解决偏视虹膜图像的定位问题和眼睑、睫毛的遮挡问题。     

管道地理位置测量系统的动态初始对准方法

针对长输油气管道地理位置测量系统的初始对准问题,提出了一种新的动态初始对准方法.建立了管道地理位置测量系统状态误差模型和以基准点之间的航向角误差、速度误差和位置误差为观测量的观测模型,设计了变尺度无迹卡尔曼滤波动态初始对准算法.结果表明,该算法所得初始对准俯仰角、航向角和横滚角的稳态误差分别为18.9'、6'和5',解决了姿态角周期性变化引起的初始对准精度差的问题,满足了管道地理位置测量系统的工程应用要求.     

Maximum likelihood registration for systemic error based on statistical linear regression

Generally,there are non-random systemic errors in target detection with the cooperative multi-sensor system.In order to solve this problem,a maximum likelihood registration algorithm based on statistical linear regression (SLR-MLR) is presented.The registration equation for the multi-sensor system is established first by jointly maximizing the likelihood function of the target state and systemic error,on the basis of which the proposed algorithm utilizes a set of diverse regression points to handle the linearization problem of the nonlinear measurement transformation.The regression equation for the target state with respect to unbiased measurement is constructed through statistical linear regression,and then the first two statistical properties of the projected state can be obtained.Moreover,the algorithm uses the likelihood maximization iteration to seek the solution of the registration equation,thus achieving the joint estimation for the systemic error and target state.Simulation results show that the SLR-MLR can achieve the registration of multiple sensors in each observation dimension,and has a higher accuracy and near computational complexity compared with the classical MLR.     

基于全局人工鱼群算法优化的DV-Hop定位算法

无线传感器网络具有大规模、自组织、可靠性、以数据为中心、集成化等特点,被广泛应用于军事、医疗、矿山监测、安全生产等领域。然而现有的无线传感器网络非测距定位算法还存在定位偏差较大问题。针对上述问题,本文提出一种基于全局人工鱼群算法优化的DV-Hop（Distance Vector Hop）定位算法（DEWF-D）。该算法对非测距定位算法中的DV-Hop算法出现误差的步骤进行优化处理,通过减小算法过程中出现的误差,最终得到较为精准的定位坐标。首先使信标节点以两种不同的通信半径传递消息,将跳数进行精确化处理,以减少跳数带来的误差,然后用最小均方误差准则和误差加权方式计算平均每跳距离,最后利用人工鱼群算法替换三边测量法进行坐标计算,同时又在人工鱼选择下一个位置时引入全局最优信息,并引入人工鱼的吞食行为,提高人工鱼群算法的精度以及收敛速度。通过仿真验证,在不同信标节点密度下,本算法与DV-Hop算法以及其他算法相比定位精度分别提升28.3%、6.9%、12.5%,而在不同通信半径下,定位精度提升了24.4%、7.6%、14.8%。证明DEWF-D算法能有效提升定位精度,解决了定位算法中出现的定位偏差较大问题。     

光电经纬仪多站交会测量布站方法及仿真

针对多台光电经纬仪交会测量时的布站问题．根据误差传递公式得到基本布站方式；采用最小二乘法对观测方程进行处理，并获得其空间坐标误差的计算公式，再进行误差仿真，从而确定最优的布站方案．结果表明，当目标位于观测站正前方范围内时，合理布站可显著提高光电经纬仪对空间飞行器坐标的测量精度，对机动大目标的坐标测量误差小于0．20m．     

Load-induced error identification of hydrostatic turntable and its influence on machining accuracy

In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the influence of load-indcued errors on machining accuracy, an identification model of load-induced errors based on the deformation caused by applied load of hydrostatic turntable of computerized numerical control(CNC) gantry milling heavy machine is proposed. Based on multi-body system theory and screw theory, the space machining accuracy model of heavy duty machine tool is established with consideration of identified load-induced errors. And then, the influence of load-induced errors on space machining accuracy and the roundness error of a milled hole is analyzed. The analysis results show that load-induced errors have a big influence on the roundness error of machined hole, especially when the center of the milled hole is far from that of hydrostatic turntable.     

基于群组的WI—FI指纹室内定位研究

WI-FI指纹定位是最常用的室内定位算法之一,但是WI-FI指纹定位存在较大的定位误差。为了提高定位精度,提出了基于群组的定位算法。首先在WI—FI指纹定位的基础上,提出了群组的概念,然后阐述了基于最小编辑距离的群组识别算法,最后利用群组中人与人之间的物理距离,设计了一种基于群组的定位算法。实验表明,基于群组的WI—FI指纹定位算法能明显减小WI-FI指纹定位的误差。     

融合光流与特征点匹配的单目视觉里程计

针对城市平坦路面准确实时定位的问题,提出将光流跟踪法与特征点匹配进行卡尔曼融合的单目视觉里程计方法.基于平面假设,利用光流跟踪法进行帧间小位移定位,同时利用传统的加速鲁棒特征点（SURF）进行帧间大位移匹配来矫正光流法结果.通过卡尔曼滤波更新机器人的位置和姿态.结果表明,融合算法克服了光流法定位精度差和特征点匹配法处理速度慢的缺点,突出了光流法实时性和特征点匹配定位准确性的优点,该方法能够提供较准确的实时定位输出,并对光照变化和路面纹理较少的情况有一定的鲁棒性.     

Relative Attitude and Position Estimation for Spacecraft from Multiple Geometric Features

This paper investigates the pose and motion estimation problem using single camera measurement for spacecraft. The leader spacecraft of three-dimensional shape is observed by a calibrated camera fixed on the follower spacecraft. Based on dual numbers, an integrated observation model is proposed based on a combination of multiple geometric features including points, lines and circles, which can improve the robustness and accuracy of the estimation algorithm. A six-degree-of-freedom relative motion model is proposed by using the dual quaternion representation, in which the rotation-translation coupling effect due to the points deviating from the center of the mass is described. Employing the proposed observation model and dynamics model, an Extended Kalman Filter is presented to estimate the relative state between the two spacecraft. Numerical simulations are performed to evaluate the proposed approaches, showing the convergence of relative estimation errors and superior estimation performance.     

非合作目标在轨服务最终接近段视觉导航算法

为解决在轨服务最终接近段传统单目视觉相对导航方法受相机视场限制以及非合作航天器无法设置人工靶标的问题,提出了以非合作航天器太阳帆板三角形支架的部分结构为测量目标的视觉相对导航算法.首先,设计了"自拍杆"相机安装结构和相机实时标定方案,给出了视觉相机安装角的计算方法;然后,基于逆投影原理构建满足三角形支架实际空间几何构型约束的优化模型,采用蚁群搜索算法求解特征点的景深,并应用绝对定位方法估计航天器之间的相对位置和姿态;最后,以非合作航天器在轨服务最终2 m~0 m的接近段为背景进行数学仿真,在相对距离小于1 m时,航天器之间的相对位置和相对姿态确定精度分别优于3 mm和0.2°,验证了算法的有效性和可行性.数学仿真结果表明:该相对导航方案可行,导航算法具有较高的精度,且相对导航的精度随着航天器之间的相对距离的逐渐减少而逐渐提高;同时,该算法对投影点测量误差具有较好的鲁棒性,在投影点测量误差较大时仍具有较高的精度.     

基于加权混合滤波和重心法的APIT定位算法

提出了一种基于加权混合滤波与重心法的近似三角形内点测试（APIT）改进定位算法（HFG-APIT）.利用混合滤波过滤突变信号强度值使数据平滑稳定输出;再引入加权中位数来提高接收信号强度（RSSI）的精度;最后采用重心法进行内点测试减少误判,提高定位精度.仿真结果表明,混合滤波算法比其他滤波方法处理RSSI数据的测距精度更高,HFG-APIT的定位误差分别为最小二乘定位算法（LSM-RSSI）和APIT定位算法的41.7%和23.8%,整体定位性能也优于其他2种算法.     

数控火焰切割系统Z轴高度补偿功能的实现

采用工业计算机和运动控制卡等硬件构建开放式数控火焰切割系统,以Visual Basic 6.0为开发工具,开发了提高异形工件火焰切割过程平稳性的系统控制软件. 采用激光位移传感器对被加工件进行非接触式扫描,获取工件在加工路径上的高度信息,并以此为依据进行切割轨迹的规划和高度补偿. 试运行结果表明,当工件表面高度发生变化时,由伺服系统进行三轴直线插补或三轴螺旋插补,能够在切割过程中使割炬与工件表面之间的距离始终保持一致,位置精度±0.02 mm,重复定位精度±0.05 mm. 整个系统保证了良好的切割质量,达到了切割过程平稳高效的目的.     

非合作航天器相对位姿的鲁棒视觉确定方法

以非合作航天器的相对状态确定为研究背景,针对无法在目标航天器上安装测量光标的问题,提出利用目标航天器自然特征的单目视觉测量方案.并针对仅利用非合作航天器自然特征而导致的粗大误差增大等问题,提出了基于Randomized RANdom SAmple Consensus(R-RANSAC)的相对位姿单目视觉确定鲁棒算法,该算法首先采用R-RANSAC剔除粗大误差,然后利用基于特征点的相对位姿确定迭代算法消除其他类型的误差影响,以进一步提高算法确定精度.与航天器交会对接视觉系统不同,该系统无需在目标航天器上安装测量光标,而是充分利用目标航天器的自身结构特征,因此更适用于非合作航天器间的相对状态测量.最后对本文算法进行了数学仿真,结果表明该算法的有效性和可靠性.     

柔性并联机器人系统的运动规划

针对500m口径大射电望远镜馈源支撑并联机器人存在悬索速度突变,导致舱体动态响应影响定位精度的问题,提出了柔性并联机器人系统的运动规划方法．为实现索长与索速度的同时控制,采用机器人关节规划理论的启发式策略生成离散点处的悬索速度;为保证离散点之间索速度与索加速度的连续性,提出了一种三次-四次多项式混合插值规划方法．研究结果表明,该运动规划方法生成的索长和索速度数据变化平滑,插值精度满足大射电望远镜的要求,可以解决因索速度突变造成的舱体动态响应和定位精度问题．