某型机载高度表指示器数字化显示电路设计

机载高度表磁电指针式显示器存在着读数精度不高、抗震性差、非线性程度不好、模拟数据不易存储等缺陷,将高度表指示器进行数字化显示处理,除了方便读取高度数据和提高读数精度外,还能将高度数据存储到计算机内配合其他作战数据处理系统使用,进而提高设备的综合性能;针对这一问题,根据模拟高度电压信号特点,利用MCS-51单片机及接口电路设计了高度表指示器数字化显示电路。通过接口电路功能扩展和软件编程对高度表模拟高度电压进行采样量化、A/D转换、非线性修正以及LED数码显示;实践结果表明,该数字化电路显示精度高、数据易存储、制作成本低、通用性强,只需修改查表程序即可应用于其他高度表磁电示器的数字化显示,在模拟信号数字化显示处理方面具有一定的典型性。     

无线电高度表动态测试方法

为了对导弹无线电高度表的性能进行全面的检查,分析了目前无线电高度表采用的静态测试方法存在的高度特征点少,高度不能连续变化、不能模拟高度表真实的工作环境等问题,提出了动态测试方法,采用函数发生器和向量微波调制器对高度表发射的电磁波进行调制,得到差拍信号模拟导弹飞行高度,展宽接收信号频谱模拟导弹相对海面运动产生的杂波干扰,使高度表接收到的信号接近于真实回波信号,解决了无线电高度表动态测试问题.     

无线电高度表静态模拟测高试验结果分析

介绍某型拖靶使用的KGWXX型无线电高度表静态模拟测高试验方法，给出了试验数据，并对试验结果进行了理论分析。静态模拟测高试验结果表明：该高度表可在超低空状态下提供稳定的高度数据，可以作为某型拖靶系统的高度传感器；该高度表提供的高度数据存在着较大的阶梯误差，将影响拖靶系统的恒高精度。通过分析静态模拟测高试验结果，指出了该高度表提供的高度数据存在较大阶梯误差的原因及解决途径。     

调频连续波高度表的计算机仿真

介绍了使用SPW软件对调频连续波高度表进行计算机仿真的情况,包括高度表的工作原理、数学模型的建立和和性能仿真等内容,并给出了定性和定量的仿真结果.仿真主要针对噪声信道和理想信道,在VHF/UHF波段及S波段进行了模拟测高,结果表明工作频率对高度表的测高精度影响不大,但宽带调频高度衷具有更好的测高精度和更强的抗干扰能力.     

无线电高度表信号模拟器控制/显示模块设计

无线电高度表信号模拟器是无线电高度表进行性能测试和检修时必需的专用仪器。本文设计一种采用C8051F320单片机作为主控制单元(MCU)和PCF8576作为液晶显示器显示驱动芯片的无线电高度表信号模拟器控制/显示模块组件。该控制/显示模块的MCU检测操作键盘的按键操作,向外部的射频信号延时/衰减模块发送相应的模拟高度选择和功率衰减值设置控制信号,同时向显示驱动芯片发送相应的显示控制信号,实现控制和显示功能。实际工程应用表明,该无线电高度表信号模拟器控制/显示模块可靠性好、操作简便、性价比高,具有较高的工程推广应用价值。     

无线电高度表原位检查仪控制/显示模块程序设计

 设计一种无线电高度表原位检查仪,控制/显示模块控制产生模拟高度值选择和功率衰减量设置控制信号,并显示模拟高度值和功率衰减值。简要介绍控制/显示模块硬件电路工作原理,重点分析其程序工作流程和程序设计思想及实现方法。     

基于PXI总线的无线电高度表过程测试方法的研究与实现

针对传统的无线电高度表性能检测技术多以定高特征点位测试为主,等效高度特征点少,不能连续变化,无法对其整个工作过程进行全面考核评估的现状,从导弹无线电高度表测高工作原理和测试技术研究分析出发,提出了过程测试的方法;通过对现有导弹自动化检测系统进行功能扩展,利用可编程PXI模块作为差拍信号发生器,实现了无线电高度表和导弹高度通道的过程测试,对用作其它用途的无线电高度表的全面性能检测同样具有参考价值,进而为导弹其它控制环节的动态性能检测提供了借鉴.     

低空掠海拖靶海浪滤波器的设计与仿真

低空掠海拖靶主要用于模拟反舰导弹。在低空掠海飞行中,含有海浪杂波的无线电高度表的测量高度数据不能直接用于高度控制。在对海浪杂波进行估计的基础上,根据卡尔曼滤波器的原理,综合采用无线电高度表和加速度计的测量信号,设计了海浪滤波器。该滤波器能够有效滤除海浪杂波的干扰,获得高质量的高度信号和垂向速度信号。通过对加速度计零点漂移的估计,能够改善垂向速度和高度的精度,并且得到没有零点偏差的加速度测量。数字仿真结果表明,这种海浪滤波器能够满足系统要求。     

雷达高度表灵敏度测试系统的参数化设计方法

提出了一种参数化设计方法,实现了雷达高度表接收机灵敏度的自动化测试,提高了接收机灵敏度的测试效率和测试准确度;利用计算机程序通过GPIB协议控制直流稳压电源、信号源、示波器等标准仪器,实现了雷达高度表的加电和断电、雷达回波信号的模拟、雷达高度表输出端信号的检测;针对测试需求,充分考虑接收机灵敏度测试方案的通用性和可扩展性,设计了通用的测试模型,据此开发的软件可自动给出测试结论;在程序中设计了求取灵敏度最优频点和灵敏度的优化迭代算法,节省了测试时间;利用数据库技术对被测雷达高度表相关信息和测试数据进行管理,便于将测试结果与历史数据进行比对。     

基于STM32的高精度车载气压高度表设计

针对车载气压高度表对跨地域、长时间运行的高精度以及系统小型化、界面友好化等要求,设计了基于STM32硬件平台的车载气压高度表系统.系统中采用高精度硅压阻式压力传感器,皮托管及相关管路组成气路系统实现大气压静压的采集,并通过嵌入式实时操作系统μC/OS-Ⅱ和图形用户界面μC/GUI实现基于多任务的界面显示.实验结果表明：经实时校正后的车载气压高度表在长时间运行时测量精度优于1.2m,具有较高的测量精度,能很好地满足气压高度表车载应用的高精度高度定位要求.     

Adaptation and sensitivity to postural change in sitting

We used 3 psychophysics methods to determine perceptible changes in seat height, seat pan angle, and backrest angle using an experimental chair. In the method of adjustment, the chosen chair settings were affected by the initial setting. For example, a high initial setting of the seat height led to a high selected setting and a low setting led to a low value. The difference between settings was referred to as not noticeable difference (NND). The method of limits was used to determine acceptable chair settings using verbal limits such as "too high" and "too low." Using the method of constant stimuli, just noticeable differences (JNDs) were determined for chair height (1.5 cm), seat pan angle (1.2 degrees) and backrest angle (1.7 degrees). The corresponding values for NNDs and verbal limits were about twice as large: chair height (2.5 cm), seat pan angle (4 degrees) and backrest angle (3 degrees). NNDs and verbal limits are unobtrusive measures that are considered more valid than JNDs, which exaggerate the need for adjustability. The results have practical implications for the design of office chairs.     

机载X-波段双天线InSAR数据森林树高估测方法

短波长的干涉合成孔径雷达(InSAR)适用于数字表面模型(DSM)提取,但难以提取准确的林下地相位,在缺乏高精度数字高程模型(DEM)的森林区域,短波长InSAR数据估测树高的能力受到限制。针对这一问题,采用机载X-波段单极化(HH)双天线InSAR数据开展了森林树高估测方法研究。双天线InSAR可以忽略时间去相干的影响,并且X-波段波长较短,入射角较大(中心入射角45.77°),地表对干涉去相干的贡献可以忽略,因此可将干涉复相干作为体去相干,对体去相干模型中的结构函数进行勒让德展开,截取第0阶展开式得到了基于相干幅度的森林树高估测模型,利用均匀选取的LiDAR冠层高度模型(CHM)检验样本对估测结果进行严格的精度评价,并与差分法的树高估测结果进行对比。精度评价结果显示:相干幅度法与差分法都得到了较高的估测精度,两者的R~2、RMSE、总精度分别为0.81、0.86;1.20m、0.97m;86.4%、88.7%。研究结果表明:相干幅度与森林树高具有负相关关系,适用于估测树高,基于单极化相干幅度的估测模型也可以得到较高的估测精度,与差分法的估测结果相比,虽然估测精度略有降低,但此方法具有两方面的优势:一方面,估测结果不需要实测样地数据标定,对于没有实测样地数据的森林区域亦能进行高精度的树高估测;另一方面,相干幅度法不需要高精度的DEM,具有更强的实用性。     

Scalable Height Field Self‐Shadowing

We present a new method suitable for general purpose graphics processing units to render self‐shadows on dynamic height fields under dynamic light environments in real‐time. Visibility for each point in the height field is determined as the exact horizon for a set of azimuthal directions in time linear in height field size and the number of directions. The surface is shaded using the horizon information and a high‐resolution light environment extracted on‐line from a high dynamic range cube map, allowing for detailed extended shadows. The desired accuracy for any geometric content and lighting complexity can be matched by choosing a suitable number of azimuthal directions. Our method is able to represent arbitrary features of both high‐ and low‐frequency, unifying hard and soft shadowing. We achieve 23 fps on 1024×1024 height fields with 64 azimuthal directions under a 256×64 environment lighting on an Nvidia GTX 280 GPU.     

一种新型波高测量系统的设计

波高测量是海洋工程模型试验中的一项重要内容,为了能够准确、稳定地实时测量实验水池中的波浪,采用了一种新型的波高测量系统设计方法:首先利用液位高度与波高传感器电容量的线性关系将波高测量问题转化为电容量测量问题;其次利用波高传感器的电容量与其充放电时间的关系将波高传感器的电容量测量问题转化为充放电时间的检测问题;然后运用单片机片内模拟比较器和定时器的输入捕获功能将电容充放电时间转化为计数值;接下来将计数值通过USB接口送到上位机进行数据处理及波形显示;最后进行实验测试,实验结果表明所采用的波高测量方法是有效的,且具有线性度好、灵敏度高、精度高的优点。     

Domino Tiling: A New Method of Real-Time Conforming Mesh Construction for Rendering Changeable Height Fields

In this paper we present a novel GPU-oriented method of creating an inherently continuous triangular mesh for tile-based rendering of regular height fields. The method is based on tiling data-independent semi-regular meshes of non-uniform structure, a technique that is quite different from other mesh tiling approaches. A complete, memory efficient set of mesh patterns is created by an off-line procedure and stored into the graphics adapter's memory at runtime. At rendering time, for each tile, one of the precomputed mesh patterns is selected for rendering. The selected mesh pattern fits the required level of details of the tile and ensures seamless connection with other adjacent mesh patterns, like in a game of dominoes. The scalability potential of the proposed method is demonstrated through quadtree hierarchical grouping of tiles. The efficiency is verified by experimental results on height fields for terrain representation, where the method achieves high frame rates and sustained triangle throughput on high resolution viewports with sub-pixel error tolerance. Frame rate sensitivity to real-time modifications of the height field is measured, and it is shown that the method is very tolerant and consequently well tailored for applications dealing with rapidly changeable phenomena represented by height fields.     

基于二次曲面及多面函数的GPS高程拟合研究

为实现GPS大地高到正常高的转换,采用二次曲面拟合法和多面函数拟合法建立拟合模型,通过实例对模型关键问题和拟合精度进行分析,重点研究光滑因子的选取对核函数的影响,通过比较两种模型的拟合精度,得出在该相对平坦的研究区域二次曲面拟合精度相对较高.     

薄肋高速空切的颤振实验研究

薄肋在高速空切时产生的颤振将影响零件加工质量、表面粗糙度和刀具寿 命,为了克服此影响,对薄肋空切时,在不受外力直接激振的情况下的薄肋振幅变化进行分 析;运用有限元方法和田口实验法对薄肋进行仿真实验和动态位移激振研究,得出结论：薄 肋的宽、高、厚度尺寸会直接影响薄肋位移量,当高度一定时,宽度增加位移量会减少;当 宽度与高度一定时,随着厚度的减少,其位移量会变大;当宽度与厚度一定时,随着高度的 增加,其位移量亦会变大。探讨了薄肋动态位移内部能量的变化状态,并获得其能量完全衰 减的时间,进而设计其加工路径以避开颤振。     

基于形态学建筑物指数的城市建筑物提取及其高度估算

通过引入高分辨率影像的形态学建筑物指数和阴影指数,并结合面向对象的地物信息提取思想,准确地提取出城市建筑物及其阴影,进而实现了城市建筑物的高度估算。首先,利用形态学建筑物指数的多方向多尺度特征,将建筑物与邻近光谱相似的道路目标进行分离;其次,采用双阈值策略提取建筑物与相应的阴影,进一步提高了建筑物的提取精度;最后,根据成像时刻卫星和太阳的高度角、方位角,建立建筑物阴影长度与建筑物高度的估算模型。试验利用厦门市思明区软件园资源三号(ZY\|3)数据进行城市建筑物提取及其高度估算,证实该方法能够较准确地估算出建筑物的高度信息,并且比基于SVM的监督分类方法具有更高的建筑物提取精度,建筑物高度估算的中误差可达±1 m。     

Extracting structural characteristics of herbaceous floodplain vegetation under leaf‐off conditions using airborne laser scanner data

Hydrodynamic models of river flow need detailed and accurate friction values as input. Friction values of floodplain vegetation are based on vegetation height and density. To map spatial patterns of floodplain vegetation structure, airborne laser scanning is a promising tool. In a test for the lower Rhine floodplain, vegetation height and density of herbaceous vegetation were measured in the field at 42 georeferenced plots of 200 m² each. Simultaneously, three airborne laser scanning (ALS) surveys were carried out in the same area resulting in three high resolution, first pulse, small‐footprint datasets. The laser data surveys differed in flying height, gain setting and laser diode age. Point density of the laser data varied between 10 and 75 points m^?2. Point heights relative to the DTM derived from the ALS data were used in all analyses. Laser points were labelled as either vegetation or ground using three different methods: (1) a fixed threshold value; (2) a flexible threshold value based on the inflection point in the point height distribution; and (3) using a Gaussian distribution to separate noise in the ground surface points from vegetation. Twenty‐one statistics were computed for each of the resulting vegetation‐point distributions, which were subsequently compared with field observations of vegetation height. Additionally, the percentage index (PI) was computed to relate density of vegetation points to hydrodynamic vegetation density. The vegetation height was best predicted by using the inflection method for labelling and the 95 percentile as a regressor (R ² = 0.74–0.88). Vegetation density was best predicted using the threshold method for labelling and the PI as a predictor (R ² = 0.51). The results of vegetation height prediction were found to depend on the combined effect of flying height, gain setting or laser diode age. The quality of the estimation of vegetation height and density is also affected by point density, for densities lower than 15 points m^?2. We conclude that high resolution ALS data allows to estimate vegetation height and density of herbaceous vegetation in winter condition, but field reference data remains necessary for calibration.     

Automatic building height extraction by volumetric shadow analysis of monoscopic imagery

This article presents a new approach to automatic extraction of building heights from monoscopic urban scenes. A volumetric shadow analysis (VSA) method was proposed previously for extraction of 3D building information (height, shape, and footprint location) and for handling occluded building footprints or shadows. It determined building heights by adjusting building height manually until the projected shadows generated for an assumed height and actual shadows in the image matched. In this article, we propose an intelligent scheme based on the VSA for automatic building height extraction. We achieve this by checking the location change of projected shadow lines with respect to the actual shadow regions while building heights are increased incrementally. In this article, the performance of the proposed automatic height extraction was compared to that of manual extraction. The method was first applied to IKONOS, KOMPSAT-2, QuickBird, and Worldview-1 images with manually extracted building roofs. The root mean square error (RMSE) of building heights was under 3 m by automatic height extraction and 2 m by manual extraction. The RMSE of building footprint location was close to twice that of image ground sample distance (GSD) by automatic height extraction and under twice that of image GSD by manual extraction. These results support the capability of the proposed method in automatic height extraction from a single image efficiently and accurately, and in handling occluded building footprints and shadows. Second, the method was combined with an existing roof extraction method and tested for automated building roof extraction. The results showed that the proposed method can also provide a powerful cue for automatic building roof extraction from a single image.