激光雷达集成电路存储单元上电复位状态机设计

为了提高激光雷达集成电路存储单元上电复位的稳定性,提出基于集成DSP的激光雷达集成电路存储单元上电复位状态机设计方法。构建激光雷达集成电路存储单元复位状态机的总体结构模型,采用内核电源电路进行单极点高通滤波控制,通过由DSP集成信息模块等组成的上电复位机控制的方法,进行激光雷达集成电路存储单元的程序加载和基线恢复控制,通过基线恢复器实现激光雷达集成电路存储单元的掉电复位和连通性测试,实现激光雷达集成电路的逻辑时序控制和上电状态机设计,实现激光雷达集成电路存储单元的硬件优化设计。仿真结果表明,设计的激光雷达集成电路存储单元上电复位状态机稳定性较好,集成控制性能较强,提高了激光雷达集成信号采集能力。     

Ocean surface profiling lidar

This paper describes a waveform-sampling lidar system and field experiment. The lidar used a diode laser and a Nd: YAG laser transmitters that had different wavelengths and temporal pulse-width characteristics. The diode laser wavelength was 904 nm and the Nd:YAG laser wavelength was 1064nm. The pulse widths of the diode laser and the Nd: YAG laser were 10ns and 26ns respectively. Both transmitters shared the same lidar-receiver and data acquisition system. The data acquisition system included a high-speed waveform-sampler and a mass-storage tape drive to collect and store high-resolution lidar waveform data. This paper describes the lidar and the data acquisition systems. The lidar range, laser waveform and reflectivity data collected in airborne experiments performed over the ocean water were analysed and discussed. Simulation of lidar bathymetry data analyses using the airborne experimental results were also discussed.     

Velocity retrieval for coherent Doppler lidar

Coherent Doppler light detection and ranging (lidar) measures a component of atmospheric wind motion in the direction of the lidar beam. However, velocity vectors are needed in order to obtain more complete knowledge of flow fields in the atmospheric boundary layer (ABL). Several methods such as the velocity azimuthal display (VAD) and dual-Doppler approaches exist to retrieve two-dimensional vector fields, but these methods tend to lose local information about the flow field due to the averaging involved. A two-dimensional vector retrieval method has been adapted from radar data assimilation techniques. The retrievals are performed on data from the Joint Urban 2003 (JU2003) experiment and are shown to retain the local velocity information which is lost in a method like the VAD. A comparison with dual-Doppler retrievals shows reasonable agreement. Furthermore, radial velocities computed using the projections of the retrieved vectors from one lidar and the look direction from the other lidar compare well with the measured radial velocity from the other lidar.     

Development of Mini UAV-borne LiDAR System and It’s Application of Power Line Inspection#br#

Mini UVA borne LiDAR system is a research hotspot nowadays,It has the characteristics of low cost,easy to carry and flexible to use,and has developed rapidly in recent years.This paper proposes a complete solution of the data acquisition and processing analysis by mini-UAV-borne LiDAR system,which mounted on a multi-rotor unmanned aerial vehicle.Aiming at the time synchronization and structure integration design and settling angle error elimination involved in the development of mini UAV-borne lidar system,a complete solution for data acquisition and processing analysis of light and mini UAV-borne lidar under complex terrain conditions is proposed.The integrated system is used to carry out power line patrol application,and the number of tests are carried out.According to the analysis results,the advantages of the system in power line inspection are fully demonstrated,and its functions and performances are verified.     

Estimation of above-ground forest biomass using metrics based on Gaussian decomposition of waveform lidar data

Large-footprint waveform light detection and ranging (lidar) data have been widely used in above-ground forest biomass estimation. Waveform metrics derived from basic statistics (e.g. percentile of energy) of the lidar waveform, such as canopy height and height of median energy, have been applied to biomass estimation in numerous studies. In this study, a set of metrics based on Gaussian decomposition (GD) results were developed and evaluated for forest above-ground biomass estimation using NASA’s laser vegetation imaging sensor (LVIS) data. The GD metrics were designed to explicitly incorporate lidar intensity and vertical structures of canopy layers for biomass estimation. The proposed GD metrics used information related to the above-ground height of each Gaussian centroid and the Gaussian area index (GAI), where GAI is the area covered by a Gaussian function. Two types of novel GD metrics were developed: (1) percentile-height GAI metrics expressing the GAI summation of a subset of Gaussian centroids located within a certain percentile height range; and (2) height-weighted GAI metrics, a summation of GAIs of a waveform weighted by the corresponding heights of their Gaussian centroids. A biomass regression model was built by eight newly developed GD metrics using GAI information and five pre-existing GD-derived metrics that have not previously been used for biomass estimation. The performance of the regression model was then compared to another regression model using 12 previously published metrics (non-GD metrics). The Random Forests (RF) regression algorithm was employed for predicting biomass. The RF out-of-bag results indicated that above-ground biomass estimations using GD metrics achieved significantly better results than those derived from non-GD metrics for deciduous plots (19% lower root mean square error (RMSE), 25% higher coefficient of determination (R²), and marginally better results in coniferous plots (4% lower RSME, 6% higher R²). The combination of GD and non-GD metrics achieved comparable biomass estimation results to the model using exclusively GD metrics. GD metrics also showed strong correlation with forest attributes such as mean diameter at breast height (DBH) and stem density. This study contributes to the usage of GD results for accurate estimation of forest above-ground biomass in large-footprint lidar waveform data in temperate deciduous forests, because temperate deciduous forests have been proved challenging in regard to lidar-derived biomass estimations.     

逆向工程点云数据采集系统设计及应用

针对目前四轴激光测量机的不足,设计了一种五轴逆向工程点云数据采集系统;在四轴的基础上增加了激光测头的旋转轴,采用基于PCI总线的运动控制系统及USB总线的数据采集系统,并植入了图像采集系统,通过二次开发技术利用Windows的应用程序编程接口函数对扫描范围进行自动识别;软件系统使用了采集路径规划及测量数据优化处理算法;在原始数据测量及曲面反求建模两个方面进行了实例应用,零件大斜度面和垂直于工作台的表面均能覆盖测量,并且所有点云数据是一次测量完成,实验结果验证了本系统的可行性与稳定性。     

Estimation of the atmospheric boundary layer height during different atmospheric conditions: a comparison on reliability of several methods applied to lidar measurements

The performance of six numerical methods usually used to determine the atmospheric boundary layer (ABL) height from lidar measurements was investigated under different atmospheric conditions: results were compared with those obtained from radiosoundings to analyse their reliability for ABL-height retrievals. The selected methods were the gradient method (GM), the logarithm gradient method (LGM), the inflection point method (IPM), the wavelet covariance transform (WCT), the centroid/variance method (VM), and the cluster analysis (CA). Lidar measurements were carried out in the frame of the ‘Atmospheric Minor Species relevant to the Ozone Chemistry’ (AMISOC) project during a multi-instrument campaign conducted at the INTA/Atmospheric Observatory ‘El Arenosillo’ (INTA/ARN) in south-western Spain from 15 May to 20 June 2012. The goal of this work is to analyse the performance and robustness of the different lidar methods in this region, characterized by particular atmospheric conditions. In particular, both events of sea–land breeze regimes and episodes of Saharan dust intrusions were studied. In most days, similar results were obtained by all lidar methods in the events of sea–land breeze regimes, presenting relative absolute differences between lidar and radiosounding retrievals below 12% in average. However, big discrepancies between lidar and radiosounding retrievals are found when residual layers are present in the measurements. In such cases, the vertical extension of lidar and radiosounding profiles must to be limited to the altitude of the residual layer bottom. In a second analysis, focused on diurnal variability in the ABL heights under non-dusty (ND) and dusty (DD) conditions, the methods were tested against intensive radiosoundings launched every 4 h over 2 days. Under ND conditions, the best results were achieved for the LGM, presenting a mean of the relative absolute differences respect to radiosounding measurements of 10%. The rest of methods also provided good results with relative differences below 20% in average. Under DD conditions, however, an increase of the relative differences is found with mean values of up 32%. In this case, best results are given by CA with a mean relative difference of 20%. Despite the limited data set used in this work, results show that unlike the ND conditions for which all lidar methods provide good results respect to radiosounding retrievals, under DD conditions the election of the lidar method is a key factor for ABL estimation. However, we remark the need of extending our analysis to longer periods of time to better characterize the differences observed in this work.     

An effective approach for land-cover classification from airborne lidar fused with co-registered data

Airborne lidar provides accurate height information of objects on the earth and has been recognized as a reliable and accurate surveying tool in many applications. In particular, lidar data offer vital and significant features for urban land-cover classification, which is an important task in urban land-use studies. In this article, we present an effective approach in which lidar data fused with its co-registered images (i.e. aerial colour images containing red, green and blue (RGB) bands and near-infrared (NIR) images) and other derived features are used effectively for accurate urban land-cover classification. The proposed approach begins with an initial classification performed by the Dempster–Shafer theory of evidence with a specifically designed basic probability assignment function. It outputs two results, i.e. the initial classification and pseudo-training samples, which are selected automatically according to the combined probability masses. Second, a support vector machine (SVM)-based probability estimator is adopted to compute the class conditional probability (CCP) for each pixel from the pseudo-training samples. Finally, a Markov random field (MRF) model is established to combine spatial contextual information into the classification. In this stage, the initial classification result and the CCP are exploited. An efficient belief propagation (EBP) algorithm is developed to search for the global minimum-energy solution for the maximum a posteriori (MAP)-MRF framework in which three techniques are developed to speed up the standard belief propagation (BP) algorithm. Lidar and its co-registered data acquired by Toposys Falcon II are used in performance tests. The experimental results prove that fusing the height data and optical images is particularly suited for urban land-cover classification. There is no training sample needed in the proposed approach, and the computational cost is relatively low. An average classification accuracy of 93.63% is achieved.     

Optical parametric oscillators in lidar sounding of trace atmospheric gases in the 3–4 μm spectral range

Applicability of a KTA crystal-based laser system with optical parametric generation to lidar sounding of the atmosphere in the spectral range 3–4 μm is studied in this work. A technique developed for lidar sounding of trace atmospheric gases is based on differential absorption lidar (DIAL) technique and differential optical absorption spectroscopy (DOAS). The DIAL-DOAS technique is tested to estimate its efficiency for lidar sounding of atmospheric trace gases.     

串口通信在激光器监控系统中的应用

随着光纤激光器广泛应用与快速发展,市场竞争与成本控制不断加强,其光电系统的控制与保护成为光纤激光应用的关键;为实现激光器的智能化控制和预报警保护,降低生产和维护成本,详细介绍了激光器监控系统的软、硬件设计及其测试结果;通过Visual Basic编写USB转RS232的串口通讯软件,以STM32F407ZG单片机为核心设计了激光器功率驱动、故障保护、数据采集等硬件电路,完成PC端上位机软件对光纤激光器功率的控制(0～100％),实现对光纤激光器泵源温度、工作电流、工作状态等数据的实时采集和监测;根据对300 W光纤激光器输岀功率进行测试,可得到系统光光转换效率高达70.53％;同时经过72 h整机老化后,根据测试结果可得到激光器功率输出稳定度高达96.6％.设计已广泛应用于切割、焊接、精密打孔、3D雕刻等工业加工领域的实际生产中.     

基于IEEE1394总线的图像采集处理系统实现

针对卫星激光通信的瞄准捕获跟踪(PAT)系统的图像处理子系统对光信号的检测要求处理速度快,抗干扰能力和实时性强等特点,设计了基于IEEE1394总线的图像采集处理系统来接收CCD传出的图像数据。采用CCD摄像机作为整个系统的光信号探测器,并利用基于IEEE1394总线的图像采集处理系统来接收CCD传出的图像数据。采用了数字信号处理器DSP作为图像处理系统的主控单元,并采用了两片1394芯片分别实现链路层和物理层。对于系统的软件设计,根据角偏差算法的特点,设计处理数据方式为:每采集一个等时数据包就对该数据包进行处理并将结果累加,到下一幅图像传输开始时完成对上一幅图像的处理。经调试,该系统成功应用于卫星激光通信试验系统的激光束位置偏差信号的检测,它具有硬件实现简单,处理速度快,软件升级性好等特点。     

基于LabVIEW的数据采集系统研究

针对在虚拟仪器的使用过程中需要利用数据采集卡对实验数据进行采集,而专用数据采集卡价格较贵这一现实问题,提出了一种基于LabVIEW的数据采集系统的设计方案,介绍了该系统的硬件组成及软件设计。该系统采用双51单片机控制技术,通过USB接口实现多种数据采集对象的在线实时传送或离线大容量数据存储等功能,达到了取代专用数据采集卡的目的。     

Windows环境下高速数据采集系统软件设计

设计了基于工控机和高速模入板卡的数据采集系统,介绍了Windows多任务多线程环境下,高速同步采集数据、存储与处理数据的软件设计方法。根据系统的特点,采用半满中断方式实现数据采集传输;多线程技术使数据采集与数据处理相独立,提高了数据吞吐量和计算机的整体处理能力;缓冲队列实现了高速连续存盘而不丢点;动态虚拟技术实现线程高优先级工作。用这些方法开发出的软件已成功应用于风机的故障检测中,并取得了良好的效果。     

用于化学激光器上的智能数据采集系统

原有的化学激光器测控系统不仅外形庞大,而且数据采集不便、精度不高,采集点添加困难。为此,设计了一种基于PIC单片机的智能数据采集系统,主要由远程控制系统和数据采集模块组成。其能够远程控制激光器上各采集模块的运行,实时采集与存储压力或温度数据,并将数据无线传输到控制系统上。采集模块自带电源,模块化设计,扩展性强,可直接与传感器相连无需修改,最多可扩展65535个。系统主要用于化学激光器中的压力测量,同时还适用于工业控制、科学研究等需要大量传感器的地方。     

HF molecules laser sensing in gaseous flows

The lidar monitoring are widely used for the gaseous molecules ultra low concentration levels in atmosphere and technological gaseous flows. It demands the detail studies of the atmospheric optics basics and computer simulation of the laser sensing possibility in such a molecules detection by the laser radiation with pulse energy up to 35 mJ at the wavelength of 532 nm. The lidar signal of the HF molecule versus the sensing distance have been a subject of the simulation studies of this signal molecules concentration dependence. It has been taken into account the Sun background radiation as the minimal lidar HF signal. The HF concentration versus distance dependences for this molecules ultra low concentration level in atmosphere simulation results show the HF molecules Raman and DAS lidar sensing efficiency for low concentration in the distance range from 1 to 1000 m by chosen laser wavelength and pulse energy in the daytime ranging regime. The text was submitted by the authors in English.     

基于拉曼激光雷达的大气水汽监测系统设计

针对当前大气水汽监测系统数据处理时间长,监测准确率低的问题,设计了基于拉曼激光雷达的大气水汽监测系统;采用激光发射器,将纳米棒放置在发射器内部的绝缘硅层上,连接原子级光滑银,产生共振磁场发射激光,确保发射频率稳定性,利用光电接收器,接收发射并折返激光波,监测大气水汽并记录相关数据,运用信号处理器,由分光器件获取并交由光电倍增管缓存实时数据,完成系统硬件设计;通过拉曼激光雷达技术,采集大气水汽信号,探测大气中散射光子数和回波光干数,根据监测数据,计算大气水汽的信噪比,推导出大气中水汽占比,完成系统软件设计,实现大气水汽实时监测;实验结果表明,基于拉曼激光雷达的大气水汽监测系统的数据处理时间为21.6 s,监测准确率可高达91%,能够有效缩短数据处理时间,提高监测准确率。     

基于MCS算法的飞机起落架仿真研究

提出了一种新的自适应控制律(MCS算法)来描述飞机起落架系统,分析了MCS算法(Minimal Control Synthesis Algorithm)的优点,建立了自适应控制起落架的数学模型和线性状态控制方程.基于起落架系统的稳定性和鲁棒性,采用MCS的控制方法对起落架系统进行设计,得到了起落架的控制模型.最后通过Matlab仿真软件对采用MCS算法控制的起落架模型进行了仿真分析,仿真结果表明:MCS算法能够使起落架的控制变量快速达到理想的参考模型输出并且控制曲线平滑,同时控制系统具有很好的鲁棒性能,增强了系统的抗干扰能力.     

低成本激光和视觉相结合的同步定位与建图研究

激光雷达和视觉传感是目前两种主要的服务机器人定位与导航技术,但现有的低成本激光雷 达定位精度较低且无法实现大范围闭环检测,而单独采用视觉手段构建的特征地图又不适用于导航应用。因此,该文以配备低成本激光雷达与视觉传感器的室内机器人为研究对象,提出了一种激光和视觉相结合的定位与导航建图方法：通过融合激光点云数据与图像特征点数据,采用基于稀疏姿态调整的优化方法,对机器人位姿进行优化。同时,采用基于视觉特征的词袋模型进行闭环检测,并进一步优化基于激光点云的栅格地图。真实场景下的实验结果表明,相比于单一的激光或视觉定位建图方 法,基于多传感器数据融合的方法定位精度更高,并有效地解决了闭环检测问题。     

Airborne DIAL lidar gas analysis of the atmosphere by middle IR gas lasers: Numerical modeling

The subject of this paper is an estimation of possibility of gas analysis by differential absorption lidars (DIAL) based on gas lasers of the middle IR spectrum range. The potential of lidar systems based on CO₂ laser with radiation frequency converter for ground and onboard sensing of atmospheric water vapor and carbonic oxide concentration profiles is analyzed. Possibilities of NO and NO₂ emission detection in ground atmospheric layers using converted frequencies of CO and CO₂ laser radiation in onboard DIAL are discussed. Absorption lines for methane and ammonia sensing by lidar system based on tunable TEA CO₂ laser with frequency converter has chosen. The results of an estimation of methane leakage detection from pipelines by onboard lidar are submitted. Applicability of the DF laser in onboard DIAL for a control of atmospheric gases is reported. The text was submitted by the author in English.