CHANNEL ASSIGNMENT STRATEGIES FOR A HIGH ALTITUDE PLATFORM SPOT-BEAM ARCHITECTURE
基于里德堡原子的微波全信息测量
基于里德堡原子的微波全信息测量贾凤东1，郝建海1，崔越1，王宇翔1，刘宇晴1，王宇2，尤建琦2，白金海2，钟志萍1，3*（1.中国科学院大学 物理科学学院，北京 100049；2.航空工业北京长城计量测试技术研究所，北京 100095；3.中国科学院大学 中国科学院拓扑量子计算卓越中心，北京 100190）摘 要：介绍了里德堡原子微波电场传感器的工作原理，阐述了基于里德堡原子测量微波电场强度、相位、极化、频率等信息的技术特点，分析了基于里德堡原子的微波全信息测量的研究现状，探讨了当前绝对自校准测量和连续宽带高灵敏测量面临的困难，指出可以通过外场调控实现测量灵敏度提升和宽带连续频率测量；并可通过各种调制及解调手段简化相位、极化的测量和读取。
分析了在热原子系统中利用多光子激发消除多普勒展宽以及采用冷原子消除多普勒展宽对于提升微波测量灵敏度的潜在优势，提出未来可利用里德堡原子的高轨道角动量态、强关联等特性进一步提升里德堡原子微波电场传感器性能。
关键词：微波电场传感器；里德堡原子；电磁感应透明中图分类号：TB939；TP212；O56 文献标志码：A 文章编号：1674-5795（2024）01-0001-22Microwave full information measurement based on Rydberg atomsJIA Fengdong 1, HAO Jianhai 1, CUI Yue 1, WANG Yuxiang 1, LIU Yuqing 1,WANG Yu 2, YOU Jianqi 2, BAI Jinhai 2, ZHONG Zhiping 1,3*(1.School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China ；2.Changcheng Institute of Metrology & Measurement, Beijing 100095, China ；3.CAS Center for Excellence in TopologicalQuantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China)Abstract: This paper introduces the principles of the Rydberg atom microwave electric field sensor, elucidating the technical features of measuring the information of microwave electric field strength, phase, polarization, and frequency based on Rydberg atoms. Then it analyzes the current state of microwave full‐information measurement based on Rydberg atoms and discusses the challenges faced by absolute self‐calibration measurements and continuous broadband high‐sen‐sitivity measurements. It points out that measurement sensitivity enhancement and continuous broadband frequency mea‐surement can be achieved through external field modulation. Various modulation and demodulation techniques are sug‐gested to simplify phase and polarization measurements and data reading. The paper also explores the potential advan‐tages to eliminate Doppler broadening effect by adopting multiphoton excitation in atomic vapor cell systems and adoptingcold atomic systems to enhance microwave measurement sensitivity. It proposes the possibility for future exploration of such characteristics of Rydberg atoms as high orbital angular momentum states and strong correlations to further improvedoi ：10.11823/j.issn.1674-5795.2024.01.01收稿日期：2023-12-20；修回日期：2024-01-24基金项目：国家重点研发计划项目（2017YFA0304900、2017YFA0402300）；北京市自然科学基金项目（1212014）；中国科学院重点研究计划项目（XDPB08-3）；中央高校基本科研业务费专项资金项目引用格式：贾凤东， 郝建海， 崔越， 等. 基于里德堡原子的微波全信息测量［J ］. 计测技术， 2024， 44（1）： 1-22.Citation ：JIA F D ， HAO J H ， CUI Y ， et al. Microwave full information measurement based on Rydberg atoms ［J ］.Metrology & Measurement Technology ， 2024， 44（1）： 1-22.the performance of Rydberg atom microwave electric field sensors.Key words: microwave electric field sensor; Rydberg atom; electromagnetic induction transparency0 引言对量子状态的主动调控和操纵引发了第二次量子革命，发展出量子通信、量子计算和量子精密测量等前沿领域。
窄带相参雷达飞机目标的架次判别
文章编号：1001-2486（2005）02-0032-05窄带相参雷达飞机目标的架次判别!张汉华，王伟，陈曾平，庄钊文（国防科技大学ATR 重点实验室，湖南长沙410073）摘要：针对窄带相参雷达不仅能够提供目标回波的幅度信息，还可以提供回波的相位信息的特点，提出了MTMM 方法，对编队飞机目标架次进行判决。
实验证明，MTMM 方法为常规低分辨相参雷达平台上编队飞机目标架次判别提供了一种解决问题的新途径，具有重要的现实应用前景。
关键词：低分辨雷达；目标分类；飞机编队中图分类号：TN957.52文献标识码：AClassification of the Aircraft Formation Based onLow-resolution RadarZHANG Han-hua ，WAN Wei ，CHEN Zeng-ping ，Zhuang Zhao-wen（ATR Lab ，NationaI Univ.of Defense TechnoIogy ，Changsha 410073，China ）Abstract ：A method named MTMM for cIassification of the aircraft formation is proposed ，foIIowed by studying the narrow-band signaI with ampIitude and phase.The resuIts based on simuIated data and measured data prove that it is a heIpfuI method to cIassify the number of the airborne targets for Iow-resoIution radar.Key words ：Iow resoIution radar ；target cIassification ；aircraft formation传统雷达分辨率定义认为两个具有不同时间延迟的相同点目标，其合成响应回波出现两个峰值，则可以分辨这两个点目标，出现两个峰值的临界点即为雷达对点目标的时间延迟分辨率［1］。
液压协调自动加载系统的多通道协调性研究
液压协调自动加载系统的多通道协调性研究何乐儒;贾天娇;张海涛;李少鹏;陈晓【摘要】载荷校准试验是应变法测量飞机飞行载荷的一个重要环节.应用于载荷校准试验的液压协调自动加载技术,可实现飞机机翼多点、自动控制、协调加卸载.某型机机体结构具有大展弦比、刚度小等特点,校准试验载荷量级较大、加载点较多.本文分析了液压协调自动加载技术多点协调性的主要影响因素,以某型机机体载荷校准试验为背景对多通道协调性进行分析与总结,为供后续的研究提供参考.【期刊名称】《航空科学技术》【年(卷),期】2018(029)003【总页数】6页(P40-45)【关键词】载荷校准试验;液压协调自动加载技术;多通道;协调性【作者】何乐儒;贾天娇;张海涛;李少鹏;陈晓【作者单位】中国飞行试验研究院,陕西西安 710089;中国飞行试验研究院,陕西西安 710089;中国飞行试验研究院,陕西西安 710089;中国飞行试验研究院,陕西西安 710089;中国飞行试验研究院,陕西西安 710089【正文语种】中文【中图分类】V214.11飞行载荷测量是对飞机结构承受的外载荷进行测量的过程[1，2]，应变电桥法是工程中载荷测量的常用方法[3]。
采用应变电桥测量飞机部件载荷首先在被测部件上加装应变计，通过地面载荷校准试验，建立校准载荷和应变电桥响应的函数关系[4，5]。
飞机载荷校准试验是测量飞机飞行载荷的一个重要环节，其模拟飞行载荷的真实程度是影响载荷模型和实际载荷测量精度的主要因素[6]。
飞机地面载荷校准试验研究初期，多采用液压千斤顶等简单的手动加载设备进行人工单点加载，自2012年液压协调自动加载系统开始应用于国内飞机载荷校准。
液压协调自动加载系统是基于电液伺服控制技术的试验加载设备，在航空、航天、车辆、土木工程、医疗设备等领域得到了广泛应用，主要用于新材料、新工艺或新结构的载荷测量或静力、疲劳与耐久等强度试验。
液压协调自动加载系统克服了以往的手动加载设备加载量级小、通道少的限制，可进行多通道、大载荷的加载试验，从而提高了加载精度，促进了飞机载荷校准试验技术的发展。
基于改进ＤｅｅｐＬａｂＶ３＋的引导式道路提取方法及在震源点位优化中的应用
２０２４年３月第３９卷第２期西安石油大学学报（自然科学版）ＪｏｕｒｎａｌｏｆＸｉ’ａｎＳｈｉｙｏｕＵｎｉｖｅｒｓｉｔｙ（ＮａｔｕｒａｌＳｃｉｅｎｃｅＥｄｉｔｉｏｎ）Ｍａｒ．２０２４Ｖｏｌ．３９Ｎｏ．２收稿日期：２０２３ ０６ ０３基金项目：国家自然科学基金面上项目“基于频变信息的流体识别及流体可动性预测”（４１７７４１４２）；四川省重点研发项目“工业互联网安全与智能管理平台关键技术研究与应用”（２０２３ＹＦＧ０１１２）；四川省自然科学基金资助项目“基于超分辨感知方法的密集神经图像分割”（２０２２ＮＳＦＳＣ０９６４）第一作者：曹凯奇（１９９８ ），男，硕士，研究方向：遥感图像标注。
Ｅ ｍａｉｌ：８１９０８８３３８＠ｑｑ．ｃｏｍ通讯作者：文武（１９７９ ），男，博士，研究方向：人工智能在地球科学的应用、高性能计算。
Ｅ ｍａｉｌ：ｗｅｎｗｕ＠ｃｕｉｔ．ｅｄｕ．ｃｎＤＯＩ：１０．３９６９／ｊ．ｉｓｓｎ．１６７３ ０６４Ｘ．２０２４．０２．０１６中图分类号：ＴＥ１９文章编号：１６７３ ０６４Ｘ（２０２４）０２ ０１２８ １５文献标识码：Ａ基于改进ＤｅｅｐＬａｂＶ３＋的引导式道路提取方法及在震源点位优化中的应用曹凯奇１，张凌浩２，徐虹１，吴蔚３，文武１，周航１（１．成都信息工程大学计算机学院，四川成都６１０２２５；２．国网四川省电力公司电力科学研究院，四川成都６１００９４；３．中国石油集团东方地球物理勘探有限责任公司采集技术中心，河北涿州０７２７５０）摘要：为解决自动识别方法在道路提取时存在漏提、错提现象，提出一种引导式道路提取方法提高修正效率。
在ＤｅｅｐＬａｂＶ３＋原有输入通道（３通道）的基础上添加额外输入通道（第４通道），将道路的４个极点转化为二维高斯热图后作为额外通道输入网络，网络以极点作为引导信号，使网络适用于引导式道路提取任务；设计并行多分支模块，提取上下文信息，增强网络特征提取能力；融合类均衡二值交叉熵和骰子系数组成新的复合损失函数进行训练缓解正负样本不均衡问题。
211002137_高深宽比微结构深度测量技术的研究进展
高深宽比微结构深度测量技术的研究进展吴岳松1，2，王子政1，孙新磊1，武飞宇1，霍树春1，3，胡春光1*（1.天津大学精密测试技术及仪器国家重点实验室，天津 300072；2.北京航空航天大学前沿科学技术创新研究院，北京 100191；3.中国科学院微电子研究所，北京 100029）摘要：高深宽比孔/槽微结构现广泛应用于微机电系统（MEMS）与三维集成电路（3D-IC）等领域，是微纳器件的基础性工艺结构。
随着器件微型化与功能化的发展需求，孔/槽微结构的深宽比不断提升。
深度作为重要参数对器件加工工艺、器件性能有直接影响，微孔/槽结构深度的精确测量具有重要意义，但测量方法面临巨大挑战，成为测量领域的难题之一。
针对这一问题，按照非光学和光学测量方式将测量方法分为两大类，介绍了扫描电子显微镜、扫描探针术、白光显微干涉技术、共焦显微技术和反射光谱技术等测量方法的工作原理，在微孔/槽深度测量方面的研究现状，尝试从中总结每种测量方法的优缺点，最后，讨论了未来高深宽比微结构深度测量发展趋势以及研究重点，为之后高深宽比微结构深度的测量技术研究提供帮助。
关键词：光学测量；高深宽比微结构；深度测量；反射光谱；白光干涉；共焦显微中图分类号：TB9；TH744 文献标识码：A 文章编号：1674-5795（2023）01-0003-15 Research progress of depth measurements of high aspect ratio microstructures WU Yuesong1,2, WANG Zizheng1, SUN Xinlei1, WU Feiyu1,HUO Shuchun1，3, HU Chunguang1*(1.National Key Laboratory of Engine, Tianjin University, Tianjin 300072, China；2.Research Institute for Frontier Science, Beihang University, Beijing 100191, China；3.Institute of Microelectronics of the Chinese Academy of Sciences, Beijing 100029, China)Abstract: High aspect ratio hole/slot microstructures are now widely used in the fields of micro-electro-mechanical systems (MEMS) and three-dimensional integrated circuits (3D-IC), and are fundamental process structures for micro and nano devices. With the development need for miniaturization and functionalization of devices, the depth-to-width ratio of hole/slot microstructures is constantly increasing. As an important parameter, depth has a direct impact on the device processing and device performance. The accurate mea‑surement of the depth of micro-hole/slot structure is of great significance, but the measurement method faces great challenges and has be‑come one of the difficult problems in the field of measurement. To address this issue, the measurement methods are divided into two major categories according to the non-optical and optical measurement methods, and the working principles of measurement methods such as scanning electron microscopy, scanning probe technique, white light microscopic interferometry, confocal microscopy and reflection spec‑troscopy are introduced. The research status of the depth measurements of micro hole/slot is introduced, and the advantages and disadvan‑tages of each measurement method are summarized. Finally, the future development trend and research focus of high aspect ratio micro‑structure depth measurement are discussed to help the future research of high aspect ratio microstructure depth measurements.Key words: optical measurement; high aspect ratio microstructures; depth measurement; reflection spectroscopy; white light inter‑ference; confocal microscopydoi：10.11823/j.issn.1674-5795.2023.01.01收稿日期：2022-08-25；修回日期：2022-09-19基金项目：国家重点研发计划（2019YFB20003601）引用格式：吴岳松，王子政，孙新磊，等.高深宽比微结构深度测量技术的研究进展［J］.计测技术，2023，43（1）：3-17.Citation：WU Y S， WANG Z Z， SUN X L， et al. Research progress of depth measurements of high aspect ratio microstructures［J］. Metrology and measurement technology， 2023， 43（1）：3-17.0 引言高深宽比（High Aspect Ratio，HAR）微结构是微纳加工技术中的典型结构设计形式，深宽比是指垂直加工表面的高度与其加工表面上所具有的较小特征尺寸之比［1］。
溴到硼酸酯
Materials Chemistry C
Published on 20 November 2014. Downloaded on 08/12/2016 07:54:22.
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Cite this: J. Mater. Chem. C, 2015, 3, 861
However, these oligouorene functionalized oligomers may suffer from the unwanted long wavelength emission under long-term device operation, similar to polyuorene-based macromolecules.34–36
Received 26th September 2014 Accepted 17th November 2014 DOI: 10.1039/c4tc02173h /MaterialsC
Starburst 4,40,400-tris(carbazol-9-yl)triphenylamine-based deep-blue fluorescent emitters with tunable oligophenyl length for solution-processed undoped organic lightemitting diodes†
Introduction
Since 1987, organic light-emitting diodes (OLEDs) have attracted tremendous attention due to their potential applications in at-panel displays and solid-state lightings.1–10 To achieve fullcolor displays, three primary RGB luminescent materials with excellent stability, efficiency and color purity are required. With respect to green and red counterparts, it seems to be a big challenge to develop blue emitters, especially deep-blue ones that have a Commission Internationale de l'Eclairage (CIE) y coordinate value of <0.10, because the intrinsic wide bandgap would inevitably result in inefficient charge injection to an emitting layer (EML).11 Therefore, great efforts should be paid to the design of deep-blue emitters to push forward the commercialization of full-color OLEDs.
拉曼与AFM联用 TERS
AFM-microRaman and nanoRaman TMIntroductionThe use of Raman microscopy has become animportant tool for the analysis of materials on themicron scale. The unique confocal and spatialresolution of the LabRAM series has enabled opticalfar field resolution to be pushed to its limits withoften sub-micron resolution achievable.The next step to material analysis on a smallerscale has been the combination of Ramanspectroscopic analysis with near field optics and anAtomic force microscope (AFM). The hybridRaman/AFM combination enables nanometrictopographical information to be coupled to chemical(spectroscopic) information. The unique designsdeveloped by HORIBA Jobin Yvon enable in-situRaman measurements to be made upon variousdifferent AFM units, and for the exploration of newand evolving techniques such as nanoRamanspectroscopy based on the TERS (tip enhancedRaman spectroscopy) effect.AFM image of nano-structures on a SiN sampleHORIBA Jobin Yvon offers both off-axis and on-axisAFM/Raman coupling to better match your sampleand analysis requirements.Off-axis and inverted on-axis configurations forAFM/Raman coupling showing the laser (blue) andRaman (pink) optical pathThe LabRAM-Nano Series is based on the provenLabRAM HR system providing unsurpassedperformance for classical Raman analysis. With theAFM coupling option, it becomes the platform ofchoice for AFM/Raman experiments. The off-axisgeometry offers large sample handling capabilitiesand is ideally suited for the analysis ofsemiconductor materials, wafers and more generallyopaque samples.For biological and life science applications, theLabRAM-Nano operates in inverted on-axisconfiguration with a confocal inverted Ramanmicroscope on top of which the AFM unit is directlymounted. This system is ideally suited for the studyof transparent biological samples such as singlecells, tissue samples and bio-polymers.In both systems, AFM and SNOM fluorescencemeasurements can be combined with Ramananalysis to provide a more completecharacterisation of sample chemistry andmorphology on the same area. Several AFMsystems from leading AFM manufacturers can beadapted on these two instruments. Please contactus to find out which one is best for you!AFM- microRaman dual analysisThe seamless integration of hardware and software of both systems onto the same platform enables fast and user-friendly operation of both systems at the same time. Furthermore, the AFM/Raman coupling does not compromise the individual capabilities of either system and the imaging modes of the AFM remain available (EFM, MFM, Tapping Mode, etc.)The operator has direct access to both the nanometric topography of a sample given by the AFM, and the chemical information from the micro-Raman measurement. An AFM image can berecorded as an initial survey map, in which regions of interest can be defined for further Raman analysis, using the same software.An example of such analysis is illustrated below by an AFM image of Carbon Nanotubes (CNTs) giving information on the CNTs’ length, diameters and aggregation state. A more detailed AFM image is then obtained in which Raman analysis can be performed.Carbon nanotubes AFM images with a gold-coated tip in contact mode. The diameter of the bundles of nanotubes is between 10 and 30 nm.NanoRaman for TERS experimentsSurface Enhance Raman Scattering (SERS) has long been used to enhance weak Raman signals by means of surface plasmon resonance using nanoparticle colloids or rough metallic substrates, allowing to detect chemical species at ppm levels.The TERS effect is based on the same principle, but uses a metal-coated AFM tip (instead of nanoparticles) as an antenna that enhances the Raman signal coming from the sample area which is in contact (near-field). Although not yet fully understood, the TERS effect has attracted a lot of interest, as it holds the promise of producing chemical images with nanometric resolution.The LabRAM-Nano offers an ideal platform,combining state-of-the-art AFMs with our Raman expertise to perform exploratory TERS experiments with confidence.Raman signal TERS enhancement on a Silicon sample with far field suppression thanks to adequate polarization configuration. Red : Far field + Near Field (tip in contact)– Blue : Far field only (tip withdrawn)Technical specificationsFlexure guided scanner is used to maintain zero background curvature below 2 nm out-of-planeFor non-TERS measurements, classical Raman measurements can be made on the same spot as AFM images by translating the sample with a high-accuracy positioning stage from the AFM setup to the Raman setup (and vice et versa). The AFM map can be used to define a region of interest for the Raman analysisusing a common software.LabRAM-Nano coupled with Veeco’s Dimension 3100 AFMThe on-axis coupling configuration enables both AFM-microRaman dual analysis and TERS measurementson transparent and biological samples. The AFM is directly coupled onto the inverted microscope and directlyinterfaced to the LabRAM HR microprobe. It can also be taken off the optical microscope to obtain AFMimages in a different location. Seamless software integration is realized to provide a common platform to bothsystems for both AFM and Raman analysis of the same area and TERS investigation.Bioscope II from VeecoLabRAM-Nano coupled with Park Systems(formerly PSIA) XE-120Off-axis coupling for AFM-microRaman and nanoRaman (TERS)For both dual AFM-microRaman dual analysis and TERS measurements, the off-axis coupling is ideally suited for opaque and large samples. For opaque samples, the inverted on-axis coupling is not possible as the sample will not transmit the laser beam. This can be solved by setting the microscope objective at some angle to avoid “shadowing” effects from the AFM cantilever. Here also, seamless software integration is realized to provide a common platform to both systems. The AFM can be controlled by the Raman software (LabSpec), and mapping areas can be defined on AFM images for further Raman analysis.France : HORIBA Jobin Yvon S.A.S., 231 rue de Lille, 59650 Villeneuve d’Ascq. Tel : +33 (0)3 20 59 18 00, Fax : +33 (0)3 20 59 18 08. Email : raman@jobinyvon.fr www.jobinyvon.frUSA : HORIBA Jobin Yvon Inc., 3880 Park Avenue, Edison, NJ 08820-3012. Tel : +1-732-494-8660, Fax : +1-732-549-2571. Email : raman@ Japan : HORIBA Ltd., JY Optical Sales Dept., 1-7-8 Higashi-kanda, Chiyoda-ku, Tokyo 101-0031. Tel: +81 (0)3 3861 8231, Fax: +81 (0)3 3861 8259. Email: raman@ LabRAM-Nano coupled with Park Systems (formerly PSIA) XE-100Combined polarized Raman and atomic force microscopy:In situ study of point defects and mechanical properties in individual ZnO nanobelts Marcel Lucas,1Zhong Lin Wang,2and Elisa Riedo1,a͒1School of Physics,Georgia Institute of Technology,Atlanta,Georgia30332-0430,USA2School of Materials Science and Engineering,Georgia Institute of Technology,Atlanta,Georgia30332-0245,USA͑Received8June2009;accepted23June2009;published online4August2009͒We present a method,polarized Raman͑PR͒spectroscopy combined with atomic force microscopy͑AFM͒,to characterize in situ and nondestructively the structure and the physical properties ofindividual nanostructures.PR-AFM applied to individual ZnO nanobelts reveals the interplaybetween growth direction,point defects,morphology,and mechanical properties of thesenanostructures.In particular,wefind that the presence of point defects can decrease the elasticmodulus of the nanobelts by one order of magnitude.More generally,PR-AFM can be extended todifferent types of nanostructures,which can be in as-fabricated devices.©2009American Instituteof Physics.͓DOI:10.1063/1.3177065͔Nanostructured materials,such as nanotubes,nanobelts ͑NBs͒,and thinfilms,have potential applications as elec-tronic components,catalysts,sensors,biomarkers,and en-ergy harvesters.1–5The growth direction of single-crystal nanostructures affects their mechanical,6–8optoelectronic,9 transport,4catalytic,5and tribological properties.10Recently, ZnO nanostructures have attracted a considerable interest for their unique piezoelectric,optoelectronic,andfield emission properties.1,2,11,12Numerous experimental and theoretical studies have been undertaken to understand the properties of ZnO nanowires and NBs,11,12but several questions remain open.For example,it is often assumed that oxygen vacancies are present in bulk ZnO,and that their presence reduces the mechanical performance of ZnO materials.13However,no direct observation has supported the idea that point defects affect the mechanical properties of individual nanostructures.Only a few combinations of experimental techniques en-able the investigation of the mechanical properties,morphol-ogy,crystallographic structure/orientation and presence of defects in the same individual nanostructure,and they are rarely implemented due to technical challenges.Transmis-sion electron microscopy͑TEM͒can determine the crystal-lographic structure and morphology of nanomaterials that are thin enough for electrons to transmit through,4,14–17but suf-fers from some limitations.For example,characterization of point defects is rather challenging.14–17Also,the in situ TEM characterization of the mechanical and electronic properties of nanostructures is very challenging or impossible.15–17 Alternatively,atomic force microscopy͑AFM͒is well suited for probing the morphology,mechanical,magnetic, and electronic properties of nanostructures from the micron scale down to the atomic scale.3,6,7,10In parallel, Raman spectroscopy is effective in the characterization of the structure,mechanical deformation,and thermal proper-ties of nanostructures,18,19as well as the identification of impurities.20Furthermore,polarized Raman͑PR͒spectros-copy was recently used to characterize the crystal structure and growth direction of individual single-crystal nanowires.21Here,an AFM is combined to a Raman microscope through an inverted optical microscope.The morphology and the mechanical properties of individual ZnO NBs are deter-mined by AFM,while polarized Raman spectroscopy is used to characterize in situ and nondestructively the growth direc-tion and randomly distributed defects in the same individual NBs.Wefind that the presence of point defects can decrease the elastic modulus of the NBs by almost one order of mag-nitude.The ZnO NBs were prepared by physical vapor deposi-tion͑PVD͒without catalysts14and deposited on a glass cover slip.For the PR studies,the cover slip was glued to the bottom of a Petri dish,in which a hole was drilled to allow the laser beam to go through it.The round Petri dish was then placed on a sample plate below the AFM scanner,where it can be rotated by an angle,or clamped͑see Fig.1͒.The morphology and mechanical properties of the ZnO NBs were characterized with an Agilent PicoPlus AFM.The AFM was placed on top of an Olympus IX71inverted optical micro-scope using a quickslide stage͑Agilent͒.A silicon AFM probe͑PointProbe NCHR from Nanoworld͒,with a normal cantilever spring constant of26N/m and a radius of about 60nm,was used to collect the AFM topography and modulated nanoindentation data.The elastic modulus of the NBs was measured using the modulated nanoindentation method22by applying normal displacement oscillations at the frequency of994.8Hz,at the amplitude of1.2Å,and by varying the normal load.PR spectra were recorded in the backscattering geometry using a laser spot small enough ͑diameter of1–2m͒to probe one single NB at a time.The incident polarization direction can be rotated continuouslywith a half-wave plate and the scattered light is analyzedalong one of two perpendicular directions by a polarizer atthe entrance of the spectrometer͑Fig.1͒.Series of PR spec-tra from the bulk ZnO crystals and the individual ZnO NBswere collected with varying sample orientation͑the NBs are parallel to the incident polarization at=0͒,in the co-͑parallel incident and scattered analyzed polarizations͒and cross-polarized͑perpendicular incident and scattered ana-lyzed polarizations͒configurations.For the ZnO NBs,addi-tional series of PR spectra were collected where the incidenta͒Electronic mail:elisa.riedo@.APPLIED PHYSICS LETTERS95,051904͑2009͒0003-6951/2009/95͑5͒/051904/3/$25.00©2009American Institute of Physics95,051904-1polarization is rotated and the ZnO NB axis remained paral-lel or perpendicular to the analyzed scattered polarization ͑see supplementary information 25͒.The exposure time for each Raman spectrum was 10s for the bulk crystals and 20min for NBs.After each rotation of the NBs,the laser spot is recentered on the same NB and at the same location along the NB.Prior to the PR characterization of ZnO NBs,PR data were collected on the c -plane and m -plane of bulk ZnO crystals ͓Fig.2͑a ͔͒.In ambient conditions,ZnO has a wurtzite structure ͑space group C 6v 4͒.Group theory predicts four Raman-active modes:one A 1,one E 1,and two E 2modes.11,20,23The polar A 1and E 1modes split into transverse ͑TO ͒and longitudinal optical branches.On the c -plane ͑0001͒-oriented sample,only the E 2modes,at 99͑not shown ͒and 438cm −1,are observed,and their intensity is independent of the sample orientation ͓Fig.2͑a ͔͒.On them -plane ͑101¯0͒-oriented sample,the E 2,E 1͑TO ͒,and A 1͑TO ͒modes are observed at 99,438,409,and 377cm −1,respectively ͓Fig.2͑a ͔͒,and their intensity depends on .Peaks at 203and 331cm −1in both crystals are assigned to multiple phonon scattering processes.The intensity,center,and width of the peaks at 438,409,and 377cm −1were obtained by fitting the experimental PR spectra with Lorent-zian lines ͑see supplementary information 25͒.The successful fits of the angular dependencies by using the group theory and crystal symmetry 23indicate that PR data can be used to characterize the growth direction of ZnO NBs.It is noted that the ZnO NBs studied here have dimensions over 300nm,so the determination of the growth direction is not ex-pected to be affected by any enhancement of the polarized Raman signal due to their high aspect ratio.24AFM images and PR data of three individual ZnO NBs are presented in Figs.2͑b ͒–2͑d ͒.These NBs,labeled NB1,NB2,and NB3,have different dimensions and properties assummarized in Table I .A comparison of the PR spectra in Figs.2͑a ͒–2͑d ͒reveals differences between bulk ZnO and individual NBs.First,the glass cover slip gives rise to a weak broadband centered around 350cm −1on the Raman spectra of the NBs ͓see bottom of Fig.2͑d ͔͒.Second,there are additional Raman bands around 224and 275cm −1for NB2and NB3.These bands are observed in doped or ion-implanted ZnO crystals.11,20Their appearance is explained by the disorder in the crystal lattice due to randomly distrib-uted point defects,such as oxygen vacancies or impurities.The defect peaks area increases in the order NB1ϽNB2ϽNB3.Since the laser spot diameter is larger than the width of all three NBs,but smaller than their length,L ,the NB volume probed by the laser beam is approximated by the product of the width,w ,with the thickness,t .ThevolumeFIG.1.͑Color online ͒Schematic of the experimental setup,showing the path of the laser beam.The ZnO NBs are deposited on a glass slide,which is placed inside a rotating Petridish.FIG.2.͑Color online ͒͑a ͒PR spectra from the c and m planes of a ZnO crystal,shown in blue and green,respectively.The wurtzite structure ͑Zn atoms are brown,O atoms red ͒is also shown,where a ء,b ء,and c ءare the reciprocal lattice vectors.͓͑b ͒–͑d ͔͒AFM images ͑3ϫ3m ͒of three NBs labeled NB1,NB2,and NB3and corresponding PR spectra.In ͑d ͒a PR spectrum of the glass substrate is shown at the bottom.All the PR spectra in ͑a ͒–͑d ͒are collected in the copolarized configuration for =0and 90°.The spectra are offset vertically for clarity.TABLE I.Summary of the PR-AFM results for NB1,NB2,and NB3.w ͑nm ͒t ͑nm ͒w /t L ͑m ͒͑°͒E ͑GPa ͒Defects NB11080875 1.24028Ϯ1562Ϯ5No NB21150710 1.64972Ϯ1538Ϯ5Yes NB315104553.35966Ϯ1517Ϯ5Yesprobed decreases in the order NB1͑wϫt=9.45ϫ103nm2͒ϾNB2͑8.17ϫ103nm2͒ϾNB3͑6.87ϫ103nm2͒.This indi-cates that the density of point defects is highest in NB3,and increases with the width to thickness ratio,w/t,in the order NB1ϽNB2ϽNB3.The PR intensity variations of the438cm−1peak as a function ofin the various polarization configurations were fitted by using group theory and crystal symmetry to deter-mine the anglebetween the NB long axis͑or growth di-rection͒and the c-axis͓͑0001͔axis͒of the constituting ZnO wurtzite structure21,23͑see supplementary information25͒.In-tensity variations of the377cm−1peak,when present,are used to confirm the obtained values of.The results are shown in Table I and indicate that growth directions other than the most commonly observed c-axis are possible,par-ticularly when point defects are present.Finally,the elastic properties of NB1,NB2,and NB3are characterized by AFM using the modulated nanoindentation method.6,7,22In a previous study,the elastic modulus of ZnO NBs was found to decrease with increasing w/t and this w/t dependence was attributed to the presence of planar defects in NBs with high w/t.6,7By using PR-AFM,we can study the role of randomly distributed defects,morphology,and growth direction on the elastic properties in the same indi-vidual ZnO NB.The measured elastic moduli,E,are62GPa for NB1,38GPa for NB2,and17GPa for NB3.These PR-AFM results confirm the w/t dependence of the elastic modulus in ZnO NBs,but more importantly they reveal that the elastic modulus of ZnO NBs can significantly decrease, down by almost one order of magnitude,with the presence of randomly distributed point defects.In summary,a new approach combining polarized Raman spectroscopy and AFM reveals the strong influence of point defects on the elastic properties of ZnO NBs and their morphology.Based on a scanning probe,PR-AFM pro-vides an in situ and nondestructive tool for the complete characterization of the crystal structure and the physical properties of individual nanostructures that can be in as-fabricated nanodevices.The authors acknowledge thefinancial support from the Department of Energy under Grant No.DE-FG02-06ER46293.1Y.Qin,X.Wang,and Z.L.Wang,Nature͑London͒451,809͑2008͒.2X.Wang,J.Song,J.Liu,and Z.L.Wang,Science316,102͑2007͒.3D.J.Müller and Y.F.Dufrêne,Nat.Nanotechnol.3,261͑2008͒.4H.Peng,C.Xie,D.T.Schoen,and Y.Cui,Nano Lett.8,1511͑2008͒. 5U.Diebold,Surf.Sci.Rep.48,53͑2003͒.6M.Lucas,W.J.Mai,R.Yang,Z.L.Wang,and E.Riedo,Nano Lett.7, 1314͑2007͒.7M.Lucas,W.J.Mai,R.Yang,Z.L.Wang,and E.Riedo,Philos.Mag.87, 2135͑2007͒.8M.D.Uchic,D.M.Dimiduk,J.N.Florando,and W.D.Nix,Science305, 986͑2004͒.9D.-S.Yang,o,and A.H.Zewail,Science321,1660͑2008͒.10M.Dienwiebel,G.S.Verhoeven,N.Pradeep,J.W.M.Frenken,J.A. Heimberg,and H.W.Zandbergen,Phys.Rev.Lett.92,126101͑2004͒. 11Ü.Özgür,Ya.I.Alivov,C.Liu,A.Teke,M.A.Reshchikov,S.Doğan,V. Avrutin,S.-J.Cho,and H.Morkoç,J.Appl.Phys.98,041301͑2005͒. 12Z.L.Wang,J.Phys.:Condens.Matter16,R829͑2004͒.13G.R.Li,T.Hu,G.L.Pan,T.Y.Yan,X.P.Gao,and H.Y.Zhu,J.Phys. Chem.C112,11859͑2008͒.14Z.W.Pan,Z.R.Dai,and Z.L.Wang,Science291,1947͑2001͒.15P.Poncharal,Z.L.Wang,D.Ugarte,and W.A.De Heer,Science283, 1513͑1999͒.16A.M.Minor,J.W.Morris,and E.A.Stach,Appl.Phys.Lett.79,1625͑2001͒.17B.Varghese,Y.Zhang,L.Dai,V.B.C.Tan,C.T.Lim,and C.-H.Sow, Nano Lett.8,3226͑2008͒.18M.Lucas and R.J.Young,Phys.Rev.B69,085405͑2004͒.19I.Calizo,A.A.Balandin,W.Bao,F.Miao,and u,Nano Lett.7, 2645͑2007͒.20H.Zhong,J.Wang,X.Chen,Z.Li,W.Xu,and W.Lu,J.Appl.Phys.99, 103905͑2006͒.21T.Livneh,J.Zhang,G.Cheng,and M.Moskovits,Phys.Rev.B74, 035320͑2006͒.22I.Palaci,S.Fedrigo,H.Brune,C.Klinke,M.Chen,and E.Riedo,Phys. Rev.Lett.94,175502͑2005͒.23C.A.Arguello,D.L.Rousseau,and S.P.S.Porto,Phys.Rev.181,1351͑1969͒.24H.M.Fan,X.F.Fan,Z.H.Ni,Z.X.Shen,Y.P.Feng,and B.S.Zou, J.Phys.Chem.C112,1865͑2008͒.25See EPAPS supplementary material at /10.1063/ 1.3177065for more information on the PR spectra.Growth direction and morphology of ZnO nanobelts revealed by combining in situ atomic forcemicroscopy and polarized Raman spectroscopyMarcel Lucas,1,*Zhong Lin Wang,2and Elisa Riedo1,†1School of Physics,Georgia Institute of Technology,Atlanta,Georgia30332-0430,USA 2School of Materials Science and Engineering,Georgia Institute of Technology,Atlanta,Georgia30332-0245,USA ͑Received26June2009;revised manuscript received28September2009;published14January2010͒Control over the morphology and structure of nanostructures is essential for their technological applications,since their physical properties depend significantly on their dimensions,crystallographic structure,and growthdirection.A combination of polarized Raman͑PR͒spectroscopy and atomic force microscopy͑AFM͒is usedto characterize the growth direction,the presence of point defects and the morphology of individual ZnOnanobelts.PR-AFM data reveal two growth modes during the synthesis of ZnO nanobelts by physical vapordeposition.In the thermodynamics-controlled growth mode,nanobelts grow along a direction close to͓0001͔,their morphology is growth-direction dependent,and they exhibit no point defects.In the kinetics-controlledgrowth mode,nanobelts grow along directions almost perpendicular to͓0001͔,and they exhibit point defects.DOI:10.1103/PhysRevB.81.045415PACS number͑s͒:61.46.Ϫw,61.72.Dd,78.30.Ly,81.10.ϪhI.INTRODUCTIONControl over the morphology and structure of nanostruc-tured materials is essential for the development of future de-vices,since their physical properties depend on their dimen-sions and crystallographic structure.1–15In particular,the growth direction of single-crystal nanostructures affects their piezoelectric,1,2transport,3catalytic,4mechanical,5–9 optoelectronic,10and tribological properties.11ZnO nano-structures with various morphologies͑wires,belts,helices, rings,tubes,…͒have been successfully synthesized in solu-tion and in the vapor phase,14–19but little is known about their growth mechanism,particularly in a process not involv-ing catalyst particles.17Understanding the growth mecha-nism and determining the decisive parameters directing the growth of nanostructures and tailoring their morphology is essential for the use of ZnO nanobelts as power generators or electromechanical systems.1,2,5,6From a theoretical stand-point,a shape-dependent thermodynamic model showed that the morphology of ZnO nanobelts grown in equilibrium con-ditions depends on their growth direction,but the role of defects was not considered.20Experimentally,it was shown that the growth direction of ZnO nanostructures can be di-rected by the synthesis conditions,such as the oxygen con-tent in the furnace.19A previous study combining scanning electron microscopy and x-ray diffraction suggested a growth-direction-dependent morphology.20An atomic force microscopy͑AFM͒combined with transmission electron mi-croscopy also suggested that the morphology of ZnO nano-belts is correlated with their growth direction and highlighted the potentially important role of planar defects.5 Growth modes out of thermodynamic equilibrium and the role of point defects5,17are particularly challenging to inves-tigate experimentally,21due to the lack of appropriate experi-mental techniques.Electron microscopy can determine the crystallographic structure and morphology of conductive nanomaterials,3,17,22–24but is not suitable for the character-ization of point defects,especially when their distribution is disordered.17,22–24Raman spectroscopy has been used for the characterization of the structure of carbon nanotubes,25,26the identification of impurities,27and the determination of the crystal structure28and growth direction of individual single-crystal nanowires.29Recently,polarized Raman͑PR͒spec-troscopy has been coupled to AFM to study in situ the inter-play between point defects and mechanical properties of ZnO nanobelts.30Here,PR-AFM is used to study the growth mechanism and the relationship between growth direction,point defects, and morphology of individual ZnO nanobelts.The morphol-ogy of an individual ZnO nanobelt is determined by AFM, while the growth direction and randomly distributed defects in the same individual nanobelt are characterized by polar-ized Raman spectroscopy.II.EXPERIMENTALThe ZnO nanobelts were prepared by physical vapor deposition͑PVD͒without catalysts following the method de-scribed in Ref.17.The ZnO nanobelts were deposited on a glass cover slip,which was glued to a Petri dish.The rotat-able Petri dish was then placed on a sample plate under an Agilent PicoPlus AFM equipped with a scanner of100ϫ100m2range.Topography images of the ZnO nanobelts were collected in the contact mode with CONTR probes͑NanoWorld AG,Neuchâtel,Switzerland͒of normal spring constant0.21N/m at a set point of2nN.The AFM was placed on top of an Olympus IX71inverted optical micro-scope that is coupled to a Horiba Jobin-Yvon LabRam HR800.PR spectra were recorded in the backscattering ge-ometry using a40ϫ͑0.6NA͒objective focusing a laser beam of wavelength785nm on the sample to a power den-sity of about105W/cm2and a spot size of about2m. The incident polarization direction can be rotated continu-ously with a half-wave plate.The scattered light was ana-lyzed along one of two perpendicular directions by a polar-izer at the entrance of the spectrometer.The intensity,center, and width of the Raman bands were obtained byfitting the spectra with Lorentzian lines.The polarization dependence of the quantum efficiency of the Raman spectrometer was tested by measuring the intensity variations of the377,409,PHYSICAL REVIEW B81,045415͑2010͒1098-0121/2010/81͑4͒/045415͑5͒©2010The American Physical Society045415-1and 438cm −1bands from two bulk ZnO crystals ͑c -plane and m -plane ZnO crystals,MTI Corporation ͒.The PR data from bulk crystals were successfully fitted using group theory and crystal symmetry 28without further calibration of the spectrometer or data correction.III.RESULTS AND DISCUSSIONAFM images and PR data of two individual ZnO nano-belts are presented in Fig.1.These nanobelts have different cross-sections,1320ϫ1080nm 2͑nanobelt labeled NB A͒FIG.1.͑Color online ͒PR-AFM results on individual ZnO nanobelts.͑a ͒AFM topography image,͑b ͒typical PR spectra for different sample orientations and polarization configurations,and ͑c ͒–͑f ͒polar plots of the angular dependence of the Raman intensities for the nanobelt NB A.͑g ͒AFM topography image,͑h ͒typical PR spectra,and ͑i ͒–͑l ͒polar plots of the angular dependence of the Raman intensities for the nanobelt NB B.The Raman spectra in ͑h ͒exhibit peaks centered at 224and 275cm −1͑triangles ͒that are characteristic of defects in the nanobelt NB B.The Raman spectra are offset vertically for clarity.In ͑c ͒,͑d ͒,͑i ͒,and ͑j ͒,the nanobelt axis is rotated in a fixed polarization configuration ͑solid squares:copolarized;open squares:cross polarized ͒and is parallel to the incident polarization for =0°.In ͑e ͒,͑f ͒,͑k ͒,and ͑l ͒,the incident polarization is rotated,while the analyzed polarization and the nanobelt axis are fixed.In ͑e ͒,͑f ͒,͑k ͒,and ͑l ͒,at the angle 0°,the nanobelt is perpendicular to the incident polarization and the incident and analyzed polarizations are parallel ͑solid squares ͒or perpendicular ͑open squares ͒.Typical Raman spectra of the glass cover slip in the copolarized and cross-polarized configurations are shown as a reference in ͑b ͒and ͑h ͒,respectively.LUCAS,WANG,AND RIEDO PHYSICAL REVIEW B 81,045415͑2010͒045415-2。
多层多道焊机器人离线编程路径规划
２０２１年８月第４９卷第１５期机床与液压ＭＡＣＨＩＮＥＴＯＯＬ＆ＨＹＤＲＡＵＬＩＣＳＡｕｇ ２０２１Ｖｏｌ ４９Ｎｏ １５ＤＯＩ：１０．３９６９／ｊ ｉｓｓｎ １００１－３８８１ ２０２１ １５ ０１３本文引用格式：廖伟东，李俊渊，黄昕，等．多层多道焊机器人离线编程路径规划［Ｊ］．机床与液压，２０２１，４９（１５）：６７－７０．ＬＩＡＯＷｅｉｄｏｎｇ，ＬＩＪｕｎｙｕａｎ，ＨＵＡＮＧＸｉｎ，ｅｔａｌ．Ｒｏｂｏｔｉｃｏｆｆ⁃ｌｉｎｅｐｒｏｇｒａｍｍｉｎｇｐａｔｈｐｌａｎｎｉｎｇｆｏｒｍｕｌｔｉ⁃ｐａｔｈ／ｍｕｌｔｉ⁃ｌａｙｅｒｗｅｌｄｉｎｇ［Ｊ］．ＭａｃｈｉｎｅＴｏｏｌ＆Ｈｙｄｒａｕｌｉｃｓ，２０２１，４９（１５）：６７－７０．收稿日期：２０２０－０７－３０基金项目：广东省科技计划项目（２０１８Ｂ０３０３２３０２７）作者简介：廖伟东（１９９１ ），男，硕士研究生，研究方向为机器人仿真技术㊂Ｅ－ｍａｉｌ：１６９７６３３５６０＠ｑｑ ｃｏｍ㊂多层多道焊机器人离线编程路径规划廖伟东，李俊渊，黄昕，田吕（广州机械科学研究院有限公司中央研究所，广东广州５１０７００）摘要：面向机器人多层多道焊接轨迹人工示教编程效率低㊁难度大的问题，为了提高焊接质量与效率，基于ＯｐｅｎＣＡＳ⁃ＣＡＤＥ建模引擎，开发多层多道焊机器人离线编程软件，从工件模型中提取焊缝信息，取代在线示教操作㊂提出一种用户自定义焊层焊道数目的路径规划算法，确定每个焊道的空间位置㊁焊接速度，同时规划焊枪末端姿态，避免与工件发生碰撞㊂通过机器人加工仿真运动，表明各个焊道位置准确㊁姿态平顺，验证了路径规划的正确性与可行性，并在实际焊接试验中获得良好的焊接效果㊂关键词：多层多道焊；ＯｐｅｎＣＡＳＣＡＤＥ建模引擎；离线编程；轨迹规划中图分类号：ＴＰ２４２ ２ＲｏｂｏｔｉｃＯｆｆ－ＬｉｎｅＰｒｏｇｒａｍｍｉｎｇＰａｔｈＰｌａｎｎｉｎｇｆｏｒＭｕｌｔｉ－ｐａｔｈ／Ｍｕｌｔｉ－ｌａｙｅｒＷｅｌｄｉｎｇＬＩＡＯＷｅｉｄｏｎｇ，ＬＩＪｕｎｙｕａｎ，ＨＵＡＮＧＸｉｎ，ＴＩＡＮＬｖ（ＣｅｎｔｒａｌＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，ＧｕａｎｇｚｈｏｕＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅＣｏ．，Ｌｔｄ．，ＧｕａｎｇｚｈｏｕＧｕａｎｇｄｏｎｇ５１０７００，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ｉｎｏｒｄｅｒｔｏｉｍｐｒｏｖｅｔｈｅｗｅｌｄｉｎｇｑｕａｌｉｔｙａｎｄｅｆｆｉｃｉｅｎｃｙ，ｉｔｉｓｎｅｃｅｓｓａｒｙｔｏｓｏｌｖｅｔｈｅｐｒｏｂｌｅｍｏｆｌｏｗｅｆｆｉｃｉｅｎｃｙａｎｄｈｉｇｈｄｉｆｆｉｃｕｌｔｙｉｎｍａｎｕａｌｐｒｏｇｒａｍｍｉｎｇｏｆｍｕｌｔｉ⁃ｐａｔｈ／ｍｕｌｔｉ⁃ｌａｙｅｒｗｅｌｄｉｎｇ．Ａｒｏｂｏｔｉｃｏｆｆ⁃ｌｉｎｅｐｒｏｇｒａｍｍｉｎｇｓｏｆｔｗａｒｅｗａｓｄｅｖｅｌｏｐｅｄｆｏｒｍｕｌｔｉ⁃ｐａｓｓｗｅｌｄｉｎｇｒｏｂｏｔｂａｓｅｄｏｎＯｐｅｎＣＡＳＣＡＤＥｍｏｄｅｌｉｎｇｅｎｇｉｎｅ．Ｔｈｅｗｅｌｄｉｎｇｓｅａｍｉｎｆｏｒｍａｔｉｏｎｗａｓｅｘｔｒａｃｔｅｄｆｒｏｍｔｈｅｗｏｒｋｐｉｅｃｅｍｏｄｅｌｉｎｓｔｅａｄｏｆｔｈｅｏｎｌｉｎｅｔｅａｃｈｉｎｇｏｐｅｒａｔｉｏｎ．Ａｐａｔｈｐｌａｎｎｉｎｇａｌｇｏｒｉｔｈｍｆｏｒｕｓｅｒ⁃ｄｅｆｉｎｅｄｗｅｌｄｂｅａｄｎｕｍｂｅｒｗａｓｐｒｏｐｏｓｅｄｔｏｄｅｔｅｒｍｉｎｅｔｈｅｓｐａｃｅｐｏｓｉｔｉｏｎａｎｄｔｈｅｗｅｌｄｉｎｇｓｐｅｅｄｏｆｅａｃｈｂｅａｄ，ｔｈｅｅｎｄａｔｔｉｔｕｄｅｏｆｗｅｌｄｉｎｇｔｏｒｃｈｗａｓｐｌａｎｅｄｔｏａｖｏｉｄｃｏｌｌｉｓｉｏｎｗｉｔｈｔｈｅｗｏｒｋｐｉｅｃｅ．Ｔｈｒｏｕｇｈｔｈｅｒｏｂｏｔｍａｃｈｉｎｉｎｇｓｉｍｕｌａｔｉｏｎｍｏｖｅｍｅｎｔ，ｉｔｉｓｓｈｏｗｎｔｈａｔｔｈｅｐｏｓｉｔｉｏｎｏｆｅａｃｈｗｅｌｄｂｅａｄｉｓａｃｃｕｒａｔｅａｎｄｔｈｅａｔｔｉｔｕｄｅｉｓｓｍｏｏｔｈ，ｗｈｉｃｈｖｅｒｉｆｉｅｓｔｈｅｃｏｒｒｅｃｔｎｅｓｓａｎｄｆｅａｓｉｂｉｌｉｔｙｏｆｔｈｅｐａｔｈｐｌａｎｎｉｎｇ，ａｎｄｇｏｏｄｗｅｌｄｉｎｇｅｆｆｅｃｔｉｓｏｂｔａｉｎｅｄｉｎｔｈｅａｃｔｕａｌｗｅｌｄｉｎｇｔｅｓｔ．Ｋｅｙｗｏｒｄｓ：Ｍｕｌｔｉ⁃ｐａｔｈ／ｍｕｌｔｉ⁃ｌａｙｅｒｗｅｌｄｉｎｇ；ＯｐｅｎＣＡＳＣＡＤＥｍｏｄｅｌｉｎｇｅｎｇｉｎｅ；Ｏｆｆ⁃ｌｉｎｅｐｒｏｇｒａｍｍｉｎｇ；Ｐａｔｈｐｌａｎｎｉｎｇ０㊀前言在高压容器㊁汽车制造㊁工程机械领域，多层多道焊接是中厚板结构件加工中不可或缺的工艺，由于其结构大㊁坡口宽等特点，对其进行焊接加工具有一定难度［１］㊂随着先进制造技术与机器人技术的不断发展，工业机器人在焊接领域得到广泛的应用，由于机器人多层多道焊接路径人工在线示教编程效率低㊁难度大，难以满足机器人的工作需求，所以多层多道焊机器人离线编程仿真系统应运而生㊂针对多层多道焊接以及机器人离线编程，已有众多高校㊁研究机构进行了研究，天津工业大学成利强等［２］通过对示教轨迹点偏移设置，进行多层多道焊接路径规划以减少示教次数㊂仲德平等［３］基于ＲｏｂｏｔＳｔｕｄｉｏ离线编程软件，针对船舶曲面厚板的多层多道焊规划焊接路径，解决了焊枪与工件之间的碰撞问题㊂文献［４－６］中提出等面积型㊁等高型㊁自定义型３种对焊缝坡口截面填充规划方法，将末尾焊道近似为梯形，其余焊道近似为平行四边形，每层焊道数等于它的层数［７］㊂该规划方法针对不一样坡口角度的焊缝不具备适应性㊂为了适应不同坡口角度的焊缝类型，减少焊接参数设置，提出一种用户自定义焊层内部焊道数的等面积多层多道焊路径规划方法，基于ＯｐｅｎＣＡＳＣＡＤＥ建模引擎开发机器人离线编程软件，从焊接工件模型提取焊缝信息，根据用户定义的焊层㊁焊道数，进行多层多道焊的路径规划㊂１㊀多层多道焊路径规划１ １㊀等效焊道截面由于焊道截面形状不规则难以进行轨迹计算，必须将焊道截面简化为规则几何图形，才能进行精确的路径规划，根据文献［７］对焊道截面进行简化，每层除末尾焊道外均等效为平行四边形，末尾焊道则近似等效为梯形，具体效果如图１所示㊂图１㊀焊道截面示意１ ２㊀等面积坡口焊道位置规划等面积坡口截面规划，其中每个焊道的截面积都相等，对于Ｖ形焊缝第一层焊道数固定为１，其余焊层的焊道数大于１，具体焊道数目由用户自定义设置㊂已知Ｖ形焊缝坡口的高度为Ｈ，坡口角度为θ，其焊道规划如图２所示㊂图２㊀Ｖ形焊缝示意已知Ｖ形坡口的高度为Ｈ，坡口角度为θ，由此可得该Ｖ形焊缝坡口面积Ｓ：Ｓ＝Ｈ２㊃ｔａｎθ２（１）设焊缝需要填充的层数为ｎ，第ｉ层的焊道数为Ｔｉ，则该坡口的总焊道数ａ：ａ＝ðｎｉ＝１Ｔｉ（２）联立式（１）（２）得到单个焊道截面积Ｓｎ：Ｓｎ＝Ｈ２㊃ｔａｎθ２æèçöø÷ａ（３）如图２所示，已知前ｉ－１层的总焊道数为ａｉ－１，则第ｉ－１层顶部高度Ｈｉ－１以及宽度Ｗｉ－１：Ｈｉ－１＝Ｈａｉ－１㊃ＳｎＳ（４）Ｗｉ－１＝２ｔａｎθ２㊃Ｈｉ－１（５）根据式（４）（５），同理可求得第ｉ层顶部高度Ｈｉ，以及第ｉ层顶部宽度Ｗｉ，设第ｉ层内焊道数为ｍ，则单个焊道ｙ方向增量Δｙ：Ｗｉ－１＋Ｗｉ２ｍ㊀（Ｗｉ－Ｗｉ－１）㊃（Ｈｉ－Ｈｉ－１）／２ɤＳｎＷｉ－１ｍ－１㊀㊀（Ｗｉ－Ｗｉ－１）㊃（Ｈｉ－Ｈｉ－１）／２＞Ｓｎìîíïïïï（６）第ｉ层的起始焊道ｙ坐标参数ｙｉ０：ｙｉ０＝ｙ０－Ｈｉ－１㊃ｔａｎθ２（７）则第ｉ层ｊ道焊道ｙ坐标参数ｙｉｊ为ｙｉｊ＝ｙｉ０＋Δｙ㊃ｊ㊀㊀ｊɪ［０，ｍ）（８）综上所述第ｉ层ｊ焊道的位置坐标参数ｘｉｊ＝ｘ０ｙｉｊ＝ｙｉ０＋Δｙ㊃ｊｚｉｊ＝ｚ０＋Ｈｉ－１ìîíïïï（９）１ ３㊀焊接速度规划由第１ ２节通过对焊缝坡口焊道等面积规划，确定了每条焊道的位置参数㊂现在需要根据单道焊道面积Ｓｎ以及设置的焊接参数计算焊接速度ｖｗ㊂根据输入的焊接电流Ｉ查询焊机专家数据库确定其对应的送丝速度ｖｆ㊁焊丝直径Ｄ以及单道焊缝的填充熔敷率η，求得焊接速度ｖｗ：ｖｗ＝πＤ２ｖｆ４Ｓｎ（１０）１ ４㊀焊枪姿态规划由第１ ２㊁１ ３节确定了各个焊道的具体位置以及对应的焊接速度㊂为了获得良好的焊接效果，同时避免焊枪与工件之间的干涉，需计算每条焊道对应的焊枪姿态㊂由文献［８］可知焊枪沿坡口对称中心线处于最佳施焊位置，获取良好的焊接效果㊂焊枪姿态如图３所示㊂图３㊀焊枪姿态示意由第１ ２节求得焊道所处位置Ｐ（ｘｉ，ｙｉ，ｚｉ），其对应的虚拟坡口形状为әＡＰＢ，则焊枪姿态ＰＫ为øＡＰＢ的角平分线，øＡＰＢ为ω，øＰＡＢ为δ，记ＡＰ长度为ｂ，ＰＢ长度为ｃ：ｂ＝（Ｈ－ｚｉ）２＋（Ｈ㊃ｔａｎθ／２＋ｙｉ）２（１１）ｃ＝（Ｈ－ｚｉ）２＋（Ｈ㊃ｔａｎθ／２－ｙｉ）２（１２）根据余弦定理求得ω以及δ：ω＝ａｒｃｃｏｓｂ２＋ｃ２－（２Ｈ㊃ｔａｎθ／２）２２ｂｃæèçöø÷（１３）焊枪与坡口截面坐标系ｚ轴正方向夹角β：β＝π２－δ＋ω２æèçöø÷（１４）焊枪末端ｘ姿态与焊缝截面坐标系Ｏ的ｘ轴方向一致，绕ｘ轴旋转角度β获得焊道点Ｐ位姿相对于坐㊃８６㊃机床与液压第４９卷标系Ｏ的齐次转换矩阵ＴＰＯ：ＴＰＯ＝１００ｘｉ０ｃｏｓβ－ｓｉｎβｙｉ０ｓｉｎβｃｏｓβｚｉ０００１éëêêêêêùûúúúúú（１５）已知坡口截面坐标系Ｏ相对于机器人基座标系Ｂ的齐次转换矩阵为ＴＯＢ，则第ｉ层ｊ焊道点Ｐ相对于机器人基座标系Ｂ的齐次矩阵ＴＰＢ：ＴＰＢ＝ＴＯＢ㊃ＴＰＯ（１６）２㊀离线编程与仿真２ １㊀构建离线软件平台基于法国ＭａｔｒａＤａｔａｖｉｓｉｏｎ公司开源的ＣＡＤ／ＣＡＭ／ＣＡＥ几何模型内核Ｃ＋＋库ＯＣＣ（ＯｐｅｎＣＡＳ⁃ＣＡＤＥ），结合ＱＴ图形用户界面开发库，搭建机器人离线编程软件框架㊂ＯＣＣ是一个功能强大的三维建模引擎，提供拓扑模型中点㊁线㊁面㊁体和复杂形体的显示和交互操作，可实现纹理㊁光照㊁渲染等图形显示操作，以及模型放大㊁缩小㊁旋转等动态变换操作㊂本文作者将机器人模型轻量化为ＳＴＬ格式模型，设置其模型坐标系与机器人Ｄ－Ｈ连杆坐标系重合，调用ＯＣＣ库ＡＰＩ接口ＳｔｌＡＰＩ＿Ｒｅａｄｅｒ（）将ＳＴＬ文件转化为ＯＣＣ可识别的拓扑类型ＴｏｐｏＤＳ＿Ｓｈａｐｅ，然后调用交互类ＡＩＳ＿ＩｎｔｅｒａｃｔｉｖｅＣｏｎｔｅｘｔ中的Ｄｉｓｐｌａｙ（）函数在界面中显示机器人模型，如图４所示㊂图４㊀离线编程软件２ ２㊀多层多道焊工艺规划通过ＱＴ的ＧＵＩ接口搭建多层多道焊工艺设置界面如图５所示㊂调用ＳＴＥＰＣｏｎｔｒｏｌ＿Ｒｅａｄｅｒ类接口，实现在离线软件中导入工件ＳＴＥＰ格式三维模型，通过ＡｃｔｉｖａｔｅＳ⁃ｔａｎｄａｒｄＭｏｄｅ（）函数设置过滤器，分别从工件模型上选取焊接母线以及焊缝两侧辅助面㊂获得焊缝坡口几何参数信息，调用库函数ＧＣＰｎｔｓ＿ＵｎｉｆｏｒｍＡｂｓｃｉｓｓａ（）将焊缝母线离散，获得焊缝各个截面的原点位置；调用Ｎｏｒｍａｌ（）获取两个焊缝侧面的法矢量，以确定焊缝夹角θ；两焊缝侧面的法矢量的角平分线方向，作为焊缝姿态的ｚ轴方向，焊接母线的切向作为焊缝姿态的ｘ轴方向；从工艺设置界面输入焊丝直径㊁焊接电流㊁焊层数㊁焊道数㊁熔敷率等焊接参数，根据第１ ２节规划得各个焊道的位置㊁姿态信息㊂分别对Ｖ形㊁相贯线焊缝进行焊接路径规，如图６所示㊂图５㊀工艺界面图６㊀多层多道焊接路径２ ３㊀焊接仿真为了保证多层多道焊轨迹规划的可行性，在离线软件中对Ｖ形焊缝多层多道焊轨迹进行运动仿真如图７所示㊂仿真结果表明：焊接路径姿态平顺，能规避焊枪与工件之间的碰撞，验证了多层多道焊轨迹规划的正确性㊂图７㊀机器人焊接仿真３㊀焊接试验如图８所示，采用启帆ＳＲＤ⁃１４００型六关节机器人，焊机型号为麦格米特Ａｒｔｓｅｎ５００，焊丝直径为１ ２ｍｍ，设置总焊层数为４层，各焊层内部焊道数㊁焊接电流以及规划所得的焊接速度参数如表１所示㊂㊃９６㊃第１５期廖伟东等：多层多道焊机器人离线编程路径规划㊀㊀㊀图８㊀机器人焊接试验平台表１㊀焊接参数焊层焊道数电流／Ａ速度／（ｍｍ㊃ｓ－１）１１２１５７．１２２３２６０８．３６３５２６０８．３６４６２９０８．９７㊀㊀在离线软件中对Ｖ形焊缝坡口进行多层多道焊接轨迹规划，将规划所得的焊接路径可执行程序导出到机器人控制器实现机器人焊接工作㊂如图９所示：焊道层叠均匀㊁焊缝填充密致，焊道间没有出现咬边㊁气孔等焊接缺陷，验证了多层多道焊离线编程规划轨迹的正确性与可行性，与人工示教编程相比具有更好的焊接质量与更高的焊接效率㊂图９㊀Ｖ形坡口焊接效果４㊀结论针对多层多道焊接人工示教效率低㊁焊接效果差的不足，基于ＯｐｅｎＣＡＳＣＡＤＥ建模引擎搭建了多层多道焊离线编程软件，从工件模型中提取焊缝信息，无需人工在线示教操作，大大提高焊接加工效率㊂提出一种自定义焊层㊁焊道数的等面积焊道规划算法，根据焊丝直径㊁焊接电流等焊接参数，确定各个焊道位置与焊接速度，规划了焊枪末端姿态，避免与工件发生干涉㊂通过机器人仿真加工与实际焊接试验验证了该规划算法的正确性㊂试验结果表明：焊道堆叠均匀㊁焊缝填充密致，获得良好的焊接效果，为后续工业机器人在多层多道焊接领域的批量应用提供参考㊂参考文献：［１］李天旭，王天琪，杨华庆，等．厚板Ｖ形坡口机器人填充焊接工艺研究［Ｊ］．焊接，２０１７（９）：１３－１７．ＬＩＴＸ，ＷＡＮＧＴＱ，ＹＡＮＧＨＱ，ｅｔａｌ．ＲｅｓｅａｒｃｈｏｎｆｉｌｌｉｎｇｗｅｌｄｉｎｇｔｅｃｈｎｏｌｏｇｙｏｆＶ－ｓｈａｐｅｄｇｒｏｏｖｅｒｏｂｏｔｆｏｒｔｈｉｃｋｐｌａｔｅ［Ｊ］．Ｗｅｌｄｉｎｇ＆Ｊｏｉｎｉｎｇ，２０１７（９）：１３－１７．［２］成利强，王天琪，侯仰强，等．中厚板Ｖ形坡口多层多道焊机器人焊接技术研究［Ｊ］．焊接，２０１８（２）：１０－１３．ＣＨＥＮＧＬＱ，ＷＡＮＧＴＱ，ＨＯＵＹＱ，ｅｔａｌ．ＲｏｂｏｔｗｅｌｄｉｎｇｔｅｃｈｎｏｌｏｇｙｏｆＶｇｒｏｏｖｅｆｏｒｈｅａｖｙｐｌａｔｅｂａｓｅｄｏｎｍｕｌｔｉｌａｙｅｒａｎｄｍｕｌｔｉｐａｓｓｗｅｌｄｉｎｇ［Ｊ］．Ｗｅｌｄｉｎｇ＆Ｊｏｉｎｉｎｇ，２０１８（２）：１０－１３．［３］仲德平，徐洪泽，金晶波，等．基于ＲｏｂｏｔＳｔｕｄｉｏ的机器人曲面厚板焊接离线编程［Ｊ］．焊接技术，２０１８，４７（１）：４５－４９．［４］袁海龙，刘建春，易际明，等．中厚板复杂焊缝机器人自动跟踪系统［Ｊ］．电焊机，２０１５，４５（７）：３５－３９．ＹＵＡＮＨＬ，ＬＩＵＪＣ，ＹＩＪＭ，ｅｔａｌ．Ｒｏｂｏｔａｕｔｏｍａｔｉｃｔｒａｃｋ⁃ｉｎｇｓｙｓｔｅｍｏｆｃｏｍｐｌｅｘｗｅｌｄｆｏｒｍｅｄｉｕｍｔｈｉｃｋｐｌａｔｅ［Ｊ］．Ｅ⁃ｌｅｃｔｒｉｃＷｅｌｄｉｎｇＭａｃｈｉｎｅ，２０１５，４５（７）：３５－３９．［５］李湘文．中厚板复杂轨迹焊缝跟踪的关键技术研究［Ｄ］．湘潭：湘潭大学，２０１２．ＬＩＸＷ．Ｔｈｅｋｅｙｔｅｃｈｎｏｌｏｇｙｒｅｓｅａｒｃｈｅｓｏｆｔｈｅｐｌａｔｅｃｏｍｐｌｅｘｓｅａｍｔｒａｃｋｉｎｇ［Ｄ］．Ｘｉａｎｇｔａｎ：ＸｉａｎｇｔａｎＵｎｉｖｅｒｓｉｔｙ，２０１２．［６］张华军，张广军，蔡春波，等．厚板弧焊机器人自定义型焊道编排策略［Ｊ］．焊接学报，２００９，３０（３）：６１－６４．ＺＨＡＮＧＨＪ，ＺＨＡＮＧＧＪ，ＣＡＩＣＢ，ｅｔａｌ．Ｓｅｌｆ⁃ｄｅｆｉｎｉｎｇｐａｔｈｌａｙｏｕｔｓｔｒａｔｅｇｙｆｏｒｔｈｉｃｋｐｌａｔｅａｒｃｗｅｌｄｉｎｇｒｏｂｏｔ［Ｊ］．ＴｒａｎｓａｃｔｉｏｎｓｏｆｔｈｅＣｈｉｎａＷｅｌｄｉｎｇＩｎｓｔｉｔｕｔｉｏｎ，２００９，３０（３）：６１－６４．［７］李慨，戴士杰，孙立新，等．机器人焊接大型接头多道焊填充策略［Ｊ］．焊接学报，２００１，２２（２）：４６－４８．ＬＩＫ，ＤＡＩＳＪ，ＳＵＮＬＸ，ｅｔａｌ．Ｆｉｌｌｉｎｇｓｔｒａｔｅｇｙｏｆｍｕｌｔｉ⁃ｐａｓｓｗｅｌｄｉｎｇ［Ｊ］．ＴｒａｎｓａｃｔｉｏｎｓｏｆｔｈｅＣｈｉｎａＷｅｌｄｉｎｇＩｎｓｔｉｔｕｔｉｏｎ，２００１，２２（２）：４６－４８．［８］张文增，陈强，孙振国，等．机器人焊接几何约束工件焊枪偏角的预规划［Ｊ］．焊接学报，２００４，２５（１）：１７－２０．ＺＨＡＮＧＷＺ，ＣＨＥＮＱ，ＳＵＮＺＧ，ｅｔａｌ．Ｐｒｅｖｉｏｕｓｐｌａｎｎｉｎｇｏｆｔｉｌｔｉｎｇｄｅｇｒｅｅｏｆｗｅｌｄｉｎｇｔｏｒｃｈｆｏｒｒｏｂｏｔｗｅｌｄｉｎｇｕｎｄｅｒｇｅ⁃ｏｍｅｔｒｉｃｒｅｓｔｒｉｃｔｉｏｎｏｆｗｏｒｋｐｉｅｃｅ［Ｊ］．ＴｒａｎｓａｃｔｉｏｎｓｏｆｔｈｅＣｈｉ⁃ｎａＷｅｌｄｉｎｇＩｎｓｔｉｔｕｔｉｏｎ，２００４，２５（１）：１７－２０．（责任编辑：张艳君）㊃０７㊃机床与液压第４９卷。
多约束复杂环境下UAV航迹规划策略自学习方法
第47卷第5期Vol.47No.5计算机工程Computer Engineering2021年5月May2021多约束复杂环境下UAV航迹规划策略自学习方法邱月，郑柏通，蔡超（华中科技大学人工智能与自动化学院多谱信息处理技术国家级重点实验室，武汉430074）摘要：在多约束复杂环境下，多数无人飞行器(UAV)航迹规划方法无法从历史经验中获得先验知识，导致对多变的环境适应性较差。
提出一种基于深度强化学习的航迹规划策略自学习方法，利用飞行约束条件设计UAV的状态及动作模式，从搜索宽度和深度2个方面降低航迹规划搜索规模，基于航迹优化目标设计奖惩函数，利用由卷积神经网络引导的蒙特卡洛树搜索(MCTS)算法学习得到航迹规划策略。
仿真结果表明，该方法自学习得到的航迹规划策略具有泛化能力，相对未迭代训练的网络，该策略仅需17%的NN-MCTS仿真次数就可引导UAV在未知飞行环境中满足约束条件并安全无碰撞地到达目的地。
关键词：深度强化学习；蒙特卡洛树搜索；航迹规划策略；策略自学习；多约束；复杂环境开放科学（资源服务）标志码（OSID）：中文引用格式：邱月，郑柏通，蔡超.多约束复杂环境下UAV航迹规划策略自学习方法［J］.计算机工程，2021，47（5）：44-51.英文引用格式：QIU Yue，ZHENG Baitong，CAI Chao.Self-learning method of UAV track planning strategy in complex environment with multiple constraints［J］.Computer Engineering，2021，47（5）：44-51.Self-Learning Method of UAV Track Planning Strategy inComplex Environment with Multiple ConstraintsQIU Yue，ZHENG Baitong，CAI Chao（National Key Laboratory for Multi-Spectral Information Processing Technologies，School of Artificial Intelligence and Automation，Huazhong University of Science and Technology，Wuhan430074，China）【Abstract】In a complex multi-constrained environment，the Unmanned Aerial Vehicle（UAV）track planning methods generally fail to obtain priori knowledge from historical experience，resulting in poor adaptability to a variable environment.To address the problem，this paper proposes a self-learning method for track planning strategy based on deep reinforcement learning.Based on the UAV flight constraints，the design of the UAV state and action modes is optimized to reduce the width and depth of track planning search.The reward and punishment function is designed based on the track optimization objective.Then，a Monte Carlo Tree Search（MCTS）algorithm guided by a convolutional neural network is used to learn the track planning strategy.Simulation results show that the track planning strategy obtained by the proposed self-learning method has generalization pared with the networks without iterative training，the strategy obtained by this method requires only17%of the number of NN-MCTS simulation times to guide the UAV to reach the destination safely without collision and satisfy the constraints in an unknown environment.【Key words】deep reinforcement learning；Monte Carlo Tree Search（MCTS）；track planning strategy；strategy self-learning；multiple constraints；complex environmentDOI：10.19678/j.issn.1000-3428.00574920概述战场环境中的无人飞行器（Unmanned Aerial Vehicle，UAV）航迹规划任务需要考虑多方面的因素，如无人飞行器的性能、地形、威胁、导航与制导方法等，其目的是在低风险情况下以更低的能耗得到最优航迹。
超短波超视距通信的一种设计方法
超短波超视距通信的一种设计方法A Design Method of VHF/UHF Over Sight Communication赵利(中国电子科技集团公司第十研究所,四川成都610036)Zhao Li(The10th Research Institute of China Electronics Technology Group Corporation,Sichuan Chengdu610036)摘要：超短波通信是无线电通信的一种重要手段，在军事通信中得到了广泛应用和高度重视。
超短波频段电磁信号通常采用视距传播，其通信距离易受地球曲率和遮挡物等影响。
在地-空、地-地以及海面通信时，通信距离非常有限，迫切需要一种远距离通信保障手段，如超短波超视距通信。
文中根据超视距通信的特点，结合实际使用需求，提出了一种基于高接收灵敏度实现超短波超视距通信的设计方法。
在传统超短波接收机基础上进行改进，通过专用电路与通用电路的巧妙结合以及仿真计算分析，以比较小的代价实现了高接收灵敏度，对超短波超视距通信的设计有一定指导意义。
关键词：超视距通信；对流程散射传播；噪声系数；接收灵敏度；通信距离中图分类号：TN802文献标识码：A文章编号：1003-0107(2021)05-0015-06Abstract:VHF/UHF communication is an important way of wireless communication,it has been widely used and highly valued in military communication.The electromagnetic signal in VHF/UHF band usually propagates by line of sight,its communication distance is easily affected by the curvature and shelter of earth.In the ground to air,ground to surface and sea communication,the communication distance is very limited,a long-distance communication support means is urgently needed,like VHF/UHF over sight communication.According to the characteristics of over sight communication and the actual needs,a design method of VHF/UHF over sight communication based on reception sensitivity is presented.Through the improvement on the basis of tradi-tional VHF/UHF receiver,the ingenious combination of special circuit and general circuit,and simulation ca-lculation and analysis,high receiving sensitivity is achieved at low cost.This method can help to design VHF/ UHF over sight communication.Key words:over sight communication;tropospheric scattering propagation;noise figure;reception sensitivity; communication distanceCLC number:TN802Document code:A Article ID：1003-0107(2021)05-0015-060引言军用超短波话音/数据通信主要集中在V/U频段，该频段电磁信号频率低，空间传输损耗小，通信距离远，天线较小，便于移动通信；在对流层传播，不受太阳黑子、太阳磁暴、核爆炸和极光的影响，具有很好的抗毁性[1]，因此，超短波通信在陆、海、空等军事通信中得到广泛应用[2]，是非常重要的通信手段之一。
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CHANNEL ASSIGNMENT STRATEGIES FOR A HIGH ALTITUDE PLATFORM SPOT-BEAM ARCHITECTURE
D. Grace, C. Spillard, J. Thornton, T.C. Tozer 1 1 Communications Research Group, Department of Electronics, University of York, Heslington,
York, YO10 5DD, United Kingdom. Tel: +44 (0) 1904 432396 Fax: +44 (0) 1904 432335 Email: dg@ohm.york.ac.uk
Abstract - Channel assignment strategies for use with a high altitude platform, spot beam architecture are examined. A novel power roll-off approximation is derived to allow terrestrial simulation tools to be used, and simulation performance is compared with a theoretical lower bound derived from the Engset distribution. It is shown that the use of cell overlap considerably enhances the blocking probability performance, in addition to boosting flexibility.
Keywords – high altitude platforms, channel assignment, broadband access, spot beam antennas
I. INTRODUCTION High Altitude Platforms (HAPs) are airships or planes, which will operate in the stratosphere, at 17 - 22km altitude [1-7]. Such platforms will have the ability to be deployed rapidly and have the potential capability to serve a large number of users, using considerably less communications infrastructure than is required by a terrestrial network. The recently licensed bands of spectrum, at 2GHz and in the mm-wave bands, will allow HAPs to deliver a variety of 3G mobile and broadband applications [8,9].
To increase the capacity of a HAP architecture, multiple spot beam antennas will be used, effectively creating a cellular structure on the ground, and this will require efficient channel reuse. In a terrestrial system the main constraint on channel reuse is the reuse distance, i.e. the distance between two base stations sharing the same channel [11]. In the case of a HAP architecture, all of the base stations are co-located on the HAP, with interference in the cells arising from the overlap of the antenna main beams and side lobes. This interference mechanism also creates useable overlap between cells.
This paper will examine several channel assignment strategies for a HAP spot beam architecture, exploiting the extensive research carried out for terrestrial schemes, particularly schemes using cell overlap. Firstly, the HAP architecture will be explained, and this will be followed by a description of the power roll-off approximation used to characterise the received power variation across a cell. The channel assignment algorithms will then be discussed, followed by an assessment of their performance.
II. THE HAP ARCHITECTURE An example HAP communications architecture is shown in Figure 1. This is made up of a collection of user cells connected to a wider network through backhaul and interplatform links.
Local BackhaulNetworkAlternative Backhaul via satellite for remote areas60km Remote Hubto Hub for lessremote areasFibreFibreNetwork
LEO/MEO/GEO
User Traffic
Inter-HAP Link
Figure 1 An example of a HAP architecture The HAP cellular architecture has both similarities and differences to terrestrial and satellite architectures:
Cellular Configuration – Traffic is served from the HAP using multiple centralised spot beams in a configuration similar to satellites, whereas distributed base stations are normally deployed terrestrially.
Cell sizes – These are comparable to terrestrial configurations (approximately a few kilometres), whereas satellites tend to deliver much larger cells (at least tens of kilometres).
Cell size uniformity – It is possible to construct very regular tessellations of cells from both HAP and satellite architectures, allowing conventional channel reuse schemes to be readily exploited. In real terrestrial deployments there will often be a wide range of cell sizes, with the cell layout and size often being dominated by obstructions (e.g. terrain or buildings), local planning constraints and traffic patterns. In these situations dynamic channel allocation at a base station has been shown to deliver the highest capacity [10]. On a HAP the cell size and shape is governed by: the
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