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doi:10.3969/j.issn.1003-3106.2023.05.002引用格式:金天,苏雨,纪永亮,等.基于北斗B1C 信号的DPE 方法定位性能分析[J].无线电工程,2023,53(5):1007-1014.[JIN Tian,SU Yu,JI Yongliang,et al.Analysis of Positioning Performance of DPE Method Based on BDS B1C Signal [J].RadioEngineering,2023,53(5):1007-1014.]基于北斗B1C 信号的DPE 方法定位性能分析金㊀天,苏㊀雨,纪永亮,鞠㊀易(北京航空航天大学电子信息工程学院,北京100083)摘㊀要:城市峡谷环境的高精度定位是全球卫星导航定位系统亟待解决的重要问题之一㊂近年来提出的直接位置估计(Direct Position Estimation,DPE)方法是基于 导航域 实现位置的最优估计,现有研究集中于全球定位系统(GlobalPositioning System,GPS)信号进行分析验证,缺乏新体制信号的对比和抗多径原理分析,并且计算量过大不易实现㊂针对以上问题,基于北斗卫星导航系统(BDS)B1C 信号,设计了一种快速DPE 软件接收机,并基于城市峡谷环境下的真实信号验证了BDS B1C 新体制信号DPE 软件接收机的实际性能㊂实际试验表明,相同信号相干积分长度和卫星几何精度因子情况下,DPE 接收机使用二进制偏置载波调制(Binary Offset Carrier,BOC)新体制信号相较于二进制相移键控(Binary Phase Shift Keying,BPSK)信号在城市峡谷环境下定位精度具有显著提升㊂关键词:最优估计;B1C 信号;直接位置估计;抗多径中图分类号:TN967.1文献标志码:A开放科学(资源服务)标识码(OSID ):文章编号:1003-3106(2023)05-1007-08Analysis of Positioning Performance of DPE Method Based onBDS B1C SignalJIN Tian,SU Yu,JI Yongliang,JU Yi(School of Electronic and Information Engineering ,Beihang University ,Beijing 100083,China )Abstract :High-precision positioning in urban canyon environment is one of the important issues that need to be solved urgently inthe global satellite navigation and positioning system.The direct position estimation (DPE)method proposed in recent years is theoptimal estimation of position based on the navigation domain .Existing research focuses on the analysis and verification of Global Positioning System (GPS)signals,lacks the comparison of new system signals and the analysis of anti-multipath principles,and thecalculation is too large to be implemented.To solve the above problems,a fast DPE software receiver based on BeiDou NavigationSatellite System (BDS)B1C signal is designed,and the practical performance of BDS B1C new system signal DPE software receiver based on the real signal in the urban canyon environment is verified.The experimental results show that under the same signal coherent integration length and satellite geometry accuracy factor,DPE receivers using new Binary Offset Carrier (BOC)system signals have asignificant improvement in positioning accuracy in the urban canyon environment as compared to the Binary Phase Shift Keying(BPSK)signals.Keywords :optimal estimation;B1C signal;DPE;anti-multipath收稿日期:2022-12-25基金项目:国家自然科学基金(62071020)FoundationItem:NationalNaturalScienceFoundationofChina(62071020)0㊀引言全球导航卫星系统(Global Navigation SatelliteSystem,GNSS)在城市峡谷环境下,因受到卫星可见性差㊁几何精度因子低和附近建筑物的信号反射等影响[1],反射或其他非视距(Non Line of Sight,NLOS)信号叠加在直达视距(Line of Sight,LOS)信号之上[2],限制了独立GNSS 导航终端的定位精度[3]㊂近年来,直接位置估计(Direct Position Estima-tion,DPE)方法为城市峡谷等复杂环境下使用GNSS 信号进行定位服务提供了一种新方法㊂DPE 接收机与传统GNSS 接收机分别对接收的卫星信号进行跟踪㊁再进行导航解算的两步法不同,其将码/载波跟踪环路和导航解算集成到一个步骤当中,通过对接收信号进行一步估计获取位置㊁速度和时间(Position,Velocity,and Time,PVT)信息[4]㊂2007年, Closas等[5]分别推导了传统两步法定位方法和DPE 定位方法的克拉美罗下界(Cramér-Rao Lower Bound,CRLB),证明了DPE方法定位性能不弱于传统定位方法㊂Closas等[6]提出了基于DPE方法的GNSS接收机结构设计与实现方法,通过仿真分析证明了这种接收机结构能够在多径传播和弱信号等复杂场景提供PVT信息㊂Gusi-Amigo等[7]对传统定位方法与DPE定位方法在加性高斯白噪声信道下的定位性能进行理论分析,并推导了DPE方法的近似Ziv-Zakai边界,理论结果表明DPE方法在低信噪比场景下具有更好的鲁棒性㊂Axelrad等[8]提出了一种 集体检测 的辅助GPS技术来实现快速捕获和直接定位,其通过正确组合卫星相关值来降低位置解算所需的载噪比,室外实验显示当使用1ms数据时其水平定位精度约为50m㊂Ng等[9]使用自主研发的软件平台Py-GNSS实现了利用NLOS 全球定位系统(Global Positioning System,GPS)信号进行城市导航的DPE方法,通过实验证明DPE方法在水平方向的定位误差比传统标量跟踪方法减少了40m㊂现有的基于DPE方法的接收机研究主要集中于GPS系统的二进制相移键控(Binary Phase Shift Keying,BPSK)调制信号进行,并未考虑二进制偏置载波调制(Binary Offset Carrier,BOC)新信号体制对DPE接收机性能的影响㊂北斗卫星导航系统(BDS)B1C信号作为北斗三号最主要的公开服务信号为全球用户提供高质量的定位㊁导航及授时服务[10]㊂不少学者对北斗三号的数据质量和定位性能进行了分析与评估[11-15]㊂然而上述分析均基于传统接收机结构进行理论和实验分析,缺乏DPE方法的性能评估㊂基于此,本文从B1C信号应用于DPE方法在弱信号㊁抗多径2个方面的优势进行分析,评估了其在城市峡谷环境下的定位性能㊂1㊀接收信号模型B1C信号是北斗三号系统导航定位服务主用新体制信号[16],载波频率为1575.42MHz,带宽为32.736MHz㊂由于其载波频率与GPS L1C/A㊁伽利略卫星导航系统(GALILEO)E1OS相同,与上述2个频点的导航信号能够实现兼容与互操作㊂B1C 信号为复合包络信号,包含2个正交分量:数据分量和导频分量㊂其中,数据分量采用BOC(1,1)调制;导频分量采用QMBOC(6,1,4/33)调制[17],由低频子载波BOC(1,1)和高频子载波BOC(6,1)组成㊂目前B1C信号支持宽带接收和窄带接收2种测量方法[18]㊂B1C接收信号经过射频前端滤波㊁放大㊁下变频和AD转换后,其中频信号可以表示为: r(tk)=ðN i=1{r i B1C_data(t k)+j r i B1C_pilot(t k)}+n(t k),(1) r i B1C_data(t k)=12D i B1C_data(t k,τi,f d i,t k)C i B1C_data(t k,τi,f d i,t k)㊃sc i B1C_data(t k,τi,f d i,t k,θi,0,f IF),(2) r i B1C_pilot(t k)=32C i B1C_pilot(t k,τi,f d i,t k)㊃sc i B1C_pilot(t k,τi,fd i,t k,θi,0,f IF),(3)式中:r i B1C_data(t k)为第i颗星的数据分量, r i B1C_pilot(t k)为第i颗星的导频分量,N为可见星总数量,t k为采样时间,τi为第i颗星的传播延时,f di,t k 表示t k时刻的多普勒频移,θi,0表示第i颗星的初始载波相位,f IF为信号中频载波频率,D i B1C_data表示第i颗星数据支路导航电文数据,C i B1C_data为第i颗星数据支路测距码,sc i B1C_data为第i颗星数据支路子载波,C i B1C_pilot表示第i颗星导频支路测距码,sc i B1C_pilot 表示第i颗星导频支路子载波㊂采用直接位置估计方法进行导航参数估计时需要将所有可见星的信号在导航域进行能量累加,之后通过一步估计得到导航解㊂城市峡谷弱信号环境下,所有可见星一个码周期的能量累加值难以实现精确的位置估计㊂为了减少算法计算量和复杂度,本文仅使用信号导频支路进行信号能量累加㊂一方面,B1C信号数据信道和导频信道功率比为1ʒ3;另一方面,B1C信号导频支路有10ms码周期,具有更大的相干积分增益㊂综上所述,B1C信号相比其他GNSS信号在DPE接收机城市峡谷环境应用中具有更明显的优势㊂根据以上分析,中频信号可以简化为:㊀㊀r(t k)=ðN sat=1{j A i C i B1C_pilot(t k,τi,f d i,t k)㊃sc i B1C_pilot(t k,τi,f d i,t k,θi,0,f IF)}+n(t k),(4)式中:A i为导频支路信号幅度㊂2㊀直接位置估计方法2.1㊀极大似然估计基于导航域的直接定位方法可以实现导航参数的最优估计[19]㊂DPE的导航域待求解是一个七维的状态矢量χ=[P T,v T,δt]T,P=[x,y,z]表示接收机在ECEF坐标系下的三维位置坐标向量,v=[v x, vy,v z]表示接收机地心地固(Earth-Centered Earth-Fixed,ECEF)坐标系下三维速度向量,δt表示时钟偏差㊂DPE方法的核心思想是建立用户接收机位置坐标与用户接收机接收信号中所有卫星的传输时延和多普勒频率之间的联系㊂DPE方法可以看作传统方法的逆过程㊂传统方法通过分别在不同信号处理通道最大化接收信号和本地产生的卫星PRN序列之间的相关性来估计不同可见星的传输时延和多普勒频率㊂DEP方法通过定义一组候选位置集,将候选位置集中的每一个位置元素与时间延迟紧密联系起来,以联合方式计算所有候选位置元素处的相关能量㊂本地复制信号可以看作是可见星信号的联合信号㊂最后,通过代价函数选择最大化相关性的候选位置元素作为估计位置㊂代价函数是从接收信号中获取PVT参数的最大似然估计,可以表示为:χ^=argmaxχ{ðM i=1Λi(τi(χ),f d i(χ))},(5)式中,M表示可见星数量,Λi(τi(χ),f d i(χ))表示候选位置χ处第i个可见星的预测信号和接收信号的相关值,该相关值大小由预测码相位和多普勒频率共同决定㊂2.2㊀2层网格搜索方法式(5)所示为七维的非凸函数优化问题,为了降低直接求解庞大的计算量,本文将其问题降阶为求解三维的非凸函数优化问题㊂钟差作为先验信息添加到预测信号的生成过程中㊂导航域的状态矢量简化为:χ=[x,y,z]T㊂(6)将式(6)带入式(5)可得简化后的代价函数为:χ^=argmaxχ{ðM i=1Λi(x,y,z)}㊂(7)因此,代价函数的求解仅与待求解位置相关㊂传统的DPE接收机使用二分搜索算法[20]或稀疏度不同的离散网格搜索算法[21]实现快速位置估计㊂城市峡谷环境下根据传统定位方法获取的先验位置预测值受多径影响具有较大误差,采用传统搜索方法对式(7)进行求解时存在定位精度差㊁计算复杂度高和局部收敛等问题㊂本文使用2层网格搜索算法对式(7)进行求解,具体步骤如下:①把传统定位方法获得的定位结果χ-=[x-,y-,z-]T作为当前接收机导航状态量的先验预测值㊂②以γ-为中心,生成第一层等间隔的离散网格点[χ-1,χ-2, ,χ-N]㊂综合考虑搜索范围和计算复杂度,本文选择网格间隔为10m,网格范围为ʃ100m㊂③将2中生成的离散网格点带入式(7),得到第一层网格的粗略位置估计值χ㊃=[x㊃,y㊃,z㊃]T㊂④以第一层网格搜索位置估计结果χ㊃为中心,生成第二层精细化等间隔的离散网格点[χ㊃1,χ㊃2, ,χ㊃M]㊂考虑到参数估计更高的分辨率,本文选择网格间隔为1m,网格范围为ʃ10m㊂⑤将4中生成的精细化离散网格点带入式(7),可以得到搜索范围内的全局最优解χ^=[x^, y^,z^]T㊂2层网格搜索算法具有以下3点优势:①第一层全局粗略搜索能够有效避免传统二分搜索算法在多径误差下由先验预测值误差引起的局部最优收敛;②第二层精细化网格搜索相较于稀疏度不同的离散网格搜索算法在先验预测值存在较大多径误差情况下能够有效提高参数估计精度;③相较于全局精细化搜索,2层网格搜索算法极大减小了搜索网格点数㊂为方便理解,以x㊁y二维搜索为例,2层网格搜索算法的原理如图1所示㊂图1㊀2层网格搜索算法原理Fig.1㊀Principle of two-level grid search algorithm3㊀多径误差分析影响GNSS接收机定位精度的误差主要包括电离层延迟㊁对流层延迟㊁卫星时钟误差㊁相对论误差和多径误差等㊂其中,卫星时钟误差㊁对流层延迟㊁电离层延迟和相对论误差等可以通过理论模型㊁差分技术来抑制或者消除㊂多径误差由于其与接收机周边环境的强相关性,是目前最难消除的误差之一㊂城市峡谷环境下,天线接收信号是直射信号与多个反射信号产生干涉后的合成信号㊂多径信号对传统接收机信号处理的影响主要体现在两方面:一方面,伪码跟踪环跟踪的是合成信号的伪码相位,合成信号与本地信号的相关函数会发生畸变,从而导致延迟锁相环(Delay Loop Lock,DLL)跟踪误差;另一方面,载波跟踪环通过利用本地载波与接收信号载波直接的相位差来动态调整本地载波相位,当接收信号为合成信号而不是直射信号时,二者之间存在偏差㊂多径信号对载波跟踪的影响远小于对伪码跟踪的影响,伪码跟踪误差可以达到百米量级,载波相位误差为厘米级㊂DPE方法根据相关能量直接进行位置估计㊂本地复制伪码与合成信号的相关运算,可以看作是伪码分别与直射信号和反射信号的相关值累加结果㊂根据式(4)可以得到B1C合成信号的自相关函数:㊀㊀RΣ(τ)=R(τ)+R M(τ)=R(τ)+ðM i=1αi R(τ-τi)cosϕi,(8)式中:R(τ)表示本地复制伪码与直射信号的相关函数,R M(τ)表示本地复制伪码与反射信号的相关函数,αi㊁τi㊁ϕi分别为第i个反射信号相对于直射信号的幅值㊁延时和相位㊂由于QMBOC(6,1, 4/33)信号绝大部分功率是由BOC(1,1)组成,为了减少相关时的计算量,本文使用BOC(1,1)信号相关函数进行后面的分析㊂一方面,BOC(1,1)信号相关函数如图2所示,相对于相同码速率的GPS L1BPSK调制信号更加陡峭,具有更好的多径分辨能力[22];另一方面,直接位置估计方法本身的抗多径性能相比传统定位方法更加优异,具体建模分析如下㊂本文以直射信号存在情况下,只有1条反射路径下的信号进行叠加为例进行数学建模㊂首先对相关函数进行归一化处理,可以将式(8)中相关函数分别表示为分段函数:R(τ)=-1-τ,τɪ[-1,-0.5)3τ+1,τɪ[-0.5,0)-3τ+1,τɪ[0,0.5)τ-1,τɪ[0.5,1)ìîíïïïï,(9)RM(τ)=-α1㊃(τ-τ1)㊃cosϕ1-α1㊃cosϕ1,τɪ[τ1-1,τ-0.5)3㊃α1㊃(τ-τ1)㊃cosϕ1+α1㊃cosϕ1,τɪ[τ1-0.5,τ1)-3㊃α1㊃(τ-τ1)㊃cosϕ1+α1㊃cosϕ1,τɪ[τ1,τ+0.5)α1㊃(τ-τ1)㊃cosϕ1-α1㊃cosϕ1,τɪ[τ+0.5,τ+1)ìîíïïïï,(10)式中:ϕ1ɪ[0,2π),α1ɪ[0,1]㊂当τ1小于0.5个码片时组合信号的相关函数可以表示为:RΣ(τ)=-1-τ,τɪ[-1,τ1-1)(-1-α1㊃cosϕ1)㊃τ+α1㊃cosϕ1㊃(τ1-1)-1,τɪ[τ1-1,τ1-0.5)(3+3㊃α1㊃cosϕ1)㊃τ+(1-3㊃τ1)㊃α1㊃cosϕ1+1,τɪ[τ1-0.5,0)(3㊃α1㊃cosϕ1-3)㊃τ+(1-3㊃τ1)㊃α1㊃cosϕ1+1,τɪ[0,τ1)(-3-3㊃α1㊃cosϕ1)㊃τ+(1+3㊃τ1)㊃α1㊃cosϕ1+1,τɪ[τ1,0.5)(1-3㊃α1㊃cosϕ1)㊃τ+(1+3㊃τ1)㊃α1㊃cosϕ1-1,τɪ[0.5,τ1+0.5)(1+α1㊃cosϕ1)㊃τ-(1+τ1)㊃α1㊃cosϕ1-1,τɪ[τ1+0.5,1)α1㊃(τ-τ1)㊃cosϕ1-α1㊃cosϕ1,τɪ[1,τ1+1)ìîíïïïïïïïïïïï㊂(11)㊀㊀根据式(11),当反射波幅值α1为0.5,延时τ1为0.4码片,相对相位ϕ1为0ʎ时,合成信号的相关函数如图2(a)所示,其他参数相同,相对相位ϕ1为180ʎ时,合成信号的相关函数如图2(b)所示㊂(a)同相(b)反相图2㊀BOC信号多径误差Fig.2㊀BOC signal multipath error由图2可以看出,不论多径信号同相还是反相,合成信号的自相关函数均不再关于0码片偏移量处左右对称㊂传统定位方法通过码环鉴别器不断调整本地复制伪随机码相位,直到超前和滞后相关器输出的相关结果E 与L 相等为止,此时码环跟踪误差等于0㊂多径信号引起的码相位测量误差是以自相关函数值相等的E 和L 水平连线线段中点至0码片偏移量处的水平距离δcp ㊂同相多径信号会使伪距测量值偏大,反相多径信号会使伪距测量值偏小㊂因此,传统两步法定位方法定位结果受多径信号影响较大㊂DPE 方法直接通过对相关峰最高值的位置估计进行位置解算,从图2中可以看出,多径信号的存在情况下合成信号的自相关函数峰值与直射信号的自相关函数峰值均位于同一相位处㊂因此DPE 方法能够有效抑制多径信号对定位精度的影响㊂4㊀实验结果及分析为了对BDS B1C 信号直接定位方法在城市峡谷环境的定位性能进行评估,本文搭建了基于DPE 方法的软件接收机性能评估平台,包括天线㊁功分器㊁多通道信号采集器㊁GNSS 软件接收机㊁DPE 软件接收机和数据分析模块㊂性能评估平台工作流程如图3所示㊂图3㊀性能评估平台半实物原理Fig.3㊀Semi-physical schematic diagram of performance evaluation platform㊀㊀为了模拟更加接近真实的城市峡谷环境,选择位于环形楼宇中心的实际信号采集点,数据采集环境如图4所示㊂图4㊀实测数据采集场景Fig.4㊀Measured data acquisition scene使用功分器将天线接收信号分为2路,分别通过多通道信号采集器采集中频数据,数据采集参数如表1所示㊂表1㊀数据采集参数Tab.1㊀Data acquisition parameters参数数值中频频率/MHz 27.92采样率/MHz 112前端带宽/MHz 40数据量化位数/b 1GPS GDOP5.61BDS GDOP5.75定位卫星数量5㊀㊀采集后的中频数据,一路数据由GNSS 软件接收机进行处理,另一路数据由DPE 软件接收机进行处理㊂数据分析模块完成2种软件接收机输出结果与标定基准坐标的对比分析㊂信号采集时GPS 卫星分布如图5所示㊂信号采集时刻播发BDS B1C 信号的卫星分布如图6所示㊂分别用传统软件接收机㊁DPE 软件接收机对采集到的实际信号进行处理,相关长度均为10ms㊂图7为BDS B1C 信号和GPS L1C /A 信号使用2种定位方法的定位误差比较㊂图5㊀GPS 卫星几何分布Fig.5㊀Geometric distribution of GPS satellites图6㊀BDS 卫星几何分布Fig.6㊀Geometric distribution of BDSsatellites图7㊀不同定位方法的定位误差Fig.7㊀Positioning errors of different positioning methods表2给出了实测信号2种定位方法定位误差的均值㊁标准差和均方根误差㊂表2㊀不同定位方法定位误差比较Tab.2㊀Comparison of positioning errors of different methods单位:m接收机类型信号类型均值标准差均方根误差SDR 接收机GPS L1C /A18.90 3.5519.24BDS B1C13.16 1.5613.25DPE 接收机GPS L1C /A14.03 2.7114.29BDS B1C10.342.7210.69㊀㊀可以明显看出,在实际城市峡谷环境下,DPE 接收机使用GPS L1C /A 信号和BDS B1C 信号相较于传统接收机均方根误差分别降低了25.7%㊁19.3%㊂因此,DPE 接收机相较于传统接收机在城市复杂环境下具有明显性能优势㊂使用相同相关长度情况下,BDS B1C 信号能够显著提高DPE 接收机的定位精度,相较于使用GPS L1C /A 信号平均误差和均方根误差分别降低了26.3%和25.2%㊂采用2层网格搜索算法在不降低定位精度的情况下,三维搜索位置点数从8120601降低为18522,计算量得到显著降低㊂为了分析实际城市峡谷环境下信号相关长度对定位性能的影响,图8为DPE 软件接收机分别处理BDS B1C 信号和GPS L1C /A 信号使用不同相关长度的定位误差对比㊂图8㊀不同相关长度的定位误差Fig.8㊀Positioning errors of different correlated lengths表3给出了2种信号在不同相关长度下定位误差的均值㊁标准差和均方根误差㊂可以看出,增加信号相关长度可以显著提高定位精度㊂BDS B1C 信号和GPS L1C /A 信号在30ms 相关长度下均方根误差相比10ms 相关长度分别提升约15.4%㊁9.7%㊂BDS B1C 信号在相同相关长度下的均方根误差均小于GPSL1C /A 信号㊂表3㊀不同相关长度定位误差比较Tab.3㊀Comparison of positioning errors of different correlated lengths定位方法信号类型信号相关长度/ms均值/m 标准差/m 均方根误差/mDPEBDS B1CGPS L1C /A1010.34 2.7210.69209.63 2.9710.07308.552.949.041014.03 2.7114.292013.53 2.3613.733012.652.5712.915㊀结束语本文对BDS B1C信号在DPE方法应用中的弱信号优势和抗多径性能进行了分析,设计实现了一种基于BDS B1C信号的快速DPE软件接收机,将BDS B1C信号体制设计的优异多径分辨能力和直接位置估计方法的抗多径原理相结合来提高接收机在城市复杂环境下的定位精度,并且应用提出的2层网格搜索算法在保证全局最优求解前提下极大地降低了全局搜索的计算量㊂在城市峡谷环境中开展的实际信号定位实验结果表明,30ms相关长度下基于BDS B1C信号的DPE接收机静态定位平均误差为8.55m,均方根误差为9.04m㊂城市峡谷环境静态定位时,同等条件下基于BDS B1C信号的DPE接收机定位精度明显优于传统接收机和基于GPS L1C/A信号的DPE接收机㊂验证了基于BDS B1C信号的DPE接收机在城市峡谷环境下的性能优势,具有一定的实际应用前景㊂参考文献[1]㊀XIE P,PETOVELLO M G.Measuring GNSS MultipathDistributions in Urban Canyon Environments[J].IEEETransactions on Instrumentation and Measurement,2015,64(2):366-377.[2]㊀BRAASCH M S.Performance Comparison of Multipath Mit-igating Receiver Architectures[C]ʊ2001IEEE AerospaceConference Proceedings.Big 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未来出行方式的革新：2024年交通科技展望1. Introduction1.1 OverviewThe field of transportation has undergone significant advancements in recent years, leading to a revolution in the way people travel. With the rapid development of technology, the future of transportation looks promising and is expected to bring about transformative changes by the year 2024. This article aims to explore the innovative ways in which transportation will be revolutionized and provide a glimpse into what the future holds for commuting and traveling.1.2 BackgroundOver the past decade, there have been remarkable advancements in transportation technology that have reshaped how we move from one place to another. Autonomous driving technology, shared mobility services, and green transportation solutions have gained traction and are progressively being integrated into our daily lives. These developments have laid the foundation for further progress in transforming our modes of transportation.1.3 PurposeThe purpose of this article is to envision how transportation will evolve by 2024 and shed light on the potential futuristic trends that will redefine our travel experiences. By analyzing current trends and exploring upcoming technologies, we will gain insights into the possibilities offered by flying cars becoming commercially available, widespread adoption of high-speed magnetic levitation trains, as well as the increasing prevalence of intelligent traffic management systems. Additionally, we will also explore sustainable transportation solutions like electric vehicles' growth trajectory, hydrogen-powered transport's prospects, and the popularization of micro-mobility tools.With a comprehensive understanding of these anticipated changes in commuting patterns and travel options, readers can get a glimpse into how their personal lives might be affected by these transformations while considering potential benefits for urban development as well.Overall, this article aims to paint an exciting picture of futuristic transportation possibilities while identifying potential implications for individuals and cities alike. By exploring these forward-thinking concepts and proposing suggestions based on it all, it seeks to inspire readersabout smarter ways to commute and foster sustainable urban development opportunities.(Note: Please note that while this response provides a detailed outline for the "1. Introduction" section as requested, adapting and expanding upon it will allow for a complete and well-rounded article.)2. 交通科技的现状:2.1 自动驾驶技术:自动驾驶技术是当今交通科技领域的一个重要发展方向。
冬奥场馆黑科技英语作文英文回答：High-Tech Wonders of the Winter Olympics Venues。
The Beijing 2022 Winter Olympics showcased a plethoraof technological advancements that not only enhanced the athlete experience but also captivated spectators worldwide. From cutting-edge ice-making techniques to virtual reality training simulators, these high-tech marvels pushed the boundaries of winter sports and set new standards forfuture events.Ice-Making Perfection:The National Speed Skating Oval, dubbed the "Ice Ribbon," employed an innovative ice-making process that produced near-perfect ice conditions. Utilizing carbon dioxide refrigeration, the system maintained a constant temperature of -10.5°C while removing moisture andimpurities, resulting in a flawless surface that allowed skaters to achieve record-breaking speeds.Virtual Reality Training Simulator:Athletes in various disciplines, such as ski jumping and ice hockey, benefited from state-of-the-art virtual reality (VR) training simulators. These immersive experiences allowed athletes to practice their techniques in realistic environments, fine-tune their movements, and minimize the risk of injury.Data-Driven Performance Analysis:Sensors and tracking devices integrated into athletes' uniforms and the sports equipment provided real-time data that was analyzed by expert teams. This data enabled athletes to optimize their performance, identify areas for improvement, and make strategic adjustments during competitions.Artificial Intelligence (AI) in Decision-Making:AI algorithms played a crucial role in decision-making during events. For example, AI-powered systems assisted judges in scoring figure skating performances and determined the trajectories of ski jumpers, ensuring fairness and accuracy.Robotics for Enhanced Safety:Robotic technology played a significant role in enhancing safety for both athletes and spectators. Automated drones monitored the venues and provided real-time aerial footage, while robotic arms assisted with tasks such as ice resurfacing, minimizing the risk of accidents.These technological innovations not only transformed the Winter Olympics in Beijing but also have far-reaching implications for the future of winter sports. They promise to elevate athletic performance, enhance safety, and create immersive experiences for spectators, shaping the future of winter sports in profound ways.中文回答：冬奥场馆中的黑科技。
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文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by theeditor. I hope that after you download them,they can help yousolve practical problems. The document can be customized andmodified after downloading,please adjust and use it according toactual needs, thank you!In addition, our shop provides you with various types ofpractical materials,such as educational essays, diaryappreciation,sentence excerpts,ancient poems,classic articles,topic composition,work summary,word parsing,copyexcerpts,other materials and so on,want to know different data formats andwriting methods,please pay attention!The Winter Olympics is a showcase of cutting-edge technology that never fails to amaze and captivate audiences worldwide. From innovative sports equipment to mind-boggling virtual reality experiences, here are some mind-blowing technologies that have graced the Winter Olympics.Imagine strapping on a pair of skis that can adjust their stiffness on the fly, giving you optimal performance on any type of snow. These smart skis use embedded sensors and actuators to analyze the snow conditions and adjust their flex accordingly. With this technology, athletes can maximize their speed and control, pushing the boundaries of what is possible on the slopes.Speaking of pushing boundaries, have you ever wondered what it feels like to soar through the air like an Olympic ski jumper? Virtual reality technology has made it possible for spectators to experience the exhilaration and fear oflaunching off the ski jump ramp. By donning a VR headset, you can stand at the top of the ramp, feel the wind rushing past you, and witness the breathtaking view as you fly through the air. It's a heart-pounding experience that brings you closer to the action than ever before.When it comes to ice sports, the technology behind the ice resurfacing machines is truly remarkable. These machines, also known as Zambonis, use a combination of hot water, shavers, and squeegees to create a smooth and pristine ice surface. They work tirelessly between events to ensure that the ice is in perfect condition for the athletes. It's a behind-the-scenes marvel that often goes unnoticed but plays a crucial role in the success of the Winter Olympics.In the world of figure skating, the costumes worn by the athletes are not just for show. They are designed with the latest fabric technologies to enhance performance. These fabrics are lightweight, breathable, and flexible, allowing skaters to move freely while maintaining their body temperature. Some costumes even incorporate sensorsthat track the skater's movements and provide real-time feedback on their technique. It's a fusion of fashion and technology that adds an extra layer of excitement to the sport.As the Winter Olympics continue to evolve, we can expect to see even more mind-blowing technologies in the future. From advanced snow-making machines that can create perfect powder on demand to drones that capture breathtaking aerial footage, the possibilities are endless. The Winter Olympics will always be at the forefront of innovation, pushing the boundaries of what is possible in sports and technology. So, sit back, relax, and prepare to be amazed by the black technology of the Winter Olympics.。
擎朗智能新品 全球首show！文/赵盼李通对近年来的公司发展，特别是海外业务进展，进行了重点回顾，并且以一场机器人“走秀”的方式发布了“跨世代”多功能配送机器人T10和全新的清洁服务机器人产品C30。
“跨世代”的全新物种—T10现场展示的重磅新品——多功能配送机器人T10是擎朗智能研发团队酝酿良久、多年累积的创新技术和产品巧思的集中释放，也是配送机器人从未有过的”全新物种“。
T10集“配送高手”、“全景感知”、“多模态交互”、“广告营销”，四大特性于一身。
首先，T10具备开放式大容量托盘、AI相机检测、大幅升级的运动控制性能和全能底盘，不仅避震强化运行可靠而且有着极限59cm的狭窄过道通过能力，围绕配送本身，T10有着多样的容纳托盘、精确检测，全向运动平稳和适应极限物理环境，配送高手实至名归。
其次，T10更是打造了同品类前所未有的先进传感器融合，T10周身分布了5个深度相机模组、2个ToF雷达、4个RGB相机组成的环境传感系统，适应实际运行环境复杂光照、多层检测距离、精度、算法设计和融合都更上一层楼，第一次实现了真正意义的全景感知能力。
大幅提升了避障、定位、自主路径规划、安全配送流程，并且能够引入更高性能的人机交互；T10还创新设计了拟人化的运动头部，几乎感知不到延迟的头部动作协调，多模态语音/表情/触摸交互，浑然一体。
T10还配置了23寸高清大屏，引入了云端广告营销运营系统，实现自动任务，这也是同品类的一次大胆尝试，引流和全能配送二合一。
用心演绎创新美丽李通在现场向来访的众多媒体讲述了公司的创业初心和历程，擎朗Keenon名字的内涵就是Keen on robotics，对机器人始终保持深度热爱。
从2010年起，擎朗几乎是从零到一开辟了商用服务机器人赛道，自研核心技术、自建供应链、以一己之力去商用场景验证服务机器人的价值，经历了长时间的市场培育，到终端商户那里一遍遍聆听需求，直至今天成为中国市场的行业开创者，市场占有率第一，企业增速第一（根据近2年IDC行业报告统计），也是全球范围内商业服务机器人的领导企业。
第43卷第2期铁道学报V843 N〇.22 0 2 1 年2 月J0URNAL0FTHE2HINA RAILWAY SOCIETY F e bruary 2 0 2 1文章编号：1001-8360(2021)02-0103-08高速列车技术与产业发展机制及实施路径王军(中国中车股份有限公司，北京100039)摘要：高速列车创新发展的管理理论与方法是助推铁路装备工业繁荣的重要基础。
在分析我国高速列车发展需求基础上，运用系统工程管理理论方法，从技术与产业要素分析入手，拓展要素管理内涵，重点阐述了我国高速列车技术创新与产业发展的核心特征；剖析了高速列车技术的系统性、前沿性和演进性；分析了高速列车产业的市场性、结构性和协同性；解析了高速列车产业与技术的共生关系。
在此基础上，构建了面向高速列车技术与产业特征的双元驱动发展机制，归纳并提出了内聚要素及实施路径；最后思考了未来高速列车技术与产业深度融合发展的方向。
关键词：高速列车；技术；产业；双元驱动；融合中图分类号：293-03 文献标志码：A do i：10.3969/j.iss n. 1001-8360.2021.02.013Development Mechanism and Implementation Approach ofHigh-speed Train Technology and IndustryWANG Jun(C R R C C o.，LLd.，Beijing 100039, China)Abstracts:The management theory and metliod for the innovative development of high-speed train are an important theoretical basis for boostingtheprosperity of railway equipment industry.Based on the analysis of the development needs of high-speed trains in China as well as the technology and industry factors，the crucial characteristics of technology innovation and industry development of high-speed trains in China were demonstrated，by means of theory and metiiod of system engineering management to expand the connotation of factors management.Fo systematicness，cutting edge and evolutionary nature of high-speed train technology，the marketability，structure and synergy of the high-speed train industry were explored and the symbiotic relationship be and technology was i nvestigated.Based on these，a two-element driver model oriented to the characteristics of high-speed train technology and i ndustry was constructed，followed by the summarization and proposal of cohesive elements and implementation approaches.Finally，the future direction of the deep integration of high-speed train technology and industry was considered.Key words：high-speed trains;technology；industry；double helix；integration技术与产业是高速列车发展方法论聚焦的两大核 心要素。
小型化轻量化英语
"小型化" 可以翻译为 "miniaturization"，指的是将原本较大或复杂的物品或系统设计成更小巧、更便携的形式。
这一概念在科技和工程领域中经常被使用，例如指将电子设备、机械零件或其他产品设计成更小型化的版本。
"轻量化" 则可以翻译为 "lightweighting"，是指通过使用更轻、更高强度的材料或者优化设计来减轻产品的重量。
这一概念在汽车制造、航空航天和其他工程领域中被广泛运用，以提高产品的燃油效率、性能和可持续性。
因此，结合两者，"小型化轻量化" 可以翻译为"miniaturization and lightweighting"，指的是将产品设计成更小巧、更轻盈的形式，以满足现代社会对便携性、高效能和可持续发展的需求。
Highspeed rail,often referred to as highspeed train or bullet train,is a form of rail transport that operates significantly faster than traditional rail traffic.The development of highspeed rail has revolutionized the way we travel,offering a blend of speed,comfort, and efficiency that is unmatched by other modes of transportation.Here is an essay that introduces the concept,benefits,and impact of highspeed rail on modern society.Title:The Evolution of HighSpeed Rail:A Modern MarvelIn the21st century,the world has witnessed a remarkable advancement in transportation technology,with highspeed rail emerging as a key player in the global transportation network.Highspeed rail systems,characterized by their ability to travel at speeds exceeding200kilometers per hour,have transformed the way we perceive distance and time.Origins and DevelopmentThe concept of highspeed rail is not new it has evolved over decades of research and development.Japan was the first to introduce a highspeed rail system with the Shinkansen in1964,setting a precedent for the world.Since then,countries like France, Germany,and China have developed their own highspeed networks,each with unique features and technological advancements.Technological InnovationsThe technology behind highspeed rail is a testament to human ingenuity.It involves sophisticated engineering solutions for track design,train aerodynamics,and magnetic levitation where applicable.The trains are designed to minimize air resistance and reduce noise pollution,ensuring a smooth and quiet ride.Moreover,advanced signaling systems and safety measures are in place to maintain the high operational standards required for such speeds.Economic and Environmental BenefitsHighspeed rail has had a profound economic impact,stimulating regional development and reducing travel times between cities.It has become an essential tool for business travelers,tourists,and daily commuters alike.Economically,it has led to the creation of jobs,both directly and indirectly,and has boosted local economies along the rail routes.From an environmental perspective,highspeed rail is a sustainable mode of transport.It produces fewer greenhouse gas emissions compared to air and road travel,making it a preferred choice for ecoconscious travelers.The energy efficiency of highspeed trains is further enhanced by the use of regenerative braking systems,which convert kinetic energy back into electrical energy.Cultural and Social ImpactThe cultural and social impact of highspeed rail is equally significant.It has brought people closer together,fostering a sense of community and shared identity among regions. The accessibility of highspeed rail has also encouraged cultural exchange and tourism, allowing individuals to experience different parts of the country or the world with ease.Challenges and the FutureDespite its numerous advantages,highspeed rail faces challenges such as high initial investment costs,land acquisition issues,and competition with existing modes of transport.However,with continuous technological advancements and growing environmental concerns,the future of highspeed rail looks promising.In conclusion,highspeed rail is more than just a mode of transportation it is a symbol of progress and a catalyst for economic growth,environmental sustainability,and social cohesion.As the world moves towards a more interconnected future,the role of highspeed rail is set to expand,connecting people,places,and ideas at unprecedented speeds.This essay provides a comprehensive overview of highspeed rail,highlighting its technological,economic,environmental,and social significance in the modern world.。
我最喜欢的科技发明高铁英语作文My Favorite Technological Invention: The AmazingHigh-Speed RailHave you ever wondered what it's like to travel at incredibly fast speeds? Well, let me tell you about my favorite technological invention – the high-speed rail! It's a super-fast train that can zoom across countries and cities in no time at all. Just thinking about it makes me feel like a kid in a candy store!First of all, let's talk about how these trains work. They use special electric motors and aerodynamic designs that allow them to reach mind-blowing speeds. Some of the fastest high-speed trains in the world can go up to 350 kilometers per hour (217 miles per hour)! That's like driving on a highway at nearly three times the speed limit. Isn't that crazy?Now, imagine sitting inside one of these incredible trains. You buckle up in your comfy seat, and suddenly, the train starts accelerating. The buildings outside the window start to blur together as the train picks up speed. Before you know it, you're zipping through the countryside, past cities and towns in the blink of an eye. It's like being a superhero with the power of super-speed!But high-speed rails aren't just about going fast – they're also incredibly convenient. Instead of spending hours stuck in traffic or waiting at airports, you can hop on a high-speed train and get to your destination in record time. No more wasting time in long lines or dealing with delays. It's like having a magic carpet that whisks you away to wherever you want to go!Another thing I love about high-speed rails is how comfortable and luxurious they are. The seats are plush and spacious, and there's plenty of legroom for you to stretch out and relax. Some trains even have fancy dining cars where you can enjoy a delicious meal while watching the scenery whiz by. Talk about living the high life!High-speed rails are also great for the environment. Since they run on electricity, they produce way fewer emissions than cars or planes. Plus, they can carry a lot of people at once, which means fewer vehicles on the road. It's like giving Mother Nature a big high-five!But my favorite part about high-speed rails is the sense of adventure they bring. Every journey feels like an exciting expedition, where you get to experience new sights and sounds as you zoom across the land. It's like being an explorer, discovering new places and cultures at lightning speed.Imagine taking a high-speed rail trip across Europe, zipping from one country to another in a matter of hours. One moment you're admiring the Eiffel Tower in Paris, and the next, you're gazing at the canals of Venice or the ancient ruins of Rome. It's like having a magical passport that lets you travel through time and space!Or what about a high-speed rail journey through Asia? You could start your day sipping tea in a traditional Japanese garden and end it marveling at the towering skyscrapers of Shanghai or the beautiful temples of Bangkok. It's like being a world traveler without even needing to pack a suitcase!And let's not forget about the amazing engineering and technology behind these incredible trains. The way they're designed, built, and operated is nothing short of a modern marvel. It's like having a real-life science museum on wheels, where you can witness the wonders of human ingenuity and innovation firsthand.I could go on and on about why I love high-speed rails so much, but I think you get the idea. They're fast, convenient, comfortable, environmentally friendly, and downright thrilling. Every time I step aboard one of these amazing trains, I feel like a kid again, filled with excitement and wonder.So, the next time you're planning a trip, why not consider taking a high-speed rail adventure? Trust me, it'll be an experience you'll never forget. Who knows, you might even discover a new favorite technological invention of your own!。
Standard sonictoothbrush headsG3 Premium GumCare2-packStandard sizeHealthier gums for a healthier smileUp to 7x healthier gums in just 2 weeks*Healthy teeth start with healthy gums. Take care of yours with our G3 Premium Gum Care brush head. Soft sides flex and adapt to the contours of your gums, giving you 2x more surface contact** for superior plaque removal at the gum line.Innovative technologyPhilips Sonicare's advanced sonic technologyA utomatically selects optimal mode for ultimate results****Designed to optimize performanceTested to meet your oral health needsClick-on design for simple brush head placementA lways know when to replace. A lways get an effective clean.For exceptional gum careUp to 7x healthier gums in just 2 weeks***A n unrivaled deep cleanUp to 2x more surface contact** for an effortless deep cleanUp to 10x more plaque removal than a manual toothbrushHighlightsFocus on gumhealthWith the Philips Sonicare Premium Gum Care brush head , even the deepest clean is gentle .A s your toothbrush moves along the gum line ,Premium Gum Care ’s flexible sides andbristles absorb any excess pressure so your gums are protected , even if you brush toohard . Bristles work hard to remove plaque and bacteria along the gum line helping to improve gum health . Thanks to this brush head ’s curved design , you can be sure of maximized bristle contact .A daptive cleaningtechnologyY ou get a personalized clean every time you brush with our adaptive cleaning technology .Soft rubber sides flex to let Premium Gum Care adapt to the shape of your teeth and gums , absorbing any excess brushingpressure and enhancing our sonic cleaning power . Bristles can then adjust to the shape of your teeth and gums so you get up to 2x more surface contact than a regular brush head ** for deeper cleaning even in hard -to -reach areas .Say goodbye toplaqueThanks to its flexible design , Premium Gum Care removes up to 10x more plaque than a manual toothbrush . It moves to enhance our unique Philips Sonicare cleaning technology so that however you brush , you get an exceptional clean you can see and feel .Philips SonicaretechnologyPhilips Sonicare 's advanced sonic technology pulses water between teeth , and its brush strokes break up plaque and sweep it away for an exceptional daily clean .Brush head replacementcuesBrush heads become less e ffective after 3months of use , but with BrushSync ™ you 'll be reminded before this happens . Y our smart toothbrush will track how often and how hard you brush , and will notify you when it ’s time for a replacement . Don ’t have a smart Philips Sonicare toothbrush ? Just monitor your blue replacement bristles , and when they turn white you ’ll know it ’s time for a fresh brush head .Easy to click -onY our G 3 Premium Gum Care brush head fits perfectly with any Philips Sonicare toothbrush handle , except Philips One and Essence . Simply click on and o ff for easy replacement and cleaning .Brushing with peace ofmindA ll Philips Sonicare brush heads are safe and gentle on teeth and gums . During tests , each brush head is put through its paces to ensure durability and an exceptional performance every time you brush .BrushSync ™ mode -pairingY ou ’ll always get the best possible clean with our BrushSync ™ mode -pairing feature ****.The Philips Sonicare C 2 Optimal Clean brush head syncs with your BrushSync ™ enabled Philips Sonicare toothbrush handle ****,selecting the optimal brushing mode and intensity level for exceptional cleaning . A ll you need to do is start brushing .SpecificationsDesign and finishingSmart Brush Head RecognitionBristle stiffness feel: SoftColor: WhiteReminder bristles: Blue bristle color fade awayMaterial brush head: Soft, flexible rubber sidesSize: Standard CompatibilityBrush head system: Click-onSuitable for these models: 2 Series plaquecontrol, 2 Series plaque defense, 3 Seriesgum health, DiamondClean, DiamondCleanSmart, EasyClean, Essence+, FlexCare,FlexCare Platinum, FlexCare PlatinumConnected, FlexCare+, for Kids,HealthyWhite, HealthyWhite+, PowerUpItems includedBrush heads: 2 G3 Premium Gum CareQuality and performanceReplacement: Every 3 monthsTested: for optimal usageHealth benefitsPlaque removal: Removes 10x moreplaque*****Gum health: Up to 7x healthier gums** *in Gum Care Mode vs a manual toothbrush; measuredby GBI* *than a DiamondClean brush head* **in Gum Care Mode vs a manual toothbrush; measuredby GBI* *** BrushSync™ mode-pairing is only compatible withPhilips Sonicare BrushSync™ enabled toothbrushhandles* ****than a manual toothbrush© 2023 Koninklijke Philips N.V.A ll Rights reserved.Specifications are subject to change without notice. Trademarks are the property of Koninklijke Philips N.V. or their respective owners.Issue date 2023‑08‑16 Version: 2.2.1E A N: 87 10103 85002 1 。
JOURNAL OF TRANSPORTATIONSYSTEMS ENGINEERING AND INFORMATION TECHNOLOGY Volume 7, Issue 2, April 2007Online English edition of the Chinese language journalReceived date: 2006-12-28*E-mail: lokkeesiu@Copyright © 2007, China Association for Science and Technology. Electronic version published by Elsevier Limited. All rights reserved.Innovative Lightweight Transit Technologies for Sustainable TransportationSIU L. K.*Ascent Dynamic Consultants, Hong Kong, ChinaAbstract: In recent years, there is a phenomenon in many major cities that building more roads to relieve traffic congestionachieves nothing more than encouraging more vehicles to use them, resulting in more congestion which is one of the prime sources of bad air quality and inefficient use of energy. Facing with these problems, a number of major cities are either building or planning to build mass transit railways as a backbone, supplemented by light rails and other transit modes to enhance mobility and network connectivity. This paper reviews a number of emerging and innovative lightweight transit systems, from an urban mobility and sustainable development perspective. The objective of the paper is to serve as a reference to practitioners who are involved in the planning and design of sustainable transportation systems.Key Words: urban transit planning; innovative transit systems; automatic people mover; personal rapid transit; linear induction motor; maglev; cable drawn system; monorail1 Introduction1.1 Urban mobilityUrban mobility is one of the critical issues in urban transport planning. Traffic congestion is nowadays a prime concern of residents which is the case in very well developed cosmopolitan cities as well as their counterparts in the developing countries. Regardless of whether congestion is recurring (traffic regularly exceeds roadway capacity) or non-recurring (predictable and non-predictable events cause delays), there is one root cause of congestion: too many vehicles crowding available road space coupled with a lack of travel options.In some Scandinavian cities, over 80 % of all motorized trips are made by private cars. This presents an immediate question as to why public transit is the last choice of the traveling public. There is then a fundamental question to the policy makers and transport system planners as to what it makes people leave their cars at home and use the public transit more frequently.In developing countries, the automotive industry there is very often still in their early stages, and private ownership of cars is low; the problems of traffic jams and congestion, the deterioration of the transportation environment, and the rate of road accidents in the cities are, however, comparable to those cities in developed countries. Taking China as an example, its urbanization level is about 25−30 percent, and the demand for and number of vehicles for personal and commercial use will continue to expand, causing increasing concerns for China’s large urban areas.1.2 Congestions and increasing concerns on emissions For many years now, most major metropolitan cities in the world face the same problem in urban transport. Congestion in major cities has reduced traffic speeds to a crawl. That empty public buses fill up road space, resulting further congestion in central business districts, is a common phenomenon of a badly coordinated public transport policy. To improve such situation, transport policymakers may not have many choices. One of the useful measures is the use of heavy rail transit system as a backbone of a public transport network.When compared with road-based public transport systems, heavy rail transit systems provide high capacity, off-street, less polluting and relatively accident-free service. However, their construction involves a high capital investment. Long trains of large vehicles require wide corridors, huge platforms and stations which, if placed underground, require massive excavation and tunneling with great effort and costs. Running such huge structure on the surface or above ground, the visual intrusion due to the viaducts, huge piers and elevated stations could be very controversial and quite often costly to resolve the associated environmental issues. These high construction costs may be compensated by the revenue, provided that the envisaged system will have a sufficiently high travel demand. To achieve a financially viable heavy rail transit project, system planners exhaust ways and means to maximize catchments of passengers, and give due considerations to: coordination of different transport modes; location of the interchange stations; use of medium/light capacity feeders. Effective use of innovative transit systems as a means of feeder to the backbone system could enhance the connectivity of the rail systems to serve the local residents and maximize the utilization of railway service. In addition, it could help to improve the deteriorating environmental conditions due to vehicular emissions. According to recent surveys, rail transit could provide substantial energy conservation and emission reduction benefits, which consumes about one fifth of energy per passenger-km when compared to automobile travel, due to its high efficiency and load factors (Litman, 2004). International comparisons indicate that per capita energy consumption declines with increased transit use, in particular the use heavy rail mass transit.1.3 Renewed strength of innovative transit technologies and renaissance of citiesRecently, there are encouraging examples in which public transportation is helping to generate new vitality like never before. Beautiful, walkable town squares combine residential, retail, office, recreation and public transportation features to make community living easy. New buses and light rail extensions improve mobility and ease congestion. Along with easing congestion and improving air quality, the benefits of enhancing public transit are enormous. Transit-oriented development increases property values, property tax revenues, sales tax revenues and more. In essence, a healthy transportation system can anchor a community’s revitalization effort.Over the years, there are a considerable number of innovative transit systems conceived. Various systems still exist on paper. However, not many of them could really have a chance to go through a genuine “baptism of fire”. Lacking of market demand and design problems has sharply reduced their number. Of the handful still being active, some have found their niches of application, e.g. the Automatic People Mover (APM) originally conceived for major activity centers such as airport terminals. Taking Japan as an example, many innovative transit technologies are not only put on trial in a test-bed environment. Many of them are actually in revenue operation. Typical examples include linear metros, monorails, APM’s, and urban low speed maglev.2 Automatic people movers (APM)Automatic people movers can be defined as a light to medium scale rail transit system using small, light weight rolling stock running on rubber tyres on a dedicated guideway that is usually elevated. Unmanned APM trains are controlled by computers which help reducing staff costs.Over the last two decades, the automated people mover (APM) is one of the most significant developments in transit technology. APMs can carry from 2,000 to 25,000 passengers per hour per direction with headways as short as or even shorter than 60 seconds for small APM systems. APM vehicles travel at speeds up to 80 km/h. The vehicles, which are typically comprised cars of urban transit bus size, typically in the range of 8−12 m in length. APMs have been extensively operated within restricted major activity centers such as airports. There have been over fifty airport APM applications worldwide.APM technology has also been extended for medium capacity urban line transit services, such as the V AL system in Lille in France, Bukit Panjang, Sengkang & Puggol LRT in Singapore, all of which are significantly successful. Different APM suppliers have conducted their own R&D in the field. As a result, quite a few different APM systems were proposed. Aluminum and fibre-reinforced plastic (FRP) are two common materials in carbody construction. The train tyres are made of special rubber composites and auxiliary steel wheels to ensure that the train can continue running for some distance if a rubber tyre fails. Guidance and switching systemsare specific features of the APM technology. Typical guidanceFig. 1 Modern APM vehiclesystems include centrally mounted beam guidance, lateral guidance and central channel. Most modern APM are equipped with VVVF induction motor drives. There are mainly two different types of traction supply voltage namely, 750V DC and 600V AC 3-phase.In addition, it is worthwhile to mention the Copenhagen Metro (Fig. 2) and the Vancouver Skytrain which being a medium scale steel wheel-on-rail system have many characteristics similar to the APM’s, and could be arguably categorized as part of the APM family. They are both fully automatic system with vehicle dimensions comparable to their APM counterparts. The Copenhagen Metro rolling stock is in a 3-car articulated formation in which 3 bogies are equipped with the latest VVVF induction motor drives. The Vancouver Skytrain is essentially a “linear APM”, owing to its adoption of linear induction motor (LIM) drives. The reaction plate of the LIM is centre mounted along the track. The reaction plate is made of solid steel with an aluminum cover. There are a number of fastening and mounting methods for the cover to counteract the constant electromagnetic thrusts exerted on the plate. The steel is laminated near station and at grades to increase tractive effort. All these LIM technologies are also applicable to the linear metro.3 Maglev systemsMaglev uses magnetic thrusts for vehicle levitation whicheliminates the physical steel wheel on rail contact and provides better performance in terms of noise and vibration compared to the conventional technology. So far, two approaches have been developed for vehicle levitation namely, electromagnetic suspension (EMS) based on attractive magnetic forces, and electro dynamic suspension (EDS) based on repulsive magnetic forces. Typical examples for EMS are the high speed Transrapid (Germany) system and the low speed HSST system (Japan), both of which are commercially available in the market today. Typical example for EDS is theJapanese MLU design which utilizes super-conductingmagnets. The latter is still very much under intensive research and development, and speed trial in Yamanashi, Japan.Both EMS and EDS employ linear motors for propulsion. This allows contact-less propulsion. The linear induction motor (LIM) is simple in structure, which normally has the stator installed on the vehicle (commonly referred to as the short stator approach) and the passive rotor (reaction plate) installed along the guideway. Linear synchronous motors (LSM) are used for high speed maglev such as Transrapid, in which the stator windings are installed along the guideway (referred to as the long stator approach), and the rotor is installed on the vehicle being excited by the on-board battery or other means. All maglev systems in operation today have on-board rollers for emergency push-out, and/or low speed mode operation when the uplift force is lower than a threshold value.Currently, there are two lines being operated for revenue service namely the Shanghai Pudong Airport Demonstration Line in China based on the Transrapid technology, and theTobu Kyuryo Line in Nagoya, Japan based on the HSSTFig. 2 Copenhagen mini-metroFig. 3 LinimoHSSTFig. 4 Nagoya HSST linimo depotLinimo. The Shanghai Airport Maglev is configured as apoint-to-point airport shuttle system connecting Pudongairport and a metro station near Shanghai downtown. TheTobu Kyuryo Line is a proper light capacity system which has9 stations connecting the Nagoya City and the Expo 2005 site,passing through the City of Toyota.While these two lines are based on different technologies,they have a common goal that it is a showcase to the travelingpublic as well as rail transit planners and operators worldwide,in respect of their performance, system reliability and service availability. Currently, HSST is participating in an urbanmaglev development program with FRA in the USA. Thefollowing are the key characteristics of the two systems:Table 1 Key characteristics of HSST and TransrapidHSST-100(Linimo)TransrapidVehicle length 13.5 m (mid section)14.0 m (end section)25 m (mid section)27 m (end section)Vehicle width 2.6 m 3.7 m Vehicle height 3.45 m 4.16 mWeight per vehicle 17.5 tonne 53 tonne (end section) 50 tonne (mid section)Max. operating speed 100 km/h 300−500 km/hMin. running curve 50 m 350 m (min.)2825 m for 400 km/hMax. operatinggradient7 % 10 %Passenger carrying capacity per car 244 per 3-car train(104 seated)92 seated (end section)126 (mid section)4 Linear metrosA linear metro uses steel wheels and rails to support and guide the rolling stock. As a result, it enjoys the advantages of conventional steel wheel and linear motor propulsion system. Furthermore, it permits construction of smaller tunnels and broadens the choice of where the alignment can go through due to the fact that steering bogies can be used and the non-adhesive propulsion allows steeper gradients be adopted, compared to the conventional steel wheel-on-rail vehicles. With these merits, the linear metro lends itself readily as a medium scale transit to supplement those well established heavy rail subways in big cities, to cope with increasing traffic demand.The following summarizes some of the major developments achieved for the commercialization of the linear metro:1) Cars with smaller cross-section dimensions—vehicle floor height can be lowered to 700 mm by using smaller wheels and reducing the size of under-floor equipment. The result is a low profile, lightweight car that can be used in tunnels with an internal diameter of about 4 m;2) Ability to negotiate tight curve—a bogie steering mechanism changes the axle angle, permitting cars to run smoothly on curves with a radius of only about 50 m;3) Ability to operate on steep gradient—the linear motor provides non-adhesive propulsion that does not reply on the friction between the steel rails and wheels so cars can climb steeper grades. It can also provide an effective and predictable braking effort, if regenerative brake is used;4) Relatively lower noise levels—the bogie steering mechanism prevents wheel squeal on tight curves.Tabulated below are the characteristics of the two linear metros currently in revenue service in Japan.Table 2 Key characteristics of the two linear metros in JapanTokyo Oedo Line 12 Osaka Line 7 Gauge 1435 mm 1435 mmTraction voltage 1500 V DC 1500 V DCVehicle length 16.5 m 15.8 mVehicle width 2.5 m 2.5 mVehicle height 3.15 m 3.15 mVehicle weight 24−25 tonne (MC car) 24.5−26.5 tonne (MC car) Line speed 70 km/h 70 km/hPassenger capacityper car (seated)100 (44) 100 (40)Max. grade 8 % 8 %Min. curve 50 m 50 m5 Urban monorailsMonorail was invented much earlier than most people realize. The first suspended monorail was invented in Germany and put into operation in Wuppertal in 1901. Japan first gave serious attention to the monorail system when a suspended type was opened in 1958 in Tokyo’s Ueno Park. One purpose of the project was to test the technology and determine how it could be applied to urban transit. During the 1960’s, monorails were developed and built in different parts Fig. 5 Guangzhou metro’s LIM rolling stockof the world. In the early days, monorails were considered suitable only for theme parks, but this changed in 1964 when the Tokyo Monorail began running along the edge of Tokyo Bay between Hamamatsucho and Haneda Airport. It was constructed as an urban transport system. Recently commissioned monorails include the Okinawa Line (26.2 km), Kuala Lumpur Monorail (17.2 km) and Chongqing Monorail (27 km), which are all equipped with latest on-board technologies.Urban monorails can be divided into straddle type, in which the vehicle sits astride the rail, and the suspended type, in which the vehicle is suspended from the rail. The straddle type uses a high-strength concrete or steel girder as the rail. A bogie which is equipped with traveling wheels, guide wheels and stabilizer wheels—all made of rubber—sits astride the top and sides of the rail. The car-body is mounted on the bogie. The suspended type uses a steel track girder with an open bottom. The car body is suspended from a bogie which is equipped with traveling and guide wheels made of rubber. Both types use rubber tyres and air springs for their bogie suspension to reduce vibration and noise.Most modern urban monorails are equipped with VVVF drives, aluminum body shell and ATO system. In addition, because of the special structure of the monorail system, there is no danger of derailment. The monorail can withstand severe weather conditions, such as strong winds, ice and snow.6 Cable-drawn systemsThere are a number of emerging modern cable drawn systems which can provide policymakers and designers with more choices for planning considerations. Recent examples are the Las Vegas Mandalay Bay Linear Shuttle in the USA and the Birmingham International Airport people mover in theUK. These systems provide a system capacity at about 4000pphpd, particularly suitable for short-haul point-to-point type of shuttle applications. The operating speed falls in the range of 40−45 km/h. Time interval between trains could be as low as 60 seconds. Maximum route length is in the range of 5 km. The cable-drawn vehicle can negotiate very steep gradients, typically 10 %−12 %, subject to the available traction.Fig. 6 Modern straddle monorailTable 3 Urban monorails in JapanStraddle-beam monorailsSuspended monorails Tokyo monorail Kita kyushumonorail Osaka monorailTama monorail Shonan monorailChiba urban monorail Route length (km) 16.9 8.8 21.2 16.0 6.6 15.2Number of stations 91314198 15 Track Double Double Double Double Single DoubleTypeStraddle-beam (tyres)Straddle-beam (tyres)Straddle-beam (tyres)Straddle-beam (tyres)Suspended (tyres) Suspended (tyres) Switching system Articulated switch Articulated switch Articulated switch Articulated switch Simple switch Simple switch OperationATC with driver and conductor ATO with one driver ATC with one driver ATC with one driver ATS with driver and conductor ATC with one driver Electrical system (Vdc) 750 1500 1500 1500 1500 1500 Minimum curve (m) 120 80 100 100 50 50 Max. gradient 6 % 4 % 6 % 5.8 % 7 % 6 % Max. speed (km/h) 806575657565Car width ×height ×length (m) 3.02×2.92× 16.55 (15.20) 2.98×3.49× 14.80 (13.90) 2.90×3.74× 14.80 (13.90) 2.98×3.75× 15.50 (14.60) 2.58×3.69× 12.75 2.58×3.73× 14.80 Seating per set 584 478494415228158Capacity (pphpd) 8760 4780 3952 4200 1824 2370Construction costs (billion Yen)21.1(extension 67.6)68.1 115.3 242.2 5.3 133.7Advantages of cable drawn system are simple, proven design and no on-board propulsion equipment, hence very light weight vehicles. Typically, the cable drawn system can negotiate curves down to 30 m.The vehicles are passive and cable drawn by a stationarydrive unit, for which a large machine room is necessary for accommodating the drive, tensioning and associated components. Similar to APM technologies, bearing wheels and horizontal wheels made of rubber are used to ensure maximum lift and to reduce vibrations. The mechanical grip is a safety critical feature of the cable-drawn system. 100% redundancy will normally be provided in which each single grip is able to sustain the maximum weight of the vehicle plus the gradient effect.Vehicles can turn around at termini by means of rotating platform (turntable). For intermediate stations, systems such as the Leitner Minimetro employ a synchronization drive subsystem to resolve the middle station stops issue. With this arrangement, trains are detached from the rope and moved by the synchronization drive when the trains enter the section. Within the synchronization section, the vehicles go through a sequence of deceleration, parking and acceleration, to allow a smooth detaching and attaching from and to the rope, as well as holding the train at the loading area.Apart from the rubber wheels approach, Otis offers a cable drawn system with air suspension. The suspension system is achieved by means of providing low pressure airspace between the vehicle bottom and the track surface. In addition to the cable drawn vehicle, Otis also provides a self-propelled LIM air suspended version, the prototype of which has been in operation in Duke University, USA since 1980’s. Two types of vehicle are on offer. The size and weight of which are very similar to that of APM’s, with a top speed at 60 km/h. The system capacity is in the range of 1000 to 20000 pphpd,dependent on the train length and headway.7 Modern tram on tyres without overhead wireTram on tyres are one of the innovative guided transport systems. They are also called "intermediate systems”. In fact this technology mixes trolleybus and tramway features. In France, they are often named TRG , acronym of “transport routier guide”.The Tram on Tyres concept is very recent and derives from the research of a flexible and reversible vehicle, which works mostly in guided mode, in order to maximize the system capacity, the performances and the reduction of the reserved lanes width.The Tram on Tyres vehicles are able to be switched to trolleybus-like mode, and in some cases, running in the road traffic with autonomous power supply (batteries, diesel engine, etc.), like a normal bus. This feature could be very useful in the ancient city centers of many towns, characterized by road narrowness and many difficulties to build in heavy infrastructures.These new trams use rubber tyres, in order to maximize the on board comfort and the cinematic performances (low horizontal curve radius, high vertical gradients—in many cases more than 10%). Every tram on tyres model is characterized by a specific kind of guidance system.The Innorail system emerged as a Tram without wire for the implementation in Bordeaux, France. It involves a series of ground level switched contact rails installed between running rails, separated by insulated rail sections to ensure complete electrical isolation of each section. Each individual section is only energized when its local power rail contactor receives a coded signal from the vehicle when the vehicle is directly over the section. The beauty of this system is that it eliminates thevisual intrusion due to the overhead wire completely.Fig. 7 Cable-drawnsystemFig. 8 A modern tram on tyres8 Hybrid busesThere are a number of bus transit technologies available to date. In the last decade or so, the interest is in the drive options being explored, namely, the battery electric, hybrid-electric and fuel cells buses. Electric drives are appealing the transit operators because they offer the promise of reduced or even zero vehicle emissions and increased efficiency. Out of the three major options, only the hybrid-electric buses have recently arrived at the commercial production stage.A hybrid electric vehicle is one that combines an electricpropulsion system with another powering mechanism driven either by a conventional internal combustion engine—ICE (diesel, gasoline, propane, or natural gas), a turbine, or a fuel cell stack. In the case of hybrid electric buses, the majority in service today uses a diesel or gasoline engine with an electric motor and batteries, while a small number of hybrid buses in service use an ultra-capacitor for energy storage. These combined systems of ICE, electric motor and energy storage device provides an operator the benefits of an electric drive system, without the negatives of a pure battery-electric bus, e.g. requiring re-charging. The batteries are continuously recharged during driving. However, the battery life is still a concern area that requires further review. It also bears an implication on the life cycle costs. Unlike other light rail transit and battery-operated vehicles, hybrid-electric buses are not zero emission.9 Concluding remarksInnovative lightweight transit technology is in itself a hugetopic in which there is an array of systems with various characteristics and features. Amongst these systems, many of them have gone pass their “sale-by-date”, and a few of them still exist on paper. While the other countries are still working hard to secure funding to continue their R&D programme of innovative transit ideas, Japan is actually deploying them on a massive scale. Apart from their Shinkansen, the Japanese have extended the APM, monorail, linear metro and low speed maglev for their daily urban use. The smooth, quiet and reliable service of the HSST maglev (Linimo) in Aichi, Nagoya was witnessed and appreciated by millions of passengers and visitors to the Expo 2005.Building mass transit railways as a backbone supplemented by scalable innovative lightweight transit feeders could provide an effective means to promote urban mobility for major cities which in turn help reduction of emissions, hence improved air quality. With a better public transport service and connectivity, encouraging more residents to use public transit also helps energy conservation. A well coordinated and yet integrated transit framework could revitalize business districts, tourist and activity centers, which increase public revenues and make urban live easier. To this particular end, an effective use of innovative transit technologies, through thorough technology appraisals and integrated planning, would for certain help to achieve sustainable transportation.References[1] Eastham T R, Masada E. Electric urban transit technologies forthe reduction of air pollution in cities. In: Proceedings of the16th International Conference on Magnetically Levitated Systems and Linear Drives, Rio D J (Ed.), 2000.[2] Kera K, Isobe E, Kawahata S. Hitachi’s initiatives inFig. 9 Tram without contactwireFig. 10 Hybrid electric busaddressing the challenges of 21st century railway systems.Hitachi Review, 1999, 48(3): 103−106.[3] Lowson M V. A new approach to sustainable transport systems.London, U.K.: the 13th World Clean Air and Environmental Protection Congress, 2004.[4] Siu L K, Chan D, Kato J, et al. Failure mode and endurancetests of the CHSST 100L system. In: Proceedings of the 17thInternational Conference on Magnetically Levitated Systems and Linear Drives. Lausanne, Switzerland, 2002.[5] Litman T. Rail Transit in America Research Report, VictoriaTransport Policy Institute, 2004.[6] Shen L D, Huang J, Zhao F. Automated people moverapplications: a worldwide review. 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