Novel scheme of high precision inertial measurement for high-speed rotating carriers

In order to satisfy the requirement of high precision measurement in a high dynamic environment,a kind of gyro aided multi-accelerometer inertial measurement unit(GAMA-IMU)with six accelerometers and two gyros(6A2G)was proposed in this paper.The available configurations have the problem of low measurement precision in a high dynamic environment due to channel coupling.The three channels were decoupled when calculating the angular velocity in the proposed configuration.The yawing and pitching angular velocity were directly measured by gyros,while only the rolling angular velocity was obtained by the GAMA-IMU indirectly from the rolling angular acceleration and quadratic component of rolling angular velocity.Then a single channel rolling angular velocity calculation model was established and the extended Kalman filter(EKF)was used to do state estimation.Simulations were carried out and results indicated that the calculation precision of the proposed 6A2 Gconfiguration could meet the demand of high precision measurement for a high-speed rotating carrier.

Wireless channel estimation for high-speed rail communications:Challenges,solutions and future directions

With the development of High-Speed Rail(HSR),countries and individual passengers alike have enjoyed far ranging benefits as a result-economic,social,environment and in added convenience.One of the important parts of HSR construction is the signaling system,where wireless communications play a key role in the transmission of train control data.Channel estimation has a significant impact on the quality of the wireless communication,however,whose performance is degraded due to the fast mobility of HSR.This paper focuses on the channel estimation technology in HSR.We first summarize the key challenges for HSR channel estimation,especially the Inter-Carrier Interference(ICI)faced by Orthogonal Frequency Division Multiplexing(OFDM)systems.Then we provide a comprehensive review of existing pilot-aided channel estimation schemes from three points:channel model,estimation algorithm,joint channel estimation and ICI mitigation schemes.Lastly,we present the challenges of channel estimation for the Orthogonal Time Frequency Space(OTFS)system and Reconfigurable Intelligent Surface(RIS),which are promising techniques for HSR systems in the future sixth Generation(6G)wireless communication.

Model of Rotation Accuracy of High-Speed Spindles on Ball Bearings

For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.

A Silicon Micromachined Gyroscope Driven by the Rotating Carrier Self

This paper reported a silicon micromachined gyroscope which is driven by the rotating carrier's angular velocity,the silicon was manufactured by anisotropy etching.The design,fabrication and packing of the sensing element were introduced in the paper.The imitation experimentation and performance test have certificated that the principle of the gyroscope is correct and the gyroscope can be used to sense yawing or pitching angular velocity of the rotating carrier,and the angular velocity of the rotating carrier itself.

Electromagnetic Analysis and Optimization of High-speed Maglev Linear Synchronous Motor Based on Field-circuit Coupling

High speed maglev train has become a new non-contact transportation mode mainly studied in recent years because of its non-sticking and high speed characteristics.Firstly,the finite element model of the long stator linear synchronous motor(LSM)is established based on the structure of the test prototype.After calculation,it is compared with the experimental data and verified.On this basis,a field-circuit coupling model based on inverter circuit is established,and the influence of carrier wave ratio change on the output characteristics of LSM is calculated and analyzed.Finally,the filter circuit is introduced into the field-circuit coupling model,and the influence of the filter circuit on the output characteristics of the LSM is compared and analyzed.

Isolated attosecond pulse generation with few-cycle two-color counter-rotating circularly polarized laser pulses

Most of the schemes for generating isolated attosecond pulses(IAP) are sensitive to the carrier-envelope phase(CEP)of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized(TCCRCP) laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.

Magnetophotothermal interaction in a rotating solid cylinder of semiconductor silicone material with time dependent heat flow

A mathematical model linking thermoelasticity to photothermal experiments is proposed with the consideration of the photothermal effect.The system equations for coupled plasma,heat conduction with phase-lags(PLs),and motion equations are introduced and solved by using the Laplace transform technique.The photothermal,thermal,and elastic waves in a rotating solid cylinder of semiconductor material are analyzed with the proposed model.The cylinder surface is constrained and subjected to a time-dependent pulse heat flux.The sensitivity of the physical fields for the angular velocity,PLs,and thermal vibration parameters is investigated.In addition,the effects of the effective parameters on the physical quantities are graphically illustrated and discussed in detail.

Influence of ground effect on flow field structure and aerodynamic noise of high-speed trains

The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.

基于功率开关-二极管基本单元多电平逆变器及其功率均衡调制策略研究

针对级联H桥型多电平逆变器开关器件随逆变器输出电平数增加显著增多的问题,提出一种以功率开关器件-二极管为基本单元的新型多电平逆变器。该逆变器仅使用较少开关器件即可实现高质量电平输出,且该拓扑开关损耗低、效率高,不仅易于扩展还能有效避免级联单元间电流倒灌等问题。针对传统正负反向层叠载波调制策略调制下逆变器存在级联单元间输出功率不均衡的问题,在传统调制策略基础上推导分析区域功率,提出了一种基于部分载波循环的功率均衡调制策略,并验证了载波循环规律的普适性,所提调制策略能在保持输出电压波形质量不变的情况下,载波仅变换2(n-1)次即可在nT_(o)/2内实现级联单元输出功率均衡以及开关损耗平均分配,并提高电源利用率。最后搭建两单元七电平逆变器实验平台对所提调制策略进行了实验验证。

Towards 640 Gbit/s wavelength conversion based on nonlinear polarization rotation in a semiconductor optical amplifier

Taking into account ultra-fast carrier dynamics,this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation (NPR) in a single semiconductor optical amplifier (SOA) and investigates the performance of this kind of wavelength conversion scheme in detail.In this model,two carrier temperature equations are introduced to substitute two energy density equations,which reduce the complexity of calculation in comparison with the previous model.The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results.Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams.To further investigate the performance of the non-inverted wavelength conversion scheme,the dependence of output extinction ratio (ER) on some key parameters used in simulation is illustrated.Furthermore,simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.

FBMC/OQAM系统中改进的峰均比抑制方法

针对偏移正交幅度调制的滤波器组多载波(FBMC-OQAM)系统中峰值平均功率比(PAPR)过高会引起失真且对信道估计性能造成影响的缺点,提出了一种基于相位旋转的干扰消除法(ICM-P)。该方法产生不同的相位序列,与传输数据相乘得到多组数据序列,分别计算其PAPR,并选择PAPR最低的一组进行传输。仿真验证与分析表明:所提方法能有效降低系统过高的峰值平均功率比,误码率不高,且信道估计性能较原ICM方法没有明显下降。

MMC的载波循环正弦脉宽调制策略

悬浮电容电压均衡问题是模块组合多电平变换器(MMC)控制的关键和难点之一。此处提出一种可实现悬浮电容电压均衡的载波循环正弦脉宽调制(CRSPWM)策略,在分析载波层叠正弦脉宽调制(CDSPWM)的载波分配规律的基础上,通过载波循环的方法,重构载波与功率模块的对应关系,利用冗余开关状态来减小悬浮电容电压的充放电时间差异,实现MMC悬浮电容电压的均衡控制。实验结果表明,采用所提CRSPWM策略,无需任何电容电压控制措施可有效减小悬浮电容电压的波动幅值和各悬浮电容间的电压差异。

Comparison and Selection of Arch-Rib Construction Schemes for Continuous Beam arch Composite Bridge of High Speed Railway

The paper summarizes the four different construction schemes based on engineering cases for the arch rib construction of continuous beam-arch composite bridges for high-speed railways.These methods include in-situ assembly,segmental lifting,incremental launching and longitudinal moving,and vertical rotation.The temporary structural designs,process methods,and technological equipment for each construction scheme are described in detail.The advantages and disadvantages of each scheme and its application scope under various conditions are analyzed,and opinions and suggestions for guiding the application of each scheme are proposed.The comparison and selection analyses show that the four arch rib construction schemes have certain applicability under different conditions such as bridge site status,bridge span,and construction environment.With the continuous increase of bridge span and progress of construction technological equipment,the arch rib construction technology is developing towards the overall erection direction.This leads to more obvious technical advantages of the segmental lifting method,incremental launching and longitudinal moving method,and vertical rotation method.Therefore,it is necessary to select the best construction scheme according to the construction status and technical conditions during application.

载波轮换调制在级联H桥型STATCOM中的应用

级联H桥型静止无功补偿器(static synchronous compensator,STATCOM)通过调节单模块有功功率来达到均压的目的,但是会对输出无功电流产生影响。首先对单极倍频调制过程进行双重傅里叶分析,从理论上分析载波移相与单极倍频相结合的调制算法对单模块有功功率的影响,然后提出一种模块间载波轮换的新型调制算法,并且针对模块间如何进行同步切换以及在调制波过零点处切换的问题,给出一种在多DSP系统中的实现方案。该调制算法在不影响输出电压与输出电流质量的同时,从理论上解决了单模块有功功率不平衡的问题。仿真与实验结果验证了这种调制算法的正确性与可行性。

新型颗粒生物膜生物转盘处理有机废水的研究

采用一种新型的颗粒生物膜生物转盘处理有机废水，将盘片改为转筒状，并向其中加入特制的多孔聚合物高分子载体，考察了该系统对COD和NH3-N的去除效果及多孔聚合物载体的生物膜特性。结果表明，系统对COD和氨氮的去除效果较好，当进水COD和氨氮分别为（252—538）、（22．2～51．7）mg／L（平均值分别为386．6、33．0mg／L）时，系统对COD和氨氮的去除率分别为63．6％～96．4％（平均为85．2％）、77．8％-98．7％（平均为86．5％）；多孔聚合物高分子载体挂膜良好，平均膜厚为186．4μm。

旋转载体驱动硅微机械陀螺的设计和性能检测

提出了一种利用旋转载体自身角速度驱动的硅微机械陀螺,分析了该陀螺的工作原理,建立了这种陀螺的数学模型,设计了该陀螺的敏感结构,计算了陀螺的结构动力学参数,设计并分析了陀螺的信号检测与处理电路并针对该陀螺的特点设计了性能测试装置。理论研究和性能测试表明,利用旋转载体自身角速度驱动的硅微机械陀螺结构原理正确。

一种CORDIC算法的FPGA实现

在数字化中频接收机中,为了实现相干解调,接收端的数控振荡器需要产生一个本地相干载波,其频率和相位必须与发送端载波的频率和相位严格保持一致,因此需要用到arctan函数计算相位差。研究了一种基于CORDIC算法计算arctan函数的方法,提出了基于CORDIC算法实现arctan函数运算的硬件流水线实现结构,并在芯片上进行仿真实现,仿真结果表明,其输出误差较小,与理论值基本一致,利用其可实现数字载波同步中鉴相、鉴频功能。

基于载波频率优化的级联型APF源性谐波能量不均抑制方法

基于载波移相(CPS)调制的H桥级联型(CHB)有源电力滤波器(APF)是中高压系统谐波治理的有效手段。分析并指出了级联型拓扑在输出谐波电流时存在的源性谐波能量不均问题。当输出的谐波电流频率与单元输出电压中某一开关谐波频率一致时,将产生功率耦合,导致单元直流电容电压发散。针对性地提出了一种载波频率优化方法:通过引入载波频率偏移量,实现了单元输出电压开关谐波与APF输出谐波电流的功率解耦;讨论了不同的载波偏移量对电容电压波动的影响,并给出了最优频率偏移量计算方法。对比了载波频率优化方法和传统载波轮换方法抑制源性谐波能量不均的效果,体现了载波频率优化方法的优越性。仿真和现场应用证明了所提方法能够有效地防止直流侧电压的发散并将波动抑制在最小值。

级联型逆变器载波循环功率均衡控制方法及比较

在级联H桥型逆变器中,载波同相层叠(PD)调制策略虽然输出线电压具有最优的谐波特性,但无法实现级联单元间输出功率均衡。针对这个问题,提出两种基于PD调制策略的载波循环功率均衡控制方法,所提方法在改进型PD调制策略的基础上,通过对载波进行周期性的循环移动,可以有效实现级联单元间的功率均衡控制,且保留了PD调制策略下逆变器输出电压谐波特性最优的特点。以三单元级联H桥逆变器为例,首先对改进型PD调制策略下级联单元输出功率特性进行数学推导;其次分析两种所提功率均衡控制方法实现机理并对其特性进行比较,揭示两种功率均衡控制方法的优缺点以及适用场合。最后通过仿真和实验结果验证了理论分析的正确性与所提方法的可行性。

基于二级混沌映射的OFDM安全传输方案

基于OFDM技术,结合混沌序列的伪随机特性和初值敏感性,提出了一种数据相位混沌旋转和子载波混沌映射的安全传输方案。仿真结果和分析表明,该方案能够有效地对信息进行混沌安全传输,增强输出信号的随机特性,窃听方无法通过信号的统计特性估计出发送信息,从而保证通信的安全性。与常用的安全措施,如AES(高级加密标准)、多天线随机化传输矩阵等方法相比,所述方案能够达到较好的计算安全性。