Switching Frequency Improvement of a High Speed on/off Valve Based on Pre-excitation Control Algorithm

The high-speed on/off valve(HSV)serves as the fundamental component responsible for generating discrete fluids within digital hydraulic systems.As the switching frequency of the HSV increases,the properties of the generated discrete fluid approach those of continuous fluids.Therefore,a higher frequency response characteristic of HSV is the key to ensure the control accuracy of digital hydraulic systems.However,the current research mainly focuses on its dynamic performance,but neglect its FRC.This paper presents a theoretical analysis demonstrating that the FRC of the HSV can be enhanced by minimizing its switching time.The maximum switching frequency(MSF)is mainly determined by opening dynamic performance when HSV operates with low switching duty ratio(SDR),whereas the closing dynamic performance limits the MSF when HSV operates with high SDR.Building upon these findings,the pre-excitation control algorithm(PECA)is proposed to reduce the switching time of the HSV,and consequently enhance its FRC.Experimental results demonstrate that PECA shortens the opening delay time of HSV by 1.12 ms,the closing delay time by 2.54 ms,and the closing moving time by 0.47 ms in comparison to the existing advanced control algorithms.As a result,a larger MSF of 417 Hz and a wider controllable SDR range from 20%to 70%were achieved at a switching frequency of 250 Hz.Thus,the proposed PFCA in this paper has been verified as an effective and promising approach for enhancing the control performance of digital hydraulic systems.

Doppler frequency offset estimation and diversity reception scheme of high-speed railway with multiple antennas on separated carriage

The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is proposed based on Ricean channel model. First, a maximum likelihood estimation （MLE） algorithm for DFO is designed, show- ing that the Doppler estimation can be obtained by estimating moving velocity of the train and the path loss with the exploitation of pilots that are placed inside the frame. Then a joint detection algorithm for the receiver is proposed to exploit multi-antenna diversity gains. Last, the theoretical Crammer Rao bound （CRB） for joint channel estimation and DFO estimation is derived. The steady performance of the system is confirmed by numerical simulations. In particular, when the Ricean fading channel parameter equals 5 and the velocities of train are 100 m/s and 150 m/s, the estimation variances of DFO are very close to the theoretical results obtained by using CRB. Meanwhile, the corresponding sig- nal to noise ratio loss is less than 1.5 dB when the bit error rate is 10-5 for 16QAM signals.

Value of High-Frequency Relic Gravitational Wave (HFRGW) Detection to Astrophysics and Fabrication and Utilization of the Li-Baker HFRGW Detector

Up to the present time gravitational-wave detectors, such as LIGO and Virgo, have been sensitive to frequencies on the order of a few thousand to a small fraction of an Hz. They have been most effective in the study of black-hole mergers. We suggest that high-frequency relic gravitational wave (HFRGW) detectors be developed, especially the Li-Baker HFRGW detector, in the gigahertz and higher frequency range. We believe collecting cosmological, primordial observational data especially generated during the first few seconds after the beginning of our Universe is extremely important. One motivation for this paper is, therefore, that we are confident that observation of relic gravitational waves will provide vital information about the birth of our Universe and its early dynamical evolution. Other astrophysical applications of HFRGW detectors involve the entropy growth of the early Universe, an ability to study alternatives to inflation and to provide clues about the symmetries underlying new physics at the highest energies. A working hypothesis or theory, based upon the rollout of our Universe from infinitesimal Planck Length and Planck Time is presented. This theory involves the rapid motion of time and matter during that early time having frequencies on the order of trillions of cycles per second or more. Several alternative HFRGW detectors are described and the proposed Li-Baker HFRGW detector, which is theoretically sensitive to GW amplitudes, A, as small as 10-32, is discussed in detail. Such sensitivity may provide a means for verifying or falsifying the rollout of our Universe working hypothesis. Essentially a combination of theory and experimentation is presented. It is recommended that plans and detailed specifications for the Li-Baker HFRGW detector be prepared in order to expedite its fabrication.

The Principle and Practice of the Deviation of Power Frequency Component Relay on High Voltage Transmission Line

The research and development of ultra high speed protective relay of transmission line has got great interest and attention of protective relay engineer over the world. Several versions and schemes of ultra high speed relay have been studied and designed in recent twenty years. But only a few of them have got actual apiication in the power system. The relay based on the deviation of power frequency component (DPFC) can get very high reliability with ultra high speed so it has got wide application in Chinese power system. Thousands relay sets have been applied and its operation experience verifies their excellent performance. This paper summarizes the course of the development of the uItra high speed protective relay and compares the merits and defects of the main schemes which have been developed. The principle and successful pratice of the ultra high speed protection based on DPFC reIay are introduced.

Analysis of stress and natural frequencies of high-speed spatial parallel mechanism

In order to grasp the dynamic behaviors of 4-UPS-UPU high-speed spatial parallel mechanism, the stress of driving limbs and natural frequencies of parallel mechanism were investigated. Based on flexible multi-body dynamics theory, the dynamics model of 4-UPS-UPU high-speed spatial parallel mechanism without considering geometric nonlinearity was derived. The stress of driving limbs and natural frequencies of 4-UPS-UPU parallel mechanism with specific parameters were analyzed. The relationship between the basic parameters of parallel mechanism and its dynamic behaviors, such as stress of driving limbs and natural frequencies of parallel mechanism, were discussed. The numerical simulation results show that the stress and natural frequencies are relatively sensitive to the section parameters of driving limbs, the characteristic parameters of material on driving limbs, and the mass of moving platform. The researches can provide important theoretical base of the analysis of dynamic behaviors and optimal design for high-speed spatial parallel mechanism.

High Speed On/Off Valve Control Hydraulic Propeller

The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propeller can improve the effeciency of ROV propulsion system significantly,and provides another attractive ROV propulsion system choice for engineers.

High-Power-Factor Adjustable Speed Drive Using Diode Clamped Multilevel Inverter

This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate high dv/dt and high frequency common mode voltages which are harmful for the drive applications. It reduces the motor bearings life and conducted EMI （electro magnetic interference） deteriorates the insulation. In this paper, a diode clamped multilevel （3-level） inverter is used to perform dual task. It generates HF （high frequency） current to be injected at the input of the three-phase front-end rectifier thereby improving the harmonic spectra and the power factor. It also drives the induction motor. The salient feature of this paper is that it does not require separate converters for improving power factor and to drive induction motor. Furthermore, inverter switches operate with ZVS （zero voltage switching）, thus reducing the switching losses substantially, The voltage stress of the switches also has been reduced to half of the conventional 2-level converter. The inverter is operated with SPWM （sinusoidal pulse width modulation） technique. The simulation results for a prototype of 2.2 kW are presented.

Inter-carrier Interference Analysis for MIMO-OFDM Systems in High-Speed Train Environment

The orthogonality between the subcarriers of multipleinput multiple-output orthogonal frequency division multiplexing( MIMO-OFDM) systems is destroyed due to the Doppler frequency offset,particularly in the high-speed train( HST) environment,which leads to severe inter-carrier interference( ICI). Therefore,it is necessary to analyze the mechanism and influence factor of ICI in HST environment. In this paper, by using a non-stationary geometry-based stochastic model( GBSM) for MIMO HST channels, ICI is analyzed through investigating the channel coefficients and the carrier-to-interference power ratio( CIR). It is a fact that most of signal energy spreads on itself and its several neighborhood subcarriers. By investigating the amplitude of subcarriers, CIR is used to evaluate the ICI power level. The simulation results show that the biggest impact factor for the CIR is the multipath number L and the minimum impact factor K; when the train speed υR> 400 km / h,the normalized Doppler frequency offset ε > 0. 35,the CIR tends to zero,and the communication quality will be very poor at this condition. Finally,bit error rate( BER) is investigated by simulating a specific channel environment.

High quality-performance by changing parameters of antenna array

Several antennas based on cylindrical array and uniform hexagonal array are designed and fabricated on flexible substrate-Teflon.To validate the designed prototypes,the antennas are fabricated and their performance is analyzed.The highlight scheme is to improve the signal performance and electromagnetic field distribution by appropriately changing the parameters of the antennas array,signal frequencies,and steering angles.The proposed antennas array is capable of applying shaping radiation band technique to generate tunable power and radiation domain.The distribution of the field,and the bit-error-rate transmigration coefficient characteristics are measured.The results show that the proposed scheme can achieve better performance by searching the optimal parameters of antenna array.

铜箔粗糙度对高速高频PCB信号传输的影响研究

随着印制电路板(PCB)传输速率的日益提升,新出现的56 GB/s和112 GB/s的高速系统,以及更高的224 GB/s传输速率需求,正接近传统电子硬件的物理极限,对PCB的信号完整性提出了更大的挑战。本文主要研究在高速高频材料(如M6、M7、M8)上,不同的棕化药水对铜箔粗糙度影响导致的插损性能差异,探讨了棕化药水与PCB插损之间的关系,并提出了相应的改善措施。研究结果对于提高PCB性能具有重要的指导意义。

Detection and Determination of the Variation of the Speed of Time

Steadily increasing time is involved in most scientific analyses. Like other dimensions in spacetime we suggest that there can be a variation rate of time’s progress or speed of time in the time dimension. We study speed-of-time variation observational data in three processes: muon decay, galaxy rotation (related to dark matter) and the separation speed of celestial objects as our Universe progresses (related to dark energy). Each of these processes will have an “observed value” of their time of completion Po from an observation of the process at time t1 and an “expected value” Pe of that time at time t2. Their difference is attributed to the variation of the speed of time. We provide a possible explanation for the anomalous separation of the observed and the expected galactic velocity curves. Our conclusion is that it is unnecessary to introduce dark matter or dark energy.

背钻控制对高频高速PCB信号传输的影响研究

伴随以太网速率朝800 G、1.6T升级,PCB传输速率由56 Gbps向112 Gbps甚至224 Gbps演进。使得背钻Stub和D2M距离不断减小,对PCB背钻精度提出了巨大的挑战。传统的背钻控制方法已经不能满足高密度布线及高精度Stub对背钻的要求。本文旨在通过优化设计、提升对准度能力、降低通孔及背钻孔的孔位精度偏差、选择高精度机台等方案,将背钻Stub能力控制在0.1026±0.0508 mm,背钻对位能力提升至D+0.1524 mm的管控水平,达到降低Stub及减小背钻孔到周边线路的距离,提高高速高频PCB的传输速率。

一种5G基站用PCB的压合填孔研究

在5G基站56 bps主板设计中,常用到高频材料与高速材料混压的M+2结构。针对M+2结构的印制电路板(PCB),在常规生产工艺中的二次压合之前,需要先使用树脂塞孔将2个子板的过孔填实。但树脂塞孔流程长,且子板叠构不对称,板翘影响其他工序加工。主要介绍一种半固化片(PP)三明治塞孔工艺替代树脂塞孔工艺,对于M+2钻带结构的板,使用本工艺时,子板在二次压合前,盲孔不需要做树脂塞孔。在二次压合的时候,直接使用PP填孔,既能保证填孔的饱满度、各项PCB品质要求,又能减少流程,降低加工成本,并且还能大幅度提升生产效率。

多层PCB中高速信号传输路径的优化与仿真分析

针对多层印刷电路板(Printed Circuit Board,PCB)中高速信号传输路径优化问题,文章进行了系统性研究。采用高级设计工具与仿真软件,对多层PCB的高速信号传输路径进行优化设计和仿真分析,旨在解决信号完整性(Signal Integrity,SI)和电磁兼容性(Electro Magnetic Compatibility,EMC)问题。研究结果表明,优化后的传输路径显著提升了信号传输质量,降低了信号反射和串扰,信号传输速率达到10 Gb/s,信号损耗减少了15%。本研究的创新之处在于引入了多目标优化算法,并结合仿真工具实现了传输路径的精确优化,提高了多层PCB在高速信号传输中的性能和可靠性,具有重要的工程应用价值。

Cutting force and its frequency spectrum characteristics in high speed milling of titanium alloy with a polycrystalline diamond tool

In this paper, a series of experiments were performed by high speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) by use of polycrystalline diamond (PCD) tools. The characteristics of high speed machining (HSM) dynamic milling forces were investi- gated. The effects of the parameters of the process, i.e., cutting speed, feed per tooth, and depth of axial cut, on cutting forces were studied. The cutting force signals under different cutting speed conditions and different cutting tool wear stages were analyzed by frequency spectrum analysis. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The results indicate that a characteristic frequency in cutting force power spectrum does in fact exist. The amplitudes increase with the increase of cutting speed and tool wear level, which could be applied to the monitoring of the cutting process.

高速数字电路PCB中串扰问题的研究与仿真

针对高速数字电路PCB中传输线间串扰的严重性,从精确分析PCB中串扰噪声的角度出发,在传统的双线耦合模型的基础上,采用了一种三线串扰耦合模型。该模型由两条攻击线和一条受害线组成,两条攻击线位于受害线的两侧,线间采取平行耦合的方式。利用信号完整性仿真软件Hyperlynx对受害线上的近端串扰噪声和远端串扰噪声进行了仿真。仿真结果表明,不同的传输模式和传输线类型、信号层与地平面的距离、耦合长度、传输线间距和信号上升/下降沿等因素会对受害线上的近端串扰和远端串扰产生较大的影响。在分析仿真结果的基础上,总结出了高速PCB设计中抑制串扰的有效措施,对高速数字电路设计有一定的指导意义。

基于信号完整性理论的PCB仿真设计与分析研究

在分析高速数字电路设计中存在的几个主要问题的基础上,探讨了高速信号完整性所涉及到的基本理论,研究了在PCB仿真设计实际应用中通常采用的两种模型方法,即IBIS模型和SPICE模型,分析了仿真模型和建模方法.结合一个具体高速电路设计——小型封装可热插拔式光纤收发模块(SFP)的反射仿真实例,讨论了仿真模型的建立并对仿真结果进行了分析,研究结果表明在高速电路设计中采用基于信号完整性的仿真设计是可行的,也是必要的.

高速高密度PCB设计的关键技术与进展

高速高密度是许多现代电子产品的显著发展趋势之一,高速高密度PCB设计技术即成为一个重要的研究领域.本文介绍了高速高密度PCB设计的关键技术问题(信号完整性、电源完整性、EMC/EMI和热分析)和相关EDA技术的新进展,讨论了高速高密度PCB设计的几种重要趋势.

高速数字信号在PCB中的传输特性分析

首先分析了PCB板走线损耗特性,建立分析模型并进行了数值仿真计算,得到了一些有益的结论;然后对PCB走线串扰特性进行了研究,给出了相应的等效电路模型,分析了护卫接地技术中接地孔对串扰抑制的影响。分析结果表明,科学设计护卫接地可以有效地改善PCB走线所引起的串扰,为实现高速数字电路设计打下了基础。

高速PCB板的电磁兼容设计

以某一嵌入式系统核心PCB板设计为例,介绍了电磁兼容的基本概念及一些高速PCB板设计的基本知识,着重分析了无高频器件时高速PCB板设计中存在的电源系统干扰、地线噪声干扰和信号线间的串扰等电磁干扰,并分析了这些电磁干扰产生的主要原因,从PCB总体设计和元器件布局、布线等方面考虑,对可能存在的这些干扰,提出了防止和抑制方法以及一些提高PCB板电磁兼容性的具体措施;在工程实践中证明这些方法和措施有效可靠。