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.

Corrosion Test of the Steel Plate in a WJ-8 Fastener for High Speed Rail

It was found that the steel plate in the composite plate in the WJ-8 fastener used in high speed rail is rusty. The objective of this study is to test the zinc coating of the steel plate. A literature review was conducted to identify the zinc coating techniques, and the companies that can provide different coating service was identified. A salt fog chamber was built that was in compliance with the ANSI B117 code, and the steel plates that were coated by the identified companies were tested using the salt fog chamber. The results indicated that the coating technique that had the best performance in preventing corrosion was the Greenkote plates with passivation. The galvanized option had the roughest coating layer, and it was the most reactive in the salt water solution. This makes it non-ideal for the dynamic rail environment because the increased friction of the plate could damage the supports, especially during extreme temperatures that would cause the rail to expand or contract. Greenkote with Phosphate and ArmorGalv also provided increased corrosion prevention with a smooth, strong finish, but it had more rust on the surface area than the Greenkote with ELU passivation. The ArmorGalv sample had more rust on the surface area than the Greenkote samples. This may not be a weakness in the ArmorGalv process;rather, it likely was the result of this particular sample not having the added protection of a colored coating.

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.

Kinematical Analysis and Simulation of High-Speed Plate Carrying Manipulator Based on Matlab

In order to construct the more effective kinematics method for industry, by taking a high-speed plate handing robot as an example, the structure and parameters of the robot linkages are analyzed, and the standard Denavit-Hartenberg method is applied to establish the coordinates and the kinematic equation of the linkages. Depending on the graphics and matrix calculation ability of Matlab especially including the Robotics Toolbox, the handling robot has been modeled and its kinematics, inverse kinematics and the trajectory planning have been simulated. Therefore, the correctness of kinematic equation has been verified, meanwhile, the functions of displacement, velocity, acceleration and trajectory of all the joints are also obtained. In a further step, this has verified the validity of all the structure parameters and pro- vided a reliable basis for the theoretical research on the design, dynamics analysis and trajectory planning of the ma- nipulator control system.

EXPERIMENT AND SIMULATION FOR THICK-PLATE BENDINGBY HIGH FREQUENCY INDUCTOR

In order to produce thick plates with complicated curved surface, a prototype bending machine by the use of high frequency inductor was developed. The bending mechanism is based on the localized stresses which are induced from the difference of temperature in thickness by the high frequency inductor. The operating speed and the thickness of plate were examined from the experiment, and the variation of the temperature was measured. Finite element analysis was carried out in the second part based on the experimentally obtained temperature distribution. The so-called Mindlin plate element was used in order to perform the simulation efficiently. The strategy to produce such curved surface in the practical process was discussed and further perspective of the production system was described. (Edited author abstract) 6 Refs.

Effects of honing treatment on AIP-TiN and TiAlN coated end-mill for high speed machining

The objective of this work is to compare the tool performance of TiN and TiA1N coated carbides end-mills deposited by an arc ion plating （ALP） method, using honing treatment to polish the cutting edge surface sleekly. The curve of surface roughness versus honing time showed a rapid improvement initially and thereafter became steady, manifesting a saturation effect. The optimal honing time related to surface roughness was determined to be approximately 20 s. As the surface roughness increased, the critical loads reduced. At an average surface roughness （Ra） of 0.028 p.m, the highest critical loads of TiN and TiAlN coating layers were 98 and 114 N, respectively. Tool performances of uncoated and coated tools were conducted under high speed machining （HSM） of AISI D2 cold-worked die steel （62 HRC）. Consequently, the TiAlN coated end-mill using honing treatment showed excellent tool life under HSM conditions.

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.

Settlement Characteristics of Cement Fly-Ash GravelPile-Plate Composite Foundation of High-Speed Railway

Field tests on settlement characteristics were carried out on the cement fly-ash gravel （CFG） pile-plate composite foundation on Beijing-Xuzhou section of Beijing-Shanghai high-speed railway. The settlements of the piles and the soil between pries were measured and analyzed. The results show that the settlement-time dependency experienced three phases： rapid development phase, stable development phase and stable phase. Therefore, surcharge preloading was necessary to reduce the settlement after construction. The finite element software Plaxis was used to calculate the deformations of the pile top and the soil between piles at the embankment center, as well as the settlements of CFG pile reinforcement area and the underlying stratum under surcharge preloading. The calculation results and the field test results were compared and analyzed. Both the results show that the settlement of the composite foundation mainly occured in underlying stratum. The settlement characteristics of pile-plate composite foundation under high embankment are also concluded.

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.

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.

高速履带车辆横摆运动响应特性分析与试验验证

为研究高速履带车辆操纵特性,奠定高速电驱动履带车辆的操纵稳定性评价及控制的基础,建立了高速履带车辆非线性转向动力学模型及2自由度线性转向动力学模型,并对模型进行试验验证。利用2自由度线性模型推导了高速履带车辆横摆运动传递函数,基于此进行了高速履带车辆横摆运动时域和频域响应特性分析,提出履带车辆稳态横摆角速度增益及临界阻尼车速的定义。研究结果表明:履带车辆稳态横摆角速度增益均小于1,履带车辆具有不足转向特性;履带车辆系统阻尼比在1左右;当车速小于临界阻尼车速时,车辆系统为过阻尼系统,横摆角速度响应的上升时间在0.2 s内;当车速等于临界阻尼车速时,车辆系统为临界阻尼系统,横摆角速度响应的上升时间大于10 s;当车速大于临界阻尼车速时,车辆系统为欠阻尼系统,横摆角速度响应的上升时间迅速减小至2~3 s。

基于频域分析的高速列车侧风倾覆机理

侧风作用下列车的动态环境以轮轨相互作用为主向,以空气动力作用为主演变,列车的侧风倾覆行为成为威胁列车行车安全性的主要诱因.首先,采用精细化车-轨耦合模型开展列车侧风倾覆的频域特性分析,以明确侧风倾覆响应对列车模型的敏感性;基于考虑模态特性的频域分析框架,推导脉动风及轨道不平顺与列车倾覆动力响应间的传递函数,结合相应参数进行分析,以直观揭示列车的侧风倾覆机理.结果表明:列车倾覆行为受绕车体下心侧滚模态和车体沉浮模态控制影响,其风荷载影响要明显大于轨道不平顺;在轨道不平顺激励下,第一阶模态贡献主要由轨向不平顺引起,第二阶模态贡献主要由高低不平顺引起,在脉动风荷载激励下,其顺风向脉动风分量起主要贡献;车速、风速和风向角的增大都会引起列车动力响应的增大,进而降低列车安全运营时的最大允许风速;失效概率的增大会降低动力响应的极值,进而提高安全运营风速.

磷化镓晶体的声光特性及应用

磷化镓晶体具有高声光优值、高声速和低声衰减系数,是制作声光调制器的优良材料之一。对磷化镓晶体的关键声光参数进行了测试评估,并基于磷化镓晶体研制了光脉冲上升时间为6.6 ns的高速光纤声光调制器,移频频率为1.5 GHz的高频空间声光调制器,以及3 dB移频带宽125 MHz的大带宽光纤声光调制器。

基于轴箱高频振动的车轮不圆辨识方法研究

为实现对高速列车车轮高阶不圆的实时检测,研究了轴箱高频振动与车轮不圆的频谱特征和映射关系,采用频域积分方法对车轮不圆的幅值和阶次进行辨识.首先,通过静态测试和台架试验,研究我国高速铁路车轮多边形、钢轨波磨和轨道模态的表现形式;其次,通过高速列车长期服役性能跟踪试验,掌握转向架轴箱振动的时频特征和演化规律;最后,以现场出现车轮20阶多边形的车辆为研究对象,提出基于频域积分的车轮不圆阶次和幅值辨识方法.研究结果表明:CRTS-Ⅱ型轨道板钢轨三阶弯曲频率为592 Hz;列车以300 km/h运行时,20阶车轮多边形和136 mm波长钢轨波磨的响应频率分别为580 Hz和613 Hz;钢轨模态、车轮多边形以及钢轨波磨的振动主频较为集中,轴箱高频振动幅值随车速和镟后里程的增大而增大;采用加速度频域积分方法,从理论上可实现对车轮不圆幅值和阶次的辨识;基于线路实测轴箱加速度的20阶车轮多边形辨识结果与静态测试值相对误差不超过5%.

动车组车体模态频率贡献度和改进方法研究

针对高速列车车体低阶模态频率提升过程中,传统灵敏度分析方法存在的设计变量繁多和难以识别出优先改进部件的难题,提出了一种新颖的车体模态频率贡献度评估与结构改进方法。重点分析了铝合金车体板件厚度与模态频率的灵敏度关系,并在此基础上提出了部件模态贡献度概念,推导和建立了描述部件模态频率灵敏度与贡献度的数学模型。通过对动车组车体中各铝型材的贡献度进行计算,详细分析了车顶、侧墙、底架等六大部件对前3阶模态频率的影响。研究揭示,部件模态贡献度表示了局部部件对整体结构模态影响的大小,呈现了灵敏度无法显示的全局量化指标。车顶部件对车体前3阶模态的贡献度最大,侧墙和底架居中,底架边梁、端墙和牵枕缓最小。车顶与侧墙、侧墙与底架连接处的型材对低阶模态产生了显著影响。通过增加内外板厚度并适度降低内部筋板厚度的策略,可提升1阶垂弯模态频率。应用所提出的方法,基于车体54个部件模态贡献度,成功甄别出车顶和连接处型材等优先优化部件并进行了改进,实现了1阶垂弯模态频率从9.5 Hz提升至10.2 Hz,同时将车体重量增加控制在43 kg以内,验证了方法的有效性和高效性,为车体模态频率的优化提供了清晰的路径。该方法具有广泛的适用性,可推广应用于其他领域的结构模态改进。