Instantaneous rotation speed measurement and error analysis for variable speed hydraulic system

In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.

APPROACH OF IMPROVING PRECISION IN ULTRASONIC DOPPLER BLOODSTREAM SPEED MEASUREMENT BY CHAOS-BASED FREQUENCY DETECTING

It is critical for cerebral vascular disease diagnosis through Doppler to detect the maximum and the minimum of the carotid blood flow speed accurately. A kind of Duffing system under an external periodic power with dump is introduced in the letter, numerical analysis is carried out by four-order Runge-Kutta method. An oscillator array is designed according to the frequency of the ultrasonic wave. When the external signals are inputted, computational algorithm is used to scan the array in turn and analyze the result, and the frequency can be determined. Based on the methods above, detecting the carotid blood flow speed accurately is realized. The Signal-to-Noise Ratio (SNR) of-20.23dB is obtained by the result of experiments. In conclusion, the SNR has been improved and the precision of the measured bloodstream speed has been increased, which can be 0.069% to 0.13%.

A new method for high precsion instantaneous speedmeasurement of hydraulic system

The instantaneous speed of a hydraulic system contains a wealth of operational information,and its accurate extraction is the basis for condition monitoring and fault diagnosis.In order to solve the problem of high hardware requirement for instantaneous speed measurement based on data acquisition card,a new method of high precision measurement is proposed.In this method,the time-displacement information of each tooth is obtained from the pulsed square wave signal of the gear disk collected by magnetoelectric sensors.The time-displacement curve is interpolated by the cubic spline interpolation method,and then the instantaneous speed is calculated by the five-point digital differential formula.The experimental results show that the method improves the speed measurement resolution and reduces the quantization error.The high precision instantaneous speed signal can also be acquired by hardware devices with less teeth and low sampling frequency.The related research results provide a theoretical basis and a method for improving the accuracy of instantaneous speed measurement.

Information fusion of train speed and distance measurements based on fuzzy adaptive Kalman filter algorithm

The measurement accuracy of speed and distance in high speed train directly affects the control precision and driving efficiency of train control system. To improve the capability of train self control, a combined speed measurement and positioning method based on speed sensor and radar which is assisted by global positioning system（GPS） is proposed to improve the accuracy of measurement and reduce the dependence on the ground equipment. In consideration of the fact that the filtering precision of Kalman filter will decrease when the statistical characteristics are changing, this paper uses fuzzy comprehensive evaluation method to evaluate the sub filter, and information distribution coefficients are dynamically adjusted according to filtering reliability, which can improve the fusion accuracy and fault tolerance of the system. The sub filter is required to carry on the covariance shaping adaptive filtering when it is in the suboptimal state. The adjustment factor of error covariance is obtained according to the minimized cost function, which can improve the matching degree between the measured residual variance and the system recursive residual. The simulation results show that the improved filter algorithm can track the changes of the system effectively, enhance the filtering accuracy significantly, and improve the measurement accuracies of train speed and distance.

Research on the measurement of belt speed by video in coal mine based on improved template matching algorithm

In order to improve the intelligence of video monitoring system of belt and make up the deficiency of higher failure rate and bad real-time performance in the traditional systems of measurement of belt speed, according to the fact that the light of coal mine is uneven, the strength of light changes greatly, the direction of belt movement is constant, and the position of camera was fixed, various algorithms of speed measurement by video were studied, and algorithm for template matching based on sum of absolute differences （SAD） and correlation coefficient was proposed and improved, besides, the tracking of feature regions was realized. Then, a camera calibration method using the invariance of the cross-ratio was adopted and the real-time measurement of belt speed by the hardware platform based on DM642 was realized. Finally, experiment results show that this method not only has advantages of high precision and strong anti-jamming capability but also can real-time reflect the changes of belt speed, so it has a comprehensive applicability.

A New Approach to Speed Measurement of Rotating Objects by Laser Interference Method

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High-speed railway channel measurements and characterizations: a review

Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.

Quantum speed limit of the double quantum dot in pure dephasing environment under measurement

The quantum speed limit(QSL)of the double quantum dot(DQD)system has been theoretically investigated by adopting the detection of the quantum point contact(QPC)in the pure dephasing environment.The Mandelstam–Tamm(MT)type of the QSL bound which is based on the trace distance has been extended to the DQD system for calculating the shortest evolving time.The increase of decoherence rate can weaken the capacity for potential speedup(CPS)and delay the evolving process due to the frequently measurement localizing the electron in the DQD system.The system needs longer time to evolve to the target state as the enhancement of dephasing rate,because the strong interaction between pure dephasing environment and the DQD system could vary the oscillation of the electron.Increasing the dephasing rate can sharp the QSL bound,but the decoherence rate would weaken the former effect and vice versa.Moreover,the CPS would be raised by increasing the energy displacement,while the enhancement of the coupling strength between two quantum dots can diminish it.It is interesting that there has an inflection point,when the coupling strength is less than the value of the point,the increasing effect of the CPS from the energy displacement is dominant,otherwise the decreasing tendency of the CPS is determined by the coupling strength and suppress the action of the energy displacement if the coupling strength is greater than the point.Our results provide theoretical reference for studying the QSL time in a semiconductor device affected by numerous factors.

Application of Fiber in Blood Speed Measurement

There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.

Speed Measurement Feasibility by Eddy Current Effect in the High-Speed MFL Testing

It is known that eddy current effect has a great influence on magnetic flux leakage testing(MFL).Usually,contacttype encoder wheels are used to measure MFL testing speed to evaluate the effect and further compensate testing signals.This speed measurement method is complicated,and inevitable abrasion and occasional slippage will reduce the measurement accuracy.In order to solve this problem,based on eddy current effect due to the relative movement,a speed measurement method is proposed,which is contactless and simple.In the high-speed MFL testing,eddy current induced in the specimen will cause an obvious modification to the applied field.This modified field,which is measured by Hall sensor,can be utilized to reflect the moving speed.Firstly,the measurement principle is illustrated based on Faraday’s law.Then,dynamic finite element simulations are conducted to investigate the modified magnetic field distribution.Finally,laboratory experiments are performed to validate the feasibility of the proposed method.The results show that Bmz(r1)and Bmx(r2)have a linear relation with moving speed,which could be used as an alternative measurement parameter.

Measurement and Spatio-temporal Distribution of Urbanization Development Quality of Urban Agglomeration in China

Urbanization development quality(UDQ) of urban agglomeration(UA) is one of the important indexes to evaluate if the UA urbanization speed is reasonable,if the population urbanization process is sound,if the economic urbanization process is efficient,if the social urbanization process is harmonious and fair,which is generally composed of three parts,including economic urbanization development quality,social urbanization development quality and spa-tial urbanization security quality.With the research of evolution rules of UDQ,through the analysis on the interactive coordination relation between UDQ and urbanization level,the paper proposes three dimensional index ball and stan-dard value of comprehensive measures of UDQ,which is composed of three categories of indexes.By introducing At-kinson model,this paper constructs the sub-element measure model and segmental measure model of UDQ,and fur-ther makes an overall evaluation on the characteristic of UDQ of UAs in China.Results show that:1) UDQ of UAs lied at optimization and upgrading phase during 1995-2008 and the quality was low.Population urbanization level did not reflect the UDQ of UAs;2) the improving speed of the spatial urbanization security quality was higher than the so-cial urbanization development quality,and the improving speed of economic urbanization development quality was the lowest;3) the coordination between UDQ and urbanization level was not so good;4) there was a weak correlation re-lation between UDQ and UA scale,and it was not true that the bigger the UA was,the better the UDQ was.

Self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration

A novel self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration is proposed to solve the problem of large disturbances to sediments of the in situ equipments already in existence. By using a hydraulic driving device, the system drives four acoustic probes into sediments at an even speed, and this decreases disturbances to sediments introduced by the penetration of acoustic probes. By means of the special design of the central control unit, the system can work full-automatically and the data are stored self-containedly, and this avoids the requirement of real-time remote controlling from the ship. Its operating water depth, measuring depth and measuring frequency is 500m, 1.0m and 30kHz respectively. A set of in situ sound speeds and attenuation coefficients of sediments are obtained at 40 stations using the system. The results confirm that the data obtained by the in situ sediment acoustic system are accurate and credible.

Study on Integral Expression in Measurement of Average Ion Velocity by Multi-Grid Probe

In order to improve the interference rejection performance in the measurement of average ion velocity by multi-grid probe, an integral expression is proposed. The integral expression, differing from other expressions for probe measurement, avoids the differential operation on the I-V characteristics of multi-grid probe measurement; and by this method, the ion average velocity can be figured out directly by the I-V characteristics of multi-grid probe measurement.

A beam position measurement system of fully digital signal processing at SSRF

This fully digital beam position measurement instrument is designed for beam position monitoring and machine research in Shanghai Synchrotron Radiation Facility. The signals received from four position-sensitive detectors are narrow pulses with a repetition rate up to 499.654 MHz and a pulse width of around 100 ps, and their dynamic range could vary over more than 40 dB in machine research. By the employment of the under-sampling technique based on high-speed high-resolution A/D conversion, all the processing procedure is performed fully by the digital signal processing algorithms integrated in one single Field Programmable Gate Array. This system functions well in the laboratory and commissioning tests, demonstrating a position resolution (at the turn by turn rate of 694 kHz) better than 7 μm over the input amplitude range of -40 dBm to 10 dBm which is well beyond the requirement.

The Quantitative Density Measurement of Unsteady Flow around the Projectile

Three-dimensional density measurement of unsteady flow field around a sphere is carried out in the ballistic range at Institute of Fluid Science, Tohoku University. Simultaneous multi-angle measurement system using twelve digital cameras is installed in the test chamber of the ballistic range to achieve the three-dimensional density measurement. The Colored-Grid Background Oriented Schlieren (CGBOS) technique using colored-grid background is utilized for the reconstruction of density. The Mach number of the sphere is set to 1.5. The short pulse LEDs to illuminate the backgrounds are also installed in the chamber to capture the unsteady flow field around a flying sphere. Three-dimensional density distribution around a sphere is successfully reconstructed.

Speed Profile as a Tool to Estimate Traffic Calming Measures Efficiency

TCMs （traffic calming measures） are commonly installed in order to reduce speeds and volumes of traffic to acceptable levels and, thus, improve traffic safety as well as environmental impact when designed appropriately as a corridor or aerial implementation with proper spacing. Hence in many previous studies, their impact was mainly evaluated in scope of average and 85th percentile speed reduction. This paper presents and appraises the efficiency of calming measures of various types used in the city of Bialystok, Poland in terms of their influence zone. The assessment is based on speed profiles derived from individual test rides conducted with test vehicle equipped with GPS （global positioning system） data logger to obtain vehicle trajectory data. Speed measurements were conducted in vicinity of most commonly installed calming measures such as speed cameras, raised pedestrian crossing, raised intersection, speed bumps and speed cushion. The results reveal great differences within analysed devices and the usefulness of speed profiles in evaluation of their effectiveness. Speed bumps, most frequently used device in practice due to their low cost installation and speed reduction effectiveness, demonstrate lowest usefulness when influence zone is considered.

Warhead fragments motion trajectories tracking and spatio-temporal distribution reconstruction method based on high-speed stereo photography

High speed photography technique is potentially the most effective way to measure the motion parameter of warhead fragment benefiting from its advantages of high accuracy,high resolution and high efficiency.However,it faces challenge in dense objects tracking and 3D trajectories reconstruction due to the characteristics of small size and dense distribution of fragment swarm.To address these challenges,this work presents a warhead fragments motion trajectories tracking and spatio-temporal distribution reconstruction method based on high-speed stereo photography.Firstly,background difference algorithm is utilized to extract the center and area of each fragment in the image sequence.Subsequently,a multi-object tracking(MOT)algorithm using Kalman filtering and Hungarian optimal assignment is developed to realize real-time and robust trajectories tracking of fragment swarm.To reconstruct 3D motion trajectories,a global stereo trajectories matching strategy is presented,which takes advantages of epipolar constraint and continuity constraint to correctly retrieve stereo correspondence followed by 3D trajectories refinement using polynomial fitting.Finally,the simulation and experimental results demonstrate that the proposed method can accurately track the motion trajectories and reconstruct the spatio-temporal distribution of 1.0×10^(3)fragments in a field of view(FOV)of 3.2 m×2.5 m,and the accuracy of the velocity estimation can achieve 98.6%.

Simultaneous measurement of distance and speed using frequency-modulated continuous-wave self-mixing interferometry and all-phase fast Fourier transform

In this work,we propose a method using frequency-modulated continuous-wave(FMCW)self-mixing interferometry(SMI)and all-phase fast Fourier transform(APFFT)for simultaneous measurement of speed and distance.APFFT offers superior accuracy in frequency determination by mitigating issues like the fence effect and spectrum leakage,contributing to the high-accuracy measurement for speed and distance.Both simulations and experiments have demonstrated relative errors at the levels of 10^(−4) and 10^(−3) for distance and speed measurements,respectively.Furthermore,factors impacting measurement performance have been discussed.The proposed method provides a high-performance and cost-effective solution for distance and speed measurements,applicable across scientific research and various industrial domains.

短定子磁浮列车基于悬浮间隙实现测速和定位的算法仿真及应用

短定子磁浮列车测速和定位技术实现方式与传统轮轨不同,目前有多种技术实现方式,但都需要在磁浮列车上设置测速和定位设备或系统,且与悬浮控制系统相互独立,但悬浮控制系统对速度信号和位置信号又有一定的依赖性。因此,设计了一种基于悬浮间隙实现测速和定位的算法,并通过仿真达到算法设计预期目的,最后通过编程将算法嵌入磁浮列车的悬浮控制系统硬件平台,实现测速和定位的算法应用,测速和定位信号完全集成于悬浮控制系统中,摆脱悬浮控制系统对外置测速定位系统的依赖,提升磁浮列车在轨道交通市场的竞争力。

Relationships between the sound speed ratio and physical properties of surface sediments in the South Yellow Sea

Building empirical equations is an effective way to link the acoustic and physical properties of sediments.These equations play an important role in the prediction of sediments sound speeds required in underwater acoustics.Although many empirical equations coupling acoustic and physical properties have been developed over the past few decades,further confirmation of their applicability by obtaining large amounts of data,especially for equations based on in situ acoustic measurement techniques,is required.A sediment acoustic survey in the South Yellow Sea from 2009 to 2010 revealed statistical relationships between the in situ sound speed and sediment physical properties.To improve the comparability of these relationships with existing empirical equations,the present study calculated the ratio of the in situ sediment sound speed to the bottom seawater sound speed,and established the relationships between the sound speed ratio and the mean grain size,density and porosity of the sediment.The sound speed of seawater at in situ measurement stations was calculated using a perennially averaged seawater sound speed map by an interpolation method.Moreover,empirical relations between the index of impedance and the sound speed and the physical properties were established.The results confirmed that the existing empirical equations between the in situ sound speed ratio and the density and porosity have general suitability for application.This study also considered that a multiple-parameter equation coupling the sound speed ratio to both the porosity and the mean grain size may be more useful for predicting the sound speed than an equation coupling the sound speed ratio to the mean grain size.