High-Precision Wideband Phase-Derived Velocity Measurement for Micro-Motion Extraction

A phase-derived velocity measurement method is proposed in a wideband coherent system,based on a precise echo model considering the inner pulse Doppler effect caused by fast moving targets.The Cramer-Rao low band of velocity measurement precision is deduced,demonstrating the high precision of the proposed method.Simulations and out-field experiments further validate the effectiveness of the proposed method in high-precision measurement and micro-motion extraction for targets with weak reflection intensity.Compared with the long-time integration approaches for velocity measurement,the phase-derived method is easy to implement and meets the requirement for high data rate,which makes it suitable for micro-motion feature extraction in wideband systems.

MOTION VELOCITY SMOOTH LINK IN HIGH SPEED MACHINING

To deal with over-shooting and gouging in high speed machining, a novel approach for velocity smooth link is proposed. Considering discrete tool path, cubic spline curve fitting is used to find dangerous points, and according to spatial geometric properties of tool path and the kinematics theory, maximum optimal velocities at dangerous points are obtained. Based on method of velocity control characteristics stored in control system, a fast algorithm for velocity smooth link is analyzed and formulated. On-line implementation results show that the proposed approach makes velocity changing more smoothly compared with traditional velocity control methods and improves productivity greatly.

Motion stability of high-speed maglev systems in consideration of aerodynamic effects: a study of a single magnetic suspension system

In this study, the intrinsic mechanism of aerodynamic effects on the motion stability of a high-speed maglev system was investigated. The concept of a critical speed for maglev vehicles considering the aerodynamic effect is proposed. The study was carried out based on a single magnetic suspension system, which is convenient for proposing relevant concepts and obtaining explicit expressions. This study shows that the motion stability of the suspension system is closely related to the vehicle speed when aerodynamic effects are considered. With increases of the vehicle speed, the stability behavior of the system changes. At a certain vehicle speed,the stability of the system reaches a critical state, followed by instability. The speed corresponding to the critical state is the critical speed. Analysis reveals that when the system reaches the critical state, it takes two forms, with two critical speeds, and thus two expressions for the critical speed are obtained. The conditions of the existence of the critical speed were determined, and the effects of the control parameters and the lift coefficient on the critical speed were analyzed by numerical analysis. The results show that the first critical speed appears when the aerodynamic force is upward,and the second critical speed appears when the aerodynamic force is downward. Moreover, both critical speeds decrease with the increase of the lift coefficient.

Near-fault directivity pulse-like ground motion effect on high-speed railway bridge

The vehicle-track-bridge(VTB)element was used to investigate how a high-speed railway bridge reacted when it was subjected to near-fault directivity pulse-like ground motions.Based on the PEER NAG Strong Ground Motion Database,the spatial analysis model of a vehicle-bridge system was developed,the VTB element was derived to simulate the interaction of train and bridge,and the elasto-plastic seismic responses of the bridge were calculated.The calculation results show that girder and pier top displacement,and bending moment of the pier base increase subjected to near-fault directivity pulse-like ground motion compared to far-field earthquakes,and the greater deformation responses in near-fault shaking are associated with fewer reversed cycles of loading.The hysteretic characteristics of the pier subjected to a near-fault directivity pulse-like earthquake should be explicitly expressed as the bending moment-rotation relationship of the pier base,which is characterized by the centrally strengthened hysteretic cycles at some point of the loading time-history curve.The results show that there is an amplification of the vertical deflection in the girder's mid-span owing to the high vertical ground motion.In light of these findings,the effect of the vertical ground motion should be used to adjust the unconservative amplification constant 2/3 of the vertical-to-horizontal peak ground motion ratio in the seismic design of bridge.

Dynamic Analysis of High-Speed Boat Motion Simulator by a Novel 3-DoF Parallel Mechanism with Prismatic Actuators Based on Seakeeping Trial

In this study,we focused on a novel parallel mechanism for utilizing the motion simulator of a high-speed boat(HSB).First,we expressed the real behavior of the HSB based on a seakeeping trial.For this purpose,we recorded the motion parameters of the HSB by gyroscope and accelerometer sensors,while using a special data acquisition technique.Additionally,a Chebychev highpass filter was applied as a noise filter to the accelerometer sensor.Then,a novel 3 degrees of freedom(DoF)parallel mechanism(1T2R)with prismatic actuators is proposed and analyses were performed on its inverse kinematics,velocity,and acceleration.Finally,the inverse dynamic analysis is presented by the principle of virtual work,and the validation of the analytical equations was compared by the ADAMS simulation software package.Additionally,according to the recorded experimental data of the HSB,the feasibility of the proposed novel parallel mechanism motion simulator of the HSB,as well as the necessity of using of the washout filters,was explored.

ACCURATE DETECTION OF HIGH-SPEED MULTI-TARGET VIDEO SEQUENCES MOTION REGIONS BASED ON RECONSTRUCTED BACKGROUND DIFFERENCE

The paper first discusses shortcomings of classical adjacent-frame difference. Sec ondly, based on the image energy and high order statistic(HOS) theory, background reconstruction constraints are setup. Under the help of block-processing technology, background is reconstructed quickly. Finally, background difference is used to detect motion regions instead of adjacent frame difference. The DSP based platform tests indicate the background can be recovered losslessly in about one second, and moving regions are not influenced by moving target speeds. The algorithm has important usage both in theory and applications.

High-precision method of detecting motion straightness based on plane mirror interference

A high-precision method of detecting motion straightness was proposed based on the prin- ciple of plane mirror interference after analyzing the motion straightness error of a linear stage. De- tection experiments were carried out and the motion straightness errors were separated by the linear regression method. Finally, linear measurement uncertainty of the detection method was estimated. The results showed that this detection method was simple and accurate, and was especially suitable for precision detection of motion straightness error in the small travel movement of ultra-precision machining.

Theoretical Study on Non-transmission High Efficient Parallel Camber Grinding Machine

Be directed against the development trend of modern CNC grinding machine towards high precision and high efficiency, some general weaknesses of existing camber grinding machine are analyzed in detail. In order to develop new type CNC camber grinding machine that can grind complex die, and genuinely achieved accurate feed and high efficient grinding, a new type camber grinding machine is put forward, called non-transmission virtual-shaft CNC camber grinding machine. Its feed system is a parallel mechanism that is directly driven by linear step motor. Therefore, traditional transmission types, such as the ball lead-screw mechanisms, the gears, the hydraulic transmission system, etc. are cancelled, and the feed system of new type CNC camber grinding machine can truly possess non-creep, good accuracy retentiveness a wide range of feed-speed change, high kinematical accuracy and positioning precision, etc. In order to realize that the cutting motion is provided with high grinding speed, step-less speed variation, high rotational accuracy, good dynamic performance, and non-transmission, the driving technology of hollow rotor motor is applied to drive the spindle of new type grinding machine,thus leading to the elimination of the transmission parts of cutting motion. The principle structure model of new type camber grinding machine is advanced. The selection, control gist and driving circuit line of the linear step motor are expounded. The main technology characteristics and application advantages of non-transmission virtual-shaft CNC camber grinding machine are introduced.

Motion visualization and estimation for flapping wing systems

Studies of fluid-structure interactions associated with flexible structures such as flapping wings require the capture and quantification of large motions of bodies that may be opaque. As a case study, motion capture of a free flying Manduca sexta, also known as hawkmoth, is considered by using three synchronized high-speed cameras. A solid finite element (FE) representation is used as a reference body and successive snapshots in time of the displacement fields are reconstructed via an optimization procedure. One of the original aspects of this work is the formulation of an objective function and the use of shadow matching and strain-energy regularization. With this objective function, the authors penalize the projection differences between silhouettes of the captured images and the FE representation of the deformed body. The process and procedures undertaken to go from high-speed videography to motion estimation are discussed, and snapshots of representative results are presented. Finally, the captured free-flight motion is also characterized and quantified.

Experimental Simulation and Analysis of the Yarn Motion Track in a Hairiness-Reducing Nozzle

A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number,to study the yarn motion track in hairiness-reducing nozzle.High-speed photography was used to observe the yarn instantaneous motion state in the nozzle.The results show that the yarn motion track seems to be a cylindrical helix which is close to inner wall in the twisting chamber and kept the same with different technical parameters,such as diameter of the twisting chamber and jet pressure in orifices.According to simulation results and reasonable simplification,the motion track equation and the rotational equation of the yarn could be derived.The velocity of the swirl and hairiness is faster than that of the yarn balloon,so there is enough time for hairiness to be wrapped into the main body of yarn and hence the hairiness is reduced.

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。

水下无人航行器高速航行下的运动特性及仿真控制研究

水下无人航行器具有水下活动范围大、机动性好优点,主要用于大范围地形地貌勘探,水下高速长航程航行时,水下航行器运动特性和姿态控制是研究重点。本文建立水下航行器垂直面航行运动模型,分析高速航行下的运动特性。为保证高速航行高效稳定,提出PID方法控制纵倾和滑模方法控制深度的组合控制策略。通过仿真试验,开展高速航行运动仿真研究。研究结果表明,在高速航行下,水下航行器会产生一定纵倾,且随着航速增加,纵倾影响会越大,高速状态放大了水下航行器外形上下轻微不对称的特性,诱导产生的垂向水动力及力矩增大,进而引起纵倾;在高速航行条件下,水下航行器能稳定保持定深度长距离航行,控制策略具有很好的适用性。

空心弹高速入水机理及特性数值模拟研究

为分析空心弹高速入水的机理及其特性,基于雷诺时均Navier-Stokes方程、VOF(volume of fluid)多相流模型、Realizable k-ε湍流模型,引入Schnerr-Sauer空化模型和重叠网格技术对空心弹高速入水进行数值模拟研究,获得了通孔孔径和头部形状对空心弹的空化特性、空泡形态和入水运动特性的影响规律。研究显示数值计算的空泡形态和入水速度、位移曲线与实验结果吻合较好,验证了数值模拟方法的可行性。结果表明:当通孔孔径不同时,通孔孔径越大,空化现象越明显,通孔射流越长,但对空泡半径的影响不大;通孔孔径越小,空泡闭合时间越早,与水面碰撞产生的阻力系数峰值越高,空心弹入水稳定后其阻力系数也越大;无量纲直径在0.575~0.600之间时,空心弹的运动最为稳定。当头部锥角不同时,头部锥角越大,空泡直径越大,空化现象出现得越晚,但空化生成的速度更快;随着头部锥角的增大,阻力系数变大,空心弹的速度衰减变快,相同时间运动的距离较短;头部锥角越大,俯仰角的变化越小,空心弹的运动越稳定。

一种比例换向阀先导级用高速开关阀运动特性分析

为研究一种用于比例换向阀先导级的高速开关阀运动特性,通过编写UDF程序控制流体力、弹簧力和电磁力共同作用下的阀芯运动;通过动网格技术实现阀的流固耦合仿真,并获取阀芯精确的运动情况以及瞬态流场的变化。结果表明:编写的UDF程序能够精确地模拟实际工作时的阀芯运动状态,获得阀的开启时间为1.8 ms。该研究方法能够获得高速开关阀精确的运动特性,为高速开关阀产品的优化提供指导。

高速精密压力机多杆机构弹性动力学研究

高速精密压力机机构运动精度是冲压产品质量关键影响因素,机构弹性动力学研究对提高冲压机构运动精度有重要意义。以高速压力机双滑块六杆机构为研究对象,基于弹性动力学理论建立多杆机构弹性变形分析数学模型,提出考虑弹性变形冲压机构运动精度求解方法。以梁单元作为等效单元,综合考虑了横向位移、纵向位移、转角位移以及曲率的影响,建立机构运动微分方程,利用实振型叠加法进行求解。最终确定构件弹性变形及其导致的下死点精度误差,同时获得弹性构件最大动应力。分析结果表明弹性变形是精密冲压机械运动精度主要影响因素,高速精密压力机弹性动力学研究对运动精度设计具有理论指导意义。

淬火态30CrNi2MoVA高强度钢高速铣削参数优化研究

运用三因素三水平的正交试验方案对淬火态30CrNi2MoVA高强度钢进行高速精密铣削实验,获得了铣削参数对于铣削力的影响规律以及高速切削机理;根据各铣削力实验结果建立指数型回归模型,并对其进行显著性分析;对铣削合力线性模型进行方差分析得到铣削参数对于铣削合力变化的显著性分析结果,显著性大小依次为轴向切削深度、每齿进给量、切削速度;应用田口法与极差分析法相结合,以铣削合力进行单目标的参数优化,获得了大致相同的最优铣削参数组合;通过计算证明了田口预测方法预测值与实验值的一致性。

集成式轴承状态实时监测系统设计

为了满足航空发动机高速轴承状态实时监测的迫切需求,研制了一种基于以太网传输的集成式多通道同步在线监测系统。系统集成了电涡流传感器前置器和IEPE加速度支持单元,满足了35~4400 MHz范围内感应探头激励和IEPE供电需求,实现转速和振动传感信号高精度采集,并通过硬件抗混叠滤波和滑动滤波算法抑制轴承的杂散干扰。试验结果表明:系统在0~9000 r/min范围内保持架转速测量误差小于2 r/min,相对误差小于0.1%,振动灵敏度为200 mV/g,实时性能好,实现轴承状态的实时在线监测。

高速精密数控轧辊磨床中心架液压润滑系统的设计及其优化

中心架作为轧辊磨床的重要部分之一,起着支承和卸荷的重要作用。文中以某型高速精密数控轧辊磨床为依据,设计了其中心架的液压润滑系统,基于AMESim软件建立该液压润滑系统模型并进行仿真计算,分析得出侧瓦和底瓦静压固定活塞直径、静压固定活塞杆径及调速阀设定流量对系统中静压腔油压特性具有显著影响。采用遗传算法对影响系统静压腔油压特性的3个参数进行优化,结果表明:优化后的中心架液压润滑系统中,静压腔油压稳定性得到了显著的改善,达到稳定状态的时间明显缩短,验证了优化方案的合理性,其结果可为轧辊磨床液压润滑系统的设计及优化研究提供理论依据。

基于FPGA的雷达/GPS数据融合存储系统设计

现阶段高速测绘成像雷达回波信号数据量大、传输速率快,完整的实时存储高精度GPS信息的雷达数据是测绘成像的关键,面对此类系统要求满足高精度、数据融合编帧、大容量、高速度、全程准确存储等一系列问题,该文设计一种高速雷达融合数据接口控制存储系统。该系统主控模块以FPGA作为主控芯片,接收10路30 MB/s的LVDS数据和1路GPS串口数据,并进行组合编帧,打包数据通过以太网发送给上位机,最后通过LabView上位机软件将数据存储在硬盘内。最终通过试验验证,可以完整无误地将融合采编数据存储在硬盘内。