基于比例电磁铁的小力值发生装置应用研究

介绍了一种基于比例电磁铁的小力值发生装置。针对测力平台的动态标定要求，通过电路仿真分析得到比例电磁铁电压与电流的响应关系曲线，设计出由光电耦合器组成的开关电路来实现一定的激励电压信号，驱动比例电磁铁实现所需梯形脉冲力。实验取得的梯形脉冲力与理想梯形脉冲力的相对误差≤5％，表明使用该装置对测试系统进行动态标定是可行的。     

可控式梯形脉冲信号发生装置的研制

为对某特殊工程测试系统进行动态标定,研制出一种可控式梯形脉冲信号发生装置.可控参数包括:梯形上升段、下降段、水平段时间及其幅值.装置可以依据设置模拟出各种形状的梯形波,其性能符合GB9317-88标准,具有操作简单、可控、性价比高等优点.与传统的"静标动用"标定方法相比,应用此装置进行动态标定更能准确评价测试系统的动态特性.     

多维力传感器的动态标定研究

提出了一套对六维力传感器经行标定的系统,用于动态载荷情况下六维力传感器动态标定。该系统以lab VIEW为软件系统,以高精度伺服电机为精确动力源,以高精度砝码作为标准质量,通过伺服电机带动标准质量做匀速圆周运动产生标准动态力。配合有限元分析软件PATRAN对设计工装的强度、刚度及固有频率的分析。实现了在特定频率范围内的传感器的精确动态标定。实验结果表明系统对六维力传感器的标定是合理可靠的。     

脉冲风洞天平动态标定加载系统设计

由于脉冲风洞试验时间短,冲击载荷大,试验过程有强烈振动,影响天平的测力精度,因此,需要对天平模型进行动态标定.针对风洞天平的动态标定所需要的高频率、重载荷稳定的动态力,设计了一套动态力加载系统.机械结构运用电动机带动丝杠副的结构设计,控制部分采取嵌入式PC,在系统内虚拟出软PLC.传感器检测模块和电动机驱动模块等通过EtherCAT总线与软PLC通讯,实现硬件的模块化集成.经试验测试,该系统能满足风洞天平的测试要求.     

基于电声脉冲法的空间电荷直接测量仪的研制

研制了基于电声脉冲法(PEA)直接测量聚合物中空间电荷分布的测试装置.首先分析了普通电声脉冲法测量空间电荷的原理和测试系统传递函数,得到了一种基于测试系统传递函数倒数的陡脉冲输入波形,以消除由系统硬件带宽限制而引起的过冲;根据一种线脉冲发生器原理研制的脉冲发生器能产生脉宽8 ns的陡脉冲.通过对压电传感器引出线的特殊设计,减少了因接触气隙而导致的声脉冲色散.最后通过对测试系统的实验和标定,表明该装置能有效去除过冲,并得到样本巾的实际电荷密度值,并以此装置实测了聚酰正胺膜巾空间电荷的分布.     

基于正弦力加载的力传感器动态标定技术研究

针对国内现有动态标定装置精度不高、重复性较差的问题,提出了一种基于正弦力加载的新型力传感器动态标定方法;对该标定方法做了详细介绍,阐述了该标定系统中最关键的正弦机构的工作原理;利用基于最小二乘的曲线拟合法对力传感器和位移传感器输出正弦电压的幅值进行了求解,并以此为基础,依据相应公式在LabVIEW中设计了数据处理程序,实现了对力传感器动态灵敏度的精确求解;搭建了实验平台,对Interface 1010AJ型力传感器进行了1 Hz~5 Hz的动态标定,并分析了实验结果。研究结果表明,该新型的力传感器动态标定系统具有良好的精度,其误差在1.5%内。     

底部钻柱近钻头动态力测量及声传输方法

为研究随钻测井时底部钻柱近钻头动力学特性,设计直梁应变片式测力传感器,研制一种基于虚拟仪器平台的模拟钻柱动态力无线测量装置,用于模拟钻柱旋转过程中轴向力、侧向力和转矩的多线程检测。在此基础上,比较井下数据传输方法,以纵波为传输载体,设计模拟钻柱声传输装置,对动态力数据进行脉冲时延和OOK(On-off keying)调制,沿管轴方向对有限长模拟钻柱施加纵向激励,进行模拟钻柱信道动态力测试信号的声传输试验。结果表明,系统在实验室内实现动态力数据经时延脉冲OOK信号调制后沿模拟钻柱信道的低频声波传输,为近钻头传感器测量数据的低频声传输系统的应用提供理论与试验依据。     

机车车辆轮轨作用力测试系统研究

轮轨作用力的大小可反映列车运行的安全性与平稳性,测试系统采用单点测试的方法测试轮轨垂向力与轮轨横向力。主要研究轮轨作用力测试系统的原理与设计,该系统主要设计过程包括组桥方案设计、标定装置设计与标定加压系统设计三个方面。通过实验室与铁路现场对该测试系统进行可行性验证,表明该轮轨作用力测试系统具备试验可行性,可以投入现场使用。     

给水泵轴向力监控系统的研制

为避免大型旋转机由于轴向力过大所引起的机器损坏，保证生产的自动化和连续化，研制了一套用于TP-4113-P5-1.2型碳黑洗涤塔给水泵的轴向力在线监控装置，该装置包括测力弹性元件和轴向力智能监控仪表两部分。采用有限元法对弹性元件进行了优化设计并对弹性元件做了动态标定，采用PC机和单片机两级控制系统进行轴向力在线监控。     

离心泵轴向力测试系统的设计

离心泵轴向力是影响设备安全运行的重要因素,准确测试其轴向力对泵组安全管理运行及故障诊断具有重要的意义.为实现泵组轴向力的精确测量,本文设计了轴向力测试系统,采用正交试验和有限元分析方法得到了内置式轴向力测试弹性元件最优结构,结合SRSS3-1应力在线检测仪设计了测试电路系统和标定装置,并进行了静态标定及误差分析,得到了F-ε标定曲线,同时测试了多台离心泵在变工况下的轴向力,证明了该测试系统具有较高的稳定性和可靠性,表明本文具有较高的经济使用价值和理论意义,为工程机械的轴向力测量及研究提供了参考。     

Design, calibration and error analysis of a piezoelectric thrust dynamometer for small thrust liquid pulsed rocket engines

Small thrust liquid pulsed rocket engines operating in pulsed mode have gained a good reputation in attitude control applications for their potential reliability and efficiency. However, the pulsed characteristic creates a difficult measurement problem. In this paper, a novel thrust dynamometer with high natural frequency is developed for accurately measuring the pulsed thrust. It consists of two shear mode piezoelectric quartz crystal sensors and an integral shell. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. Stiffness equations of the shell which are used to estimate the amount of interference are derived. The thrust dynamometer is calibrated both statically and dynamically. Static calibration uncertainty is evaluated. A trapezoidal impulse force is used to simulate the pulsed thrust for further characterizing the dynamic measurement performance of the thrust dynamometer. An evaluation algorithm of dynamic error is presented and used to evaluate the results of the dynamic simulation. The results show the thrust dynamometer has high sensitivity and natural frequency, good linearity and repeatability, and excellent dynamic performance. It can accurately trace trapezoidal thrust signal of 50 Hz without waveform distortion.     

Influence of current impulse on machining characteristics in EDM

Electrical discharge machining (EDM) is a machining process transforming electric energy into thermal energy to remove materials. The current impulse is a very important factor for machining characteristics of EDM. A series of experiments were performed to investigate the influence of current impulse on machining characteristics. The features of current impulse have initial current, current rising slope and impulse pattern. The used patterns of current impulse included rectangular current impulse, trapezoidal current impulse and the 1^st order current impulse. The machining characteristics are associated with relative wear ratio (RWR) and material removal rate (MRR). Experimental showed that using trapezoidal current impulse with small initial current or little current rising slope reduced relative wear ratio and material removal rate as well. However, larger relative wear ratio was obtained for workpiece of tungsten carbide when current rising slope was too little. Using the 1^st order current impulse with 20 μs current rising time can improve relative wear ratio about 30 % while remain material removal rate the same as rectangular current impulse for tungsten carbide.     

不同螺纹下无损伤微型机器人的驱动研究

研究了一种利用螺旋旋转产生牵引力的无损伤微型机器人的驱动机构。详细分析计算了微型机器人在采用矩形、梯形和三角形圆柱螺旋时所产生的轴向摩擦牵引力和动压粘液膜承载量。通过对比三种螺纹下微型机器人的运动特性参数,得出微型机器人采用矩形螺纹最为合理。     

Thrust stand for low-thrust liquid pulsed rocket engines

A thrust stand is developed for measuring the pulsed thrust generated by low-thrust liquid pulsed rocket engines. It mainly consists of a thrust dynamometer, a base frame, a connecting frame, and a data acquisition and processing system. The thrust dynamometer assembled with shear mode piezoelectric quartz sensors is developed as the core component of the thrust stand. It adopts integral shell structure. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. The thrust is transferred to the sensors by means of static friction forces of fitting surfaces. The sensors could produce an amount of charges which are proportional to the thrust to be measured. The thrust stand is calibrated both statically and dynamically. The in situ static calibration is performed using a standard force sensor. The dynamic calibration is carried out using pendulum-typed steel ball impact technique. Typical thrust pulse is simulated by a trapezoidal impulse force. The results show that the thrust stand has a sensitivity of 25.832 mV/N, a linearity error of 0.24% FSO, and a repeatability error of 0.23% FSO. The first natural frequency of the thrust stand is 1245 Hz. The thrust stand can accurately measure thrust waveform of each firing, which is used for fine control of on-orbit vehicles in the thrust range of 5-20 N with pulse frequency of 50 Hz.     

Biomechanical effect of in-line skating wrist guards on the prevention of wrist fracture

A biomechanical study was conducted in this study to investigate if in-line skating wrist guards can effectively reduce the impact forces so as to protect the wrist from fracture. The forearm specimens with and without wrist guards were dropped using a specially designed sled to simulate the impact on the wrist while falling. A force plate was used to measure the total impact force on the dropping weight whereas a load cell was attached to the proximal end of the specimen and used to quantify the impact transmitted through the wrist joint. From the nondestructive tests, mean peak force measured from a force plate showed no difference between the guarded and unguarded groups whereas mean impulse of the guarded group was significantly greater than that of the unguarded group (p<0.01). Comparing the peak force and impulse measured from the load cell, the peak force of the guarded group was significantly less than that of the unguarded group (p<0.001), while the impulse values were similar. When the specimens were dropped from a higher position (2.5 ft vs. 1 ft), all unguarded specimens had severe wrist fractures whereas fracture was found in three out of 5 guarded specimens. Comparison of mean peak forces and impulses showed a significant difference between the guarded and unguarded groups only in the mean impulse measured from the force plate. These results suggest that the wrist guard may protect the wrist by attenuating the peak force transmitted to radius and ulnar although it may not be effective when the wrist is subjected to an impact sufficiently large to cause fractures.     

Development of an improved method for investigating the frictional properties of lubricants under transient EHD conditions

In the design and evaluation of mechanical system performance it is important to know the frictional qualities of the lubricant. Without correct numerical treatment of the lubricant during simulations of large systems, e.g., drive trains in trucks and buses, the results will, to a large extent, be inaccurate. However, obtaining detailed information places demands on the test equipment as the events are both transient and highly loaded. Under quasi‐static conditions, forces are measured with force transducers, but in elasto‐hydrodynamically lubricated conjunctions, where pressures are so high that the surrounding surfaces deform elastically, this cannot be done without permanently damaging the equipment. The conceptual design of the test equipment must therefore incorporate the measuring process in transient conditions (loading‐unloading times of 200–500 μs) being performed in real time, and allow extreme pressures of up to 3 GPa without component destruction. One way to obtain accurate friction data successfully is to apply a concentrated force pulse to a non‐instrumented surface and to measure the response from that pulse elsewhere. The development of a measurement technique, the Lulea ball and bar apparatus, which utilises wave propagation theory, is presented in this paper. An oblique impact on a robust end plate on a rod was used to generate both non‐dispersive compression waves and dispersive flexural waves. The normal force created by the axial wave was measured using strain gauges, while the transverse force was derived from the fast Fourier transforms of two lateral acceleration histories, using dynamic beam theory. The relation between the normal and tangential force histories showed the frictional properties at the impact as a function of time. A variety of lubricants was also studied at Hertzian pressures of up to 2.5 GPa, and the development of the method and results are presented. Experiments indicate that different lubricants exhibit different frictional properties and that the resolution in the test equipment is sufficient to indicate this.     

基于实测冲击响应的转子碰摩力方向识别方法

提出了基于实测冲击响应的转子碰摩故障诊断特征提取方法.实验表明,该方法能够克服已有方法的缺点,可以准确提取信号中的冲击响应成分,且易于实际应用.在此基础上,提出了确定转子碰摩方向即静子碰摩位置的方法,该方法将转子轴心轨迹中的冲击响应成分投影到各初始相位不同的旋转坐标系中,进而以初始相位为参数,以投影能量最大化为目标进行寻优,从而确定碰摩力方向.并通过实验验证了方法的可行性.     

脉冲激振枪

Impulse exciting gun is a new type of impulse exciter developed by authors. When it works, the shock head in the gun impacts the object to be measured at a certain speed, so that an impulse. Force is exerted on the object in fraction of a second. At the same time, the force transaucer with the shock head converts the impulse force into electrical signal for output. Thus the impulse excition for the objects to be measured as well as dynamic measurement have been completed just once. Impulss exciting gun involves three main parts called adjusting mechanism, localizing mechanism and returning mechanism. Adjusting mechanism can easily change rigidity of impulse head and the initial velocity of impact, in order to control contact continuance (force impulse breadth) and maximal presure Fm.. (force impulse peak value) between the 'shock head and the object. The function of localizing mechanism is to control exerted force point and its direction more accuratly. And setting up a returning mechanism is to avoid touching again between the shock head and the object after they collide with each other. Outward appearance of the gun is in figure 1. As for main technique indexes of impulse exciting gun see table 1 and figue 4-3.Impulse exciting gun is not only of simple structure, but also reliable and convenient to use. Furthermore, force impulse breadth and its peak value and exerted force point and its direction may be accuratly controlled when used. Those special advantages of the gun over impulse exciters now available make it come into vise in some scientific research departments and colleges.     

动压气浮马达轴承间隙测量设备

动压气浮陀螺马达轴承间隙尺寸是决定其运转性能的重要指标。为提高轴承间隙测量的精度和自动化程度,并实现快速批量测量,研制了一台动压气浮陀螺马达轴承间隙自动测量设备。采用外部加力方式,使转子体与定子产生相对位移,从而将内部气膜间隙转化为外部微位移。设备整体结构采用模块化设计理念,包括夹持模块、自动施力模块和位移测量模块。夹持摸块实现被测动压马达定子在两轴端的固定,采用柔性支撑方式有利于保护被测件和保证施加力的平顺性;自动施力模块主要由三维精密位移平台集成三轴测力传感器构成,测量时转子体与力传感器通过夹指连接,位移平台使转子体与定子产生相对位移,三轴测力传感器则实现施加力的精确控制和定子的调中心控制;测量模块由二维精密位移平台集成双电感测头构成,基于相对测量原理实现微小位移测量。实验表明:设备测量精度在0.3μm以内。该设备可以实现外力的可控连续加载,适用于批量测量。     

An alternative method for the measurement of the mechanical impulse of a vertically directed blast

An alternative method for the measurement of the total mechanical impulse of a vertically directed blast due to an explosive charge is presented. The method differs from apparatus that employ a vertically displaced mass (similar in principle to the ballistic pendulum) in that a relatively compact spring-damper system is employed to constrain the movement of the mass. The mechanical impulse is determined by integrating, with respect to time, the net force applied to the spring-damper system. The details of an explosive impulse measuring instrument rated to 12 kN s are presented.