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英文翻译外文文献翻译352外文翻译--对振动侦查和测量的一种实用方法——物理原则和侦查技术
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英文翻译外文文献翻译352外文翻译--对振动侦查和测量的一种实用方法——物理原则和侦查技术,机械毕业设计英文翻译
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附录 1 中文译文 对振动侦查和测量的一种实用方法 物理原则和侦查技术 作者： John Wilson, 动态顾问 , LLC 这篇 论文 论述 振动物理 、 弹簧质量系统 的动力学 ， 阻止 、 位移、速度和加速度 ， 并且查出和测量这些物产传感器的操作原理。 振动摆动由振动或作用在机构的力的变化引起振动的摆动。 振动行动反向。由于我们将看到，这振荡可能是在经过若干时间有价值的周期连续不断的或者可能间断的。 它可能是周期性或非周期性 , 那就是说，它可能或者可能不呈现一规则的周期的重复。 动摆的本质取决于力量的本质驾驶它和结构被驾驶 。 运动是一个矢量，呈现一个方向和一个量。振动的方向通常被描述依据一些独立的坐标系（典型地笛卡尔的或者直角的）其运动的方向被称作坐标轴。这些坐标轴的正交座标系的原点是被任意地被定义在一些适当的的位置。 机构的多数振动的响应可以用当做单自由度弹簧质量系统模型，并且许多振动传感器使用他们的一个弹簧质量系统当做转导机构的机械部分。除外形尺寸之外，一个弹簧质量系统可以用弹簧的刚度 K，和质量 M，或者质量的重量 W等性能参数来阿描述。这些特征不仅决定来这机构的静态特性（静变位 d），而且决定来它的动态特性。 如果 g 是重力的 加速度 : F = MA W = Mg K = F/d = W/d d = F/K = W/K = Mg/K 一个弹簧质量系统 的 动力学 一个弹簧质量系统的动力学的可以被体系的特性在自由振动及有效 的 振动表示。 自由振动 自由振动被那情况情形哪里那弹簧是偏斜于是释放以及允许到自由地摇摆。例子包括一个跳板、一个跳簧跨接管，以及一个摆或摇摆偏斜以及留某事给自由地振动处理。 两个 特征特性应该注意。 第一、阻尼在那体系表示原因的那振幅的那振荡到减少将来。 那包括市区及郊区的那阻尼、那更快的那振 幅随时间减小。（只要弹性极限不是超过），那频率或时期的那振荡无关原始的大小原始的偏转的的。 那自然地发生频率的那自由振动被呼叫那自然频率 fn: nts受迫振动 受迫振动当能量是连续地被加到那弹簧质量系统由申请振动的力在一些受迫振动频率时的情 形 ff. 两个二例子连续地推一个孩子上去一个摇摆和一失衡旋转电机元件。如果提供充足的能量到克服那阻尼是，那动作就会延续长达那激励延续之久。受迫振动可以取自励的或外部地激发振动的形式。自激振动发生在激发力是产生在或上去那悬挂质量的时候；外部地激发振动发生在激发力作用于弹簧的时候。这是那情形、例如：、当那基础对此那弹簧附属于是移动时。 传导能力 当基础正在振动，而且力整个弹簧被传输到中止的质量时候 ,质量的动作将会是来自基础的动作差积。 我们将会认为基础的动作是输入， I, 和质量的动作响应 , R. 比率半 径 /我被定义为传输度 ,Tr: Tr = R/I 共振 在力频率好低于体系的固有频率， R I, 和 Tr 1。 由于作用力的频率接近那固有频率，由于共振，所以传递率增加。共振是在机械系统中的量的存储。在力频率接近那固有频率、能量是存储和积聚、导致增加响应振幅。阻尼也增加由于增加响应振幅、然而，并且最后那能量为阻尼所吸收、每一周期、等于能量增加由激振力，并且平衡状态到达。我们发现当 ff fn.时最大传递率发生，这个情况被称作共振。 隔振 如果激振力频率超过 fn， R降低。当 ff = 1.414 fn, R = I 或 Tr = 1时，在比较高的频率 R 0.1英寸，到使他们成为现实的。 一束对准在一个反射面上光束在强度或者角度的的变化能被使用当做一距离指示从震源的角度之上方面。如果该探测仪器是足够快的，变化的距离也可以被测定。最灵敏的、准确的和精密的测定距离或位移的光学装置是激光干扰仪。利用这个仪器，一束反射激光束间杂有原来的入射光束。这由相位差形成的干涉图样可以测量位移下至 1 MHz 震动加速度仪。 最现代的 PR传感器是用单个碎片硅制造的。一般说来，造型整体传感器的优点从一个单一的材料块是更好的稳定性，较少热量的失配在部分之间，并且较高的可靠性。欠阻尼的 PR 加速度仪容易不比 PE 装置高低不平。 单一晶体矽能有特别的降伏强度 ,特别地以高的应变率，但是它是然而一个脆的事物。 矽的内磨擦非常低，因此，谐振扩大可能是比较高的超过对于 PE 传动器。 两者的这些功能成为它的比 较易脆性的因素 , 虽然如果适当地设计而且安装他们被规律性用测量震动很好上述的 100,000 g 。他们通常有较宽的频带宽度胜于 PE 传动器 (比较相似实物大小范围的模型 ), 连同较小的非线性，零的移位和磁滞特性。 因为他们有直流电反应，他们在将要产生长期计量时才使用。 在 PR 加速度仪的一个典型独石矽可察元件中 ,1 毫米角尺矽芯片合并整个的弹簧，质量和四个臂的 PR 应变计桥总成。 感知器经由各向异性的浸蚀和显微机械加工技术是利用一个单一晶体矽做成的。 应变计被本来平的矽一个杂物的图案造形。 沟流的后 来浸蚀释放规并且同时地定义如只是最初厚度的矽区域的质量。 桥路可以由放置并联补偿电阻或者级数用任何这木头支架平衡了，做相配的或者这阻抗值及价值的变化用温度的修正。补偿是一种艺术 ; 因为 PR 传动器能有非线性特性 , 用激发来自它被制作或校正的条件差积操作它是不受劝告的。 举例来说， PR 灵敏度只有大约成比例激发 , 通常是一个固定的电压或 , 在一些外壳 , 定流中有一些性能利益。因为热的性能将会大体上和激发电压的变化 ,在灵敏度和激发之间没有一个精密的比例。 另外的预防在处理电压驱动的桥方面 , 特别地有低的电阻 那些 , 是确认桥拿适当的激发。 输入熔断丝的级数电阻担任一个分压器。注意这输入导线有低电阻，或者那一六线的大小是制成的（用读出线在这桥梁趋于允许这激励被校准）所以这桥梁获得这特有的激励。 恒定电流激励工作没有这些用串联电阻的问题。然而， PR 传动器通常被补整傲慢的固定电压激发并且不可能用定流给被需要的性能。 PR 桥的平衡是它的健康最敏感衡量 , 而且通常是传动器的总不确定度的占优势的功能。 平衡 ,有时叫做了偏向 , 零偏位 , 或 ZMO( 零可测量产量 ,和 0 g 的产量 ),能被通常是热的特性或在内部或外 面地诱导了感知器的应变变化的一些效应改变。传动器外壳设计尝试隔离来自外面的应变 , 像是热的暂态，基本的应变或固定转矩的感知器。 内部的应变变化 ,举例来说，环氧基树脂蠕升 ,容易成为长期的不稳定的因素。所有的这些比较对于锕加倍的装置因为他们在直流者加倍传动器的较宽频带中更时常发生，通常低周波效应对直流传动器是更重要的。 一些 PR设计，尤其是高灵敏度传感器，是设计有阻尼延长频带和过量程的能力。 阻尼系数 0.7 是考虑过的理想。 如此的设计时常使用油或一些其他的粘滞液体。 二个特性听写技术是有用的只有在相对地低 周波 : 阻尼军队成比例流过速度 ,而且适当的流量速度被藉由用大的位移泵流体达到。 这是在那敏感的传动器的一个快乐的巧合他们在低的加速度频率操作位移足够大哪里。粘滞阻尼可以有效地除去共振放大率，延长过量程的能力，并且比加倍有效带宽。然而，因为缓冲液的粘性是一温度的强函数，传感器的有用的温度范围实质上是受限制的。 nts可变电容 VC传感器是通常平行板空隙电容器其中的设计运动垂直于电镀层。在一些设计中屏从一个边缘被把建成悬臂式，因此，动作实际上是转动 ; 其他的屏在圆周的周围被支援 , 当做在一个弹网中。 由于加速 度的在 VC 元件的电容方面的改变被一对目前检波器感觉皈依者进入电压产量之内的变化。许多 VC传感器是微电机一致地在一间隔一点点微米厚的趋于允许空气减震中间插进的腐蚀剂硅片。事实是空气粘度变化由只有一点百分比在一宽的工作温度范围提供一频率响应比是可完成的用油阻尼 PR设计更坚固的上方。 在一 VC加速度记录器中，一个高频振荡器给 VC元件提供必要的激励。电容变化被这检流器检测。输出电压与电容变化成正比因此，趋于加速度。这结合的超程停留在这间隔可以提高高低不平的在这灵敏的方向，虽然阻力趋于过量程的在横向必须信任单独地 靠这悬浮的力量，按现状对全部的其他的传感器设计没有超程停止来说是正确的。一些设计可以继续存在极其大加速度过量程的工况是 1000倍的测量范围。 一台典型微电机 VC加速度记录器的传感器是由三硅元件胶合到一起形成的密封的装配。元件中的二个是空气介质，平行板积蓄器的电极。 中央的元件用化学被蚀刻造形被薄又易曲手指中止的一个硬的中央质量。 阻尼特性被位于质量之上的孔气体流量控制。 VC传感器可以提供好传感器的特色测定类型论述初期的中许多：大的过量程的，直流电响应，低阻抗的输出端，和单纯的外部信号工况。缺点是成本并且 以那在板子上调节的增加错综度按规定尺寸制作关联。 同时 , 高频电容检波电路被用，而且一些高频载波通常在产量信号上出现。它是通常连达到（即， 1000倍）比输出信号的频率高三数量级也不被注意到。 伺服系统（力平衡） 虽然伺服加速度计是主要地使用在惯性制导系统，但是一些他们的工作特性必然使他们在一定的振动应用中是合乎需要的。所有的在先前被描述的加速度仪类型是开环装置在哪一产量由于可察元件的挠曲被直接地读。在倍力器中 -控制 , 或闭合回路，加速度仪 , 挠曲信号被用当一个身体上地驱动或再平衡返回平衡位的质量电路的 反馈。 倍力器加速度仪制造业者建议仰赖位移 (也就是 ,晶体和 piezoresistive 元件的绷皮操作 ) 时常生产一个产量信号的开环仪器引起非线性错误。在闭合回路中设计 ,内部的位移被试验过的质量电再平衡保持极端小 ,将非线性减到最少。 除此之外，闭合回路设计被说有较高的精确度胜于开环打字。 然而，期间精确度的定义改变。以传感器制造商校核。伺服加速度计可以使两个基本几何结构的其中任何一个：线的（例如，扩音器）和摆动的（仪表的测量机构）。 振动的几何结构是商业的设计中应用最广泛的。直到最近，伺服机构是主要地以 电磁原则为基础。力通常被藉由在一个磁场之前经过在质量上的线圈驾驶电流提供。 在和一个电磁的再平衡机构的下垂倍力器加速度仪中，下垂的质量发展对试验过的质量和那应用的加速度的产品转矩比例项。 质量的动作被位感知器 ( 典型地电容的感知器 ) 发现 , 送一个误差讯号给伺服系统。 误差讯号引起对产量的倍力器放大器对转矩电动机的一个反馈电流 ,发展相等在量中到来自下垂的质量加速度产生的转矩一个反对转矩。输出端是激励电流它本身（或者交叉一输出端电阻器）作用的，与偏转环传感器相似，跟外加力成比例因此趋于加速度。 和开环传感器 的高低不平的弹簧元件相反，再平衡压入回路加速度记录器的箱体中主要地有关电的并且只有当有动力提供时存在。当能实行的和大多数的阻nts尼被提供透过电子学的时候，弹簧在敏感的方向中是如易坏的。不像独自地仰赖可察元件 (s) 的特性其他的直流 - 响应加速度仪，它是闭合回路设计的反馈电子学控制使存偏见稳定性。因此伺服加速度计倾向于提供较少零点飘移，是我们在振动测量中使用他们的主要的理由。一般说来，他们有一个 0.1 in., to make them practical. The change in intensity or angle of a light beam directed onto a reflective surface can be used as an indication of its distance from the source. If the detection apparatus is fast enough, changes of distance can be detected as well. The most sensitive, accurate, and precise optical device for measuring distance or displacement is the laser interferometer. With this apparatus, a reflected laser beam is mixed with the original incident beam. The interference patterns formed by the phase differences can measure displacement down to 1 MHz in some PR shock accelerometers. Most contemporary PR sensors are manufactured from a single piece of silicon. In general, the advantages of sculpting the whole sensor from one homogeneous block of material are better stability, less thermal mismatch between parts, and higher reliability. Underdamped PR accelerometers tend to be less rugged than PE devices. Single-crystal silicon can have extraordinary yield strength, particularly with high strain rates, but it is a brittle material nonetheless. Internal friction in silicon is very low, so resonance amplification can be higher than for PE transducers. Both these features contribute to its comparative fragility, although if properly designed and installed they are used with regularity to measure shocks well above 100,000 g. They generally have wider bandwidths than PE transducers (comparing models of similar full-scale range), as well as smaller nonlinearities, zero shifting, and hysteresis characteristics. Because they have DC response, they are used when long-duration measurements are to be made. In a typical monolithic silicon sensing element of a PR accelerometer, the 1 mm square silicon chip incorporates the entire spring, mass, and four-arm PR strain gauge bridge assembly. The sensor is made from a single-crystal silicon by means of anisotropic etching and micromachining techniques. Strain gauges are formed by a pattern of dopant in the originally flat silicon. Subsequent etching of channels frees the gauges and simultaneously defines the masses as simply regions of silicon of original thickness. The bridge circuit can be balanced by placing compensation resistor(s) in parallel or series with any of the legs, correcting for the matching of either the resistance values and/or the change of the values with temperature. Compensation is an art; because the PR transducer can have nonlinear characteristics, it is inadvisable to operate it with excitation different from the conditions under which it was manufactured or calibrated. For example, PR sensitivity is only approximately proportional to excitation, which is usually a constant voltage or, in some cases, constant current, which has some performance advantages. Because thermal performance will in general change with excitation voltage, there is not a precise proportionality between sensitivity and excitation. Another precaution in dealing with voltage-driven bridges, particularly those with low resistance, is to verify that the bridge gets the proper excitation. The series resistance of the input lead wires acts as a voltage divider. Take care that the input lead wires have low resistance, or that a six-wire measurement be made (with sense lines at the bridge to allow the excitation to be adjusted) so the bridge gets the proper excitation. Constant current excitation does not have this problem with series resistance. However, PR transducers are generally compensated assuming constant voltage ntsexcitation and might not give the desired performance with constant current. The balance of the PR bridge is its most sensitive measure of health, and is usually the dominant feature in the total uncertainty of the transducer. The balance, sometimes called bias, zero offset, or ZMO (zero measurand output, the output with 0 g), can be changed by several effects that are usually thermal characteristics or internally or externally induced shifts in strains in the sensors. Transducer case designs attempt to isolate the sensors from external strains such as thermal transients, base strain, or mounting torque. Internal strain changes, e.g., epoxy creep, tend to contribute to long-term instabilities. All these generally low-frequency effects are more important for DC transducers than for AC-coupled devices because they occur more often in the wider frequency band of the DC-coupled transducer. Some PR designs, particularly high-sensitivity transducers, are designed with damping to extend frequency range and overrange capability. Damping coefficients of 0.7 are considered ideal. Such designs often use oil or some other viscous fluid. Two characteristics dictate that the technique is useful only at relatively low frequencies: damping forces are proportional to flow velocity, and adequate flow velocity is attained by pumping the fluid with large displacements. This is a happy coincidence for sensitive transducers in that they operate at the low acceleration frequencies where displacements are adequately large. Viscous damping can effectively eliminate resonance amplification, extend the overrange capability, and more than double the useful bandwidth. However, because the viscosity of the damping fluid is a strong function of temperature, the useful temperature range of the transducer is substantially limited. Variable Capacitance. VC transducers are usually designed as parallel-plate air gap capacitors in which motion is perpendicular to the plates. In some designs the plate is cantilevered from one edge, so motion is actually rotation; other plates are supported around the periphery, as in a trampoline. Changes in capacitance of the VC elements due to acceleration are sensed by a pair of current detectors that convert the changes into voltage output. Many VC sensors are micromachined as a sandwich of anisotropically etched silicon wafers with a gap only a few microns thick to allow air damping. The fact that air viscosity changes by just a few percent over a wide operating temperature range provides a frequency response more stable than is achievable with oil-damped PR designs. In a VC accelerometer, a high-frequency oscillator provides the necessary excitation for the VC elements. Changes in capacitance are sensed by the current detector. Output voltage is proportional to capacitance changes, and, therefore, to acceleration. The incorporation of overtravel stops in the gap can enhance ruggedness in the sensitive direction, although resistance to overrange in transverse directions must rely solely on the strength of the suspension, as is true of all other transducer designs without overtravel stops. Some designs can survive ntsextremely high acceleration overrange conditions-as much as 1000 full -scale range . The sensor of a typical micromachined VC accelerometer is constructed of three silicon elements bonded together to form a hermetically sealed assembly. Two of the elements are the electrodes of an air dielectric, parallel-plate capacitor. The middle element is chemically etched to form a rigid central mass suspended by thin, flexible fingers. Damping characteristics are controlled by gas flow in the orifices located on the mass. VC sensors can provide many of the best features of the transducer types discussed earlier: large overrange, DC response, low-impedance output, and simple external signal conditioning. Disadvantages are the cost and size associated with the increased complexity of the onboard conditioning. Also, high-frequency capacitance detection circuits are used, and some of the high-frequency carrier usually appears on the output signal. It is generally not even noticed, being up to three orders of magnitude (i.e., 1000 ) higher in frequency than the output signals. Servo (Force Balance). Although servo accelerometers are used predominantly in inertial guidance systems, some of their performance characteristics make them desirable in certain vibration applications. All the accelerometer types described previously are open-loop devices in which the output due to deflection of the sensing element is read directly. In servo-controlled, or closed-loop, accelerometers, the deflection signal is used as feedback in a circuit that physically drives or rebalances the mass back to the equilibrium position. Servo accelerometer manufacturers suggest that open-loop instruments that rely on displacement (i.e., straining of crystals and piezoresistive elements) to produce an output signal often cause nonlinearity errors. In closed-loop designs, internal displacements are kept extremely small by electrical rebalancing of the proof mass, minimizing nonlinearity. In addition, closed-loop designs are said to have higher accuracy than open-loop types. However, definition of the term accuracy varies. Check with the sensor manufacturer. Servo accelerometers can take either of two basic geometries: linear (e.g., loudspeaker) and pendulous (meter movement). Pendulous geometry is most widely used in commercial designs. Until recently, the servo mechanism was primarily based on electromagnetic principles. Force is usually provided by driving current through coils on the mass in the presence of a magnetic field. In the pendulous servo accelerometer with an electromagnetic rebalancing mechanism, the pendulous mass develops a torque proportional to the product of the proof mass and the applied acceleration. Motion of the mass is detected by the position sensors (typically capacitive sensors), which send an error signal to the servo system. The error signal triggers the servo amplifier to output a ntsfeedback current to the torque motor, which develops an opposing torque equal in magnitude to the acceleration-generated torque from the pendulous mass. Output is the applied drive current itself (or across an output resistor), which, analogous to the deflection in the open-loop transducers, is proportional to the applied force and therefore to the acceleration. In contrast to the rugged spring elements of the open-loop transducers, the rebalancing force in the case of the closed-loop accelerometer is primarily electrical and exists only when power is provided. The springs are as flimsy in the sensitive direction as feasible and most damping is provided through the electronics. Unlike other DC-response accelerometers whose bias stability depends solely on the charact
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