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传感器通信电子工程类外文文献翻译、中英文翻译、外文翻译

What is a smart sensor

One of the biggest advances in automation has been the development and spread of smart sensors. But what exactly is a "smart" sensor? Experts from six sensor manufacturers define this term.

A good working "smart sensor" definition comes from Tom Griffiths, product manager, Honeywell Industrial Measurement and Control. Smart sensors, he says, are "sensors and instrument packages that are microprocessor driven and include features such as communication capability and on-board diagnostics that provide information to a monitoring system and/or operator to increase operational efficiency and reduce maintenance costs."

No failure to communicate

"The benefit of the smart sensor," says Bill Black, controllers product manager at GE Fanuc Automation, "is the wealth of information that can be gathered from the process to reduce downtime and improve quality." David Edeal, Temposonics product manager, MTS Sensors, expands on that: "The basic premise of distributed intelligence," he says, is that "complete knowledge of a system, subsystem, or component's state at the right place and time enables the ability to make 'optimal' process control decisions."

Adds John Keating, product marketing manager for the Checker machine vision unit at Cognex, "For a (machine vision) sensor to really be 'smart,' it should not require the user to understand machine vision."

A smart sensor must communicate. "At the most basic level, an 'intelligent' sensor has the ability to communicate information beyond the basic feedback signals that are derived from its application." says

Edeal. This can be a HART signal superimposed on a standard 4-20 mA process output, a bus system, or wireless arrangement. A growing factor in this area is IEEE 1451, a family of smart transducer interface standards intended to give plug-and-play functionality to sensors from different makers.

Diagnose, program

Smart sensors can self-monitor for any aspect of their operation, including "photo eye dirty, out of tolerance, or failed switch," says GE Fanuc's Black. Add to this, says Helge Hornis, intelligent systems manager, Pepperl+Fuchs, "coil monitoring functions, target out of range, or target too close." It may also compensate for changes in operating conditions. "A 'smart' sensor," says Dan Armentrout, strategic creative director, Omron Electronics LLC, "must monitor itself and its surroundings and then make a decision to compensate for the changes automatically or alert someone for needed attention."

Many smart sensors can be re-ranged in the field, offering "settable parameters that allow users to substitute several 'standard' sensors," says Hornis. "For example, typically sensors are ordered to be normally open (NO) or normally closed (NC). An intelligent sensor can be configured to be either one of these kinds."

Intelligent sensors have numerous advantages. As the cost of embedded computing power continues to decrease, "smart" devices will be used in more applications. Internal diagnostics alone can recover the investment quickly by helping avoid costly downtime.

Sensors: Getting into Position

As the saying goes, 'No matter where you go, there you are.' Still, most applications require a bit more precision and repeatability than that, so here's advice on how to select and locate position sensors.

The article contains online extra material.

What's the right position sensor for a particular application? It depends on required precision, repeatability, speed, budget, connectivity, conditions, and location, among other factors. You can bet that taking the right measurement is the first step to closing the loop on any successful application.

Sensor technologies that can detect position are nearly as diverse as applications in providing feedback for machine control and other uses. Spatial possibilities are linear, area, rotational, and

three-dimensional. In some applications, they're used in combination. Sensing elements are equally diverse.

Ken Brey, technical director, DMC Inc., a Chicago-based system integrator, outlined some the following position-sensing options.

Think digitally

For digital position feedback:

?Incremental encoders are supported by all motion controllers; come in rotary and linear varieties and in many resolutions; are simulated by many other devices; and require a homing process to reference the machine to a physical marker, and when power is turned off.

?Absolute encoders are natively supported by fewer motion controllers; can be used by all controllers that have sufficient available digital inputs; report a complete position within their

range (typically one revolution); and do not require homing.

?Resolvers are more immune to high-level noise in welding applications; come standard on some larger motors; simulate incremental encoders when used with appropriate servo amps; and can simulate absolute encoders with some servo amps.

?Dual-encoder feedback, generally under-used, is natively supported by most motion controllers; uses one encoder attached to the motor and another attached directly to the load; and is beneficial when the mechanical connection between motor and load is flexible or can slip.

?Vision systems , used widely for inspection, can also be used for position feedback. Such systems locate objects in multiple dimensions, typically X, Y, and rotation; frequently find parts on

a conveyor; and are increasing in speed and simplicity.

A metal rolling, stamping, and cut-off application provides an example of dual-encoder feedback use, Brey says. 'It required rapid and accurate indexing of material through a roll mill for a stamping process. The roll mill creates an inconsistent amount of material stretch and roller slip,' Brey explains.

'By using the encoder on the outgoing material as position feedback and the motor resolver as velocity feedback in a dual-loop configuration, the system was tuned stable and a single index move provided an accurate index length. It was much faster and more accurate than making a primary move, measuring the error, then having to make a second correction move,' he says.

Creative, economical

Sam Hammond, chief engineer, Innoventor, a St. Louis, MO-area system integrator, suggests that the application's purpose should guide selection of position sensors; measurements and feedback don't have to be complex. 'Creative implementations can provide simple, economical solutions,' he says. For instance, for sequencing, proximity sensors serve well in many instances.

Recent sensor applications include the AGV mentioned in lead image and the following.

?In a machine to apply the top seals to tea containers, proximity and through-beam sensors locate incoming packages. National Instruments vision system images are processed to find location of

a bar code on a pre-applied label, and then give appropriate motor

commands to achieve the desired position (rotation) setting to apply one of 125 label types. Two types of position sensors were used. One was a simple inductive proximity sensor, used to monitor machine status to ensure various motion components were in the right position for motion to occur. The camera also served as a position sensor, chosen because of its multi purpose use, feature location, and ability to read bar codes.

? A progressive-die stamping machine operates in closed loop. A linear output proximity sensor provides control feedback for optimizing die operation; a servo motor adjusts die position in the bend stage. A linear proximity sensor was selected to give a dimensional readout from the metal stamping operation; data are used in a closed-loop control system.

?Part inspection uses a laser distance measurement device to determine surface flatness. Sensor measures deviation in return beams, indicating different surface attributes to 10 microns in

size. An encoder wouldn't have worked because distance was more than

a meter. Laser measurement was the technology chosen because it had

very high spatial resolution, did not require surface contact, and had a very high distance resolution.

An automotive key and lock assembly system uses a proximity sensor for detecting a cap in the ready position. A laser profile sensor applied with a robot measures the key profile.

What to use, where?

Sensor manufacturers agree that matching advantages inherent to certain position sensing technologies can help various applications.

David Edeal, product marketing manager, MTS Sensors Div., says, for harsh factory automation environments, 'the most significant factors even above speed and accuracy in customer's minds are product durability and reliability. Therefore, products with inherently non-contact sensing technologies (inductive, magnetostrictive, laser, etc.) have a significant advantage over those that rely on physical contact (resistive, cable extension, etc.)'

Other important factors, Edeal says, are product range of use and application flexibility. 'In other words, technologies that can accommodate significant variations in stroke range, environmental conditions, and can provide a wide range of interface options are of great value to customers who would prefer to avoid sourcing a large variety of sensor types. All technologies are inherently limited with respect to these requirements, which is why there are so many options.'

Edeal suggest that higher cost of fitting some technologies to a certain application creates a limitation, such as with linear variable

differential transformers. 'For example, LVDTs with stroke lengths longer than 12 inches are rare because of the larger product envelope (about twice the stroke length) and higher material and manufacturing costs. On the other hand, magnetostrictive sensing technology has always required conditioning electronics. With the advent of microelectronics and the use of ASICs, we have progressed to a point where, today, a wide range of programmable output types (such as analog, encoder, and fieldbus) are available in the same compact package. Key for sensor manufacturers is to push the envelope to extend the range of use (advantages) while minimizing the limitations (disadvantages) of their technologies.'

Listen to your app

Different sensor types offer distinct advantages for various uses, agrees Tom Corbett, product manager, Pepperl+Fuchs. 'Sometimes the application itself is the deciding factor on which mode of sensing is required. For example, a machine surface or conveyor belt within the sensing area could mean the difference between using a standard diffused mode sensor, and using a diffused mode sensor with background suppression. While standard diffused mode models are not able to ignore such background objects, background suppression models evaluate light differently to differentiate between the target surface and background surfaces.'

Similarly, Corbett continues, 'a shiny target in a retro-reflective application may require use of a polarized retro-reflective model sensor. Whereas a standard retro-reflective sensor could falsely trigger when presented with a shiny target, a polarized retro-reflective model uses a polarizing filter to distinguish the shiny target from the reflector.'

MTS' Edeal says, 'Each technology has ideal applications, which tend to magnify its advantages and minimize its disadvantages. For example, in

the wood products industry, where high precision; varied stroke ranges; and immunity to high shock and vibration, electromagnetic interference, and temperature fluxuations are critical, magnetostrictive position sensors are the primary linear feedback option. Likewise, rotary optical encoders are an ideal fit for motor feedback because of their packaging, response speed, accuracy, durability, and noise immunity. When applied correctly, linear position sensors can help designers to ensure optimum machine productivity over the long haul.'

Thinking broadly first, then more narrowly, is often the best way to design sensors into a system. Edeal says, 'Sensor specifications should be developed by starting from the machine/system-level requirements and working back toward the subsystem, and finally component level. This is typically done, but what often happens is that some system-level specifications are not properly or completely translated back to component requirements (not that this is a trivial undertaking). For example, how machine operation might create unique or additional environmental challenges (temperature, vibration, etc.) may not be clear without in-depth analysis or past experience. This can result in an under-specified sensor in the worst situation or alternatively an over-specified product where conservative estimates are applied.'

Open or closed

Early in design, those involved need to decide if the architecture will be open-loop or closed-loop. Paul Ruland, product manager, AutomationDirect, says, 'Cost and performance are generally the two main criteria used to decide between open-loop or closed-loop control in electromechanical positioning systems. Open-loop controls, such as stepping systems, can often be extremely reliable and accurate when properly sized for the system. The burden of tuning a closed-loop system

prior to operation is not required here, which inherently makes it easy to apply. Both types can usually be controlled by the same motion controller. A NEMA 23 stepping motor with micro-stepping drive is now available for as little as $188, compared to an equivalent servo system at about $700.'

Edeal suggests, 'Control systems are created to automate processes and there are many good examples of high-performance control systems that require little if any feedback. However, where structural system (plant) or input (demand or disturbance) changes occur, feedback is necessary to manage unanticipated changes. On the process side, accuracy—both static and dynamic—is important for end product quality, and system stability and repeatability (robustness) are important for machine productivity.

'For example,' Edeal says, 'in a machining or injection molding application, the tool, mold or ram position feedback is critical to the final dimension of the fabricated part. With rare exceptions, dimensional accuracy of the part will never surpass that of the position sensor. Similarly, bandwidth (response speed) of the sensor may, along with response limitations of the actuators, limit production rates.

'Finally, a sensor that is only accurate over a narrow range of operating conditions will not be sufficient in these types of environments where high shock and vibration and dramatic temperature variations are common.'

The latest

What are the latest position sensing technologies to apply to manufacturing and machining processes and why?

Ruland says, 'Some of the latest developments in positioning technologies for manufacturing applications can be found in even the simplest of

devices, such as new lower-cost proximity switches. Many of these prox devices are now available for as little as $20 and in much smaller form factors, down to 3 mm diameter. Some specialty models are also available with increased response frequencies up to 20 kHz. Where mounting difficulties and cost of an encoder are sometimes impractical, proximity switches provide an attractive alternative; many position control applications can benefit from increased performance, smaller package size, and lower purchase price and installation cost.'

Corbett concurs. 'Photoelectric sensors are getting smaller, more durable, and flexible, and are packed with more standard features than ever before. Some new photoelectrics are about half the size of conventional cylindrical housings and feature welded housings compared with standard glued housings. Such features are very desirable in manufacturing and machining applications where space is critical and durability is a must. And more flexible connectivity and mounting options—side mount or snout mount are available from the same product—allow users to adapt a standard sensor to their machine, rather than vice versa.'

Another simple innovation, Corbett says, is use of highly visible,

360-degree LED that clearly display status information from any point of view. 'Such enhanced LED indicates overload and marginal excess gain, in addition to power and output. Such sensors offer adjustable sensitivity as standard, but are available with optional tamperproof housings to prevent unauthorized adjustments.'

Photoelectric Sensors

Photoelectric sensors are typically available in at least nine or more sensing modes, use two light sources, are encapsulated in three categories of package sizes, offer five or more sensing ranges, and can be purchased

in various combinations of mounting styles, outputs, and operating voltages. It creates a bewildering array of sensor possibilities and a catalog full of options.

This plethora of choices can be narrowed in two ways: The first has to do with the object being sensed. Second involves the sensor's environment.

Boxed in

The first question to ask is: What is the sensor supposed to detect? "Are we doing bottles? Or are we detecting cardboard boxes?" says Greg Knutson, a senior applications engineer with sensor manufacturer Banner Engineering.

Optical properties and physical distances will determine which sensing mode and what light source work best. In the case of uniformly colored boxes, for example, it might be possible to use an inexpensive diffuse sensor, which reflects light from the box.

The same solution, however, can't be used when the boxes are multicolored and thus differ in reflectivity. In that case, the best solution might be an opposed or retroreflective mode sensor. Here, the system works by blocking a beam. When a box is in position, the beam is interrupted and the box detected. Without transparent boxes, the technique should yield reliable results. Several sensors could gauge boxes of different heights.

Distance plays a role in selecting the light source, which can either be an LED or a laser. LED is less expensive. However, because LED are a more diffuse light source, they are better suited for shorter distances. A laser can be focused on a spot, yielding a beam that can reach long distances. Tight focus can also be important when small features have to

be sensed. If a small feature has to be spotted from several feet, it may be necessary to use a laser.

Laser sensors used to cost many times more than LED. That differential has dropped with the plummeting price of laser diodes. There's still a premium for using a laser, but it's not as large as in the past.

Environmental challenges

Operating environment is the other primary determining factor in choosing a sensor. Some industries, such food and automotive, tend to be messy, dangerous, or both. In the case of food processing, humidity can be high and a lot of fluids can be present. Automotive manufacturing sites that process engines and other components may include grit, lubricants, and coolants. In such situations, the sensor's environmental rating is of concern. If the sensor can't handle dirt, then it can't be used. Such considerations also impact the sensing range needed because it may be necessary to station the sensor out of harm's way and at a greater distance than would otherwise be desirable. Active alarming and notification may be useful if lens gets dirty and signal degrades.

Similar environmental issues apply to the sensor's size, which can range from smaller than a finger to something larger than an open hand. A smaller sensor can be more expensive than a larger one because it costs more to pack everything into a small space. Smaller sensors also have a smaller area to collect light and therefore tend to have less range and reduced optical performance. Those drawbacks have to be balanced against a smaller size being a better fit for the amount of physical space available.

Sensors used in semiconductor clean room equipment, for example, don't face harsh environmental conditions, but do have to operate in tight spaces. Sensing distances typically run a few inches, thus the sensors

tend to be small. They also often make use of fiber optics to bring light into and out of the area where changes are being detected.

Mounting, pricing

Another factor to consider is the mounting system. Frequently, sensors must be mechanically protected with shrouds and other means. Such mechanical and optical protection can cost more than the sensor itself—a consideration for the buying process. If vendors have flexible mounting systems and a protective mounting arrangement for sensors, the products could be easier to implement and last longer.

List prices for standard photoelectric sensors range from $50 or so to about $100.

Laser and specialty photoelectric sensors cost between $150 and $500. Features such as a low-grade housing, standard optical performance, and limited or no external adjustments characterize the lower ends of each category. The higher end will have a high-grade housing, such as stainless steel or aluminum, high optical performance, and be adjustable in terms of gain or allow timing and other options. Low-end products are suitable for general applications, while those at the higher end may offer application-specific operation at high speed, high temperature, or in explosive environments.

Finally, keep in mind that one sensing technology may not meet all of the needs of an application. And if needs change, a completely different sensor technology may be required. Having to switch to a new approach can be made simpler if a vendor offers multiple technologies in the same housing and mounting footprint, notes Ed Myers, product manager at sensor manufacturer Pepperl+Fuchs. If that's the case, then one technology can be more easily swapped out for another as needs change.

译文

什么是智能传感器

自动化领域所取得的一项最大进展就是智能传感器的发展与广泛使用。但究竟什么是“智能”传感器？下面，自6个传感器厂家的专家对这一术语进行了定义。

据Honeywell工业测量与控制部产品经理Tom Griffiths的定义：“一个良好的‘智能传感器’是由微处理器驱动的传感器与仪表套装，并且具有通信与板载诊断等功能，为监控系统和/或操作员提供相关信息，以提高工作效率及减少维护成本。”

无故障通信

“智能传感器的优势，”GE Fanuc自动化公司控制器产品经理Bill Black 说，“是能从过程中收集大量的信息以减少宕机时间及提高质量。”MTS传感器公司Temposonics（磁致伸缩位移传感器）产品经理David Edeal对此补充说：“分布式智能的基本前提是，在适当位置和时间拥有有关系统、子系统或组件的状态的全部知识，以进行‘最优的’过程控制决策。”

Cognex公司Checker机器视觉部产品营销经理John Keating继续补充说，“对于一种真正的‘智能’（机器视觉）传感器，它应该不需要使用者懂得机器视觉。”

智能传感器必须具备通信功能。“最起码，除了满足最基本应用的反馈信号，‘智能’传感器必须能传输其它信息。” Edeal表示。这可以是叠加在标准4-20 mA过程输出、总线系统或无线安排上的HART（可寻址远程传感器高速通道的开放通信协议）信号。该领域正在增长的因素是IEEE 1451——一系列旨在为不同厂家生产的传感器提供即插即用能力的智能传感器接口标准。

诊断与程序

智能传感器可对其运行的各个方面进行自监控，包括“摄像头的污浊，超容忍限或不能开关等，”GE Fanuc自动化公司的Black说。Pepperl+Fuchs公司智能系统经理Helge Hornis补充说，“（除此之外），还有线圈监控功能，目标超出范围或太近。”它也可以对工况的变化进行补偿。“‘智能’传感器，”Omron电子

有限公司战略创意总监Dan Armentrout表示，“必须首先能监视自身及周围的环境，然后再决定是否对变化进行自动补偿或对相关人员发出警告。”

很多智能传感器都能重装到控制现场，通过提供“可设置参数，使用户能替换一些‘标准’传感器，”Hornis说道，“例如，典型的传感器一般都设置为常开（NO）或常关（NC），而智能传感器则能设置为以上任何一种状态。”

智能传感器拥有很多优势。随着嵌入式计算功能的成本继续减少，“智能”器件将被更多地应用。独立的内部诊断功能可避免代价高昂的宕机，从而迅速收回投资。

传感器：越来越到位

正如人们所说的：“无论你到哪里，他都与你同在。”因为大多数的应用仍然都要求这所表达的更高精度和更好的可重复性，所以这里介绍关于如何选择和安装位置传感器的建议。

什么样的传感器才是对特定应用的传感器呢？这取决于对精度、可重复性、速度、预算、连接性、环境和位置的要求，以及其他一些因素。你说的没错，选用正确的测量方法是任何成功应用中闭合回路的第一步。

可检测位置的传感器技术几乎与为机器控制和其他用途提供反馈的应用一样多种多样。空间可能是直线的、平面的、旋转的和三维的。在一些应用中，它们结合使用。传感元件同样也是多种多样。

DMC公司（总部位于芝加哥的系统集成商）的技术总监Ken Brey勾画了选择位置传感器的几点选择。

数字化思考

对数字式位置回馈：

增量型编码器所有的运动控制器都支持；有旋转和直线类型以及多种解决方案；被多种其他设备仿真；当断电时，要求具有回复原位过程，以实现为机器提供物理标记参

考。

绝对编码器天生就只有很少的运动控制器支持；可以用于具有足够多可用数字输入的控制器；在它们的范围内（通常是一个旋转）可以报告完整的位置；不要求回复原位。

解算器在焊接应用中对高等级噪声有很高的免疫力；在一些较大的电机中成为使用标准；当配合恰当的伺服放大器使用时可模拟增量型编码器；和一些伺服放大器共同使用可以模拟绝对编码器。

双编码器反馈通常未被充分利用，天生地可被大部分的运动控制器支持；一个编码器安放在电机上，另一个直接安放在负载上；当电机和负载间的机械连接是柔性的或者是能滑动的时候，是非常有益处的。

视觉系统广泛地用于检测，也可用于位置反馈。这样的系统可在多维空间定位目标，典型的是X、Y和旋转；通常用于查找传送带上的元件，目前正在提高速度和简单易用性。

一个金属轧制、冲压和切割应用提供了双编码反馈使用实例。“它要求通过轧机为冲压过程快速和精确地标定材料指数。轧机产生数量不一致的材料伸展和辊子滑移” Brey解释说。

“通过在双回路配置中，在输出的材料上使用编码器作为位置反馈和电机解算器作为速度反馈，系统被调节得稳定，且单一标定移动提供精确的标定长度。这比先移动、后测量误差，再不得不进行第二次校正移动要快得多，且更精确。”他说。

有创造性，经济节约

Innoventor公司(密苏里州圣路易斯市的系统集成商) 的总工程师 Sam Hammond建议说：应用目的决定位置传感器的选择；测量与反馈不应该很复杂。“创造性的实施可提供简单、经济的解决方案，”他说。例如，对排序问题，接近开关在许多场合可发挥很好的作用。

近来传感器的应用包括在前面图片中提到的AGV（自动引导车）以及下面一些。

在一个用于密封茶叶容器顶盖的机器中，接近开关和对射式传感器定位靠近的包装。NI公司的视觉系统获得图像并被处理，来发现提前印在标签上的条形码的位置，然后给出恰当的电机指令以实现理想的位置（旋转）放置来应用125

种标签类型中的一种。其中用到了两种类型的位置传感器。一种是简单的感应式接近开关，用于监测机器状态以确保即将发生运动的各种运动元件处于正确的位置。照相机也作为位置传感器使用，选择它是因为它的多目的用途、特征定位和读条码能力。

连续冲模（progressive-die）冲床闭环运行。线性输出接近开关为优化冲模运行提供控制反馈；伺服电机在弯曲阶段调整冲模位置。选用线性接近开关从金属冲压运行状态给出尺寸读数；数据用于闭环控制系统。

元件检查使用激光距离测量设备来确定表面光滑度。传感器测量返回光束的偏移，由10微米的尺寸即可指示出不同的表面。编码器在距离大于1米的时候不能工作。选择激光测量技术是因为它具有非常高的空间分辨率，不要求表面接触，以及具有相当高的距离分辨率。

汽车钥匙和门锁集成系统使用接近开关监测在就位位置的顶盖。与自动机械装置一起应用的激光外形传感器测量钥匙外形。

使用什么？在哪里使用？

传感器供应商认为发挥各种位置传感技术的内在优势能有利于各种应用。

MTS 公司传感器部的产品市场经理David Edeal说：“对苛刻的工厂自动化环境来说，在顾客眼中最重要的因素，是产品的耐用性和可靠性，这甚至超过速度和精度。因此，具有内在非接触式传感技术（电磁感应、磁致伸缩、激光等）的产品比那些依靠物理接触的技术（电阻式、电缆扩展等）具有非常巨大的优势。”

其他重要的因素是产品使用范围和应用灵活性。Edeal说：“换句话说，能够适应行程范围、环境条件的重大变化和能够提供大范围接口选择的技术对更喜欢避免使用多种传感器类型的客户具有重大价值。关于这些要求，所有技术天生都有缺陷，这就是为什么会有这么多种选择。”

Edeal暗示使某些技术适合特定应用的高额成本带来了一种限制，例如对线形可变差动变压器（LVDT）的限制。“行程长度超过12英尺的线性可变差动变压器少见，因为较大的产品外壳（约是行程长度的两倍）和很高的原料和制造成本。另一方面，磁致伸缩传感技术总是要求调节电子设备。随着微电子学的出现和专用集成电路的应用，今天我们已经前进到了这样一点，在相同的紧凑封装中

有多种可编程输出类型（如模拟、编码器和现场总线）可用。传感器供应商的关键是推动封装的发展，以扩展使用范围（优点），同时最小化他们技术上的局限。”

听听你的应用

不同的传感器类型对不同的用途提供特有的优点， Pepperl+Fuchs 公司的产品经理Tom Corbett同意这一点。“有时应用本身是需要哪一种传感模式的决定因素。例如，在感应区域内的机器表面或传送带将意味着使用标准扩散模式传感器与使用带背景抑制的扩散模式传感器会有不同。虽然标准扩散模式不能够忽略这样的背景目标，但是背景抑制模型能稍有不同地评估区别目标表面和背景表面。”

Corbett继续说，“相似的，在反射应用中，一个发亮的对象会要求使用偏振反射式的传感器。尽管标准反射式传感器在对准一个闪亮目标时会误触发，但偏振反射式采用偏振滤光片来区分发光物体和反射体。”

MTS公司的 Edeal说：“每一种技术都有理想的应用，此时它容易放大它的优点并最小化它的缺点。例如，在木材制品行业中高精度，可变行程范围，抵抗高冲击与振动、电磁干扰和温度起伏的能力是非常重要的；磁致伸缩位置传感器是线性反馈的首选。同样，旋转光编码器是电机反馈的理想适用品，因为他们具有的封装、响应速度、精度、耐用性和对噪声的抵抗力。如果应用正确，线性位置传感器能帮助设计者在很长一段时间内确保最佳的机器生产率。”

先从大范围考虑，再缩小考虑范围，这常常是为系统设计传感器的最佳方法。Edeal说：“传感器的规范应该从机器/系统级的要求开始制订，然后向后朝子系统级细化，最终到达元件级。这是典型的做法，但是经常发生的是一些系统级的规范没有恰当地或完整地向后细化翻译为元件要求（这并非是一件微不足道的工作）。例如，在没有深入分析或不具备以往经验的情况下，机器如何运行会产生独特的或额外的环境挑战（温度、振动等）可能是不清楚的。这会导致在最坏的情况下过低的指定了传感器，或者另外一种情况是应用于保守估计的情况下，过高地指定了产品。”

开环还是闭环

在设计的初期，那些涉及需要决定结构体系的因素是开环还是闭环。AutomationDirect 公司的产品经理Paul Ruland说：“成本和性能通常是用于决定在电机定位系统中采用开环控制还是闭环控制的两个主要标准。开环控制，如步进系统，当恰当地制定它的步长大小的时候，常常能极其可靠和精确。这里没有运行前调节闭环系统的负担，这天生地使其易于应用。两种类型通常都可由相同的运动控制器控制。一个带微步进驱动器的NEMA 23步进电机目前仅需188

美元就可购得，比较之下，相同功能的伺服系统约要700美元。”

Edeal说：“创造控制系统是为了使生产过程自动化，目前就有很多高性能控制系统的优秀实例，这些控制系统即便有反馈也要求极少。但是在结构体系（设备）或输入（需求或扰动）发生了变化的地方，反馈则是必需的，以应付不曾预料的变化。在处理侧，精度（既有静态又有动态）对最终产品的质量非常重要，且系统的稳定性与可重复性（耐用性）对机器的生产率也非常重要。”

“例如，”Edeal说，“在切削或喷射造型应用中，工具、模子或活塞的位置反馈对所制造零件的最终尺寸非常关键。除了极少的例外，零件尺寸的精度永远不会超过位置传感器的精度。同样的，传感器的带宽（响应速度）与执行器的响应限制一起可能会限制生产效率。”

“最后，在高冲击与振动和温度动态变化很常见的环境类型中，一个只是在很窄的运行条件范围内精确的传感器是不够用的。”

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电子信息工程专业课程翻译中英文对照表

电子信息工程专业课程名称中英文翻译对照（2009级培养计划）

实践环节翻译

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本科生毕业设计（论文）外文科技文献译文译文题目(外文题目)学院(系)Socket网络编程的设计与实现A Design and Implementation of Active Network Socket Programming 机械与能源工程学院专学业号机械设计制造及其自动化 071895 学生姓名李杰林日期2012年5月27日指导教师签名日期

摘要：编程节点和活跃网络的概念将可编程性引入到通信网络中，并且代码和数据可以在发送过程中进行修改。最近，多个研究小组已经设计和实现了自己的设计平台。每个设计都有其自己的优点和缺点，但是在不同平台之间都存在着互操作性问题。因此，我们引入一个类似网络socket编程的概念。我们建立一组针对应用程序进行编程的简单接口，这组被称为活跃网络Socket编程（ANSP）的接口，将在所有执行环境下工作。因此，ANSP 提供一个类似于“一次性编写，无限制运行”的开放编程模型，它可以工作在所有的可执行环境下。它解决了活跃网络中的异构性，当应用程序需要访问异构网络内的所有地区，在临界点部署特殊服务或监视整个网络的性能时显得相当重要。我们的方案是在现有的环境中，所有应用程序可以很容易地安装上一个薄薄的透明层而不是引入一个新的平台。关键词：活跃网络；应用程序编程接口；活跃网络socket编程

1 导言 1990年，为了在互联网上引入新的网络协议，克拉克和藤农豪斯[1]提出了一种新的设计框架。自公布这一标志性文件，活跃网络设计框架[2，3，10]已经慢慢在20世纪90 年代末成形。活跃网络允许程序代码和数据可以同时在互联网上提供积极的网络范式，此外，他们可以在传送到目的地的过程中得到执行和修改。ABone作为一个全球性的骨干网络，开始进行活跃网络实验。除执行平台的不成熟，商业上活跃网络在互联网上的部署也成为主要障碍。例如，一个供应商可能不乐意让网络路由器运行一些可能影响其预期路由性能的未知程序，。因此，作为替代提出了允许活跃网络在互联网上运作的概念，如欧洲研究课题组提出的应用层活跃网络（ALAN）项目[4]。在ALAN项目中，活跃服务器系统位于网络的不同地址，并且这些应用程序都可以运行在活跃系统的网络应用层上。另一个潜在的方法是网络服务提供商提供更优质的活跃网络服务类。这个服务类应该提供最优质的服务质量（QOS），并允许路由器对计算机的访问。通过这种方法，网络服务提供商可以创建一个新的收入来源。对活跃网络的研究已取得稳步进展。由于活跃网络在互联网上推出了可编程性，相应地应建立供应用程序工作的可执行平台。这些操作系统平台执行环境（EES），其中一些已被创建，例如，活跃信号协议（ASP）[12]和活跃网络传输系统（ANTS）[11]。因此，不同的应用程序可以实现对活跃网络概念的测试。在这些EES 环境下，已经开展了一系列验证活跃网络概念的实验，例如，移动网络[5]，网页代理[6]，多播路由器[7]。活跃网络引进了很多在网络上兼有灵活性和可扩展性的方案。几个研究小组已经提出了各种可通过路由器进行网络计算的可执行环境。他们的成果和现有基础设施的潜在好处正在被评估[8，9]。不幸的是，他们很少关心互操作性问题，活跃网络由多个执行环境组成，例如，在ABone 中存在三个EES，专为一个EES编写的应用程序不能在其他平台上运行。这就出现了一种资源划分为不同运行环境的问题。此外，总是有一些关键的网络应用需要跨环境运行，如信息收集和关键点部署监测网络的服务。在本文中，被称为活跃网络Socket编程（ANSP）的框架模型，可以在所有EES下运行。它提供了以下主要目标： ??通过单一编程接口编写应用程序。由于ANSP提供的编程接口，使得EES的设计与ANSP 独立。这使得未来执行环境的发展和提高更加透明。

电子电流外文翻译外文文献英文文献高度稳压直流电源

高精度稳压直流电源文摘:目前对于可调式直流电源的设计和应用现在有很多微妙的,多种多样的,有趣的问题。探讨这些问题(特别是和中发电机组有关),重点是在电路的经济适用性上,而不是要达到最好的性能。当然，对那些精密程度要求很高的除外。讨论的问题包括温度系数，短期漂移，热漂移，瞬态响应变性遥感和开关preregualtor型机组及和它的性能特点有关的的一些科目。介绍从商业的角度来看供电领域可以得到这样一个事实，在相对较低的成本下就可以可以获得标准类型的0.01%供电调节。大部分的供电用户并不需要这么高的规格，但是供应商不会为了减少客户这么一点的费用而把0.1%改成0.01%。并且电力供应的性能还包括其他一些因素，比如说线路和负载调解率。本文将讨论关于温度系数、短期漂移、热漂移,和瞬态的一些内容。目前中等功率直流电源通常采用预稳压来提高功率/体积比和成本，但是只有某些电力供应采用这样的做法。这种技术的优缺点还有待观察。温度系数十年以前，大多数的商业电力供应为规定的0.25%到1%。这里将气体二极管的温度系数定位百分之0.01[1]。因此，人们往往会忽视TC（温度系数）是比规定的要小的。现在参考的TC往往比规定的要大的多。为了费用的减少，后者会有很大的提高，但是这并不是真正的TC。因此，如果成本要保持在一个低的水平，可以采用TC非常低的齐纳二极管，安装上差动放大电路，还要仔细的分析低TC绕线电阻器。如图1所示，一个典型的放大器的第一阶段，其中CR1是参考齐纳二极管，R是输出电位调节器。

图1 电源输入级图2 等效的齐纳参考电路假设该阶段的输出是e3，提供额外的差分放大器，在稳定状态下e3为零，任何参数的变化都会引起输出的漂移；对于其他阶段来说也是一样的，其影响是减少了以前所有阶段的增益。因此，其他阶段的影响将被忽略。以下讨论的内容涵盖了对于TC整体的无论是主要的还是次要的影响。 R3的影响 CR1-R3分支的等效的电路如图2所示，将齐纳替换成了它的等效电压源E'和内部阻抗R2。对于高增益调节器，其中R3的变化对差分放大器的输入来说可以忽略不计，所以前后的变化由R3决定。如果进一步假定IB << Iz;从（1）可以得到同时，

传感器外文翻译

Basic knowledge of transducers A transducer is a device which converts the quantity being measured into an optical, mechanical, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction. Transducers are classified according to the transduction principle involved and the form of the measured. Thus a resistance transducer for measuring displacement is classified as a resistance displacement transducer. Other classification examples are pressure bellows, force diaphragm, pressure flapper-nozzle, and so on. 1、Transducer Elements Although there are exception ,most transducers consist of a sensing element and a conversion or control element. For example, diaphragms,bellows,strain tubes and rings, bourdon tubes, and cantilevers are sensing elements which respond to changes in pressure or force and convert these physical quantities into a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrical elements form electromechanical transducing devices or transducers. Similar combination can be made for other energy input such as thermal. Photo, magnetic and chemical,giving thermoelectric, photoelectric,electromaanetic, and electrochemical transducers respectively. 2、Transducer Sensitivity The relationship between the measured and the transducer output signal is usually obtained by calibration tests and is referred to as the transducer sensitivity K1= output-signal increment / measured increment . In practice, the transducer sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input= output-signal increment / K1. 3、Characteristics of an Ideal Transducer The high transducer should exhibit the following characteristics a) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured; there should be minimum distortion. b) There should be minimum interference with the quantity being measured; the presence of the transducer should not alter the measured in any way. c) Size. The transducer must be capable of being placed exactly where it is needed.

跨境电商外文翻译参考文献

跨境电商外文翻译参考文献(文档含中英文对照即英文原文和中文翻译)

译文：跨境电子商务在欧盟的发展动力和壁垒摘要互联网的兴起，往往是与“距离的消亡”或至少减少相关的地理距离在供应信息相关。我们研究距离事宜仍在实物商品的网上交易是否。我们使用的数据从一个网络消费者调查小组对网上跨境货物贸易中的一个语言支离破碎的欧盟市场。分析结果表明，相比线下交易在同一商品的距离相关的交易成本大大降低。然而，语言相关的交易成本的增加。此外，网上交易介绍新能源贸易成本如包裹递送和在线支付系统。在平衡，没有迹象显示在线贸易不偏向于国内市场的产品比线下交易支持。我们提供给政策制定者推动欧盟数字单一市场的跨境电子商务的选项。在高效灵活的跨境支付系统的使用增加1%可以增加多达7%的跨境电子商务。我们还表明，在线交易给英语语言输出国家的比较优势。关键词电子商务/引力方程/欧盟 1.介绍本文实证研究的在线电子商务跨境贸易模式的影响。互联网的兴起，更一般地，数字通信技术，具有LED许多观察家宣布，距离“死”（Cairncross，1997）。在这方面，它不在乎信息所在的位臵因为它只是一个鼠标点击和信息成本不再是物理距离有关。在传统的线下实物商品贸易，证据却指向距离成本增加（disdier和头，2008）。贸易相结合的基础上的信息和物理的货物运输。问题是是否将贸易从线下到线上平台是一个足够大的凹痕在信息成本改变贸易总成本因此货物贸易模式。Blum 和Goldfarb（2006）表明，即使是纯粹的信息产品，距离仍然起着重要的作用。他们认为这是文化上的差异，随着物理距离的增加。除了信息成本的影响，可能会有副作用，对贸易模式的影响。网上贸易开辟了一个潜在的更大的地理汇水面积，为供应商和消费者，在产品品种和价格竞争的增加。这两