传感器技术(共9页).doc

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1、精选优质文档-倾情为你奉上Sensor TechnologyA sensor is a device，which responds to an input quantity by gener-ating a functionally related output usually in the form of an electrical oroptical signal.Sensors and sensor systems perform a diversity of sensing functi-ons allowing the acquisition, capture, communicat

2、ion, processing, anddistribution of information about the states of physical systems. Thismay be chemical composition, texture and morphology, large-scale str- ucture, position, and so on. Few products and services of the modernsociety would be possible without sensors.The sensor value chainSensor t

3、echnology is distinctly interdisciplinary1. Few organizations have all the competencies necessary for the realization of a sensor solution in-house.The realization of a sensor product requires tasks to be completed, ranging all the way from product definition to final product and subseq-uent marketi

4、ng and service. The diagram shows this value chain of sen-sor development and the main application areas.Wireless sensor technologyFor applications within health care2, industrial automation, cons-umer products3, and security there is a strong and growing need forwireless, self-powered4 sensors. Rad

5、io frequency identification technol-ogy (RFID)5 is an example of an emerging application with great poten-tial. Sensors with wireless connections and no internal power supply are anticipated to become of great importance in areas like health care, consumer products, and structural health monitoring，

6、Energy tapping6 , i.e.The figure illustrates a sensor field where a large number of co-nnected sensor nodes are embedded. Each node will consist of a wirel-ess sensor often without any internal power supply. The sensor interac-ts with a transceiver which is again connected to an infrastructure, pos-

7、sibly to a so-called sink. The collection of data may be controlled by a managing device. Biometric sensorsThis is another area where some markets are expected to exhibit strong growth over the next years. Fingerprint identification7 equipment and iris scanners8 are examples of such markets that are

8、 spurred by the increasing demand within security.Non-invasive9 & non-contact sensors10An increasing number of applications call for noncontact sensing. Light and sound play important roles both independently and combined. Here, combinations of ultrasound and light are expected to become im-portant

9、in order to overcome the limitations inherent when using either light or sound independently.Miniaturization11 and integration12Sensors are often used in large production plants. However, on-line sensing often has to be done in areas with limited space. Hostile envir-onments require robust sensors a

10、nd robustness may be obtained by miniaturization and integration. In optics, this may imply new system and fibre optics. In acoustics, new non-contact methods for excitation are being devised.Novel materials13New materials are needed if a number of very different functional requirem-ents are to be f

11、ulfilled at sufficiently low cost. It may be systems combining mic-rofluidics with light generation and detection. Polymers are anticipated to play an increasingly larger role, both due to potential low cost and due to great flexi-bility in functional properties. Recent development of advanced micro

12、scopes has made it possible to see and even move single atoms and molecules. This opens opportunities for creating entirely new materials and processes. The tec-hnology has become known as nanotechnology14 and currently receives a lot of attention.Not many companies have thus far reached the stage o

13、f commercialization, but intense research is in progress and expectations are very high.Sensor fusion and sensor networksComplex systems will often be monitored by a number of very different types of sensors. X-ray can reveal properties of weldings on-line, optics candetect chemical composition and

14、macroscopic dynamics, whereas ultrasound may provide information about the inner structures of systems.Sensor fusion is combining such multisensory information in order to obta-in new functionality.Moreover, systems with a large number of low-cost sensors coupled in networks are becoming increasingl

15、y important.Technological advancements in process monitoring, control andautomation over the past decades have contributed greatly to improve the productivity of virtually all manufacturing industries throughout the world.While 90% of global production is still controlled by analog instrum-entation,

16、 almost all the controls installed as a part of a new plant or plant expansion are Digital Control Systems1 DCS connected by digital networks.Nowadays, in this era of digital buses, one can plug in a laptop or use a wireless hand tool to instantly establish access to all the data, displays and intel

17、ligence that resides anywhere on the DCS network. This capability, in combination with the self-turning, self-diagnosing and optimizing features of modern process control, makes both startup acti-vity and operational routines much easier and more efficient.Similarly, Distributed Control Systems2 DCS

18、 offer process modeling and simulation, something that can improve operator training a great deal. An accurate simulation model allows operators to train under live conditions without exposing the plant to the consequences oftheirmistakes.The following paragraphs will provide information to engineer

19、s, pro-fessionals and everybody who is interested in process automationand control.Controller System for Industrial AutomationThe element linking the measurement and the final control element is the controller. Before the advent of computers, the controllers are usually single-loop3 PID4 controllers

20、. These are manufactured to execute PID control functions. These days, the controllers can do a lot more. However, easily 80 to 90% of the controllers are still PID controllers.Analogue vs Digital ControllersIt is indeed difficult to say that analogue controllers are definitelybetter than digital co

21、ntrollers. The point is, they both work. Analogue controllers are based on mechanical parts that cause changes to the process via the final control element. Again like final control elements, these moving parts are subjected to wear and tear over time and that causes the response of the process to b

22、e somewhat different with time. Analogue controllers control continuously. Digital controllers do not have mechanical moving parts. Instead, they use processors to calculate the output based on the measured values. Since they do not have moving parts, they are not susceptible to deterioration with t

23、ime. Digital controllers are not continuous. They execute at very high frequencies, usually 2-3 times a second.Process Control Elements in the LoopA simple process control5loop consists of three elements： the measurement, the controller and the final control element. Measuremen- ts have got to be on

24、e of the most important equipment in any processi-ng plant. Any decision made on what the plant should do is based on what the measurements tell us. With the advent of computers, it is now possible to do inferential measurements, meaning telling the val-ue of a parameter without actually measuring i

25、t physically.Final control elements can refer to three things, control valves, var-iable speed drives and dampers. In any chemical process plant, more than 90% of the time, a final control element is a control valve. The is-sues relating to final control elements will be most relevant to control val

26、ves although they are applicable to a large extend to dampers and in some cases variable speed drives.What is Advanced Process ControlNowadays, advanced control is synonymous with the implementat-ion of computer based technologies. It has been reported thatadvan-ced process control can improve produ

27、ct yield; reduce energycons-umption; increase capacity; improve product quality and consisten-cy; reduce product giveaway; increase responsiveness; improved process safety and reduce environmental emissions6.Depending on an individuals background, advanced process con-trol may mean different things.

28、 It could be the implementation of feed forward orcascade control schemes, of time-delay compensators, of self-tuning or adapti-ve algorithms or of optimization strategies. Here, the views of academics andpracticing engineers can differ significant- ly. We prefer to regard advanced control as more t

29、han just the use of multi-processor computers or state-of-the-art7 software environments. Neither does it refer to the singular use of sophisticated control algorit-hms. It describes a practice, which draws upon elements from many disciplines ranging from Control Engineering, Signal Processing, Stat

30、i-stics, Decision Theory, Artificial Intelligence8 to hardware and softw are engineering.传感器技术传感器是一种能够接受外界的输入量，并将其转换成电或光输出信号的装置。传感器和传感器系统能执行各种各样的检测功能，并能够采集，获取，传递，处理和分配物理系统的状态信息。这些可能是化学成份，晶体结构和构造，大型结构，位置等等。现代社会几乎没有一种产品和设备不用到传感器。传感器的价值链传感器技术在各学科间有明显的区别。很少有构件完全有能力内部实现的传感器的功能。传感器产品的实现需要完成一些任务，这些任务涉及到从产品

31、的确定到生成成品以及随后的销售和服务。图表显示的就是传感器开发的价值链及其主要的应用领域。 无线传感技术卫生保健、工业自动化、消费品和安全等领域，对无线、自给供电的传感器的需求不断增长。射频识别技术便是一个实例，并显示了其巨大的应用潜力。无线连接和没有内部电源的传感器将在卫生保健、消费品和能源发掘等领域发挥重要的作。图中所示的是一个传感器现场，其中包含了大量的传感器连接节点。每一个节点都由无线传感器构成，通常不含内部电源。这些传感器与无线收发器相连接，再与其下属元器件相联，有可能是与一个所谓的接收器相连。数据的收集是由管理系统控制。生物传感器这是又一个领域，这个领域的市场有望在随后的几年中呈现

32、很强的增长势头。比如指纹识别装置和虹膜扫描设备便是由于人们不断提高的安全方面的需求而发展起来的。非插入式传感器和非接触式传感器越来越多的科学应用要求使用非接触式传感器。光和声音正在这个领域独立或共同发挥着很重要的作用。在此，为了克服光或声音单独使用时固有的局限性，超声波和光的组合运用正变得越来越重要。小型化和集成化在大型的生产车间经常要用到传感器。然而在线检测却只能在有限的空间使用。恶劣的环境需要优质的传感器，而其优良的性能可以通过小型化和集成化来获得。在光学方面，这意味着新的系统和光纤的使用。在声学方面，正在研发新的非接触式声激励装置新型材料如果要以足够低的成本实现大量完全不同的功能，就要用

33、到新型的材料。它可能是一些这样的系统，结合使用了光生成和探测技术的微流控技术。高分子聚合物将在这个领域扮演越来越重要的角色，不仅是因为它成本低，还由于它功能上具有很高的柔韧性。新近发展的先进的显微镜已经能够看到甚至利用它可以移动单个的原子和分子。这就为人们创造全新的材料和加工工艺提供了机遇。这就是人们通常所说的纳米技术，并且目前已受到了广泛的关注。能够将这一领域的发展达到工业化程度的公司还不多，很多都只是在进行积极的研究工作，并寄予着很高的期望。传感器整合和传感器网络复杂的系统经常是用大量不同类型的传感器进行监控。比如X光就可以在线显示焊接的质量，光可观测化学合成和宏观动力学，而超声波能提供反

34、映系统内部构造的信息。传感器整合技术是结合了多个检测信息以获得新的功能。此外，与网络连接的使用了大量低成本的传感器系统也变得越来越重要。数十年来，过程监控、过程控制和自动化领域的技术进步大大提高了全世界制造产业的生产率。虽然全球的产品仍然由模拟测量仪表测量，但是几乎所有新工厂或新扩建工厂的控制系统都是数字网络连接的数字控制系统。如今，在数字总线的时代，人们通过使用笔记本电脑或无线的掌上工具可以立即获得数字控制系统网络上任何地方的数据、图形信息和情报。这种功能，与现代过程控制的自调整、自诊断和最优化等功能相结合，使得设备的运行和操作更加容易和有效。类似的，分布式控制系统为人们提供了过程建模和仿真

35、，有些大大改进了操作者的培训方式。一个精确的仿真模型使操作者能在生动的环境下进行培训，而不会使设备受到他们操作失误的影响。以下的段落将为工程师、专业技术人员和任何对过程自动化和过程控制有兴趣的人们提供一些信息。工业自动化控制器系统结合测量和末控制元件的部件是控制器。在计算机发明之前，这些控制器通常是单回路PID控制器，用来执行比例积分微分控制功能。现在，这种控制器能执行更多功能。然而，毫无疑问，仍有80%到90%的控制器是PID控制器。模拟控制器和数字控制器确实很难说模拟控制器就明显好于数字控制器。关键是它们都能够发挥作用。模拟控制器是机械零件，这些零件通过末控元件改变控制过程。另外，如同末控

36、元件那样，这些运动部件随着时间的推移会发生磨损和破裂，这将使控制过程的反应与时间不同步。模拟控制器是进行不间断的连续控制。数字控制器没有作机械运动的部件。它们采用处理器对测量到的输出值进行计算。因为它们没有运动部件，所以也不会随着时间的消逝而老化。数字控制器的控制不是连续的。它们以很高的频率执行操作，通常达到每秒钟2-3次。回路中过程控制的基本要素一个简单的过程控制回路包括三个基本要素：测量装置，控制器和末控元件。任何一种加工设备，测量装置都已经成为最重要的一种装置之一。任何有关于设备所要进行的操作，都是由测量装置提供的信息来决定的。随着计算机的出现，现在能做一些推理性的测量，这就意味着无须进

37、行实际的物理测量就能得到参数值。末控元件是指的控制阀、变速器和阻尼器等。在任何一个化工厂，90%以上的时候，末控元件就是控制阀。那些涉及到末控元件的论点中虽然很大程度上适用于阻尼器，有时也适用于变速器，但最多的还是与控制阀有关。什么是先进的过程控制？现在，先进控制是与计算机技术同步的。据报道，先进的过程控制可以提高产量，降低能量损耗，提高产品性能，改善产品品质和特性，减少贱价产品，增加敏感度，提高安全性能和减少废气废料的排放。根据不同的情况，先进的过程控制可能有着不同的含意。它有可能是执行前馈控制或串级控制方案，延时补偿，自调节或自适应运算法则或最优策略。对此，理论和实践的观点可能有明显的区别。我们更愿意将先进控制不仅仅只当作是多处理器计算机的运用或最新技术软件的应用，也不是单一对复杂控制算法的运用。它所描述的工作，其原理涉及到很多学科，涵盖了从控制工程，信号处理，统计，决策理论，人工智能到硬件和软件工程。专心-专注-专业