外文翻译[五篇范文]

第一篇：外文翻译

东 莞 理 工 学 院

本 科 毕 业 论 文

外 文 翻 译

毕业论文题目：唯美陶瓷公司普工流失的问题与对

策

学生姓名：李华辉

学号：20042101229

系别：工商管理系

专业班级：人力资源管理2班 指导教师姓名及职称：莫安达 起止时间：2008年1月—2008年6月

项目经理高成本的离职

你试想以下这样的一个情景，一个大型制药机构的高级经理沮丧地说：“我们公司在过去的一年里流失了很多项目经理，由此产生的问题持续影响着对股东提供的质量服务，然而我们却不知道是什么原因造成的。”这听起来很熟悉，并不陌生吧？我记得导演伍迪艾伦曾经说过“成功有80%是表面文章”。然而，更大的挑战是设法去留住那些员工。

员工离职在商业社会里面是一件很普遍的事情，员工留在企业与其共同成长和发展的日子一逝不复返。调查显示，员工进入企业里里最多五年就离职，而零离职率是没可能的，公司持续增加的离职率表明工作环境存在着严重的问题。在对项目经理进行随机调查的报告中显示，以下原因促使现今很多企业的项目经理离职变得频繁。

1、内部沟通

2、比较差的时间管理

3、人员安排和调度的问题

4、项目经理授权和经验的缺乏

5、贫乏的员工培训

6、没有项目管理工具

7、薪酬问题

公司处在日益发展的阶段，需要大量有经验和专业技能的项目经理，但是事实上招到的是大批没有经验的人到这个行业。那么为什么一些企业面临着离职率的上升？总的来说,美国劳工统计局最近发现40％的员工离职是因为他们觉得在公司里面缺乏赏识和关心，并且没有团队合作，产生严重的负荷。截至2005年2月，美国企业的员工平均流失率为3.1％，虽然这个数字看起来是很低，但如果这和美国的劳动人口相结合，那是一个多么惊人的数字，并且还有很多企业的离职率是没有统计上去的。

在今天竞争激烈的市场里，某些公司的高层只把员工离职作为日常事务的一部分，而有成本意识的成功企业应该看到离职对生产率、产品质量、服务水平等的不利影响。伯明翰认为员工离职存在六个共同点。分别如下

1、离职的必然性

2、部分员工离职是是有利的3、离职的成本是昂贵的4、薪酬并不是员工离职的唯一原因

5、管理是留住人才的关键的措施

6、加强组织的承诺来降低员工的离职率

上述的六个共同点也适用于专业的项目经理。

多米诺骨牌效应，在项目的任何阶段失去项目经理都是一个灾难的信号，虽然很多时候项目管理的方法是由项目管理办公室提出的，并且每个人都有着独立的系统去完成工作任务。但在剩余的时间里面因项目经理个人离职而把项目搁置下来了，在项目经理离开后，项目人员会问以下的问题。

1、他们将会去哪里？

2、谁将会来接管他们？

3、他们是有组织的吗？

4、他们对他们所做的工作了解吗？

5、按原来效率还是加快速度去完成剩余的工作？

6、是把项目经理的工作分到每个成员还是培养一个新经理更加有效？

7、股东是否被告知事件的最新发展情况？

8、财政预算是否已经超支？

事实上项目经理的离职影响以下的各项：

1、范围——那些需要完成的事情

2、时间——增加了项目的时间

3、成本——增加了加班费和培训费

4、质量——截止期限影响工程后期的质量

5、沟通——不能履行所作出的承诺

6、采购——难以选择外部供应商

因此，如何防止项目经理的离职？正如我们在开始时讨论的一样，零离职率是没可能的，并且一定的人员离职对公司来说是合理的，那样可以带来新鲜的血液，新的方法和思路，改革工作的落后环节，促进组织的发展。很多企业对员工离职没有完全了解，未能认识到高成本与离职在很大程度上密切相关。员工的离职对公司来说是一个沉重的负担，因为你要招聘、考核和培训一个新员工，并且你将会增加现有员工的负担，生产力会下降，要付出加班费，实际公司大约花费新员工薪水的三分一去替换员工。如果组织愿意花更多的时间去重视离职率，把他当成企业的重要事项，而不是日常的事务性工作，那么将会节省数万美元。

有一种办法不仅能够降低公司的离职人数，并且能够为员工离职做好准备。在这次对项目经理随机调查中显示，以下方式可以降低项目经理的离职率。

1、通过培训提高知识水平

2、评估不断变化的劳动人口文化

3、衡量公司的离职率

4、员工成本

5、雇佣合适的人选

6、设立有效的变革管理

当变革在组织中不可避免时，你可以有所准备。在日常的项目活动和突发事件中发生问题要把握好时限和团队的势头，以及维护股东的利益，变革管理在这方面起作用。变革管理能够快速的实施一个变革管理计划，产生即时反应，减少对项目发展的影响，获得成功。变革管理可以：

1、降低生产力的损失

2、鼓励抵抗变革的员工

3、尽量减少对生产力和生产质量的影响

4、减少对股东的影响

留下问题不解决会导致整个项目的破坏甚至是失败。当正在进行一个变革管理计划时，有些问题是需要考虑的。

1、故障的责任

2、额外的培训

3、需要的时间

4、更换内部人员

5、超时需要

6、谁能够作横向调动

变革管理计划是降低员工离职成本的有效办法，以至工程能够在预定的时间

和标准范围内完成，不影响公司的利益。

测量你公司的离职率吧！

很多企业对他们公司的离职率知之甚少，此外他们也不太在乎一个员工离职的所包含的成本，按照以下公式测量年职率将会变得很容易。

离职率＝过去12个月离职员工总数/平均员工人数

例如：在过去的一年中有25个员工离职，而公司的平均人数是250人，那么他的离职率就是10％。

员工离职的成本可以被测量，并且在年终应该加以审核，以下的公式可以帮你计算员工离职的费用。

TC=(DHC+IHC)/T

TC：员工流失成本

DHC：直接招聘费用（广告费、摊位费、招聘人员费用等）

T：离职职位总数

我们统计出了以上需要的数据，但是员工离职这个问题在公司里面还不是很清楚，即使通过离职面谈，也可能得不到最真实的反馈，他们回答中最常见离职原因是想得到更高的薪酬或者是想找到一份更加好的工作。这就需要管理人员花费更多的时间去调查，了解存在的问题。高离职率是一个警告的标志，它预示着你公司内部存在一定的问题，其中一些原因是由于高层经理所造成的，员工的离职率得不到应有的关注，高离职率应该使你质疑工作环境如公司提供的文化、物质以及财政方面。问一问你自己这些问题：

1、这是我想去管理员工的方式吗？

2、员工能够得到金钱和感情的补偿吗？

3、公司把员工当作是成本的因素吗？

他们曾经被认为是对公司忠心耿耿，全身心为公司奉献，但是现在他们离职了，为的是更好的满足他们高质量的生活和家庭所需，这意味着现在的组织想要留住员工就要从内心去激发和鼓励他们，参与和授权是减少员工离职率的最有效工具之一。据国际发展维度收集的收据显示，如果公司有高度向心力，员工的离职率是很低的。你公司是如何维持的？

1、听取员工的意见

2、尊重员工

3、鼓励工作出色的员工

4、要求员工投入

5、信任员工

6、公平公正

7、坚定但不残暴

8、勇于承认错误

9、愉快的工作环境

10、优质的住宿环境

虽然对员工离职暂时还没有一个根本的解决方法，但是还是有很多有效的措施来降低员工的离职率，我们不能忘记那些为我们工作的员工特别是从开始到结束为公司工作的员工，我们依靠他们的知识、技能，而且他们当中的大多数人承诺及时地完成高质量的工作。作为雇主，要用时间去赞赏那些为了你公司成功而付出努力的员工，最重要的是了解他们所需要的并想办法尽力满足他们。成功有80%是表面文章，其他的20％是你用行动来留他们下来。

第二篇：外文翻译

当今时代是一个自动化时代，交通灯控制等很多行业的设备都与计算机密切相关。因此，一个好的交通灯控制系统，将给道路拥挤，违章控制等方面给予技术革新。随着大规模集成电路及计算机技术的迅速发展，以及人工智能在控制技术方面的广泛运用，智能设备有了很大的发展，是现代科技发展的主流方向。本文介绍了一个智能交通的系统的设计。该智能交通灯控制系统可以实现的功能有：对某市区的四个主要交通路口进行控制：个路口有固定的工作周期，并且在道路拥挤时中控制中心能改变其周期：对路口违章的机动车能够即时拍照，并提取车牌号。在世界范围内，一个以微电子技术，计算机和通信技术为先导的，一信息技术和信息产业为中心的信息革命方兴未艾。而计算机技术怎样 与实际应用更有效的结合并有效的发挥其作用是科学界最热门的话题，也是当今计算机应用中空前活跃的领域。本文主要从单片机的应用上来实现十字路口交通灯智能化的管理，用以控制过往车辆的正常运作。

研究交通的目的是为了优化运输，人流以及货流。由于道路使用者的不断增加，现有资源和基础设施有限，智能交通控制将成为一个非常重要的课题。但是，智能交通控制的应用还存在局限性。例如避免交通拥堵被认为是对环境和经济都有利的，但改善交通流也可能导致需求增加。交通仿真有几个不同的模型。在研究中，我们着重于微观模型，该模型能模仿单独车辆的行为，从而模仿动态的车辆组。

由于低效率的交通控制，汽车在城市交通中都经历过长时间的行进。采用先进的传感器和智能优化算法来优化交通灯控制系统，将会是非常有益的。优化交通灯开关，增加道路容量和流量，可以防止交通堵塞，交通信号灯控制是一个复杂的优化问题和几种智能算法的融合，如模糊逻辑，进化算法，和聚类算法已经在使用，试图解决这一问题，本文提出一种基于多代理聚类算法控制交通信号灯。

在我们的方法中，聚类算法与道路使用者的价值函数是用来确定每个交通灯的最优决策的，这项决定是基于所有道路使用者站在交通路口累积投票，通过估计每辆车的好处(或收益)来确定绿灯时间增益值与总时间是有差异的，它希望在它往返的时候等待，如果灯是红色，或者灯是绿色。等待，直到车辆到达目的地，通过有聚类算法的基础设施，最后经过监测车的监测。

我们对自己的聚类算法模型和其它使用绿灯模拟器的系统做了比较。绿灯模拟器是一个交通模拟器，监控交通流量统计，如平均等待时间，并测试不同的交通灯控制器。结果表明，在拥挤的交通条件下，聚类控制器性能优于其它所有测试的非自适应控制器，我们也测试理论上的平均等待时间，用以选择车辆通过市区的道路，并表明，道路使用者采用合作学习的方法可避免交通瓶颈。

本文安排如下：第2部分叙述如何建立交通模型，预测交通情况和控制交通。第3部分是就相关问题得出结论。第4部分说明了现在正在进一步研究的事实，并介绍了我们的新思想。

The times is a automation times nowadays,traffic light waits for much the industey equipment to go hand in hand with the computer under the control of.Therefore,a good traffic light controls system,will give road aspect such as being crowded,controlling against rules to give a technical improvement.With the fact that the large-scale integrated circuit and the computer art promptness develop,as well as artificial intelligence broad in the field of control technique applies,intelligence equipment has had very big development,the main current being that modern science and technology develops direction.The main body of a book is designed having introduccd a intelligence traffic light systematically.The function being intelligence traffic light navar’s turn to be able to come true has：The crossing carries out supervisory control on four main traffic of some downtown area;Every crossing has the fixed duty period,charges centrefor being able to change it’s period and in depending on a road when being crowded;The motro vehicle breaking rules and regulations to the crossing is able to take a photo immediately,abstracts and the vehicle shop sign.Within world range ,one uses the microelectronics technology,the computer and the technology communicating by letter are a guide’s,centering on IT and IT industry information revolution is in the ascendant.But,how,computer art applies more effective union and there is an effect’s brought it’s effect into play with reality is the most popular topic of scientific community,is also that computer applications is hit by the unparalleled active field nowadays.The main body of a book is applied up mainly from slicing machine’s only realizing intellectualized administration of crossroads traffic light,use operation in controlling the vehicular traffic regularity.Transportation research has the goal to optimize transportation flow of people and goods.As the number of road users constantly increases, and resources provided by current infras-tructures are limited, intelligent control of traffic will become a very important issue in thefuture.However, some limitations to the usage of intelligent tra?c control exist.Avoidingtraffic jams for example is thought to be beneficial to both environment and economy, butimproved traffic-flow may also lead to an increase in demand [Levinson, 2003].There are several models for traffic simulation.In our research we focus on microscopicmodels that model the behavior of individual vehicles, and thereby can simulate dynam-ics of groups of vehicles.Research has shown that such models yield realistic behavior[Nagel and Schreckenberg, 1992, Wahle and Schreckenberg, 2001].Cars in urban traffic can experience long travel times due to inefficient traffic light con-trol.Optimal control of traffic lights using sophisticated sensors and intelligent optimizationalgorithms might therefore bevery beneficial.Optimization of traffic light switching increasesroad capacity and traffic flow, and can prevent tra?c congestions.Traffic light control is acomplex optimization problem and several intelligent algorithms, such as fuzzy logic, evo-lutionary algorithms, and reinforcement learning(RL)have already been used in attemptsto solve it.In this paper we describe a model-based, multi-agent reinforcement learningalgorithm for controlling traffic lights.In our approach, reinforcement learning [Sutton and Barto, 1998, Kaelbling et al., 1996]with road-user-based value functions [Wiering, 2000] is used to determine optimal decisionsfor each traffic light.The decision is based on a cumulative vote of all road users standingfor a traffic junction, where each car votes using its estimated advantage(or gain)of settingits light to green.The gain-value is the difference between the total time it expects to waitduring the rest of its trip if the light for which it is currently standing is red, and if it is green.The waiting time until cars arrive at their destination is estimated by monitoring cars flowingthrough the infrastructure and using reinforcement learning(RL)algorithms.We compare the performance of our model-based RL method to that of other controllersusing the Green Light District simulator(GLD).GLD is a traffic simulator that allows usto design arbitrary infrastructures and traffic patterns, monitor traffic flow statistics such asaverage waiting times, and test different traffic light controllers.The experimental resultsshow that in crowded traffic, the RL controllers outperform all other tested non-adaptivecontrollers.We also test the use of the learned average waiting times for choosing routes of cars through the city(co-learning), and show that by using co-learning road users can avoidbottlenecks.

第三篇：外文翻译

设计一个位于十字路口的智能交通灯控制系统

摘要：本文模型使用模糊本体的交通灯控制域，并把它应用到控制孤立十字路口。本文最重要的目的之一是提出一个独立的可重复使用的交通灯控制模块。通过这种方式，增加软件的独立性和为其他的软件开发活动如测试和维护，提供了便利。专家对本体论进行手动的开发和评估。此外，交通数据提取和分类路口使用的人工神经网络的图像处理算法。根据预定义的XML架构，这种信息转化为XML实例映射到适合使用模糊推理引擎的模糊规则的模糊本体。把本系统的性能与其他类似的系统性能进行比较。比较结果显示：在所有的交通条件下，在每个周期中，对每辆车它有低得多的平均延迟时间与其他的控制系统相比。

关键词:模糊本体,智能代理,智能交通系统(ITS),交通信号灯控制(TLC),孤立的十字路口,图像处理,人工神经网络

1.引言

作为城市交通增加的结果,道路网络的能力有限和发展交通工具和方法的技术方面，许多实体，关系，情况和规则已经进入交通灯控制域和转化成为一个知识领域。这个领域的建模知识帮助交通代理和应用有效地管理关于实时条件下的交通。全面知识建模领域的一个最合适的方法是使用本体概念。“本体论是一个正式的、明确的一个共享的概念化的规范。以前的模型是基本的本体建设的基础，为下列建立一个共享的语义丰富的知识域。除了本体作为概念化的形式主义的重要性，它有可能超过所代表的数据。这种能力将提高有关性能的决定和其他非智能系统的功能特点。在近年来，本体论上的研究正成为一个新的热点话题在不同的活动，如人工智能，知识管理，语义网络，电子商务和几个其他应用领域。这些领域之一是智能交通系统。一些努力已制成这个通过展示和使用本体检测交通领域拥塞，管理非城市道路气象事件，驾驶阿德福—索里系统，共享和整合一个智能交通系统。本文的目的是介绍一个红绿灯有效控制孤立交叉口这方面的知识重用的控制本体。这种新的办法适用于智能代理使用知识决策模糊。该系统采用的图像来自安装了监控摄像机拍摄的路口。这些图像处理利用图像处理算法和神经网络的方法，然后发送到一个智能代理。第2节中，我们将简要地解释了在这项工作中运用的技术包括seman-TIC网络技术，智能代理技术和交通的回地面光控制方法。在第3节，新的系统架构是基于分层语义网络架构。第4节介绍交通灯控制的模糊本体的建设。第五节从路口提取的图像信息解释。在第6节，智能系统的运作被完整描述，最后在第7节对所提出的方法进行评估，对结论进行阐述。

2.背景

本节说明在这项工作中的应用技术包括语义网络技术，特别本体和模糊本体。此外，国家的交通灯控制的艺术方法是简要介绍。2.1.语义网络技术

语义网络被定义为当前Wed的延伸，这些网站的信息都给出明确的含义;使电脑与人更好的合作。有几层语义Web的建议源自伯纳斯滞后阶段。在此类别中的所有规则如表1所示。图.4显示输出模式的示意图。本次评选有助于智能系统，以确定下一步的阶段测序。

另一种模糊的规则类别涉及估计优化周期时间。这些规则的模糊变量是天气条件，时间，每天平均车辆拥堵情况。出于这个原因，60个模糊规则被定义了。从气象研究所取得气象条件。日期和时间也是在交通专家的知识的基础上以模糊变量形式预先定义的。图5显示日期，时间和周期时间的隶属函数。当天的参数是在日历基础上基于假期和正常的一天与周期时间量的关系预定义的。例如，假期期间的周期时间是较平日少。因此，平日的隶属度比假期多。

例如一个阶段选型的模糊规则如下所述：“如果一个路口的类型是四的方式，平均车辆拥堵低，平均行人拥堵是中等，然后相类型是简单的两阶段”。此外，为周期时间估计的模糊规则表示如下：“如果天气条件是晴天，时间是早晨，天是正常的，平均车辆拥堵是低，则周期时间短”。在此类别中的所有规则都列在附录A。

在此步骤结束时，应该对交通灯逻辑控制的项目的有效性进行评估。此功能是使用专家的意见。评价过程的主要目的是显示发展的本体和其相关的软件环境的用处。虽然所有的信息，尤其是交通灯控制规则已提取国际标准和科学交通文学，专家的知识优势是他们最后的正确性验证标准。所有模糊规则，包括优化周期时间和相位类型的规则，在这个过程中，准备以调查问卷形式和展现给一些专家包括从德黑兰警察局交通上校和两名来自德黑兰的交通组织工程师。由于德尔菲专家的意见，约有84％的淘汰型规则和优化周期时间的87％被接受。此外，所有交通逻辑控制的元素包括概念，关系，属性和公理都被这些专家进行了评估和验证。我们评估逻辑交通控制是基于理论知识的。在这个过程中进行了两项活动，包括检查的要求和能力的问题，并在目标应用环境测试本体。由于逻辑交通控制已建成的基础上，如指定要求优化循环时间，逐步淘汰型，交通的移动和优化绿灯时间，每个阶段的序列中，第一项活动是最好的结果。逻辑交通控制满足所有的交通灯控制的需求，并能回答的能力问题。绩效评估机制，可以支持这种说法。在部分实验结果我们验证了这一过程。

第四篇：外文翻译

中原工学院毕业设计（论文）译文

超声测距系统设计

原文出处：传感器文摘 布拉福德：1993年第13页

摘要：超声测距系统技校在工业场车辆导航水声工程等领域都具有了广泛的应用价值，目前已应用于物理测量，机器人自动导航以及空气中与水下的目标探测、识别定位等场合，因此，深入研究超声的探测理论和方法具有重要的实践意义，为了进一步提高测量的精确度，满足工程人员对测量精度测距量程和测距仪使用的要求，本文研制了一套基于单片机的使拱式超声测距系统。关键词：超声波 测距仪 单片机

1、前言

随着科技的发展，人们生活水平的提高，城市发展建设加快，城市给排水系统也有较大发展，其状况不断改善，但是，由于历史原因合成时间性的许多不可预见因素，城市给排水系统，特别是排水系统往往落后于城市建设，因此，经常出现开挖已经建设好的建筑设施来改造排水系统的现象。城市污水给人们带来的困扰，因此箱的排污疏通对大城市给排水系统污水理，人们生活舒适显得非常重要。而设计研制箱涵排水疏通移动机器人的自动控制系统，保证机器人在箱涵中自由排污疏通，是箱涵排水系统疏通机器人的设计研制的核心部分，控制系统核心部分就是超声波测仪的研制。因此，设计好的超声波测距仪就显得非常重要了。

1.1课题背景

随着经济的发展与汽车科学技术的进步，公路交通呈现出行驶高速化、车流密集化和驾驶员非职业化的趋势。同时，随着汽车工业的飞速发展，汽车的产量和保有量都在急剧增加。但公路发展、交通管理却相对落后，导致了交通事故与日剧增，城市里尤其突出。智能交通系统ITS是目前世界上交通运输科学技术的前沿技术，它在充分发挥现有基础设施的潜力，提高运输效率，保障交通安全，缓解交通赌塞，改善城市环境等方面的卓越效能，已得到各国政府的广泛关注。中国政府也高度重视智能交通系统的研究开发与推广应用。汽车防撞系统作为ITS 发展的一个基础，它的成功与否对整个系统有着很大的作用。从传统上说，汽车的安全可以分为两个主要研究方向:一是主动式安全技术，即防止事故的发生，该种方式是目前汽车安全研究的最终目的;二是被动式安全技术，即事故发生后的乘员保护。目前汽车安全领域被动安全研究较多，主要从安全气囊、ABS(防抱死系统)和悬架等方面着手，以保证驾乘人员的安全。从经济性和安全性两方面来说，中原工学院毕业设计（论文）译文

这些被动安全措施是在事故发生时刻对车辆和人员进行保护，有很大的局限性，因而车辆的主动安全研究尤为重要，引出了本文研究的基于单片机的超声波测距系统。这个系统是一种可向司机预先发出视听语音信号的探测装置。它安装在汽车上，能探测企图接近车身的行人、车辆或周围障碍物;能向司机及乘员提前发出即将发生撞车危险的信号，促使司机采取应急措施来应付特殊险情，避免损失。

1.2 课题设计的意义

随着现代社会工业化程的发展，汽车这一交通工具正为越来越多的人所用，但是随之而来的问题也显而易见，那就是随着车辆的增多，交通事故的频繁发生，由此导致的人员伤亡和财产损失数目惊人。对于公路交通事故的分析表明，80%以上的车祸事由于驾驶员反应不及所引起的，超过65%的车辆相撞属于追尾相撞，其余则属于侧面相撞。奔驰汽车公司对各类交通事故的研究表明：若驾驶员能够提早1S 意识到有事故危险并采取相应的正确措施，则绝大多数的交通事故都可以避免。因此，大力研究开发如汽车防撞装置等主动式汽车辅助安全装置，减少驾驶员的负担和判断错误，对于提高交通安全将起到重要的作用。显然，此类产品的研究开发具有极大的实现意义和广阔的应用前景。

1.3超声波测距在汽车上应用的介绍

超声波倒车测距仪(俗称电子眼)是汽车倒车防撞安全辅助装置，能以声音或者更为直观的数字形式动态显示周围障碍物的情况。其较早的产品是用蜂鸣器报警，蜂鸣声越急，表示车辆离障碍物越近。后继的产品可以显示车后障碍物离车体的距离。其大多数产品探测范围在0.4～1.5m，有的产品能达到0.35～2.5m，并有距离显示、声响报警、区域警示和方位指示，有些产品还具备开机自检功能。目前市场上还出现了具有语音报警功能的产品。这些产品存在的主要问题是测量盲区大，报警滞后，未考虑汽车制动时的惯性因素，使驾驶者制动滞后，抗干扰能力不强，误报也较多。汽车防撞雷达之所以能实现防撞报警功能，主要有超声波这把无形尺子, 它测量最近障碍物的距离, 并告诉给车主。其实超声测距原理简单: 它发射超声波并接收反射回波, 通过单片机计数器获得两者时间差t, 利用公式S=Ct/2计算距离, 其中S为汽车与障碍物之间的距离, C为声波在介质中的传播速度。

本文介绍的超声测距系统共有2只超声波换能器(俗称探头),分别布置在汽车的后左、后右2个位置上。能检测前进和倒车方向障碍物距离, 通过后视镜内置的

中原工学院毕业设计（论文）译文

显示单元显示距离和方位, 发出一定的声响, 起到提示和警戒的作用。系统采用一片STC89C52单片机对两路超声波信号进行循环采集。超声波是指频率高于20HHZ的机械波。为了以超声波作为检测手段，必须产生超生波和接收超声波。完成这种功能的装置就是超声波传感器，习惯上称为超声波换能器或超声波探头。超声波传感器有发送器和接收器，但一个超声波传感器也可具有发送和接收声波的双重作用。超声波传感器是利用压电效应的原理将电能和超声波相互转化，即在发射超声波的时候，将电能转换，发射超声波；而在收到回波的时候，则将超声振动转换成电信号。超声波测距的原理一般采用渡越时间法。首先测出超声波从发射到遇到障碍物返回所经历的时间，再乘以超声波的速度就得到二倍的声源与障碍物之间的距离。测量距离的方法有很多种，短距离的可以用尺，远距离的有激光测距等，超声波测距适用于高精度的中长距离测量。因为超声波在标准空气中的传播速度为331.45米/秒，由单片机负责计时，单片机使用12.0M晶振，所以此系统的测量精度理论上可以达到毫米级。由于超声波指向性强，能量消耗缓慢，在介质中传播距离远，因而超声波可以用于距离的测量。利用超声波检测距离，设计比较方便，计算处理也较简单，并且在测量精度方面也能达到要求。超声波发生器可以分为两类：一类是用电气方式产生超声波，一类是用机械方式产生超声波。本设计属于近距离测量，可以采用常用的压电式超声波换能器来实现触发单元。

利用超声波测距的工作，就可以根据测量发射波与反射波之间的时间间隔，从而达到测量距离的作用。其主要有三种测距方法：

（1）相位检测法，相位检测法虽然精度高，但检测范围有限；

（2）声波幅值检测法，声波幅值检测法易受反射波的影响；

（3）渡越时间检测法，渡越时间检测法的工作方式简单，直观，在硬件控制和软件设计上都非常容易实现。其原理为：检测从发射传感器发射超声波，经气体介质传播到接收传感器的时间，这个时间就是渡越时间。本设计的超声波测距就是使用了渡越时间检测法。在移动车辆中应用的超声波传感器，是利用超声波在空气中的定向传播和固体反射特性（纵波），通过接收自身发射的超声波反射信号，根据超声波发出及回波接收的时间差和传播速度，计算传播距离，从而得到障碍物到车辆的距离。

中原工学院毕业设计（论文）译文 超声波测距原理

2.1 压电式超声波发生器原理

压电式超声波发生器实际上是利用压电晶体的谐振来工作的。超声波发生器内部结构，它有两个压电晶片和一个共振板。当它的两极外加脉冲信号，其频率等于压电晶片的固有振荡频率时，压电晶片将会发生共振，并带动共振板振动，便产生超声波。反之，如果两极板间未加电压，当共振板接收到超声波时，将压迫压电晶片做振动，将机械能转换为电信号，这是它就成为超声波接收器了。

测量脉冲到达时间的传统方法是以拥有固定参数的接收信号开端为基础的。这个信号恰恰选于噪音水平之上，然而脉冲到达时间被定义为脉冲信号刚好超过界限的第一时刻。一个物体的脉冲强度很大程度上取决于这个物体的自然属性尺寸还有它与传感器的距离。进一步说，从脉冲起始点到刚好超过界限之间的时间段随着脉冲的强度而改变。结果，一种错误便出现了——两个拥有不同强度的脉冲在不同时间超过界限却在同一时刻到达。强度较强的脉冲会比强度较弱的脉冲超过界限的时间早点，因此我们会认为强度较强的脉冲属于较近的物体。

2.2 超声波测距原理

超声波发射器向某一方向发射超声波，在发射时刻的同时开始计时，超声波在空气中传播，途中碰到障碍物就立即返回来，超声波接收器收到反射波就立即停止计时。超声波在空气中的传播速度为340m/s，根据计时器记录的时间t，就可以计算出发射点距离障碍物的距离(s)，即：s=340t/2

中原工学院毕业设计（论文）译文

3、超声波测距系统的电路设计

系统的特点是利用单片机控制超声波的发射和超声波自发射至接受往返时间的计时，单片机选用C51，经济易用，且片内有4K的ROM，便于编程。电路的原理如图1所示。

图1 电路原理图

中原工学院毕业设计（论文）译文

3.1 40kHz脉冲的产生与超声波发射

测距系统中的超声波传感器采用UCM40的压电陶瓷，它的工作电压是40kHz的脉冲信号，这由单片机执行下面的程序来产生。puzel：mov 14h，#12h

here： cp1.0；

nop；

nop；

nop；

djnz 14h，here；

Ret

前方测距电路的输出端接单片机P1.0端口，单片机执行上面的程序后，在P1.0端口输出一个40khz的脉冲信号，经过三极管T放大，驱动超声波发射头UCM40T，发出40khz的脉冲超声波，且持续发射200ms。右侧合作侧测距电路的输入端分别接P1.1和P1.2端口，工作原理和前方测距电路相同。

超声波发射持续200ms 输出40kHz方波

3.2 超声波的接收与处理

接收头采用与发射头配对的UCM40R，将超声波调制脉冲变为电压信号，经运算放大器ic1a和ic1b两级放大后加至IC2,。IC2是带有锁定环的音频译码集成块LM567，内部压控振荡器的中心频率f0=1/1.1R8C3，电容C4决定其带宽。调节R8在发射的载频上，则LM567输入信号大于25mv，输出端8脚由5由高电平跃变为低电平，作为中断请求信号，送至单片机处理。

前方测距电路的输出端接至单片机INT0端口，中断优先级最高，左、右测距电路的输出通过与门IC3A的输出接单片机的INT1端口，同时单片机P1.3和P1.4接到IC3A的输入端，中断源的识别由程序查询来处理，中断优先级为先右后左。部分源程序如下： receive1：push psw

push acc

clr ex1；关中断源1

jnb p1.1，right;P1.1引脚为0，转至右侧距电路中断服务程序

jnb p1.2,left;P1.2 引脚为0，转至左测距中断电路服务程序 returne：SETB EX1；

开外部中断1

pop acc

中原工学院毕业设计（论文）译文

pop psw

reti right：

...；

右测距电路中断服务程序入口

ajmp return

left：

...；

左测距电路中断服务程序入口

ajmp return

3.3 计算超声波传播时间

在启动发射电路的同时启动单片机内部的定时器T0，利用定时器的计数功能，记录超声波发射的时间和受到反射波的时间。当收到超声波反射波时，接受电路输出端产生一个负跳变，在INT0或INT1端产生一个中断请求信号，单片机响应外部中断请求，执行外部中断服务子程序，读取时间差，计算距离。其部分源程序如下：

RECEIVEO: PUSH PSW

PUSH ACC CLR EX0;

关外部中断0 读取时间值

MOV R7,TH0;MOV R6,TL0 CLR C MOV A,R6 SUBB A,#0BBH;MOV 31H,A;MOV A,R7 SUBB A,#3CH MOV 30H,A SETB EX0;POP ACC

POP PSW

RETI 对于一个平坦的目标，测量距离包括两个阶段：粗糙的测量和精细的测量。第一步：脉冲的传送产生一种简单的超声波

第二步：根据公式改变回波放大器的获得量直到回拨被检测到。第三步：检测两种回波的振幅与过零时间。

计算时间值 存储结果

开外部中断0

中原工学院毕业设计（论文）译文

第四步：设置回波放大器的所得规格输出，假定是3v。通过脉冲的周期设置下一个脉冲。根据第二部的数据设定时间窗。

第五步：发射两窜脉冲产生干扰波。测量过零时间与回波振幅。如果逆向发生在回波中，决定要不通过在低气压插入振幅。

第六步：通过公式计算距离y。

中原工学院毕业设计（论文）译文

4、超声波测距系统的软件设计

软件分为俩部分，主程序和中断服务程序。主程序完成初始化工作、各路超声波发射和接收顺序的控制。定时中断服务子程序完成三方向超声波的轮流发射，外部中断服务子程序主要完成时间值的读取、距离计算、结果的输出等工作。

中原工学院毕业设计（论文）译文

5、结论

对所要求测量范围30cm-200cm内的平面物体做了多次测量发现，其最大误差为1.5cm，且重复性好。可见基于单片机设计的超声波测距系统具有硬件结构简单、工作可靠、测量误差小等特点。因此，它不仅可用于移动机器人，还可以用在其他检测系统中。

思考：至于为什么不用接收管做放大电路，因为放大倍数搞不好，集成放大电路，还带自动电平增益控制，放大倍数为76db，中心频率是38k到40k，刚好是超声波传感器的谐振频率。

中原工学院毕业设计（论文）译文

参考文献

1.Fox，J.D.，Khuri-Yakub，B.T.and Kino，G.S.，“High Frequency Acoustic Wave Measurement in Air”，in Proceedings of IEEE 1983 Ultrasonic Symposium，October 31-2 November，1983，Atlanta，GA，pp.581-4.2.Martin Abreu，J.M.，Ceres,R.And Freire,T.,“Ultrasonic Ranging: Envelope Analysis Gives Improved Accuracy”,Sensor Review, Vol.12 No.1,1992,pp.17-21.3.Parrilla， M., Anaya,J.J and Fritsch C.,‖Digital Signal Processing Techniques for High Accuracy Ultrasonic Range Measurement:,IEEE Transactions: Instrumentation and Measurement.Vol.40 No.4, August 1991,pp.750-63.4.Canali, C., Cicco, G.D., Mortem, B., Prudenziati, M., and Taron, A., ―A Temperature Compensated Ultrasonic Sensor Operating in Air for Distance and Proxinmity Measurement‖, IEEE Trasaction on Industry Electronics, Vol, IE-29 No.4,1982, pp.336-41.5.Martin, J.M., Ceres, R., Calderon, L and Freire, T., ‖Ultrasonic Ranging Gets Themal Correction‖, Sensor Review, Vol, 9 No.3, 1989,pp.153-5.中原工学院毕业设计（论文）译文

Ultrasonic ranging system design Publication title: Sensor Review.Bradford:1993.Vol.13 ABSTRACT: Ultrasonic ranging technology has wide using worth in many field, such as the industrial locale, vehicle navigation and sonar engineering.Now it has been used in level measurement, self-guided autonomous vehicles, fieldwork robots automotive navigation, air and underwater target detection, identification ,location and so on.So there is an important practicing meaning to learn the ranging theory and ways deeply.To improve the precision of the ultrasonic ranging system in hand, satisfy the request of the engineering personal for the precision,the bound and the usage, a portable ultrasonic ranging system based on the single chip processor was developed.Keywords: Ultrasound r, Ranging System, Single Chip Processor

1.Introductive With the development of science and technology, the improvement of people’s standard of living, speeding up the development and construction of the city.Urban drainage system have greatly developed their situation is constantly improving.However, due to historical reasons many unpredictable factors in the synthesis of her time, the city drainage system.In particular drainage system often lags behind urban construction.Therefore, there are often good building excavation has been building facilities to upgrade the drainage system phenomenon.It brought to the city sewage, and it is clear to the city sewage and drainage culvert in the sewage treatment system.Confort is very important to people’s lives.Mobile robots designed to clear the drainage culvert and the automatic control system Free sewage culvert clear guarantee robot, the robot is designed to clear the culvert sewage to the core.Control System is the core component of the development of ultrasonic range finder.Therefore, it is very important to design a good ultrasonic range finder.1.1 subject background

With the development of economy and car scientific and technological progress, highway traffic presents driving fast pace, traffic dense is changed and the driver not professional trend.At the same time, along with the rapid development of auto industry, automobile yield and quantities are increased dramatically.But road development，中原工学院毕业设计（论文）译文

transportation management is relatively backward, leading to a large number of traffic accidents in some cities, especially prominent.Intelligent transportation system in the world, ITS transportation science and technology of advanced technology, ITS exerting existing infrastructure of potential, enhance the transport efficiency, safeguard traffic safety and ease traffic wager plug, improving urban environment aspects of outstanding performance, has received the governments of widespread concern.The Chinese government is also highly intelligent transportation system of the development and popularization applications.The automotive anti-collision system as ITS development of a base, ITS success to the whole system has a very significant role.Traditionally, auto safety said can be divided into two main research direction: first,it is active safety technology, including the prevention of accidents, the way is now automotive safety research ultimate purpose;second, it is passive safety technique, namely the occupant protection after the accident.Now automotive safety field passive safety more research, mainly from the airbag, ABS(antilock brakes)and suspension from the aspects such as to ensure safety of personnel rides.From the economic and safety two ways, these passive safety measures is the accident of vehicle and personnel moments protection, with great limitations, thus vehicle active safety research is particularly important, leads to a of this study is based on single chip ultrasonic ranging system.This system is a kind of can advance to the driver issued audio-visual speech signal detection devices.It is installed in cars that can detect trying to approach the body of a car pedestrians and vehicles or around obstacles, Can send to the driver and crew imminent danger ahead of the signal, prompting a crash drivers take emergency measures to cope with special danger, avoid the loss.1.2 question design significance

Along with the development of modern society industrialization process, car this traffic tools are used for more and more people, but any problem has obvious that along with the increase in vehicles, traffic accident, which led to the frequent occurrence of casualties and property losses number astonishing.For highway traffic accident analysis showed that more than 80% of the accident due to the driver reaction inferior things, caused more than 65% of vehicle collision, the rest belongs to tracing cauda collided belongs to the side collision.Mercedes-benz Automobile Company for all kinds of traffic accident research shows that: if the driver can early 1S are aware

中原工学院毕业设计（论文）译文

that a accident risk and take the appropriate corrective measures, the overwhelming majority of traffic accidents can be avoided.Therefore, vigorously research and development as the automotive anti-collision device etc active car auxiliary safe device, reduce the burden and misjudgments drivers to improve the traffic safety will play an important role.Obviously, this kind of product research and development has great realize meaning and broad application prospects.1.3 Ultrasonic ranging in automotive applications introduced

Ultrasonic back-draft rangefinder(known as electron optics)automotive anti-collision reversing device, can safe adjunct to sound or more intuitive digital form the dynamic display of around obstacles.Its earlier products is to use buzzer alarm, hum more anxious, and says vehicles from obstructions closer.Subsequent product can display the car from the body after the obstacles distance.Most of its products detection range in 0.4 ~ 1.5 m, some product can achieve 0.35 ~ 2.5 m, and have distance display, sound alarm, area-warning and azimuth instructions, some products also has the boot self-checking function.Still appeared on the market at present with voice alarm function of products.These products are the main problem is big, alarm measuring blind area lags behind, without considering the automobile braking inertial factors and make drivers brake lag, the anti-interference ability is not strong, misstatement or more.The automotive anti-collision radar is able to realize impact-proof alarm functions, basically have ultrasonic this intangible ruler, it recently obstacles distance measurement, and told to the owner.Actually ultrasonic range-finding principle simple: it emit ultrasonic echo, and receive reflected by microcontroller counter obtain both lag using formula S = t, Ct / 2 calculating distances, including S for cars and obstacles, C for the distance between the sound wave propagation in the medium speed.This paper introduces the ultrasonic ranging system only have 2 ultrasonic transducer(known as probe)respectively, decorate in cars left and right after after 2 position.Capable of detecting forward and reverse direction obstacle distance, the rearview mirror built-in display element display distance and direction, issued must be sound, plays the role of hints and alert.System USES a STC89C52 SCM two way ultrasonic signal cyclicly acquisition.Ultrasonic refers to the 20HHZ wave frequency is over.In order to use the ultrasonic detection means, must generate as ultrasonic wave and receiving damnation.Complete the functions of the device is called the

中原工学院毕业设计（论文）译文

ultrasonic sensor, habit, ultrasonic transducer or ultrasonic probe.Ultrasonic sensors have both transmitters and receivers, but a ultrasonic sensors can also has the sending and receiving the sound waves of the dual role.Ultrasonic sensors is using the principle of piezoelectric effect and ultrasonic energy conversion, be in namely emit ultrasonic, energy conversion, launch ultrasonic, And in the stockades, received echo ultrasonic vibration into electrical signal.Ultrasonic ranging principle generally USES the time method for the crossing.First measured ultrasonic from the launch to meet obstacles returns experience of time, again multiply ultrasonic speed of get twice the distance between the sound source and obstacles.Measuring distance a variety of ways, short can use ruler, long-range laser displacement etc, are suitable for high accuracy of ultrasonic ranging in long distance measurement.Because of ultrasound in standard air of propagation speed 331.45 meters per second, by single-chip microcomputer is responsible for timing, SCM use 12.0 M crystals, so the system of measurement precision theory can achieve mm level.Because of ultrasonic directivity strong, energy consumption is slow, in a medium transmission distance, thus ultrasonic can be used for distance measurement.Using ultrasonic detection distance, the design is more convenient, computing procese also relatively simple, and the measurement precision can also meet the requirements.Ultrasonic generator can be divided into two kinds: one kind is to use electrical means producing ultrasonic, one kind is with mechanical approach to producing ultrasonic.This design belongs to nearly distance measurement, can use commonly used the piezoelectric ultrasonic transducer to achieve trigger unit.Using ultrasonic ranging work, can according to measuring launch reflection wave wave and the time interval between the measured distance, so as to achieve the effect.It mainly have three ranging methods:

(1)phase assay, phase assays high precision, but detection though limited range，(2)sound amplitude assay, acoustic amplitude assay vulnerable reflection wave influence;

(3)ferrying more time assay, crossing the time assay way of working is simple, intuitive, in hardware control and software design are very easy to implement.Its principle is: from the launch emit ultrasonic detection sensor, the gas medium spread to receive sensor of time, this time is crossing the more time.This design is the use of ultrasonic ranging the crossing the time assay.In the mobile vehicles of the application 15

中原工学院毕业设计（论文）译文

of ultrasonic sensor is the use of ultrasound in air of directional spread and solid reflective characteristics(p-wave)and by receiving their launch ultrasonic reflecting signal, according to the ultrasonic issued and echo receiving the Windows and propagation speed, calculate transmission distance, thus obtains the obstacles to vehicle distance.中原工学院毕业设计（论文）译文

2.A principle of ultrasonic distance measurement

2.1 the principle of piezoelectric ultrasonic generator

Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to work.Ultrasonic generator, the internal structure as shown, it has two piezoelectric chip and a resonance plate.When it’s two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip will happen piezoelectric resonance, and promote the development of plate vibration resonance, ultrasound is generated.Conversely, if the two are not inter-electrode voltage, when the board received ultrasonic resonance, it will be for vibration suppression, then it becomes the ultrasonic receiver.The traditional way to determine the moment of the echo’s arrival is based on thresholding the received signal with a fixed reference.The threshold is chosen well above the noise level, whereas the moment of arrival of an echo is defined as the first moment the echo signal surpasses that threshold.The intensity of an echo reflecting from an object strongly depends on the object’s nature, size and distance from the sensor.Further, the time interval from the echo’s starting point to the moment when it surpasses the threshold changes with the different intensities arriving exactly at the same tome will surpass the threshold at different moments.The stronger one will surpass the threshold earlier than the weaker, so it will be considered as belonging to a nearer object.2.2 The principle of ultrasonic distance measurement Ultrasonic transmitter in a direction to launch ultrasound, in the moment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstracles on his way to return immediately, the ultrasonic reflected wave wave received by the reveiver immediately stop the clock.Ultrasonic in the air as the propagation velocity of 340m/s, according to the timer records the time t, we can calculate the distance between the launch distance barrier(s), that is:s=340t/2

中原工学院毕业设计（论文）译文

3.Ultrasonic Ranging System for the Second Circuit Design

System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, single-chip selection of 8751,economic-to –use, and the chip has 4K of ROM, to facilitate programming.Circuit schematic diagram shown in Figure 1.Figure 1 circuit principle diagram

中原工学院毕业设计（论文）译文

3.1 40 kHz ultrasonic pulse generated with the launch

Ranging system using the ultrasonic sensor of piezoelectric sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the single-chip implementation of the following procedures to generate.Puzel:mov 14h,# 12h;ultrasonic firing continued 200ms here:cpl pl.0;output 40 kHz square wave

nop;

nop;nop;djnz 14h, here;ret Ranging in front of single-chip termination circuit P1.0 input port, single chip implementation of the above procedure, the P1.0 port in a 40kHz pulze output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of 200ms.Ranging the right and the left side of the circuit, respectively, then input port P1.1 and P1.2, the working principle and circuit in front of the same location.3.2 Reception and processing of ultrasonic

Used to receive the first launch of the first pair UCM40R, the ultrasonic pulse modulation signal into an alternating voltage, the op-amp amplification IC1A and after polarization IC1B to IC2.IC2 is locked loop with audio decoder chip LM567, internal voltage-controlled oscillator center frequency of f0=1/1.1R8C3, capacitor C4 determine their target bandwidth.R8-conditioning in the launch of the carrier frequency on the LM567 input signal is greater than 25Mv, the output from the high jump 8 feet into a low-level, as interrupt request signals to the single-chip processing.Ranging in front of single-chip termination circuit port INT0 interrupt the highest priority, right or left location of the output circuit with output gete IC3A access INT1 port single-chip, while single-chip P1.3 and P1.4 received input IC3A, interrupted by the process to identify the source code is as follows: receivel:

push psw

push ace

中原工学院毕业设计（论文）译文

cir ex1: related external interrupt 1

jnb p1.1, right;P1.1 pin to 0, ranging from right to interrupt service rountine circuit

jnb p1.2, left;P1.2 pin to 0, to the left ranging circuit

interrupt service routine return:SETB EX1;open external interrupt 1

pop

acc pop

psw reti right:…;right location entrance circuit interrupt service rountine

Ajmp Return left:…;left Ranging entrance circuit interrupt service rountine

Ajmp Return

3.3 The calculation of ultrasonic propagation time

When you start firing at the same time start the single-chip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received time when you receive the ultrasonic reflected wave, the receiver circuit outputs a negative jump in the end of INT0 or INT1 interrupt request generates a signal, single-chip microcomputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the distance.Some of its source is as follows: RECEIVE0: PUSH PSW PUSH ACC CLR EX0;related external interrupt 0 MOV R7, TH0;read the time value MOV R6, TL0 CLR C MOV A, R6 SUBB A,#0BBH;calculate the tome difference MOV 31H, A;storage results MOV A, R7 SUBB A,#3CH

中原工学院毕业设计（论文）译文

MOV 30H,A SETB EX0;open external interrupt 0 POP ACC POP PAW RETI For a flat target, a distance measurement consists of two phases: a coarse measurement and, a fine measurement: Step 1: Transmission of one pulse train to produce a simple ultrasonic

Wave.Step 2: Changing the gain of both echo amplifiers according to equation，until the echo is detected.Step 3:detection of te amplitudes anf zero-crossing times of both echoes.Step 4:setting the gains of both echo amplifiers to normalize the output at, say 3 volts.Setting the period of the next pulses according to the: period of echoes.Setting the time window according to the data of step 2.Step 5:sending two pulse trains to produce an interfered wave.Testing the zero-crossing in the echo,detemine to otherwise calculate to by interpolation using the amplitudes near the trough.Derive t sub ml and t sub m2.Step6: Calculation of the distance y using equation.中原工学院毕业设计（论文）译文

4.The ultrasonic ranging system software design

Software is divided into two parts, the main program and interrupt service routine.Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving control.Tnterrupt service routines from time to complete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to resd the value of completion time, distance calculation, the results of the output and so on.中原工学院毕业设计（论文）译文

5.Conclusions

Required measuring range of 30cm~200cm objects inside the plane to do a number of measurements found that the maximum error is 0.5cm, and good reproducibility.Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement error.Therefore, it can be used not only for mobile robot can be used in other detection systems.Thoughts: As for why the receiver do not have the transistor amplifier circuit, because the magnification well, integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency.中原工学院毕业设计（论文）译文

REFERENCES 1.Fox,J.D.,Khuri-Yakub, B.T.and Kino, G.S., ‖High Frequency Acoustic Wave Measurement in Air‖, in Proceedings of IEEE 1983 Ultrasonic Symposium, October 31-2 November, 1983, Atlanta, GA, pp.581-4.2.Martin Abreu,J.M.,Ceres,R.and Freire, T.,‖Ultrasonic Ranging: Envelope Analysis Gives Improved Accuracy‖, Sensor Review, Vol.12No.1,1992, pp.17-21.3.Parrilla， M., Anaya,J.J and Fritsch C.,‖Digital Signal Processing Techniques for High Accuracy Ultrasonic Range Measurement:,IEEE Transactions: Instrumentation and Measurement.Vol.40 No.4, August 1991,pp.750-63.4.Canali, C., Cicco, G.D., Mortem, B., Prudenziati, M., and Taron, A., ―A Temperature Compensated Ultrasonic Sensor Operating in Air for Distance and Proxinmity Measurement‖, IEEE Trasaction on Industry Electronics, Vol, IE-29 No.4,1982, pp.336-41.5.Martin, J.M., Ceres, R., Calderon, L and Freire, T., ‖Ultrasonic Ranging Gets Themal Correction‖, Sensor Review, Vol, 9 No.3, 1989,pp.153-5.24

第五篇：外文翻译

Low Voltage Flyback DC-DC Converter For

Power Supply Applications Hangzhou Liu1, John Elmes2, Kejiu Zhang1, Thomas X.Wu1, Issa Batarseh1

Department of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32816, USA Advanced Power Electronics Corporation, Orlando, FL 32826, USA Abstract ：In this paper, we design a low voltage DC-DC converter with a flyback transformer.The converter will be used as a biased power supply to drive IGBTs.The flyback transformer using planar EI-core is designed and simulated using ANSYS PExprt software.Besides, anLT3574 IC chip from Linear Technology has been chosen for converter control.Finally, the converter modeling and simulation are presented and PCB layout is designed.Keywords：Flyback, anLT3574IC, PCB

I.INTRODUCTION The goal of this project is to develop and build a prototype of a high-efficiency, high-temperature isolated DC-DC converter to be used as a biased power supply for driving a complementary IGBT pair.It is important that the converter can deliver the required power at an ambient temperature of up to 100℃;therefore it has to be efficient so that its components do not exceed their maximum temperature ratings.The final converter will be completely sealed and potted in a metal case.The input voltage range for this converter is from 9V to 36V.The output sides have two terminals, one is﹢16V and the other one is﹣6V.In order to get the desired performance, anLT3574 IC chip from Linear Technology is used.The key to this design is the flyback transformer.The transformer using planar EI-core is designed and simulated using ANSYS PExprt software.Finally, the PCB layout of the converter will be presented.II.KEY DESIGN OUTLINE For this flyback topology, the output voltage can be determined by both the transformer turns ratio and the flyback loop resistor pairs.Therefore, at the initial design stage, we can choose a convenient turn’s ratio for the transformer, and modify it later on if necessary to make sure the output performance is desirable and the transformer will not saturate [1].The relationship between transformers turns ratio and duty cycle can be found as

Where n is the transformer turns ratio, D is the duty cycle, VO` is the sum of the output voltage plus the rectifier drop voltage, VIN is the input voltage of the transformer.The value of feedback resistor can be calculated as

Where RREF is the reference resistor, whose value is typically 6.04kΩ;α is a constant of 0.986;VBG is the internal band gap reference voltage, 1.23V;and VTC is normally 0.55V [1].With a specific IC chosen, the converter circuit can be designed based on a demo circuit and some parameters may need to be modified if necessary to optimize the performance.Furthermore, in LT Spice, a large number of simulations need to be done with different conditions such as load resistor values and input voltage levels.It is important to make sure that the output voltage can be regulated well with all these different conditions.The most critical part of the design is the flyback transformer.With high switching frequency, the AC resistance can only be estimated based on some traditional methods such as Dowell’s curve rule [2].In order to get more accurate values of AC resistance values;we propose to use finite element electromagnetic software ANSYS PExprt to do the design [3].At the initial design stage, key parameters such as the worst-case input voltage, frequency, material, inductance values will be decided.After that, these data will be imported to the software, from which an optimized solution will be generated.III.CONVERTER SIMULATION RESULTS We choose LT3574 chip in this design.From the simulation results in Figure 1 and Table 1, it clearly shows that the output voltages which are﹢16V and-6V respectively can be regulated pretty well with the input voltage range from 9V to 36V.The voltage tolerance ranges are from ﹢15V to ﹢19V and-12V toDC converter for low voltage power supply application has been designed.The modeling and simulation results are presented.Based on the design specifications, a suitable IC from Linear Technology is chosen.A large amount of circuit simulations with different conditions such as load resistor values and input voltage levels are presented to get the desirable output voltage and current performance.The transformer has been designed including electrical, mechanical and thermal properties.With all the specific components decided, the PCB layout of the converter has been designed as well.REFERENCE

[1] Linear Technology Application Notes , Datasheet of Isolated Flyback Converter Without an Opto-Coupler, http://cds.linear.com/docs /Datasheet/3574f.pdf.[2] P.L.Dowell, “Effect of eddy currents in transformer windings” Proceedings of the IEE, NO.8 PP.1387-1394, Aug 1966.[3] S.Xiao, “Planar Magnetics Design for Low-Voltage DC-DC Converters” MS, 2004.[4] ANSYS Application Notes, PEmag Getting Started: A Transformer Design Example, http://www.xiexiebang.com/download/ EDA/Maxwell9/planarGS0601.pdf.[5] K.Zhang;T.X.Wu;H.Hu;Z.Qian;F.Chen.;K.Rustom;N.Kutkut;J.Shen;I.Batarseh;“Analysis and design of distributed transformers for solar power conversion” 2011 IEEE Applied Power Electronics Conference and Exposition(APEC), v l., no., pp.1692-1697, 6-11 March 2011.[6] Zhang.;T.X.Wu.;N.Kutkut;J.Shen;D.Woodburn;L.Chow;W.Wu;H.Mustain;I.Batarseh;,“Modeling and design optimization of planar power transformer for aerospace applic ation,” Proceedings of the IEEE 2009 National, Aerospace & Electronics Conference(NAECON), vol., no., pp.116-120, 21-23 July 2009.[7] Ferroxcube Application Notes, Design of Planar Power Transformer,