外文翻译---三坐标测量机测头的误差校准.docx

附录2Study and Design no Automation Control System of the Thermal Power Unit from the System Point of view.Tian Jianyan liu sifeng Pan lizhen（1. Nanjing University of Aeronautics and Astronautics ,Nanjing 210016 China)（2. Taiyuan University of Technology ,Taiyuan 030024 China)Abstract: From the system point of view, the feature of the thermal power unit and the demand on its control system are analyzed and research in details in this paper. The character that the boils and the steam turbine are a whole of relative independence is fully considered. By coordinate control, the purpose of the optimal whole operating effect of the system is realize adopting the key techniques of communication, computer and intelligent information process etc. The adaptation and whole property of the system is emerged by interaction and coordination between subsystems.1IntroductionThe system is an organic whole certain structure and function ,which consists of several element with interrelation , interdependence and interplay .The thermal power unit is a typical system ,composed of generator ,steam turbine ,boiler and many anxiliary equipment .Its main function is to produce the power load according to power network requirement .System engineering is the science used to study and design the complex system .In the meantime, It is also the theory and method used to deal with systems in term of definite aim in order to achieve the optimal whole of the system .From the system point of view, the coordinate control system of the thermal power unit has been studied and designed in this paper .2 Study and Design on Automation Control System of the Thermal Power unit from the System Point of View 2.1 Function of Automation Control System of the Power unit At first the thermal power unit as the controlled object is deeply studied before its automation control system is studied and designed .The thermal power unit is a huge group of equipments ,which is composed of generator, ,steam turbine ,boiler and many auxiliary equipments. Its process flow is complex and pipelines intervenient .Especially the large-scale power unit is a typical coupling ,nonlinear ,varying complex controlled object with multi-input and multi-output .Thousands of parameters are measured ,operated and controlled .The character of object is changeful because of many different operating modes and switch relation .With enlarging of industry production scale and the raising of peoples living standard ,the required quantity of power energy is increasing and the difference of apex and vale of power load is increasing .So the new and higher require is put forward for automation control system of the power unit .（1.）Load control :Along with the increase of the unit capacity ,early load control mode of “boiler follows steam turbine ”or “steam turbine follows boiler ” has not already satisfied the requirements so we must adopt more suitable load control scheme ,which is the unit coordinate control .（2.）Reliability: The design of system must be reliable, ensuring safe and economic operation of the unit .In addition, The tolerance fault, redundant technology ,self-diagnosis of software and hardware must be adopted to improve the reliability of system .（3.）Communication and man-machine interface: Because there are many parameters need to be measured and controlled and its varying speed is quick when the large scale unit is running , communication system must have quick real-time response and high reliability ;man-machine interface must be good at the operator station including operating terminal and large-area display that provides synthetic menus and information about the whole production process for the operators. 2.2 Structure of Automation Control system of the power unit The design of automation control system of thermal power unit mainly includes control, alarm monitor, protect etc . In accordance with the above analysis .So we divide the complex system into several subsystems in order to make the whole system optimal .（1.）Data acquisition system(DAS):It is information center of whole system and provides credible rapid objective operating records ,which is the base of safe and economical operating of equipments .Function of ,print of accident list and incident review ,property calculate ,operate guidance etc（2）Boiler control system :Boiler control system such as boiler combustion ,steam temperature ,feedwater ,auxiliary control system and the boiler safe supervisory system and boiler combustion management system. There subsystem coordinate each other and make boiler operate in safe ,efficient and steady state to satisfy the load instruction of power network in various operating modes .（3.）Steam turbine control system :Steam turbine control system realizes load control and rotative velocity control of steam turbine by DEH (Digital Electro-Hydraulic ).In addition ,the auxiliary system of steam turbine include the deoxygenation water lever control ,deoxygenation pressure control ,the condenser hot well water level control and the heater water lever control etc （4.）Auxiliary system :Besides the main systems mentioned above ,the auxiliary system also has by-pass control system etcThe main system and auxiliary system are a organic whole through close connection of information communication network .They are inter-permeable and .Inter-dependent so as to form the main part of the automation control system of the large-scale unit.2.3 Design of Automation Control System of the Thermal Power Unit From the system point of view, we analyze and study the principle of two basic feedback control method early that “boiler follows steam turbine” and “steam turbine follows boiler” in order to find out the existent problem ad be able to design more reasonable control method.2.3.1 Boiler follows steam turbine mode This kind of control mode is first to let steam turbine trail the needs of power network load ,then let boiler trail steam turbine .Its advantage is to be able to fully use the heat accumulation of boiler ,make the unit meet the change of power network load comparatively quickly. But because the inertia and delay of boiler are greater ,the regulation of former turbine pressure pt cannot follow the speed of load regulation, thus pt has greater fluctuation, which is disadvantageous to the steady operation of boiler .The range and speed change of the units output must be restricted .2.3.2. Steam turbine follows boiler mode This kind of control mode is first to let boiler train the needs of power network load, then let steam turbine train boiler .It can be better to maintain steam pressure stabilize and beneficial to boiler steady operation .But it do not fully utilize the heat accumulation f boiler to regulate the units output ,it is more slowly that the unit meets the loads demand ,so this control mode is only to be applied to the unit undertaking basic load .2.3.3 Coordinate control modAccording to the analysis above, it must use the heat accumulation of boiler fully and reasonably when the unit has better adaptability to power network load in safe operation. That is to let former turbine pressure changes, then to coordinate the interaction between two loops of power regulation and pressure regulation reasonably, so that units output meets the needs of the power network load promptly, and guarantee the control demand of unit steady operation. The practical method is to lead into properly feedforward control systems mentioned above and make boiler and steam turbine coordinate each other so that the schemes of various coordinate controls suitable to practical project can be attained, such as: coordinate control system based on“ boiler follows steam turbine” or“ steam turbine follows boiler”。. Basic function of coordinate control system. Coordinate control system of the thermal power unit should usually have following function:(l) select different load instruction according to the unit operating condition and the requirement of power network for the unit.(2) restrict the change rate of load instruction.(3). Calculate the biggest possible output of the unit and restrict the biggest and minimum amplitude of load.(4). Have the function of RUNBACK.(5). Select different running mode according to the unit operating condition.(6). Calculate actual unit output.(7). Let automation control system have enough steady abundant quantity and better wholeness.(8). Have necessary safe measures such as starting by-pass system and preventing steam turbine from exceeding the speed limit etc, when the unit and power network unite suddenly because of accident. Basic composition of coordinate control system of the unit. Now the coordinate control system of the unit is composed of two parts, which are load instruction process and coordinate control of boiler and steam turbine, shown as fig.1. Fig.1 Unit Coordinate Control SystemIn which, load instruction process is composed of unit calculation loop, unit Allowed load calculation loop and load restriction loop. Coordinate and steam turbine controller.. Implementation of coordinate control system of the thermal power unit Modern large-scale thermal power unit adopts distributed control system to realize the unit automation control that guarantees safe economic operation of the unit. TEKEPERM-ME of SIEMENS is chosen to realize coordinate control system of the thermal power unit including several parts shown as Fig.2.Fig 2 Implementation diagram of unit coordinate control systemWhen each subsystem of the unit normally run, start the mode of coordinate control mode. In this mode , steam turbine and boiler accept load instruction in parallel. Boiler maintains main steam pressure through changing combustion rate, and steam turbine pressure and set value. When the deviation of former turbine pressure and set value exceeds certain limit value, open degree instruction of steam value given by steam turbine main control loop is restricted, up to this deviation within the pressure control scope of the boiler.3. Conclusion. In one word, from the system point of view, the automation control system of the thermal power unit is divided into several subsystems as well as the design and implementation of unit coordinate control system is demonstrated in this paper. The large scale unit coordinate control has faster trailing performance and better stability and robustness. The purpose of the optimal whole operation effect of the unit is realized by coordinate the subsystems.Reference1Xiong Shuyan , Wangxingye ,Tianyan .Distributed Control System of thermal power plant ,Scientific Press .Beijing P.R China ,20003 2 Zhong xinyuan .Application of DEB Coordinated Control System in Thermal power plants ,electric power Science And Engineering ,2003(3):50-53.Author Biographies Jianyan Tian , associate professor ,is a Doctoral student in Nanjing University of Aeronautics and Astronautics .Her research is aimed at intelligent control ,System Engineering and Grey System theory .Lizhen pan is a student for Master Degree in 2002 .Her research is aimed at intelligent control theory and its application.附录3三坐标测量机测头的误差校准内容摘要:经过几十年的快速发展，坐标测量技术已臻成熟，测量精度得到极大提高，测量软件功能更加强大，操作界面也日益完善，生产厂家遍布全球，开发出了适于不同用途的三坐标测量机型。几十年的发展充分证明，现代三坐标测量系统打破了传统的测量模式，具有通用、灵活、高效等特点，可以通过计算机控制完成各种复杂零件的测量，符合机械制造业中柔性自动化发展的需要，能够满足现代生产对测量技术提出的高精度、高效率要求。 除用于空间尺寸及形位误差的测量外，应用坐标测量机对未知数学模型的复杂曲面进行测量，提取复杂曲面的原始形状信息，重构被测曲面，实现被测曲面的数字化，不仅是坐标测量机应用的一个重要领域，也是反求工程中的关键技术之一，近年来也得到快速发展。关键词：补偿误差 探针 找正 校准 三维特性 触发坐标测量机及其特点坐标测量机是一种具有很强柔性的尺寸测量设备，CMM在工业界的应用开始于对棱柱零件的快速、精确测量。但随着CMM各方面技术的发展（如回转工作触发式测头的产生），特别是计算机的CMM的出现，目前，CMM已广泛应用于对各类零件的自动检测。与投影仪、轮廓测量仪、圆度测量仪、激光测量仪等比较，CMM具有适应性强，功能完善等特点。坐标测量机的出现，不仅提高了检测设备的水平，而且在自动化检测中也是一个生重要的突破。CMM在自动化程度方面有很大的差别。计算机控制的CMM具有自动执行检测、分析检测数据和输出检测结果的功能，而一般的CMM仅有手动控制功能或手动控制加示教功能。目前，随着计算机硬件性能的提高和价格降低，绝大部分CMM均配有计算机，利用计算机可对测量所得的数据进行在线分析，以判别被控件是否合格。同时也可以使用统计技术来确定工艺能力是否满足，分析误差等来源。 除了再质量检测方面使用CMM外，CMM还可以用于对实物的仿物的信制加工中，即所谓逆向工程。在这种情况下，由CMM测量实际工件，并将测量所得的数据传到系统中，由CAD/CAM系统对这些数据进行加工处理，建立CAD模型，并进一步生成加工指令来指导加工。 CMM测头测头是CMM非常重要的部件，可以这样说，测头的发展先进程度就标志着CMM的发展先进程度。CMM可以配置不同类型的测头传感器。接触类的测头主要包括触发式、模拟式两种。非接触式包括激光三角测量、激光成像、机器视觉等。最初人们使用CMM时，由操作人员移动坐标轴，所用的测头是刚性的，当刚性测头以一定的接触力接触到被测表面时，人为记录下各坐标轴的坐标值。这种初期的 CMM不可能具有自动检测的能力，使用范围受到了极大的限制。但是由于它具有了三坐标的雏形，在使用测头钻孔的位置时也相当有效。CMM能被广泛地应用，其主要的一个原因是发明了触发式测头，触发式测头的最大功能是它的触发功能，即当探针接触被测表面并有一定的微笑位移时，测头就发出一电信号，利用此信号可以立即锁定当前坐标轴的位置，从而自动记录坐标值。触发式测头是由雷尼绍公司发明的，现在该公司生产一系列的触发式测头，可用于CNC加工中心，雷尼绍公司的生产的CMM测头现已成为行业标准配置，广泛地用于各大生产厂家的CMM上。常见的测头再运动学上，探针处于由三个圆柱棒6个球组成的6个触点唯一确定的位置上，用一个轻型的有参紧力的弹簧维持这一位置。6个 触点图中的方式依次连接，并接一个恒定电流电源。当探针接触被测表面，并产生微小位移时，6个触点中将有一个或一个以上的触点断开，从而使回路中的电阻迅速增大。当回路中的电阻增大到一定数值时，两端超过一定数值的电压将将起到开关电路发出信号。利用此信号就可以读取当前的测量位置数据。这种测头的特点是具有三维特性，即X,Y,Z三个方向的移动接触均能引起触发。因此，可以从不同的方向接触被测表面，而不会影响测量结果。 在触发式测头进行测量的过程中，探针必须偏移一个固定的数量才会触发开关，因此，测量结果中要对这段偏移进行补偿。探针接触被测表面后，为了避免移动过量而折段，探针需要反方向退出一定距离。因此测量速度比硬探头扫描测量速度低。CMM是用探针端部球的中心坐标值作为点的输入数据。因此，在测量时必须用恰当的方法推断测头端部球与被测零件的触点位置。在非CAD指导的检测系统中，通常在触点附近作三点测量，从而近似地找出通过该三点的平面法线，这不仅要耗费很多时间，从而测量精度也比较低。在CAD指导的检测系统中可以根据被测工件的CAD模型直接计算出被测点法向，让测头从法向接触被测点，这样就比较容易判断触点的位置。如图所为触点坐标，为测头端部球心坐标，8，a分别为测点法向与z轴夹角及法向在xy平面内投影与y轴夹角，则接触点的坐标可表示为：x=x-R sinB.sinay=x-R sinb.sinaz=X-R sinb.sina 图所示为探针的形状。它的作用是为红宝石球提供一个固定的支撑，当探针接触被测表面时，探针的微笑移动可触发开关，从而发出信号。探针有不同的类型。如图所示，根据不同的需要可以选择不同的类型的探针。为了获得较高的测量精度，建议在实际测量时遵循以下两条原则：1、尽量使用长度短的和刚性好的探针。测量时探针的弯曲越大，偏移越大，测量的重复精度就越低。2、尽量选用直径大的红宝石探针。选用直径大的红宝石探针，一方面可以减小加工表面缺陷时测量精度的影响，另一方面可以增大探针的有效工作长度。如图7-8所示。1 测头的分类 测量头作为测量传感器，是坐标测量系统中非常重要的部件。三坐标测量机的工作效率、精度与测量头密切相关，没有先进的测量头，就无法发挥测量机的卓越功能。坐标测量机的发展促进了新型测头的研制，新型测头的开发又进一步扩大了测量机的应用范围。按测量方法，可将测头分为接触式（触发式）和非接触式两大类。触发式测量头又分为机械接触式测头和电气接触式测头；非接触式测头则包括光学显微镜、电视扫描头及激光扫描头等。本文讨论的重点为触发式测头。 (1)机械接触式测头 接触式测头又称为“刚性测头”、“硬测头”，一般用于“静态”测量，大多作为接触元件使用。这种测头没有传感系统，无量程、不发讯，只是一个纯机械式接触头。机械接触式测头主要用于手动测量。由于人工直接操作，故测头的测量力不易控制，只适于作一般精度的测量。由于其明显的缺点，目前这种测头已很少使用。 (2)电气接触式测头 电气接触式测头又称为“软测头”，适于动态测量。这种测头作为测量传感器，是唯一与工件接触的部件，每测量一个点时，测头传感部分总有一个“接触偏转发讯回复”的过程，测头的测端与被测件接触后可作偏移，传感器输出模拟位移量的信号。这种测头不但可用于瞄准(即过零发讯)，还可用于测微(即测出给定坐标值的偏差值)。因此按其功能，电气接触式测头又可分为作瞄准用的开关测头和具有测微功能的三向测头。电气接触式测头是目前使用最多的测头。 2 测球半径补偿误差 (1)测针的选择 正确选择和使用测头是影响坐标测量机的测量精度的重要因素。测针安装在测头上，是测量系统中直接接触工件的部分，它与测头的通讯式连接渠道称作触发信号。如何选用合适的测针类型和规格取决于被测工件的特征，但是在任何情况下，测针的刚性和测球的球度都是不可或缺的。 工业用红宝石是高硬度的陶瓷材料，红宝石测球具有很好的球度，测量时红宝石测球的球头磨损可忽略不计。测针针杆一般用非磁性的不锈钢针杆或碳钨纤维针杆，以保证测针的刚性。测针的有效工作长度(EWL)使得测针接触工件时可获得精确的测点位置。球头尺寸和测针有效工作长度的选取取决于被测工件。可能的情况下，选择球头直径尽可能大、测杆尽可能短的测针，以保证最大的球头/测杆距，获得最佳的有效工作长度和测针刚性。需要时可加长测杆以增大探测深度，但值得注意的是，使用测针加长杆会降低刚性，从而降低测量精度。（3）探针的校准在对工件进行实际检测之前，首先要对测量过程中用到的探针进行校准。因为在许多尺寸的测量当中需要沿不同的方向进行探测