外文翻译---自动控制基础.docx

附录 英文资料及其译文chapter 1 basis of the automatic control1. 1. out line this device is temperature control experimental device of temperature, lever, pressure , that are the most common control subject for water treatment plants, chemical factories and power plants. at the experiment of automatic control, it is very important to keep the balance of system. automatic control system is composed of control subjects and to keep control device. especially process control has many control subjects to keep self-balance, so the experimental results is conducted with balance condition.this experimental device experiments about the relation of input signal and output signal to keep the balance (system characteristics) at the cascade experiment and fixed command control, also experiments on dynamic characteristic (balance condition without time variation),static characteristic (balance condition considerating time variation).and you record the change of control amount which was input handling amount or establishment of characteristic experiment. these typical response can be thought step response . you experiment optimum control experiment , fixing p . i. d constant of control device, relating this step response.2. process control process control keeps the balance of the system, automatically correcting toward deviation, and compares every variable to operating toward deviation, and compares every variable to operation condition of industrial process of flux, temperature, surface, pressure, etc with the established goal.process control is decided into closed loop and open loop control.3. kinds of automatic control control is composed of detection (measurement), comparison, judgment, operation and manual control is done by mans hand and automatic control is done by measure or adjuster or other machinery.at present, automatic control is taken at the many plants . moreover , we cannot think plant control without automatic control.kinds of automatic control is decided like below.automatic control open loop control feed forward control sequential control closed loop controlfeedback control 113-1 . feed back control feed back control detects (measure) compares , judges ,operates ,automatically. and it measures the results every moment , and corrects automatically if there is any differential between the desired value (set value).feed back control is one of the main process control . this is the control that detecting (measuring) the results (control amount: tank water lever ) with differential transmitter, and comparing the value with the set water lever and correct the deviation(opening operation flow control of the control value) like the above, feed back control automatically does the movement of measurement(detection) comparison calculation modernfication. feed back system has the element of doing these functions. at the diagram 3-1 block line diagram it is the closed loop and it transmitted the correcting signal of the opposition toward the process flow. controlling means final controlpart controlobjectprimary controlelementsetting partdisturbancediagram 31 block line diagram of feed back control corollaryblock line diagram: indicating the constructing element of control system in block , and connecting the line expressing the signal flow.signal :the amount being used for transmit the information3-2.feed forward control feed forward control is the control method doing necessary correct movement before the influence appears to the control system , when disturbance enters into the control system.at feed back control, it starts correct movement to erase the deviation after the influence by disturbance appears, so in case of sudden change of disturbance or set value, then control disorders transiently and arises many problems. feed forward control breaks down this weak point. at feed forward control, results of the controller is not done feedback and becomes open-loop control, not being close-loop control. accordingly, in case of feed back control, the relation between cause and effect of disturbance and the results of control must be understood well. that is ,relation of influence to the control amount toward load change, and operating amount needed to compensate it should be clear.but it is generally difficult. in many cases it is difficult that all the disturbance is detected, and to get the perfect process model in actual process.moreover it is difficult to avoid constant deviation, so it is used combined with feed back control.3-3 sequence controlsequence control processes the fixed process in advance step by step. this sequence control is used in neon signs, vending machines, or electric washing machines. on the other hand, it is needed in the producing process at chemical factory, automobile factory, conveyer, automatic warehouse as automation.3.4 classification of control methods production method by continuous process is employed, when scale of process industry gets bigger and larger production amount id requested. you need to make proper use of the control method on some different condition of operation. to classfy automatic control system is difficult strictly because their control system has correlation. but general method of cassification will be like below.4-1 classification by desired value automatic control fixed command controlfollowing control follow up control program control4-1-1 fixed command control most of the controls belong to this control when desired value is constant.4-1-2 following command control servo mechanism composed to follow the change belongs to this control when desired value changes optionally.4-1-3 program control it is used for the control in which desired value changes according to fixed time schedule. normally , it is well used to temp. control of fever process of metal or batch process at the chemical industry.4-2. classification by control method automatic control unity control loop ratio control cascade control4-2-1 ratio control it is well used to flow control of 2 fluid when desired value keeps with other fluid (other amount) constantly.you compare and measure if special ratio keeps toward basic fluid (b), then maintain the ratio as the purpose.4-2-2 cascade control it is the control method that more than 2 automatic control systems control by output of other control device. in short, control circuit is combined in series. you change the desired value of flow by output of flux adjuster. if you control the desired value of flow control to fix water level in water tank, then you can prevent the influence to the level such as main pressure change of flow itself. the purpose of cascade control method is to absorb disturbance at first control, also to make easy the next step control, and to progress the control on the whole.3.5control action at control action, movement to reduce control deviation, giving operating amount in accordance with a movement signal is called control action. the following is this classification.5-1 continuous controlit does constantly correct movement toward deviation with desired value,measuring continuously toward controlled variable change.5-1-1 proportional actionit is the movement that operating amount y is in proportion to movement signal and deviation. suppose you make deviation as e, gain as kp,3.6 automatic control apparatus following apparatus are necessary for each part, like a block diagram( see diagram 3-2) of feedback control. primary detecting element final control element controlling means6-1 primary detecting element this is the part to take out necessary signals from controlling object , and transmit on control devece.(1) expanding thermometer (bimetal type)bimetal is the joined two metal boards which have different thermal expansion coefficient. it curves by temp.change.(2) pressure type thermometer ( vapor pressure )you put vaporlizable liquied like propane or ether into thermal sensitivity part.these liquid has certain vapor pressure, by contact surface with gas, and it deflects the needle, by changing pressure measuring mechanism. (3) resistance thermometer it is well known that in thermometry resistor (rt). its resistance increases as electric resistance changes by temp. and temp. rises.you build a bridge with thermometry resistor, and when its resistance value changes by temp., unbalanced current generates at the bridge. from this, you will know the temperature. (4) thermoelectric thermometer (thermocouple)zeebesk effect is employed. you connect different kinds of metal. and make one connecting point temp.(thermometry contact point) higher than another connecting point (standard contact point) . then thermoelectromotive force is generated between both connecting points. (5) radiant thermometer solid emits radiant energy in proportion to the square of four of absolute temp., like stefan-boltzmanns formula. (6) thermocouple and thermometry resistor detecting part (temp.sensor) of temp.control experimental device (spc-201) is mostly used in industrial tem.measurement.and it employs thermocouple and thermometry resistor with which you can measure in high accuracy and easily. 6-2. final control element ( control valve) control valve receives output of adjuster and converts it into process variable control valve is the element to feedback to the process. so decides valve specifications. understanding each controlled objects.6-2-1 control valve feature(1) flow feature( proper feature)relation of lift of control valve. that is , valve operation signal, with flux is called flow feature,equal percentage feature and on-off feature represent.1、 near feature2、 queral percentage feature3、 on-off feature linear featurevalve opening degree and flow are in proportion. accordingly, flux changes 10% linearly,as opening degree changes 10%. equal percentage featureflow increasing modulus becomes constant toward unit change of valve lift . suppose there is flow increasing modulus at 10%, toward n% change of lift. then flow will be. when 10 l/min weighting is 10*0.1=1 l/min when 50 l/min weighting is 50*0.1=1 l/min when 90 l/min weighting is 90*0.1=1 l/min even if the same n% lift change, flow change is small, if flow is small. and it becomes big if flow is big. so, it has fine adjustment feature over wide flow range. on-off feature flow soon reaches to the max.value, when a valve shift starts to move. it is usually used for 2-positioning control.it is called on-off feature or quick open feature.7. relation of pid value and disturbance and control response toward setting change. collect the relationship of pid value and control response toward disturbance, from experimental results, acquired at experiments.(1) proportional (p) action effect to increase proportional gain to decrease off set amount (in case of no-integral action)to become oscillative ,and be hunting conditionto get shouter the period of oscillation (2) integral (i) action results following things are conducted in a experiment ,changed only integral time ti and shortening ti.to lose off set amountthe first mountain gets smallerto become oscillative. amplitude damping ratio gets bigger to finally exhale returning time initially to setting value is shortened.(3) differential (d) action effect following thing is conducted in a experiment ,changing only differential time and making td longer.off set amount does not change (in case of no-integral action)the first mountain gets smalleroscillation is restrained. amplitude damping ratio gets smaller. but ,if differential time is too long ,it becomes oscillative again.oscillaion period is shortened.8. p.i.d adjustment procedureyou shall understand pid feature and nature from experiments you did ,however, have difficulty in finding true value ,despite the adjustment .(1) adjust p-i-d in order. make step change toward desirable value, changing each constant. then confirm and record the results.(2) change proportional (p) band from large number to small number. stop it when measuring value causes hunting.(3) change integral time (ti) from large number to small number, too. stop it when measuring value causes hunting, and bring a little back larger.(4) change differential time (td) from small number to large number. stop it when measuring value causes hunting, and bring a little back smaller.(5) when you wish to shorten setting time, make p much smaller, and check the change of measuring value.9. optimum adjustment to arrange the control purpose based on the former experiments.(1) when you change desirable value, make measuring value and desirable value agree, as soon as possible. (desirable value change, step response)(2) if measuring value deviates from desirable value, owing to changes of surrounded condition temporarily, put it back as soon as possible. (disturbance response)as for (1) , time passage to make them agree is the problem. measuring value change on pid value, in case of desirable value change, will be normally like diagram 9-1.at this diagram, temporarily it gets over desirable value. this is called overshoot. to decrease this over amount, and to shorted time to settle down measuring value (setting time) do not normally coexist. in short, adjusting not to get over makes the setting time longer.also, control process may have some trouble, if you shorten the setting time, ignoring over amount. on the other hand, it may be better to reach the desirable value sooner in spite of over amount. so, establishing guideline of overshoot, and you have and adjusting method, making time minimum within the range. it is called optimum adjustment, to adjust pid constant.自动控制基础1、 提纲这套设备是用来测量温度、流量、液位、压力的实验设备中的温度的设备。温度、流量、液位、压力这些控制量是水处理厂、化工厂、电厂中最普遍的控制对象。在这些自动控制实验中，最重要的是保持系统平衡。自动控制系统是由控制对象、控制装置组成的。尤其是过程控制，它要求有多种控制对象来保持自身平衡。因此，实验结果是在平衡的情况下得到的。在串级实验和固定命令控制下，这套实验装置通过测试输入与输出的关系来保持系统的平衡。因此，这套系统有静态特性和动态特性。这个反映是阶跃响应的结果。2、 过程控制过程控制是保持系统的平衡，自动调整偏差。根据工业过程中液面、压力、流量、温、等要求的目标来比较，自动调节偏差。过程控制分为开环控制和闭环控制。3、 自动控制的种类控制是由检测装、比较装置、调节装置、执行装置组成并且手动控制是由人通过手工实现的，自动控制是通过机械、调节器、检测器实现的。在目前，自动被用于许多工厂中，甚至，我们无法想象，在工厂中没有过程控制会怎样。各种过程控制的分类如下所示：3-1反馈控制自动控制 开环控制 前馈控制 顺序控制 闭环控制 反馈控制反馈控制主要依据比较部分来实现自动操作。它返回的每部分的测量结果，如果测量值与给定值产生偏差，那么根据二者之差将操作值也作相应的调整。反馈控制是一种主要的过程控制，我们将以如图3-1的液位控制系统为例进行介绍。这个控制系统检测结果（被控参数：水塔的液位）被测量变送器转化之后，与设定液位进行比较，然后根据比较结果阀的开度，直至最后使液位达到平衡。3-2、前馈控制前馈控制特点：按干扰作用的大小进行控制，可以克服扰动或给定突然改变带来的问题，一般比反馈控制要及时，但一种前馈控制只能克服一种干扰；反馈控制属于闭环而前馈控制属于开环控制，且其使用的是视对象特性而定的特殊控制器。一般前馈控制很难达到控制要求，因为对实际系统来说将所有的扰动区分开来去建立一个实际模型是不可能的。因此，前馈控制通常与反馈控制、串级控制共同使用以达到良好的控制效果。3-3、顺序控制顺序控制适用于高级单步执行系统。这种顺序控制常用在霓虹灯广告牌，全自动洗衣机或电动洗衣机等领域，另一方面，化工厂、汽车厂、转化器、自动仓库的生产过程中也经常使用顺序控制器。4、控制方法的分类实际和产经常使用连续的生产方式，而生产过程中很少有要求太大的被控量。4-1 根据给定值分类自动控制： 定值控制 随动控制：随动控制程序控制4-1-1 恒值控制实际生产中，大多数的控制都属于给定值为常数的恒值控制。4-1-2 随动控制随动控制是输出随给定变化的控制。4-1-3 程序控制它是给定值按固定的程序设定时间而变化，通常被用在化工生产中温度的过程化控制。4-2 根据控制方法分类自动控制：单元控制、 比值控制、 串级控制4-2-1 比值控制实现两个或两个以上参数符合一定比例关系的控制系统，通常以保持两种或几种物料的流量为一定比例关系的系统。经过比较、测量确定两种物料中处于主导地位物料便于实现比值控制。6、自动控制部分下面将要介绍各个部分对于反馈控制是必不可少的。基本检测单元、执行单元、 控制单元6-1基本检测要素在控制设备中，这是从被控对象上提取重要的信号的部分。用压力检测的基本要素如下：6-1-1 流量检测我们通常辨别物质为三种状态：固体、液体、气体。固体的形状是固定的，几乎不能改变。液体是容易改变形状和体积的。在三种物态中，液体和气体被通称为流体。单位时间里通过一定区域的流动流体的体积或质量称为流量。测量流量有以下几种方法：（）差压式流量计将一个节流装置即带孔的金属盘放在流体流过的管子中，流体在通过盘前后是产生不同的压力。流体通过节流装置时，节流装置的上游、下游之间产生压差。这个压差与流量有关，所以我们就可以通过测量这个压力差得到流量。（）转子流量计将浮子放入一个锥形管子中，被测流体由底部向上涨，引起浮子上移。浮子上移的数量与流量有关，这个值随流量改变。（）电磁流量计在磁感应强度均匀的磁场中，垂直于磁场方向放置一个不导磁的管道，在该管道上与磁场垂直方向设置一对同被测介质相接触的电极，管道与电极之间绝缘。当导电流体流过管道时，相当于一根长度为管道内径的导线在切割磁力线，因而产生了感应电势，并由两个电极引出。感应电势与被测介质的流量成线性关系。（）超声波流量计超声波在流体中的传播速度与流体的平均流量有关。可以通过测量传播速度、管长、流体流动的速度来确定流量。 （）动态压力流量计装在管子中心的元件获得的功率与流量的倍成正例。因此当功率传送到上面的传感器时，就可以知道流量的大小。（）椭圆齿轮流量计当流体有下向上流过，由于压力损失，使出口和入口产生压差，椭圆齿轮在此压差作用下产生力矩而转动。当椭圆齿轮与壳间的半月牙容积一定时，只要测出椭圆齿轮的转速，便可知被测流体的体积流量，即（7）水坝式流量计在水流的方向上建以个水坝，让水流流过坝，使水流增大，水位升高。这就固定了流量与坝形状的关