System Design an Compensation Techniques
Control systems are designed to perform specific tasks.The requirements imposed on the control system are usually referred as performance imposed on the control system are usually referred as performance specifications.They generally relate to accuracy,relative stability and speed of response.
Generally,the performance specifications should not be more stringent than necessary to perform the given task.If the accurary at steady-state operation is of prime importance in a given control system,then we should not require unnecessarily rigid performance specifications on the transient response since such specifications will require expensive components.We should remember that the most important part of control system design is to state the performance specifications precisely so that they will yield an optimal control system for a given purpose.
In this lesson,we are going to briefly introduce the design and compensation procedure of single-input-single-output-(SISO),linear time-invariant (LTI) control systems by the frequency response and root-locus approaches,Compensation is the modification of the modification of the system dynamics to satisfy the given specifications.
Setting the gain is the first step in adjusting the system for satisfactory performance.In many cases,increasing the gain value will improve the steady-state behavior but will result in poor stability or even instability,Then it is necessary to redesign the system (by modifying the structure or by incorporating additional devices or components) to alter the overall behavior so that the system will behave as desired.
Fig.8.1 shows the configuration where the compensator G(s) is placed in series with the plant.This scheme is called series compensation. Another kind or compensation is feedback compensation.Generally,series compensation may be simpler than feedback compensation,
In discussing compensators,we frequently use terminology as lead network,and lag-lead network.If a sinusoidal input ei is applied to the input of a network and the steady-state output e0 (which is also sinusoidal) has a phase lead,then the network is called a lead network.Similarly, if the steady-state output e0 has a phase lag,then the network is called a lag network.In a lag-lead network,phase lag and phase lead both occur in the output but in different frequency regions;phase lag occurs in the low-frequency region and phase lead occurs in the high-frequency region.
The root-locus method is a graphical method for determining the locations of all closed-loop poles from knowledge of the locations of the locations of the open-loop poles and zeros as some parameter(usually the gain) is varied from zero to infinity.The method yields a clear indication of effects of parameter adjustment.In practice,the root-locus plot of a system may indicate that the desired performance cannot be achieved just by the adjustment of gain.Then it is necessary to reshape the root loci to meet the performance specifications.
In designing a control system,we may modify the original root loci by inserting a suitable compensator Gc(s) (as shown in Fig.8.1).Once the effects on the root locus of the addition of the poles and/or zeros are fully understood,we can readily determine the locations of the pole(s) and zero(s) of the compensator that will reshape the root locus as desired.In the design by the root-locus method,the root-loci of the system are reshaped through the use of a compensator so that a pair of dominant closed-loop poles can be placed at the desired locations.(Usually,the damping ratio and undamped natural frequency may be specified by the location of a pair of dominant closed-loop poles.)
The addition of a pole to the open-loop transfer function has the effect of pulling the root locus to the right,tending to lower the system's relative stability and to slow down the settling of the response.The addition of a zero has the effect of pulling the root locus to the left,tending to make the system more stable and to speed up the settling of the response.
The root-locus approach to design is very powerful when the specifications are given in term
of time domain quantities,such as the damping ratio and undamped natural frequency,maximum overshoot,rise time and setting time.
Let us consider a design problem.The original system either is unstable for all values of gain or is stable but has undesirable transient response characteristics.In this case,the reshaping of the root locus is necessary in order that the dominant closed-loop poles be at desired locations in the complex plane.Inserting an appropriate lead compensator in cascade with the feed-forward transfer function may solve this problem.
It is important to note that in a control system design,transient-reponse performance is usually most important.In the frequency-response approach,we specify the transient-response in term of the phase and gain margin,resonant peak magnitude,the gain crossover frequency,resonant frequency response is indirect,the frequency domain specification can be met conveniently by means of Bode diagram.
Design in the frequency domain is simple and straightforward.After the open loop has been designed by frequency response method,the closed loop poles and zeros can be determined.The transient response characters must be checked to see whether the designed system meets the requirements in the time domain.If it does not,the compensator has to be modified and the analysis must be repeated until a satisfactory result is obtained.
Basically,there are two approaches in the frequency-domain design.One is the polar plot approach and the other is the Bode diagram approach.It is more convenient to work with Bode diagram.A Bode diagram of the compensator can be simply added to the original Bode diagram,and thus plotting the complete Bode diagram is a simple matter.Also,if the open loop gain is varied,the magnitude curve is shifted up or down without changing the slope of the curve,and the phase curve remains the same.
A common approach to the Bode diagram is that we first adjust the open loop gain so that the requirement on the steady state accuracy is met.Then we plot the magnitude and phase curves of the uncompensated open loop.If the specification on the phase margin and gain margin are not satisfied,then a suitable compensator that will reshape the open loop transfer function is determined.
In many practical cases,compensation is essentially a compromise between steady-state accuracy and relative stability.In order to have a high value of the velocity error constant and yet satisfactory relative stability,we find it necessary to reshape the open loop frequency response curve.The gain in the low-frequency region should be large enough to satisfy the steady-state accuracy requirements.For the medium-frequency region (near the gain crossover frequency wc from both directions),the slope of the log-magnitude curve in the Bode diagram should be -20dB per decade. This slope should extend over a sufficient wide frequency band to assure a proper phase margin.For the high-frequency region,the gain should be attenuated as rapidly as possible to minimize the effects of noise.
The basic characteristics of lead,lag,and lag-lead compensation are as following.lead compensation essentially yields an appreciable improvement in transient response and a small change in steady-state accuracy.It may accentuate high-frequency noise effects.On the other hand ,lag compensation yields an appreciable improvement in steady-state accuracy at the expense of increasing the transient-response https://www.doczj.com/doc/8816907724.html,g compensation will suppress the effects of high-frequency noise https://www.doczj.com/doc/8816907724.html,g-lead compensation combines the characteristics of both lead compensation and lag compensation.
Discrete-time Systems and the z-Transform Method Discrete-time systems,or sampled-data system,are dynamic systems in which one or more variables can change only at discrete instants of time.These intstants,which we shall denote by kt or tk(k=0,1,2,........),may specify the time at which some physical measurement is performed or the time at which the memory of a digital computer is read out,etc.The time interval between these discrete instants can be approximated by simple interpolation.
Discrete-time systems differ from continuous-time ones in that the signals for a discrete-time system are in sample-data form.
Discrete-time systems arise in practice whenever the measurements neccessary for control are obtained in an intermittent fashion,or a large scale controller or computer is time-shared by several plants so that a control signal is sent out to each plant only periodically or whenever a digital computer is used to perform computations necessary for control.Many modern industrial control systems are in time.Sometimes,however,sampling operation,or discretization may be entirely fictitious and introduced only to simplify the analysis of control system which actually contains only continuous elements.whose inputs and/or outputs are in time.Sometimes,however,sampling operation,or discretization,may be entirely fictitious and introduced only to simplify the analysis of control system which actually contain only continuous elements.
In this lesson,we shall be concerned with discrete-time systems which the signal representing the control efforts is piecewise constant and changes only st discrete points in time.Since there are several different types of sampling operation of practical importance,we shall list them as follows:
(1)Periodic(conventional) sampling:In this case,the sampling instants are equally spaced,or tk=kt(k=1,2,3....)
Multiple-order sampling:The pattern of the tk is repeated periodically,or tk+r - tk=constant for all k.
Multiple-order-rate sampling:In this case,two concurrent sampling operations occur at tk=pT1 and qT2,where T1,T2 are contants and p ,q are integers.
Random sampling:In this case,the sampling instants are random,or tk is a random variable. Here we shall treat only the case which the samplng is periodic.
Quantization.The inclusion of digital computer in an otherwise analog system produces in digital form(usually as binary numbers) in part of the system.The system then takes the form of a mixed digital-analog combination.The introduction of a digital computer in a control system requires the use of digital-to-digital converters.The conversion of an analog signal to the corresponding digital signal(binary number)is an approximation because the analog signal can take an infinite number of values,whereas the variety of different numbers which can be formed by a finite number of values,whereas the variety of different numbers which can be formed by a finite set of digits is limited.This approximation process is called quantization. The process of quantizing (converting a signal in analog form to digital form)may be fulfilled by means of some specific circuits.The range of input magnitudes is divided into a finite number of disjoint intervals hi which are not necessarily equal.All magnitudes fallinjg within each interval are equated to a single value within the interval.This single value is the digital approximation to the magnitudes of the analog input signal.Thus,if x si the analog input,the digital output is given by y=Q(x )
Where Q is the quantizing function.
The function x(t) is a discrete-time function.The operation of digital control systems involves quantization both in amplitude and in time.We s hall next present the definitions of several terms.
Transducer.A transducer is a device which converts an input signal into an output signal of another form.(The output signal.in general,depends on the past history of the input).
Analog transducer.An analog transducer is a device which converts an input signal into an ouput signals occur only at discrete instants of time (usually periodic),but the magnitudes of these signals may be any value within the physical limitations of the system.
Sampled-data transducer.This is a transducer in which the input and output signals occur only at discrete instants of time(usually periodic),but the magnitudes of the signal,as in the case of the analog transducer,are unquantized.
Digital transducer.A digital transducer is one in which the input signal is a continuous function of time and the output signal is a quantized signal which can assume only certain discrete levels.
Analog-to-digital transducer.A digital-to-analog transducer is one in which the input signal is a quantized signal and the output signal is a smoothed continuous function of time.
Analog controllers and digital controllers.In considering the types of controllers which are used in industrial control system,we may divide them into the following three categories: Analog controllers or computers:Analog controllers or computer represent the variables in the equations by continuous physical quantities.Analog controllers can be designed which will satisfactorily serve as nondecision making controllers.
Digital controllers or computers:These operate only on numbers.Decision-making is an important function in digital controllers,and they are currently being used for the solution of problems
Involving the optimal overall operation of industrial plants.
Analog-digital controllers or computers:These are often called hybrid controllers.They are combinations of amalog controllers and digital controllers.Some of high performance controllers are of this type.
Advantages of digital controllers over analog controller.Some of the advantages of digital controllers over amalog controllers may be summarized as follows:
(1)Digital controllers are capable of performing complex computations with constant accuracy at high speed.Digital computers can have almost any desired accuracy in computations at relatively little increase in cost.On the other hand,the cost of analog computers increases rapidly as the complexity of the computations increase if constant accuracy is to be maintained.
(2)Digital controllers are extremely versatile. By merely issuing a new program,one can completely change the operations being performed.This feature is particularly important if the control system is to receive operating information or instructions from some computing center,where economic analysis and optimization studies are being made.
Because of the inability of conventional techniques to adequately handle complex control problems,it has been customary to subdivide a process into smaller units and handle each of these as a separate control problem. Human operators are normally used to coordinate the operation of units.Recent advances in computer control systems have caused changes in this use of industrial process controls.Recent developments in large-scale computers and mathematical methods provide a basis for use of all available information in the control system.In conventional control,this part of the control loop is being done directly by humans. Computer control of complex systems.Current trends in the control of large-scale systems are to consolidate the multiplicity of independently controlled units into single optimally controlled processes.In industrial process control system,it is,in general,not practical to operate for a very long time at steady state because certain changes in production requirements,raw materials,economic factors,and processing equipment and techniques,may occur.Thus,the transient behavior of industrial processes must be taken into consideration.Since there are interactions among process variable,using only one process variable for each control agent is not suitable for really complete control.By use of computer control,it is possible to take into account all process variables together with economic factors,production requirements,equipment performance,etc..,and to thereby accomplish optimal control of industrial processes.
Note that a system capable of controlling a process as completely as possible will have to solve complex equations.The more complete the control of industrial processes.
Note that a system capable capable of controlling a process as completely as possible will have to solve complex equations.The more complete the control,the more important it is that
the correct relations between operating variables be known and be used.The system must be capable of accepting instructions from such varied sources as computer and human operators and must also be capable of changing its control subsystem completely in a short time.
Introductions to PID controllers
PID controllers can be stand-alone controllers (also called songle loop controllers), controllers in PLCs, embedded controllers, or software in Visual Basic or C# computer programs.
PID controllers are process controllers with the following characteristics:
·Continuous process control
·Analog output(also known as “measurement” or “Process Variable” or “PV”)
·Analop output (referred to simply as “output”)
·Setpoint(SP)
·Proportional(P), Integral(I), and/or Derivative(D) constants
Examples of “continuous process control” are temperature, pressure, flow, and level control. For example, controlling the heating of a tank. For simple control, you have temperature limit sensors(one low and one high) and then switch the heater on when the low temperature limit sensor turns on and then turn the heater off when the temperature rises to the high temperature limit sensor. This is similar to most home air conditioning & heating thermostats.
In contrast, the PID controller would receive input as actual temperature and control a valve that regulates the flow of gas to the heater, The PID controller automatically finds the correct (constant) flow of gas to the heater that kepps the temperature steady at the setpoint. Instead of the temperature bouncing back and forth between two points, the temperature is held steady. If the setpoint is lowered, then the PID controller automatically reduces the amount of gas flowing to the heater. If the setpoint is raised, then the PID controller automatically increases the amount of gas flowing to the heater. Likewise the PID controller would automatically for hot, sunny days (when it is hotter outside the heater) and for cold, cloudy days.
The analog input (measurement) is called the “process variable” or “PV”. You want the PV to be a highly accurate indication of the process parameter you are trying to control. For example, if you want to maintain a temperature of + or – one degree then we typically strive for at least ten times that or one-tenth of a degree. If the analog input is a 12 bit analog input and the temperature range for the sensor is 0 to 400 degrees then our “theoretical”accuracy is calculated to be 400 degrees divided by 4,096 (12bit) =0.09765625 degrees. We say “theoretical” because it would assume there was no noise and error in our temperature sensor, wiring, and analog converter. There are other assumptions such as linearity, etc .. The point being-with 1/10 of a degree “theoretical” accuracy should easily be attainable.
The analog output is often simply referred to as “output”. Often this is given as 0～100 percent. In this heating example, it would mean the valve is totally closed (0%) or totally open (100%).
The setpoint (SP) is simply-what process value do you want. In this example-what temperature do you want the process at?
The PID controller’s jod is to maintain the output at a level so that there is no difference (error) between the process variable (PV) and the setpoint (SP)
In Fif.1, the valve could be controlling the gas going to a heater, the chilling of a cooler, the pressure in a pipe, the flow through a pipe, the level in a tank, or any other process control system.
What the PID controller is looking at is the difference (or “error”) between the PV and the SP. It looks at the absolute error and the rate of change of error. Absolute error means- is there a big difference in the PV and SP or a little difference? Rate of change of error means- si the difference between the PV or SP getting smaller or larger as time goes on.
When there is a “process upset”, meaning, when the process variable or the setpoint quickly changes- the PID controller has to quickly change the output to get the process variable back equal to the setpoint. If you have a walk-in cooler with a PID controller and someone opens the door and walk in, the temperature (process variable) could rise very quickly. Therefore the PID controller has to increase the cooling (output) to compensate for this rise in temperature.
Once the PID controller has the process variable equal to the setpoint, a good PID controller wlii not vary the output. You want the output to be very steady (not changing). If the valve (motor, or other control element) is constantly changing, instead of maintaing a constant value, this could cause more wear on the control element.
So there are these two contradictory goals. Fast response (fast change in output) when there is a “process” upset, but slow response (steady output) when the PV is close to the setpoint.
系统设计和补偿技术
控制系统被设计用来执行特定任务。对控制系统的要求通常被称为系统的性能指标。它们通常和系统精确度、相对稳定性及响应速度有关。
一般地，系统的性能指标不应该比系统执行给定任务事所必须达到的指标更加苛刻。对于某一个给定的系统而言，如果稳态运行精度是最为重要的，那么，我们就不应该提出不必要的过高的暂态性能指标要求。满足这些过高的暂态性能指标往往需要昂贵的部件。我们应该牢记，控制系统设计过程中最重要的一个环节就是把性能要求精确的表达出来，这样才会设计出对于给定的任务而言最优的控制系统。
在本课中，我们将要简单的介绍使用频率响应法和跟轨迹法对但输入但输出线性定常系统进行设计和补偿的方法。补偿是指改变系统的动态特性以满足给定的指标。
调节一个系统以得到满意性能的第一步是设定它的增益。在很多情况下，增加增益值将改善系统的稳态性能，但是也将使系统稳定性变差，甚至变得不稳定。于是必须重新设计系统（修改结构或者增加装置或是部件），改变总体特性，使系统按照我们所希望的那样运行。
补偿器G（s）和被控对象串联连接。这种方法称为串联补偿。另外一种补偿是反馈补偿。串联补偿通常比反馈补偿简单。
在讨论补偿器时，我们经常使用的术语是超前网络、滞后网络以及滞后超前网络。如果一个正弦信号ei加到一个网络上，它的稳态输出eo（也是正弦信号）相位超前，则该网络称为超前网络。在滞后超前网络中，相位滞后和相位超前两种情况都会出现，但是出现在不同的频率范围内；相位滞后出现在低频段，相位超前出现在高频段。
跟轨迹法是一种图解的方法。已知开环零点和极点的位置，当某个参数（通常是增益）的值从零变化到无穷大时，可以确定所有可能的闭环极点的位置。本方法清楚地显示出参数调节的效果。实际上，系统的跟轨迹图表明，仅仅通过调节增益并不能获得理想的性能。于是，必须改变跟轨迹的形状来满足性能指标。
在设计控制系统时，我们可以通过插入一个合适的补偿器G（s）来改变原来的跟轨迹。一旦完全了解了增加极点和/或零点对于跟轨迹的影响，我们就可以很方便的确定补偿器零点极点的位置，以使跟轨迹变成我们所希望的形状。在用跟轨迹法设计的过程中，通过使用补偿器改变系统跟轨迹的形状，以使闭环系统一对主导极点位于理想的位置。（通常，阻尼比及无阻尼自然振荡频率是由闭环系统一对主导极点的位置确定的）
在开环传递函数中增加一个极点的效果是把跟轨迹向右推，倾向于降低系统的相对稳定性，并且降低系统的收敛速度。增加一个零点的效果是把跟轨迹向左推，倾向于使系统更加稳定，并且加快系统的响应。
当系统的性能指标以时域的量（如阻尼比及无阻尼自然频率、最大超调量、上升时间
和调节时间）给出时，采用跟轨迹法设计是非常有效的。
让我们考虑一个设计的问题。原系统要么对所有的增益值均不稳定，要么虽然稳定但是动态响应特性不理想。这种情况下必须改变跟轨迹的形状，以使闭环主导极点位于复平面的理想位置上。在前向传递函数中串联插入一个适当的超前补偿器，就可以解决这个问题。
需要注意，在控制系统的设计中，暂态响应性能通常是最重要的。在频率响应法中我们用相角裕量及增益裕量、谐振峰值幅度、增益穿越频率、谐振频率和带宽来表示暂稳态响应。尽管暂态响应和频率响应的相互关系是间接的，但是频域的指标可以由伯德图很方便达到。
频域中的设计简单而直观。当开环系统由频率设计完成后，闭环的零点和极点就可以确定了。必须检查暂态响应特性，以确认设计的系统是否满足时域的要求。如果不满足要求，必须修改补偿器，重新分析，直到获得满意的结果。
频域中的设计主要有两种方法。一种是极坐标图法，另一钟是伯德图法。用伯德图更方便一些。补偿器的伯德图可以简单的加在原伯德图上，因此画完整的伯德图是简单的事。而且，如果改变开环增益，幅值曲线上下移动，曲线的斜率不变，并且相位曲线也保持不变。
用伯德图设计的常用方法是，我们首先调节开环增益，以使稳态精度的要求得到满足。然后，我们画出尚没有校正的开环幅值曲线和相位曲线。如果对于相位裕量和幅值裕量的指标没有满足，就确定一个改造开环传递函数的合适的补偿器。
在多数情况下，补偿实际上是在稳态精度和相对稳定性之间作一个折衷。为了获得较大的速度误差常数以及满意的相对稳定性，我们发现需要重新构造开环频率响应曲线。低频段的增益应该大到满足稳态精度的要求。中频段（从这两个方向靠近幅频曲线的穿越频率wc），伯德图中对数幅频曲线的斜率应该-20dB/dec。这一斜率应该具有足够宽的频率范围，以确保得到适当的相角裕度。对于高频段，幅值曲线应该尽可能快的衰减，以减小噪声的影响。
超前补偿、滞后补偿和滞后超前补偿的基本特性如后面所述。超前补偿对于暂态响应有明显的改进，对稳态精度改进较小。它可能加强高频噪声的影响。另一方面，滞后补偿明显提高了稳态精度，代价是增加了暂态响应时间。滞后补偿会抑制高频噪声信号的影响。滞后超前补偿综合了超前补偿和滞后补偿两者的特点。
离散系统和Z变换
离散系统或数据采样系统是指一个或多个变量仅在离散系统的瞬时变化的动态系统。这些瞬时值可以用KT或Tk表示，指完成测量的时间或者数字计算机内存的读取时间。两个离散时刻的间隔取得很短，这样这些离散时刻之间的数据可以用简单的插值法近似。离散系统不同于连续系统，它的信号是采样数据形式。
在实际应用中，当控制所需要的测量以间断的方式进行时，或者当大型的控制器或计算机被多个控制对象所共享，导致传送到每一个控制对象去的控制信号仅为周期性信号时，或者在采用数字计算机时去完成控制所必需包含的一些输入输出量在时间上的离散器件。当然，采样操作或离散化有时完全是假设，其引进目的仅仅是为了简化实际上只包含连续性元件的控制系统分析。
在本课本中，我们将讨论作为控制作用的信号是断续的常量离散系统，且该常量仅在离散的时间点上变化。因为存在几种不同类型且有使用价值的采样运算，我们就将它们列举如下：
（1）周期（普通）采样：采样时刻的间隔相等，即tk=kT(k=1,2,3)。
（2）多级采样：tk在形式上周期性地出现，即对于所有的k，tk+1-tk=常量。
（3）多速采样：两个同时进行的采样操作分别发生在tk=PT1和tk=qT2。其中p、q是整数，T1、T2是常数。
（4）随机采样：采样时刻是随机的，即tk是随机变量。
这里我们只讨论周期采样的情况。
量化当模拟系统中包含数字计算机时，系统的某一部分就产生数字形式的信号（通常是二进制数）。因此，系统就呈现出数字模拟式的混合结构形式。在控制系统中引入数字计算机，就要使用数模和模数转换器。因为模拟信号具有无穷的数值，而由一组确定的数值表示数的数量是有限的，所以，模拟量信号转换为相应的数字信号（二进制数）是一种近似。这种近似过程称为量化。
量化的过程（将模拟量转化为数字量）由一些特定的电路来完成。输入量的幅值范围被分为许多有限的区间hi，hi不一定相等。一个区间的所有幅值都取区间内唯一值。这个唯一值就是对模拟输入信号幅值的数字近似。因此，如果x为模拟输入，输出的数字值就由y=Q（x）确定，其中Q为量化函数。
函数X（t）是一个离散信号。数字控制系统的操作包括幅值和时间的量化。下面我们介绍一些术语的定义。
转换器：转换器是将输入信号转换为另一种形式输出的装置（输出信号通常取决于输入信号的历史值）。
模拟转换器：模拟转换器是输入和输出信号都是时间的连续函数的转换器。这些信号可以取系统物理限制范围内的任意值。
采样数据转换器：采样数据转换器是输入和输出信号只在离散的瞬间出现的转化器，并且其幅值和模拟转换器的情况一样，未被量化。
数字转换器：数字转换器是输入和输出信号只在离散的瞬间出现的转换器，其幅值是被量化的，即信号只取特定的离散值。
数字模拟转换器：数字模拟转换器的输入信号为量化信号，而输出信号为时间的平滑连续函数。
模拟控制器和数字控制器就工业控制系统中采用的控制器类型而言，我们可以将它们分为以下3类：
模拟控制器或计算机：模拟控制器或计算机是用连续的物理量表示方程中的变量。模拟控制器可以设计为令人满意的非决策控制器。
数字控制器或计算机：它们仅对数字进行操作。决策是数字控制器的一个重要功能。并常用它们来解决工业对象中总体运行的优化问题。
模拟数字控制器或计算：它们通常被称为混合控制器，是模拟控制器和数字控制器的一种组合。一些高性能控制器属于这种类型。
数字控制器相对于模拟控制器的优点数字控制器相对于模拟控制器的优点可以总结如下：
（1）数字控制能以一定精度高速完成复杂的运算。在运算中，数字计算机能在增加较少成本的情况下实现希望的精度。但是，若保持精度不变，运算越复杂，模拟计算机的成本也就越高。
（2）数字控制器具有很好的通用性。仅仅更新一段程序，就能改变现有的操作。如果控制系统接受进行经济分析和优化研究的计算中心发出的操作信息或指令时，这种优点就尤为重要了。
传统的方法不能处理复杂的控制问题，所以它通常是将过程细分为更小的单元，然后分别作为独立的控制问题来处理。人工操作员通常用于协调多个单元的操作。近来，随着计算机控制系统的发展，改变了工业过程控制的这种状况。大型计算机和数学方法的发展为控制系统中利用所有有用信息奠定了基础。传统控制中的这部分控制回路由人工
完成。
复杂系统的计算机控制大规模系统当前的发展趋势是将多个独立控制单元合并为一
个最优的过程。一般来说，由于产品需求、原材料、经济因素、加工设备和方法的变化，工业过程控制系统并不能长时间工作于固定的状态。因此，我们必须考虑工业过程控制系统并不能长时间工作于固定的状态。因此，我们必须考虑工业过程中的动态特性。因为过程变量之间相互影响，所以，每个控制单元只采用一个过程变量，对于真正的全面控制来说是不适当的。通过使用计算机，可以将所有过程变量和经济因素、产品要求、设备性能等都考虑在内，实现工业过程的最优控制。
值得一提的是，一个尽可能全面地控制过程的系统必须能解复杂的方程。越是全面的控制，了解和应用操作变量之间的正确关系就越重要了。系统必须能接收诸如计算机和操作员这样的不同信号源所发出的指令，并且能在短时间内改变其控制的子系统。
离散系统分析的z变换法和状态空间法离散系统的分析可以很容易采用Z变化法和状态空间法中的任意一种。
Z变换与线性定常离散系统的关系，就像是拉氏变换与线性定常连续系统的关系一样。这部分只介绍线性时不变离散系统的Z变换法。
PID控制器的介绍
PID控制器可以是独立控制器（也可以叫做单回路控制器），可编程控制器（PLC）中的控制器，嵌入式控制器或者是用Vb或C#编写的计算机程序设计。
PID控制器是过程控制器，它具有如下特征：
·连续过程控制
·模拟输入（也被称为“测量量”或“过程变量”或“PV”）
·模拟输出（简称为“输出”）
·基准点
·比例、积分以及/或者微分常数
“连续过程控制”的例子有温度、压力、流量及水位控制。例如。控制一个容器的热量。对于简单的控制，你使用两个具有温度限定功能的传感器（一个限定低温，一个限定高温）。当低温限定传感器接通时就会打开加热器，当温度升高到高温限定传感器时就会关闭加热器。这类似于大多数家庭使用的空调及供暖系统的温度自动调节器。
反过来，PID控制器能够接受像实际温度这样的输入，控制阀门，这个阀门能控制进入加热器的气体流量。PID控制器自动地找到加热器中气体的合适流量，这样就保持了温度在基准点稳定。温度稳定了，就不会在高低两点间上下跳动了。如果基准点降低了，PID控制器就会自动降低加热器中气体流量。如果基准点升高，PID控制就hi自动的增加加热器中气体的流量。同样地，对于高温，晴朗的天气（当外界温度高于加热器时）及阴冷，多云的天气，PID控制器都会自动调节。
模拟输入（测量量）也叫做“过程变量”或“PV”。你希望PV能够达到你所孔子过程参数的高精确度。例如，如果我们想要保持温度为+1度或是-1度，我们至少要为此努力，使其精度保持在0.1度。如果是一个12位的模拟输入，传感器的温度范围是从0度到400度，我们计算的理论精确度就是4096除400度=0.097656度。我们之间所以说就是理论上因为我们假定温度传感器，电线及模拟转换器上没有噪音和误差。还有其他的假定。加入，线性等等。及时是有大量的噪音和其他问题，那理论精度的1/10计算，1度精确度的数值应该很容易得到的。
模拟实处经常被简称为“输出”。经常在0%到100%之间给出。早这个热量的例子中，
阀门完全闭（0%），完全打开（100%）。
基准点(SP)很简单，即你想要什么样的过程量。在这个例子中-你想要过程处于怎样的温度。
PID控制器的任务是维持输出在一个程度上，这样在过程变量（PV）和基准点（SP）上就没有偏差（误差）。
在图中魔法门用来控制进入加热器的气体，冷却器的制冷，水管的压力，水管的流量，容量的水位或其他的过程控制系统。
PID控制器所观察的是PV和SP之间的偏差（或误差）。它观察绝对偏差和偏差变换了。绝对偏差就是-PV和SP之间偏差是大还是小。偏差变换率就是-PV和SP之间的偏差随着时间的变化是越来越小还是越来越大。
如果存在过程扰动，即过程变量或基准点变化时—PID控制器就要迅速改变输出，这样过程变量就返回到基准点。如果你有一个PID控制器的可加入的冷冻装置，某个人打开门进入，温度（过程变量）将会迅速升高。因此，PID控制器不得不提高冷度（输出）来补偿这个温度的升高。
一旦过程变量等同于基准点，一个好的PID控制器就不会改变输出。你所要的输出就会稳定（不改变）。如果阀门（发动机或其它控制元件）不断改变，而不是维持恒量，这将造成控制元件更多的磨损。
这样就有了两个矛盾的目标。当有“过程扰动”时能够快速反应（快速改变输出）。当PV接近基准点时就缓慢反应
华北电力大学科技学院 毕业设计（论文）附件 外文文献翻译 学号：121912020115姓名：彭钰钊 所在系别：动力工程系专业班级：测控技术与仪器12K1指导教师：李冰 原文标题：Infrared Remote Control System Abstract 2016 年 4 月 19 日
红外遥控系统 摘要 红外数据通信技术是目前在世界范围内被广泛使用的一种无线连接技术，被众多的硬件和软件平台所支持。红外收发器产品具有成本低，小型化，传输速率快，点对点安全传输，不受电磁干扰等特点，可以实现信息在不同产品之间快速、方便、安全地交换与传送，在短距离无线传输方面拥有十分明显的优势。红外遥控收发系统的设计在具有很高的实用价值，目前红外收发器产品在可携式产品中的应用潜力很大。全世界约有1亿5千万台设备采用红外技术，在电子产品和工业设备、医疗设备等领域广泛使用。绝大多数笔记本电脑和手机都配置红外收发器接口。随着红外数据传输技术更加成熟、成本下降，红外收发器在短距离通讯领域必将得到更广泛的应用。 本系统的设计目的是用红外线作为传输媒质来传输用户的操作信息并由接收电路解调出原始信号，主要用到编码芯片和解码芯片对信号进行调制与解调，其中编码芯片用的是台湾生产的PT2262，解码芯片是PT2272。主要工作原理是：利用编码键盘可以为PT2262提供的输入信息，PT2262对输入的信息进行编码并加载到38KHZ的载波上并调制红外发射二极管并辐射到空间，然后再由接收系统接收到发射的信号并解调出原始信息，由PT2272对原信号进行解码以驱动相应的电路完成用户的操作要求。 关键字：红外线；编码；解码；LM386；红外收发器。 1 绪论
微软Visual Studio 1微软Visual Studio Visual Studio 是微软公司推出的开发环境，Visual Studio可以用来创建Windows平台下的Windows应用程序和网络应用程序，也可以用来创建网络服务、智能设备应用程序和Office 插件。Visual Studio是一个来自微软的集成开发环境IDE，它可以用来开发由微软视窗，视窗手机，Windows CE、.NET框架、.NET精简框架和微软的Silverlight支持的控制台和图形用户界面的应用程序以及Windows窗体应用程序，网站，Web应用程序和网络服务中的本地代码连同托管代码。 Visual Studio包含一个由智能感知和代码重构支持的代码编辑器。集成的调试工作既作为一个源代码级调试器又可以作为一台机器级调试器。其他内置工具包括一个窗体设计的GUI应用程序，网页设计师，类设计师，数据库架构设计师。它有几乎各个层面的插件增强功能，包括增加对支持源代码控制系统（如Subversion和Visual SourceSafe）并添加新的工具集设计和可视化编辑器，如特定于域的语言或用于其他方面的软件开发生命周期的工具（例如Team Foundation Server的客户端：团队资源管理器）。 Visual Studio支持不同的编程语言的服务方式的语言，它允许代码编辑器和调试器（在不同程度上）支持几乎所有的编程语言，提供了一个语言特定服务的存在。内置的语言中包括C/C + +中（通过Visual C++）,https://www.doczj.com/doc/8816907724.html,（通过Visual https://www.doczj.com/doc/8816907724.html,），C＃中（通过Visual C＃）和F＃（作为Visual Studio 2010），为支持其他语言，如M,Python,和Ruby等，可通过安装单独的语言服务。它也支持的 XML/XSLT,HTML/XHTML ,JavaScript和CSS.为特定用户提供服务的Visual Studio也是存在的：微软Visual Basic，Visual J＃、Visual C＃和Visual C++。 微软提供了“直通车”的Visual Studio 2010组件的Visual Basic和Visual C＃和Visual C + +，和Visual Web Developer版本，不需任何费用。Visual Studio 2010、2008年和2005专业版，以及Visual Studio 2005的特定语言版本（Visual Basic、C++、C＃、J＃），通过微软的下载DreamSpark计划，对学生免费。 2架构 Visual Studio不支持任何编程语言，解决方案或工具本质。相反，它允许插入各种功能。特定的功能是作为一个VS压缩包的代码。安装时，这个功能可以从服务器得到。IDE提供三项服务：SVsSolution，它提供了能够列举的项目和解决方案; SVsUIShell，它提供了窗口和用户界面功能（包括标签，工具栏和工具窗口）和SVsShell，它处理VS压缩包的注册。此外，IDE还可以负责协调和服务之间实现通信。所有的编辑器，设计器，项目类型和其他工具都是VS压缩包存在。Visual Studio 使用COM访问VSPackage。在Visual Studio SDK中还包括了管理软件包框架(MPF)，这是一套管理的允许在写的CLI兼容的语言的任何围绕COM的接口。然而，MPF并不提供所有的Visual Studio COM 功能。
Load and Ultimate Moment of Prestressed Concrete Action Under Overload-Cracking Load It has been shown that a variation in the external load acting on a prestressed beam results in a change in the location of the pressure line for beams in the elastic range.This is a fundamental principle of prestressed construction.In a normal prestressed beam,this shift in the location of the pressure line continues at a relatively uniform rate,as the external load is increased,to the point where cracks develop in the tension fiber.After the cracking load has been exceeded,the rate of movement in the pressure line decreases as additional load is applied,and a significant increase in the stress in the prestressing tendon and the resultant concrete force begins to take place.This change in the action of the internal moment continues until all movement of the pressure line ceases.The moment caused by loads that are applied thereafter is offset entirely by a corresponding and proportional change in the internal forces,just as in reinforced-concrete construction.This fact,that the load in the elastic range and the plastic range is carried by actions that are fundamentally different,is very significant and renders strength computations essential for all designs in order to ensure that adequate safety factors exist.This is true even though the stresses in the elastic range may conform to a recognized elastic design criterion. It should be noted that the load deflection curve is close to a straight line up to the cracking load and that the curve becomes progressively more curved as the load is increased above the cracking load.The curvature of the load-deflection curve for loads over the cracking load is due to the change in the basic internal resisting moment action that counteracts the applied loads,as described above,as well as to plastic strains that begin to take place in the steel and the concrete when stressed to high levels. In some structures it may be essential that the flexural members remain crack free even under significant overloads.This may be due to the structures’being exposed to exceptionally corrosive atmospheres during their useful life.In designing prestressed members to be used in special structures of this type,it may be necessary to compute the load that causes cracking of the tensile flange,in order to ensure that adequate safety against cracking is provided by the design.The computation of the moment that will cause cracking is also necessary to ensure compliance with some design criteria. Many tests have demonstrated that the load-deflection curves of prestressed beams are approximately linear up to and slightly in excess of the load that causes the first cracks in the tensile flange.(The linearity is a function of the rate at which the load is applied.)For this reason,normal elastic-design relationships can be used in computing the cracking load by simply determining the load that results in a net tensile stress in the tensile flange(prestress minus the effects of the applied loads)that is equal to the tensile strength of the concrete.It is customary to assume that the flexural tensile strength of the concrete is equal to the modulus of rupture of the
A Wavelet Based Approach for Fast Detection of Internal Fault in Power Transformers The power transformer is one of the most expensive elements of power system and its protection is an essential part of the overall system protection strategy. The differential protection provides the best protection for power transformer. Its operation principle is based on this point that the differential current during an internal fault is higher than normal condition. But, a large transient current (inrush current) can cause mal-operation of differential relays. Then, studies for the improvement of the transformer protection have focused on discrimination between internal short circuit faults and inrush currents in transformers. The magnetizing inrush current has a large second order harmonic component in comparison to internal faults. Therefore , some transformer protection systems are designed to halt operating during the inrush current by sensing this large second order harmonic. The second harmonic component in the magnetizing inrush currents tend to be relatively small in modern large power transformers because of improvements in the power transformer core materials. Also , it has been seen that the fault current can contain higher second order harmonics than the inrush current due to nonlinear fault resistance, CT saturation .the distributed capacitance in the transmission line, which transformer is connected to, or due to the use of extra high voltage underground cables. Various methods have been suggested for overcoming this protection system mal-operation. This paper presents a wavelet based method for discrimination among inrush current, internal short circuit ,external short circuit and energizing and it is not affected by CT saturation and it is able to detect internal faults while transformer energization. Unlike Artificial Neural Network and Fuzzy logic based algorithms. This approach is not system dependent. The operating time of the scheme is less than 10ms. The Daubechies mother wavelet is used with a sample rate of 5 kHz. Then , the differential currents of the three phases are decomposed into two details and only the second level will be considered by using db5 mother wavelet. Discrete Wavelet Transform The wavelet transform is a powerful tool to extract information from the non-stationary signals simultaneously in both time and frequency domains. The ability of the wavelet transform to focus on short time intervals for high-frequency components and long intervals for low-frequency components improves the analysis
A convection-conduction model for analysis of the freeze-thaw conditions in the surrounding rock wall of a tunnel in permafrost regions Abstract Based on the analyses of fundamental meteorological and hydrogeological conditions at the site of a tunnel in the cold regions, a combined convection-conduction model for air flow in the tunnel and temperature field in the surrounding has been constructed. Using the model, the air temperature distribution in the Xiluoqi No. 2 Tunnel has been simulated numerically. The simulated results are in agreement with the data observed. Then, based on the in situ conditions of sir temperature, atmospheric pressure, wind force, hydrogeology and engineering geology, the air-temperature relationship between the temperature on the surface of the tunnel wall and the air temperature at the entry and exit of the tunnel has been obtained, and the freeze-thaw conditions at the Dabanshan Tunnel which is now under construction is predicted. Keywords: tunnel in cold regions, convective heat exchange and conduction, freeze-thaw. A number of highway and railway tunnels have been constructed in the permafrost regions and their neighboring areas in China. Since the hydrological and thermal conditions changed after a tunnel was excavated，the surrounding wall rock materials often froze, the frost heaving caused damage to the liner layers and seeping water froze into ice diamonds，which seriously interfered with the communication and transportation. Similar problems of the freezing damage in the tunnels also appeared in other countries like Russia, Norway and Japan .Hence it is urgent to predict the freeze-thaw conditions in the surrounding rock materials and provide a basis for the design，construction and
外文出处： 《Exploiting Software How to Break Code》By Greg Hoglund, Gary McGraw Publisher : Addison Wesley Pub Date : February 17, 2004 ISBN : 0-201-78695-8 译文标题： JDBC接口技术 译文： JDBC是一种可用于执行SQL语句的JavaAPI（ApplicationProgrammingInterface应用程序设计接口）。它由一些Java语言编写的类和界面组成。JDBC为数据库应用开发人员、数据库前台工具开发人员提供了一种标准的应用程序设计接口，使开发人员可以用纯Java语言编写完整的数据库应用程序。 一、ODBC到JDBC的发展历程 说到JDBC，很容易让人联想到另一个十分熟悉的字眼“ODBC”。它们之间有没有联系呢？如果有，那么它们之间又是怎样的关系呢？ ODBC是OpenDatabaseConnectivity的英文简写。它是一种用来在相关或不相关的数据库管理系统（DBMS）中存取数据的，用C语言实现的，标准应用程序数据接口。通过ODBCAPI，应用程序可以存取保存在多种不同数据库管理系统（DBMS）中的数据，而不论每个DBMS使用了何种数据存储格式和编程接口。 1．ODBC的结构模型 ODBC的结构包括四个主要部分：应用程序接口、驱动器管理器、数据库驱动器和数据源。应用程序接口：屏蔽不同的ODBC数据库驱动器之间函数调用的差别，为用户提供统一的SQL编程接口。 驱动器管理器：为应用程序装载数据库驱动器。 数据库驱动器：实现ODBC的函数调用，提供对特定数据源的SQL请求。如果需要，数据库驱动器将修改应用程序的请求，使得请求符合相关的DBMS所支持的文法。 数据源：由用户想要存取的数据以及与它相关的操作系统、DBMS和用于访问DBMS的网络平台组成。 虽然ODBC驱动器管理器的主要目的是加载数据库驱动器，以便ODBC函数调用，但是数据库驱动器本身也执行ODBC函数调用，并与数据库相互配合。因此当应用系统发出调用与数据源进行连接时，数据库驱动器能管理通信协议。当建立起与数据源的连接时，数据库驱动器便能处理应用系统向DBMS发出的请求，对分析或发自数据源的设计进行必要的翻译，并将结果返回给应用系统。 2．JDBC的诞生 自从Java语言于1995年5月正式公布以来，Java风靡全球。出现大量的用java语言编写的程序，其中也包括数据库应用程序。由于没有一个Java语言的API，编程人员不得不在Java程序中加入C语言的ODBC函数调用。这就使很多Java的优秀特性无法充分发挥，比如平台无关性、面向对象特性等。随着越来越多的编程人员对Java语言的日益喜爱，越来越多的公司在Java程序开发上投入的精力日益增加，对java语言接口的访问数据库的API 的要求越来越强烈。也由于ODBC的有其不足之处，比如它并不容易使用，没有面向对象的特性等等，SUN公司决定开发一Java语言为接口的数据库应用程序开发接口。在JDK1．x 版本中，JDBC只是一个可选部件，到了JDK1．1公布时，SQL类包（也就是JDBCAPI）
附件1：外文资料翻译译文 包装对食品发展的影响 一个消费者对某个产品的第一印象来说包装是至关重要的，包括沟通的可取性，可接受性，健康饮食形象等。食品能够提供广泛的产品和包装组合，传达自己加工的形象感知给消费者，例如新鲜包装/准备，冷藏，冷冻，超高温无菌，消毒（灭菌），烘干产品。 食物的最重要的质量属性之一，是它的味道，其影响人类的感官知觉，即味觉和嗅觉。味道可以很大程度作退化的处理和/或扩展存储。其他质量属性，也可能受到影响，包括颜色，质地和营养成分。食品质量不仅取决于原材料，添加剂，加工和包装的方法，而且其预期的货架寿命（保质期）过程中遇到的分布和储存条件的质量。越来越多的竞争当中，食品生产商，零售商和供应商；和质量审核供应商有显着提高食品质量以及急剧增加包装食品的选择。这些改进也得益于严格的冷藏链中的温度控制和越来越挑剔的消费者。 保质期的一个定义是：在食品加工和包装组合下，在食品的容器和条件，在销售点分布在特定系统的时间能保持令人满意的食味品质。保质期，可以用来作为一个新鲜的概念，促进营销的工具。延期或保质期长的产品，还提供产品的使用时间，方便以及减少浪费食物的风险，消费者和/或零售商。包装产品的质量和保质期的主题是在第3章中详细讨论。 包装为消费者提供有关产品的重要信息，在许多情况下，使用的包装和/或产品，包括事实信息如重量，体积，配料，制造商的细节，营养价值，烹饪和开放的指示，除了法律准则的最小尺寸的文字和数字，有定义的各类产品。消费者寻求更详细的产品信息，同时，许多标签已经成为多语种。标签的可读性是为视障人士的问题，这很可能成为一个对越来越多的老年人口越来越重要的问题。 食物的选择和包装创新的一个主要驱动力是为了方便消费者的需求。这里有许多方便的现代包装所提供的属性，这些措施包括易于接入和开放，处置和处理，产品的知名度，再密封性能，微波加热性，延长保质期等。在英国和其他发达经济体显示出生率下降和快速增长的一个相对富裕的老人人口趋势，伴随着更加苛
文献出处：Thronson P. Toward Comprehensive Reform of America’s Emergency Law Regime [J]. University of Michigan Journal of Law Reform, 2013, 46(2). 原文 TOWARD COMPREHENSIVE REFORM OF AMERICA’S EMERGENCY LAW REGIME Patrick A. Thronson Unbenownst to most Americans, the United States is presently under thirty presidentially declared states of emergency. They confer vast powers on the Executive Branch, including the ability to financially incapacitate any person or organization in the United States, seize control of the nation’s communications infrastructure, mobilize military forces, expand the permissible size of the military without congressional authorization, and extend tours of duty without consent from service personnel. Declared states of emergency may also activate Presidential Emergency Action Documents and other continuity-of-government procedures, which confer powers on the President—such as the unilateral suspension of habeas corpus—that appear fundamentally opposed to the American constitutional order.
文献翻译 原文 Combining JSP and Servlets The technology of JSP and Servlet is the most important technology which use Java technology to exploit request of server, and it is also the standard which exploit business application .Java developers prefer to use it for a variety of reasons, one of which is already familiar with the Java language for the development of this technology are easy to learn Java to the other is "a preparation, run everywhere" to bring the concept of Web applications, To achieve a "one-prepared everywhere realized." And more importantly, if followed some of the principles of good design, it can be said of separating and content to create high-quality, reusable, easy to maintain and modify the application. For example, if the document in HTML embedded Java code too much (script), will lead the developed application is extremely complex, difficult to read, it is not easy reuse, but also for future maintenance and modification will also cause difficulties. In fact, CSDN the JSP / Servlet forum, can often see some questions, the code is very long, can logic is not very clear, a large number of HTML and Java code mixed together. This is the random development of the defects. Early dynamic pages mainly CGI (Common Gateway Interface, public Gateway Interface) technology, you can use different languages of the CGI programs, such as VB, C / C + + or Delphi, and so on. Though the technology of CGI is developed and powerful, because of difficulties in programming, and low efficiency, modify complex shortcomings, it is gradually being replaced by the trend. Of all the new technology, JSP / Servlet with more efficient and easy to program, more powerful, more secure and has a good portability, they have been many people believe that the future is the most dynamic site of the future development of technology. Similar to CGI, Servlet support request / response model. When a customer submit a request to the server, the server presented the request Servlet, Servlet responsible for handling requests and generate a response, and then gave the server, and then from the server sent to
河南科技学院新科学院 2013届本科毕业生论文（设计） 英文文献及翻译 Foreign capital inflows and welfare in an economy with imperfect competition 学生姓名：王艳杰 所在院系：经济系 所学专业：国际经济与贸易 导师姓名：侯黎杰 完成时间：2013年4月15日
Foreign capital inflows and welfare in an economy with imperfect competition Abstract:This paper examines the resource allocational and welfare effects of exogenous inflows of foreign capital in a general-equilibrium model with oligopolistic competition and unemployment. Although the welfare impact for the short run is ambiguous and dependent upon the strength of excess profits and scale economies relative to unemployment in manufacturing, in the long run additional inflows of foreign capital always improve national welfare with capital mobility. Hence, attracting foreign capital remains a sound policy for economies characterized by imperfect competition, scale economies,and regional unemployment. Keywords: International capital mobility; Imperfect competition; Welfare 1.Introduction The welfare effects of exogenous inflows of foreign capital in the presence of trade restrictions have been extensively studied. Brecher and Diaz Alejandro (1977) show that when imports are subject to tariffs, an introduction of fo reign capital inflows accentuates the tariff distortion and hence reduces national welfare if the import-competing sector is relatively capital-intensive. In contrast, Dei (1985) shows that when imports are restricted by quotas,foreign capital inflows in the presence of foreign-owned capital always improve welfare by depressing the rental and so lowering the payments to existing foreign-owned capital. Recently, Neary (1981), using a common framework for both tariffs and quotas, obtains more general results of foreign capital inflows; the welfare effect of such inflows depends crucially on whether foreign-owned capital exists initially in the home country. In addition, Khan (1982) and Grinols (1991) have examined the effects of foreign capital inflows for a generalized Harris-Todaro economy under tariff protection. Khan finds that the result by Brecher and Diaz Alejandro is still valid even in the presence of unemployment, whereas Grinols argues that increased foreign capital need not be detrimental to welfare if the opportunity costs of labor are sufficiently low. Noteworthy is that the models used by these authors are all based upon the premise of perfect competition along with constant returns-to-scale technology. Although perfect competition serves as a useful assumption in crystallizing theoretical insights, it nevertheless fails to depict many of the real-world phenomena. The real-world economy is characterized, to a large extent, by imperfect competition and economies of scale. The policy implications of imperfect competition and economies
南京理工大学 毕业设计(论文)外文资料翻译 教学点：南京信息职业技术学院 专业：电子信息工程 姓名：陈洁 学号： 014910253034 外文出处：《 Pci System Architecture 》 (用外文写) 附件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 该生外文翻译没有基本的语法错误，用词准确，没 有重要误译，忠实原文；译文通顺，条理清楚，数量与 质量上达到了本科水平。 签名： 年月日 注：请将该封面与附件装订成册。
附件1：外文资料翻译译文 64位PCI扩展 1.64位数据传送和64位寻址：独立的能力 PCI规范给出了允许64位总线主设备与64位目标实现64位数据传送的机理。在传送的开始，如果回应目标是一个64位或32位设备，64位总线设备会自动识别。如果它是64位设备，达到8个字节（一个4字）可以在每个数据段中传送。假定是一串0等待状态数据段。在33MHz总线速率上可以每秒264兆字节获取（8字节／传送＊33百万传送字／秒），在66MHz总线上可以528M字节／秒获取。如果回应目标是32位设备，总线主设备会自动识别并且在下部4位数据通道上（AD[31::00]）引导，所以数据指向或来自目标。 规范也定义了64位存储器寻址功能。此功能只用于寻址驻留在4GB地址边界以上的存储器目标。32位和64位总线主设备都可以实现64位寻址。此外，对64位寻址反映的存储器目标（驻留在4GB地址边界上）可以看作32位或64位目标来实现。 注意64位寻址和64位数据传送功能是两种特性，各自独立并且严格区分开来是非常重要的。一个设备可以支持一种、另一种、都支持或都不支持。 2.64位扩展信号 为了支持64位数据传送功能，PCI总线另有39个引脚。 ●REQ64#被64位总线主设备有效表明它想执行64位数据传送操作。REQ64#与FRAME#信号具有相同的时序和间隔。REQ64#信号必须由系统主板上的上拉电阻来支持。当32位总线主设备进行传送时，REQ64#不能又漂移。 ●ACK64#被目标有效以回应被主设备有效的REQ64#（如果目标支持64位数据传送），ACK64#与DEVSEL#具有相同的时序和间隔（但是直到REQ64#被主设备有效，ACK64#才可被有效）。像REQ64#一样，ACK64#信号线也必须由系统主板上的上拉电阻来支持。当32位设备是传送目标时，ACK64#不能漂移。 ●AD[64::32]包含上部4位地址／数据通道。 ●C/BE#[7::4]包含高4位命令/字节使能信号。 ●PAR64是为上部4个AD通道和上部4位C/BE信号线提供偶校验的奇偶校验位。 以下是几小结详细讨论64位数据传送和寻址功能。 3.在32位插入式连接器上的64位卡