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模糊控制 英文文献

模糊控制  英文文献
模糊控制  英文文献

CONTROL, PID CONTROL, AND

ADVANCED FUZZY CONTROL

FOR SIMULATING A NUCLEAR

REACTOR OPERATION

XIAOZHONG LI and DA RUAN*

elgian Nuclear Research Centre (SCKoCEN

Boeretang 200, 8-2400 Mol, Belgium

(Received 15 March 1999)

Based on the background of fuzzy control applications to the first nuclear reactor in Belgium (BRI) at the Belgian Nuclear Research Centre (SCK.CEN), we have made a real fuzzy logic control demo model. The demo model is suitable for us to test and com- pare some new algorithms of fuzzy control and intelligent systems, which is

advantageous because it is always difficult and time-consuming, due to safety aspects, to do all experiments in a real nuclear environment. In this paper, we first report briefly on the construction of the demo model, and then introduce the results of a fuzzy control,

a proportional-integral-derivative (PID) control and an advanced fuzzy control, in which

the advanced fuzzy control is a fuzzy control with an adaptive function that can

Self-regulate the fuzzy control rules. Afterwards, we present a comparative study of those

three methods. The results have shown that fuzzy control has more advantages in terms

of flexibility, robustness, and easily updated facilities with respect to the PID control of

the demo model, but that PID control has much higher regulation resolution due to its integration term. The adaptive fuzzy control can dynamically adjust the rule base,

therefore it is more robust and suitable to those very uncertain occasions.

Keywords: Fuzzy control; PID control; fuzzy adaptive control; nuclear reactor

I INTRODUCTION

Today the techniques of fuzzy logic control are very mature in most

engineering areas, but not in nuclear engineering, though some research has been done (Bernard, 1988; Hah and Lee, 1994; Lin et al. 1997; Matsuoka, 1990). The main reason is that it is impossible to do experiments in nuclear engineering as easily as in other industrial areas. For example, a reactor is usually not available to any individual. Even for specialists in nuclear engineering, an official licence for doing any on-line test is necessary. That is why we are still

conducting projects such as "fuzzy logic control application" in BRl (the first nuclear reactor in Belgium) (Li and Ruan, 1997a; Ruan, 1995; Ruan and Li, 1997; 1998; Ruan and van der Wal, 1998). In the framework of this project, we find that although there are already many fuzzy logic control applications, it is difficult to select the most sui-

table for testing and comparison of our algorithms. Moreover, due to the safety regulations of the nuclear reactor, it is not realistic to perform many experiments in BRl. In this situation, we have to conduct part of the pre-processing experiments outside the reactor, e.g., com-

parisons of different methods and the preliminary choices of the parameters. One solution is to make a simulation programme in a computer, but this has the disadvantage that in which, however, the real time property cannot be well reflected. Therefore another solution has adopted, that is, we designed and made a water-level

control system, referred to as the demo model, which is suitable for our testing and experiments. In particular, this demo model (Fig. 1) is designed to simulate the power control principle of BRl (Li et al., 1996a,b; Li and Ruan, 1997b).

In this demo model, our goal was to control the water level in tower TI at a desired level by means

of tuning VL (the valve for large control tower T2) and VS (the valve for small control tower T3). The pump keeps on working to supply water to T2 and T3. All taps are for manual tuning at this time. VI and V2 valves are used to control the water levels in T2 and T3 respectively. For example, when the water level in T2 is lower than photoelectric switch sensor 1 then the on-off valve V, will be opened (on), and when the water level in T2 is higher than photoelectric switch sensor 2 then the on-off valve Vl will be closed (off). The same is true of V2. Only when both VI and V2 are closed V3 will be opened, because it can decrease the pressure of the pump and thereby prolong its working life. The pressure sensor is used to detect the height of water level in TI. So for TI, it is a dynamic system with two entrances and one exit for water flow.

COMPARATIVE STUDY OF FUZZY CONTROL

The Demo Model Structure

FIGURE 1 The working principle of the demo model.

BRI is a 42-year old research reactor, in which the control method is the simple on-off method. Many methods called traditional meth- ods, when compared to fuzzy logic, are still very new to the BR1 reactor. One of these, proportional-integral-derivative (PID) control, has to be tested as well as fuzzy logic method. So far, we have tested the normal fuzzy control, traditional PID control, and an advanced fuzzy control on this demo model. To obtain a better demonstration, these three approaches have been programmed and integrated into one con- roller system based on the programmable logic controller (PLC) of the OMRON company. The purpose of tlus paper is to report comparative experimental results of these three methods from the demo model. Section 2 simply introduces a normal fuzzy control and its result.

Section 3 introduces a PID control and its result.

Section 4 introduces an advanced fuzzy control which is able to self-regulate the Fuzzy control rules. Section 5 compares the previous three methods and their results.

2 FUZZY CONTROL

The fuzzy control algorithm in this demo model is a normal algorithm based on the Mamdani model. To simulate the BRl reactor, we use two fuzzy controllers (FLCl and FLC2) to control VL and VS separately (note: it is possible to use one fuzzy logic controller with two outputs to control VL

and VS and the related result can be referred to (Li and Ruan, 1997b)). Let D be the difference between the actual value (P) of water level and the set value (S) and DD be the derivative of D, in other words, the speed and direction of the change of water level. VL and VS represent the control signal to VL (Iarge valve) and VS (small valve), respectively. When D is too big, we use FLC1 to control VL (main-tuning); When D is small, we use FLC2 to control VS

(fine-tuning). We choose D and DD as inputs of the fuzzy logic con- troller, and VL or VS as the output of the fuzzy logic controller. D and DD must be fuzzified before fuzzy inference. Suppose the universes of discourse (or input variables' intervals) of D and DD are -d, dj and [-dd,dd], respectively. We use 7 fuzzy sets to partition hem, i.e., Negative Large (NL), Negative Middle (NM), Negative Small (NS), Zero (ZE), Positive Small (PS), Positive Middle (PM), and Positive Large (PL). As for VL and VS, because the result of fuzzy reasoning is also a fuzzy linguistic value, the universes of discourse of VL and VS also need to be fuzzified. We use those 7 fuzzy linguistic erms too. Symmetrical trianglar-shaped functions are used to define the membership functions for input variables (Li et al., 1995; 1996a,b), and singletons are for output variables (Ornron, 1992). Each fuzzy controller has one rule base which contains 49 fuzzy control rules. The its rule can be represented as the following form: if D is Ai and DD is Bi, then VL (or VS) is Ci where A, Bi, and Ci are fuzzy linguistical values, such as NL, PS, and so on. The above rule is sometimes abbreviated as (Ai, Bi : Ci). Figure 2 shows a control effect of a synthetic control process. It first goes up from 0 to 20cm then keeps on at 20 an, next drops down from 20 to 10 cm and finally keeps on at 10 cm.

In view of this figure, we know that the fuzzy control has quick responses (quickly approaching the set value) and small overshoot (almost invisible), but with a small steady error (not so smooth in a steady state).

COMPARATWE STUDY OF FUZZY CONTROL

FIGURE 2 The control effect of fuzzy control to the demo model.

3 PID CONTROL

In the PID control, it is difficult to control VL and VS separately like the previous fuzzy control with a good control result, because the integration term of the PID control needs some time, and this will result in an oscillation when switching control signal between VL and VS. From this point of view the PID control is worse than the fuzzy control. Therefore, in our tests, VL and VS have to be controlled by the same signal. We use the following formula:

dt

de

d i p

e T dt T e

K U(t)++=?

By substitution,

dt de

d i

e pe K dt K K U(t)++=?

where U(I): control value to VL and VS at time r; e: the set value-the real value at time I; Kp: the proportional parameter and Kp = (1IPB) x loo%, where PB is the proportional band; Ki: the integration

FlGURE 3 The trajectory of the water level by the PID control.

parameter and Ki = l/Ti where Ti is the integration time; Kd: the differential parameter and Kd = Td where Td is the differential time. In practice, a discrete form of the above formula is used

)]1()([)](....)2()1([K e(t)K U(t)i P --+

+++=t e t e T K t e e e T s

d s wher

e T, is the sample period. Figure 3 shows a result o

f the PID control,where PB= l5%, Ti=30s, Td= 10s. In view of this figure, the PID control is very stable (very smooth in steady states), and has quick responses too, but with visible overshoots.

4 ADVANCED FUZZY CONTROL

The kernel part of the fuzzy logic control is the fuzzy rule base with linguistic terms, though the membership functions and scale factors also have an important effect on the fuzzy logic controller. There are some papers which discuss how to adjust membership functions and/or scale factors (Batur and Kasparian, 1991; Chou and Lu, 1994; Tonshoff and Walter, 1994; Zheng, 1992). This section focuses on rules. Normally the methods of deriving rules can be broadly divided into two types, sourceable and non-sourceable. The sourceable method means the rules are obtained from some information source, such as human experience or historical input-output data. Experience has been widely used by the fuzzy engineers, especially by the early fuzzy engineers. The problem of using human experience is that it is time-consuming, and to some degree subjective. In order to overcome these problems, particularly avoiding the subjectivity, historical input -output data-if available can be used. To obtain rules from such data, many methods are used, one of the popular approaches is neural net- works (NN) (Berenji and Khedkar, 1992; Halgamuge and Glesner, 1994; Jang, 1992; Kosko, 1992; Li et al., 1995; Lin ez al., 1995; Takagi

and Hayashi, 1991; Wang and Mendel, 1992). One problem of the sourceable method is that it depends strictly on the source which will be transformed into rules. In the case that the source is noisy, then the rules might be biased. Another problem of the sourceable method is that it is usually non-adaptive, i.e., all the rules are fixed, therefore it cannot perform well under a dynamic environment.

The non-source- able methods are source-free and they produce and choose rules according to a performance measurement of the controller, such as

genetic algorithms (GA) (Karr, 1991; Lim et al., 1996; Qi and Chin, 1997) (mostly also generating membership functions and scale factors) and self-organizing controllers (SOC) (He er al., 1993; Li et al., 1996a,b; Lin et al., 1997, Procyk and Mamdani, 1979; Shao, 1988; Tanscheit

and Scharf, 1988; Wu et al., 1992). With GA it is possible to find integratedly optimal parameters but GA is very computation rich, and furthermore, it is almost impossible to apply GA in a real complex system without a simulation model. Perhaps the SOC is the only method which has the following advantages: objective, adaptive, less computation required, more error-tolerant, and simple.

FIGURE 4 An adaptive function is incorporated into a fuzzy control system.

The general principle of the SOC is that the controller monitors its own performance and adjusts its control rules to improve performance for time-varying and unknown plants. The problem of the SOC show to perform the performance measurement. The basic way is to design a performance measurement table which looks like a fuzzy control rule table and to use it to assess the performance of the controller rules) (Procyk and Mamdani, 1979), but to design such a performance measurement table is also very difficult (Chung and Oh, 1993) and it is system-dependent. Based on the SOC, this section will introduce an adaptive method which uses a set of new norms to replace the ormer performance measurement. The new norms are very simple

and system-independent, therefore they can be easily applied to most fuzzy controllers. In this section, the advanced fuzzy control means the above SOC, in other words, a fuzzy control with an adaptive function, where the adaptive function contains two steps: performance judgement and changing fuzzy control rules. Figure 4 illustrates how an adaptive function is incorporated into the fuzzy control system. At the beginning of each cycle, the controller's last behaviour is judged and then the rule base is changed accordingly. In this cycle, the controller will use the new rule base and output the result to the controlled object. The behaviour of the new rule base will be judged and changed again in the next cycle.

4.1 The Principle of the Adaptive Function

Let D and DD represent error (the difference between the actual value and the desired value) and change in error, respectively. Let D(t) and DD(t) represent error and change in error at time t, respectively. They are two input variables. Let U be an output variable, and assume thetotal number of the rules is n, then every rule has the following form: if D is A, DD is Bi, then U is C;, i= 1,2 ,..., n, where A, Bi, and Ci are fuzzy linguistic values and i is an index pointing out each rule's position in the rule table (or the rule data file). User[i] to represent the fuzzy control magnitude (conclusion fuzzy set) of the ith rule, and let simply

][

i r

7,6,5,4,3,2,1

where 1=NL,2=NM,3=NS,4=ZE,5=PS,6=PMY7=PL.

In general, a control locus may be expressed with Fig. 5, and it can be regarded as having up to four feature sections and four feature points. For each feature part, we offer a norm to guide the regulation of the fuzzy control rules. For example, the current water level P(t) is in the feature part (I), then after the fuzzy controlling using the current control rules, we measure the water level P(t + l) at the next time which has three possibilities:

P(l) < P(t + 1)

P(t + 1) < S and P(t + 1)

P(t+l)>S.

FIGURE 5 Any trajectory has up to four feature sections and four feature points.

The related norm to guide how to change rules is the following:

(i) if D(I + 1) 5 0 and DD(t + I) > 0, that is, P(t) < P(t + 1) 5 S, then r[i] = r[i]

(ii) if D(i f 1) < 0 and DD(t + 1) < 0, that is, P(t +1) < S and P(t + 1) < P(t), then r[i] = r[i] +a,

(iii) if D(t + 1) > 0, that is, P(t + 1) > S, then r[i] = r[i] - a,

where a is a step size and a = 1,2,3,4,5,6. In case (i), the fuzzy con-

troller makes the water level P(t f 1) closer to the set value S, therefore the behaviour of the fuzzy controller is good, no rules should be changed; In case (ii), the fuzzy controller makes the water level P(t + 1) further from the set value S, therefore the behaviour of the fuzzy con- troller is not good,

the strength is too weak and the action of the corresponding rules 'should be stronger; In case (iii), the fuzzy controller makes the water level P(t $1) overpass the set value S, therefore the behaviour of the fuzzy controller is not good, the strength is too strong and the action of the corresponding rules should be weakened. Not all rules but some of those that are activated in last cycle should be regulated. We use the following formula to describe which should

be adjusted:

))()(A ()()(A j j i i DD B D DD B D i

j C C ∧∨=∧= which means the ith rule is changed only if it is the largest activated among those activated rules which have the same conclusion part. For example, (NL, NM : PL) and (NM, NM : PL) are two activated rules and have the same conclusion part, i.e., PL. Comparing NL(D) A NM(DD) with NM(D) A NM(DD), the larger one corresponds to the rule which should be adjusted.

4.2 An Experimental Result

To guarantee no overshoot, the best way is to initialize all rules as the same conclusion part: NL, as shown in Table I. In this table, for example, NL at the row 2 and column 3 means: if D is NM and DD is NL then VL or VS is NL. All rules have the same conclusion part though condition parts are different. Figure 6 illustrates

TABLE I The initial rule table for both FLCl and FLC2

FIGURE 6 Comparison between adaptive fuzzy control and fuzzy control.

the comparison result between fuzzy adaptive control and. fuzzy con-

trol with the above rule base. In this example, the set value is 20cm.

Both start from Ocm. During the first stage, i.e., increasing from zero,

some analytic rules manipulate the valves and not fuzzy control. Only

after the water level reaches 18cm does the fuzzy controllers start to

operate VL and VS. Apparently, the adaptive fuzzy control has a much

better result by self-regulating gradually fuzzy control rules. The nor-

mal fuzzy control without adaptive function cannot self-regulate rules,

therefore it cannot draw up the water level.

About 10 min later, we observe the rule tables on the screen and find

both rule tables have changed a lot. Table I1 gives the result of FLCl and Table 111 gives the result

of FLC2, where the regulated rules are

marked by bold fonts.

4.3 Some Remarks for the Adaptive Function

The initial idea about the previously described norms of the adaptive function, which was published in (Li et al., 1996a,b), and where a simulated inverted pendulum system and a real industrial heating system were used to make testings, gave satisfactory results . a The parameter a is influential on the overshoot and response time (rise time). When cr is too big, there will be a large overshoot possibly; when a is too smaI1, possibly there will be a long response time (Li el al., 1996a,b). The adaptive function considers only the last value, that is, it uses P(r - 1) not P(t - T) (T is the delay) to decide P(t), but our experimental results show the effect is good, although the valves of the demo model have a maximum delay of 90 s. The adaptive function selects only some of the rules according to formula (1) for adjustment, not all activated rules like (Lin et al., 1997). This makes the transition of the rules more smooth, i.e., without or with less resonance. Selecting initial rules appropriately will benefit the control effect. For example, if the overshoot is strictly limited, we may initialize all rules with the conclusion part of NL, as was done in the previous experiment. Once some experience has been obtained, it can be

transformed into the initial rules of the adaptive function, the advantage being that the rise time will be shorter (Li and Ruan, 1998). The rule, "if D is ZE and DD is ZE then U is ZE,"

should be fixed, and this will help the system to become stable. The adaptive function is very helpful in keeping the system stable in a steady state. It cannot guarantee no overshoot if the initial rules are randomly selected. The adaptive function cannot adjust membership functions and scale factors.

5 COMPARATIVE STUDY

Each method has both advantages and disadvantages, the details of which are described in Table IV, where * is used to represent the degree of a property, and the more *, the higher the degree. For example, the realization of an adaptive fuzzy logic controller (FLC) is more difficult than a normal fuzzy controller, but a normal fuzzy controller is more difficult to realize than a PID controller. The PID control has the smallest static error and steady error. The dynamic regulation of TABLE IV Comparative study of FLC, PID and adaptive FLC the control rules in an adaptive controller can help in reducing the static error and steady error (Li et al., 1996a,b). As for robustness, it has been accepted that FLC is more robust than PID. Herein we also give one example, as shown as in Fig. 7. This experiment was carried out after tuning the Tap 1 (see Fig. 1) to make the outflow much smaller. We found that the reaction of FLC was better than that of PID, hough the FLC had a small static error. If we count the total number of * for each method, we will find that PID and FLC have the same score, 17. Adaptive FLC has a higher score of 20. This interesting result can be explained by the following facts. PID and FLC have their own strong points, and they compensate each other. Adaptive FLC adds an adaptive function to a normal FLC, therefore its score should be higher than that of FLC. A natural result is that combining FLC and PID should be better than each method alone. The comparative method above is perhaps a little subjective, but it does reflect some objective properties and relationships among those three methods. In the real world, one may use other ways to evaluate these methods. For example, if robustness is stressed, then it should be highly weighted when the total scores are calculated.

For further descriptions of comparative studies between FLC and PID, readers may refer to Boverie et al. (1991), Chao and Teng (1997), Misir et al. (1996), Mizumoto (1995), Moon (1995), and Wu and Mizumoto (1996).

FIGURE 7 FLC is more robust than PID.

6 CONCLUSION

This paper gives comparisons between fuzzy control, PID control, and advanced fuzzy control based on the experimental results of a demo model which simulates the control principle of the BR1 reactor. Fuzzy control is more robust than PID control, but with a well-characterized system, such as a reactor, it should be better to use a hybrid method which inherits the advantages of both methods. Furthermore, the adaptive fuzzy control is able to aid the designer in finding the fuzzy control rules, especially for systems possessing much of dynamical uncertainty. References

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电气工程及其自动化专业_外文文献_英文文献_外文翻译_plc方面

1、 外文原文 A: Fundamentals of Single-chip Microcomputer Th e si ng le -c hi p m ic ro co mp ut er i s t he c ul mi na ti on of both t h e de ve lo pm en t o f t he d ig it al co m pu te r an d th e i n te gr at ed c i rc ui t a rg ua bl y t h e to w m os t s ig ni f ic an t i nv en ti on s o f t he 20th c e nt ur y [1]. Th es e t ow ty pe s of ar ch it ec tu re a re fo un d i n s in g le -ch i p m i cr oc om pu te r. So m e em pl oy t he spl i t pr og ra m/da ta m e mo ry o f th e H a rv ar d ar ch it ect u re , sh ow n in Fi g.3-5A -1, o th ers fo ll ow t he p h il os op hy , wi del y a da pt ed f or ge n er al -p ur po se co m pu te rs a nd m i cr op ro ce ss o r s, o f ma ki ng n o log i ca l di st in ct ion be tw ee n p r og ra m an d d at a m e mo ry a s i n t he P r in ce to n ar ch ite c tu re , sh ow n i n F ig.3-5A-2. In g en er al te r ms a s in gl e -chi p m ic ro co mp ut er i s c h ar ac te ri ze d b y t h e i nc or po ra ti on o f a ll t he un it s of a co mp uter i n to a s in gl e d ev i ce , as s ho wn in Fi g3-5A -3. Fig.3-5A-1 A Harvard type Program memory Data memory CPU Input& Output unit memory CPU Input& Output unit

管理信息系统MIS(Management Information System)

MIS(Management Information System) the term in the interest of the administration. In the wake of the development of MIS, much business sit up the decentralized message concentration to establish the information system ministry of directly under director, and the chief of information system ministry is ordinarily in the interest of assistant manager’s grade. After the authority of business is centralized up high-quality administration personnel staff’s hand, as if causing much sections office work decrease, hence someone prophesy, middle layer management shall vanish. In reality, the reappearance phase employed layer management among the information system queen not merely not to decrease, on the contrary there being the increase a bit. This is for, although the middle layer management personnel staff getting off exonerate out through loaded down with trivial details daily routine, yet needs them to analyses researching work in the way of even more energy, lift further admonishing the decision of strategic importance level. In the wake of the development of MIS, the business continuously adds to the demand of high technique a talented person, but the scarce thing of capability shall be washed out gradually. This compels people by means of study and cultivating, and continuously lifts individual’s quality. In The wake of the news dispatch and electric network and file transmission system development, business staff member is on duty in many being living incomparably either the home. Having caused that corporation save the expenses enormously, the work efficiency obviously moves upward American Rank Zeros corporation the office system on the net, in the interest of the creativity of raise office personnel staff was produced the advantageous term. At the moment many countries are fermenting one kind of more well-developed manufacturing industry strategy, and become quickly manufacturing the business. It completely on the basis of the user requirement organization design together with manufacture, may carry on the large-scale cooperation in the interest of identical produce by means of the business that the flow was shifted the distinct districts, and by means of the once more programming to the machinery with to the resources and the reorganization of personnel staff , constituted a fresh affrication system, and causes that manufacturing cost together with lot nearly have nothing to do with. Quickly manufacturing the business establishes a whole completely new strategy dependence relation against consumer, and is able to arouse the structure of production once more revolution. The management information system is towards the self-adoption and Self-learning orientation development, the decision procedure of imitation man who is be able to be better. Some entrepreneurs of the west vainly hope that consummate MIS is encircles the magic drug to govern the business all kinds of diseases; Yet also someone says, and what it is too many is dependent on the defeat that MIS be able to cause on the administration. It is adaptable each other to comprehend the effect to the business of MIS, and is favor of us to be living in development and the research work, and causes the business organization and administer the better development against MIS of system and administration means , and establish more valid MIS. 英文翻译文章的出处:Russ Basiura, Mike Batongbacal 管理信息系统: 管理信息系统就是我们常说的MIS(Management Information System), 在强调管理,

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发展战略-模糊逻辑与模糊控制技术的发展 精品

模糊逻辑与模糊控制技术的发展 宁廷群1 肖英辉1任惠英2 (1山东科技大学机电学院山东青岛 266510 2山东兖矿集团机械制修厂山东邹城 273500)The Development of Fuzzy Logic and Fuzzy Control Technology 摘要:针对现代工业控制领域的模糊控制技术的新发展,综合介绍了当代该领域的基本理论和发展现状,展望了未来的发展应用。 关键词:模糊控制;应用发展;自适应控制。 Abstract: This paper introduces the development of fuzzy logic and fuzzy control technology in modern control domain, and discusses the basic theory and main development in integration. At last it gives some prospects. Key words: fuzzy control, development and application, adaptive control 一、引言 在现代工业控制领域,伴随着计算机技术的突飞猛进,出现了智能控制的新趋势,即以机器模拟人类思维模式,采用推理、演绎和归纳等手段,进行生产控制,这就是人工智能。其中专家系统、模糊逻辑和神经网络是人工智能的几个重点研究热点。相对于专家系统,模糊逻辑属于计算数学的范畴,包含有遗传算法,混沌理论及线性理论等内容,它综合了操作人员的实践经验,具有设计简单,易于应用、抗干扰能力强、反应速度快、便于控制和自适应能力强等优点。近年来,在过程控制、建摸、估计、辩识、诊断、股市预测、农业生产和军事科学等领域得到了广泛应用。为深入开展模糊控制技术的研究应用,本文综合介绍了模糊控制技术的基本理论和发展状况,并对一些在电力电子领域的应用作了简单介绍。 二、模糊逻辑与模糊控制 1、模糊逻辑与模糊控制的概念 1965年,加州大学伯克利分校的计算机专家Lofty Zadeh提出“模糊逻辑”的概念,其根本在于区分布尔逻辑或清晰逻辑,用来定义那些含混不清,无法量化或精确化的问题,对于冯˙诺依曼开创的基于“真-假”推理机制,以及因此开创的电子电路和集成电路的布尔算法,模糊逻辑填补了特殊事物在取样分析方面的空白。在模糊逻辑为基础的模糊集合理论中,某特定事物具有特色集的隶属度,他可以在“是”和“非”之间的范围内取任何值。而模糊逻辑是合理的量化数学理论,是以数学基础为为根本去处理这些非统计不确定的不精确信息。 模糊控制是基于模糊逻辑描述的一个过程的控制算法。对于参数精确已知的数学模型,我们可以用Berd图或者Nyquist图来分析家其过程以获得精确的设计参数。而对一些复杂系统,如粒子反应,气象预报等设备,建立一个合理而精确的数学模型是非常困难的,对于电力传动中的变速矢量控制问题,尽管可以通过测量得知其模型,但对于多变量的且非线性变化,起精确控制也是非常困难的。而模糊控制技术仅依据与操作者的实践经验和直观推断,也依靠设计人员和研发人员的经验和知识积累,它不需要建立设备模型,因此基本上是自适应的,具有很强的鲁棒性。历经多年发展,已有许多成功应用模糊控制理论的案例,如Rutherford,Carter 和Ostergaard分别应用与冶金炉和热交换器的控制装置。 2、分析方法探讨 工业控制系统的稳定性是探讨问题的前提,由于难以对非线性和不统一的描述,做出判断,因此模糊控制系统的分析方法的稳定性分析一直是一个热点,综合近年来各位学者的发表的论文,目前系统稳定性分析有以下集中: 1、李普亚诺夫法:基于直接法的离散时间(D-T)和连续时间模糊控制的稳定性分析和设计方法,相对而言起稳定条件比价保守.

电气自动化专业毕业论文英文翻译

电厂蒸汽动力的基础和使用 1.1 为何需要了解蒸汽 对于目前为止最大的发电工业部门来说, 蒸汽动力是最为基础性的。 若没有蒸汽动力, 社会的样子将会变得和现在大为不同。我们将不得已的去依靠水力发电厂、风车、电池、太阳能蓄电池和燃料电池,这些方法只能为我们平日用电提供很小的一部分。 蒸汽是很重要的,产生和使用蒸汽的安全与效率取决于怎样控制和应用仪表,在术语中通常被简写成C&I(控制和仪表 。此书旨在在发电厂的工程规程和电子学、仪器仪表以 及控制工程之间架设一座桥梁。 作为开篇,我将在本章大体描述由水到蒸汽的形态变化,然后将叙述蒸汽产生和使用的基本原则的概述。这看似简单的课题实际上却极为复杂。这里, 我们有必要做一个概述:这本书不是内容详尽的论文,有的时候甚至会掩盖一些细节, 而这些细节将会使热力学家 和燃烧物理学家都为之一震。但我们应该了解,这本书的目的是为了使控制仪表工程师充 分理解这一课题,从而可以安全的处理实用控制系统设计、运作、维护等方面的问题。1.2沸腾:水到蒸汽的状态变化 当水被加热时,其温度变化能通过某种途径被察觉(例如用温度计 。通过这种方式 得到的热量因为在某时水开始沸腾时其效果可被察觉,因而被称为感热。 然而,我们还需要更深的了解。“沸腾”究竟是什么含义?在深入了解之前,我们必须考虑到物质的三种状态:固态,液态,气态。 (当气体中的原子被电离时所产生的等离子气体经常被认为是物质的第四种状态, 但在实际应用中, 只需考虑以上三种状态固态,

物质由分子通过分子间的吸引力紧紧地靠在一起。当物质吸收热量,分子的能量升级并且 使得分子之间的间隙增大。当越来越多的能量被吸收,这种效果就会加剧,粒子之间相互脱离。这种由固态到液态的状态变化通常被称之为熔化。 当液体吸收了更多的热量时,一些分子获得了足够多的能量而从表面脱离,这个过程 被称为蒸发(凭此洒在地面的水会逐渐的消失在蒸发的过程中,一些分子是在相当低的 温度下脱离的,然而随着温度的上升,分子更加迅速的脱离,并且在某一温度上液体内部 变得非常剧烈,大量的气泡向液体表面升起。在这时我们称液体开始沸腾。这个过程是变为蒸汽的过程,也就是液体处于汽化状态。 让我们试想大量的水装在一个敞开的容器内。液体表面的空气对液体施加了一定的压 力,随着液体温度的上升,便会有足够的能量使得表面的分子挣脱出去,水这时开始改变 自身的状态,变成蒸汽。在此条件下获得更多的热量将不会引起温度上的明显变化。所增 加的能量只是被用来改变液体的状态。它的效用不能用温度计测量出来,但是它仍然发生 着。正因为如此,它被称为是潜在的,而不是可认知的热量。使这一现象发生的温度被称为是沸点。在常温常压下,水的沸点为100摄氏度。 如果液体表面的压力上升, 需要更多的能量才可以使得水变为蒸汽的状态。 换句话说, 必须使得温度更高才可以使它沸腾。总而言之,如果大气压力比正常值升高百分之十,水必须被加热到一百零二度才可以使之沸腾。

房地产信息管理系统的设计与实现 外文翻译

本科毕业设计(论文)外文翻译 译文: ASP ASP介绍 你是否对静态HTML网页感到厌倦呢?你是否想要创建动态网页呢?你是否想 要你的网页能够数据库存储呢?如果你回答:“是”,ASP可能会帮你解决。在2002年5月,微软预计世界上的ASP开发者将超过80万。你可能会有一个疑问什么是ASP。不用着急,等你读完这些,你讲会知道ASP是什么,ASP如何工作以及它能为我们做 什么。你准备好了吗?让我们一起去了解ASP。 什么是ASP? ASP为动态服务器网页。微软在1996年12月推出动态服务器网页,版本是3.0。微软公司的正式定义为:“动态服务器网页是一个开放的、编辑自由的应用环境,你可以将HTML、脚本、可重用的元件来创建动态的以及强大的网络基础业务方案。动态服务器网页服务器端脚本,IIS能够以支持Jscript和VBScript。”(2)。换句话说,ASP是微软技术开发的,能使您可以通过脚本如VBScript Jscript的帮助创建动态网站。微软的网站服务器都支持ASP技术并且是免费的。如果你有Window NT4.0服务器安装,你可以下载IIS(互联网信息服务器)3.0或4.0。如果你正在使用的Windows2000,IIS 5.0是它的一个免费的组件。如果你是Windows95/98,你可以下载(个人网络服务器(PWS),这是比IIS小的一个版本,可以从Windows95/98CD中安装,你也可以从微软的网站上免费下载这些产品。 好了,您已经学会了什么是ASP技术,接下来,您将学习ASP文件。它和HTML文 件相同吗?让我们开始研究它吧。 什么是ASP文件? 一个ASP文件和一个HTML文件非常相似,它包含文本,HTML标签以及脚本,这些都在服务器中,广泛用在ASP网页上的脚本语言有2种,分别是VBScript和Jscript,VBScript与Visual Basic非常相似,而Jscript是微软JavaScript的版本。尽管如此,VBScript是ASP默认的脚本语言。另外,这两种脚本语言,只要你安装了ActiveX脚本引擎,你可以使用任意一个,例如PerlScript。 HTML文件和ASP文件的不同点是ASP文件有“.Asp”扩展名。此外,HTML标签和ASP代码的脚本分隔符也不同。一个脚本分隔符,标志着一个单位的开始和结束。HTML标签以小于号(<)开始(>)结束,而ASP以<%开始,%>结束,两者之间是服务端脚本。

从“雷人”的英语翻译说起———谈英语语言的重点

从“雷人”的英语翻译说起———谈英语语言的? ? 摘要:双关修辞是英语语言中常见的一种修辞格,大体可以分为语(谐)音双关、语义双关、词性双关和仿拟双关。英语双关修辞历史悠久,广泛运用在英 语各种文体中:文学作品、广告、谜语等,在我们周围无处不在。因此,要想 精准地翻译一篇英文,必须了解并熟悉双关修辞,且经过反复练习,吸收更广 泛的知识,才能战胜这一翻译的难点,越过这个可译性障碍,使译文与原文达 到最大限度的等值。关键词:修辞手法双关语翻译我在十几年的英语教学中, 深切地感受到学生对英语又敬又畏的心情,爱它可又驾驭不了它。于是学生在 与英语的焦灼对峙中,出现了一些雷人的英语翻译,让人叹为观止。1.How are you?How old are you?怎么是你,怎么老是你?2.We two who and who?咱俩谁跟 谁呀。3.You me you me.彼此彼此。4.You give me stop!你给我站住!5.Go past no mistake past.走过路过,不要错过。其实英语与汉语一样,也有多种修辞手法。其中双关运用就在英语语言中占有举足轻重的地位,如果我们对英语的修辞手法,尤其是双关运用不熟悉的话,就会出现更多雷人的语言。下面我将重点阐 述英语语言的双关运用。一、语(谐)音双关词语之间因拼写相似、发音相同 或相近而构成的双关用法。它是利用发音相同或相近但意义不同的词来代替所 要表达的本意,它会让语言变得风趣俏皮,增加感染力。1.There was a man in the restaurant.“You’re not eating your fish.”the waitress said to him, “Anything wrong with it?”“Long time no sea.”the man replied.其中“see”与“sea”发音相同,但意义完全不同。这个顾客的回答,表面上听“Long time no see.”是好久不见的意思,但实际上是说那些鱼离开大海很久了,已经不新 鲜了。2.What is the clearest animal?什么动物最聪明?The pigs that nose everything.什么都能闻的猪。nose是“闻”的意思,碰巧与knows(知道)谐音。如此一来,“什么都能闻的猪”就变成了“什么都知道的猪”,那当然是最聪 明的动物。3.What country has a good appetite?哪个国家的人胃口很好?Hungary. 匈牙利。因为“Hungary”这个国家单词的发音与“hungry”(饥饿)的发音相近,于是在这则笑话中,“Hungary”因语音双关而成为最能吃的国家。二、语义双关因为词语的多重含义而构成的双关用法。在字面上虽然只有一个词语, 而实际上却同时兼顾着两种不同的意义,言在此而意在彼,从而造成一种含蓄、深沉委婉、耐人寻味的意境,增强了语言的表达效果。1.Why is a river rich?Because it always has two banks.“bank”一词有两个含义,一个意思为“河岸”,另一个意思则表示“银行”。大家想想,有两个河岸(银行)的河流能 不富有吗?2.The professor rapped on his desk and shouted,“Gentlemen,order.”The entire class yelled“beer”.这则幽默同样用了双关手法中的同形异义词。

模糊控制综述

模糊控制研究及发展现状综述

模糊控制研究及发展现状综述 摘要:模糊控制是智能控制的重要组成部分。本文主要介绍了模糊控制理论的研究及发展的现状等 ,详细介绍了模糊控制理论的原理、模糊控制的数学基础, 其发展现状中介绍了模糊 PID 控制、自适应模糊控制、神经模糊控制、遗传算法优化的模糊控制、专家模糊控制等 , 还介绍了一些模糊控制的软硬件产品, 对模糊控制系统的稳定性作了简单介绍, 最后对模糊控制的发展作了展望。 关键词:模糊控制;模糊控制器

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