機械設(shè)計制造及其自動化畢業(yè)設(shè)計外文翻譯

1、英文原文名 ADVANCED WEIGHING TECHNOLOGY 中文譯名 現(xiàn)代稱重技術(shù) 現(xiàn)代稱重技術(shù)第一章 秤的功能與結(jié)構(gòu)1.1 基本結(jié)構(gòu)和稱重原理 兩種不同類型的機械秤示于圖1.1。那么，秤的基本結(jié)構(gòu)和稱重原理方面的共同特征是什么呢？ 對于圖1.1(a)所示的天平或杠桿秤，放在載荷盤上的被測物體的質(zhì)量，與放在砝碼盤上的砝碼的質(zhì)量是利用它們的自重對支點的力矩，通過計量杠桿進行比較的。這也可以看作是對物體載荷產(chǎn)生的作用力與砝碼自重產(chǎn)生的反作用力進行比較，而且兩者同時作用在計量杠桿上。對于圖1.1(b)所示彈簧秤，由彈簧伸長而產(chǎn)生的恢復力，應被視為反作用力或抗力。綜上所述，我們認識到通常可以

2、把秤分解成三個功能部分，即載荷接受部分 或受載器，力比較部分、反力部分。載荷接受部分（例如載荷盤等），它作為秤的一部分用于接受載荷，并將載荷產(chǎn)生的力施加到力比較部分上。反力部分（例如，帶砝碼的砝碼盤或彈簧等），它作為秤的一部分產(chǎn)生反作用力，并將其施加到力比較部分上。力比較部分（例如計量杠桿等），它作為秤的一部分接受以上兩種力。 (a)天平或者杠桿秤 (b)彈簧秤圖1.1 機械秤的兩種類型當我們檢查任何一種機械秤時，會注意到它們通常都具有以上結(jié)構(gòu)。所以，我們可以認為這種結(jié)構(gòu)式秤的基本結(jié)構(gòu)。此外，測量是以物體質(zhì)量產(chǎn)生的作用力與反力部分產(chǎn)生的反作用力之間的平衡為基礎(chǔ)的。所以，我們可以認為秤的稱重原理

3、是利用了力的平衡?，F(xiàn)代科技的發(fā)展，使我們在質(zhì)量測量方面不僅能夠利用力的靜平衡，而且還可以利用力的動平衡。載荷傳遞杠桿應該包括在載荷接受部分之中。對于料斗秤中稱重傳感器直接支撐料斗的情形，可以認為它屬于力比較部分被省略的一種特例。對于天平或杠桿秤，其測得值可以從反力部分上的砝碼變化中獲得。對于彈簧秤，其測得值可以從反力部分的彈簧伸長變化中獲得。一般來說，機械秤的測得值可以從反力部分產(chǎn)生的某些量值變化中獲得。1.2 電秤和電子稱系統(tǒng)的構(gòu)成機械秤是指包括顯示功能在內(nèi)的所有功能都能通過機械手段實現(xiàn)的一種秤，而電秤和電子稱具有一個能將反力部分產(chǎn)生的變化轉(zhuǎn)換成電量的傳感器，還具有一個能處理電量信號以獲得測

4、量值的信號處理裝置。所以，電秤和電子稱的特征在于有傳感器和信號處理裝置。圖1.2說明了電秤和電子稱的基本系統(tǒng)構(gòu)成。傳感器將轉(zhuǎn)化了的電信號，輸送給由3種基本電路組成的信號處理裝置，它們是輸入電路、數(shù)據(jù)處理電路、輸出電路。輸入電路上有例如濾波器、放大器、A/D轉(zhuǎn)換電路等，它們將傳感器的輸出信號變換成更適用于數(shù)據(jù)處理的信號。數(shù)據(jù)處理電路通過處理其輸入信號，來獲取測得值以及與測量有關(guān)的必須值。輸出電路則是傳輸處理好的測量結(jié)果的電路。圖1.2 電秤和電子稱基本系統(tǒng)框圖按照反力部分是否承受了反作用力，可以將傳感器如圖1.3所示劃分為兩類，即非反力型傳感器和反力型傳感器。圖1.3 秤用傳感器按是否承受反力所

5、作的分類1.3 工業(yè)秤的功能及其系統(tǒng)構(gòu)成1.3.1 功能特征和分類工業(yè)秤主要用于工業(yè)稱重，它們具有以下特征：(1) 對載荷接受部分的加載或卸載時自動進行的。(2) 用物體自重W確定物體質(zhì)量值M的過程是自動進行的。這種秤的系統(tǒng)框圖示于圖1.4。此外大多數(shù)工業(yè)秤還有以下一個特征，即(3) 具有質(zhì)量值的控制功能。典型工業(yè)秤的名稱和功能列于表1.1。 表1.1 工業(yè)秤的名稱及其功能 圖1.4 工業(yè)自動秤的系統(tǒng)框圖1.3.2 控制的目的若注意觀察一下加到載荷接受部分上的物體的質(zhì)量流動狀態(tài)，及其與經(jīng)過測量后的物體的質(zhì)量流動狀態(tài)之間的差異，我們可以得知表1.1中所說的質(zhì)量值控制的目的就是為了控制質(zhì)量流動的狀

6、態(tài)。從這個觀點出發(fā)，料斗秤或包裝秤的控制目的，就是為了獲得一種斷續(xù)流動狀態(tài)，而每次斷續(xù)流動的量都是預定的。聯(lián)合（分選組合）秤的控制目的也屬于這種類型。檢重秤的目的，是為了按照預定質(zhì)量等級獲得離散的流量動狀態(tài)。至于喂料的控制，則是為了獲得一個預定質(zhì)量的流動狀態(tài)，或者獲得一個總量與預定值相同的流量東狀態(tài)。1.3.3 系統(tǒng)的結(jié)構(gòu)一個控制系統(tǒng)通常包括被控對象、檢測部分、調(diào)節(jié)部分或控制器，以及操作部分。在工業(yè)稱重系統(tǒng)中，被控對象包括供料裝置、分配裝置、排放裝置、而被控變量就是被測質(zhì)量。圖1.4所示的系統(tǒng)相當于一個檢測部分，而各種執(zhí)行器則用于操作部分。圖1.5顯示了從系統(tǒng)構(gòu)成觀點對工業(yè)稱重系統(tǒng)的分類情況。

7、圖1.5（a）所示為料斗秤或包裝秤的系統(tǒng)構(gòu)成圖。被控對象是供料裝置，其典型實例為螺旋喂料器。此時操作部分是驅(qū)動喂料器的一個變速電機。稱量斗相當于載荷接受部分。目標值用符號R表示，操作變量用符號C表示。符號m和m分別代表質(zhì)量流動的狀態(tài)；用不同的符號意指兩種狀態(tài)有所不同。圖1.5（b）所示為一臺喂料秤的系統(tǒng)構(gòu)成圖，它的典型實例是一臺變速的皮帶喂料秤，載荷接受部分皮帶稱重段和稱重托輪組成。被控對象時皮帶喂料器或供料裝置，而操作部分是變速點擊，被檢測質(zhì)量的總量用符號Q表示。選擇Q或其對時間的導數(shù)Q為被控變量，為了得到Q值，就需要測量皮帶的運行速度v。圖1.5（c）所示為一臺檢重秤的系統(tǒng)構(gòu)成圖。被控對象

8、是分配裝置，而皮帶輸送機通常被用作載荷接受部分。圖1.5（d）所示為一臺聯(lián)合（分選組合）秤的系統(tǒng)構(gòu)成圖，通常以一些小的稱量斗作為載荷接受部分，并且每個斗都裝有一個用執(zhí)行器控制的閥門。這些閥門就是被控對象，而執(zhí)行器即為控制元件操作部分。對于圖1.5（a）和1.5（b）中所示的秤，由于在測量質(zhì)量的同時必須控制質(zhì)量的流動狀態(tài)，所以應采用反饋控制。另一方面，對于圖1.5（c）和（d）中所示的秤，由于對質(zhì)量流動狀態(tài)的控制是在測量質(zhì)量之后進行的，所以基本上是進行順序控制。 （a）料斗秤的系統(tǒng)框圖 （b）喂料秤的系統(tǒng)框圖（c）檢重秤的系統(tǒng)框圖 （d）聯(lián)合秤（分選組合秤）的系統(tǒng)框圖圖1.5 工業(yè)稱重系統(tǒng)的構(gòu)成

9、框圖第2章 秤的靜力學2.1 杠桿的靜力學2.1.1 杠桿的分類通常把具有交點軸，載荷軸和力軸的直杠桿稱為基本杠桿。每個軸的位置分別被稱為支點、重點和力點。支點就是杠桿的支承點，杠桿可以圍繞它轉(zhuǎn)動。重點和力點分別是載荷和力的作用點。按照以上3個點的分布，可以把基本的杠桿分為3種類型，即第一類杠桿，第二類杠桿和第三類杠桿。在圖2.1所示的分類圖中，F(xiàn)是支點，A是重點，B是力點，它們作用在同一直線上。（a） 第一類杠桿 （b）第二類杠桿 （c）第三類杠桿圖2.1 杠桿的分類按照聯(lián)接杠桿的數(shù)量可以將杠桿（系）稱為單一杠桿或復合杠桿（系）。單一杠桿是獨立的，例如天平的橫梁，而復合杠桿則是由相關(guān)聯(lián)的杠桿

10、組合而成的一個杠桿系。支點、重點和力點的數(shù)量，在一個杠桿上并不限于一個。例如對于圖2.2所示的杠桿，我們可以看作是一個雙聯(lián)杠桿，它有兩個支點和兩個重點。包含這種雙聯(lián)杠桿的一個符合杠桿系，見圖2.3所示。 圖2.2 雙聯(lián)杠桿 圖2.3 復合杠桿系2.1.2 單一杠桿在實際應用中，杠桿在載荷作用下保持其靜平衡位置的情況有兩種：第一，總是與空載下杠桿的平衡位置相一致（第一種情況）；第二，平衡位置隨載荷而變化（第二種情況）。當我們研究以上兩種情況下的靜平衡條件時，我們將杠桿設(shè)想為一個剛體。（1） 靜平衡條件，單一杠桿保持平衡的必要和充分條件是 （諸力）=0 和 （諸力矩）=0 （2.1）為了研究單一杠

11、桿在第一種情況和第二種情況下的靜平衡條件，我們將上述充分必要條件應用于那些支點、力點和重點不在同一直線上的杠桿。假設(shè)當載荷為零時，杠桿在初始力的作用下保持靜平衡，如圖2.4所示。W0作用于A點，P0作用于B點，R0作用于F點，G作用于C點（重心）。再假設(shè)當施加載荷W和反力P時，杠桿仍保持在相同的位置上。那么，靜平衡條件在加載前后即為 W0+P0+G+R0=0 W0a+P0b+Gc=0 （2.2）并且 （W0+W)+(P0+P)+G+(R0+R)=0 (W0+W)a+(P0+P)b+Gc=0 （2.3）式中，R是作用于F點的力的增量。在圖2.4中，我們必須考慮力的符號和作用點。向下的力為正，而向

12、上的力為負，以支點為原點，當力的作用點位于重點一方時為正，而位于力點一方時為負。所以，逆時針方向的力矩為正，順時針的力矩為負。圖2.4 單一杠桿的靜平衡條件ADVANCED WEIGHING TECHNOLOGYCHAPTER 1 FUNCTIONS AND STRUCTURES OF SCALES1.1 BASIC STRUCTURE AND WEIGHING PRINCIPLETwo different types of the mechanical scale are illustrated in Fig.1.1.What are the common features to the s

13、cales in basic structure and weighing principle? (a) Balance (b)Spring scaleFigure 1.1 Mechanical scaleIn the balance or lever scale illustrated in Fig.1.1(a),the mass of the object to be measured and located at the load plate is compared with the mass of the weights to be locates at the weight plat

14、e as the moments due to their gravity around the fulcrum by means of the weighbeam. This can be considered a comparison of the force due to the load of object with counterforce due to the weights,both acting on the weighbeam.As for the spring scale illustrated in Fig.1.1(b),the restoring force due t

15、o the elongation of spring is considered the counterforce or resistant.The above consideration leads us to the recognition that those scales can be divided into three functional elements in common,which are the load receiving element or load receptor,the force comparing element and the counterfore e

16、lement.The load receiving element,such ad a load plate,is a portion of the scale which receives an object to be measured and applies the force caused by the mass of the object to the force comparing element.The counterforce element,such as a weight plate with weights or a spring,is a portion of the

17、scale which develops a counterforce,applying it to the force comparing element. The force comparing element, such as a weighbeam, is a portion of the scale to which the above two forces are applied.When examining any types of the mechanical scale, we notice they have the above structure in common. T

18、hen, the structure can be regarded as the basic structure of scales. Furthermore, the measurement is based on the equilibrium in the force due to the mass of an object and the counterforce developed in a counterforce element. Therefore, the application of the equilibrium in forces can be regarded as

19、 the weighing principle of scales. The modern technological development enables us to apply not only the static equilibrium but also the dynamic equilibrium in forces for mass measurement.The load transmitting levers should be included in the load receiving element. For the hopper scale whose hopper

20、 is directly supported by loadcclls, we should regard it as a case that the force comparing element is omitted.In the balance or lever scale, the measured value can be obtained from the weight change in the counterforce element. In the spring scale the measured value can be obtained from the elongat

21、ion change of the spring as a counterforce element. Generally, the measured value in the mechanical scale can be obtained by using some quantity changes developed in the counterforce element.1.2 SYSTEM CONFIGURATION OF ELECTRICAL AND ELECTRONIC SCALESA mechanical scale is a scale in which all functi

22、ons including display function are realized by mechanical means. On the hand, an electrical and electrical scale is a scale with a transducer which inverts the change developed in the counterfore element to an electrical quantity and with a signal processing device which processes the signal of that

23、 electrical quantity to obtain the measured value. Therefore, the electrical and electronic scale are characterized by the transducers and signal processing devices.Figure 1.2 shows the basic system configuration of the electrical and electronic scale. The electrical signal converted with the transd

24、ucer is sent to the signal processing device composing of three functional circuits, which are input circuit, data processing circuit, and output circuit. The input circuit functional circuits, which are input circuit, data processing circuit, and output circuit. The input circuit is associated with

25、 the circuits, such as filtering, amplifying and A/D converting circuits, which manipulate the output signal from the transducer into a more usable signal for data processing. The data processing circuit is a circuit which processes the input signal to obtain the measured value and the necessary val

26、ues related to the measurement. The output circuit is a circuit which send out the processed results.Figure 1.2 basic system configuration of the electrical and electronic scaleAccording to whether or not they undertake the counterforces as counterforce elements, the transducers are classified into

27、two types which are the noncounterforce-type and the counterforce-type transducer,as shown in Fig.1.3.Figure 1.3 Classification of transducers1.3 FUNCTIONS AND SYSTEM CONFIGURATIONS OF THE SCALES FOR INDUSTRIAL UES1.3.1 Functional Characteristics and ClassificationThe scales mainly used for industri

28、al weighing hace the following features: 1)The loading on and unloading from the load receiving element are automatic. 2)the determination process of the mass value M of the object by using its weight W is automatic.The system configuration of such scales is shown in Fig.1.4. In addition,most of the

29、 scales have the following feature: 3)The scale has a function of mass control.The name and function of representative scales for industrial use are tabulated in Table 1.1 Table 1.1 Industrial scales and their functionsFigure 1.4 System configuration of the scale for industrial use1.3.2 Control Purp

30、ose Paying attention to the difference of the mass flow of the object being fed onto the load receiving element and the mass flow of the object after the measurement, we could say the purpose of the mass control written in table 1.1 is mass flow control of the object. From this point of view, the co

31、ntrol purpose of the hopper scale or the weigh packer is to attain an intermittent flow each amount of which is pre-determined. The associative(selective combination) weigher is also regarded as this type of control. The control purpose of the checkweigher is to attain the diverging flows according

32、to the pre-determined grades in mass. As for the weigh feeder, the purpose is to attain a flow of pre-determined flow rate in mass or to attain a flow the total amount of which coincides with the pre-determined value.1.3.3 System ConfigurationsGenerally, a control system is composed of a controlled

33、object, detecting means, controlling means or controller and control element.In the industrial weighing systems, the controlled objects include the feeding devices, distributing devices, and discharging devices, and mass is the controlled variable. The system shown in Fig.1.4 corresponds to the dete

34、cting means, and various kinds of actuators are used as the control element.Figure 1.5 shows the classification, from the view point of the system configuration, of the industrial weighing systems. The system configuration of a hopper scale or a weigh packer is shown in Fig.1.5(a). The controlled ob

35、ject is a feeding device,whose typical example is a screw feeder. The control element is a variable speed motor driving the feeder in the case. The hopper corresponds to the load receiving element The desired value is denoted by the symbol R and the manipulated variable the symbol C. The symbols m a

36、nd mrepresent respectively the states of mass flow and the differences in symbol mean the differences between the two states.Figure 1.5(b) shows the system configuration of a weigh feeder, the typical example of which is a variable speed belt-feeder. The load receiving element is composed of a porti

37、on of the belt and the weigh roller(s). The controlled object is the belt-feeder and the control element is the variable speed motor. The total amount of the detected mass is denoted by the symbol Q .Either Q or its derivative Qis chosen as the controlled variable and the measurement of the belt spe

38、ed V is needed for obtaining the value Q.Figure1.5(c) shows the system configuration of a checkweigher. The controlled object is the distributing device and the belt conveyer is normally adopted as the load receiving element.Figure1.5(d) shows the system configuration of an associative(selective com

39、bination) weigher. Normally, small hoppers are used for the load receiving elements, each of which is equipped with a gate controlled by an actuator. The gates are controlled objects and the actuators are the control elements.For the scales shown in Figs. 1.5(a) and 1.5(b), feedback control is adopt

40、ed since the mass flow control has to be carried out while measuring the mass. On the other hand, for the scales shown in Figs.1.5(c) and 1.5(d), the mass flow control is fundamentally sequential control since the control is carried out after the measurement of the mass.(a) Hopper scale or weigh pac

41、ker (b) Weigh feeder(c) Checkweigher (d) Associative weigherFigure 1.5 Industrial scales with mass controlCHAPTER 2 STATICE OF SCALES2.1 STATICE OF LEVERS 2.11 Classification of LeversA straight lever normally has a fulcrum pivot, load pivot, and power pivot, which is referred to as the fundamental

42、lever. Each position of the pivots is referred respectively to as fulcrum point, the load point, and the power point. The fulcrum point is a point at which a lever is supported and about which it is vibrationable. The load and power points are points at which a load and counterbalancing force are ap

43、plied,respectively.Fundamental levers are classified into three types according to the arrangement of the above three points; the first-order lever, the second-order-lever, and the third-order-lever. The detail is shown in Fig.2.1 in which point F is the fulcrum point, point A the load point, and po

44、int Bthe power point, being in a straight line.(a) First-order lever (b) Second-order lever (c) Third-order leverFigure 2.1 Classification of levers The lever (system) is called the single lever or the compound lever ( system) according to the number of connected levers. The single lever is a lever

45、used independently, such as a weigh beam of balance, and the compound lever is a lever system composed of connected levers.Each number of the fulcrum point, load point, and power point is not limited to one point for one lever. For example, The lever illustrated in Fig.2.2, which may be regarded as

46、a two-united lever, has two fulcrum point and two load points. A compound lever system including such levers is shown in Fig.2.3.Figure 2.2 A two-united lever Figure 2.3 Compound lever system2.12 Single leversIn practical application, there are two cases as to the position of a lever in static equilibrium under loading;the case that the position is always identical with the position under a zero load(Case 1), and the c