拖拉機(jī)液壓懸掛系統(tǒng)自動控制系統(tǒng)研究設(shè)計(jì)含CAD圖

拖拉機(jī)液壓懸掛系統(tǒng)自動控制系統(tǒng)研究設(shè)計(jì)含CAD圖,拖拉機(jī),液壓,懸掛,吊掛,系統(tǒng),自動控制系統(tǒng),研究,鉆研,設(shè)計(jì),cad 附錄2: Microcomputer Systems Electronic systems are used for handing information in the most general sense; this information may be telephone conversation, instrument read or a company’s accounts, but in each case the same main type of operation are involved: the processing, storage and transmission of information. in conventional electronic design these operations are combined at the function level; for example a counter, whether electronic or mechanical, stores the current and increments it by one as required. A system such as an electronic clock which employs counters has its storage and processing capabilities spread throughout the system because each counter is able to store and process numbers. Present day microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different section of the system. This partitioning into three main functions was devised by Von Neumann during the 1940s, and was not conceived especially for microcomputers. Almost every computer ever made has been designed with this structure, and despite the enormous range in their physical forms, they have all been of essentially the same basic design. In a microprocessor based system the processing will be performed in the microprocessor itself. The storage will be by means of memory circuits and the communication of information into and out of the system will be by means of special input/output(I/O) circuits. It would be impossible to identify a particular piece of hardware which performed the counting in a microprocessor based clock because the time would be stored in the memory and incremented at regular intervals but the microprocessor. However, the software which defined the system’s behavior would contain sections that performed as counters. The apparently rather abstract approach to the architecture of the microprocessor and its associated circuits allows it to be very flexible in use, since the system is defined almost entirely software. The design process is largely one of software engineering, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when producing software. The figure1.1 illustrates how these three sections within a microcomputer are connected in terms of the communication of information within the machine. The system is controlled by the microprocessor which supervises the transfer of information between itself and the memory and input/output sections. The external connections relate to the rest (that is, the non-computer part) of the engineering system. Fig.1.1 Three Sections of a Typical Microcomputer Although only one storage section has been shown in the diagram, in practice two distinct types of memory RAM and ROM are used. In each case, the word ‘memory’ is rather inappropriate since a computers memory is more like a filing cabinet in concept; information is stored in a set of numbered ‘boxes’ and it is referenced by the serial number of the ‘box’ in question. Microcomputers use RAM (Random Access Memory) into which data can be written and from which data can be read again when needed. This data can be read back from the memory in any sequence desired, and not necessarily the same order in which it was written, hence the expression ‘random’ access memory. Another type of ROM (Read Only Memory) is used to hold fixed patterns of information which cannot be affected by the microprocessor; these patterns are not lost when power is removed and are normally used to hold the program which defines the behavior of a microprocessor based system. ROMs can be read like RAMs, but unlike RAMs they cannot be used to store variable information. Some ROMs have their data patterns put in during manufacture, while others are programmable by the user by means of special equipment and are called programmable ROMs. The widely used programmable ROMs are erasable by means of special ultraviolet lamps and are referred to as EPROMs, short for Erasable Programmable Read Only Memories. Other new types of device can be erased electrically without the need for ultraviolet light, which are called Electrically Erasable Programmable Read Only Memories, EEPROMs. The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor. The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor. The microprocessor , memory and input/output circuit may all be contained on the same integrated circuit provided that the application does not require too much program or data storage . This is usually the case in low-cost application such as the controllers used in microwave ovens and automatic washing machines . The use of single package allows considerable cost savings to e made when articles are manufactured in large quantities . As technology develops , more and more powerful processors and larger and larger amounts of memory are being incorporated into single chip microcomputers with resulting saving in assembly costs in the final products . For the foreseeable future , however , it will continue to be necessary to interconnect a number of integrated circuits to make a microcomputer whenever larger amounts of storage or input/output are required. Another major engineering application of microcomputers is in process control. Here the presence of the microcomputer is usually more apparent to the user because provision is normally made for programming the microcomputer for the particular application. In process control applications the benefits lf fitting the entire system on to single chip are usually outweighed by the high design cost involved, because this sort lf equipment is produced in smaller quantities. Moreover, process controllers are usually more complicated so that it is more difficult to make them as single integrated circuits. Two approaches are possible; the controller can be implemented as a general-purpose microcomputer rather like a more robust version lf a hobby computer, or as a ‘packaged’ system, signed for replacing controllers based on older technologies such as electromagnetic relays. In the former case the system would probably be programmed in conventional programming languages such as the ones to9 be introduced later, while in the other case a special-purpose language might be used, for example one which allowed the function of the controller to be described in terms of relay interconnections, In either case programs can be stored in RAM, which allows them to be altered to suit changes in application, but this makes the overall system vulnerable to loss lf power unless batteries are used to ensure continuity of supply. Alternatively programs can be stored in ROM, in which case they virtually become part of the electronic ‘hardware’ and are often referred to as firmware. More sophisticated process controllers require minicomputers for their implementation, although the use lf large scale integrated circuits ‘the distinction between mini and microcomputers, Products and process controllers of various kinds represent the majority of present-day microcomputer applications, the exact figures depending on one’s interpretation of the word ‘product’. Virtually all engineering and scientific uses of microcomputers can be assigned to one or other of these categories. But in the system we most study Pressure and Pressure Transmitters. Pressure arises when a force is applied over an area. Provided the force is one Newton and uniformly over the area of one square meters, the pressure has been designated one Pascal. Pressure is a universal processing condition. It is also a condition of life on the planet: we live at the bottom of an atmospheric ocean that extends upward for many miles. This mass of air has weight, and this weight pressing downward causes atmospheric pressure. Water, a fundamental necessity of life, is supplied to most of us under pressure. In the typical process plant, pressure influences boiling point temperatures, condensing point temperatures, process efficiency, costs, and other important factors. The measurement and control of pressure or lack of it-vacuum-in the typical process plant is critical. The working instruments in the plant usually include simple pressure gauges, precision recorders and indicators, and pneumatic and electronic pressure transmitters. A pressure transmitter makes a pressure measurement and generates either a pneumatic or electrical signal output that is proportional to the pressure being sensed. In the process plant, it is impractical to locate the control instruments out in the place near the process. It is also true that most measurements are not easily transmitted from some remote location. Pressure measurement is an exception, but if a high pressure of some dangerous chemical is to be indicated or recorded several hundred feet from the point of measurement, a hazard may be from the pressure or from the chemical carried. To eliminate this problem, a signal transmission system was developed. This system is usually either pneumatic or electrical. And control instruments in one location. This makes it practical for a minimum number of operators to run the plant efficiently. When a pneumatic transmission system is employed, the measurement signal is converted into pneumatic signal by the transmitter scaled from 0 to 100 percent of the measurement value. This transmitter is mounted close to the point of measurement in the process. The transmitter output-air pressure for a pneumatic transmitter-is piped to the recording or control instrument. The standard output range for a pneumatic transmitter is 20 to 100kPa, which is almost universally used. When an electronic pressure transmitter is used, the pressure is converted to electrical signal that may be current or voltage. Its standard range is from 4 to 20mA DC for current signal or from 1 to 5V DC for voltage signal. Nowadays, another type of electrical signal, which is becoming common, is the digital or discrete signal. The use of instruments and control systems based on computer or forcing increased use of this type of signal. Sometimes it is important for analysis to obtain the parameters that describe the sensor/transmitter behavior. The gain is fairly simple to obtain once the span is known. Consider an electronic pressure transmitter with a range of 0～600kPa.The gain is： defined as the change in output divided by the change in input. In this case, the output is electrical signal (4～20mA DC) and the input is process pressure (0～600kPa). Thus the gain. Beside we must measure Temperature Temperature measurement is important in industrial control, as direct indications of system or product state and as indirect indications of such factors as reaction rates, energy flow, turbine efficiency, and lubricant quality. Present temperature scales have been in use for about 200 years, the earliest instruments were based on the thermal expansion of gases and liquids. Such filled systems are still employed, although many other types of instruments are available. Representative temperature sensors include: filled thermal systems, liquid-in-glass thermometers, thermocouples, resistance temperature detectors, thermostats, bimetallic devices, optical and radiation pyrometers and temperature-sensitive paints. Advantages of electrical systems include high accuracy and sensitivity, practicality of switching or scanning several measurements points, larger distances possible between measuring elements and controllers, replacement of components(rather than complete system), fast response, and ability to measure higher temperature. Among the electrical temperature sensors, thermocouples and resistance temperature detectors are most widely used. 附錄3： 單片機(jī)系統(tǒng) 廣義地說，微處理系統(tǒng)是用于處理信息的，這種信息可以是電話交談，儀器讀數(shù)或企業(yè)帳戶，但是各種情況下都涉及相同的主要操作：信息處理、存儲和傳遞。在常規(guī)的電子設(shè)計(jì)中，這些操作都是以功能平臺方式組合起來的，例如計(jì)數(shù)器，無論是電子還是機(jī)械的，都要存儲當(dāng)前值，并按要求將該值增1。諸如采用計(jì)數(shù)器的電子鐘之類的任一系統(tǒng)要使其存儲和處理能力遍布整個系統(tǒng)，因?yàn)槊總€計(jì)數(shù)器都能存儲和處理一些數(shù)字。 當(dāng)前微處理化系統(tǒng)與上述的常規(guī)方法不同，它將處理，存儲和傳輸三個功能分離形成不同的系統(tǒng)單元。這種形成三個主要單元的分離方法是馮-諾依曼在20世紀(jì)40年代所設(shè)想出來的，并且是針對微計(jì)算機(jī)的設(shè)想。從此幾乎所有制成的計(jì)算機(jī)都是用這種結(jié)構(gòu)設(shè)計(jì)的，盡管包含寬廣的物理形式，從根本上來說他們均是具有相同的基本設(shè)計(jì)。 在微處理器系統(tǒng)中，處理是由微處理器本身完成的。存儲是利用存儲器電路，而進(jìn)入和出自系統(tǒng)的信息傳輸則是利用特定的輸入/輸出（I/O）電路。要在一個微處理器化時(shí)鐘中找出執(zhí)行計(jì)數(shù)功能的一個特殊硬件是不可能的，因?yàn)闀r(shí)間存儲在存儲器中，而在固定的時(shí)間間隔下由微處理器控制增值。但是，規(guī)定系統(tǒng)運(yùn)轉(zhuǎn)過程的軟件包含實(shí)現(xiàn)計(jì)數(shù)器功能的單元。由于系統(tǒng)幾乎完全由軟件所定義，所以對微處理器結(jié)構(gòu)和其輔助電路這種看起來非常抽象的處理方法使其在應(yīng)用時(shí)非常靈活。這種設(shè)計(jì)過程主要是軟件工程，而且在生產(chǎn)軟件時(shí)，就會遇到產(chǎn)生于常規(guī)工程中相似的構(gòu)造和維護(hù)問題。 圖1.1 微型計(jì)算機(jī)的三個組成部分 圖1.1顯示出了微型計(jì)算機(jī)中這三個單元是如何按照機(jī)器中的信息通信方式而聯(lián)接起來的。該系統(tǒng)由微處理器控制，它管理自己與存儲器和輸入/輸出單元的信息傳輸。外部的連接與工程系統(tǒng)的其余部分（即非計(jì)算機(jī)部分）有關(guān)。 盡管圖中顯示的只有一個存儲單元，實(shí)際中有RAM和ROM兩種不同的存儲器被使用。由于概念上的計(jì)算機(jī)存儲器更像一個公文柜，上述的“存儲器”一詞是非常不恰當(dāng)?shù)?；信息存放在一系列已?biāo)號的“箱子”中，而且可按問題由“箱子”的序列號進(jìn)行信息的參考定位。 微計(jì)算機(jī)常使用RAM（隨機(jī)存取存儲器），在RAM中數(shù)據(jù)可被寫入，并且在需要時(shí)可被再次讀出。這種數(shù)據(jù)能以任一所希望的次序從存儲器中讀出，不必按寫入時(shí)的相同次序，所以有“隨機(jī)” 存取存儲器。另一類型ROM（只讀存儲器）用來保持不受微處理器影響的固定的信息標(biāo)本；這些標(biāo)本在電源切斷后不會丟失，并通常用來保存規(guī)定微處理器化系統(tǒng)運(yùn)轉(zhuǎn)過程的程序。ROM可像RAM一樣被讀取，但與RAM不一樣的是不能用來存儲可變的信息。有些ROM在制造時(shí)將其數(shù)據(jù)標(biāo)本放入，而另外的則可通過特殊的設(shè)備由用戶編程，所以稱為可編程ROM。被廣泛使用的可編程ROM可利用特殊紫外線燈察除，并被成為EPROM，即可察除可編程只讀存儲器的縮寫。另有新類型的期器件不必用紫外線燈而用電察除，所以稱為電可察除可編程只讀存儲器EEPROM。 微處理器在程序控制下處理數(shù)據(jù)，并控制流向和來自存儲器和輸入/輸出裝置的信息流。有些輸入/輸出裝置是通用型的，而另外一些則是設(shè)計(jì)來控制如磁盤驅(qū)動器的特殊硬件，或控制傳給其他計(jì)算機(jī)的信息傳輸。大多數(shù)類型的I/O裝置在某種程度下可編程，允許不同形式的操作，而有些則包含特殊用途微處理器的I/O裝置不用主微處理器的直接干預(yù)，就可實(shí)施非常復(fù)雜的操作。 假如應(yīng)用中不需要太多的程序和數(shù)據(jù)存儲量，微處理器、存儲器和輸入/輸出可全被包含在同一集成電路中。這通常是低成本應(yīng)用情況，例如用于微波爐和自動洗衣機(jī)的控制器。當(dāng)商品被大量地生產(chǎn)時(shí)，這種單一芯片的使用就可節(jié)省相當(dāng)大的成本。當(dāng)技術(shù)進(jìn)一步發(fā)展，更強(qiáng)更強(qiáng)的處理器和更大更大數(shù)量的存儲器被包含形成單片微型計(jì)算機(jī)，結(jié)果使最終產(chǎn)品的裝配成本得以節(jié)省。但是在可預(yù)見的未來，當(dāng)需要大量的存儲器或輸入/輸出時(shí)，還是有必要繼續(xù)將許多集成電路相互聯(lián)結(jié)起來，形成微計(jì)算機(jī)。 微計(jì)算機(jī)的另一主要工程應(yīng)用是在過程控制中。這是，由于裝置是按特定的應(yīng)用情況由微機(jī)編程實(shí)現(xiàn)的，對用戶來說微計(jì)算機(jī)的存在通常就更加明顯。在過程控制應(yīng)用中，由于這種設(shè)備以較少的數(shù)量生產(chǎn)，將整個系統(tǒng)安裝在單個芯片上所獲取的利益常比不上所涉及的高設(shè)計(jì)成本。而且，過程控制器通常更為復(fù)雜，所以要將他們做成單獨(dú)的集成電路就更為困難?？刹捎脙煞N處理，將控制器做成一種通用的微計(jì)算機(jī)，正像較強(qiáng)版本的業(yè)余計(jì)算機(jī)那樣；或者做成“包裹”式系統(tǒng)，按照像電磁繼電器那樣的較老式的技術(shù)進(jìn)行設(shè)計(jì)，來取代控制器。對前一種情況，系統(tǒng)可以用常規(guī)的編程語言來編程，正如以后要介紹的語言那樣；而另一種情況，可采用特殊用途的語言，例如那種使控制器功能按照繼電器相互連接的方法進(jìn)行描述。兩種情況下，序均能存于RAM，這讓程序能按應(yīng)用情況變化時(shí)進(jìn)行相應(yīng)的變化，但是這使得總系統(tǒng)易受掉電影響而工作不正常，除非使用電池保證供電連續(xù)性。另一種選擇是將程序在ROM中，這樣他們就變成電子“硬件”的一部分并常被稱為“固件”。 盡管大規(guī)模集成電路的應(yīng)用使小型和微型計(jì)算機(jī)的差別變得“模糊”，更復(fù)雜的過程控制器需要小型計(jì)算機(jī)實(shí)現(xiàn)他們的過程。各種類型的產(chǎn)品和過程控制器代表了當(dāng)今微計(jì)算機(jī)應(yīng)用的廣泛性，而具體的結(jié)構(gòu)取決于對“產(chǎn)品”一詞的解釋。實(shí)際上，計(jì)算機(jī)的所有工程和科學(xué)上的應(yīng)用都能指定來進(jìn)行這些種類的某一或某些工作。而在本設(shè)計(jì)中壓力和壓力變送器當(dāng)某一力加到某一面積上，就形成壓力，假如這力是1牛頓均勻地加在1平方米的面積上，這壓力被定義為1帕斯卡。壓力是一種普遍的工藝狀態(tài)，它也是這個星球上的一個生活條件：我們生活在向上延伸許多英里的大氣海洋的底部?？諝馕镔|(zhì)是有重量的，而且這種下壓的重量形成大氣壓。水，是生活的必需品，也是在壓力之下提供給我們中的大多數(shù)人。在典型的過程工廠中，壓力影響沸點(diǎn)溫度、凝固點(diǎn)溫度、過程效率、消耗和其他重要因數(shù)。壓力的測量和控制，或者壓力的不足—真空，在典型的過程控制中是極為重要的。 工廠中的工作儀器通常包括壓力計(jì)、精密紀(jì)錄儀、以及氣動和電動的壓力變送器。壓力變送器實(shí)現(xiàn)壓力測量并產(chǎn)生正比于所傳感壓力的氣動或電信號輸出。 在過程工廠中，將控制儀表遠(yuǎn)遠(yuǎn)放在過程的附近是不現(xiàn)實(shí)的，并且大多數(shù)測量是不容易從遠(yuǎn)處傳來的。壓力測量是一個例外，但是，如果要離測量點(diǎn)幾百英尺外指示或記錄某種危險(xiǎn)化學(xué)品的高壓，就會有來自這個壓力所載的化學(xué)品所引發(fā)的危險(xiǎn)。為了消除這一問題，開發(fā)了一種信號傳輸系統(tǒng)。這種系統(tǒng)常?？墒菤鈩踊蛘唠妱拥摹Ｊ褂眠@種系統(tǒng)，就可以在某一地點(diǎn)安裝大多數(shù)的指示、記錄和控制儀器。這也是最少數(shù)量的操作者有效的運(yùn)行工廠成為現(xiàn)實(shí)。 當(dāng)使用氣動傳送系統(tǒng)時(shí)，測量信號就由變送器將比例為0%～100%的測量值轉(zhuǎn)換為氣動信號。變送器安裝在靠近過程中的測量點(diǎn)上。變送器輸出—對氣動變送器是輸出壓力—通過管道傳給記錄或控制儀表。氣動變送器的標(biāo)準(zhǔn)輸出范圍是20～100kPa，這信號幾乎在全球使用。 當(dāng)使用電子壓力變送器時(shí)，壓力就被轉(zhuǎn)換成電流或電壓形式的電信號。其標(biāo)準(zhǔn)范圍對電流來說是4～20mA DC，對電壓信號來說是1～5V DC。當(dāng)今，另一種電信號形式變的越來越常用，就是數(shù)字或離散信號?；谟?jì)算機(jī)或微處理器的儀器或控制系統(tǒng)的應(yīng)用正推動這類信號的應(yīng)用不斷增加。有時(shí)，分析獲取描述傳感器/變送器特性的參數(shù)是很重要的。當(dāng)量程已知，去獲取增益就非常簡單。假定電子壓力傳感器的量程為0～600kPa，增益定義為輸出變化除以輸入變化。這里，輸出的電信號（4～20mA DC），而輸入的過程壓力（0～600kPa），這樣增益就為： 此外我們在本設(shè)計(jì)中還必須對溫度進(jìn)行測量，溫度測量在工業(yè)控制中是很重要的，因?yàn)樗鳛橄到y(tǒng)或產(chǎn)品狀態(tài)的直接指標(biāo)，或者作為如反應(yīng)率、能量流、渦輪機(jī)效率和潤滑質(zhì)量等間接指標(biāo)?，F(xiàn)行的溫度分度已使用了約200年，最初的儀器是基于氣體和液體的熱膨脹?，F(xiàn)在盡管有許多其他類型的儀器在使用，這些填充式系統(tǒng)仍常用于直接的溫度測量。有代表性的溫度傳感器包括：填充式熱系統(tǒng)、玻璃液體溫度計(jì)、熱電偶、電阻溫度探測器、熱敏電阻、雙金屬器件、光學(xué)和輻射高溫計(jì)和熱敏涂料。 電氣系統(tǒng)的優(yōu)點(diǎn)包括高的精度和靈敏度，能實(shí)現(xiàn)開關(guān)切換或掃描多個測量點(diǎn)，可在測量元件和控制器之間長距離傳輸，出現(xiàn)事故時(shí)可調(diào)換元件，快速響應(yīng)，以及具有測量高溫的能力。其中熱電偶和電阻溫度探測器則被最廣泛的使用。