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機械與電氣工程學院
畢業(yè)設計（論文）外文翻譯
所在學院： 機械與電氣工程學院
班 級： 08機自一班
姓 名： 高 升
學 號： 08141010105
指導教師： 張薇薇
合作導師：
年 月 日
應用于電氣系統(tǒng)的可編程序控制器
此項目主要是研究電氣系統(tǒng)以及簡單有效的控制氣流發(fā)動機的程序和氣流系統(tǒng)的狀態(tài)。它的實踐基礎包括基于氣流的專有控制器、自動化設計、氣流系統(tǒng)的控制程序和基于微控制器的電子設計。
1.簡介
使用電氣技術的自動化系統(tǒng)主要由三個組成部分：發(fā)動機或馬達，感應器或按鈕，狀如花瓣的控制零部件。現(xiàn)在，大部分的系統(tǒng)邏輯操作的控制器都被程序邏輯控制器（PLC）所取代。PLC的感應器和開關是輸入端，而發(fā)動機的直接控制閥是輸出端，其中有一個內部程序操控所有運行必需的邏輯，模擬其他的裝置如計算器、定時器等，對整個系統(tǒng)的運行狀態(tài)進行控制。
因為可以根據(jù)需要無數(shù)次創(chuàng)建和模擬這樣的系統(tǒng)，所以藉由PLC的使用，此項目有靈活的優(yōu)點。因此，可以節(jié)省時間，減少失誤的危險，同時在使用相同材料的情況下，它可以更加精密。
市場上的許多家公司都使用了常規(guī)的PLC，它不僅可以用氣流系統(tǒng)來控制，還可以用各種電氣設備。PLC 的用途廣泛，可以應用于許多工業(yè)生產中，甚至用于建筑物的安全和自動化系統(tǒng)中。
由于以上的各種特性，在一些實際應用中PLC提供了很多的資源，甚至包括不控制系統(tǒng)的資源，電氣系統(tǒng)就是一種這樣的應用。對于自動化的工程，PLC的使用是比較昂貴的，尤其是對那些小型的系統(tǒng)。
針對這種情況可行的一種辦法是創(chuàng)建一個可提供特定尺寸和功能的控制器。這種控制器可以根據(jù)微控制器來制作。
這種基于微控制器的控制器的適用范圍比較小，只能用于一個類型的機器或者可以用做一個像普通PLC一樣可以被編程的控制器，那樣它就可以通過可變化的邏輯程序來進行各種作業(yè)。所有的這些特性根據(jù)具體需要的不同而不同，具體的設計者的經驗的不同而不同。但是這種設計的主要優(yōu)點在于設計人員非常了解自己的控制器，可以自由掌握控制器的大小尺寸，改變它的功能。這就意味著此項目有更多的獨特性，但同時系統(tǒng)的控制也由它的設計者所控制。
2.電氣系統(tǒng)
人們可以從一個自動化系統(tǒng)中找到三個上文中提到的基本部件，外加一個控制系統(tǒng)的邏輯線路。只有成熟先進的技術能做出特定的邏輯線路和執(zhí)行正確操作所需要的部件升級。
對于一個簡單的運動，系統(tǒng)自動程序可以完成，但是對于間接或更加復雜的運動，系統(tǒng)的程序就會產生復雜的線路和錯誤的信號。這是就需要另一種方法可以節(jié)省時間，產生清晰線路，能夠防止偶然的信號交疊和線路堵塞。
這種方計的不同標準的線路基法叫循序漸進式或規(guī)則系統(tǒng)，它對氣流和電氣系統(tǒng)非常有效，而且也是此項目的一個基礎。它包括根據(jù)發(fā)動機狀態(tài)各個不同變化所設礎上的系統(tǒng)。
圖1 氣壓系統(tǒng)標準回路 圖2 電控氣壓系統(tǒng)標準回路
第一步是為每個步驟設計那些種標準的線路。第二步是聯(lián)編標準的線路，最后一步是連接接收來自感應器，開關和先前的運動信號，同時把空氣或電傳送給每個步驟的補給線。如圖中所示， 1 和 2 標準線路是為氣流的和電氣系統(tǒng)服務。我們能夠很清楚的看到每一步驟和下一個步驟之間的聯(lián)系。
3.控制器內部的應用原理
上述方法可以使發(fā)動機的每一個運動都被很好地用步驟來定義。這也就是說發(fā)動機的每一次運動變化都是系統(tǒng)的一個新的狀態(tài)，而兩個不同狀態(tài)之間的轉變叫做步驟。
先前提到的標準線路可以幫助設計人員定義系統(tǒng)的不同狀態(tài)和不同步驟的變化所帶來的不同環(huán)境。在設計的最后階段，系統(tǒng)中會有一個從來不變化的序列和明確的輸入和輸出端。我們把一個序列從輸入端輸入，經過轉換后，由輸出端輸出。
這些步驟的所有過程都是在微控制器內部進行的，并且以同樣的方式在運行著。部件的序列在控制器里被 5個位元組規(guī)劃; 每個部分都有程序的一個步驟結構。輸入端有二個位元組，輸出端有一個，其他結構部分和附加功能步驟有兩個。 在編程之后，部件序列被內部微控制器的記憶所儲藏，因此，他們是可讀的而且可以運行。
不同于傳統(tǒng)的PLC，這種控制器的工作目的是成為特定領域設計的多用控制器。傳統(tǒng)的 PLC 的系統(tǒng)運行程序是一個循環(huán)的線路：輸入一個圖像,運行所有的內部程序, 然后升級輸出的狀態(tài)。 這一個控制器以不同的方式工作,它讀取步驟的結構,等待輸入,然后升級或輸出，然后直接跳躍到下一個步驟，開始另一次的程序運行。
它也有局限性，例如這種控制器有時會不執(zhí)行指令，在同一程序指令下，會出現(xiàn)某一個運行的反復等等，但是這一個問題可以通過外部的邏輯運行解決。另外，這中控制器在沒有序列的系統(tǒng)上不能夠被應用。這些局限性也是這個系統(tǒng)的特性，這種系統(tǒng)的每一個應用都必須要有相應的系統(tǒng)分析。
4.控制器的特色
這種控制器以微集成電路微控制器 PIC16F877為基礎,它擁有全部此次項目所需要的資源。它有足夠的插孔，線路連續(xù)通訊 EEPROM 記憶解救系統(tǒng)的所有結構和步驟的序列。它提供了項目所需要的所有的運行，例如定時器和分岔等。
我們做出了控制器的資源目錄，想盡可能的使它變的完善。在步驟的運行過程中，程序自動選擇如何讀取每一步驟的結構。這個操作有兩個位元組位于電子輸入處。一個位元組位于輸出端，還有一個被用作內部定時器，類似輸入或暫停功能。EEPROM 記憶內部是 256 位元組，可以儲藏所有步驟的運行,即可以儲藏 48個步驟之間的所有運行。
除了一個互動菜單外，這種控制器還有一個控制臺和一些指令按鈕，他們一起控制各個步驟的運行和連續(xù)性，也控制其他的一些裝置。
4.1交互作用
在實際運行操作中，控制器需要有一些輔助設備幫助它和使用者進行互動，可以提供可靠的操作監(jiān)控，同時對氣流系統(tǒng)進行邏輯控制。
1、交互工作模式： 在主要的程序中，使用者可以根據(jù)指導發(fā)出信號來進行具體步驟的操作
2、LCD 平臺可以顯示系統(tǒng)工作的狀態(tài)，衡量輸入，輸出，計時器和運行的數(shù)據(jù)等。
3、嘀嘀聲用來提示重要警示，停止，開始和一些緊急情況的發(fā)生
4、亮燈表示接通電源，和輸入，輸出狀態(tài)。
4.2 安全性
如果想正常運行程序，必須保證每一個步驟都正確的執(zhí)行。更重要的是，應該有預防運行故障和問題的解決方法?？刂破魈峁┝诉@種可能性，通過使用兩個內部虛擬線路同時運行。他們可以重新啟動程序，隨時恢復到程序的原有狀態(tài)。有兩個輸入端共同工作可以快速的運行這些功能。
4.3 接口
程序運行序列可以用控制器的接口來編程。一臺計算機的接口也可以用來升級使用程序。使用者能利用接口配置一連串定義序列的步驟位元組。但是也可以設計一個程序,利用可視資源為使用者翻譯所需要的信息。
但是，如果想聯(lián)結電腦接口和控制器，至少應該有一個儀器來保證數(shù)據(jù)的可靠性。
4.4 固件
主要的線環(huán)是通過讀取EEPROM 記憶中的每一資訊步驟進行工作。
在每個步驟中，系統(tǒng)的狀態(tài)被儲存，同時它也在顯示器上被顯示。根據(jù)使用者的構造,它能利用分流或暫停應付緊急線路情況來保證系統(tǒng)安全。
5 電氣系統(tǒng)例子
這種系統(tǒng)不只是適應于特定的機器。它由四個主動器組成。 主動器 A，B 和C是兩倍的，只有D是單倍的。第一步，主動器A開始運行，并保持在一個特定的位置一直到一個循環(huán)的結束，如圖 5 所示它可以確定某一對象的下一運動。第二步，當A完成了它的工作后，主動器C連同B一起開始盡可能多的產生電流圈，并受B的運行速度的限制，而B速度由一個流動的控制活瓣管理。B和C是一起工作的主動器的例子，當B慢慢地推動一個物體的時候，C有時則重復它的工作。
圖5 A，B，C，D 傳動裝置時間曲線
第三步，當B到達最后的位置時候，C停止立刻它的循環(huán)運動并且回到開始的位置。利用回旋的電流工作的主動器 D連同返回來的C一起工作。第四步，主動器D快速往返來回運動一次。D可以充當一個工具，在物體上的表面上打洞。當D返回開始的位置時候，A和B也同時返回，這是第五個步驟。
圖 6 顯示了程序設計的第一部分。我們把每個步驟的所有運行統(tǒng)稱為 [2]. (A+) 表示主動器 A 向前推動，而 (A-) 表示返回到開始的位置。 同時發(fā)生的運動在相同的步驟中被一起疊加。這個系統(tǒng)共有有五個步驟。
圖6 A ,B ,C ,D 傳動裝置傳動順序
圖5和6所表現(xiàn)的系統(tǒng)運行清楚的描述了所有序列。 利用他們我們可以用必需的邏輯語言設計整個的控制線路。但是現(xiàn)在還它還不是一個完整的系統(tǒng)，因為它還缺少一些輔助設施（圖中沒有顯示）。
對于程序的最后運行，這些輔助設施十分的重要，因為他們能使線路有更多的功能。他們中最重要的是連接在每一步驟中的平行線路。那一個線路能夠隨時停止序列而且將主動器的狀態(tài)換成一個特定的位置。它可以重起系統(tǒng)或是應付緊急情況。圖7和8顯示的是在沒有使用控制器的情況下會發(fā)生的一些結果。這些照片是控制線路的電圖表,包括感應器，控制鍵和電的活瓣卷。
圖7 電氣圖表舉例
圖8 電氣圖表舉例
另外的一些輔助設施也包括在這個系統(tǒng)中，比如自動機械/手動調控器，他們可以使系統(tǒng)不斷的循環(huán)工作；兩個開始控制鍵，他們能讓操作員手動控制系統(tǒng)的開始和停止，這樣就減少了發(fā)生意外事件的危險。
6 使用者變更例子規(guī)劃
氣流線圈在前面已經詳細說明過：它可以讓我們了解到控制一個系統(tǒng)所需要的條件，那就是在系統(tǒng)的實際運行中必須提供所有的功能設施。但是,如前面提到的那樣,使用一個PLC或特定的控制器，這種控制就變得比較容易的，而且系統(tǒng)的精密性也會提高。
表2所示的是控制上面提到的系統(tǒng)的必需設施。通過時間圖表，表2，和圖5和6描述了每一步驟的程序和系統(tǒng)的各個部件。這說明記錄所有步驟的運行結構圖并把他們送給控制器 (表3和4所示)。
使用傳統(tǒng)的PLC的，如圖7，8所示，在繪制接口處的電圖表時，要注意線路的邏輯。使用這種可編程的控制器，使用者必須知道運行方法的觀念并且規(guī)劃每個步驟的結構。
那就是說，使用傳統(tǒng)的PLC，使用者清楚各個操作之間的關系。一般情況下，使用者可以在接口上運行一個模擬程序尋找邏輯上的錯誤同之前所述的一樣，新的編程允許每一步驟的結構被分割。序列獨自被定義，但每一步驟只被輸入和輸出端描述。
圖9 A ,B 傳動裝置和傳感器
圖10 C ,D 傳動裝置和傳感器
表 5 表現(xiàn)的是使用系統(tǒng)如何被儲藏在控制器里,這在前文中也詳細說明過。序列被 25個位元組所定義。這些位元組被分成5組，每一組描述系統(tǒng)運行的一個步驟。（圖 9 和 10）
7 結論
這種控制器是專門為這一項目所設計的。它不需要為了獲取微控制器里的資源而安裝外部記憶器或外部的定時器。除了微控制器之外，只有少量的零部件執(zhí)行一些如輸出，輸入，類比輸入,顯示接口和連續(xù)運行的情況等功能。
單獨使用內部記憶，我們可以控制一個有48個步驟的氣流系統(tǒng)，但是如果使用一個比較簡單的系統(tǒng)，就會達到60個步驟.控制器的變成不使用 PLC 語言，而是用一個比較簡單的和直覺的結構。利用電氣系統(tǒng)，我們的項目應用了相同的技術，但同時我們的設計更加直接。
一種非常簡單的機械語言能讓設計者用四或五個位元組定義步驟所有結構構成。這就要看他使用控制器的經驗如何了。這種控制器雖然不能和商業(yè)的 PLC 相比，但是它原本就是為特定的的目的而設計的，所以很難說哪一個好哪一個壞?？傊?，我們的這個系統(tǒng)是基于微控制器而設計，簡單快捷。
Programmable designed for electro-pneumatic systems controller
This project deals with the study of electro-pneumatic systems and the programmable controller that provides an effective and easy way to control the sequence of the pneumatic actuators movement and the states of pneumatic system. The project of a specific controller for pneumatic applications join the study of automation design and the control processing of pneumatic systems with the electronic design based on microcontrollers to implement the resources of the controller.
1. Introduction
The automation systems that use electro-pneumatic technology are formed mainly by three kinds of elements: actuators or motors, sensors or buttons and control elements like valves. Nowadays, most of the control elements used to execute the logic of the system were substituted by the Programmable Logic Controller (PLC). Sensors and switches are plugged as inputs and the direct control valves for the actuators are plugged as outputs. An internal program executes all the logic necessary to the sequence of the movements, simulates other components like counter, timer and control the status of the system.
With the use of the PLC, the project wins agility, because it is possible to create and simulate the system as many times as needed. Therefore, time can be saved, risk of mistakes reduced and complexity can be increased using the same elements.
A conventional PLC, that is possible to find on the market from many companies, offers many resources to control not only pneumatic systems, but all kinds of system that uses electrical components. The PLC can be very versatile and robust to be applied in many kinds of application in the industry or even security system and automation of buildings.
Because of those characteristics, in some applications the PLC offers to much resources that are not even used to control the system, electro-pneumatic system is one of this kind of application. The use of PLC, especially for small size systems, can be very expensive for the automation project.
An alternative in this case is to create a specific controller that can offer the exactly size and resources that the project needs [3, 4]. This can be made using microcontrollers as the base of this controller.
The controller, based on microcontroller, can be very specific and adapted to only one kind of machine or it can work as a generic controller that can be programmed as a usual PLC and work with logic that can be changed. All these characteristics depend on what is needed and how much experience the designer has with developing an electronic circuit and firmware for microcontroller. But the main advantage of design the controller with the microcontroller is that the designer has the total knowledge of his controller, which makes it possible to control the size of the controller, change the complexity and the application of it. It means that the project gets more independence from other companies, but at the same time the responsibility of the control of the system stays at the designer hands
2. Electro-pneumatic system
On automation system one can find three basic components mentioned before, plus a logic circuit that controls the system. An adequate technique is needed to project the logic circuit and integrate all the necessary components to execute the sequence of movements properly.
For a simple direct sequence of movement an intuitive method can be used [1, 5], but for indirect or more complex sequences the intuition can generate a very complicated circuit and signal mistakes. It is necessary to use another method that can save time of the project, make a clean circuit, can eliminate occasional signal overlapping and redundant circuits. The presented method is called step-by-step or algorithmic [1, 5], it is valid for pneumatic and electro-pneumatic systems and it was used as a base in this work.
The method consists of designing the systems based on standard circuits made for each change on the state of the actuators, these changes are called steps.
The first part is to design those kinds of standard circuits for each step, the next task is to link the standard circuits and the last part is to connect the control elements that receive signals from sensors, switches and the previous movements, and give the air or electricity to the supply lines of each step. In Figs. 1 and 2 the standard circuits are drawn for pneumatic and electro-pneumatic system [8]. It is possible to see the relations with the previous and the next steps.
3. The method applied inside the controller
The result of the method presented before is a sequence of movements of the actuator that is well defined by steps. It means that each change on the position of the actuators is a new state of the system and the transition between states is called step.
The standard circuit described before helps the designer to define the states of the systems and to define the condition to each change between the states. In the end of the design, the system is defined by a sequence that never chances and states that have the inputs and the outputs well defined. The inputs are the condition for the transition and the outputs are the result of the transition.
All the configuration of those steps stays inside of the microcontroller and is executed the same way it was designed. The sequences of strings are programmed inside the controller with 5 bytes; each string has the configuration of one step of the process. There are two bytes for the inputs, one byte for the outputs and two more for the other configurations and auxiliary functions of the step. After programming, this sequence of strings is saved inside of a non-volatile memory of the microcontroller, so they can be read and executed.
The controller task is not to work in the same way as a conventional PLC, but the purpose of it is to be an example of a versatile controller that is design for an specific area. A conventional PLC process the control of the system using a cycle where it makes an image of the inputs, execute all the conditions defined by the configuration programmed inside, and then update the state of the outputs. This controller works in a different way, where it read the configuration of the step, wait the condition of inputs to be satisfied, then update the state or the outputs and after that jump to the next step and start the process again.
It can generate some limitations, as the fact that this controller cannot execute, inside the program, movements that must be repeated for some time, but this problem can be solved with some external logic components. Another limitation is that the controller cannot be applied on systems that have no sequence. These limitations are a characteristic of the system that must be analyzed for each application.
4. Characteristics of the controller
The controller is based on the MICROCHIP microcontroller PIC16F877 [6,7] with 40 pins, and it has all the resources needed for this project .It has enough pins for all the components, serial communication implemented in circuit, EEPROM memory to save all the configuration of the system and the sequence of steps. For the execution of the main program, it offers complete resources as timers and interruptions.
The list of resources of the controller was created to explore all the capacity of the microcontroller to make it as complete as possible. During the step, the program chooses how to use the resources reading the configuration string of the step. This string has two bytes for digital inputs, one used as a mask and the other one used as a value expected. One byte is used to configure the outputs value. One bytes more is used for the internal timer , the analog input or time-out. The EEPROM memory inside is 256 bytes length that is enough to save the string of the steps, with this characteristic it is possible to save between 48 steps （Table 1）.
The controller (Fig.3) has also a display and some buttons that are used with an interactive menu to program the sequence of steps and other configurations.
4.1. Interaction components
For the real application the controller must have some elements to interact with the final user and to offer a complete monitoring of the system resources that are available to the designer while creating the logic control of the pneumatic system (Fig.3):
?Interactive mode of work; function available on the main program for didactic purposes, the user gives the signal to execute the step.
?LCD display, which shows the status of the system, values of inputs, outputs, timer and statistics of the sequence execution.
?Beep to give important alerts, stop, start and emergency.
? Leds to show power on and others to show the state of inputs and outputs.
4.2. Security
To make the final application works property, a correct configuration to execute the steps in the right way is needed, but more then that it must offer solutions in case of bad functioning or problems in the execution of the sequence. The controller offers the possibility to configure two internal virtual circuits that work in parallel to the principal. These two circuits can be used as emergency or reset buttons and can return the system to a certain state at any time [2]. There are two inputs that work with interruption to get an immediate access to these functions. It is possible to configure the position, the buttons and the value of time-out of the system.
4.3. User interface
The sequence of strings can be programmed using the interface elements of the controller. A Computer interface can also be used to generate the user program easily. With a good documentation the final user can use the interface to configure the strings of bytes that define the steps of the sequence. But it is possible to create a program with visual resources that works as a translator to the user, it changes his work to the values that the controller understands.
To implement the communication between the computer interface and the controller a simple protocol with check sum and number of bytes is the minimum requirements to guarantee the integrity of the data.
4.4. Firmware
The main loop works by reading the strings of the steps from the EEPROM memory that has all the information about the steps.
In each step, the status of the system is saved on the memory and it is shown on the display too. Depending of the user configuration, it can use the interruption to work with the emergency circuit or time-out to keep the system safety. In Fig.4,a block diagram of micro controller main program is presented.
5. Example of electro-pneumatic system
The system is not a representation of a specific machine, but it is made with some common movements and components found in a real one. The system is composed of four actuators. The actuators A, B and C are double acting and D-single acting. Actuator A advances and stays in specified position till the end of the cycle, it could work fixing an object to the next action for example (Fig. 5) , it is the first step. When A reaches the end position, actuator C starts his work together with B, making as many cycles as possible during the advancing of B. It depends on how fast actuator B is advancing; the speed is regulated by a flowing control valve. It was the second step. B and C are examples of actuators working together, while B pushes an object slowly, C repeats its work for some time.
When B reaches the final position, C stops immediately its cycle and comes back to the initial position. The actuator D is a single acting one with spring return and works together with the back of C, it is the third step. D works making very fast forward and backward movement, just one time. Its backward movement is the fourth step. D could be a tool to make a hole on the object.
When D reaches the initial position, A and B return too, it is the fifth step.
Fig. 6 shows the first part of the designing process where all the movements of each step should be defined [2]. (A+) means that the actuator A moves to the advanced position and (A?) to the initial position. The movements that happen at the same time are joined together in the same step. The system has five steps.
These two representations of the system (Figs. 5 and 6) together are enough to describe correctly all the sequence. With them is possible to design the whole control circuit with the necessary logic components. But till this time, it is not a complete system, because it is missing some auxiliary elements that are not included in this draws because they work in parallel with the main sequence.
These auxiliary elements give more function to the circuit and are very important to the final application; the most important of them is the parallel circuit linked with all the others steps. That circuit should be able to stop the sequence at any time and change the state of the actuators to a specific position. This kind of circuit can be used as a reset or emergency buttons.
The next Figs. 7 and 8 show the result of using the method without the controller. These pictures are the electric diagram of the control circuit of the example, including sensors, buttons and the coils of the electrical valves.
The auxiliary elements are included, like the automatic/manual switcher that permit a continuous work and the two start buttons that make the operator of a machine use their two hands to start the process, reducing the risk of accidents.
6. Changing the example to a user program
In the previous chapter, the electro-pneumatic circuits were presented, used to begin the study of the requires to control a system that work with steps and must offer all the functional elements to be used in a real application. But, as explained above, using a PLC or this specific controller, the control becomes easier and the complexity can be increase also.
Table 2 shows a resume of the elements that are necessary to control the presented example.
With the time diagram, the step sequence and the elements of the system described in Table 2 and Figs. 5 and 6 it is possible to create the configuration of the steps that can be sent to the controller (Tables 3 and 4).
While using a conventional PLC, the user should pay attention to the logic of the circuit when drawing the electric diagram on the interface (Figs. 7 and 8), using the programmable controller, described in this work, the user must know only the concept o f the method and program only the configuration of each step.
It means that, with a conventional PLC, the user must draw the relation between the lines and the draw makes it hard to differentiate the steps of the sequence. Normally, one needs to execute a simulation on the interface to find mistakes on the logic
The new programming allows that the configuration of the steps be separated, like described by the method. The sequence is defined by itself and the steps are described only by the inputs and out