電氣畢業(yè)論文設(shè)計(jì)英語(yǔ)文獻(xiàn)原文翻譯

1、外文翻譯院 （系）專業(yè)班級(jí)姓 名學(xué) 號(hào)指導(dǎo)教師 年 月 日Programmable designed for electro-pneumatic systems controllerJohn F.WakerlyThis 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

2、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. IntroductionThe

3、 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

4、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 sys

5、tem. 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

6、 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.B

7、ecause 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 alt

8、ernative 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 m

9、achine 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 mai

10、n 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 co

11、mpanies, but at the same time the responsibility of the control of the system stays at the designer hands2. Electro-pneumatic systemOn 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

12、 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

13、. 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 use

14、d 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 circ

15、uits 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 pos

16、sible 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 o

17、f 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

18、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 stri

19、ngs 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

20、 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 pr

21、ocess 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 co

22、ndition 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 pro

23、blem 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

24、 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 t

25、he 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

26、 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

27、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

28、.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 o

29、f 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. L

30、eds 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 execu

31、tion 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

32、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 us

33、ed 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

34、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 strin

35、gs 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 ke

36、ep 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 a

37、ctuators. 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 h

38、is 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 repe

39、ats 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 move

40、ment, 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.

41、 (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 correctl

42、y 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.

43、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 spe

44、cific 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 electric

45、al 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 pre

46、vious 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 be

47、comes 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

48、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 kno

49、w 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 interf

50、ace 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 outputs for each step. The structure of the configuration follows the orde

51、r: 1-byte: features of the step;2-byte: mask for the inputs; 3-byte: value expected on the inputs; 4-byte: value for the outputs;5-byte: value for the extra function. Table 5 shows how the user program is saved inside the controller, this is the program that describes the control of the example show

52、n before. The sequence can be defined by 25 bytes. These bytes can be divided in five strings with 5 bytes each that define each step of the sequence (Figs. 9 and 10). 7. Conclusion The controller developed for this work (Fig. 11) shows that it is possible to create a very useful programmable contro

53、ller based on microcontroller. External memories or external timers were not used in case to explore the resources that the microcontroller offers inside. Outside the microcontroller, there are only components to implement the outputs, inputs, analog input, display for the interface and the serial c

54、ommunication. Using only the internal memory, it is possible to control a pneumatic system that has a sequence with 48 steps if all the resources for all steps are used, but it is possible to reach sixty steps in the case of a simpler system. The programming of the controller does not use PLC langua

55、ges, but a configuration that is simple and intuitive. With electro-pneumatic system, the programming follows the same technique that was used before to design the system, but here the designer work s directly with the states or steps of the system. With a very simple machine language the designer c

56、an define all the configuration of the step using four or five bytes. It depends only on his experience to use all the resources of the controller. The controller task is not to work in the same way as a commercial PLC but the purpose of it is to be an example of a versatile controller that is desig

57、ned for a specific area. Because of that, it is not possible to say which one works better; the system made with microcontroller is an alternative that works in a simple way. 應(yīng)用于電氣系統(tǒng)的可編程序控制器約翰 F.維克里此項(xiàng)目主要是研究電氣系統(tǒng)以及簡(jiǎn)單有效的控制氣流發(fā)動(dòng)機(jī)的程序和氣流系統(tǒng)的狀態(tài)。它的實(shí)踐基礎(chǔ)包括基于氣流的專有控制器、自動(dòng)化設(shè)計(jì)、氣流系統(tǒng)的控制程序和基于微控制器的電子設(shè)計(jì)。1.簡(jiǎn)介使用電氣技術(shù)的自動(dòng)化系統(tǒng)主

58、要由三個(gè)組成部分：發(fā)動(dòng)機(jī)或馬達(dá)，感應(yīng)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(yīng)器和開關(guān)是輸入端，而發(fā)動(dòng)機(jī)的直接控制閥是輸出端，其中有一個(gè)內(nèi)部程序操控所有運(yùn)行必需的邏輯，模擬其他的裝置如計(jì)算器、定時(shí)器等，對(duì)整個(gè)系統(tǒng)的運(yùn)行狀態(tài)進(jìn)行控制。因?yàn)榭梢愿鶕?jù)需要無(wú)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(xiàng)目有靈活的優(yōu)點(diǎn)。因此，可以節(jié)省時(shí)間，減少失誤的危險(xiǎn)，同時(shí)在使用相同材料的情況下，它可以更加精密。市場(chǎng)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(lái)控制，還可以用各種電氣設(shè)備。PLC 的用途廣泛，可以應(yīng)用于許多工業(yè)生產(chǎn)中，甚至用于建筑物的安全和自動(dòng)化系統(tǒng)中。由于以上的各種特性，在一些實(shí)際應(yīng)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(yīng)用。對(duì)于自動(dòng)化的工程，PLC的使用是比較昂貴的，尤其是對(duì)那些小型的系統(tǒng)。針對(duì)這種情況可行的一種辦法是創(chuàng)建一個(gè)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(lái)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(gè)類型的機(jī)器或者可以用做一個(gè)像普通PLC一樣可以被編程的控制器，那樣它就可以通過(guò)可變化的邏輯程序來(lái)進(jìn)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