电气毕业论文英语文献原文+翻译

1、外文翻译院 （系）专业班级姓 名学 号指导教师 年 月 日 第 25 页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 mo

2、vement 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. Introduc

3、tionThe 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

4、 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

5、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

6、 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 buil

7、dings.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

8、.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 ki

9、nd 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

10、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 o

11、ther companies, 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 proj

12、ect 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 m

13、istakes. 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

14、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 standa

15、rd 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

16、 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

17、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 c

18、hances 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

19、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

20、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

21、 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

22、 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 t

23、his 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 contro

24、ller 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

25、. 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

26、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

27、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 configura

28、tions.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

29、 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 emerg

30、ency. 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 th

31、e 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 wor

32、k 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 als

33、o 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 w

34、ork 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 th

35、e 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-ou

36、t 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

37、 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 s

38、tarts 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,

39、 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 backwa

40、rd 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 def

41、ined 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 c

42、orrectly 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 seq

43、uence. 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 t

44、o 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 e

45、lectrical 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

46、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 con

47、trol 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 configu

48、ration 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 m

49、ust 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

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

51、he order: 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 examp

52、le shown 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

53、 controller 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 s

54、erial communication. 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

55、 languages, 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 des

56、igner can 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 i

57、s designed 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. 应用于电气系统的可编程序控制器约翰 F.维克里此项目主要是研究电气系统以及简单有效的控制气流发动机的程序和气流系统的状态。它的实践基础包括基于气流的专有控制器、自动化设计、气流系统的控制程序和基于微控制器的电子设计。1.简介使用电气技术

58、的自动化系统主要由三个组成部分：发动机或马达，感应器或按钮，状如花瓣的控制零部件。现在，大部分的系统逻辑操作的控制器都被程序逻辑控制器（PLC）所取代。PLC的感应器和开关是输入端，而发动机的直接控制阀是输出端，其中有一个内部程序操控所有运行必需的逻辑，模拟其他的装置如计算器、定时器等，对整个系统的运行状态进行控制。因为可以根据需要无数次创建和模拟这样的系统，所以藉由PLC的使用，此项目有灵活的优点。因此，可以节省时间，减少失误的危险，同时在使用相同材料的情况下，它可以更加精密。市场上的许多家公司都使用了常规的PLC，它不仅可以用气流系统来控制，还可以用各种电气设备。PLC 的用途广泛，可以应用于许多工业生产中，甚至用于建筑物的安全和自动化系统中。由于以上的各种特性，在一些实际应用中PLC提供了很多的资源，甚至包括不控制系统的资源，电气系统就是一种这样的应用。对于自动化的工程，PLC的使用是比较昂贵的，尤其是对那些小型的系统。针对这种情况可行的一种办法是创建一个可提供特定尺寸和功能的控制器。这种控制器可以根据微控制器来制作。这种基于微控制器的控制器的适用范围比较小，只能用于一个类型的机器或