电气系统可编程序控制器毕业论文中英文资料外文翻译文献

电气系统可编程序控制器

中英文资料外文翻译文献

英文原文

Programmable controller designed for electro-pneumatic systems 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.

Fig.1.Standard circuit for the pneumatic system.

Fig.2.Standard circuit for the electro-pneumatic system.

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 to connect the control element that receive signals from sensors, switches and the previous movement 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 ha 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.

The controller 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:

.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.

https://www.360docs.net/doc/e91507525.html,er 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. 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.3), 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.

Fig.3.Time diagram of A,B,C and D actuators.

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.4 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.

Fig.4.Step sequence of A,B,C and D actuators.

These two representations of the system(Figs.3 and 4) 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.5 and 6 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.

Fig.5.Electric diagram of the example.

Fig.6.Electric diagram of the example.

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.

It 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 Figs.3 and 4 it is possible to create the configuration of the steps that can be sent to the controller.

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.5and 6), using the programmable controller, describe in this work, the user must know only the concept of 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 outputs for each step.

The structure of the configuration follows the order:

1-byte: features of the step;

2-byte: for the inputs;

3-byte: value expected on the inputs;

4-byte: value for the outputs;

5-byte: value for the extra function.

Fig.7.Actuators A and B, and sensors.

Fig.8.Actuators C and D, and sensors.

Table 5 shows how the user program is saved inside the controller, this is the program that describes the control of the example 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.7 and 8).

7. Conclusion

The controller developed for this work shows that it is possible to create a very useful programmable 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 serial 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 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 works directly with the states or steps of the system.

With a very simple machine language the designer 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 is 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.

References

[1]E.Nelli Silva,Fluid-mechanics systems Manual, Escola Politecnica USP,2002(in Portuguese).

[2]J.Swider,Control and Automation of Technological Process and Mechatronic systems,Silesian University Publishing Company,Gli-wice,2002(redaction in Polish).

[3]J.Swider, G.Wszolek, W.Carvalho. Example of the system prepared to be controlled by the controller based on microcontroller,in:12 International Scientific Conference—Achievements in Mechanical and Materials

Engineering,Gliwice-Zakopane,Poland,2003,pp.965-970.

[4]J.Swider,G.Wszolek,W.Carvalho, Controller based on microcontroller designed to execute the logic control of pneumatic systems, in:12International Scientific Conference—Achievements in Mechanical and Materials Engineering,Gliwice-Zakopane,Poland,2003,pp. 959–964.

[5]J.Swider,G.Wszoek, The methodical collection of laboratory and project tasks of technological process control in Pneumatic and Electro-pneumatic Systems with Logical PLC Control, Silesian University Publishing Company,Gliwice,2003.

[6]PIC 16f87xDatasheet.MICROCHIP,2001.

[7]Application notes AN587 and AN546.MICROCHIP,1997.

[8]Fundamental of electro-pneumatic—FESTODidactic,2000.

中文翻译

应用于电气系统的可编程序控制器

摘要

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[3,4]。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者可以用做一个像普通PLC一样可以被编程的控制器，那样它就可以通过可变化的逻辑程序来进行各种作业。所有的这些特性根据具体需要的不同而不同，具体的设计者的经验的不同而不同。但是这种设计的主要优点在于设计人员非常了解自己的控制器，可以自由掌握控制器的大小尺寸，改变它的功能。这就意味着此项目有更多的独特性，但同时系统的控制也由它的设计者所控制。

2.电气系统

人们可以从一个自动化系统中找到三个上文中提到的基本部件，外加一个控制系统的逻辑线路。只有成熟先进的技术能做出特定的逻辑线路和执行正确操作所需要的部件升级。

对于一个简单的运动，系统自动程序[1,5]可以完成，但是对于间接或更加复杂的运动，系统的程序就会产生复杂的线路和错误的信号。这是就需要另一种方法可以节省时间，产生清晰线路，能够防止偶然的信号交叠和线路堵塞。

这种方计的不同标准的线路基法叫循序渐进式或规则系统[1,5]，它对气流和电气系统非常有效，而且也是此项目的一个基础。它包括根据发动机状态各个不同变化所设基础上的系统。

图一气压系统标准回路

图二电控气压系统标准回路

第一步是为每个步骤设计那些种标准的线路。第二步是联编标准的线路，最后一步是连接接收来自感应器，开关和先前的运动信号，同时把空气或电传送给每个步骤的补给线。如图中所示，1 和 2 标准线路是为气流的和电气系统[8]服务.我们能够很清楚的看到每一步骤和下一个步骤之间的联系。

3.控制器内部的应用原理

上述方法可以使发动机的每一个运动都被很好地用步骤来定义。这也就是说发动机的每一次运动变化都是系统的一个新的状态，而两个不同状态之间的转变叫做步骤。

先前提到的标准线路可以帮助设计人员定义系统的不同状态和不同步骤的变化所带来的不同环境。在设计的最后阶段，系统中会有一个从来不变化的序列和明确的输入和输出端。我们把一个序列从输入端输入，经过转换后，由输出端输出。

这些步骤的所有过程都是在微控制器内部进行的，并且以同样的方式在运行着。部件的序列在控制器里被5个位元组规划; 每个部分都有程序的一个步骤结构。输入端有二个位元组,输出端有一个，其他结构部分和附加功能步骤有两个。在编程之后，部件序列被内部微控制器的记忆所储藏，因此，他们是可读的而且可以运行。

不同于传统的PLC，这种控制器的工作目的是成为特定领域设计的多用控制器。传统的PLC 的系统运行程序是一个循环的线路：输入一个图像,运行所有的内部程序, 然后升级输出的状态。这一个控制器以不同的方式工作,它读取步骤的结构,等待输入,然后升级或输出，然后直接跳跃到下一个步骤，开始另一次的程序运行。

它也有局限性，例如这种控制器有时会不执行指令，在同一程序指令下，会出现某一个运行的反复等等，但是这一个问题可以通过外部的逻辑运行解决。另外，这中控制器在没有序列的系统上不能够被应用。这些局限性也是这个系统的特性，这种系统的每一个应用都必须要有相应的系统分析。

4.控制器的特色

这种控制器以微集成电路微控制器PIC16F877[6,7]为基础,它拥有全部此次项目所需要的资源。它有足够的插孔，线路连续通讯EEPROM 记忆解救系统的所有结构和步骤的序列。它提供了项目所需要的所有的运行，例如定时器和分岔等。

我们做出了控制器的资源目录，想尽可能的使它变的完善。在步骤的运行过程中，程序自动选择如何读取每一步骤的结构。这个操作有两个位元组位于电子输入处。一个位元组位于输出端，还有一个被用作内部定时器，类似输入或暂停功能。EEPROM 记忆内部是256 位元组，可以储藏所有步骤的运行,即可以储藏48个步骤之间的所有运行。

除了一个互动菜单外，这种控制器还有一个控制台和一些指令按钮，他们一起控制各个步骤的运行和连续性，也控制其他的一些装置。

4．1交互作用

在实际运行操作中，控制器需要有一些辅助设备帮助它和使用者进行互动，可以提供可靠的操作监控，同时对气流系统进行逻辑控制。

交互工作模式：在主要的程序中，使用者可以根据指导发出信号来进行具体

步骤的操作

?LCD 平台可以显示系统工作的状态，衡量输入，输出，计时器和运行的数据

等。

?嘀嘀声用来提示重要警示，停止，开始和一些紧急情况的发生

?亮灯表示接通电源，和输入，输出状态。

4．2 安全性

如果想正常运行程序，必须保证每一个步骤都正确的执行。更重要的是，应该有预防运行故障和问题的解决方法。控制器提供了这种可能性，通过使用两个内部虚拟线路同时运行。他们可以重新启动程序，随时恢复到程序的原有状态[2]。有两个输入端共同工作可以快速的运行这些功能。

4．3 接口

程序运行序列可以用控制器的接口来编程。一台计算机的接口也可以用来升级使用程序。使用者能利用接口配置一连串定义序列的步骤位元组。但是也可以设计一个程序,利用可视资源为使用者翻译所需要的信息。

但是，如果想联结电脑接口和控制器，至少应该有一个仪器来保证数据的可靠性。

4.4. 固件

主要的线环是通过读取EEPROM 记忆中的每一资讯步骤进行工作。

在每个步骤中，系统的状态被储存，同时它也在显示器上被显示。根据使用者的构造,它能利用分流或暂停应付紧急线路情况来保证系统安全。

5. 电气系统例子

这种系统不只是适应于特定的机器。它由四个主动器组成。主动器 A ，B 和 C 是两倍的，只有D是单倍的。第一步，主动器A 开始运行，并保持在一个特定的位置一直到一个循环的结束，如图 5 所示它可以确定某一对象的下一运动。第二步，当A 完成了它的工作后，主动器 C 连同 B 一起开始尽可能多的产生电流圈，并受 B 的运行速度的限制，而B 速度由一个流动的控制活瓣管理。B 和 C 是一起工作的主动器的例子,当 B 慢慢地推动一个物体的时候, C 有时则重复它的工作。

图三A,B,C,D传动装置时间曲线

第三步，当 B 到达最后的位置时候, C 停止立刻它的循环运动并且回到开始的位置。利用回旋的电流工作的主动器 D 连同返回来的C一起工作。第四步，主动器 D 快速往返来回运动一次。D 可以充当一个工具，在物体上的表面上打洞。当 D 返回开始的位置时候, A和 B 也同时返回，这是第五个步骤。

图4 显示了程序设计的第一部分。我们把每个步骤的所有运行统称为[2]. (A+) 表示主动器A 向前推动，而(A-) 表示返回到开始的位置。同时发生的运动在相同的步骤中被一起叠加。这个系统共有有五个步骤。

图四A,B,C,D传动装置传动顺序

图3 和4 所表现的系统运行清楚的描述了所有序列。利用他们我们可以用必需的逻辑语言设计整个的控制线路。但是现在还它还不是一个完整的系统，因为它还缺少一些辅助设施，（图中没有显示）。

对于程序的最后运行，这些辅助设施十分的重要，因为他们能使线路有更多的功能。他们中最重要的是连接在每一步骤中的平行线路。那一个线路能够随时停止序列而且将主动器的状态换成一个特定的位置。它可以重起系统或是应付紧急情况。图5 和 6 显示的是在没有使用控制器的情况下会发生的一些结果。这些照片是控制线路的电图表,包括感应器，控制键和电的活瓣卷。

图五电气图表举例

图六电气图表举例

另外的一些辅助设施也包括在这个系统中,比如自动机械/ 手动调控器，他们可以使系

统不断的循环工作；两个开始控制键,他们能让操作员手动控制系统的开始和停止，这样就减少了发生意外事件的危险。

6. 使用者变更例子规划

气流线圈在前面已经详细说明过：它可以让我们了解到控制一个系统所需要的条件，那就是在系统的实际运行中必须提供所有的功能设施。但是,如前面提到的那样,使用一个PLC 或特定的控制器, 这种控制就变得比较容易的，而且系统的精密性也会提高。

所示的是控制上面提到的系统的必需设施。通过时间图表，和图 3 和4描述了每一

步骤的程序和系统的各个部件。这说明记录所有步骤的运行结构图并把他们送给控制器。

使用传统的PLC的,如图7，8所示，在绘制接口处的电图表时，要注意线路的逻辑。使用这种可编程的控制器,使用者必须知道运行方法的观念并且规划每个步骤的结构。

那就是说，使用传统的PLC ，使用者清楚各个操作之间的关系。一般情况下，使用者可以在接口上运行一个模拟程序寻找逻辑上的错误同之前所述的一样，新的编程允许每一步骤的结构被分割。序列独自被定义，但每一步骤只被输入和输出端描述。

图七A,B传动装置和传感器

图八C,D传动装置和传感器

表现的是使用系统如何被储藏在控制器里,这在前文中也详细说明过。序列被25个位元组所定义。这些位元组被分成5组，每一组描述系统运行的一个步骤。（图7 和8）

7. 结论

这种控制器是专门为这一项目所设计的。显示了一个以微控制器为基础的非常有用的可编程的控制器。它不需要为了获取微控制器里的资源而安装外部记忆器或外部的定时器。除了微控制器之外,只有少量的零部件执行一些如输出，输入，类比输入,显示接口和连续运行的情况等功能。

单独使用内部记忆,我们可以控制一个有48个步骤的气流系统，但是如果使用一个比较简单的系统，就会达到60个步骤.控制器的变成不使用PLC 语言，而是用一个比较简单的和直觉的结构。利用电气系统，我们的项目应用了相同的技术，但同时我们的设计更加直接。

一种非常简单的机械语言能让设计者用四或五个位元组定义步骤所有结构构成。这就要看他使用控制器的经验如何了。这种控制器虽然不能和商业的PLC 相比，但是它原本就是为特定的目的而设计的，所以很难说哪一个好哪一个坏。总之，我们的这个系统是基于微控制器而设计，简单快捷。