2022年毕业设计方案 .pdf

1 / 27 毕业设计 论文）开题报告含文献综述、外文翻译）题目 PLC张力检测系统姓名陈灵犀学号 3080433011 专业班级自动化 081 指导教师胡超学院系）信息分院开题日期年月日宁波理工学院精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 1 页，共 27 页2 / 27 文献综述内容1.PLC 起源1968 年美国通用汽车公司提出取代继电器控制装置的要求；1969 年，美国数字设备公司研制出了第一台可编程逻辑控制器PDP 14 ，在美国通用汽车公司的生产线上试用成功，首次采用程序化的手段应用于电气控制，这是第一代可编程逻辑控制器，称Programmable ，是世界上公认的第一台 PLC 。1969 年，美国研制出世界第一台PDP-14；1971 年，日本研制出第一台DCS-8；1973 年，德国研制出第一台PLC；1974 年，中国研制出第一台PLC。发展20 世纪 70 年代初出现了微处理器。人们很快将其引入可编程逻辑控制器，使可编程逻辑控制器增加了运算、数据传送及处理等功能，完成了真正具有计算机特征的工业控制装置。此时的可编程逻辑控制器为微机技术和继电器常规控制概念相结合的产物。个人计算机发展起来后，为了方便和反映可编程控制器的功能特点，可编程逻辑控制器定名为Programmable Logic ControllerPLC）。20 世纪 70 年代中末期，可编程逻辑控制器进入实用化发展阶段，计算机技术已全面引入可编程控制器中，使其功能发生了飞跃。更高的运算速度、超小型体积、更可靠的工业抗干扰设计、模拟量运算、PID 功能及极高的性价比奠定了它在现代工业中的地位。20 世纪 80 年代初，可编程逻辑控制器在先进工业国家中已获得广泛应用。世界上生产可编程控制器的国家日益增多，产量日益上升。这标志着可编程控制器已步入成熟阶段。20 世纪 80 年代至 90 年代中期，是可编程逻辑控制器发展最快的时期，年增长率一直保持为3040% 。在这时期， PLC在处理模拟量能力、数字运算能力、人机接口能力和网络能力得到大幅度提高，可编程逻辑控制器逐渐进入过程控制领域，在某些应用上取代了在过程控制领域处于统治地位的DCS系统。20 世纪末期，可编程逻辑控制器的发展特点是更加适应于现代工业的需要。这个时期发展了大型机和超小型机、诞生了各种各样的特殊功能单元、生产了各种人机界面单元、通信单元，使应用可编程逻辑控制器的工业控制设备的配套更加容易。精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 2 页，共 27 页3 / 27 PLC 技术发展方向1：产品规模向大、小两个方向发展大：I/O 点数达 14336 点、32 位为微处理器、多 CPU 并行工作、大容量存储器、扫描速度高速化。小：由整体结构向小型模块化结构发展，增加了配置的灵活性，降低了成本。2：PLC 在闭环过程控制中应用日益广泛3：不断加强通讯功能4：.新器件和模块不断推出高档的 PLC 除了主要采用 CPU 以提高处理速度外，还有带处理器的 EPROM 或 RAM 的智能 I/O 模块、高速计数模块、远程I/O 模块等专用化模块。5：编程工具丰富多样，功能不断提高，编程语言趋向标准化有各种简单或复杂的编程器及编程软件，采用梯形图、功能图、语句表等编程语言，亦有高档的PLC指令系统6：发展容错技术采用热备用或并行工作、多数表决的工作方式。7：追求软硬件的标准化。张力检测的应用PLC 在张力检测中有非常广泛的应用，如拉丝机、绕线机、纸张卷取等应用领域。如上图 拉丝机的使用非常广泛 ,其张力控制是最关键的环节。采用PLC 作为高速拉丝机的控制系统 ,发挥PLC 控制能力强、体积小、编程简单、可靠性高等特点,大大提高了拉丝机的可靠性、生产效率和产品质量。本拉丝机主电机由变频器控制,速度可任意调节 ,最高速度可以达到 3000m/ min。入线从入口进入拉丝部分, 经过拉丝塔轮组及拉丝眼模后形成接近成品线径的线,再经过出口与定速轮之间的拉线眼模修整后线径达到成品线径, 最后经过定速轮到达收排线机构 , 将成品收在收线轴上。在拉丝的过程中需要一定的张力来形成线与轮子之间的摩擦力 , 从而在拉丝眼模形成拉拔力, 完成拉丝过程。本设备的主马达由变频器控制 , 实现线速度在 0 - 3000m/ min 范围内无级可调。因为收线轴的收卷动作, 使收线轴上线材逐渐增多 , 导致轴径逐步增大 , 使张力逐步加大 , 于是采用双锥轮张力调节部分调整收线线速度 , 使其与拉线线速度保持匹配, 确保拉线的张力在一定范围内。本设备在定速轮与三沟导轮处设置检测点, 分别检测拉线速度与收线速度。精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 3 页，共 27 页4 / 27 PLC特点优点： 结构简单，可靠性高，抗干扰能力强，配套齐全，功能完善，适用性强，因而长期广泛应用。缺点： 采用固定的接线方式。一旦生产要求和生产过程发生变化，必须重新设计线路，重新接线安装。不利于产品的更新换代。还有灵活性、通用性差、速度慢等特点。工业中常用的控制器西门子 S7系列欧姆龙 CPM1A 系列三菱 FX2N 系列松下电工 FP1系列AB 公司 PLC5 系列参考文献：1 超声传感器精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 4 页，共 27 页5 / 27 开题报告内容包括选题的背景与意义、研究的基本内容与拟解决的主要问题、研究的方法与技术路线、研究的总体安排与进度、主要参考文献）张力传感器张力传感器也叫张力检测器，是张力控制过程中，用于测量卷材张力值大小的仪器。按其工作原理又可分为应变片型和微位移型。应变片型是张力应变片和压缩应变片按照电桥方式连接在一起，当受到外压力时应变片的电阻值也随之改变，改变值的多少将正比于所受张力的大小；微位移型是通过外力施加负载，使板簧产生位移，然后通过差接变压器检测出张力，由于板簧的位移量极小，大约200m ，所以称作微位移型张力检测器。另外，由外型结构上又分为：轴台式、穿轴式、悬臂式等。张力传感器放大器A/D 转换PLC 显示PC 串口通信精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 5 页，共 27 页6 / 27 外文翻译稿应用于电气系统的PLC 此工程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 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。精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 9 页，共 27 页10 / 27 图 6 A ,B ,C ,D 传动装置传动顺序图5和6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。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9 A ,B 传动装置和传感器精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 11 页，共 27 页12 / 27 图10 C ,D 传动装置和传感器表 5 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。. 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 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 13 页，共 27 页14 / 27 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. 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 14 页，共 27 页15 / 27 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 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 15 页，共 27 页16 / 27 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 has also a display and some buttons that are used with an interactive menu to program the sequence of steps and other configurations.精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 16 页，共 27 页17 / 27 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 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 17 页，共 27 页18 / 27 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 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 18 页，共 27 页19 / 27 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 th