毕业设计(论文)外文参考资料及译文-基于PLC的磨板废水自动控制处理系统设计.doc
《毕业设计(论文)外文参考资料及译文-基于PLC的磨板废水自动控制处理系统设计.doc》由会员分享,可在线阅读,更多相关《毕业设计(论文)外文参考资料及译文-基于PLC的磨板废水自动控制处理系统设计.doc(15页珍藏版)》请在三一文库上搜索。
1、毕 业 设 计(论 文)外 文 参 考 资 料 及 译 文设计(论文)题目:基于PLC的磨板废水自动控制处理系统设计 学生姓名: 张凤林 学 号: 0704111019 专 业: 自动化 所在学院: 机电工程学院 指导教师: 李志臣 职 称: 讲师 2011 年 2月 20 日Control Devices and PLCJoseph La FauciFrom Wikipedia, the free encyclopediaSeveral types of control devices are used in industry to satisfy the following control
2、 needs.Mechanical Control、Pneumatic Control、Electromechanical Control、Electronic Control、Computer Control、Programmable Logic Control (PLC)Mechanical control includes cams and governors. Although they have been used for the control of very complex machines, to be cost effectively, today they are used
3、 for simple and fixed-cycle task control. Some automated machines, such as screw machines, still use cam-based control. Mechanical control is difficult to manufacture and is subject to wear.Pneumatic control is still very popular for certain applications. It uses compressed air, valves, and switches
4、 to construct simple control logic, but is relatively slow. Because standard components are used to construct the logic, it is easier to build than a mechanical control. Pneumatic control parts are subject to wear.As does a mechanical control, an electromechanical control use switches, relays, timer
5、s, counters, and so on, to construct logic. Because electric current is used, it is faster and more flexible. The controllers using electromechanical control are called relay devices.Electric control is similar to electromechanical control, except that the moving mechanical components in an electrom
6、echanical control device are replaced by electronic switches, which works faster and is more reliable.Computer control is the most versatile control system. The logic of the control is programmed into the computer memory using software. It not only can be for machine and manufacturing system control
7、, but also for data communication. Very complex control strategies with extensive computations can be programmed. The first is the interface with the outside world. Internally, the computer uses a low voltage (5 to 12 volts) and a low current (several milliamps). Machine requires much higher voltage
8、s (24, 110, or 220 voltages) and currents (measured in amps). The interface not only has to convert the voltage difference, but also must filter out the electric noise usually found in the shop. The interface thus must be custom-built for each application.In order to use the advantages of all those
9、controllers and eliminate the difficulties, the programmable logic controllers were invented. A PLC was a replacement for relay devices. They are programmed using a ladder diagram, which is standard electric wiring diagram. As PLCs become more flexibility, high-level as well as low-level languages a
10、re available to PLC programmers. PLCs have the flexibility of computers as well as a standard and easy interface with processes and other devices. They are widely accepted in industry for controlling from a single device to a complex manufacturing facility.Automatic of many different processes, such
11、 as controlling machines or factory assembly lines, is done through the use of small the computers called a programmable logic controller (PLC), PLCs were first created to serve the automobile industry, and the first PLC project was developed in 1968 for General Motors to replace hard-wired relay sy
12、stems with an electronic controller. Since the advent of PLCs, the ability to centralize factory processes, especially in the automotive industry, has improved greatly. Automatic control has become an important consideration in most industrial processes where certain repetitive operations are perfor
13、med. This applies to situations such as the automatic assembly of modules and products where a cycle of events is conducted in a consistent and uniform manner. Applications generally include a combination of feeding, handing, drilling, cutting, assembling, discharging, inspecting, packaging and tran
14、sporting by conveyor.Prior to the introduction of computer-based control systems the automation of such events was achieved by using either electrical relay logic circuits or pneumatic logic circuits. Although these are conceptionally simple and easy to maintain, they are somewhat bulky and can be e
15、xpensive. More important is the fact that the resulting control circuits are inflexible and do not lend themselves to easy system control alterations. The late 1960s saw the introduction of the programmable logic controller (PLC) as a direct replacement for the relay sequence controllers. In essence
16、 the PLC replaces the hardwired relay or pneumatic logic with a more flexible programmable logic. It offers a simple, flexible and low-cost means of implementing a sequence control strategy where outputs for switching devices on and off are set according to input conditions as read from digital sens
17、or states. It should be noted that, particularly in the USA, the PLC is often referred to as a programmable controller with the abbreviation of PC. It should not be confused with the personal computer PC or IBM-PC.The PLC is composed of the same ingredients as a microcomputer such as a microprocesso
18、r, memory and input/output facilities. The processor executes the instructions held in memory by operating on inputs derived from the controlled process and providing outputs in accordance with the logic sequence defined in the control program. Its basic principle of operation during the execution o
19、f the program is that the program is scanned very fast, typically 1 to 20 us per step, to record all input states. The outputs are then set according to the logic specified in the program. The sequence is continually repeated for each scan period of the controller. Small PLCs dedicated to sequential
20、 control have typically 12 inputs and 8 outputs with the possibility of expansion up to 128 I/O lines. They come complete with an input interface to accommodate a range of input signals from the controlled process which are then converted to an appropriate from for the processor. Similarly, provisio
21、n is made at the output of the PLC to interface with a variety of process hardware such as lamps, motors, relays and solenoids. The typical handing voltages are 24V DC and 110V AC. Program instructions can be input into the battery backup RAM of a PLC by means of either a hand-held programming keypa
22、d or a connected PC with an appropriate software development package. Some LCD programming consoles incorporate a limited graphical display which illustrates the program in ladder logic format as the programmer builds it up using symbolic keys. This is also the principle of the PC-based development
23、system where additionally the programmer has access to a lager visual display and the PCs disk operating system for data storage and retrieval. Once the program has been debugged and the control strategy verified by simulation, the codes can be loaded into an erasable and programmable read only memo
24、ry chip (EPROM) which can then be installed in the PLC.There are a large number of manufacturers of PLCs. Although some use their own particular software language the majority are based on the ladder logic diagram. Historically this was introduced in order to gain the acceptance of customers who wer
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 毕业设计 论文 外文 参考资料 译文 基于 PLC 废水 自动控制 处理 系统 设计
链接地址:https://www.31doc.com/p-3280715.html