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基于plc的線纜加工控制系統(tǒng)的設(shè)計-資料下載頁

2024-11-10 03:32本頁面

【導(dǎo)讀】本文論述了一種基于PLC的線纜加工控制系統(tǒng)的設(shè)計過程。電線加工計算機控制系統(tǒng)是主要以PLC為基礎(chǔ),并利用PLC和組態(tài)軟件實現(xiàn)電線加工系統(tǒng)設(shè)計過程,其控制系統(tǒng)工藝大致可以分為:放線、擠塑、冷卻、測徑、耐壓測試、打字和收線等主要環(huán)節(jié)。控溫環(huán)節(jié)能夠進(jìn)行溫度采集與顯示、控制。外徑測量采用外徑測量儀,充當(dāng)線徑控制系統(tǒng)中的測量元件。火花檢測儀用于檢測產(chǎn)品絕緣層的耐壓特性。火花檢測和線徑檢測環(huán)節(jié)檢測并報警。本系統(tǒng)中需要檢測溫度值、張力值和線徑值。所用到的傳感器有溫度傳感器、張力傳感器和測徑儀。選配CPM1A-AD041模擬量單元作為這些傳感器配置的模擬量擴展單元,可通過軟、硬件的結(jié)合來協(xié)調(diào)控制來完成這個系統(tǒng)。第一部分是方案的設(shè)計,第二部分介紹傳感器,第三部分介紹了可編程控制器PLC,第四部分介紹了PLC程序的設(shè)計,第五部分?jǐn)⑹隽私M態(tài)軟件,最后一部分分析了PLC與組態(tài)王通訊的實現(xiàn)。電線電纜行業(yè)是我國的基礎(chǔ)產(chǎn)業(yè)。它產(chǎn)品種類眾多,應(yīng)用范

  

【正文】 ly PLCs did not have acpanying programming terminals that were capable of graphical representation of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more mon for ladder logic to be used, for the aforementioned reasons. Newer formats such as State Logic and Function Block (which is similar to the way logic is depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic. A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats.Early PLCs, up to the mid1980s, were programmed using proprietary programming panels or specialpurpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were very minimal due to lack of memory capacity. The very oldest PLCs used nonvolatile magnetic core memory.More recently, PLCs are programmed using application software on personal puters. The puter is connected to the PLC through Ethernet, RS232, RS485 or RS422 cabling. The programming software allows entry and editing of the ladderstyle logic. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal puter to the PLC though a programming board which writes the program into a removable chip such as an EEPROM or EPROM.The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and networking. The data handling, storage, processing power and munication capabilities of some modern PLCs are approximately equivalent to desktop puters. PLClike programming bined with remote I/O hardware, allow a generalpurpose desktop puter to overlap some PLCs in certain the practicality of these desktop puter based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop puters run on less stable operating systems than do PLCs, and because the desktop puter hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of desktop based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the logic may not always respond to changes in logic state or input status with the extreme consistency in timing as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs.In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have bee more mon and accepted. These are very much like PLCs, and are used in light industry where only a few points of I/O (. a few signals ing in from the real world and a few going out) are involved, and low cost is desired. These small devices are typically made in a mon physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and 12 digital inputs, 4 and 8 digital outputs, and up to 2 analog inputs. Size is usually about 4 wide, 3 high, and 3 deep. Most such devices include a tiny postage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are acpanied by a 4way rocker pushbutton plus four more separate pushbuttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS232 or RS485 to a personal puter so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and pushbutton set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.The main difference from other puters is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of plex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a puter network that plugs into the PLC.A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O.Modular PLCs have a chassis (also called a rack) into which are p
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