關(guān)于plc的畢業(yè)設(shè)計外文及翻譯-plc設(shè)計-文庫吧
2025-04-17 16:02 本頁面
【正文】 in the process. And furthermore, they need all these capabilities while remaining costeffective and simple to program. Another primary development that has literally revolutionized the way PLCs are programmed, municate with each other and interface with PCs for HMI, SCADA or DCS applications, came from the puting world. Use of Ether munications on the plant floor has doubled in the past five years. While serial munications remain popular and reliable, Ether is fast being the munications media of choice with advantages that simply can39。t be ignored, such as: * Network speed. * Ease of use when it es to the setup and wiring. * Availability of offtheshelf working ponents. * Builtin munications setups. Integrated Motion Control Another responsibility the PLC has been tasked with is motion control. From simple openloop to multiaxis applications, the trend has been to integrate this feature into PLC hardware and software. There are many applications that require accurate control at a fast pace, but not exact precision at blazing speeds. These are applications where the standalone PLC works well. Many nano and micro PLCs are available with highspeed counting capabilities and highfrequency pulse outputs built into the controller, making them a viable solution for openloop control. The one caveat is that the controller does not know the position of the output device during the control sequence. On the other hand, its main advantage is cost. Even simple motion control had previously required an expensive option module, and at times was restricted to more sophisticated control platforms in order to meet system requirements. More sophisticated motion applications require higherprecision positioning hardware and software, and many PLCs offer highspeed option modules that interface with servo drives. Most drives today can accept traditional mands from host (PLC or PC) controls, or provide their own internal motion control. The trend here is to integrate the motion control configuration into the logic controller programming software package. Programming Languages A facet of the PLC that reflects both the past and the future is programming language. The IEC 611313 standard deals with programming languages and defines two graphical and two textual PLC programming language standards: * Ladder logic (graphical). * Function block diagram (graphical). * Structured text (textual).Instruction list (textual). This standard also defines graphical and textual sequential function chart elements to organize programs for sequential and parallel control processing. Based on the standard, many man
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