【正文】 ystems are economic due to the lower cost of the ponents, which can be optimally chosen instead of a generic solution, and where the nonrecurring engineering charges are spread over thousands or millions of units. For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities. A microcontrollerbased design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the enduser would not need to alter the control. Automotive applications are an example。 ③ adaptability good。 晉 中 學(xué) 院 本科畢業(yè) 設(shè)計(jì) 英文參考資料 題 目 Programmable Logic Controller PLC 院 系 機(jī)械學(xué)院 專(zhuān) 業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 姓 名 黨佳明 學(xué) 號(hào) 1014312109 學(xué)習(xí)年限 2020 年 09 月至 2020 年 07 月 指導(dǎo)教師 王 麗珍 職稱(chēng) 講師 申請(qǐng)學(xué)位 工學(xué) 學(xué)士學(xué)位 2020年 05月 20日 1 英文 原文： Programmable Logic Controller PLC 1 PLC Introduce PLC Introduction Programmable controller is the first in the late 1960s in the United States, then called PLC programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented PLC General Motors and the basic design is the puter functional improvements, flexible, generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices bined controller hardware is standard and overall. According to the practical application of target software in order to control the content of the user procedures memory controller, the controller and connecting the accused convenient target. In the mid1970s, the PLC has been widely used as a central processing unit microprocessor, import export module and the external circuits are used, largescale integrated circuits even when the PLC is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data munications functions. International Electro technical Commission (IEC) standards promulgated programmable controller for programmable controller draft made the following definition: programmable controller is a digital electronic puters operating system, specifically for applications in the industrial design environment. It used programmable memory, used to implement logic in their internal storage operations, sequence control, timing, counting and arithmetic operations, such as operating instructions, and through digital and analog input and output, the control of various types of machinery or production processes. Programmable controller and related peripherals, and industrial control systems easily linked to form a whole, to expand its functional design. Programmable controller for the user, is noncontact equipment, the procedures can be changed to change production processes. The programmable controller has bee a powerful tool for factory automation, widely popular replication. Programmable controller is useroriented industries dedicated control puter, with many distinctive features. 2 ① high reliability, antiinterference capability。 ② programming visual, simple。 ④ functional improvements, strong functional interface. Programmable Logic Controllers (PLC), a puting device invented by Richard E. Morley, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with softwired logic or socalled relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days. Although PC based control has started to e into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan, an increase of the annual sales volume to 15 million PLC per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of puting hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5billion industry at the present time. Though PLC are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trialanderror. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating: “If houses were built like software projects, a single woodpecker could destroy civilization.” Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLC are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that lowcost PLC can be used. In general, the productivity in generating PLC is far behind pared to other domains, for instance, VLSI design, where efficient puter aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLCprogramming requires a simultaneous consideration of 3 hardware and software. The softw