关于plc的毕业设计外文翻译-plc设计(编辑修改稿)

关于plc的毕业设计外文翻译-plc设计(编辑修改稿)内容摘要：

thoroughly how system functions. Electrical supply is used in bringing electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you’ll find electrical supply as a separate module. Those are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current. This electrical supply is usually not used to start external input or output. User has to provide separate supplies in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC. Part 4 PLC design criteria A systematic approach to designing PLC software can overe deficiencies in the traditional way of programming manufacturing control systems, and can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equivalently, by state machines. Formal representations provide a highlevel description of the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired goals. Secondly, a 滨州学院 专 科毕业设计 (外文翻译 ) 6 state machine description provides a structured representation to convey the logical requirements and constraints such as detailed safety rules. Thirdly, welldefined control systems design outes are conducive to automatic code generation An ability to produce control software executable on mercial distinct logic controllers can reduce programming leadtime and labor cost. In particular, the thesis is relevant with respect to the following aspects. In modern manufacturing, systems are characterized by product and process innovation, bee customerdriven and thus have to respond quickly to changing system requirements. A major challenge is therefore to provide enabling technologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused in realtime, therefore, giving a significant petitive edge in industrial practice. Studies have shown that programming methodologies in automation systems have not been able to match rapid increase in use of puting resources. For instance, the programming of PLCs still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in programming are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards [IEC 60848, 1999。 IEC611313, 1993。 IEC 61499, 1998。 ISO 157451, 1999] have been formed to fix and disseminate stateoftheart design methods, but they normally cannot participate in advancing the knowledge of efficient program and system design. A systematic approach will increase the level of design automation through reusing existing software ponents, and will provide methods to make largescale system design manageable. Likewise, it will improve software quality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railroads. The software industry is regarded as a performance destructor and plexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimization and efficiency. The result is that massive and less efficient software code on one hand outpaces the gains in hardware performance on the other hand. Secondly, software proliferates into plexity of unmanageable dimensions。 software redesign and maintenanceessential in modern automation systemsbees nearly impossible. Particularly, PLC programs have evolved from a couple lines of code 25 years 滨州学院 专 科毕业设计 (外文翻译 ) 7 ago to thousands of lines of code with a similar number of 1/O points. Increased safety, for instance new policies on fire protection, and the flexibility of modern automation systems add plexity to the program design process. Consequently, the lifecycle cost of software is a permanently growing fraction of the total cost. 8090% of these costs are going into software maintenance, debugging, adaptation and expansion to meet changing needs. Today, the primary focus of most design research is based on mechanical or electrical products. One of the byproducts of this proposed research is to enhance our fundamental understanding of design theory and methodology by extending it to the field of engineering systems design. A system design theory for largescale and plex system is not yet fully developed. Particularly, the question of how to simplify a plicated or plex design task has not been tackled in a scientific way. Furthermore, building a bridge between design theory and the latest epistemological outes of formal representations in puter sciences and operations research, such as discrete event system modeling, can advance future development in engineering design. From a logical perspective, PLC softw。