发布时间 : 星期日 文章(完整版)基于PLC的锅炉汽包水位控制系统设计毕业设计更新完毕开始阅读63dd7553cd7931b765ce0508763231126edb77b7
图6.7模拟量输入模块组态
最后根据硬件配置情况，输入输出端口地址可以做以下分配：
汽包水位：Local:3:I.Ch1Data 蒸汽流量：Local:3:I.Ch2Data 送水流量：Local:3:I.Ch3Data
接触器KM1控制信号：Local:5:O.Data.0 接触器KM2控制信号：Local:5:O.Data.1 6.3.3通讯模块组态
由于该设计需要DeviceNet与变频器通信，因此还需要进行通讯模块组态。选择通讯模块1756-DNBA并设置其槽号为4，如图6.8所示。
图6.8DeviceNet模块组态
完成通讯模块组态后可以根据DeveiceNet网络组态确定变频器给定信号地址为：Local:4:O.Data[0]。 6.3.4梯形图程序设计
根据以上所述的模块组态情况，可以在控制器标签里（Controller tags）建立以下三个标签：w-level、 w-float、s-float分别表示汽包水位信号、送水流量信号、蒸汽流量信号在程序标签里（Program tags）建立以下三个标签：. PAC for Industrial Control, the Future of Control. National Instrument. 2006, (2):9～14
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Prentice PC and PLC wane, with PLC using commercial of the shelf (COTS) Research Corporation (ARC), stands for Programmable Automation Controller and is used to describe a new generation of industrial controllers that combine the functionality of a PLC and a PC. The PAC acronym is being used both by traditional PLC vendors to describe their , PLC over networks, and new programming standards such as IEC. However, engineers create 80 percent of industrial applications with digital IO, a few analog IO points, and simple programming techniques. Experts from ARC, Venture Development Corporation (VDC), and the online PLC training source PLCS.net estimate that:
? 77% of PLC are used in small applications (less than 128 IO) ? 72%of PLC IO is digital
? 80%of PLC application challenges are solved with a set of 20 ladder-logic instructions
Because 80 percent of industrial applications are solved with traditional tools, there is strong demand for simple low-cost PLC. This controller technology, where 80 percent of applications require simple, low cost controllers and 20percent relentlessly push the capabilities of traditional control systems. The applications the 20 percent are built by engineers who require with the enterprise net work. In the 80s and 90s, these “20 percenters” evaluated PCs for industrial control. The PC provided the software capabilities to perform advanced tasks, offered a graphical rich programming and user environment, and utilized COTS
components allowing control engineers to take advantage of technologies developed for other applications. These technologies include floating point processors; -volatile data storage; and graphical development software tools. The PC also provided unparalleled flexibility, incorporating advanced functionality, such as analog control and simulation database connectivity, web based functionality, and communication with third party devices, the PLC still ruled the control realm. The main problem with PC-based control was that standard PCs were not designed for rugged environments.
The PC presented three main challenges:
1. Stability: Often, the PC’s general-purpose operating system was not stable enough for control. PC-controlled installations were forced to -industrially manually force a coil to a desired state, and quickly patch the affected code to quickly override a system. However, PC systems require operators learn new, more advanced tools.
Although some engineers use special industrial computers with rugged addition, the devices used within a PC for different automation tasks such as IO, communications, or motion, may of the code and a PC for the more advanced functionality. This is the reason many factory floors today conjunction with PCs for data logging, connecting to bar code scanners，inserting information into databases, and publishing data to the Web. The big problem with this type of setup is that these systems are often difficult to construct, troubleshoot and maintain. The system engineer often is left with the unenviable task of incorporating , engineers with complex