PLC的程序结构

介绍PLC几种典型的程序结构,为PLC的用户和国产PLC厂家提出了选择PLC程序结构的建议。     

基于化工自动化系统中PLC控制系统的应用分析

文中基于化工自动化系统中PLC控制系统的应用,分析了PLC控制化工自动化系统功能、PLC控制系统硬件设计及工作原理以及PLC控制系统的软件设计等方面。     

基于计算机链接协议的S7-200PLC与FX2N PLC的通信

介绍以S7-200PLC为主站、三菱FX2N PLC为从站,实现三菱公司专用计算机链接通信协议的技术方案,解决了S7-200PLC采用串行通信方式可靠读取FX2N PLC内部数据的工程难题,给出S7-200PLC与第三方PLC之间数据通信的一般方法.     

D70轮胎均匀性试验机控制系统的升级

针对D70轮胎均匀性试验机控制系统的特点，确定将PLC－2／17 CPU升级至PLC－5／20CPU。了解了ABPLC2槽寻址及PLC－2与PLC－5的异同后，用AB编程软件将转换后的PLC控制程序下载至PLC－5CPU中，联机调试后，整个升级工作顺序完成。     

PLC在矿山机电设备中的应用研究

PLC技术在煤矿企业广泛应用,的本文基于PLC技术的基本概念及其应用现状,分析了PLC在矿山机电控制中的主要优势,以期推动PLC控制技术在矿山机电中的应用发展。     

利用PLC系统功能实现报警信息的准确记录

简要介绍了我厂主控室两套PLC系统(合成氨PLC、尿素PLC)的基本情况,以及利用现有的PLC,开发实现联锁报警信息准确采集记录的方法.     

PLC电气系统中故障原因与维护处理

随着PLC在设备电气系统中应用越来越多,PLC电气系统的故障原因及维护逐渐受到人们的重视。本文首先探讨了PLC电气系统的故障和数显仪表的故障原因,并给出了几点PLC电气系统故障的维护策略,为PLC电气系统故障的排查和维护提供资料参考。     

浅谈电气设备中PLC控制系统故障的排除

以锅炉吹灰器PLC控制系统为例,介绍PLC的特点和处理PLC控制系统故障的一般方法。     

论述PLC在机床电气系统中故障原因及维护处理技术

随着PLC在机床电气系统中的应用逐渐普及,PLC的故障维修与处理逐渐受到人们的重视。本文首先对PLC在机床电气系统中的故障原因进行分析,并总结了几点PLC机床电气系统的故障维修方法,为机床电气系统PLC故障的维修与处理提供资料参考。     

PLC的系统接地重要性及干扰的抑制

PLC在数控系统中占据了很重要的地位。一般大型的PLC中,都配备了职能接口,可以用来完成一些独立的用途,因此PLC得到了广泛的使用。在安装和试运行整个系统的时候,需要接地来保证PLC的正常运行。PLC控制系统的抗干扰能力强弱会影响整个系统的运行情况。安装接地系统能够抑制对PLC运行造成影响的因素。     

Bacillus Mycoides磷脂酶C部分特性研究

对一种纯化自Bacillus mycoides 970发酵上清液的磷脂酶C的部分特性进行了研究.SDS-PAGE检测表明该纯化磷脂酶C由一条多肽链组成,分子量为75.1 kDa.热稳定性实验表明该纯化磷脂酶C对温度敏感,具有热不稳定性.金属离子依赖性检测表明该纯化磷脂酶C属于金属磷脂酶C家族,Ca2 、Mg2 、Zn2 和Ba2 对该磷脂酶C催化活性的发挥必不可少.血平板及卵黄平板检测表明该磷脂酶C没有溶血活性和卵磷脂酶活性.     

Characteristics of polymer light conduits from different manufacturing processes

The characteristics of polymer light conduits (PLCs) prepared from three different processes are compared: (1) a bulk polymerization and melt spinning process (PLC1), (2) a thermal polymerization (PLC2), and (3) a UV curing photopolymerization (PLC3–PLC4) of a monomer mixture in a fluorinated ethylene propylene tube. PLC1 and PLC2 were obtained from Toray and Lumenyte, respectively. New PLCs, PLC3 and PLC4, were prepared from the monomer mixtures consisted of methyl methacrylate, 2-ethyl-hexyl acrylate, and the crosslinking agent polyethylglycol 200 diacrylate and diallyl phthalate, respectively. All four polymer light conduits contain the acrylic moiety. PLC2 may also contain the plasticizer additives, which resulted in an excellent flexibility but with a poor thermal stability. The flexibilities of PLC2 and PLC3 were significantly improved from that of PLC1 due to the insertion of a plasticizer and the long alkyl chain monomer 2-EHA, respectively. The much larger numerical apertures of PLC2–PLC4 than that of PLC1 suggest that PLC2–PLC4 can have a wide angle application. The transmitted distance of PLC1 is larger than those of PLC2–PLC4. However, the illumination intensity of PLC1 is worse than those of PLC2–PLC4. This result indicates that PLC1 is suitable for the applications as PLCs with the characteristics of long distance and low illumination intensity, while PLC2–PLC4 are suitable for short distance and high illumination intensity applications. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2103–2109, 1997     

基于PLC和组态软件的油库罐区监控系统

设计了基于S7—300系列PLC和力控组态软件的油库罐区监控系统,介绍了其硬件结构和软件设计。该系统通过工业以太网实现上位机和PLC的通信,采用上位机双机冗余和PLC软冗余结构,可以充分发挥PLC和计算机的优势,有助于提高监控系统的可靠性。     

Rigid-chain polyesters grafted with flexible-chain vinyl polymers

The concept of “molecular reinforcement” has been advanced, in the last decade, as an alternative to conventional fibre reinforcement of thermoplastics: In blends with normal (flexible-chain) thermoplastics, rigid chains of main-chain LC polymers (PLC) can act as strengthening fibres on the molecular scale. However, the rigid PLC chains must be well dispersed which is improbable since PLC and normal polymers are usually incompatible. A related concept is “micellar reinforcement”: Graft copolymers made of a rigid-chain PLC backbone and flexible-chain grafts can form a microphase morphology of cylinderic micelles where the PLC chains act as reinforcing fibres on a micellar scale. Such rigid-flexible graft copolymers are discussed in this study. They were pepared from a polyester of terephthaloyl, dihexoxyterephthaloyl and phenylhydroquinone moieties with special comonomer units carrying a double bond onto which styrene was grafted via radical copolymerisation. Grafting occurred with high efficiency, leading to products with the desired morphology of cyclindric micelles.     

基于Modicon PLC和intouch的污水处理控制系统

介绍了污水处理系统中Modicon PLC和intouch组态软件的应用。详细阐述了该系统的硬件及软件组成以及PLC的具体配置,软件的编程思想及流程。     

Thermal expansivity and thermal conductivity of amorphous thermoplastic polyimide and polymer liquid crystal blends

Linear thermal expansivities α_L and thermal conductivities of polyimide (TPI) and polymer liquid crystal (PLC) blends were studied. The glass transition temperatures T_g of our amorphous TPI and the PLC are, respectively, 240 and 220°C. The addition of the PLC induces orientation through the channeling process, as predicted by an extension of the Flory statistical‐mechanical theory of PLCs (27). Channeling was observed at PLC concentrations as low as 5 wt%. Thermal conductivity decreases with the addition of the PLC to the TPI. The anisotropic expansivity of the blends shows a strong dependence on PLC concentration and orientation direction. The pure PLC shows a maximum on the along‐the‐flow expansivity vs. temperature curves and also negative α_L values. TPI addition moves the expansivities to positive values, but the maximum persists, even for 5% PLC only.     

双变频器组成的调速系统在高炉主卷扬上的应用

由2台小型PLC分别控制2台变频器,构成在线备用模式,应用在高炉上料主卷扬上。介绍构成这一系统的硬件组成及PLC控制程序,以及变频器参数设定和调试方法。     

煤气交换机PLC控制技术的应用

介绍了可编程序控制器(PLC)控制技术在5.5m焦炉JM-3型煤气交换机上的应用情况,详述了PLC选择、开关量建立、模块配置、控制过程、硬件措施和软件设计等。应用PLC控制技术后,实现了交换程序紊乱保护,使煤气交换机电控系统更加安全可靠。     

PLC在压铸机控制系统改造中的应用

介绍采用PLC对传统卧式冷室压铸机的控制系统进行改造,根据系统控制要求,设计了基于双CPU的PLC冗余控制系统,提高了控制系统的可靠性,并且采取一些抗干扰措施,降低故障率。