水泥企业PLC控制系统的常见故障与处理

目前，可编程序控制器（PLC）在水泥行业应用十分广泛，应该说PLC运行是安全可靠的，其中央处理单元CPU很少出现故障，但其电源模块、存储模块、输入输出模块及其外围线路，由于设计不合理或使用维护不当、元器件质量问题，或者由于软件故障，常常使PLC控制系统出现故障。现以我公司各型号PLC自动控制系统为例，对其出现的若干问题进行分类分析，供同行参考。     

面砖生产线上PLC的应用

可编程控制器PLC以其工作平稳，可靠，抗干扰能力强等特点，在面砖生产线上得到了越来越广泛的应用，本介绍了PLC在安装时应注意的问题，以确保PLC在使用时得到更加安全可靠的效果。     

PLC过程控制系统常见故障的分布分析及维护

为了延长PLC控制系统的寿命，在系统设计和生产使用中要对该系统的设备消耗、元器件设备故障发生点有较明白的估计，也就是说，要知道整个系统哪些部件最容易出故障，以便采取措施。现以我厂特种水泥1号线的PLC过程控制系统为例，对PLC过程控制系统故障分布规律进行分析，希望能对PLC过程控制系统的系统设计和日常维护有所帮助。     

水泥厂PLC故障处理及案例分析

PLC广泛应用于水泥生产的各种控制中，其主要构成元器件是以半导体器件为主体，由于受到外部环境和设备的影响以及随着使用时间的增长，造成其元件失灵。同时由于PLC程序本身的问题、系统设计时的欠缺、维护不到位以及外部电路的故障，影响了PLC系统的可靠运行，给生产造成很大影响。     

在PLC中实现单按钮控制启动/停止的方法

由于PLC具有可靠性高，编程简单，使用和维护方便等一系列优点，应用越来广泛。在设计采用PLC控制方案时，应考虑如何减少所需PLC的输入点数问题。为了减少（简化）所需PLC的输入点数，区别不同情况，其实现方法有多种，其中一种实现方法就是采用单按钮控制启动／停止。这种方法和很多家用电器的开机和关机的情形一样，但是它是由机械结构来实现，而在PLC中是通过程序使一个普通的按钮具有启动／停止的功能，这样不仅能够节约所需PLC的输入点数一个，而且控制方便，具有很高的实用价值。笔根据实际的工作经验，以OMRON的H系列PLC为例总结了以下的几种方法，在此提出与同行商讨。     

PLC在冷端分片装置的应用

PLC广泛应用于玻璃制造领域，为玻璃生产自动化控制设备提供了非常可靠的控制应用。本文针对薄玻璃生产中辊道运干亍速度快，末端取片压力大等缺点，提出应用PLC和变频器来控制分片机以实现增加支线取片的目的，并对PLC程序设计思路、方法及变频器参数设置做了详细的描述。     

浅析陶瓷过滤机PLC自动控制系统及故障诊断

陶瓷过滤机自动控制系统是以PLC为核心的控制系统。本文从系统的硬件配置、软件设计两方面介绍PLC自动控制系统在过滤机中的应用，以及故障诊断和排除方法。     

对PLC--可编程控制器的初步解析

可编程控制器由于抗干扰能力强，可靠性高，编程简单，性能价格比高，在工业控制领域得到越来越广泛应用。随着PLC的推广普及， PLC产品的种类和数量越来越多。近年来，从国外引进的PLC产品、国内厂家或自行开发的产品已有几十个系列，上百种型号。PLC的品种繁多，其结构形式、性能、容量、指令系统、编程方法、价格等各有不同，使用场合也各有侧重。因此，合理选择PLC对于提高PLC控制系统的技术经济指标起着重要作用。     

浅谈POC的选择

近年来，随着PLC的普及应用，许多工厂在进行控制改造时，越来越多地趋向于采用PLC控制技术替代传统的继电器控制技术。由于PLC种类繁多，其结构形式、性能、容量、指令系统、编程方式、性能价格比等各有不同，其所能适应的环境场所也各不相同。合理地选择PLC，对提高PLC控制系统运行的可靠性及性能价格比等技术经济指标至关重要。     

西门子PLC S7系列在双复合挤出生产线上的应用

利用西门子PLC S7改造双复合挤出机旧的控制系统。新系统采用1个PLC主站、3个PLC从站、2个远程I/O、34台直流驱动器和1台工控机。可实时显示各种工艺参数，所有电机转速以接取电机为准。改造后稳定性及产品质量等均提高。     

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     

MW级风力发电系统偏航控制器的硬件设计

本文中利用PLC作为偏航控制器,单片机为主的外围电路作为PLC的信号转换和处理单元。通过对各种信号的转换、处理,匹配成PLC能够接受的信号,再通过PLC实现的偏航控制程序,输出相应的控制信号控制执行机构,来达到自动对风的目的。     

基于多模式无线控制的PLC设计与研究

在采用单片机设计PLC的基础上,给出了PLC的无线红外模式、无线调频模式和GSM短信模式的无线控制构架,讨论了对应的软、硬件设计,实现了在基本PLC 上的多模式无线控制,并结合PLC变频调试系统和TM2运动控制机构,完成了多模式无线控制PLC的运动控制系统的设计.最后设计了基于组态软件MCGS的驱动程序,实现了PLC与...     

Thermal conductivity of homogeneous alignment networks formed with mono‐ and bi‐functional polymerizable liquid crystals

Mixtures consisting of mono‐functional polymerizable liquid crystals (PLC) having a polymerizable moiety on the molecular short axis terminal and a bi‐functional PLC having the polymerizable moieties on the molecular long axis terminals were prepared. These mixtures had a wide liquid crystal range. Uniaxially aligned films were prepared from the PLC mixtures by photo polymerization after aligning the molecular directions by the rubbing method. The thermal conductivity of the films increased from 0.45 to 0.68 W/m · K with the increase ofthe content of the bi‐functional PLC. The relation between the thermal conductivity and the PLC network styles was investigated from the aspect of the molecular order. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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.     

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.     

The Role of Phospholipase C in GABAergic Inhibition and Its Relevance to Epilepsy

Epilepsy is characterized by recurrent seizures due to abnormal hyperexcitation of neurons. Recent studies have suggested that the imbalance of excitation and inhibition (E/I) in the central nervous system is closely implicated in the etiology of epilepsy. In the brain, GABA is a major inhibitory neurotransmitter and plays a pivotal role in maintaining E/I balance. As such, altered GABAergic inhibition can lead to severe E/I imbalance, consequently resulting in excessive and hypersynchronous neuronal activity as in epilepsy. Phospholipase C (PLC) is a key enzyme in the intracellular signaling pathway and regulates various neuronal functions including neuronal development, synaptic transmission, and plasticity in the brain. Accumulating evidence suggests that neuronal PLC is critically involved in multiple aspects of GABAergic functions. Therefore, a better understanding of mechanisms by which neuronal PLC regulates GABAergic inhibition is necessary for revealing an unrecognized linkage between PLC and epilepsy and developing more effective treatments for epilepsy. Here we review the function of PLC in GABAergic inhibition in the brain and discuss a pathophysiological relationship between PLC and epilepsy.     

Tunable positive liquid coefficient of an anisotropically conductive carbon nanotube-polymer composite

The anisotropic carbon nanotubes (CNTs)/polycarbonate (PC)/polyethylene (PE) conductive polymer composite possesses a strong positive liquid coefficient (PLC), which can be attributed to the microfibrillar structure in the composite. A facile method, namely the isothermal treatment (IT), is proposed to manipulate the PLC of the CNTs/PC/PE composite. Different PLC intensities are achieved by controlling IT temperature and time. The PLC can even be eliminated when a proper IT temperature is chosen, exhibiting superb anti-solvent feature.     

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。     

以太网实现锡槽调功器远程控制

利用德国赫优讯Hilscher的NETLINK转换器通过以太网连接西门子s7-300PLC,进行程序下载．并通过组态软件与PLC之间进行以太网数据通讯实现锡槽调功器的远程控制,使控制更准确,对老厂锡槽调功控制系统改造有一定的参考意义。