LS-1200型往复锯PLC的修复

山河屯林业局山亚木制品有限公司使用的LS-1200型全自动循环往复锯是1988年从日本购进的,该锯的生产过程由可编程序控制器(以下简称PLC)控制。2003年3月份该锯出现故障,其PLC的用户程序丢失,使该锯停产。1PLC性能概述这套PLC由日本SANEN公司生产,所用的设定器型号为A-21P,输入48点,输出64点,I/O的总点数为112点,属于小型机。该PLC的I/O接口有两种形式,一种为输入接口模块,其中包括直流24V输入模块,交流信号输入模块和模拟量输入模块;另一种为输出接口模块,其中包括直流输出模块,交流220V输出模块,继电器输出模块,以及模拟量输出…     

PLC在移动式膜法提纯沼气生产生物天然气工程中的应用

指出了随着当代自动、智能化的发展,自动化控制技术已广泛应用于各个行业。其中,在移动式膜法提纯沼气生产生物天然气工程中的应用将成新的亮点。分析了传统的沼气提纯工艺的不足,而用PLC控制生产装置,能大幅提高生产及安全生产效率。同时对比了移动式膜法提纯沼气生产生物天然气工程装置的优势:采用模块化、智能化设计,具有易安装、易操作、易监控的特点,提纯装置控制系统可以在各种检测传感器的配合下对沼气提纯生产过程进行实时监测,并依据所检测数据对各工艺设备进行控制;系统通过PROFIBUS现场总线实现PLC与自动控制系统设备及各模块单元通讯,采用MPI、Modous RTU协议实现PLC与上位机系统之间的通讯。     

PLC在草方格铺设机器人控制系统中的应用

在详细阐述了铺设草方格工作原理和工艺流程下，选择了PLC作为控制核心，并根据工作要求给出了软硬件的设计与实现方案，及对车用测距雷达进行改造实现横向自动调节功能的方法，经过现场试验证明了该系统是一套综合、高效的控制系统。它对PLC在机器人上的应用具有一定的指导意义和参考价值。     

PLC和变频器在镗孔机床中的应用

我公司根据生产需要，自行设计出了简易组合镗孔机床，经一段时间的使用，又将原有电气部分的继电器——接触器控制方式做了改进，采用PLC(可编程序控制器)控制方案，缩小了电控装置的体积，省去了复杂的接线，提高了工作的可靠性，减少了机床维修人员的工作量。     

多规格木板自动码垛机控制系统设计与实现

为了实现对一种错位双链木板循环输送码垛机结构的多传动系统协调控制,以提高木板的码垛效率,满足多规格木板码垛需求,设计了一种多输入多输出的木板码垛柔性控制系统。基于分模块控制系统设计理论,以PLC及扩展接口为核心,多激光传感器和触点开关为反馈信息输入,协调控制不同传动系统的多个电机,以实现木板的输送、规整和码垛。通过样机的试验,所设计的控制系统功能完整、性能稳定,自动化木板码垛比人工码垛效率高、效果好。     

PLC结合变频技术在定位控制中的应用

从升降系统的控制原理、系统设计、触摸屏画面设计、程序设计等方面,阐述了应用PLC结合变频调速技术,加上旋转编码器作位置反馈,实现精确定位控制的方法,并分析和评估控制系统的定位精度以及实现砂光机升降精确定位控制的可行性,为在国内同类设备中的应用提供借鉴。     

自走式喷灌机控制系统设计

自走式喷灌机由轨道桁架、喷灌机主机、喷灌机架、控制系统和供水系统组成.本文阐述了自走式喷灌机控制系统设计方案.即采用PLC(可编程控制器)、步进电机及其驱动器设计自走式喷灌机的控制系统,利用PLC控制喷灌机的自动行走、灌水位置、灌水时间或重复灌溉次数,利用触摸屏实现很好的人机界面操作.该系统具有移动方便和经济实用等特点,适合我国较大型日光温室的喷灌机械化作业.     

基于嵌入式的农田自动灌溉系统设计

为实现对无人值守农田的灌溉作业控制,基于嵌入式STM32控制器和PLC设计一款农田自动化灌溉系统。STM32控制器对农田中温度传感器、光照传感器和湿度传感器采集的数据进行运算整理,将结果反馈给Web服务器和PLC,用户可运用移动设备登录Web服务器查看和设置灌溉参数,PLC根据STM32采集和用户设置的参数,应用USS通信协议控制变频器输出频率大小,实现对水泵电机运转频率的控制,最终达到对农田灌溉水量的精准自动化调控。详细阐述了系统的硬件和软件设计过程,并通过田间试验验证了系统应用的有效性。     

基于WinCC的中密度纤维板热压工段监控软件的设计

在中密度纤维板(MDF)生产过程中,热压环节是整个生产过程的中心环节,热压温度、热压压力、热压时间是热压工艺的主要参数.热压过程中用可编程控制器(PLC)对热压温度、热压压力、热压时间等物理参数进行检测,PLC再将这些参数传递给上位机;在上位机上运行监控软件,显示各工序状态及参数变化情况,并且采用相应的算法计算输出参数发送给PLC;由PLC控制热压机各电磁阀的导通和闭合,从而达到实现热压工艺曲线的目的.     

刨花计量料仓控制系统的设计与分析

介绍了应用于刨花板生产线上刨花计量料仓控制系统的设计。利用可编程逻辑控制器(PLC)和人机界面(HMI)等硬件组成控制系统,分析了控制系统误差的来源。在设计时增加了控制系统的稳定性和可靠性研究,以减小误差。刨花计量料仓采用PID控制方式实现对刨花流量的精确控制。利用MATLAB/Simulink模块对控制系统进行模拟仿真分析并整定PID参数。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.