浅谈做好水利工程监理的三控制

对水利工程项目监理"质量控制、进度控制、投资控制"的三控制的原则、程序和方法进行阐述.工程建设监理的控制管理主要包括"质量控制、进度控制、投资控制"三大内容.三大内容中投资控制是基础,进度控制是条件,质量控制是核心.因此,工程建设监理必须抓住质量这个核心.     

智能仿真控制探讨

提出一种新的控制方法,即用计算机模拟人类的控制方式去完成控制.主要论述人类的控制方式的优点、传统控制方式的不足、人类的控制方式与传统控制的不同点和控制模型的建立过程,将控制理论由"频域"应用扩展到"时域".     

棒材成品飞剪的新型控制方法研究

棒材成品飞剪控制一般分为轴定位控制和分段剪切控制两部分,容易出现剪刃位置控制不准和钢材长度测量不精确的问题,影响剪切精度和控制稳定性。本文介绍的控制方法是在常规控制的基础上,利用新的轴定位控制和精确尺寸控制方法实现对倍尺飞剪的优化控制,控制精度较高,稳定性较好。     

基于Simulink的电气比例阀压力控制研究

随着机械行业的发展,压力控制越来越精确化,在许多地方,都要实现压力的精确控制。本文提出以密闭容器的压力控制为研究对象,使用电气比例阀作为压力控制元件,对密闭容器压力精确控制进行研究,采用建立压力控制数学模型和Simulink仿真的方式,将普通控制、PID控制和模糊PID控制进行对比,选择出最精确的控制方式,获得了三种控制方式的控制曲线,结果表明,模糊PID控制的电气比例阀精度最高,可以实现压力的精确控制,为工业生产中的压力控制提供理论依据。     

烘丝机出口含水率智能控制方法研究

烟草烘丝机控制具有高度非线性,大滞后、高耦合等特点,传统PID控制在越来越严格的工艺指标控制中变得的力不能及。在工业控制中智能控制替代传统PID控制已成为新的发展方向。将介绍智能控制在烘丝机控制上的应用,着重讨论烘丝机控制的两种控制策略:应对控制,预测控制。并介绍各自可使用的控制方法。     

浅析容错控制应用的新进展

容错控制是提高自动控制系统安全性与可靠性的有效方法。本文对容错控制的基本原理和最新的研究成果进行了综述,介绍了经典容错控制以及其他一些容错控制方法的应用,重点评述了主动容错控制、被动容错控制、网络控制系统的容错控制、基于Delta算子的鲁棒容错控制、人工智能容错控制和非线性系统的容错控制,最后介绍了容错控制的一些应用研究成果并展望了未来的发展。     

三相永磁同步电机直接转矩控制技术研究

电动机控制的核心是实现对其电磁转矩的控制,其控制方法有矢量控制和直接转矩控制等,相比矢量控制而言,直接转矩控制省去了磁场定向、矢量变换和电流控制等复杂环节,具有优良的动静态性能。介绍了直接转矩控制技术的原理,并在MATLAB/Simulink中建立了三相永磁同步电机的直接转矩控制模型,通过对模型仿真结果的分析,可以看到直接转矩控制具有良好的转矩控制效果和快速响应能力。     

数字式控制仪表的控制周期及其设计

控制周期是数字式控制仪表的重要技术指标之一。本文从控制仪表本身的要求提出控制周期的两种设计方式:控制周期固定式和控制周期不固定式。可供参考。     

PID控制模式在大负荷大迟延中的运用

本文针对攀钢新3#高炉TRT对顶压控制过程中出现的问题进行分析,对顶压控制过程中存在控制滞后、控制输出恒量进行分析,在现有控制模式基础上,提出解决控制滞后和控制输出恒定的方法,最终达到控制要求.     

永磁同步电机模型预测控制的现状与发展

模型预测控制是一种优化控制算法,近年来已经成为电机控制领域研究的热点。模型预测控制根据过去和现在的信息,对系统的状态量进行预测,并综合考虑控制对象的预期值和控制量的变化等评价指标,得到最优的控制量。该文综述了基于线性模型预测的永磁同步电机的直接转矩控制、矢量控制、直接电流控制、混合控制等算法的特点,以及基于非线性模型预测的永磁同步电机控制的研究现状,阐述了模型预测控制理论与应用方面有待进一步研究的几个主要问题。     

Histochemical and ultrahistochemical localization of heavy metals in calf organs

Cadmium, zinc, selenium, and copper were administered, singly or in combination, orally or subcutaneously. Experiment I included 32 calves of both sexes; six received Cd (two groups), Zn, Cd, and Zn, and Cd and Se (two groups) and one group was a control. In Experiment II (21 bulls), three were given Cd, Cd, and Cu, and Cd and Zn, respectively, and one group was a control. For light microscopy, in Experiment I the highest amounts of silver granules were present in the samples of liver, small intestine, and vesicular gland of all the exposed groups; in Experiment II the most affected organs were liver, kidney, and small intestine. For electron microscopy, in Experiment I, after administration of Cd and Zn, the highest amounts of granules were seen in the cytoplasm of hepatocytes and cells of the proximal and distal renal tubules and the lowest amounts were found in glandular cells of the pancreas. Administration of Cd and Se resulted in the presence of large numbers of granules in the nuclei and nucleoli of spermatogonies. In Experiment II, ingestion of Cd and Zn in feed led to the appearance of highest amounts of granules in the nucleoli, nuclei, and cytoplasm of cells in testes, kidneys, and pancreas. Following Cd intake, the highest accumulation of granules was observed in the nucleoli of hepatocytes and cells of the proximal and distal renal tubules. Combined Cd and Cu produced the highest number of granules in cells of the proximal and distal renal tubules and in the nucleoli and nuclei of germinal epithelium.     

可展开固体反射面机构设计及运动学分析

针对传统固体反射面机构主反射面型面精度和收拢率较低的问题,设计了一种可展开固体反射面机构。首先,提出4种固体反射面机构可展单元构型并对其机构自由度进行分析,对比分析构型方案优缺点确定构型方案4作为可展单元基础构型,并对其结构和展开原理进行详细设计。通过D-H坐标变换建立该机构可展单元的运动学模型,根据几何约束条件建立机构位置矢量方程,利用向量封闭投影法解出各回转角间的关系,结合MATLAB软件编程对机构的位置、速度和加速度进行分析。应用ADAMS软件建立机构仿真模型,验证了机构运动学分析的正确性。最后根据机构中回转角的限制条件和结构尺寸关系,分析回转角和结构尺寸对可展开固体反射面机构收拢率的影响,确定2.2m可展开固体反射面机构的回转角和旋转角分别为78°和30°,中心圆盘半径、铰支座一孔纵向尺寸、切换连杆横向尺寸、纵向尺寸分别为245,8,40,18mm,收拢率为0.326,从而为可展开固体反射面机构的设计提供参考。     

可控式增压复合油缸设计及其性能分析

针对大压力、小压力行程的重型液压设备的结构尺寸大、油泵功率大、利用系数低、液压系统复杂等问题,提出一种压力随机可调、工作效率高、结构紧凑、性能稳定可靠的复合式高增压油缸结构。对比分析了复合缸液压机和普通单缸液压机的工作过程;论述了复合缸液压机的运行原理和设计要求;介绍了可控式增压复合油缸性能及应用。结果表明:通过增压缸将液压系统提供的压力油转换为增压油提供给主油缸,使其产生大的压力输出,可有效地减小设备主机尺寸;通过控制缸随时进行高低压转换,各阶段速度压力按需配置,实现成形工艺的最优搭配,成形周期缩短;可以提高油泵的利用系数,减小泵站装机容量;液压系统工作负荷低,性能稳定可靠,寿命长。     

人-椅8自由度车辆系统的平顺性和稳定性研究

文中在Matlab/Simulink中搭建了人-椅8自由度车辆系统仿真模型,在仿真分析时考虑汽车前、后轮之间的延迟性,以路面随机信号作为输入激励,研究了汽车平顺性的时频特性,且分别通过4个轮胎的输入激励研究了汽车的稳定性.研究结果表明:路面输入为随机信号时,车身垂直加速度,车身俯仰角加速度,人-椅垂直加速度,前、后悬架...     

基于FLUENT的液体动静压轴承的动态特性分析

应用计算流体力学软件FLUENT对超高速磨削用五腔动静压轴承进行动态特性研究,得到动静压轴承内部压力场和温度场分布;计算轴承的承载力、温度、刚度、阻尼等动态参数,分析这些动态参数与偏心率以及转速之间的关系。结果表明:在保持供油压力和轴承偏心率不变的情况下,随着转速的提高,油温上升,轴承承载力及偏位角不断增大;在保持供油压力和主轴转速不变的情况下,随着偏心率的增大,轴承流量有所减少,轴承的承载能力不断增大,偏位角基本保持不变。     

电过滤纸喷雾离子源的性能优化及应用研究

常压离子源是质谱技术在生命科学、环境保护、医药卫生、食品安全等领域的研究热点之一.随着质谱分析技术的应用范围越来越广,直接快速分析复杂体系的化合物组成和含量越发重要.本工作基于已研制的小型化离子阱质谱和电过滤纸喷雾离子源,对其分析性能和应用进行深入研究.以提高质谱信号强度和检测灵敏度为目标,对所用滤纸的孔径、离子源尖端...     

Discussion on advanced manufacturing

Advanced manufacturing consists of continuity of manufacturing, its broad sense, and the core of the manufacturing process. The technology of continuous manufacturing is discussed according to both historical and modern perspectives. The relationship between human development and manufacturing technology is also discussed. Manufacturing is a continuously evolving topic. It is not only the foundation and means of imagination, conception, the science, and the technology of material change, but also the expression of national economy, national defense, and the support industries. The broad sense of manufacturing theory, which extends the concept of manufacturing, is an important development in the 20th century. The sense is analyzed in connection with design, material forming theory, synthesis of manufacturing technology, manufacturing modes, life cycle of product, hardware and software, and support environment, etc. At the same time, the core action and the development of the theory and technology of process is also discussed. At the end of this paper, the development directions of mechanical manufacturing science and technology are mentioned.     

Wear mechanism of disc-brake block material for new type of drilling rig

To improve friction and wear performance and service life of the disc-brake pair material of a drilling rig, a new type of asbestos-free frictional material with better performance for disc-brake blocks is developed, and its wear mechanism is investigated by friction and wear experiments. Topography and elementary components of the brake block’s wear surface are analyzed by employing SEM and EDAX patterns, revealing its tribological behaviour and wear mechanism. When the frictional temperature is lower, the surface film of the brake block is thinner, dense, smooth with plasticity, and divided into the mixture area, Fe-abundant area, carbon-abundant area and spalling area. The mixture area consists of various constituents of frictional pairs without ploughing and rolling trace. The Fe-abundant area mainly consists of iron and other constituents. The carbon-abundant area is the zone where graphite and organic fibre are comparatively gathered, while the spalling area is the zone where the surface film is spalled and its surface is rough and uneven, with a loose and denuded state. During the period of high frictional temperature, the frictional surface is also divided into the mixture area, Fe-abundant area and spalling area. In this case, the mixture area consists of abrasive dust from friction pairs, and the surface film is distributed with crumby hard granules, exiguous oxide, carbide granules and sheared slender fibre. The Fe-abundant area is mostly an oxide layer of iron with a flaky distribution. Fracture and spalling traces as well as an overlapping structure of multilayer surface films can be easily found on the surface film. The components of the spalling area are basically the same as that of the matrix. At the beginning of wear, the hard peaks from the friction surface of the disc-brake plough on the surface of the brake block. With increasing frictional temperature, the friction surface begins to soften and expand, and oxidized wear occurs at the same time. During the high-temperature wear period, severely influenced by friction heat, obvious softening and plastic flow can be found on the friction surface of the brake block, its anti-shearing ability is weakened, and adhesive wear is intensified. Thermal decomposition of cohesive material in the brake block is simultaneously strengthened, so that constituents shed due to loss of adhesion. Organic fibre is in a flowing state and obviously generates drawing, shearing, carbonization and oxidization. In addition, thermal cracking, thermal oxidization, carbonization and cyclization of organic substances on the surface of brake block can make the friction surface produce pores or cracks, thus fatigue wear occurs.     

Considerations for the incorporation of measured surfaces in finite element models

This work discusses some of the benefits, techniques, challenges, and considerations associated with the incorporation of measured surfaces in finite element (FE) models including how much surface data to measure and import into the model, the shape of the surface geometry to create, the presence and effect of surface layers and impurities, the required mesh density for rough surfaces, the nature of the element formulations and material properties at small length scales, the differences between measurement and FE coordinate systems, the limitations and idealizations of the FE method, issues associated with boundary conditions and their ability to impose or prevent conformal contact, and issues associated with the size of the pinball region and the contact stiffness relative to the nature of the surface. It also describes some current and future research directions that can be used to validate and expand existing techniques and to improve our understanding of surface phenomena.     

智能垃圾分拣系统的模拟与实现

针对当今世界城市生活垃圾不断增长造成的自然环境污染和资源浪费等问题,对我国和欧美等发达国家的城市生活垃圾分类收集和分类处理方面进行了对比研究,对发达国家在城市生活垃圾处理过程中的安全分类处理方式和垃圾再利用策略进行了归纳,结合国内外垃圾分类处理所遇到的问题和不足,设计制造出了一套实现垃圾桶颜色识别、路线识别、机械手动作和到达指定位置的自动化垃圾分拣系统模型,利用Code Warrior 5.0软件开发平台对系统程序在线调试,通过系统的反复运行对智能分拣小车的自动寻迹进行了累积误差统计试验.研究结果表明,智能垃圾分拣系统的累积误差波动稳定,寻迹的能力比较准确、可靠,实现了垃圾自动分拣的过程,为工业的应用实现提供了有利的参考和理论依据.