类GPS超声定位系统及两基站定位性能分析

介绍了类GPS超声定位系统及其工作原理,给出了两基站定位的解析算法并对其定位精度作了分析。理论分析表明,目标的定位精度与它在空间中的位置和基站的几何布局有关。在基站几何布局一定的情况下,为获得较高的定位精度,应根据目标所在空间中的不同位置选择不同的定位基站。根据PDOP(平面位置精度因子)在定位空间中的分布图,给出了两基站定位时的基站选择原则。最后通过仿真验证了上述分析的正确性。     

复合共鸣腔Janus宽带换能器

提出了一种复合共鸣腔Janus换能器设计思想.在Janus-Helmholtz换能器基础上,增加Janus-Hammer Bell的圆环谐振模态,利用换能器三种工作模态的互相耦合,有效拓宽了换能器的工作频带.同时换能器整体采用溢流设计,实现内外静水压力平衡,适用于深水工作.文章首先介绍了复合共鸣腔的工作原理,给出了圆环...     

水大流量标准装置控制系统设计及性能评价

水大流量标准装置是负责开展大口径流量仪表测试、确保大流量量值溯源与传递准确可靠的核心设备,而测控系统是流量标准装置的重要组成部分。目前国内专门针对水大流量装置控制系统的研究开展较少,已有的研究成果已远远滞后于水大流量计量技术现状,且难以满足社会对大口径流量仪表自动化、智能化、高准确度的检定校准需求,而这些问题的存在又反过来对流量标准装置的进一步推广和应用造成了制约。设计并开发了一套适用于水大流量标准装置的控制系统,并通过稳定性和流量调节响应时间这两个性能指标对系统性能水平进行了评价,测试结果表明:管路流量处于480～7 800 m3/h范围内的系统稳定性Eq=0.193%<0.2%、流量从0提升至8 500 m3/h的稳定流量对应的系统响应时间约为110 s,其性能水平较为出色。     

复合铝热剂配方及其性能研究

为了改善铝热剂的点火和燃烧性能,采用均匀设计法对Al-Fe₃O₄、Al-Ba(NO₃)₂和Al-MnO₂进行配方优化设计,然后选用SPSS(statistical program for social sciences)软件进行二次回归分析,确定了一种铝热剂配方,并外掺占其质量25%的黏结剂,获得复合铝热剂。研究其燃烧性能,试验结果表明,该复合铝热剂点燃性能好,燃烧过程分成两个阶段,整个燃烧时间持续约140 s,最高燃烧温度达1 893.32 K,能够形成较好的高温纵火效果,30 g复合铝热剂能够可靠熔穿2 mm铝板。     

空调建筑复合墙体热工性能的计算分析

本文首先对夏热冬暖地区空调建筑复合墙体的研究及应用情况进行了调查分析,然后对该地区常用的外墙主材与保温材料EPS板和XPS板进行复合计算,得出了这些复合墙体的热工性能参数,并结合《夏热冬暖地区居住建筑节能设计标准》的墙体热工要求,对其进行了节能性分析。     

基于流变学的CNTs/SBS复合改性沥青性能及储存稳定性研究

为了探究碳纳米管(CNTs)对苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青的高低温性能及储存稳定性的改善效果,采用动态剪切流变试验(DSR)与弯曲梁蠕变试验(BBR)对CNTs/SBS复合改性沥青的流变特性进行评价,并基于软化点差值、流变学指数和荧光显微镜图像分析胶结料中聚合物分散状态。结果表明：CNTs加入后进一步增强了SBS改性沥青的高温抗车辙性能,且随CNTs掺量增加,高温性能逐步提升。CNTs的加入对改性沥青低温蠕变性能有不利影响,1.0%CNTs掺量下复合改性沥青更具性能效益。CNTs可以显著地提升SBS在沥青中的分布状态,CNTs与SBS形成均匀网状结构,在提升储存稳定性的同时具备增强沥青抗变形的能力,且CNTs的最佳掺量为1.0%。     

浅谈GPS的定位原理及误差分析

简述了全球定位系统（GPS）的基本结构和测量原理，总结了GPS应用的特点，分析了影响GPS测量精度的误差来源，并对减小误差的方法进行了初步的探讨。     

300kV复合套管抗震性能分析和试验

GIS设备是输配电系统的重要构成部分,其市场容量与电力事业的发展紧密相连,因此对于GIS设备及其连接模块的抗震也相应提出了更高的要求.本文以300 kV复合套管为研究目标,对套管、钢架支撑进行三维建模和有限元分析.采用静态系数法来模拟复合套管和钢架支撑在0.5 g峰值加速度下的应力及应变响应,并进一步通过公式和第四强度...     

带钢活套控制系统的工作原理及应用分析

本文介绍了南钢带钢厂活套控制系统的工作原理和应用情况,分析了现场使用中出现的问题,并提出了操作规范及改进措施,为该系统的科学运行提供了帮助。     

空心球/铝基复合泡沫材料制备及性能研究

采用粉末冶金技术制备了不同孔隙率的空心球/铝基复合泡沫材料,对其进行T7热处理,并开展了不同孔隙率材料压缩性能及隔声性能的测试。结果表明,制备的泡沫材料中空心球均匀分布于基体内,且空心球与基体之间形成明显的过渡层;空心球/铝合金基复合泡沫材料的压缩应力-应变曲线呈现线弹性、应力平台、致密化3个阶段。随着孔隙率的增加,空心球/铝合金基复合泡沫材料的压缩峰值应力、平台应力及能量吸收能力均呈先上升后下降的变化趋势;随着孔隙率的增加,复合泡沫材料隔声性能逐渐下降。     

Method for measuring the resonant frequency of an oscillating system

A method for measuring the resonant frequency of an oscillating system providing high accuracy under low Q-factor conditions and a distorted form of amplitude-frequency characteristic of the oscillating system is proposed. A structural diagram of the device is described and time charts are provided explaining the operating principle and advantages of the proposed method.Translated from Izmeritelnaya Tekhnika, No. 9, pp. 49–53, September, 2004.     

恒电流系统直流推进电机的模糊控制

根据对恒电流双闭环控制系统的分析，提出了基于模糊控制理论的直流推进电机调速设计方法，建立了相应的模糊控制规则,仿真结果表明，通过在原控制系统速度调节器两端并入模糊控制器，系统的抗干扰能力和动态性能都有了明显提高。     

交流伺服电机动态定位系统基于高速终端反馈的改进

介绍了交流伺服电机定位系统静态定位工作原理,提出了在动态定位时遇到的精度不足的问题．在对动态精度问题产生原因进行分析的基础上,给出了一种基于高速终端反馈的解决办法．     

Active aeroelastic flutter analysis and vibration control of supersonic composite laminated plate

The active aeroelastic flutter analysis and vibration control at the flutter bounds of the supersonic composite laminated plates with the piezoelectric patches are studied. The piezoelectric patches are bonded on the top and bottom surfaces of the composite laminated plate to act as the sensor and actuator so that the active aeroelastic flutter suppression and vibration control for the supersonic laminated plate can be conducted. The unsteady aerodynamic pressure in supersonic flow is computed by using the supersonic piston theory. Hamilton’s principle with the assumed mode method is used to develop the governing equation of the structural system. The controller is designed by the velocity feedback and proportional feedback control algorithm, and the active damping and stiffness are obtained. The solutions for the complex eigenvalue problem are obtained by using the generalized eigenvalue methodology. The natural frequencies and damping ratios are also gotten. The aeroelastic flutter bounds of the supersonic composite laminated plate are calculated to investigate the characteristics of the aeroelastic flutter. The impulse responses of the structural system are calculated by using the Houbolt numerical algorithm to study the active aeroelastic vibration control. The influences of ply angle of the laminated plate and the control method on the characteristic of flutter and active vibration control are analyzed. From the numerical results it is observed that the aeroelastic flutter characteristics of the supersonic composite laminated plate can be improved and that the aeroelastic vibration response amplitudes can be reduced, especially at the flutter points, by the proportional feedback or the velocity feedback control algorithm using the piezoelectric actuator/sensor pairs. The effectiveness of the flutter control by the two control algorithms is also compared. The results of this study are of great significance to the flutter analysis and aeroelastic design of the aircraft.     

基于梳状扇形孔周期性结构的纵-扭复合模态超声振动系统

纵-扭超声振动系统可以提高加工效率与精度、增加表面强度,因而日益受到青睐,但是现有的纵-扭振动系统存在扭转分量较小,转化效率低等问题,基于此,论文对基于周期性结构的复合模态超声振动系统进行了研究,通过有限元仿真对复合模态周期性结构换能器的振动模态、谐振频率等特性进行分析验证。研究结果表明,两维梳状扇形孔周期和斜槽结构,可以增大纵、扭振振幅,位移旋度和剪切应力以及法向应力等,从而提高纵-扭转化能力。     

多共振消声器串联系统声学特性分析及应用

针对内燃机进气系统需良好的低频消声效果而可用空间有限的问题,研究多个消声器串联后的声学特性。基于共振消声器集中参数模型,推导消声器串联后系统主消声频率公式并验证。结果表明,双共振消声器串联系统有两主消声频率,即小于、大于下端消声器的偏频;增加体积比时较小的接近偏频,较大的远离偏频;长度比等于1、面积比小于等于1时串联系统所需体积小。串联系统消声器结构参数均相同时主消声频率个数与消声器个数相同。基于此,对某商用车进气系统进行降噪设计,使200 Hz以内的传声损失整体提高约5 dB。     

模糊PID控制在光电跟踪控制系统中的应用

频率特性法和PID控制是光电跟踪控制系统中普遍采用的方法,对于稳态过程它们具有良好的控制性能,但对控制环境以及目标状态发生较大变化时却无法处理。介绍一种既能改善控制系统的过渡过程、减小超调量,又能保证系统跟踪精度的模糊PID控制算法,并给出了相应的实验数据。实验结果表明,模糊PID控制可显著改善控制系统对高速动态目标的捕获跟踪能力,提高跟踪精度,增强系统的鲁棒性。     

绳系单体系统面内运动的定位控制

建立了绳系单体系统的非线性动力学模型,分析了弱非线性条件下受控系统的稳定性.设计了一实验系统并对绳系单体系统的面内运动进行了定位控制研究.实验结果表明,计人摩擦补偿的线性力反馈控制可以有效抑制原非线性系统的面内运动.     

The performance analysis and design optimization of fuel temperature control for the injection combustion engine

The purpose of the paper is to analyze the performance and design optimization of fuel temperature control in the injection combustion engine. There is a fuel temperature control device designed between the injection and fuel pump to cool down or warm up the fuel. Thermoelectric module (TEC) chips are applied in the device to absorb or dissipate heat from the fuel. There are several results relating exhaust emission and engine output performance to fuel temperature in this paper to display the optimization of fuel temperature for the injection engine. The experimental results indicate that increasing fuel temperature will result in an increase in CO, HC, and in a decrease in NO_x. Increasing the fuel temperature may affect the fuel consumption and engine output for a gasoline engine at different A/F (air to fuel) ratios. With enhanced understanding and analyses, the effects of fuel temperature on engine performance, fuel consumption and emissions can be taken into account in engine design and evaluation.     

Transient analysis and control of delaminated composite plates in hygrothermal environment using active fiber composite actuator

Abstract

In the present article, the transient analysis and control of delaminated composite plates under hazardous environmental conditions using active fiber composite (AFC) is discussed. Top and bottom layers of the laminated composite plate are embedded AFC layers. The present investigation utilizes AFC as an actuator and sensor. A finite element model for centrally located delamination is developed and coded in Matlab. The proportional controller is used to control the undesirable response in real time. The transient response of the smart delaminated plate is studied for different temperatures and moisture conditions. The feedback control of the dynamic response is performed with the help of velocity and displacement feedback gain to the AFC actuator. The key observations from the numerical studies are; the dynamic response and the frequency response of composite plate increase due to delamination and also with the increase of the temperature and moisture concentrations. The response reduces when the feedback control loop is activated. So, the overall performance of the delaminated plate structure in hygrothermal environment may be enhanced.