便携式土壤水分测试系统设计

土壤水分含量不仅对农作物生长有较大的影响,而且对越野车辆地面通过性也有重要的影响.设计了一种基于时域反射法的土壤含水量测试系统.通过直接数字频率合成器(DDS)产生电磁波测试其介电常数;然后利用介电常数-含水量经验模型得出土壤含水量.系统还配备了GPS接收系统,能记录每次测量的经纬度坐标,并且根据经纬度地名对照表在记录中存储相应的地名.系统通过扩展存储容量使测试记录数可达上万条,并且能通过串口把数据上传到计算机中进行进一步处理.该测试系统具有便携、快速、原位测量的特点,便于构建时空尺度的土壤含水量演变立体分布图,为车辆地面通过性判断提高依据.     

GZB-104型双桥电阻应变压力传感器

GZB-104型双桥电阻应变压力传感器(以下简称双桥探头),是天津市自动化仪表六厂于近年来试制成功的新产品。其样机性能符合技术条件,现场运行正常,满足了设计要求。一、概述双桥探头是用于建筑、交通、水利、矿山等工程勘察中测量地层土壤阻力和摩擦力的传感器。它与我厂生产的XWD-261型小型长图自动平衡记录仪配套,可以组成一个自动测量、记录系统,将地层不同深度的土壤阻力和摩擦力转变成电信号並自动记录在仪表上。工程地     

液位测量中的信号采集与处理

在超声波探头上施加一电脉冲信号,探头发出超声波,在遇到不同介质界面时被反射,超声波探头接收回波并将之变为电脉冲信号。利用P89LPC935的捕捉功能测量发射波和回波之间的时间间隔,通过环境温度测量准确测量出超声波传播速度,进而测量出超声波的传输距离,通过这种方法测量出液位高度。     

基于高频电容原理的土壤剖面水分传感器研究

为了实现土壤剖面不同深度的水分测量,基于高频电容原理,研制了一种能够自动、连续监测土壤剖面动态含水量的水分传感器。通过实验,建立了传感器数学标定模型,并对传感器进行了相关性能测试。通过对比分析土壤水分实际值与传感器测量值,结果表明:传感器最大绝对误差为-5.10%。传感器测量水分梯度变化明显,可用于土壤剖面不同深度水分的测量,具有低成本、低功耗的特点,可应用于农林业实际生产。     

一种多通道超声波测厚系统的研究

本文主要对超声波多通道实时在线测厚系统进行了以下几个方面的研究:超声波的传播特性、超声波传感器测厚原理、多通道测厚模型的建立、超声波多通道测量探头的分布及其触发方式、数据的微机化处理方法.系统将被测参数经超声传感器换成模拟信号,再由模拟输入通道进行信号调理和数据采集,转换成微机要求的数字形式送人微机进行必要的处理.介绍...     

基于KL25的高精度无盲区超声波测距系统

在双探头近距离的超声波测距系统中,存在着测量精度不高的问题,并且距离越近误差越大,在测量距离小于10 cm时,由于探头之间的相互影响,将导致无法测量该段距离。本系统根据超声波传播过程中的叠加原理,通过分析探头之间干扰波与从被测物反射的回波的相互叠加,从而消除在近距离测量时的测距盲区。在发射和接收探头之间距离不同时,分析其对测量误差的影响,选择最理想的探头放置距离,并且结合温度对声速传播的影响,设计出近距离高精度无盲区超声波测距系统。     

超声波液体密度传感器

介绍了超声波密度传感器的工作原理和超声波探头的选择与制作工艺要点。所设计的硬件电路包括发射电路、放大接收电路和检波整形电路。超声波传播时间的测量是通过ATMEGA16L单片机内部的高速计数器实现的。针对环境温度对密度的测量有较大的影响,采用集成温度传感器AD590与单片机共同完成温度补偿。经测试证明:传感器的准确度达到±0.25%。     

TY—1000数字式土壤坚实度仪

介绍一种土壤坚实度测量仪,它能测量探头入上深度及该深度土层的土壤坚实度值,实现了定深度自动采样土壤坚实度值,该仪器使用方便,测量精度高,功耗低,特别适合于野外测试.     

一种高精度超声波测距系统的设计

设计了一种收发一体式超声波测距系统,在硬件设计上选用高速单片机W77E58做微处理器,提高测量时间的分辨率.超声波接收电路中的自动增益控制(AGC)电路有效地解决了远距离测量时回波信号过于微弱而导致系统测量误差加大的问题.在软件设计上考虑系统的硬件响应时间和超声波探头的压电材料与探头表面的距离,对测量结果进行修正.实验结果表明:测距精度高、重复性好,可靠性高.     

模糊逻辑控制系统研究

汽车倒车防撞系统在车辆倒车时利用模糊逻辑控制方式,通过安装在车身上的5个超声波探头测量汽车两侧及车尾与障碍物的距离,当车上装的探头与障碍物的距离大于设定的极限值发出声音报警,提醒驾驶员而实现安全倒车。本文介绍了超声波测距工作原理;并对汽车倒车系统进行仿真实验,通过仿真、实验验证了本系统的可行性和有效性。     

Remote flood monitoring system based on plastic optical fibres and wireless motes

This paper summarises an effort in the development of a remote flood monitoring system based on plastic optical fibre (POF) sensors and a wireless mote network. The wireless mote, comprising of a network of MICA2DOT™ units, was used as a platform to monitor and record the signal from the POF sensors and transmit this information to a base station wirelessly. A prototype of the integrated wireless POF sensor unit has been constructed, rendering it possible to deploy the autonomous unit remotely at multiple monitoring points as required. A flood monitoring simulation was carried out in a 24 m × 10 m × 0.9 m wave basin where four of these wireless optical fibre mote sensors were used to detect the rising water level in the basin. The novelty of the work lies in the successful integration of the wireless platform to a POF-based liquid level sensor and the subsequent demonstration of the prototype of the system for the purposes of flood monitoring applications.The sensing principle of the POF sensor developed here is well-known and is based on the loss of total internal reflection of the optical signal as the sensor probe comes in contact with the liquid. Compared to optical fibre-based sensors reported previously in the literature, the probe profile used in this study differs in terms of its simplicity in design, while exhibiting an excellent signal intensity loss ratio without the need for additional attachments to the probe such as optical prisms. The tests carried out showed that the POF sensor is capable of detecting a variety of fluids. Exhibiting good signal stability, the sensor also detects the liquid level reliably when the liquid rises or falls to the predetermined level. The responsiveness of the optical fibre sensor was evaluated by simulating different rates at which the liquid rises by immersing the sensor tip into the liquid and vice-versa at various speeds ranging from 1 mm/min to 500 mm/min.     

履带车辆软土通过性能影响因素仿真

研究履带预张力对车辆软土通过性能的影响规律. 采用MSC Adams软件的ATV工具箱建立履带车辆与地面的相互作用模型. 仿真结果表明,适当增加履带预张力可有效降低车辆的平均最大压力并提高其挂钩牵引性能. 该结论对履带车辆的设计者和使用者有一定的指导意义.     

Agent oriented intelligent fault diagnosis system using evidence theory

Multi sensors fusion is a very important process for fault diagnosis system. Information obtained from multi sensors need to be fused because no single sensor can get all the information for fault diagnosis. Moreover, information from different sensors may be uncertainty, inaccuracy, or even conflicting. Evidence theory can be used for information fusion, which is regarded as an extension form of Bayesian reasoning, but it has a better fusion result by simple reasoning process using belief function without knowing the prior probability. All the information collected from multi sensors in the system can be described as the evidence for diagnosis so that the fault diagnosis problem can then be modeled as a problem of evidence fusion and decision. In this paper, the classical Dempster-Shafer evidence theory is discussed, and the disadvantages of the combination rule are also analyzed. The notion of support degree of focal element is suggested in order to evaluate the conflicts between multi sensors. The new combination rule is then built to allocate the conflicted information from multi sensors based on the support degree of focal element. Furthermore, the decision rules for fault diagnosis are also proposed, as well as the architecture of the agent oriented intelligent fault diagnosis system. Finally, a case study is given to illustrate the performance of the proposed model.     

A2PI型磁场传感器的非线性数学模型

本文在介绍Ａ＾２ＰＩ型磁场传感器原理的基础上,从剖析其电磁转换过程入手,利用等效电路对其暂态过程进行分析,建立该传感器的非线性数学模型。通过详细深入的数学分析和推导,得到非晶态合金在高频下的非线性磁导率的解算方法,从而解决数学模型的非线性问题。     

基于SDI-12总线的生态水文数据采集系统设计与实现

介绍了一种土壤温湿度、盐度、电导率等生态水文数据采集系统。该系统以单片机为核心控制单元,结合土壤参数传感器,设计了传感器接口电路、通信时序控制、SD卡存储电路及显示电路等;同时根据黑河生态水文传感器网络试验对实验的要求,实现了基于SDI-12总线的数据采集器和传感器之间的通信协议,以及生态水文数据的测量、存储及传输。在此基础上,结合网络通信和流域数据管理平台,可以实现完整的生态水文无线传感器网络。     

饱和土有效应力传感器的研制

饱和土有效应力传感器是岩土介质力学测试中所急需的一种传感器,通过对饱和土中孔隙水压力传感器的分析,建立了传感器滤水结构动态特性的数学模型,通过对该模型动态响应特性的分析,设计的传感器能有效应用于动态荷载作用下饱和土有效应力的测试,试验和实际应用效果良好。     

高g光学微腔加速度计的结构设计

针对高量程加速度测试需求,提出了一种基于光弹效应的新型光学加速度传感器;利用MATLAB软件和时域差分有限元(FDTD)对微环谐振腔悬臂梁加速度计的结构进行优化设计,详细分析了波导传输模态,传感器灵敏度以及工作带宽与波导尺寸、微悬臂梁尺寸的关系。在优化设计的基础上,通过ANSYS软件对悬臂梁的抗冲击性能进行仿真,其抗冲击可达104gn,灵敏度为10-2pm/gn,能有效满足高冲击、强烈振动场合的特殊测试要求,可以应用于侵彻系统,并为集成小型化高灵敏抗冲击微光机电系统(MOEMS)传感器提供理论参考。     

Divide-and-conquer architecture based collaborative sensing for target monitoring in wireless sensor networks

Most surveillance applications in wireless sensor network (WSN) have stringent accuracy requirements in targets surveillance with maximized system lifetime, while large amount of continuous sensing data and limited resource in WSNs pose great challenges. So it is necessary to select appropriate sensors that can collaboratively work with each other in order to obtain balance between accuracy and system lifetime. However, because of sensing diversity and big data from WSN, most existing methods can not select appropriate sensors to cover all critical monitoring locations in large scale real deployments. Accordingly, an AdaBoost based algorithm is first proposed to identify valid sensors with contribution towards accuracy improvement, which can reduce computation and communication overhead by excluding invalid sensors. The valid sensors are combined and work in a collaborative way, which can obtain better performance than other ways. Then, because of independence of each monitoring location, a divide-and-conquer architecture based method (EasiSS) is proposed to select the most informative sensor clusters from the valid sensors for critical monitoring locations. EasiSS can obtain higher classification accuracy at different user requirement. Finally, according to the experiment on real data, we demonstrate that our proposed method can get a better performance of sensor selection, comparing with traditional methods.     

非等齿耦合位移传感器的研究

为了提高位移传感器的测量精度,在最大开槽数一定时获得更多的极对数。对原有时栅位移传感器进行改进,提出了一种新的位移传感器结构,介绍了传感器的工作原理和结构。该传感器在最大开槽数一定的情况下,可以得到较多的极对数和测头数,从而利于提高测量精度。通过实验得出以高精度光栅为基准时传感器的角位移测量误差为±6.5″。