【作者】 刘驰；

【导师】 郭文川；

【作者基本信息】 西北农林科技大学 ， 农业电气化与自动化， 2012， 硕士

【摘要】 秸秆是农作物生产系统中一项重要的生物资源。人类对于秸秆的利用由来已久，随着传统农业向现代农业的转变，秸秆的利用技术呈现多样化的发展趋势。含水率是诸多秸秆利用技术的一项重要参考指标，含水率的高低影响着秸秆的贮存及一些主要的加工工艺环节，有时甚至直接决定了其成品的品质，因此对其含水率的检测显得尤为重要。然而现有的秸秆含水率检测的仪器设备较少，且成本过高，传统的加热烘干法又存在周期长，不能实现连续测量等缺点，在一定程度上制约着秸秆的综合利用效率。所以开发一种操作简便，价格低廉，且能实现快速、连续测量的秸秆含水率测量装置显得很有必要。本文在总结现有农业物料含水率无损检测方法研究成果的基础上，基于电容检测法，设计了以AT89S52单片机为核心的秸秆含水率测量仪，并利用相应的含水率预测模型实现了秸秆含水率的检测。本文主要研究内容和取得的成果如下：(1)研究了农作物秸秆含水率对其综合利用技术的影响，提出了基于介电特性的电容检测法的设计方法，并对电容检测法的基本原理及其相关影响因素（温度、容积密度等）进行了深入的分析，进而确立了秸秆含水率测量仪设计的理论依据。(2)设计了以AT89S52单片机为核心的测量仪硬件系统。首先，设计了平行极板式电容传感器，用于测量秸秆电容，DS18B20温度传感器为测温元件，FSR402压力传感器用于秸秆容积密度的间接测量。然后进行了硬件电路的设计，包括电容、温度及压力信号检测电路、A/D转换电路、单片机控制电路、液晶显示电路及功能键模块。最后设计制作了测量仪硬件系统电路板。(3)利用单片机C语言，采用模块化的编程思想编写了测量仪软件系统的整体程序，包括系统主程序、A/D转换、温度采集、液晶显示和含水率计算等模块。(4)以小麦秸秆为试验对象，研究了秸秆含水率、温度、容积密度与其电容之间的变化规律，在此基础上建立了小麦秸秆含水率预测模型，并通过试验验证了模型的合理性，结果表明：该模型的决定系数R2=0.987。(5)对测量仪的含水率检测性能进行了试验验证，分析了试验数据，结果表明：与加热烘干法相比，该测量仪对含水率为10%~20%，温度在5℃~35℃之间变化的小麦秸秆含水率的测量误差为±2.2%，响应时间为2s，具有良好的应用前景。更多还原

【Abstract】 Straw is an important biological resource in the crop production system. Human usestraw for a long time. With the transformation of traditional agriculture to modern agriculture,the utilization technologies of straw present a diversified development trend. Water content isan important reference index for many utilization technologies of straw. Water content affectsthe storage and some of processing links of straw, and sometimes even determines the qualityof its finished products directly, therefore the detection of straw water content is veryimportant. However, existing detection equipments of straw water content are less and tooexpensive, and traditional drying method has many shortcomings, such as long detectionperiod, not continues measurement, to some extent, water content restricts the utilizationefficiency of straw. So, it is quite necessary to develop a straw water content meter withsimple and convenient operating, low price, quickly and continuously measuring. Summariedthe results of existing non-destruction testing methods of water content of agriculturalmaterials, a straw water content meter, based on capacitance detection method and AT89S52microcontroller as core, has designed in this paper, it achieved the detection of straw watercontent by the prediction model of water content.The main tasks and results of this paper areas follows:(1) Studied the impact of water content on comprehensive utilization technologies ofcrop straw, put forward the design method of the capacitance detection method, and made anin-depth analysis on the basic principles and related factors(temperature, bulk density, etc) ofcapacitance detection method. Then the theoretical basis of the straw water content meter wasestablished.(2) The hardware system of the meter, as the core of AT89S52microcontroller, wasdesigned. Firstly, designed the parallel plate capacitance sensor, it used to detect capacitance,DS18B20temperature sensor used to detect temperature, and FSR402pressure sensors used todetect bulk density indirectly. Then, the hardware circuit was designed, it includes detectioncircuits of capacitance signal, temperature signal and force signal, circuit of A/D conversion,SCM controling, liquid crystal display, function keys. Finally, the hardware circuit board ofthe meter was manufactured.(3) The software of the meter was written in C language. It includes system’s primary function, A/D conversion, temperature acquisition, liquid crystal display and water contentcalculating, etc.(4) The straw of wheat was used as experimental subject to study the change law of itscapacitance, water content, temperature and bulk density. A prediction model of straw watercontent was established, and the results of validation proves that the determination coefficientof the model is0.987.(5) The detection performance of the meter was verified by experiment. The results showthat: compared drying method, the meter’s water content detection error is in±2.2%,response time is2s at the water content from10%to20%, temperature from5℃to35℃, andit has good application prospects.更多还原