双频率交替法电容土壤水分测试技术研究

发布时间：2018-09-10 16:49

【摘要】：在信息技术和人工智能技术迅猛发展的浪潮下,逐渐产生了对农作物实施定位管理、对农作物进行按需投入等农业生产的精准管理思想,最终形成了精准农业的概念。精准农业中一个极其关键的环节即是获得土壤的各种参数,例如：土壤有机质含量、土壤压实度、土壤电导率、土壤含水量等。这些参数中,土壤含水量是必不可少的。在国内,用来检测土壤含水量的仪器基本都是便携式,而新的时代会提出新的要求,本文的目的是设计一个车载土壤含水量检测系统。目前国内外土壤含水量测量常用方法有以下几种：外观触摸法、烘干法、张力计法、电阻法、中子法、遥感法、时域反射法、频域反射法、驻波率法、电容传感器法等。其中许多方法显而易见不适合车载,只能于实验室使用；有的性能不错,但是成本太高；有的受力则容易损坏。在对土壤含水量检测机理进行探究之后,对比分析了国内外常用的土壤含水量检测方法,结合实际情况,最后选用介电特性法中的电容传感器法为基础来设计车载土壤含水量检测系统。电容传感器法的优点是显而易见的,如容易构建、适合车载、安装简单、操作方便等。本文在电容法的基础上,提出了三种检测方法：附加电阻法；交直流交替法；双频率交替法。并对这三种方法进行了理论分析和数学推导,在比较分析后,采用双频率交替法来测量土壤含水量。首先测量计算出土壤电容传感器的等效电容值,然后依据等效电容值与土壤含水量之间的拟合关系曲线,来获得土壤含水量的值。基于上述原理,作者开发了一套车载土壤含水量检测系统,该系统能实现车载的土壤含水量测量,操作方便,响应速度快,测试数据可以直接显示,也可传输给上位机处理显示,精度较好。为了进一步论证此方法的可行性,在安徽省怀远县龙亢农场进行了实地检测,结果表明：用此方法测量土壤含水量,结果较为准确；土壤含水量与土壤等效电容可近似拟合成直线关系。
[Abstract]:With the rapid development of information technology and artificial intelligence technology, the concept of precision agriculture was gradually formed, such as positioning management of crops, input of crops on demand and so on. One of the most important steps in precision agriculture is to obtain soil parameters, such as soil organic matter content, soil compactness, soil conductivity, soil moisture content and so on. Among these parameters, soil moisture content is essential. In China, the instruments used to detect soil moisture content are basically portable, and new requirements will be put forward in the new era. The purpose of this paper is to design a vehicle-mounted soil moisture detection system. At present, there are several common methods for measuring soil water content at home and abroad: appearance touch method, drying method, tensometer method, resistance method, neutron method, remote sensing method, time-domain reflection method, frequency-domain reflection method, standing wave rate method, capacitance sensor method and so on. Many of these methods are obviously unsuitable for vehicles and can only be used in the laboratory; some have good performance, but the cost is too high; others are easily damaged. After probing into the measuring mechanism of soil water content, this paper compares and analyzes the common methods of soil water content measurement both at home and abroad, combining with the actual situation, Finally, based on the capacitance sensor method of dielectric characteristic method, a vehicle soil moisture detection system is designed. The advantages of capacitive sensor method are obvious, such as easy to build, suitable for vehicle, easy to install and easy to operate. On the basis of capacitance method, three detection methods are proposed in this paper: additional resistance method, alternating AC / DC method and double frequency alternating method. The theoretical analysis and mathematical derivation of the three methods were carried out. After comparison and analysis, the soil moisture content was measured by the double frequency alternating method. The equivalent capacitance of the soil capacitance sensor was measured and calculated firstly, and then the soil moisture content was obtained according to the fitting curve between the equivalent capacitance value and the soil moisture content. Based on the above principle, the author has developed a set of on-board soil moisture content measurement system. The system can realize the measurement of soil water content on the vehicle, which is easy to operate, quick to respond, and can be displayed directly. Can also be transmitted to the upper computer processing display, the accuracy is good. In order to further prove the feasibility of this method, a field test was carried out in Longkang Farm, Huaiyuan County, Anhui Province. The results showed that the method was more accurate in measuring soil moisture content. The relationship between soil moisture content and soil equivalent capacitance can be approximately quasi-synthetic linear.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S152.7

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