【作者】 张亚秋；

【导师】 吴文福；

【作者基本信息】 吉林大学 ， 农业电气化与自动化， 2012， 博士

【摘要】 粮食问题是关系国计民生的重大课题，粮食的安全储藏显得尤为重要。利用干燥设备降低水分是粮食安全储藏的重要环节。而在粮食干燥过程中，水分在线检测和控制是制约干燥环节的主要问题。由于影响因素复杂，直接测量其含水率比较困难，一般通过测量影响粮食含水率的一些因素(如粮食温湿度、热风温湿度和粮食重量变化等)间接测量。而测量影响粮食含水率的这些间接因素很方便。如果要利用其实现控制，就需要对所测变量与粮食含水率建立关联，然后通过控制某个或某几个因素的方法间接控制粮食的出机含水率，从而实现粮食干燥过程的自动控制。本文在对粮食干燥过程水分检测和控制的综合研究分析基础上，研究不同干燥阶段玉米温度变化特点及玉米温度与含水率的变化关系，探索了利用玉米温度变化率进行水分预测的可行性；研究了基于粮仓局部压力和总重量变化的粮食水分检测的方法；最后基于现场总线和触摸屏技术开发了玉米干燥过程智能控制系统。本文是依托于“十二五”国家科技支撑计划项目“粮食保质节能烘干技术与装备的研究开发与示范”的子课题“粮食干燥数控技术及真空组合干燥工艺”中的内容开展的工作，从理论和试验两方面研究粮食干燥过程水分检测与自动控制。主要研究内容如下：1、通过数值模拟研究了玉米深层干燥过程中温湿度变化特点及二者的关系，建立了玉米温度与含水率的模拟方程，并进行了实验验证；探讨了利用玉米温度变化率控制水分的可行性；2、从理论和实验两个方面，研究了矩形筒仓内动静压力与含水率之间的变化关系，以此探讨了利用仓内饱和压力检测含水率；3、研究了压力式水分传感器的结构及数据采集系统，采用BP神经网络对温度的非线性校正，实现了水分在线检测；4、建立了基于粮食总重探测的循环式干燥机模拟系统，分析了粮食总重量变化对水分的影响，为实际干燥过程控制奠定了基础；5、开发了基于现场总线和触摸屏技术的玉米干燥过程智能控制系统，成功与实际干燥机配套使用，可通过粮食总重量、粮食温度及机内饱和压力三种方式实现粮食水分的检测和控制。更多还原

【Abstract】 Food is a major topic of people’s livelihood, food security storage is particularlyimportant. Use of grain drying equipment to reduce grain moisture is an important part ofsafe storage of food. While in the process of grain drying, on-line monitoring and control ofwater is a main restricting issue. As the impact of complex factors, direct measuring isdifficult, while some indirect affecting factors are easy to measure. Generally grain moistureis indirectly measured by measuring some affecting factors such as grain temperature, airtemperature and overall grain weight change, etc. For more precise control, you need tomeasure these variables, and then by controlling one or a few factors to indirectly control thewater content of the discharge, in order to achieve automatic control of the grain dryingprocess.On the basis of comprehensive analysis and study of moisture monitoring and controlduring food drying process, the paper made numerical simulation analysis of the corndeep-bed drying process, study the change characteristic of corn temperature and therelationship between the temperature and moisture change of corn. explored the feasibility ofmoisture prediction by change rate of corn temperature; studied grain moisture detectionmethod based on the change of the partial pressure and the total weight of granary; at leastdeveloped intelligent control system based on fieldbus and touch screen technology. Thisresearch work is based on the sub-project CNC Grain Drying technology and VacuumCombination Drying Process from12th Five-Year National Science and Technology SupportProgram: Research, Development and Demonstration of Grain Energy-saving and QualityDrying Technology and Equipment. From both theoretical and experimental aspects, thegrain drying process moisture detection and automatic control were studied. The maincontents are as follows:1. Researched the relationship and changes between temperature and humidity duringdeep-bed drying process by Numerical Simulation; established the simulation equations ofcorn temperature and moisture content. And carried out a series of experimental verification;explore the feasibility of using changing rate of corn temperature to control water;2. From both the theoretical and experimental aspects,studied the changing relationshipbetween the static-dynamic pressure and moisture content in the rectangular silos, in order to investigate the detection of moisture content using the saturated pressure;3. Studied the structure and data acquisition system of the pressure-type moisture sensor,using the BP neural network nonlinear correction for temperature to detect water online;4. Established the simulation system of circulating dryer based on the detection for thetotal grain weight, analyzing the impact of total mass change on the water, and laid thefoundation for the control of the actual drying process;5. Developed a intelligent control system for corn drying process based on fieldbus andtouch-screen technology, succeed in using the actual dryer to, the total grain weight, graintemperature and saturation pressure within the machine are three ways to achieve thedetection and control of food moisture.更多还原