基于温度激励的植物茎流采集系统的研究

发布时间：2019-01-30 21:37

【摘要】：树干边材液流速率是研究整株树木蒸腾规律的重要指标。目前主要的测量方法中,热扩散法和热脉冲法由于需要获取零茎流速率参照值,根据经验公式来推算茎流速率,存在引入误差和在不同树种间通用性差等缺陷;另外现有市场上的茎流测量产品存在价格昂贵、稳定性不好等问题。针对上述问题,本文研究了一种改进热脉冲法的测量技术,基于热示踪原理,设计了一种“温度峰-峰值”茎流测量方法,克服了标准参数获取、通用性差等问题,并开发了一套完整的植物茎流采集系统设备,采用便携式结构,传感器安装简便。本文研究内容包括以下几个方面:(1)根据“温度峰-峰值”测量方法的需求,设计了一种插针式茎流传感器,通过优化结构设计,实现了传感器热量注入的高精度、可重现性控制以及边材液流温度变化的高灵敏度感知;设计了相应的传感器信号处理电路和数据采集模块,并基于MCGS组态软件设计上位机系统。(2)通过分析树干边材液流的特征,结合实际试验总结边材液流传导热量引起温升曲线的变化特点,设计了高频率采样、门限检测、软件滤波、多次校验的峰值捕捉方法,在北京市农林科学院内以杨树、梧桐树、枣树、侧柏四个树种为样本进行的测试结果表明观察“峰-峰值”现象的最佳间距为30mm到35mm。(3)研究植物伤口机理、环境因子对测量精度的影响,根据Swanson等提出的数值计算模型模拟热对流及传导现象得出的伤口修正模型,对误差进行修正。通过搭建模拟测量系统和实体测量对系统进行测试:模拟测量结果与实际流速之间的差值低于0.01 mm/s;以杨树为样本进行的多组实体测量结果显示,测量数据重复性好,日茎流变化趋势一致,表明本文设计的茎流传感器及其数据采集系统稳定可靠。
[Abstract]:The sap flow rate of sapwood is an important index to study the transpiration of the whole tree. At present, the main measuring methods are thermal diffusion method and thermal pulse method, because of the need to obtain the reference value of zero stem flow rate, according to the empirical formula to calculate the stem flow rate, there are some defects such as introducing error and poor generality among different tree species. In addition, the existing market stem flow measurement products are expensive, poor stability and other problems. In order to solve the above problems, an improved thermal pulse method is studied in this paper. Based on the principle of thermal tracer, a "temperature peak-peak" stem flow measurement method is designed, which overcomes the problems of obtaining standard parameters and generality. A complete plant stem flow acquisition system is developed, which adopts portable structure and is easy to install. The research contents of this paper include the following aspects: (1) according to the requirement of "temperature peak-peak" measurement method, a stylus type stem flow sensor is designed. By optimizing the structure design, the high precision of heat injection is realized. Reproducibility control and high sensitivity perception of temperature change of sapwood liquid flow; The corresponding sensor signal processing circuit and data acquisition module are designed, and the upper computer system is designed based on MCGS configuration software. (2) the characteristics of sap flow of sapwood are analyzed. The characteristics of temperature rise curve caused by heat conduction from liquid flow of sapwood were summarized, and the peak capture method of high frequency sampling, threshold detection, software filtering and multiple check was designed. Poplars and sycamore trees were used in Beijing Academy of Agriculture and Forestry Sciences. The test results of four species of jujube and Platycladus orientalis showed that the best distance between peak and peak was between 30mm and 35mm. (3) the mechanism of plant wound and the effect of environmental factors on measurement accuracy were studied. According to the numerical model proposed by Swanson et al to simulate the heat convection and conduction phenomena, the wound correction model is obtained, and the error is corrected. The system is tested by building a simulated measurement system and a solid measurement system: the difference between the simulated measurement results and the actual velocity is less than 0. 01 mm/s; The results of multi-group solid measurement with poplar as the sample show that the measured data have good repeatability and the trend of daily stem flow change is the same, which indicates that the stem flow sensor and its data acquisition system designed in this paper are stable and reliable.
【学位授予单位】：湖南工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S126;TP274

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