【作者】 沈晓东；

【导师】 宋飞虎； 朱赟煜；

【作者基本信息】 江南大学 ， 机械工程（专业学位）， 2023， 硕士

【摘要】 风速风向的测量与我们日常生活息息相关,作为气象监测的两项重要指标,对其及时准确测量非常重要。目前气象行业使用较多的测量仪器有杯式风速计、超声波风速计、热式风速计等。虽然上述测量仪器均有各自的优势,但是市场上尚缺乏微型风速风向测量设备。微型化便于携带、部署、移植,同时也是体积受限的应用场合中进一步扩展测量要素和功能或提高续航的重要手段。为了实现整体结构的小型化、集成化、低成本且可同时测量风速风向,本文将基于流场与温度场的相互影响设计一款热场式风速风向传感器,并通过仿真分析与实验研究相结合的方法对传感器性能进行测试。主要研究内容如下:(1)提出了一种基于热温差原理的微型热式测风传感器模型。从热式测风传感器的传热理论出发,分析了传感器工作过程中的三种传热形式,并对热式测风传感器三大测风方式优缺点加以概括,确定了以NTC热敏电阻和加热线圈为感测核心,分布于直径为20 mm圆形薄片底板上的模型结构,传感器采用热温差检测原理。(2)通过流体动力学软件FLUENT研究了热场随流场分布规律并对风速风向判别进行了设计,同时对传感器测风性能影响因素进行了分析。仿真结果表明,热场在风场作用下的高温覆盖区域在±35°左右,八路测温NTC方案可以更有效地获取热场分布信息。基于热场风分布规律,对比高斯曲线拟合和傅里叶拟合测风速风向,发现后者在低风速下仍具备较高地拟合精度。同时,结合仿真分析和对流换热的场协同理论证明1.0 mm加热线圈螺距更有利于对流换热,3.6 mm测温电阻间距,20 mm底板直径以及1.2 mm底板厚度的模型结构可以在保证传感器强度和小型化的前提下具备良好的灵敏度。最后,针对环境温度变化带来的风速大小判定影响,给出了线性插值的误差修正方法。(3)硬件及软件作为传感器系统的核心,合理设计可以大大提升传感器性能。硬件方面选用STM32微处理器作为主控芯片,24位高精度模/数转换器ADS131M08采集热场分布信息,通过地磁计HMC5883L实现传感器自动定北功能。为降低传感器功耗,设计了一种加热功率控制电路方案,可实现恒功率加热与脉冲加热间的转化,并通过软件Multisim验证了电路的可行性。软件方面着重对风速风向测量进行了设计,针对风向测量过程中HMC5883L易受外界磁场干扰的问题,给出了椭圆假设磁场修正方案,保证罗盘精度。(4)为验证传感器性能是否符合设计要求,搭建了风速及风向测试实验平台。实验结果表明,设计的热场式风速风向传感器风速检测范围可达1～30 m/s,精度为0.01 m/s,误差在±(0.5+0.03v)m/s内;风向检测范围在0～360°,精度为0.1°,误差在±5°内。该传感器对环境温度引起的误差进行了线性插值修正,可在-10～40℃环境温度下正常工作,最大系统功耗为0.635 W。更多还原

【Abstract】 The measurement of wind speed and direction is closely related to our daily life.As two important indicators for meteorological monitoring,it is important to measure them timely and accurately.Currently,a number of measuring instruments are employed in the meteorological industry such as cup anemometers,ultrasonic anemometers and thermal anemometers.While all of these instruments have their advantages,there is a lack of miniature wind speed and direction measurement equipment on the market.Miniaturization of measuring instrument is the trend of future development,which facilitates portability,deployment and removal,and is also an important means of further extending measurement elements and functionality or increasing range in restricted environment.To achieve a miniaturised,integrated,lowcost and simultaneous measurement of wind speed and direction,in this project,a thermal wind sensor based on the interaction between the flow and temperature fields was designed,and the sensor was tested through a combination of simulation and experimental studies.The main contents are as follows:(1)A miniature thermal wind sensor model based on the thermal temperature difference principle was proposed.According to the heat transfer theory of thermal wind sensor,three forms of heat transfer during the operation of the sensor were analyzed.Meanwhile,the advantages and disadvantages of the three major wind measurement methods of the thermal wind sensor were outlined.The model was structured by the measuring core with NTC thermistors and a heating coil,distributed on a 20 mm diameter circular sheet base plate.The detection principle of thermal temperature difference was adopted.(2)The distribution law of thermal field in the flow field was analyzed by the fluid dynamics software FLUENT and the wind speed and direction discrimination was designed.In the meantime,the factors influencing the sensor testing of wind speed and direction were also analyzed.The simulation results showed that the high temperature coverage area of the thermal field under the action of the wind field was around ±35°,and the eight-way temperature measurement NTC scheme could obtain the thermal field distribution information more effectively.Compared Gaussian curve fitting with Fourier fitting to measure wind speed and direction based on the wind distribution law of the thermal field,the result showed that the latter still had a higher fitting accuracy at low wind speed.At the same time,the model structure of 1.0 mm heating coil pitch,3.6 mm temperature resistor pitch,20 mm base plate diameter and 1.2 mm base plate thickness could provide good sensitivity while ensuring the strength and miniaturization of the sensor.Finally,a linear interpolation error correction method was presented for the effect of wind speed determination due to ambient temperature variations.(3)As the core of the sensor system,reasonable design of hardware and software could greatly improve sensor performance.The STM32 microprocessor was adopted as the main control chip and the 24-bit high-precision ADS131M08 analog to digital conversion was used to collect the thermal field distribution information.The HMC5883 L,a geomagnetometer,was employed to achieve the automatic north setting function of the sensor.A heating power control circuit was designed to reduce the power consumption of the sensor,which can realize the conversion between constant power heating and pulse heating.The feasibility of the circuit was verified by software Multisim.In the software aspect,the project focused on the wind speed and direction measurement.Targeting the problem that the electronic magnetic compass HMC5883 L is susceptible to external magnetic field interference in wind direction measurement process,an elliptical hypothetical magnetic field correction scheme was proposed to ensure the accuracy of the compass.(4)To verify whether the sensor performance meets the design requirements,a wind speed and direction test platform was built.The experimental results showed that the designed thermal wind sensor could detect wind speed in the range of 1～30 m/s with an accuracy of 0.01 m/s and an error within ±(0.5+0.03v)m/s.The wind direction could be detected in the range of 0～360° with an accuracy of 0.1° and an error within±5°.The sensor was linearly interpolated to correct errors caused by ambient temperature and could operate normally at ambient temperatures from-10 to 40 °C with a maximum system power consumption of 0.635 W.更多还原