Research On Assembly Of Miniaturized MEMS Wind Sensor

Wind sensors play an important role in many fields such as weather forecasting,navigation engineering,agricultural production and industrial control.Compared with traditional wind sensors,MEMS thermal wind sensors have the advantages of small size,high accuracy and easy mass production.With the operating environment of wind sensors becomes more and more diverse and complex,the handheld and miniaturization of wind sensor has gradually become a trend.The size of sensor developed by research team in the early stage is relatively large and is restricted in a special using environment.Therefore,the design and implementation of miniaturized MEMS wind sensor are proposed.With the purpose of reducing the overall size of the sensor,improvements are made through the modification of the shell and hardware circuit,the contents and highlights of the thesis include:(1)By means of simulation and experiment,the influence of structural parameters of aerodynamic housing on the sensor is studied,including the number,diameter,height of pillars and the curvature of the curved top cover.First,simulation software COMSOL is applied to create a physical model of sensor,the influence is analyzed by changing a certain structural parameter while remaining other parameters unchanged.The simulation results show that the smaller the pillar diameter,the better the symmetry of the sensor,but too small size will reduce the mechanical strength.Taking both the performance and mechanical strength into account,the pillar diameter is selected as 1mm;when pillar number is greater than 32,the sensor is less affected by the angle of the wind direction,but as the number continues to increase,it will cause turbulence.Considering symmetry and laminar flow,the pillar number is selected as 32;the reduction in the height of pillars will improve the speed performance of sensor.However,if the pillar is too low,it is easy to create turbulence.As a result of considering both the performance and laminar flow,the pillar height is selected as 0 mm;compared with the flat top cover,the curved top cover can reduce the wind speed inside the housing and indirectly expand the range.In addition,the smaller the curvature,the greater the reduction.On this basis,housings of different sizes was fabricated by using 3D printing technology and tested in the wind tunnel.The results show that the experiment was basically consistent with the simulation,as to determine the optimized structure parameters of the housing,which provided a basis for the manufacture of the housing.(2)In order to achieve the application requirements of miniaturization of MEMS wind sensor,the assembly shell parts and measurement and control circuits that meet the size requirements of the project were designed and realized,and the packaged sensor is assembled.All of the assembly parts are all fabricated by using 3D printing technology,the measurement and control circuit was realized through PCB technology.The CTD heating control module is made of to achieve the control of temperature difference between chip and environment.C8051F411 MCU is employed as the control device of the senor system to sample the heating voltage of chip and the signal of temperature difference between upstream and downstream of the chip.The sampling,filtering and calculation of wind speed and direction information are achieved through software algorithms.What's more,the information is transmitted to the LCD display screen in real time through the IIC protocol in order to complete the interaction.After measurement,the assembled sensor has a diameter of 4.5cm,as well as one PCB circuit board of 3cm in diameter,which are all significantly reduced compared with the sensor currently developed by research group.(3)Performance test of the assembled miniaturized MEMS wind sensor is carried out,mainly including measuring range,accuracy,benchmark point and power consumption.It is indicated that the wind speed measuring range of the sensor can reach more than 28.1m/s.In the low wind speed(less than 17.5m/s),the wind speed measuring error can be less than 0.5m/s,and within 3.3% when wind speed is high.The wind direction error is less in 4.5°.In addition,there is a slight benchmark drift.When wind speed is zero,the overall power consumption of the sensor is 179 m W,reaches 264.5m W at a speed of 28.1m/s.The performance basically meets the requirements of the miniaturized MEMS wind sensor.