Optimization For The Design Of MEMS Thermal Wind Sensor System

MEMS wind sensor was studied by many researchers due to its advantages of low power consumption,miniaturization and intelligence.In order to make it more widely used in meteorological testing,agricultural production and all aspects of daily life,the study of optimization is also ongoing.In this thesis,the existing compensation methods and limitations of the temperature drift of the thermal wind sensor in the laboratory are first analyzed.Then a software method to realize the MEMS thermal wind sensor system operated on constant temperature difference(CTD)mode is proposed.The purpose of using software modules instead of the original Wheatstone bridge to obtain temperature information and using MCU to achieve CTD control is to eliminate the temperature drift caused by the difference in the temperature coefficients of the temperature measurement elements when using the Wheatstone bridge for temperature difference information sampling.Meanwhile,it is possible to control heating power precisely.The main contents of this project are as follows:(1)Carrying out the design of hardware circuit and software module for the wind sensor system,and the current flowing through the heating element is changed by the feedback control in order to adjust the heating power to achieve CTD control for the system;(2)Carrying out the optimal design and experimental verification of the key links in the software algorithm.The temperature sampling and filtering algorithm and the CTD control core algorithm are optimized and the recursive mean filtering algorithm and the PID algorithm are determined as the final scheme of the system software algorithm;(3)Testing the performance of the optimized wind sensor system;(4)Carrying out analysis and experimentally verification of the static temperature drift characteristics of the system and then conforming that the drift mainly comes from the detection error of the temperature coefficient of the temperature measurement elements and then conducting compensation.The test of the system shows that under a temperature difference of 15?,the system has a wind speed measurement range of Om/s to 19m/s with the sensitivity of 4.5mW/(m · s-1)at low wind speed section and 1.7mW/(m · s-1)at high wind speed section and its response time is less than 40s.And the maximum sensitivity of the x-direction and the y-direction is 22.4 mV/(m·s-1)and 14 mV/(m·s-1)respectively.Thus the wind detection can be achieved basically.Besides,after compensation,the test about temperature shows that the static output power of the system changes only 2mW when the ambient temperature changes from-20? to 40 ?,resulting in a change of the static wind speed output value less than 0.5m/s.Thus the static temperature drift has been improved.