The Research And Design Of Ultrasonic Wind Measurement System Based On ARM

With the development of science and technology,the measurement of wind speed and direction is widely used in military,meteorological monitoring,navigation and aviation. The current commonly used wind measurement instruments including mechanical anemometer, laser doppler anemometer and ultrasonic anemometer, the ultrasonic anemometer with no moving parts, low mechanical loss,have gradually become the mainstream wind instrument When the ultrasonic propagate stationary distance in the air,there is a spread time delay between downwind and headwind,the time delay has a linear relationship with the measured wind speed. So this time delay has become a key factor in the wind speed measurement system,how to improve the measurement accuracy of this time delay ,which has become the key elements of this thesis.Wind speed is measured by the propagation time of ultrasonic waves in the downwind and upwind, the measurement of ultrasonic propagation time is related to the accuracy of wind speed ,time delay estimation algorithm is an important method to improve the accuracy of ultrasonic anemometer.In order to improve the precision of time delay estimation, this article proposes a phat weighted cross correlation time delay estimation algorithm based on lms.Firstly, the ultrasonic signal received by the sensor is adaptively filtered to improve the similarity of the received signal. the signal is weighted by phat to improve the signal-to-noise ratio (SNR) and obtain the accurate time delay estimation.Experimental results show that the proposed method have a stronger anti-noise performance and improve the accuracy of time delay estimation.Because of the complexity of signal processing, the system uses a 32 bit microprocessor LPC1768 as the control core ,designing the main control board,the transmitter board and the receiving board.The transmitter board including ultrasonic driver circuit ,the drive circuit can drive ultrasonic transducer ;The receiving board mainly comprise a preamplifier circuit, a filter circuit, a detection circuit and a threshold comparison circuit.The serial port communication circuit can transmit wind speed and wind direction data to the remote observation platform.For the software part, the software part using modular programming,including the start code,system initialization, ultrasonic transceiver module, wind speed calculation module. By using visual c software tools, the article develop a PC based c language, it is a real-time monitoring system with the storage of measurement data and analysis data.