| China has a vast territory and many rivers.In the process of national social development,the comprehensive utilization of river water plays an important role.River water generally flows downstream along the terrain as a source in high mountains,and finally flows into the ocean or lake.With the rapid development of China’s economy,the management and management of river water environment need to use scientific and technological means and methods,which is a complex system engineering.In the northeast of China,the average temperature is usually around-20℃ in winter,and the river water will freeze.In this case,there are many difficulties in the measurement of the flow velocity of the river under the ice: firstly,the temperature is low,and the field measurement environment is very bad;secondly,there are ice flowers in the river under the ice layer;the existing measurement method is to break the ice and put the flow velocity measurement instrument in the water,which is the measurement method.The method needs a fast time to measure the velocity.If the measurement time is too long,the river will be frozen again,which will cause great damage to the measuring instruments.Most of the current river current meters are used to measure the velocity of the ice free river,but few are used to measure the velocity of the ice water.Based on this situation,this paper designs a measuring device based on Ultrasonic Doppler method,which can measure the velocity of river water without breaking ice.By collecting and receiving the difference value of Doppler frequency shift signal and calculating with formula,the device can realize the function of measuring the velocity of river under ice.Based on the Ultrasonic Doppler method,the device for measuring the velocity of river water under ice includes three parts: transmitting system,receiving system and upper computer.The transmitting system transmits the ultrasonic signal of certain frequency to the river water under the ice through the transmitting transducer.Firstly,the H-bridge circuit based on the IRFP460 is designed,and according to the characteristics of the switching device and the H-bridge transmitting waveform,the timing signal generating circuit and the isolation driving circuit based on FPGA chip are designed.Secondly,in the receiving system,the signal amplifying circuit,band-pass filter,multiplier and low-pass filter in the system process the signals of the receiving transducer.The processed data are sampled with high precision by ADS7841 chip.Through the serial port module,the collected data are stored in STM32 single chip microcomputer and sent to the upper computer.Finally,the upper computer Lab VIEW software is designed to realize the Fast Fourier Transform of the collected data by STM32 single chip.And the software realize the function of processing and displaying the working state of the receiving system,and calculate the velocity of the river water at the measuring point through the formula,then,display the velocity value in the upper computer software interface,and store the measured data in the upper computer.After the completion of the design,the performance indexes of each part of the device are tested first,and the field measurement is carried out in the Ziyou Bridge of Changchun City,Yitong River,to measure the river flow velocity of the measuring point.The measurement proves the effectiveness of the instrument in the field measurement and the feasibility of the measurement method. |
