Design And Research Of Expendable Sound Velocity Profiler Based On TOF

Sound velocity measurements are an important part of the marine development and research process,having a significant impact on many civil and military defense areas such as marine surveying and marine mapping.In marine development and research projects,a wide range of sonar measurement equipment is used.With the continuous improvement and upgrading of various sonar measurement equipment,the accuracy of sound velocity measurement also needs to meet higher and higher requirements,therefore,the Expendable Sound Velocity(XSV)has been created,which has the characteristics of low cost,high measurement accuracy,low power consumption and easy to be used.Based on the current global ocean development,countries around the world are paying more and more attention to the measurement of various physical quantities in the ocean.China is also gradually developing and improving the technology related to the measurement of sound velocity in seawater,but there are still gaps compared to the international advanced level,such as poor stability,low measurement accuracy and slow computing speed.This paper proposes a solution of a TOF-based Expendable Sound Velocity in order to fix the problems as mentioned.The XSV consists of a measurement system of underwater sound velocity,a signal modulation system,an enameled wire,an above-water signal demodulation system and a display system on the computer end.The measurement system of underwater sound velocity measure the sound velocity of seawater by using the method of time difference,and the underwater unit and the overwater unit use binary differential phase shift keying(2DPSK)for data transmission.In terms of hardware circuitry,an idea of modular circuit applies to design the circuits of the sound speed and temperature measurements,signal modulation,signal amplification,high voltage bias,serial communication and voltage stabilization of power supply.In terms of system control,the STM32L151 microcontroller acquires the sound speed and temperature data via SPI communication in order to realize measurement system of underwater sound velocity.While the STM32L151 microcontroller converts the sound speed and temperature data into 2DPSK signals in order to realize a signal modulation system,which are transmitted to a single doublestranded enameled wire via an underwater driver circuit.During the transmission of the signal,the enameled wire is identical to multiple low-pass filters in series to filter the signal passing through the channel.In the above-water signal demodulation system,the circuits of signal amplification and signal reception have been designed that needs STM32H743 microcontroller to carry out the signal acquisition,in the meantime,the signal demodulation is completed by 2DPSK demodulation algorithm.The RS-232 serial communication circuit is designed to demodulate the output sound velocity and temperature data in real time,and the drop depth of the Expendable Sound Velocity is calculated by the empirical formula of drop depth,which allows the profile of the ocean sound velocity distribution to be plotted on the computer side.After completing the design of the overall scheme,the hardware and software of the Expendable Sound Velocity have been debugged.Moreover,the measured sound velocity data has calibrated and can improve the accuracy of the sound velocity measurement of the Expendable Sound Velocity.This design meets all the requirements of the project and achieves expected results of the project.