Views:1 Author:Site Editor Publish Time: 2019-03-12 Origin:Site
Submarine intelligent includes underwater acoustic communication,One of the technical difficulties to overcome the intelligent for submarine pipeline maintenance is how to realize the underwater communication system of the intelligent to complete the remote operation of the platform. Due to the particularity of the marine environment, underwater acoustic wireless communication is adopted. The underwater acoustic communication system is different from the traditional wireless communication system, and it must transmit information through a very special underwater acoustic channel, that is, through seawater medium,The seawater medium is extremely complex and variable. The absorption of sound energy and the expansion of the wavefront by the medium during the propagation process lead to the attenuation of the signal; the scattering and reflection of sound waves by the sea surface and the sea floor lead to multipath phenomenon; and the unevenness of piezoceramic cylinder ceramic transducer. And there is a lot of interference noise underwater, which will make the underwater acoustic signal distorted. The main work of this paper completes the research and selection of underwater acoustic transducers, which play an important role in the communication process, and determines the underwater transmission frequency of the signals through water test experiments.
The ultrasound cylinder ceramic transducer is a device that realizes mutual conversion of electroacoustic energy, and can be classified into a transmitter and a receiver (or a hydrophone) according to the use. The intelligent of communication signal flow is shown . The main research of this communication system is to issue command data from the mother ship or platform computer operation interface, and convert the digital signal into analog signal through modem, and send it to the underwater acoustic transducer through the power amplification matching circuit to convert it into an acoustic signal. As an important research direction in the field of engineering water acoustics, underwater acoustic transducers and their arrays are the comprehensive use of multiple disciplines, involving hydroacoustics, physics, electronics, mechanics, materials science and even chemistry. Its research provides an important technical guarantee for the reliable transmission and exchange of underwater information.
Main performance parameters of the underwater acoustic transducer
The main performance parameters of underwater acoustic transducer considered in the selection process of the underwater acoustic transducer (1) The operating frequency of the transducer is selected according to the sonar equation under certain conditions, and other important performances. Indicators such as directivity, transmitted sound power, and receiving sensitivity vary with frequency. For the transmitter, it is generally operated at the resonant fundamental frequency to achieve high power transmission and high efficiency characteristics. For hydrophones, it is expected to operate in a frequency band with a flat receive response.
Bandwidth Δf and mechanical quality factor Qm
The bandwidth Δf of piezo ceramic materials has the following relationship with the quality factor Qm: 1Qm = Δff0, where f0 is the mechanical resonance frequency. The quality factor Qm is related to the material, structural size, mechanical loss and radiation resistance of the transducer. The greater mechanical loss and radiation resistance and the smaller is the equivalent mass near the resonant frequency, the lower the Qm and the wider the bandwidth.
Emission voltage response:
The voltage response Sv of piezo cylinder tube is an important parameter to measure the performance of the sound system radiating sound wave energy into the water. It is defined at a certain frequency, the transmitting transducer (or transducer array) is away from the specified direction (the sound axis direction). The ratio of the free field sound pressure Pf produced at the effective acoustic center reference distance to the excitation voltage rms V at the input of the transducer.Sv=Pf(1m)·d0V(Pa·m/v) reference distance d0=1m, the decibel of Sv is expressed as the emission voltage response level: SvL=20lgSv(Sv)ref(dB) reference value (Sv)ref=1μPa· m/v. The transducer has other features, such as directivity.
Underwater sound transducer, After investigation and selection, the underwater acoustic emission transducer is used in the water test experiment.it is a cylindrical piezoelectric ceramic transducer developed by the Institute of Hydroacoustics, Piezoelectric ceramic transducers are a type of transducer that is widely used in the field of underwater acoustics. They are main advantages (1) when it is in the transmitting state, it can be used as a strong power radiator, and its electroacoustic efficiency is also high,it is about 30-70%;When it is used in the receiving state as a receiver, it has a higher receiving sensitivity of Pzt piezoceramic cylinder tube, about tens to hundreds of microvolts / Pa; (3) it can be used as a transducer of various shapes, such as a composite rod type, column and ball transducers. It has the characteristics of simple structure and stable working performance. The sequence produces the resulting time error between the two interrupts. Then start the loop count, that is, num plus 1, when num is added to 20, which will generate 1s interrupt, then start num clear and second unit plus 1, and then start to judge the second, minute, whether to carry or cleared program.