2009 results about "Underwater acoustics" patented technology

The invention discloses a penetration probe-based deep sea multi-element comprehensive observation system, which comprises an upper computer and a data recovery cabin, wherein the upper end and the lower end of the data recovery cabin are connected with a probe rod through a hydraulic separation releaser and a launching device respectively; a small-sized pile driver is arranged in the launching device; the launching device is provided with an underwater search light, an underwater camera and an underwater acoustic communication transceiver; the top of the data recovery cabin is provided with a floating body; a central controller is included in the data recovery cabin; the outer side face of the data recovery cabin is provided with an underwater acoustic transducer; and the outer surface of the probe rod is provided with more than 10 annular electrodes and more than 2 pore water pressure sensors which are connected with the central controller. The system has a simple structure, is reliable in work and accurate in control, can carry various sensors and adapt to a deep sea high pressure environment, and can synchronously and automatically observe and record states and changes of sea water and sediments within a 10m depth range close to a sea water-sediment interface with over 2,000m water depth, including the state of sediments of 6-7m below a sea bottom surface, the condition ofsea water of a bottom layer of 3-4m above the sea bottom surface and the dynamic change in position of the sea bottom surface.

The present invention relates to a method and a system of a high code speed low error probability underwater acoustic coherent communication for underwater transferring instruction, data and image. The communication system includes a host machine installed on a mother ship or a main control underwater vehicles A and a guest machine installed on an underwater vehicle B, wherein the host machine comprises an electronic subassembly, a transducer and a receiving line array which is vertically deployed and consists of more than two hydrophones, and the guest machine comprises an electronic subassembly and a transmitting/receiving transducer. The signal processing method of the present invention is based on the joint technology of the space diversity, the self-optimized adaptive decision feedback equalizer and self-optimized adaptive phase tracker so as to overcome the affection of motion of the channel and the vehicles, such that the received signal could be quite close to the transmitted signal, and the bit error probability is low.

The invention discloses a method for estimating pulse noise in an OFDM (Orthogonal Frequency Domain Multiplexing) underwater acoustic communication system. At a receiving end, sparse estimation is performed on pulse noise on an OFDM signal in an underwater acoustic channel transmission process according to a frequency domain signal subjected to redundant Doppler frequency shift compensation, and frequency offset compensation is performed on the frequency domain signal subjected to the redundant Doppler frequency shift compensation with void subcarriers. Under the consideration of mutual interference between the pulse noise and a carrier frequency offset in underwater acoustic communication, compensation of the carrier frequency offset is added in an iteration process while the pulse noise is estimated with all subcarriers and a posteriori distribution under a framework of conventional sparse Bayesian learning, and the frequency domain signal subjected to the redundant Doppler frequency shift compensation and a measurement diagonal matrix for estimating the pulse noise are updated continuously in order to lower influences between the two types of interference. Moreover, the pulse noise is estimated by full utilization of all the subcarriers in the method, so that the spectrum efficiency and the performance of the communication system are improved.

The invention provides an underwater acoustic transducer, comprising a piezoelectric ceramic wafer pack and metal cover plates on upper and lower ends thereof. The piezoelectric ceramic wafer pack is in a cylindrical shape and stacked by several circular piezoelectric ceramic wafers. Polarization direction of the piezoelectric ceramic wafers is along the thickness direction. 2 to 8 piezoelectric ceramic wafers form a group, and the wafer pack contains one or several groups of wafers, each is separated by a rubber chip. Metal sheets are clamped between adjacent wafers and between a wafer and a rubber chip. Contact conductors are welded on the metal sheets. The piezoelectric ceramic wafer pack and the upper and lower metal cover plates are further separated by the rubber chips. The cylindrical stacked wafer transducer of the invention is not only capable of maintaining characteristics of large transmitting sound energy density of traditional stacked wafer transducer and high sensitivity by reasonably designing diameter of piezoelectric stacked wafers, but capable of adjusting axial directivity open angle of the transducer by changing thickness of the piezoelectric wafer stack or adjusting the group number.

Advantageous underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. The apparatus, systems and methods employ nonbinary low density parity check (LDPC) codes that achieve excellent performance and match well with the underlying modulation. The nonbinary LDPC codes of the proposed apparatus, systems and methods are formed, at least in part, from a generator matrix that has a high density to reduce the peak-to-average-power ratio (PAPR) with minimal overhead. The disclosed apparatus, systems and methods employ nonbinary regular LDPC cycle codes if the constellation is large and nonbinary irregular LDPC codes if the constellation is small or moderate. The nonbinary irregular and regular LDPC codes enable: i) parallel processing in linear-time encoding; ii) parallel processing in sequential belief propagation decoding; and iii) considerable resource reduction on the code storage for encoding and decoding.

An underwater diving simulation system includes at least three surface electronics units defining a diving area in proximity to a desired dive location. Each surface electronics unit includes a microprocessor-controlled transceiver that receives x-y-z position data from an underwater acoustical transponder located on a diver who is located in the diving area. The system provides user selectable, variable underwater virtual reality data to the diver via a communication link. A plurality of sensors in proximity to the diver's head transmits real-time rate of change, horizontal and vertical position of the diver's head to a signal decoder located on at least one of the surface electronics units via said communication link. A pair of projectors and optical elements are typically provided, one for each of the diver's eyes on a diving mask. The virtual reality images are generated by a graphics-processing unit in real-time response to the position and orientation of the diver and the diver's head whereby the diver can experience a virtual reality of diving in a user selectable location and with user selectable sea creatures.

The transducer includes piezoelectric ceramic tube (PCT) with up supporting rack and low supporting rack being installed on two ends of the tube. The transducer is installed inside a tubular oil bag. Being fixed on the opening end of the oil bag, the base seals the oil bag. An output socket for two electrodes is set up on the base. Through connecting wires, pins of electrodes are respectively connected to inner wall and outer wall of PCT electrically. An oil hole in use for injecting oil to the oil bag is set up on the base. An oil nozzle is installed inside the oil hole. Silicone oil is filled up the oil bag. The method includes following steps: (1) enclosing integral PCT into the oil bag; (2) packaging the output socket on the base; (3) ring tightening the oil bag on the base; (4) debubbling the silicone oil, and injecting it to cavity of the transducer. Features are: wide working frequency band, high sensitivity, semi spatial directivity, and high anti hydrostatic pressure.

The invention relates to a method of using a reverberation pool to carry out reciprocity calibration of an underwater acoustic transducer. The method of using a reverberation pool to carry out reciprocity calibration of an underwater acoustic transducer includes the steps: 1) according to the lowest frequency to be calibrated for an underwater acoustic transducer to be calibrated, selecting a reverberation pool with the corresponding size; 2) using any one nondirectional sound source and one hydrophone to form an emission/reception energy transducer pair, measuring the output voltage of an open circuit being 1m away from a sound source equivalent sound center in the reverberation pool and recording the emission/reception parameters of the apparatus; and 3) placing the emission/reception energy transducer pair in the reverberation pool, adjusting the same emission/reception parameters, and using a space averaging method to measure the output voltage of the open circuit of the hydrophone. If the method of using a reverberation pool to carry out reciprocity calibration of an underwater acoustic transducer is used to perform calibration of an underwater acoustic transducer, a plurality of hydrophones can be calibrated at the same time, so that the requirement for the experiment pool is reduced. Therefore, even in a reverberation pool with small size or a non anechoic pool, the method of using a reverberation pool to carry out reciprocity calibration of an underwater acoustic transducer can also be used for calibration only when the frequency range for calibration is satisfied.

The invention provides an ultra-wideband underwater acoustic transducer, which comprises an arc beam, a U-shaped beam, a transition block and a driving element, wherein the arc beam is a cylindrical shell, the section of which is elliptical arc; the U-shaped beam is a U-shaped curved translation body; the arc beam and the U-shaped beam form a flextensional shell, and two end faces of the flextensional shell are closed by cover plates; and the driving element and the transition block form a vibrator assembly, and the vibrator assembly is arranged in the flextensional shell and rigidly connected with the inner wall of the U-shaped beam. The ultra-wideband underwater acoustic transducer has the characteristics of low frequency, high power, compact structure, small size and light weight, and can be applied in the fields of underwater acoustic detection, antagonism, communication, measurement, marine resource exploration and the like.

A method and apparatus for determining the geophysical position of an autonomous underwater system utilizing underwater acoustic modems that exchange broadband underwater acoustic signals. The method of the invention includes the steps of initiating an exchange of broadband acoustic signals between the autonomous system of unknown geophysical position and a base system of known geophysical position wherein the depths of both systems is known. A bearing calculation is made on one of the signals transmitted between the systems, preferably through the use of an array of hydrophones placed closely together at predetermined locations on either the autonomous or base system. Also, the range between the two systems is determined by measuring the time of travel of at least one signal. By the acoustic transmission and sharing of information, as needed, about the known depths of the systems, the known geophysical position of the base system, and the range between the systems, sufficient data is gathered at one or both systems and used to determine the geophysical position of the autonomous system.

An underwater communications system includes an antenna array, a sound transmission source for transmitting communication packets, and a receiver including a processor. The processor is programmed for receiving and detecting a Doppler-sensitive probe signal and training sequence, for estimating a channel impulse response function for correlating the received signal to yield a plurality of processed channel outputs, and for summing the channel outputs to yield a common receiver output. The common receiver output is applied to a Decision Feedback Equalizer (DFE) for adaptive correction of the inter-symbol interference and to retrieve the transmitted communication message.

The invention discloses a Doppler factor estimation and compensation method of mobile underwater acoustic communication, related to underwater acoustic communication. The Doppler factor estimation andcompensation method of the mobile underwater acoustic communication comprises the following steps: 1) large scale Doppler estimation and compensation; 2) residual Doppler estimation and compensation;and 3) Doppler phase rotation compensation. In order to accurately and efficiently estimate the Doppler factor in the mobile underwater acoustic communication environment, overcome the more obvious Doppler effect compared with the terrestrial radio channel and eliminate the adverse effects on the underwater acoustic OFDM communication system of the Doppler effect, a Doppler factor estimation andcompensation method of the mobile underwater acoustic communication considering both the accuracy and the computationcomplexity is needed. Because the estimation is carried out in the frequency domainand aims at the characteristics of the underwater acoustic channel, the Doppler factor estimation and compensation method of the mobile underwater acoustic communication, especially the Doppler factor estimation and compensation method applied to the mobile underwater acoustic OFDM system is more suitable for the fast changing mobile underwater acoustic channel based on the traditional Doppler estimation and compensation. The estimation accuracy is high; and meanwhile, the computation complexity is reduced appropriately, therefore, the practicability is excellent.

The invention discloses a fidelity enhanced beamforming method based on a distorted towed array, comprising the following steps: (1) simulating the radiation noise s(t) of an underwater acoustic target; (2) simulating the observation array signal xi(t), i =1,2,...,M, M is the number of elements in the towed array; (3) Roughly estimate the target orientation based on ideal beamforming as the steering angle when the target signal beam energy is maximum; (4) Detect the L of the target signal The line spectrum position l=1,2,...,L with the largest power; (5) Estimate the average delay difference △τi of each array element in the towed array from the phase difference at the strong line spectrum position, i=1 ,2,...,M; (6) Obtain fidelity-enhanced target tracking beam based on estimated time delay This method uses time delay estimation to correct the influence of distortion of the towed line array on beamforming, and obtain fidelity-enhanced target radiation Noise tracking beam.

The invention discloses an underwater acoustic sparse channel estimation variable step sparsity adaptive matching tracking method, which fully utilizes the underwater acoustic channel sparse multipathcharacteristic and avoids the waste of frequency spectrum resources caused by the excessive number of pilots in the traditional channel estimation technology. The method does not need sparseness as apriori information, and the size of the support set is the estimated sparseness at the end of iteration by expanding the support set through step size. In addition, the signal reconstruction processis divided into several stages by combining stage idea and variable step size, the number of atoms in the support set in a certain phase remains constant, and the adjacent phases gradually expand thesupport set by different step sizes. The invention improves the recovery accuracy on the premise of not significantly increasing the calculation amount, that is, obtains a better trade-off between thereconstruction accuracy and the calculation complexity. Compared with the prior classical greedy algorithm, the invention does not need sparseness as a prior information, and the step size adaptive change can give consideration to the algorithm accuracy and the operation efficiency.

The invention discloses an underwater cultural relic integrated detection device based on an ROV platform, which includes a deck device and an underwater integrated detection device, and belongs to the technical field of marine detection. Deck installations include the mother ship, GPS system, ultra-short baseline transceiver and ROV console. The underwater detection device integrates magnetometer, multi-beam sonar, side-scan sonar, high-definition camera, shallow stratum profiler (shallow profiler) and ultra-short baseline acoustic beacon on the ROV platform. The magnetometer is used to measure the magnetic anomalies in the detection area and roughly determine the location of the underwater cultural relics. The shallow profiler is used to describe the cross-sectional structure of the underwater strata, which is used to detect the location of cultural relics buried below the mud surface. Multi-beam sonar and side-scan sonar are used to provide high-resolution underwater acoustic images, combined with high-definition cameras to detect the location of cultural relics on mud surfaces. The device of the invention integrates and fuses various sensor information, realizes the visualized and refined real-time detection of underwater cultural relics, and improves the detection efficiency of underwater cultural relics archaeological operations.

The invention discloses a device for recovering an autonomous underwater vehicle by an unmanned ship based on a guide cable. The device for recovering the autonomous underwater vehicle is characterized in that the water surface unmanned ship, a recovery device carried on the water surface unmanned ship, the recovered or arranged autonomous underwater vehicle and a guide recovery control system arranged on the autonomous underwater vehicle are included; an underwater acoustic transducer is arranged at the bottom of the water surface unmanned ship and is used for underwater acoustic communication of the water surface unmanned ship and the autonomous underwater vehicle; a hydraulic telescopic rod connected with the recovery device is arranged in a cabin of the water surface unmanned ship; motion of the recovery device in the vertical direction can be achieved through the hydraulic telescopic rod; and an arc-shaped guide arm and cable fastening pliers are arranged at the top end of the bowof the autonomous underwater vehicle. The device for recovering the autonomous underwater vehicle has the beneficial effects that a USV serves as a water surface platform, and the device and method for autonomously recovering the autonomous underwater vehicle (AUV) through a guide cable are adopted so as to overcome the defects that in the prior technological means, water surface arrangement recovery is greatly influenced by sea wind waves, and people and equipment safety risk exists.

A method for emitting and combining underwater super wideband sound array includes applying underwater sound synthetic technique and multiarray emission technique of sub frequency channel and multimode vibration ¿C emission transducer to realize free selection of sweep frequency signal combination on sea detecting instruments and any program controlled adjustment of emission operating parameter. An emitting system device of underwater super wideband combined sound array is also disclosed.

The invention provides a mobile underwater acoustic communication method which includes the following steps: carrying out channel encoding and digital modulation on a data source at a sending end to get serial data, and converting the serial data into a parallel data flow; inserting pilot data into each group of parallel data, and carrying out sub-carrier modulation through inverse fractional Fourier transformation; adding a guard interval to modulated symbols, converting the modulated symbols into serial data, and sending the serial data; carrying out serial-to-parallel conversion and removing the guard interval at a receiving end, and searching for the optimal order through an order scanning search iterative algorithm; carrying out sub-carrier modulation on signals through optimal-orderfractional Fourier transformation, and carrying out channel estimation and equalization in the fractional Fourier domain at the receiving end; and after equalization, removing the pilot data, carryingout parallel-to-serial conversion to get serial data, carrying out digital demodulation and channel decoding, and outputting obtained data from the receiving end. The method has the advantages of simple structure and high calculation speed. The algorithm complexity of the transmitter and the receiver is reduced. The Doppler frequency shift in underwater acoustic mobile communication is reduced. The communication effect is improved.

The invention discloses an underwater acoustic anti-Doppler multicarrier modulation and demodulation method based on linear frequency modulation. The method comprises the following steps: step one, transmitting terminal multicarrier modulation is performed; step two, Doppler frequency shift factor estimation is performed; and step three, receiving terminal demodulation is performed. The invention also discloses a modulation and demodulation device of the underwater acoustic anti-Doppler multicarrier modulation and demodulation method based on linear frequency modulation. The device comprises a transmitting device and a receiving device which are interconnected. The method has advantages of being high in anti-Doppler capability, wide in applicability, diverse in realization method, low in cost, easy to realize, high in efficiency, etc.

The invention relates to an apparatus and method for the in-situ real-time observation of submarine sand waves. The apparatus includes an observation system and auxiliary devices. The auxiliary devices comprise an auxiliary ship and a hoisting device; the observation system includes a gravity anchor, a fiber grating floating earth weight sensor, a Kevlar cable, an underwater acoustic releaser group, a lower floating ball bracket, a wave and tide gauge, an upper floating ball bracket, an MRU three-dimensional attitude sensor, a satellite communication machine, an imaging sonar, a solar cell anda main floating body. The principle of the apparatus and the method is characterized in that submarine pressure change caused by the migration of the submarine sand waves is observed, the time interval, elevation and wavelength data of two adjacent extreme submarine pressures are analyzed, and the migration rate of the submarine sand waves is calculated. The method includes the following steps: selection of an observation point and a deployment time, system deployment, recovery, and data processing. The apparatus and the method provide a new idea for the in-situ real-time observation of the submarine sand waves, have the characteristics of simple and easy device, long in-situ real-time measurement period and wide applicable water range, and can realize the in-situ real-time long-term observation of the migration of the submarine sand waves.