CN102252745A - Measurement device of underwater sound signal transmit time and measurement method thereof - Google Patents

Abstract

The invention discloses a measurement device of the underwater sound signal transmit time and a measurement method thereof and relates to the distance measurement and positioning in a limited space liquid yield environment. The method comprises the following steps: a first m-sequence generator generates an m-sequence; a first signal generator generates a first carrier signal, the m-sequence is used to modulate the first carrier signal and obtain a first modulation signal, the output and amplified modulation signal drives a transmitter underwater acoustic transducer to emit an underwater sound signal and also emit a synchronizing signal at the same time to trigger a signal collection circuit to work; a second m-sequence generator generates another m-sequence; a second signal generator generates a second carrier signal which is the same as the first carrier signal, the m-sequence is used to modulate the second carrier signal and obtain a second modulation signal; a receiver underwater acoustic transducer receives the underwater sound signal; the signal collection circuit processes the underwater sound signal; and a computer performs calculation to the second modulation signal and the treated signal to obtain the underwater sound signal transmit time. By adopting the method, the measurement accuracy of the transmit time can be increased.

Description

The measurement mechanism of a kind of underwater sound signal transit time and measuring method thereof

Technical field

The present invention relates to range finding and location in the liquid environment of the finite space, the measurement mechanism of particularly a kind of underwater sound signal transit time and measuring method thereof.

Background technology

Underwater sound local positioning system has more application in occasions such as wastewater treatment, liquid environment detection and submarine target tracking in the liquid environment of the finite space, for realizing that the information detection in the liquid environment provides positional information, receives more research and concern in recent years.The liquid field of the finite space is meant space environment limited, that be filled with fluent meterial, in this environment, often need environmental information is understood, the general method that adopts is the acquisition sensor of difference in functionality to be put into liquid field carry out parameter detecting, and for rugged surroundings as having in corrosivity, the poisonous or confined space, realize measuring very difficulty, so underwater robot arises at the historic moment, it can carry acquisition sensor, independently in the space that needs are surveyed, move about, thereby realization is to the detection of environmental information.Underwater robot also is in the research process at present, and does not also have specific detector carrying equipment for the liquid environment beyond the water body.Survey in the process of a liquid environmental information at carrying equipment, need the positional information of carrying equipment be write down or control, i.e. underwater positioning system.Underwater positioning system all is to adopt underwater sound signal to realize, common have long baseline, short baseline and a ultra short baseline locating system, these systems all are used widely in marine environment, in the liquid environment of the finite space, can not directly use, because the liquid environment of the finite space is different from large-scale water environment, be faced with different problems.

Underwater sound local positioning system in the liquid environment of the finite space adopts the distance between a plurality of acoustic transducers and the localizing objects generally by means of underwater acoustic transducer, can obtain the three-dimensional position of localizing objects by positioning equation.Ultimate principle:,, a underwater acoustic transducer is installed on the target that is positioned as setting base at 4 underwater acoustic transducers of location space mounting.Setting base emission underwater sound signal, underwater acoustic transducer on the target that is positioned receives underwater sound signal, by measuring the transit time of underwater sound signal, can determine setting base and the distance between the target of being positioned, can be by 4 distances in the hope of the position of the target that is positioned.Positioning equation is:

$P1={\mathrm{ct}}_r+\sqrt{{(x_1-x_R)}^2+{(y_1-y_R)}^2+{(z_1-z_R)}^2}$

$P2={\mathrm{ct}}_r+\sqrt{{(x_2-x_R)}^2+{(y_2-y_R)}^2+{(z_2-z_R)}^2}$

(1)

$P3={\mathrm{ct}}_r+\sqrt{{(x_3-x_R)}^2+{(y_3-y_R)}^2+{(z_3-z_R)}^2}$

$P4={\mathrm{ct}}_r+\sqrt{{(x_4-x_R)}^2+{(y_4-y_R)}^2+{(z_4-z_R)}^2}$

P wherein _i(i=1,2,3,4) are four setting bases and the distance between the target of being positioned, (x _i, y _i, z _i) (i=1,2,3,4) be the position coordinates of four setting bases, (x _R, y _R, z _R) being the position coordinates of the target that is positioned, c is a underwater sound propagation speed, t _rBe four synchronous errors between the setting base.P in this equation _i(i=1,2,3,4) are distance value, (x _R, y _R, z _R), t _rBe the unknown, can obtain the position coordinates of localizing objects by top positioning equation.As can be seen, the key of location is a range information from this equation.So the accuracy of subaqueous sound ranging is very big to location precision.In liquid, the underwater sound signal velocity of propagation is very fast, in the part, when closely locating, underwater sound signal can produce a large amount of multipath reflection echoes, produce serious reverberation phenomenon simultaneously, these factors all have very large influence to distance accuracy, and the result that causes finding range produces than mistake, even causes the measurement result mistake.How to realize the inhibition of underwater sound multipath and reverberation in a liquid environment of the finite space, it is significant to improve distance accuracy.It is long-pending that distance equals underwater sound signal velocity of sound from be transmitted into used time (transit time) of reception and liquid.Because in the even liquid environment of the finite space, the velocity of sound can be regarded constant as, so the accuracy of range finding is just determined by the accuracy of the transit time that measures.At present, also be not specifically designed to the effective ways of the underwater sound signal transit time measurement under the liquid environment of the finite space.

Measurement for the transit time of acoustical signal in the liquid field, general square-wave signal or the pulse signal that adopts the sine wave signal of continuous sine wave signal, limit cycle, continuous square-wave signal, limit cycle of classic method, The common calculation methods has threshold method, curve-fitting method and cross-correlation method.

After threshold method is meant that transmitting transducer sends signal, receiving transducer picks up counting and begins received signal, after the signal of receiving transducer reception exceeds certain prior preset threshold, judge and receive the signal that transmitting transducer sends, this moment is as the time of reception, this moment is poor with the moment that picks up counting, is the transit time of the signal that transmitting transducer sends.

Curve fitting method is that the start-up portion of signal that receiving transducer is received adopts non-linear least square method to carry out match, and for example, during the transmit square waves signal, the fitting formula of the square-wave signal that receiving transducer is received is a ₀(t-t ₀) ²Suppose τ ₁And τ ₂Be two prior preset threshold (τ ₁＞τ ₂), t ₁And t ₂Be the moment that two threshold values satisfy, the transit time can be satisfied following formula:

τ ₁＝α ₀(t ₁-t ₀) ²

(2)

τ ₂＝α ₀(t ₂-t ₀) ²

Elimination factor α ₀After, the transit time can be solved by following formula:

${\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="HDA0000054193770000032.png,HDA0000054193770000033.png"\; state="\{\{state\}\}">t</figure-callout>}}_0=\frac{\sqrt{{\mathrm{\&tau;}}_2/{\mathrm{\&tau;}}_1}{t}_1-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000054193770000031.png,HDA0000054193770000032.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}{\sqrt{{\mathrm{\&tau;}}_2/{\mathrm{\&tau;}}_1}-1}---\left(3\right)$

Cross-correlation method is a tolerance that is used for representing similarity between two signals, for two signal x (t) and y (t), their cross correlation function R _Xy(τ) be defined as:

$R_{\mathrm{xy}}\left(\mathrm{\&tau;}\right)={\lim }_{T\&RightArrow;\&infin;}\frac{1}{T}{\&Integral;}_0^{T}x\left(t\right)y(t-\mathrm{\&tau;})\mathrm{dt}---\left(4\right)$

According to the character of related function, at the strongest moment cross correlation function R of correlativity _Xy(τ) will reach peak value.Therefore, the detection of determining just to have become the related function peak of time delay τ.Be exactly to carry out cross-correlation calculation by the signal that signal that transmitting transducer is sent and receiving transducer receive in measuring in the underwater sound signal transit time, the peak value of searching for then in the result data of cross-correlation calculation comes estimated delay.When transmit to received signal between when the most similar the value of simple crosscorrelation reach maximal value, the pairing moment of this maximal value is the transit time.

The inventor finds that there is following shortcoming at least in prior art in realizing process of the present invention:

Threshold method and curve-fitting method are very responsive to noise, and measurement effect instability, cross-correlation method are at multipath, measurement performance greatly reduced when reverberation existed.There is the measurement of carrying out the underwater sound signal transit time in the serious finite space liquid environment for multipath and reverberation, also do not have a kind of effective method.

Summary of the invention

In order to overcome deficiency of the prior art, get access to the measuring method of the underwater sound signal transit time more accurate, stable with respect to classic method, satisfy the needs in the practical application, the invention provides measurement mechanism and the measuring method thereof of a kind of underwater sound signal transit time, see for details hereinafter and describe:

The measurement mechanism of a kind of underwater sound signal transit time, described measurement mechanism comprises: be arranged on transmitting terminal underwater acoustic transducer, receiving end underwater acoustic transducer, signal generating module and signal receiving processing module in liquid, wherein, described transmitting terminal underwater acoustic transducer is identical with described receiving end underwater acoustic transducer; Described signal generating module comprises: the m sequencer, first signal generator that driven by programmed computer; Described signal receiving processing module comprises: the 2nd m sequencer, secondary signal generator, signal acquisition circuit and the computing machine that driven by programmed computer;

A described m sequencer that driven by programmed computer produces the m sequence; Described first signal generator produces the first carrier signal, described m sequence is modulated described first carrier signal, obtain first modulation signal, described first modulation signal is amplified, modulation signal after output is amplified drives described transmitting terminal underwater acoustic transducer and sends underwater sound signal, and described first signal generator sends a synchronizing signal and triggers described signal acquisition circuit and start working simultaneously; Described the 2nd m sequencer that driven by programmed computer produces identical described m sequence; Described secondary signal generator produces second carrier signal identical with described first carrier signal, and described m sequence is modulated described second carrier signal, obtains second modulation signal; Described receiving end underwater acoustic transducer receives the described underwater sound signal of propagating in the liquid environment; Described signal acquisition circuit is handled described underwater sound signal, obtains the signal after the processing; The signal of described computing machine after to described second modulation signal and described processing calculates, and obtains the underwater sound signal transit time.

The measuring method of a kind of underwater sound signal transit time said method comprising the steps of:

(1) by software programming, utilize a m sequencer to generate the m sequence of a default exponent number, first signal generator produces the first carrier signal, according to the frequency of operation of used transmitting terminal underwater acoustic transducer, determines the first carrier signal frequency;

(2) adopt the BPSK modulation system, the m sequence is modulated described first carrier signal, obtain the first modulation signal M1;

(3) the described first modulation signal M1 is amplified by described first signal generator, drive described transmitting terminal underwater sound generator, send underwater sound signal M2 by impedance matching circuit;

(4) described first signal generator sends a synchronizing signal M3, and the trigger pip Acquisition Circuit is started working;

(5) the receiving end underwater acoustic transducer receives the described underwater sound signal M2 that propagates in the liquid environment, described signal acquisition circuit to described underwater sound signal M2 amplify, conversion and Filtering Processing, obtain the signal M4 after the processing;

(6) by software programming, utilize the 2nd m sequencer to generate same described m sequence, the secondary signal generator produces second carrier signal identical with described first carrier signal, adopts the BPSK modulation system, obtains the identical signal M5 with described underwater sound signal M2;

(7) the signal M4 of computing machine after to described signal M5 and described processing carries out the broad sense computing cross-correlation, obtains the broad sense cross correlation results;

(8) described broad sense cross correlation results is searched for, obtain peak point, described peak point moment corresponding is the underwater sound signal transit time.

The beneficial effect of technical scheme provided by the invention is:

The invention provides measurement mechanism and the measuring method thereof of a kind of underwater sound signal transit time, the present invention adopts the spread-spectrum signal transmission, utilize the broad sense simple crosscorrelation, realize measurement result more accurately, have higher measurement accuracy and robustness than the method for traditional employing sine wave signal, basic simple crosscorrelation; The present invention can effectively suppress because serious multipath and the reverberation phenomenon that underwater sound signal produces when propagating in limited liquid space, improves the accuracy that the transit time measures, for subaqueous sound ranging, location provide reliable basis.

Description of drawings

Fig. 1 is the structured flowchart of the measurement mechanism of underwater sound signal transit time provided by the invention;

Fig. 2 is the process flow diagram of the measuring method of underwater sound signal transit time provided by the invention;

Fig. 3 is one the 7 rank m sequence waveform figure that m sequencer provided by the invention generates;

Fig. 4 is the schematic diagram of m sequencer provided by the invention;

Fig. 5 is the oscillogram of the part signal after the modulation provided by the invention;

Fig. 6 is the first correlation curve figure of result of calculation provided by the invention;

Fig. 7 is the second correlation curve figure of result of calculation provided by the invention;

Fig. 8 is the 3rd correlation curve figure of result of calculation provided by the invention.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, embodiment of the present invention is described further in detail below in conjunction with accompanying drawing.

In order to overcome deficiency of the prior art, get access to the measuring method of the underwater sound signal transit time more accurate, stable with respect to classic method, satisfy the needs in the practical application, the embodiment of the invention provides measurement mechanism and the measuring method thereof of a kind of underwater sound signal transit time, referring to Fig. 1, see for details hereinafter and describe:

The measurement mechanism of a kind of underwater sound signal transit time, this measurement mechanism comprises: be arranged on transmitting terminal underwater acoustic transducer, receiving end underwater acoustic transducer, signal generating module and signal receiving processing module in liquid, wherein, the transmitting terminal underwater acoustic transducer is identical with the receiving end underwater acoustic transducer; Signal generating module comprises: the m sequencer, first signal generator that driven by programmed computer; The signal receiving processing module comprises: the 2nd m sequencer, secondary signal generator, signal acquisition circuit and the computing machine that driven by programmed computer;

A m sequencer that driven by programmed computer produces the m sequence; First signal generator produces the first carrier signal, the m sequence is modulated the first carrier signal, obtain first modulation signal, first modulation signal is amplified, modulation signal after output is amplified drives the transmitting terminal underwater acoustic transducer and sends underwater sound signal, and while first signal generator sends a synchronizing signal trigger pip Acquisition Circuit and starts working; The 2nd m sequencer that driven by programmed computer produces identical m sequence; The secondary signal generator produces second carrier signal identical with the first carrier signal, and the m sequence is modulated second carrier signal, obtains second modulation signal; The receiving end underwater acoustic transducer receives the underwater sound signal of propagating in the liquid environment; Signal acquisition circuit is handled underwater sound signal, obtains the signal after the processing; Computing machine to second modulation signal and the signal after handling calculate, obtain the underwater sound signal transit time.

The measuring method of a kind of underwater sound signal transit time, referring to Fig. 2, see for details hereinafter and describe:

101: by software programming, utilize a m sequencer to generate the m sequence of a default exponent number, first signal generator produces the first carrier signal, according to the frequency of operation of used transmitting terminal underwater acoustic transducer, determines the first carrier signal frequency;

Wherein, the value of default exponent number is specially 3-11, during specific implementation, can set according to practical application, and the embodiment of the invention does not limit this.For example: by software programming, utilize a m sequencer to generate the m sequence that default exponent number is 7 rank, sequence waveform as shown in Figure 3, frequency of operation according to used transmitting terminal underwater acoustic transducer, the first carrier signal frequency of determining is 80kHz, be the resonance frequency of transmitting terminal underwater acoustic transducer, by the band spectrum modulation of m sequence realization to the first carrier signal.

Wherein, the resonance frequency 80kHz of the transmitting terminal underwater acoustic transducer that above-mentioned first carrier signal frequency is used, can also be according to the transmitting terminal underwater acoustic transducer of practical application, select carrier frequency corresponding, range of choice can be 100Hz-1MHz, during specific implementation, can set according to practical application, the embodiment of the invention does not limit this.

The m sequencer is a kind of feedback shift type structure, and it adds the distance feedback by the shift register of presetting exponent number k position and forms, as shown in Figure 4.Its sequence length N=2 ^k-1, be called the longest linear serial code generator.Because its structure finalizes the design, and feedback function and type of attachment all have certain rule, therefore utilizes the method for tabling look-up just can design sequence code.The m sequence is that the ring counter of being made up of the partial sum gate of feedback shift register can produce m sequence pseudo-random code by the longest a kind of sequence of cycle of the shift register generation of band linear feedback.The advantage of m sequence is to be easy to generate, and autocorrelation performance is good, and is pseudorandom, and the cross correlation between m sequence and the noise is very low.Spread spectrum is spread-spectrum (Spread Spectrum), be with information data to be transmitted by pseudorandomcode (be frequency expansion sequence: modulation Spread Sequence), realize transmission again after the spread spectrum.Spread spectrum is a kind of information transmission mode, the expansion of frequency band be by one independently a sign indicating number sequence finish, realize with the method for modulating.

The basic theories basis of spread spectrum is the channel capacity formula of Shannon in the information theory (CEShannon)

$C={B\log }_2(1+\frac{S}{N})---\left(5\right)$

In the formula: C---channel capacity, b/s;

B---channel width, Hz;

S---signal power, W;

N---noise power, W.

The ability that shannon formula has shown a channel zero defect ground transmission information is with being present in the signal to noise ratio (S/N ratio) in the channel and being used to relation between the channel width of the information of transmitting.

Make C wish the channel capacity have, promptly the information rate of Yao Qiuing is carried out conversion to (5) formula

$\frac{C}{B}=1.44\ln (1+\frac{S}{N})---\left(6\right)$

For the typical case in the interference environment, when

The time, with power series expansion (6) formula, and omit high-order term and get

$\frac{C}{B}=1.44\frac{S}{N}---\left(7\right)$

Or

$B=0.7C\frac{N}{S}---\left(8\right)$

(8)

Can find out by formula (7) and (8),,, just can be increased in the speed C of transmission information in zero defect ground in the channel as long as increase the bandwidth B that is used to the information of transmitting for any given noise signal power ratio N/S.In other words in channel when the signal power to noise power ratio S/N of transmission system descends, can keep channel capacity C constant with the way that increases system transmission bandwidth B.

This has just illustrated increase channel width B, can be under the situation of low signal to noise ratio (S/N ratio), channel still can be under identical capacity transmission information.Even under the situation that signal is flooded by noise, as long as the corresponding signal bandwidth that increases also can keep reliable communication.Spread spectrum utilizes this principle just, expands the means of information signal bandwidth to be transmitted with the spreading code of two-forty, reaches the purpose of raising system antijamming capability.Wherein, spread spectrum has following two characteristics: 1, the bandwidth of transmission signals is far longer than the bandwidth of the original information signal that is transmitted; 2, mainly by the decision of spread spectrum function, this spread spectrum function is pseudorandom (pseudo noise) coded signal normally for the bandwidth of transmission signals.Adopt the m sequence in the embodiment of the invention.The characteristics of spread spectrum maximum are its abilities with very strong anti-interference, anti-multipath.The related function of m sequence is

$R_{\mathrm{xy}}\left(\mathrm{\&tau;}\right)=\left\{\begin{array}{cc}1& \mathrm{\&tau;}=0\\ -\frac{1}{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA0000054193770000032.png,HDA0000054193770000033.png"\; state="\{\{state\}\}">N</figure-callout>}}& 0<\mathrm{\&tau;}\&le;N-1\end{array}\right.---\left(9\right)$

Wherein N is the maximum cycle length of m sequence.When N was very big, the related function of m sequence was close with the related function of discrete two formula white noise sequences, thus with it as frequency expansion sequence.

102: adopt the BPSK modulation system, the m sequence is modulated the first carrier signal, obtain the first modulation signal M1;

Wherein, with the discrete value of digital signal the phase place of first carrier signal is carried out keying, this modulation system is very good in aspect performances such as anti-additive noise ability, signal spectrum utilization factors.BPSK (binary phase shift keying) is exactly two level according to digital baseband signal, a kind of phase modulating method that carrier phase is switched between two different numerical value.Wherein, the modulation formula is

s(t)＝m(t)cos(2πft) 0≤t≤T (10)

M in the formula (t) is the m sequence, and f represents carrier frequency, and T is the bit period of m sequence, and modulation waveform as shown in Figure 5.

103: the first modulation signal M1 is amplified by first signal generator, drive the transmitting terminal underwater sound generator, send underwater sound signal M2 by impedance matching circuit;

Wherein, underwater sound signal M2 is identical with the first modulation signal M1 form but amplitude is bigger.

Further, the driving function of above-mentioned amplification to the first modulation signal M1 by first signal generator realizes.Card ARB1410 specifically takes place for random waveform in first signal generator, also comprise and be used for DA4300, PCI-8100, ES1335, PCI-8103, PCI8238, PCI8603, PCI2005, PCI2007C and the 72xx card series data output card that signal produces, during specific implementation, can select according to the needs in the practical application, the embodiment of the invention does not limit this.

Signal generator sent a synchronizing signal M3 in 104: the first, and the trigger pip Acquisition Circuit is started working;

105: the receiving end underwater acoustic transducer receives the underwater sound signal M2 that propagates in the liquid environment, signal acquisition circuit to underwater sound signal M2 amplify, conversion and Filtering Processing, obtain the signal M4 after the processing;

Wherein, the receiving end underwater acoustic transducer receives the underwater sound signal M2 that propagates in the liquid environment by the underwater acoustic transducer identical with the transmitting terminal underwater acoustic transducer.Wherein, signal acquisition circuit can adopt NI-S series synchronous data collection card, the integrated signal condition data collecting card of NI-C series, NI-M series multifunctional data collecting card, pci data capture card, during specific implementation, select according to the needs in the practical application, the embodiment of the invention does not limit this.

106: by software programming, utilize the 2nd m sequencer to generate same m sequence, the secondary signal generator produces second carrier signal identical with the first carrier signal, adopts the BPSK modulation system, obtains the identical signal M5 with underwater sound signal M2;

107: computing machine to signal M5 and the signal M4 after handling carry out the broad sense computing cross-correlation, obtain the broad sense cross correlation results;

Wherein, the signal M4 after signal M5 and signal acquisition circuit are handled carries out the broad sense computing cross-correlation, and the basic thought of broad sense computing cross-correlation is to utilize the generalized correlation function of two signals to come postpone estimated time, corresponding to the underwater sound signal transit time.This computing is weighted processing according to different optiaml ciriterions to input signal, is equivalent to carry out the pre-filtering processing before calculating related function in two signals, thereby has improved signal to noise ratio (S/N ratio), makes relevant peaks more sharp-pointed, thereby improves estimated performance.The embodiment of the invention adopts the broad sense cross-correlation method based on the phase tranformation technology, and formula is:

$R\left(\mathrm{\&tau;}\right)={\&Integral;}_{-\&infin;}^{\&infin;}W\left(\mathrm{\&omega;}\right)X_T\left(\mathrm{\&omega;}\right)X_R^{*}\left(\mathrm{\&omega;}\right)e^{\mathrm{j\&omega;t}}\mathrm{d\&omega;}---\left(11\right)$

Wherein R (τ) is the broad sense cross correlation results of two signal M4, M5, and W (ω) is a weight function, X _T(ω) be the Fourier transform of the signal M4 after handling,

Conjugation for the Fourier transform of signal M5.Weight function adopts the weights based on PHAT (Phase Transform, phase tranformation), and is as follows:

$V_{\mathrm{PHAT}}=\frac{1}{\left|X_T\left(\mathrm{\&omega;}\right)X_R^{*}\left(\mathrm{\&omega;}\right)\right|}---\left(12\right)$

108: the broad sense cross correlation results is searched for, obtain peak point, the peak point moment corresponding is the underwater sound signal transit time.

Wherein, the broad sense cross correlation results is carried out the maximum value search, find peak point in the data by order method relatively, the peak point moment corresponding is the underwater sound signal transit time, computing method are: according to the sample frequency that signal acquisition circuit is set, determine the required time between per two sampled points, be designated as Ts, then from the point that begins to gather as counting zero point, the sequence number at peak point place multiply by Ts and is the underwater sound signal transit time.

Simply verify the measurement mechanism of a kind of underwater sound signal transit time that the embodiment of the invention provides and the feasibility of measuring method thereof with one below, signal acquisition circuit in the embodiment of the invention adopts the PCI-6132 (synchronous collecting card of America NI company, four tunnel synchronous acquisition, 2.5MS/s, acquisition range is-10V～+ 10V) realize, the signal that collects is sent into computing machine, realize conversion, the Filtering Processing of acquired signal by software, obtain signal and be designated as M4, see for details hereinafter and describe:

(carry out the experiments of measuring of underwater sound signal transit time between transmitting terminal underwater acoustic transducer and the receiving end underwater acoustic transducer among 1.5m * 1.5m * 1.4m), the distance between transmitting terminal underwater acoustic transducer and the receiving end underwater acoustic transducer changes between the interval of 2cm is from 2cm to 90cm in the pond of a finite space.Curve among Fig. 6 _■The result that expression adopts curve fitting method to obtain; _●The result that expression adopts cross-correlation method to obtain; _▲The result that expression adopts the broad sense cross-correlation method to obtain; Curve among Fig. 7 _■The result that expression adopts curve fitting method to obtain; _●The result that expression adopts cross-correlation method to obtain; _▲The result that expression adopts the broad sense cross-correlation method to obtain; Curve among Fig. 8 _■The result that expression adopts curve fitting method to obtain; _●The result that expression adopts cross-correlation method to obtain; _▲The result that expression adopts the broad sense cross-correlation method to obtain; From Fig. 6, Fig. 7 and Fig. 8 as can be seen, there is bigger deviation in the result of calculation of cross-correlation method, measurement result accuracy is relatively poor, the result of calculation deviation of curve-fitting method and broad sense cross-correlation method is less, and the result of calculation standard deviation of broad sense cross-correlation method is littler, shows that this measurement mechanism and measuring method thereof have better stability.

In sum, the embodiment of the invention provides measurement mechanism and the measuring method thereof of a kind of underwater sound signal transit time, the embodiment of the invention adopts the spread-spectrum signal transmission, utilize the broad sense simple crosscorrelation, realize measurement result more accurately, have higher measurement accuracy and robustness than the method for traditional employing sine wave signal, basic simple crosscorrelation; The embodiment of the invention can effectively suppress because serious multipath and the reverberation phenomenon that underwater sound signal produces when propagating in limited liquid space, improves the accuracy that the transit time measures, for subaqueous sound ranging, location provide reliable basis.

It will be appreciated by those skilled in the art that accompanying drawing is the synoptic diagram of a preferred embodiment, the invention described above embodiment sequence number is not represented the quality of embodiment just to description.

The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (2)

1. the measurement mechanism of a underwater sound signal transit time, it is characterized in that, described measurement mechanism comprises: be arranged on transmitting terminal underwater acoustic transducer, receiving end underwater acoustic transducer, signal generating module and signal receiving processing module in liquid, wherein, described transmitting terminal underwater acoustic transducer is identical with described receiving end underwater acoustic transducer; Described signal generating module comprises: the m sequencer, first signal generator that driven by programmed computer; Described signal receiving processing module comprises: the 2nd m sequencer, secondary signal generator, signal acquisition circuit and the computing machine that driven by programmed computer;

A described m sequencer that driven by programmed computer produces the m sequence; Described first signal generator produces the first carrier signal, described m sequence is modulated described first carrier signal, obtain first modulation signal, described first modulation signal is amplified, modulation signal after output is amplified drives described transmitting terminal underwater acoustic transducer and sends underwater sound signal, and described first signal generator sends a synchronizing signal and triggers described signal acquisition circuit and start working simultaneously; Described the 2nd m sequencer that driven by programmed computer produces identical described m sequence; Described secondary signal generator produces second carrier signal identical with described first carrier signal, and described m sequence is modulated described second carrier signal, obtains second modulation signal; Described receiving end underwater acoustic transducer receives the described underwater sound signal of propagating in the liquid environment; Described signal acquisition circuit is handled described underwater sound signal, obtains the signal after the processing; The signal of described computing machine after to described second modulation signal and described processing calculates, and obtains the underwater sound signal transit time.

2. the measuring method of a underwater sound signal transit time is characterized in that, said method comprising the steps of:

(1) by software programming, utilize a m sequencer to generate the m sequence of a default exponent number, first signal generator produces the first carrier signal, according to the frequency of operation of used transmitting terminal underwater acoustic transducer, determines the first carrier signal frequency;

(2) adopt the BPSK modulation system, the m sequence is modulated described first carrier signal, obtain the first modulation signal M1;

(3) the described first modulation signal M1 is amplified by described first signal generator, drive described transmitting terminal underwater sound generator, send underwater sound signal M2 by impedance matching circuit;

(4) described first signal generator sends a synchronizing signal M3, and the trigger pip Acquisition Circuit is started working;

(5) the receiving end underwater acoustic transducer receives the described underwater sound signal M2 that propagates in the liquid environment, described signal acquisition circuit to described underwater sound signal M2 amplify, conversion and Filtering Processing, obtain the signal M4 after the processing;

(6) by software programming, utilize the 2nd m sequencer to generate same described m sequence, the secondary signal generator produces second carrier signal identical with described first carrier signal, adopts the BPSK modulation system, obtains the identical signal M5 with described underwater sound signal M2;

(7) the signal M4 of computing machine after to described signal M5 and described processing carries out the broad sense computing cross-correlation, obtains the broad sense cross correlation results;

(8) described broad sense cross correlation results is searched for, obtain peak point, described peak point moment corresponding is the underwater sound signal transit time.

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