CN105115492B - Underwater terrain matching navigation system based on acoustic Doppler log - Google Patents

Abstract

The invention discloses an underwater terrain matching navigation system based on an acoustic Doppler log, comprising: a multi-beam integrated Doppler log, a differential global positioning system, a platform compass, a data acquisition module and a seabed terrain matching module , multi-beam integrated Doppler log, differential global positioning system, platform compass, and seabed terrain matching module are all connected to the data acquisition module. The multi-beam comprehensive Doppler log of the invention has the advantages of more measuring points, full coverage and high precision, and can more accurately and comprehensively reflect the ups and downs of the underwater topography. The multi-beam comprehensive Doppler log is combined with the seabed terrain matching module to form the underwater terrain matching navigation system based on the acoustic Doppler log of the present invention. Compared with the traditional underwater terrain navigation system, the present invention is not limited by time, and can also ensure the accuracy of real-time navigation information during long-time navigation.

Description

Underwater terrain matching navigation system based on acoustic Doppler log

technical field

The invention relates to the technical field of underwater navigation application of underwater vehicles, in particular to an underwater terrain matching navigation system based on an acoustic Doppler log.

Background technique

Autonomous underwater vehicles are marine vehicles vigorously developed by countries all over the world. They have great application value in the fields of marine protection and marine resource development, such as underwater search, seabed mapping, seabed monitoring, pipeline laying, and seabed operations. Navigation is one of the main technical challenges faced by the application of underwater vehicles. Navigation capability is an important requirement for effective work and safe recovery of underwater vehicles. The research on navigation methods for underwater vehicles has always been a research hotspot at home and abroad.

Due to the limitations of the underwater environment, the current main methods of underwater vehicle navigation are dead reckoning, INS (inertial navigation system), and underwater acoustic log navigation. In the absence of correction information, the above various navigation methods will accumulate or diverge errors with the increase of navigation time or distance, and it is difficult to meet the requirements of long-term navigation and positioning. Moreover, the traditional acoustic Doppler log also has many limitations, such as only one working mode, fewer transmitting beams, fewer measuring points, inaccurateness, and low efficiency.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a high-precision, high-efficiency underwater terrain matching navigation system based on an acoustic Doppler log.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

1. Multi-beam integrated Doppler log, including:

Acoustic matrix, GPS module, INS module, sound velocity profiler, processing system, multi-channel transceiver conversion module and multi-channel phase-controlled power amplifier, acoustic matrix, multi-channel transceiver module, multi-channel phase-controlled power amplifier, processing The systems are connected sequentially. In addition, the processing system is also connected with the GPS module, INS module, and sound velocity profiler;

Among them, the acoustic matrix is a circular plane matrix formed by 484 first piezoelectric elements and 484 second piezoelectric elements arranged at intervals, and the specifications of the first piezoelectric elements and the second piezoelectric elements are the same ; The circular planar matrix is arranged in 32 rows and 32 columns, the number of piezoelectric elements in each row and each column is an even number, and the distance between the centers of adjacent piezoelectric elements is half of the wavelength of the emitted wave; The independent taps of one piezoelectric element are connected in parallel to obtain 32 sub-arrays in the X direction; the independent taps of the second piezoelectric element in each column of the acoustic matrix are respectively connected in parallel to obtain 32 sub-arrays in the Y direction.

Both the above-mentioned first piezoelectric element and the second piezoelectric element are square.

The multi-channel transceiver conversion unit includes 64 transmitters and 64 receivers, each transmitter drives each sub-array, and each receiver receives the echo signal received by each sub-array.

2. Underwater terrain matching navigation system based on acoustic Doppler log, including:

Multi-beam integrated Doppler log, differential global positioning system, platform compass, data acquisition module and submarine terrain matching module, multi-beam integrated Doppler log, differential global positioning system, platform compass, and submarine terrain matching module Connect with the data acquisition module; where:

The multi-beam integrated Doppler log is used to obtain the depth data of multiple measuring points and the longitudinal velocity and lateral velocity of the underwater vehicle; the differential global positioning system is used to obtain the latitude and longitude information and heading information of the underwater vehicle; the platform compass It is used to obtain the attitude information of the underwater vehicle in the navigation state; the data acquisition module is used to collect and store the data obtained by the multi-beam integrated Doppler log, differential global positioning system, and platform compass; the submarine terrain matching module is used to Seabed terrain matching is performed based on the data collected by the data acquisition module.

Compared with the prior art, the present invention has the following characteristics and beneficial effects:

The present invention transforms the traditional acoustic Doppler log and designs a multi-beam integrated Doppler log. The multi-beam integrated Doppler log does not affect the wet end structure of the underwater vehicle itself, nor Affects the structural strength of the underwater vehicle itself. The traditional acoustic Doppler log can only emit four beams, while the multi-beam comprehensive log sonar can emit multiple beams, and also has the functions of speed measurement and depth sounding.

The multi-beam comprehensive Doppler log of the invention has the advantages of more measuring points, full coverage and high precision, and can more accurately and comprehensively reflect the ups and downs of the underwater topography. The multi-beam comprehensive Doppler log is combined with the seabed terrain matching module to form the underwater terrain matching navigation system based on the acoustic Doppler log of the present invention. Compared with the traditional underwater terrain navigation system, the present invention is not limited by time, and can also ensure the accuracy of real-time navigation information during long-time navigation.

Description of drawings

Fig. 1 is the structural representation of underwater terrain matching navigation system of the present invention;

Fig. 2 is the working flowchart of seabed terrain matching module;

Fig. 3 is a schematic diagram of the sounding working principle of the acoustic Doppler log;

Fig. 4 is the specific structure schematic diagram of multi-beam comprehensive Doppler log of the present invention;

Fig. 5 is a schematic diagram of the specific structure of the acoustic matrix of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

See Fig. 1, the underwater terrain matching navigation system of the present invention mainly comprises multi-beam comprehensive Doppler log, DGPS positioning system (differential global positioning system), platform compass, data acquisition module and seabed terrain matching module. As the sensor of this system, the multi-beam integrated Doppler log is used to measure the water depth data of multiple measuring points and the longitudinal velocity and lateral velocity of the underwater vehicle. Time-sharing measurement of beam bathymetry and velocimetry. The DGPS positioning system is used to provide high-precision latitude and longitude information of underwater vehicles, and provide heading information of underwater vehicles for ship operation. The platform compass is used to provide the attitude information of the underwater vehicle in the sailing state, such as the pitch, roll and heading of the ship. The data acquisition module is used to collect and store the data obtained by the multi-beam integrated Doppler log, DGPS positioning system and platform compass. The seabed terrain matching module is used to construct a terrain reference database and perform terrain matching according to the data collected by the data acquisition module.

See Fig. 2, the workflow of the seabed terrain matching module of the present invention is:

1) Obtain real-time seabed terrain data:

Seabed topographic data is collected by seabed topographic sensors. In the present invention, the seabed terrain sensor is a multi-beam comprehensive Doppler log, and the multi-beam comprehensive Doppler log is used to actually measure the seabed topography data. In the simulation system, it is necessary to model the error of the seabed terrain sensor, and intercept and add noise to the reference data as the real-time data of the simulation.

2) Preprocessing of real-time seabed terrain data:

Digital seabed terrain reference data is digital information distributed according to certain specifications, such as dividing the earth datum evenly into grids and storing the average value of seabed topography depth information in the grids. Since the submarine terrain sensor acquires digital information distributed irregularly, when the attitude angle of the underwater vehicle in the horizontal direction is not zero, coordinate transformation is required to obtain real-time data directly below the underwater vehicle, which is the terrain matching premise.

In addition, although sound waves can travel long distances in the ocean, in the process of propagation, ocean tides, waves, eddies, temperature distribution and salinity distribution of sea water, sea surface, and various inhomogeneous bodies contained in the sea such as bubbles and organisms, etc. All can have a great impact, so that there are large errors in the data measured by sound waves. When data is preprocessed, these factors should be considered, and modeling and compensation should be carried out. Since the INS (inertial navigation system) can provide high-precision navigation information, the real-time data can be preprocessed according to the position, velocity, attitude and other information output by the INS, thereby generating real-time seabed terrain data that can be used for terrain matching.

3) Discrimination of matchability of real-time seabed terrain data:

According to the pre-designed performance indicators (such as matching probability, matching speed, etc.), the matchability of the preprocessed real-time seabed topography data is judged. Only when the real-time seabed topography data meets the design performance index requirements can the terrain match be performed, otherwise Directly transfer to navigation information fusion processing without terrain matching.

4) Combined with the submarine terrain database for terrain matching:

The submarine topographic database is used to store the digital topographic reference map of the seabed, which adopts two-dimensional plane coordinates and the WGS-84 geodetic coordinate system. At present, the more commonly used methods for making seabed digital topographic reference maps include ship-borne sonar, sonar array, side-scan sonar, multi-beam sonar, airborne laser ranging system, etc., supplemented by GPS for direct measurement to obtain seabed Raw data for terrain. After data processing in the later period, a digital chart for terrain-assisted navigation is obtained. At present, the main steps of post-processing include: rasterizing the original terrain, and each grid records the "representative elevation" of the corresponding terrain, usually the "representative elevation" is taken as the average elevation of the grid. The size of the grid distance is related to the required positioning accuracy and storage capacity. Generally, the grid distance can be 50-100m, and the grid is taken as a square.

The storage of digital maps is usually stored directly in the form of grids, or stored in a compressed way to save storage space. However, judging from the current development trend of microelectronics, the issue of storage capacity can be ignored. Another problem is reading. According to the current computer computing power and reading and writing speed, for underwater vehicles, it can basically meet the data IO requirements.

Match the preprocessed real-time seabed topographic data with the seabed digital topographic reference map, and output the matching information.

5) Performance evaluation:

At each terrain matching navigation time point, the collected seabed topography data is matched with the seabed digital topographic reference map, whether the matching information is available and the information weight of the matching information in the final information fusion need to be evaluated to determine the matching information The usability of the seabed terrain is eliminated, and the unavailable matching information is eliminated, and finally the data fusion is performed on the effective seabed terrain matching information.

6) Intelligent information fusion:

Intelligently fuse effective submarine terrain matching information and INS output information to obtain navigation parameter information and correct INS.

See Figure 3, the sounding working principle of the acoustic Doppler log is as follows:

The acoustic Doppler log is based on the Doppler effect to achieve seabed sounding. If the underwater vehicle in flight transmits sound waves obliquely to the seabed and receives the reflected signal from the seabed, then the difference f _d between the frequency f _np of the received signal and the frequency f _u of the transmitted signal depends on the speed of the underwater vehicle:

f _d =f _np -f (1)

At present, the acoustic Doppler log uses a dual-beam array, and the beams are symmetrically arranged on both sides of the vertical line, so that the nonlinear relationship between Doppler frequency and velocity is eliminated when a single beam is used. Doppler shift Determined by the frequency difference between the array beam signals received by the bow and stern:

The sailing speed V of the underwater vehicle is:

In the formulas (2) to (3), V represents the speed of the underwater vehicle; c represents the speed of sound in the ocean; f _npF represents the frequency of the array beam signal received by the stern, and f _npB represents the frequency of the array beam signal received by the stern; α represents the beam depression angle, that is, the angle between the beam emission direction and the underwater vehicle's navigation direction; Indicates the frequency gain factor.

The sounding range of the acoustic Doppler log can reach several kilometers, and the sounding accuracy is 1%-2%. Ground speed measurement accuracy, when the speed is ≤10 knots, the error is <0.1 knots; when the speed is >10 knots, the error is <1%.

In practical application, the sound wave emission of the acoustic Doppler log is carried out simultaneously along the four beam directions of the array, as shown in Figure 3, the array beams 1 and 3 are symmetrically arranged on the radial plane of the underwater vehicle, and the array beams 2 and 4 are symmetrically arranged on the radial and transverse planes of the underwater vehicle to form the "JANUS" structure of the array directional diagram. The beam has a certain inclination angle to the vertical line, so that the simultaneous measurement of the lateral and longitudinal speed of the ship can be realized.

At the same time, the acoustic Doppler log is an active underwater acoustic device that works in a pulse mode. It uses the pulse ranging method to measure depth by using the time difference between the received echo and the transmitted pulse signal. It can be seen from Figure 3 that array beam 1, array beam 2, array beam 3, and array beam 4 are respectively launched into the water along four directions, front, rear, left, and right, that is, measuring points A, B, and C can be measured at the same time. , Water depth information at D. In this way, when the underwater vehicle is navigating, the water depth data of three lines can be measured at the same time, that is, line AC and two lines passing through point D and point B respectively and parallel to AC.

The traditional acoustic Doppler log is a four-beam echometer. Due to the small number of beams, the present invention further designs a multi-beam integrated Doppler log. The schematic diagram of its structure is shown in Figure 4. The multi-beam integrated Doppler log is composed of acoustic matrix, GPS unit, INS unit (inertial navigation unit), sound velocity profiler, processing system, multi-channel transceiver conversion unit and multi-channel phase-controlled power amplification unit. The GSP unit is used to provide the current position information of the underwater vehicle. Different depths of water layers have different seawater components, resulting in different propagation speeds of sound waves. The sound velocity profiler is used to measure the sound velocity of the corresponding water layer, and then use the formula (3) to calculate the speed of the underwater vehicle. The INS unit is used to realize the underwater positioning of the underwater vehicle. Because sea water will greatly weaken the electromagnetic signal, when the underwater vehicle is underwater for a long time, it will not be able to receive GPS positioning information, and it needs to rely on the INS unit for positioning. However, there are accumulated errors in the positioning of the INS unit, so when the underwater vehicle surfaced, the GPS unit was used to correct the positioning information of the underwater vehicle. The multi-channel phase-controlled power amplification unit controls the working state (transmitting state or receiving state) of the multi-channel transceiver conversion unit according to the instructions of the processing system. The multi-channel transceiver conversion unit transmits sound waves through the acoustic matrix or receives echoes from the acoustic matrix. Since electric signals propagate between the multi-channel phase-controlled power amplifying unit, the multi-channel transceiver conversion unit and the acoustic array, the multi-channel phase-controlled power amplifier unit, the multi-channel transceiver conversion unit, and the acoustic array are electrically connected in sequence.

When transmitting sound waves, the processing system controls the multi-channel phase-controlled power amplifier unit to amplify the transmitted signal, and transmits it to the acoustic matrix through the multi-channel transceiver conversion unit, and controls the acoustic matrix to emit sound waves underwater with a larger opening angle.

When receiving the echo, the echo signal received by the acoustic matrix is transmitted to the multi-channel phase power amplification unit through the multi-channel transceiver conversion unit, and then sent to the processing system. The processing system combines the GPS unit, the INS unit, and the sound velocity profiler to obtain The information is comprehensively processed to obtain the water depth data of the survey point and the longitudinal and lateral speeds of the underwater vehicle.

Since the multi-beam integrated Doppler log can receive dozens or even hundreds of sound waves at the same time, each time a sound wave is emitted, a set of water depth data can be obtained in the direction of the vertical course. Compared with the traditional four-beam echometer, the biggest advantage of the multi-beam comprehensive Doppler log is multi-measuring points, full coverage, and high precision, so that it can more accurately and comprehensively reflect the fluctuation of underwater terrain.

Figure 5 is a schematic diagram of the specific structure of the acoustic matrix. The acoustic matrix is a circular planar matrix formed by arranging 968 piezoelectric elements of the same specification. The circular planar matrix is arranged in 32 rows and 32 columns, each row The number of piezoelectric elements in each column is even, and the distance between the centers of adjacent piezoelectric elements is half of the wavelength of the emitted wave. The piezoelectric element is divided into a first piezoelectric element and a second piezoelectric element, and the first piezoelectric element and the second piezoelectric element are arranged at intervals, that is, adjacent piezoelectric elements of the first piezoelectric element The elements are all the second piezoelectric primitives, and the adjacent piezoelectric primitives of the second piezoelectric primitives are all the first piezoelectric primitives. In this specific implementation, the number of the first piezoelectric primitives and the second piezoelectric primitives Both are 484. As shown in FIG. 5 , the piezoelectric primitive with a dot in the center represents the first piezoelectric primitive, and the remaining piezoelectric primitives are the second piezoelectric primitive.

For the i-th row of the acoustic matrix, the independent taps of the first piezoelectric element in the row are connected in parallel to form a sub-array in the Xi direction, and the sub-arrays in the Xi direction (i=1, 2, ... 32) form the basis in the X direction. array. Similarly, for the jth column of the acoustic matrix, the independent taps of the second piezoelectric element in the column are connected in parallel to form a Y _j -direction sub-array, and the Y _j -direction sub-array (j=1, 2,...32 ) constitute the matrix in the Y direction. In this specific implementation, both the X-direction matrix and the Y-direction matrix include 32 sub-arrays, that is, the acoustic matrix includes 64 sub-arrays.

Since the acoustic base array includes 64 sub-arrays, 64 transmitters and 64 receivers are used, and each transmitter drives each sub-array separately to form a phased beam in both the X direction and the Y direction; The echo signals received by each sub-array are received. Based on the existing half-wavelength array technology, the acoustic base array of the present invention has a beam width of about 3.2 degrees. Considering the combination of transceivers, it is assumed that the multi-beam function needs to reach 4 times the water depth coverage, that is, the beam opening angle is 126 degrees. 42 beams.

The 42 narrow beams are divided into 14 groups, each group has 3 narrow beams.

The launch sequence is as follows:

1st narrow beam of group 1, 1st narrow beam of group 2, ..., 1st narrow beam of group 14;

2nd narrow beam of group 1, 2nd narrow beam of group 2, ..., 2nd narrow beam of group 14;

3rd narrow beam of group 1, 3rd narrow beam of group 2, ..., 3rd narrow beam of group 14.

The 64 sub-arrays can be controlled by independent phase technology, that is, the 64 sub-arrays input the same amplitude and out-of-phase signals, and their phases can be controlled, and the speed measurement and depth sounding functions can be realized in time-sharing, and the time division can be adjusted for self-use and flexible control.

(1) Speed measurement mode

Because of the independent phase, X ₁ -X ₈ direction sub-array, X ₁₇ -X ₂₄ direction sub-array, Y _1- Y ₈ direction sub-array, Y ₁₇ -Y ₂₄ direction sub-array input the first signal with the same amplitude and same phase , X ₉ -X ₁₆ direction subarray, X ₂₅ -X ₃₂ direction subarray, Y ₉ -Y ₁₆ direction subarray, Y ₂₅ -Y ₃₂ direction subarray input the second signal with the same amplitude and same phase, the first The phase difference between the signal and the second signal is 180 degrees, so that four independent beams can be formed in directions of ±30° in the X direction and the Y direction. The speed measurement function can be realized by using the traditional speed measurement technology.

(2) Sounding mode

For the X ₁ -X ₃₂ direction sub-array and the Y ₁ -Y ₃₂ direction sub-array, the required 42 beams can be obtained by adopting the traditional Rotated Directional Transmitting technology. The sounding function can be realized by using the traditional sounding technology.

The invention is defined by the appended claims and the description provided above should therefore be considered as an illustration of the nature applicable to different possible implementation examples.

Claims (4)

1. multi-beam integrated Doppler log, it is characterised in that including：

Acoustics basic matrix, GPS unit, INS units, Sound speed profile instrument, processing system, multichannel transmitting-receiving converting unit and multichannel are phased Power amplification unit, acoustics basic matrix, multichannel receive and dispatch converting unit, multichannel phase control power amplifying unit, processing system phase successively Even, in addition, processing system is also connected with GPS unit, INS units, Sound speed profile instrument；

Wherein, acoustics basic matrix is the circular flat being spaced by 484 the first piezoelectricity primitives and 484 the second piezoelectricity primitives Face basic matrix, the first piezoelectricity primitive and the second piezoelectricity primitive specification are identical；Circular flat basic matrix is arranged in 32 rows 32 and arranged, each row and each The piezoelectricity primitive number of row is even number, and adj acent piezoelectric primitive center spacing is the half of transmitted wave wavelength；Respectively by acoustics basic matrix The independent tap of first piezoelectricity primitive of each row is in parallel, obtains 32 submatrixs of X-direction；Acoustics basic matrix is respectively arranged respectively second The independent tap of piezoelectricity primitive is in parallel, obtains 32 submatrixs of Y-direction.

2. multi-beam integrated Doppler log as claimed in claim 1, it is characterised in that：

Described the first piezoelectricity primitive and the second piezoelectricity primitive is square.

3. multi-beam integrated Doppler log as claimed in claim 1, it is characterised in that：

Described multichannel transmitting-receiving converting unit includes No. 64 emitters and No. 64 receivers, and each road emitter drives each son respectively Battle array, each road receiver receives the echo-signal that each submatrix is received respectively.

4. the underwater terrain matching navigation system based on acoustic Doppler log, it is characterised in that including：

Multi-beam integrated Doppler log described in claim 1, DGPS, platform compass, data acquisition Module and sea-floor relief matching module, multi-beam integrated Doppler log, DGPS, platform compass, seabed Terrain match module is connected with data acquisition module；Wherein：

Multi-beam integrated Doppler log be used for obtain multi-measuring point bathymetric data and submarine navigation device longitudinal velocity and Lateral velocity；DGPS is used for obtaining the latitude and longitude information and course information of submarine navigation device；Platform compass is used To obtain attitude information of the submarine navigation device under operational configuration；Data acquisition module is more for gathering and storing multi-beam synthesis It is general to strangle the data that log, DGPS, platform compass are obtained；Sea-floor relief matching module is used for adopting based on data Collect the data of module collection, build landform benchmark database, and carry out sea-floor relief matching.