Ocean current measurement method and system based on unmanned ship

Abstract

An ocean current measurement method based on an unmanned ship comprises the following steps: selecting an observation point, and planning a track around the observation point; the unmanned ship is controlled to sail along the track according to the preset navigational speed, and the real-time navigational speed of the unmanned ship is recorded; in the navigation process of the unmanned ship, meteorological equipment carried on the unmanned ship is used for detecting sea surface hydrological parameters; correcting the real-time navigational speed by using the sea surface hydrological parameters to obtain an actual navigational speed; calculating component estimation values of the at least two ocean current speeds based on the actual navigational speed; and calculating the actual value of the ocean current flow velocity of the observation point based on all the component estimation values. The invention provides an ocean current measurement method and system based on an unmanned ship, and the method and system can be used in an offshore sea area and an open sea area, are high in universality, are low in complexity, and are easy to realize.

Description

Technical Field

[0001] The invention relates to the technical field of ocean current measurement, in particular to an ocean current measurement method and system based on an unmanned boat. Background Art

[0002] Ocean currents, also known as ocean currents, are the flow of different water masses in the ocean under the influence of wind stress, density gradient force, Coriolis force, tidal force, etc., and are one of the common forms of movement of seawater. The unit of ocean current velocity is meter per second according to the SI unit system, recorded as m / s; the flow direction is expressed in geographic azimuth, which refers to the direction in which the seawater flows, which is exactly the opposite of the definition of wind direction.

[0003] The measurement of ocean current speed and direction generally uses different current meters, including drifting current meters and acoustic Doppler current profilers ADCP. Ocean current detection generally requires the use of manned ships to go out to sea, deploy drifting buoys, anchored buoys or submerged buoys, and load different current meters on the buoys. For offshore current measurement, this method is very costly and difficult to operate and maintain. Technical deployment and ship measurement are also subject to weather and sea conditions.

[0004] You can also use shore-based and ship-based high-frequency radars and lidars to measure the Doppler frequency shift signal of the scattered echo reflected from the sea surface and invert the radial flow velocity detected by the radar. However, this does not provide complete information on the flow velocity, and the detection range is limited to the nearshore waters. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a current measurement method and system based on an unmanned boat, which can be used in both nearshore waters and offshore waters, has strong versatility, low complexity, and is easy to implement.

[0006] In order to achieve the above object, the specific scheme adopted by the present invention is: a method for measuring ocean currents based on an unmanned boat, comprising the following steps: Select observation points and plan the track around the observation points; Control the unmanned boat to sail along the track at a preset speed and record the real-time speed of the unmanned boat; During the navigation of the unmanned boat, the meteorological equipment carried on the unmanned boat is used to detect the sea surface hydrological parameters; The real-time speed is corrected using sea surface hydrological parameters to obtain the actual speed; Calculating at least two component estimates of current velocity based on actual ship speed; The actual value of the current velocity at the observation point is calculated based on all component estimates.

[0007] As a further optimization of the above-mentioned ocean current measurement method based on unmanned boats: when planning the track around the observation point, the track is a rectangular track and is composed of four baselines connected end to end, two of which extend in the north-south direction and the other two extend in the east-west direction.

[0008] As a further optimization of the above-mentioned ocean current measurement method based on the unmanned boat: when the unmanned boat is controlled to sail along the track at a preset speed, the preset speed is greater than the predicted value of the ocean current velocity at the observation point.

[0009] As a further optimization of the above-mentioned ocean current measurement method based on the unmanned boat: after recording the real-time speed of the unmanned boat, the parts before and after the unmanned boat's navigation direction changes in the real-time speed are deleted.

[0010] As a further optimization of the above-mentioned ocean current measurement method based on unmanned boats: sea surface hydrological parameters include sea surface wind speed and sea surface wind direction. When the real-time speed is corrected using the sea surface hydrological parameters, the real-time speed is corrected using the sea surface wind speed and sea surface wind direction.

[0011] As a further optimization of the above-mentioned ocean current measurement method based on unmanned boats: the specific method of using sea surface wind speed to correct the real-time speed is: Generate a speed correction factor based on the drifting speed, sea surface wind speed and sea surface wind direction of the unmanned boat under calm water conditions; Determine a number of correction intervals from the track, and calculate the average of the real-time speed of the unmanned boat within the correction intervals; The speed correction factor is used to correct the mean of the real-time speed to obtain the actual speed.

[0012] As a further optimization of the above-mentioned ocean current measurement method based on unmanned boats: the specific method for calculating the component estimation value of the ocean current velocity includes: Determine the component directions of all component estimates; The part of the track parallel to the component direction is selected as the calculation part, and each component estimate corresponds to two calculation parts; The difference between the actual speeds corresponding to the two calculation parts is calculated as the component estimate.

[0013] As a further optimization of the above-mentioned ocean current measurement method based on unmanned boats: the component estimates include north-south estimates and east-west estimates.

[0014] As a further optimization of the above-mentioned ocean current measurement method based on unmanned boats: a method for calculating the actual value of the ocean current velocity at the observation point based on all component estimates is: vector summing all component estimates to obtain the actual value of the ocean current velocity at the observation point.

[0015] A current measurement system based on an unmanned boat is used to implement the above-mentioned current measurement method based on an unmanned boat. The system includes an unmanned boat and a land monitoring station. The unmanned boat is provided with meteorological equipment. Both the unmanned boat and the meteorological equipment are connected to the land monitoring station through a Beidou communication module.

[0016] Beneficial effects: The present invention does not require the use of special sensors for current observation, has lower costs, can be used in both nearshore and offshore areas, and has strong versatility. In addition, the present invention has low complexity and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the present invention; Figure 2 This is a schematic diagram of the embodiment when the ocean current is in a due north-south direction; Figure 3 It is a schematic diagram of the embodiment when the ocean current is in any direction. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, a method for measuring ocean currents based on an unmanned boat includes S1 to S6.

[0020] S1. Select an observation point and plan a track around the observation point. When selecting an observation point, you can choose an observation point in the nearshore waters or offshore waters, as long as the unmanned boat can return smoothly. The specific form of the track can be determined according to the actual measurement needs, for example, a circular track, a square track or a diamond track can be selected. Considering that in practice, the measurement results of ocean currents are mainly used to guide and warn offshore facilities or ships, and are usually expressed in four directions of east, west, south and north or two directions of longitude and latitude. Therefore, in order to simplify the measurement method and avoid changing the direction of the final measurement results, when planning the track around the observation point, the track is a rectangular track and is composed of four baselines connected end to end, two of which extend in the north-south direction, and the other two extend in the east-west direction. In this embodiment, the side length of the track is set to 200-300m. As a better choice, the track can be planned as a square track, and the side length is set to 250m.

[0021] S2, control the unmanned boat to sail along the track at a preset speed, and record the real-time speed of the unmanned boat. The real-time speed of the unmanned boat can be output by the unmanned boat's own drive system, and sent to the land monitoring station in the form of a Beidou short message, or the real-time speed of the unmanned boat can be determined based on the Beidou navigation system based on the position of the unmanned boat. Because the present invention mainly determines the ocean current speed by the influence of the ocean current speed on the speed of the unmanned boat, in order to make the ocean current speed affect the speed of the unmanned boat, and at the same time, it will not cause the unmanned boat to be unable to sail, when the unmanned boat is controlled to sail along the track at a preset speed, the preset speed is greater than the predicted value of the ocean current speed at the observation point. In this embodiment, the preset speed is set to 1.5-2m / s. The predicted value of the ocean current speed can be determined based on the historical value of the ocean current speed measured at the observation point. On the other hand, under the premise of planning the track as a rectangular track, the speed of the unmanned boat will change before and after the turn of the track, mainly in that it needs to slow down when it is about to turn and accelerate when the turn ends, so as to ensure that the unmanned boat can successfully complete the turn. In the process of acceleration and deceleration, the speed of the unmanned boat will not reach the required preset speed, and the relationship between the change of speed and the speed of the current is complex, making it difficult to accurately calculate the relationship between the speed and the speed of the current, and the acceleration and deceleration results will also affect the accuracy of the final measurement results. In order to avoid this situation, after recording the real-time speed of the unmanned boat, the part of the real-time speed before and after the change of the navigation direction of the unmanned boat is deleted. The amount of real-time speed data to be deleted can be determined according to the size of the track and the parameters of the unmanned boat itself. Specifically, it is first necessary to determine the turning radius and the turning time consumed by the unmanned boat when navigating based on the preset speed. On the basis of the turning time consumed, a deletion time is determined before and after the turn, and the distance of the unmanned boat corresponding to the part to be deleted is calculated in combination with the preset speed and the deletion time. The distance is combined with the turning radius to obtain a local track containing a complete turning path. On the basis that the ratio of the local track to the overall length of the track does not exceed the preset threshold, the deletion time can be determined, and the real-time speed within the deletion time is deleted.

[0022] S3. During the navigation of the unmanned boat, the meteorological equipment carried on the unmanned boat is used to detect the sea surface hydrological parameters. The sea surface hydrological parameters include sea surface wind speed and sea surface wind direction. When the real-time speed is corrected using the sea surface hydrological parameters, the real-time speed is corrected using the sea surface wind speed and sea surface wind direction. In the process of the unmanned boat sailing along the track, in addition to being affected by the ocean current, the flow of sea surface air will also interfere with the unmanned boat. Therefore, it is necessary to consider the impact of the sea surface hydrological parameters on the real-time speed of the unmanned boat. In actual situations, when the component of the sea surface wind speed in the direction of the unmanned boat is positive, the sea surface wind speed will cause the actual speed of the unmanned boat to increase. When the component of the sea surface wind speed in the direction of the unmanned boat is negative, the sea surface wind speed will cause the actual speed of the unmanned boat to decrease. Therefore, it is necessary to use meteorological equipment to detect the sea surface wind speed. The detection result of the sea surface wind speed is a vector, which is jointly determined by the sea surface wind direction and the absolute value of the wind speed.

[0023] S4. Correcting the real-time speed using sea surface hydrological parameters to obtain the actual speed. After determining the sea surface wind speed, the specific method of correcting the real-time speed using the sea surface wind speed is S41 to S43.

[0024] S41. Generate a speed correction factor based on the drifting speed, sea surface wind speed and sea surface wind direction of the unmanned boat under calm water conditions. In S3, it has been described that the relationship between the sea surface wind speed, sea surface wind direction and heading will affect the real-time speed of the unmanned boat. Therefore, the speed correction factor needs to be generated based on the drifting speed, sea surface wind speed and sea surface wind direction. The speed correction factor can be the opposite of the component of the sea surface wind speed in the direction of travel of the unmanned boat, that is, the speed correction factor is obtained by taking the negative operation of the component.

[0025] S42, determine several correction intervals from the track, and calculate the mean of the real-time speed of the unmanned boat in the correction interval. In S2, in order to avoid the change of the actual speed during the acceleration and deceleration of the unmanned boat affecting the accuracy of the final measurement result, it is necessary to delete the real-time speed of the acceleration part and the deceleration part, and the remaining part is the part where the unmanned boat is in a straight line and the real-time speed is uniform, which is the correction interval. Because the track is a rectangular track, and the acceleration part and the deceleration part are both parts of the baseline close to the turning point of the track, that is, the part close to the turning position, the correction interval is actually the middle part of each baseline. Because the unmanned boat is sailing in the correction interval, its real-time speed is relatively stable, that is, it is basically equal to the preset speed. In order to further simplify the calculation, the mean of the real-time speed of the unmanned boat in the correction interval is first calculated, and then the mean is corrected, so that there is no need to correct the real-time speed at every moment, so as to achieve the effect of simplifying the calculation and improving the overall measurement efficiency.

[0026] S43. Use the speed correction factor to correct the mean of the real-time speed to obtain the actual speed. Specifically, the speed correction factor and the mean of the real-time speed can be directly summed, and the result obtained is the actual speed of the unmanned boat. When the speed correction factor is a positive value, the actual speed is greater than the mean of the real-time speed, and when the speed correction factor is a negative value, the actual speed is less than the mean of the real-time speed.

[0027] S5. Calculate at least two estimated values ​​of the components of the ocean current velocity based on the actual ship speed. The specific method of calculating the estimated values ​​of the components of the ocean current velocity includes S51 to S53.

[0028] S51. Determine the component directions of all component estimates. Because the ocean current velocity is a vector, it can project a vector in the direction of travel of the unmanned boat. The projected vector is the component of the ocean current velocity. Therefore, it is necessary to first determine the component direction of the component estimate. When the component direction is the same as the direction of the actual speed of the unmanned boat, the actual speed of the unmanned boat can be used to determine the component estimate.

[0029] S52, select the part of the track that is parallel to the component direction as the calculation part, and each component estimate corresponds to two calculation parts. In this embodiment, the track is planned as a rectangular track, so there are four directions of the actual speed of the unmanned boat, and each component estimate corresponds to two directions of the actual speed that are parallel to each other but in opposite directions. On this basis, the calculation part is actually equivalent to the correction interval determined by correcting the real-time speed, that is, the middle part of each baseline in the track.

[0030] S53, calculating the difference between the actual speeds corresponding to the two calculation parts as the component estimated value. It should be noted that the difference here is the difference between the speed values ​​of the two actual speeds, and the direction of the component estimated value is determined by the direction of the one with the larger absolute value of the two actual speeds. In this embodiment, the component estimated value includes a north-south estimated value and an east-west estimated value.

[0031] S6. Calculate the actual value of the ocean current velocity at the observation point based on all component estimated values. The method for calculating the actual value of the ocean current velocity at the observation point based on all component estimated values ​​is: perform vector summation on all component estimated values ​​to obtain the actual value of the ocean current velocity at the observation point.

[0032] The measuring principle of the present invention is further described below in conjunction with the accompanying drawings.

[0033] like Figure 2 As shown in the figure, if the ocean current is from due south to due north and is recorded as Cv, the unmanned boat sails counterclockwise along the planned rectangular track, and the preset speed is recorded as the set speed V0, that is, the speed of the unmanned boat in still water is V0, and the actual speed of the east part of the track to the north is recorded as Vn, then: Vn=V0+Cv.

[0034] At the same time, the actual speed of the southward part of the western part of the track is recorded as Vs, then: Vs=V0-Cv.

[0035] Based on Vn and VS, the actual value Cv of the ocean current velocity can be calculated as follows: Cv=(Vn-Vs) / 2.

[0036] In addition, if the calculated result of Cv is a negative value, it means that the direction of the ocean current is actually from due north to due south.

[0037] Similarly, if the ocean current is from due east to due west, or from due west to due east, the actual value of the ocean current velocity can be calculated using the following formula; Cu = (Ve-Vw) / 2, where Ve is the actual speed of the south part of the track heading east, and Vw is the actual speed of the measured west part of the track.

[0038] like Figure 3 As shown, when the direction of the ocean current velocity is in any direction, denoted as Cx, it can be decomposed into an east-west component and a north-south component, and then combined with the above-mentioned Cv and Cu for calculation, the actual value of the ocean current velocity can be obtained, that is, Cx=Cv+Cu.

[0039] It can be seen from the above that the present invention has a simple calculation process and higher efficiency when it is actually applied. In addition, the preset speed of the unmanned boat is not applied when the actual value of the current velocity is finally calculated. Therefore, when setting the preset speed, it is sufficient to satisfy that the preset speed is greater than the predicted value of the current velocity determined by the historical value of the current velocity. In addition, the speed of the existing small solar unmanned boat can already meet the requirements of the preset speed, while vehicles such as wave gliders cannot do so at present. Therefore, the present invention is implemented based on the existing small solar unmanned boat.

[0040] The present invention further provides an unmanned boat-based current measurement system for realizing the above-mentioned unmanned boat-based current measurement method, wherein the system includes an unmanned boat and a land monitoring station, wherein the unmanned boat is provided with meteorological equipment, and both the unmanned boat and the meteorological equipment are connected to the land monitoring station through a Beidou communication module. The unmanned boat adopts an existing small solar unmanned boat, such as the hydrological test unmanned boat model IBoat BS12 produced by Guangzhou Zhonghaida Satellite Navigation Technology Co., Ltd. The meteorological equipment can adopt an existing automatic weather station, such as the micro weather station model NHQXZ-W-609 produced by Wuhan Zhongke Nenghui Technology Development Co., Ltd. The land monitoring station communicates with the unmanned boat and the meteorological equipment through a Beidou communication module based on an ordinary computer.

[0041] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring ocean currents based on an unmanned boat, characterized in that: The steps include: Select observation points and plan the track around the observation points; Control the unmanned boat to sail along the track at a preset speed and record the real-time speed of the unmanned boat; During the navigation of the unmanned boat, the meteorological equipment carried on the unmanned boat is used to detect the sea surface hydrological parameters; The real-time speed is corrected using sea surface hydrological parameters to obtain the actual speed; Calculating at least two component estimates of current velocity based on actual ship speed; The actual value of the current velocity at the observation point is calculated based on all component estimates.

2. The method for measuring ocean currents based on an unmanned boat according to claim 1, characterized in that: When planning a track around an observation point, the track is a rectangular trajectory and consists of four baselines connected end to end, two of which extend in the north-south direction and the other two extend in the east-west direction.

3. The method for measuring ocean currents based on an unmanned boat according to claim 1, characterized in that: When the unmanned boat is controlled to sail along the track at a preset speed, the preset speed is greater than the predicted value of the ocean current velocity at the observation point.

4. The method for measuring ocean currents based on an unmanned boat according to claim 1, characterized in that: After recording the real-time speed of the unmanned boat, the parts before and after the unmanned boat's navigation direction changes in the real-time speed are deleted.

5. The method for measuring ocean currents based on an unmanned boat as claimed in claim 4, characterized in that: Sea surface hydrological parameters include sea surface wind speed and sea surface wind direction. When the real-time speed is corrected using the sea surface hydrological parameters, the real-time speed is corrected using the sea surface wind speed and sea surface wind direction.

6. The method for measuring ocean currents based on an unmanned boat as claimed in claim 5, characterized in that: The specific method of using sea surface wind speed to correct the real-time speed is: Generate a speed correction factor based on the drifting speed, sea surface wind speed and sea surface wind direction of the unmanned boat under calm water conditions; Determine a number of correction intervals from the track, and calculate the average of the real-time speed of the unmanned boat within the correction intervals; The speed correction factor is used to correct the mean of the real-time speed to obtain the actual speed.

7. The method for measuring ocean currents based on an unmanned boat according to claim 1, characterized in that: The specific method for calculating the component estimates of the ocean current velocity includes: Determine the component directions of all component estimates; The part of the track parallel to the component direction is selected as the calculation part, and each component estimate corresponds to two calculation parts; The difference between the actual speeds corresponding to the two calculation parts is calculated as the component estimate.

8. The method for measuring ocean currents based on an unmanned boat as claimed in claim 7, characterized in that: The component estimates include north-south estimates and east-west estimates.

9. The method for measuring ocean currents based on an unmanned boat according to claim 1, characterized in that: The method for calculating the actual value of the ocean current velocity at the observation point based on all component estimated values ​​is: vector summing all component estimated values ​​to obtain the actual value of the ocean current velocity at the observation point.

10. An unmanned boat-based ocean current measurement system, used to implement an unmanned boat-based ocean current measurement method as claimed in claim 1, characterized in that: The system includes an unmanned boat and a land monitoring station. The unmanned boat is provided with meteorological equipment. Both the unmanned boat and the meteorological equipment are connected to the land monitoring station through a Beidou communication module.

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