A two-stage fine-drag-based bottom-imitating detection platform and a bottom-imitating navigation control method

Abstract

This invention relates to a two-stage precision towed bottom-following exploration platform and its navigation control method, belonging to the field of marine exploration technology. It includes a platform body, a first traction system, a first connecting cable, a first-stage towed body, a second connecting cable, a second-stage towed body, and a second traction system. The first-stage towed body is equipped with topographic detection equipment to detect the seabed topography in front of the second-stage towed body. Both the first and second-stage towed bodies are equipped with height detection equipment to measure their real-time seabed clearance. The control center calculates the deviation Δh between the real-time seabed clearance of the second-stage towed body and a preset target height. When the deviation Δh exceeds a preset threshold range, the control center, based on the slope value in the slope information, controls the platform body's travel speed and the deployment and retraction of the first and second traction systems according to different slope value ranges. This invention enables long-duration, high-precision seabed-following navigation, achieving high-precision, wide-range acoustic, optical, and magnetic detection.

Description

Technical Field

[0001] This invention relates to the field of marine exploration technology, specifically to a two-stage precision towed bottom-following exploration platform and a bottom-following navigation control method. Background Technology

[0002] Seabed exploration is a core technological means for marine scientific research, resource exploration, and environmental monitoring. Its accuracy and operational efficiency directly depend on the adaptability of the exploration platform to the seabed environment. Currently, mainstream seabed exploration mainly relies on unmanned underwater vehicles (UUVs), remotely operated underwater vehicles (ROVs), and conventional deep-towed systems. However, all three types of platforms have significant technical limitations in practical applications, making it difficult to simultaneously meet the comprehensive requirements of long-term, large-scale, and high-precision seabed exploration.

[0003] Although unmanned underwater vehicles (UUVs) have autonomous navigation capabilities, they are limited by energy supply and power system efficiency, making it difficult to operate over long periods and large areas. Existing UUVs usually rely on battery packs for power, and the contradiction between energy consumption and mission cycle is particularly prominent when operating continuously over long periods and large areas, making it difficult to achieve continuous and routine exploration of vast sea areas.

[0004] Remotely operated underwater vehicles (ROVs) are connected to the mother ship via an umbilical cable, which provides them with a continuous power supply and real-time control capabilities. However, their operating range is limited by the length of the umbilical cable, and they can usually only work in a limited area around the mother ship.

[0005] Conventional deep-towed systems operate close to the seabed by towing detection equipment with cables. While they offer a certain degree of wide-area coverage, their navigation stability is severely hampered by the movement of the surface mother ship. The mother ship's heave, roll, and other movements are directly transmitted to the towed body via the towline, causing violent fluctuations in the towed body's attitude and resulting in a very high risk of collision with the seabed when navigating close to the bottom. Existing deep-towed systems typically maintain the towed body at an operating height of over 50 meters to avoid collisions. However, this height prevents distance-sensitive detection methods such as optical imaging and magnetic detection from effectively reaching seabed targets. This makes it difficult to effectively capture crucial information such as weak magnetic anomalies and small objects on the seabed, severely restricting the realization of high-precision seabed exploration.

[0006] In summary, existing seabed exploration platforms suffer from irreconcilable contradictions in terms of energy supply, operational range, navigation stability, and detection accuracy. This is particularly true for complex exploration missions requiring long-duration operation, wide-area coverage, and high-precision data acquisition; traditional technologies are no longer sufficient to meet the demands of modern marine exploration. Therefore, there is an urgent need to develop a seabed-following exploration platform capable of stable, long-duration, wide-area, and high-precision navigation close to the seabed to meet the needs of optical, magnetic, and other detection methods for exploring the seabed. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention provides a two-stage precision towed bottom-following exploration platform and a bottom-following navigation control method, which can navigate stably close to the seabed for extended periods with high precision, achieving high-precision optical and magnetic detection with a wide detection range.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A bottom-following detection platform based on a two-stage precision tow body is characterized in that the bottom-following detection platform includes a platform body, a first traction system, a first connecting cable, a first-stage tow body, a second connecting cable, a second-stage tow body, and a second traction system;

[0010] The platform body and the first-level tow body are connected by the first connecting cable controlled by the first traction system. The first traction system is installed on the platform body and is used to control the extension and retraction of the first connecting cable.

[0011] The secondary towing body is connected to the primary towing body via a second connecting cable controlled by the second pulling system. The second pulling system is located inside the primary towing body and is used to control the extension and retraction of the second connecting cable.

[0012] The first-stage towed body is equipped with a terrain detection device for detecting the seabed topography in front of the second-stage towed body;

[0013] The first-stage towed body and the second-stage towed body are respectively equipped with height detection devices, which are used to measure the real-time height of the first-stage towed body and the second-stage towed body relative to the seabed.

[0014] The platform body is equipped with a control center, which receives the seabed topography and the real-time seabed clearance height. The seabed topography information includes slope information. The control center calculates the deviation Δh between the real-time seabed clearance height of the secondary tow body and a preset target height, and compares it with a preset threshold. When the deviation Δh exceeds the preset threshold range, the control center controls the traveling speed of the platform body, the deployment and retraction of the first traction system and the second traction system according to different slope value ranges based on the slope value in the slope information.

[0015] Furthermore, the control center determines whether the slope is uphill or downhill based on the slope value of the seabed topography;

[0016] For uphill terrain, the control center calculates the pitch angle α between the primary towed body and the secondary towed body using the following formula: Where H1 is the absolute depth of the first-level tow body, H2 is the absolute depth of the second-level tow body, and S is the cable length of the second connecting cable between the first-level and second-level tow bodies.

[0017] The seabed topography information is used to read the seabed slope β. If α≤β, the real-time height of the secondary towed body off the seabed is monitored. The second traction system retracts and extends the cable by a preset length to maintain the real-time height of the secondary towed body off the seabed at a preset target height. If α>β, the platform body stops moving forward or moves in the opposite direction. At the same time, the second traction system retracts the cable by a preset length to bring the real-time height of the secondary towed body off the seabed close to the preset target height until α≤β.

[0018] For downhill terrain, the cable laying of the first traction system and / or the second traction system is controlled based on the slope.

[0019] When the real-time height of the secondary tow body above the bottom is not greater than the preset target height.

[0020] The first slope threshold ≤ slope β < 0°, and the control center controls the second traction system to slowly release the cable of the preset length ΔL2;

[0021] If the second slope threshold is less than or equal to the first slope threshold, the control center controls the platform body to reduce its speed by ΔV1 and controls the second traction system to quickly release the cable by a preset length ΔL1.

[0022] If the slope β < the second slope threshold, the control center controls the platform body to reduce its speed by ΔV2, and controls the first traction system and the second traction system to quickly release the cable by a preset length ΔL1 respectively.

[0023] When the real-time clearance of the secondary tow body from the bottom is greater than the preset target height...

[0024] When the first slope threshold is ≤ slope β < 0°, the control center controls the second traction system to quickly release the cable by a preset length ΔL1; when the second slope threshold is ≤ slope β < the first slope threshold, the control center controls the platform body speed to decrease by ΔV2 and controls the second traction system to quickly release the cable by a preset length ΔL1; when the slope β < the second slope threshold, the control center controls the platform body speed to decrease by ΔV2 and controls the first traction system and the second traction system to quickly release the cable by a preset length ΔL3 respectively.

[0025] Furthermore, the primary towing body is an open metal frame structure, and the secondary towing body can be placed inside the tail of the frame structure; the secondary towing body is a streamlined shell made of aluminum alloy frame covered with synthetic material, and the streamlined shell has at least one control wing on the outside and buoyancy material inside;

[0026] The first connecting cable is a heavy-duty armored optical-electric composite tow cable; the second connecting cable is a neutral zero-buoyancy optical-electric composite cable.

[0027] Furthermore, the bow of the first-stage towed body is also equipped with a first attitude sensor and a first-stage micro-power adjustment device; the first attitude sensor is used to monitor the attitude information of the first-stage towed body and upload it to the control center; the attitude information includes roll, pitch and yaw angle; the control center controls the first-stage micro-power adjustment device to adjust the attitude of the first-stage towed body according to the attitude information;

[0028] The secondary tow body is also equipped with a second attitude sensor and a secondary micro-power adjustment device; the second attitude sensor is used to measure the attitude information of the secondary tow body and upload it to the control center via the primary tow body; the control center controls the secondary micro-power adjustment device to adjust the attitude of the secondary tow body according to the attitude information of the secondary tow body.

[0029] Furthermore, both the primary micro-power adjustment device and the secondary micro-power adjustment device include a vertical thruster, a longitudinal thruster, an elevator, and a rudder; the vertical thruster is arranged along the Z-axis of the towed body, and the longitudinal thruster is arranged along the Y-axis of the towed body; the elevator is hinged to the horizontal wing surface of the towed body, and the rudder is hinged to the vertical wing surface of the towed body.

[0030] Furthermore, the first traction system is a heavy-duty water winch system, and all its winches are constant tension winches.

[0031] Furthermore, the platform body is also equipped with an ultra-short baseline system consisting of a USBL acoustic array and two underwater acoustic beacons; the USBL acoustic array is disposed on the platform body and electrically connected to the control center, and the two underwater acoustic beacons are respectively disposed on the first-stage towed body and the second-stage towed body; the USBL acoustic array transmits acoustic interrogation signals underwater and receives response signals from the underwater acoustic beacons to calculate the relative position information of the first-stage towed body and the second-stage towed body underwater.

[0032] This invention also discloses a bottom-following navigation control method for a two-stage precision towed bottom-following exploration platform, characterized in that the bottom-following navigation control method for the two-stage precision towed bottom-following exploration platform described in any one of the above-mentioned methods includes the following steps:

[0033] S1. The main body of the platform travels at a predetermined speed, and the first traction system lowers the first tow body, which is loaded with the second tow body, to a predetermined depth.

[0034] S2. Activate the second traction system to release the secondary tow body from the primary tow body until it is a predetermined distance behind the primary tow body, and the height of the primary tow body off the ground is within the preset target height range.

[0035] S3. After the second-stage towed body reaches the preset target height, the control center issues a detection command, and the core detection payload conducts seabed detection. During the detection process, active control based on dynamic cable length adjustment is introduced to maintain the second-stage towed body's height above the seabed within the preset target height range. The steps are as follows:

[0036] S31, the secondary control unit uploads the collected real-time ground clearance and depth data of the secondary towed body to the primary control unit after filtering and calibration. The data is then integrated and transmitted to the information relay unit. Simultaneously, the forward-looking imaging sonar, the first depth sensor, and the first altimeter collect the forward terrain feedforward information, depth, and ground clearance of the primary towed body and upload them to the primary control unit. After the primary control unit completes data filtering and calibration, it transmits the effective monitoring data to the information relay unit in the form of data packets.

[0037] S32. The information relay unit summarizes the data from the first-level and second-level tow bodies, performs photoelectric signal conversion, and transmits the data back to the control center.

[0038] S33. The control center receives and integrates all data, and calculates the deviation of the second-stage towed body's height from the bottom Δh = h –h0, where h is the real-time height of the second-stage towed body from the bottom, and h0 is the preset target height.

[0039] S34. When the deviation Δh exceeds the preset threshold, the control center, based on the slope value in the terrain information, controls the traveling speed of the platform body and the preset extension / retraction length ΔL of the first and second traction systems according to different slope value ranges, and fine-tunes the expected height of the secondary tow body off the ground in advance. This ensures that the real-time lift height of the secondary tow body remains within the preset target height range.

[0040] Furthermore, in step S34, when the terrain ahead is uphill, the control center calculates the pitch angle between the first-stage towed body and the second-stage towed body using the following formula: Where H1 is the absolute depth of the first-level tow body, H2 is the absolute depth of the second-level tow body, and S is the cable length of the second connecting cable between the first-level and second-level tow bodies.

[0041] The control center obtains the slope β of the terrain ahead based on the received seabed topographic information and monitors the real-time height h of the secondary towed body above the seabed.

[0042] If α≤β, when the real-time height h above the bottom exceeds the preset target height h0, the second traction system retracts or extends the cable by a preset length to maintain the real-time height above the bottom of the secondary towed body at the preset target height; if α>β, the platform body stops moving forward or moves in the opposite direction, and the second traction system retracts the cable by a preset length to bring the real-time height above the bottom of the secondary towed body close to the maximum threshold of the preset target height, until α≤β.

[0043] Furthermore, in step S34, when the path ahead is downhill, the control center compares the real-time clearance height of the secondary tow body with the preset target height;

[0044] When the real-time height of the secondary tow body above the bottom is not greater than the preset target height.

[0045] The first slope threshold ≤ slope β < 0°, and the second traction system slowly releases the cable with a preset length ΔL2;

[0046] When the second slope threshold is less than or equal to the slope β, and the first slope threshold is less than or equal to the first slope threshold, the platform's main speed decreases by ΔV1, and the second traction system quickly releases the cable to the preset length ΔL1.

[0047] When the slope β < the second slope threshold, the platform's main speed decreases by ΔV2, and the first and second traction systems quickly release the cable for a preset length ΔL1, respectively.

[0048] When the real-time clearance of the secondary tow body from the bottom is greater than the preset target height...

[0049] The first slope threshold ≤ slope β < 0°, and the second traction system quickly releases the cable with a preset length ΔL1;

[0050] When the second slope threshold is less than or equal to the slope β, and the first slope threshold is less than or equal to the first slope threshold, the platform's main speed decreases by ΔV2, and the second traction system quickly releases the cable to the preset length ΔL1.

[0051] When the slope β is less than the second slope threshold, the platform's main speed decreases by ΔV2, and the first and second traction systems quickly release the cable to the preset length ΔL3.

[0052] The beneficial effects of this invention are:

[0053] The present invention discloses a bottom-following detection platform and a bottom-following navigation control method based on a two-stage precision tow, which can perform long-term, high-precision and high-stability bottom-following navigation, achieve high-precision optical and magnetic detection, and has a wide detection range.

[0054] This invention utilizes the deployment and retrieval of a heavy-duty armored photoelectric composite tow cable and a neutral zero-buoyancy photoelectric composite cable to complete the water entry arrangement of the first and second stage towed bodies. It introduces active control based on dynamic cable length adjustment to actively adjust the real-time bottom clearance height of the second stage towed body, ensuring it remains within a preset target height range. This meets the high-precision detection requirements of optics and magnetism, achieving high-precision detection at a depth of 2 meters (±1 meter) above the bottom. It is applicable to various detection tasks such as high-precision magnetic exploration and continuous visual image sampling. The mother ship continuously supplies power to underwater electrical equipment via the tow cable, enabling long-term bottom-following navigation. Furthermore, the combined use of the heavy-duty armored photoelectric composite tow cable and the neutral zero-buoyancy photoelectric composite cable extends the tow cable length and expands the detection range.

[0055] This invention, through the coordinated operation of a winch system and a micro-power adjustment device, can support stable navigation within a speed range of 0 to 6 knots, as well as high-precision detection of the detection payload at speeds of 2 to 4 knots.

[0056] The first-stage towed body of this invention relies on its own large weight and motion inertia and is located in a deep-water operation area to achieve an initial significant attenuation of depth fluctuation disturbances transmitted from the mother ship. Furthermore, since the neutral zero-buoyancy optical-electric composite cable has no effective longitudinal force transmission, it can isolate most of the motion disturbances remaining in the first-stage towed body from the mechanical structure level. In addition, through active control based on dynamic cable length adjustment, the disturbances from the mother ship can be effectively filtered out, improving the accuracy and stability of bottom-following navigation, thereby improving the quality of detection data.

[0057] The winch used in the heavy-duty winch system of this invention is a constant tension main winch, which can effectively eliminate the slack and impact load (i.e., 'water hammer effect') generated by the heavy armored photoelectric composite tow cable under severe sea conditions, ensuring the mechanical stability of towing. It not only protects the heavy armored photoelectric composite tow cable and underwater equipment from instantaneous overload damage, but also significantly improves the all-weather operation capability and data acquisition accuracy of the bottom-following exploration platform in complex marine environments.

[0058] The first-stage tow body of this invention features an open metal frame structure, which effectively reduces underwater towing drag, weakens eddy current disturbances and turbulent interference during navigation, improves towing stability, and meets the reliability requirements for long-term underwater operations. The second-stage tow body, with its streamlined outer shell featuring control wings and internal buoyancy material, not only adjusts the second-stage tow body to a zero-buoyancy and balanced state underwater, achieving stable towing navigation, but also increases towing speed, significantly improving detection efficiency. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the overall operation of the bottom-following detection platform based on the two-stage precision towing method of the present invention;

[0060] Figure 2 This is a schematic diagram of the internal structure and composition of the primary towing body of the present invention;

[0061] Figure 3 This is a diagram showing the towing motion cable of a primary towing body of different weights according to the present invention.

[0062] Figure 4 This is a schematic diagram of the internal structure and composition of the secondary towing body of the present invention;

[0063] Figure 5 This is a flow field distribution diagram of the second-stage towed body at a speed of 2kn according to the present invention. In the diagram, the upper left corner indicator represents the velocity vector of the fluid in the simulation.

[0064] Figure 6This is a flow field distribution diagram of the second-stage towed body at a speed of 4kn according to the present invention, wherein the upper left corner indicator represents the velocity vector of the fluid in the simulation;

[0065] Figure 7 This is a comparison diagram of the oscillation amplitudes of the mother ship end and the secondary towing body on the water surface in state 1 (neutral zero buoyancy optical-electric composite cable bow amplitude 0.5m, period 10 seconds);

[0066] Figure 8 This is a comparison diagram of the oscillation amplitudes of the first-stage and second-stage tow bodies in state 1 of the present invention;

[0067] Figure 9 This is a comparison diagram of the oscillation amplitudes of the mother ship end and the secondary towing body in state 2 (neutral zero buoyancy optical-electric composite cable bow end amplitude 1m, period 10 seconds).

[0068] Figure 10 This is a comparison diagram of the oscillation amplitudes of the first-stage and second-stage tow bodies in state 2 of the present invention;

[0069] Figure 11 This is a comparison diagram of the oscillation amplitudes of the mother ship end and the secondary towing body in state 3 (neutral zero buoyancy optical-electric composite cable bow end amplitude 2m, period 20 seconds);

[0070] Figure 12 This is a comparison diagram of the oscillation amplitudes of the first-stage and second-stage tow bodies in state 3 of the present invention;

[0071] Figure 13 This is a diagram showing the depth control of the first-stage towed body according to the present invention;

[0072] Figure 14 This is a diagram showing the height control of the secondary tow body in this invention.

[0073] Figure 15 This is a flowchart of the data acquisition process for the secondary drag body in this invention.

[0074] The components are as follows: 1-Mother ship, 1.1-Control center, 2-Heavy-duty winch system, 3-Heavy-duty armored electro-optical composite tow cable, 4-First-stage tow body, 4.1-Power distribution unit, 4.2-Forward-looking imaging sonar, 4.3-First depth sensor, 4.4-First altimeter, 4.5-First-stage control unit, 5-Neutral zero-buoyancy electro-optical composite cable, 6-Second-stage tow body, 6.1-Second-stage control unit, 6.2-Magnetometer, 6.3-Underwater camera and lighting components, 6.4-Second altimeter, 6.5-Second depth sensor, 6.6-Second attitude sensor, 6.7-Second underwater acoustic beacon, 6.8-Vertical thruster, 6.9-Longitudinal thruster, 6.10-Elevator, 6.11-Rudder, 7-Underwater winch system. Detailed Implementation

[0075] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0076] The terms used in this application, such as top, bottom, left, right, inside, outside, front end, rear end, head, and tail, are based on the orientations or positional relationships shown in the accompanying drawings. Different drawings may result in different positional relationships, therefore they should not be construed as limiting the scope of protection.

[0077] In this invention, the terms "installation," "connection," "interlocking," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, or a connection that allows communication between components. They can also refer to a direct connection or an indirect connection through an intermediate medium. Furthermore, they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0078] This embodiment describes a bottom-following exploration platform and a bottom-following navigation control method based on a two-stage precision towed system. It adopts a rigid-flexible coupled two-stage deep-towed system to achieve bottom-following exploration, which not only increases the exploration range, but also enables stable navigation close to the seabed for a long time and achieves high-precision optical and magnetic detection.

[0079] like Figure 1 As shown, the bottom-probing platform mainly includes a mother ship 1, a heavy-duty surface winch system 2, a heavy-duty armored optoelectronic composite tow cable 3, a first-stage towed body 4, a neutral zero-buoyancy optoelectronic composite cable 5, a second-stage towed body 6, and an underwater winch system 7. The heavy-duty surface winch system 2 and the underwater winch system 7 are traction systems. The heavy-duty surface winch system 2 is mounted on the mother ship 1 and is connected to the first-stage towed body 4 via the heavy-duty armored optoelectronic composite tow cable 3. The entry depth of the first-stage towed body 4 is adjusted by raising and lowering the heavy-duty armored optoelectronic composite tow cable 3. The underwater winch system 7 is mounted on the first-stage towed body 4 and is connected to the second-stage towed body 6 via the neutral zero-buoyancy optoelectronic composite cable 5. The underwater winch system 7 adjusts the height of the second-stage towed body 6 above the bottom by raising and lowering the neutral zero-buoyancy optoelectronic composite cable 5.

[0080] The mother ship 1 serves as the main body of the entire bottom-simulating exploration platform. It houses a control center 1.1 with a data processing unit, used to collect and process the acquired data. The control center 1.1 controls the surface heavy-duty winch system 2 to deploy and retrieve the heavy-duty armored electro-optical composite tow cable 3, and issues corresponding control commands to the primary tow body 4, secondary tow body 6, and underwater winch system 7 via the heavy-duty armored electro-optical composite tow cable 3. Additionally, the mother ship 1 is equipped with an Ultra-Short Baseline (USBL) system consisting of a USBL acoustic array and two underwater acoustic beacons. The USBL acoustic array is mounted on the mother ship 1 and electrically connected to the control center 1.1. The first and second underwater acoustic beacons are respectively mounted on the primary tow body 4 and secondary tow body 6. The USBL acoustic array transmits acoustic interrogation signals underwater and receives response signals from the underwater acoustic beacons to calculate the relative position information of the primary tow body 4 and secondary tow body 6, achieving coordinate positioning and preventing the tow bodies from deviating from the preset survey line.

[0081] In this embodiment, all winches in the heavy-duty winch system 2 are constant tension winches. Each constant tension winch is equipped with a winch and cable-laying mechanism, a tension sensor, and a closed-loop hydraulic / electric control unit. The closed-loop hydraulic / electric control unit is electrically connected to the control center 1.1, the winch and cable-laying mechanism, and the tension sensor. The control center 1.1 or a person manually issues a retraction / release command to the closed-loop hydraulic / electric control unit, which controls the winch and cable-laying mechanism to retract and release the heavy-duty armored optoelectronic composite tow cable 3 to adjust the submersion depth of the underwater primary tow body 4. The tension sensor is used to detect the tension of the heavy-duty armored optoelectronic composite tow cable 3 in real time and feeds the tension signal back to the closed-loop hydraulic / electric control unit. The control center 1.1 issues a preset tension threshold to the closed-loop hydraulic / electric control unit. During towing operations, when the mother ship 1 experiences heave or swaying due to waves, the closed-loop hydraulic / electric control unit calculates the tension deviation ΔF = real-time tension F1 - tension threshold F0. Using the tension deviation as the control input, the unit adjusts the drum output torque via hydraulic pressure and simultaneously adjusts the hydraulic oil flow rate based on the amplitude and rate of change of the tension deviation, thereby changing the drum's cable release and take-up speed. When the tension deviation ΔF > 0, the towing cable is taut, and the closed-loop hydraulic / electric control unit controls the winch and cable laying mechanism to reduce the output torque and increase the cable release speed, quickly releasing the cable. When the tension deviation ΔF < 0, the towing cable is slack, and the closed-loop hydraulic / electric control unit controls the winch and cable laying mechanism to increase the output torque and increase the take-up speed, quickly retrieving the cable. The larger the absolute value of ΔF, the faster the cable release and take-up speed. The constant tension winch automatically and quickly adjusts the drum's cable release and take-up speed and torque to dynamically compensate for the relative displacement between the mother ship 1 and the underwater first-stage towing body 4, stabilizing the tension of the heavy-duty armored electro-optical composite towing cable 3.

[0082] The heavy-duty armored optoelectronic composite tow cable 3 and the neutral zero-buoyancy optoelectronic composite cable 5 are connecting cables, both including a conductive core and optical fiber. The conductive core is used to transmit power, and the optical fiber is the main communication link, used for real-time data exchange between the mother ship 1 and the underwater actuators such as the first-stage tow body 4 and the second-stage tow body 6. The neutral zero-buoyancy optoelectronic composite cable 5 has a weight close to zero in seawater (about 5 kg / km) and has neutral buoyancy characteristics. It transmits almost no axial tension, which is the key to achieving motion decoupling between the first-stage tow body 4 and the second-stage tow body 6 and passively isolating the mother ship 1 from disturbances.

[0083] In this embodiment, the primary tow body 4 mainly functions as a "relay station" and "stabilizing platform," responsible for towing the secondary tow body 6 at a fixed depth and providing it with support. For example... Figure 2 As shown, the first-stage towed body 4 is an open metal frame structure, which effectively reduces underwater towing resistance, weakens eddy current disturbances and turbulent interference during navigation, and improves the overall towing stability of the first-stage towed body 4. Furthermore, it has high overall rigidity and excellent load-bearing capacity, meeting the reliability requirements for long-term underwater operations. The stern of the frame structure supports the second-stage towed body 6, while the bow of the frame structure houses a power distribution unit 4.1, environmental sensing equipment, an information relay unit, a first attitude sensor, a first-stage micro-power adjustment device, and a first-stage control unit 4.5. The power distribution unit 4.1, environmental sensing equipment, information relay unit, first attitude sensor, and first-stage micro-power adjustment device are all electrically connected to the first-stage control unit 4.5. Each component within the frame structure is configured to withstand the environmental pressure at the operating water depth.

[0084] The power distribution unit 4.1 functions as an underwater substation. The control center 1.1 of the mother ship 1 transmits 3000VAC high-voltage power to the first-stage tow body 4 through the conductive core of the heavy-duty armored photoelectric composite tow cable 3. Under the control of the first-stage control unit 4.5, the power distribution unit 4.1 steps down the 3000VAC high-voltage power to 380VAC (for the underwater winch system 7 and the second-stage tow body 6) and 24VDC / 12VDC (for the sensors of the first-stage tow body 4 itself and the first-stage control unit 4.5), thus realizing hierarchical power distribution.

[0085] The environmental sensing equipment includes a forward-looking imaging sonar (Tritech Super SeaKing DST) 4.2, a first depth sensor 4.3, and a first altimeter 4.4. The forward-looking imaging sonar 4.2 is mounted at the front of the frame structure with its front end tilted downwards. An imaging sonar with a detection range of not less than 300 meters is selected, preferably a commercially available and mature imaging sonar such as the Teledyne P450 / M450 series or the SeaKing MS8240, equipped with multi-beam processing software such as MBPro. Any imaging sonar of the same type with a raw echo data output interface and supporting secondary development can replace the equipment selected in this embodiment. The forward-looking imaging sonar 4.2 scans the seabed topography and suspended obstacles ahead using sound waves over a long distance. Simultaneously, the sonar hardware performs echo signal filtering, gain compensation, and coordinate calculation to generate continuous, visualized seabed topographic images. It also simultaneously analyzes and extracts topographic feature parameters such as slope, obstacle height, beam slant range, uphill / downhill markers, and lateral obstacle positions. The generated visualized topographic images and the extracted topographic feature parameters together constitute topographic feedforward information, which is transmitted to the control center 1.1 to provide forward topographic data for the attitude and altitude control of the second-stage towed body 6. The first depth sensor 4.3 is used to measure the absolute depth of the first-stage towed body 4 in real time. The first altimeter 4.4 is used to measure the height of the first-stage towed body 4 from the bottom in real time. Meanwhile, the forward-looking imaging sonar 4.2, the first depth sensor 4.3, and the first altimeter 4.4 transmit the detected data to the primary control unit 4.5. Additionally, an angle sensor electrically connected to the primary control unit 4.5 is mounted on the primary tow body 4 to detect the pitch angle of the forward-looking imaging sonar 4.2 in real time.

[0086] The information relay unit uses, but is not limited to, Model 907 series photoelectric conversion modules, and is electrically connected to the control center 1.1 on the mother ship 1 through the heavy-duty armored photoelectric composite tow cable 3. It photoelectrically converts the sensor data (i.e., the data information transmitted by the environmental sensing device) transmitted to the primary control unit 4.5 and the detection data uploaded by the secondary tow body 6, and then uploads them to the control center 1.1 on the mother ship 1 through the optical fiber in the heavy-duty armored photoelectric composite tow cable 3. At the same time, it sends the control commands of the mother ship 1 to the primary control unit 4.5, and the primary control unit 4.5 transmits each control command to the corresponding actuator.

[0087] The first attitude sensor is used to monitor the roll, pitch, and heading angle of the first-stage towed body 4. The attitude information is transmitted back to the control center 1.1 via the first-stage control unit 4.5. The control center 1.1 sends corresponding adjustment commands to the first-stage micro-power adjustment equipment based on the attitude information. The first-stage micro-power adjustment equipment performs corresponding actions according to the adjustment commands to ensure the stable navigation of the first-stage towed body 4.

[0088] The primary micro-power control system includes a vertical thruster, a longitudinal thruster, an elevator, and a rudder. The vertical thruster, longitudinal thruster, elevator, and rudder are electrically connected to the primary control unit 4.5. In the middle of the primary tow body 4, two vertical thrusters are symmetrically arranged vertically along the Z-axis, providing vertical thrust. Two longitudinal thrusters are symmetrically arranged along the Y-axis on the front and rear sides of the primary tow body 4, providing horizontal thrust. The vertical and longitudinal thrusters output transient thrust vectors to the primary tow body 4 via hydraulic drive units. The transient thrust vectors output by the vertical and longitudinal thrusters are used for dynamic compensation and fine adjustment of the tow body's pitch angle, roll angle, and vertical height. In this embodiment, the vertical and longitudinal thrusters can be SMD HT230 type or equivalent underwater thrusters. Two elevators are horizontally and symmetrically hinged to both sides of the stern of the first-stage towed body 4. The rudder is hinged along the Z-axis to the intersection of the central axis of the stern of the first-stage towed body 4 and the center of the two elevators. The elevators and rudder are driven to deflect via hydraulic drive units to maintain the steady navigation of the first-stage towed body 4. The hydraulic drive units are located inside the first-stage towed body 4.

[0089] The underwater winch system 7 is installed in the middle of the first-stage towed body 4 and is used to deploy and retrieve the neutral zero-buoyancy optical-electric composite cable 5 connecting to the second-stage towed body 6. The central axis of the drum of the underwater winch system 7 is aligned with or close to the center of gravity of the first-stage towed body 4 in the horizontal direction, thereby ensuring the fluid attitude stability of the first-stage towed body 4 under complex sea conditions. The underwater winch system 7 includes a hydraulic drive unit, a winch and cable laying mechanism, a cable length encoder, and a tension sensor. The hydraulic drive unit controls the winch and cable laying mechanism to deploy and retrieve the neutral zero-buoyancy optical-electric composite cable 5 by hydraulic drive, thereby adjusting the height of the second-stage towed body 6 above the seabed. The hydraulic drive unit is electrically connected to the cable length encoder, tension sensor, and first-stage control unit 4.5, respectively. The cable length encoder is coaxially mounted at the end of the drum of the winch and cable laying mechanism, and collects the number of rotations and angular velocity of the drum in real time, converting them into the deployed length and deployment speed of the neutral zero-buoyancy optical-electric composite cable 5. The converted deployed length and deployment speed are then transmitted to the hydraulic drive unit. Tension sensors are installed on the tow cable path to collect the real-time tension of the neutral zero-buoyancy optical-electric composite cable 5 and transmit the tension value to the hydraulic drive unit. The primary control unit 4.5 sends preset tow cable release length and tension setting thresholds to the hydraulic drive unit. Based on the deviation between the real-time release length and the preset tow cable release length, as well as the deviation between the real-time tension and the tension setting threshold, the hydraulic drive unit automatically and quickly retracts and releases the neutral zero-buoyancy optical-electric composite cable 5 at the corresponding retraction and release speed through a winch and cable laying mechanism. This achieves precise control over the release length and real-time tension of the neutral zero-buoyancy optical-electric composite cable 5, thereby dynamically compensating for the relative displacement between the primary tow body 4 and the secondary tow body 6.

[0090] In addition, simulation tests showed that the total weight of the primary tow body 4 and its loaded equipment affects the deep towing depth of the secondary tow body 6, as shown in Table 1 and... Figure 3 The simulation comparison of the three types of first-level towed bodies 4 shows that the basic state is the release of a 5000-meter heavy armored optoelectronic composite tow cable 3 towed at a speed of 4kn.

[0091] Table 1. Simulation results of the influence of the weight of the primary towing body on the working depth of the deep towing.

[0092] Maximum tension T (kg) of the towing cable 11806.7123 14338.1315 27622.3972 Depth Z (m) at the end of the tow cable 1468.0794 1961.4419 2998.3915

[0093] The simulation results show that, with the same cable length and towing speed, the greater the weight of the first-stage towing body 4, the greater the depth of the entire system, and the greater the tension on the towing cable.

[0094] In this embodiment, the secondary tow body 6 serves as the platform for mounting the detection payload, such as... Figure 4 As shown, it is a streamlined shell made of aluminum alloy frame covered with synthetic material. The synthetic material can be a non-metallic composite material that is resistant to seawater corrosion, and it is equipped with buoyancy material inside to adjust the secondary towing body 6 to a zero buoyancy and balance state underwater.

[0095] The streamlined outer shell of the secondary tow body 6 has at least one control wing, with a towing speed of 2-4 knots, which can greatly improve detection efficiency. For example... Figure 5 and Figure 6 As shown, the fluid performance of the two-stage towed body 6 with this shape was analyzed and calculated using the commercial fluid analysis software Fluent. The results showed that no obvious wake vortex appeared in the wake field at the operating speed (2~4kn), indicating that the two-stage towed body 6 can achieve stable towing.

[0096] The secondary tow body 6 integrates a core detection payload, auxiliary navigation and attitude control equipment, secondary micro-power adjustment equipment, and a secondary control unit 6.1. The core detection payload, auxiliary navigation and attitude control equipment, and secondary micro-power adjustment equipment are electrically connected to the secondary control unit 6.1, which is electrically connected to the primary control unit 4.5 via a neutral zero-buoyancy optical-electric composite cable 5.

[0097] The core detection payload includes a magnetometer 6.2 and an underwater camera and lighting assembly 6.3. The second-stage towed body 6 has a retractable tail support controlled by a hydraulic drive unit. The magnetometer 6.2 (commonly known as a magnetic detector) is mounted on this tail support and is used to detect ferromagnetic targets such as buried submarine optical cables. When the magnetometer 6.2 needs to detect optical cables, the tail support extends backward from the second-stage towed body 6 to maintain a certain distance between the magnetometer 6.2 and the second-stage towed body 6. After detection, the tail support retracts into the second-stage towed body 6 along with the magnetometer 6. The magnetometer 6.2 can be, but is not limited to, a high-precision fluxgate magnetometer. The underwater camera and lighting assembly 6.3 is installed in the bow space of the second-stage towed body 6 and is used for optical identification and target confirmation. It can be, but is not limited to, a high-definition color underwater camera and lighting assembly. The magnetometer 6.2 and the underwater camera and lighting assembly 6.3 transmit the detection results to the first-stage control unit 4.5 via the second-stage control unit 6.1.

[0098] The auxiliary navigation and attitude control equipment includes a second altimeter 6.4, a second depth sensor 6.5, a second attitude sensor 6.6, and an inertial navigation module. The second altimeter 6.4 and the second depth sensor 6.5 are respectively installed in the bow space of the second-stage towed body 6. The second altimeter 6.4 measures the real-time height h of the second-stage towed body 6 relative to the seabed and transmits it to the second-stage control unit 6.1, serving as the core feedback signal for bottom-following control. The second altimeter 6.4 can be a high-precision altimeter with a sampling frequency of not less than 10Hz. The second depth sensor 6.5 is used to measure the absolute depth of the second-stage towed body 6 in real time. The data is then transmitted to the secondary control unit 6.1. The second attitude sensor 6.6 and the inertial navigation module are respectively installed in the middle of the secondary towed body 6. The second attitude sensor 6.6 is used to measure the roll, pitch, and heading angles of the secondary towed body 6 in real time and transmit the data to the secondary control unit 6.1. This second attitude sensor 6.6 can be, but is not limited to, a high-performance tactical-grade fiber optic gyroscope (FOG) inertial measurement unit, with a zero-bias stability better than 0.1° / h. The inertial navigation module is used to detect the motion attitude, speed, real-time calculated position, and motion state parameters of the secondary towed body 6, and is redundantly and complementaryly calibrated with the data on the height above the bottom, depth, and relative spatial position measured by the second altimeter 6.4, the second depth sensor 6.5, and the second underwater acoustic beacon 6.7.

[0099] The secondary micro-power adjustment device is installed in the middle of the secondary tow body 6, with its thrust line coinciding with the center of gravity of the secondary tow body 6. This effectively suppresses coupling interference during attitude adjustment and ensures smooth trajectory during bottom-following navigation. The secondary micro-power adjustment device is the same as the primary micro-power adjustment device, with a similar layout. The secondary micro-power adjustment device also includes a vertical thruster 6.8, a longitudinal thruster 6.9, an elevator 6.10, and a rudder 6.11. The vertical thruster 6.8, longitudinal thruster 6.9, elevator 6.10, and rudder 6.11 are electrically connected to the secondary control unit 6.1. The two sets of vertical thrusters 6.8 are arranged vertically along the Z-axis in the middle of the secondary tow body 6, providing it with vertical thrust. The two sets of longitudinal thrusters 6.9 are symmetrically arranged along the Y-axis on both sides of the stern of the secondary tow body 6, providing it with horizontal thrust. The vertical thruster 6.8 and longitudinal thruster 6.9 output transient thrust vectors to the secondary tow body 3 via hydraulic drive units. The transient thrust vectors output by the vertical thruster 6.8 and the longitudinal thruster 6.9 are used to dynamically compensate for and finely adjust the pitch angle, roll angle, and vertical height of the towed body. This counteracts fluid disturbances caused by complex micro-topography and attitude deviations due to tow cable traction, ensuring that the second-stage towed body 6 maintains a preset target altitude and a stable detection attitude with the seabed. The elevator 6.10 and rudder 6.11 are the control wings of the second-stage towed body 6. The elevator 6.10 is hinged to the trailing edge of the horizontal wing surface of the second-stage towed body 6, and the rudder 6.11 is hinged to the trailing edge of the vertical wing surface of the second-stage towed body 6. The elevator 6.10 and rudder 6.11 are deflected by hydraulic drive units inside the second-stage towed body 6 to maintain the stability of its navigation.

[0100] The secondary micro-power adjustment device, in coordination with the underwater winch system 7, actively intervenes in the attitude and altitude of the secondary towed body 6 to cope with sudden changes in local micro-topography. Specifically, when the secondary towed body 6 travels to a local area with drastic seabed topography, the control center 1.1, based on real-time detected seabed height and pitch angle, sends vertical thrust commands, longitudinal thrust commands, and yaw angle commands to the secondary control unit 6.1 via the primary control unit. When the real-time seabed height is lower than the preset target height, the vertical thruster 6.8 outputs upward lift, simultaneously driving the elevator 6.10 to deflect upward, generating upward hydrodynamic force. The vertical thruster 6.8 and the elevator 6.10 work together to lift the secondary towed body 6. Conversely, it controls the vertical thruster 6.8 to output downward thrust and the elevator 6.10 to deflect downward, achieving fine-tuning of the secondary towed body 6's descent. When the pitch angle exceeds a threshold, the longitudinal thruster 6.9 and the rudder 6.11 work together to fine-tune the pitch angle of the secondary towed body 6 in the opposite direction, keeping it level.

[0101] The primary control unit 4.5 and the secondary control unit 6.1 used in this embodiment can both be built on the PC104 embedded industrial control computer to construct the main control hardware platform. They adopt serial communication protocol to realize the stable transmission of various sensor data and control commands, which meets the requirements of underwater towed body deployment in a narrow space and long-term reliable communication.

[0102] The bottom-following detection platform based on a two-stage precision towed structure used in this embodiment, when the mother ship 1 carrying the platform experiences heave and undulation, the vertical disturbance generated by the hull is transmitted to the first-stage towed body 4 via the heavy-duty armored electro-optical composite tow cable 3. Relying on the large self-weight, inertia, and deep-water operation area of ​​the first-stage towed body 4, the depth-related disturbance transmitted from the mother ship 1 can be significantly attenuated initially. Because the neutral zero-buoyancy electro-optical composite cable 5 connecting the first-stage towed body 4 and the second-stage towed body 6 has no effective longitudinal force transmission, it can mechanically isolate most of the residual motion disturbance from the first-stage towed body 4. Simulation tests have verified that this structure can attenuate residual disturbances by more than 85%, thus completing the pre-positioned passive mechanical filtering of the second-stage towed body 6 and effectively avoiding the adverse effects of the heave and undulation of the mother ship 1 and the small attitude fluctuations of the first-stage towed body 4 on the operating attitude and detection accuracy of the second-stage towed body 6.

[0103] Considering the effects of wind and waves, and using a straight-line towing speed of 4 knots, a total tow cable length of 8955 meters, and a basic constant depth of 3000 meters as a reference, the surface mother ship 1 begins to sway, causing oscillations at the bow ends of the heavy-duty armored electro-optical composite tow cable 3 and the neutral zero-buoyancy electro-optical composite cable 5, thus inducing oscillating motion of the entire system in the vertical plane. Simulation tests were conducted on the primary tow body 4 and the secondary tow body 6 connected by the neutral zero-buoyancy electro-optical composite cable 5 under the following three conditions, and the results are as follows... Figures 7 to 12 As shown.

[0104] State 1: Amplitude of 0.5m at the bow of the tow cable, period of 10 seconds.

[0105] State 2: The amplitude of the tow cable bow is 1m and the period is 10 seconds.

[0106] State 3: Amplitude of 2m at the bow of the tow cable, period of 20 seconds.

[0107] The simulation results under the above three conditions show that the depth change curves of the first-stage towed body 4 and the second-stage towed body 6 are significantly different. The movement of the second-stage towed body 6 is significantly smoother and the influence of sea waves is greatly attenuated, which can meet the working requirements of the detection equipment.

[0108] However, as the oscillations intensify, the oscillations of the second-stage towed body 6 also tend to intensify. To further reduce the impact of the mother ship's disturbances on the second-stage towed body 6, this embodiment further introduces active control based on dynamic cable length adjustment. By precisely controlling the length of the neutral zero-buoyancy optical-electric composite cable 5 deployed and retracted by the underwater winch system 7 through the control center 1.1, the real-time height of the second-stage towed body 6 above the bottom is actively adjusted so that it is always kept within the preset target height range (e.g., 2 meters ± 1 meter), thereby achieving high-precision and stable bottom-following navigation of the second-stage towed body 6.

[0109] Specifically, the bottom-following navigation control method of the two-stage precision towed bottom-following detection platform in this embodiment is as follows:

[0110] 1. The mother ship 1 sails at a predetermined speed (e.g., 2-4 knots). The heavy-duty winch system 2 on the mother ship 1 is activated to lower the first-stage tow body 4, which is loaded with the second-stage tow body 6, to the predetermined depth.

[0111] Specifically, when the bottom-probing platform is activated, the control center 1.1 of the mother ship 1 sends a lowering command and a preset tension threshold to the closed-loop hydraulic / electric control unit of the heavy-duty winch system 2. Based on the lowering command, the closed-loop hydraulic / electric control unit activates the winch and cable-laying mechanism to release the heavy-duty armored photoelectric composite tow cable 3, thereby lowering the first-stage tow body 4.

[0112] During the lowering process, the first-stage tow body 1 is controlled at a constant depth, such as... Figure 13 As shown, the first depth sensor 4.3, first altimeter 4.4, and first underwater acoustic beacon mounted on the first-stage towed body 4 transmit the collected depth, height above the bottom, and relative position information of the first-stage towed body 4 to the first-stage control unit 4.5 in real time, and then transmit it back to the control center 1.1 of the mother ship 1 via the heavy-duty armored photoelectric composite tow cable 3 through the information relay unit. The control center 1.1 can visualize the received real-time depth, height above the bottom, and position information in real time, and compare it with preset relevant thresholds to determine whether it deviates from the threshold. When the deviation exceeds the preset range, it issues relevant control commands. The system determines whether the first-stage towed body 4 has reached the designated depth of the predetermined position based on the deviation value between the real-time depth and the preset specified depth, and decides whether to continue lowering the first-stage towed body 4. When the first-stage towed body 4 reaches the specified depth, the control center 1.1 issues a stop lowering command to the closed-loop hydraulic / electric control unit, and the heavy-duty winch system 2 stops lowering the first-stage towed body 4.

[0113] The closed-loop hydraulic / electric control unit of the heavy-duty winch system 2 compares the real-time tension collected by the tension sensor with the tension threshold. As the mother ship rises and falls, the heavy-duty armored photoelectric composite tow cable 3 is rapidly deployed and retracted in real time to dynamically compensate for the relative displacement between the mother ship 1 and the underwater first-stage tow body 4, ensuring that the first-stage tow body 4 is maintained at the specified depth.

[0114] 2. Start the underwater winch system 7 to release the secondary tow body 6 from the primary tow body 4 until it is a predetermined distance (e.g., 200-300 meters) behind the primary tow body 4, and its height above the bottom is within the preset target height range.

[0115] Specifically, after the primary tow body 4 reaches the designated depth, the control center 1.1 issues a command to the primary control unit 4.5 to release the secondary tow body 6. The primary tow body 4 opens the locking mechanism and hatch corresponding to the secondary tow body 6, and starts the underwater winch system 7. The underwater winch system 7 releases the secondary tow body 6 by releasing the neutral zero-buoyancy optical-electric composite cable 5 according to the command.

[0116] During the descent and exploration process, altitude control is maintained for the secondary towed body 6: the neutral zero-buoyancy optical-electric composite cable 5 is released to a set length, and after the secondary towed body 6 detaches from the primary towed body 4 and exits the cabin, the control center 1.1 sends a command via the primary control unit 4.5 to the secondary control unit 6.1 of the secondary towed body 6 to activate the auxiliary navigation and attitude control equipment. For example... Figure 14 As shown, the actuators, including the second altimeter 6.4, the second depth sensor 6.5, the second attitude sensor 6.6, the inertial navigation module, and the second underwater acoustic beacon 6.7, collect real-time data on the second-stage towed body 6, including its height above the bottom, depth, pitch angle, inertial navigation operation data (i.e., inertial navigation data), and spatial relative position information (i.e., positioning data), and simultaneously upload this data to the second-stage control unit 6.1. After data filtering and calibration, the second-stage control unit 6.1 uploads the effective monitoring data to the first-stage control unit 4.5 via the neutral zero-buoyancy optical-electric composite cable 5, and then the data is transmitted back to the control center 1.1 via the heavy-duty armored optical-electric composite towed cable 3 through the information relay unit.

[0117] The control center 1.1 performs a comprehensive analysis of the feedback data, compares it with the preset threshold, determines whether the secondary tow body 6 has reached the specified liftoff height and whether the navigation attitude has become stable, and issues corresponding instructions to the secondary control unit 6.1 based on the determination results (such as instructions to continue releasing the secondary tow body 6, propulsion instructions, and attitude control instructions).

[0118] The propulsion command issued by the control center 1.1 is transmitted to the vertical thruster 6.8 and longitudinal thruster 6.9 via the secondary control unit 6.1. The attitude control command is transmitted to the hydraulic drive unit of the corresponding servo motor of the elevator 6.10 and rudder 6.11. The vertical thruster 6.8, longitudinal thruster 6.9, elevator 6.10, and rudder 6.11 complete the corresponding action adjustment according to the received command, so that the secondary tow body 6 is stably lowered to the preset target height range and sails stably.

[0119] During navigation, the secondary control unit 6.1 collects real-time operating condition data such as propeller speed, rudder deflection angle, and magnetometer 6.2 attitude, and transmits them back to the control center 1.1 step by step to achieve closed-loop monitoring and precise control throughout the entire process.

[0120] 3. After the second-stage towed body 6 reaches the preset target height, the control center 1.1 issues a detection command, and the core detection payload conducts seabed detection, ensuring that the height of the second-stage towed body 6 above the seabed is always maintained within the preset target height range.

[0121] The secondary control unit 6.1 activates the core detection payload on the secondary towed body 6 according to the detection command. Specifically, the tail support of the secondary towed body 6 extends under the drive of the hydraulic drive unit, and the magnetometer 6.2 detects the optical cable located on the seabed. The underwater camera and lighting assembly 6.3 captures images and uses optical identification and confirmation of the target. The detection results are synchronously fed back to the primary control unit 4.5, and then transmitted back to the control center 1.1 via the information relay unit.

[0122] During the detection process, the secondary tow body 6 feeds back information such as propeller speed, rudder angle data and magnetic probe attitude to the secondary control unit 6.1 in real time, and then transmits it back to the control center 1.1 step by step.

[0123] Active control based on dynamic cable length adjustment is introduced during detection to ensure that the height of the secondary towed body 6 above the bottom is maintained within a preset ideal window (i.e., a preset target height range). The control method is as follows:

[0124] (1) For example Figure 15 As shown, the secondary control unit 6.1 inside the secondary tow body 6 filters and calibrates the raw data such as real-time height above the bottom, depth, positioning and inertial navigation collected by the second altimeter 6.4, the second depth sensor 6.5, the second underwater acoustic beacon 6.7 and the inertial navigation module, and then uploads it to the primary control unit 4.5 through the neutral zero buoyancy optical-electric composite cable 5. After data integration, it is transmitted to the information relay unit.

[0125] Simultaneously, the forward-looking imaging sonar 4.2, the first depth sensor 4.3, the first altimeter 4.4, and other actuators collect real-time data such as terrain feedforward information, depth, and ground clearance in front of the first-stage towed body 4, and upload this data to the first-stage control unit 4.5. After data filtering and calibration, the first-stage control unit 4.5 transmits the effective monitoring data to the information relay unit in the form of data packets.

[0126] (2) The information relay unit summarizes the pre-processed effective monitoring data and the detection data uploaded by the secondary tow body 6, performs photoelectric signal conversion, and uploads it to the control center 1.1 of the mother ship 1 through the heavy armored photoelectric composite tow cable 3.

[0127] (3) The control center 1.1 of the mother ship 1 receives and integrates all data, calculates the deviation of the second-stage tow body 6 from the bottom, and determines whether it is within the preset threshold range.

[0128] The deviation of the second-stage tow body 6 from the bottom height is Δh = h – h0.

[0129] Where h is the real-time height of the secondary tow body 6 off the bottom, and h0 is the preset target height.

[0130] Typically, 1.5m ≤ h0 ≤ 2.5m. If h0 is 2.0m, then Δh = h - 2.0m.

[0131] (4) When the deviation Δh of the second-stage towed body 6 from the bottom exceeds the preset threshold, the control center 1.1, based on the terrain trend ahead, performs feedforward compensation on the preset target height h0 in advance when the terrain undulation increases, and dynamically fine-tunes the expected height of the second-stage towed body 6 from the bottom. Make the real-time height from the bottom h equal to the desired height from the bottom. The deviation Δh' meets the preset threshold to achieve a smooth transition and avoid control lag.

[0132] Specifically, the control center 1.1 determines the terrain trend ahead (such as terrain slope, uphill / downhill markers, obstacle height, etc.) based on the forward-looking imaging sonar 4.2 scanned by the first-stage towed body 4, and calculates the expected ground clearance of the second-stage towed body 6. Calculation formula:

[0133] Where L is the measured slant range (i.e., beam slant range) from the forward-looking imaging sonar on the first-stage towed body 4 to the seabed detection point, h0 is the preset target height, k is the steep slope correction coefficient (the larger the slope, the larger the coefficient; for gentle slopes, k=1), β is the seabed topographic slope, and H1 is the absolute depth of the first-stage towed body. For the vertical installation offset of the forward-looking imaging sonar 4.2, 1 represents the pitch angle for the installation of the forward-looking imaging sonar. The pitch angle is 4 for the first-level towed body.

[0134] Control Center 1.1 calculates the real-time and expected bottom clearance heights of the secondary tow body 6. The deviation Δh' is used to dynamically fine-tune the expected height of the secondary tow body 6 from the bottom when the deviation exceeds the threshold. If the deviation continues to decrease, fine-tune in the uphill mode; otherwise, fine-tune in the downhill mode to keep the deviation Δh' within the preset threshold range.

[0135] If the terrain ahead is uphill, use the uphill mode to fine-tune the desired ground clearance of the secondary tow body 6. The pitch angle between the first-stage towed body 4 and the second-stage towed body 6 is calculated using the following formula: ,

[0136] Wherein, H1 is the absolute depth of the first-stage towed body, H2 is the absolute depth of the second-stage towed body, and S is the cable length of the neutral zero-buoyancy optical-electric composite cable 5 between the first-stage and second-stage towed bodies, which corresponds to the slant distance between the two towed bodies.

[0137] The control center 1.1 obtains the forward topographic slope β (i.e., seabed pitch angle) from the seabed topographic information detected by the forward-looking imaging sonar 4.2, and simultaneously monitors the real-time seabed clearance h of the secondary towed body 6. If α≤β, and the real-time seabed clearance h exceeds the preset target height h0, the underwater winch system 7 retracts or extends the cable by a preset length to maintain the real-time seabed clearance of the secondary towed body 6 within the preset target height range. If α>β, the mother ship 1 stops moving forward or reverses a predetermined distance. Simultaneously, the underwater winch system 7 retracts the cable by a preset length and monitors the real-time seabed clearance of the secondary towed body 6 to bring it closer to the preset target height. Preferably, the real-time seabed clearance of the secondary towed body 6 approaches the maximum threshold of the preset target height until α≤β.

[0138] The following describes the active dynamic adjustment of the length of the neutral zero-buoyancy optical-electric composite cable under three scenarios, using 1.5m ≤ preset target height h0 ≤ 2.5m as an example:

[0139] 1) Scenario A: Risk of hitting the bottom (real-time height from the bottom h < 1.5 meters)

[0140] The control center 1.1 of the mother ship 1 issues a "rapid cable retrieval" command to the underwater winch system 7. The hydraulic drive unit of the underwater winch system 7 reverses according to the command, retrieving a pre-set length ΔL1 (e.g., 0.2 meters) of neutral zero-buoyancy optical-electric composite cable 5 at a relatively fast speed (e.g., 0.1 m / s). The neutral zero-buoyancy optical-electric composite cable 5 is tightened, generating a small upward pull that overcomes part of the negative buoyancy of the secondary tow body 6, slightly "lifting" it and increasing the desired height above the bottom. .

[0141] The second altimeter 6.4 detects the real-time change in the height h above the bottom. When h rises to more than 1.5 meters, the underwater winch system 7 stops reeling in the cable.

[0142] 2) Scenario B: Too high off the ground (h > 2.5 meters)

[0143] The control center 1.1 of the mother ship 1 issues a "slow cable release" command to the underwater winch system 7. The hydraulic drive unit rotates forward according to the command and releases a pre-set length ΔL1 (e.g., 0.2 meters) of neutral zero-buoyancy optical-electric composite cable 5 at a relatively slow speed (e.g., 0.05 m / s). The neutral zero-buoyancy optical-electric composite cable 5 slackens, and the secondary tow body 6 sinks naturally under its own weight, reducing its real-time height h above the bottom.

[0144] The second altimeter 6.4 detects the real-time change in the height h above the bottom. When h drops below 2.5 meters, the cable-laying action of the underwater winch system 7 stops.

[0145] 3) Scenario C: Ideal window (1.5m ≤ h ≤ 2.5m)

[0146] The control center 1.1 of the mother ship 1 keeps the underwater winch system 7 stationary and does not adjust the length of the neutral zero-buoyancy optical-electric composite cable 5. At this time, navigation is maintained entirely by the passive filtering effect of the neutral zero-buoyancy optical-electric composite cable 5 and the hydrodynamic stability of the secondary tow body 6 itself.

[0147] If the terrain ahead is downhill, use downhill mode to fine-tune the desired ground clearance of the secondary tow body 6. Based on the received slope adjustment instructions, the system controls the travel speed of the mother ship 1, as well as the operation of the surface heavy winch system 2 and the underwater winch system 7, to control the sinking of the second-stage towed body 6, and calculates in real time the desired height of the second-stage towed body 6 above the bottom. To avoid control lag. h0 and slope threshold can be adjusted according to working conditions. This embodiment takes 1.5m ≤ preset target height h0 ≤ 2.5m, first slope threshold -30° and second slope threshold -60° as an example for explanation.

[0148] 1) When the real-time height above the bottom h ≤ 2.5 meters:

[0149] When the slope β < 0° and the mother ship's control center 1.1 sends a "slow cable release" command to the underwater winch system 7, the hydraulic drive unit rotates forward according to the command and releases a pre-set length ΔL2 (e.g., 0.1 meters) of neutral zero-buoyancy optical-electric composite cable 5 at a relatively slow speed (e.g., 0.05 m / s). The neutral zero-buoyancy optical-electric composite cable 5 slackens, and the secondary tow body 6 sinks naturally under its own weight.

[0150] When the slope β is less than -30° (-60° ≤ slope β < -30°), the control center 1.1 instructs the mother ship 1 to reduce its speed by ΔV1 (e.g., 0.5 knots) and issues a "rapid cable release" command to the underwater winch system 7. The hydraulic drive unit rotates forward according to the command and releases a pre-set length ΔL1 (e.g., 0.2 meters) of neutral zero-buoyancy optical-electric composite cable 5 at a relatively fast speed (e.g., 0.1 m / s). The neutral zero-buoyancy optical-electric composite cable 5 relaxes and reduces the towing speed on the secondary tow body 6, causing the secondary tow body 6 to sink naturally while decelerating.

[0151] When the slope β < -60°, the control center 1.1 instructs the mother ship 1 to reduce its speed by ΔV2 (e.g., 1 knot) and issues a "rapid cable release" command to the surface heavy-duty winch system 2 and the underwater winch system 7. The hydraulic drive unit rotates forward according to the command, releasing a pre-set length ΔL1 (e.g., 0.2 meters) of the heavy-duty armored electro-optical composite towing cable 3 and the neutral zero-buoyancy electro-optical composite cable 5 at a relatively fast speed (e.g., 0.1 m / s). The neutral zero-buoyancy electro-optical composite cable 5 slackens and significantly reduces the towing speed on the secondary towing body 6, causing the secondary towing body 6 to sink naturally while decelerating.

[0152] 2) When the real-time height h above the bottom is greater than 2.5 meters:

[0153] When the slope β < 0° and the mother ship's control center 1.1 sends a "rapid cable release" command to the underwater winch system 7, the hydraulic drive unit rotates forward according to the command and releases a pre-set length ΔL1 (e.g., 0.2 meters) of neutral zero-buoyancy optical-electric composite cable 5 at a relatively fast speed (e.g., 0.1 m / s). The neutral zero-buoyancy optical-electric composite cable 5 slackens, and the secondary tow body 6 sinks naturally under its own weight.

[0154] When the slope β is less than -30° (-60° ≤ slope β < -30°), the control center 1.1 instructs the mother ship 1 to reduce its speed by ΔV2 (e.g., 1 knot) and issues a "rapid cable release" command to the underwater winch system 7. The hydraulic drive unit rotates forward according to the command and releases a pre-set length ΔL1 (e.g., 0.2 meters) of neutral zero-buoyancy optical-electric composite cable 5 at a relatively fast speed (e.g., 0.1 m / s). The neutral zero-buoyancy optical-electric composite cable 5 relaxes and reduces the towing speed on the secondary tow body 6, causing the secondary tow body 6 to sink naturally while decelerating.

[0155] When the slope β < -60°, the control center 1.1 instructs the mother ship 1 to reduce its speed by ΔV2 (e.g., 1 knot) and issues a "rapid cable release" command to the surface heavy-duty winch system 2 and the underwater winch system 7. The hydraulic drive unit rotates forward according to the command, and the surface heavy-duty winch system 2 and the underwater winch system 7 release a pre-set length ΔL3 (e.g., 0.25 meters) of the heavy-duty armored electro-optical composite tow cable 3 and the neutral zero-buoyancy electro-optical composite cable 5 at a relatively fast speed (e.g., 0.1 m / s). The towing speed of the secondary tow body 6 decreases significantly, and it sinks rapidly and naturally under the influence of the sinking primary tow body 4.

[0156] Although the principles of the present invention have been described in detail above with reference to preferred embodiments, those skilled in the art should understand that the above embodiments are merely illustrative explanations of the implementation of the present invention and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute a limitation on the scope of the present invention. Any obvious changes, such as equivalent transformations or simple substitutions, based on the technical solutions of the present invention without departing from the spirit and scope of the present invention fall within the protection scope of the present invention.

Claims

1. A bottom-following detection platform based on a two-stage precision towed system, characterized in that, The simulated bottom detection platform includes a platform body, a first traction system, a first connecting cable, a primary tow body (4), a second connecting cable, a secondary tow body (6), and a second traction system; The platform body and the first-level tow body (4) are connected by the first connecting cable controlled by the first traction system. The first traction system is set on the platform body and is used to control the extension and retraction of the first connecting cable. The secondary towing body (6) and the primary towing body (4) are connected by the second connecting cable controlled by the second pulling system. The second pulling system is located inside the primary towing body (4) and is used to control the extension and retraction of the second connecting cable. The first-stage towed body (4) is equipped with a terrain detection device for detecting the seabed topography in front of the second-stage towed body (6); The first-stage towed body (4) and the second-stage towed body (6) are respectively equipped with height detection devices, which are used to measure the real-time height of the first-stage towed body (4) and the second-stage towed body (6) relative to the seabed. The platform body is equipped with a control center (1.1), which receives the seabed topography and the real-time height above the seabed; wherein, the seabed topography information includes slope information; the control center (1.1) calculates the deviation Δh between the real-time height above the seabed of the secondary tow body (6) and the preset target height, and compares it with a preset threshold. When the deviation Δh exceeds the preset threshold range, the control center (1.1) controls the travel speed of the platform body, the deployment and retraction of the first traction system and the second traction system according to different slope value ranges based on the slope value in the slope information.

2. The bottom-following detection platform based on a two-stage precision towed system according to claim 1, characterized in that, The control center (1.1) determines uphill and downhill based on the slope value of the seabed topography; For uphill terrain, the control center (1.1) calculates the pitch angle α between the first-stage towed body (4) and the second-stage towed body (6) using the following formula: Where H1 is the absolute depth of the first-level tow body, H2 is the absolute depth of the second-level tow body, and S is the cable length of the second connecting cable between the first-level and second-level tow bodies. The seabed topography information is used to read the seabed slope β. If α≤β, the real-time height of the secondary towed body (6) above the bottom is monitored. The second traction system retracts and extends the cable by a preset length to keep the real-time height of the secondary towed body (6) above the bottom at the preset target height. If α>β, the platform body stops moving forward or moves in the opposite direction. At the same time, the second traction system retracts the cable by a preset length to make the real-time height of the secondary towed body (6) above the bottom close to the preset target height until α≤β. For downhill terrain, the cable laying of the first traction system and / or the second traction system is controlled based on the slope. When the real-time height of the secondary tow body (6) from the bottom is not greater than the preset target height, The first slope threshold ≤ slope β < 0°, and the control center (1.1) controls the second traction system to slowly release the cable of the preset length ΔL2; If the second slope threshold is less than or equal to the first slope threshold, the control center (1.1) controls the platform body to reduce its speed by ΔV1 and controls the second traction system to quickly release the cable by a preset length ΔL1. If the slope β < the second slope threshold, the control center (1.1) controls the platform body to reduce its speed by ΔV2, and controls the first traction system and the second traction system to quickly release the cable by a preset length ΔL1 respectively; When the real-time height of the secondary tow body (6) above the bottom is greater than the preset target height, When the first slope threshold is ≤ slope β < 0°, the control center (1.1) controls the second traction system to quickly release the cable by a preset length ΔL1; when the second slope threshold is ≤ slope β < the first slope threshold, the control center (1.1) controls the platform body speed to decrease by ΔV2 and controls the second traction system to quickly release the cable by a preset length ΔL1; when the slope β < the second slope threshold, the control center (1.1) controls the platform body speed to decrease by ΔV2 and controls the first traction system and the second traction system to quickly release the cable by a preset length ΔL3 respectively.

3. The bottom-following detection platform based on a two-stage precision towed system according to claim 1, characterized in that, The first-stage towing body (4) is an open metal frame structure, and the second-stage towing body (6) can be placed inside the tail of the frame structure; the second-stage towing body (6) is a streamlined shell made of aluminum alloy frame covered with synthetic material, and the streamlined shell has at least one control wing on the outside and buoyancy material inside; The first connecting cable is a heavy-duty armored optical-electric composite tow cable (3); the second connecting cable is a neutral zero-buoyancy optical-electric composite cable (5).

4. The bottom-following detection platform based on a two-stage precision tow truck as described in claim 3, characterized in that, The bow of the first-stage tow body (4) is also equipped with a first attitude sensor and a first-stage micro-power adjustment device; the first attitude sensor is used to monitor the attitude information of the first-stage tow body (4) and upload it to the control center (1.1); the attitude information includes roll, pitch and heading angle; the control center (1.1) controls the first-stage micro-power adjustment device to adjust the attitude of the first-stage tow body (4) according to the attitude information; The secondary tow body (6) is also equipped with a second attitude sensor (6.6) and a secondary micro-power adjustment device; the second attitude sensor (6.6) is used to measure the attitude information of the secondary tow body (6) and upload it to the control center (1.1) via the primary tow body (4); the control center (1.1) controls the secondary micro-power adjustment device to adjust the attitude of the secondary tow body (6) according to the attitude information of the secondary tow body (6).

5. The bottom-following detection platform based on a two-stage precision towed system according to claim 4, characterized in that, The secondary micro-power adjustment equipment includes a vertical thruster (6.8), a longitudinal thruster (6.9), an elevator (6.10), and a rudder (6.11). The vertical thruster (6.8) is arranged along the Z-axis of the tow body, and the longitudinal thruster (6.9) is arranged along the Y-axis of the tow body; the elevator (6.10) is hinged to the horizontal wing surface of the tow body, and the rudder (6.11) is hinged to the vertical wing surface of the tow body.

6. The bottom-following detection platform based on a two-stage precision towed system according to claim 1, characterized in that, The first traction system is a heavy-duty water winch system, and all its winches are constant tension winches.

7. The bottom-following detection platform based on a two-stage precision towed system according to claim 1, characterized in that, The platform body is also equipped with an ultra-short baseline system consisting of a USBL acoustic array and two underwater acoustic beacons. The USBL acoustic array is set on the platform body and electrically connected to the control center (1.1). The two underwater acoustic beacons are respectively set on the first-stage towed body (4) and the second-stage towed body (6). The USBL acoustic array transmits acoustic interrogation signals underwater and receives response signals from the underwater acoustic beacons to calculate the relative position information of the first-stage towed body (4) and the second-stage towed body (6) underwater.

8. A bottom-following navigation control method based on a two-stage precision towed bottom-following detection platform, characterized in that, The bottom-following navigation control method of any one of claims 1 to 7 based on a two-stage precision towed bottom-following detection platform comprises the following steps: S1. The main body of the platform sails at a predetermined speed, and the first traction system lowers the first-stage tow body (4) loaded with the second-stage tow body (6) to a predetermined depth. S2. Start the second traction system to release the secondary tow body (6) from the primary tow body (4) until it is a predetermined distance behind the primary tow body (4) and the height of the primary tow body (4) from the bottom is within the preset target height range; S3. After the secondary towed body (6) reaches the preset target height, the control center (1.1) issues a detection command, and the core detection payload conducts seabed detection. During the detection process, active control based on dynamic cable length adjustment is introduced to maintain the height of the secondary towed body (6) above the seabed within the preset target height range. The steps are as follows: S31, the secondary control unit (6.1) uploads the real-time ground clearance and depth of the secondary towed body (6) to the primary control unit (4.5) after filtering and calibration. The data is then integrated and transmitted to the information relay unit. At the same time, the forward-looking imaging sonar (4.2), the first depth sensor (4.3), and the first altimeter (4.4) collect the forward terrain feedforward information, depth, and ground clearance of the primary towed body (4) and upload them to the primary control unit (4.5). After the primary control unit (4.5) completes data filtering and calibration, it transmits the effective monitoring data to the information relay unit in the form of a data packet. S32. The information relay unit summarizes the data of the first-level tow body (4) and the second-level tow body (6), performs photoelectric signal conversion, and transmits it back to the control center (1.1). S33. The control center (1.1) receives and integrates all data and calculates the deviation of the second-stage towed body (6) from the bottom, Δh = h – h0, where h is the real-time height of the second-stage towed body (6) from the bottom and h0 is the preset target height. S34. When the deviation Δh exceeds the preset threshold, the control center (1.1) controls the traveling speed of the platform body and the preset length ΔL of the first and second traction systems according to different slope ranges based on the slope value in the terrain information, and finely adjusts the expected height of the secondary tow body (6) from the bottom in advance. This ensures that the real-time height of the secondary tow body (6) above the bottom remains within the preset target height range.

9. The bottom-following navigation control method based on a two-stage precision towed bottom-following detection platform according to claim 8, characterized in that, In step S34, when the terrain ahead is uphill, the control center (1.1) calculates the pitch angle between the first-stage towed body (4) and the second-stage towed body (6) using the following formula: Where H1 is the absolute depth of the first-level tow body, H2 is the absolute depth of the second-level tow body, and S is the cable length of the second connecting cable between the first-level and second-level tow bodies. The control center (1.1) obtains the slope β of the terrain ahead based on the received seabed topographic information and monitors the real-time height h of the secondary towed body (6) above the seabed. If α≤β, when the real-time height h above the bottom exceeds the preset target height h0, the second traction system retracts or extends the cable by a preset length to keep the real-time height above the bottom of the secondary tow body (6) at the preset target height; if α>β, the platform body stops moving forward or moves in the opposite direction, and the second traction system retracts the cable by a preset length to make the real-time height above the bottom of the secondary tow body (6) close to the maximum threshold of the preset target height, until α≤β.

10. The bottom-following navigation control method based on a two-stage precision towed bottom-following detection platform according to claim 8, characterized in that, In step S34, when the road ahead is downhill, the control center (1.1) compares the real-time clearance height of the secondary tow body (6) with the preset target height; When the real-time height of the secondary tow body (6) from the bottom is not greater than the preset target height, The first slope threshold ≤ slope β < 0°, and the second traction system slowly releases the cable with a preset length ΔL2; When the second slope threshold is less than or equal to the slope β, and the first slope threshold is less than or equal to the first slope threshold, the platform's main speed decreases by ΔV1, and the second traction system quickly releases the cable to the preset length ΔL1. When the slope β < the second slope threshold, the platform's main speed decreases by ΔV2, and the first and second traction systems quickly release the cable for a preset length ΔL1, respectively. When the real-time height of the secondary tow body (6) above the bottom is greater than the preset target height, The first slope threshold ≤ slope β < 0°, and the second traction system quickly releases the cable with a preset length ΔL1; When the second slope threshold is less than or equal to the slope β, and the first slope threshold is less than or equal to the first slope threshold, the platform's main speed decreases by ΔV2, and the second traction system quickly releases the cable to the preset length ΔL1. When the slope β is less than the second slope threshold, the platform's main speed decreases by ΔV2, and the first and second traction systems quickly release the cable to the preset length ΔL3.

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