Long-endurance underwater small target autonomous detection AUV

Abstract

The invention relates to a long-endurance underwater small target autonomous detection AUV (Autonomous Underwater Vehicle), which sequentially comprises a collision avoidance unit, a collision avoidance unit, a collision avoidance unit and a collision avoidance unit from a bow part to a tail part along the axial direction, and the collision avoidance unit comprises a collision avoidance sonar and an electronic compass; the small target detection unit comprises a flash lighting lamp and a synthetic aperture sonar, and two transducers of the synthetic aperture sonar are symmetrically installed on the broadside of the head of the AUV; the front electronic cabin unit comprises a communication sonar, a depth gauge, an exchange board, a sensing processing board, a first liquid leakage sensor and a first semicircular secondary lithium battery; and the navigation unit comprises wireless communication positioning equipment, inertial navigation equipment and a Doppler log. Through multiple means of integrating high-resolution detection load, optimizing platform energy and power efficiency, adopting light-weight and high-strength structural design and the like, the ultra-long endurance working capacity of the AUV is achieved, and the imaging quality and autonomous detection efficiency of the AUV on underwater small targets are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of autonomous underwater small target detection technology, specifically relating to a long-endurance autonomous underwater small target detection AUV. Background Technology

[0002] Underwater small targets such as mines and bottom moorings are highly concealed due to their small size, weak echoes, and susceptibility to being obscured by complex seabed backgrounds. Small AUV platforms carrying detection payloads are typically used for close-range detection to obtain high-resolution images and achieve autonomous target acquisition. Existing small AUV autonomous detection platforms mostly carry side-scan sonar and illumination imaging payloads as imaging detection payloads. For example, the REMUS 300M, equipped with the MK II Arc Scout 900 / 1800 kHz side-scan sonar, has a maximum detection endurance of 30 hours. However, it suffers from the following problems: 1) Low imaging resolution for small targets such as mines and bottom moorings, resulting in a high false alarm rate for autonomous identification; 2) Limited energy, short continuous operating time, requiring frequent deployment and retrieval for recharging, making it impossible to conduct continuous underwater detection for extended periods, resulting in low detection efficiency.

[0003] Therefore, there is an urgent need for an autonomous underwater vehicle (AUV) capable of long endurance, high-resolution detection, and effectively reducing false alarm rates for small underwater targets. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide an AUV for long-endurance autonomous underwater small target detection. By integrating high-resolution detection payloads, optimizing platform energy and power efficiency, and adopting lightweight and high-strength structural design, the invention aims to achieve ultra-long endurance operation capability of the AUV and significantly improve its imaging quality and autonomous detection efficiency for underwater small targets.

[0005] The technical solution of this invention is to provide a long-endurance autonomous underwater vehicle (AUV) for detecting small underwater targets. The AUV features a streamlined, low-drag design with a main body diameter of 200mm and a total length of 2200mm. It includes a hemispherical bow, a parallel midsection, and a conical stern. It employs a two-bladed propeller with a disk area ratio of 20% and a diameter 0.85 times the main body diameter. From bow to stern, it sequentially includes a collision avoidance unit, a small target detection unit, a forward electronics unit, a navigation unit, a rear electronics unit, a battery unit, a camera unit, and a high-efficiency propulsion unit. The collision avoidance unit and the small target detection unit are watertight compartments, while the remaining units are interconnected sealed compartments. The watertight compartments are watertightly isolated from the rear sealed compartments via a front end cover, through which all power and signals are transmitted. The sealed compartments are tightly connected using internal through-bolts and tie rods, ensuring the overall structural strength and sealing reliability.

[0006] The collision avoidance unit includes a collision avoidance sonar and an electronic compass for detecting obstacles ahead and measuring heading. The electronic compass is mounted on the head to avoid interference from other AUV equipment.

[0007] The small target detection unit includes a flash and a synthetic aperture sonar. The synthetic aperture sonar comprises a synthetic aperture sonar electronics module and two synthetic aperture sonar transducers, symmetrically mounted on either side of the AUV's nose, for high-resolution acoustic imaging of the seabed along the navigation path. The unit is internally filled with buoyancy material to achieve a zero-buoyancy state.

[0008] The forward electronics compartment unit includes a communication sonar, a depth gauge, a switching board, a sensing and processing board, a first leak sensor, and a first semi-circular secondary lithium battery. The sensing and processing board is specifically used to process camera images and synthetic aperture sonar data. The communication sonar includes a communication sonar transducer and a communication sonar signal processing module; the communication sonar transducer is suspended below the forward electronics compartment. The first leak sensor is used for leak detection and alarm.

[0009] The navigation unit includes a wireless communication positioning device, an inertial navigation device, and a Doppler log, providing high-precision underwater positioning and navigation information for the AUV.

[0010] The rear electronic compartment unit includes a low-power main control board, a switch board, a second leakage sensor, and a second semi-circular secondary lithium battery. The low-power main control board serves as the control core of the entire system. The second leakage sensor is used for leakage detection and alarm.

[0011] The battery unit's pressure-resistant casing houses the third and fourth semi-circular secondary lithium batteries, arranged vertically. The pressure-resistant casings of the front and rear electronic compartments and the battery unit are all made of carbon fiber to minimize structural weight and free up more space and weight for the batteries.

[0012] The camera unit is part of the sealed cabin and includes a flash power supply board and a camera.

[0013] The high-efficiency propulsion unit includes a servo motor, a propulsion motor, and a high-efficiency two-bladed propeller. The propeller has a disk area ratio of 20% and a diameter that is 0.85 times the diameter of the AUV body (i.e., 170 mm), which, together with the streamlined hull, forms a high-efficiency propulsion system.

[0014] The flash, flash power supply board, and camera together constitute the underwater flash illumination imaging detection payload. During operation, the camera emits a TTL level signal to trigger a momentary strobe flash. The camera completes the exposure of the seabed within the extremely short time of the strobe flash, thereby achieving high-definition optical imaging under underwater conditions without ambient light.

[0015] This invention features a high-resolution dual-mode detection payload:

[0016] Synthetic aperture sonar: Mounted on both sides of the AUV's head, it uses platform movement to synthesize a large aperture, enabling high-resolution, wide-range acoustic imaging of the seabed on both sides of the navigation path. It is particularly suitable for detecting small buried or semi-buried targets.

[0017] Underwater flash illumination imaging system: Composed of a high-power flash illuminator located at the bow of the AUV and a high-speed camera located at the stern. The flash illuminator is precisely triggered by the TTL (transistor-to-transistor logic) level signal of the camera, completing the optical imaging of the seabed within an extremely short exposure time. This effectively overcomes the motion blur problems caused by insufficient underwater natural light and continuous illumination, obtaining high-definition optical images.

[0018] To achieve long driving range, this invention optimizes the system's energy and structure as follows:

[0019] Lightweight and pressure-resistant shell: The pressure-resistant shells of the front and rear electronics compartments and battery units of the AUV are all made of carbon fiber composite materials. This significantly reduces the weight of the shell while ensuring the structural strength required for a working depth of 300 meters, making it possible to load more battery power within a limited internal space.

[0020] Streamlined low-drag casing and efficient propulsion system:

[0021] Appearance: The AUV features a streamlined design, smoothly connecting a hemispherical bow, a cylindrical parallel midsection, and a convex conical stern, effectively reducing underwater drag.

[0022] Propulsion: The high-efficiency propulsion unit at the tail employs a high-efficiency two-bladed propeller with a disk area ratio of 20% and a diameter 0.85 times (170 mm) of the AUV's main body diameter (200 mm). This design, matched with the streamlined tail, significantly improves propulsion efficiency and reduces energy consumption at the same speed.

[0023] Distributed high-capacity energy system: The power supply of this invention is provided by four lithium battery packs connected in parallel. Each of the front and rear electronic compartment units has a semi-circular secondary lithium battery installed below it, and each battery unit has a semi-circular secondary lithium battery installed above and below it. The power supply voltage range is 21.6V~33.6V. Each device is directly connected to the lithium battery, eliminating the need for an additional power conversion module and reducing line loss.

[0024] Intelligent power management system: It is designed with a low-power operation mode and a detection operation mode, which can be intelligently switched through the main control board.

[0025] Low-power operation mode: In this mode, only equipment necessary for basic navigation and safety is activated, including the low-power main control board, switchboard, depth gauge, leak sensor, electronic compass, DVL, communication sonar, and propulsion system. Navigation utilizes a combination of electronic compass and DVL to reduce energy consumption of the AUV platform during transit and improve the platform's energy efficiency.

[0026] Detection Mode: Once the AUV arrives at the mission area, it switches to this mode. In addition to the low-power mode, the switching board, inertial navigation system, sensing processing board, collision avoidance sonar, and wireless communication positioning equipment are activated. Navigation switches to a more precise inertial navigation / DVL combination. Simultaneously, the switching board powers the synthetic aperture sonar and underwater flash illumination imaging payload as needed for active detection. This intelligent switching between the two modes avoids unnecessary energy consumption during non-detection phases.

[0027] This invention uses a low-power main control board as the core hub to directly manage devices with simple communication needs that are always on (wireless communication positioning devices, inertial navigation devices, Doppler logs (DVL), depth gauges, communication sonars, switchboards, electronic compasses, leakage sensors, propulsion motors, servo motors, and lithium batteries). Devices with high data throughput or intermittent operation (such as collision avoidance sonars, the electronic compartment of synthetic aperture sonars, sensing processing boards, and cameras) are connected to the main control board through a switching board to form a local area network, facilitating high-speed data exchange and flexible management.

[0028] In this invention, the two transducers of the synthetic aperture sonar payload are respectively installed on the front side of the AUV, enabling high-resolution acoustic imaging detection of both sides during the AUV's navigation.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The maximum working depth of this invention is 300 meters, which can cover the needs of shallow sea area exploration. The AUV weighs less than 70kg and can be manually deployed by two people, meeting the requirements for portable use.

[0031] 2. This invention uses flash illumination imaging to achieve high-definition optical imaging of the seabed and synthetic aperture sonar to achieve high-resolution acoustic imaging of the seabed, which improves the imaging resolution of small targets such as mines and bottom moorings, effectively reduces the false alarm rate of autonomous identification, and improves the detection efficiency of AUVs for autonomous detection of small targets.

[0032] 3. This invention employs multiple methods to improve the working range of AUVs and effectively enhance the detection efficiency of autonomous AUVs for small target detection, including: implementing power management design that can switch between low-power mode and detection mode according to mission status, avoiding energy consumption during transit and detection; adopting a streamlined shell design and optimizing the design of the two-bladed propeller to improve propulsion efficiency and reduce drag during navigation; and using a carbon fiber pressure-resistant shell to increase the proportion of lithium battery energy under limited space and weight conditions, further improving the driving range. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the external structure of the present invention.

[0034] Figure 2 This is a schematic diagram of the external structure of the two-bladed propeller of the present invention.

[0035] Figure 3 This is a cross-sectional view of the internal structure of the present invention.

[0036] Figure 4 This is a diagram showing the connection configuration of each unit in this invention.

[0037] Figure 5 This is a schematic diagram of the electrical connections of the present invention.

[0038] The components include: A. Collision avoidance unit; B. Small target detection unit; C. Front electronic cabin unit; D. Navigation unit; E. Rear electronic cabin unit; F. Battery unit; G. Camera unit; H. High-efficiency propulsion unit.

[0039] 1. Electronic compass; 2. Collision avoidance sonar; 3. Flashlight; 4. Synthetic aperture sonar pod; 5. Synthetic aperture sonar transducer; 6. Communication sonar transducer; 7. Communication sonar signal processing module; 8. Depth gauge; 9. Sensing processing board; 10. Switching board; 11. First semi-circular secondary lithium battery; 12. First leakage sensor; 13. Doppler log; 14. Wireless communication positioning antenna; 15. Inertial navigation device; 16. Second leakage sensor 2; 17. Second semi-circular secondary lithium battery; 18. Low-power main control board; 19. Switching board; 20. Third semi-circular secondary lithium battery; 21. Fourth semi-circular secondary lithium battery; 22. Camera; 23. Flashlight power supply board; 24. Servo motor; 25. Propulsion motor; 26. Rudder blade; 27. Propeller; 28. Forward pod end cap; 29. ​​Watertight connector. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0041] like Figure 1 , 2As shown in Figure 3, the long-endurance autonomous underwater vehicle (AUV) for detecting small targets provided by this invention has a smooth, streamlined outer shell, consisting of a hemispherical bow, a cylindrical parallel midsection, and a conical constricted tail section. This shape effectively reduces underwater drag. The propulsion system uses a specially designed two-bladed propeller 27 with a disk-to-surface ratio of 20% and a diameter 0.85 times the main body diameter, i.e., 170 mm, forming an overall structure with high-efficiency propulsion and a low drag coefficient, effectively improving the overall propulsion efficiency of the AUV. The hemispherical bow is mainly composed of collision avoidance unit A, the conical tail is mainly composed of high-efficiency propulsion unit H, and the cylindrical parallel midsection is formed by connecting the remaining functional units.

[0042] Specifically, such as Figure 1 , 2 As shown in Figures 3 and 4, the AUV's interior is divided into eight functional units along the axial direction, from bow to stern: a collision avoidance unit A, a small target detection unit B, a forward electronics unit C, a navigation unit D, a rear electronics unit E, a battery unit F, a camera unit G, and a high-efficiency propulsion unit H. Among these, collision avoidance unit A and small target detection unit B are water-permeable chambers, allowing seawater to freely enter. Collision avoidance unit A is equipped with a collision avoidance sonar 2 and an electronic compass 1; small target detection unit B is equipped with a flash illuminator 3 for optical illumination and a synthetic aperture sonar for small target detection. Its internal gaps are filled with buoyancy material to achieve an overall zero-buoyancy state. The electronic compass 1 is mounted at the bow to avoid interference from other AUV equipment. In this embodiment, the synthetic aperture sonar includes a synthetic aperture sonar electronics unit 4 and two synthetic aperture sonar transducers 5.

[0043] The remaining functional units are interconnected sealed chambers. The permeable chamber and the sealed chamber are sealed and isolated by the forward electronics compartment end cap 28. A watertight connector 29 is installed on the end cap, and communication and power supply between the permeable chamber and the sealed chamber are achieved through a watertight cable connected to the watertight connector. In other words, from the forward electronics compartment unit C to the high-efficiency propulsion unit H, there is a connected sealed pressure-resistant chamber.

[0044] The forward electronics compartment unit C centrally houses the communication sonar, depth gauge 8, switching board 10, sensing processing board 9, first semi-circular secondary lithium battery 11, and first leakage sensor 12. The communication sonar includes a communication sonar transducer 6 and a communication sonar signal processing module 7. The communication sonar transducer 6 is suspended below the forward electronics compartment, while the communication sonar signal processing module 7 is installed within the forward electronics compartment unit C along with the other components. The sensing processing board 9 processes image data from the camera 22 and side-scan data from the synthetic aperture sonar electronics compartment 4.

[0045] The navigation unit D is equipped with a Doppler log 13, a wireless communication positioning antenna 14, and an inertial navigation device 15, which are used to provide positioning and navigation information for the AUV during underwater navigation.

[0046] The aft electronics unit E houses a low-power main control board 18 as the control core, a power distribution switch board 19, a second semi-circular secondary lithium battery 17, and a second leakage sensor 16. Inside the battery unit F, a third semi-circular secondary lithium battery 20 and a fourth semi-circular secondary lithium battery 21 are mounted side-by-side. The camera unit G partially overlaps with battery unit F and houses a camera 22 and a power supply board 23 for its accompanying flash. Finally, the high-efficiency propulsion unit H houses a servo motor 24, a propulsion motor 25, rudder blades 26, and a propeller 27.

[0047] The first leak sensor 12 and the second leak sensor 16, installed below the front electronic compartment unit C and the rear electronic compartment unit E, are used for leak detection and alarm. The flash lamp 3 of the small target detection unit B, together with the flash lamp power supply board 23 and the camera 22 of the camera unit G, form an underwater flash illumination imaging detection payload.

[0048] The power supply of this invention is provided by the above-mentioned four lithium battery packs connected in parallel, including a first semi-circular secondary lithium battery 11 and a second semi-circular secondary lithium battery 17 installed below the front electronic compartment unit C and the rear electronic compartment unit E, and a third semi-circular secondary lithium battery 20 and a fourth semi-circular secondary lithium battery 21 installed above and below the battery unit F. The power supply voltage range is 21.6V~33.6V. Each device is directly connected to the lithium battery, bypassing the power module and reducing line loss. Among them, the pressure-resistant shells of the front electronic compartment unit C, the rear electronic compartment unit E, and the battery unit F are made of carbon fiber material, which achieves extreme lightweighting while ensuring pressure resistance and improving the utilization rate of platform weight.

[0049] like Figure 4 As shown, the permeable compartment is fastened to the front electronics compartment end cover 28 with screws. All cables that need to cross this interface are sealed together using watertight connectors 29 installed on the end cover 28. The compartments are connected by internal screws and tie rods to ensure overall strength.

[0050] This embodiment employs a power management design, including two operating modes: low power and detection. In low power mode, only the low power main control board 18, switch board 19, depth gauge 8, first leakage sensor 12, second leakage sensor 16, electronic compass 1, Doppler log 13, communication sonar, and the servo motor 24 and propulsion motor 25 in the power system are activated, reducing the energy consumption of the AUV platform during transit and improving the platform's energy utilization efficiency. In detection mode, based on the low power mode, the switch board 10, inertial navigation device 15, sensing processing board 9, collision avoidance sonar 2, and wireless communication positioning device 14 are activated. At the same time, the synthetic aperture sonar payload and underwater flash illumination imaging payload (flash illumination lamp 3, flash lamp power supply board 23, and camera 22) are switched according to the mission requirements. Each device is powered on and off through the switch board 19. In the low-power mode, an electronic compass and DVL are used for underwater integrated navigation. In the working mode, an inertial navigation system and DVL are used for underwater high-precision integrated navigation. When switching navigation modes, the system first surfaces to calibrate the position and then aligns the inertial navigation system.

[0051] like Figure 5 As shown, in this invention, the wireless communication positioning device 14, inertial navigation device 15, Doppler log 13, depth gauge 8, communication sonar, switch board 19, electronic compass 1, first leakage sensor 12, second leakage sensor 16, propulsion motor 25, servo motor 24, and four lithium batteries are directly connected to the low-power main control board 18 for communication. The collision avoidance sonar 2, synthetic aperture sonar, sensing processing board 9, and camera 22 are connected to the low-power main control board 18 on the switching board 10, and interact with each other via network communication.

[0052] In this invention, the bow flash is triggered by the camera's TTL level and flashes. During the flash, the camera directly images downwards, enabling high-definition optical imaging of the bottom of the AUV during its navigation in a dark underwater environment.

[0053] In this invention, two synthetic aperture sonar transducers 5 are symmetrically installed on the front side of the AUV to enable high-resolution acoustic imaging detection of both sides during the AUV's navigation.

[0054] This invention is designed with a maximum operating depth of 300 meters, covering the needs of shallow sea area exploration. The AUV weighs less than 70 kg and can be manually deployed by two people, meeting the requirements for portability. This invention uses flash illumination imaging to achieve high-definition optical imaging of the seabed and synthetic aperture sonar to achieve high-resolution acoustic imaging of the seabed, improving the imaging resolution of small targets such as mines and bottom moorings. This effectively reduces the false alarm rate of autonomous identification and improves the detection efficiency of the autonomous AUV for small target detection. Simultaneously, this invention employs multiple methods to improve the AUV's operating range and effectively enhance the detection efficiency of the autonomous AUV for small target detection, including: power management design that can switch between low-power mode and detection mode according to mission status, avoiding energy consumption during transit and exploration; a streamlined shell design and optimized two-bladed propeller design to improve propulsion efficiency and reduce drag during navigation; and a carbon fiber pressure-resistant shell to increase the proportion of lithium battery energy under limited space and weight conditions, further improving the operating range.

[0055] The above description only illustrates preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. Any equivalent procedural modifications made using this specification are included within the patent protection scope of this invention.

Claims

1. A long-endurance autonomous underwater target detection AUV, characterized in that: It features a streamlined hull consisting of a hemispherical bow, a parallel midsection, and a convex conical tail. Along the axial direction from front to back, it comprises, in sequence, a collision avoidance unit, a small target detection unit, a forward avionics compartment unit, a navigation unit, a rear avionics compartment unit, a battery unit, a camera unit, and a high-efficiency propulsion unit. The collision avoidance unit includes collision avoidance sonar and electronic compass; The small target detection unit includes a flash illuminator and a synthetic aperture sonar; The forward electronic compartment unit includes a communication sonar, depth gauge, switching board, sensing and processing board, first leakage sensor, and first semi-circular secondary lithium battery; The aft electronic compartment unit includes a low-power main control board, a switch board, a second leakage sensor, and a second semi-circular secondary lithium battery. The battery unit includes a third semi-circular secondary lithium battery and a fourth semi-circular secondary lithium battery arranged vertically. The camera unit includes a flash power supply board and a camera; The navigation unit includes a wireless communication positioning device, an inertial navigation device, and a Doppler log. The high-efficiency propulsion unit includes a servo motor, a propulsion motor, and a two-bladed propeller driven by the propulsion motor; the two-bladed propeller has a disk area ratio of 20% and a diameter of 0.85 times the diameter of the AUV body; The flash illumination lamp, flash power supply board, and camera together constitute the underwater flash illumination imaging detection payload; the low-power main control board, switch board, sensing processing board, and switching board constitute the power management system, which is configured to switch between low-power operation mode and detection mode according to the mission status; the parallel middle section has at least several carbon fiber pressure-resistant shell sections, which are used to house the battery unit, the front electronic compartment unit, and the rear electronic compartment unit, respectively, in order to reduce the weight of the shell and increase the battery capacity.

2. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The collision avoidance unit and the small target detection unit are water-permeable chambers, while the remaining units are interconnected sealed chambers. The water-permeable chambers and the sealed chambers are sealed and isolated by the front electronic chamber end cover, and are connected for communication and power supply via watertight connectors and watertight cables; the sealed chambers are fixedly connected to each other.

3. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The small target detection unit is filled with buoyancy material to make the unit achieve a state of zero buoyancy as a whole.

4. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The first, second, third, and fourth semi-circular secondary lithium batteries are connected in parallel to power the entire system, with a power supply voltage range of 21.6V to 33.6V.

5. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The specific operating modes of the power management system are as follows: Low-power operation mode: The low-power main control board, switch board, depth gauge, first and second leakage sensors, electronic compass, Doppler log, communication sonar, and high-efficiency propulsion unit are turned on, and navigation is performed using a combination of electronic compass and Doppler log; Detection mode: In addition to the device in the low power operation mode, the switching board, inertial navigation device, sensing processing board, collision avoidance sonar and wireless communication positioning device are also turned on. The combination of inertial navigation device and Doppler log is used for navigation. The switching board is controlled according to the mission requirements to selectively supply power to the synthetic aperture sonar and the underwater flash illumination imaging detection payload.

6. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The low-power main control board is directly connected to and communicates with the wireless communication positioning device, inertial navigation device, Doppler odometer, depth gauge, communication sonar, switch board, electronic compass, first and second leakage sensors, propulsion motor, servo motor, and four secondary lithium batteries; the collision avoidance sonar, synthetic aperture sonar, sensing processing board, and camera interact with the low-power main control board through the switching board via network communication.

7. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The sensing processing board is used to process image data from the camera and detection data from the synthetic aperture sonar.

8. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The streamlined outer shell has a diameter of 200mm and a total length of 2200mm.

9. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The flash illumination is triggered by the TTL level of the camera to achieve high-definition optical imaging underwater.

10. The long-endurance autonomous underwater small target detection AUV according to claim 1, characterized in that: The maximum operating depth of the AUV is 300 meters, and its overall weight is less than 70 kg.

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