Low-frequency acoustic transducer and propeller integrated system for underwater unmanned submersibles

Abstract

The present invention proposes an integrated low-frequency acoustic transducer and propeller system for underwater unmanned underwater vehicles, belonging to the technical field of UUV-specific mission payloads and equipment. This system consists of a propulsion device, a dual-coil fixture, and a permanent magnet structure. The propulsion device is connected to the dual-coil fixture as a mover, and the permanent magnet structure is a stator. When the propulsion device's motor is energized, the propeller rotates, thereby providing underwater propulsion power for the UUV. A low-frequency alternating current is input into the wires of the dual-coil fixture, causing the fixed panel to vibrate and driving the propeller propeller to reciprocate. The water medium radiates low-frequency acoustic signals outward due to the coupling effect of the propeller's rotational motion and the low-frequency reciprocating motion of the propulsion device. This invention solves the problems of large size and inconvenient installation and integration of UUV low-frequency acoustic transducers, while also providing underwater propulsion functions, effectively reducing the size and weight of the UUV mission payload and significantly reducing equipment costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of dedicated mission payloads and equipment for underwater unmanned underwater vehicles (UUVs), and in particular relates to an integrated system of a low-frequency underwater acoustic transducer and a propeller for a UUV. Background Art

[0002] Underwater long-range acoustic detection and communication technologies are increasingly developing towards low and very low frequencies. However, due to the long wavelength of underwater low-frequency sound waves, low-frequency acoustic transducers are large, heavy, and expensive. On the other hand, due to factors such as load, endurance, and cost, the low-frequency acoustic transducer payloads of underwater unmanned platforms are significantly limited in size, weight, energy consumption, and cost. To meet the development needs of UUV underwater propulsion and low-frequency detection and communication mission payloads, the development of low-cost, miniaturized, lightweight, integrated acoustic transducer and propulsion technology and equipment is an important future development direction. Summary of the Invention

[0003] In view of this, in order to solve the technical problems mentioned in the above background technology, the present invention proposes an integrated system of low-frequency underwater acoustic transducer and propeller suitable for UUV, which can ensure that while providing UUV with propulsion power, it can also realize functions such as low-frequency underwater acoustic detection and communication. In addition, the outer shell of the propeller has good waterproof performance and can work in deep water, meeting the working requirements of UUV. The present invention has the following outstanding advantages: (1) It realizes a lightweight low-frequency underwater acoustic transducer system suitable for integration with UUV; (2) It can perform tasks such as underwater acoustic detection, communication and underwater propulsion, realizing a multifunctional payload technology dedicated to UUV; (3) It has the significant advantage of low cost.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solutions: a low-frequency hydroacoustic transducer and propeller integrated system for an underwater unmanned submersible, comprising a propulsion device, a dual-coil fixing device and a permanent magnet structure, wherein the propulsion device comprises a propeller and a motor, which provide power for underwater propulsion of the platform, the dual-coil fixing device comprises a copper wire, a coil bracket and a fixed panel, the copper wire is used to conduct alternating current, the copper wire is wound on the coil bracket, the coil bracket is vertically connected to the fixed panel, the propulsion device is connected to the fixed panel, the permanent magnet structure comprises a neodymium iron boron magnet spliced ​​cylindrical ring and an electrical pure iron magnetic conductive shell, the electrical pure iron magnetic conductive shell comprises a cylindrical main body containing a cavity and several fan-shaped cover plates on it, the neodymium iron boron magnet spliced ​​cylindrical ring is placed in the cavity of the cylindrical main body, and an air gap with two magnetic cores is provided on the inner and outer sides of the neodymium iron boron magnet spliced ​​cylindrical ring.

[0005] Furthermore, the NdFeB magnet spliced ​​cylindrical ring is a cylindrical ring formed by splicing several NdFeB magnets.

[0006] Furthermore, each NdFeB magnet is a sector-shaped structure with an inner radius r = 30 mm, a thickness t = 8 mm, a height h = 50 mm, and a sector angle =30°, the magnetizing direction is radial.

[0007] Furthermore, the air gap height h1 = 70 mm, and the air gap width t1 = 5 mm.

[0008] Furthermore, a plurality of through holes are designed below the cylindrical main body of the electrical pure iron magnetic conductive shell.

[0009] Furthermore, the coil support includes an outer coil support and an inner coil support, the outer coil support and the inner coil support are coaxial annular, and the outer coil support is arranged on the outer ring of the inner coil support.

[0010] Furthermore, the upper end of the coil bracket is a hollow structure, and the upper end of the coil bracket is connected to the fixed panel.

[0011] Furthermore, the shell is fixed to the outer periphery of the permanent magnet structure.

[0012] Furthermore, the fixed panel, coil support and shell are all made of aluminum alloy.

[0013] Furthermore, the copper wire is a copper enameled wire.

[0014] Compared with the prior art, the low-frequency acoustic transducer and propeller integrated system for underwater unmanned submersibles described in the present invention effectively miniaturizes the low-frequency transducer and integrates it with the underwater propeller. The beneficial effects of this device include the following aspects:

[0015] (1) The low-frequency acoustic transducer and propeller integrated system for underwater unmanned submersibles proposed in the present invention can effectively solve the problem that traditional low-frequency transducers are large in size and inconvenient to carry. Since the generation of high-power, low-frequency sound waves underwater requires the water medium to have a large volume velocity, the transducer is required to have a sufficiently large driving force. The permanent magnet structure design of the traditional moving coil low-frequency transducer adopts an axially magnetized magnet, resulting in only one air gap in the magnetic core, and the air gap length is short, and the effective length of the coil is insufficient. In the prior art, the pure iron in the permanent magnet structure adopts a base plus magnetic plate structure ( Figure 11 As shown in the figure), leakage flux increases and the magnetic field strength decreases. To obtain a higher sound source level, a greater driving force is required, so the volume of the transducer can only be increased. The present invention uses radially magnetized magnets, which increases the length of the magnetic core air gap and has two air gaps, thereby increasing the effective length of the coil. Pure iron adopts a semi-enclosed design, which reduces leakage flux and ensures the magnetic field strength. Therefore, under the premise of a small volume, sufficient driving force can be achieved.

[0016] (2) The permanent magnet structure described in the present invention utilizes radially magnetized NdFeB magnets spliced ​​into a cylindrical ring, combined with a closed magnetic circuit design of electrical pure iron, effectively enhancing the magnetic induction intensity of the core air gap. Furthermore, the coil fixture utilizes two aluminum alloy coil brackets, increasing the effective length of the coil and thereby enhancing the driving force of acoustic radiation.

[0017] (3) The permanent magnet structure of the present invention adopts a closed magnetic circuit design, which effectively reduces the magnetic flux leakage in the air gap of the magnetic core, while ensuring the magnetic field strength, making the permanent magnet structure lightweight and miniaturized.

[0018] (4) The integrated system of the present invention can be used for UUV propulsion while also realizing functions such as low-frequency underwater acoustic detection and communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 This is a typical application scenario of the low-frequency acoustic transducer and propeller integrated system for underwater unmanned submersibles described in the present invention;

[0021] Figure 2 1. It is a schematic diagram of the three-dimensional structure of the low-frequency underwater acoustic transducer and propeller integrated system of the present invention;

[0022] Figure 3 is a front view of the integrated system of the present invention;

[0023] Figure 4 is a three-dimensional schematic diagram of the propeller structure of the present invention;

[0024] Figure 5 is a three-dimensional schematic diagram of the coil fixing device of the present invention;

[0025] Figure 6 is a cutaway perspective schematic diagram of the permanent magnet structure of the present invention;

[0026] Figure 7 is a schematic diagram of the connection between the permanent magnet structure and the coil fixing device of the present invention;

[0027] Figure 8 This is a front view of the NdFeB magnet cylindrical ring structure of the present invention;

[0028] Figure 9 is a top view of the NdFeB magnet cylindrical ring structure of the present invention;

[0029] Figure 10is a sound source level curve diagram of the propeller of the present invention in actual testing within the frequency range of 20-300 Hz;

[0030] Figure 11 This is a schematic diagram of a base plus magnetic plate structure for pure iron in the existing permanent magnet structure. The left side represents the magnetic flux density, and the right side is a traditional permanent magnet structure model. Putting the two in one figure can more intuitively express the change in magnetic flux density.

[0031] In the figure: 1-fixed panel; 2-1-external coil bracket; 2-2-inner coil bracket; 3-1-outer copper coil; 3-2-inner copper coil; 4-electrical pure iron magnetic shell; 5-cylindrical ring with neodymium iron boron magnet splicing; 7-UUV platform. DETAILED DESCRIPTION

[0032] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features therein can be combined with each other in the absence of conflict, and the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0033] See also Figure 1-10 This embodiment describes an integrated low-frequency hydroacoustic transducer and propeller system for an underwater unmanned submersible, including a propulsion device, a dual-coil fixing device and a permanent magnet structure. The propulsion device includes a propeller and a motor to provide power for the UUV to move. The dual-coil fixing device includes a copper wire, a coil bracket and a fixed panel 1. The copper wire is used to conduct alternating current. The copper wire is wound on the coil bracket, and the coil bracket is vertically connected to the fixed panel 1. The propulsion device is connected to the fixed panel 1, and the fixed panel 1 is used to fix the coil bracket and the propulsion device. The permanent magnet structure includes a neodymium iron boron magnet spliced ​​cylindrical ring 5 and an electrical pure iron magnetic shell 4 for providing a magnetic field. The electrical pure iron magnetic shell 4 includes a cylindrical body containing a cavity and several fan-shaped cover plates on it. The neodymium iron boron magnet spliced ​​cylindrical ring 5 is placed in the cavity of the cylindrical body, and an air gap with two magnetic cores is provided on the inner and outer sides of the neodymium iron boron magnet spliced ​​cylindrical ring 5.

[0034] The permanent magnet structure is surrounded by a housing composed of three sections of an aluminum alloy cylindrical ring shell. The housing has an outer diameter (R) of 120 mm and an overall height (H) of 260 mm. The cylindrical ring design facilitates installation and provides a waterproof seal. The permanent magnet structure is fixedly connected to the housing, which is then fixedly connected to the UUV housing.

[0035] The coil supports include an outer coil support 2-1 and an inner coil support 2-2. The outer coil support 2-1 and the inner coil support 2-2 are coaxially annular, with the outer coil support 2-1 positioned outside the inner coil support 2-2. The coil supports are designed as thin cylindrical rings. The outer coil support 2-1 can be wound with multiple turns of copper wire. Both coil supports are fixed to the radiation panel 1.

[0036] The NdFeB magnet splicing cylindrical ring 5 is a cylindrical ring formed by splicing a number of NdFeB magnets. In this specific embodiment, 12 NdFeB magnets are preferably used. Each NdFeB magnet is a sector-shaped structure with an inner radius r = 30mm, a thickness t = 8mm, a height h = 50mm, and a sector angle =30°, and the magnetization direction of a single NdFeB magnet 5 is radial. Radially magnetized magnets can increase the length of the core air gap, effectively increasing the effective length of the coil, thereby increasing the driving force.

[0037] The electrical pure iron magnetic conductive shell 4 adopts a semi-enclosed structure, forming two closed magnetic circuits inside, thereby improving the magnetic induction intensity of the magnetic core air gap.

[0038] The permanent magnet structure and the housing constitute a stator.

[0039] The propulsion device and the double-coil fixing device constitute a mover.

[0040] The working principle of the low-frequency underwater acoustic transducer and propeller integrated system for UUV is as follows:

[0041] This integrated system can be installed on the rear of a UUV. The motor in the propulsion unit drives the propeller, providing propulsion power for the platform. This propeller rotation causes the surrounding water medium to acquire a velocity opposite to the platform's direction of travel. Furthermore, a permanent magnet structure provides a magnetic field, generating magnetic induction within the air gap. Dual coils are located within the magnetic circuit air gap and are evenly wound around a coil support. During operation, the moving coils reciprocate along the entire axis. A copper conductor is placed within the air gap, which has a certain magnetic induction intensity. When an alternating current is applied to the copper conductor, an Ampere force is generated. This Ampere force drives the propulsion unit in reciprocating motion. The propeller's motion generates flow velocity in the water medium, and the reciprocating motion of the propulsion unit generates signal pressure pulses. The water medium, coupled with the propeller's rotational motion and the propulsion unit's low-frequency reciprocating motion, radiates outward, emitting a low-frequency underwater acoustic signal.

[0042] When the integrated system is working, it is assumed that the effective normal velocity of the propeller surface is The distance from the propeller center along the axis generated by the velocity distribution on the propeller surface S can be expressed using the Green function form of the Rayleigh integral x The sound pressure field at

[0043] (1)

[0044] In formula (1), is the frequency of the propulsion device's reciprocating motion, is the density of water, is the size of the position vector from the center of the propeller to the desired point, i and j are imaginary units, π and e are constants, and k is the wave number.

[0045] The working mode and conditions of the low-frequency underwater acoustic transducer and propeller integrated system for UUV are as follows:

[0046] The motor in the propulsion unit is energized, driving the propeller to rotate and thus providing underwater propulsion for the UUV. Furthermore, a low-frequency alternating current is input through the wires in the dual-coil fixture of the propulsion unit, causing the fixed panel 1 to vibrate and drive the propeller to reciprocate. This process generates a low-frequency acoustic signal (see Equation 1). This system shifts the transducer's radiation impedance from being dominated by reactance (mass load) to being dominated by resistance (fluid velocity), ensuring the transducer's drive power.

[0047] Regarding the material requirements for the thruster: The fixed panel, coil bracket, and outer shell of the dual-coil fixture are all made of a low-density aluminum alloy, which can reduce the overall weight and make the thruster lightweight. The wires in the dual-coil fixture are made of copper enameled wire, which has lower resistance. The selection of magnetic materials takes into account the coercive force, intrinsic coercive force, residual magnetic flux density, residual magnetization intensity, and maximum magnetic energy product, and neodymium iron boron magnets are selected. The selection of magnetic conductive materials takes into account the saturation magnetization intensity, residual magnetic induction intensity, coercive force, initial magnetic permeability, and maximum magnetic permeability, and electrical pure iron is selected.

[0048] Figure 1 This figure demonstrates the application of the present invention in transmitting low-frequency acoustic signals during underwater propulsion of a UUV. The figure illustrates the propulsion and transmission of low-frequency acoustic signals for underwater unmanned submersibles. The dotted circle in the figure indicates the installation location of the integrated low-frequency acoustic transducer and propeller system. This invention addresses the issues of bulky low-frequency acoustic transducers in UUVs, as well as the inconvenient installation and integration, while also providing the functionality of an underwater propeller. This multifunctional, integrated design effectively reduces the size and weight of the UUV's mission payload and saves equipment costs.

[0049] Figure 2 A three-dimensional view of the integrated system of low-frequency underwater acoustic transducer and propeller is shown. The main visible part is the cylindrical shell, which serves as a sealing protection. The dual-coil fixing device and permanent magnet structure cannot be directly exposed to water when working, and are located inside the shell.

[0050] Figure 3The front view of the integrated low-frequency underwater acoustic transducer and propeller system is shown. The maximum diameter of the shell is R=120mm, and the shell height is H=260mm. The overall size meets the installation size restrictions of UUV.

[0051] Figure 4 The motor and propeller are displayed. There are no specific restrictions on these two components, and the appropriate combination can be selected according to actual needs.

[0052] Figure 5 The three-dimensional structure of the dual-coil fixture is shown. The coil supports, consisting of an outer coil support 2-1 and an inner coil support 2-2, are constructed from aluminum alloy, ensuring both lightweight and excellent heat dissipation while meeting strength requirements. The coil winding portion of the support is grooved to reduce overall weight and facilitate coil positioning and winding, preventing loosening and misalignment. The upper end of the coil support is hollowed out, both to reduce weight and to facilitate internal air circulation. The outer copper coil 3-1 and the inner copper coil 3-2 are pre-wound coils, constructed from highly conductive copper wire. Polyester enameled wire is used for insulation requirements. Considering corrosion resistance and production costs, the radiation panel 1 is constructed from aluminum alloy, with reinforcing ribs designed inside to ensure strength and secure and position the coil supports.

[0053] Figure 6 A cutaway 3D view of the permanent magnet structure is shown. The electrically pure iron magnetic housing 4 is a semi-enclosed structure, consisting of a cylindrical main body containing a cavity and six sector-shaped cover plates above. Multiple through-holes are designed beneath the cylindrical main body to ensure airflow between the moving coil and the outside world during operation, enhancing heat dissipation. A cylindrical ring 5, composed of spliced ​​NdFeB magnets, is secured within the cavity of the electrically pure iron magnetic housing 4.

[0054] Figure 7 A schematic diagram of the connection structure between the permanent magnet structure and the moving coil is shown, where the permanent magnet structure is the stator and the moving coil moves in the magnetic field generated by the permanent magnet structure.

[0055] Figure 8-9 The front and top views of the NdFeB magnet spliced ​​cylindrical ring are shown, with a height of h = 50 mm, an inner radius of r = 30 mm, a thickness of t = 8 mm, and a sector angle of =30°.

[0056] Figure 10 The figure shows the actual sound source level curve of the sound wave signal transmitted from 20Hz to 300Hz when the integrated system is operating normally. The maximum sound source level is 162dB at the resonant frequency of 30Hz, and the average sound source level within the operating frequency band is 159.6dB.

[0057] Figure 11A schematic diagram shows a conventional permanent magnet structure using pure iron as a base and a magnetic plate. This permanent magnet structure has only a single, relatively short magnetic flux gap. The non-closed-loop magnetic circuit design also increases magnetic flux leakage.

[0058] The embodiments of the present invention disclosed above are intended only to illustrate the present invention. The embodiments do not describe all details in detail, nor do they limit the present invention to the specific embodiments described. Numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

Claims

1. A low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible, characterized by: The working frequency band is 20Hz~300Hz, and it includes a propulsion device, a double-coil fixing device and a permanent magnet structure. The propulsion device provides power for the underwater unmanned submersible to move forward. The double-coil fixing device includes a copper wire, a coil bracket and a fixed panel (1). The copper wire is used to conduct alternating current. The copper wire is wound on the coil bracket. The coil bracket is vertically fixedly connected to the fixed panel (1). The propulsion device is connected to the fixed panel (1). The permanent magnet structure includes a neodymium iron boron magnet spliced ​​cylindrical ring (5) and an electrical pure iron magnetic conductive shell (4). The electrical pure iron magnetic conductive shell (4) includes a cylindrical main body containing a cavity and a plurality of fan-shaped cover plates on the upper surface. The neodymium iron boron magnet spliced ​​cylindrical ring (5) is placed in the cavity of the cylindrical main body, and an air gap with two magnetic cores is provided on the inner and outer sides of the neodymium iron boron magnet spliced ​​cylindrical ring (5). The NdFeB magnet spliced ​​cylindrical ring (5) is a cylindrical ring formed by splicing a number of NdFeB magnets, each NdFeB magnet is a fan-shaped structure, and the magnetization direction is radial; The coil support comprises an outer coil support (2-1) and an inner coil support (2-2); the outer coil support (2-1) and the inner coil support (2-2) are coaxial annular; the outer coil support (2-1) is arranged on the outer ring of the inner coil support (2-2).

2. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 1, characterized in that: Each NdFeB magnet in the sector structure has an inner radius r = 30 mm, a thickness t = 8 mm, a height h = 50 mm, and a sector angle = 30°.

3. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 1, characterized in that: The air gap height h1 = 70 mm, and the air gap width t1 = 5 mm.

4. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 1, characterized in that: A plurality of through holes are designed below the cylindrical main body of the electrical pure iron magnetic conductive shell (4).

5. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 1, characterized in that: The upper end of the coil support is a hollow structure, and the upper end of the coil support is connected to the fixed panel (1).

6. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 1, characterized in that: A shell is fixed to the outer periphery of the permanent magnet structure.

7. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 6, characterized in that: The fixed panel (1), coil support and housing are all made of aluminum alloy.

8. The low-frequency acoustic transducer and propeller integrated system for an underwater unmanned submersible according to claim 1, characterized in that: The copper wire is a copper enameled wire.

Images