Variable-pitch coaxial reverse propeller propelling system based on UUV (Unmanned Underwater Vehicle)

Abstract

The invention discloses a variable-pitch coaxial reverse propeller propulsion system based on a UUV (unmanned underwater vehicle), and belongs to the technical field of propulsion of the UUV. The propelling system is mainly composed of a variable-pitch system and a coaxial reverse propeller system, and a variable-pitch motor drives a variable-pitch worm to be matched with a variable-pitch rack to drive a driving push rod and a driven push rod so that the pitch of fan blades can be changed; the main pushing motor drives the driving shaft, the driving shaft and the driven shaft coaxially and reversely rotate at the same speed through the bevel gear set, and the fan blades are driven to coaxially rotate reversely. The innovation point is that the variable propeller pitch system adopts worm and rack transmission, the structure is simple, and the self-locking property is realized; the coaxial reverse propeller system uses a bevel gear set, and the transmission efficiency is high. The propelling system adopts dynamic sealing to improve underwater performance and prolong the service life. Data are collected through a sensor, an algorithm based on model predictive control (MPC) is utilized, a motor is controlled to run through a communication module, and fault diagnosis and fault tolerance functions are achieved. The problems that a traditional UUV propulsion system is unbalanced in torque, low in propulsion efficiency, poor in low-speed maneuverability and the like are effectively solved, the maneuverability, efficiency and environmental adaptability of the UUV are remarkably improved, and the UUV propulsion system has wide application prospects in the fields of marine environment monitoring, resource exploration, military reconnaissance, scientific research and the like.

Description

Technical Field

[0001] The present invention relates to the field of underwater unmanned vehicle (UUV) propulsion technology, and in particular to a variable pitch coaxial counter-propeller propulsion system based on UUV, which aims to significantly improve the maneuverability, efficiency and environmental adaptability of UUV through dynamic pitch adjustment and double-propeller counter-rotation design. Background Art

[0002] With the continuous deepening of marine scientific exploration and the rapid development of underwater detection technology, unmanned underwater vehicles (UUVs) are increasingly widely used in many fields. In terms of marine environmental monitoring, UUVs can obtain real-time data on seawater temperature, salinity, dissolved oxygen, etc. at different depths, providing key information for marine ecological research; in the field of resource exploration, it can go deep into the deep sea to detect the distribution of mineral resources and help the development of marine resources; in military reconnaissance, UUVs perform intelligence collection tasks with their concealment advantages; in scientific research, UUVs provide strong data support for deep-sea geological structure and biodiversity research.

[0003] However, traditional UUV propulsion systems have many limitations and are difficult to meet the operational requirements of complex underwater environments. Most traditional propulsion systems use fixed-pitch propeller thrusters. Although they can maintain stable thrust under specific working conditions, their maneuverability and energy efficiency are poor in the face of complex and changeable underwater environments. The underwater environment varies significantly, and the water flow speed, depth and seawater density in different areas are different. Fixed pitch cannot adapt to these changes. In deep sea areas, the seawater density is high, and fixed-pitch propellers need to consume more energy to maintain propulsion; in shallow sea complex water flow areas, it is difficult to flexibly adjust the propulsion force, resulting in low energy efficiency of the propeller at different sailing speeds and working depths.

[0004] In addition, traditional propulsion systems are poor at precise control and have slow response speeds. When performing complex tasks such as maneuvering in narrow spaces and high-precision underwater positioning, UUVs need to quickly and accurately adjust propulsion and direction, but traditional propulsion systems are difficult to achieve rapid steering and acceleration and deceleration operations, which greatly limits the operating efficiency and application scope of UUVs.

[0005] Variable pitch design provides an effective way to solve these problems. By adjusting the pitch of the blades, the variable pitch design can optimize the performance of the propeller under different working conditions. Increasing the pitch when sailing at low speed can provide greater thrust to help the UUV overcome resistance; reducing the pitch when sailing at high speed can reduce resistance and improve energy efficiency. This not only improves the maneuverability of the UUV, but also significantly reduces energy consumption and extends the endurance. The realization of variable pitch design depends on high-precision mechanical transmission systems and advanced control algorithms. With the help of sensors to monitor the working status of the propeller in real time, the control system can dynamically adjust the pitch according to actual needs to ensure that the propeller always operates efficiently, so that the UUV can operate stably in complex underwater environments.

[0006] The coaxial counter-propeller design is also innovative. Traditional unidirectional rotating blades will generate a large number of eddies during the propulsion process, which will increase energy consumption and affect the stability of the propeller. The coaxial counter-propeller design installs two sets of counter-rotating blades on the same axis, which interact with each other to offset the eddies, effectively reduce energy loss, and improve propulsion efficiency. At the same time, by adjusting the speed and pitch of the two sets of blades, more precise thrust control can be achieved, significantly improving the control accuracy, maneuverability and response speed of the UUV. This design has obvious advantages in tasks with high positioning and maneuverability requirements, such as underwater archaeology and environmental monitoring.

[0007] The variable pitch coaxial reverse propeller propulsion system based on UUV has broad application prospects. With the continuous growth of global marine resource exploration and environmental protection needs, the market demand for high-performance UUV propulsion systems is also increasing. The propulsion system of the present invention is expected to occupy an important position in the future underwater vehicle market and promote the development of marine industry. Summary of the invention

[0008] 1. Purpose of the invention: The purpose of the present invention is to provide a specific structure of a variable pitch coaxial counter-propeller propulsion system based on UUV, so as to solve the problems of torque imbalance, low propulsion efficiency, poor low-speed maneuverability, etc. existing in the current underwater UUV single-propeller or fixed-pitch propulsion system.

[0009] 2. Technical solution: A variable pitch coaxial reverse propeller propulsion system based on UUV, including a variable pitch system and a coaxial reverse propeller system. The variable pitch motor is fixed on the variable pitch motor bracket, the variable pitch worm is fixed on the variable pitch motor by bolts, the variable pitch worm and the variable pitch rack are mechanically meshed, the variable pitch rack and the main propeller motor are fixed on the main propeller motor bracket, the variable pitch rack and the active push rod are connected through the left end cross roller bearing, the left side of the right end of the active push rod is connected to the right variable pitch slider, the right variable pitch slider and the left variable pitch slider are connected through the right end cross roller bearing, the left variable pitch slider is connected to the driven push rod, the driven push rod and the active push rod are connected to the slider shaft, and the slider shaft is connected to the fan blade. The main propeller motor is fixedly connected to the active shaft by bolts, the active shaft is fixedly connected to the active large bevel gear by bolts, and the driven large bevel gear is fixedly connected to the driven shaft by bolts. Among them, the main propulsion motor adopts a hollow motor, the variable pitch motor and the main propulsion motor output power coaxially and collinearly, and the variable pitch motor and the main propulsion motor are sealed together in the UUV tail end casing.

[0010] 3. Preferred solution The variable pitch system uses a variable pitch motor to drive the pitch worm to rotate, and the pitch worm rotation drives the pitch rack to produce horizontal push-pull movement. Compared with the current variable pitch transmission scheme, this scheme adopts the worm rack transmission form, completes the transmission through two parts, has mechanical self-locking performance, and has a simple structure and higher stability.

[0011] The variable pitch system uses two crossed roller bearings, which can effectively reduce the interference and friction caused by the high-speed rotation of the blades on the active push rod and the driven push rod.

[0012] The variable pitch system converts the push-pull motion of the active push rod and the driven push rod into the rotational motion of the slider shaft through the meshing motion of the slider, thereby directly driving the fan blades to rotate. The transmission form is simplified, and the transmission is direct and efficient.

[0013] The variable pitch system realizes the push-pull movement of the active push rod and the driven push rod through the right-end cross roller bearing. At the same time, through the appropriate meshing movement of the sliders, the rotation directions of the slider shafts on both sides are opposite, that is, the fan blades on both sides can be reversed. The transmission form is streamlined, and the transmission is direct and efficient.

[0014] The coaxial reverse propeller system uses a bevel gear set to achieve coaxial and speed reverse rotation of the driving shaft and the driven shaft. Compared with planetary gear transmission and chain or belt transmission, the bevel gear set has the advantages of high transmission efficiency, compact structure and strong reliability.

[0015] A UUV-based variable pitch coaxial counter-propeller propulsion system adopts dynamic seals to improve its underwater performance and lifespan. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is an overall schematic diagram of a propulsion system based on UUV in an embodiment of the present invention.

[0017] Figure 2 Schematic diagram of the overall UUV tail propulsion system in an embodiment of the present invention.

[0018] Figure 3 The figure is a schematic diagram of the appearance of a variable pitch coaxial counter-propeller propulsion system in an embodiment of the present invention.

[0019] Figure 4 Schematic diagram of the structure of a variable pitch coaxial counter-propeller propulsion system in an embodiment of the present invention.

[0020] Figure 5 It is a top view of the structure of a variable pitch coaxial counter-propeller propulsion system in an embodiment of the present invention.

[0021] Figure 6 It is a structural diagram of the variable pitch rack / worm gear and the main propulsion motor bracket in an embodiment of the present invention.

[0022] Figure 7 Schematic diagram of the active push rod structure in an embodiment of the present invention.

[0023] Figure 8 Schematic diagram of the active shaft structure in an embodiment of the present invention.

[0024] Fig. 9 It is a front view of the driven shaft and driven push rod structure in an embodiment of the present invention.

[0025] Fig.10 It is a schematic diagram of the slider shaft and fan blade structure in an embodiment of the present invention.

[0026] In the figure, 1. UUV main body shell; 2. UUV tail end shell; 3. variable pitch coaxial reverse propeller propulsion system; 4. variable pitch motor bracket; 5. variable pitch motor; 6. variable pitch rack; 7. variable pitch worm; 8. left end cross roller bearing; 9. active push rod; 10. main push motor bracket; 11. main push motor; 12. active shaft; 13. bevel gear set bracket; 14. active large bevel gear; 15. driven small bevel gear; 16. driven large bevel gear; 17. driven shaft; 18. driven push rod; 19. variable pitch slider; 20. right end cross roller bearing; 21. slider shaft; 22. fan blade. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] A variable pitch coaxial reverse propeller propulsion system based on UUV consists of a variable pitch system and a coaxial reverse propeller system. Its operation in actual application scenarios depends on the coordinated work of multiple key parts. The specific implementation method is described in detail below with reference to the accompanying drawings.

[0030] 1. Overall structure and layout (combined with Figure 1 - Figure 3) FIG1 (Overall Schematic Diagram of the Propulsion System Based on UUV) is an overall schematic diagram of the propulsion system based on UUV in an embodiment of the present invention. It can be clearly seen from the figure that the propulsion system is installed inside the UUV main shell 1 and the UUV tail shell 2, and is closely integrated with the overall structure of the UUV. It is the core component for the UUV to achieve efficient underwater movement. The UUV main shell 1 and the UUV tail shell 2 provide protection and installation basis for the entire propulsion system, ensuring its safety in complex underwater environments.

[0031] Figure 2 (Overall Schematic Diagram of the UUV Tail Propulsion System) shows the overall schematic diagram of the UUV tail propulsion system in the embodiment of the present invention. Through this figure, the specific installation position and size ratio of the propulsion system at the tail of the UUV can be intuitively observed. This is of great significance for understanding the layout of the entire propulsion system on the UUV and its coordinated work with other components, and provides a key reference for the overall design and optimization of the UUV.

[0032] Figure 3 (Schematic diagram of the appearance of a variable pitch coaxial counter-propeller propulsion system) is a schematic diagram of the appearance of a variable pitch coaxial counter-propeller propulsion system in an embodiment of the present invention, showing the external outline and general structure of the propulsion system. From the appearance, one can preliminarily understand its overall shape and the approximate position distribution of each part, laying the foundation for a subsequent in-depth understanding of the internal structure and working principle.

[0033] 2. Working process of variable pitch system (combined with Figure 4 - Figure 7, Figure 10) FIG4 (schematic diagram of the structure of a variable pitch coaxial counter-propeller propulsion system) is a schematic diagram of the structure of a variable pitch coaxial counter-propeller propulsion system in an embodiment of the present invention, and FIG5 (top view of the structure of a variable pitch coaxial counter-propeller propulsion system) is a top view of the structure of a variable pitch coaxial counter-propeller propulsion system in an embodiment of the present invention. By combining these two figures, the specific structural composition of the variable pitch system and the connection relationship between the components can be clearly observed from different perspectives, thereby having a more intuitive three-dimensional understanding of the variable pitch system.

[0034] When the variable pitch system is running, the variable pitch motor 5 is fixed on the variable pitch motor bracket 4, and the start of the variable pitch motor 5 is precisely controlled by the UUV control system. When the UUV needs to adjust the propulsion force to adapt to different underwater working conditions, the control system will analyze and process the data collected by various sensors (such as the navigation speed, depth, water flow speed and direction of the UUV), and then send instructions to the variable pitch motor 5.

[0035] After receiving the command, the pitch motor 5 drives the pitch worm 7 to generate rotational motion. The pitch worm 7 and the pitch rack 6 are mechanically meshed, and their meshing structures can be clearly seen from Figures 4 and 5. The rotation of the pitch worm 7 drives the pitch rack 6 to generate horizontal push-pull motion. Compared with other transmission schemes, this worm rack transmission method is not only simple in structure, but also has mechanical self-locking performance, which can ensure the stability of the pitch system under certain circumstances and effectively prevent accidental changes in pitch.

[0036] FIG6 (structural diagram of pitch rack / worm and main propulsion motor bracket) is a structural diagram of the pitch rack / worm and main propulsion motor bracket in an embodiment of the present invention. From this figure, the specific transmission form of the variable pitch of the present invention can be clearly recognized, and the installation position and mutual coordination relationship of the pitch worm 7 and the pitch rack 6, as well as their connection method with the main propulsion motor bracket 10 are further clarified, which provides an important reference for understanding the transmission principle of the variable pitch system.

[0037] The pitch rack 6 and the active push rod 9 are fixedly connected through the left end cross roller bearing 8. The left end cross roller bearing 8 can effectively reduce the interference and friction on the active push rod 9 when the blade rotates at high speed, and ensure the stability of motion transmission. Figure 7 (schematic diagram of the active push rod structure) is a schematic diagram of the active push rod structure in an embodiment of the present invention. The active push rod 9 is an active transmission component of the variable pitch. Its structural design ensures that it can stably perform horizontal push-pull movement under the drive of the pitch rack 6. The active push rod 9 performs horizontal push-pull movement under the drive of the pitch rack 6. Since the active push rod 9 and the driven push rod 18 are both connected to the slider shaft 21, the movement of the active push rod 9 drives the driven push rod 18 to perform horizontal push-pull movement synchronously.

[0038] The push-pull movement of the active push rod 9 and the driven push rod 18 drives the slider shaft 21 to generate rotational movement, thereby driving the blade 22 to rotate. Figure 10 (schematic diagram of the slider shaft and blade structure) is a schematic diagram of the slider shaft and blade structure in an embodiment of the present invention, showing the connection method of the slider shaft 21 and the blade 22 and their structural characteristics. The right-side variable pitch slider 19 and the left-side variable pitch slider 19 are connected through the right-end cross roller bearing 20. This structural design cooperates with the appropriate meshing movement of the slider so that the left and right slider shafts 21 rotate in opposite directions, thereby realizing the reverse pitch of the left and right blades 22. For example, when the UUV is sailing at a low speed and needs to overcome a large resistance, the control system controls the pitch motor 5 to rotate the pitch worm 7, driving the pitch rack 6 to push the active push rod 9, thereby increasing the pitch of the blades 22 on both sides and providing greater thrust; while at high speed, the pitch motor 5 rotates in the opposite direction, so that the blades 22 on both sides reduce the pitch, reduce resistance, and improve energy efficiency.

[0039] 3. Working process of coaxial reverse propeller system (combined with Figures 4 - 5, 8 - 9) The operation of the coaxial reverse propeller system depends on the drive of the main propulsion motor 11. Figures 4 and 5 show the position of the coaxial reverse propeller system in the entire propulsion system and the connection relationship of each component. The main propulsion motor 11 adopts a hollow motor, which is fixedly connected to the driving shaft 12 by bolts, and the variable pitch motor 5 and the main propulsion motor 11 coaxially output power and are sealed together in the UUV tail end shell 2. When the UUV starts propulsion, the control system sends an operation command to the main propulsion motor 11 according to the mission requirements and underwater environmental conditions.

[0040] The main push motor 11 drives the driving shaft 12 to generate rotational motion. The driving shaft 12 is fixedly connected to the driving large bevel gear 14 by bolts, so the rotation of the driving shaft 12 drives the driving large bevel gear 14 to rotate synchronously. FIG8 (schematic diagram of the driving shaft structure) is a schematic diagram of the driving shaft structure in an embodiment of the present invention, showing the structural features of the driving shaft 12 and the connection parts with other components. Its structural design ensures that it can rotate stably under the drive of the main push motor 11 and effectively transmits power to the driving large bevel gear 14.

[0041] The driving large bevel gear 14 meshes with the driven small bevel gears 15 on both sides, and the rotation of the driving large bevel gear 14 drives the driven small bevel gears 15 on both sides to rotate. The driven small bevel gear 15 is connected to the driven large bevel gear 16, and the rotation of the driven small bevel gear 15 drives the driven large bevel gear 16 to rotate, and the driven large bevel gear 16 then drives the driven shaft 17 to rotate. Figure 9 (front view of the driven shaft and driven push rod structure) is a front view of the driven shaft and driven push rod structure in an embodiment of the present invention, showing the structure of the driven shaft 17 and the driven push rod 18 and the connection relationship between them. The driven shaft 17 achieves stable rotation under the drive of the driven large bevel gear 16.

[0042] Finally, the driving shaft 12 and the driven shaft 17 realize the same-speed reverse rotation movement, driving the blades 22 on both sides to produce the same-axis and same-speed reverse rotation movement, realizing the coaxial reverse propeller movement. This mode of movement effectively reduces the eddy current generated by the rotation and improves the propulsion efficiency. During the UUV mission, the control system can accurately control the speed of the main propulsion motor 11 according to the navigation attitude and required propulsion force of the UUV. When performing underwater fixed-point operations, reduce the speed of the main propulsion motor 11 to reduce the propulsion force; when fast movement is required, increase the speed of the main propulsion motor 11 to enhance the propulsion force, and cooperate with the variable pitch system to achieve precise control of the UUV propulsion force and navigation attitude.

[0043] 4. Specific implementation of the control system In practical applications, the control system is a key part to achieve efficient operation of the variable pitch coaxial counter-propeller propulsion system. The core of the control system usually uses a high-performance microprocessor, such as an embedded chip with powerful computing power and rich interface resources, to ensure that a large amount of sensor data can be quickly processed and control instructions can be issued in a timely manner.

[0044] In terms of sensors, the UUV is equipped with a variety of sensors to collect key information. The speed sensor monitors the UUV's navigation speed in real time, the depth sensor measures the depth of the UUV, and the water flow sensor obtains data such as the speed and direction of the water flow. These sensors convert the collected analog signals into digital signals through the analog-to-digital conversion module and transmit them to the microprocessor.

[0045] The control algorithm is the core part of the control system. Advanced adaptive control algorithms are used, such as the model predictive control (MPC) method. The algorithm predicts the motion state of the UUV in the future based on the current state (speed, depth, attitude, etc.) of the UUV and sensor data, combined with the mathematical model of the propulsion system. Then, the optimal control parameters (pitch and speed) of the variable pitch motor 5 and the main propulsion motor 11 are calculated through the optimization algorithm to achieve efficient and stable operation of the UUV in a complex underwater environment.

[0046] For example, when the UUV encounters a strong current in a shallow sea area, the speed sensor and the current sensor detect the speed change and current information, and the microprocessor uses the MPC algorithm to predict the movement trend of the UUV based on these data. If the UUV is likely to be washed away by the current, the control system will instruct the variable pitch motor 5 to increase the pitch and increase the speed of the main propulsion motor 11, so that the UUV can generate greater thrust to resist the current and maintain a stable navigation track.

[0047] The communication module is used to realize data transmission between the control system and the pitch motor 5 and the main propulsion motor 11. A high-speed and reliable communication protocol, such as the CAN bus protocol, is used to ensure that the control instructions can be accurately and timely transmitted to the motor driver, and the motor driver accurately controls the operation of the motor according to the received instructions.

[0048] In addition, the control system also has fault diagnosis and fault tolerance functions. By monitoring the current, voltage and other parameters of the motor, as well as the rationality of the sensor data, it can be determined whether the propulsion system has a fault. If a fault is detected, the control system will take corresponding measures in a timely manner, such as reducing the power of the propulsion system, switching to backup equipment or issuing an alarm to ensure the safe operation of the UUV.

[0049] Through the above detailed explanation of the working process of the variable pitch system and the coaxial reverse propeller system, as well as the description of the specific implementation of the control system, combined with the display of the structure and working principle of each part of the entire propulsion system in the accompanying drawings, the working principle and implementation method of the variable pitch coaxial reverse propeller propulsion system based on UUV in practical applications of the present invention are clearer and more complete, which is helpful for further understanding and application of the invention technology.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the specific implementation modes of the present invention can still be modified or replaced by equivalents, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A variable pitch coaxial reverse propeller propulsion system based on UUV, characterized in that: The invention comprises a variable pitch system and a coaxial reverse propeller system; the variable pitch system comprises a variable pitch motor (5), a variable pitch worm (7), a variable pitch rack (6), an active push rod (9), a driven push rod (18), a slider shaft (21), a fan blade (22), a variable pitch motor bracket (4), a main push motor bracket (10), a left end cross roller bearing (8), a right end cross roller bearing (20) and a variable pitch slider (19), wherein the variable pitch motor (5) is fixed on the variable pitch motor bracket (4), and the variable pitch worm (7) is fixed on the right end cross roller bearing (20) and the variable pitch slider (19). ) is fixed to the pitch motor (5) by bolts, the pitch worm (7) and the pitch rack (6) are mechanically meshed, the pitch rack (6) and the main propulsion motor (11) are fixed to the main propulsion motor bracket (10), the pitch rack (6) and the active push rod (9) are connected through the left end cross roller bearing (8), the right end of the active push rod (9) is connected to the right pitch slider (19), the right pitch slider (19) and the left pitch slider (19) are connected through the right end cross roller bearing (20), the left pitch The slider (19) is connected to the driven push rod (18), the driven push rod (18) and the driving push rod (9) are both connected to the slider rotating shaft (21), and the slider rotating shaft (21) is connected to the fan blade (22); the coaxial reverse propeller system comprises a main propulsion motor (11), a driving shaft (12), a driving large bevel gear (14), a driven small bevel gear (15), a driven large bevel gear (16), a driven shaft (17), and a bevel gear set bracket (13); the main propulsion motor (11) is fixedly connected to the driving shaft (12) by bolts, and the driving shaft (12) is connected to the fan blade (22). The driving large bevel gear (14) is fixedly connected by bolts, the driven large bevel gear (16) is fixedly connected to the driven shaft (17) by bolts, the driving large bevel gear (14) and the driven small bevel gears (15) on both sides are meshed with each other, and the driven small bevel gear (15) is connected to the driven large bevel gear (16); wherein the main propulsion motor (11) adopts a hollow motor, the variable pitch motor (5) and the main propulsion motor (11) output power coaxially and collinearly, and the variable pitch motor (5) and the main propulsion motor (11) are sealed together in the UUV tail end casing (2).

2. A variable pitch coaxial reverse propeller propulsion system based on UUV according to claim 1, characterized in that: The variable pitch system uses a variable pitch motor (5) to drive the variable pitch worm (7) to rotate, and the rotation of the variable pitch worm (7) drives the variable pitch rack (6) to generate horizontal push-pull movement.

3. A variable pitch coaxial reverse propeller propulsion system based on UUV according to claim 1, characterized in that: The variable pitch system uses two crossed roller bearings (8, 20) to reduce the interference and friction caused by the high-speed rotation of the blades on the active push rod (9) and the driven push rod (18).

4. A variable pitch coaxial reverse propeller propulsion system based on UUV according to claim 1, characterized in that: The variable pitch system converts the push-pull movement of the active push rod (9) and the driven push rod (18) into the rotational movement of the slider shaft (21) through the meshing movement of the slider (19), thereby driving the fan blades (22) to rotate.

5. The variable pitch coaxial reverse propeller propulsion system based on UUV according to claim 1, characterized in that: The variable pitch system realizes the push-pull movement of the active push rod (9) and the driven push rod (18) through the right end cross roller bearing (20), and at the same time, through the appropriate meshing movement of the slider (19), the slider shafts (21) on both sides rotate in opposite directions, so that the fan blades (22) on both sides change the pitch in the opposite direction.

6. The variable pitch coaxial reverse propeller propulsion system based on UUV according to claim 1, characterized in that: The coaxial counter-propeller system uses a bevel gear set to achieve coaxial and speed counter-rotating motion of the driving shaft (12) and the driven shaft (17).

7. The variable pitch coaxial reverse propeller propulsion system based on UUV according to claim 1, characterized in that: The propulsion system uses dynamic seals to improve its performance and life underwater.

8. A control method for a variable pitch coaxial reverse propeller propulsion system based on a UUV, applied to the propulsion system according to any one of claims 1 to 7, characterized in that: include: The sensors on the UUV collect data such as the navigation speed, depth, water flow speed and direction of the UUV; the collected analog signals are converted into digital signals through an analog-to-digital conversion module and transmitted to the microprocessor of the control system; the control system adopts a model predictive control (MPC) method to predict the motion state of the UUV in the future based on the current state of the UUV and sensor data, combined with the mathematical model of the propulsion system; the optimal control parameters of the variable pitch motor (5) and the main propulsion motor (11), including the pitch and the rotation speed, are calculated through an optimization algorithm; a high-speed and reliable communication protocol, such as the CAN bus protocol, is used to transmit the control instructions to the motor driver, and the motor driver accurately controls the operation of the motor according to the received instructions; the control system determines whether the propulsion system has a fault by monitoring the current, voltage and other parameters of the motor and the rationality of the sensor data, and if a fault is detected, timely takes corresponding measures, such as reducing the power of the propulsion system, switching to backup equipment or sounding an alarm.

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