A multi-directional pulse propulsion underwater soft robot based on bistable SMA drive and its working method

Abstract

This invention proposes a multi-directional pulse propulsion underwater soft robot and its operating method based on bistable SMA (Stable Motion Assisted Mullion) drive, belonging to the field of underwater robot technology. It solves the problems of slow swimming speed and low energy utilization efficiency of traditional underwater flexible soft robots, as well as the slow engine reset, requirement for a dedicated reset mechanism, inability to achieve continuous motion, and single-direction pulse jet propulsion of SMA-driven soft robots. The robot includes a biomimetic bell-shaped jar, a propulsion actuator, and a center-of-gravity adjustment mechanism. The biomimetic bell-shaped jar surrounds the propulsion actuator and the center-of-gravity adjustment mechanism. The propulsion actuator includes a support transmission structure and a bistable SMA actuator. The bistable SMA actuator includes two sets of SMA springs arranged in an antagonistic manner, achieving continuous pulse propulsion through alternating on and off-circuit power. The center-of-gravity adjustment mechanism includes an azimuth rotation component and a radial displacement component, achieving 360° omnidirectional center-of-gravity adjustment in the horizontal plane. It is mainly used for deep-sea exploration and continuous underwater monitoring operations.

Description

Technical Field

[0001] This invention belongs to the field of underwater robot technology, and in particular relates to a multi-directional pulse propulsion underwater soft robot based on bistable SMA drive and its working method. Background Technology

[0002] Soft underwater robots possess advantages such as flexible movement, strong stealth, high environmental adaptability, and low disturbance. They show broad application prospects in fields such as marine exploration, environmental monitoring and disaster response, and biodiversity research. Existing soft underwater robots mostly use smart materials such as dielectric elastomers, ion-conducting polymers, and piezoelectric materials as actuators. These actuators are mostly slow in response and low in output force, resulting in slow swimming speed and poor maneuverability. Shape memory alloy (SMA) springs are often used as actuating elements for soft robots due to their large actuation strain, high power density, and low actuation voltage. However, traditional SMA underwater robots use a single SMA spring operating mode of power-on operation - power-off cooling - external force reset, requiring an additional reset mechanism. This leads to complex structure, increased weight, long reset time, discontinuous movement, high reset energy consumption, and significant energy waste, failing to meet the requirements of continuous operation. Summary of the Invention

[0003] In view of this, the present invention aims to propose a multi-directional pulse propulsion underwater soft robot and its working method based on bistable SMA drive, so as to solve the problems of slow swimming speed and low energy utilization efficiency of traditional underwater flexible soft robots; slow engine reset of SMA driven soft robots, requiring a special reset mechanism, inability to achieve continuous motion, and single pulse jet propulsion direction.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a multi-directional pulse-driven underwater soft robot based on bistable SMA (Stable Multi-Actuation Matrix) propulsion, comprising a biomimetic bell-shaped radome, a propulsion actuator, and a center-of-gravity adjustment mechanism. The lower end of the center-of-gravity adjustment mechanism is connected to the propulsion actuator. The biomimetic bell-shaped radome surrounds the propulsion actuator and the center-of-gravity adjustment mechanism. The biomimetic bell-shaped radome is a hollow parabolic structure made of flexible material. The propulsion actuator includes a support transmission structure and a bistable SMA actuator. The support transmission structure includes a transmission part and a support part. The transmission part includes a central rod, a fixed hub, and a sliding hub. The upper end of the central rod is connected to the center-of-gravity adjustment mechanism, and the lower end of the central rod is connected to the fixed hub. The sliding hub is slidably connected to the central rod. Multiple support parts are evenly distributed along the circumference of the central rod. The support unit includes a connecting rod, an outer support ring, and a support member. One end of the connecting rod is hinged to a sliding hub, and the other end of the connecting rod is hinged to the outer support ring. One end of the support member is hinged to the outer support ring, and the other end of the support member is hinged to a center of gravity adjustment mechanism. The bistable SMA actuator includes two sets of SMA springs, which are arranged in an antagonistic manner. The two sets of SMA springs are an upper SMA spring set and a lower SMA spring set. The two ends of the upper SMA spring set are connected to the center of gravity adjustment mechanism and the sliding hub, respectively. The two ends of the lower SMA spring set are connected to the sliding hub and the fixed hub, respectively. Both sets of SMA springs are connected to a controller. The center of gravity adjustment mechanism realizes the adjustment of the robot's center of gravity in any direction of 360° in the horizontal plane through polar coordinate drive, and the robot can turn by adjusting the position of its center of gravity.

[0005] Furthermore, the center of gravity adjustment mechanism includes an orientation rotation component, a radial displacement component, and a mass box. The orientation rotation component is connected to the radial displacement component and drives the radial displacement component to rotate around the central rod axis. The end of the radial displacement component is connected to the mass box and drives the mass box to move radially.

[0006] Furthermore, the orientation rotation component includes a rotary motor and a power transmission platform. The rotary motor is connected to the top cover, and the output shaft of the rotary motor is connected to the power transmission platform. The radial displacement component is a telescopic rod component, on which a telescopic motor is mounted. The telescopic rod component is connected to the power transmission platform and to a mass box. The mass box is an integrated mass box, which integrates a controller and a power supply battery. A top cover is connected above the top cover.

[0007] Furthermore, the wall thickness of the biomimetic bell-shaped jar gradually decreases from the head to the tail.

[0008] Furthermore, the biomimetic bell-shaped cover extends along the robot's torso to form a passive flap.

[0009] Furthermore, the number of support parts is four, and the outer support ring is a quarter-circle arc structure.

[0010] Furthermore, the support member is provided with several ribs, which extend horizontally along the bionic bell-shaped cover, and both the support member and the ribs are in contact with the inner wall of the bionic bell-shaped cover.

[0011] Furthermore, both sets of SMA springs are encapsulated within a silicone insulating layer.

[0012] Furthermore, the support member and the outer support ring are connected by a curved pin hinge, and the connecting rod and the outer support ring are connected by a regular pin hinge.

[0013] This invention also provides a working method for a multi-directional pulse propulsion underwater soft robot based on bistable SMA drive, as detailed below: Energy storage stage: The controller energizes the upper SMA spring assembly, which contracts to generate driving force, pulling the sliding hub upward along the central rod. The sliding hub drives the hinged connecting rod to move synchronously, pushing the outer support ring to expand radially, thus opening the bionic bell-shaped jar. At this time, water is drawn into the cavity through the opening at the tail of the bionic bell-shaped jar, completing energy storage. When the sliding hub moves to the midpoint of the central rod, the connecting rod is in a horizontal state, and the bionic bell-shaped jar reaches its maximum expansion state, storing the most energy. Energy release propulsion phase: The upper SMA spring assembly is de-energized, and the controller simultaneously energizes the lower SMA spring assembly. The lower SMA spring assembly contracts to generate driving force, pulling the sliding hub down along the central rod. The connecting rod drives the outer support ring to contract, and the bionic bell-shaped jar contracts synchronously. The water inside the cavity is squeezed out from the tail opening, generating a reaction force that propels the robot forward. At the same time, the upper SMA spring assembly naturally resets under the combined action of the elastic restoring force of the bionic bell-shaped jar, the water pressure, and its own elasticity. Two sets of SMA springs alternately turn on and off, causing the energy storage phase and the energy release propulsion phase to cycle, achieving continuous pulse-type jet propulsion.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention effectively solves the problems of slow reset, the need for a dedicated reset mechanism, interruptions during movement, and energy waste in traditional SMA-driven robots by employing an antagonistic bistable SMA actuator combined with a biomimetic bell-shaped jar design. Two sets of SMA springs are arranged in an antagonistic, vertical configuration. When one set is energized, the other set can naturally reset using the elastic restoring force of the bell-shaped jar, water pressure, and its own elasticity, eliminating the need for an additional reset mechanism. This not only simplifies the structure and reduces weight but also eliminates cooling time, enables continuous pulse jet propulsion, significantly reduces reset energy consumption, and improves energy utilization efficiency.

[0015] The box jellyfish, with its highly efficient pure jet propulsion and adaptable slender bell-shaped structure, offers new insights into biomimetic design. The biomimetic bell-shaped shield of this invention employs a hollow parabolic structure made of flexible material, extending along the body to form passive flaps, with its wall thickness gradually decreasing from head to tail. This design, combined with the pulse propulsion characteristics of a bistable SMA actuator—slow expansion for energy storage and rapid contraction for energy release—enables the robot to propel itself efficiently in a pure jet mode. Compared to traditional soft-bodied robots like those of carp and rays that rely on oscillating flexible components to slap the water, this invention significantly improves swimming speed and reduces energy consumption per unit distance, thereby greatly enhancing the robot's propulsion performance and endurance, better meeting the requirements of underwater robots for low energy consumption and long endurance.

[0016] This invention incorporates a rotary telescopic center of gravity adjustment mechanism in the robot's head. This mechanism, driven by a rotary motor, operates an electric actuator and a mass box, enabling continuous omnidirectional center of gravity adjustment with no blind spots in the horizontal plane. Compared to traditional solutions that utilize SMA wires to achieve only limited directional center of gravity shifts, this invention can precisely control the rotation angle and telescopic distance to adjust the center of gravity to any position within the horizontal plane of the head, providing stable and accurate steering torque. This significantly enhances the robot's underwater maneuverability and steering flexibility.

[0017] Because the entire structure uses a flexible silicone bell-shaped shroud as its main component, generating power through the contraction and jetting of water, this invention features flexible and lightweight materials, a gentle movement, and minimal disturbance to marine life. Furthermore, it boasts low driving costs, a simple structure, and a low failure rate. More importantly, the flexible structure eliminates the need for a heavy, pressure-resistant metal shell and a complex pressure compensation system, achieving self-balancing of internal and external pressure. This perfectly adapts to the high-pressure environment of the deep sea, significantly reducing the robot's weight, structural complexity, and manufacturing costs. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1This is a schematic diagram of the overall structure of a multi-directional pulse propulsion underwater soft robot based on bistable SMA drive as described in this invention. Figure 2 This is a schematic diagram of the connection structure between the propulsion actuator and the center of gravity adjustment mechanism described in this invention; Figure 3 This is a schematic diagram of the center of gravity adjustment mechanism described in this invention; Figure 4 This is a schematic diagram of the telescopic rod component structure described in this invention; Figure 5 This is a schematic diagram of the power transmission platform structure described in this invention; Figure 6 This is a schematic diagram of the rotary motor structure described in this invention; Figure 7 This is a perspective view of the integrated mass box structure described in this invention; Figure 8 This is a top view schematic diagram of the integrated mass box structure described in this invention; Figure 9 This is a schematic diagram of the propulsion actuator structure described in this invention; Figure 10 This is a schematic diagram of the sliding hub structure described in this invention; Figure 11 This is a schematic diagram of the bistable SMA actuator state during the energy release and propulsion phase of the biomimetic underwater soft robot described in this invention. Figure 12 This is a schematic diagram of the bistable SMA actuator state during the energy storage stage of the biomimetic underwater soft robot described in this invention.

[0019] In the picture: 1-Bionic bell-shaped cover, 2-Propulsion actuator, 3-Center of gravity adjustment mechanism, 4-Top cover, 5-Top cap, 6-Rotary motor, 7-Support component, 8-Upper SMA spring assembly, 9-Outer support ring, 10-Curvature pin, 11-Connecting rod, 12-Ordinary pin, 13-Sliding hub, 14-Lower SMA spring assembly, 15-Mass box, 16-Telescopic rod component, 17-Telescopic motor, 18-Power transmission platform. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0021] See Figures 1-12This embodiment describes a multi-directional pulse-driven underwater soft robot based on bistable SMA (Self-Modulating Actuator), comprising a biomimetic bell-shaped jar 1, a propulsion actuator 2, and a center-of-gravity adjustment mechanism 3. The lower end of the center-of-gravity adjustment mechanism 3 is connected to the propulsion actuator 2, while the biomimetic bell-shaped jar 1 surrounds the propulsion actuator 2 and the center-of-gravity adjustment mechanism 3, forming a complete biomimetic box jellyfish shape.

[0022] The bionic bell-shaped jar 1 serves as the robot's main outer shell, made of flexible silicone material. It can adapt to significant expansion and contraction deformation while maintaining structural strength to prevent excessive damage in the underwater environment. The bionic bell-shaped jar 1 has a hollow parabolic structure. Its wall thickness is designed to gradually decrease from head to tail; preferably, the head thickness is approximately 2 mm and the tail thickness is approximately 1 mm. This gradual thickness design enhances the structural strength of the head cavity wall while ensuring the flexibility of tail contraction. The bionic bell-shaped jar 1 extends naturally along the robot's torso, forming a passive flap structure. When the bionic bell-shaped jar 1 contracts and agitates the water flow, the passive flaps effectively reduce water backflow, thereby increasing the thrust of jet propulsion. Compared to traditional bionic robots without flaps, its propulsion efficiency is superior. The outer support ring 9 is directly connected to multiple sets of parallel connecting rods 11, providing direct power for the radial expansion or contraction of the bionic bell-shaped jar 1. The support member 7 extends ribs along the horizontal direction of the bell-shaped cover 1. These ribs fit tightly against the inner wall of the bell-shaped cover 1. During the stroke of the power engine module, they can effectively limit the inward collapse of the silicone bell-shaped cover 1 and ensure that the water in the cavity can be concentrated and squeezed during contraction.

[0023] The propulsion actuator 2 is the core of the robot's propulsion power generation. It includes a support transmission structure and a bistable SMA actuator. The support transmission structure includes a transmission part and a support part. The transmission part includes a central rod, a fixed hub, and a sliding hub 13. The upper end of the central rod is rigidly connected to the lower end of the center of gravity adjustment mechanism 3, and the lower end of the central rod is rigidly connected to the fixed hub, thus ensuring a constant distance between the top cover 5 and the bottom fixed hub, providing a stable support foundation for the entire mechanism. The sliding hub 13 is slidably connected to the central rod and can slide freely up and down between the top cover 5 and the fixed hub along the central rod.

[0024] There are four sets of support sections, evenly distributed along the circumference of the central rod. Each support section includes a connecting rod 11, an outer support ring 9, and a support member 7. The outer support ring 9 has a quarter-circle arc structure. One end of the connecting rod 11 is hinged to the sliding hub 13 via a common pin 12, and the other end is hinged to the outer support ring 9 via a common pin 12. One end of the support member 7 is hinged to the outer support ring 9 via a curved pin 10, and the other end is hinged to the center of gravity adjustment mechanism 3. The support member 7 is also provided with several ribs, which extend horizontally along the bionic bell-shaped cover 1 and fit tightly against the inner wall of the bell-shaped cover 1. Their function is to limit the inward collapse of the flexible bell-shaped cover 1 during propulsion, ensuring that the water flow is effectively squeezed. In this embodiment, the top cover 4, top cap 5, outer support ring 9, fixed hub, and sliding hub 13 are all made of resin material, which has high temperature resistance and can withstand the heat generated when the SMA spring is working. The linkage 11 mechanism is laser-cut from a 2mm thick acrylic sheet, which is easy to manufacture, lightweight, and allows for quick size changes during iterative design and testing. Moving parts are connected using snap-fit ​​nylon rivets and other methods to reduce weight and adapt to underwater environments.

[0025] The bistable SMA actuator is the drive source and includes two sets of SMA springs: an upper SMA spring set 8 and a lower SMA spring set 14. The two sets of springs are arranged in an antagonistic manner and are both encapsulated within a silicone insulating layer to prevent underwater corrosion. The two ends of the upper SMA spring set 8 are connected to the top cover 5 of the center of gravity adjustment mechanism 3 and the sliding hub 13, respectively. The two ends of the lower SMA spring set 14 are connected to the sliding hub 13 and the fixed hub at the bottom, respectively. Both sets of SMA springs are electrically connected to a controller integrated within the mass box 15.

[0026] A center-of-gravity adjustment mechanism 3 is installed on the robot's head to adjust the robot's center-of-gravity position for flexible steering. It mainly includes an orientation rotation assembly, a radial displacement assembly, and a mass box 15. The orientation rotation assembly includes a rotary motor 6 and a power transmission platform 18. The rotary motor 6 is fixedly installed below the top cover 5, and its output shaft passes through the top cover 5 and is rigidly connected to the power transmission platform 18 located above the top cover 5. The radial displacement assembly is a telescopic rod component 16, on which a telescopic motor 17 drives its extension and retraction. The base of the telescopic rod component 16 is fixedly installed on the power transmission platform 18, and the movable end of its telescopic rod is connected to the mass box 15 by bolts or other means. A top cover 4 is also connected above the top cover 5 to protect the internal mechanisms. The center of the power transmission platform 18 is hollowed out to fit the shape of the base of the telescopic motor 17 of the telescopic rod component 16 above it, minimizing frictional loss during rotational transmission.

[0027] Mass box 15 is an integrated mass box that houses the robot's controller and power supply battery. The controller receives external commands and precisely controls the on / off timing of the rotary motor 6, the telescopic motor 17, and the two sets of SMA springs. Mass box 15 employs a sealed structure design to prevent water intrusion.

[0028] The robot's basic propulsion mode is pulse jet propulsion, and its working cycle is divided into two stages: energy storage stage and energy release propulsion stage.

[0029] During the energy storage phase, the controller energizes the upper SMA spring assembly 8. The upper SMA spring assembly 8, heated by the electricity, undergoes a shape memory effect, generating a contraction driving force. This force pulls the sliding hub 13 upwards along the central rod. The sliding hub 13 drives the four connecting rods 11, which are hinged to it, to move upwards synchronously. The connecting rods 11 then push the four outer support rings 9 to expand radially outwards. The expansion of the outer support rings 9 opens the flexible bionic bell-shaped jar 1, increasing its volume. At this time, external water is drawn into the cavity through the opening at the tail of the bell-shaped jar 1, completing energy storage. When the sliding hub 13 moves to the midpoint of the central rod, the connecting rods 11 are in a horizontal state, and the bionic bell-shaped jar 1 expands to its maximum volume, maximizing energy storage.

[0030] During the energy release propulsion phase, the controller cuts off the power to the upper SMA spring assembly 8 while simultaneously energizing the lower SMA spring assembly 14. The lower SMA spring assembly 14 also contracts due to the shape memory effect, generating a downward driving force that pulls the sliding hub 13 rapidly downward along the central rod. The sliding hub 13, through the connecting rod 11, drives the outer support ring 9 to contract radially inward, causing the bionic bell-shaped housing 1 to contract rapidly. The water drawn into the cavity is violently compressed and ejected at high speed from the tail opening of the bionic bell-shaped housing 1, generating a reaction force that propels the robot forward. During this process, the upper SMA spring assembly 8 is stretched under the combined action of the elastic restoring force of the bionic bell-shaped housing 1, the external water pressure, and the spring's own elasticity, naturally returning to its initial state, preparing for the next work cycle and achieving uninterrupted continuous drive cycles. By alternately energizing the two sets of SMA springs, continuous pulse propulsion of slow expansion for energy storage and rapid contraction for energy release is achieved, eliminating the need for a dedicated reset mechanism and cooling waiting time.

[0031] The shape memory effect of the two sets of SMA springs refers to their ability to remember their preset original shape under specific temperature conditions, and to automatically return to their original shape after deformation due to temperature changes or external forces (such as through heating). This is the core working principle of their use as a driving element. Specifically, in the application of this invention, it can be divided into two key stages: Deformation stage: The SMA spring is in the preset stretched / unstressed original shape at room temperature. When no drive is required, it can undergo stretched or compressed deformation under the action of the elastic force of the bionic bell-shaped cover 1, the water flow pressure and / or the tension of another set of SMA springs. At this time, the spring is in the energy storage state. Shape recovery stage: When the controller energizes the SMA springs, the Joule heat generated by the current raises the spring temperature to the phase transition temperature, triggering the shape memory effect. The springs will automatically contract and return to the original preset contracted shape, generating a stable pulling force, which in turn pulls the sliding hub 13, mass box 15 and other components to move, realizing propulsion or center of gravity adjustment functions.

[0032] When the robot needs to turn, the center of gravity adjustment mechanism 3 starts working. First, the controller drives the rotary motor 6 to rotate, which in turn drives the entire telescopic rod component 16 and its end mass box 15 to rotate around the robot's central axis through the power transmission platform 18, until the telescopic rod component 16 is aligned with the target turning direction. Then, the controller drives the telescopic motor 17 of the telescopic rod component 16 to push the mass box 15 to extend radially outward. As the mass box 15 moves away from the robot's central axis, the robot's center of gravity shifts in the horizontal plane. At this time, the propulsion actuator 2 is activated to perform pulse injection. Since the line of action of the propulsion force is not collinear with the shifted center of gravity, a yaw torque is generated, which drives the robot to turn in the direction of the mass box 15. By coordinating the rotation angle of the rotary motor 6 and the extension length of the telescopic rod component 16, the robot's center of gravity can be adjusted to any position in the horizontal plane of the head, achieving 360-degree omnidirectional, continuous, and flexible turning control.

[0033] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A multi-directional pulse propulsion underwater soft robot based on bistable SMA drive, characterized in that: It includes a biomimetic bell-shaped jar (1), a propulsion actuator (2), and a center of gravity adjustment mechanism (3). The lower end of the center of gravity adjustment mechanism (3) is connected to the propulsion actuator (2). The biomimetic bell-shaped jar (1) surrounds the propulsion actuator (2) and the center of gravity adjustment mechanism (3). The biomimetic bell-shaped jar (1) is a hollow parabolic structure made of flexible material. The propulsion actuator (2) includes a support transmission structure and a bistable SMA actuator. The support transmission structure includes a transmission part and a support part. The transmission part includes a central rod, a fixed hub, and a sliding hub (13). The upper end of the central rod is connected to the center of gravity adjustment mechanism (3), and the lower end of the central rod is connected to the fixed hub. The sliding hub (13) is slidably connected to the central rod. There are multiple support parts, which are evenly distributed along the circumference of the central rod. The support part includes a connecting rod (11), an outer support ring (9), and a support member (7). The connecting rod (11) One end of the connecting rod (11) is hinged to the sliding hub (13), and the other end of the connecting rod (11) is hinged to the outer support ring (9). One end of the support member (7) is hinged to the outer support ring (9), and the other end of the support member (7) is hinged to the center of gravity adjustment mechanism (3). The bistable SMA actuator includes two sets of SMA springs. The two sets of SMA springs are arranged in an antagonistic manner. The two sets of SMA springs are the upper SMA spring group (8) and the lower SMA spring group (14). The two ends of the upper SMA spring group (8) are connected to the center of gravity adjustment mechanism (3) and the sliding hub (13), respectively. The two ends of the lower SMA spring group (14) are connected to the sliding hub (13) and the fixed hub, respectively. Both sets of SMA springs are connected to the controller. The center of gravity adjustment mechanism (3) realizes the adjustment of the robot's center of gravity in any direction of 360° in the horizontal plane through polar coordinate drive. The robot's steering is realized by adjusting the position of its center of gravity.

2. The underwater soft robot based on bistable SMA-driven multi-directional pulse propulsion according to claim 1, characterized in that: The center of gravity adjustment mechanism (3) includes an orientation rotation component, a radial displacement component, and a mass box (15). The orientation rotation component is connected to the radial displacement component and drives the radial displacement component to rotate around the axis of the central rod. The end of the radial displacement component is connected to the mass box (15) and drives the mass box (15) to move radially.

3. The underwater soft robot based on bistable SMA-driven multi-directional pulse propulsion according to claim 2, characterized in that: The orientation rotation component includes a rotary motor (6) and a power transmission platform (18). The rotary motor (6) is connected to the top cover (5). The output shaft of the rotary motor (6) is connected to the power transmission platform (18). The radial displacement component is a telescopic rod component (16). A telescopic motor (17) is provided on the telescopic rod component. The telescopic rod component (16) is connected to the power transmission platform (18). The telescopic rod component (16) is connected to the mass box (15). The mass box (15) is an integrated mass box. The integrated mass box integrates a controller and a power supply battery. A top cover (4) is connected above the top cover (5).

4. The underwater soft robot based on bistable SMA-driven multi-directional pulse propulsion according to claim 1, characterized in that: The wall thickness of the biomimetic bell-shaped jar (1) gradually decreases from the head to the tail.

5. The multi-directional pulse propulsion underwater soft robot based on bistable SMA drive according to claim 1, characterized in that: The biomimetic bell-shaped cover (1) extends along the robot's torso to form a passive flap.

6. The underwater soft robot based on bistable SMA-driven multi-directional pulse propulsion according to claim 1, characterized in that: The number of support parts is four, and the outer support ring (9) is a quarter-circle arc structure.

7. The underwater soft robot based on bistable SMA-driven multidirectional pulse propulsion according to claim 1, characterized in that: The support member (7) is provided with several ribs, which extend horizontally along the bionic bell-shaped cover (1). The support member (7) and the ribs are both attached to the inner wall of the bionic bell-shaped cover (1).

8. The underwater soft robot based on bistable SMA-driven multi-directional pulse propulsion according to claim 1, characterized in that: Both sets of SMA springs are encapsulated within a silicone insulating layer.

9. The multi-directional pulse propulsion underwater soft robot based on bistable SMA drive according to claim 1, characterized in that: The support member (7) is hinged to the outer support ring (9) by a curved pin (10), and the connecting rod (11) is hinged to the outer support ring (9) by a common pin (12).

10. A method for operating a multi-directional pulse propulsion underwater soft robot based on bistable SMA drive as described in any one of claims 1-9, characterized in that: Energy storage stage: The controller powers on the upper SMA spring assembly (8), which contracts to generate driving force, pulling the sliding hub (13) upward along the central rod. The sliding hub (13) drives the hinged connecting rod (11) to move synchronously. The connecting rod (11) pushes the outer support ring (9) to expand radially, thereby opening the bionic bell-shaped jar (1). At this time, water is sucked into the cavity through the tail opening of the bionic bell-shaped jar (1), completing energy storage. When the sliding hub (13) moves to the midpoint of the central rod, the connecting rod (11) is in a horizontal state, and the bionic bell-shaped jar (1) reaches its maximum expansion state, storing the most energy. Energy release propulsion stage: The upper SMA spring group (8) is de-energized, and at the same time the controller energizes the lower SMA spring group (14). The lower SMA spring group (14) contracts to generate driving force, pulling the sliding wheel hub (13) to move downward along the central rod. The connecting rod (11) drives the outer support ring (9) to contract, and the bionic bell-shaped cover (1) contracts synchronously. The water in the cavity is squeezed and sprayed out from the tail opening, generating a reaction force to propel the robot forward. At the same time, the upper SMA spring group (8) naturally resets under the combined action of the elastic restoring force of the bionic bell-shaped cover (1), the water pressure, and its own elasticity. Two sets of SMA springs alternately turn on and off, causing the energy storage phase and the energy release propulsion phase to cycle, achieving continuous pulse-type jet propulsion.

Images