Variable-cross-section multi-configuration underwater snakelike robot

Abstract

The invention provides a variable cross-section multi-configuration underwater snakelike robot, and relates to an underwater robot, the variable cross-section multi-configuration underwater snakelike robot comprises a plurality of unit bodies, all the unit bodies are sequentially connected in series through joint modules, each joint can independently drive the unit body connected with the joint to swing, and the overall shape of the robot is formed by a series of variable cross-section lofting perpendicular to the x axis. The invention has the following beneficial effects: the head can effectively delay boundary layer separation and minimize differential pressure resistance; the elliptical cross section of the main body has larger projection width in the transverse direction of the body, stronger counter-acting force applied by fluid is obtained, the difference between transverse inertia moment and vertical inertia moment is introduced by the shape change of the cross section, driving energy can be more concentrated in an expected swinging plane, and the energy utilization efficiency is improved; the tail part can efficiently excite and control the shedding of a trailing vortex, and the asymmetry of left and right swing amplitudes can generate a yaw moment to realize course adjustment; and different parts of the robot can adapt to different fluid functions, so that the multi-index performance is considered at the same time.

Description

Technical Field

[0001] This invention relates to the field of underwater robot technology, and in particular to a variable cross-section multi-configuration underwater snake robot. Background Technology

[0002] As marine engineering develops towards deep-sea and large-scale operations, traditional rigid-configuration underwater robots, due to insufficient maneuverability and poor environmental adaptability, are unable to meet the demands of complex underwater tasks. Snake-like robots, with their multi-jointed flexible bodies and highly flexible locomotion, have demonstrated significant advantages in areas such as navigating confined spaces, pipeline inspection, and military reconnaissance, and have become one of the hot topics in international marine engineering research.

[0003] Most existing snake-like robots adopt a uniform cross-section (mainly circular and elliptical) shape design, which differs significantly from the morphology of real biological organisms, resulting in poor hydrodynamic performance. Their appendage structures are mostly fixed configurations, which cannot be adapted and replaced according to different mission requirements such as high-speed cruising, long endurance or high-precision control, resulting in poor mission adaptability. Summary of the Invention

[0004] In view of this, in order to solve the problems of poor hydrodynamic performance, single task mode and insufficient adaptability of snake robots in the prior art, the embodiments of the present invention provide a variable cross-section multi-configuration underwater snake robot.

[0005] Embodiments of the present invention provide a variable cross-section multi-configuration underwater snake robot, comprising multiple unit bodies, all of which are connected in series via joint modules. Each joint can independently drive the connected unit body to swing. The overall shape of the robot is formed by a series of variable cross-section lofts perpendicular to the x-axis.

[0006] The robot's total length is It is divided into three segments along the x-axis: head, body, and tail, with corresponding lengths of... , , ; On the X-axis, the starting coordinates of the main body are: End coordinates of the main body: Robot end-effector coordinates: ; For axial position Any cross section on the surface has a profile that satisfies the equation of an ellipse:

[0007] Where a(x) is the length of the major semi-axis of the cross section, and b(x) is the length of the minor semi-axis of the cross section; Based on streamlined end cap design and main body lofting strategy, the overall shape function of the robot and The definition is as follows: ; ; in, and is the shape fitting coefficient, n is the polynomial order, and R is the length of the major semi-axis of the main body's initial cross section.

[0008] Furthermore, based on the streamlined end cap design and the main body lofting strategy, the main body starting section, the main body ending section, and the robot end section are all located on the x-axis, and are smoothly lofted and connected by non-uniform rational B-spline curves.

[0009] Furthermore, the head is hemispherical.

[0010] Furthermore, the tail portion is semi-ellipsoidal.

[0011] Furthermore, it also includes a pectoral fin module that can be detachably installed on the head. The pectoral fin module includes a retaining ring and pectoral fin plates that are rotatably installed on both sides of the retaining ring. The retaining ring is detachably fitted onto the head.

[0012] Furthermore, the pectoral fin plate is connected to the retaining ring via a ball joint.

[0013] Furthermore, it also includes a tail fin module that can be detachably installed at the tail, the tail fin module having a tail edge.

[0014] Furthermore, the trailing edge is a concave trailing edge, a square trailing edge, or a convex trailing edge.

[0015] Furthermore, the unit body has a rotating joint at the front end and a drive shaft at the rear end. The drive shaft of the former unit body is rotatably connected to the rotating joint of the latter unit body. The joint module includes a motor and a gear mechanism connected to the motor. The gear mechanism of the joint module in the latter unit body is connected to the drive shaft.

[0016] Furthermore, it also includes a controller connected to each of the motors to control the rotation angle and frequency of each of the motors.

[0017] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: The variable cross-section multi-configuration underwater snake robot of the present invention has an overall shape formed by a series of variable cross-sections lofted perpendicular to the x-axis. The head adopts a circular cross-section with a constant radius. Based on the principle of streamline drag reduction, it can effectively delay boundary layer separation, minimize pressure drag, and guide the water flow to smoothly transition along the body surface, providing a stable and low-turbulence inflow condition for the wave dynamics generation of subsequent unit bodies, laying the foundation for an efficient propulsion flow field. The cross-sectional geometric parameters of multiple unit bodies located in the main body continuously change along the axial direction, smoothly transitioning from a circular head to a laterally flattened ellipse. The major axis of the ellipse is perpendicular to the body swing plane, and the elliptical cross-section has a larger projected width in the transverse (y-direction) direction of the body. According to the fluid momentum theorem, when this section of the unit body swings laterally, the increased projected area allows it to push a larger mass of fluid per unit time, thereby obtaining a stronger reaction force applied by the fluid. Under the coordination of the body traveling wave, the axial component of this force is superimposed and converged to form a net forward thrust. Meanwhile, the change in cross-sectional shape introduces a difference in lateral and vertical moments of inertia, which helps to concentrate the driving energy more in the desired swing plane and improve energy utilization efficiency. The tail unit adopts a highly flat elliptical cross-section, whose cross-sectional area is significantly reduced compared to the middle section. Its small cross-section has a low moment of inertia, allowing for a larger angular displacement under the same driving torque, thereby achieving a high-amplitude end swing. This swing is based on the flexible body vortex control principle, which can efficiently excite and control the shedding of the tail vortex to form an anti-Kármán vortex street. The wave energy is ultimately converted into thrust through the reaction force (vortex propulsion principle) during the vortex shedding process. On the other hand, by controlling the asymmetry of the left and right swing amplitude, a yaw moment can be generated to achieve heading adjustment. In this way, the robot's variable cross-section design allows different parts of the robot to adapt to different fluid functions through the gradually changing cross-sectional shape along the axis, thereby taking into account multiple performance indicators at the same time. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a variable cross-section multi-configuration underwater snake robot according to the present invention; Figure 2 This is a schematic diagram of each unit body of the variable cross-section multi-configuration underwater snake robot of the present invention; Figure 3 This is a simplified model schematic diagram of a variable cross-section multi-configuration underwater snake robot according to the present invention; Figure 4 This is a schematic diagram showing the connection between adjacent unit cells; Figure 5 It is a cross-sectional view of adjacent unit cells; Figure 6 This is a schematic diagram of another embodiment of the variable cross-section multi-configuration underwater snake robot of the present invention; Figure 7This is a schematic diagram of the pectoral fin module; Figure 8 This is a schematic diagram of a concave tail edge; Figure 9 This is a schematic diagram of a square tail edge; Figure 10 This is a schematic diagram of a convex tail edge; Figure 11 This is a computational model diagram of a variable cross-section multi-configuration underwater snake robot according to the present invention; Figure 12 This is a simplified model diagram of Scale 1; Figure 13 This is a simplified model diagram of Scale 2; Figure 14 These are charts showing the hydrodynamic performance calculation results of this embodiment, Comparative Example 1, and Comparative Example 2.

[0019] In the diagram: 1. Unit body; 2. Head; 3. Main body; 4. Tail; 5. Pectoral fin module; 6. Rotary joint; 7. Drive shaft; 8. Drive gear; 9. Driven gear; 10. Battery; 11. Snap ring; 12. Pectoral fin plate; 13. Ball joint; 14. Tail fin module; 15. Tail edge; 16. Main body starting section; 17. Main body middle section; 18. Main body end section. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0021] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0022] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0024] In the description of this invention, it should be noted that the circuits, electronic components and modules involved in this invention are all prior art, which can be fully implemented by those skilled in the art, and need not be elaborated upon.

[0025] It should be further noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Please refer to Figure 1-3 The present invention discloses a variable cross-section multi-configuration underwater snake robot designed based on the morphological characteristics of lampreys. Specifically, the body cross-section shape changes regularly along the body axis: the head is round (to reduce frontal drag), the body transitions to an elliptical shape (to enhance fluid interaction), and the tail gradually flattens (to optimize vortex generation).

[0027] An embodiment of the present invention provides a variable cross-section multi-configuration underwater snake robot comprising multiple unit bodies 1, all unit bodies 1 being sequentially connected in series via joint modules, each joint being capable of independently driving the connected unit body 1 to swing, the overall shape of the robot being formed by a series of variable cross-section loftings perpendicular to the x-axis: The robot's total length is It is divided into three sections along the x-axis: head 2, main body 3, and tail 4, with corresponding lengths of... , , ; On the X-axis, the starting coordinates of the main body are: End coordinates of the main body: Robot end-effector coordinates: ; For axial position Any cross section on the surface has a profile that satisfies the equation of an ellipse:

[0028] Where a(x) is the length of the major semi-axis of the cross section, and b(x) is the length of the minor semi-axis of the cross section; Based on streamlined end cap design and main body lofting strategy, the overall shape function of the robot and The definition is as follows: ; ; in, and is the shape fitting coefficient, n is the polynomial order, and R is the length of the major semi-axis of the main body's initial cross section.

[0029] Specifically, the overall shape of the variable cross-section multi-configuration underwater snake robot of the present invention is simplified as follows: Figure 3 The rod-shaped model shown.

[0030] Regarding the main body of the robot: In the Cartesian coordinate system xyz, the cross-sectional shape of the robot body 3 continuously changes along the x-axis from head to tail. The outline of the body 3 is formed by three cross-sections of different shapes smoothly transitioning along a central axis. Specifically, based on the streamlined end cap design and the body lofting strategy, the initial cross-section 16, the middle cross-section 17, and the final cross-section 18 of the body are all located on the x-axis and are smoothly lofted and connected by a non-uniform rational B-spline curve. The semi-major axis of the robot body's cross-section... and short half shaft as follows:

[0031]

[0032] That is when The corresponding robot body part , For example, if n=2, the corresponding... ; .

[0033] For the robot's head portion, the head 2 is hemispherical, with a diameter equal to the major axis of the initial cross section of the main body 3.

[0034] For the robot's tail section, tail 4 is semi-ellipsoidal, and the corresponding trajectory equation is: , where L is the length of the semi-axis of the ellipsoid in the x-axis direction.

[0035] In addition, please refer to Figure 6 and 7In some embodiments, the variable cross-section multi-configuration underwater snake robot of the present invention further includes a pectoral fin module 5 detachably mounted on the head. The pectoral fin module 5 includes a retaining ring 11 and pectoral fin plates 12 rotatably mounted on both sides of the retaining ring 11. The retaining ring 11 is detachably sleeved on the unit body 1 of the head 2. The pectoral fin plates 12 are connected to the retaining ring 11 via ball joints 13 to realize the rotation of the pectoral fin plates 12. This allows the two pectoral fin plates 12 to deflect around their connection point, realizing the robot's pitch maneuver. By driving the ball joints 13, the pectoral fin plates 12 can deflect within a range of -60° to +60° (defining the counterclockwise direction as positive). When the pectoral fin plates 12 deflect in a positive angle direction, a torque is generated that causes the robot to dive; when they deflect in a negative angle direction, a torque is generated that causes the robot to float. Preferably, to achieve efficient diving, the deflection angle of the pectoral fin plate 12 is set to +45°; to achieve efficient surfacing while also considering energy consumption, the deflection angle of the pectoral fin plate 12 is set to -30°.

[0036] In some other embodiments, the variable cross-section multi-configuration underwater snake robot of the present invention further includes a tail fin module 14 detachably mounted on the tail, the tail fin module 14 having a tail edge 15. The tail fin module 14 is detachably connected to the end of the last unit 1 of the tail, for example, by means of a pin to a pin hole at the end of the unit 1.

[0037] The trailing edge 15 can be selected with different shapes and structures to suit different working environments. For example, the trailing edge 15 can be selected as follows: Figure 8 The concave trailing edge shown has an inwardly recessed structure, resulting in the optimal balance between thrust and drag, making it suitable for operational scenarios requiring precise control. The trailing edge 15 can be selected as follows... Figure 9 The square trailing edge shown has a straight design, resulting in excellent swimming speed and thrust, making it suitable for high-speed cruising. The trailing edge 15 can be selected as follows... Figure 10 The convex tail edge shown has an outward convex structure, which has the best energy economy and the lowest energy consumption per unit distance.

[0038] Please refer to Figure 4 and 5The unit 1 has a rotating joint 6 at its front end and a drive shaft 7 at its rear end. The drive shaft 7 of the preceding unit 1 is rotatably connected to the rotating joint 6 of the following unit 1. The joint module includes a motor and a gear mechanism connected to the motor. The gear mechanism of the joint module in the following unit 1 is connected to the drive shaft 7. The drive shaft 7 of the joint module is parallel to the y-axis. The gear mechanism includes a driving gear 8 and a driven gear 9. The driving gear 8 is connected to the output shaft of the motor, and the driven gear 9 is mounted on the drive shaft 7. The driving gear 8 and the driven gear 9 mesh. The unit 1 generally also contains a battery, which is connected to the motor to supply power. The motor can drive the driving gear 8 to rotate, which in turn drives the driven gear 9 to rotate, thereby driving the drive shaft 7 to drive the connected unit 1 to swing, thus realizing the robot's meandering movement in a two-dimensional plane.

[0039] Furthermore, the variable cross-section multi-configuration underwater snake robot of the present invention also includes a controller, which is connected to each of the motors to control the rotation angle and frequency of each motor. Specifically, the controller integrates an upper-level control system and, through a controller area network (CAN) bus, distributes the control of the movement angle and frequency of each unit 1 to the motors inside each unit 1, ultimately achieving precise control of the entire snake robot's swimming gait.

[0040] This application also compares and calculates the hydrodynamic performance of the aforementioned variable cross-section multi-configuration underwater snake robot.

[0041] In the multi-configuration underwater snake robot of this embodiment The main body's initial section 16 is located at x=25mm, and it is a circular section with a radius of 25mm.

[0042] The central section 17 of the main body is located at x=1255mm. It is an elliptical section with a major axis radius of 40mm and a minor axis radius of 25mm. The direction of the major axis is perpendicular to the swing plane of the body.

[0043] The end section 18 of the main body is located at x=2505mm, with a major axis radius of 25mm and a minor axis radius of 5mm. Its major axis direction is consistent with the major axis direction of the middle section of the main body.

[0044] Based on the above three cross sections, a quadratic curve fitting was performed on the major and minor axes.

[0045] Its piecewise functions for the major and minor axes are as follows:

[0046]

[0047] The main design parameters of the computational model of the variable cross-section multi-configuration underwater snake robot in this embodiment are shown in the table below, where the centroid is... The orientation is the coordinate value in the body coordinate system, and the moment of inertia is the principal moment of inertia, in order as follows: The diagonal value of the inertia tensor is negligible, and the method for establishing a spatial volumetric rectangular coordinate system is as follows: Figure 11 As shown, the CAD model was imported into the software, and a sufficiently large fluid computational domain was established, with dimensions of 18m x 8m x 6m. The calculation employed a self-propelled approach, requiring overlapping meshes. The overlapping regions had dimensions of 4.5m x 2m x 2m. Due to the self-propelled method, the computational domain boundary condition was set to a pressure outlet, the overlapping mesh was designated as an overlapping mesh, and the robot surface was set as a wall. A total of 508,725 computational mesh cells were generated.

[0048] The main design parameter table of the computational model in this embodiment

[0049] This application selects as follows Figure 12 The circular cross-section calculation model shown is used as Comparative Example 1. The main design parameters of the calculation model are shown in the table below: Main design parameter table of the calculation model for Comparative Example 1

[0050] This application selects as follows Figure 13 The elliptical cross-section calculation model shown is used as Comparative Example 2. The main design parameters of the calculation model are shown in the table below: Main design parameter table of the calculation model for Comparative Example 2

[0051] The propulsion performance of the calculation models in this embodiment, Comparative Example 1, and Comparative Example 2 under the form of the reference displacement control equation is compared. The periodic average values ​​of several periodically changing propulsion indicators are calculated using an "autocorrelation-based periodic detection and averaging algorithm," such as... Figure 14 As shown: Comparing the hydrodynamic performance calculation results of this embodiment, Comparative Example 1, and Comparative Example 2, it can be seen that the connection of the variable cross-section unit 1 in this embodiment gives the robot an overall biomimetic shape of "rounded head - thick middle section - flat tail". This shape has the following advantages in the flow field generated during swimming: A stable anti-Kármán vortex street is formed: the flat cross-section at the tail (5mm short axis at the tail in this embodiment) makes the vortex shedding frequency more uniform and the Strouhal number more stable. In a state of efficient progress The edge of the interval (close to the optimal value), compared to a circular cross section ( More stable; Uniform thrust distribution: The thrust coefficient of this embodiment is 12.9% higher than that of a circular cross section, and the thrust fluctuation amplitude (±0.5N) is 37.5% lower than that of a circular cross section (±0.8N), making the overall movement more stable and suitable for scenarios requiring high thrust.

[0052] Energy loss is reduced in a coordinated manner: The smooth transition design at the connection of unit 1 avoids eddy current separation at the connection of the robot with equal cross-section. The overall drag coefficient is reduced by 24.9% compared with the elliptical robot with equal cross-section. Combined with gait parameter optimization (long wavelength + low frequency), the "form-motion coupling effect" is achieved.

[0053] This invention presents a variable cross-section multi-configuration underwater snake robot that addresses the problem of poor hydrodynamic performance caused by the common constant cross-section design of existing snake robots, which does not conform to the morphology of real organisms. It innovatively introduces a "biomimetic variable cross-section shape design." This design allows the robot's body to smoothly transition from a full head to a flattened tail, more closely resembling the streamlined morphology optimized through natural evolution of aquatic organisms such as lampreys. This shape can more effectively guide water flow, reduce pressure drag and eddy current generation, thereby significantly reducing energy loss during swimming. Computational fluid dynamics (CFD) simulation results confirm that the variable cross-section multi-configuration underwater snake robot of this invention can generate maximum thrust and is suitable for high-load operations.

[0054] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0055] Where there is no conflict, the embodiments and features described above can be combined with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A variable cross-section multi-configuration underwater snake robot, characterized in that, The robot comprises multiple unit cells, all of which are connected in series via joint modules. Each joint can independently drive the connected unit cell to swing. The overall shape of the robot is formed by a series of variable cross-section lofts perpendicular to the x-axis. The robot's total length is It is divided into three segments along the x-axis: head, body, and tail, with corresponding lengths of... , , ; On the X-axis, the starting coordinates of the main body are: End coordinates of the main body: Robot end-effector coordinates: ; For axial position Any cross section on the surface has a profile that satisfies the equation of an ellipse: Where a(x) is the length of the major semi-axis of the cross section, and b(x) is the length of the minor semi-axis of the cross section; Based on streamlined end cap design and main body lofting strategy, the overall shape function of the robot and The definition is as follows: ； ； in, and is the shape fitting coefficient, n is the polynomial order, and R is the length of the major semi-axis of the main body's initial cross section.

2. The variable cross-section multi-configuration underwater snake robot as described in claim 1, characterized in that: Based on the streamlined end cap design and the main body lofting strategy, the main body's starting section, middle section, and end section are all located on the x-axis, and are smoothly connected by non-uniform rational B-spline curves.

3. The variable cross-section multi-configuration underwater snake robot as described in claim 1, characterized in that: The head is hemispherical.

4. The variable cross-section multi-configuration underwater snake robot as described in claim 1, characterized in that: The tail is semi-ellipsoidal.

5. The variable cross-section multi-configuration underwater snake robot as described in claim 1, characterized in that: It also includes a pectoral fin module that can be detachably installed on the head. The pectoral fin module includes a retaining ring and pectoral fin plates that are rotatably installed on both sides of the retaining ring. The retaining ring is detachably fitted onto the head.

6. The variable cross-section multi-configuration underwater snake robot as described in claim 5, characterized in that: The pectoral fin plate is connected to the retaining ring via a ball joint.

7. The variable cross-section multi-configuration underwater snake robot as described in claim 1, characterized in that: It also includes a tail fin module that can be detachably installed at the tail, the tail fin module having a tail edge.

8. The variable cross-section multi-configuration underwater snake robot as described in claim 7, characterized in that: The trailing edge can be concave, square, or convex.

9. The variable cross-section multi-configuration underwater snake robot as described in claim 1, characterized in that: The unit body has a rotating joint at the front end and a drive shaft at the rear end. The drive shaft of the former unit body is rotatably connected to the rotating joint of the latter unit body. The joint module includes a motor and a gear mechanism connected to the motor. The gear mechanism of the joint module in the latter unit body is connected to the drive shaft.

10. A variable cross-section multi-configuration underwater snake robot as described in claim 9, characterized in that: It also includes a controller connected to each of the motors to control the rotation angle and frequency of each of the motors.

Images