Stiffness-variable robotic fish

Abstract

The embodiment provides a variable-stiffness robotic fish, which comprises a variable-stiffness fish tail, the variable-stiffness fish tail comprising: an elastic spine; a plurality of blocking blocks connected to the elastic spine in sequence along the length direction of the elastic spine, wherein one of any two adjacent blocking blocks has a first cylindrical surface protruding outward, and the other has a second cylindrical surface recessed inward, the first cylindrical surface and the second cylindrical surface are in concave-convex matching and can rotate relative to each other along with the bending of the elastic spine, one end of a pull wire passes through wire passing holes of the plurality of blocking blocks and is fixed to a blocking block close to the rear end of the elastic spine, the other end of the pull wire is fixed to a wire wheel, a stiffness adjusting steering engine can drive the wire wheel to rotate to wind or release the pull wire, thereby adjusting the contact pressure of the first cylindrical surface and the second cylindrical surface; and a fish tail driving unit is connected to the front end of the elastic spine and used for driving the elastic spine to swing left and right. The fish tail can be quickly and widely adjusted in stiffness.

Description

Technical Field

[0001] This invention relates to the field of underwater robots, and more specifically to a variable stiffness robotic fish. Background Technology

[0002] In recent years, as a fusion of underwater engineering and biomimetic technology, biomimetic underwater robots have been playing an increasingly important role in underwater resource exploration and mining, underwater archaeology, and other fields. These robots mimic the movement mechanisms of underwater organisms; for example, variable-stiffness robotic fish replicate the swimming motion of fish, demonstrating advantages such as high propulsion efficiency, excellent maneuverability, and good stealth.

[0003] Studies have shown that fish improve their swimming performance by dynamically adjusting the stiffness of their tails through the coordination of muscles, tendons, and other tissues. Inspired by this mechanism, scholars both domestically and internationally have explored various variable stiffness schemes from a biomimetic perspective and designed corresponding biomimetic fish tail structures. Currently, the variable stiffness methods adopted by variable stiffness robotic fish mainly cover several categories, including smart materials, fluid actuation, and traditional mechanical structures. However, existing methods still face several technical bottlenecks: on the one hand, they cannot simultaneously possess the characteristics of rapid stiffness adjustment and a wide range of adjustable stiffness; on the other hand, some methods based on smart materials suffer from problems such as high additional power consumption and low adjustment efficiency; while fluid actuation-based variable stiffness methods exhibit response hysteresis, resulting in limited stiffness adjustment speed, and the system has high requirements for sealing performance. The weight and size of the air pump itself also restrict the miniaturization of the robotic fish and the realization of unrestricted swimming capabilities.

[0004] For the reasons mentioned above, there is an urgent need to explore a variable stiffness robotic fish with a simple and stable structure and control. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a variable stiffness robotic fish to solve at least one technical problem existing in the prior art. The variable stiffness robotic fish proposed in this invention has the advantages of simple and stable structure and control, and can achieve rapid and wide-range stiffness adjustment of the biomimetic fish tail, thereby improving its motion performance.

[0006] One embodiment of the present invention provides a variable stiffness robotic fish, including a variable stiffness tail, comprising: an elastic spine; multiple blocking blocks sequentially connected to the elastic spine along its length, wherein one of any two adjacent blocking blocks has an outwardly convex first cylindrical surface and the other has an inwardly concave second cylindrical surface, the first and second cylindrical surfaces engaging in a concave-convex fit and being able to rotate relative to each other as the elastic spine bends; a pull line, one end of which passes through a line hole in one of the multiple blocking blocks and is fixed to a blocking block near the rear end of the elastic spine; a stiffness adjustment unit, including a stiffness adjustment servo and a reel, the other end of which is fixed to the reel, the stiffness adjustment servo driving the reel to rotate and wind or release the pull line, thereby adjusting the contact pressure of the first and second cylindrical surfaces; and a tail drive unit connected to the front end of the elastic spine for driving the elastic spine to swing left and right.

[0007] Furthermore, in some embodiments, the variable stiffness robotic fish also includes a spring, the pull line includes a first pull line and a second pull line, the spring is connected between the first pull line and the second pull line, one end of the first pull line passes through the line hole of a plurality of blocking blocks and is fixed to the blocking block near the rear end of the elastic spine among the plurality of blocking blocks, and one end of the second pull line is fixed to the reel.

[0008] Furthermore, in some embodiments, the elastic spine is plate-shaped, and a slot extending along its length is provided in the middle of the elastic spine. Multiple blocking blocks are locked in the slot, and guide grooves for the edge of the slot to be inserted are provided on opposite sides of each blocking block.

[0009] Furthermore, in some embodiments, the guide groove penetrates the blocking block along the length of the elastic spine, and the two oppositely distributed sidewalls of the guide groove are both arc-shaped walls that bulge into the interior of the guide groove in the middle.

[0010] Furthermore, in some embodiments, each blocking block has a fan-shaped wire groove on its cylindrical surface facing the rear end of the elastic spine. One end of the fan-shaped wire groove is connected to the wire hole of the blocking block to which it is located, and the other end gradually expands outward in a fan shape. The fan-shaped wire groove is used to accommodate the first pull wire during the relative rotation of two adjacent blocking blocks.

[0011] Furthermore, in some embodiments, the included angle between the opposite side walls of the fan-shaped wire groove ranges from 60° to 80°.

[0012] Furthermore, in some embodiments, the variable stiffness fishtail further includes: a limiting member, the limiting member having a limiting hole for the first pull wire to pass through, the fishtail drive unit including an output shaft, the fishtail drive unit driving the elastic spine to swing around the axis of the output shaft, and the limiting hole being located on the axis of the output shaft.

[0013] Furthermore, in some embodiments, the limiting member includes a limiting fixing member and two bearings. The two bearings are respectively fixed to the limiting fixing member by bearing fixing shafts. A limiting hole is formed between the two bearings, and an annular limiting groove is provided on the outer peripheral surface of each bearing. The annular limiting groove can accommodate the first pull wire from the side to limit the first pull wire from moving axially in the output shaft.

[0014] Furthermore, in some embodiments, the variable stiffness fishtail further includes: a fishtail connector, with the elastic spine connected to the fishtail connector; the fishtail drive unit includes a first fishtail drive servo connector, a fishtail drive servo, and a second fishtail drive servo connector, the fishtail drive servo being fixed to the first fishtail drive servo connector, and the second fishtail drive servo connector connecting the output shaft of the fishtail drive servo and the fishtail connector.

[0015] Furthermore, in some embodiments, the variable stiffness robotic fish further includes: a fish-head shell, the interior of which has sealed and unsealed cavities distributed front and rear, with the stiffness adjustment unit and the tail drive unit both located in the unsealed cavity; and a biomimetic tail fin connected to the rear end of the elastic spine.

[0016] Furthermore, in some embodiments, the stiffness adjustment unit and the fishtail drive unit are distributed front and back within the unsealed cavity.

[0017] The variable stiffness robotic fish provided by this invention adjusts the contact pressure between two adjacent blocking blocks in the tail by coordinating a stiffness adjustment servo with a cable. This utilizes the frictional force of the blocking effect to adjust the tail's bending stiffness. The tail stiffness offers advantages such as real-time and rapid adjustment, a wide adjustment range, and minimal susceptibility to external factors. Furthermore, the variable stiffness robotic fish boasts a simple and stable structure and control, making it highly practical.

[0018] Further aspects and / or advantages of the general concept of the invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the general concept of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a variable stiffness robotic fish provided in one embodiment of this application; Figure 2This is another structural schematic diagram of a variable stiffness robotic fish provided in one embodiment of this application; Figure 3 This is a schematic diagram of the internal structure of a variable stiffness robotic fish provided in one embodiment of this application; Figure 4 This is a schematic diagram of the internal structure of a variable stiffness fishtail provided in one embodiment of this application; Figure 5 This is a partial structural schematic diagram of a variable stiffness fishtail provided in one embodiment of this application; Figure 6 This is a schematic diagram of the structure of an elastic spine provided in one embodiment of this application; Figure 7 This is a schematic diagram of the structure of a blocking block provided in one embodiment of this application; Figure 8 This is a schematic diagram of the structure of several blocking blocks provided in one embodiment of this application; Figure 9 This is a schematic diagram of the structure of a thread reel provided in one embodiment of this application; Figure 10 This is a schematic diagram of the structure of a limiting member provided in one embodiment of this application.

[0021] Figures 1 to 10 Explanation of icon numbers: 100-Variable stiffness fishtail; 110 - Flexible spine; 1101 - Socket; 120 - Blocking block; 121 - First blocking block; 122 - Second blocking block; 123 - Third blocking block; 1201 - Through hole; 1202 - Guide groove; 1203 - Second cylindrical surface; 1204 - First cylindrical surface; 1205 - Sector-shaped wire groove; 130 - Spring; 140 - Pull line; 141 - First pull line; 142 - Second pull line; 150 - Limiting component; 151 - Limiting and fixing component; 152 - Bearing; 153 - Bearing fixing shaft; 1501 - Clearance; 160 - Stiffness adjustment unit; 161 - Wire reel; 162 - Stiffness adjustment servo mounting hardware; 163 - Stiffness adjustment servo; 1611 - Wire groove; 1612 - Wire fixing hole; 170 - Fish tail drive unit; 171 - First connector of fish tail drive servo; 172 - Fish tail drive servo; 173 - Second connector of fish tail drive servo; 180 - Fishtail connector; 181 - First fishtail connector; 182 - Second fishtail connector; 183 - Third fishtail connector; 184 - Fishtail connector gasket; 190 - Fish tail shell; 191 - First fish tail shell; 192 - Second fish tail shell; 200-Bionic tail fin; 300 - Imitation fish head shell; 310 - Imitation fish head first shell; 320 - Imitation fish head second shell; 330 - Imitation fish head third shell; 340 - Imitation fish head fourth shell. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "first" and "second," etc., are used to clearly describe the product components and do not represent any substantial difference. "Inner," "outer," etc., are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0024] It should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly, for example, it can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the invention based on the specific circumstances. As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more. The term "multiple" represents any number of two or more. In this application, "front" and "rear" refer to the direction of travel of the variable stiffness robotic fish, as shown in the attached... Figure 1 The positive direction of the X-axis.

[0025] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains upon understanding the invention. Unless expressly defined herein, terms such as those defined in a general dictionary shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and in this invention, and shall not be interpreted in an idealized or overly formalistic manner.

[0026] The following will combine Figures 1 to 10 This invention introduces a variable stiffness robotic fish provided by an embodiment of the present invention.

[0027] like Figures 1 to 4 As shown, one embodiment of the present invention provides a variable stiffness robotic fish, including: a variable stiffness fish tail 100, a bionic tail fin 200, and a fish head shell 300.

[0028] The variable stiffness fishtail 100 includes: an elastic spine 110; multiple blocking blocks 120 sequentially connected to the elastic spine 110 along its length; in any two adjacent blocking blocks 120, one has an outwardly convex first cylindrical surface 1204, and the other has an inwardly concave second cylindrical surface 1203; the first cylindrical surface 1204 and the second cylindrical surface 1203 are in a concave-convex fit and can rotate relative to each other as the elastic spine 110 bends; and a pull wire 140, one end of which passes through the multiple blocking blocks 120. The cable has a through hole 1201 and is fixed to the blocking block 120 near the rear end of the elastic spine 110 among multiple blocking blocks 120; the stiffness adjustment unit 160 includes a stiffness adjustment servo 163 and a reel 161, the other end of the pull cable 140 is fixed to the reel 161, and the stiffness adjustment servo 163 can drive the reel 161 to rotate and wind or release the pull cable 140, thereby adjusting the contact pressure of the first cylindrical surface 1204 and the second cylindrical surface 1203; the fishtail drive unit is connected to the front end of the elastic spine 110 and is used to drive the elastic spine 110 to swing left and right.

[0029] The variable stiffness robotic fish provided in this embodiment uses a stiffness adjustment servo motor 163 to drive a reel 161 to rotate and wind the pull line 140, thereby compressing multiple blocking blocks 120. This allows for adjustment of the pressure on the contact surfaces (first cylindrical surface 1204 and second cylindrical surface 1203) of two adjacent blocking blocks 120, thus adjusting the friction between adjacent blocking blocks 120 and adjusting the bending stiffness of the fish tail. It has the advantages of simple and stable structure and control. Moreover, the stiffness of the fish tail can be adjusted quickly and in real time over a wide range, and is less affected by external factors (such as pressure and temperature), making it highly practical.

[0030] In practical applications, when the variable stiffness robotic fish is in water, the tail drive unit drives the elastic spine 110 and multiple blocking blocks 120 connected to the elastic spine 110 to swing. Due to water resistance, the elastic spine 110 will bend. When a rapid sprint is desired, the tail needs to be stiffened to powerfully propel the water like a paddle; when slow cruising or turning flexibly, the tail needs to be softened for smoother, more energy-efficient swinging. Therefore, during the swimming process of the variable stiffness robotic fish, the stiffness of the tail usually needs to be changed to meet the corresponding requirements. In this embodiment, the stiffness adjustment servo 163 drives the reel 161 to rotate, and the tension is applied through the pull line 140 to convert it into contact pressure between two adjacent blocking blocks 120, thereby indirectly changing the friction between them and realizing the adjustment of the tail stiffness. The greater the friction, the less easily the elastic spine 110 deforms; the greater the stiffness, the less friction, and the more easily the elastic spine 110 deforms. The stiffness adjustment structure in this embodiment is simple in structure and convenient and flexible in adjustment. Furthermore, the rotation angle of the reel 161 can be controlled according to the required stiffness, allowing for a wide range and rapid adjustment of stiffness, thereby improving the motion performance of the variable stiffness robotic fish.

[0031] Furthermore, the overall shape of the flexible spine 110 can be designed according to requirements, such as mimicking the converging spine of a fish. As an example, the flexible spine 110 can be plate-like in shape, and may be rectangular or trapezoidal. In addition, the flexible spine 110 can have resilience, that is, it can return from a bent state to a straight and stable state after the external force is released.

[0032] Furthermore, in some embodiments, the variable stiffness robotic fish also includes a spring 130, and a pull line 140 including a first pull line 141 and a second pull line 142. The spring 130 is connected between the first pull line 141 and the second pull line 142. One end of the first pull line 141 passes through the line hole 1201 of a plurality of blocking blocks 120 and is fixed to the blocking block 120 near the rear end of the elastic spine 110. One end of the second pull line 142 is fixed to the reel 161.

[0033] In these embodiments, when the stiffness adjustment servo 163 drives the reel 161 to rotate, a tension force is applied to the spring 130 via the second pull wire 142. The elastic force of the spring 130 is then converted into contact surface pressure between the two adjacent blocking blocks 120 via the first pull wire 141. The output angle of the stiffness adjustment servo 163 can be positively correlated with the elastic force of the elastic segment, that is, positively correlated with the contact surface pressure between the two adjacent blocking blocks 120. By using the spring 130 as a buffer element, the elastic force of the overall pulling part can be increased, thereby improving the controllable range of the stiffness adjustment servo 163 and preventing the stiffness adjustment servo 163 from stalling.

[0034] Furthermore, in some embodiments, such as Figure 4 , Figure 9 and Figure 10 As shown, the variable stiffness fishtail 100 may also include a limiting member 150, which has a limiting hole for the pull wire 140 to pass through. The fishtail drive unit 170 includes an output shaft, which drives the elastic spine 110 to swing around the axis of the output shaft. The limiting hole is located on the axis of the output shaft.

[0035] In this way, during the tail swing, the pull cable 140 is constrained by the limiting member 150, ensuring that it always passes through the axis of the output shaft of the tail drive unit 170. If the stiffness adjustment servo 163 drives at a constant angle, and the bending amplitude of the variable stiffness tail 100 remains constant, the distance from the limiting hole to the last blocking block 120 remains constant, and the length of the pull cable 140 will not change. This ensures that the pull cable 140 and the spring 130 will not slack or tighten during the tail swing, meaning that the tail swing does not affect the contact surface pressure of the two adjacent blocking blocks 120.

[0036] As an example, such as Figure 9 and Figure 10 As shown, the limiting member 150 may include a limiting fixing member 151 and two bearings 152. The two bearings 152 are respectively fixed to the limiting fixing member 151 via bearing fixing shafts 153. The gap 1501 between the two bearings 152 forms a limiting hole, and each bearing 152 has an annular limiting groove on its outer circumferential surface. The annular limiting groove can accommodate the pull wire 140 from the side to limit the pull wire 140 from moving axially on the output shaft. Using two bearings 152 to limit the pull wire 140 provides a good limiting effect and is less likely to cause wear to the pull wire 140.

[0037] Furthermore, in some embodiments, such as Figure 7 and Figure 8 As shown, each blocking block 120 can also have a fan-shaped wire groove 1205 on its cylindrical surface facing the rear end of the elastic spine 110. One end of the fan-shaped wire groove 1205 is connected to the wire hole 1201 of the blocking block 120 it is located in, and the other end gradually expands outward in a fan shape to accommodate the pull wire 140 when two adjacent blocking blocks 120 rotate relative to each other. In this way, when two adjacent blocking blocks 120 rotate relative to each other, the pull wire 140 can move within the fan-shaped wire groove 1205, so that the pull wire 140 will not be pulled by the relative rotation of the two adjacent blocking blocks 120, which can ensure that the two adjacent blocking blocks 120 rotate smoothly, ensure that the elastic spine 110 bends smoothly, and ensure that the pull wire 140 does not become loose, tight, or even stuck when the two adjacent blocking blocks 120 rotate relative to each other.

[0038] As an example, the center of the sector-shaped guide groove 1205 can intersect with the center of the cylindrical surface, so that the sector-shaped guide groove 1205 communicates with the through hole 1201 located at the corresponding center of the cylindrical surface. The included angle between the two opposing side walls of the sector-shaped guide groove 1205 can range from 60° to 80°, such as 66°, 70°, or 78°. Alternatively, a sector-shaped guide groove 1205 can also be provided on the cylindrical surface of the blocking block 120 facing the front end of the elastic spine 110, and the two share the same housing for the pull wire 140.

[0039] Furthermore, in some embodiments, such as Figure 4 As shown, the variable stiffness fishtail 100 may further include: a fishtail connector 180, with the elastic spine 110 connected to the fishtail connector 180; the fishtail drive unit 170 includes a first fishtail drive servo connector 171, a fishtail drive servo 172, and a second fishtail drive servo connector 173. The fishtail drive servo 172 is fixed to the first fishtail drive servo connector 171, and the second fishtail drive servo connector 173 connects the output shaft of the fishtail drive servo 172 and the fishtail connector 180, so that the fishtail drive unit 170 can drive the fishtail connector 180 to swing, thereby driving the elastic spine 110 and multiple blocking blocks 120 and other components located thereon to swing synchronously.

[0040] Here, the output shaft of the fishtail-driven servo 172 can be extended downwards as shown in the diagram, making the second connector 173 of the fishtail-driven servo roughly L-shaped, facilitating the fishtail-driven servo 172 to drive the fishtail connector 180 to swing left and right. The second connector 173 of the fishtail-driven servo and the fishtail connector 180 can be a separate structure or a single piece.

[0041] The specific structure of the variable stiffness fishtail 100 can be as described in the following embodiment.

[0042] Example 1: The variable stiffness fishtail 100 includes an elastic spine 110, multiple blocking blocks 120, a spring 130, a pull wire 140, a limiting member 150, a stiffness adjustment unit 160, a fishtail drive unit 170, a fishtail connector 180, and a fishtail shell 190.

[0043] The components include: a blocking block 120 comprising a first blocking block 121, a second blocking block 122, and a third blocking block 123; a pull cable 140 comprising a first pull cable 141 and a second pull cable 142; a limiting member 150 comprising a limiting fixing member 151, a bearing 152, and a bearing fixing shaft 153; a stiffness adjustment unit 160 comprising a reel 161, a stiffness adjustment servo fixing member 162, and a stiffness adjustment servo 163; a fishtail drive unit 170 comprising a first fishtail drive servo connector 171, a fishtail drive servo 172, and a second fishtail drive servo connector 173; a fishtail connector 180 comprising a first fishtail connector 181, a second fishtail connector 182, a third fishtail connector 183, and a fishtail connecting gasket 184; and a fishtail outer shell 190 comprising a first fishtail outer shell 191 and a second fishtail outer shell 192.

[0044] like Figure 6 As shown, the flexible spine 110 adopts a planar plate structure and has a trapezoidal shape. A slot 1101 extending along its length can be provided in the middle of the flexible spine 110. The slot 1101 is rectangular, with one end penetrating through the front end of the flexible spine 110, while the other end does not. This facilitates the insertion of multiple blocking blocks 120 into the slot 1101 through the opening at the front end. Furthermore, the rear end of the flexible spine 110 maintains a one-piece structure, ensuring good integrity and facilitating powerful water-pounding.

[0045] The elastic spine 110 is axially symmetrically distributed, and the slot 1101 is also axially symmetrical along the axial symmetry line of the elastic spine 110, so that multiple blocking blocks 120 can adjust the stiffness of the elastic spine 110 in the middle of the elastic spine 110, and the adjustment effect is good.

[0046] Correspondingly, such as Figures 2 to 5 , Figure 7 and Figure 8 As shown, each blocking block 120 has guide grooves 1202 on opposite sides for the edge of the slot 1101 to be inserted. The guide grooves 1202 penetrate the blocking block 120 along the length of the elastic spine 110. Multiple blocking blocks 120 are sequentially engaged in the slots 1101 of the elastic spine 110 through the guide grooves 1202, which can prevent the blocking blocks 120 from falling off. Further optionally, as Figure 5 and Figure 7 As shown, the two sidewalls of the guide groove 1202 can be arc-shaped walls that bulge into the center of the guide groove 1202, which facilitates the bending of the elastic spine 110 without causing it to get stuck due to the guide groove 1202.

[0047] Any two adjacent blocking blocks 120 are in contact with each other through their cylindrical surfaces, specifically through the concave second cylindrical surface 1203 and the convex first cylindrical surface 1204. This interlocking contact prevents the elastic spine 110 from getting stuck when it bends. When the elastic spine 110 bends, it causes the two adjacent blocking blocks 120 to rotate along the cylindrical direction. The friction of their contact surfaces (i.e., the second cylindrical surface 1203 and the first cylindrical surface 1204) can resist the bending of the elastic spine 110, thereby changing the bending stiffness of the fishtail.

[0048] like Figure 5 , Figure 7 and Figure 8 As shown, the multiple blocking blocks 120 may include a first blocking block 121, a second blocking block 122, and a third blocking block 123. The first blocking block 121 is the most basic structure and there may be at least one. The second blocking block 122 and the third blocking block 123 are located at the front and rear ends, respectively, and are both optimized from the first blocking block 121, designed to adapt to the structures at both ends of the elastic spine 110. For example, the second blocking block 122 needs to match the third fishtail connector 183, so its front second cylindrical surface 1203 can be optimized as a plane; the rear end of the third blocking block 123 needs to fix the first pull wire 141, so its rear first cylindrical surface 1204 can be optimized as a concave surface. The structures of the multiple blocking blocks 120 may not be completely identical.

[0049] When assembling multiple blocking blocks 120, a second blocking block 122, multiple first blocking blocks 121 and a third blocking block 123 can be connected in series from front to back, and the number of first blocking blocks 121 can be configured according to actual needs.

[0050] Alternatively, the first cylindrical surface 1204 of the preceding blocking block 120 can be in contact with the second cylindrical surface 1203 of the following blocking block 120. Of course, a reverse cylindrical contact method can also be used, i.e., the second cylindrical surface 1203 of the preceding blocking block 120 is in contact with the first cylindrical surface 1204 of the following blocking block 120. There is no fundamental difference between the two methods. Correspondingly, the structure at both ends can be adapted by optimizing the front end of the second blocking block 122 and the rear end of the third blocking block 123.

[0051] like Figure 4 , Figure 5 , Figure 7 , Figure 8 and Figure 9As shown, the center of the blocking block 120 has a through-hole 1201. Preferably, the line connecting the through-holes 1201 of the multiple blocking blocks 120 can overlap with the axis of symmetry of the elastic spine 110 and the central axis of the variable stiffness fishtail 100. The pull wire 140 includes a first pull wire 141 and a second pull wire 142. One end of the first pull wire 141 is fixed to the rear end of the third blocking block 123, for example, by tying a knot in the first pull wire 141 to prevent it from detaching from the third blocking block 123. The first pull wire 141 passes sequentially through the through-holes 1201 of all the first blocking blocks 121 and the second blocking blocks 122 and the limiting member 150 along the central axis of the variable stiffness fishtail 100, and the other end is fixed to the rear end of the spring 130. One end of the second pull cable 142 is fixed to the front end of the spring 130. The second pull cable 142 is wound around the groove 1611 of the spool 161, and the other end is fixed to the spool 161. For example, the second pull cable 142 can be fixed through the pull cable fixing hole 1612 on the spool 161. The spool 161 is fixedly connected to the output shaft of the stiffness adjustment servo 163, and the stiffness adjustment servo 163 is fixed on the stiffness adjustment servo fixing member 162.

[0052] The blocking block 120 is also provided with a fan-shaped wire groove 1205. The center of the fan-shaped wire groove 1205 intersects with the center of the cylindrical contact surface, which is used to ensure that the first pull wire 141 will not become loose, tight or even stuck when two adjacent blocking blocks 120 rotate relative to each other.

[0053] like Figure 4 and Figure 9 As shown, the limiting fixing member 151 is fixedly connected to the second connecting member 173 of the fishtail drive servo motor; two grooved bearings 152 are respectively fixed to the limiting fixing member 151 through the bearing fixing shaft 153, and a gap 1501 can be formed between the two grooved bearings 152 for the first pull cable 141 to pass through. The gap 1501 formed by the two grooved bearings 152 intersects with the rotation center of the fishtail drive unit 170 (in this embodiment, the output shaft of the fishtail drive servo motor 172), that is, the gap 1501 is located on the axis of the output shaft, thereby ensuring that the pull cable 140 and the spring 130 will not loosen or tighten when the fishtail swings, that is, the fishtail swing does not affect the contact surface pressure of the two adjacent cylindrical layer blocking blocks 120.

[0054] According to the variable stiffness robotic fish provided in this embodiment, the stiffness adjustment servo 163 drives the reel 161 to rotate and applies tension to the spring 130 through the second pull line 142; the elastic force of the spring 130 is then converted into the contact surface pressure of the two adjacent blocking blocks 120 through the first pull line 141, thereby indirectly changing the contact surface friction of the two adjacent cylindrical blocking blocks 120.

[0055] Specifically, the stiffness adjustment servo 163 adjusts the elastic force of the spring 130, thereby adjusting the contact surface pressure of the two adjacent cylindrical blocking blocks 120, thus indirectly changing the friction of the contact surface and realizing the stiffness adjustment of the fishtail. That is, the stiffness of the variable stiffness fishtail 100 can be continuously adjusted by controlling the output angle of the stiffness adjustment servo 163.

[0056] The rear end of the stiffness adjustment servo mounting part 162 is connected to the first connector 171 of the fishtail drive servo, the fishtail drive servo 172 is fixed on the first connector 171 of the fishtail drive servo, and the second connector 173 of the fishtail drive servo is connected to the output shaft of the fishtail drive servo 172.

[0057] The elastic spine 110 is connected to the second connector 173 of the fishtail drive servo via the fishtail connector 180. Specifically, the first fishtail connector 181 and the second fishtail connector 182 are respectively fixed to both sides of the second connector 173 of the fishtail drive servo, and the third fishtail connector 183 is fixed to the rear end of the first fishtail connector 181 and the second fishtail connector 182. The elastic spine 110 is fixed to the rear end of the third fishtail connector 183 via the fishtail connecting gasket 184.

[0058] Specifically, the second fishtail connector 173, the first fishtail connector 181, the second fishtail connector 182, and the third fishtail connector 183 of the fishtail drive servo can be designed as an integral structure, and the stiffness adjustment servo fixing part 162 and the first fishtail drive servo connector 171 can also be designed as an integral structure.

[0059] Furthermore, the structure directly or indirectly connected to the output shaft of the fish tail drive servo 172 includes an elastic spine 110, a blocking block 120, a limiting member 150, a second connector 173 for the fish tail drive servo, a fish tail connector 180, and a bionic tail fin 200 as a swinging part. This allows for the simulation of a fish swinging left and right by controlling the fish tail drive servo 172. The fish tail drive unit 170 has one rotational degree of freedom, provided by the fish tail drive servo 172, and can be used to drive the swinging part, including the elastic spine 110, the cylindrical blocking block 120, the limiting member 150, the second connector 173 for the fish tail drive servo, the fish tail connector 180, and the bionic tail fin 200, to achieve the simulation of a fish tail swinging left and right.

[0060] Example 2: The difference from the above embodiment 1 is that the overall shape of the elastic spine 110 is different, and correspondingly, the structure of the blocking block 120 is also adapted.

[0061] The overall shape of the flexible spine 110 is not limited to the trapezoidal shape mentioned above; it can also be rectangular or the like.

[0062] The slot 1101 can pass through the rear end of the elastic spine 110, rather than the front end, so that multiple blocking blocks 120 can be inserted into the slot 1101 from the rear end of the elastic spine 110.

[0063] The number of card slots 1101 can also be two, or even more, along... Figure 6 The upper and lower positions are spaced apart, so that multiple blocking blocks 120 are arranged in multiple rows in multiple slots 1101, and the stiffness of the elastic spine 110 is adjusted in multiple positions.

[0064] Furthermore, the flexible spine 110 may also lack the slot 1101, and instead directly connect multiple blocking blocks 120 to the opposite edges of the flexible spine 110, for example... Figure 6 The upper and lower edges of the block 120 are arranged in two rows. Correspondingly, one side of the blocking block 120 should have a guide groove 1202. Alternatively, there can be two pull wires 140, each pressing against one of the two rows of blocking blocks 120. Here, a single stiffness adjustment unit 160 can be used to pull both pull wires 140 simultaneously; for example, a stiffness adjustment servo motor 163 can simultaneously drive two reels 161 to rotate, thereby pulling both pull wires 140. Alternatively, two stiffness adjustment units 160 can be used to pull one pull wire 140 each. Thus, the overall stiffness of the elastic spine 110 can be adjusted by adjusting the stiffness of its two edges.

[0065] Example 3: The differences from Embodiment 1 above may be in the connection structure and connection method between the fishtail drive unit 170 and the elastic spine 110, and the specific structure of the limiting member 150, etc., and are not limited to the above examples.

[0066] Furthermore, in some embodiments, such as Figures 1 to 5 As shown, the variable stiffness robotic fish may also include a bionic tail fin 200, which is connected to the rear end of the elastic spine 110. The bionic tail fin 200 can be designed in different shapes as needed, and can be designed to be rigid or flexible, and is fixed to the rear end of the elastic spine 110 of the variable stiffness tail 100 to provide the main propulsion for the robotic fish.

[0067] Furthermore, in some embodiments, such as Figures 1 to 3 As shown, the variable stiffness robotic fish may also include a fish head shell 300, the interior of which can form a sealed cavity and a non-sealed cavity, and the stiffness adjustment unit 160 and the fish tail drive unit 170 are both located in the non-sealed cavity.

[0068] As an example, such as Figure 2 and Figure 3As shown, the fish-head-like shell 300 includes a first fish-head-like shell 310, a second fish-head-like shell 320, a third fish-head-like shell 330, and a fourth fish-head-like shell 340. The first and second fish-head-like shells 310 and 320 form a sealed cavity for waterproofing and can house components such as the control system, sensors, and batteries. The third and fourth fish-head-like shells 330 and 340 form a non-sealed cavity that can enclose the stiffness adjustment unit 160, the fish tail drive unit 170, etc., to ensure the overall shape of the robotic fish is streamlined.

[0069] As an example, the sealed cavity and the unsealed cavity can be distributed front to back. The stiffness adjustment unit 160 and the tail drive unit 170 can be distributed front to back in the unsealed cavity, which can reduce the width of the tail, which is beneficial to reducing the volume of the variable stiffness robotic fish and making it easier for it to enter narrower and lower areas.

[0070] In addition, the connection between the variable stiffness fish tail 100 and the fish head shell 300 can be achieved by fixing the fish head second shell 320 and the stiffness adjustment servo fixing part 162.

[0071] The fish tail shell 190 includes a first fish tail shell 191 and a second fish tail shell 192. The first fish tail shell 191 and the second fish tail shell 192 are fixed to the fish tail connector 180 and extend to the front end to ensure that the overall shape of the robotic fish is streamlined. There is also a movable gap between the fish tail shell 190 and the imitation fish head shell 300 to facilitate the flexible swinging of the fish tail.

[0072] The variable stiffness robotic fish proposed in this application adjusts the bending stiffness of the fish tail by using a stiffness adjustment servo to drive a reel. Through the synergy of the cable and spring, the output force is converted into contact pressure between two adjacent blocking blocks, thereby indirectly adjusting the friction of the contact surface. The variable stiffness robotic fish proposed in this embodiment has the advantages of simple and stable structure and control, and it can achieve rapid and wide-range stiffness adjustment of the fish tail, thus improving its motion performance.

[0073] While embodiments of the present invention have been described in detail above, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. It should be understood that, to those skilled in the art, these modifications and variations will still fall within the spirit and scope of the embodiments of the present invention as defined in the claims.

Claims

1. A variable stiffness robotic fish, characterized in that, Includes a variable stiffness fishtail (100), said variable stiffness fishtail (100) comprising: Flexible spine (110); Multiple blocking blocks (120) are sequentially connected to the elastic spine (110) along its length. Among any two adjacent blocking blocks (120), one has an outwardly convex first cylindrical surface (1204), and the other has an inwardly concave second cylindrical surface (1203). The first cylindrical surface (1204) and the second cylindrical surface (1203) are in concave-convex fit and can rotate relative to each other as the elastic spine (110) bends. A pull wire (140) is provided, one end of which passes through the wire hole (1201) of the plurality of blocking blocks (120) and is fixed to the blocking block (120) near the rear end of the elastic spine (110). The stiffness adjustment unit (160) includes a stiffness adjustment servo (163) and a reel (161). The other end of the pull cable (140) is fixed to the reel (161). The stiffness adjustment servo (163) can drive the reel (161) to rotate and wind or release the pull cable (140), thereby adjusting the contact pressure between the first cylindrical surface (1204) and the second cylindrical surface (1203). The fishtail drive unit (170) is connected to the front end of the elastic spine (110) and is used to drive the elastic spine (110) to swing left and right.

2. The variable stiffness robotic fish according to claim 1, characterized in that, The variable stiffness robotic fish also includes a spring (130), and the pull line (140) includes a first pull line (141) and a second pull line (142). The spring (130) is connected between the first pull line (141) and the second pull line (142). One end of the first pull line (141) passes through the line hole (1201) of the plurality of blocking blocks (120) and is fixed to the blocking block (120) near the rear end of the elastic spine (110) among the plurality of blocking blocks (120). One end of the second pull line (142) is fixed to the reel (161).

3. The variable stiffness robotic fish according to claim 1, characterized in that, The elastic spine (110) is plate-shaped, and a slot (1101) extending along its length is provided in the middle of the elastic spine (110). The plurality of blocking blocks (120) are locked in the slot (1101), and each of the blocking blocks (120) has a guide groove (1202) on its opposite sides for the edge of the slot (1101) to be inserted.

4. The variable stiffness robotic fish according to claim 3, characterized in that, The guide groove (1202) penetrates the blocking block (120) along the length of the elastic spine (110), and the two groove sidewalls of the guide groove (1202) are both arc-shaped walls that bulge into the center of the guide groove (1202).

5. The variable stiffness robotic fish according to claim 1, characterized in that, Each of the blocking blocks (120) has a fan-shaped wire groove (1205) on its cylindrical surface facing the rear end of the elastic spine (110). One end of the fan-shaped wire groove (1205) is connected to the wire hole (1201) of the blocking block (120) to which it is located, and the other end gradually expands outward in a fan shape. The fan-shaped wire groove (1205) is used to accommodate the pull wire (140) during the relative rotation of two adjacent blocking blocks (120).

6. The variable stiffness robotic fish according to claim 1, characterized in that, The variable stiffness fishtail (100) also includes: A limiting member (150) is provided with a limiting hole for the pull wire (140) to pass through. The fish tail drive unit (170) includes an output shaft. The fish tail drive unit (170) drives the elastic spine (110) to swing around the axis of the output shaft. The limiting hole is located on the axis of the output shaft.

7. The variable stiffness robotic fish according to claim 6, characterized in that, The limiting member (150) includes a limiting fixing member (151) and two bearings (152). The two bearings (152) are respectively fixed to the limiting fixing member (151) by bearing fixing shaft (153). The limiting hole is formed between the two bearings (152), and an annular limiting groove is provided on the outer peripheral surface of each bearing (152). The annular limiting groove can accommodate the pull wire (140) from the side to limit the pull wire (140) from moving in the axial direction of the output shaft.

8. The variable stiffness robotic fish according to claim 1, characterized in that, The variable stiffness fishtail (100) also includes: Fish tail connector (180), the elastic spine (110) is connected to the fish tail connector (180); The fishtail drive unit (170) includes a first connector (171) for the fishtail drive servo, a fishtail drive servo (172) and a second connector (173) for the fishtail drive servo. The fishtail drive servo (172) is fixed to the first connector (171) for the fishtail drive servo, and the second connector (173) for the fishtail drive servo connects the output shaft of the fishtail drive servo (172) and the fishtail connector (180).

9. The variable stiffness robotic fish according to claim 1, characterized in that, The variable stiffness robotic fish also includes: The fish head shell (300) has sealed and unsealed cavities distributed front and back inside the fish head shell (300), and the stiffness adjustment unit (160) and the fish tail drive unit (170) are both located in the unsealed cavity. A biomimetic tail fin (200) is connected to the rear end of the elastic spine (110).

10. The variable stiffness robotic fish according to claim 9, characterized in that, The stiffness adjustment unit (160) and the fishtail drive unit (170) are distributed front and back in the unsealed cavity.

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