CN118790444A - A rigid-flexible coupling robotic fish based on a rope-driven structure - Google Patents

Abstract

A rigid-flexible coupling robot fish based on a rope-driven tensioning structure comprises a rigid head, a flexible swinging part and a rope-driven tensioning mechanism, wherein the rigid head consists of an upper rigid shell and a lower rigid shell to form a closed space, and the rope-driven tensioning mechanism is arranged in the closed space. The flexible swinging part comprises a rigid framework, a front middle-set sheet, a rear middle-set sheet and a flexible skin, wherein the front part forms an active swinging part, and the rear part forms a passive swinging part. The active swinging part realizes multidirectional bending through the framework unit and the front middle plate and simulates the swinging of tail fins of real fishes. The passive swinging part utilizes a rear middle-placed sheet and a solid skin to improve swinging frequency and power. The sectional design of the flexible swinging part better fits the tail state of the fish in real swimming, and the passive swinging part improves the local rigidity of the part connected with the skeleton unit while ensuring the flexibility of the flexible tail, so that the swinging frequency and the output power are improved, and the problems of low swimming speed, insufficient output force, low output power, stiff swinging posture and the like of the traditional soft robot fish are solved.

Description

A rigid-flexible coupling robotic fish based on a rope-driven structure

Technical Field

The present invention belongs to the technical field of robots, and more specifically, relates to a rigid-flexible coupling robotic fish based on a rope-driven structure.

Background Art

The ocean and underwater environment occupy most of the earth's surface and contain rich resources. With the advancement of robotics technology, the design and application of various underwater robots have provided new solutions for ocean exploration and development. In recent years, bionic robot fish, as a new type of underwater robot, has developed rapidly due to its excellent environmental adaptability and potential application value.

In the current research, according to different application scenarios and bionic objects, the driving structure of bionic robot fish can be roughly divided into single rigid joint, multi-rigid joint, soft intelligent material and wire structure. These design structures have jointly promoted the development of bionic robot fish and underwater robots. Traditional single-joint robot fish generally use rigid tail fins to generate forward power, which is simple to control. However, this structure is quite different from the real fish motion mode, the degree of bionics is low, and there is also the problem of low propulsion efficiency. Multi-joint robot fish can achieve more swimming postures, such as straight-line fast swimming, C-shaped turning, etc. This design is mostly a single motor driving a single joint, and the rhythmic movement between joints is used to effectively simulate the smooth swing and swimming posture of fish. However, with the introduction of joints, the complexity of control and the requirements for driving motors are also increased. The successful application of various new soft materials also provides new possibilities for the development of robot fish driven by material properties. Most of these drives are based on the deformation of functional materials under different specific conditions, so they also have the obvious limitations of most functional materials, that is, strict triggering conditions and low driving efficiency, and limit the carrying and operation capabilities of robot fish. Therefore, a new bionic robotic fish that can imitate the smooth swimming and movement modes of fish, maintain high propulsion efficiency, and is relatively simple to control has high scientific research value and potential engineering application capabilities.

In summary, there is still a lack of a design method for bionic robot fish that has both motion compliance and a relatively simple structure. There is also a lack of a design method that has a relatively simple control model and high driving efficiency and is universal in multiple scenarios. It is difficult to further improve the upper limit of the capabilities of bionic robot fish using existing structural mechanisms and design concepts.

It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field.

Summary of the invention

The main purpose of the present invention is to solve the problems existing in the above-mentioned background technology and provide a rigid-flexible coupling robotic fish based on a rope-driven structure.

To achieve the above object, the present invention adopts the following technical solutions:

A rigid-flexible coupling robotic fish based on a rope-driven tensioning structure, comprising a rigid head, a flexible swinging part and a rope-driven tensioning mechanism:

The rigid head comprises an upper rigid shell and a lower rigid shell, which cooperate to form a closed space, and the rope-driven tensioning mechanism is installed inside; the rope-driven tensioning mechanism acts on the flexible swinging part with a driving rope, and causes the flexible swinging part to swing by tensioning the driving rope;

The flexible swinging part includes a rigid skeleton, a front center piece, a rear center piece and a flexible skin, wherein the flexible skin is divided into a front hollow part and a rear solid part, the rigid skeleton and the front center piece are arranged in the front hollow part, the rigid skeleton includes a plurality of skeleton units connected to the front center piece, the plurality of skeleton units open the front hollow part of the flexible skin to form a fishtail-shaped active swinging part, the skeleton unit located at the rear is connected to the rear center piece, the rear center piece is interference-fitted with the hollow groove of the rear solid part, and is connected to the tail fin of the robot fish to form a passive swinging part; each skeleton unit is provided with a rope threading hole for the driving rope to be tensioned, the front center piece is made of flexible material, and when the driving rope is tensioned, it drives each skeleton unit and the front center piece to bend symmetrically and asymmetrically, so as to realize symmetrical and asymmetrical swinging of the active swinging part, and the rear center piece swings in a cantilever beam mode on the relatively static skeleton unit, thereby improving the swing frequency and output power of the passive swinging part.

Furthermore, it also includes a TPU clamping sheet disposed between the upper rigid shell and the lower rigid shell; the upper rigid shell and the lower rigid shell are connected by bolts and clamped with the TPU (Thermoplastic Polyurethane) clamping sheet unit. The TPU clamping sheet has a lower Shore hardness and a certain degree of flexibility. Compared with the upper rigid shell being directly connected to the lower rigid shell, the contact area is larger, the pressure distribution is more uniform, and the sealing is better.

Furthermore, the multiple skeleton units are four sheet skeleton units, the four sheet skeleton units are provided with two rope holes on the shaft side, the driving rope is terminated at the fourth rigid skeleton unit at the rear, the first, second and third rigid skeleton units at the front are provided with two through holes on the side, and are connected to the front middle sheet through a connector; the fourth rigid skeleton unit is provided with four through holes on the side, the two through holes in the front row are connected to the front middle sheet through a connector, and the two through holes in the rear row are connected to the rear middle sheet through a connector. The four rigid skeleton units tension the front hollow part of the flexible skin into the active swinging part of the flexible swinging part of the rigid-flexible coupling robotic fish.

Furthermore, the rope-driven tensioning mechanism includes a driving motor, a reversing unit and a symmetrical tensioning unit. The driving motor is coupled to the symmetrical tensioning unit through the reversing unit. The reversing unit is used to reverse the motor torque, thereby regulating the motion mode. The symmetrical tensioning unit is composed of two symmetrically distributed winding units. The two winding units tension two driving ropes respectively. The winding unit includes a boss gear, a winding drum and a wire fixing component. The boss gear rotates coaxially with the winding drum. The winding drum is connected to the wire fixing component to drive the wire fixing component to rotate. The wire fixing component is used to clamp the driving rope.

Furthermore, the reversing unit includes a commutator unit, an input shaft unit, an output shaft unit and at least one pair of mutually meshing bevel gear units, the input shaft unit and the output shaft unit are respectively coupled to the drive motor and the symmetrical tensioning unit, and the bevel gear unit realizes the right-angle reversal of the motor output torque to the symmetrical tensioning unit; the commutator unit includes a commutator housing, at least two deep groove ball bearing units are arranged outside the commutator housing, and the deep groove ball bearing units are used to support the rotation of the input shaft unit and the output shaft unit; the input shaft unit and the output shaft unit are respectively provided with a slot, each slot is matched with a retaining spring, the upper side of the retaining spring is in contact with the commutator housing, and the positioning of the output shaft and the input shaft unit and the commutator housing is realized by the meshing of the bevel gears and the interference of the retaining spring; the reversing unit is connected to the drive motor through a coupling to realize the power transmission of the motor.

Furthermore, a through hole of equal aperture is opened between the boss gear and the winding drum, which is interference fit with the mother screw of the mother screw; the boss gear is coaxial with the winding drum; after the sub-screw of the mother screw cooperates with the mother screw on the lower side of the winding drum, the winding drum is limited; the boss gear is meshed with the matching gear on the output shaft of the commutator unit, and the matching gear on the output shaft is interference fit with the output shaft to drive the boss gear and the winding drum to rotate.

Furthermore, the rope-driven tensioning mechanism also includes a fixed frame unit, which envelops the symmetrical tensioning unit; the fixed frame unit includes an upper clamping plate, a lower clamping plate, a fixed shell, a sub-fixing plate and a sub-fixing shell; the boss gear is clamped between the upper clamping plate and the lower clamping plate, and the sub-fixing shell is connected and clamps the symmetrical tensioning unit through studs; the sub-fixing plate is connected to the sub-fixing shell through bolts and connects the sub-fixing shell to the fixed shell; the fixed shell is connected to the commutator housing of the commutator unit through bolts.

Furthermore, a motor fixing frame is also arranged in the closed space of the rigid head, the driving motor is connected to the motor fixing frame via bolts, and the motor fixing frame is connected to the lower rigid shell.

Furthermore, the rigid head adopts nonlinear coupling of elliptic curve and parabola to perform parameterized design of streamlined shell, following the following functional equation:

Among them, D is the maximum diameter of the cross section; Lc is the length of the front half of the head; _Lr is the length of the back half _of the fish body.

Furthermore, D is 75 mm, L _c is 118.5 mm, and L _r is 185 mm.

In some embodiments of the present invention, a rigid-flexible coupling robot fish includes a rigid head, a flexible swinging part and a rope-driven tensioning mechanism, wherein: the rigid head includes an upper rigid shell, a lower rigid shell and a middle TPU clamping sheet, and the rigid head and the flexible swinging part are connected in a three-layer static sealing manner. When the robot fish swims straight, the rigid head mainly reduces the travel resistance of the robot fish, and the flexible swinging part mainly generates a tail vortex to provide propulsion for the robot fish to move forward; when the robot fish turns left or right, the flexible swinging part is dominant, and the robot fish achieves left or right turning through the asymmetric swing of the flexible swinging part. The rigid head concentrates the main functional modules and weight distribution of the robot fish, and also determines the overall shape of the robot fish.

In some embodiments, the flexible swinging part includes four sheet-like frame units at the tail, a tail fin unit, a front center sheet, a rear center sheet and a silicone skin. The four sheet-like frame units are equidistantly connected to the front center sheet by bolts. The sheet-like frame unit opens the front hollow part of the silicone skin to form the fishtail-shaped active swinging part of the robot fish. The four sheet-like frame units fit tightly with the silicone skin, and the silicone skin makes the flexible swinging part airtight. The rear center sheet cooperates with the rear solid part of the silicone skin to form the passive swinging part of the flexible swinging part.

In some embodiments, the present invention has a hollow groove in the middle of the rear solid part of the silicone skin, and the shape of the hollow groove is an equidistant scale of the rear center plate; the rear center plate and the silicone skin are interference fit in the hollow groove in the rear solid part to form a passive swinging part of the flexible swinging part; compared with the passive swinging part without the rear center plate, the passive swinging part with the rear center plate has a faster swing frequency.

In some embodiments, the upper rigid shell adopts a double-layer design with a platform board inside; the power module and the boost module are placed on the upper side of the platform board, and the power module and the boost module are bonded and fixed to the platform board by double-sided foam glue; the lower side of the platform board prevents the control board and the Bluetooth module; the Bluetooth is connected to the control board through pins, and the control board and the platform are bonded to each other by foam glue; nine through holes are distributed on the outer side of the upper rigid shell, and nut sleeves are embedded in the through holes; the lower rigid shell is also distributed with threaded holes corresponding to the upper rigid shell.

In some embodiments, the upper rigid shell and the lower rigid shell are sprayed with waterproof paint to prevent water seepage and leakage. The shell is streamlined in shape, and the length, width, height and cross-section are parametrically designed, and they cooperate with each other to form a spindle-shaped space corresponding to the croaker fish.

The present invention has the following beneficial effects:

The present invention provides a design method of a rigid-flexible coupling robot fish based on a rope-driven tensioning structure, which solves the problems of large and complicated body, complex control system, rigid swimming posture and low driving efficiency of traditional robot fish. The robot fish combines the advantages of high driving efficiency of rigid robot fish and strong adaptability to unstructured environment of soft robot fish. It not only has high output power and good potential engineering application value, but also realizes the continuity and flexibility of tail swinging at a high level of space utilization and greatly simplifies the control model through the rope-driven flexible tail design, thereby realizing a good combination of high bionic degree of fish, propulsion efficiency and simple control model. This rigid-flexible coupling robot fish provides an efficient and novel solution for the design of new underwater robots, especially bionic robot fish, in various complex underwater and marine unstructured environments, meeting the requirements of easy control, high efficiency and low energy consumption.

The flexible swinging part of the robot fish of the present invention is a tension swinging system driven by a single motor, and is composed of an active swinging part composed of a sheet-like skeleton unit and a passive swinging part embedded in a middle sheet. Different from the swinging part of the existing robot fish, the segmented design of the flexible swinging part better fits the tail state of the fish in real swimming. At the same time, the passive swinging part of the middle sheet embedded with a material with good resilience and fatigue resistance improves the local stiffness of the part connected to the skeleton unit while ensuring the flexibility of the flexible tail, thereby increasing the swing frequency of the passive swinging part and its output power, thereby overcoming the problems of slow swimming speed, insufficient output force and low output power of traditional soft robot fish.

The embodiment of the present invention optimizes the rope-driven tensioning mechanism, and adopts a tensioning system of a motor combined with a commutator and a gear box, thereby realizing a highly integrated mechanism design under extremely limited volume and space conditions. The rope-driven tensioning mechanism is used to tension the driving rope, thereby driving the skeleton unit to achieve the bending of the active part of the flexible swinging part, and the active part drives the passive part, thereby realizing the symmetrical, asymmetrical and high-frequency swinging of the entire swinging part. When the motor continues to rotate, unlike the single servo design adopted by most rope-driven robot fishes at present, the motor and the gears rotate the pull wire to make the commutation of the rope-driven tensioning smoother, and the driven swinging part can show a higher driving frequency and a waveform that is more suitable for the sinusoidal output wave, thereby overcoming the inherent problems of the rigid robot fish, such as the rigid swinging posture, low continuity and poor flexibility.

The rigid head preferably adopts the nonlinear coupling of elliptical curve and parabola to perform parameterized design of the streamlined shell. Following the proposed functional equation, the obtained shape greatly reduces the travel resistance of the robot fish when swimming. The resistance of an object when moving in a fluid is caused by two reasons: internal friction and vortex. When the speed is very small, the size of the resistance is mainly determined by the internal friction. When the speed is large, it is mainly determined by the vortex. The faster the speed, the greater the effect of the vortex. In order to effectively reduce the resistance, it is necessary to try to avoid the formation of vortex. By observing the swimming of fish, it is found that all fast-swimming fish, such as hairtail, shark, etc., have a special cigar-like shape. Through a large number of experiments, it is concluded that making the robot fish into the above shape can reduce the vortex effect or avoid the formation of vortex, thereby greatly reducing the resistance of the fluid to it.

Other beneficial effects of the embodiments of the present invention will be further described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a main cross-sectional view of a rigid-flexible coupling robotic fish constructed according to a preferred embodiment of the present invention;

FIG2 is a front view of a rigid-flexible coupling robotic fish constructed according to a preferred embodiment of the present invention;

FIG3 is an axonometric view of a rigid-flexible coupling robotic fish constructed according to a preferred embodiment of the present invention;

FIG4 is a top cross-sectional view of a rigid-flexible coupling robotic fish constructed according to a preferred embodiment of the present invention;

FIG5 is a side view of a rigid-flexible coupling robotic fish constructed according to a preferred embodiment of the present invention;

FIG6 is a schematic diagram of the structure of the rigid head mechanism in the rigid-flexible robotic fish provided by the present invention;

FIG7 is a schematic structural diagram of a flexible swinging part mechanism in a rigid-flexible coupling robotic fish provided by the present invention;

FIG8 is a schematic structural diagram of a rope-driven tensioning mechanism in a rigid-flexible coupling robotic fish provided by the present invention;

Reference numerals:

1-motor, 2-lower rigid shell, 3-TPU clamping plate, 4-upper rigid shell, 5-control board, 6-power supply module, 7-Bluetooth module, 8-fixed shell, 9-clamping plate, 10-wire fixing member, 11-winding reel, 12-fin, 13-first rigid skeleton unit, 14-silicone skin, 15-second rigid skeleton unit, 16-third rigid skeleton unit, 17-fourth rigid skeleton unit, 18-tail fin, 19-rear center plate, 20-front center plate, 21-commutator housing, 22-motor fixing frame, 23-bevel gear set, 24-deep groove ball bearing, 25-end cover, 26-input and output shafts, 27-coupling, 28-boss gear, 29-gear, 30-pectoral fin.

DETAILED DESCRIPTION

The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for fixing as well as for coupling or communication.

It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

1 to 8 , an embodiment of the present invention provides a rigid-flexible coupling robotic fish based on a rope-driven tensioning structure, including a rigid head, a flexible swinging part, and a rope-driven tensioning mechanism:

The rigid head comprises an upper rigid shell 2 and a lower rigid shell 4, which cooperate to form a closed space, and a fish fin 12 and a pectoral fin 30 can be arranged on the outside, and the rope-driven tensioning mechanism is installed inside; a tail fin 18 is arranged at the rear end of the flexible swinging part; the rope-driven tensioning mechanism acts on the driving rope to the flexible swinging part, and the flexible swinging part swings through the rope-driven tensioning; the rigid head is used to form the overall shape of the robot fish and integrate the main functional modules; the rope-driven tensioning mechanism is used to drive the flexible swinging part to swing and control the motion mode of the robot fish; the flexible swinging part is used to simulate the swing of the tail fin of a real fish, and provide propulsion and steering capabilities;

Wherein, the flexible swinging part includes a rigid frame, a front center piece 20, a rear center piece 19 and a flexible skin such as a silicone skin 14, the rigid frame is provided with a rope threading hole, the silicone skin 14 is divided into a front hollow part and a rear solid part, the rigid frame and the front center piece 20 are arranged in the front hollow part, the rigid frame has a plurality of frame units (such as the first to fourth rigid frame units 13, 15, 16, 17) connected to the front center piece 20, the plurality of frame units open the front hollow part of the silicone skin 14 to form a fishtail-shaped active swinging part, the rear center piece 19 is connected to the frame unit located at the rear, the rear center piece 19 is interference fit with the hollow groove of the rear solid part, and is connected to the tail fin 18 such as a slot-type fit to form a passive swinging part. Swinging part; the active swinging part and the passive swinging part cooperate with each other through the rear center plate 19; wherein, each skeleton unit is provided with two rope holes for two driving ropes to be tensioned, and the front center plate 20 is made of flexible material. When the driving rope is tensioned, it drives each skeleton unit and the front center plate 20 to bend symmetrically and asymmetrically, which is manifested as the symmetrical and asymmetrical swinging of the active swinging part of the front; when the driving rope tension drives the active swinging part to swing, the rear center plate 19 swings in a cantilever beam mode on the relatively static skeleton unit, and the local stiffness and polar moment of inertia of the passive swinging part increase in a step-like manner, thereby improving the swing frequency and output power of the passive swinging part; thereby simulating the swimming of real fish, so that the robot fish has efficient propulsion ability and good environmental adaptability, and is particularly suitable for underwater environment exploration and operations.

The specific embodiments of the present invention are further described below.

As shown in FIGS. 1 to 8 , an embodiment of the present invention provides a rigid-flexible coupling robotic fish based on a rope-driven tensioning structure, the robotic fish comprising a rigid head, a flexible swinging part, a rope-driven tensioning mechanism and other devices, wherein:

The rigid head includes an upper rigid shell 4, a lower rigid shell 2 and a middle-layer TPU clamping piece 3. The upper rigid shell 4 and the lower rigid shell 2 clamp the middle-layer TPU clamping piece 3 and are connected by threaded connection. After assembly, the rigid head is streamlined, which is a nonlinear coupling of elliptical curves and parabolas. The overall shape is close to the appearance and proportion of real fish, which reduces the friction resistance when swimming; the middle-layer TPU clamping piece 3 avoids the sealing problem caused by the direct connection between the upper rigid shell 4 and the lower rigid shell 2 and the insufficient contact of the joint surface, and can be disassembled repeatedly; the internal space of the shell is stacked in layers, with high integration, high utilization rate, and reasonable space arrangement.

The rigid head adopts the nonlinear coupling of elliptic curve and parabola to perform parameterized design of streamlined shell, following the following functional equation:

Wherein, D is the maximum diameter of the cross section; L _c is the length of the head in the front half; L _r is the length of the body in the back half. Preferably, D is 75 mm, L _c is 118.5 mm, and L _r is 185 mm.

The rigid head shape designed in this way can greatly reduce the travel resistance of the robot fish when it swims.

The flexible swinging part consists of two parts. The first part is the front active swinging part formed by the front center plate 20 and four rigid skeleton units 13, 15, 16, and 17 cooperating with the front hollow part of the rear tensioned silicone skin 14; the second part is formed by the rear center plate 19 and the rear solid part of the silicone skin 14.

Furthermore, the first, second, third and fourth rigid skeleton units 13, 15, 16 and 17 of the front active swinging part of the flexible swinging part are connected to the front center plate 20 by threaded connection, wherein the first and fourth rigid skeleton units 13 and 17 are respectively bolted to the rigid head device and the rear center plate 19. Therefore, the connection between the front active swinging part of the flexible swinging part and the rigid head is realized by the first rigid skeleton unit 13; the first to fourth rigid skeleton units 13, 15, 16 and 17 are each provided with two rope holes for tensioning the driving rope; the front center plate 20 is made of a material with good resilience and fatigue resistance. After the driving rope is tensioned by the rope-driven tensioning mechanism, it drives the first to fourth rigid skeleton units 13, 15, 16 and 17 and the front center plate 20 connected thereto to perform symmetrical and asymmetrical bending. In terms of movement form, it manifests as symmetrical and asymmetrical swinging of the front active swinging part.

Furthermore, the rear driven swinging part of the flexible swinging part is formed by the cooperation of the rear center plate 19 and the rear solid part of the silicone skin 14. Since the slot of the rear solid part of the silicone skin 14 is an equidistant scale of the rear center plate 19, the rear center plate 19 and the silicone skin 14 form an interference fit, and the fit is tight. Therefore, the active swinging part and the driven swinging part of the flexible swinging part cooperate with each other through the rear center plate 19; accordingly, the local stiffness and polar moment of inertia of the rear driven swinging part of the flexible swinging part increase in a step-like manner, thereby improving the swing frequency and output power of the driven swinging part; after the rear center plate 19 and the tail fin 18 are slot-type matched, a complete flexible swinging part is formed; when the driving rope is tensioned to drive the active swinging part to swing, the rear center plate 19 and the fourth rigid skeleton unit 17 connected thereto swing, and to a certain extent, after the fourth rigid skeleton unit 17 is regarded as a stationary state, the rear center plate 19 can be regarded as a cantilever beam model under the action of alternating force.

The flexible swinging part of the robot fish is a tension swinging system driven by a single motor, which consists of an active swinging part composed of a sheet skeleton unit and a passive swinging part embedded in the middle sheet. Unlike the swinging part of existing robot fish, the segmented design of the flexible swinging part better fits the tail state of the real swimming fish. At the same time, the passive swinging part embedded in the middle sheet made of materials with good resilience and fatigue resistance such as PETG (Polyethylene Terephthalate Glycol) ensures the flexibility of the flexible tail while improving the local stiffness of the part connected to the skeleton unit, thereby increasing the swing frequency of the passive swinging part and its output power, overcoming the problems of slow swimming speed, insufficient output force and low output power of traditional soft robot fish.

The rope-driven tensioning mechanism is composed of the motor unit 1, the coupling unit 27, the commutator device, the symmetrical tensioning unit and the fixing device; the motor unit 1 and the commutator are connected through the coupling unit 27, and the output torque is transmitted to the symmetrical tensioning unit through the commutator device. The symmetrical tensioning unit is fixed by the fixing device and tensions the driving rope to drive the flexible swinging part to swing.

Furthermore, the commutator unit is composed of a commutator housing unit 21, a bevel gear set 23 and an input-output shaft unit 26. The motor unit 1 is input through the input shaft of the coupling 27, and the input torque is commutated to the input shaft 26 through the bevel gear set 23. The input shaft 26 has an interference fit with the cylindrical gear 29, that is, the cylindrical gear unit 29 rotates.

Furthermore, the cylindrical gear unit 29 meshes with the two boss gears 28 of the symmetrical tensioning unit, and the two boss gears 28 rotate coaxially with the coaxially fixed winding drum 11, and the winding drum 11 drives the wire fixing member 10 meshed therewith to rotate.

Furthermore, the fixed shell 8 of the fixing device is connected to the commutator shell body 21 by bolts, and at the same time, the fixed shell 8 and the commutator shell 21 interfere with each other left and right; the upper and lower clamping plates 9 of the fixing frame unit fix the symmetrical tensioning unit, and the sub-fixing plate clamps the symmetrical tensioning unit and the fixed shell 8, and is bolted to the fixed shell 8 through the sub-fixing shell.

The embodiment of the present invention optimizes the rope-driven tensioning mechanism, and adopts a tensioning system composed of a motor combined with a commutator and a gear box, so as to realize a highly integrated mechanism design under extremely limited volume and space. The mechanism can have three modes when working. One is that the motor continuously rotates in one direction, and the two gear winding mechanisms continuously and symmetrically extend and contract with each other, and the phase difference ψ is approximately π; the other is that the motor reciprocates from 0° to a certain clockwise angle (less than 360°), that is, the reciprocating motion of one side stretching and the other side contracting realizes two modes of left turn and right turn. The DC motor of the tensioning mechanism is connected to the input shaft of the right-angle steering gear through a coupling, and a gear is connected to the output shaft of the steering gear, which is respectively meshed with the boss gears on the left and right sides. The boss gears on the left and right sides drive the coaxial fixed wire member to rotate to tension the drive rope, thereby driving the joint piece to realize the bending of the active part of the flexible swing part, and the active part drives the passive part, thereby realizing the symmetrical, asymmetrical and high-frequency swing of the entire swing part. When the motor continues to rotate, unlike the single servo design used in most current rope-driven robot fish, the DC motor with gears rotating the pull wire can make the commutation of rope-driven tensioning smoother, and the driven swinging part can show a higher driving frequency and a waveform that is more consistent with the sinusoidal output wave, overcoming the inherent problems of rigid robot fish with stiff swinging posture, low continuity and poor flexibility.

Furthermore, based on the CPG (Central Pattern Generator) bionic control method, the equilibrium state and stability analysis of the CPG model using the Hoof oscillator (Harmonically Oscillating Overdrive Function oscillator, an oscillator that can generate rich harmonics and has an overload function) are carried out; the CPG model with a ring topology structure is combined with the kinematic model to add an offset to build a COG (Center of Gravity) control model for the designed robot fish; finally, the PWM (Pulse Width Modulation) wave converted into different duty cycles is used to control the motor signal to complete the swing control of the robot fish; as the motor 1 changes at different speeds, angles, frequencies, etc., the flexible swinging part of the robot fish also performs different swinging postures accordingly; macroscopically, different motion modes of the robot fish such as turning left, turning right, and swimming straight are presented.

After adding coupling terms p ( x , y ) and q ( x , y ) to the CPG oscillator, a control network can be formed, which can then enable the bionic fish to produce different swimming patterns. After adding the coupling terms, the oscillator is shown as follows:

Adopting the adjacent bidirectional coupling, the coupling terms are generated by the coupling and rotation matrix method:

in is the coupling matrix, is the rotation matrix.

According to the above two equations, the following coupling terms can be obtained:

_Where , xi and yi represent the x -direction and y -direction state variables of the ith oscillator, respectively. hi _,j represents the coupling weight coefficient between the ith and i -1th _CPG oscillators. According to the analysis in 4.1.3, the coefficient of hi _,j affects the convergence speed of the oscillator. _i,j represents the phase difference between the i- th CPG oscillator and the j -th CPG oscillator.

Taking yi as the output signal of the CPG model and adding a bias term to it, the CPG model of the bionic fish is finally constructed _as follows:

The above content is a further detailed description of the present invention in combination with specific/preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims (10)

1. A rigid-flexible coupling robotic fish based on a rope-driven tensioning structure, characterized in that it includes a rigid head, a flexible swinging part, and a rope-driven tensioning mechanism: The rigid head comprises an upper rigid shell and a lower rigid shell which cooperate to form a closed space, and the rope-driven tensioning mechanism is installed inside; the rope-driven tensioning mechanism acts on the flexible swinging part with a driving rope, and causes the flexible swinging part to swing by tensioning the driving rope; The flexible swinging part includes a rigid skeleton, a front center piece, a rear center piece and a flexible skin, wherein the flexible skin is divided into a front hollow part and a rear solid part, the rigid skeleton and the front center piece are arranged in the front hollow part, the rigid skeleton includes a plurality of skeleton units connected to the front center piece, the plurality of skeleton units open the front hollow part of the flexible skin to form a fishtail-shaped active swinging part, the skeleton unit located at the rear is connected to the rear center piece, the rear center piece is interference-fitted with the hollow groove of the rear solid part, and is connected to the tail fin of the robot fish to form a passive swinging part; each skeleton unit is provided with a rope threading hole for the driving rope to be tensioned, the front center piece is made of flexible material, and when the driving rope is tensioned, it drives each skeleton unit and the front center piece to bend symmetrically and asymmetrically, so as to realize symmetrical and asymmetrical swinging of the active swinging part, and the rear center piece swings in a cantilever beam mode on the relatively static skeleton unit, thereby improving the swing frequency and output power of the passive swinging part. 2. The rigid-flexible coupled robotic fish based on a rope-driven tensioning structure as described in claim 1 is characterized in that it also includes a TPU clamping plate arranged between the upper rigid shell and the lower rigid shell; the upper rigid shell and the lower rigid shell are connected by bolts and clamped with the TPU clamping plate. 3. The rigid-flexible coupling robot fish based on a rope-driven tensioning structure as described in claim 1 is characterized in that the multiple skeleton units are first to fourth rigid skeleton units in sheet form, the first to fourth rigid skeleton units are provided with two rope threading holes on the axial side, the driving rope is terminated at the fourth rigid skeleton unit at the rear, and the first, second and third rigid skeleton units at the front have two through holes on the side, which are connected to the front center sheet through a connecting piece; the fourth rigid skeleton unit has four through holes on the side, the two through holes in the front row are connected to the front center sheet through a connecting piece, and the two through holes in the rear row are connected to the rear center sheet through a connecting piece. 4. The rigid-flexible coupled robotic fish based on a rope-driven tensioning structure according to any one of claims 1 to 3 is characterized in that the rope-driven tensioning mechanism includes a driving motor, a reversing unit and a symmetrical tensioning unit, the driving motor is coupled to the symmetrical tensioning unit through the reversing unit, the reversing unit is used to reverse the motor torque, thereby regulating the motion mode, the symmetrical tensioning unit is composed of two symmetrically distributed winding units, and the two winding units respectively tension two driving ropes, the winding unit includes a boss gear, a winding drum and a wire fixing component, the boss gear rotates coaxially with the winding drum, the winding drum is connected to the wire fixing component, drives the wire fixing component to rotate, and the wire fixing component is used to clamp the driving rope. 5. The rigid-flexible coupling robotic fish based on a rope-driven tensioning structure as described in claim 4 is characterized in that the commutation unit includes a commutator unit, an input shaft unit, an output shaft unit and at least one pair of mutually meshing bevel gear units, the input shaft unit and the output shaft unit are respectively coupled to the drive motor and the symmetrical tensioning unit, and the bevel gear unit realizes the right-angle commutation of the motor output torque to the symmetrical tensioning unit; the commutator unit includes a commutator housing, and at least two deep groove ball bearing units are arranged outside the commutator housing, and the deep groove ball bearing units are used to support the rotation of the input shaft unit and the output shaft unit; the input shaft unit and the output shaft unit are respectively provided with a clamping groove, each of which is matched with a clamping spring, and the upper side of the clamping spring is in contact with the commutator housing, and the positioning of the output shaft and the input shaft unit and the commutator housing is realized by the meshing of the bevel gears and the interference of the clamping spring; the commutation unit is connected to the drive motor through a coupling to realize the power transmission of the motor. 6. The rigid-flexible coupling robot fish based on a rope-driven tensioning structure as described in claim 4 is characterized in that a through hole of equal aperture is opened between the boss gear and the winding drum, which is interference fit with the mother screw of the mother screw; the boss gear is coaxial with the winding drum; after the sub-screw of the mother screw cooperates with the mother screw on the lower side of the winding drum, the winding drum is limited; the boss gear is meshed with the matching gear on the output shaft of the commutator unit, and the matching gear on the output shaft is interference fit with the output shaft to drive the boss gear and the winding drum to rotate. 7. The rigid-flexible coupled robotic fish based on a rope-driven tensioning structure as described in claim 4 is characterized in that the rope-driven tensioning mechanism also includes a fixed frame unit, and the fixed frame unit envelopes the symmetrical tensioning unit; the fixed frame unit includes an upper clamping plate, a lower clamping plate, a fixed shell, a sub-fixing plate and a sub-fixing shell; the boss gear is clamped between the upper clamping plate and the lower clamping plate, and the sub-fixing shell is connected and clamps the symmetrical tensioning unit through a stud; the sub-fixing plate is connected to the sub-fixing shell through bolts and connects the sub-fixing shell to the fixed shell; the fixed shell is connected to the commutator housing of the commutator unit through bolts. 8. The rigid-flexible coupling robotic fish based on a rope-driven tensioning structure according to any one of claims 4 to 7 is characterized in that a motor fixing frame is also provided in the enclosed space of the rigid head, the driving motor is connected to the motor fixing frame by bolts, and the motor fixing frame is connected to the lower rigid shell. 9. The rigid-flexible coupling robotic fish based on a rope-driven tension structure according to any one of claims 1 to 3, characterized in that the rigid head adopts nonlinear coupling of elliptic curves and parabolas to perform parameterized design of a streamlined shell, following the following functional equation: ; Among them, D is the maximum diameter of the cross section; Lc is the length of the front half of the head; _Lr is the length of the back half _of the fish body. 10. The rigid-flexible coupling robotic fish based on a rope-driven tensioning structure according to claim 9, characterized in that D is 75 mm, L _c is 118.5 mm, and L _r is 185 mm.