Self-adaptive variable-stiffness flexible tail handle based on non-Newtonian fluid and robotic fish with self-adaptive variable-stiffness flexible tail handle

Abstract

The invention belongs to the field of underwater bionic robots, and particularly relates to a self-adaptive variable-rigidity flexible tail handle based on non-Newtonian fluid and a robotic fish with the structure. According to the self-adaptive variable-rigidity flexible tail handle, the rigidity can be automatically adjusted according to the swing frequency of the body of the robotic fish, so that the tail handle completes self-adaptive rigidity adjustment on the driving frequency, that is, the higher the frequency is, the harder the tail handle is, and the adaptive capacity of the bionic robotic fish in different scenes can be further improved. The invention further provides a robotic fish with the self-adaptive variable-rigidity flexible tail handle based on the non-Newtonian fluid, a flexible joint is adopted for the fish tail, a four-cylinder plunger pump is adopted for providing pressure, a pressure regulating valve and an electromagnetic reversing valve are omitted, the fish tail is of a rigid-flexible coupling structure, the two ends of a driving unit are fixed to a connecting body, and the driving unit is connected with the connecting body. An oil conveying pipe and a flexible sensor are further arranged in the fishtail, pectoral fins can rotate, a hydraulic loop is internal circulation, the requirement for cost reduction is met, and underwater swing can be smoother.

Description

Technical Field

[0001] The invention belongs to the field of underwater bionic robots, and in particular relates to an adaptive variable-rigidity flexible tail stalk based on non-Newtonian fluid and a robot fish with the structure. Background Art

[0002] Compared with traditional propeller-driven underwater vehicles, bionic robotic fish propel themselves through tail swinging, which has a series of advantages such as high efficiency, strong flexibility, and good environmental adaptability. Therefore, they have been greatly developed in the past three decades. According to biological research, in addition to the unique propulsion mechanism, another reason why fish can maintain such excellent athletic ability is the ability to adjust the stiffness of the caudal peduncle. The caudal peduncle is a key position on the body of fish, connecting the swinging body and the caudal fin that can amplify the output force. The caudal peduncle tendon is connected to the muscles on the body on one side and to the fin line on the caudal fin on the other side. Through experiments and simulations, biologists have found that fish can use the antagonistic effect of the caudal peduncle tendon to adjust the stiffness of the caudal peduncle, thereby adjusting the phase difference of movement from the body to the caudal fin and generating the optimal backward fish body wave. The stiffness of the caudal peduncle of fish matches the swinging frequency. As the frequency increases, the caudal peduncle gradually hardens to suppress the excessive water striking angle of the caudal fin and avoid dynamic stall.

[0003] In recent years, some robot fish have added a variable stiffness tail stalk design to the fuselage according to the principle of bionics, but it is usually in the form of active adjustment, requiring additional motors and stiffness conversion mechanisms, which will not only increase energy consumption, but also increase the complexity, weight and failure rate of the overall structure. The technical solutions similar to the present invention are a flexible bionic robot fish with variable stiffness regulated by air pressure disclosed in patent number CN105292425A and a bionic robot fish with variable stiffness based on a hydraulically driven multi-channel fluid structure disclosed in CN109515668A. Although the technical solutions disclosed in the two patents are different in specific forms, both achieve variable stiffness adjustment of the robot fish by actively changing the internal pressure of the flexible channel. Summary of the invention

[0004] The purpose of the present invention is to provide an adaptive variable-stiffness flexible tail stalk based on non-Newtonian fluid, which can automatically adjust the stiffness according to the swinging frequency of the robot fish body, that is, the faster the frequency, the harder the tail stalk becomes, which can further improve the adaptability of the bionic robot fish in different scenarios.

[0005] A self-adaptive variable-rigidity flexible tail stalk based on non-Newtonian fluid comprises a tail stalk flexible matrix, a plurality of symmetrical cavities are provided inside the tail stalk flexible matrix, and a shear-thickening non-Newtonian fluid is filled in the symmetrical cavities; the symmetrical cavities comprise a left cavity and a right cavity, and the left cavity and the right cavity are connected by a narrow cavity channel.

[0006] Furthermore, when the adaptive variable stiffness flexible tail stalk bends to the left, the left cavity squeezes the internal shear-thickening non-Newtonian fluid into the right cavity; when the adaptive variable stiffness flexible tail stalk of the robotic fish bends to the right, the right cavity squeezes the internal shear-thickening non-Newtonian fluid into the left cavity;

[0007] While the robot fish is swimming, the adaptive variable stiffness flexible tail stalk bends left and right continuously as the robot fish swings, and the shear-thickening non-Newtonian fluid inside the left cavity and the right cavity is continuously exchanged; the higher the swinging frequency, the greater the viscosity of the shear-thickening non-Newtonian fluid, making the macroscopic stiffness of the adaptive variable stiffness flexible tail stalk stronger, thereby realizing the adaptive variable stiffness flexible tail stalk's adaptive adjustment of the stiffness of the swinging frequency.

[0008] The present invention also provides a robotic fish with the above-mentioned adaptive variable stiffness flexible caudal stalk based on non-Newtonian fluid, comprising a fish head and a fish tail; the fish tail comprises a large connector, a middle connector, a small connector, a flexible joint I, a flexible joint II, an adaptive variable stiffness flexible caudal stalk and a caudal fin;

[0009] The large connector is connected to the fish head, the large connector is connected to the middle connector via a flexible joint I, the middle connector is connected to the small connector via a flexible joint II, and the small connector is connected to the tail fin via an adaptive variable stiffness flexible tail stalk;

[0010] A driving assembly is provided inside the fish head; the flexible joint I and the flexible joint II both include a flexible matrix and a driving unit located inside the flexible matrix; the driving units are respectively arranged on the left and right sides of the mid-axis surface of the flexible joint and arranged along the axial direction of the fish body;

[0011] When the driving medium is pumped into the driving unit, the driving unit contracts axially, and when the driving medium is sucked out of the driving unit, the driving unit expands radially; the driving medium is pumped into the driving unit on one side of the axial surface of the flexible joint through the driving component, and the driving medium is sucked out from the driving unit on the other side of the axial surface of the flexible joint, so that the flexible joint as a whole deflects toward the side where the driving medium is pumped; the driving medium is alternately pumped in from one side and sucked out from the other side, thereby driving the flexible joint to swing.

[0012] Further, the front side of the large connector is provided with four groups of hydraulic cylinder oil delivery port interfaces, and the rear side is provided with a large connector left drive unit oil delivery port, a large connector right drive unit oil delivery port and two groups of large connector oil delivery ports. All large connector left drive unit oil delivery ports are connected to one group of hydraulic cylinder oil delivery port interfaces through pipelines inside the large connector, and all large connector right drive unit oil delivery ports are connected to another group of hydraulic cylinder oil delivery port interfaces through pipelines inside the large connector. The other two groups of hydraulic cylinder oil delivery port interfaces are respectively connected to the two groups of large connector oil delivery ports through pipelines inside the large connector.

[0013] The front side of the middle connector is provided with a middle connector drive unit joint and two groups of middle connector oil delivery ports, and the rear side of the middle connector is provided with a middle connector left drive unit oil delivery port and a middle connector right drive unit oil delivery port, one group of middle connector oil delivery ports is connected to the middle connector left drive unit oil delivery port through a pipeline inside the middle connector, and the other group of connector oil delivery ports is connected to the middle connector right drive unit oil delivery port through a pipeline inside the middle connector;

[0014] A small connector driving unit joint is arranged on the front side of the small connector, and the rear side of the small connector is connected to the tail fin.

[0015] Furthermore, the flexible matrix of the flexible joint I is provided with a mid-axis left side joint I driving unit group, a mid-axis right side joint I driving unit group and two groups of oil pipelines; the flexible matrix of the flexible joint II is provided with a mid-axis left side joint II driving unit group and a mid-axis right side joint II driving unit group;

[0016] In the said drive unit group of the left side joint I of the central axis surface, the front end of the drive unit is connected to the oil delivery port of the left side drive unit of the large connector, and the rear end is connected to the joint of the drive unit of the middle connector; in the said drive unit group of the right side joint I of the central axis surface, the front end of the drive unit is connected to the oil delivery port of the right side drive unit of the large connector, and the rear end is connected to the joint of the drive unit of the middle connector; the front end of the said oil delivery pipe is connected to the oil delivery port of the large connector, and the rear end is connected to the oil delivery port of the middle connector;

[0017] In the left side joint II drive unit group of the central axis surface, the front end of the drive unit is connected to the oil delivery port of the left side drive unit of the central connector, and the rear end is connected to the joint of the small connector drive unit; in the right side joint II drive unit group of the central axis surface, the front end of the drive unit is connected to the oil delivery port of the right side drive unit of the central connector, and the rear end is connected to the joint of the small connector drive unit.

[0018] Furthermore, the number of oil delivery ports of the left drive unit of the large connector matches the number of drive units in the drive unit group of the left joint I of the mid-axis surface, the number of oil delivery ports of the right drive unit of the large connector matches the number of drive units in the drive unit group of the right joint I of the mid-axis surface, the number of drive unit joints of the middle connector matches the number of drive units in the flexible joint I, the number of oil delivery ports of the left drive unit of the middle connector matches the number of drive units in the drive unit group of the left joint II of the mid-axis surface, the number of oil delivery ports of the right drive unit of the middle connector matches the number of drive units in the drive unit group of the right joint II of the mid-axis surface, and the number of drive unit joints of the small connector matches the number of drive units in the flexible joint II.

[0019] Furthermore, the driving assembly includes a four-cylinder plunger pump having four groups of oil delivery ports, and the four groups of hydraulic cylinder oil delivery port interfaces on the front side of the large connector are correspondingly connected to the four groups of oil delivery ports of the four-cylinder plunger pump.

[0020] Furthermore, the four-cylinder plunger pump includes a hydraulic cylinder body; the hydraulic cylinder body is a four-cylinder structure, including two pairs of upper and lower cylinder bodies, each of which is equipped with a piston; the hydraulic cylinder body is provided with servo fixing plates on the upper and lower sides, each of which is equipped with a pair of plunger pump servos, and the output shaft of each plunger pump servo is connected to the piston in a group of cylinder bodies in the hydraulic cylinder body through a crank slider mechanism, and the rotational motion of the plunger pump servo output shaft is converted into reciprocating motion of the piston inside the cylinder body through the crank slider mechanism.

[0021] Furthermore, a dorsal fin is provided on the top surface of the fish head, and pectoral fins are provided on the left and right sides of the fish head; the driving assembly includes a pectoral fin assembly; the pectoral fin assembly includes a pectoral fin bracket, and pectoral fin servo gear units are connected to the two sides of the pectoral fin bracket, and the output shaft of the pectoral fin servo gear unit is connected to the pectoral fin unit through a connecting shaft group. During the operation of the robot fish, the angle of the pectoral fins on the left and right sides of the fish head is adjusted to enable the robot fish to float up and dive down.

[0022] Furthermore, a flexible sensor is provided on the central axis of the flexible matrix of flexible joint I and the flexible matrix of flexible joint II, which is used to detect the swing angles of flexible joint I and flexible joint II; an antenna is installed on the top surface of the fish head, a fish head support frame is provided inside the fish head, a partition with a grid is provided on the fish head support frame, a large PCB board and a small PCB board are installed above the partition, and a battery pack is installed below the partition; a voltage stabilizing module and a current sensor module are provided on the large PCB board, and a control single-chip computer and a signal transmitter are provided on the small PCB board.

[0023] The beneficial effects of the present invention are:

[0024] The adaptive variable stiffness flexible tail stalk provided by the present invention can automatically adjust the stiffness according to the swing frequency of the robot fish body, so that the tail stalk completes the adaptive stiffness adjustment of the driving frequency, that is, the faster the frequency, the harder the tail stalk becomes, which can further improve the adaptability of the bionic robot fish in different scenarios. The present invention also provides a robot fish with an adaptive variable stiffness flexible tail stalk based on a non-Newtonian fluid, the fish tail adopts a flexible joint, the flexible joint includes a flexible matrix and a driving unit located inside the flexible matrix, the driving unit is respectively arranged on the left and right sides of the axial plane of the flexible joint and arranged along the axial direction of the fish body, and the driving medium is alternately pumped in from one side and sucked out from the other side to drive the fish tail to produce a swinging motion. The present invention adopts a four-cylinder plunger pump to provide pressure, eliminating the pressure regulating valve and the electromagnetic reversing valve, the fish tail is a rigid-flexible coupling structure, the two ends of the driving unit are fixed to the connector, and an oil pipeline and a flexible sensor are also provided inside the fish tail, the pectoral fin can rotate, and the hydraulic circuit is an internal circulation, which not only achieves the requirement of reducing costs, but also can achieve a smoother underwater swing. The present invention can effectively overcome the limitations of existing hydraulic flexible robotic fish such as low energy density, low frequency response and slow speed, and has broad application prospects in the fields of underwater exploration, underwater rescue and so on. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the overall structure of a robotic fish with an adaptive variable-stiffness flexible caudal stalk based on non-Newtonian fluid.

[0026] Figure 2 This is an exploded view of the fish head.

[0027] Figure 3 An exploded view of the drive assembly.

[0028] Figure 4 This is the working principle diagram of the four-cylinder plunger pump.

[0029] Figure 5 This is an exploded view of the fishtail part.

[0030] Figure 6 It is the axonometric view of the large connector, the middle connector and the small connector.

[0031] Figure 7 This is the deformation principle diagram of the fishtail.

[0032] Figure 8 This is the working principle diagram of the adaptive variable stiffness flexible tail handle.

[0033] The above drawings include the following reference numerals:

[0034] 1. Fish head; 2. Fish tail; 3. Adaptive variable stiffness flexible tail handle;

[0035] 1-1, upper cover; 1-2, switch group; 1-3, antenna; 1-4, charging interface; 1-5, control microcontroller; 1-6, signal transmitter; 1-7, small PCB board; 1-8, voltage regulator module; 1-9, large PCB board; 1-10, current sensor module; 1-11, fish head support frame; 1-12, battery assembly; 1-13, battery package assembly; 1-14, lower cover; 1-15, drive assembly; 1-15-1, pectoral fin assembly; 1-15-1-1, pectoral fin; 1-15-1-2, connection Shaft assembly; 1-15-1-3, pectoral fin steering gear assembly; 1-15-1-4, pectoral fin bracket; 1-15-2, four-cylinder plunger pump; 1-15-2-1, plunger pump steering gear; 1-15-2-2, steering gear fixing plate; 1-15-2-3, rudder arm; 1-15-2-4, thin pin; 1-15-2-5, connecting rod; 1-15-2-6, thick pin; 1-15-2-7, piston; 1-15-2-8, hydraulic cylinder body; 1-15-2-9, longitudinal counterweight group; 1-15-2-10 transverse counterweight group;

[0036] 2-1, large connector; 2-1-1, hydraulic cylinder oil port interface; 2-1-2, large connector sensor slot; 2-1-3, large connector oil port; 2-1-4, large connector drive unit oil port; 2-2, joint I flexible matrix; 2-3, joint I drive unit group on the right side of the central axis; 2-4, joint I flexible sensor; 2-5, oil pipe; 2-6, joint I drive unit group on the left side of the central axis; 2-7, middle connector; 2-7-1, middle connector drive unit connector; 2-7-2, Middle connector sensor slot; 2-7-3, middle connector oil delivery port; 2-7-4, middle connector drive unit oil delivery port; 2-8, joint II flexible matrix; 2-9, joint II drive unit group on the right side of the central axis; 2-10, joint II flexible sensor; 2-11, joint II drive unit group on the left side of the central axis; 2-12, small connector; 2-12-1, small connector drive connector; 2-12-2, small connector slot; 2-13, tail fin; 2-A, flexible joint I; 2-B, flexible joint II;

[0037] 3-1, flexible matrix of caudal peduncle; 3-2, left cavity; 3-3, right cavity. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings.

[0039] The present invention provides an adaptive variable stiffness flexible tail stalk based on non-Newtonian fluid, which can not only automatically adjust the stiffness according to the swinging frequency of the robot fish body, but also has the advantages of strong integrity, simple and reliable structure and easy manufacturing. Its innovation lies mainly in combining the rheological properties of non-Newtonian fluid with the design of flexible matrix cavity, which can enable the tail stalk to complete the adaptive stiffness adjustment of the driving frequency, that is, the faster the frequency, the harder the tail stalk becomes, which can further improve the adaptability of bionic robot fish in different scenarios. The adaptive variable stiffness flexible tail stalk of the present invention is a passive form, and the fluid used inside is a non-Newtonian fluid with specific rheological properties.

[0040] A self-adaptive variable-rigidity flexible tail stalk based on non-Newtonian fluid includes a tail stalk flexible matrix 3-1, multiple groups of symmetrical cavities are opened inside the tail stalk flexible matrix, and the symmetrical cavities are filled with shear-thickening non-Newtonian fluid; the symmetrical cavities include a left cavity 3-2 and a right cavity 3-3, and the left cavity 3-2 and the right cavity 3-3 are connected through a narrow cavity channel 3-4.

[0041] like Figure 8The figure shows the working principle of the adaptive variable stiffness flexible tail stalk. When the adaptive variable stiffness flexible tail stalk bends to the left, the left cavity 3-3 squeezes the shear-thickening non-Newtonian fluid inside into the right cavity 3-2; when the adaptive variable stiffness flexible tail stalk of the robotic fish bends to the right, the right cavity 3-2 squeezes the shear-thickening non-Newtonian fluid inside into the left cavity 3-3;

[0042] When the robot fish swims, the adaptive variable stiffness flexible tail stalk bends left and right continuously as the robot fish swings, and the shear-thickening non-Newtonian fluid inside the left cavity 3-3 and the right cavity 3-3 are continuously exchanged; the higher the swinging frequency, the greater the viscosity of the shear-thickening non-Newtonian fluid, making the macroscopic stiffness of the adaptive variable stiffness flexible tail stalk stronger, thereby realizing the adaptive variable stiffness flexible tail stalk's adaptive adjustment of the swinging frequency.

[0043] The present invention also provides a robot fish with an adaptive variable stiffness flexible tail stalk based on non-Newtonian fluid, including a fish head and a fish tail, wherein the fish tail includes three connectors of large, medium and small sizes and a tail fin, and a flexible joint is provided between two adjacent connectors, and each flexible joint has a drive unit group arranged in pairs along the axial direction of the fish body, and a flexible sensor is provided on the neutral layer of the joint to provide real-time feedback of the driver angle, and the entire joint is wrapped by a flexible matrix. A four-cylinder plunger pump alternately pumps the drive medium into or out of the paired drive unit groups, and the drive unit groups will contract when subjected to pressure, thereby driving the joints to bend, and further causing the fish tail to swing. The present invention can effectively break through the limitations of existing hydraulic flexible robot fish such as low energy density, low frequency response and slow speed, and has broad application prospects in the fields of underwater exploration and underwater rescue.

[0044] like Figure 1 As shown, a robotic fish with an adaptive variable stiffness flexible tail stalk based on a non-Newtonian fluid mainly includes a fish head 1, a fish tail 2, and an adaptive variable stiffness flexible tail stalk 3. The exploded view of the fish head 1 is shown in FIG. Figure 2 As shown, the upper cover 1-1 and the lower cover 1-14 are respectively installed at the upper and lower openings of the fish head support frame 1-11. Four mounting holes are reserved at the top of the upper cover 1-1, the switch group 1-2 is installed in the two front mounting holes, and the antenna 1-3 and the charging interface 1-4 are respectively installed in the two rear mounting holes.

[0045] There is a gridded partition in the middle of the fish head support frame 1-11, and a large PCB board 1-9 and a small PCB board 1-7 are installed above the partition. The voltage regulator module 1-8 and the current sensor module 1-10 are welded on the large PCB board 1-9, and the control microcontroller 1-5 and the signal transmitter 1-6 are welded on the small PCB board 1-7. A battery pack 1-12 and a battery wrapping weight group 1-13 are installed below the partition of the fish head support frame 1-11. The end of the battery wrapping weight group 1-13 is connected to the partition of the fish head support frame 1-11, and the battery pack 1-12 is wrapped inside. A drive component 1-15 is connected to the rear side of the partition of the fish head support frame 1-11.

[0046] The exploded view of the drive assembly 1-15 is shown in FIG. Figure 3 As shown, the drive assembly 1-15 includes two parts: a pectoral fin assembly 1-15-1 and a four-cylinder plunger pump 1-15-2.

[0047] The pectoral fin assembly 1-15-1 mainly includes a pectoral fin bracket 1-15-1-4, and pectoral fin servo assemblies 1-15-1-3 are connected to both sides of the pectoral fin bracket. The output shaft of the pectoral fin servo assembly drives the pectoral fin 1-15-1-1 through the connecting shaft assembly 1-15-1-2. During the operation of the robot fish, the angle of the driving pectoral fin 1-15-1-1 can be adjusted to make the robot fish float up and dive down.

[0048] The four-cylinder plunger pump 1-15-2 mainly includes a hydraulic cylinder body 1-15-2-8, which is a four-cylinder structure with two pairs of cylinder bodies, each of which is equipped with a piston 1-15-2-7. The hydraulic cylinder body 1-15-2-8 is connected to steering gear fixing plates 1-15-2-2 at the top and bottom, respectively. Each steering gear fixing plate 1-15-2-2 fixes a pair of plunger pump steering gears 1-15-2-1, and the lower steering gear fixing plate 1-15-2-2 is connected to the longitudinal counterweight group 1-15-2-9 and the transverse counterweight group 1-15-2-10. The output shaft of each plunger pump servo 1-15-2-1 is connected to the rudder arm 1-15-2-3, the rudder arm 1-15-2-3 is hinged to the connecting rod 1-15-2-5 through the fine pin 1-15-2-4, and the connecting rod 1-15-2-5 is hinged to the piston 1-15-2-7 through the thick pin 1-15-2-6. Therefore, the servo and the rudder arm 1-15-2-3, the hinged connecting rod 1-15-2-5 and the piston 1-15-2-7 together constitute a "crank-slider" motion, and the output shaft of the plunger pump servo 1-15-2-1 rotates to drive the piston to reciprocate inside the cylinder.

[0049] The four-cylinder plunger pump 1-15-2 is divided into two groups of upper and lower plunger pumps. Taking one of the groups of plunger pumps as an example, the working principle of the four-cylinder plunger pump 1-15-2 is introduced. The cross-sectional view AA of the upper plunger pump group is as follows: Figure 4As shown, in state AA-1, the output shaft of the upper servo rotates counterclockwise to drive the piston 1-15-2-6 to slide outward, and the driving medium is sucked from the oil delivery port 1-15-2-8-1. At the same time, the output shaft of the lower servo drives the piston 1-15-2-6 to slide inward counterclockwise to pump the driving medium out of the oil delivery port 1-15-2-8-1. Then the state is switched to AA-2, the output shaft of the upper servo rotates clockwise to drive the piston 1-15-2-6 to slide inward and outward, and the driving medium is pumped out of the oil delivery port 1-15-2-8-1. At the same time, the output shaft of the lower servo drives the piston 1-15-2-6 to slide outward clockwise to suck the driving medium from the oil delivery port 1-15-2-8-1. During the working process of the bionic robot fish, the two states are constantly switched.

[0050] The top view of fishtail 2 is as follows Figure 5 As shown, the symmetry plane of the fishtail 2 is defined as the medial axis plane, and the fishtail 2 includes flexible joint I (2-A) and joint II (2-B). The fishtail 2 mainly includes a large connector 2-1, a middle connector 2-7 and a small connector 2-12, and its axonometric view is shown in FIG. Figure 6 As shown, the large connector 2-1 is connected to the fish head support frame 1-11, and the four hydraulic cylinder oil delivery ports 2-1-1 on the front side are correspondingly connected to the four oil delivery ports 1-15-2-8-1 of the hydraulic cylinder body 1-15-2-8. The hydraulic cylinder oil delivery port interface 2-1-1 on the upper left side of the middle axis is connected to the five large connector drive unit oil delivery ports 2-1-4 on the left side of the middle axis, and the hydraulic cylinder oil delivery port interface 2-1-1 on the upper right side of the middle axis is connected to the five large connector drive unit oil delivery ports 2-1-4 on the right side of the middle axis. The five large connector drive unit oil delivery ports 2-1-4 on the left side of the middle axis are correspondingly connected to the joint I drive unit group 2-6 on the left side of the middle axis, and the five large connector drive unit oil delivery ports 2-1-4 on the right side of the middle axis are correspondingly connected to the joint I drive unit group 2-3 on the right side of the middle axis. The oil delivery port interface 2-1-1 at the lower left of the central axis is connected to the upper large connector oil delivery port 2-1-3, and the oil delivery port interface 2-1-1 at the lower right of the central axis is connected to the lower large connector oil delivery port 2-1-3. The two large connector oil delivery ports 2-1-3 are correspondingly connected to two oil delivery pipes 2-5. The joint I flexible sensor 2-4 is located in the neutral layer, and the front end is embedded in the large connector sensor slot 2-1-2.

[0051] The five middle connector drive unit joints 2-7-1 on the left side of the middle axis are connected to the middle axis joint I drive unit group 2-6 on the left side, and the five middle connector drive unit joints 2-7-1 on the right side of the middle axis are connected to the middle axis joint I drive unit group 2-3 on the right side. Two oil delivery pipes 2-5 are connected to the two middle connector oil delivery ports 2-7-3, wherein the upper middle connector oil delivery port 2-7-3 is connected to the middle connector drive unit oil delivery port 2-7-4 on the left side of the middle axis, and the lower middle connector oil delivery port 2-7-3 is connected to the middle connector drive unit oil delivery port 2-7-4 on the right side of the middle axis. The three middle connector drive unit oil delivery ports 2-7-4 on the left side of the middle axis are connected to the joint II drive unit group 2-11 on the left side of the middle axis, and the three middle connector drive unit oil delivery ports 2-7-4 on the right side of the middle axis are connected to the joint II drive unit group 2-9 on the right side of the middle axis. The rear end of the joint I flexible sensor 2-4 is embedded in the middle connector sensor slot 2-7-2, and the front end of the joint II flexible sensor 2-10 is embedded in the middle connector sensor slot 2-7-2. The left joint I drive unit group 2-6, the right joint I drive unit group 2-3, the oil delivery pipe 2-5 and the joint I flexible sensor 2-4 are all wrapped and fixed by the joint I flexible matrix 2-2.

[0052] The small connector driver joint 2-12-1 on the left side of the three central axis planes is connected to the joint II driver unit group 2-11 on the left side of the central axis plane, and the small connector driver joint 2-12-1 on the right side of the three central axis planes is connected to the joint II driver unit group 2-9 on the right side of the central axis plane. The rear end 2-10 of the joint II flexible driver is embedded in the small connector slot 2-12-2, and the rear side of the small connector is connected to the tail fin 2-13. The left joint II driver unit group 2-11, the right joint II driver unit group 2-9 and the joint II flexible sensor 2-10 are all wrapped and fixed by the joint II flexible matrix 2-8.

[0053] The working principle of Fishtail 2 is as follows Figure 7 As shown, the drive unit group 2-6 of the left side joint I of the middle axis, the drive unit group 2-3 of the right side joint I of the middle axis, the drive unit group 2-11 of the left side joint II of the middle axis and the drive unit group 2-9 of the right side joint II of the middle axis all adopt McKibben type drive units, which are cylindrical and will shrink axially and expand radially under the action of pressure. When the drive medium is pumped into the drive unit group 2-6 of the left side joint I of the middle axis by the four-cylinder plunger pump 1-15-2, the drive unit group 2-6 of the left side joint I of the middle axis shrinks, and at the same time, the drive medium in the drive unit group 2-3 of the right side joint I of the middle axis is sucked out by the four-cylinder plunger pump 1-15-2 to restore the original state, so the flexible joint I (2-A) deflects to the left side of the middle axis.

[0054] Similarly, when the driving medium is pumped into the joint II drive unit group 2-11 on the left side of the central axis by the four-cylinder plunger pump 1-15-2 through the oil pipe 2-5, the joint II drive unit group 2-11 on the left side of the central axis contracts, and at the same time, the driving medium in the joint II drive unit group 2-9 on the right side of the central axis is sucked out by the four-cylinder plunger pump 1-15-2 through the oil pipe 2-5 to restore the original state, so the flexible joint II (2-B) deflects to the left side of the central axis.

[0055] When the direction of the driving medium is reversed, the state of the fish tail 2 changes, and each joint deflects in the opposite direction. It should be noted that the movements of the flexible joint Ⅰ (2-A) and the flexible joint Ⅱ (2-B) are independent. During the swimming of the bionic fish, the driving medium is continuously sucked out and pumped in from the symmetrical drive group, thereby driving the fish tail 2 to swing continuously. By adjusting the rotation angle, commutation frequency and rotation phase difference of the plunger pump steering gear group 1-15-2-1, the swing amplitude, swing frequency and phase difference between the flexible joint Ⅰ (2-A) and the flexible joint Ⅱ (2-B) can be adjusted.

[0056] The present invention adopts a four-cylinder plunger pump to provide pressure, eliminating the pressure regulating valve and the electromagnetic reversing valve. The fish tail is a rigid-flexible coupling structure, and both ends of the driving unit are fixed to the connector. An oil pipeline and a flexible sensor are also provided inside the fish tail. The pectoral fins can rotate, and the hydraulic circuit is an internal circulation, which not only achieves the requirement of reducing costs, but also makes the underwater swing smoother.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An adaptive variable stiffness flexible tail handle based on non-Newtonian fluid, characterized by: The invention comprises a tail stalk flexible matrix (3-1), wherein a plurality of symmetrical cavities are provided inside the tail stalk flexible matrix, and a shear-thickening non-Newtonian fluid is filled in the symmetrical cavities; the symmetrical cavities comprise a left cavity (3-2) and a right cavity (3-3), and the left cavity (3-2) and the right cavity (3-3) are connected via a narrow cavity channel (3-4).

2. The adaptive variable stiffness flexible tail stalk of a robotic fish based on non-Newtonian fluid according to claim 1, characterized in that: When the adaptive variable stiffness flexible tail stalk bends to the left, the left cavity (3-3) squeezes the shear-thickening non-Newtonian fluid inside into the right cavity (3-2); when the adaptive variable stiffness flexible tail stalk of the robotic fish bends to the right, the right cavity (3-2) squeezes the shear-thickening non-Newtonian fluid inside into the left cavity (3-3); When the robot fish swims, the adaptive variable stiffness flexible tail stalk bends left and right continuously as the robot fish swings, and the shear-thickening non-Newtonian fluid inside the left cavity (3-3) and the right cavity (3-3) are continuously exchanged; the higher the swing frequency, the greater the viscosity of the shear-thickening non-Newtonian fluid, making the macroscopic stiffness of the adaptive variable stiffness flexible tail stalk stronger, thereby realizing the adaptive variable stiffness flexible tail stalk's stiffness adaptive adjustment to the swing frequency.

3. A robotic fish with the adaptive variable stiffness flexible caudal stalk based on non-Newtonian fluid as claimed in claim 1, characterized in that: It comprises a fish head (1) and a fish tail (2); the fish tail (2) comprises a large connector (2-1), a middle connector (2-7), a small connector (2-12), a flexible joint I (2-A), a flexible joint II (2-B), an adaptive variable stiffness flexible tail stalk (3) and a tail fin (2-13); The large connector (2-1) is connected to the fish head (1), the large connector (2-1) is connected to the middle connector (2-7) via a flexible joint I (2-A), the middle connector (2-7) is connected to the small connector (2-12) via a flexible joint II (2-B), and the small connector (2-12) is connected to the tail fin (2-13) via an adaptive variable stiffness flexible tail handle (3); A driving assembly (1-15) is provided inside the fish head (1); the flexible joint I (2-A) and the flexible joint II (2-B) both include a flexible matrix and a driving unit located inside the flexible matrix; the driving units are respectively arranged on the left and right sides of the mid-axis surface of the flexible joint and arranged along the axial direction of the fish body; When the driving medium is pumped into the driving unit, the driving unit contracts axially, and when the driving medium is sucked out of the driving unit, the driving unit expands radially; the driving medium is pumped into the driving unit on one side of the axial surface of the flexible joint through the driving component (1-15), and the driving medium is sucked out from the driving unit on the other side of the axial surface of the flexible joint, so that the flexible joint as a whole deflects toward the side where the driving medium is pumped; the driving medium is alternately pumped in from one side and sucked out from the other side, so as to drive the flexible joint to swing.

4. A robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 3, characterized in that: The large connector (2-1) is provided with four groups of hydraulic cylinder oil delivery port interfaces (2-1-1) on the front side, and with a large connector left drive unit oil delivery port, a large connector right drive unit oil delivery port (2-1-4) and two groups of large connector oil delivery ports (2-1-3) on the rear side; all large connector left drive unit oil delivery ports are connected to one group of hydraulic cylinder oil delivery port interfaces (2-1-1) through pipelines inside the large connector (2-1); all large connector right drive unit oil delivery ports (2-1-4) are connected to another group of hydraulic cylinder oil delivery port interfaces (2-1-1) through pipelines inside the large connector (2-1); and the other two groups of hydraulic cylinder oil delivery port interfaces (2-1-1) are respectively connected to the two groups of large connector oil delivery ports (2-1-3) through pipelines inside the large connector (2-1); The front side of the middle connector (2-7) is provided with a middle connector drive unit joint (2-7-1) and two groups of middle connector oil delivery ports (2-7-3); the rear side of the middle connector (2-7) is provided with a middle connector left drive unit oil delivery port and a middle connector right drive unit oil delivery port (2-7-4); one group of middle connector oil delivery ports (2-7-3) is connected to the middle connector left drive unit oil delivery port through a pipeline inside the middle connector (2-7); and the other group of connector oil delivery ports (2-7-3) is connected to the middle connector right drive unit oil delivery port (2-7-4) through a pipeline inside the middle connector (2-7); A small connector drive unit joint (2-12-1) is provided on the front side of the small connector (2-12), and the rear side of the small connector (2-12) is connected to the tail fin (2-13).

5. A robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 4, characterized in that: The flexible matrix (2-2) of the flexible joint I (2-A) is provided with a mid-axis left side joint I drive unit group (2-6), a mid-axis right side joint I drive unit group (2-3) and two groups of oil pipelines (2-5); the flexible matrix (2-8) of the flexible joint II (2-B) is provided with a mid-axis left side joint II drive unit group (2-11) and a mid-axis right side joint II drive unit group (2-9); In the said central axis surface left side joint I drive unit group (2-6), the front end of the drive unit is connected to the left side drive unit oil delivery port of the large connector, and the rear end is connected to the middle connector drive unit joint (2-7-1); in the said central axis surface right side joint I drive unit group (2-3), the front end of the drive unit is connected to the right side drive unit oil delivery port (2-1-4) of the large connector, and the rear end is connected to the middle connector drive unit joint (2-7-1); the front end of the said oil delivery pipe (2-5) is connected to the large connector oil delivery port (2-1-3), and the rear end is connected to the middle connector oil delivery port (2-7-3); In the middle axis surface left side joint II drive unit group (2-11), the front end of the drive unit is connected to the oil delivery port of the middle connector left side drive unit, and the rear end is connected to the small connector drive unit joint (2-12-1); in the middle axis surface right side joint II drive unit group (2-9), the front end of the drive unit is connected to the oil delivery port (2-7-4) of the middle connector right side drive unit, and the rear end is connected to the small connector drive unit joint (2-12-1).

6. A robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 5, characterized in that: The number of oil delivery ports of the left drive unit of the large connector matches the number of drive units in the drive unit group (2-6) of the left joint I of the central axis, the number of oil delivery ports (2-1-4) of the right drive unit of the large connector matches the number of drive units in the drive unit group (2-3) of the right joint I of the central axis, the number of drive unit joints (2-7-1) of the middle connector matches the number of drive units in the flexible joint I (2-A), the number of oil delivery ports of the left drive unit of the middle connector matches the number of drive units in the drive unit group (2-11) of the left joint II of the central axis, the number of oil delivery ports (2-7-4) of the right drive unit of the middle connector matches the number of drive units in the drive unit group (2-9) of the right joint II of the central axis, and the number of drive unit joints (2-12-1) of the small connector matches the number of drive units in the flexible joint II (2-B).

7. The robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 3, characterized in that: The driving assembly (1-15) comprises a four-cylinder plunger pump (1-15-2), the four-cylinder plunger pump (1-15-2) having four groups of oil delivery ports (1-15-2-8-1), and the four groups of hydraulic cylinder oil delivery port interfaces (2-1-1) on the front side of the large connector (2-1) are correspondingly connected to the four groups of oil delivery ports (1-15-2-8-1) of the four-cylinder plunger pump (1-15-2).

8. The robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 7, characterized in that: The four-cylinder plunger pump (1-15-2) comprises a hydraulic cylinder body (1-15-2-8); the hydraulic cylinder body (1-15-2-8) is a four-cylinder structure, comprising two pairs of upper and lower cylinder bodies, each of which is equipped with a piston (1-15-2-7); the hydraulic cylinder body (1-15-2-8) is provided with steering gear fixing plates (1-15-2-2) on the upper and lower sides, each of which is fixed with a pair of plunger pump steering gears (1-15-2-1), the output shaft of each plunger pump steering gear (1-15-2-1) is connected to the piston (1-15-2-7) in a group of cylinder bodies in the hydraulic cylinder body (1-15-2-8) through a crank slider mechanism, and the rotational motion of the output shaft of the plunger pump steering gear (1-15-2-1) is converted into the reciprocating motion of the piston (1-15-2-7) inside the cylinder body through the crank slider mechanism.

9. The robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 3, characterized in that: The top surface of the fish head (1) is provided with a dorsal fin, and the left and right sides of the fish head (1) are provided with pectoral fins (1-15-1-1); the driving component (1-15) includes a pectoral fin component (1-15-1); the pectoral fin component (1-15-1) includes a pectoral fin bracket (1-15-1-4), and pectoral fin steering gear units (1-15-1-3) are connected to the two sides of the pectoral fin bracket (1-15-1-4); the output shaft of the pectoral fin steering gear unit (1-15-1-3) is connected to the pectoral fin unit (1-15-1-1) via a connecting shaft unit (1-15-1-2); during the operation of the robot fish, the angles of the pectoral fins (1-15-1-1) on the left and right sides of the fish head (1) are adjusted to enable the robot fish to float up and dive down.

10. The robotic fish with an adaptive variable stiffness flexible caudal peduncle based on non-Newtonian fluid according to claim 3, characterized in that: A flexible sensor is provided on the central axis of a flexible matrix (2-2) of a flexible joint I (2-A) and a flexible matrix (2-8) of a flexible joint II (2-B) for detecting the swing angle of the flexible joint I (2-A) and the flexible joint II (2-B); an antenna (1-3) is installed on the top surface of the fish head (1); a fish head support frame (1-11) is provided inside the fish head (1); a partition with a grid is provided on the fish head support frame (1-11); a large PCB board (1-9) and a small PCB board (1-7) are installed above the partition; and a battery pack (1-12) is installed below the partition; a voltage stabilizing module (1-8) and a current sensor module (1-10) are provided on the large PCB board (1-9); and a control single chip computer (1-5) and a signal transmitter (1-6) are provided on the small PCB board (1-7).

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