Boxfish type bionic robotic fish driven by shape memory alloy

Abstract

The application discloses a boxfish type bionic robot fish driven by a shape memory alloy, which comprises a bionic fish base body, a pectoral fin, a flexible skin, a stroke amplification mechanism and a shape memory alloy wire driving mechanism arranged in the base body, and the stroke amplification mechanism is connected with the pectoral fin and the shape memory alloy wire driving mechanism at two ends respectively; the pectoral fin comprises upper and lower swing parts in Z-shaped structure, and the vertically extended two ends are a water-encountering part and a connecting part respectively; the front surface of the water-encountering part is arc-shaped, and the back surface is planar; when electric current is applied, the shape memory alloy wire contracts, the stroke amplification mechanism drives the pectoral fin to swing backward, the back water flow pushes the back surface of the water-encountering part, and the pectoral fin is opened to provide forward power for the bionic fish; when the application of electric current is stopped, the shape memory alloy wire restores to the original length, a spring pushes the sliding block and the shape memory alloy wire to the initial position, the stroke amplification mechanism drives the pectoral fin to swing forward, the front water flow pushes the front surface of the water-encountering part of the swing structure, the pectoral fin is closed, and the resistance is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to underwater bionic robots, in particular to a shape memory alloy driven boxfish type bionic robot fish. BACKGROUND

[0002] In the field of underwater robots, the traditional vehicle has defects such as insufficient propulsion efficiency, large noise disturbance, and easy to be found. Fish swimming has the advantages of high propulsion efficiency, good maneuvering performance, and good concealment performance, so bionic robot fish has gradually become a research hotspot. The traditional bionic robot fish has complex mechanical structure and power elements built-in, so the volume and weight of the bionic robot fish are large, and therefore the intelligent material driven bionic robot fish represented by shape memory alloy has attracted more attention.

[0003] Chinese patent CN207860416U discloses a bionic fish driven by tail fin driven by shape memory alloy, which utilizes memory alloy to drive the tail fin to swing, and then makes the bionic fish move forward, but the controller of the bionic fish cannot well control the swing direction of the tail fin, and the bionic fish swimming speed is slow due to the small extension rate and extension amount of the memory alloy wire; Chinese patent CN108974301A discloses a shape memory alloy driven soft body pectoral fin bionic fish, which has a simple control structure, and the resistance wire wound on the memory alloy plate is heated to make the fish swim, and the fish fin is rotated by the memory alloy spring to float and sink; but it uses more memory alloy, the structure is complex, the time to reach the phase change temperature of the memory alloy is increased, and the motion performance of the bionic fish is reduced. SUMMARY

[0004] The present application aims to provide a boxfish type bionic robot fish driven by shape memory alloy, which can improve the motion performance.

[0005] Technical solution: The boxfish type bionic robot fish driven by the shape memory alloy comprises a bionic fish body, a pectoral fin and a flexible skin, the bionic fish body is internally provided with a stroke amplification mechanism and a memory alloy wire driving mechanism, the stroke amplification mechanism is connected with the pectoral fin and the memory alloy wire driving mechanism at two ends respectively, and is used for amplifying the extension and contraction amount of the memory alloy; the pectoral fin is in a T-shaped structure, comprising a connecting rod, a fixed connecting part and symmetrically arranged upper swing parts and lower swing parts on both sides of the fixed connecting part; the upper swing part is in a Z-shaped structure, extends vertically at two ends, one end is a water-facing part, the front surface is in an arc surface, the back surface is a plane, the other end is a connecting part, a groove is formed in the middle, and through holes are arranged on the protrusions on both sides of the groove and are used for being connected with the fixed connecting part; the lower swing part is different from the upper swing part in that a protrusion with a through hole is arranged in the middle of the connecting part and is used for being connected with the fixed connecting part; the fixed connecting part comprises a convex-shaped limiting block and a mounting block extending vertically at two ends of the limiting block, and the mounting block is used for mounting the upper swing part and the lower swing part; a tubular boss extends from the tail end of the fixed connecting part, is used for connecting the fixed connecting part with the connecting rod, and the other end of the connecting rod is connected with the stroke amplification mechanism; when the current is applied, the shape memory alloy wire of the memory alloy wire driving mechanism is heated and shrunk, the stroke amplification mechanism moves, drives the pectoral fin to swing backward, the back water flow pushes the back surface of the water-facing part of the upper swing part and the lower swing part, the pectoral fin is opened to provide forward power for the bionic fish; when the current is stopped, the shape memory alloy wire is cooled to restore the original length, the spring of the memory alloy wire driving mechanism pushes the sliding block and the shape memory alloy wire to the initial position, the stroke amplification mechanism moves, drives the pectoral fin to swing forward, the front water flow pushes the front surface of the water-facing part of the upper swing part and the lower swing part, the fish fin is closed, and the water flow resistance of the fish fin is reduced.

[0006] Further, the memory alloy wire driving mechanism comprises a shape memory alloy wire, two groups of sliding rails symmetrically installed on both sides of a Z-shaped beam frame of the bionic fish body, a spring, a front end spring fixing part and a rear end spring fixing part, a through hole is formed in a sliding block matched with the sliding rail, one end of the sliding block is fixed on the corresponding stroke amplification mechanism, the other end is connected with the front end spring fixing part; the spring is sleeved between the front end spring fixing part and the rear end spring fixing part, the front end spring fixing part and the rear end spring fixing part both comprise a boss and a limiting column with through holes, the limiting column is used for fixing the spring and limiting the deformation of the spring, the rear end spring fixing part is fixed on a small boss at the tail of the bionic fish body and is used for limiting the extension and contraction direction of the shape memory alloy wire and limiting and fixing the spring; one end of the shape memory alloy wire is fixed on the sliding block, the other end passes through the through holes of the front end spring fixing part and the rear end spring fixing part, is connected with the controller through a lead wire, and a conductive path is formed.

[0007] Further, the bionic fish base is of a boxfish type, the head of the base is arched and protrudes forward, the arched and non-closed end is connected with a horizontal plane structure of the middle section, the tail is of a shuttle-shaped structure, and the middle section gradually shrinks and closes from the middle section to the tail end, the two sides are closed planes, the bionic fish base is internally provided with a stroke amplification mechanism and a memory alloy wire driving mechanism.

[0008] Further, the bionic fish base comprises a middle fish body, an outer plate and a sealing gasket, the head of the middle fish body is arched and protrudes forward, the tail is of a shuttle-shaped structure, the middle section is connected through upper and lower planes, the middle fish body is internally provided with a Z-shaped beam frame, and the two sides are fixed with a stroke amplification mechanism and a memory alloy wire driving mechanism; the middle fish body extends inwardly, and the extension part is provided with a threaded hole for fixing the outer plate; the tail part in the middle fish body is provided with a small boss for fixing the memory alloy wire driving mechanism; the outer plate is provided with a straight slot-shaped boss in the middle part near the front part, which is in communication with the middle fish body and is used for connecting the pectoral fin and the flexible skin.

[0009] Further, the flexible skin is of a hollow funnel-shaped structure, the front end is of a circular cross section, extends to a closed curved surface towards the tail, and the tail end of the flexible skin is of a straight slot-shaped cross section.

[0010] Advantages: compared with the prior art, the bionic fish robot has the following advantages: 1. the pectoral fin structure enables the bionic fish robot to move forward, the pectoral fin is subjected to the forward thrust of the water flow, the swing structure of the pectoral fin is opened under the action of the thrust to increase the contact area of the pectoral fin and the water, and when the pectoral fin returns to the original position, the swing structure of the pectoral fin is automatically closed under the influence of the water resistance to reduce the water resistance; 2. the pectoral fin is driven by a single shape memory alloy wire, which is beneficial to the rapid deformation of the shape memory alloy wire, thereby increasing the movement efficiency of the bionic fish; 3. the scissor-type stroke amplification mechanism makes up for the small extension rate and extension amount of the shape memory alloy wire; 4. when the memory alloy wire returns to the original length, the sliding block of the sliding rail is quickly returned to the original position under the pushing of the spring, thereby improving the movement efficiency of the bionic fish. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the bionic fish robot;

[0012] Figure 2 It is a structural schematic diagram of the sealing gasket;

[0013] Figure 3 It is a structural schematic diagram of the middle fish body;

[0014] Figure 4 It is a structural schematic diagram of the outer plate;

[0015] Figure 5 It is an exploded view of the pectoral fin

[0016] Figure 6A schematic diagram of the structure of the pectoral fin when it swings backward;

[0017] Figure 7 This is a front view of the pectoral fin when it is swinging forward.

[0018] Figure 8 This is a rear view of the pectoral fin when it is swinging forward.

[0019] Figure 9 This is a schematic diagram of the flexible skin structure;

[0020] Figure 10 This is a schematic diagram of the stroke amplification mechanism;

[0021] Figure 11 This is a schematic diagram of the shape memory alloy wire drive mechanism. Detailed Implementation

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] like Figure 1 As shown, the biomimetic fish of this invention includes a biomimetic fish substrate 1, pectoral fins 5, flexible skin 4, a stroke amplification mechanism 11, and a shape memory alloy wire driving mechanism 12. The biomimetic fish substrate 1 is made of photosensitive resin material using 3D printing. The biomimetic fish substrate 1 is shaped like a boxfish, with an arched head protruding forward. The non-closed end of the arch is connected to a horizontal planar structure in the middle section. The tail has a spindle-shaped structure, gradually contracting and closing from the middle section towards the tail end, with closed planes on both sides. The interior of the biomimetic fish substrate 1 is used to install the stroke amplification mechanism 11 and the shape memory alloy wire driving mechanism 12. The biomimetic fish substrate 1 includes a middle fish body 15, outer plates 3, and sealing gaskets 2. An outer plate 3 is installed on each side of the middle fish body, and a sealing gasket 2 is added between the outer plate 3 and the middle fish body 15 to ensure a good seal inside the substrate.

[0024] like Figure 2 As shown, the sealing gasket 2 is made of silicone and has a closed, hollow ring structure. Its outer contour is the same as that of the outer plate. A ring of through holes is arranged on the sealing gasket 2. Each part with a through hole protrudes a semi-circular arc surface towards the center. The sealing gasket 2 is installed between the middle fish body 15 and the outer plate 3. After being tightened with screws, it can seal the fish body.

[0025] like Figure 3 As shown, the middle fish body 15 is made of photosensitive resin material by 3D printing. Inside the middle fish body 15, there is a Z-shaped beam 14 for mounting and fixing the stroke amplification mechanism 11 and the memory alloy wire drive mechanism 12 on both sides. The middle fish body 15 extends inward around its perimeter, and threaded holes for fixing to the outer plate are arranged in the extension. A small boss 13 is set at the rear end of the middle fish body 15 for fixing the memory alloy wire drive mechanism 12.

[0026] As Figure 4 shown, the outer plate 3 is made of photosensitive resin material by 3D printing, and the outer plate 3 is a whole plane structure, the cross-sectional shape of which is the same as the outer shape of the middle fish body 15, and the middle front part has a middle hollow straight slot type boss 31. The boss 31 on the outer plate 3 is used to connect the pectoral fin 5 and the flexible skin 4, and a through hole is arranged on the upper end of the platform, and a circle of through holes is arranged on the edge, which is used to connect with the middle fish body 15 through screws.

[0027] As Figures 5 to 8 shown, the pectoral fin 5 is a whole T-shaped structure, which is composed of four parts, which are divided into an upper swing part 52, a lower swing part 53, a fixed connection part 51 and a connecting rod 55. The upper swing part 52, the lower swing part 53 and the fixed connection part 51 are made of photosensitive resin material by 3D printing, and the connecting rod 55 is made of aluminum alloy. The swing part 52 is a whole Z-shaped structure, and the two ends extend vertically, one end is a water-facing part, the front is a curved surface, and the back is a plane, the other end is a connecting part, a groove is opened in the middle, and through holes are arranged on the two sides of the groove. The through holes are connected with the fixed connection part 51 through the sub-mother rivet. The lower swing part 53 is different from the upper swing part 52 in that a protrusion with a through hole is arranged in the middle of the connecting part, and the through hole is connected with the fixed connection part 51 through the sub-mother rivet; the fixed connection part 51 includes a convex-shaped limiting block and a mounting block vertically extending at both ends of the limiting block, and a through hole is arranged on the mounting block, which can be connected with the upper swing part 52 and the lower swing part 53 through the sub-mother rivet. A tubular boss 54 is protruded behind the tail end of the protruding platform, and a pin hole is arranged on the side surface, which is connected with the connecting rod 55 through the pin after being inserted into the connecting rod 55. The front water-facing surface of the upper swing part 52, the lower swing part 53 and the fixed connection part 51 is an arc when it is completely unfolded, so as to achieve the purpose of reducing water resistance. The connecting rod 55 is a hollow metal pipe, one side of the front end is arranged with a pin hole, the middle rear part is arranged with a through hole, and the rear end is arranged with a through hole. The front end of the connecting rod 55 is connected with the fixed connection part 51, and the other end is connected with the outer plate boss 31 and the internal stroke amplification mechanism 11.

[0028] As Figure 9 shown, the flexible skin 4 is made by pouring silica gel into a mold, and then demolding after solidification. The flexible skin 4 is a whole hollow funnel-shaped structure, the front end is a circular cross section, and extends to a closed curved surface towards the tail end, and the tail end is a straight slot type cross section. The front end of the flexible skin 4 is connected with the pectoral fin 5, and the tail end is connected with the outer plate boss 31 to seal the boss 31 of the outer plate.

[0029] As Figure 10As shown, the stroke amplification mechanism 11 is composed of a scissor structure 113 and a connecting body 111. The scissor structure 113 is composed of four short connecting rods and four long connecting rods. The two ends of the four short connecting rods are provided with through holes, and the two ends and the middle of the four long connecting rods are provided with through holes. The short connecting rods are arranged at the two ends of the scissor structure 113. The through holes at one end between every two short connecting rods are connected by a step screw 112, and the through holes at the other end are connected to the through holes at one end of the long connecting rods by a sub-mother rivet. The four long connecting rods are arranged at the middle part of the scissor structure 113. The long connecting rods are connected to each other in a cross shape through three through holes. The through holes at the two ends of the long connecting rods are connected to each other by a sub-mother rivet, and the middle through holes are connected by a step screw 112. One end of the scissor structure is connected to the connecting body 111 by a step screw 112, and the other end is connected to the sliding block 1221 of the slide rail by a step screw 112. The connecting body 111 is a U-shaped structure made of photosensitive resin material by 3D printing, and the two ends and the bottom thereof are provided with through holes. The through holes at the two ends of the connecting body 111 are connected to the connecting rod 55 of the pectoral fin, and the through hole at the bottom is connected to the step screw 112 at the connection between the short connecting rods of the scissor structure. The stroke amplification device 11 functions to amplify the extension and contraction amount of the memory alloy wire. When one end of the memory alloy wire is extended or contracted, the other end will be amplified by two times through the scissor structure, thereby achieving the purpose of increasing the swing amplitude of the fish fin. The stroke amplification device 11 is installed and fixed on the Z-shaped beam frame 14 of the fish body and the memory alloy wire driving mechanism 12, and the stroke amplification mechanism 11 is connected to the connecting rod 55 of the pectoral fin by a pin.

[0030] As Figure 11As shown, the memory alloy wire driving mechanism 12 is composed of a shape memory alloy wire, a slide rail 122, a front end spring fixing part 123, a rear end spring fixing part 125 and a spring 124. The shape memory alloy wire has a length of 200 mm and a diameter of 0.3 mm, and its expansion rate is about 5%. One end of the shape memory alloy wire is fixed on a slide block 1221, and the other end passes through the through holes of the front end spring fixing part 123 and the rear end spring fixing part 125, and is connected with the controller through a wire to form a conductive path. The slide rail 122 is horizontally installed on the horizontal middle section of the Z-shaped beam frame 14 of the middle fish body, and the threaded hole 121 of one end of the slide block of the slide rail is fixed together with the through hole 112 of the connection place of the short connecting rod of the stroke amplification mechanism 11 by a screw, and the threaded hole of the other end of the slide block is connected with the front end through hole of the front end spring fixing part 123 by a screw. The front end of the front end spring fixing part 123 is an L-shaped boss, and through holes are arranged at both ends of the L-shaped boss, and a cylindrical body is arranged at the lower end of the L-shaped boss for fixing the spring 124 and limiting the deformation of the spring 124. The front end spring fixing part 123 is installed on the slide block 1221 of the slide rail, and is used for connecting the shape memory alloy wire and the slide rail 122, and limiting and fixing the spring 124. The front end of the rear end spring fixing part 125 is a cylindrical body for fixing the spring and limiting the deformation of the spring, and the rear part of the cylindrical body is an L-shaped boss, and through holes are arranged at both ends. The rear end spring fixing part 125 is installed on the small boss 13 at the rear part of the fish body, and is used for limiting the extension direction of the shape memory alloy wire and limiting and fixing the spring 124. The spring 124 is sleeved in the middle of the front end spring fixing part 123 and the rear end spring fixing part 125. When the shape memory alloy wire is electrified, it will heat and shrink, driving the slide rail to move; when the electrification is stopped, the memory alloy wire will restore the original length and be pushed to the initial state by the spring 124, and then the slide block 1221 and the memory alloy wire are pushed to the initial state, and the slide block 1221 of the slide rail drives the scissor type structure 113 to expand and contract, and finally the purpose of swinging the fish fin is achieved, and the fish moves.

Claims

1. A shape memory alloy-driven boxfish-shaped biomimetic robotic fish, comprising a biomimetic fish body (1), pectoral fins (5), and flexible skin (4), characterized in that, The biomimetic fish substrate (1) is equipped with a stroke amplification mechanism (11) and a shape memory alloy wire drive mechanism (12). The stroke amplification mechanism (11) is connected to the pectoral fin and the shape memory alloy wire drive mechanism at both ends, respectively, to amplify the extension and retraction of the shape memory alloy. The pectoral fin (5) has a T-shaped structure, including a connecting rod (55), a fixed connection part (51), and an upper swing part (52) and a lower swing part (53) symmetrically arranged on both sides of the fixed connection part (51). The upper swing part (52) is Z-shaped. The structure has two vertically extending ends. One end is the water-facing part with an arc-shaped front and a flat back. The other end is the connecting part with a groove in the middle and through holes on both sides of the groove for connecting with the fixed connecting part (51). The lower swing part (53) differs from the upper swing part (52) in that the connecting part has a protrusion with through holes in the middle for connecting with the fixed connecting part (51). The fixed connecting part (51) includes a U-shaped limiting block and mounting blocks extending vertically at both ends of the limiting block. Used for mounting the upper swing part (52) and the lower swing part (53); the tail end of the fixed connection part (51) extends into a tubular boss (54) for fixing the connection part (51) to the connecting rod (55), and the other end of the connecting rod (55) is connected to the stroke amplification mechanism (11); when current is applied, the shape memory alloy wire of the memory alloy wire drive mechanism (12) is heated and shrinks, the stroke amplification mechanism (11) moves, driving the pectoral fin (5) to swing backward, and the water flow behind pushes the upper swing part (52) and the lower swing part (53) to the upper swing part (53). On the back of the water-facing part of the swing part (53), the pectoral fin (5) opens to provide forward power for the bionic fish; when the current is stopped, the shape memory alloy wire cools and returns to its original length, the spring of the shape memory alloy wire drive mechanism (12) pushes the slider and the shape memory alloy wire to the initial position, the stroke amplification mechanism (11) moves, driving the pectoral fin (5) to swing forward, the water flow in front pushes the front of the water-facing part of the upper swing part (52) and the lower swing part (53), the pectoral fin (5) closes, and the resistance of the water flow to the pectoral fin is reduced.

2. The shape memory alloy-driven boxfish-type biomimetic robotic fish according to claim 1, characterized in that, The shape memory alloy wire drive mechanism (12) includes a shape memory alloy wire and two sets of slide rails (122) symmetrically installed on both sides of the Z-shaped beam frame of the bionic fish base (1), a spring (124), a front spring fixing part (123), and a rear spring fixing part (125). The slide rail (122) and its cooperating slider (1221) have through holes. One end of the slider (1221) is fixed on the corresponding stroke amplification mechanism (11), and the other end is connected to the front spring fixing part (123). The spring (124) is sleeved on the front spring fixing part (123) and the rear spring fixing part. Between (125), the front spring fixing part (123) and the rear spring fixing part (125) both include a boss with a through hole and a limiting post. The limiting post is used to fix the spring and limit the deformation of the spring. The rear spring fixing part (125) is fixed on the small boss at the tail of the bionic fish base (1) to limit the extension and retraction direction of the shape memory alloy wire and limit and fix the spring. One end of the shape memory alloy wire is fixed on the slider (1221), and the other end passes through the through hole of the front spring fixing part (123) and the rear spring fixing part (125) and is connected to the controller through a wire to form a conductive path.

3. The shape memory alloy-driven boxfish-type biomimetic robotic fish according to claim 1, characterized in that, The biomimetic fish substrate (1) is modeled after a boxfish. The head of the substrate is arched and protrudes forward. The non-closed end of the arch is connected to the horizontal planar structure of the middle section. The tail has a spindle-shaped structure that gradually contracts and closes from the middle section to the middle of the tail end. The two sides are closed planes. The interior of the biomimetic fish substrate (1) is used to install a stroke amplification mechanism and a memory alloy wire drive mechanism.

4. The shape memory alloy-driven boxfish-type biomimetic robotic fish according to claim 1, characterized in that, The biomimetic fish substrate (1) includes a middle fish body (15), an outer plate (3), and a sealing gasket (2). The head of the middle fish body (15) is arched and protrudes forward, and the tail is spindle-shaped. The middle part is connected by two planes. The middle fish body (15) is equipped with a Z-shaped beam frame, and a stroke amplification mechanism and a memory alloy wire drive mechanism are fixed on both sides. The middle fish body (15) extends inward, and the extension part is provided with threaded holes for fixing with the outer plate (3). The tail part of the middle fish body (15) is provided with a small boss for fixing the memory alloy wire drive mechanism. The front part of the middle of the outer plate (3) is provided with a straight groove-shaped boss (31) that runs through the middle fish body (15) for connecting the pectoral fin and the flexible skin.

5. The shape memory alloy-driven boxfish-type biomimetic robotic fish according to claim 1, characterized in that, The flexible skin (4) is a hollow funnel-shaped structure with a circular cross-section at the front end and extends to the rear end to form a closed curved surface. The rear end of the flexible skin has a straight groove-shaped cross-section.

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