CN113525684B

CN113525684B - Bionic aircraft and manufacturing method thereof

Info

Publication number: CN113525684B
Application number: CN202111014680.9A
Authority: CN
Inventors: 张一慧; 籍梓垚; 宋洪烈; 阎东佳; 金天棨
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2023-08-08
Anticipated expiration: 2041-08-31
Also published as: CN113525684A

Abstract

The application provides a bionic aircraft and a manufacturing method of the bionic aircraft. The bionic aircraft comprises a central part (1) and a plurality of wing parts (2), wherein the wing parts (2) are formed or connected with the central part (1) in a circumferential array. The wing parts (2) tilt relative to the central part (1) so that the bionic aircraft is bowl-shaped. The material of the bionic aircraft comprises a thermoplastic shape memory polymer. The manufacturing method of the bionic aircraft comprises the following steps: providing a two-dimensional structure of the bionic aircraft, wherein the two-dimensional structure of the bionic aircraft comprises a connecting point (3) arranged on the wing part (2); providing a pre-stretched assembled substrate platform comprising a connection area thereon; transferring the two-dimensional structure of the bionic aircraft to a prestretched assembly substrate platform, wherein a connecting point (3) is connected to a connecting area of the prestretched assembly substrate platform; and releasing the pretension of the assembly substrate platform to obtain the buckling deformation bionic aircraft.

Description

Bionic aircraft and manufacturing method thereof

Technical Field

The application relates to the technical field of advanced manufacturing, in particular to a bionic aircraft and a manufacturing method of the bionic aircraft.

Background

The micro aircraft has the characteristics of flexibility, good concealment, low cost and the like, and has wide application prospect. For micro aircrafts, reducing the structural volume and the flight noise is the most urgent problem to be solved in development.

The development of new micro-aircraft systems is mainly limited by their dimensions: (I) the overall machine size directly limits the functional modules. The volume of the micro aircraft is reduced, and great challenges are brought to the integrated design and manufacture of functional circuits and structures such as an airborne sensor, an antenna and the like; (II) downsizing presents challenges for power systems. When active propulsion is adopted, the engine is required to be small in size and high in energy density. And, the propeller cannot generate effective thrust when the mini-aircraft wing span size is below 7.6 cm. Therefore, low volume flying structures are a hotspot of current research.

At present, the main preparation method of the three-dimensional structure comprises a 3D printing and residual stress assembly method, but the problems that the multifunctional integration of the three-dimensional structure cannot be realized or the assembled three-dimensional structure is simple in configuration and the like exist in the methods.

Disclosure of Invention

In order to improve or solve at least one of the problems mentioned in the background art, the present application provides a bionic aircraft and a method for manufacturing the bionic aircraft.

The bionic aircraft comprises a central part and a plurality of wing parts, wherein the plurality of wing parts are formed in or connected with the central part in a circumferential array, the wing parts tilt relative to the central part, so that the bionic aircraft is bowl-shaped,

the material of the bionic aircraft comprises a thermoplastic shape memory polymer.

In at least one embodiment of the present application, the fin includes a connection point near the center portion and a fin tip remote from the center portion, the connection point and the fin tip connecting lines defining two sides of the fin,

the midpoints on the two sides of each fin are a first fin midpoint and a second fin midpoint, the included angle between the connecting line of the first fin midpoint and the second fin midpoint and the plane where the center part is located is an inclined angle, and the inclined angle is smaller than 10 degrees.

In at least one embodiment of the present application, the tilt angle is 2 to 5 °.

In at least one embodiment of the present application, the fin includes a fin tip distal from the central portion, the furthest distance between the fin tips being a span, the span being less than 30mm.

In at least one embodiment of the present application, the span is 3 to 20mm.

In at least one embodiment of the present application, the number of fins is 4 to 12, and the fins are crescent-shaped.

The bionic aircraft in the manufacturing method of the bionic aircraft is the bionic aircraft,

the manufacturing method comprises the following steps:

providing a two-dimensional structure of the bionic aircraft, wherein the two-dimensional structure of the bionic aircraft comprises connection points arranged on the wing parts;

providing a pre-stretched assembled substrate platform comprising a connection area thereon;

transferring the two-dimensional structure of the bionic aircraft to the pre-stretched assembly substrate platform, wherein the connecting points are connected to the connecting areas of the pre-stretched assembly substrate platform;

and releasing the pretension of the assembly substrate platform to obtain the buckling deformation bionic aircraft.

In at least one embodiment of the present application, the manufacturing method further comprises:

preparing a shape memory polymer film by a spin coating curing method, and cutting the shape memory polymer film by laser to obtain the two-dimensional structure of the bionic aircraft.

In at least one embodiment of the present application, the location of the connection point is offset from the tip of the fin.

and preparing a wire on the two-dimensional structure of the bionic aircraft, and welding a circuit module, wherein the circuit module comprises at least one of a capacitor, a resistor and a light emitting diode.

The bionic aircraft provided by the application realizes long-time slow flight through the plurality of fins circumferentially arranged at the central part, and enables miniaturization and light weight of the bionic aircraft to be possible through the thermoplastic shape memory polymer.

In the manufacturing method of the bionic aircraft, the mechanical guiding microscale three-dimensional assembly method is utilized, so that the assembly process of the bionic aircraft is realized, and the minimum size limit of the aircraft is broken through.

Drawings

Fig. 1 shows a design and manufacturing flow diagram of a bionic aircraft according to an embodiment of the application.

Fig. 2 shows a two-dimensional topology of the star vine seed.

Fig. 3 shows a two-dimensional schematic of a bionic aircraft according to an embodiment of the present application.

Fig. 4 shows a wing area coefficient-lift relationship diagram of a bionic aircraft according to an embodiment of the present application.

Fig. 5 shows a wing inclination angle-lift relationship diagram of a bionic aircraft according to an embodiment of the present application.

Fig. 6 shows a three-dimensional schematic of a bionic aircraft according to an embodiment of the present application.

Fig. 7 shows a three-dimensional structural side view of a biomimetic aircraft according to an embodiment of the present application.

Description of the reference numerals

1 a central portion; 2 fins; 21 one side; 22 on the other side; 23 wingtips; a 3 connection point; a1, a first fin midpoint; a2 a second fin midpoint; c tilt angle.

Detailed Description

Exemplary embodiments of the present application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are merely illustrative of how one skilled in the art may practice the present application and are not intended to be exhaustive of all of the possible ways of practicing the present application nor to limit the scope of the present application.

It is observed that wing-shaped wind-driven seeds of plants such as maples, star-fruits and the like are rotated to fall and fly by taking the wing-shaped seeds as a flying structure in order to spread the seeds farther and increase the falling time as much as possible. In addition, in the falling process of the plant seeds, unlike animals which rely on muscle driving, the plant seeds only use a wing-shaped seed coat structure, so that the whole plant seeds stably fall down, the dead time is maximized, and a bionic model is provided for the design of a dead flight structure.

The present application describes a bionic aircraft and a manufacturing method provided by the present application with reference to a design and manufacturing flow shown in fig. 1 by using star vine seeds as a bionic model.

Step s101, obtaining a bionic topological structure. The two-dimensional bionic topological structure of the star vine seeds shown in fig. 2 can be obtained by scanning the star vine seeds, and comprises a central part 1 and a plurality of wing parts 2. A plurality of fin portions 2 are formed in a circumferential array around the center portion 1 or connected to the center portion 1.

Step s102, structural design is performed on the bionic aircraft. The bionic topological structure obtained in the step s101 can be used as a design basis of a two-dimensional structure and a three-dimensional structure of the bionic aircraft. It will be understood that the present application refers to flat planar structures by two-dimensional structures and to three-dimensional structures as assembled three-dimensional structures by planar structures.

Step s103, finite element simulation and flow field analysis are carried out on the bionic aircraft. The three-dimensional structure of the bionic aircraft can be simulated by finite elements, and the mechanical characteristics of the bionic aircraft can be analyzed. The three-dimensional structure of the bionic aircraft is approximately bowl-shaped (if adjacent wing parts 2 are connected), the central part 1 is a bowl bottom, and the wing parts 2 are bowl walls. And then using multi-physical field simulation software to perform flow field simulation and pneumatic analysis on the three-dimensional structure. For example, the three-dimensional structure of the bionic aircraft is kept still, a flow field with speed and rotation is applied, the lift-drag ratio of the bionic aircraft structure is calculated corresponding to the falling process of the spin stabilization of the actual structure, the rotational inertia of the structure is analyzed, and the falling speed of the structure when the structure falls stably is calculated. The lift-drag ratio can be adjusted by adjusting the size characteristics, so that the stability of the falling structure is ensured.

As shown in fig. 4 and 5, the present application reflects the landing speed or the dead time of the bionic aircraft through the lift force. The higher the lift, the slower the descent speed representing the bionic aircraft. Through a large number of experimental simulations, the application finds that parameters affecting the spin-down speed of the bionic aircraft mainly comprise the weight of the whole structure, the area of the wing part and the inclination angle c of the wing part.

The lighter the weight of the overall structure of the bionic aircraft, the slower the falling speed thereof. Therefore, the overall weight of the bionic aircraft can be reduced as much as possible in the manufacturing process, for example, the wing part 2 is manufactured by selecting materials with smaller density and the wing part 2 with thinner design thickness. Shape memory polymers (described below) are preferred as the material for the fin 2.

As shown in fig. 4, the larger the area of the wing part 2, the slower the falling speed of the bionic aircraft (the abscissa area coefficient in the figure refers to the ratio of the area of the wing part 2 to the area of the prototype blade of the star vine seed). The area of the fin 2 can be increased as much as possible during the manufacturing process. The area of the central part 1 has little influence on the falling speed of the bionic aircraft, and the area of the central part 1 can be adaptively adjusted according to the number of circuit modules (described later) to be added. In addition, in order to facilitate twisting of the fin portions 2 (described later), the individual fin portions 2 may be provided in a crescent shape.

An exemplary fin 2 configuration is described herein with reference to fig. 3. The fin 2 is crescent-shaped. The two long sides of the fin 2 protrude toward the same direction, one side 21 protrudes toward the other side 22, and the other side 22 protrudes away from the one side 21, and the radius of curvature of the one side 21 is larger than that of the other side 22, so that the width of the middle portion of the fin 2 (the distance between the one side 21 and the other side 22) is larger than the width of both end portions of the fin 2 in the longitudinal direction of the fin 2 (the direction in which the fin 2 extends from the center portion 1).

Where shape memory polymers are used as the material for the fins 2, the present application provides a preferred range of span (the location of the fins 2 away from the central portion 1 has fin tips, the furthest distance between the fin tips of the fins 2 being the span in a three-dimensional structure) and the overall weight (mass) of the bionic aircraft. For example, when the span is 20mm, the mass is preferably 7 to 40mg. The mass is preferably 10.5-60 mg when the span is 30mm.

It will be appreciated that the specific dimensions of the wing span are not limited in this application, but the wing span dimensions are preferably 3-20 mm, taking into account the combined effect of the overall structure weight and wing area on the descent speed of the bionic aircraft, combined with the advantages of the micro aircraft.

As shown in fig. 6 and 7, the connection point of the fin 2 nearer to the center portion 1 and the fin tip farther from the center portion 1 define two sides (i.e., one side 21 and the other side 22) of the fin 2. The included angle between the connecting line of the midpoints of the two sides of the fin part 2 and the plane of the central part 1 is an inclined angle c. In one embodiment, the midpoint of one edge 21 is the first fin midpoint a1 and the midpoint of the other edge 22 is the second fin midpoint a2. The angle of inclination c may be 0 to 10 °, preferably 2 to 5 °. As shown in fig. 5, when the inclination angle c of the fin 2 is 2 to 5 °, the descent speed of the bionic aircraft is relatively slow, and the dead time is longest. It is understood that the present application does not limit the magnitude of the inclination angle c.

The method for assembling the two-dimensional structure into the three-dimensional structure is realized by using a mechanical guide microscale three-dimensional assembly method. The mechanical guide micro-scale three-dimensional micro-assembly method is based on the traditional planar micro-electronic manufacturing process, and the shrinkage of the pre-stretching elastic substrate is used for inducing the buckling of the two-dimensional film, so that the high-precision assembly of the two-dimensional to three-dimensional electronic element is realized, the planar micro-processing process is compatible, and the forming difficulty of the high-performance complex three-dimensional semiconductor structure under the micro-scale is solved. As an emerging design and preparation method, the method has wide application prospect in the fields of energy environment, aerospace, electronic information, mechanical manufacturing, biological medicine and the like. The method creatively applies the prior art of the mechanical guiding microscale three-dimensional micro-assembly method to the three-dimensional assembly of the bionic aircraft, breaks through the minimum size limit of the aircraft, and better realizes the integration of the flight structure and the functional circuit.

Step s104, determining assembly parameters. By adjusting the assembly parameters of the three-dimensional structure of the bionic aircraft, the configuration can be secondarily optimized. The assembly parameters may include the location of the connection areas (e.g. bonding areas) of the assembly substrate platform, the pretensioning strains εx and εy, and the location of the connection points 3 of the bionic aircraft. As shown in fig. 2 and 3, a connection point 3 may be provided on an edge of the fin 2, and the connection point 3 may be integrally formed with the fin 2. In particular, connection points 3 may be provided on the other edge 22 at a distal end of the fin 2 remote from the central portion 1 (but offset from the location of the fin tip 23), the assembly substrate platform having corresponding bonding areas thereon, the connection points 3 being for bonding with the bonding areas on the assembly substrate platform. After the pretensioned assembly substrate platform is released, the two-dimensional structure is buckled and deformed to become a three-dimensional structure. The fin 2 is tilted with respect to the center 1 to form a bowl shape. The degree of inclination of the fin 2 relative to the central portion 1 (bowl wall relative to bowl bottom) is not limited in this application.

As shown in fig. 3, the location of the connection point 3 on the fin 2 may be offset from the fin tip 23. The crescent shape of the wing part 2 and the connection point 3 deviating from the wing tip lead the wing part 2 to bear asymmetric force in the assembling process, the wing part 2 generates a twisting form as shown in fig. 6 and 7, and the inclination angle c is obtained, which is beneficial to the slow-flight of the bionic aircraft. It will be appreciated that the inclination angle c reflects the degree of twisting of the fin 2, as opposed to the degree of inclination of the fin 2 relative to the central portion 1 (bowl wall relative to bowl bottom).

Step s105, detecting whether the flight requirement is satisfied. Whether the falling speed, stability, load target and the like meet the actual requirements or not can be detected, and the two-dimensional structure, the buckling three-dimensional structure and the assembly parameters are corrected and optimized again, so that the bionic aircraft has higher stability and longer dead time when falling.

After determining design parameters of the bionic aircraft, a method of manufacturing the bionic aircraft is described below.

Step s106, preparing the SMP film and cutting the two-dimensional structure. Shape Memory Polymer (SMP) films may be prepared by spin-on curing. The shape memory polymer film mentioned in the application can be a product of epoxy resin E44 after being cured by curing agent polyetheramine D230, or other thermoplastic shape memory polymer films with a transition temperature lower than 100 ℃.

For example, a thermoplastic shape memory polymer film having a thermal transition temperature of 80℃may be prepared, and the spin-coating speed may be set to 1000 to 1500 rpm to obtain a shape memory polymer film having a thickness of, for example, 30 to 80. Mu.m, preferably 50. Mu.m. The thermoplastic shape memory polymer is cooled after being heated, so that the structure can keep the original configuration, the bionic aircraft is heated and then is solid, and the required three-dimensional structure is kept. The shape memory polymer is light and thin, and is beneficial to reducing the descent speed of the bionic aircraft.

The circuit module can be prepared on the surface of the shape memory polymer film by using a planar electronic processing technology. The circuit may include a capacitor, a resistor, a light emitting diode, and the like. For example, a 50 μm copper wire is prepared by photolithography, and after the photoresist is cleaned, circuit modules such as a capacitor, a resistor, a light emitting diode, and the like are soldered. After the capacitor is charged, the LED can always keep a lighting state when the bionic aircraft falls down, and the LED plays a role in marking. It will be appreciated that the circuit modules may be centrally located in the central portion 1 or may be located in the fin portion 2.

The two-dimensional structure of the bionic aircraft can be obtained by cutting the shape memory polymer film by a laser cutting machine, the two-dimensional structure is transferred onto a prestretched assembly substrate platform (such as silica gel), and the connection point 3 of the two-dimensional structure is bonded with the area of the substrate design. Bonding may be by, for example, glue bonding, or by means of silica vapor deposition. It will be appreciated that bonding is the preferred attachment means, but the means by which the fin 2 is attached to the substrate is not limited in this application. The fin 2 may be integrally formed with the central portion 1, or the fin 2 and the central portion 1 may be cut separately and then fixedly connected.

Step s107, assembling, heating, cooling and molding. The assembly substrate platform (not shown) may be pre-stretched according to the assembly parameters obtained at the design stage. For example, the axial tension Fx and Fy are loaded along the x-axis and y-axis directions, respectively, such that the x-axis and y-axis strains of the assembled substrate platform are εx and εy, respectively.

And releasing the assembly substrate platform, and buckling and deforming the two-dimensional structure bonded on the assembly substrate platform to form a three-dimensional structure.

The three-dimensional structure is heated to, for example, 80 ℃ (the thermal transition temperature of the shape memory polymer), cooled, for example, 2 minutes, and the connection points 3 protruding from the fin portions 2 are removed by laser cutting or other cutting methods, so that the structure is solid and separated from the substrate, thereby obtaining the bionic aircraft.

The bionic aircraft provided by the application can dig and abandon power propulsion, adopts a spin falling mode to realize the slow flight, and has high stability and high dead time in the spin falling mode without noise. The micro-flight structure and functional circuit integrated circuit structure is manufactured by mechanical guiding micro-scale three-dimensional structure assembly, is compatible with the advantages of a plane micro-machining process, and can be well integrated. Meanwhile, the method can be compatible with mass production and is environment-friendly, and is easy to be compatible with the current semiconductor manufacturing process, so that the development of subsequent functions is facilitated.

While the foregoing is directed to the preferred embodiments of the present application, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the present application, such changes and modifications are to be considered as within the scope of the present application.

Claims

1. A bionic aircraft is characterized in that,

the bionic aircraft comprises a central part (1) and a plurality of wing parts (2), wherein the wing parts (2) are formed in or connected with the central part (1) in a circumferential array, the wing parts (2) tilt relative to the central part (1) to enable the bionic aircraft to be bowl-shaped,

the material of the bionic aircraft comprises thermoplastic shape memory polymer,

the fin part (2) comprises a connecting point close to the central part (1) and a fin tip (23) far away from the central part (1), the connecting line of the connecting point and the fin tip (23) defines two sides of the fin part (2),

the midpoints on the two sides of each fin (2) are a first fin midpoint (a 1) and a second fin midpoint (a 2), an included angle between a connecting line of the first fin midpoint (a 1) and the second fin midpoint (a 2) and a plane where the central portion (1) is located is an inclined angle (c), and the inclined angle (c) is smaller than 10 degrees.

2. The bionic aircraft according to claim 1, wherein the aircraft is characterized in that,

the inclination angle (c) is 2-5 degrees.

3. The bionic aircraft according to claim 1, wherein the aircraft is characterized in that,

the furthest distance between the tips (23) is the span, which is less than 30mm.

4. The bionic aircraft according to claim 3, wherein,

the wingspan is 3-20 mm.

5. The bionic aircraft according to claim 1, wherein the aircraft is characterized in that,

the number of the fin parts (2) is 4 to 12, and the fin parts (2) are crescent-shaped.

6. A method for manufacturing a bionic aircraft, characterized in that the bionic aircraft is a bionic aircraft according to any one of claims 1 to 5,

the manufacturing method comprises the following steps:

providing a two-dimensional structure of the bionic aircraft, wherein the two-dimensional structure of the bionic aircraft comprises a connecting point (3) arranged on the wing part (2);

transferring the two-dimensional structure of the bionic aircraft to the pre-tensioned assembly substrate platform, the connection points (3) being connected to the connection areas of the pre-tensioned assembly substrate platform;

7. The method of claim 6, wherein the method comprises the steps of,

the manufacturing method further comprises the steps of:

8. The method of claim 6, wherein the method comprises the steps of,

the location of the connection point (3) is offset from the tip (23) of the fin (2).

9. The method of claim 6, wherein the method comprises the steps of,

the manufacturing method further comprises the steps of: