Bionic butterfly based on flapping wing structure

Abstract

The invention discloses a bionic butterfly based on a flapping wing structure, and belongs to the field of flapping wing type aircrafts, a butterfly main body comprises a rack, two motors assembled with speed reduction groups, two couplings, two wings and two wing connecting pieces; the wing connecting piece comprises connecting parts and a transmission shaft which are connected with each other, and the two wings are respectively fixed on the two connecting parts; the rack is T-shaped, longitudinal mounting holes matched with a transmission shaft in shape are formed in the two ends of the transverse part of the rack, and semicircular fixing grooves matched with a motor in shape are formed in the two sides of the tail end of the longitudinal part of the rack; the two transmission shafts are respectively mounted in the two mounting holes; the two motors are respectively bonded in the two fixing grooves; one ends of the two couplings are connected with the output ends of the two speed reduction sets respectively, and the other ends of the two couplings are connected with the two transmission shafts respectively. The flapping wing type bionic butterfly provided by the invention is small in size and light in weight, and more efficient flapping wing driving and more stable flight control can be realized.

Description

Technical Field

[0001] This invention belongs to the field of flapping-wing aircraft, and more specifically, relates to a biomimetic butterfly based on a flapping-wing structure. Background Technology

[0002] With the development of biomimetic robotics, microelectromechanical systems (MEMS), and novel materials technologies, flapping-wing flying robots have gradually become an important research direction in the field of micro-aircraft. Among them, biomimetic butterfly robots, by mimicking the flapping-wing flight mechanism of butterflies in nature under low Reynolds number conditions, can generate stable lift and propulsion at relatively low flight speeds, exhibiting characteristics such as low noise, high maneuverability, and a highly biomimetic structural shape. Compared with traditional rotary-wing or fixed-wing UAVs, flapping-wing biomimetic butterflies demonstrate significant advantages in confined spaces, complex environments, and application scenarios with high requirements for concealment and safety. Therefore, they have broad application prospects in environmental monitoring, indoor inspection, covert reconnaissance, agricultural assistance, science popularization, and human-computer interaction.

[0003] In practical applications, flapping-wing biomimetic butterflies can be used for gas composition detection, temperature and humidity monitoring, and airflow sensing in indoor or semi-enclosed spaces. They can also be used for close-range observation and data collection of vegetation growth in agricultural or natural environments. Furthermore, due to their resemblance to real insects, they are less likely to attract attention in security and reconnaissance scenarios, enabling them to perform low-visibility information gathering tasks. In education and demonstration, biomimetic butterflies can intuitively demonstrate the principles of biological flight, possessing high educational and demonstrative value. With the advancement of micro-sensors and embedded computing capabilities, the potential of biomimetic butterflies in autonomous flight and intelligent control continues to increase, and their application scope continues to expand.

[0004] In terms of mechanical structure, existing biomimetic butterflies typically employ a lightweight fuselage structure, with symmetrically arranged flexible wings that flap periodically via a drive mechanism. Their wings are mostly composed of thin-film materials and a lightweight skeleton, capable of passive deformation during flapping to enhance lift and propulsion efficiency. Regarding the drive method, existing technologies often use dual motors or dual servos to control the reciprocating oscillation of the wings to simulate the flapping motion of a butterfly. Some solutions also use motors in conjunction with linkages and other mechanical structures to achieve the reciprocating oscillation. In terms of control systems and methods, the system generally includes a microprocessor, attitude sensors, and a power management module. By adjusting the flapping frequency, amplitude, or phase difference between the left and right wings, flight attitude control and direction of motion adjustment are achieved. Simultaneously, a closed-loop control strategy based on sensor feedback is employed. By estimating the body's attitude angle and angular velocity, proportional-integral-derivative control or simplified model control methods are used to maintain flight stability.

[0005] However, existing biomimetic butterflies still have many shortcomings in terms of structural design and control methods. Structurally, to achieve biomimicry, the size and weight of the biomimetic butterfly cannot be too large, thus limiting its structural complexity. Many existing butterflies have complex drive mechanisms, resulting in a large overall size, reduced biomimetic similarity, and mechanical wear and vibration issues in some structures during operation, severely impacting flight performance. Furthermore, the size and weight limitations restrict the number and types of sensors that can be carried, hindering stable flight and adjustment of motion direction. In terms of control methods, flapping-wing flight inherently possesses highly nonlinear and coupled dynamic characteristics; the flexible deformation of the wings interacts with aerodynamic forces, making it difficult to accurately establish a flight model. Existing control methods often lack stability and robustness when facing airflow disturbances or load changes, easily leading to oscillations or attitude instability. Simultaneously, existing structures typically rely on complex transmission mechanisms, requiring numerous components and high assembly precision, increasing manufacturing and maintenance costs and limiting the overall system's reliability and consistency.

[0006] In summary, while existing flapping-wing biomimetic butterfly designs have achieved certain research results in terms of structural form and flight principle, they still have significant shortcomings in terms of structural simplification, control robustness, and practical application adaptability. Therefore, how to achieve more efficient flapping-wing drive, more stable flight control, and stronger practical application capabilities, thereby promoting the further development of biomimetic flapping-wing aircraft in engineering applications, remains an urgent technical challenge to be solved. Summary of the Invention

[0007] In response to the shortcomings and improvement needs of existing technologies, this invention provides a biomimetic butterfly based on a flapping wing structure. The purpose is to propose a small-sized and lightweight flapping wing biomimetic butterfly, making it possible to achieve more efficient flapping wing drive and more stable flight control.

[0008] To achieve the above objectives, the present invention provides a biomimetic butterfly based on a flapping wing structure, comprising: a butterfly body; the butterfly body includes: a frame, two motors equipped with reduction gears, two couplings, two wings, and two wing connectors; The wing connector includes interconnected connecting parts and a drive shaft, with the two wings fixed to the two connecting parts respectively; The frame is T-shaped, with longitudinal mounting holes at both ends of its horizontal section that match the shape of the drive shaft, and semi-circular fixing grooves at both ends of its vertical section that match the shape of the motor. The drive shafts of the two wing connectors are respectively installed in the two mounting holes; the two motors are respectively glued to the two fixing slots; one end of the two couplings is respectively connected to the output end of the reduction gear, and the other end of the two couplings is respectively connected to the drive shafts of the two wing connectors.

[0009] Furthermore, each wing is equipped with a potentiometer to detect the flapping angle of the wings in real time.

[0010] Furthermore, the biomimetic butterfly based on flapping wing structure provided by the present invention also includes: an inertial measurement unit and a core control board; The inertial measurement unit and the core control board are respectively located on the upper and lower sides of the longitudinal section of the frame of the bionic butterfly; The core control board is connected to two potentiometers, two motors, and an inertial measurement unit, and is used to control the butterfly body to fly along a preset target trajectory based on the measurement results of the potentiometers and the inertial measurement unit.

[0011] Furthermore, the core control board controls the bionic butterfly to fly along a preset target trajectory, including: Based on the target trajectory, determine the target angles and corresponding baseline flapping parameters of the two wings of the biomimetic butterfly in each flapping cycle, as well as the desired posture of the biomimetic butterfly in each flapping cycle, and then perform the following steps: S1: During the current flapping cycle, the actual flapping angle of the two wings is collected in real time by the potentiometer, and the actual flapping angle is compared with the target flapping angle to generate an angle error signal; S2: Generate a drive signal based on the angle error signal and send it to two motors, so that the motors apply a corresponding driving force to the wings to reduce the angle error signal between the actual flapping angle of the wings and the target flapping angle. S3: Obtain the angular velocity and linear acceleration of the bionic butterfly through the inertial measurement unit, and calculate the real-time attitude of the bionic butterfly through Kalman filtering; S4: Compare the real-time posture of the biomimetic butterfly with the desired posture to obtain the posture error signal, and map the posture error signal into the flapping parameter adjustment of the two wings; S5: Adjust the reference flapping parameters for the next flapping cycle according to the flapping parameter adjustment amount, and correct the target angle for the next flapping cycle according to the adjusted reference flapping parameters to complete the control of the current flapping cycle; S6: If the flight ends, control ends; otherwise, switch to S1 to begin the next flapping cycle.

[0012] Furthermore, the core control board includes two motor drive chips, which are connected to two motors respectively and are used to drive the two motors.

[0013] Furthermore, the motor driver chip is a DRV8833 motor driver chip, and the connection relationship of its various ports is as follows: AIN1, AIN2, BIN1, and BIN2 ports serve as four control signal input terminals; Ports AOUT1, AOUT2, BOUT1, and BOUT2 serve as four output ports; AISEN and BISEN ports are grounded; The nSLEEP port acts as an enable switch; pulling it high enables the chip to operate. The VM port serves as the power input terminal, with a voltage regulator capacitor connected in between. The GND port is grounded.

[0014] Furthermore, the core control board also includes the ESP32-C3FN4 main control chip, and the connection relationships of its various parts are as follows: In the reset circuit, button SW1 is used. Under normal conditions, the enable port CHIP_EN is kept at a high level through the pull-up resistor R24, and the chip works normally. When SW1 is pressed, CHIP_EN is pulled to a low level, the chip stops working, and the reset function is realized. The crystal oscillator circuit uses a 40MHz crystal oscillator, along with capacitors to ensure stable crystal frequency and provide a high-speed operating clock for the main control chip. In the control circuit, the four output pins IO7, IO5, IO4, and IO3 of EP32C3 are connected to AIN1, AIN2, BIN1, and BIN2 of the DRV8833 motor driver chip, respectively.

[0015] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: (1) The bionic butterfly provided by the present invention has a main frame designed as a “T” shape. The two ends of its horizontal part are provided with longitudinal mounting holes that match the shape of the drive shaft of the wing connector. After the fixed part of the wing connector is connected to the wing, its drive shaft is installed in the longitudinal mounting hole. The two sides of the end of the longitudinal part of the “T” frame are provided with semi-circular fixing grooves that match the shape of the motor. The two motors used to drive the flapping of the wings are fixed in the semi-circular fixing grooves by adhesive bonding. Based on this minimalist structural design, while ensuring the basic functions, the present invention removes a large number of redundant structures and effectively reduces the size and weight of the bionic butterfly. This makes it possible for the bionic butterfly to carry more sensors and achieve more efficient and stable flight control.

[0016] (2) If only the butterfly wings are controlled by angle, due to factors such as assembly error, friction difference or potentiometer zero bias, even if the left and right wings are manually controlled by the program to perform the specified movement, the left and right wings may not be able to reach the target angle. Based on the control of the flapping angle of the butterfly wings by the potentiometer equipped on the wings, this invention further uses the difference between the actual attitude estimated by the inertial measurement unit (IMU) and the desired attitude, outputs the deviation to the flapping parameter mapping algorithm, outputs the adjustment amount, corrects the reference flapping parameters, and obtains the target angle trajectory of the left and right wings respectively. Thus, even under the conditions of assembly error, friction difference or potentiometer zero bias, the bionic butterfly can fly according to the preset target trajectory, which improves the stability and robustness of the bionic butterfly flapping flight.

[0017] (3) By coordinating the control of the left and right wings, the present invention can achieve precise maneuvering and trajectory control while maintaining stable flight attitude, thereby improving flight flexibility and the ability to perform complex tasks. At the same time, it reduces the dependence on mechanical assembly precision, extends system life and reduces manufacturing costs.

[0018] Overall, this invention provides a small, lightweight flapping-wing biomimetic butterfly and achieves precise and highly robust flight control over it. Attached Figure Description

[0019] Figure 1 A schematic diagram of a biomimetic butterfly based on flapping wing structure provided in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the main frame of the biomimetic butterfly provided in an embodiment of the present invention.

[0021] Figure 3 This is a control diagram illustrating angle closed-loop control using the PD algorithm.

[0022] Figure 4 This is a schematic diagram of the coordinated control based on IMU attitude closed loop and wing angle closed loop provided in an embodiment of the present invention.

[0023] Figure 5 This is a schematic diagram of the core control board provided in an embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of an existing crank-rocker structure. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0027] To realize a small and lightweight flapping-wing bionic butterfly, this invention provides a bionic butterfly based on a flapping-wing structure and its control system. The overall concept is to remove redundant structures while ensuring the basic functions are realized, so as to reduce the size and weight of the bionic butterfly, making it possible for the bionic butterfly to carry more sensors and achieve more efficient and stable flight control.

[0028] The following is an example.

[0029] Example 1: A biomimetic butterfly based on flapping wing structure, comprising: butterfly body.

[0030] like Figure 1 As shown, the main body of the butterfly includes: a frame, two motors equipped with reduction gears, two couplings, two wings, and two wing connectors; The wing connector includes interconnected connecting parts and a drive shaft, with the two wings fixed to the two connecting parts respectively; like Figure 2 As shown, the frame is T-shaped, with longitudinal mounting holes at both ends of its horizontal section that match the shape of the drive shaft, and semi-circular fixing grooves at both ends of its vertical section that match the shape of the motor. like Figure 1 As shown, the drive shafts of the two wing connectors are respectively installed in the two mounting holes; the two motors are respectively glued to the two fixing slots; one end of the two couplings is respectively connected to the output end of the reduction gear, and the other end of the two couplings is respectively connected to the drive shafts of the two wing connectors.

[0031] The bionic butterfly provided in this embodiment has a main frame designed in a "T" shape. The two ends of its horizontal part are provided with longitudinal mounting holes that match the shape of the drive shaft of the wing connector. After the fixed part of the wing connector is connected to the wing, its drive shaft is installed in the longitudinal mounting holes. The two ends of the longitudinal part of the "T"-shaped frame are provided with semi-circular fixing grooves that match the shape of the motors. The two motors used to drive the flapping of the wings are fixed in the semi-circular fixing grooves by adhesive bonding. Based on this minimalist structural design, while ensuring basic functions, this embodiment eliminates a large number of redundant structures, effectively reducing the size and weight of the bionic butterfly.

[0032] For biomimetic butterflies, servo control and PID algorithms are usually used for angle control. In this embodiment, to facilitate the control of biomimetic butterflies, each of the two wings is equipped with a potentiometer to detect the flapping angle of the wings in real time.

[0033] Optionally, in this embodiment, the motor is a hollow cup motor with a star wheel reduction gear.

[0034] In this embodiment, for one wing, the power transmission path is as follows: the motor passes through a planetary gear reducer to achieve speed reduction and torque increase; the output end of the reducer is connected to a coupling to extend the output end; the coupling uses a potentiometer (sensor) to read the rotation state of the motor shaft; the end of the coupling is connected to the wing via a wing connector to achieve power output.

[0035] Since the two wings are controlled independently, theoretically, the butterfly's flight attitude can be kept stable by remote control (manual flight) or gyroscope (autonomous flight), and the turning function can be achieved by the differential speed of the two wings.

[0036] Optionally, in this embodiment, the wing manufacturing process includes: (1) After determining the basic dimensions of the wings using simulation software, the wing skeleton and outer contour are drawn using CAD. The airfoil contour is cut out on the plate according to the drawn wing skeleton and outer contour by laser cutting to form a mold. (2) Cover the wing material (such as skin, film, etc.) onto the mold and fix it tightly, and use a marker to draw the outline of the wings; Optionally, in this embodiment, the wing material of the butterfly wings is TPU film. (3) Place the skeleton material (carbon fiber in this embodiment) along the contour and fix it with glue or heat (choose according to the different wing material); (4) On a flat workbench, use a weight to press down the entire wing until the frame and wing material are completely fixed, and then cut off the excess material along the outline.

[0037] The biomimetic butterfly based on flapping wing structure provided in this embodiment also includes an inertial measurement unit and a core control board; The inertial measurement unit and the core control board are respectively located on the upper and lower sides of the longitudinal section of the frame of the bionic butterfly; The core control board is connected to two potentiometers, two motors, and an inertial measurement unit, and is used to control the bionic butterfly to fly along a preset target trajectory based on the measurement results of the potentiometers and the inertial measurement unit.

[0038] In this embodiment, an inertial measurement unit (IMU) is installed in addition to the potentiometer. The IMU can measure angular velocity and linear acceleration, and calculate the real-time attitude information of the butterfly body, including roll angle, pitch angle, and yaw angle, through Kalman filtering. Since the bionic butterfly based on flapping wing structure provided in Embodiment 1 is small in size and light in weight, the overall weight can still ensure stable flight even after the IMU is installed. That is to say, the additional IMU will not affect the flight stability of the bionic butterfly. Based on more sensors, this embodiment can consider both angle and attitude information when controlling the flight of the bionic butterfly, thus achieving more precise, efficient, and stable control.

[0039] Limited by sensor settings, traditional bionic butterflies can often only perform angle control. However, if servo control and PID algorithms are used, then... Figure 3 As shown, the control flow is roughly as follows: The actual flapping angle of the wings at the initial stage of startup Flapping angle with the target The difference At maximum speed, the motor rotates rapidly toward the target angle; the forward and reverse rotation of the motor is controlled by... The sign is determined; As the actual flapping angle of the wings Angle from the target Getting closer and closer, Gradually decrease, as the actual flapping angle of the wings... Approaching the target angle At that time, the motor speed dropped rapidly; When the target angle position is reached At that time, the motor nearly stopped, eventually coming to a stop at the target angle position; When external disturbances occur, the motor system responds quickly by generating a counter-torque, keeping the motor shaft at the target angle position.

[0040] The above control function is implemented by the PID algorithm. The PID adjustment block diagram is shown in the figure (only the PD controller is used in this scheme). The proportional coefficient kp dominates the system response speed, enabling the motor to quickly reach the maximum speed during the start-up phase, which is the key to improving the flapping frequency of the butterfly. The derivative coefficient kd mainly prevents overshoot and overshoot.

[0041] In reality, due to factors such as assembly errors, friction differences, or potentiometer zero bias, even if the left and right wings are manually controlled by a program to perform a specified movement, the left and right wings may not be able to reach the target angle. In other words, in reality, the above-mentioned angle control method cannot enable the bionic butterfly to accurately track the target trajectory.

[0042] Considering that factors such as assembly errors, friction differences, or potentiometer zero bias may cause the two wings to fail to reach the target angle, resulting in a deviation from the desired flight attitude, this embodiment proposes to simultaneously consider angle and attitude information for flight control. Specifically, the potentiometer forms a closed-loop control circuit through its interface with the core control board. It compares the real-time measured wing angle with the preset target angle, generates an angle error signal, and uses a motor to apply a corresponding driving force to the wings. This achieves precise tracking control of the wing angle, ensuring that the wing movement conforms as closely as possible to the predetermined trajectory within a single flapping cycle, thus realizing closed-loop control of the wing angle.

[0043] In addition to angle closed-loop control, this embodiment acquires the real-time attitude of the biomimetic butterfly via an IMU, compares it with the desired attitude, and generates an attitude error signal. This error signal is then mapped to the parameter adjustment amounts of the left and right wings using a flapping parameter mapping algorithm. This adjusts parameters such as the butterfly's wing amplitude and flapping frequency, ultimately generating the target angle trajectories for each wing. This achieves coordinated control based on IMU attitude closed-loop and wing angle closed-loop. Accordingly, in this embodiment, the specific steps for the core control board to control the biomimetic butterfly to fly according to the preset target trajectory include: Based on the target trajectory, determine the target angles and corresponding baseline flapping parameters of the two wings of the biomimetic butterfly in each flapping cycle, as well as the desired posture of the biomimetic butterfly in each flapping cycle, and then perform the following steps: S1: During the current flapping cycle, the actual flapping angle of the two wings is collected in real time by the potentiometer, and the actual flapping angle is compared with the target flapping angle to generate an angle error signal; S2: Generate a drive signal based on the angle error signal and send it to two motors, so that the motors apply a corresponding driving force to the wings to reduce the angle error signal between the actual flapping angle of the wings and the target flapping angle. S3: Obtain the angular velocity and linear acceleration of the bionic butterfly through the inertial measurement unit, and calculate the real-time attitude of the bionic butterfly through Kalman filtering; S4: Compare the real-time posture of the biomimetic butterfly with the desired posture to obtain the posture error signal, and map the posture error signal into the flapping parameter adjustment of the two wings; S5: Adjust the reference flapping parameters for the next flapping cycle according to the flapping parameter adjustment amount, and correct the target angle for the next flapping cycle according to the adjusted reference flapping parameters to complete the control of the current flapping cycle; S6: If the flight ends, control ends; otherwise, switch to S1 to begin the next flapping cycle.

[0044] The collaborative control based on IMU attitude closed loop and wing angle closed loop proposed in this embodiment is as follows: Figure 4 As shown.

[0045] Based on the above control method, when the bionic butterfly's flight attitude perfectly matches the expectation, the output of the flapping parameter mapping is 0. At this time, the bionic butterfly flaps its wings exactly according to the set benchmark flapping parameters. When factors such as assembly errors, friction differences, or potentiometer zero bias prevent the left and right wings from reaching the target angle, the bionic butterfly's flight attitude deviates from the desired attitude. The difference between the actual attitude estimated by the IMU and the desired attitude is calculated, and the deviation is output to the flapping parameter mapping algorithm. The algorithm outputs an adjustment amount to correct the benchmark flapping parameters, obtaining the target angle trajectories of the left and right wings. These two trajectories represent the angular positions that the left and right wings should reach within one control cycle. Unlike the ideal situation, the target angles of the two wings are different at this time. Their combined motion effect causes the bionic butterfly's attitude to gradually approach the desired attitude, ultimately achieving stable flight attitude.

[0046] In this embodiment, the core control board that implements the above-mentioned flight control is as follows: Figure 5 As shown: The biomimetic butterfly uses the DRV8833 motor driver chip, which is only 4mm × 4mm in size. The DRV8833 is a dual-channel H-bridge motor driver capable of driving two DC motors, meeting the driving requirements of the two motors in the biomimetic butterfly. This minimizes the overall size and weight while maintaining the basic functionality of the biomimetic butterfly. In the circuit, AIN1, AIN2, BIN1, and BIN2 are four control signal input ports, and AOUT1, AOUT2, BOUT1, and BOUT2 are four output ports used to output voltage signals. These four output ports are connected to the motors. AISEN and BISEN are current control switches, which are not used here and are therefore grounded; nSLEEP is the enable switch, pulling it high to activate the chip; VM is the power input, with a bypass capacitor for voltage regulation. The GND port is grounded.

[0047] The main control chip for the biomimetic butterfly uses the ESP32-C3FN4, which is only 5mm x 5mm in size. It can output 6 channels of PWM and has multiple GPIOs for receiving sensor signals. It supports timers, Bluetooth, and Wi-Fi communication, thus minimizing the overall size and weight while maintaining the basic functions of the biomimetic butterfly. The power input voltage is 3.3V, and multiple sets of capacitors (C24, C25, C26) are used for power filtering to stabilize the chip's power supply voltage and reduce noise interference. Signals acquired by the potentiometer are input to the main control chip through the analog port, and signals acquired by the IMU are input through the I... 2 The C port inputs to the main control chip. The reset circuit uses button SW1. Normally, the enable port CHIP_EN is held high through pull-up resistor R24, allowing the chip to operate normally. When SW1 is pressed, CHIP_EN is pulled low, stopping the chip and resetting it. The crystal oscillator circuit uses a 40MHz crystal, with capacitors (C30, C31) ensuring frequency stability and providing a high-speed clock for the main control chip. In the control circuit, the four output pins of the EP32C3 (IO7, IO5, IO4, IO3) correspond to the four input pins of the motor drive: AIN1, AIN2, BIN1, and BIN2. The remaining ports are pulled to their corresponding high and low levels according to the chip design requirements.

[0048] The advantages of the proposed biomimetic butterfly in terms of weight and control are analyzed and verified below by combining two comparative schemes.

[0049] In addition to the aforementioned dual-motor solution, this invention further proposes a dual-servo motor solution and a single-motor combined with a crank-rocker structure, as follows: Dual servo motor solution: Its main parts are as follows Figure 1 As shown. The fuselage uses GDW DS1906A servos, so the servo mounting hardware is designed according to the servo's dimensions. The left and right servo mounting hardware together form the main body of the butterfly fuselage. The tail section is composed of carbon fiber tubes, each fitted with a 3D-printed platform to house components such as the microcontroller and receiver. Adjusting the position of the control board platform allows for adjustment of the butterfly's center of gravity. The front and rear connectors consist of a flexible hose, providing a soft connection between the fuselage and the tail.

[0050] The manufacturing process for its wings is the same as that in Example 1 above.

[0051] The material selection is shown in Table 1.

[0052] Table 1 Material Selection for Dual Servo Scheme

[0053] The dual-servo design, employing direct drive, avoids excessive connecting structures at the drive end, resulting in more stable drive, clearer and simpler code logic for controlling the servo's yaw, and more flexible adjustments, allowing for a relatively smaller overall size. However, its flapping frequency is low, requiring additional mechanisms to increase it; the two servos are also too heavy and difficult to lighten, failing to generate sufficient lift under limited wingspan conditions.

[0054] Single motor combined with crank-rocker structure: Since the motor outputs rotary motion, and the butterfly wings require reciprocating motion, the wing mechanism can be determined to be a crank-rocker mechanism.

[0055] Crank rocker structure as follows Figure 6 As shown, the process for determining the relevant structural dimensions is as follows: To control the amplitude of the butterfly's arm swing, two extreme cases are considered: left and right. and

[0056] Based on the initial size of the butterfly, the crank length d = 16mm and the frame length a = 50mm were determined. The maximum angle of the butterfly's arms is around 40°.

[0057] The lengths of the rocker arm and connecting rod can be determined from the initial dimensional requirements. The steps to solve for the lengths of the remaining rods using the law of cosines are as follows: As shown in the figure, a is the frame length, b and d are the connecting rod lengths, and c is the connecting rod length. From the designed trajectory, we can obtain:

[0058]

[0059] Assuming that the connecting rod d is the shortest rod in the mechanism and the connecting rod c is the longest rod, we can obtain the following from the conditions for the existence of the crank in a crank-rocker mechanism:

[0060] By the Law of Cosines:

[0061] Substituting (1) and (2) into (3) and (4), we get:

[0062] For ease of manufacturing, the dimensions are rounded, i.e., c=62mm, b=60mm. The lengths of all four rods are now determined: a=50mm, b=60mm, c=62mm, and d=16mm.

[0063] The motor is a 610 coreless motor with a reduction ratio of approximately 33 and an output no-load speed of 17.67 r / s.

[0064] The material selection and weight of each part are shown in Table 2.

[0065] The single-motor combined with crank-rocker structure is significantly lighter than the dual-servo structure, and the flapping frequency can reach 6-7 Hz. However, the poor machining precision of the gears in the crank-rocker structure leads to poor meshing and high frictional resistance; the motor is also prone to stalling. In addition, the single-motor solution is essentially a pure open-loop control, which cannot effectively control the butterfly's attitude or achieve steering. Moreover, the large radial and axial forces during gear meshing make assembly and fixing difficult, and the structure may become unstable over long-term operation.

[0066] Table 2 Material Selection for Single-Motor Combined Crank-Rocker Structure Scheme

[0067] Finally, the comparison of the three schemes is shown in Table 3: Table 3 Comparison of Schemes

[0068] The dual-servo motor scheme is simple to control, and the drive mechanism is simple and stable, but it is heavy; the single-motor scheme is lightweight, but the structure is relatively complex and difficult to control; the dual-motor scheme provided by this invention combines the advantages of the dual-servo motor scheme and the single-motor scheme. As can be seen from the comparison results shown in Table 3, the biomimetic butterfly based on flapping wing structure and its control system provided by this invention have significant comprehensive advantages in terms of weight and control.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biomimetic butterfly based on a flapping wing structure, characterized in that, include: Butterfly body; The butterfly body includes: a frame, two motors equipped with reduction gears, two couplings, two wings, and two wing connectors; The wing connector includes interconnected connecting parts and a drive shaft, with the two wings fixed to the two connecting parts respectively; The frame is T-shaped, with longitudinal mounting holes at both ends of its horizontal portion that match the shape of the drive shaft, and semi-circular fixing grooves at both ends of its vertical portion that match the shape of the motor. The drive shafts of the two wing connectors are respectively installed in the two mounting holes; the two motors are respectively glued to the two fixing slots; one end of the two couplings is respectively connected to the output end of the two reduction gears, and the other end of the two couplings is respectively connected to the drive shafts of the two wing connectors.

2. The biomimetic butterfly based on flapping wing structure as described in claim 1, characterized in that, Each wing is equipped with a potentiometer to detect the flapping angle of the wings in real time.

3. The biomimetic butterfly based on a flapping wing structure as described in claim 2, characterized in that, Also includes: Inertial measurement unit and core control board; The inertial measurement unit and the core control board are respectively located on the upper and lower sides of the longitudinal part of the frame of the bionic butterfly; The core control board is connected to two potentiometers, two motors, and the inertial measurement unit, and is used to control the butterfly body to fly along a preset target trajectory based on the measurement results of the potentiometers and the inertial measurement unit.

4. The biomimetic butterfly based on flapping wing structure as described in claim 3, characterized in that, The core control board controls the butterfly body to fly along a preset target trajectory, including: Based on the target trajectory, determine the target angles and corresponding baseline flapping parameters of the two wings of the biomimetic butterfly in each flapping cycle, as well as the desired posture of the biomimetic butterfly in each flapping cycle, and then perform the following steps: S1: During the current flapping cycle, the actual flapping angle of the two wings is collected in real time by the potentiometer, and the actual flapping angle is compared with the target flapping angle to generate an angle error signal; S2: Generate a drive signal based on the angle error signal and send it to two motors, so that the motors apply a corresponding driving force to the wings to reduce the angle error signal between the actual flapping angle of the wings and the target flapping angle. S3: Obtain the angular velocity and linear acceleration of the bionic butterfly through the inertial measurement unit, and calculate the real-time attitude of the bionic butterfly through Kalman filtering; S4: Compare the real-time posture of the biomimetic butterfly with the desired posture to obtain a posture error signal, and map the posture error signal into the flapping parameter adjustment amount of the two wings; S5: Adjust the reference flapping parameters for the next flapping cycle according to the adjustment amount of the flapping parameters, and correct the target angle for the next flapping cycle according to the adjusted reference flapping parameters to complete the control of the current flapping cycle; S6: If the flight ends, control ends; otherwise, switch to S1 to begin the next flapping cycle.

5. The biomimetic butterfly based on a flapping wing structure as described in claim 4, characterized in that, The core control board includes two motor drive chips, which are connected to two motors respectively and are used to drive the two motors.

6. The biomimetic butterfly based on a flapping wing structure as described in claim 5, characterized in that, The motor driver chip is a DRV8833 motor driver chip, and the connection relationship of its various ports is as follows: AIN1, AIN2, BIN1, and BIN2 ports serve as four control signal input terminals; Ports AOUT1, AOUT2, BOUT1, and BOUT2 serve as four output ports; AISEN and BISEN ports are grounded; The nSLEEP port acts as an enable switch; pulling it high enables the chip to operate. The VM port serves as the power input terminal, with a voltage regulator capacitor connected in between. The GND port is grounded.

7. The biomimetic butterfly based on a flapping wing structure as described in claim 6, characterized in that, The core control board also includes an ESP32-C3FN4 main control chip, and the connection relationships of its various parts are as follows: In the reset circuit, button SW1 is used. Under normal conditions, the enable port CHIP_EN is kept at a high level through the pull-up resistor R24, and the chip works normally. When SW1 is pressed, CHIP_EN is pulled to a low level, the chip stops working, and the reset function is realized. The crystal oscillator circuit uses a 40MHz crystal oscillator, along with capacitors to ensure stable crystal frequency and provide a high-speed operating clock for the main control chip. In the control circuit, the four output pins IO7, IO5, IO4, and IO3 of EP32C3 are connected to AIN1, AIN2, BIN1, and BIN2 of the DRV8833 motor driver chip, respectively.

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