Design method for driving system of ornithopter

Abstract

The invention discloses a design method for a driving system of a flapping-wing air vehicle, and relates to the technical field of flapping-wing air vehicles. Comprising the following steps: S1, determining an initial design parameter combination of a flapping wing driving system; s2, establishing an experiment driving system; s3, flapping wing parameter optimization design is carried out; s4, selecting the required capacity of the battery; s5, selecting an electronic speed regulator; s6, selecting an alternative motor; s7, matching parameters of the flapping wing driving system; s8, designing a speed reducer and a flapping mechanism; and S9, carrying out integration and comprehensive testing on the flapping wing driving system so as to complete the design of the flapping wing air vehicle driving system. The ornithopter driving system designed through the method has the advantages of being complete in motion function, good in parameter matching and high in efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of flapping-wing aircraft. Background Art

[0002] The flapping-wing aircraft drive system converts the energy of the flapping-wing aircraft power source into flight motion, which is the key link to achieve high-performance bionic motion of the platform. For flapping-wing aircraft with flight time and load requirements, the most mainstream and effective way is to use battery power and motor drive. For a complete flapping-wing drive system, there is a strong coupling relationship between the battery, motor, reducer, flapping mechanism and flapping wing. The speed and torque requirements of the flapping wing determine the selection of the motor. The discharge characteristics of the battery determine the working characteristics of the motor and affect the reduction ratio of the reducer. The reducer realizes the conversion of motor speed and torque. The flapping mechanism realizes the specific motion law of the flapping wing. The matching of the motor, reducer and flapping wing affects the working point of the motor and determines the power consumption and efficiency of the drive system.

[0003] In previous designs, the focus was on functional design, with the goal of ensuring that the drive system could drive the flapping wings to the required flapping frequency. This resulted in the need for continuous attempts to achieve the desired drive capacity. In addition, this design, which mainly focuses on motion functions, ignores the parameter matching relationship between the motor, reducer, flapping mechanism and flapping wing, which greatly reduces the energy conversion efficiency of the flapping wing drive system, which in turn directly affects the flight time and load capacity of the flapping wing aircraft.

[0004] Therefore, the existing flapping-wing drive system design has many problems such as unclear design goals, a lot of repetitive work, long development cycle, low energy conversion efficiency, etc., and lacks a complete and efficient systematic design method. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flapping-wing aircraft drive system design method, starting from the flapping-wing drive system design requirements, comprehensively considering the system composition and the internal and external interface relationship, and realizing the forward design of the system. Through this method, the functional and efficient design requirements of the system can be taken into account.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for designing a flapping-wing aircraft drive system, wherein the drive system is a mechanical drive system driven by a motor using a battery as energy source, including a battery, an electronic speed regulator, a motor, a reducer and a flapping mechanism, and includes the following steps:

[0008] S1: Determine the initial design parameter combination of the flapping-wing drive system:

[0009] S1-1: Determine the flapping frequency. According to the scaling law formula and the design index of the take-off weight m of the flapping-wing aircraft, determine the flapping frequency. The flapping frequency can be expressed as a function of the take-off weight m:

[0010] f0=3.98m -0.27

[0011] Where: f0 is the flapping frequency; m is the takeoff weight;

[0012] S1-2: Determine the value of the flapping angle:

[0013] The flapping angle can be decomposed into the following three basic motion angles: the sweep angle ψ0 along the y-axis of the body coordinate system, the torsion angle ζ0 along the z-axis of the body coordinate system, and the flapping angle φ0 along the x-axis of the body coordinate system; the sweep angle ψ0 and the torsion angle ζ0 are determined according to the design requirements of the flapping-wing aircraft; the flapping angle φ0 is determined according to the following formula:

[0014]

[0015] Where: is the period average angular velocity, m is the takeoff weight, φ0 is the flapping angle, and f0 is the flapping frequency;

[0016] In order to facilitate the subsequent study of the influence of variable parameters and determine the final optimal flapping parameter combination, the value of the flapping angle can be varied within a range;

[0017] S1-3: Determine flight power P fly , based on the take-off weight m design index of the flapping-wing aircraft, calculate the flight power P fly :

[0018] According to the power fitting formula of flapping-wing aircraft, the flight power P fly Expressed as a function of takeoff weight m:

[0019] P fly =72.544m 0.78

[0020] Where: m is the take-off weight;

[0021] S2: Establishing an experimental drive system. According to the initial design parameter combination determined in step S1, design and manufacture an experimental drive system for a flapping wing wind tunnel experiment. Since it is a ground-based experimental system, when selecting a motor for the experimental drive system, a motor with sufficient power and torque is selected so as to have a wider parameter output range.

[0022] S3: Optimize the design of flapping wing parameters. Based on the experimental drive system designed and manufactured in step S2, optimize the design of flapping wing parameters through wind tunnel experiments. With the goal of minimizing power consumption, obtain the parameter combination under lift-thrust balance conditions:

[0023] S3-1: The flapping frequency under lift-thrust balance condition is taken as the design frequency f1 of the flapping-wing drive system;

[0024] S3-2: The flapping angle under lift-thrust balance condition is taken as the design flapping angle of the flapping-wing drive system, and the design flapping angle includes the design flapping angle φ1 along the x-axis of the body coordinate system, the design sweep angle ψ1 along the y-axis of the body coordinate system, and the design torsion angle ζ1 along the z-axis of the body coordinate system;

[0025] S3-3: The flight power under lift-thrust balance condition is taken as the design flight power P of the flapping-wing drive system fly1 ;

[0026] S3-4: Taking the flapping wing root torque under lift-thrust balance condition as the design of flapping wing drive system root ;

[0027] S4: Select the required battery capacity, based on the designed flight power P obtained in step S3 fly1 According to the flight time requirements of flapping-wing aircraft, the required battery capacity is selected, and the constant power P fly1 The test results show that the discharge curve of the battery is: platform voltage U e , maximum voltage U1, cut-off voltage U0;

[0028] S5: Select an electronic speed regulator. The electronic speed regulator is selected according to the battery voltage range obtained in step S4. The minimum operating voltage of the electronic speed regulator must be lower than the battery cut-off voltage U0, and the maximum operating voltage must be higher than the battery maximum voltage U1;

[0029] S6: Select an alternative motor, based on the design flight power P obtained in step S3-3 fly1 and the battery platform voltage U obtained in step S4 e Select the candidate motor, use the dynamometer to obtain the characteristic relationship curve of the candidate motor under voltage U0, and obtain the functional relationship:

[0030]

[0031] Where: I m is the input current of the alternative motor; n m is the output speed of the alternative motor; η m is the efficiency of the alternative motor; P m is the output power of the alternative motor; T m is the output torque of the alternative motor;

[0032] S7: Perform flapping-wing drive system parameter matching:

[0033] The parameter matching of the flapping-wing drive system is the matching of the reducer reduction ratio i. The reducer reduction ratio i must satisfy both the speed constraint and the torque constraint:

[0034] The speed constraint that the reducer reduction ratio i needs to meet is that the reducer output speed is not less than the design frequency f1 of the flapping-wing drive system:

[0035]

[0036] Where: i is the reduction ratio of the reducer; n m is the output speed of the alternative motor; f1 is the design frequency of the flapping-wing drive system;

[0037] The torque constraint that the reducer reduction ratio i must satisfy is that the reducer output torque is not less than the designed flapping wing root torque T root :

[0038]

[0039] Where: η g is the reducer efficiency; η f For the efficiency of the flapping mechanism;

[0040] Solve the constraints and select the reduction ratio corresponding to the minimum output torque point of the alternative motor in the feasible domain as the optimal parameter matching solution, at which the system transmission efficiency is the highest;

[0041] S8: Design the reducer and flapping mechanism:

[0042] S8-1: Determine the layout of the reducer according to the reduction ratio obtained in step S7, allocate the reduction ratio based on the transmission requirements and the structural size requirements, design the gear set and the frame based on the obtained reducer scheme, and perform structural optimization design;

[0043] S8-2: According to the designed flapping angle of the flapping-wing drive system in step S3-2, the flapping mechanism is designed, a three-dimensional model is established, kinematic and dynamic simulation analysis is further performed, and a weight reduction design is performed;

[0044] S9: Flapping-wing drive system integration and comprehensive testing:

[0045] S9-1: Electronic prototype integration and testing: Based on the design results, establish the electronic prototype model of the flapping-wing drive system, conduct interference checks, and perform kinematic and dynamic simulation analysis; further design the tolerances of system components, and arrange the processing and assembly process;

[0046] S9-2: Physical prototype integration and testing: Based on the electronic prototype, the components are processed and manufactured, assembled into a physical prototype, and further ground comprehensive experimental tests are carried out on the physical prototype, including functional tests, efficiency tests, and reliability tests, so as to complete the design of the flapping-wing aircraft drive system.

[0047] The present invention is further improved in that:

[0048] The value of the flapping angle in step S1-2 is variable within the range of ±15%.

[0049] The beneficial effects of adopting the above technical solution are:

[0050] The present invention fully considers the force and electricity transmission relationship of each component of the flapping-wing aircraft drive system, and comprehensively matches factors such as the speed and torque requirements of the flapping wing, the discharge characteristics of the battery, the characteristics of the drive motor, the reduction ratio of the reducer, the motion law of the flapping mechanism, etc., so as to design a flapping-wing drive system with perfect motion function, good parameter matching and high efficiency, reduce the risk of later physical verification, avoid a large number of physical tests, and accelerate the development process of flapping-wing aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a flow chart of the method of the present invention;

[0052] Figure 2 It is the kinematic diagram of the crank-rocker mechanism;

[0053] Figure 3 It is a battery discharge curve graph;

[0054] Figure 4 It is the characteristic relationship curve diagram of the alternative motor;

[0055] Figure 5 is the feasible region diagram of the reduction ratio;

[0056] Figure 6 It is the layout diagram of the reducer;

[0057] Figure 7 It is a three-dimensional model diagram of the driving mechanism;

[0058] Figure 8 It is the result diagram of the motion simulation of the driving mechanism;

[0059] Fig. 9 This is the test result diagram of the drive system. DETAILED DESCRIPTION

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0061] This embodiment takes a certain type of flapping-wing aircraft as an example to design the drive system. The design indicators of this type of flapping-wing aircraft are: take-off weight m is 0.03kg, and the flight time is not less than 30min. The specific process is:

[0062] S1: Determine the initial design parameter combination of the flapping-wing drive system:

[0063] S1-1: According to the take-off weight m design index of the flapping-wing aircraft, determine the flapping frequency according to the scaling law formula;

[0064] f0=3.98m -0.27

[0065] Where: f0 is the flapping frequency; m is the takeoff weight;

[0066] According to the above formula, the flapping frequency f0 is 10.26 Hz.

[0067] S1-2: Determine the value of the flapping angle:

[0068] The flapping angle can be decomposed into three basic motion angles: the sweep angle ψ0 along the y-axis of the body coordinate system, the torsion angle ζ0 along the z-axis of the body coordinate system, and the flapping angle φ0 along the x-axis of the body coordinate system; there is no special requirement for the sweep angle ψ0 and the torsion angle ζ0 in the design requirements of flapping-wing aircraft. At the same time, considering that the take-off weight of the aircraft is small, adding additional motion angles will increase the design difficulty and weight of the mechanism, so the sweep angle ψ0 and the torsion angle ζ0 are both set to 0; the flapping angle φ0 is determined according to the following formula:

[0069]

[0070] Where: is the period average angular velocity, m is the takeoff weight, φ0 is the flapping angle, and f0 is the flapping frequency;

[0071] According to the above formula, the average angular velocity of the period is obtained It is 24.669rad / s, and the flapping angle φ0 is 68.88 degrees.

[0072] In order to facilitate the subsequent study of the influence of variable parameters and determine the final optimal flapping parameter combination, the value of the flapping angle is variable within a range, and the flapping angle is adjusted to three values ​​of 60 degrees, 70 degrees and 80 degrees.

[0073] S1-3: Calculate the flight power P based on the take-off weight m of the flapping-wing aircraft design index. fly :

[0074] According to the power fitting formula of flapping-wing aircraft, the flight power P fly Expressed as a function of takeoff weight m:

[0075] P fly =72.544m 0.78

[0076] Where: m is the take-off weight;

[0077] According to the above formula, the flight power P is obtained fly It is 4.707W.

[0078] S2: Based on the initial design parameter combination determined in step S1, an experimental drive system for flapping wing wind tunnel experiment is designed and manufactured; since it is a ground experimental system, a motor with sufficient power and torque is selected to have a wider parameter output range; the motor model selected for this experimental drive system is a DP03 brushless motor.

[0079] The experimental drive system uses a two-stage cylindrical gear reducer with a reduction ratio of 31.5; the flapping mechanism uses a single crank double rocker structure, and the mechanism movement principle is as follows Figure 2 As shown. According to the size of the reduction group, the sizes of OC and CD are 30mm and 10mm respectively. Given that the size of the connecting rod AB is 30mm and the size of the rocker BD is 10mm, the lengths of the crank OA corresponding to the three amplitudes from small to large are obtained by the equation group, which are 5mm, 5.725mm and 6.401mm respectively.

[0080] S3: Based on the experimental drive system designed and manufactured in step S2, the flapping wing parameter optimization design is carried out through wind tunnel experiments, with the goal of minimizing power consumption, and the parameter combination under lift-thrust balance conditions is obtained:

[0081] S3-1: The flapping frequency under lift-thrust balance condition is taken as the design frequency f1 of the flapping-wing drive system, and its value is 10.17 Hz;

[0082] S3-2: The flapping angle under lift-thrust balance conditions is taken as the design flapping angle of the flapping-wing drive system. The design flapping angle is the design flapping angle φ1 along the x-axis of the body coordinate system, and its value is 80 degrees.

[0083] S3-3: The flight power under lift-thrust balance condition is taken as the design flight power P of the flapping-wing drive system fly1 , its value is 3.56W.

[0084] S3-4: Taking the flapping wing root torque under lift-thrust balance condition as the design of flapping wing drive system root , and its value is 25.073mN·m.

[0085] S4: Design flight power P obtained in step S3 fly1 And the flight time requirements of flapping-wing aircraft, the capacity of the required battery must be greater than 481mah.

[0086] Through constant power P fly1 The discharge curve of the battery obtained by the test is as follows Figure 3 As shown, the platform voltage U e It is 3.9V, the maximum voltage U1 is 4.6V, and the cut-off voltage U0 is 3.5V.

[0087] S5: According to the battery voltage range in step S4, the electronic speed controller model is selected as MCPX 3.5A brushless ESC. The minimum operating voltage of the electronic speed controller must be lower than the battery cut-off voltage U0, which is 3.3V, and the maximum operating voltage must be higher than the battery maximum voltage U1, which is 5V.

[0088] S6: Design flight power P obtained in step S3-3 fly1 and the battery platform voltage U obtained in step S4 e Select the alternative motor model JQ03-KV7000, and use the dynamometer to obtain the characteristic relationship curve of the alternative motor under voltage U0. Figure 4 As shown,

[0089] And get the functional relationship:

[0090]

[0091] Where: I m is the input current of the alternative motor; n m is the output speed of the alternative motor; η m is the efficiency of the alternative motor; P m is the output power of the alternative motor; T m is the output torque of the alternative motor;

[0092] S7: Perform flapping-wing drive system parameter matching:

[0093] The parameter matching of the flapping-wing drive system is the matching of the reducer reduction ratio i. The reducer reduction ratio i must satisfy both the speed constraint and the torque constraint:

[0094] The speed constraint that the reducer reduction ratio i needs to meet is that the reducer output speed is not less than the design frequency f1 of the flapping-wing drive system:

[0095]

[0096] Where: i is the reduction ratio of the reducer; n m is the output speed of the alternative motor; f1 is the design frequency of the flapping-wing drive system;

[0097] The torque constraint that the reducer reduction ratio i must satisfy is that the reducer output torque is not less than the designed flapping wing root torque T root :

[0098]

[0099] Where: η g is the reducer efficiency, its value is 0.85; η f is the flapping mechanism efficiency, and its value is 0.82;

[0100] Solve the constraints, such as Figure 5 As shown in the figure, the reduction ratio corresponding to the minimum point of the output torque of the alternative motor in the feasible domain is selected as the optimal parameter matching solution. At this time, the system transmission efficiency is the highest, the reduction ratio is 30.5, and the drive system efficiency is 48.38%;

[0101] S8: Design the reducer and flapping mechanism:

[0102] S8-1: According to the reduction ratio obtained in step S7, the layout of the reducer is determined to be a two-stage parallel gear form, such as Figure 6 As shown. Based on the transmission requirements and structural size requirements, the reduction ratio is allocated, the first-stage reduction ratio is 5.556, and the second-stage reduction ratio is 5.5. Based on the obtained reducer scheme, the gear set and frame are designed, and the structural optimization design is performed;

[0103] S8-2: Design the flapping mechanism according to the designed flapping angle of the flapping-wing drive system in step S3-2.

[0104] The flapping mechanism also adopts a single crank double rocker structure, and its motion principle is consistent with the wind tunnel test drive mechanism. According to the size of the reduction group, the sizes of OC and CD are determined to be 16.5mm and 6.3mm respectively. Given that the length of the crank OA is 3.3mm, the size of the connecting rod AB is 16.67mm and the size of the rocker BD is 5.187mm through the constraint relationship of the equation group.

[0105] Establish a three-dimensional model, conduct further kinematic and dynamic simulation analysis, and carry out weight reduction design;

[0106] S9: Flapping-wing drive system integration and comprehensive testing:

[0107] S9-1: Electronic prototype integration and testing: Based on the design results, establish the electronic prototype model of the flapping-wing drive system, such as Figure 7 shown.

[0108] Conduct interference checks, and perform kinematic and dynamic simulation analysis; such as Figure 8 As shown in the figure, the law of change of the motion angle of the driving mechanism within a flapping cycle, in which the flapping amplitude of the rocker arm is a sinusoidal motion, the upper and lower flapping symmetry is 40 degrees and there is no sharp return, which meets the design requirements.

[0109] Further design the tolerances of system components and arrange the processing and assembly process;

[0110] S9-2: Physical prototype integration and testing: Based on the electronic prototype, the components are processed and manufactured, assembled into a physical prototype, and further ground comprehensive experimental tests are carried out on the physical prototype, including functional tests, efficiency tests, and reliability tests. The test results are as follows: Fig. 9 shown.

[0111] This completes the design of the flapping-wing aircraft drive system.

Claims

1. A method for designing a flapping-wing aircraft drive system, wherein the drive system is a mechanical drive system driven by a motor using a battery as energy source, and comprises a battery, an electronic speed regulator, a motor, a reducer and a flapping mechanism, characterized in that: The method comprises the following steps: S1: Determine the initial design parameter combination of the flapping-wing drive system: S1-1: Determine the flapping frequency. According to the scaling law formula and the design index of the take-off weight m of the flapping-wing aircraft, determine the flapping frequency. The flapping frequency can be expressed as a function of the take-off weight m: f0=3.98m -0.27 Where: f0 is the flapping frequency; m is the takeoff weight; S1-2: Determine the value of the flapping angle: The flapping angle can be decomposed into the following three basic motion angles: a sweep angle ψ0 along the y-axis of the body coordinate system, a torsion angle ζ0 along the z-axis of the body coordinate system, and a flapping angle φ0 along the x-axis of the body coordinate system; the sweep angle ψ0 and the torsion angle ζ0 are determined according to the design requirements of the flapping-wing aircraft; the flapping angle φ0 is determined according to the following formula: Where: is the period average angular velocity, m is the takeoff weight, φ0 is the flapping angle, and f0 is the flapping frequency; In order to facilitate the subsequent study of the influence of variable parameters and determine the final optimal flapping parameter combination, the value of the flapping angle is variable within a range; S1-3: Determine flight power P fly , based on the take-off weight m design index of the flapping-wing aircraft, calculate the flight power P fly : According to the power fitting formula of flapping-wing aircraft, the flight power P fly Expressed as a function of takeoff weight m: P fly =72.544m 0.78 Where: m is the takeoff weight; S2: Establishing an experimental drive system. According to the initial design parameter combination determined in step S1, design and manufacture an experimental drive system for a flapping wing wind tunnel experiment. Since it is a ground-based experimental system, when selecting a motor for the experimental drive system, a motor with sufficient power and torque is selected so as to have a wider parameter output range. S3: Optimize the design of flapping wing parameters. Based on the experimental drive system designed and manufactured in step S2, optimize the design of flapping wing parameters through wind tunnel experiments. With the goal of minimizing power consumption, obtain the parameter combination under lift-thrust balance conditions: S3-1: The flapping frequency under lift-thrust balance condition is taken as the design frequency f1 of the flapping-wing drive system; S3-2: The flapping angle under the lift-thrust balance condition is used as the design flapping angle of the flapping-wing drive system, wherein the design flapping angle includes a design flapping angle φ1 along the x-axis of the body coordinate system, a design sweep angle ψ1 along the y-axis of the body coordinate system, and a design torsion angle ζ1 along the z-axis of the body coordinate system; S3-3: The flight power under lift-thrust balance condition is taken as the design flight power P of the flapping-wing drive system fly1 ; S3-4: Taking the flapping wing root torque under lift-thrust balance condition as the design of flapping wing drive system root ; S4: Select the required battery capacity, based on the designed flight power P obtained in step S3 fly1 According to the flight time requirements of flapping-wing aircraft, the required battery capacity is selected, and the constant power P fly1 The test results show that the discharge curve of the battery is: platform voltage U e , maximum voltage U1, cut-off voltage U0; S5: Select an electronic speed regulator. The electronic speed regulator is selected according to the battery voltage range obtained in step S4. The minimum operating voltage of the electronic speed regulator must be lower than the battery cut-off voltage U0, and the maximum operating voltage must be higher than the battery maximum voltage U1; S6: Select an alternative motor according to the designed flight power P obtained in step S3-3 fly1 and the battery platform voltage U obtained in step S4 e Select the candidate motor, use the dynamometer to obtain the characteristic relationship curve of the candidate motor under voltage U0, and obtain the functional relationship: Where: I m is the input current of the alternative motor; n m is the output speed of the alternative motor; η m is the efficiency of the alternative motor; P m is the output power of the alternative motor; T m is the output torque of the alternative motor; S7: Perform flapping-wing drive system parameter matching: The flapping wing drive system parameter matching is the speed reducer ratio i matching, and the speed reducer ratio i must satisfy both the speed constraint and the torque constraint: The speed constraint that the speed ratio i of the reducer needs to satisfy is that the output speed of the reducer is not less than the design frequency f1 of the flapping-wing drive system: Where: i is the reduction ratio of the reducer; n m is the output speed of the alternative motor; f1 is the design frequency of the flapping-wing drive system; The torque constraint that the reducer reduction ratio i needs to satisfy is that the reducer output torque is not less than the designed flapping wing root torque T root : Where: η g is the reducer efficiency; η f For the efficiency of the flapping mechanism; Solve the constraints and select the reduction ratio corresponding to the minimum output torque point of the alternative motor in the feasible domain as the optimal parameter matching solution, at which the system transmission efficiency is the highest; S8: Design the reducer and flapping mechanism: S8-1: Determine the layout of the reducer according to the reduction ratio obtained in step S7, allocate the reduction ratio based on the transmission requirements and the structural size requirements, design the gear set and the frame based on the obtained reducer scheme, and perform structural optimization design; S8-2: According to the designed flapping angle of the flapping-wing drive system in step S3-2, the flapping mechanism is designed, a three-dimensional model is established, kinematic and dynamic simulation analysis is further performed, and a weight reduction design is performed; S9: Flapping-wing drive system integration and comprehensive testing: S9-1: Electronic prototype integration and testing: Based on the design results, establish the electronic prototype model of the flapping-wing drive system, conduct interference checks, and perform kinematic and dynamic simulation analysis; further design the tolerances of system components, and arrange the processing and assembly process; S9-2: Physical prototype integration and testing: Based on the electronic prototype, the components are processed and manufactured, assembled into a physical prototype, and the physical prototype is further subjected to comprehensive ground experimental testing, including functional testing, efficiency testing, and reliability testing, thereby completing the design of the flapping-wing aircraft drive system.

2. The method for designing a flapping-wing aircraft drive system according to claim 1, characterized in that: The value of the flapping angle in step S1-2 is variable within the range of ±15%.

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