Modular reconfigurable coaxial aircraft, controllability analysis and control redistribution method

Abstract

The application discloses a modular reconfigurable coaxial aircraft, controllability analysis and control redistribution method. The aircraft comprises a flight unit module. The controllability analysis method comprises the following steps: obtaining a control distribution matrix of the modular reconfigurable coaxial aircraft according to the up and down propeller rotation directions of each flight unit module in the modular reconfigurable coaxial aircraft; obtaining an actuator efficiency loss matrix according to the state of the up and down propeller actuators; obtaining a control distribution matrix considering the actuator state according to the control distribution matrix and the actuator efficiency loss matrix; and performing controllability analysis according to the control distribution matrix considering the actuator state. The application provides the modular reconfigurable coaxial aircraft which can be quickly disassembled and randomly combined. The application also provides a mathematical modeling method, performs controllability analysis on the reconfigurable coaxial aircraft, and provides a control redistribution method, so that the reconfigurable coaxial aircraft has a certain fault tolerance.

Description

Technical Field

[0001] This invention relates to a modular reconfigurable coaxial aircraft, controllability analysis, and control redistribution method, belonging to the field of aircraft. Background Technology

[0002] With the continuous development of drone technology, drones are being used more and more in daily life. Among them, rotary-wing drones with hovering capabilities are widely used in aerial photography, fire rescue, logistics transportation, geological surveying, power line inspection and other fields due to their advantages such as stable flight, simple operation and small size.

[0003] The performance requirements for drones vary across different fields. To adapt to different application scenarios, different drones often need to be customized based on requirements such as endurance, size, and payload capacity, increasing manufacturing costs. By introducing modularity into multi-rotor aircraft, these aircraft can be combined in various ways to form configurations that meet mission requirements. Since the modules in a modular aircraft are identical, the components can be universalized, significantly reducing design and manufacturing costs. Therefore, researching modular aircraft that can adapt to different environments and be versatile enough to meet diverse mission requirements through various combinations is of great significance. Summary of the Invention

[0004] To address the problem that existing aircraft cannot adapt to different application scenarios, this invention provides a modular reconfigurable coaxial aircraft, controllability analysis, and control redistribution method.

[0005] The technical solution of this invention is:

[0006] According to a first aspect of the present invention, a method for controllability analysis of a modular reconfigurable coaxial aircraft is provided, comprising: obtaining a control allocation matrix of the modular reconfigurable coaxial aircraft based on the rotation direction of the upper and lower propellers in each flight unit module of the modular reconfigurable coaxial aircraft; obtaining an actuator efficiency loss matrix based on the state of the upper and lower propeller actuators in each flight unit module of the modular reconfigurable coaxial aircraft; obtaining a control allocation matrix considering the actuator state based on the control allocation matrix of the modular reconfigurable coaxial aircraft and the actuator efficiency loss matrix; and performing controllability analysis based on the control allocation matrix considering the actuator state.

[0007] The control allocation matrix for the modular reconfigurable coaxial aircraft is expressed as follows:

[0008]

[0009] Among them, B CA This represents the control assignment matrix for a modular, reconfigurable coaxial aircraft; xup,i y up,i Let x and x represent the positions of the upper propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft in the body coordinate system. dw,i y dw,i Let represent the positions of the lower propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft in the body coordinate system, where i = {1, 2, ..., N} represents the i-th flight unit module in the modular reconfigurable coaxial aircraft, and N represents the number of flight unit modules in the modular reconfigurable coaxial aircraft; k up,i Let k represent the rotation direction of the upper propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft. dw,i This indicates the rotation direction of the lower propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft.

[0010] The actuator efficiency loss matrix is ​​expressed as: Λ=diag(λ up,1 ,λ dw,1 ,λ up,2 ,λ dw,2 ,…λ up,N ,λ dw,N );λ up,i , λ dw,i ∈[0,1] represents the upper and lower brushless motor state values ​​of the i-th flight unit module of the modular reconfigurable coaxial aircraft.

[0011] Based on the modular reconfigurable coaxial aircraft control allocation matrix and the actuator efficiency loss matrix, a control allocation matrix considering actuator states is obtained, expressed as follows:

[0012] B Γ =B CA Λ;

[0013] Among them, B Γ B represents the control allocation matrix considering actuator states; CA Λ represents the control allocation matrix of a modular, reconfigurable coaxial aircraft; Λ represents the actuator efficiency loss matrix.

[0014] The controllability analysis based on the control allocation matrix considering the actuator state includes: if the rank of the control allocation matrix considering the actuator state is equal to a preset value, it is considered controllable; otherwise, it is uncontrollable.

[0015] According to a second aspect of the present invention, a control redistribution method for a modular reconfigurable coaxial aircraft is provided, comprising: determining, based on a controllability analysis method, that the reconfigurable coaxial aircraft meets controllability conditions; calculating, based on the desired trajectory of altitude and attitude, the virtual control input of the reconfigurable coaxial aircraft; and, based on the obtained control allocation matrix considering actuator states, finally obtaining the redistribution input vector of the actuator after actuator failure of the reconfigurable coaxial aircraft.

[0016] According to a third aspect of the present invention, a modular reconfigurable coaxial aircraft is provided, comprising a flight unit module (27), the flight unit module (27) comprising a coaxial twin-rotor aircraft (18) and a mechanical connection device (19); two adjacent flight unit modules (27) are connected by the mechanical connection device (19); the coaxial twin-rotor aircraft (18) comprises a frame, a power assembly and a steering assembly, the frame being used to mount the power assembly and the steering assembly.

[0017] The power assembly includes an upper propeller 2, a lower propeller 5, an upper brushless motor 1, a lower brushless motor 6, a motor flange 17, and a main shaft 4. The upper brushless motor 1 is fixed on the top plate 3, and its output shaft is located on the side away from the upper panel 3 in the frame. The upper propeller 2 is fixed on the output shaft of the upper brushless motor 1. The motor flange 17, which is fixed on the other side of the top plate 3, is fixed to one end of the main shaft 4. The lower brushless motor 6 and the lower propeller 5 are sequentially mounted on the main shaft, and the extended end of the main shaft 4 is used to fix to the fisheye bearing 10 of the steering assembly and then passes through the tilting plate 11 of the steering assembly to be fixed to the lower panel 8 in the frame. The lower brushless motor 6, which is fixed on the motor flange 17, drives the lower propeller 5, and the upper brushless motor 1 drives the upper propeller 2.

[0018] The steering assembly includes a fisheye bearing 10, a swashplate 11, a servo motor 12, a servo motor linkage 14, and a tie rod 15. The fisheye bearing 10 is mounted on the main shaft 4 of the power assembly. The inner ring of the swashplate 11 is connected to the outer ring of the fisheye bearing 10 by an interference fit. The rotation of the servo motor 12 sequentially pulls the swashplate 11 connected to the tie rod 15, which is connected to the servo motor linkage 14 and the servo motor linkage 14 respectively, thereby changing the pitch of the lower propeller 5.

[0019] The mechanical connection module 19 includes a first gripper, a second gripper, a reduction motor 22, a connecting rod 23, a crank 24, a vertical plate 25, a first slot, and a second slot. The vertical plate 25 is used to fix the frame. The reduction motor 22 drives the crank 24 at its output end to rotate. The rotation of the crank 24 drives the first gripper and the second gripper, which are eccentrically connected to the upper and lower ends of the crank 24, to open and close. The opening and closing movement of the first gripper and the second gripper of one flight unit module 27 enables them to cooperate with the first slot and the second slot on the vertical plate 25 of another flight unit module 27.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention proposes a modular, reconfigurable coaxial aircraft that can be quickly assembled and disassembled and freely combined. On the one hand, the flight unit module is based on a coaxial dual-propeller aircraft, which can realize the combination of any number of modules for flight; and the coaxial dual-propeller aircraft of this invention provides lift for the UAV by having two propellers with opposite rotation directions mounted on the same axis rotate together, enabling the flight unit module to fly independently; the coaxial dual-propeller aircraft is small in size and light in weight, and the modules are not easily deformed when assembling multiple modules, thus having greater adaptability and flexibility. On the other hand, the mechanical connection device enables the rapid assembly of multiple flight unit modules. Since each power module has a limited load capacity, assembling multiple flight unit modules increases the UAV's payload capacity to accommodate loads of varying weights. Due to the reconfigurable nature of the aircraft, a single design can achieve the functionality of multiple UAVs, saving on R&D and manufacturing costs. Specifically, a mechanical connection device based on a crank-connecting rod mechanism was designed. During the gripper closing phase, the dead-point characteristic of the connecting rod mechanism is utilized—that is, when the crank and connecting rod are aligned, the mechanism cannot be started regardless of the driving force—thus ensuring the reliability of the connection between flight unit modules. Furthermore, the control module is installed on the vertical axis of each flight unit module, using distributed cooperative control for modular, reconfigurable, coaxial flight. Since each flight unit module is equipped with a control module and can fly independently, even if one or more flight unit module motors fail during cruise, the aircraft can still maintain stable flight and complete the given mission, provided there is sufficient power.

[0022] 2. This invention proposes a mathematical modeling method for modular reconfigurable coaxial aircraft, conducts controllability analysis on reconfigurable coaxial aircraft, and proposes a control redistribution method, enabling reconfigurable coaxial aircraft to have a certain fault tolerance capability. Attached Figure Description

[0023] Figure 1 This is the four-module reconfigurable coaxial flight vehicle configuration provided in the embodiments of the present invention;

[0024] Figure 2 This is the attitude trajectory tracking curve of the modular coaxial aircraft provided in the embodiments of the present invention;

[0025] Figure 3 This is the modular coaxial aircraft state switching law provided in the embodiments of the present invention;

[0026] Figure 4 These are the aircraft attitude trajectory tracking curves under different actuator states provided in the embodiments of the present invention;

[0027] Figure 5This is an exploded view of the flight unit module of the present invention;

[0028] Figure 6 This is a schematic diagram of the flight unit module of the present invention;

[0029] Figure 7 This is a schematic diagram of the triangular configuration reconfigurable coaxial aircraft of the present invention;

[0030] Figure 8 These are schematic diagrams of different configurations of the aircraft according to the present invention;

[0031] Figure 9 Assembly diagram of the mechanical connection device of the present invention Figure 1 ;

[0032] Figure 10 Assembly diagram of the mechanical connection device of the present invention Figure 2 ;

[0033] Figure 11 This is a schematic diagram of the gripper of the mechanical connecting device of the present invention opening;

[0034] Figure 12 This is a schematic diagram of the clamping jaws closing in the mechanical connection device of the present invention;

[0035] Figure 13 This is a schematic diagram of the connection and assembly of the two flight unit modules of the present invention;

[0036] Figure 14 This is a schematic diagram of the power system for the flight unit module of the present invention. Figure 1 ;

[0037] Figure 15 This is a schematic diagram of the power system for the flight unit module of the present invention. Figure 2 ;

[0038] The labels in the diagram are as follows: 1-Upper brushless motor, 2-Upper propeller, 3-Upper panel, 4-Main shaft, 5-Lower propeller, 6-Lower brushless motor, 7-Bearing housing, 8-Lower panel, 9-Propeller bracket, 10-Fisheye bearing, 11-Swashplate, 12-Servo, 13-Servo arm, 14-Servo linkage, 15-Pull rod, 16-Control module, 17-Motor flange, 18-Coaxial dual propeller module, 19-Mechanical connection device, 20-Gear motor mounting component, 21-Left gripper, 22-Gear motor, 23-Linkage, 24-Crank, 25-Connecting device plate, 26-Right gripper, 27-Flight unit module, 28-Slot. Detailed Implementation

[0039] The invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of the invention is not limited to the description.

[0040] Example 1: As Figure 1-15 As shown, according to one aspect of the present invention, a method for controllability analysis of a modular reconfigurable coaxial aircraft is provided, comprising: obtaining a control allocation matrix of the modular reconfigurable coaxial aircraft based on the rotation direction of the upper and lower propellers in each flight unit module of the modular reconfigurable coaxial aircraft; obtaining an actuator efficiency loss matrix based on the state of the upper and lower propeller actuators in each flight unit module of the modular reconfigurable coaxial aircraft; obtaining a control allocation matrix considering the actuator state based on the control allocation matrix of the modular reconfigurable coaxial aircraft and the actuator efficiency loss matrix; and performing controllability analysis based on the control allocation matrix considering the actuator state.

[0041] Furthermore, the control allocation matrix of the modular reconfigurable coaxial aircraft is expressed as follows:

[0042]

[0043] Among them, B CA This represents the control assignment matrix for a modular, reconfigurable coaxial aircraft; x up,i y up,i Let x and x represent the positions of the upper propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft in the body coordinate system. dw,i y dw,i Let represent the positions of the lower propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft in the body coordinate system, where i = {1, 2, ..., N} represents the i-th flight unit module in the modular reconfigurable coaxial aircraft, and N represents the number of flight unit modules in the modular reconfigurable coaxial aircraft; k up,i Let k represent the rotation direction of the upper propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft. dw,i This indicates the rotation direction of the lower propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft.

[0044] Furthermore, the actuator efficiency loss matrix is ​​expressed as: Λ=diag(λ up,1 ,λ dw,1 ,λ up,2 ,λ dw,2 ,…,λ dw,N );λ up,i , λ dw,i ∈[0,1] represents the upper and lower brushless motor state values ​​of the i-th flight unit module of the modular reconfigurable coaxial aircraft.

[0045] Furthermore, based on the modular reconfigurable coaxial aircraft control allocation matrix and the actuator efficiency loss matrix, the control allocation matrix considering the actuator state is obtained, and its expression is:

[0046] BΓ =B CA Λ

[0047] Among them, B Γ B represents the control allocation matrix considering actuator states; CA Λ represents the control allocation matrix of a modular, reconfigurable coaxial aircraft; Λ represents the actuator efficiency loss matrix.

[0048] Furthermore, the controllability analysis based on the control allocation matrix considering the actuator state includes: if the rank of the control allocation matrix considering the actuator state is equal to a preset value, it is considered controllable; otherwise, it is uncontrollable.

[0049] According to a second aspect of the present invention, a control redistribution method for a modular reconfigurable coaxial aircraft is provided, comprising: determining, based on a controllability analysis method, that the reconfigurable coaxial aircraft meets controllability conditions, and calculating, based on the desired trajectory of altitude and attitude, the virtual control input u of the reconfigurable coaxial aircraft. v Based on the calculated control allocation matrix B considering the actuator state Γ Finally, the redistribution input vector u of the actuator after the actuator of the reconfigurable coaxial aircraft fails is obtained. re .

[0050] According to a third aspect of the present invention, a modular reconfigurable coaxial aircraft is provided, including a flight unit module 27, the flight unit module 27 being composed of a coaxial twin-rotor aircraft 18 and a mechanical connection device 19; two flight unit modules 27 are connected to each other via the mechanical connection device 19; the coaxial twin-rotor aircraft 18 includes a frame, a power assembly and a steering assembly, the frame being used to mount the power assembly and the steering assembly.

[0051] Furthermore, the power assembly includes an upper propeller 2, a lower propeller 5, an upper brushless motor 1, a lower brushless motor 6, a motor flange 17, and a main shaft 4. The upper brushless motor 1 is fixed to the upper plate 3 by a threaded connection, and its output shaft is located on the side away from the upper plate. The upper propeller 2 is fixed to the output shaft of the upper brushless motor 1. The motor flange 17, which is fixed to the other side of the upper plate 3, is fixed to one end of the main shaft 4. The lower brushless motor 6 and the lower propeller 5 are sequentially mounted on the main shaft, and the extended end of the main shaft 4 is used to fix to the fisheye bearing 10 of the steering assembly and then passes through the tilting plate 11 of the steering assembly to be fixed to the lower plate 8 in the frame. The lower brushless motor 6, which is fixed to the motor flange 17, drives the lower propeller 5, and the upper brushless motor 1 drives the upper propeller 2.

[0052] Furthermore, the steering assembly includes a fisheye bearing 10, a swashplate 11, a servo motor 12, a servo motor linkage 14, and a tie rod 15. The fisheye bearing 10 is mounted on the main shaft 4. The inner ring of the swashplate 11 is connected to the outer ring of the fisheye bearing 10 by an interference fit. The rotation of the servo motor 12 sequentially pulls the swashplate 11 connected to the tie rod 15, which is connected to the servo motor linkage 14 and the servo motor linkage 14 respectively, thereby changing the pitch of the lower propeller 5.

[0053] Furthermore, the mechanical connection module 19 includes a first gripper, a second gripper, a reduction motor 22, a connecting rod 23, a crank 24, a vertical plate 25, a first slot, and a second slot. The vertical plate 25 is used to fix it to the frame. The reduction motor 22 drives the crank 24 at its output end to rotate. The rotation of the crank 24 drives the first gripper and the second gripper, which are eccentrically connected to the upper and lower ends of the crank 24, to open and close. The opening and closing movement of the first gripper and the second gripper of one flight unit module 27 enables them to cooperate with the first slot and the second slot on the vertical plate 25 of the other flight unit module 27.

[0054] The optional structures of the present invention will be described in detail below with reference to the accompanying drawings:

[0055] A modular, reconfigurable coaxial aircraft includes a flight unit module 27, with two flight unit modules connected by a mechanical connection device 19. The flight unit module 27 consists of a coaxial twin-propeller aircraft 18 and the mechanical connection device 19.

[0056] like Figure 5As shown, the coaxial twin-rotor aircraft 18 includes a frame, a power assembly, and a steering assembly. The frame includes an upper panel 3 and a lower panel 8. The upper and lower panels have the same structure and are made of carbon fiber panels. The outer ring of the panel is a regular hexagon, and the inner ring is a circle with connecting rods in the radial direction. The power assembly includes an upper propeller 2, a lower propeller 5, an upper brushless motor 1, a lower brushless motor 6, a motor flange 17, and a main shaft 4. The upper brushless motor 1 is fixed to the upper plate 3 by a threaded connection, with its output shaft located on the side away from the upper plate. The upper propeller 2 is fixed to the output shaft of the upper brushless motor 1. The motor flange 17, fixed to the upper plate 3, is fixed to one end of the main shaft 4. The other end of the main shaft 4 is successively fitted with the lower brushless motor 6 and the lower propeller 5 with clearance, fitted with the fisheye bearing 10 of the steering assembly with interference fit, and fitted with the swashplate 11 of the steering assembly with clearance before passing through to be fixed to the lower plate 8 by set screws. The lower brushless motor 6 is fixed to the motor flange 17 by a threaded connection. The lower propeller 5 is fixed to the outer rotor of the lower brushless motor 6. The lower brushless motor 6 drives the lower propeller 5, and the upper brushless motor 1 drives the upper propeller 2. The steering assembly includes a fisheye bearing 10, a swashplate 11, and a servo motor 12. The fisheye bearing 10 is mounted on the main shaft 4. The inner ring of the swashplate 11 is connected to the outer ring of the fisheye bearing 10 by an interference fit. The servo motor 12 is fixed by a servo motor bracket on the lower panel. The rotation of the servo motor 12 sequentially drives the servo motor linkage 14 connected to the swing arm 13 of the servo motor 12 and the pull rod 15 connected to the servo motor linkage 14 to pull the swashplate 11 connected to the pull rod 15, thereby changing the pitch of the lower propeller 5. (Both ends of the servo linkage 14 are equipped with universal joints. One end of the universal joint is connected to the swing arm 13, and the other end of the universal joint is connected to the swashplate 11. One end of the pull rod 15 is connected to the swashplate 11 by a universal joint, and the other end of the pull rod 15 is rotatably connected to the mounting bracket of the lower propeller 5.) This enables the coaxial twin-rotor aircraft 18 to move horizontally. In this configuration, the upper propeller 2 and lower propeller 5 within the same flight unit module are located on the same central axis. The upper and lower brushless motors drive the propellers to rotate in opposite directions, thus counteracting the counter-torque generated by the rotor rotation when the flight unit module is hovering. Furthermore, the upper brushless motor 1 is a brushless motor with its own output shaft; the lower brushless motor 6 is a gimbal motor without an output shaft.

[0057] like Figure 6 , Figure 14 , Figure 15As shown, the coaxial dual-propeller UAV 18, equipped with an upper propeller 2 and a lower propeller 5, has propellers rotating in opposite directions. Furthermore, the upper brushless motor 1 and the lower brushless motor 6 rotate in opposite directions. When the servo motor 12 is in the neutral position, the rotation of the upper and lower brushless motors provides upward lift to the coaxial dual-propeller UAV 18, enabling the vertical movement of the flight unit module 27. The flight unit module 27 can also drive the swashplate 11 via the servo motor 12 to rotate, thereby pulling the lower propeller 5 to change its pitch, altering the roll and pitch angles of the flight unit module 27, thus enabling horizontal movement. Two hexagonal carbon fiber panels form a regular hexahedron. Mechanical connection devices 19 connect to the upper panel 3 and the lower panel 8 via threaded connections on the six outer surfaces of the hexahedron. The mechanical connection devices 19 facilitate quick assembly and disassembly between the flight unit modules.

[0058] Using the mechanical connection module 19, flight unit modules can be combined into arbitrary configurations to create an aircraft configuration that meets mission requirements. This allows for the assembly of multiple UAVs with only a single design, saving on research and development and manufacturing costs. In this embodiment, the mechanical connection device 19 connects six flight unit modules to form a triangular-configured modular reconfigurable coaxial aircraft. The controllability analysis method is shown in the connection assembly diagram. Figure 7 As shown. Each flight unit module has a certain load capacity, but when the weight of the object exceeds the load of a single flight unit module, the payload capacity of the UAV can be greatly increased by using multiple flight unit modules spliced ​​together. Using an aircraft configuration that matches the weight of the object can save energy. The controllability analysis method of modular reconfigurable coaxial aircraft with different configurations can adapt to different application scenarios. Through the mechanical connection device 19, multiple flight unit modules can be quickly spliced ​​together, and aircraft with different configurations can be arbitrarily combined and spliced, such as... Figure 8 As shown, this allows multiple drones to be assembled from a single design, saving on research and development and manufacturing costs.

[0059] like Figure 9 , Figure 10As shown in the assembly diagram of the mechanical connection device 19, the mechanical connection device 19 enables the rapid assembly and disassembly of the flight unit module. Its main structure is a clamping mechanism, which is based on a crank-connecting rod mechanism. The components include a geared motor fixing part 20, a left gripper 21, a geared motor 22, a connecting rod 23, a crank 24, a vertical plate 25, a right gripper 26, and a slot 28. The mechanical connection device is driven by a geared motor 22, which is threadedly mounted on the vertical plate 25 via a motor bracket and secured with the geared motor fixing part 20. Crank 24 is connected to the output shaft of geared motor 22 via a set screw; one end of connecting rod 23 is hinged to crank 24, and the other end is hinged to gripper 26 to achieve motion transmission; left gripper 21 and right gripper 26 are staggered vertically and rotate with vertical plate 25, wherein if left gripper 21 is on top, right gripper 26 is on the bottom, and vice versa (the figure shows the case where left gripper 21 is on top and right gripper 26 is on the bottom). Taking the figure as an example, the upper one is designated as the first gripper, and the lower one as the second gripper. The lower part of the first gripper has a first slot with one open end, and the upper part of the second gripper has a second slot with one open end. The openings of the first and second slots are arranged opposite each other. Based on this design, rapid connection can be achieved even when all mechanical connection devices of the flight unit modules are assembled in the same way. According to the motion principle of crank-connecting rod mechanism, when geared motor 22 drives crank to rotate, it can drive gripper 26 to open and close. Figure 11 The image shows the mechanical connection device in the open state. Figure 12 The diagram shows the closed state of the mechanical connection device. During the gripper closing phase, the dead-point characteristic of the linkage mechanism is utilized; that is, when the crank and connecting rod are aligned, the mechanism cannot be started regardless of the driving force. This ensures the reliability of the connection between flight unit modules. The flight unit module connection assembly diagram is shown below. Figure 13 As shown, the controllability analysis method for modular, reconfigurable coaxial aircraft can be infinitely expanded through mechanical connection devices.

[0060] The coaxial dual-propeller UAV 18 uses two propellers with opposite rotation directions mounted coaxially, ensuring they rotate in opposite directions at the same speed. Utilizing the lift and pitch control system generated by the propellers, the UAV's lift and attitude can be controlled. Position and direction of movement are controlled by adjusting the motor speed, enabling independent flight of each flight unit module. In multi-module assembly, each flight unit module is controlled by an independent flight controller, achieving independent flight. Multiple flight unit modules coordinate through a communication system to complete tasks together. Because each flight unit module has independent flight capabilities and can be freely combined, there is no requirement for the number of flight unit modules; any number of modules can be assembled, improving the system's scalability and flexibility.

[0061] Control module 16 is installed on the vertical axis of each flight unit module, and the controllability analysis method of the modular reconfigurable coaxial aircraft is used for flight. Since each flight unit module is equipped with control module 16, if one or more flight unit module motors fail during flight using the controllability analysis method of the modular reconfigurable coaxial aircraft, the aircraft can still fly or land stably if there is sufficient power, ensuring the safety of the aircraft.

[0062] The dynamic model of a reconfigurable coaxial aircraft is used to describe the relationship between the forces and torques acting on the reconfigurable coaxial aircraft and its motion. Before modeling the reconfigurable coaxial aircraft, the variables used in the model are defined, where p = [x, y, z]. T The position information of the reconfigurable coaxial aircraft in the world coordinate system is represented by φ, θ, and ψ, respectively; ω represents the angular velocity of the reconfigurable coaxial aircraft in the body coordinate system; N represents the number of flight unit modules (27) in the reconfigurable coaxial aircraft; m represents the mass of a single flight unit module (27); g = [0, 0, g] T Let g be the gravity vector, and g represent the gravitational acceleration; I B This represents the inertial tensor of a reconfigurable coaxial vehicle at its center of mass.

[0063] Establish a dynamic model for the reconfigurable coaxial aircraft:

[0064]

[0065] in, and M = [τ x ,τ y ,τ z ] T This represents the forces and torques generated by the propulsion system of a reconfigurable coaxial aircraft in the body coordinate system; f i =f up,i +f dw,i i represents the number of the flight unit module (27), f up,i f dw,i These represent the forces generated by the upper propeller and the lower propeller of the i-th flight unit module (27), respectively. This represents the rotation matrix used to transform from the body coordinate system to the world coordinate system.

[0066]

[0067] Among them, sφ=sin(φ), cφ=cos(φ).

[0068] Assuming that the structure of each individual flight unit module is completely symmetrical and that each flight unit module is identical, the moment of inertia of the flight unit module is a diagonal matrix, I = diag(I xx ,I yy ,I zz ), I xx ,I yy ,I zz Let I represent the moments of inertia of the flight unit module about the x, y, and z axes of the module coordinate system, respectively; As a reconfigurable coaxial aircraft with an arbitrarily changeable structure, its inertial tensor I... B It is closely related to the configuration of reconfigurable coaxial aircraft. Using the parallel axis theorem, once the configuration of the reconfigurable coaxial aircraft is determined, the relationship between the configuration of the reconfigurable coaxial aircraft and the rotational inertia of the flight unit modules can be established.

[0069]

[0070] In the formula: x Bi and y Bi This indicates the position of the geometric center of the i-th flight unit module (27) in the body coordinate system.

[0071] Simplifying the expression, we get:

[0072]

[0073] In the formula,

[0074] Each flight unit module of the reconfigurable coaxial aircraft generates lift and torque by rotating a propeller via a motor. The magnitude of lift and torque is related to the motor's rotational speed ω, K. f K is the lift coefficient of the propeller. m ω is the torque coefficient of the propeller. up,i This represents the rotational speed of the brushless motor (1) of the i-th flight unit module.

[0075]

[0076] Note: All motors and propellers in this article are of the same model, so the parameters of the lower propeller are expressed in the same way as those of the upper propeller.

[0077] To implement the controllability analysis method for the modular reconfigurable coaxial aircraft's motion in space, it is necessary to control four variables: altitude, roll angle, pitch angle, and yaw angle. These four variables can be altered by appropriately changing the lift generated by each motor. The translational motion equations of the reconfigurable coaxial aircraft are expressed as follows:

[0078]

[0079] Similarly, according to Newton's and Euler's formulas, the rotational motion equations of a reconfigurable coaxial aircraft are expressed as follows:

[0080]

[0081] In the formula τ x ,τ y ,τ z Represents the reconfigurable coaxial vehicle's coordinate system x around the body. B ,y B ,z B Rotational torque of three axes.

[0082]

[0083] Among them, T z L represents the resultant force acting on a reconfigurable coaxial aircraft. up,i L dw,i These represent the counter-torque generated when the upper and lower propellers of the i-th flight unit module rotate, respectively. k represents the rotation direction of the propellers in the reconfigurable coaxial aircraft; k = 1 when the propeller blades rotate counter-clockwise and k = 2 when the blades rotate clockwise. In this embodiment of the invention, k represents k... up,i k dw,i ; where k up,i Let k represent the rotation direction of the upper propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft. dw,i This represents the rotation direction of the lower propeller in the i-th flight unit module of the modular reconfigurable coaxial aircraft.

[0084] Reconfigurable coaxial aircraft generate lift and torque τ by rotating propellers driven by motors. x ,τ y ,τ z This enables motion in all directions. Since there are no actuators in the system that directly generate thrust and torque, the thrust generated by the motor is used as the actual input vector to the actuators, while the input maintaining the motion of the reconfigurable coaxial aircraft is used as the virtual control input vector. The basic function of control allocation is to rationally and uniquely allocate the virtual control commands corresponding to the control law to each actuator according to mission requirements or performance indicators, in order to achieve the desired control performance. The relationship between the virtual control input and the actual actuator input is shown in the following equation:

[0085] u v =K·B CA u m (9)

[0086] Where K = diag(K) f ,K f ,K f ,K m) is the actuator coefficient matrix, u v =[T z ,τ x ,τ y ,τ z ] T For virtual control input, ω is the actual input to the actuator. dw,i B represents the rotational speed of the lower brushless motor (6) of the i-th flight unit module. CA The control allocation matrix reflects the mapping relationship between virtual control inputs and actual inputs.

[0087] Reconfigurable coaxial aircraft are characterized by the ability to freely connect modules and the variable structure of the aircraft, resulting in different configurations of reconfigurable coaxial aircraft, but they can all be described by formulas.

[0088]

[0089] According to the formula, it can be found that the value of the control allocation matrix is ​​only related to the positional distribution of the actuators of the reconfigurable coaxial aircraft and the propeller rotation direction.

[0090] To discuss the controllability of reconfigurable coaxial aircraft in the event of power system failure or malfunction, we introduce a diagonal matrix Λ to describe the state of each rotor.

[0091] Λ=diag(λ up,1 ,λ dw,1 ,λ up,2 ,λ dw,2 ,…,λ dw,N ),λ up,i , λ dw,i ∈[0,1] (11)

[0092] In the formula, Λ represents the actuator efficiency loss matrix. Where λ up,i =0 indicates that the brushless motor 1 of the i-th flight unit module is completely failed; 0<λ up,i <1 indicates that the brushless motor section has failed; λ up,i =1 indicates that the upper brushless motor is in perfect health, and the same applies to the lower brushless motor.

[0093] If an actuator malfunctions or fails during flight of a reconfigurable coaxial aircraft, the actual input value of the actuator needs to be adjusted promptly to ensure stable flight. re Given the actuator redistribution input vector after an actuator failure in a reconfigurable coaxial aircraft, the actuator allocation strategy considering the failure can be expressed as follows:

[0094]

[0095] In the formula, u v =[T z ,τ x ,τ y ,τ z ] T For virtual control input, K = diag(K) f ,K f ,K f ,K m B is the actuator coefficient matrix. Γ B represents the control assignment matrix containing actuator states. CA To control the allocation matrix, Λ represents the actuator efficiency loss matrix.

[0096] Let H re To control the redistribution matrix:

[0097]

[0098] in, Representing matrix KB Γ The right pseudo-inverse. The reallocated output vector of the actuator is represented as:

[0099]

[0100] In the formula, This is the actual input to the actuator.

[0101] Therefore, the output of each actuator after reallocation can be obtained. The calculation of reallocation considering actuator failure is complete. To ensure the reconfigurable coaxial aircraft can continue stable flight after actuator failure, matrix B... Γ The rank must satisfy:

[0102] rank(B Γ ) = rank(B CA )=4 (15)

[0103] The formula is a necessary condition for the controllability of a reconfigurable coaxial aircraft, and it also ensures that the reconfigurable coaxial aircraft can still perform its mission according to the energy-optimal actuator allocation strategy after actuator failure. Analysis Figure 1 The reconfigurable coaxial flight configuration is shown.

[0104] In the four-module reconfigurable coaxial aircraft shown in the diagram above, assuming that all flight modules are identical, the upper propeller rotates clockwise, the lower propeller rotates counterclockwise, and the side length of the flight unit module is 200mm, the following can be calculated: Figure 1 The control allocation matrix B for the reconfigurable coaxial aircraft configuration is shown. CA :

[0105]

[0106]

[0107] To verify the controllability of the reconfigurable coaxial vehicle after actuator failure, consider Figure 1 The reconfigurable coaxial aircraft configuration shown is tested and verified using numerical simulations when there are no actuator failures, but simultaneous failures of actuators 1 (upper propeller), 3 (lower propeller), and 4 (lower propeller), and simultaneously failures of actuators 1 (lower propeller), 2 (lower propeller), 3 (upper propeller), and 4 (upper propeller). Γ .

[0108] When there is no actuator failure:

[0109]

[0110] When the No. 1 upper propeller actuator, the No. 3 lower propeller actuator, and the No. 4 lower propeller actuator all fail simultaneously:

[0111]

[0112] When the No. 1 lower propeller actuator, the No. 2 upper propeller actuator, the No. 3 upper propeller actuator, and the No. 4 lower propeller actuator all fail simultaneously:

[0113]

[0114] Based on the calculated control allocation matrix B, which takes actuator failure into account... Γ The formula was used to verify whether the reconfigurable coaxial aircraft was controllable after a failure. Calculations showed that:

[0115]

[0116] According to the formula, when the No. 1 lower propeller actuator, the No. 2 upper propeller actuator, the No. 3 upper propeller actuator, and the No. 4 lower propeller actuator all fail simultaneously, the row rank of the corresponding control allocation matrix considering actuator failure is not full, and the modular coaxial aircraft becomes uncontrollable.

[0117] To verify the controllability and control redistribution theory of a reconfigurable coaxial aircraft after actuator failure, a numerical simulation experiment of altitude and angle path tracking of the reconfigurable coaxial aircraft was designed, yielding tracking curves. In the numerical simulation, the control allocation matrix B, considering actuator failure, was first calculated using the position information of each flight unit module in the body coordinate system and the rotation direction information of the upper and lower propellers.Γ This is used to determine whether the reconfigurable coaxial aircraft is controllable. Once the controllability conditions are met, the virtual control input u of the reconfigurable coaxial aircraft can be calculated based on its altitude and desired trajectory. v The control allocation matrix B, considering actuator failure, is calculated based on the formula. Γ Finally, the redistribution input vector u of the actuator after the actuator of the reconfigurable coaxial aircraft fails is obtained. re Ensure that the reconfigurable coaxial aircraft can still fly stably after an actuator failure.

[0118] In the numerical simulation experiment, considering the time interval of 0–13s, the reconfigurable coaxial aircraft did not experience actuator failure, and its control assignment matrix was B. Γ1 At 13s, the actuator state is switched to a state where actuators 1 (lower propeller), 2 (upper propeller), 3 (upper propeller), and 4 (lower propeller) simultaneously fail. At this time, the control allocation matrix is ​​B. Γ3 The simulation results are as follows: Figure 2 As shown.

[0119] Depend on Figure 2 It can be seen that the modular coaxial aircraft did not experience any actuator failures in the first 13 seconds, and the modular coaxial aircraft was able to track the expected curve well. At 13 seconds, actuators No. 1 (lower propeller), No. 2 (upper propeller), No. 3 (upper propeller), and No. 4 (lower propeller) all failed simultaneously, and the modular coaxial aircraft became unstable, verifying the effectiveness of the proposed controllability analysis based on the modular coaxial aircraft.

[0120] To verify the effectiveness of control reallocation, we used Figure 3 The state switching law shown switches the actuator states of the modular coaxial aircraft. When the switching law is equal to 1, the modular coaxial aircraft has no actuator faults. When the switching law is equal to 2, the No. 1 upper propeller actuator, the No. 3 lower propeller actuator, and the No. 4 lower propeller actuator of the modular coaxial aircraft simultaneously malfunction.

[0121] For the altitude z and attitude angles (roll angle φ, pitch angle) of the modular coaxial aircraft By performing trajectory tracking with the attitude angle ψ, we can obtain the following results: Figure 4 The simulation results are shown below. Figure 4 As is known, when modular coaxial aircraft are in Figure 3 Under the switching law shown, trajectory tracking can still be achieved, verifying that the control redistribution method can enable the modular coaxial aircraft to continue to fly stably after actuator failure.

[0122] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for controllinglability analysis of a modular, reconfigurable coaxial aircraft, characterized in that, include: Based on the rotation direction of the upper and lower propellers in each flight unit module of the modular reconfigurable coaxial aircraft, the control allocation matrix of the modular reconfigurable coaxial aircraft is obtained. Based on the state of the upper and lower propeller actuators in each flight unit module of the modular reconfigurable coaxial aircraft, the actuator efficiency loss matrix is ​​obtained. Based on the control allocation matrix of the modular reconfigurable coaxial aircraft and the actuator efficiency loss matrix, a control allocation matrix considering the actuator state is obtained. Based on the control allocation matrix that takes into account the actuator state, a controllability analysis is performed; The control allocation matrix for the modular reconfigurable coaxial aircraft is expressed as follows: ； in, This represents the control assignment matrix for a modular, reconfigurable coaxial aircraft. , These represent the first, second, and third parts of the modular reconfigurable coaxial aircraft. The position of the upper propeller in the airframe coordinate system within each flight unit module. , These represent the first, second, and third parts of the modular reconfigurable coaxial aircraft. In the flight unit module, the lower propeller's position in the body coordinate system is i = {1, 2, ..., N}, which represents the position of the i-th propeller in the modular reconfigurable coaxial aircraft. N represents the number of flight unit modules in the modular reconfigurable coaxial aircraft; The first modular reconfigurable coaxial aircraft The rotation direction of the upper propeller in each flight unit module, The first modular reconfigurable coaxial aircraft The rotation direction of the lower propeller in each flight unit module; The actuator efficiency loss matrix is ​​expressed as follows: ; The first modular reconfigurable coaxial aircraft The status values ​​of the upper and lower brushless motors of each flight unit module.

2. The controllability analysis method for a modular reconfigurable coaxial aircraft according to claim 1, characterized in that, Based on the modular reconfigurable coaxial aircraft control allocation matrix and the actuator efficiency loss matrix, a control allocation matrix considering actuator states is obtained, expressed as follows: ； in, This represents the control allocation matrix that takes into account the actuator state; This represents the control assignment matrix for a modular, reconfigurable coaxial aircraft. This represents the actuator efficiency loss matrix.

3. The controllability analysis method for a modular reconfigurable coaxial aircraft according to claim 1, characterized in that, The controllability analysis based on the control allocation matrix considering the actuator state includes: If the rank of the control allocation matrix considering the actuator state is equal to the preset value, it is considered controllable; otherwise, it is uncontrollable.

4. A control redistribution method for a modular, reconfigurable coaxial aircraft, characterized in that, include: According to the controllability analysis method described in any one of claims 1-3, after determining that the reconfigurable coaxial aircraft meets the controllability conditions, the virtual control input of the reconfigurable coaxial aircraft is calculated based on the desired trajectory of altitude and attitude. The control allocation matrix considering the actuator state is obtained, and finally the redistribution input vector of the actuator after the actuator of the reconfigurable coaxial aircraft fails is obtained.

5. A modular, reconfigurable coaxial aircraft, characterized in that, The controllability analysis method for implementing any one of claims 1-3 includes a flight unit module (27), the flight unit module (27) including a coaxial twin-rotor aircraft (18) and a mechanical connection device (19); two adjacent flight unit modules (27) are connected by the mechanical connection device (19); the coaxial twin-rotor aircraft (18) includes a frame, a power assembly and a steering assembly, the frame being used to mount the power assembly and the steering assembly; The power assembly includes an upper propeller (2), a lower propeller (5), an upper brushless motor (1), a lower brushless motor (6), a motor flange (17), and a main shaft (4). The upper brushless motor (1) is fixed on the top plate (3) and its output shaft is located on the side away from the upper panel (3) of the frame. The upper propeller (2) is fixed on the output shaft of the upper brushless motor (1). The motor flange (17) fixed on the other side of the top plate (3) is fixed to one end of the main shaft (4). The lower brushless motor (6) and the lower propeller (5) are sequentially mounted on the main shaft. The extended end of the main shaft (4) is used to fix to the fisheye bearing (10) of the steering assembly and then passes through the tilting plate (11) of the steering assembly to be fixed to the lower panel (8) of the frame. The lower brushless motor (6) fixed on the motor flange (17) drives the lower propeller (5), and the upper brushless motor (1) drives the upper propeller (2).

6. The modular reconfigurable coaxial aircraft according to claim 5, characterized in that, The steering assembly includes a fisheye bearing (10), a swashplate (11), a servo motor (12), a servo motor linkage (14), and a tie rod (15). The fisheye bearing (10) is mounted on the main shaft (4) of the power assembly. The inner ring of the swashplate (11) is connected to the outer ring of the fisheye bearing (10) by an interference fit. The rotation of the servo motor (12) sequentially pulls the swashplate (11) connected to the tie rod (15) connected to the servo motor (12) via the servo motor linkage (14) connected to the servo motor (12) and the tie rod (15) connected to the servo motor linkage (14), thereby changing the pitch of the lower propeller (5).

7. The modular reconfigurable coaxial aircraft according to claim 5, characterized in that, The mechanical connection device (19) includes a first gripper, a second gripper, a reduction motor (22), a connecting rod (23), a crank (24), a vertical plate (25), a first slot, and a second slot. The vertical plate (25) is used to fix the frame. The reduction motor (22) drives the crank (24) at the output end to rotate. The rotation of the crank (24) drives the first gripper and the second gripper, which are eccentrically connected to the upper and lower ends of the crank (24), to perform opening and closing movements. The opening and closing movements of the first gripper and the second gripper of one flight unit module (27) are used to cooperate with the first slot and the second slot on the vertical plate (25) of another flight unit module (27).

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