Key performance evaluation method for geometrically invariant configuration fully-actuated multirotor unmanned aerial vehicle

Abstract

The application discloses a kind of geometric invariant configuration full-drive multi-rotor unmanned aerial vehicle key performance evaluation method.It includes the following steps:S1, obtaining full-drive multi-rotor unmanned aerial vehicle, initial information is collected;S2, establishing performance evaluation model, the flight ability, flat flying acceleration performance, attitude operating performance, configuration influence degree on controllability of unmanned aerial vehicle are evaluated based on the initial information;Wherein, the evaluation standard of the flight ability is the minimum value in each orientation maximum pull force and the ratio of total machine gravity, the evaluation standard of the flat flying acceleration performance is the maximum translational acceleration of unmanned aerial vehicle along the three-axis direction of body coordinate system, the evaluation standard of the attitude operating performance is the maximum angular acceleration of rotation around the three-axis direction of body coordinate system, and the evaluation standard of the configuration influence degree on controllability is the change degree of inertia tensor with attitude reference coordinate system;S3, output evaluation result.The application has the characteristics of comprehensive, intuitive and efficient evaluation.

Description

Technical Field

[0001] The present invention relates to the field of unmanned aerial vehicle (UAV) performance evaluation, and in particular to a key performance evaluation method for a geometrically invariant fully driven multi-rotor UAV. Background Art

[0002] A multirotor drone is a specialized unmanned helicopter with three or more rotor shafts. Each shaft's electric motor drives the rotors, generating lift and thrust. Unlike conventional helicopters, the collective rotor pitch is fixed, unlike a conventional helicopter's variable pitch. By varying the relative rotational speed of the rotors, the propulsion force per shaft can be adjusted, thereby controlling the drone's trajectory. It offers excellent maneuverability, capable of vertical takeoff and landing, and hovering. It is primarily suitable for low-altitude, low-speed missions requiring vertical takeoff and landing, as well as hovering. Its rotors typically have an even number of configurations, such as four or eight, and primarily come in two types: "x" and "+" configurations. The rotors are evenly distributed around the aircraft, with paired forward and reverse propellers. By controlling the motor's rotational speed, the drone's flight posture can be controlled. Due to its simple production, small size, and ease of operation, it can adapt to various environments. In particular, compared to single-rotor drones of the same size, it has a stronger load capacity, superior anti-interference ability, and superior controllability. In recent years, it has gradually emerged in the field of drones and has become a hot research field. It is used in various tasks, including aerial filming, inspection and surveying, and search and rescue. However, since the rotors of conventional multi-rotor drones can only generate lift in the direction perpendicular to the fuselage, it is necessary to tilt the fuselage to generate a component force in the horizontal plane when flying forward. Therefore, the horizontal movement of the fuselage is coupled with the pitch and roll movements, and the drone has only four independently controllable degrees of freedom. Due to the under-actuated characteristics of conventional multi-rotor drones, they can only be used as an aerial motion platform to carry operating equipment to perform operating tasks, and their application scenarios are limited. In order to further expand the scope of application of multi-rotor drones, researchers at home and abroad have begun to study fully-driven multi-rotor drones with more than four independently controlled degrees of freedom. This type of drone can independently generate forces and torques in all directions and can achieve horizontal movement without tilting the fuselage. Therefore, it has higher anti-interference and flexibility than traditional under-actuated drones, and is more advantageous in completing complex tasks involving environmental force interactions such as grasping and carrying, screwing valves, and installing pipes.

[0003] With the rapid development of drone technology, the widespread adoption of drones, and the booming growth of miniaturized multi-rotor drones, flight quality issues have become a significant constraint on the steady growth of rotary-wing drones, drawing significant attention from both domestic and international drone suppliers and buyers. Various application areas place high demands on all aspects of drone platform performance, especially when using different flight control algorithms or carrying different measurement payloads. Drone performance evaluation is crucial for subsequent precise testing and adjustments.

[0004] Currently, there are two main structural design approaches for fully actuated rotorcraft UAV platforms: variable geometry and fixed geometry. The former achieves full actuation by varying the power unit's orientation and rotor thrust during flight, while the latter achieves full actuation through non-parallel rotor thrust variations. A special category of fully actuated multirotors is the omnidirectional multirotor. The former only achieves full actuation within a specific attitude range, while the latter can achieve independent control of six degrees of freedom in any attitude. Fixed geometry fully actuated multirotor UAVs offer advantages such as simple structure and easy maintenance. However, performance evaluation of these UAVs remains challenging. This is due to the limited published research results or reference literature on the flight performance of miniaturized multirotor UAVs, and the lack of comprehensive evaluations. Furthermore, multirotor UAVs differ significantly from manned aircraft in various aspects, making existing flight performance specifications based on manned aircraft unsuitable for the development of multirotor UAVs. However, existing UAV testing often relies excessively on pilots, evaluating UAV performance based on their intuitive perceptions. This method is time-consuming and labor-intensive, unintuitive and inefficient. It can also easily cause damage to the drone and even pose a threat to personal safety. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a comprehensive, intuitive and efficient method for evaluating the key performance of a fully driven multi-rotor UAV with a geometrically invariant configuration.

[0006] Technical solution: The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV of the present invention comprises the following steps:

[0007] S1. Obtain a fully-driven multi-rotor drone and collect initial information;

[0008] S2. Establishing a performance evaluation model to evaluate the UAV's flight capability, level flight acceleration performance, attitude maneuverability, and the impact of the configuration on controllability based on the initial information;

[0009] The flight capability evaluation standard is the ratio of the minimum value of the maximum pull in each direction to the total gravity of the aircraft. The level flight acceleration performance evaluation standard is the maximum translational acceleration of the UAV along the three axes of the aircraft coordinate system. The attitude maneuverability evaluation standard is the maximum angular acceleration of the UAV around the three axes of the aircraft coordinate system. The configuration's impact on controllability is evaluated by the degree of change in the inertia tensor along the attitude reference coordinate system.

[0010] S3. Output the evaluation results.

[0011] Furthermore, the initial information includes the number of rotors, rotor position coordinates, rotor direction coordinates, rotor pull range and counter-torque range, and the total mass of the UAV.

[0012] Furthermore, when evaluating the flight capability, the evaluation is based on the resultant force and resultant torque generated by all the rotors of the UAV. The resultant force and resultant torque are as follows:

[0013]

[0014] Where, F b is the resultant force, b indicates that the variable is defined in the body coordinate system; M b is the resultant moment, b indicates that the variable is defined in the body coordinate system; k f is a constant value, representing the relationship between rotor speed and thrust, the unit is N / (rad / s) 2 , f indicates that the variable is used to characterize the relationship between rotor thrust and rotor speed; x is the motor position; r is the motor direction; ω is the speed; σ is a constant, and σ=k τ / k f , k τ is the relationship between rotor counter torque and rotor speed, unit is N·m / (rad / s) 2 , τ indicates that this variable is used to characterize the relationship between the rotor anti-torque and the rotor speed.

[0015] Furthermore, when evaluating the level flight acceleration performance, the translational acceleration a caused by the rotor aerodynamic force is b Evaluation, the translational acceleration formula is as follows:

[0016]

[0017] Where R is the real number field, R 3 represents a three-dimensional real vector space; m is the mass of the drone; a b is the translational acceleration; F b is the resultant force, and b indicates that the variable is defined in the body coordinate system.

[0018] Furthermore, when evaluating the attitude maneuverability, the rotational acceleration caused by the rotor aerodynamic force is evaluated, and the rotational acceleration formula is as follows:

[0019]

[0020] Where J0 is the inertia tensor matrix in the UAV body coordinate system; α b is the rotational acceleration; M b is the resultant torque, and b indicates that the variable is defined in the body coordinate system.

[0021] Furthermore, when evaluating the influence of the configuration on the controllability, the evaluation is based on the inertia tensor.

[0022] Furthermore, in the attitude reference coordinate system, the origin of the coordinate system coincides with the center of gravity of the fuselage, the projection of the X-axis of the fuselage coordinate system in the horizontal plane is the X-axis, the Z-axis is perpendicular to the ground and points downward, and the Y-axis is defined according to the right-hand rule.

[0023] Furthermore, in the performance evaluation model, the minimum value of the maximum pulling force in each direction, the maximum translational acceleration, and the maximum angular acceleration are obtained by constructing an envelope diagram.

[0024] Furthermore, when the UAV has an arbitrary posture, the minimum value of the maximum pulling force in each direction is selected, which includes the following process: determining the reachable force envelope diagram based on the resultant force, and when the ratio of the maximum inscribed sphere radius of the reachable force envelope diagram to the gravity of the UAV is greater than 1, the UAV has the ability to fly in any posture.

[0025] Furthermore, the degree of change of the inertia tensor with the attitude reference coordinate system is determined by a change index, and the change index formula is as follows:

[0026] ζ=avg({||(J s -J0) / J0||2,R bs ∈SO(3)})

[0027] Where ζ is the change index; ||·||2 is the matrix norm; avg(·) is the average value of the elements in the set; R bs is the rotation matrix from the body axis system to the attitude reference coordinate system; SO(3) is the rotation group; J s is the inertia matrix in the attitude reference coordinate system; J0 is the inertia matrix in the body axis system.

[0028] Beneficial effects: The present invention has the following significant effects: 1. Comprehensive evaluation: On the one hand, the present invention evaluates the flight capability, level flight acceleration performance, attitude operation performance, and the influence of configuration on controllability of the UAV, and adopts multiple key performance indicators; on the other hand, the present invention can obtain the minimum value of the maximum tension in each direction and the degree of change of the inertia tensor with the attitude reference coordinate system through the change index of the UAV in any attitude, so the evaluation is more comprehensive, which is convenient for obtaining data and subsequent data processing; 2. Intuitive and efficient: The present invention obtains the minimum value of the maximum tension in each direction, the maximum translational acceleration, and the maximum angular acceleration by constructing an envelope diagram. The formed envelope diagram displays the relevant indicators in a visual form, which is more intuitive, convenient for observation and analysis, and improves processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1Schematic diagram of the key performance evaluation method proposed in the present invention;

[0030] Figure 2 Schematic diagram of the core calculation process of the key performance evaluation method;

[0031] Figure 3 Several motor position layouts are provided so that the inertia tensor does not change with rotation;

[0032] Figure 4 This is a front view of the fully-driven six-rotor drone proposed by the present invention;

[0033] Figure 5 This is an isometric view of the fully driven six-rotor drone proposed in the present invention;

[0034] Figure 6 Schematic diagram of the reach envelope corresponding to the UAV;

[0035] Figure 7 Schematic diagram of the reachable torque envelope corresponding to the UAV;

[0036] Figure 8 This is a schematic diagram of the envelope of the translational acceleration of the entire aircraft caused by the rotor force;

[0037] Figure 9 Schematic diagram of the envelope of the whole machine rotation acceleration caused by the rotor force. DETAILED DESCRIPTION

[0038] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0039] See also Figures 1 to 2 As shown, the present invention discloses a key performance evaluation method for a geometrically invariant fully driven multi-rotor UAV. The evaluation method comprises the following steps:

[0040] S1. Obtain a fully-driven multi-rotor drone and collect initial information.

[0041] S2. Establish a performance evaluation model to evaluate the UAV's flight capability, level flight acceleration performance, attitude operation performance, and the degree of influence of the configuration on controllability based on the initial information.

[0042] Among them, the evaluation standard of the flight capability is the ratio of the minimum value of the maximum pulling force in each direction to the gravity of the whole machine, the evaluation standard of the level flight acceleration performance is the maximum translational acceleration of the UAV along the three-axis direction of the body coordinate system, the evaluation standard of the attitude operation performance is the maximum angular acceleration of the rotation around the three-axis direction of the body coordinate system, and the evaluation standard of the degree of influence of the configuration on controllability is the degree of change of the inertia tensor with the attitude reference coordinate system.

[0043] S3. Output the evaluation results.

[0044] In this embodiment, in the body coordinate system, the origin coincides with the center of gravity of the fuselage, the X-axis points toward the nose, the Z-axis is perpendicular to the X-axis and points downward, and the Y-axis is defined according to the right-hand rule and points to the right. Because fully-driven drones can hover in any attitude, an attitude reference coordinate system is introduced to facilitate describing current attitude changes. In this attitude reference coordinate system, the origin coincides with the center of gravity of the fuselage, the projection of the X-axis of the body coordinate system into the horizontal plane is the X-axis, the Z-axis is perpendicular to the ground and points downward, and the Y-axis is defined according to the right-hand rule. In the performance evaluation model in step S2, envelope diagrams are constructed to obtain the minimum value of the maximum tension, maximum translational acceleration, and maximum angular acceleration in each orientation.

[0045] In step S1, the initial information of the UAV includes the number of rotors, rotor position coordinates, rotor direction coordinates, rotor pull range and anti-torque range, and the total mass of the UAV. Figures 3 to 5 As shown, the UAV design uses bidirectional rotors, and the maximum pulling force of the motor in both directions is consistent. When only considering the motor position, the UAV has three symmetry planes and the three symmetry planes are parallel to each other, thus satisfying the condition that the inertia tensor about the center of gravity does not change with rotation. After connecting the UAV motor positions in a certain order, a regular octahedron structure can be formed, so the UAV motor positions are arranged in a regular octahedron configuration. The total mass of this UAV is 1.85kg, that is, the gravity of the UAV is 1.85kg×9.8m / s 2 =18.13N. The inertia tensor matrix is ​​a diagonal matrix, so J s =J0.

[0046] When evaluating flight capability in step S2, in this embodiment, the drone's flight capability in any posture is evaluated. First, there are two conditions for a drone to possess the ability to fly in any posture: the first condition is that the lift generated by the drone is greater than its gravity, and the second condition is that, even after satisfying condition one, the drone can still generate a certain control torque. Therefore, the drone's flight capability in any posture can be evaluated based on its power configuration. The quantitative evaluation criterion is the ratio of the minimum value of the drone's maximum pulling force in each direction to the total gravity of the drone. Selecting the minimum value of the maximum pulling force in each direction when the drone is capable of any posture includes the following process: determining a reachable force envelope based on the resultant force. The drone possesses the ability to fly in any posture only when the ratio of the maximum inscribed sphere radius of the reachable force envelope to the gravity of the drone is greater than 1.

[0047] The process of evaluating the flight capability and obtaining the minimum value of the maximum pulling force in each direction is as follows:

[0048] S211, input the number of rotors of the drone, the rotor position coordinate matrix and orientation coordinate matrix, the pull range and anti-torque range of each rotor, and the total mass of the drone and process them. For a multi-rotor drone with N rotors, use the 3×N matrix x=[x1 x2 … x N ] represents the position of the rotor, using a 3×N matrix r=[r1 r2… r N ] represents the direction of the rotor, where N is the number of rotors.

[0049] S212, determine the resultant force and torque. The core of this evaluation method is to determine whether the total pulling force of the drone can overcome gravity, so it is necessary to first calculate the total pulling force of the rotor. If the aerodynamic interference between the rotors is ignored, the resultant force F generated by the entire rotor is b With the resultant moment M b It can be calculated as follows:

[0050]

[0051]

[0052] Where, f i is the magnitude of the thrust generated by the i-th rotor; f imin is the minimum thrust of the i-th rotor; f imax is the maximum thrust of the i-th rotor; τ i is the magnitude of the counter-torque generated by the i-th rotor; the first term f in formula (2) i (x i ×r i ) represents the torque generated by the rotor thrust not passing through the center of gravity of the fuselage, and the second term τ i r i represents the counter torque caused by the rotor aerodynamic drag; N is the number of rotors; r i is the direction vector of the i-th rotor in the body coordinate system, and r i is a unit vector; x i is the position vector of the i-th rotor in the body coordinate system. For a fixed-pitch rotor, it is generally believed that only forces and moments along the rotor axis can be generated, and the magnitude of the pulling force |f| and the magnitude of the counter-torque |τ| are both proportional to the square of the rotational speed ω 2 Therefore, the pulling force is also proportional to the counter torque, which can be expressed as:

[0053]

[0054] Among them, k f and k τ are all fixed values, k f Represents the relationship between rotor speed and thrust, unit is N / (rad / s)2 ;k τ Represents the relationship between rotor anti-torque and thrust, unit is N·m / (rad / s) 2 Since the rotor thrust range is limited, for a given power combination, the thrust range generated is:

[0055]

[0056] Where, f is the rotor thrust, is the maximum positive tension, The maximum thrust in the reverse direction, the unidirectional rotor Usually it is 0. The maximum thrust of the bidirectional rotor in both directions is the same, that is

[0057] The total force F generated by the rotor can also be b With the resultant moment M b , that is, formula (1) and formula (2) are written in matrix form as:

[0058]

[0059]

[0060] Where σ = k τ / k f =τ imax / f imax , F b is the resultant force, b indicates that the variable is defined in the body coordinate system; M b is the resultant moment, b indicates that the variable is defined in the body coordinate system; k f is a constant value, representing the relationship between rotor speed and thrust, the unit is N / (rad / s) 2 , f indicates that the variable is used to characterize the relationship between rotor thrust and rotor speed; x is the motor position; r is the motor direction; ω is the speed; σ is a constant, and σ=k τ / k f , k τ is the relationship between rotor counter torque and rotor speed, unit is N·m / (rad / s) 2 , τ indicates that this variable is used to characterize the relationship between the rotor anti-torque and the rotor speed.

[0061] S213. Construct a reachable set of resultant forces and torques based on the resultant forces and torques, and further establish a reasonable envelope diagram and a resultant torque envelope diagram. For a given aircraft model, the motor position x and orientation r are both constant. Since the thrust of a single rotor is limited, the resultant forces and torques that the entire aircraft can generate are also limited. Taking a variable speed rotor as an example, the reachable set of the total force and torque of the entire aircraft is:

[0062]

[0063]

[0064] Where f=[f1 f2 … f3] T is the aggregate of the thrusts of individual rotors; and They are the reachable sets of the total force and total torque of the whole machine, representing the various total forces and total torques that can be generated by the UAV through different rotor thrust combinations.

[0065] Due to the force F b is a three-dimensional space vector, each F in the set b As the coordinate point of three-dimensional space, By plotting the points in the set in a three-dimensional coordinate system, we can visualize the set of reachable forces, thereby generating an envelope diagram of the reachable forces. Similarly, we can plot the envelope diagram of the reachable torques. Points on the reachable force envelope diagram represent the maximum pulling forces that the drone can generate in any direction. For any point P (x0, y0, z0) on the envelope diagram, if the distance between point P and the coordinate origin O is greater than the drone's gravity mg, the drone has the ability to overcome gravity in the corresponding attitude. Aligning the z-axis of the drone's coordinate system with the OP vector yields the drone's attitude at point P. Therefore, if the drone's reachable force envelope diagram completely encloses a sphere centered at the origin and with the drone's gravity as its radius, the drone has the ability to take off in any attitude. The quantitative evaluation criterion for a drone's arbitrary attitude is the ratio of the maximum inscribed sphere radius of the reachable force envelope diagram to the drone's gravity. A value greater than 1 indicates the drone has the ability to overcome gravity in any attitude.

[0066] In this embodiment, the maximum pulling force of the motor in both directions is the same, and the motor pulling table can be used to measure f max =|f min |=30N,τ max =|τ min |=0.3N·m, σ=k τ / k f =τ imax / f imax = 0.01. The number of rotors N of the drone is 6, so the corresponding motor position and motor orientation description matrices are both 3×6 matrices. Specifically:

[0067]

[0068]

[0069] See also Figures 6 and 7 The figure shows the envelope of the reachable force and the reachable torque of the drone. The total mass of the drone is 1.85 kg, that is, the gravity of the drone is 1.85 kg × 9.8 m / s 2 = 18.13N. When a sphere is drawn with the origin as its center and gravity as its radius, it lies completely within the reachable force envelope. Therefore, the reachable force envelope demonstrates the drone's ability to overcome gravity in all postures. The reachable force envelope also shows that the radius of the sphere inscribed within the aircraft's pull envelope is 33, and its ratio to gravity is 1.825.

[0070] When evaluating the level flight acceleration performance in step S2, Newton's second law shows that the UAV's translational acceleration is related to the UAV's net external force and the total mass of the UAV. Therefore, the set of UAV translational accelerations can be calculated based on the set of forces that the UAV can generate. The quantitative evaluation standard is the maximum translational acceleration of the UAV along the three axes of the body coordinate system.

[0071] The process of evaluating the level flight acceleration performance and obtaining the maximum translational acceleration is as follows:

[0072] S221, determine the translational acceleration. According to the reachable force set From the mass m of the drone, we can know that the translational acceleration a of the drone caused by the rotor aerodynamic force is b for:

[0073]

[0074] For electric multi-rotors, m is usually a fixed value; R is a real number domain, R 3 represents a three-dimensional real vector space; m is the mass of the drone; a b is the translational acceleration; F b is the resultant force, and b indicates that the variable is defined in the body coordinate system.

[0075] S222, determine the reachable set based on the translational acceleration, and then determine the corresponding envelope diagram. According to the definition of the reachable force and reachable torque envelope diagram, the reachable set of the translational acceleration caused by the rotor pull of the UAV can be obtained. as follows.

[0076]

[0077] Since the UAV needs to overcome gravity when flying in the air, the reachable set of the UAV's translational acceleration is:

[0078]

[0079] Where R ebis the rotation matrix from the earth axis to the body axis. When the UAV is horizontal, R eb is the identity matrix; is the reachable set of translational accelerations.

[0080] gather All elements in the set are actually All elements in the vector R eb [0 0 -g] T Since vector translation does not change the relative positions of elements in the collection, it can still be achieved through The maximum translational acceleration of the UAV is obtained from the envelope diagram of . In this embodiment, please refer to Figure 8 As shown in the figure, the envelope diagram of the translational acceleration of the drone caused by the rotor force is shown. It can be seen from the figure that the maximum translational acceleration of the drone along the x-direction and the y-direction is 29.21m / s respectively. 2 and 34.42 m / s 2 , the maximum acceleration of climbing upward is 35.78-g=25.98m / s 2 .

[0081] When evaluating the attitude operation performance in step S2, the fixed-axis rotation theorem shows that the rotational acceleration of the drone is related to the total external torque of the drone and the inertia tensor about the center of gravity. Therefore, the set of rotational accelerations of the drone can be calculated based on the set of torques that the drone can generate. The quantitative evaluation standard is the maximum angular acceleration of the drone around the three axes of the body coordinate system.

[0082] The process of evaluating attitude operation performance and obtaining maximum angular acceleration is as follows:

[0083] S231, reachable torque set And the inertia tensor matrix in the UAV attitude reference coordinate system, the rotational acceleration α caused by the rotor aerodynamic force of the UAV b It can be expressed as:

[0084]

[0085] Where J0 is the inertia tensor matrix in the UAV body coordinate system; α b is the rotational acceleration; M b is the resultant torque, and b indicates that the variable is defined in the body coordinate system.

[0086] S232. Based on the definition of the reachable force and reachable torque envelope, the reachable set of the rotational acceleration of the UAV caused by the rotor pull can be defined as follows:

[0087]

[0088] S233, the maximum angular acceleration of the UAV around the three axes of the body coordinate system can be obtained from the reachable envelope diagram of the UAV rotation acceleration. Figures 4 and 5 The figure below shows the design of a drone. When only considering the motor positions, the drone has three planes of symmetry, and the three planes of symmetry are parallel to each other, thus satisfying the condition that the inertia tensor about the center of gravity does not change with rotation. After connecting the drone motor positions in a certain order, a regular octahedron structure can be formed. Using qualitative analysis methods, it can be determined that the inertia matrix about the center of gravity of the drone does not change with random body rotation. Figure 3 Shown are several layouts where the inertia tensor does not change with the rotation of the body.

[0089] The total mass of the drone is 1.85 kg. It is assumed that the mass of the drone is concentrated at the six motor positions. The mass of a single motor is 0.308 kg, and the distance between the motor mass and the center of gravity is 0.203 m. Therefore, the inertia matrix of the drone is calculated as:

[0090]

[0091] The inertia matrix is ​​a multiple of a third-order identity matrix, and the calculation results also show that the inertia tensor of the drone about the center of gravity does not change with rotation.

[0092] See also Figure 9 As shown in the figure, it is the envelope diagram of the rotation acceleration of the whole drone caused by the rotor force. It can be seen from the figure that the maximum rotation acceleration of the drone around the three axes is 10.28rad / s 2 、13.35rad / s 2 and 10.92 rad / s 2 .

[0093] The reason for evaluating the influence of the configuration on controllability in step S2 is that, since the fully-driven UAV can achieve arbitrary flight posture, the controllability of the UAV will change with the change of the fuselage posture. The change of controllability will affect the flight quality of the UAV. Therefore, the influence on controllability needs to be considered when selecting the configuration.

[0094] When evaluating the impact of configuration on controllability, the quantitative evaluation criterion is the change in the drone's inertia tensor relative to the attitude reference coordinate system. Drone controllability is related to the rotor force / torque, the overall mass, and the drone's inertia tensor. However, for electric multi-rotor drones, the overall mass is primarily concentrated in the battery and motors. The drone's configuration generally determines the mass distribution and, therefore, the inertia tensor. Therefore, the impact of the drone's configuration on controllability can be measured by the change in the inertia tensor relative to the drone's attitude. This evaluation model requires the drone's inertia tensor in the body coordinate system as input.

[0095] The specific process is as follows: Establish a rotation matrix to describe the relationship between the body coordinate system and the attitude reference coordinate system, where the rotation matrix corresponding to the rotation from the body coordinate system to the attitude reference coordinate system is R bs , and there are:

[0096]

[0097] Where, J S is the inertia tensor of the UAV in the attitude reference coordinate system; J0 is the inertia tensor in the body coordinate system; R bs is the rotation matrix corresponding to the rotation from the body coordinate system to the attitude reference coordinate system. For a fully driven multi-rotor flying in any attitude, R bs It can be any three-dimensional rotation, that is, R bs ∈SO(3)(rotation group).

[0098] Therefore, the change of the UAV's inertial tensor with random body rotation can be obtained by formula (17). At the same time, a change index is proposed. The change index represents the influence of the UAV configuration on the change of controllability. When ζ = 0, it means that the UAV's rotor has no effect on controllability under this configuration. The larger the ζ value, the greater the influence of the UAV's rotation on controllability. The change index formula is as follows:

[0099] ζ=avg({||(J s -J0) / J0||2,R bs ∈SO(3)}) (18)

[0100] Where ζ is the inertia tensor J S The change index of random body rotation; ||·||2 is the matrix norm; avg(·) is the average value of the elements in the set; R bs is the rotation matrix from the body axis system to the attitude reference coordinate system; SO(3) is the rotation group; J s is the inertia matrix in the attitude reference coordinate system; J0 is the inertia matrix in the body axis system.

[0101] In this embodiment, the inertia tensor matrix is ​​a diagonal matrix, so J s =J0. According to formula (18), ζ = 0, so when the UAV of this configuration flies in any posture, the inertia tensor will not cause the change of the controllability of the UAV.

Claims

1. A key performance evaluation method for a geometrically invariant fully driven multi-rotor UAV, characterized in that: The evaluation method comprises the following steps: S1. Obtain a fully-driven multi-rotor drone and collect initial information; S2. Establishing a performance evaluation model to evaluate the UAV's flight capability, level flight acceleration performance, attitude maneuverability, and the impact of the configuration on controllability based on the initial information; The flight capability evaluation standard is the ratio of the minimum value of the maximum pulling force in each direction to the total gravity of the aircraft. The level flight acceleration performance evaluation standard is the maximum translational acceleration of the UAV along the three axes of the aircraft coordinate system. The attitude operation performance evaluation standard is the maximum angular acceleration of the rotation around the three axes of the aircraft coordinate system. The configuration's impact on controllability is evaluated by the degree of change in the inertia tensor along the attitude reference coordinate system. In the performance evaluation model, the minimum value of the maximum pulling force in each direction, the maximum translational acceleration, and the maximum angular acceleration are obtained by constructing an envelope diagram; Selecting the minimum value of the maximum pulling forces in each direction when the drone has an arbitrary posture, including the following process: determining a reachable force envelope based on the resultant force generated by all rotors of the drone, and when the ratio of the maximum inscribed sphere radius of the reachable force envelope to the gravity of the drone is greater than 1, the drone has the ability to fly in any posture; S3. Output the evaluation results.

2. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: The initial information includes the number of rotors, rotor position coordinates, rotor direction coordinates, rotor pull range and anti-torque range, and the total mass of the UAV.

3. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: When evaluating the flight capability, the evaluation is based on the resultant force and torque generated by all the rotors of the drone. The resultant force and torque are as follows: Where, For the joint efforts, Indicates that the variable is defined in the body coordinate system; is the resultant moment, Indicates that the variable is defined in the body coordinate system; is a constant value, representing the relationship between rotor speed and thrust, and its unit is , Indicates that this variable is used to characterize the relationship between rotor thrust and rotor speed; is the motor position; is the direction of the motor; is the rotational speed; is a constant, and , is the relationship between the rotor anti-torque and the rotor speed, and the unit is , This variable is used to characterize the relationship between rotor anti-torque and rotor speed.

4. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: When evaluating the level flight acceleration performance, the translational acceleration caused by the rotor aerodynamic force is Evaluation, the translational acceleration formula is as follows: Where, is the field of real numbers, represents a three-dimensional real vector space; For drone quality; is the translational acceleration; For the joint efforts, Indicates that the variable is defined in the body coordinate system.

5. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: When evaluating the attitude maneuverability, the rotational acceleration caused by the rotor aerodynamic force is evaluated. The rotational acceleration formula is as follows: Where, is the inertia tensor matrix in the UAV body coordinate system; is the rotational acceleration; is the resultant moment, Indicates that the variable is defined in the body coordinate system.

6. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: When evaluating the influence of the configuration on the controllability, the inertia tensor is evaluated.

7. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: In the attitude reference coordinate system, the origin of the coordinate system coincides with the center of gravity of the fuselage, the projection of the X-axis of the fuselage coordinate system in the horizontal plane is the X-axis, the Z-axis is perpendicular to the ground and points downward, and the Y-axis is defined according to the right-hand rule.

8. The key performance evaluation method of the geometrically invariant fully driven multi-rotor UAV according to claim 1 is characterized in that: The degree of change of the inertia tensor with the attitude reference coordinate system is determined by the change index, and the change index formula is as follows: Where, is an indicator of change; is the two-norm of the matrix; is the average value of the elements in the set; is the rotation matrix from the body axis system to the attitude reference coordinate system; is the rotation group; is the inertia matrix in the attitude reference coordinate system; is the inertia matrix of the body axis system.

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