A modeling and attitude control method for a tilt-rotor aircraft

Abstract

The present invention relates to the technical field of aircraft, and is a modeling and attitude control method for a tiltrotor aircraft. First, a dynamic model of "multi-rotor-tiltrotor-tiltrotor and aerodynamic shape" is established. Then, control parameters are obtained by designing a simple aircraft controller with the same mass and moment of inertia. Then, the controller parameters of the tiltrotor aircraft with an aerodynamic shape are designed based on these parameters through a regression strategy based on the least squares method. The present invention completes the attitude control of the tiltrotor aircraft with an aerodynamic shape in such a bottom-up and step-by-step manner. The controller design method proposed by the present invention has a simple structure, does not require the establishment of an additional complex aircraft model, and can meet the aircraft system performance requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft, and in particular to a modeling and attitude control method for a tilt-rotor aircraft. Background Art

[0002] In the past few decades, aircraft have experienced tremendous development and have been widely used in various fields. At present, most aircraft can be divided into two categories, namely fixed-wing aircraft and rotary-wing aircraft. The former generates the required lift through the aerodynamic shape of the wing, and can fly at high speed over long distances. However, it requires specially designed runways or landing equipment; the latter generates lift through the vertical upward rotor, can work in a small space, and has a unique hovering ability. However, the flight speed and endurance are insufficient.

[0003] Compared with traditional aircraft, tilt-rotor aircraft have fixed wings and multiple tiltable rotors. There are three flight modes according to the tilt angle of the rotors, namely helicopter mode, airplane mode and transition mode. Therefore, tilt-rotor aircraft can combine the advantages of two types of aircraft and have a very bright application prospect.

[0004] However, the tilt-rotor aircraft is a highly complex system, and its structure and aerodynamic characteristics vary significantly and are coupled between the three flight modes, making it difficult to establish its dynamic model. Existing methods mostly use nonlinear dynamic models established by the Newton-Euler method or the Euler-Lagrange method, which have the following defects: first, the lack of key parameters makes it difficult to establish the dynamic model; second, the model structure is complex, the controller is difficult to design, and the control parameters are difficult to adjust; third, most studies only test by computer software simulation experiments through simplified models, and performance and safety tests are still required in actual aircraft. To this end, the present invention proposes a modeling and attitude control method for tilt-rotor aircraft to solve the above defects. Summary of the invention

[0005] The object of the present invention is to provide a modeling and attitude control method for a tilt-rotor aircraft to solve the problems raised in the above background technology.

[0006] To achieve the above object, a modeling and attitude control method for a tilt-rotor aircraft comprises the following steps:

[0007] Step S1, establishing a dynamic model of "multi-rotor-tilt rotor-tilt rotor and aerodynamic shape";

[0008] Step S2, designing a multi-rotor aircraft attitude control PD controller with the same mass and moment of inertia to obtain control parameters;

[0009] Step S3, based on the least squares regression strategy, designing the PD parameter setting of the attitude control of the tilt-rotor aircraft with an aerodynamic shape on the basis of the parameters in step S2;

[0010] Step S4, distributing attitude control parameters of the tilt-rotor aircraft having an aerodynamic shape to each controller;

[0011] Step S5, according to the control parameter allocation method of the controller, the PD control parameters of the aileron, rudder and elevator of the tilt-rotor aircraft with an aerodynamic shape are obtained respectively, and the control of the inclination angle and rotation speed of each rotor is completed to complete the attitude control of the entire aircraft.

[0012] Preferably, in step S1, the torque magnitude of the tilt-rotor aircraft around each axis is determined by the thrust, the rotor tilt angle and the rotor axial moment coefficient, and the torque magnitude of the fixed-wing aircraft around each axis is determined by the aerodynamic shape of the aircraft.

[0013] Preferably, the expression of the dynamic model of the tilt-rotor aircraft in step S1 is as follows:

[0014]

[0015]

[0016]

[0017] Among them, l z , l x represents the distance from the rotor axis to the center of mass of the aircraft on the propeller plane, (x CG ,y CG ,z CG ) is the coordinate of the center of gravity of the aircraft, (x i ,y i ,z i ) is the coordinate of the rotor axis, μ is the axial moment coefficient of the rotor (M ax =μT), representing thrust T and axial moment M ax The linear relationship between

[0018] For fixed-wing aircraft, the dynamic model is expressed as follows:

[0019]

[0020]

[0021]

[0022] Where q = 0.5ρV 2represents dynamic pressure, ρ represents air density, V represents airspeed, S represents wing area, L represents wing span, and b A represents the average aerodynamic chord length of the wing, α represents the angle of attack, β represents the slip angle, ω x ,ω y ,ω z represents the component of angular velocity, Represents the rolling moment and the slip angle β, aileron angle δa and angular velocity ω x The coefficient between Represents the yaw moment and the slip angle β, rudder angle δr and angular velocity ω y The coefficient between z0 represents the pitching moment coefficient at zero angle of attack, Denote the angle of attack α, the elevator angle δe and the angular velocity ω z Coefficient for the pitching moment.

[0023] Preferably, the expression of the PD controller of the multi-rotor aircraft in step S2 is as follows:

[0024]

[0025]

[0026]

[0027] in, represents the calculated control values ​​of the roll, pitch and yaw moment coefficients, represents the proportional and differential coefficients of the controller, γ is the roll angle, ψ is the yaw angle, θ is the pitch angle, ω x ,ω y ,ω z is the current angular velocity component of the aircraft, γ d ,ψ d ,θ d Indicates the target attitude angle position of the multirotor aircraft.

[0028] Preferably, the step S3 adopts a segmented PD controller, divides the flight into stages according to different flight states of the aircraft, and calculates the corresponding PD parameters of each stage by the least squares method.

[0029] Preferably, the controller expression based on the least squares regression strategy in step S3 is as follows:

[0030]

[0031]

[0032]

[0033] i=1,...,n

[0034] in, represents the proportional and differential coefficients of the aerodynamically shaped tiltrotor controller, γ err =γ d -γ,ψ err =ψ d -ψ,θ err =θ d -θ is the angular position error of the aerodynamically shaped tiltrotor aircraft.

[0035] Preferably: the expression for controlling the allocation in step S4 is as follows:

[0036]

[0037]

[0038]

[0039] in, are the proportional and differential coefficients of the aileron controller for the aerodynamically shaped tiltrotor aircraft, are the proportional and differential coefficients of the rudder controller for the aerodynamically shaped tiltrotor aircraft, are the proportional and differential coefficients of the elevator controller for a tiltrotor aircraft with an aerodynamic shape.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The "multi-rotor-tilt rotor-with aerodynamic shape" modeling method proposed in the present invention is completed step by step from bottom to top. Since it does not require the direct establishment of a complex aircraft model, it has a simple structure and is easy to construct. At the same time, the proposed controller parameter tuning method based on the least squares regression strategy designs the corresponding controller parameters in real time according to the different flight states of the aircraft. Such a refined adaptive real-time optimization method has a simple structure and can effectively enhance the overall stability and attitude control accuracy of the aircraft, meeting the performance requirements of the aircraft system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the method of the present invention;

[0043] Figure 2 It is the decomposition of the tiltrotor thrust in the X and Y axis directions;

[0044] Figure 3 is the torque of the tiltrotor aircraft around the X axis;

[0045] Figure 4is the torque of the tiltrotor aircraft around the Y axis;

[0046] Figure 5 is the torque of the tiltrotor aircraft around the Z axis;

[0047] Figure 6 is the control effect of two sets of control coefficients on the roll angle position;

[0048] Figure 7 is the control effect of two groups of control coefficients at the pitch angle position;

[0049] Figure 8 is the control effect of two groups of control coefficients on yaw angle position;

[0050] Fig. 9 The response of a tilt-rotor aircraft with an aerodynamic shape to a rolling disturbance;

[0051] Fig.10 The response of a tilt-rotor aircraft with an aerodynamic shape to a pitch disturbance;

[0052] Fig.11 The response of a tilt-rotor aircraft with an aerodynamic shape to a yaw disturbance. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the implementation regulations described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Example

[0055] See also Figure 1-Figure 11 , FIG. 1 is a preferred embodiment of the present invention, a modeling and attitude control method of a tilt-rotor aircraft, comprising the following steps:

[0056] Step S1, establishing a dynamic model of "multi-rotor-tilt rotor-tilt rotor and aerodynamic shape";

[0057] Step S2, designing a multi-rotor aircraft attitude control PD controller with the same mass and moment of inertia to obtain control parameters;

[0058] Step S3, based on the least squares regression strategy, designing the PD parameter setting of the attitude control of the tilt-rotor aircraft with an aerodynamic shape on the basis of the parameters in step S2;

[0059] Step S4, distributing attitude control parameters of the tilt-rotor aircraft having an aerodynamic shape to each controller;

[0060] Step S5, according to the control parameter allocation method of the controller, the PD control parameters of the aileron, rudder and elevator of the tilt-rotor aircraft with an aerodynamic shape are obtained respectively, and the control of the inclination angle and rotation speed of each rotor is completed to complete the attitude control of the entire aircraft.

[0061] Further, such as Figure 2 As shown, the rotor thrust of the tilt-rotor aircraft is decomposed in the X and Y axis directions:

[0062]

[0063] Among them, T i is the thrust generated by propeller i, φ i is the angle of the force generated by propeller i relative to the horizontal direction, satisfying 0≤φ i ≤90°.

[0064] In this embodiment, refer to Figure 3-Figure 5 , for a tiltrotor aircraft, the moments about the X, Y, and Z axes are They are expressed as:

[0065]

[0066] in, represents the calculated control values ​​of the roll, pitch and yaw moment coefficients, represents the proportional and differential coefficients of the controller, γ is the roll angle, ψ is the yaw angle, θ is the pitch angle, ω x ,ω y ,ω z is the current angular velocity component of the aircraft, γ d ,ψ d ,θ d Indicates the target attitude angle position of the multirotor aircraft.

[0067] Furthermore, for a fixed-wing aircraft with an aerodynamic shape, the moments about the X-axis, Y-axis, and Z-axis are They are expressed as:

[0068]

[0069]

[0070] Where q = 0.5ρV 2 represents dynamic pressure, ρ represents air density, V represents airspeed, S represents wing area, L represents wing span, and b A represents the average aerodynamic chord length of the wing, α represents the angle of attack, β represents the slip angle, ω x ,ωy ,ω z represents the component of angular velocity, Represents the rolling moment and the slip angle β, aileron angle δa and angular velocity ω x The coefficient between Represents the yaw moment and the slip angle β, rudder angle δr and angular velocity ω y The coefficient between z0 represents the pitching moment coefficient at zero angle of attack, Denote the angle of attack α, the elevator angle δe and the angular velocity ω z Coefficient for the pitching moment.

[0071] After the dynamic models of the tilt-rotor aircraft and the fixed-wing aircraft are established respectively, the control system can be designed, and there is no need to establish a more complex dynamic model of the tilt-rotor aircraft with an aerodynamic shape.

[0072] The design of the aircraft control system is carried out from simple to complex. Starting from the classic quadcopter, the PD controller is designed through the error between the current aircraft angular position and the target angular position and the speed of the aircraft around each axis to obtain the control values ​​of the roll, pitch and yaw moment coefficients:

[0073]

[0074] in, represents the calculated control values ​​of the roll, pitch and yaw moment coefficients, represents the proportional and differential coefficients of the controller, γ is the roll angle, ψ is the yaw angle, θ is the pitch angle, ω x ,ω y ,ω z is the current angular velocity component of the aircraft; γ d ,ψ d ,θ d Indicates the target attitude angle position of the multirotor aircraft.

[0075] At the same time, compared with the quadrotor aircraft, the attitude controller of the tilt-rotor aircraft with an aerodynamic shape needs to be designed based on the existing quadrotor control system to address the differences brought about by the aerodynamic shape. The specific form is as follows:

[0076]

[0077] in, represents the proportional and differential coefficients of the aerodynamically shaped tiltrotor controller, γ err =γ d -γ,ψ err =ψ d -ψ,θ err =θd -θ is the angular position error of the aerodynamically shaped tiltrotor aircraft.

[0078] Furthermore, the controller design of the above formula (5) needs to determine the size of the angle of attack α and the sideslip angle β. However, in the quadrotor flight model with tilt rotors, the information of both is not clearly provided. The values ​​of α and β can be obtained by the following formula:

[0079]

[0080] Among them, T x represents the longitudinal thrust, and X, Y, and Z represent the aerodynamic components resolved on the velocity axis.

[0081] The tilt-rotor aircraft with an aerodynamic shape is a complex multi-body dynamic system with variable configuration. The structure and aerodynamic characteristics under the three flight modes are significantly different. The PD controller with fixed parameters designed by formula (5) is single in form and cannot effectively control the attitude angle position of the tilt-rotor aircraft with an aerodynamic shape under each flight mode. Therefore, the present invention adopts a segmented PD controller, divides the stage according to the different flight states of the aircraft, and calculates the corresponding PD parameters of each stage by the least squares method:

[0082]

[0083]

[0084] in, represents the proportional and differential coefficients of the aerodynamically shaped tiltrotor controller, γ err =γ d -γ,ψ err =ψ d -ψ,θ err =θ d -θ is the angular position error of the aerodynamically shaped tiltrotor aircraft.

[0085] Furthermore, the above formula (7) converts the PD control parameters of the aircraft's roll, pitch and yaw angle positions into the PD controller parameters of the aircraft's ailerons, rudder and elevator, making the aircraft's control easier to operate through parameter allocation.

[0086]

[0087] in, are the proportional and differential coefficients of the aileron controller for the aerodynamically shaped tiltrotor aircraft, are the proportional and differential coefficients of the rudder controller for the aerodynamically shaped tiltrotor aircraft, are the proportional and differential coefficients of the elevator controller for a tiltrotor aircraft with an aerodynamic shape.

[0088] In order to evaluate the effectiveness of the proposed method, the following experiments were conducted, focusing on the attitude control of a quadrotor aircraft (representing a simplified aircraft) and a tilt-rotor aircraft with an aerodynamic shape (representing a more complex aircraft type).

[0089] Experiment 1: A simulation experiment was conducted based on the PD controller (Equation 4) to control the attitude of a quadrotor. The experiment used two sets of coefficients: and To control a mass m = 90 kg and a moment of inertia J x =6kg·m 2 ,J y =12kg·m 2 ,J z =12kg·m 2 A virtual quadcopter is used to observe the response of the roll, pitch and yaw angle position information of the aircraft after the initial disturbance under different control parameters. The speed of each channel response and the nature of the transient process are used as the standard to judge the quality of the control coefficient;

[0090] Table 1 shows two sets of PD coefficient values ​​on the roll, pitch and yaw channels;

[0091] Depend on Figure 6-Figure 8 It can be seen that the second set of data has a faster response time after being disturbed by the roll, pitch and yaw angle positions, so it is more appropriate to use the second set of data.

[0092] Experiment 2: A simulation experiment was conducted based on the segmented PD controller (Equation 7) based on the least squares regression strategy to complete the attitude control of the tilt-rotor aircraft with an aerodynamic shape at different flight stages. The experiment selected a virtual tilt-rotor aircraft with an aerodynamic shape with the same mass and moment of inertia as Experiment 1 to perform attitude control from position 1 to position 6. Table 2 shows the PD controller parameters for each flight stage; Table 3 shows the roll, pitch and yaw angle position information of the tilt-rotor aircraft with an aerodynamic shape at each position.

[0093] Table 1

[0094]

[0095] Table 2

[0096]

[0097]

[0098] Table 3

[0099]

[0100] Experiment 3: According to the segmented PD controller (Equation 7) based on the least squares regression strategy, an actual experiment is carried out to complete the attitude control of the tilt-rotor aircraft with an aerodynamic shape at different flight stages. Figure 9-11 It can be seen that the tilt-rotor aircraft with an aerodynamic shape can quickly adjust its attitude after being disturbed by the roll, pitch and yaw angle positions during actual flight.

[0101] Based on the above, the advantage of the present invention is that the proposed "multi-rotor-tilt rotor-with aerodynamic shape" modeling method is completed from bottom to top and step by step. Since there is no need to directly establish a complex aircraft model, the structure is simple and easy to construct. The proposed controller parameter tuning method based on the least squares regression strategy designs the corresponding controller parameters in real time according to the different flight states of the aircraft. Such a refined adaptive real-time optimization method has a simple structure and can effectively enhance the overall stability and attitude control accuracy of the aircraft, meeting the performance requirements of the aircraft system.

[0102] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, some simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of protection determined by the claims submitted for the present invention.

Claims

1. A modeling and attitude control method for a tilt-rotor aircraft, characterized in that: The steps include: Step S1, establishing a dynamic model of "multi-rotor-tilt rotor-with aerodynamic shape"; Step S2, designing attitude control PD control parameters of multi-rotor aircraft with the same mass and moment of inertia; Step S3, based on the least squares regression strategy, designing the PD control parameter setting of the tilt-rotor aircraft attitude control with an aerodynamic shape on the basis of the parameters in step S2; Step S4, allocating the attitude control PD control parameters of the tilt-rotor aircraft with an aerodynamic shape to each controller; Step S5, according to the PD control parameter allocation method of the controller, the PD control parameters of the aileron, rudder and elevator of the tilt-rotor aircraft with an aerodynamic shape are respectively obtained, and the tilt angle and speed of each rotor are controlled to complete the attitude control of the entire tilt-rotor aircraft; The expression of the dynamic model of the tilt rotor and the aerodynamic shape in step S1 is as follows: Among them, (x CG ,y CG ,z CG ) is the coordinate of the center of gravity of the aircraft, (x i ,y i ,z i ) is the coordinate of the rotor axis, μ is the axial moment coefficient of the rotor, which represents the thrust T and axial moment M ax The linear relationship between are the moments of the tiltrotor around the X-axis, Y-axis and Z-axis respectively; T i is the thrust generated by propeller i, φ i is the angle of the force generated by propeller i relative to the horizontal direction, satisfying 0≤φ i ≤90°; The expressions for the dynamic model of a multi-rotor with an aerodynamic shape are as follows: Where q = 0.5ρV 2 represents dynamic pressure, ρ represents air density, V represents airspeed, S represents wing area, L represents wing span, and b A represents the average aerodynamic chord length of the wing, α represents the angle of attack, β represents the slip angle, ω x ,ω y ,ω z represents the component of angular velocity, Represents the rolling moment and the slip angle β, aileron angle δa and angular velocity ω x The coefficient between Represents the yaw moment and the slip angle β, rudder angle δr and angular velocity ω y The coefficient between z0 represents the pitching moment coefficient at zero angle of attack, Denote the angle of attack α, the elevator angle δe and the angular velocity ω z Coefficient for the pitching moment.

2. The method for modeling and attitude control of a tilt-rotor aircraft according to claim 1, characterized in that: In step S1, the torque magnitude of the tilt rotor around each axis is determined by the thrust, the rotor tilt angle and the rotor axial moment coefficient, and the torque magnitude of the multi-rotor around each axis is determined by the aerodynamic shape of the aircraft.

3. The method for modeling and attitude control of a tilt-rotor aircraft according to claim 1, characterized in that: The expression of the PD controller for the attitude control of the multi-rotor aircraft in step S2 is as follows: in, represents the calculated control values ​​of the roll, yaw and pitch moment coefficients, represents the proportional and differential coefficients of the PD controller, γ is the roll angle, ψ is the yaw angle, is the pitch angle, ω x ,ω y ,ω z is the current angular velocity component of the multirotor aircraft, γ d ,ψ d , Indicates the target attitude angle position of the multirotor aircraft.

4. The method for modeling and attitude control of a tiltrotor aircraft according to claim 3, characterized in that: The step S3 adopts a segmented attitude control PD controller, divides the stage according to different flight states of the tilt-rotor aircraft, and calculates the attitude control PD parameters corresponding to each stage by the least square method.

5. The method for modeling and attitude control of a tilt-rotor aircraft according to claim 4, characterized in that: The controller expression based on the least squares regression strategy in step S3 is as follows: i=1,...,n in, represents the proportional and differential coefficients of the aerodynamically shaped tiltrotor controller, γ err =γ d -γ,ψ err =ψ d -ψ, is the angular position error of a tilt-rotor aircraft with an aerodynamic shape.

6. The method for modeling and attitude control of a tiltrotor aircraft according to claim 5, characterized in that: The expression for controlling the allocation in step S4 is as follows: in, are the proportional and differential coefficients of the aileron controller for the aerodynamically shaped tiltrotor aircraft, are the proportional and differential coefficients of the rudder controller for the aerodynamically shaped tiltrotor aircraft, are the proportional and differential coefficients of the elevator controller for a tiltrotor aircraft with an aerodynamic shape.

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