A compound wing aircraft and a multi-modal smooth transition control method thereof

Abstract

The embodiment of the application provides a kind of compound wing aircraft and its multimode smooth transition control method, method includes obtaining the current air speed of aircraft;According to the transition start air speed threshold and the transition end air speed threshold of pre-set, determine transition interval;Current air speed is normalized, and transition variable μ is constructed.Based on transition variable, construct continuous weight function, and continuous weight function includes fixed wing aerodynamic control weight and rotor control weight, and satisfy μ (0) =1, μ (1) =0.According to continuous weight function, desired moment is distributed to rotor system and fixed wing aerodynamic system, and the mixed rotor control output and fixed wing control output are obtained.According to the mixed rotor control output, rotor speed instruction is generated, and according to the mixed fixed wing control output, rudder deflection angle instruction is generated, to realize the multimode smooth transition control of aircraft, solves the problem that compound wing aircraft is unstable when switching between multiple modes.

Description

Technical Field

[0001] This application relates to the field of flight control for compound wing aircraft, specifically to a compound wing aircraft and its multimodal smooth transition control method. Background Technology

[0002] Compound wing aircraft combine the vertical takeoff and landing capabilities of multi-rotor aircraft with the efficient cruise capabilities of fixed-wing aircraft. When switching between various flight modes such as hovering, transition, and cruise, its rotor system and fixed-wing aerodynamic system work simultaneously, resulting in complex aerodynamic coupling effects and placing high demands on flight control.

[0003] In existing technologies, multimodal control of compound wing aircraft typically employs segmented switching methods or gain scheduling methods based on airspeed thresholds, using different controllers or control parameters at different flight phases. However, such methods usually employ hard switching at mode transition boundaries, and abrupt changes in controller structure or parameters can easily lead to jumps in control commands, causing attitude fluctuations or even instability in the aircraft.

[0004] Therefore, it is necessary to propose a control strategy that can achieve a continuous and smooth transition between multiple modes of a compound wing aircraft. By smoothly allocating control rights between the rotor and the control surfaces, the overall handling characteristics and flight safety of the aircraft during the transition phase can be improved. Summary of the Invention

[0005] In view of the above problems, this application provides a compound wing aircraft and its multimodal smooth transition control method, which overcomes or at least partially solves the above-mentioned problem of instability when the compound wing aircraft switches between multiple modes.

[0006] A first aspect of this application provides a multimodal smooth transition control method for a compound wing aircraft, the method comprising: acquiring the current airspeed of the aircraft. ; Based on the preset transition start airspeed threshold and transition end airspeed threshold Determine the transition range; the transition range is defined as the airspeed meets the following conditions. Range; for airspeed After normalization, a transition variable μ is constructed, satisfying the following: when When μ=0; when When μ=1; When air speed When within the transition range, the transition variable μ varies with the air velocity. The increase of varies continuously within the interval (0,1); Based on the transition variables, a continuous weighting function is constructed, which includes the aerodynamic control weights for the fixed wing. And rotor control weight And satisfy This causes the rotor control weight to decrease continuously with increasing airspeed, while the fixed wing aerodynamic control weight to increase continuously with increasing airspeed. Based on the continuous weighting function, the desired torque is distributed to the rotor system and the fixed-wing aerodynamic system to obtain the mixed rotor control output and fixed-wing control output, so that the rotor system and the fixed-wing aerodynamic system simultaneously output control torque in the transition range and their respective output torques show a continuous trend of mutual inversion. The rotor speed command is generated based on the mixed rotor control output, and the control surface deflection command is generated based on the mixed fixed-wing control output, so as to achieve smooth multi-modal transition control of the aircraft.

[0007] This application drives the continuous adjustment of the continuous weighting function through the continuous change of the transition variable μ, enabling the control weight allocation to smoothly follow changes in flight speed. This overcomes the shortcomings of existing allocation methods that struggle to match the nonlinear changing trends of aerodynamic characteristics, and expands the adaptability of the aircraft under complex operating conditions. By constructing a continuous weighting function and satisfying… This design allows the rotor control weight to continuously decrease with increasing airspeed, while the fixed-wing aerodynamic control weight continuously increases with increasing airspeed. Both systems simultaneously output torque within the transition range, exhibiting a continuous, inversely related trend. This avoids attitude disturbances caused by abrupt control command changes in hard-switching modes, effectively improving the aircraft's attitude stability during mode transitions. By distributing the desired torque to the two actuators based on a continuous weight function, the rotor and control surfaces coordinate rather than conflict during the transition phase. This avoids the control efficiency reduction caused by a lack of unified coordination mechanisms, improving control quality and flight safety during the transition phase.

[0008] In one alternative approach, the transition variable μ is constructed as follows:

[0009] in, The current airspeed, The transition start airspeed threshold, The transition end airspeed threshold, () is a limiting function that restricts the output to the interval [0,1]. when At that time, the aircraft is in rotor hovering mode, μ=0; when At this time, the aircraft is in transition mode, μ∈(0,1); when At that time, the aircraft is in cruise mode, μ=1.

[0010] In one alternative approach, the continuous weight function is constructed based on the Sigmoid function, specifically in the form:

[0011] in, To adjust the constant of the transition rate, These are the preset transition center parameters.

[0012] In one alternative approach, preset transition center parameters are used. The value is 0.5, which is used to enable the rotor system and the fixed-wing aerodynamic system to complete the exchange of main control at the midpoint of the transition zone.

[0013] In one alternative approach, when As the value increases, the exchange process between the fixed-wing aerodynamic control weights and the rotor control weights becomes steeper and the transition time is shortened; when When the value decreases, the exchange process between the fixed-wing aerodynamic control weight and the rotor control weight becomes slower and the transition time is prolonged.

[0014] In one alternative approach, the desired torque is distributed to the rotor system and the fixed-wing aerodynamic system according to a continuous weighting function, resulting in a mixed rotor control output and a fixed-wing control output, specifically in the following form:

[0015] in, The desired torque calculated by the rotor system based on the current flight conditions. The desired torque calculated by the fixed-wing aerodynamic system based on the current flight conditions. This is the control output for the hybrid rotor. This is the output of the combined fixed-wing aerodynamic control.

[0016] In one alternative approach, when At that time, the aerodynamic control weights of the fixed-wing aircraft are forcibly set. Rotor control weight This allows the aircraft to be completely controlled independently by the rotor system; when At that time, the aerodynamic control weights of the fixed-wing aircraft are forcibly set. Rotor control weight =0, which makes the aircraft completely independently controlled by the fixed-wing aerodynamic system.

[0017] This embodiment avoids physical mismatch problems such as low control surface efficiency at low speeds and rotor waste drag at high speeds by forcibly setting a single system exclusive control outside the transition range.

[0018] A second aspect of the embodiments of this application provides a compound wing aircraft, which uses the multimodal smooth transition control method provided in the first aspect of the embodiments of this application for flight control.

[0019] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The flight mode division provided in the embodiments of this application.

[0022] Figure 2 A graph of the transition variables provided for this application.

[0023] Figure 3 This is a schematic diagram of the change curve of the aerodynamic control weights of a fixed wing as a function of the transition variable.

[0024] Figure 4 A schematic diagram of the change curve of the continuous weighting function is provided in another embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0027] The terms "comprising" and "having," and any variations thereof, used in the specification, claims, and drawings of this application are intended to cover without excluding other meanings. The words "a" or "an" do not exclude the presence of multiples.

[0028] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0030] In the description of this application, unless otherwise stated, "multiple" means two or more (including two), and similarly, "multiple groups" means two or more (including two groups).

[0031] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, "connection" or "linkage" in mechanical structures can refer to a physical connection, such as a fixed connection, for example, a connection fixed by fasteners, such as a connection fixed by screws, bolts, or other fasteners; a physical connection can also be a detachable connection, such as a snap-fit ​​or interlocking connection; a physical connection can also be an integral connection, such as a connection formed by welding, bonding, or integral molding. In circuit structures, "connection" or "linkage" can refer not only to a physical connection but also to an electrical connection or a signal connection. For example, it can be a direct connection, i.e., a physical connection, or an indirect connection through at least one intermediate component, as long as the circuit is connected; it can also refer to the internal connection of two components. Signal connection can refer not only to signal connection through a circuit but also to signal connection through a media, such as radio waves. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0032] Some embodiments of this application provide a multimodal smooth transition control method for a compound wing aircraft. The method includes: obtaining the current airspeed of the aircraft. Based on the preset transition start airspeed threshold. and transition end airspeed threshold Determine the transition range; the transition range is defined as the airspeed meets the following conditions. Range; for airspeed After normalization, a transition variable μ is constructed, satisfying: when When μ=0; when At that time, μ=1. When the airspeed When within the transition range, the transition variable μ varies with the air velocity. The increase of varies continuously within the interval (0,1). Based on the transition variable, a continuous weighting function is constructed, which includes the fixed-wing aerodynamic control weights. And rotor control weight And satisfy This causes the rotor control weight to continuously decrease with increasing airspeed, while the fixed-wing aerodynamic control weight to continuously increase with increasing airspeed. Based on the continuous weighting function, the desired torque is distributed to the rotor system and the fixed-wing aerodynamic system, resulting in a mixed rotor control output and a fixed-wing control output. This allows both the rotor system and the fixed-wing aerodynamic system to simultaneously output control torque within the transition range, with their respective output torques exhibiting a continuous inverse relationship.

[0033] The rotor speed command is generated based on the mixed rotor control output, and the control surface deflection command is generated based on the mixed fixed-wing control output, so as to achieve smooth multi-modal transition control of the aircraft. Figure 1 The flight mode division provided in the embodiments of this application is based on... and The flight process is divided into hovering mode, transition mode, and cruise mode, among which... In rotor-dominated control mode, when This is a transitional mode, when At that time, it was the fixed-wing aerodynamic-dominated control mode.

[0034] This application drives the continuous adjustment of the continuous weighting function through the continuous change of the transition variable μ, enabling the control weight allocation to smoothly follow changes in flight speed. This overcomes the shortcomings of existing allocation methods that struggle to match the nonlinear changing trends of aerodynamic characteristics, and expands the adaptability of the aircraft under complex operating conditions. By constructing a continuous weighting function and satisfying… This design allows the rotor control weight to continuously decrease with increasing airspeed, while the fixed-wing aerodynamic control weight continuously increases with increasing airspeed. Both systems simultaneously output torque within the transition range, exhibiting a continuous, inversely related trend. This avoids attitude disturbances caused by abrupt control command changes in hard-switching modes, effectively improving the aircraft's attitude stability during mode transitions. By distributing the desired torque to the two actuators based on a continuous weight function, the rotor and control surfaces coordinate rather than conflict during the transition phase. This avoids the control efficiency reduction caused by a lack of unified coordination mechanisms, improving control quality and flight safety during the transition phase.

[0035] In some embodiments, the transition variable μ is constructed as follows:

[0036] in, The current airspeed, The transition start airspeed threshold, The transition end airspeed threshold, () is a limiting function that restricts the output to the interval [0,1]. When When the aircraft is in rotor hover mode, μ=0; when When the spacecraft is in transition mode, μ∈(0,1); when At that time, the aircraft is in cruise mode, μ=1. Figure 2 The graph of the transition variables provided in this application is by Figure 2 It can be seen that this application will use transition variables It is constrained to the interval [0,1], so that it only changes continuously in the transition interval and remains constant in the non-transition interval, thereby realizing the interval constraint of the transition process.

[0037] In some embodiments, the preset transition center parameter It can be set to 0.5, which is used to enable the rotor system and the fixed-wing aerodynamic system to complete the exchange of main control at the midpoint of the transition zone.

[0038] In some embodiments, the continuous weighting function is constructed based on the Sigmoid function, specifically in the form of:

[0039] in, To adjust the constant of the transition rate, The preset transition center parameters, Greater than 0.

[0040] Since the Sigmoid function curve aligns with the trend of fixed-wing aerodynamic control capability gradually increasing with speed, this application further improves the existing transition variable μ and the Sigmoid function as continuous weighting functions, enabling nonlinear smooth allocation of control power. Thus, control power is continuously transferred as flight state changes, improving stability and control consistency during the transition phase.

[0041] In some embodiments, when As the value increases, the exchange process between the fixed-wing aerodynamic control weights and the rotor control weights becomes steeper and the transition time is shortened; when When the value decreases, the exchange process between the aerodynamic control weight of the fixed wing and the control weight of the rotor becomes slower, the transition time is prolonged, and the attitude change is smoother. Figure 3This is a schematic diagram illustrating the variation of aerodynamic control weights as a function of transient variables for a fixed-wing aircraft. (Reference) Figure 3 Different parameters To correspond to different rates of change, adjust the parameters. This allows for adjustment of the speed of the control transfer process to adapt to different aircraft characteristics and transition requirements. In practical applications, parameters can be adjusted according to the aircraft's dynamic characteristics and transition control requirements. Adjustments can be made. For example, for aircraft with large inertia or high stability requirements, a smaller [size / weight] can be selected. The value can be increased to slow down the rate of change of control and improve the smoothness of the transition; for aircraft with high response speed requirements, the value can be appropriately increased. Values ​​are adjusted to improve the response speed of mode switching.

[0042] In some embodiments, the desired torque is distributed to the rotor system and the fixed-wing aerodynamic system according to a continuous weighting function, resulting in a mixed rotor control output and a fixed-wing control output, specifically in the form of:

[0043] in, The desired torque calculated by the rotor system based on the current flight conditions. The desired torque calculated by the fixed-wing aerodynamic system based on the current flight conditions. This is the control output for the hybrid rotor. This is the output of the combined fixed-wing aerodynamic control.

[0044] In some embodiments, when At that time, the aerodynamic control weights of the fixed-wing aircraft are forcibly set. Rotor control weight This allows the aircraft to be completely controlled independently by the rotor system; when At that time, the aerodynamic control weights of the fixed-wing aircraft are forcibly set. Rotor control weight =0, which makes the aircraft completely independently controlled by the fixed-wing aerodynamic system.

[0045] This embodiment avoids physical mismatch problems such as low control surface efficiency at low speeds and rotor waste drag at high speeds by forcibly setting a single system exclusive control outside the transition range.

[0046] In practical applications, a transition start airspeed threshold can be set. Transition end airspeed threshold Construct the following normalized transition variable. :

[0047] in, The function is used to... Restricted to the interval [0,1], it can be specifically defined as follows:

[0048] When the airspeed of the aircraft ,correspond The aircraft is in rotor-dominated control mode; when the aircraft's airspeed... ,correspond The aircraft is in a transitional phase; when ,correspond The aircraft entered fixed-wing cruise mode.

[0049] The continuous weight function is constructed as follows:

[0050] in, To adjust the constant of the transition rate, These are the preset transition center parameters. Used to determine the central location of a change in control, typically taken as... This indicates that the main control of the rotor system and the fixed-wing aerodynamic system is switched near the midpoint of the transition interval; in specific applications, it can also be adjusted according to the aerodynamic characteristics of the aircraft and the transition requirements.

[0051] Figure 4 Another embodiment of this application provides a schematic diagram of the change curve of the continuous weighting function, in Figure 4 middle, The value is 10. (From...) Figure 4 As can be seen, this embodiment uses the Sigmoid function to construct a continuous weight function, which can achieve a smooth change in control from the rotor system to the fixed-wing aerodynamic system.

[0052] After the weighting function is constructed, the desired torques of the rotor system and fixed-wing system are calculated based on the control law designed according to the state variables of the aircraft. and The control law can be implemented using proportional-integral-derivative control, state feedback control, or nonlinear control methods to ensure the aircraft's attitude and trajectory tracking performance. Based on a continuous weighting function, the desired torque is distributed to the rotor system and the fixed-wing aerodynamic system, resulting in the mixed rotor control output and fixed-wing control output, specifically in the following form:

[0053] The rotor speed command is generated based on the mixed rotor control output, and the control surface deflection command is generated based on the mixed fixed-wing control output, so as to achieve smooth multi-modal transition control of the aircraft.

[0054] Another embodiment of this application provides a compound wing aircraft, which uses the multimodal smooth transition control method provided in the foregoing embodiments of this application for flight control.

[0055] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0056] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A multimodal smooth transition control method for a compound wing aircraft, characterized in that, The method includes: Obtain the airspeed of the aircraft ; Based on the preset transition start airspeed threshold and transition end airspeed threshold Determine the transition range, where the airspeed satisfies... The range; for the airspeed After normalization, a transition variable μ is constructed, satisfying the following: when When μ=0; when When μ=1; When the airspeed When within the transition range, the transition variable μ varies with the airspeed. The increase of varies continuously within the interval (0,1); Based on the aforementioned transition variables, a continuous weighting function is constructed, which includes fixed-wing aerodynamic control weights. And rotor control weight And satisfy This causes the rotor control weight to decrease continuously as airspeed increases, while the fixed wing aerodynamic control weight increases continuously as airspeed increases. According to the continuous weighting function, the desired torque is distributed to the rotor system and the fixed-wing aerodynamic system to obtain the mixed rotor control output and fixed-wing control output, so that the rotor system and the fixed-wing aerodynamic system simultaneously output control torque in the transition range and their respective output torques show a continuous trend of one increasing and the other decreasing. The rotor speed command is generated based on the mixed rotor control output, and the control surface deflection command is generated based on the mixed fixed-wing control output, so as to achieve multi-modal smooth transition control of the aircraft.

2. The method according to claim 1, characterized in that, The transition variable μ is constructed as follows: in, The current airspeed, The transition start airspeed threshold, The transition end airspeed threshold, () is a limiting function that restricts the output to the interval [0,1]. when At that time, the aircraft is in rotor hovering mode, μ=0; when At this time, the aircraft is in transition mode, μ∈(0,1); when At that time, the aircraft is in cruise mode, μ=1.

3. The method according to claim 1, characterized in that, The continuous weighting function is constructed based on the Sigmoid function, and its specific form is as follows: in, To adjust the constant of the transition rate, These are the preset transition center parameters.

4. The method according to claim 3, characterized in that, The preset transition center parameters The value is set to 0.5, which is used to enable the rotor system and the fixed-wing aerodynamic system to complete the exchange of main control at the midpoint of the transition interval.

5. The method according to claim 3, characterized in that, when As the value increases, the exchange process between the fixed-wing aerodynamic control weight and the rotor control weight becomes steeper and the transition time is shortened; when When the value decreases, the exchange process between the fixed-wing aerodynamic control weight and the rotor control weight becomes slower and the transition time is prolonged.

6. The method according to claim 3, characterized in that, The desired torque is distributed to the rotor system and the fixed-wing aerodynamic system according to the continuous weighting function, resulting in a mixed rotor control output and fixed-wing control output, specifically in the following form: in, The desired torque calculated by the rotor system based on the current flight state. The desired torque calculated by the fixed-wing aerodynamic system based on the current flight state. This is the control output for the hybrid rotor. This is the aerodynamic control output of the hybrid fixed-wing aircraft.

7. The method according to claim 1, characterized in that, when At that time, the aerodynamic control weights of the fixed wing are forcibly set. The rotor control weights This allows the aircraft to be completely independently controlled by the rotor system; when At that time, the aerodynamic control weights of the fixed wing are forcibly set. The rotor control weights This allows the aircraft to be completely controlled independently by the fixed-wing aerodynamic system.

8. A compound wing aircraft, characterized in that, Flight control is performed using the multimodal smooth transition control method as described in any one of claims 1 to 7.

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