Method for controlling transition process of vertical take-off and landing aircraft with tilting airframe

Abstract

The invention relates to the technical field of flight control, and discloses a control method for a transition process of a tilt-body vertical take-off and landing aircraft, and the method comprises the following steps: S1, building a transition corridor model used for calculating a full flight profile of the tilt-body vertical take-off and landing aircraft; and S2, carrying out full-speed-domain and full-angle-of-attack simulation calculation on the aircraft by adopting a CFD (Computational Fluid Dynamics) method to obtain high-fidelity aerodynamic parameters. The control method for the transition process of the vertical take-off and landing aircraft with the tilting airframe has the advantages of being flexible in control method, stable in safe state and the like, and solves the problem that in the prior art, the precision of an optimization calculation result is difficult to guarantee, and the control effect is reduced if the robustness of the aircraft is excessively enhanced. The problems that in the transition process of an airplane, generally, attitude and accelerator control are seriously coupled, the control method is not flexible, coordinated control over an accelerator and an angle cannot be achieved, and it is difficult to guarantee that the airplane is always in a safe state, namely in a flight envelope are solved.

Description

Technical Field

[0001] The present invention relates to the field of flight control technology, and in particular to a method for controlling a transition process of a tilting body vertical take-off and landing aircraft. Background Art

[0002] Currently, research on vertical take-off and landing (VTOL) aircraft is gaining momentum and finding widespread application across various fields. Existing aircraft can be broadly categorized into two types based on their structure: fixed-wing and rotary-wing. For the past 20 years, fixed-wing and rotary-wing configurations have dominated electric UAV design. While each has its advantages, they also exhibit inherent limitations. Fixed-wing aircraft offer the advantages of high speed and long flight time, but require a taxiway or other launch and recovery equipment for takeoff and landing, which is subject to environmental and facility constraints. Rotary-wing aircraft offer the advantages of vertical take-off and landing (VTOL) and maneuverability, but suffer from lower speeds and shorter flight times. While each type of aircraft possesses its own unique characteristics, technological advancements are driving increasingly complex and diverse missions, both in military and civilian applications. This creates an urgent need for an aircraft capable of adapting to diverse environments, achieving both high-speed forward flight and the flexibility and maneuverability of vertical take-off and landing. Vertical take-off and fixed-wing aircraft combine the advantages of both and represent the future direction of multi-purpose UAV development.

[0003] Tilt-body VTOL aircraft, similar in configuration to tail-seat aircraft, are a new type of VTOL aircraft with both rotor and fixed-wing characteristics. They feature flexible transitions, a large flight envelope, and significant control difficulty. Research and analysis of the transition process of tilt-body VTOL aircraft is highly significant, as it not only analyzes the configuration's safe flight envelope but also highlights its advantages. Certain mission scenarios, such as terrain-following flight and variable-speed tracking, place extremely high demands on flight over a wide speed range and at large angles. Therefore, understanding the transition process of tilt-body VTOL aircraft is crucial.

[0004] There are several methods for transient process control:

[0005] 1. Calculate and optimize the transition path from takeoff and landing to cruising, and from cruising to takeoff and landing. Once the aircraft enters the transition process, it actively follows the optimal transition trajectory.

[0006] 2. Set the transition control strategy in advance. For example, during the transition from takeoff and landing to cruising, maintain a constant high throttle and achieve speed control by controlling the angle; while during the transition from cruising to takeoff and landing, maintain a constant low throttle and achieve speed control by controlling the angle.

[0007] In the existing technology, the first method has the problem of difficulty in ensuring the accuracy of the optimization calculation results, while over-enhancing the robustness of the aircraft will reduce the control effect. The second method usually has a serious coupling between the attitude and throttle control of the aircraft during the transition process. This control method is inflexible and cannot achieve coordinated control of the throttle and angle. It is also difficult to ensure that the aircraft is always in a safe state, that is, within the flight envelope.

[0008] In summary, the existing technical methods do not provide good transition process control for this type of vertical take-off and landing aircraft. Therefore, a control method for the transition process of a tilt-body vertical take-off and landing aircraft is proposed to solve the above-mentioned problems. Summary of the Invention

[0009] (1) Technical problems solved

[0010] In response to the shortcomings of the existing technology, the present invention provides a control method for the transition process of a tilt-body vertical take-off and landing aircraft, which has the advantages of flexible control method and stable safety state. It solves the problem in the existing technology that the accuracy of the optimization calculation results is difficult to ensure, and excessive enhancement of the robustness of the aircraft will reduce the control effect. During the transition process, the aircraft's attitude and throttle control are usually severely coupled, the control method is inflexible, and coordinated control of the throttle and angle cannot be achieved. It is also difficult to ensure that the aircraft is always in a safe state, that is, the problem in the flight envelope.

[0011] (2) Technical solution

[0012] The present invention solves the above-mentioned technical problem with the following technical solution: A method for controlling the transition process of a tilting body vertical take-off and landing aircraft, comprising the following steps:

[0013] S1: Establish a transition corridor model for calculating the full flight profile of a tilt-body vertical take-off and landing aircraft;

[0014] S2: Use CFD method to simulate the aircraft at all speeds and angles of attack to obtain high-fidelity aerodynamic parameters;

[0015] S3: Solve the flight envelope of the aircraft through the transition corridor model and aerodynamic parameter design numerical solution method;

[0016] S4: Within the flight envelope, the trim point data is used as the feedforward quantity and combined with the existing total energy control method to achieve aircraft transition process control.

[0017] The beneficial effects of the present invention are: the flight envelope of the aircraft itself is calculated according to the formula, the safe flight envelope area is explored, and then the control method is used to meet the safe and reliable speed and altitude control of the aircraft within the envelope, ensuring safety while achieving reliable control of the aircraft transition process.

[0018] The control method for the transition process of the tilting body vertical take-off and landing aircraft has the advantages of flexible control method and stable safety state.

[0019] On the basis of the above technical solution, the present invention can also be improved as follows.

[0020] Furthermore, the transition corridor model for calculating the transition process of the tilting body vertical take-off and landing aircraft consists of two parts: a propeller slipstream model and a basic nonlinear flight dynamics model.

[0021] Furthermore, the paddle slipstream model is:

[0022]

[0023] Due to the influence of propeller slipstream, the effective lift coefficient is:

[0024]

[0025] According to the momentum disk theory, when the incoming flow velocity is 0, the induced velocity at the propeller disk is:

[0026]

[0027] When there is an incoming flow, the propeller disc induced velocity is:

[0028]

[0029] When the incoming flow exists, the propeller flow tube will shrink behind the propeller disc. Assuming that the flow velocity on the wing surface is uniform and the influence of the propeller-induced airflow on the wing does not vary with the spanwise and chordwise directions in the slipstream region, xwake is the distance between the wing's quarter chord line and the propeller disc.

[0030]

[0031] The stream tube radius at its location is:

[0032]

[0033] The actual aerodynamic force and aerodynamic moment are analyzed by calculating the proportion of the slipstream area to the wing, namely:

[0034]

[0035] Obtain high-fidelity aerodynamic parameters under different blade thrusts.

[0036] Among them, the induced airflow velocity generated by the propeller disc is related to the generated drag. The flow velocity vector is added to the induced airflow velocity vector on the wing surface, that is, the airflow on the actual wing surface. According to the principle of vector addition, the effective airflow velocity and effective angle of attack of the propeller slipflow model can be obtained.

[0037] Among them, the V wake is the propeller-induced velocity vector at the wing, V ∞ is the incoming flow velocity vector, Δα is the angle of attack reduced due to the propeller-induced airflow, V eff is the actual effective velocity vector after vector superposition, α eff is the actual effective angle of attack of the wing, is the true aerodynamic coefficient at the effective angle of attack, is the equivalent aerodynamic coefficient relative to the incoming flow pressure.

[0038] Furthermore, the aircraft transition corridor model is:

[0039]

[0040] The magnitude of the aerodynamic force depends on the speed and angle of attack of the wing, where G is gravity, θ is the pitch angle, T represents propeller thrust, n represents the number of propellers, and L represents the maximum value of the aerodynamic force. x Represents lift force L a Along the machine system b x b Axis component, D z Represents resistance D a Along the machine system b z b Component, M represents the pitching moment

[0041] Furthermore, the aerodynamic parameters in the aircraft transition corridor model are all obtained through high-fidelity calculations using CFD software. Specifically, the aerodynamic parameters and control parameters of the bare aircraft (i.e., the aircraft without propellers) are solved using CFD calculation methods to obtain the aerodynamic parameters under different combinations of rudder deflection angles, different speeds, and different angles of attack.

[0042] The CFD calculations take into account the effects of different rudder deflection angles on the aircraft's aerodynamic parameters. The aerodynamic parameters with the subscripts "up" and "down" represent the full positive or negative deflection of the elevator during the parameter simulation.

[0043] Furthermore, a numerical method is used to solve the transition corridor model. Since the aircraft motor differential provides the pitching torque required for balancing, the control surface margin is sufficient to complete longitudinal and lateral maneuvering control. For the level flight trim of the tilt-body aircraft, once the control mode is determined, considering the windless condition, it can be almost considered that the level flight speed V, the angle of attack α (pitch angle θ), and the thrust T are in a one-to-one correspondence. Therefore, the full-speed range level flight data calculated in the transition corridor is used to calculate the required trim value T based on the expected speed. trim and θ trim The force is fed into the TECS controller through feedforward. When designing the flight controller, the mission profile is divided into low-speed, medium-speed and high-speed sections based on speed, and it is assumed that the resistance in each section remains unchanged.

[0044] The beneficial effect of adopting the above-mentioned further solution is that the TECS parameters are adjusted in stages and combined with gain scheduling to achieve full-speed flight control of the tilt-body aircraft, that is, constant speed to height, constant height to speed, and variable speed to height. During the speed change process, the pitch angle and angle of attack will be dynamically adjusted to ensure the balance of aerodynamic force and torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the changes in aerodynamic parameters of the present invention;

[0046] Figure 2 Schematic diagram of the angle of attack flight envelope of the transition corridor model of the present invention;

[0047] Figure 3 Schematic diagram of the pitch angle flight envelope of the transition corridor model of the present invention;

[0048] Figure 4 This is a schematic diagram of the speed flight envelope of the transition corridor model of the present invention;

[0049] Figure 5 Schematic diagram of the flight envelope of the rudder deflection angle of the transition corridor model of the present invention;

[0050] Figure 6 For the present invention trim Schematic diagram of feedforward transmission;

[0051] Figure 7 For the present invention trim Schematic diagram of feedforward transmission;

[0052] Figure 8 This is a schematic diagram of a simulation of a longitudinal flight controller according to the present invention;

[0053] Figure 9 This is a schematic diagram of the balancing envelope of the present invention. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments 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 making creative efforts are within the scope of protection of the present invention.

[0055] In the embodiment, Figure 1-9 A method for controlling a transition process of a tilt-body vertical take-off and landing aircraft is provided, the method comprising the following steps:

[0056] S1: Establish a transition corridor model for calculating the full flight profile of a tilt-body vertical take-off and landing aircraft;

[0057] S2: Use CFD method to simulate the aircraft at all speeds and angles of attack to obtain high-fidelity aerodynamic parameters;

[0058] S3: Solve the flight envelope of the aircraft through the transition corridor model and aerodynamic parameter design numerical solution method;

[0059] S4: Within the flight envelope, the trim point data is used as the feedforward quantity and combined with the existing total energy control method to achieve aircraft transition process control;

[0060] The transition corridor model for calculating the transition process of tilt-body vertical take-off and landing aircraft consists of two parts: propeller slipstream model and basic nonlinear flight dynamics model;

[0061] The paddle slipstream model is:

[0062]

[0063] Due to the influence of propeller slipstream, the effective lift coefficient is:

[0064]

[0065] According to the momentum disk theory, when the incoming flow velocity is 0, the induced velocity at the propeller disk is:

[0066]

[0067] When there is an incoming flow, the propeller disc induced velocity is:

[0068]

[0069] When the incoming flow exists, the propeller flow tube will shrink behind the propeller disc. Assuming that the flow velocity on the wing surface is uniform and the influence of the propeller-induced airflow on the wing does not vary with the spanwise and chordwise directions in the slipstream region, xwake is the distance between the wing's quarter chord line and the propeller disc.

[0070]

[0071] The stream tube radius at its location is:

[0072]

[0073] The actual aerodynamic force and aerodynamic moment are analyzed by calculating the proportion of the slipstream area to the wing, namely:

[0074]

[0075] Obtain high-fidelity aerodynamic parameters under different blade thrusts;

[0076] Among them, the induced airflow velocity generated by the propeller disc is related to the generated drag. The flow velocity vector is added to the induced airflow velocity vector on the wing surface, that is, the airflow on the actual wing surface. According to the principle of vector addition, the effective airflow velocity and effective angle of attack of the propeller slipstream model can be obtained.

[0077] Among them, V wake is the propeller-induced velocity vector at the wing, V ∞ is the incoming flow velocity vector, Δα is the angle of attack reduced due to the propeller-induced airflow, V eff is the actual effective velocity vector after vector superposition, α eff is the actual effective angle of attack of the wing, is the true aerodynamic coefficient at the effective angle of attack, is the equivalent aerodynamic coefficient relative to the incoming flow pressure;

[0078] The aircraft transition corridor model is:

[0079]

[0080] The magnitude of the aerodynamic force depends on the speed and angle of attack of the wing, where G is gravity, θ is the pitch angle, T represents propeller thrust, n represents the number of propellers, and L represents the maximum value of the aerodynamic force. x Represents lift force L a Along the machine system b x b Axis component, D z Represents resistance D a Along the machine system b z b Component, M represents the pitching moment

[0081] The aerodynamic parameters in the aircraft transition corridor model were obtained through high-fidelity calculations using CFD software. Specifically, the aerodynamic parameters and control parameters of the bare aircraft (i.e., the aircraft without propellers) were solved using CFD calculation methods. The aerodynamic parameters were obtained under different combinations of rudder deflection angles, speeds, and angles of attack.

[0082] The CFD calculations take into account the effects of different rudder deflection angles on the aircraft's aerodynamic parameters. The aerodynamic parameters with subscripts up and down represent the full positive or negative elevator deflection during the simulation.

[0083] The transition corridor model is solved by a numerical method. Since the aircraft motor differential provides the pitching torque required for balancing, the control surface margin is sufficient to complete longitudinal and lateral maneuvering control. For the level flight trim of the tilt-body aircraft, once the control mode is determined, considering the windless condition, it can be almost considered that the level flight speed V, the angle of attack α (pitch angle θ), and the thrust T are in a one-to-one correspondence. Therefore, the full-speed range level flight data calculated in the transition corridor is used to calculate the required trim value T based on the expected speed. trim and θ trim The force is fed into the TECS controller through feedforward. When designing the flight controller, the mission profile is divided into low-speed, medium-speed and high-speed sections based on speed, and it is assumed that the resistance in each section remains unchanged.

[0084] By adjusting TECS parameters in sections and combining them with gain scheduling, full-speed flight control of the tilt-body aircraft can be achieved, i.e., constant speed to altitude, constant altitude to speed, and variable speed to altitude. During speed changes, the pitch angle and angle of attack are dynamically adjusted to ensure a balance between aerodynamic forces and torque.

[0085] Working principle:

[0086] Step 1: Establish a transition corridor model for calculating the full flight profile of a tilt-body vertical take-off and landing aircraft;

[0087] Step 2: Use CFD method to simulate the aircraft at all speeds and angles of attack to obtain high-fidelity aerodynamic parameters;

[0088] Step 3: Solve the flight envelope of the aircraft through the transition corridor model and aerodynamic parameter design numerical solution method;

[0089] Step 4: Within the flight envelope, the trim point data is used as the feedforward quantity and combined with the existing total energy control method to realize the aircraft transition process control.

[0090] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0091] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for controlling a transition process of a tilt-body vertical take-off and landing aircraft, characterized in that: The steps include: S1: Establish a transition corridor model for calculating the full flight profile of a tilt-body vertical take-off and landing aircraft; S2: Use CFD method to simulate the aircraft at all speeds and angles of attack to obtain high-fidelity aerodynamic parameters; S3: Solve the flight envelope of the aircraft through the transition corridor model and aerodynamic parameter design numerical solution method; S4: Within the flight envelope, the trim point data is used as the feedforward quantity and combined with the existing total energy control method to achieve aircraft transition process control.

2. The method for controlling a transition process of a tilting body vertical take-off and landing aircraft according to claim 1, characterized in that: The transition corridor model for calculating the transition process of the tilting body vertical take-off and landing aircraft consists of two parts: a propeller slipstream model and a basic nonlinear flight dynamics model.

3. The method for controlling a transition process of a tilting body vertical take-off and landing aircraft according to claim 2, characterized in that: The paddle slipstream model is: Due to the influence of propeller slipstream, the effective lift coefficient is: According to the momentum disk theory, when the incoming flow velocity is 0, the induced velocity at the propeller disk is: When there is an incoming flow, the propeller disc induced velocity is: When the incoming flow exists, the propeller flow tube will shrink behind the propeller disc. Assuming that the flow velocity on the wing surface is uniform and the influence of the propeller-induced airflow on the wing does not vary with the spanwise and chordwise directions in the slipstream region, xwake is the distance between the wing's quarter chord line and the propeller disc. The stream tube radius at its location is: The actual aerodynamic force and aerodynamic moment are analyzed by calculating the proportion of the slipstream area to the wing, namely: Obtain high-fidelity aerodynamic parameters under different blade thrusts.

4. The method for controlling a transition process of a tilting body vertical take-off and landing aircraft according to claim 2, characterized in that: The aircraft transition corridor model is:

5. The method for controlling a transition process of a tilt-body vertical take-off and landing aircraft according to claim 2, characterized in that: The aerodynamic parameters in the aircraft transition corridor model are all obtained through high-fidelity calculations using CFD software. Specifically, the aerodynamic parameters and control parameters of the bare aircraft (i.e., the aircraft without propellers) are solved using CFD calculation methods, and the aerodynamic parameters under different rudder angles, different speeds, and different angles of attack are obtained.

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