A safe flight trajectory planning method for the transition phase of tiltrotor and compound wing manned aircraft

Abstract

This invention discloses a safe flight trajectory planning method for the transition phase of tiltrotor and compound wing manned aircraft. The method includes initializing the flight trajectory planning problem, constructing and solving a trajectory optimization problem, and reconstructing a complete flight trajectory for high-sampling-rate transition processes based on the trajectory optimization results for flight control. This approach incorporates the thrust vector angle into the planning variables and restricts the pitch angle to zero throughout the transition, thus avoiding the analysis of complex aerodynamic characteristics required in traditional methods. It also provides occupants with a flight experience similar to that of ground vehicles. This method is adaptable to arbitrary aerodynamic characteristics and actuator layouts, supports bidirectional transition phases, and comprehensively considers safe and comfortable flight as well as time and energy consumption dimensions. It is applicable to tiltrotor and compound wing aircraft with arbitrary aerodynamic characteristics and power layouts.

Description

Technical Field

[0001] This invention belongs to the fields of tiltrotor and hybrid wing vertical take-off and landing aircraft, motion trajectory planning and flight control, and low-altitude economical manned general aviation, specifically involving a safe flight trajectory planning method for the transition phase of tiltrotor and hybrid wing manned aircraft. Background Technology

[0002] In recent years, with the vigorous promotion of the low-altitude economy concept, a large number of cargo or manned aircraft technologies, characterized by composite materials, electric propulsion, vertical takeoff and landing (VTOL), and horizontal cruise, have seen significant development. Based on current industry trends, the future of the low-altitude economy will be dominated by fixed-wing aircraft capable of VTOL, namely tiltrotor and hybrid-wing aircraft.

[0003] However, given the current state of technology, the realization of tiltrotor and hybrid-wing aircraft still faces numerous theoretical and engineering challenges. Most notably, both types of aircraft encounter complex aerodynamic changes and high control output dimensions during the bidirectional transition flight phase, leading to significant flight control difficulties. To ensure the reliable application of these two types of aircraft in manned flight scenarios with the highest safety standards, optimized trajectories based on safety, energy consumption, and time are of paramount importance and practical value. Therefore, a trajectory planning method with engineering feasibility is needed. Summary of the Invention

[0004] The purpose of this invention is to provide a safe flight trajectory planning method for the transition phase of tiltrotor and compound wing manned aircraft. This method is applicable to tiltrotor and compound wing aircraft with arbitrary aerodynamic characteristics and power configurations. Based on specified cost and constraint functions, it optimizes the flight trajectory within the longitudinal flight profile during the takeoff and landing transition phase. The method incorporates the thrust vector angle into the planning variables and restricts the pitch angle to zero throughout the transition, thereby avoiding the analysis of complex aerodynamic characteristics required in traditional methods. It also provides occupants with a flight experience similar to that of a ground vehicle, adapting to arbitrary aerodynamic characteristics and actuator configurations, supporting bidirectional transition phases, and comprehensively considering safe and comfortable flight as well as time and energy consumption dimensions.

[0005] The specific technical solution for achieving the objective of this invention is as follows:

[0006] A method for planning a safe flight trajectory during the transition phase of a tiltrotor and compound wing manned aircraft includes the following steps;

[0007] Step 1: Initialize the flight trajectory planning problem;

[0008] Step 2: Construct the trajectory optimization problem and solve iteratively;

[0009] Step 3: Based on the trajectory optimization results, reconstruct the complete flight trajectory of the high sampling rate transition process for flight control.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] (1) This scheme is applicable to tiltrotor and hybrid wing aircraft with arbitrary aerodynamic shape and power layout. According to the specified cost function, the zero pitch angle flight trajectory in the longitudinal flight profile during the take-off and landing transition phase is optimized. This not only effectively avoids the threat of complex aerodynamic characteristics to the transition phase, but also provides passengers with a smooth and comfortable flight experience.

[0012] (2) In the optimization process, this scheme uses a zero pitch angle dimension reduction inverse dynamics model to reconstruct the trajectory, supports the use of the thrust vector angle change rate as a planning variable, thereby accurately limiting the maximum directional change rate of the tilting mechanism, and meeting the hardware characteristics of the actual tilting mechanical mechanism which generally has a low response bandwidth.

[0013] (3) The planning method of this scheme is mainly based on matrix operation, which has high computational efficiency and solution success rate. It takes into account the safety and energy management efficiency of the transition flight phase of the vertical take-off and landing aircraft, and can meet the application requirements of actual flight missions.

[0014] The present invention will be further described below with reference to specific embodiments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the safe flight trajectory planning method for the transition phase of tiltrotor and compound wing manned aircraft in this scheme.

[0016] Figure 2 This is a schematic diagram of the flight state of the aircraft during the transition phase in the coordinate system of this embodiment. Detailed Implementation

[0017] Example

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0020] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0021] Combination Figure 1 A method for planning a safe flight trajectory during the transition phase of a tiltrotor and compound wing manned aircraft, characterized by the following steps;

[0022] Step 1: Initialize the flight trajectory planning problem;

[0023] Step 1-1: Determine the thrust vector angle of the aircraft during the transition phase. and flight altitude At the initial zero time and the final time Boundary conditions:

[0024] ,

[0025] The initial trajectories for thrust vector angle and flight altitude are constructed using the bilateral undetermined coefficient method. and The expression, in the form of a fifth-order polynomial, serves only as an initial reference value for optimization iterations. For the transition phase from vertical takeoff to horizontal cruise, there is typically... For the transition phase from horizontal cruise to vertical descent, there are usually: There are no special restrictions on the initial and final states of motion.

[0026] Steps 1-2: Construct the aircraft trajectory based on the initial trajectory segment. , The multi-segment evenly distributed time-normalized trajectory, that is, selecting an appropriate number of segments based on the computing power of the computing platform. Each segment of the initial trajectory and uniformly divided into Segment, forming These intermediate states are pieced together sequentially. , The zero to second derivatives at each time step form the decision vector. Furthermore, a terminal time dimension can be added to the end of the decision vector, resulting in the following structure. Initial value of decision vector:

[0027]

[0028] Steps 1-4: Determine the actual physical constraints of the thrust vector angle and its first and second derivatives, altitude, rate of climb, and climb acceleration in the decision vector, and construct two... dimensional vector , , as a decision vector The upper and lower bounds of the values ​​for each element.

[0029] Step 2: Construct the trajectory optimization problem and solve iteratively;

[0030] Combination Figure 2 The total aerodynamic forces within the longitudinal flight profile of the aircraft are decomposed along the longitudinal and vertical axes of the fuselage to obtain... and Combined with the aerodynamic torque along the fuselage transverse axis Together they form an attack angle The three-degree-of-freedom aerodynamic characteristic function is the only independent variable;

[0031] Based on the maximum pitch-holding torque that the aircraft's propulsion system can generate and maximum total thrust Construct cost functions for overall time consumption, pitch holding torque energy consumption, and total thrust energy consumption:

[0032]

[0033] in, , and These are the weighting coefficients, This indicates the pitch-holding torque of the aircraft. Indicates the total thrust of the aircraft;

[0034] The nonlinear constraint function can be defined as a function of any state quantity at any time during the flight process. In this embodiment, the constraint function is designed to limit the tilt angular velocity, tilt driving torque, and total thrust within the feasible region.

[0035] For example, in an embodiment, the nonlinear constraint function of the cost function is:

[0036]

[0037] in, and These represent the intermediate result and the maximum value of the first derivative of the thrust vector angle, respectively, during the planning process.

[0038] The solution process includes:

[0039] definition Indicates taking The first of the matrix arrive A submatrix composed of columns.

[0040] Construct a zero-pitch angle dimensionality-reduced inverse dynamics model suitable for the longitudinal flight profile of tiltrotor and compound wing aircraft, and utilize decision vectors. Reconstruct the complete three-degree-of-freedom flight state of the aircraft;

[0041] Using decision vectors When reconstructing the complete three-degree-of-freedom flight state of the aircraft, in order to calculate arbitrary decision vectors... corresponding cost function The value must first be determined based on the decision vector. Obtain the trajectory of the aircraft , The polynomial coefficient matrix of the multi-segment time-normalized trajectory is used to complete the state vector with thrust vector angle and altitude:

[0042] , ,

[0043]

[0044] Each time normalization interval corresponds to the actual time. , Change with change;

[0045] The given two-sided conditions can use zero to second derivatives, and the corresponding polynomial trajectory is a fifth-order polynomial. The highest time value in the corresponding time-normalized sampling matrix is ​​the fifth power. The uniform division into multiple trajectory segments, with each segment undergoing time normalization, can stabilize most matrices in subsequent calculations, thereby greatly reducing the computational load of optimization iterations. Specifically:

[0046] A time-normalized sampling matrix and its several submatrices are constructed for fast sampling of the trajectory and its multiple derivatives. Based on the hardware computing power, any positive integer such as... Define the normalized time step The trajectory of a fifth-order polynomial is constructed as follows: Constant matrix:

[0047]

[0048] For example, in this embodiment, the number of samples is 100, corresponding to a normalized time step of 0.01. The time-normalized sampling matrix for the fifth-degree polynomial is as follows: Constant matrix:

[0049]

[0050] Alternate construction and .

[0051] For multiple normalized time intervals For any one-dimensional physical quantity that evolves continuously within the region, its trajectory is fitted using a series of fifth-order polynomials. The coefficient matrix of the multi-segment time-normalized trajectory for thrust vector angle and altitude is calculated in batches using the following formula:

[0052]

[0053] in Indicates the thrust vector angle or flight altitude Using this matrix, the fifth-order polynomial coefficient matrix of the time-normalized trajectory of multiple segments of any physical quantity can be calculated in batches by a single matrix multiplication in subsequent calculation steps, thus ensuring the computational efficiency of the method.

[0054] The above equation yields the polynomial coefficient matrix of the thrust vector angular trajectory and the polynomial coefficient matrix of the altitude trajectory. and Then, construct the first derivative coefficient matrix column by column using the following method. and Second derivative coefficient matrix and :

[0055] Given a column vector of coefficients of any fifth-degree polynomial Then the coefficient vectors of the first and second derivative polynomials of the fifth-degree polynomial are: , .

[0056] Based on this, the thrust vector angle and its first derivative, climb velocity, and climb acceleration of the aircraft are calculated in batches using the time-normalized sampling matrix and the polynomial coefficient matrix, resulting in the following four sets:

[0057] , , ,

[0058] Based on the above set, the complete three-degree-of-freedom flight state can be quickly reconstructed using a zero-pitch angle dimensionality reduction inverse dynamics model.

[0059] The zero-pitch angle dimensionality reduction inverse dynamics model is a method that maintains the pitch angle of a manned aircraft at zero degrees during the two-way transition phase, based on an arbitrarily given thrust vector angle. and height The model rapidly reconstructs the differential flat mathematical model of the longitudinal profile flight trajectory using a recursive approach. Thanks to the cleverly selected combination of independent variables, the model can adapt to any form of three-degree-of-freedom aerodynamic characteristics of an aircraft. Because the model recursively reconstructs the trajectory, it can also perform extreme value search operations on any physical quantity of interest, thus naturally giving the upper and lower bounds of the physical quantity at the end of the iteration, which can be used to calculate the nonlinear boundary constraints in trajectory planning.

[0060] Given any initial horizontal position Horizontal initial velocity ,Depend on Time recursion The spacecraft's state parameters at any given time. Indicates the sampling step size:

[0061]

[0062] Among them, the thrust vector angle Pointing to the front of the aircraft is 0, pointing to the back of the aircraft is 0. , For the angle of attack, For dynamic pressure, air density, The total mass of the aircraft of These are the equivalent wing area and chord length, respectively. The total thrust required instantaneously. To maintain pitch torque; when the aircraft's airspeed is zero, the angle of attack does not exist, so the aerodynamic characteristic terms can be ignored.

[0063] Calculation using the above model At this time, the horizontal position can be ignored. Only record transient horizontal acceleration and speed This reduces computational load and resource consumption. According to the complete... , Sample the set and calculate the discrete values ​​of the cost function.

[0064]

[0065] In addition, the recursive process of reconstructing the flight trajectory using zero-pitch angle dimensionality reduction and inverse dynamics can incidentally perform an extremum search operation to obtain the extrema of the physical quantities of interest, such as... , , and .

[0066] Based on the cost functions obtained from solving the inverse dynamics equations for the aircraft's pitch holding moment and total thrust, mature nonlinear programming algorithms can be used to solve the aforementioned optimization problem. Examples include traditional interior-point methods, sequential quadratic programming, and heuristic algorithms such as genetic algorithms and particle swarm optimization. The algorithm then checks whether the aircraft's state parameters satisfy the nonlinear constraint functions. If they do, a new decision vector is generated iteratively using gradient descent based on the values ​​of the cost function and the nonlinear constraint functions. This process is repeated until the algorithm's termination condition is met, returning the optimal decision vector. .

[0067] Step 3: Based on the trajectory optimization results, reconstruct the complete flight trajectory of the high sampling rate transition process for flight control:

[0068] Based on the optimal decision vector obtained through optimization The complete three-degree-of-freedom motion state of the aircraft is reconstructed using a zero-pitch angle dimensionality-reduced inverse dynamics model, and the sampling rate is not limited by the time-normalized sampling matrix. For example, a sampling period of 1 millisecond can be specified to obtain... , , , and High sampling rate trajectory sampling;

[0069] Depending on the specific power layout of the tiltrotor or compound wing aircraft, and according to the corresponding control quantity allocation mechanism, and Mapped to the actual actuator group, the underlying control input is obtained, which ultimately serves as the feedforward signal for flight control during the takeoff and landing transition phase.

[0070] The optimization method of this scheme involves adjusting the thrust vector angle within the longitudinal flight profile. and height As a degree of freedom in decision-making, it helps reduce the global computational load of trajectory planning and precisely limits attributes such as the rate of change of thrust vector angle, adapting to the low response bandwidth of the rotor tilt mechanism and ensuring that the planned flight trajectory is engineering-feasible. The final planned trajectory locks the pitch angle at zero degrees during the transitional flight process, thus providing a stable fuselage attitude, minimizing flight hazards caused by complex time-varying aerodynamic characteristics, and providing a comfortable flight experience for passengers. Furthermore, the planning method ensures that the control quantities of the actuators corresponding to the trajectory are within a feasible range.

[0071] This solution is applicable to tiltrotor and hybrid wing aircraft with any aerodynamic shape and power layout. Based on the specified cost function, it optimizes the zero pitch flight trajectory in the longitudinal flight profile during the takeoff and landing transition phase. This not only effectively avoids the threat of complex aerodynamic characteristics to the transition phase, but also provides passengers with a smooth and comfortable flight experience.

[0072] Meanwhile, this scheme uses a zero-pitch angle dimensionality reduction inverse dynamics model to reconstruct the trajectory during the optimization process, and supports using the thrust vector angle change rate as a planning variable, thereby accurately limiting the maximum directional change rate of the tilting mechanism and meeting the hardware characteristics of actual tilting mechanical mechanisms that generally have low response bandwidth.

[0073] This solution also provides a safe flight trajectory planning system for the transition phase of tiltrotor and compound wing manned aircraft, including the following modules;

[0074] Initialization module: Used to initialize the flight trajectory planning problem;

[0075] Optimization and Solving Module: Used to construct trajectory optimization problems and solve them iteratively;

[0076] Trajectory Reconstruction Module: Used to reconstruct the complete flight trajectory of the high sampling rate transition process based on the trajectory optimization results for flight control.

[0077] This solution also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to perform the following steps;

[0078] Step 1: Initialize the flight trajectory planning problem;

[0079] Step 2: Construct the trajectory optimization problem and solve iteratively;

[0080] Step 3: Based on the trajectory optimization results, reconstruct the complete flight trajectory of the high sampling rate transition process for flight control.

[0081] This solution also provides a computer-storable medium having a computer program stored thereon, wherein the computer program, when executed by a processor, performs the following steps;

[0082] Step 1: Initialize the flight trajectory planning problem;

[0083] Step 2: Construct and solve the trajectory optimization problem;

[0084] Step 3: Based on the trajectory optimization results, reconstruct the complete flight trajectory of the high sampling rate transition process for flight control.

[0085] The embodiments described above are merely one implementation method of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for planning a safe flight trajectory during the transition phase of a tiltrotor and compound wing manned aircraft, characterized in that, Includes the following steps; Step 1: Initialize the flight trajectory planning problem; Step 2: Construct the trajectory optimization problem and solve iteratively; Step 3: Based on the trajectory optimization results, reconstruct the complete flight trajectory of the high sampling rate transition process for flight control.

2. The method for safe flight trajectory planning during the transition phase of a tiltrotor and compound wing manned aircraft according to claim 1, characterized in that, The initialization in step 1 specifically includes: Step 1-1: Determine the thrust vector angle of the aircraft during the transition phase. and flight altitude At the initial zero time and the end Boundary conditions at time: ， ； And construct single-segment initial trajectories for thrust vector angle and flight altitude respectively. and ; Steps 1-2: Construct the aircraft trajectory based on the initial trajectory segment. , The multi-segment evenly divided time-normalized trajectory, that is, based on a determined number of segments... Each segment of the initial trajectory and uniformly divided into Segment, forming These intermediate states are pieced together sequentially. , The initial values ​​of the decision vector are formed from the zero to second derivatives at time t: ； Steps 1-4: Determine the upper and lower bounds of the decision vector values ​​based on the physical constraints of each value in the decision vector.

3. The method for safe flight trajectory planning during the transition phase of a tiltrotor and compound wing manned aircraft according to claim 2, characterized in that, The objective function for trajectory optimization in step 2 is: Based on the maximum pitch holding moment that the aircraft's propulsion system can generate and maximum total thrust A cost function is constructed that integrates time consumption, pitch holding torque energy consumption, and total thrust energy consumption: ； in, , and These are the weighting coefficients, This indicates the pitch-holding torque of the aircraft. This indicates the total thrust of the aircraft.

4. The method for safe flight trajectory planning during the transition phase of a tiltrotor and compound wing manned aircraft according to claim 3, characterized in that, The nonlinear constraint function of the cost function restricts the tilt angular velocity, tilt driving torque, and total thrust of the aircraft within the feasible region, specifically as follows: ； in, This represents the rate of change of the maximum thrust vector angle throughout the current trajectory during the planning process. This represents the maximum permissible value of the rate of change of the thrust vector angle. This indicates the maximum pitch holding moment of the current trajectory throughout the planning process. This indicates the maximum pitch holding torque that the power system can provide; and This represents the minimum and maximum total thrust throughout the current trajectory during the planning process. This indicates the maximum total thrust that the power system can provide.

5. The method for safe flight trajectory planning during the transition phase of a tiltrotor and compound wing manned aircraft according to claim 3, characterized in that, The solution process includes: Construct a zero-pitch angle dimensionality-reduced inverse dynamics model suitable for the longitudinal flight profile of tiltrotor and compound wing aircraft, and utilize decision vectors. Reconstruct the complete three-degree-of-freedom flight state of the aircraft, given any initial horizontal position. Horizontal initial velocity ,Depend on Time recursion The spacecraft's state parameters at any given time. Indicates the sampling step size: ； Among them, the thrust vector angle Pointing to the front of the aircraft is 0, pointing to the back of the aircraft is 0. , For the angle of attack, For dynamic pressure, air density, The total mass of the aircraft of These are the equivalent wing area and chord length, respectively. The cost function is calculated based on the pitch holding moment and total thrust of the aircraft obtained from solving the inverse dynamics equations. It is then determined whether the aircraft state parameters satisfy the nonlinear constraint functions. If all are satisfied, a nonlinear programming algorithm is used to iteratively generate a new decision vector through gradient descent based on the values ​​of the cost function and the nonlinear constraint functions. This process is repeated until the algorithm's termination condition is met, returning the optimal decision vector. .

6. The method for safe flight trajectory planning during the transition phase of a tiltrotor and compound wing manned aircraft according to claim 5, characterized in that, definition Indicates taking The first of the matrix arrive A submatrix composed of columns; Using decision vectors When reconstructing the complete three-degree-of-freedom flight state of the aircraft, in order to calculate arbitrary decision vectors... corresponding cost function The value must first be determined based on the decision vector. Obtain the trajectory of the aircraft , The polynomial coefficient matrix of the multi-segment time-normalized trajectory is used to complete the state vector with thrust vector angle and altitude: ， ， ； ； Each time normalization interval corresponds to the actual time. , Change with change; The coefficient matrix of the multi-segment time-normalized trajectory for thrust vector angle and altitude is calculated in batches using the following formula: ； in Indicates the thrust vector angle or flight altitude The thrust vector angular trajectory polynomial coefficient matrix and the altitude trajectory polynomial coefficient matrix are obtained. and And construct the first derivative coefficient matrix of the fifth-degree polynomial according to the following formula. and Second derivative coefficient matrix and : Given a column vector of coefficients of any fifth-degree polynomial Then the coefficient vectors of the first and second derivative polynomials of the fifth-degree polynomial are: , ; Construct a separate time-normalized sampling matrix: ； ； ； Based on this, the thrust vector angle and its first derivative, climb velocity, and climb acceleration of the aircraft are calculated in batches using the time-normalized sampling matrix and the polynomial coefficient matrix, resulting in the following four sets: ， ， ， ； Based on the above set, the complete three-degree-of-freedom flight state can be quickly reconstructed using a zero-pitch angle dimensionality reduction inverse dynamics model.

7. The method for safe flight trajectory planning during the transition phase of a tiltrotor and compound wing manned aircraft according to claim 2, characterized in that, The flight control in step 3 specifically includes: Based on the optimal decision vector obtained through optimization The complete three-degree-of-freedom motion state of the aircraft is reconstructed using a zero-pitch angle dimensionality-reduced inverse dynamics model, resulting in high-sampling-rate trajectory sampling of the aircraft's state parameters. Depending on the specific power layout of the tiltrotor or compound wing aircraft, and according to the corresponding control quantity allocation mechanism, and Mapped to the actual actuator group, the underlying control input is obtained, which ultimately serves as the feedforward signal for flight control during the takeoff and landing transition phase.

8. A safe flight trajectory planning system for the transition phase of a tiltrotor and compound wing manned aircraft, characterized in that, Includes the following modules; Initialization module: Used to initialize the flight trajectory planning problem; Optimization and Solving Module: Used to construct trajectory optimization problems and solve them iteratively; Trajectory Reconstruction Module: Used to reconstruct the complete flight trajectory of the high sampling rate transition process based on the trajectory optimization results for flight control.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-7.

10. A computer-storable medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-7.

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