A route re-planning algorithm based on online flight capability evaluation of control surface failure

Abstract

The application belongs to the technical field of aircraft route planning, and relates to a route replanning algorithm based on rudder surface fault online flight capability evaluation. The algorithm mainly comprises two parts. Firstly, the basic flight capability of the aircraft after damage and fault is evaluated online to obtain the basic flight performance of the aircraft after fault. Secondly, the evaluation result of the basic flight capability of the aircraft is applied to the A* route planning algorithm, so that the route is replanned under the condition of aircraft rudder surface structural damage and fault, and finally a new route that can be tracked after aircraft rudder surface damage or fault is obtained. At present, there is little research on online route planning of the aircraft considering the basic flight performance of the aircraft after the aircraft encounters rudder surface damage and fault. The algorithm provided by the application provides a new idea for whether the online route planning of the aircraft can be performed and the flight task can be continued after the aircraft rudder surface damage and fault.

Description

Technical Field

[0001] This invention belongs to the field of aircraft flight path planning technology, and relates to a flight path replanning algorithm based on online flight capability assessment of control surface failure. Background Technology

[0002] Aircraft trajectory planning refers to the process of planning the optimal flight path given a fixed starting point, target point, and some target nodes, based on factors such as the aircraft's operational performance, the geographical environment of the flight area, and potential threats. The goal of trajectory planning is to calculate the optimal or near-optimal flight path within a suitable timeframe using a pre-defined digital map. Currently, trajectory planning methods for aircraft missions mainly include mathematical programming-based methods, landmark map-based methods, spatial decomposition-based methods, potential field-based methods, stochastic programming-based methods, as well as many intelligent algorithms and machine learning-based algorithms.

[0003] Currently, in terms of trajectory planning, the research on trajectory planning can be mainly divided into three steps: first, to initially plan the flight trajectory of the aircraft under various threat environments and flight constraints; second, to further optimize and find the best route through various optimization search algorithms; and third, to smooth the trajectory to obtain the final route.

[0004] When planning the flight path of an aircraft, it is first necessary to define the flight constraints. For conventional aircraft, there are mainly two types of constraints:

[0005] (1) Flight environment constraints

[0006] The flight environment that constitutes an aircraft's mission generally includes the geographical conditions of the flight area and the distribution of threat areas. Terrain features mainly include undulating areas such as mountains, hills, and valleys. Threat distribution includes radar detection threats, air defense missile threats, and enemy aircraft interception threats.

[0007] (2) Flight kinematic constraints

[0008] Flight kinematic constraints are determined by the aircraft's navigation requirements and the results of flight mission planning. They mainly include the following types of track constraints transformed from the aircraft's actual kinematic parameters: maximum range constraints, flight altitude constraints, maximum turning angle constraints, and minimum straight flight trajectory constraints.

[0009] In conventional flight path planning, once the flight constraints are clearly defined, the plan can be made in advance based on the flight mission and environment, allowing the aircraft to fly along the predetermined route. However, when the aircraft's control surfaces malfunction or are damaged, its flight capabilities change rapidly, affecting route tracking. In such cases, it is necessary to assess the aircraft's flight capabilities and replan the flight path simultaneously, which places real-time demands on the flight path planning algorithm.

[0010] Based on the numerous algorithms that have been studied so far, most of them plan ahead based on flight missions and environmental constraints while the aircraft is on the ground. Because most of these algorithms require the collection and processing of large amounts of information, their computational speed is slow, their efficiency is low, and they are difficult to adapt to real-time requirements.

[0011] When an aircraft's aerodynamic control surfaces are damaged or jammed, its aerodynamic / torque characteristics change, which in turn causes significant changes in its model parameters. This results in changes to the aircraft's basic flight performance, such as minimum turning radius and range, making it impossible to continue tracking its original trajectory.

[0012] Moreover, there is currently very little research on direct online trajectory planning for aircraft after they have encountered control surface damage or malfunction. Summary of the Invention

[0013] To address the aforementioned problems, this invention studies an online flight capability assessment algorithm and designs an online trajectory replanning strategy for aircraft control surface damage or failure. This algorithm, based on flight performance assessment results, provides a new approach to enabling online trajectory planning and continued flight mission completion after control surface damage or failure. The strategy consists of two main parts: first, an online assessment of the aircraft's basic flight capabilities after damage or failure, yielding the aircraft's basic flight performance; second, the application of this assessment result to the A* trajectory planning algorithm, thereby replanning the trajectory under control surface damage or failure, ultimately resulting in a new, trackable trajectory after control surface damage or failure.

[0014] This invention selects the A* algorithm for online route replanning. As a heuristic search algorithm, the A* algorithm has the advantages of rapid response to the environment, direct search path, simplicity, and ease of implementation. Furthermore, this algorithm has been widely applied in various fields, and many mature C language and MATLAB programs are available for reference, demonstrating its strong feasibility for engineering applications. Therefore, this invention applies it to route planning under conditions of aircraft control surface damage and failure.

[0015] The technical solution of this invention:

[0016] A route replanning algorithm based on online flight capability assessment of control surface failure is as follows:

[0017] (1) Online flight capability assessment algorithm based on online route replanning under aircraft control surface damage or failure

[0018] (1.1) Flight constraints

[0019] For online replanning of flight routes, it is generally necessary to first clarify the flight constraints. As mentioned above, flight constraints refer to flight environment constraints and flight kinematic constraints. However, when the aircraft control surfaces are damaged or malfunctioning, the flight environment constraints do not change much. The flight kinematic constraints of the aircraft are the main constraints that limit the aircraft's flight route tracking capability.

[0020] As described above, the flight kinematic constraints of an aircraft are determined by the aircraft's navigation requirements and the results of flight mission planning. These constraints mainly fall into the following categories, which are derived from the aircraft's actual kinematic parameters:

[0021] (1.1.1) Maximum range constraint

[0022] In conventional flight path planning, the total amount of fuel carried by an aircraft determines its maximum range. When planning a flight path, the aircraft's range obviously cannot exceed the maximum range allowed by its fuel capacity. Furthermore, fuel consumption is somewhat uncertain; therefore, a certain margin should be left beyond the maximum allowable range. In addition, damage or malfunction of control surfaces will significantly impact the aircraft's basic flight performance and range. Therefore, combining the above descriptions, the aircraft's range constraint can be expressed as:

[0023] J c +△ c ≤J max (1.1)

[0024] In the formula, J c For a certain flight path, △ c To reserve the range, J maxTo determine the maximum permissible distance, the distance index constraint for a track with n waypoints can be expressed as:

[0025]

[0026] In the formula, J i-l This represents the distance traveled between the il-th waypoint and the i-th waypoint.

[0027] (1.1.2) Maximum rotation angle constraint

[0028] When an aircraft turns, the effect of the turn on its trajectory is ultimately reflected in the turning angle at the turning point; that is, the turning angle of an aircraft should be within a certain limit. Generally speaking, if the maximum allowable turning angle for a specific type of aircraft is θ, then for any turning angle, we have:

[0029]

[0030] in The maximum turning angle refers to the turning angle at the i-th track point, which can be further divided into the vertical and horizontal directions.

[0031] Due to limitations in aircraft maneuverability, pitching or tilting movements in the vertical direction must be within a certain angular range. Exceeding this range will affect flight safety. Therefore, the planned trajectory's turning angle in the vertical direction should be less than this range. The maximum vertical turning angle constraint can be expressed as:

[0032]

[0033] In the formula, i represents the current i-th segment of the track, (x i ,y i ,z i ) and (x i+1 ,y i+1 ,z i+1 θ represents the coordinates of the current waypoint and the candidate waypoint in the planned space, respectively. max This indicates the maximum turning angle of the aircraft in the vertical direction.

[0034] Similar to the vertical direction, the aircraft is also subject to certain angle limitations when turning in the horizontal direction. The maximum horizontal turning angle can be expressed as:

[0035]

[0036] It should be noted that the horizontal turning angle limit of an aircraft is determined by its turning radius, which is given below.

[0037] When an aircraft makes a turn, its maneuverability limits it to a certain radius, which cannot be less than a certain value. Therefore, there should be a certain turning radius constraint when turning on a planned flight path. The minimum turning radius constraint can be expressed as:

[0038] R i ≥R min (1.6)

[0039] In the formula, R i The turning radius for the i-th turn in the planned trajectory; R min The maximum turning radius of the aircraft is calculated using the following formula:

[0040]

[0041] In the formula, V min Let γ be the minimum turning speed of the aircraft, γ be the turning angle of the aircraft, and g be the acceleration due to gravity.

[0042] (1.2) Flight performance

[0043] In conventional flight path planning, aircraft typically need to plan their paths in advance while on the ground or before performing a mission. However, when the aircraft's control surfaces suffer structural damage or malfunction, it is necessary to be able to plan flight paths online. The prerequisite for online flight path planning is to conduct online flight performance assessments.

[0044] Therefore, this invention combines flight motion constraints from online flight path planning to perform online flight performance evaluation under conditions of aircraft damage and malfunction. The following flight performance characteristics were primarily evaluated:

[0045] (1.2.1) Range capability

[0046] For jet-powered aircraft, the formula for calculating their range is:

[0047]

[0048] Where V is the cruising speed, c is the engine fuel consumption rate, L / D is the aircraft lift-to-drag ratio, and W... initial W is the weight of the aircraft during cruising. final It is the weight of the aircraft at the end of its cruise.

[0049] At this point, it is necessary to calculate the aircraft's cruise speed and maximum lift-to-drag ratio:

[0050] At the maximum lift-to-drag ratio, zero lift drag equals induced drag:

[0051]

[0052] In the formula, L is lift, D is drag, cl is the lift coefficient, cd0 is the sum of all drag coefficients except the induced drag coefficient, and A is the induced drag coefficient. λ is the aspect ratio of the missile wing; δ is the correction value for the planar shape of the missile wing, with a theoretical value of 0.

[0053] Since lift equals gravity during cruising, then:

[0054]

[0055] Solve the above equations simultaneously:

[0056]

[0057] Where S is the wing area and W is the aircraft weight; since the weight of the aircraft gradually decreases, for a typical jet aircraft, two cruise methods can be used: one is to maintain a constant speed at a certain Mach number, although the speed remains constant, fuel consumption gradually increases; the other is to gradually decrease the speed according to changes in the aircraft's flight status, which can save fuel and increase the aircraft's range. The former is called high-speed cruise, and the latter is called long-distance cruise.

[0058] (1.2.2) Balancing capability

[0059] An aircraft's trim capability includes its maximum angle of attack, minimum angle of attack, maximum sideslip angle, and minimum sideslip angle. Trim capability determines the aircraft's flight speed. During normal cruise flight, the flight speed is high, and the trim angle of attack is sufficient. However, when the aircraft turns, the trim angle of attack affects the turning speed, thus affecting the aircraft's turning radius.

[0060] Furthermore, as can be seen from the formula for the turning radius above, the turning radius of an aircraft is related not only to the minimum trim speed but also to the aircraft's roll angle. Therefore, the following flight capabilities were mainly evaluated here:

[0061] Ignoring the smaller term in the moment coefficient, the equilibrium condition of the aircraft is:

[0062]

[0063] in, It is the longitudinal static stability coefficient of the aircraft. It is the elevator effectiveness coefficient, δ z It's elevator deflection. It is the lateral static stability coefficient. It is the rudder effectiveness coefficient, δ y It's rudder deflection, from which we can deduce:

[0064] Maximum angle of attack α max:

[0065]

[0066] Minimum angle of attack α min :

[0067]

[0068] Maximum sideslip angle β max :

[0069]

[0070] Minimum sideslip angle β min :

[0071]

[0072] (1.2.3) Mobility

[0073] When an aircraft performs turns and longitudinal maneuvers, its maneuverability also needs to be assessed (BTT turning maneuver).

[0074] Its overload in three directions can be written as:

[0075]

[0076] In the formula, L is lift, D is drag, T is engine thrust, and n x Along the direction of flight speed, it is usually called tangential overload or axial overload; n y and n z All are perpendicular to the flight velocity vector, and their sum is overload. This is called normal overload.

[0077] As mentioned above, the tangential overload of an aircraft is mainly related to engine thrust, while the normal overload is related to lift and roll angle. Lift is mainly determined by the trim angle of attack, while the limit of the roll angle is expressed by the following formula:

[0078]

[0079] As shown in the above formula, due to the relationship between lift, roll angle and gravity, it can be deduced that the greater the lift, the greater the maximum roll angle. Therefore, the maximum lift is the maximum roll angle that can be achieved at the current time. So, it is necessary to solve for the lift coefficient and then solve for the maximum lift under the trim angle of attack.

[0080] Assuming the identification model is The relationship between lift coefficient and angle of attack is as follows: It can be obtained The angle of attack corresponding to the maximum lift can be calculated using the extreme value theorem, and then the current lift can be obtained, thus yielding the roll angle limit.

[0081]

[0082] Among them, cl α It is the derivative of the lift coefficient with respect to the angle of attack. It is the derivative of the lift coefficient with respect to elevator deflection, cl 0 It has a zero lift coefficient. After obtaining its roll angle limit, its maximum lateral overload n can be obtained. z overload n y The solution can be obtained using the following formula:

[0083] When the angle of attack α and sideslip angle β are not very large (less than ±10°), the lift of the aircraft can be written in the following form:

[0084]

[0085] Where, δ z This refers to the elevator deflection angle.

[0086] Ignoring the smaller term in the moment coefficient, the equilibrium condition of the aircraft is:

[0087]

[0088] The projection of the overload vector onto the velocity coordinate system is:

[0089]

[0090] Where, γ V It is the velocity roll angle, which, after simplification, can be used to obtain n at equilibrium. y The relationship between the control surface deflection angle and the control surface angle:

[0091]

[0092] (2) Online replanning algorithm for flight path under aircraft control surface damage or failure

[0093] This invention uses the A* algorithm as a trajectory replanning algorithm after aircraft damage or malfunction. The A* algorithm is a type of heuristic search algorithm, a commonly used pathfinding and graph traversal algorithm that combines Dijkstra's algorithm and BFS algorithm, belonging to the category of spatial decomposition methods.

[0094] The steps of trajectory planning based on the A* algorithm are as follows:

[0095] (2.1) Construct a grid navigation map with nodes at uniform intervals based on the flight area.

[0096] (2.2) Based on constraints such as enemy radar and no-fly zones, risk zones are set up.

[0097] (2.3) Design trajectory optimization indices, using a weighted method based on the shortest trajectory and minimum detectability index as the trajectory performance index:

[0098]

[0099] Based on this, it is transformed into a performance metric function for node problems:

[0100]

[0101]

[0102] Where J is the route length; w s The cost of airway threats is linked to the detectability index of the aircraft, which is calculated based on the distance between the aircraft and the threat position; w d The fuel cost for the flight route is represented by k, which is a weighting coefficient.

[0103] (2.4) Set the starting point of the path (x s y s ) and endpoint (x e y e Create open and close tables to store f(i), g(i), h(i) and the parent node. The formula for calculating f(i) is as follows:

[0104] f(i)=g(i)+h(i) (1.27)

[0105] Where h(i) is the heuristic function, and represents the distance from node i to the endpoint (x). e y e The Manhattan distance, i.e.:

[0106]

[0107] g(i) is the starting point (x s y s The performance metrics from node i to node i are:

[0108]

[0109] The parent node is the previous route node of node i.

[0110] (2.5) All threat costs w around node i s,rNodes with non-zero values ​​are added to the open list as exploration nodes. The node t with the lowest estimated route cost is taken from the open list and inserted into the close list. Here, r is a neighboring node of node i, and node r is reachable.

[0111] (2.6) Determine whether the newly inserted node t is the target point. If not, then add all threat costs w around node t. s,v Non-zero nodes are added to the open list as exploration nodes. The node with the lowest estimated route cost is taken from the open list and added to the close list again, until the newly inserted node is the target point.

[0112] (2.7) Find the endpoint (x) based on the close table e y e The parent node (x) n y n Based on this, recursively search (x) n y n The parent node (x) f y f ), and so on, until the parent node becomes the starting point (x). s y s If the route is not specified, it is saved as waypoints, as follows:

[0113] path = [(x s y s ) (x f y f … (x) i y i … (x) v y v … (x) e y e )]

[0114] The algorithm described above is used for trajectory replanning after damage or failure of the aircraft's control surfaces. It is run after flight capability assessment following damage or failure of the aircraft's control surfaces, and finally a new trajectory can be obtained.

[0115] (3) Flight performance assessment and trajectory replanning after control surface damage and failure

[0116] Before performing trajectory planning, it is necessary to accurately provide flight kinematic constraints, namely the two flight kinematic constraints given in step (1.1), the maximum range constraint and the minimum turning angle constraint, which are all related to the damage and failure of the aircraft's control surfaces.

[0117] When using the A* algorithm for aircraft trajectory planning, the above constraints can be converted into two types: the maximum path length and the planning grid size. The maximum range of the aircraft limits the maximum path length, while the minimum turning angle and minimum straight flight segment constraints limit the planning grid size.

[0118] Based on the above, the basic flight capabilities of the aircraft in step (1.2) need to be evaluated under the condition of damage and failure of the aircraft control surfaces, and then the path length and grid size planned by the A* algorithm are determined.

[0119] As can be seen from the above, when planning the trajectory of an aircraft after damage and failure, the range constraint corresponds to the range capability in the basic flight performance evaluation. Therefore, the constraint on the length after A* algorithm planning is as follows:

[0120] J <J max (1.29)

[0121] However, the minimum turning angle constraint cannot be directly constrained. Therefore, this invention combines the online evaluation of the aircraft's basic flight performance with the actual implementation process of the A* algorithm to conduct relevant analysis on this constraint and obtain its specific implementation method.

[0122] As can be seen from the above technical solutions, the minimum turning angle constraint in the horizontal direction is actually manifested as the minimum turning radius constraint, and the constraint in the vertical direction is actually manifested as the minimum trajectory curvature radius. The two concepts are the same. The following uses the minimum turning radius constraint to explain the relationship between the turning radius constraint and the aircraft's trim capability and maneuverability.

[0123] The turning radius R of the aircraft min Written as:

[0124]

[0125] It can also be written as

[0126]

[0127] It can be seen that it is related to the minimum turning speed and the maximum roll bank angle or the maximum lateral overload. Among the above basic flight performance characteristics, the maximum angle of attack and the maximum and minimum sideslip angles determine the minimum trim speed of the aircraft, which, together with the maximum lateral overload in maneuverability, determines the minimum turning radius.

[0128] The minimum turning radius has the following relationship with the size d of the A* algorithm grid:

[0129] d>3·R min (1.32)

[0130] This imposes constraints on the mesh of the A* algorithm.

[0131] In summary, when using the A* algorithm for path planning, the two conditions of path length and grid size mentioned above must be met. If these conditions are not met, the grid size of the A* algorithm needs to be changed and the path needs to be replanned. If the range constraints of the planned path still cannot be met, the pathfinding process needs to continue. If no path can be found, the forced landing endpoint will be used to carry out the forced landing.

[0132] In summary, the results of the online flight capability assessment limited the trajectory planned by the A* algorithm, achieving the expected effect and obtaining the replanned trajectory of the aircraft after the control surface failure.

[0133] The beneficial effects of this invention are:

[0134] This invention considers the scenario of damaged or malfunctioning aircraft control surfaces. Based on this, it first evaluates the basic flight performance of the aircraft using flight data and aircraft model data, combined with trajectory planning constraints. Then, it performs online trajectory replanning based on the results of the online flight performance evaluation, ultimately obtaining a new trackable trajectory for the aircraft under conditions of control surface loss or malfunction. Using this algorithm, the aircraft's flight capability can be evaluated in real time after a malfunction, and trajectory planning can be performed simultaneously to obtain a safe flight path, thus improving flight safety after a malfunction. This strategy provides a new approach for online replanning algorithms for aircraft. Attached Figure Description

[0135] Figure 1 This is a flowchart of an online flight performance evaluation algorithm.

[0136] Figure 2 This is a diagram of the forces acting on an aircraft during roll.

[0137] Figure 3 This is a flowchart of the optimal route planning process using the A* algorithm;

[0138] Figure 4 It is a spatial model diagram of air route planning;

[0139] Figure 5 This is a simulation example framework diagram;

[0140] Figure 6 This is the simulation result of the flight path due to the missing left elevator;

[0141] Figure 7 This is the roll angle-time simulation result for a missing left elevator fault;

[0142] Figure 8 This is the pitch angle-time simulation result for a missing left elevator fault;

[0143] Figure 9 The simulation results of left elevator deflection-time are for a missing left elevator fault.

[0144] Figure 10 This is the angle-of-attack time simulation result of the missing left elevator fault;

[0145] Figure 11 This is the simulation result of the flight path when the left elevator is stuck.

[0146] Figure 12 The results are from the roll angle-time simulation of the left elevator jamming fault.

[0147] Figure 13 This is the angle-of-attack simulation result of the left elevator jamming fault;

[0148] Figure 14 The simulation results of left elevator deflection-time are for a left elevator stuck fault.

[0149] Figure 15 This is the angle-of-attack simulation result of the left elevator jamming fault;

[0150] Figure 16 This is the simulation result of the flight path due to a left elevator limitation fault;

[0151] Figure 17 The results are from the roll angle-time simulation of the left elevator limitation fault.

[0152] Figure 18 The results are from the pitch angle-time simulation of the left elevator limitation fault.

[0153] Figure 19 The simulation results of left elevator deflection-time are from a left elevator limitation fault.

[0154] Figure 20 The results are from the angle-of-attack time simulation of the left elevator limitation fault. Detailed Implementation

[0155] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0156] Force analysis of the aircraft during roll as follows Figure 2As shown, damage and malfunction of aircraft control surfaces mainly include three aspects: missing control surfaces, stuck control surfaces, and restricted control surfaces. Damage to aircraft control surfaces leads to decreased handling stability and deteriorated control quality. It also alters the aircraft's basic flight performance, potentially preventing it from following its initial flight path and thus hindering mission completion. Therefore, trajectory planning is a crucial issue when aircraft control surfaces are damaged or malfunctioning. It should be noted that this invention currently focuses on horizontal plane trajectory planning, and the specific implementation is illustrated by the following simulation example. Figure 1 This is a basic flowchart of the present invention. Figure 5 This is a framework diagram of the simulation example. As shown in the framework, this program mainly consists of three parts: a flight control module, an aircraft dynamics model module, and a control surface fault input module. The flight control system internally includes a module for evaluating flight performance after control surface damage and faults, as well as a route planning module. Additionally, it includes a trajectory and attitude control module, which will not be discussed here. Therefore, this section will cover the following: inputting the initial state, establishing the aircraft dynamics model, evaluating flight performance after control surface damage and faults, replanning the trajectory, and finally providing simulation examples for different faults. The basic process of trajectory planning based on the A* algorithm is as follows: Figure 3 As shown, the route planning spatial model is as follows: Figure 4 As shown.

[0157] (1) Input the initial state and give the target state.

[0158] The aircraft maintains cruising level at an altitude of 5000m along the initial route. During the flight along the given route, under any waypoint conditions, the aircraft switches to control surface failure mode. The aircraft is able to maintain stable flight control and, combined with its own flight capabilities, completes route replanning and switching, ultimately arriving at the destination safely.

[0159] This example uses a combat aircraft experiencing a malfunction during the cruise phase, simulating a BTT (Bank to Turn) maneuver. The aircraft data is shown below:

[0160] Table 1 Simulation Parameters

[0161]

[0162] (2) Establishing the aircraft dynamics model

[0163] In order to accurately describe the motion state of the aircraft and facilitate the force analysis of the aircraft, it is necessary to select a suitable coordinate system. In the modeling process, this invention mainly uses the ground coordinate system, the body coordinate system and the airflow coordinate system. The definitions of each coordinate system are based on the Soviet coordinate system.

[0164] (1) Ground coordinate system

[0165] Origin O e Take a point on the ground (usually the aircraft's takeoff point), axis o e x e Pointing to the initial flight path direction of the aircraft, o e y e Vertically upwards from the ground, o e z e Perpendicular to o e x e y e To the right, the positional relationship of the aircraft is generally described using a ground coordinate system.

[0166] (2) Body coordinate system

[0167] Origin O b The coordinates are located at the center of mass of the spacecraft, and the three coordinate axes are fixed to the spacecraft. b x b The axis lies within the aircraft's plane of symmetry. It aligns with the fuselage axis and points forward; b y b Located on the plane of symmetry of the aircraft and perpendicular to o b x b Upward is positive, o b z b Perpendicular to o b x b y b In a plane, right is positive.

[0168] (3) Determine the velocity coordinate system

[0169] Origin O a Taken at the center of mass of the spacecraft, o a x a The axis coincides with the instantaneous airspeed direction of the spacecraft's center of mass. a y a The axis lies in the plane of symmetry of the aircraft and is perpendicular to o. a x a The upward axis is positive, o a z a The axis is perpendicular to o a x a y b In a plane, right is positive.

[0170] (4) The six-degree-of-freedom model of the Soviet-type aircraft body is described as follows:

[0171]

[0172] γ is the roll angle, θ is the pitch angle, ψ is the yaw angle, α is the angle of attack, β is the sideslip angle, θ is the trajectory inclination angle, and ψ is the pitch angle. V γ is the trajectory deflection angle. V For the velocity roll angle, ω x Let ω be the rolling angular velocity, and its direction satisfy the right-hand rule. y Let ω be the yaw angular velocity, and let its direction satisfy the right-hand rule. z Let V be the pitch angular velocity, and let its direction satisfy the right-hand rule. The velocity component V is... x Ground velocity body axis components, with the positive x-axis as positive, velocity component V y : Ground velocity body axis components, positive y-axis is positive, velocity component V z : Earth velocity body axis components, positive z-axis is positive, M x M is the rolling torque. y For the yaw moment, M z This is the pitching moment.

[0173] (4) Simulation example of flight path replanning and control under aircraft control surface damage or failure

[0174] To illustrate the practical effectiveness of this invention, simulations were conducted under different fault conditions. The initial simulation conditions are shown in the table below:

[0175] Table 2 Simulation Status of Flight Path Replanning and Control under Aircraft Control Surface Damage or Failure

[0176]

[0177] Simulations were primarily conducted on different faults of the left elevator:

[0178] (1) The left elevator experienced a 70% loss failure at 30 seconds.

[0179] like Figure 6-10 As shown, the flight simulation curve with 70% of the left elevator surface missing was obtained. The graph indicates that the aircraft experienced a malfunction at 30 seconds and simultaneously replanned its flight path, resulting in the following... Figure 6 The new flight path shown indicates that the final landing point is emergency landing point 1. The image also shows that the position tracking error is much less than 50m. Furthermore, the roll, pitch, and angle of attack have also changed accordingly. The roll angle command changes because it needs to track the newly generated flight path, while the pitch and angle of attack change simultaneously because corresponding lift is needed to balance gravity during roll.

[0180] (2) The left elevator jammed at 5° at 90s.

[0181] like Figure 11-15As shown, the simulation curve of the flight state with the left elevator surface stuck at 5° was obtained. It can be seen from the figure that the aircraft malfunctioned at 180s, and the flight path was replanned, resulting in a new trajectory. It can be seen that the final landing point of the newly planned trajectory is the forced landing point 2. Similar to the simulation in (1), the roll angle, pitch angle and angle of attack also changed accordingly. Finally, the actual size of the left and right elevator surfaces can also be seen. Here it can be clearly seen that the left elevator surface is stuck at 5°, which causes its control surface command to be different from the actual control surface. This is also the fundamental reason for the changes during flight.

[0182] (3) The left elevator experienced a limited-angle failure (-1° to -3°) at 350s.

[0183] like Figure 16-20 As shown, the flight state simulation curve with the left elevator constrained to (-1°, -3°) was obtained. It can be seen from the figure that the aircraft malfunctioned at 350s and simultaneously replanned its flight path, resulting in the new trajectory shown in the figure. It can be seen that the final landing point of the newly planned trajectory is the endpoint. Similar to the simulations in (1) and (2), the roll angle, pitch angle, and angle of attack also underwent similar changes. The difference is that the trajectory planned by the aircraft here is the same as the initial trajectory, which also indicates that when the distance to the endpoint is relatively close, the range impact is small, and the main influencing factor is the constraint of the turning radius.

Claims

1. A route replanning algorithm based on online flight capability assessment of control surface faults, characterized in that, Specifically as follows: (1) Online flight capability assessment algorithm based on online route replanning under aircraft control surface damage or failure (1.1) Flight constraints (1.1.1) Maximum range constraint The aircraft range constraint is expressed as: (1.1) ； In the formula, This refers to the distance indicator for a certain flight path. For the reserved range, To determine the maximum permissible flight distance, the number of waypoints for a single waypoint is... The flight path, and its range constraint, are expressed as follows: (1.2) ； In the formula, Indicates the first The first waypoint and the first The distance of the track segment between waypoints; (1.1.2) Maximum rotation angle constraint If the maximum allowable turning angle of the aircraft is For any turning angle, we have: (1.3) ； in Refers to the first The turning angle of each track point, the maximum turning angle is further divided into vertical and horizontal directions; The maximum vertical turning angle constraint is expressed as: (1.4) ； In the formula, This indicates that the current number is the [number]. Duan Hangji, and These represent the coordinates of the current waypoint and the candidate waypoint within the planned space, respectively. This indicates the maximum turning angle of the aircraft in the vertical direction; Similar to the vertical direction, the maximum turning angle in the horizontal direction is expressed as: (1.5) ； The horizontal turning angle limit of an aircraft is determined by its turning radius, and the minimum turning radius constraint is expressed as: (1.6) ； In the formula, To plan the flight path Turning radius during the second turn; The minimum turning radius of the aircraft is calculated using the following formula: (1.7) ； In the formula, This is the minimum turning speed of the aircraft. The turning bank angle of the aircraft. It is the acceleration due to gravity; (1.2) Flight performance (1.2.1) Range capability For jet-powered aircraft, the formula for calculating their range is: (1.8) ； in, It's cruising speed. It is the engine fuel consumption rate. It is the lift-to-drag ratio of the aircraft. It is the weight of the aircraft during cruise. It is the weight of the aircraft at the end of its cruise phase; At this point, it is necessary to calculate the aircraft's cruise speed and maximum lift-to-drag ratio: At the maximum lift-to-drag ratio, zero lift drag equals induced drag: (1.9) ； In the formula, It's lift. It is resistance. It is the lift coefficient. It is the sum of all drag coefficients except the induced drag coefficient, where The induced drag coefficient, , For the aspect ratio of the missile wings; This is a correction value for the planar shape of the missile wing; Since lift equals gravity during cruising, then: (1.10) ； Solve the above equations simultaneously: (1.11) ； in, It is the wing area. It is the weight of the aircraft; (1.2.2) Balancing capability The following flight capabilities were primarily assessed: Ignoring the smaller term in the moment coefficient, the equilibrium condition of the aircraft is: (1.12) ； in, It is the longitudinal static stability coefficient of the aircraft. It is the elevator efficiency coefficient. It's elevator deflection. It is the lateral static stability coefficient. It is the rudder effectiveness coefficient. It's rudder deflection, from which we can deduce: Maximum angle of attack : (1.13) ； Minimum angle of attack : (1.14) ； Maximum sideslip angle : (1.15) ； Minimum sideslip angle : (1.16) ； (1.2.3) Mobility When an aircraft makes turns and longitudinal maneuvers, it is also necessary to assess the aircraft's maneuverability. Overload in three directions is written as: (1.17) ； In the formula It's lift. It is resistance. It is engine thrust. Along the direction of flight speed, it is usually called tangential overload or axial overload; and All are perpendicular to the flight velocity vector, and their sum is overload. This is called normal overload; The tangential overload of an aircraft is mainly related to engine thrust, while the normal overload is related to lift and roll angle. Lift is mainly determined by the trim angle of attack, while the roll angle is limited by the following formula: (1.18) ； Because of the relationship between lift, roll angle and gravity, it can be deduced that the greater the lift, the greater the maximum roll angle. Therefore, the maximum lift is the maximum roll angle that can be rolled at the current time. So we need to solve for the lift coefficient and then solve for the maximum lift under the trim angle of attack. Assuming the identification model is , The relationship between lift coefficient and angle of attack is: It can be obtained According to the extreme value theorem, the angle of attack corresponding to the maximum lift is calculated, and then the current lift is obtained, thus yielding the roll angle limit: (1.19) ； in, It is the derivative of the lift coefficient with respect to the angle of attack. It is the derivative of the lift coefficient with respect to elevator deflection. It has a zero lift coefficient, and after obtaining its roll angle limit, its maximum lateral overload is obtained. overload The solution is then obtained using the following formula: When the angle of attack of flight and sideslip angle All less than °, the lift of the aircraft can be written in the following form: (1.20) ； in, Elevator deflection angle; Ignoring the smaller term in the moment coefficient, the equilibrium condition of the aircraft is: (1.21) ； The projection of the overload vector onto the velocity coordinate system is: (1.22) ； in, It is the speed roll angle; after simplification, the equilibrium position is obtained. The relationship between the control surface deflection angle and the control surface angle: (1.23) ； (2) Online replanning algorithm for flight path under aircraft control surface damage or failure Use A The algorithm, used for trajectory replanning after aircraft damage or malfunction, consists of the following steps: (2.1) Construct a grid navigation map with nodes at uniform intervals based on the flight area; (2.2) Based on the constraints of enemy radar and no-fly zones, risk zones are set up; (2.3) Design trajectory optimization indices, using a weighted method based on the shortest trajectory and minimum detectability index as the trajectory performance index: (1.24) ； Based on this, it is transformed into a performance metric function for node problems: (1.25) ； (1.26) ； in, This refers to the length of the flight route. The cost of airway threats is linked to the detectability index of the aircraft, which is calculated based on the distance between the aircraft and the threat position; For the cost of fuel consumption during the flight, These are weighting coefficients; (2.4) Set the starting point of the path and the finish line Create open and close tables to store... , , With the parent node, where The calculation formula is as follows: (1.27) ； in, For heuristic functions, for Node to End Point The Manhattan distance, i.e.: (1.28) ； Starting point arrive The performance metrics of a node are: (1.28) ； Parent node is The previous route node of the node; (2.5) Node All surrounding threats cost Nodes with non-zero values ​​are added to the open list as exploration nodes. The node with the minimum estimated route cost is then retrieved from the open list. Insert it into the close table; where, For nodes The adjacent nodes, and the nodes Reachable; (2.6) Determine the newly inserted node Is it the target point? If not, then move the node... All surrounding threats cost Non-zero nodes are added to the open list as exploration nodes. The node with the lowest estimated route cost is taken from the open list and added to the close list again, until the newly inserted node is the target point. (2.7) Find the endpoint based on the close table parent node Based on this, recursively search parent node And so on, until the parent node becomes the starting point. The route is then saved as waypoints, in the following format: ； A new trajectory is obtained using the algorithm described above; (3) Flight performance assessment and trajectory replanning after control surface damage and failure Before performing trajectory planning, it is necessary to accurately provide flight kinematic constraints, namely the two flight kinematic constraints given in step (1.1), the maximum range constraint and the minimum turning angle constraint, which are both related to the damage and failure of the aircraft's control surfaces; Using A When the algorithm plans the flight path of an aircraft, the above constraints can be converted into two types: the maximum path length and the planning grid size. The maximum range of the aircraft limits the maximum path length, while the minimum turning angle and minimum straight flight segment constraints limit the planning grid size. Therefore, it is necessary to assess the basic flight capabilities of the aircraft in step (1.2) under conditions of damage and malfunction of the aircraft's control surfaces, and then determine A. The algorithm plans the path length and grid size; In particular, when planning the flight path of an aircraft after damage or malfunction, the range constraint corresponds to the range capability in the basic flight performance assessment. Therefore, for A... The length constraint after algorithm planning is shown in the following formula: (1.29) ； However, the minimum turning angle constraint cannot be directly constrained, so we conduct a related analysis on these two constraints to obtain their specific implementation methods. The minimum turning angle constraint in the horizontal direction is actually manifested as the minimum turning radius constraint, and the constraint in the vertical direction is actually manifested as the minimum trajectory curvature radius. The two concepts are the same. The following uses the minimum turning radius constraint to illustrate the relationship between the turning radius constraint and the aircraft's trim capability and maneuverability. Turning radius of the aircraft Written as: (1.30) ； It can also be written as: (1.31) ； It can be seen that it is related to the minimum turning speed and the maximum roll bank angle or the maximum lateral overload; among the above basic flight performance, its maximum angle of attack and maximum and minimum sideslip angles determine the minimum trim speed of the aircraft, which together with the maximum lateral overload in maneuverability determine the minimum turning radius. The minimum turning radius is related to A. Algorithm grid size The following relationship exists between them: (1.32) ； Using A When the algorithm plans a path, it must satisfy two conditions: path length and grid size. If these conditions are not met, then A needs to be changed. The algorithm adjusts the grid size and replans the path. If the planned path still fails to meet the range constraints, the pathfinding process continues. If no path can be found, the forced landing endpoint will be used to initiate a forced landing.

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