A threat area flyaround predictive-correction guidance method and system

Abstract

The application provides a threat area fly-around prediction-correction guidance method and system. The method comprises the following steps: constructing a reentry motion model and determining an initial state of an aircraft; determining a state value of a transition point between an initial descent segment and a glide segment according to a nominal attack angle and a constant roll angle acting on the model based on the initial state of the aircraft; in the longitudinal guidance design, taking the state value of the transition point as the initial state of the glide segment, determining a five-segment resistance acceleration profile according to a reentry range requirement, generating a longitudinal range analytical solution, determining a roll angle amplitude based on the resistance acceleration profile and a controller requirement, and inputting the roll angle amplitude into the lateral guidance; in the lateral guidance design, updating a heading angle corridor according to the state value of the transition point and the roll angle amplitude, determining a roll angle reverse logic for flying around the forbidden flight area, and outputting a roll angle sign. The application can improve the range calculation speed and adapt to different configurations and multiple threat areas.

Description

Technical Field

[0001] This invention relates to the field of aircraft guidance, and in particular to a method and system for predicting and correcting flight around threats. Background Technology

[0002] When our hypersonic vehicles strike enemy ground targets, they will be threatened by the enemy's anti-missile system. The effective detection range of the anti-missile system forms an interception threat zone. Our gliding hypersonic vehicles need to fly around the threat zone during reentry to complete the mission of striking the target.

[0003] In predictive-correction guidance, traditional longitudinal guidance methods cannot obtain an analytical form of the range and can only calculate the range through numerical integration. Furthermore, in studies on aircraft reentry and bypassing threat zones, most studies are designed for one or two threat zones. The algorithms cannot adapt to situations with multiple threat zones of different configurations, and cannot perform bypassing based on the threat level of the threat zone. Summary of the Invention

[0004] The purpose of this invention is to provide a threat zone avoidance prediction-correction guidance method and system to solve the problem that the flight path calculation speed is slow during the prediction-correction guidance process and that the avoidance mission cannot be completed under different configurations and multiple threat zones.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A threat zone bypass prediction-correction guidance method includes:

[0007] Based on the constraints, the reentry energy of the spacecraft is used as the independent variable to construct a reentry motion model and determine the initial state of the spacecraft. The constraints include thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero tilt angle quasi-equilibrium gliding conditions, and terminal constraints.

[0008] Initial descent segment:

[0009] Based on the initial state of the aircraft, the nominal angle of attack and the constant roll angle are obtained, and the variable values ​​of each state equation are determined according to the combined effect of the nominal angle of attack and the constant roll angle on each state equation.

[0010] Determine the state values ​​of the transition points between the initial descent segment and the gliding segment based on the values ​​of the variables in the state equations.

[0011] Glide phase: includes longitudinal guidance design and lateral guidance design;

[0012] In the longitudinal guidance design, a five-segment drag acceleration profile is determined based on the state value of the transfer point and the reentry range requirement, and an analytical solution for the longitudinal range is generated. Based on the state variables related to longitudinal guidance in the longitudinal guidance design, the billet angle magnitude is determined according to the analytical solution for the longitudinal range, and the billet angle magnitude is input into the lateral guidance process.

[0013] In the lateral guidance design, based on the state value of the transfer point, the tilt angle amplitude, and the reduced-order lateral guidance motion, the heading angle boundary of each no-fly zone is considered, the heading angle corridor is updated according to the threat level of the no-fly zone, the tilt angle reversal logic for bypassing the no-fly zone is determined, and the tilt angle sign is output.

[0014] The tilt angle command is determined based on the tilt angle magnitude and the tilt angle sign; the tilt angle command is used to control the aircraft to fly around each no-fly zone.

[0015] Optionally, based on the state values ​​at the transfer point and the reentry range requirements, a five-segment drag acceleration profile is determined to generate a longitudinal range analytical solution. Then, based on the state variables related to longitudinal guidance in the longitudinal guidance design, the billet angle magnitude is determined according to the longitudinal range analytical solution. Specifically, this includes:

[0016] The resistance-energy re-entry corridor is determined based on the state value of the transfer point and the constraints.

[0017] The five-segment drag acceleration profile is determined based on the drag-energy reentry corridor; the main adjustment values ​​of the five-segment drag acceleration profile include adjustment values ​​for range and adjustment values ​​for lateral maneuverability.

[0018] Adjust the segmented drag acceleration values ​​based on the five-segment drag acceleration profile to determine the analytical solution for the longitudinal range.

[0019] Based on the state variables related to longitudinal guidance in the longitudinal guidance design, predict the longitudinally related terminal function;

[0020] The roll angle magnitude is determined based on the analytical solution of the longitudinal range and the terminal function.

[0021] Optionally, the five-segment drag acceleration profile for:

[0022]

[0023] in, This is the normalized energy value; This represents the energy value at the transition point after normalization. This is the energy value that equals 0.3 after normalization; This is the energy value that is normalized to 0.5; This is the energy value that is normalized to 0.7; This is the energy value that is normalized to 0.8; The energy value of the terminal energy management section; D c D1 represents the drag acceleration value at the transfer point; D2 represents the adjustment value for adjusting the range; D3 represents the adjustment value for adjusting the lateral maneuverability. f This represents the drag acceleration value of the terminal energy management section.

[0024] Optionally, the roll angle magnitude is determined based on the longitudinal range analytical solution and the terminal function, specifically including:

[0025] Based on the analytical solution of the longitudinal flight path and the terminal function, determine whether the reentry longitudinal terminal condition is met;

[0026] If so, track the five-segment drag acceleration profile and output the tilt angle amplitude;

[0027] If not, correct the adjustment value of the adjusted range and update the five-segment drag acceleration profile.

[0028] Optionally, the five-segment drag acceleration profile is tracked, and the roll angle amplitude is output, specifically including:

[0029] Within one guidance cycle, the five-segment drag acceleration profile is planned, and the roll angle amplitude is output, specifically including:

[0030] Set the initial adjustment values ​​for the flight range and the adjustment values ​​for the lateral maneuverability, and check whether the lateral maneuverability of the aircraft meets the requirements for flying around the no-fly zone under the current conditions.

[0031] If so, the adjustment value of the adjusted range is adjusted using Newton's iteration method;

[0032] If not, adjust the adjustment value of the lateral maneuverability by a fixed increment to increase the lateral maneuverability. Then, adjust the adjustment value of the range by Newton's iteration method and check again whether the lateral maneuverability of the aircraft meets the requirements for flying around the no-fly zone until the desired range is reached. Determine the final five-segment drag acceleration profile and output the roll angle amplitude.

[0033] Optionally, based on the state value of the transfer point, the tilt angle amplitude, and the reduced-order lateral guidance motion, considering the heading angle boundaries of each no-fly zone, the heading angle corridor is updated according to the threat level of the no-fly zone, the tilt angle reversal logic for bypassing the no-fly zone is determined, and the tilt angle sign is output, specifically including:

[0034] Determine the detour direction for each no-fly zone based on the status values ​​of the transfer point and the target point;

[0035] The reduced-order lateral guidance motion is determined based on the flight direction and the tilt angle amplitude;

[0036] The state variables related to lateral guidance are determined based on the reduced-order lateral guidance motion;

[0037] Calculate the heading angle boundaries for flying around each no-fly zone based on the state variables, and update the heading angle corridors according to the threat level of the no-fly zones;

[0038] The lateral reversal logic is determined based on the updated heading angle corridor;

[0039] The sign of the tilt angle is determined based on the aforementioned lateral flight reversal logic.

[0040] Optionally, the heading angle boundaries for flying around each no-fly zone are calculated based on the state variables, and the heading angle corridors are updated according to the threat level of the no-fly zones, specifically including:

[0041] Calculate the heading angle boundary of the aircraft relative to the target and determine the initial heading angle corridor;

[0042] Generate a threat level sequence based on the threat level of the no-fly zone;

[0043] Calculate the detour direction for each of the no-fly zones according to the threat level sequence, and determine the heading angle boundary for detour around the no-fly zones;

[0044] The initial heading angle corridor is updated by using the heading angle boundary of the first no-fly zone in the threat level sequence to generate an updated heading angle corridor;

[0045] Based on the threat level sequence, the updated heading angle corridor is updated using the heading angle boundary of the next no-fly zone.

[0046] A threat zone avoidance prediction-correction guidance system includes:

[0047] The initial state determination module is used to construct a reentry motion model based on constraints, using the reentry energy of the aircraft as the independent variable, and determine the initial state of the aircraft. The constraints include thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero roll angle quasi-equilibrium gliding conditions, and terminal constraints.

[0048] Initial descent segment:

[0049] The variable value determination module for each state equation is used to obtain the nominal angle of attack and constant roll angle based on the initial state of the aircraft, and determine the variable values ​​of each state equation according to the combined effect of the nominal angle of attack and the constant roll angle on each state equation.

[0050] The state value determination module for the transition point is used to determine the state value of the transition point between the initial descent segment and the gliding segment based on the variable values ​​of each state equation.

[0051] Glide phase: includes longitudinal guidance design and lateral guidance design;

[0052] The longitudinal guidance design module is used to determine a five-segment drag acceleration profile based on the state value of the transfer point and the reentry range requirements in the longitudinal guidance design, generate an analytical solution for the longitudinal range, and determine the billing angle magnitude based on the state variables related to longitudinal guidance in the longitudinal guidance design and the analytical solution for the longitudinal range, and input the billing angle magnitude into the lateral guidance process.

[0053] The lateral guidance design module is used in the lateral guidance design to, based on the state value of the transfer point, the tilt angle amplitude and the reduced-order lateral guidance motion, consider the heading angle boundary of each no-fly zone, update the heading angle corridor according to the threat level of the no-fly zone, determine the tilt angle reversal logic for flying around the no-fly zone, and output the tilt angle sign;

[0054] The tilt angle command determination module is used to determine the tilt angle command based on the tilt angle amplitude and the tilt angle sign; the tilt angle command is used to control the aircraft to fly around each no-fly zone.

[0055] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: The present invention provides a threat zone bypass prediction-correction guidance method and system, including longitudinal guidance design and lateral guidance design; wherein, the longitudinal guidance design adopts a range analysis prediction-correction guidance method, by planning the drag acceleration profile as a five-segment linear function, the analytical expression of the reentry range is obtained, and on this basis, the prediction-correction guidance method is adopted to obtain the correction parameter values ​​that meet the desired range and lateral maneuver requirements, thereby obtaining the corresponding drag acceleration profile, and obtaining the amplitude of the control quantity roll angle under this profile.

[0056] Lateral guidance design prioritizes no-fly zone bypass methods with high threat levels. By taking into account the heading angle boundaries generated by all no-fly zones and updating the heading angle corridor in sequence according to the threat level, it can successfully complete no-fly zone bypass.

[0057] This invention realizes online trajectory planning of a prediction-correction guidance method based on analytical solutions through the interaction of longitudinal guidance design and lateral guidance design. By applying this analytical form, the calculation speed and solution accuracy can be improved. The lateral guidance logic can be adapted to no-fly zone bypass missions of different configurations and numbers. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 The flowchart shows the trajectory planning process for the prediction-correction guidance method based on analytical methods.

[0060] Figure 2 A schematic diagram of the newly defined coordinate system;

[0061] Figure 3 A complete flowchart of the longitudinal guidance design;

[0062] Figure 4 A schematic diagram of the planned drag acceleration profile;

[0063] Figure 5 A complete flowchart of the lateral guidance design;

[0064] Figure 6 This is a schematic diagram of the heading angle boundary; Figure 6 (a) is a heading angle corridor diagram relative to the target; Figure 6 (b) is a heading angle corridor diagram for flying around the threat zone from below; Figure 6 (c) is a heading angle corridor diagram for flying around the threat zone;

[0065] Figure 7 This is a typical diagram of a no-fly zone detour mission;

[0066] Figure 8 A schematic diagram illustrating an aircraft's reentry and circumnavigation of a no-fly zone. Figure 8 (a) is a schematic diagram of the no-fly zone for Mission 1; Figure 8 (b) is a schematic diagram of the no-fly zone for Mission 2; Figure 8 (c) is a schematic diagram of the no-fly zone for Mission 3; Figure 8 (d) is a schematic diagram of the no-fly zone for Mission 4;

[0067] Figure 9 A schematic diagram illustrating the changes in reentry heading angle under different missions; Figure 9 (a) is a schematic diagram of the reentry heading angle change for Mission 1; Figure 9 (b) is a schematic diagram of the reentry heading angle change for Mission 2; Figure 9 (c) is a schematic diagram of the reentry heading angle change for Mission 3; Figure 9 (d) is a schematic diagram of the reentry heading angle change for Mission 4;

[0068] Figure 10A schematic diagram showing the change in roll angle during reentry into a no-fly zone; Figure 10 (a) is a schematic diagram of the change in the roll angle during re-entry into the no-fly zone for Mission 1; Figure 10 (b) is a schematic diagram of the change in the roll angle during re-entry into the no-fly zone for Mission 2; Figure 10 (c) is a schematic diagram of the change in the roll angle during re-entry into the no-fly zone for Mission 3; Figure 10 (d) is a schematic diagram of the change in the roll angle during re-entry into the no-fly zone for Mission 4;

[0069] Figure 11 This is a drag acceleration profile and tracking diagram planned after the aircraft undergoes longitudinal guidance during reentry. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, 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.

[0071] The purpose of this invention is to provide a threat zone avoidance prediction-correction guidance method and system, which can improve the speed of range calculation during the prediction-correction guidance process and can quickly complete the avoidance mission even with different configurations and multiple threat zones.

[0072] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0073] Example 1

[0074] This invention decomposes the reentry guidance problem of gliders flying around no-fly zones into two parts: longitudinal guidance design and lateral guidance design. The two parts can interact and successfully complete the reentry guidance.

[0075] This invention mainly comprises two parts: longitudinal guidance design and lateral guidance design.

[0076] The longitudinal guidance method primarily obtains the amplitude of the control quantity's bank angle by providing a drag acceleration profile that meets range requirements. The lateral flight avoidance logic mainly determines the bank angle reversal logic for avoiding the no-fly zone, thus obtaining the sign of the control quantity's bank angle. These two parts are not independent; they interact and simultaneously have a comprehensive impact on reentry and no-fly zone avoidance guidance.

[0077] For longitudinal guidance, obtaining the drag acceleration profile that satisfies the desired range is crucial. In this process, the accuracy of the range calculation and the computation time become significant factors affecting reentry guidance. Therefore, this invention presents a profile form that yields an analytical expression for the range, which improves computation speed and accuracy. Furthermore, this invention proposes a lateral flight logic adaptable to different configurations and numbers of no-fly zones. This logic is relatively simple in form, has a fast computation speed, and can be applied to engineering practice.

[0078] Figure 1 The flowchart illustrates the trajectory planning process for a prediction-correction guidance method based on analytical approaches. As shown, this method consists of two phases: an initial phase and a gliding phase. The gliding phase is the primary stage of trajectory planning, and circumnavigating no-fly zones is one of its main tasks. When the aircraft re-enters from its initial point during the initial phase, its altitude is relatively high, resulting in relatively weak aerodynamic forces and a drastic descent, insufficient for balanced gliding. Therefore, in this phase, given a fixed nominal angle of attack profile, a constant roll angle is sufficient as a control input. The initial phase ends at a certain re-entry altitude. As mentioned earlier, the magnitude of the aerodynamic forces acting on the aircraft depends primarily on atmospheric density, which is mainly affected by altitude. Therefore, at a certain re-entry altitude, the aerodynamic forces will allow the aircraft to meet the conditions for balanced gliding. At this point, the initial descent phase ends, and the aircraft enters the balanced gliding phase.

[0079] The present invention provides a threat zone bypass prediction and correction guidance method, characterized in that it includes:

[0080] Based on the constraints, the reentry energy of the spacecraft is used as the independent variable to construct a reentry motion model and determine the initial state of the spacecraft. The constraints include thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero tilt angle quasi-equilibrium gliding conditions, and terminal constraints.

[0081] Reentry dynamics equations:

[0082] In motion process modeling and analysis, the traditional method generally selects a position-velocity space and obtains the reentry motion equations of the aircraft by analyzing the changes of motion variables in this space over time. The relevant state variables include six types: distance, velocity, longitude, latitude, heading angle, and flight path angle. However, in this invention, to facilitate the reduction of the order of the motion equations to obtain a simpler model, an analytical method is presented, using the reentry energy of the aircraft as the independent variable to establish the reentry motion model.

[0083] The relative motion between the detection vehicle and the maneuvering target under nonlinear kinematics can be expressed as:

[0084] E=V2 / 2-μ / r (1)

[0085] In the formula, E gradually decreases as it reaches the terminal, V is the velocity of the spacecraft, r is the distance from the spacecraft to the Earth's center, and μ is the Earth's gravitational constant. Treating energy as the independent variable and considering the spacecraft as a point mass during reentry, its three-degree-of-freedom equation of motion can be expressed as:

[0086]

[0087] In the formula, λ and φ are longitude and latitude, θ is the flight path angle, and ψ is the heading angle with true north as the positive direction. The gravitational acceleration constant is g = μ / r. 2 L and D are the lift and drag accelerations, respectively, and their forms are L = ρV. 2 S ref C L / 2m and D=ρV 2 S ref C D / 2m, where S ref Let m be the reference surface area, m be the mass of the reentry vehicle, and C be the mass of the reentry vehicle. L and C D These are the aerodynamic lift and aerodynamic drag coefficients, respectively, and their values ​​depend on the angle of attack α and the Mach number.

[0088] The calculation of aerodynamic forces acting on an aircraft depends on atmospheric density, which is generally given based on a specific atmospheric model.

[0089] The exponential model is one of the most commonly used approximate atmospheric models. This exponential model is related to the values ​​of L and D mentioned above. L and D affect the model shown in (2). It expresses the relationship between atmospheric density and altitude in the form of an exponential function. Its specific calculation method is given by the following formula:

[0090]

[0091] In the formula, ρ represents the atmospheric density at an altitude of h, and ρ0 is the atmospheric density at sea level, where ρ0 = 1.225 kg / m³. 3 h s It is a constant with a value of h. s =7110.

[0092] The Coriolis acceleration term C in equation (2) σ C θ and centripetal acceleration term for

[0093]

[0094] In the formula, ω e It represents the angular velocity of rotation.

[0095] Redefining the coordinate system simplifies reentry trajectory planning algorithms. For example... Figure 2 As shown, assume O E O1 is the Earth's center, O1 is the position of the spacecraft, ω e Let be the Earth's rotational angular velocity. Normally, the X and Y axes in a coordinate system lie in the equatorial plane, and the Z axis points due north. By using the projection point of the spacecraft's reentry point and the plane containing the target position as the new "equatorial plane," the spacecraft reentry planning algorithm can be simplified.

[0096] Figure 2 As shown For the new spacecraft re-entry motion coordinate system, coordinate axes Keeping consistent with the initial position vector of the aircraft, Perpendicular to And it lies in the plane containing the reentry point projection point and the target position. The coordinate system satisfies the right-hand rule and points to the new true north direction P. The coordinate system is transformed as follows: Then, the state variables are transformed from λ, φ, ψ, V, θ, and r into new state variables. and Before and after the coordinate system transformation, the three state variables—distance from the Earth's center, flight path angle, and velocity—remain unchanged. and Based on the above definition of the new coordinate system, Since the defined plane can encompass both the projection point of the reentry point and the target point, the longitudinal and transverse strokes of the spacecraft's reentry can be expressed as follows: and

[0097] The dynamic model obtained in the new coordinate system has the same form as the model shown in equation (2), except for the Coriolis acceleration and centripetal acceleration terms. They can be expressed in the new coordinate system as follows:

[0098]

[0099] In the formula, ω ex ω ey and ω ez coordinate system ω e The components. To facilitate the subsequent algorithm derivation, λ, φ, ψ, V, θ, and r are uniformly used to represent the state variables in the new coordinate system.

[0100] The path and terminal constraints specifically include: thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero tilt angle quasi-equilibrium gliding conditions, and terminal constraints.

[0101] The main control variables during the aircraft reentry process are the angle of attack α and the bank angle υ. In this invention, the change in the angle of attack is a pre-set piecewise function, i.e.

[0102]

[0103] Therefore, the main control variable designed in this invention is the tilt angle σ, and its control constraint is |σ|≤σ. max , During the gliding phase of a reentry vehicle, it is primarily constrained by thermal flux, dynamic pressure, and aerodynamic overload, which can be expressed as follows:

[0104]

[0105] In the formula, k is a constant, and g0 = 9.81 m / s 2 , q max n max These represent the maximum values ​​of heat flux, dynamic pressure, and aerodynamic overload, respectively. Equation (7) shows the hard constraint conditions that must be met for reentry gliding. In addition, the zero roll angle quasi-equilibrium gliding condition (gV) is also required. 2 / r)-L≤0 is a soft constraint condition that the aircraft must satisfy for balanced gliding, and this condition does not need to be strictly enforced. In the design of the longitudinal guidance algorithm, this invention mainly adopts the method of planning drag acceleration profile. Therefore, it is necessary to transform the above constraint into drag-energy profile.

[0106]

[0107] In the formula, D q D n and D E These are the drag acceleration constraints corresponding to the maximum heat flow rate, dynamic pressure, aerodynamic overload, and quasi-equilibrium gliding conditions shown in Equation (7).

[0108] Given a fixed nominal angle of attack, the upper and lower bounds of the drag-energy reentry corridor can be obtained, in the form of:

[0109]

[0110] The drag acceleration profile obtained by the longitudinal guidance method should be within the reentry corridor to meet the hard constraint conditions of gliding flight.

[0111] The reentry guidance method studied in this invention takes into account the situation of no-fly zones caused by geopolitical or anti-missile threat zones.

[0112] In this invention, it is assumed that the no-fly zone is an infinitely high circular area, the center of which and its radius are known. If the trajectory of the reentry vehicle is controlled such that the distance from every point on the trajectory to the center of the no-fly zone is greater than the radius of the no-fly zone, then it can be demonstrated that the vehicle can fly around the no-fly zone.

[0113] Assume the terminal phase of the aircraft's reentry flight is a terminal energy management segment located at a certain distance and altitude from the target point. The introduction of the terminal energy management segment necessitates that the aircraft meet certain terminal constraints to achieve precise control of the aircraft's terminal guidance. These terminal constraints are expressed as follows:

[0114] h f =h TAEM V f =V TAEM ,S f =S TAEM (10)

[0115] Initial descent segment:

[0116] Based on the initial state of the aircraft, the nominal angle of attack and the constant roll angle are obtained, and the variable values ​​of each state equation are determined according to the combined effect of the nominal angle of attack and the constant roll angle on each state equation.

[0117] The state values ​​of the transition points between the initial descent segment and the gliding segment are determined based on the values ​​of the variables in the state equations.

[0118] In practical applications, during the initial descent phase, the nominal angle of attack profile is designed as a piecewise function of velocity, and the corresponding angle of attack input value is given by the change in the aircraft velocity. During the initial descent phase, the constraint that needs to be considered is the heat flux constraint of the aircraft. As can be seen from equation (7), the main factor affecting the heat flux is velocity. Therefore, a high angle of attack input strategy is adopted in the phase with a large heat flux. The maximum angle of attack input shown in equation (6) is 20°. After the velocity begins to decrease, the angle of attack input is reduced synchronously and reaches a certain value to maintain a high lift-to-drag ratio. As shown in the flowchart, a suitable constant tilt angle υ0 is selected as the input and acts together with the nominal angle of attack on the state equation to obtain the values ​​of each state variable. At the same time, it is checked whether the transition conditions are met. If the transition conditions are met, the values ​​of each state variable are output to the gliding phase for calculation. The transition point between the initial descent phase and the gliding phase is determined by the following equation.

[0119] |dr / dV-(dr / dV) QEGC |<δ (11)

[0120] In the formula, δ is a small positive value, and dr / dV = -Vsinθ / (D + gsinθ), (dr / dV) QEGCIt is the slope of the equilibrium gliding condition at the current point (r, V), which can be obtained by finding the derivative of the equilibrium gliding condition with respect to velocity. The state variable at the transition point is...

[0121] The sign of the constant roll angle is determined by the reference point of the first no-fly zone to be circled. First, it is necessary to determine which side of the no-fly zone to circle from. Assume the center position and radius of the no-fly zone are (λ... z ,φ z ) and R z If an aircraft flies around a no-fly zone, the reference point at that time is (λ). z ,φ z +R z / R e ), R e Where is the Earth's radius. Otherwise, the reference point is (λ). z ,φ z -R z / R e Based on a defined reference point, the sign of the constant tilt angle υ0 can be determined.

[0122] sign(ψ0) = -sign(ψ0 - ψ0) LOS (12)

[0123] In the formula, ψ0 is the initial heading angle, ψ LOS The line-of-sight angle between the reentry point and the reference point.

[0124] Gliding phase: includes longitudinal guidance design and lateral guidance design.

[0125] In practical applications, the balanced gliding phase of the aircraft is the key design phase of this invention. This phase mainly consists of two parts: longitudinal guidance design and lateral guidance design. They are also important components of the predictive-correction guidance method based on analytical methods.

[0126] In the longitudinal guidance design phase, a drag acceleration profile that satisfies the desired range needs to be provided, thereby obtaining the amplitude of the control input roll angle. In the lateral guidance design phase, a roll angle reversal logic that satisfies the requirement to bypass no-fly zones needs to be provided, thereby obtaining the sign of the roll angle. It is important to note that the drag acceleration profile and desired range value must be updated after each guidance cycle. The primary reason for this is that the longitudinal and lateral guidance methods are not independent; the lateral bypass logic affects the desired range value obtained from the longitudinal calculation of the drag acceleration profile. The initial desired range is approximated as the great circle length (i.e., longitudinal range) from the reentry point's projection point to the target. However, when bypassing no-fly zones is required, the aircraft may need to perform large lateral maneuvers. In this case, the longitudinal range from the aircraft to the target will deviate significantly from the actual range. Updating the desired range value and drag acceleration profile within each guidance cycle effectively avoids this problem, which is essentially the core of the predictive-corrective guidance method.

[0127] In the longitudinal guidance design, a five-segment drag acceleration profile is determined based on the state value of the transfer point and the reentry range requirement, generating an analytical solution for the longitudinal range. Based on the state variables related to longitudinal guidance in the longitudinal guidance design, the billet angle magnitude is determined according to the analytical solution for the longitudinal range.

[0128] Figure 3 This is a complete flowchart of the longitudinal guidance design. The core parts of the longitudinal guidance method design are the three steps of adjusting the segmented drag acceleration value, the longitudinal range and analytical solution, and predicting the longitudinally related terminal function.

[0129] The "analytical method" proposed in this invention is mainly reflected in the fact that the longitudinal distance can be solved analytically. Unlike other methods that require integrating the equations of motion to obtain the numerical solution of the distance, the analytical method of the distance proposed in this invention can improve the calculation speed of online solution.

[0130] Glide phase longitudinal guidance design: The fundamental purpose of the longitudinal guidance method is to design a drag acceleration profile in the drag-energy reentry corridor to meet the desired reentry range requirements. In the design process, the impact of the no-fly zone on the desired range and lateral maneuverability needs to be considered. The no-fly zone satisfies the following assumptions: (1) The area of ​​effect of the no-fly zone is an infinitely high cylinder; (2) The no-fly zone is located on the necessary path of the aircraft's reentry.

[0131] To provide a simpler analytical method that avoids numerical integration, and to facilitate the planning of the drag-acceleration profile, the energy during reentry is used as the independent variable. Since the change in altitude h during reentry is much smaller than the distance r from the spacecraft to the Earth's center, r is treated as r = (r0 + r) when calculating the upper and lower boundaries of the drag-energy reentry corridor. f) / 2. At this point, for each energy value E in the reentry process, all the inequality constraints shown in equation (8) depend only on the nominal angle of attack. The drag acceleration value shown in equation (9) will change with the angle of attack α∈[α min ,α max The trend is monotonically increasing; therefore, it can be concluded that at an angle of attack α = α max and α=α min The maximum and minimum boundary values ​​of drag acceleration are given. The drag acceleration profile is expressed as a five-piece function after energy normalization, such as... Figure 5 As shown. To simplify the drag acceleration profile planning process, and (E) f D f ) is fixed, (E) c D c The energy value can be obtained from the state at the transition point. The actual energy value and the normalized energy value of the reentry process satisfy...

[0132]

[0133] In the formula, E0 is the energy value at the initial reentry point, E f This represents the energy value of the terminal.

[0134] In this invention, The value is like Figure 4 As shown, (D1, D2) are the main adjustment values ​​for the drag acceleration profile. Other parameters are either fixed or vary with (D1, D2). This design simplifies calculations and improves solution speed. Once the values ​​of (D1, D2) are determined, the entire profile planning is complete. D1 is mainly used to adjust the range, and D2 is mainly used to adjust the lateral maneuverability.

[0135] Figure 4 The five-segment drag acceleration profile shown can be expressed as:

[0136]

[0137] The reentry range of the aircraft can be approximated as:

[0138]

[0139] Substituting equation (14) into equation (15), we can obtain the analytical expression for the flight distance of each segment as follows:

[0140]

[0141] The total voyage distance can then be expressed as:

[0142]

[0143] S represents the total range during the reentry guidance process; S i The range value corresponds to each energy segment in Equation 14; i is 1 to 5, representing a total of 5 energy segments.

[0144] The following is an algorithm for planning the drag acceleration profile within one guidance cycle:

[0145] Step 1: Set the initial (D1, D2) values ​​and check whether the aircraft's lateral maneuverability meets the requirements for bypassing the no-fly zone under the current conditions. If the lateral maneuverability is sufficient to bypass the no-fly zone, proceed to Step 2; otherwise, proceed to Step 3.

[0146] Step 2: Under the condition of satisfying the lateral maneuverability, the value of D1 is adjusted by Newton's iteration method.

[0147]

[0148] In the formula, δD is a small positive quantity. The analytical solution of equation (17) corresponds to and The actual flight distance.

[0149] Step 3: If the lateral maneuverability is not satisfied, adjust the value of D2 by a fixed increment to increase the lateral maneuverability. After adjusting D2, adjust the value of D1 by the Newton-Raphson iteration method shown in equation (18) to achieve the desired range S. * .

[0150] Step 4: Check again whether it is possible to successfully fly around the no-fly zone. If it is, stop the algorithm; if not, restart the algorithm.

[0151] It is important to note that the expected range S within each guidance cycle is... * It is determined by the transfer point, the current point, and the target point, and its form is as follows:

[0152]

[0153]

[0154]

[0155] In the formula, This represents the distance traveled from the transfer point to the current point. This represents the distance traveled from the current point to the target point.

[0156] The magnitude of the tilt angle can be obtained from the designed drag acceleration profile. Differentiating both sides of equation (3) simultaneously yields...

[0157]

[0158] The derivative of the drag acceleration D can be expressed as:

[0159]

[0160] From equations (22) and (23), we can obtain

[0161]

[0162] In the formula,

[0163] Differentiating both sides of equation (24) simultaneously yields

[0164]

[0165] Throughout the reentry process, the flight path angle θ is very small, and sinθ = θ and cosθ = 1 can be approximated. Regarding Another equation can be obtained by differentiating the fifth equation of equation (42).

[0166]

[0167] From equations (25) and (26), we can obtain

[0168]

[0169] In the formula,

[0170] a = -h s V 2

[0171]

[0172] Therefore, the tilt angle amplitude of the aircraft can be obtained by equation (27).

[0173] In the lateral guidance design, based on the state value of the transfer point, the tilt angle amplitude, and the reduced-order lateral guidance motion, the heading angle boundary of each no-fly zone is considered, the heading angle corridor is updated according to the threat level of the no-fly zone, the tilt angle reversal logic for bypassing the no-fly zone is determined, and the tilt angle sign is output.

[0174] The tilt angle command is determined based on the tilt angle magnitude and the tilt angle sign; the tilt angle command is used to control the aircraft to fly around each no-fly zone.

[0175] Figure 5 This is a complete flowchart of the lateral guidance design, in which the heading angle corridor update algorithm and the lateral flight reversal logic are the core parts of the lateral guidance method design.

[0176] Figure 5 The "heading angle corridor update algorithm" is the main innovation. Its algorithm design has low complexity. It only needs to update the heading angle boundary value of the no-fly zone from the target point to the nearest point.

[0177] Lateral guidance design during the glide phase:

[0178] Lateral guidance motion equations reduced in order: As mentioned earlier, the flight path angle θ is very small, making cosθ = 1 approximately true. Because the change in altitude is particularly small relative to the Earth's radius, the distance from the spacecraft to the Earth's center is treated as a fixed constant, thus reducing the order of the lateral guidance equations. Based on the above analysis, the reduced lateral motion equations are expressed as follows:

[0179]

[0180] In the formula, C σ and Simplified to

[0181]

[0182] After the longitudinal guidance method provides the drag acceleration profile, the state variables (λ, φ, ψ) at each energy value E depend only on Because D and [the desired values ​​were derived through the designed longitudinal guidance method] Therefore, we can obtain the following formula: amplitude

[0183]

[0184] Once the sign of the tilt angle is determined, the values ​​of each state variable in the lateral motion equation can be solved. The logic for determining the sign of the tilt angle will be given in the subsequent algorithm design stage.

[0185] Heading angle boundary and roll angle reversal logic:

[0186] Traditional lateral guidance methods involve designing tilt angle reversal logic to control the aircraft's heading angle, guiding it toward the target. For example... Figure 6 As shown, the heading angle corridor boundary required by the roll angle reversal logic is as follows: Figure 6 As shown in (a), the upper and lower boundaries of the corridor can be represented as

[0187]

[0188] In the formula, ψ LOS Let Δψ be the line-of-sight angle of the aircraft relative to the target. LOS ψ is half the width of the corridor. LOS The following equation can be solved to obtain

[0189]

[0190] For traditional reentry missions where there is no no-fly zone threat, the roll angle reversal logic needs to ensure that the aircraft's heading angle is within the heading angle corridor. Therefore, the roll angle reversal logic can be expressed as follows:

[0191]

[0192] In the formula, σ p This is the tilt angle command from the previous guidance cycle.

[0193] However, when a no-fly zone appears on the reentry trajectory, the heading angle corridor needs to further consider the additional heading angle boundary constraints imposed by the no-fly zone. For example... Figure 6 As shown in (b), when an aircraft flies around a no-fly zone from below, in order to avoid the no-fly zone, the aircraft's heading angle cannot be lower than ψ. NZ , ψ NZ This refers to the heading angle when tangent to a no-fly zone. Therefore, circumventing a no-fly zone requires limiting the heading angle corridor to...

[0194]

[0195] In the formula, Δψ NZ To avoid no-fly zones, the minimum width of the corridor must be such that it cannot be too small, otherwise it will lead to frequent tilt angle reversals.

[0196] like Figure 6 As shown in (c), when an aircraft flies around a no-fly zone from below, the heading angle corridor needs to be limited to [specific value].

[0197]

[0198] Regardless of the flight detour situation Figure 6 (b) or Figure 6 (c) Aircraft should avoid no-fly zones by taking the shorter flight path, because a longer path will consume too much energy and the aircraft will not be able to reach the terminal target.

[0199] Heading angle corridor update algorithm:

[0200] Most existing corridor update algorithms based on inverse logic are designed for single or two no-fly zones. When using such methods to handle reentry missions with multiple no-fly zones, it may be impossible to bypass the next no-fly zone after successfully bypassing the previous one. The corridor update algorithm designed in this invention can consider the situation of bypassing multiple no-fly zones and is adaptable to different configurations of multiple no-fly zones. When dealing with the heading angle boundary constraints generated by different no-fly zones, the algorithm prioritizes the one with the highest threat level, thus prioritizing bypassing the no-fly zone with the highest threat level. The algorithm has a simple structure and good engineering application value. For flight missions facing N no-fly zones, the algorithm design is as follows:

[0201] Step 1: Calculate the heading angle boundary of the aircraft relative to the target to obtain the initial heading angle corridor.

[0202] Step 2: Based on the determined detour direction of the Nth no-fly zone, calculate its heading angle boundary value and update the heading angle corridor.

[0203] Step 3: Based on the determined detour direction of the (N-1)th no-fly zone, calculate its heading angle boundary value and update the heading angle corridor.

[0204] ...

[0205] Step N+1: Based on the detour direction of the first no-fly zone, calculate its heading angle boundary value and update the heading angle corridor.

[0206] This algorithm first considers the heading angle boundary for the target, and then, from farthest to nearest, considers the heading angle boundary for the no-fly zone. The heading angle corridor is updated sequentially in this order until the no-fly zone closest to the aircraft is updated. This algorithm design allows aircraft to prioritize bypassing no-fly zones that pose a high threat level, without needing to perform detours around specific no-fly zones.

[0207] Figure 7 This is a typical diagram of a no-fly zone detour mission, such as... Figure 7 The diagram shows a typical no-fly zone detour mission using four no-fly zones as an example. As can be seen from the diagram, the aircraft needs to detour both above and below the no-fly zones. Furthermore, the four no-fly zones are located on the aircraft's inevitable path to the target, and this configuration poses a strong threat to the aircraft.

[0208] Based on the aforementioned algorithm, the heading angle corridor for bypassing no-fly zones is updated in each guidance loop. First, the heading angle corridor is updated based on the aircraft's heading angle boundary relative to the target. Then, it is updated in the order of no-fly zones 4, 3, 2, and 1. When updating the heading angle corridor, it is necessary to distinguish between two cases: bypassing from above and bypassing from below. Taking bypassing no-fly zones 4 and 3 as an example, the algorithm requires first updating the heading angle corridor for no-fly zone 4, determining that bypassing no-fly zone 4 is an overhead bypass, in which case the updated heading angle corridor is...

[0209]

[0210] Next, based on the updated heading angle corridor of No-Fly Zone 3, it is determined that the flight around No-Fly Zone 3 is a flight from below, and the heading angle corridor is updated to...

[0211]

[0212] The subsequent updates to the heading angle corridors for No-Fly Zone 2 and No-Fly Zone 1 are similar to those in equations (37) and (38).

[0213] like Figure 7 As shown, when the aircraft is at position A, ψ will appear. NZ4 Less than ψ NZ3 In this situation, it is impossible to simultaneously satisfy the heading angle constraints for both no-fly zones. This is because, in this case, no-fly zone 3 poses a greater threat, and according to the proposed heading angle corridor update algorithm, the heading angle constraint generated by no-fly zone 3 will be given priority. However, when the aircraft reaches position B, ψ will appear... NZ4 Greater than ψ NZ3 In this situation, the heading angle constraint generated by no-fly zone 3 can always be satisfied. According to the proposed heading angle corridor update algorithm, the heading angle corridor after updating for no-fly zone 4 will not change, and the aircraft will focus on bypassing no-fly zone 4. In fact, regardless of whether no-fly zone 3 can be successfully bypassed, as ψ NZ3 As the value increases, Equation (38) will have no effect on the update of the heading angle corridor. This means that even if the current no-fly zone is not successfully bypassed, the aircraft will focus on bypassing the next no-fly zone. Similarly, before and after the aircraft avoids no-fly zone 4, the effect of the heading angle corridor update shown in Equation (38) will gradually decrease. Finally, the aircraft will fly towards the target according to the constraints of Equation (32).

[0214] The aforementioned longitudinal guidance method provides a reference drag acceleration profile D. r This section requires designing a drag acceleration profile tracking method to track the designed profile and generate the corresponding roll angle magnitude. In this section, a practical PID controller is used to track the drag acceleration profile, and its specific form is as follows:

[0215]

[0216] In the formula, ω, ζ, and k1 are the proportional, derivative, and integral gains in the drag acceleration PID tracking controller, respectively.

[0217] make From equations (27) and (38), the control input for tracking the reference profile can be obtained as follows:

[0218]

[0219] Simulation verification:

[0220] In this invention, the CAV-H model is used to verify the proposed analytical-based prediction-correction guidance method. Table 1 shows the basic parameters of the CAV-H model's reentry flight. The lift-to-drag ratio of the aircraft during reentry varies with the angle of attack α∈[α...]. min ,α max The lift-to-drag ratio increases monotonically, with a maximum lift-to-drag ratio limited to 3.5. The reentry starting position of the aircraft is (0°, 0°), and the target position is (90°, 0°). Specific data on the no-fly zone threats encountered during reentry are shown in Table 2, which is the no-fly zone parameter table for Mission 1.

[0221] The aircraft's initial flight path angle and heading angle are 0° and 80° respectively, and its desired energy management segment terminal is a distance S from the target. f =90km, height is h f =27km, speed is V f =2000m / s position.

[0222] Table 1

[0223]

[0224]

[0225] Table 2

[0226] No-fly zone 1 (35°,9°) 700m No-fly zone 2 (50°,-9°) 900m No-fly zone 3 (65°,9°) 1000m No-fly zone 4 (80°,-9°) 1100m

[0227] Figure 8 Table 2 shows a schematic diagram of the no-fly zones for aircraft reentry and orbit. The locations and radii of the no-fly zones for Mission 1 are shown in Table 2. Except for the longitude values ​​of the no-fly zones for Missions 2 and 3, which differ from those in Table 2, the other parameters are consistent with those for Mission 1. There are four no-fly zones, and their configurations are as follows: Figure 8In all four missions shown, the aircraft was able to complete the flight maneuver and reach the terminal energy management position. Therefore, the lateral guidance method proposed in this invention can adapt to flight maneuvers under different no-fly zone configurations. Table 3 shows the range error for different missions. As shown in Table 3, the terminal range errors for different missions are 0.012km, 2.572km, 3.838km, and 1.043km, respectively. Although the corridors that need to be updated for the aircraft to fly around the no-fly zone in missions two and three are relatively simple, the range errors they generate during reentry are relatively large. The main reason for the range error is the lateral range traversed by the aircraft during reentry, and the secondary reasons are factors such as the tracking accuracy of the drag acceleration profile and the width of the reentry corridor.

[0228] Table 3

[0229]

[0230]

[0231] Figure 9 The diagram illustrates the reentry heading angle changes under different missions. Missions 1 and 4 show significant changes in the heading angle corridor, indicating that the heading angle constraints imposed by the no-fly zone are considered more during reentry. Missions 2 and 4 show less change in the heading angle corridor, suggesting that they prioritize heading angle constraints for target-oriented flight. The primary cause of the aforementioned range error is the lateral distance traversed during reentry. This is also evident in the heading angle change diagrams; Missions 2 and 3 exhibit a larger range of heading angle changes during reentry compared to Missions 1 and 4, indicating a greater range of lateral distance changes and resulting in larger lateral distance variations. Furthermore, in Missions 2 and 3, the reentry corridor for target-oriented flight becomes increasingly narrow, causing excessive heading angle reversals and contributing to range errors. Missions 1 and 4 may experience heading angles exceeding the heading angle corridor. This is due to the lower heading angle rate of the aircraft; when the corridor is rapidly updated according to time-varying constraints, the heading angle temporarily exceeds the corridor. However, this does not necessarily mean the aircraft will enter the no-fly zone. In actual missions, the aircraft was able to successfully fly around the no-fly zone.

[0232] Figure 10 This is a schematic diagram illustrating the change in the bank angle during reentry into a no-fly zone. Figure 10As can be seen, the number of roll angle reversals during Missions 2 and 3 is higher than that during Missions 1 and 4. Looking at the changes in longitude along the horizontal axis, the closer the aircraft is to the target, the higher the frequency of roll angle reversals. As mentioned earlier, this is due to the excessively narrow heading angle corridor. At this point, the heading angle boundary in the heading angle corridor update algorithm is only provided by the boundary of the aircraft's flight relative to the target, resulting in frequent reversals. From the perspective of roll angle reversals, a better configuration for the aircraft to fly around the no-fly zone is similar to the configuration in Mission 1.

[0233] Figure 11 This diagram illustrates the drag acceleration profile and tracking diagram planned after longitudinal guidance during spacecraft reentry. The solid black line represents the planned value, and the dashed black line represents the tracked value. In the initial stage of reentry, the spacecraft is at a relatively high altitude and experiences relatively small aerodynamic forces, employing a constant roll angle for reentry. Once it reaches an altitude sufficient for balanced gliding, the spacecraft enters the gliding phase. At this point, the spacecraft is positioned at the transition point between the descent and gliding phases. From this transition point, the longitudinal guidance method begins planning the drag acceleration profile. The planned profile is a five-segment linear function. Figure 11 Parameters D1 and D2 are used as adjustment parameters for the predictive-correction guidance method to meet the requirements of reentry range and lateral maneuvering. A tracker is designed to track the planned profile and generate roll angle control commands. The maximum tracking error in the simulation is 0.2 m / s². 2 .

[0234] Example 2

[0235] In order to implement the method corresponding to Embodiment 1 above and achieve the corresponding functions and technical effects, a threat zone bypass prediction-correction guidance system is provided below.

[0236] A threat zone avoidance prediction-correction guidance system includes:

[0237] The initial state determination module is used to construct a reentry motion model based on constraints, using the reentry energy of the aircraft as the independent variable, and determine the initial state of the aircraft. The constraints include thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero tilt angle quasi-equilibrium gliding conditions, and terminal constraints.

[0238] Initial descent segment:

[0239] The variable value determination module for each state equation is used to obtain the nominal angle of attack and constant roll angle based on the initial state of the aircraft, and to determine the variable values ​​of each state equation according to the combined effect of the nominal angle of attack and the constant roll angle on each state equation.

[0240] The state value determination module for the transition point is used to determine the state value of the transition point between the initial descent segment and the gliding segment based on the variable values ​​of each state equation.

[0241] Gliding phase: includes longitudinal guidance design and lateral guidance design.

[0242] The longitudinal guidance design module is used to determine a five-segment drag acceleration profile based on the state value of the transfer point and the reentry range requirement in the longitudinal guidance design, generate an analytical solution for the longitudinal range, and determine the billing angle magnitude based on the state variables related to longitudinal guidance in the longitudinal guidance design and the analytical solution for the longitudinal range.

[0243] The lateral guidance design module is used in the lateral guidance design to, based on the state value of the transfer point, the tilt angle amplitude and the reduced-order lateral guidance motion, consider the heading angle boundary of each no-fly zone, update the heading angle corridor according to the threat level of the no-fly zone, determine the tilt angle reversal logic for flying around the no-fly zone, and output the tilt angle sign.

[0244] The tilt angle command determination module is used to determine the tilt angle command based on the tilt angle amplitude and the tilt angle sign; the tilt angle command is used to control the aircraft to fly around each no-fly zone.

Claims

1. A threat zone flyaround predictive - correction guidance method, characterized in that, include: Based on the constraints, the reentry energy of the aircraft is used as the independent variable to construct a reentry motion model and determine the initial state of the aircraft. The constraints include thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero tilt angle quasi-equilibrium gliding conditions, and terminal constraints. Initial descent segment: Based on the initial state of the aircraft, the nominal angle of attack and the constant roll angle are obtained, and the variable values ​​of each state equation are determined according to the combined effect of the nominal angle of attack and the constant roll angle on each state equation. Determine the state values ​​of the transition points between the initial descent segment and the gliding segment based on the values ​​of the variables in the state equations. Glide phase: includes longitudinal guidance design and lateral guidance design; In the longitudinal guidance design, a five-segment drag acceleration profile is determined based on the state values ​​at the transfer point and the reentry range requirements, generating an analytical solution for the longitudinal range. Based on the state variables related to longitudinal guidance in the longitudinal guidance design, the billet angle magnitude is determined according to the analytical solution for the longitudinal range, specifically including: The resistance-energy re-entry corridor is determined based on the state value of the transfer point and the constraints. The five-segment drag acceleration profile is determined based on the drag-energy reentry corridor; the main adjustment values ​​of the five-segment drag acceleration profile include adjustment values ​​for range and adjustment values ​​for lateral maneuverability. Adjust the segmented drag acceleration values ​​based on the five-segment drag acceleration profile to determine the analytical solution for the longitudinal range. The flight path of the reentry of the aircraft is approximately expressed as ; The voyage analytical expression of each segment is obtained as ; Where S is the total range of the reentry guidance process; This is the normalized energy value; This represents the energy value at the transition point after normalization. This is the energy value that equals 0.3 after normalization; This is the energy value that is normalized to 0.5; This is the energy value that is normalized to 0.7; This is the energy value that is normalized to 0.8; The energy value of the terminal energy management section; This represents the drag acceleration value at the transfer point; Adjustment values ​​for adjusting the flight distance; To adjust the value for lateral mobility; This represents the drag acceleration value of the terminal energy management section; Energy value; This is a five-segment drag acceleration profile; Based on the state variables related to longitudinal guidance in the longitudinal guidance design, predict the longitudinally related terminal function; The roll angle magnitude is determined based on the analytical solution of the longitudinal range and the terminal function; The tilt angle amplitude is input into the lateral guidance process; In the lateral guidance design, based on the state value of the transfer point, the bill of lading amplitude, and the reduced-order lateral guidance motion, the heading angle boundaries for bypassing each no-fly zone are considered. The heading angle corridor is updated according to the threat level of the no-fly zone, the bill of lading reversal logic for bypassing the no-fly zone is determined, and the bill of lading sign is output. Specifically, this includes: Determine the detour direction for each no-fly zone based on the status values ​​of the transfer point and the target point; The reduced-order lateral guidance motion is determined based on the flight direction and the tilt angle amplitude; The state variables related to lateral guidance are determined based on the reduced-order lateral guidance motion; Calculate the heading angle boundaries for flying around each no-fly zone based on the state variables, and update the heading angle corridors according to the threat level of the no-fly zones; The lateral reversal logic is determined based on the updated heading angle corridor; The sign of the tilt angle is determined based on the aforementioned lateral flight reversal logic; The tilt angle command is determined based on the tilt angle magnitude and the tilt angle sign; the tilt angle command is used to control the aircraft to fly around each no-fly zone.

2. The threat zone flyaround predictive-correction guidance method of claim 1, wherein, The five-segment resistance acceleration profile Is: in, This is the normalized energy value; This represents the energy value at the transition point after normalization. This is the energy value that equals 0.3 after normalization; This is the energy value that is normalized to 0.5; This is the energy value that is normalized to 0.7; This is the energy value that is normalized to 0.8; The energy value of the terminal energy management section; This represents the drag acceleration value at the transfer point; Adjustment values ​​for adjusting the flight distance; To adjust the value for lateral mobility; This represents the drag acceleration value of the terminal energy management section.

3. The threat zone flyaround predictive-correction guidance method of claim 2, wherein, The roll angle magnitude is determined based on the analytical solution of the longitudinal range and the terminal function, specifically including: Based on the analytical solution of the longitudinal flight path and the terminal function, determine whether the reentry longitudinal terminal condition is met; If so, track the five-segment drag acceleration profile and output the tilt angle amplitude; If not, correct the adjustment value of the adjusted range and update the five-segment drag acceleration profile.

4. The threat zone flyaround predictive-correction guidance method of claim 3, wherein, Tracking the five-segment drag acceleration profile, the output tilt angle amplitude specifically includes: Within one guidance cycle, the five-segment drag acceleration profile is planned, and the roll angle amplitude is output, specifically including: Set the initial adjustment values ​​for the flight range and the adjustment values ​​for the lateral maneuverability, and check whether the lateral maneuverability of the aircraft meets the requirements for flying around the no-fly zone under the current conditions. If so, the adjustment value of the adjusted range is adjusted using Newton's iteration method; If not, adjust the adjustment value of the lateral maneuverability by a fixed increment to increase the lateral maneuverability. Then, adjust the adjustment value of the range by Newton's iteration method and check again whether the lateral maneuverability of the aircraft meets the requirements for flying around the no-fly zone until the desired range is reached. Determine the final five-segment drag acceleration profile and output the roll angle amplitude.

5. The threat zone flyaround predictive-correction guidance method of claim 1, wherein, Calculate the heading angle boundaries for flying around each no-fly zone based on the state variables, and update the heading angle corridors according to the threat level of the no-fly zones, specifically including: Calculate the heading angle boundary of the aircraft relative to the target and determine the initial heading angle corridor; Generate a threat level sequence based on the threat level of the no-fly zone; Calculate the detour direction for each of the no-fly zones according to the threat level sequence, and determine the heading angle boundary for detour around the no-fly zones; The initial heading angle corridor is updated using the heading angle boundary of the first no-fly zone in the threat level sequence, generating an updated heading angle corridor; Based on the threat level sequence, the updated heading angle corridor is updated using the heading angle boundary of the next no-fly zone.

6. A threat zone flyaround predictive - correction guidance system characterized by, The threat zone bypass prediction-correction guidance method according to any one of claims 1-5 includes: The initial state determination module is used to construct a reentry motion model based on constraints, using the reentry energy of the aircraft as the independent variable, and determine the initial state of the aircraft. The constraints include thermal flow constraints, dynamic pressure constraints, aerodynamic overload constraints, zero roll angle quasi-equilibrium gliding conditions, and terminal constraints. Initial descent segment: The variable value determination module for each state equation is used to obtain the nominal angle of attack and constant roll angle based on the initial state of the aircraft, and determine the variable values ​​of each state equation according to the combined effect of the nominal angle of attack and the constant roll angle on each state equation. The state value determination module for the transition point is used to determine the state value of the transition point between the initial descent segment and the gliding segment based on the variable values ​​of each state equation. Glide phase: includes longitudinal guidance design and lateral guidance design; The longitudinal guidance design module is used to determine a five-segment drag acceleration profile based on the state value of the transfer point and the reentry range requirements in the longitudinal guidance design, generate an analytical solution for the longitudinal range, and determine the billing angle magnitude based on the state variables related to longitudinal guidance in the longitudinal guidance design and the analytical solution for the longitudinal range, and input the billing angle magnitude into the lateral guidance process. The lateral guidance design module is used in the lateral guidance design to, based on the state value of the transfer point, the tilt angle amplitude and the reduced-order lateral guidance motion, consider the heading angle boundary of each no-fly zone, update the heading angle corridor according to the threat level of the no-fly zone, determine the tilt angle reversal logic for flying around the no-fly zone, and output the tilt angle sign; The tilt angle command determination module is used to determine the tilt angle command based on the tilt angle amplitude and the tilt angle sign; the tilt angle command is used to control the aircraft to fly around each no-fly zone.

Images