Space-time four-dimensional coordinated guidance method for unpowered high-speed aircraft during dive phase

Abstract

The application discloses a kind of unpowered high-speed aircraft dive segment space-time four-dimensional coordination guidance method, specific steps are S1, the guidance model of constructing the angle control of aircraft's dive terminal time;S2, the optimal guidance of dive satisfying angle and position constraint;S3, two-stage dive space-time coordination guidance satisfying time constraint;S4, online robustness compensation is carried out to environment and ontology deviation.The application solves the contradiction between time and space control in traditional method;With the aid of dynamics equation inverse solution technique, robustness is enhanced, real-time deviation estimation and compensation are realized;At the same time, using two-stage switching logic based on terminal time prediction and numerical integration optimization method, the time control precision is improved;The application not only improves the flexibility and adaptability of guidance, but also enhances the robustness of system, significantly improves the striking precision and overall performance of aircraft when performing complex tasks.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft guidance control, and particularly relates to a time-space four-dimensional coordinated guidance method for a powered hypersonic aircraft in a dive phase. BACKGROUND

[0002] The dive phase, as the last stage of the flight trajectory of a powered hypersonic aircraft, is crucial for precisely attacking a target. The dive guidance is always a core problem of the hypersonic aircraft, and requires the aircraft to complete diversified flight tasks under the condition of meeting various process constraints. In the dive phase guidance, the angle and time constraints are two important factors, which have an important influence on the design and application of the guidance law. The dive guidance faces the challenges of random variable flight environment and body model deviation, various severe process and terminal constraints, fast time-varying flight state, and complex and diversified flight tasks. SUMMARY

[0003] The purpose of the embodiment of the application is to provide a time-space four-dimensional coordinated guidance method for a powered hypersonic aircraft in a dive phase, improve the accuracy of the terminal constraint, the robustness of the process deviation, and the adaptability of the diversified guidance task.

[0004] To solve the above technical problems, the technical scheme adopted by the application is a time-space four-dimensional coordinated guidance method for a powered hypersonic aircraft in a dive phase, comprising the following steps:

[0005] S1, constructing a dive terminal time and angle control guidance model of the aircraft;

[0006] S2, dive optimal guidance meeting the angle and position constraints;

[0007] S3, two-stage dive time-space coordinated guidance meeting the time constraints;

[0008] S4, online robustness compensation for the environment and body deviation.

[0009] Further, the specific process of S1 is:

[0010] S101, establishing an aircraft motion equation:

[0011]

[0012] Wherein, v is the speed of the aircraft relative to the earth, is the change rate of the speed of the aircraft relative to the earth, θ is the speed inclination angle, σ is the speed azimuth angle from north clockwise, f is the distance from the center of the earth, λ and φ are the longitude and latitude respectively, ρ is the atmospheric density, m is the mass of the aircraft, S m is the reference area of the aircraft, g = μ M / r2 is the gravitational acceleration, μ M is the Earth gravitational constant, C D is the Earth gravitational constant, C L are the drag coefficient, lift coefficient, respectively, υ is the bank angle, is the rate of change of the velocity azimuth angle from north clockwise, is the rate of change of the longitude; is the rate of change of the latitude, is the rate of change of the geocentric distance, is the rate of change of the velocity bank angle;

[0013] S102, establish the control quantity attack angle α and bank angle υ constraint:

[0014]

[0015] wherein, α min and α max are the minimum, maximum attack angle constraint values, is the maximum rate of change of the attack angle; is the rate of change of the bank angle; is the rate of change of the attack angle; υ min and υ max are the minimum, maximum bank angle constraint values, is the maximum rate of change of the bank angle;

[0016] S103, determine the terminal constraint:

[0017]

[0018] is the time constraint, is the velocity bank angle constraint, is the azimuth angle constraint, is the longitude constraint, is the latitude constraint, is the altitude constraint, tar represents the state of the target.

[0019] Further, the specific process of S2 is:

[0020] S201, decompose the aircraft dive segment motion into longitudinal dive plane motion and lateral turning plane motion, wherein the longitudinal dive plane is defined as the plane passing through the aircraft M, the target O and the geocenter O E determined plane, the lateral turning plane is defined as the plane passing through the target and the center of mass and perpendicular to the longitudinal dive plane;

[0021] S202, establish the aircraft dive relative motion equation:

[0022]

[0023] where, is the second order differential of the line-of-sight angle, is the second order differential of the line-of-sight angle in the turn plane, v is the vehicle's velocity relative to the earth, is the rate of change of the vehicle's velocity relative to the earth, d is the line-of-sight distance from the vehicle's center of mass to the target, is the rate of change of the line-of-sight distance from the vehicle's center of mass to the target, is the rate of change of the line-of-sight angle, is the rate of change of the line-of-sight angle in the turn plane, is the rate of change of the azimuth angle of the velocity in the dive plane, is the rate of change of the azimuth angle of the velocity in the turn plane;

[0024] S203, determining the rate of change of the azimuth angle of the velocity in the line-of-sight coordinate system:

[0025]

[0026] where, is the rate of change of the velocity dip angle, is the rate of change of the azimuth angle, λ T is the actual azimuth angle, is the rate of change of the actual azimuth angle, λ D is the line-of-sight angle, T g is the time to go calculated theoretically:

[0027]

[0028] converting the rate of change of the azimuth angle of the velocity in the line-of-sight coordinate system into the velocity coordinate system:

[0029]

[0030] where and are the required rate of change of the velocity dip angle and the azimuth angle respectively; σ is the azimuth angle of the velocity, which is measured clockwise from north, and the overloads N y , N z required in the longitudinal and lateral directions of the vehicle are compensated for the earth's gravity term.

[0031]

[0032] where, g0 is the earth's gravitational acceleration at sea level.

[0033] Further, the two-stage dive space-time coordinated guidance described in S3 includes a constant lateral maneuvering stage and an optimal guidance stage; the S3 controls the terminal time by changing the switching time of the two stages.

[0034] Further, when the desired time to go is Greater than the predicted waiting time t p When necessary, perform constant lateral maneuvering phase to extend flight time; otherwise, switch to optimal guidance phase until dive guidance ends.

[0035] Furthermore, the predicted waiting time t p The specific process of determining is as follows:

[0036]

[0037] Among them, L R For range, R L For aerodynamic lift, R D For aerodynamic drag, L Rc For the current firing range, L Rf For the terminal range, x c This represents the current flight state in the three-degree-of-freedom equations of motion of the aircraft. Represents the terminal state constraint, ρ is the atmospheric density, and S m Let x be the reference area of ​​the aircraft, and v be the velocity of the aircraft relative to the Earth; in the prediction process, the current flight state of the aircraft x is used. c As the initial value, use the proportional derivative function f p (PNG) The calculation can satisfy the terminal state constraints. The guidance command is given, and the drag coefficient C of the device is utilized. D With lift coefficient C L The aerodynamic forces of the aircraft are calculated through repeated iterations until the target is reached. The time at which the numerical integration ends is the predicted waiting time t of the aircraft. p .

[0038] Furthermore, the maneuver commands for the constant lateral maneuver phase are as follows:

[0039]

[0040] Where, N zd For lateral maneuvering overload, For azimuth constraints, σ v0 The initial velocity azimuth angle of the dive; N z For lateral overload; sgn() and Sign() are sign functions; where, when σ v0 Less than At that time, lateral maneuver overload N zd It is negative; when σ v0 Greater than At that time, the motor overload is positive, when σ v0 equal At that time, lateral maneuver overload N zd It is 0.

[0041] Further, the guidance rate of the two-stage diving space-time coordination guidance of S3 is:

[0042]

[0043] wherein, and are the required velocity pitch rate and azimuth rate of guidance respectively, v is the relative earth speed of the aircraft, g0 is the earth gravity acceleration at sea level, N y and N z are the required longitudinal and lateral overloads of the aircraft, sgn() is the sign function, N zd is the lateral maneuvering overload, σ v0 is the initial velocity azimuth of diving, is the azimuth constraint, t p is the predicted waiting time, is the expected waiting time; based on the required longitudinal and lateral overloads N y and N z of the aircraft and the inverse interpolation of the lift coefficient determine the attack angle α:

[0044]

[0045] wherein, m is the mass of the aircraft, S m is the reference area of the aircraft;

[0046] the roll angle υ is:

[0047] υ = arctan2(N z , N y ).

[0048] Further, the specific process of S4 is:

[0049] S401, determine the aerodynamic drag estimation value based on the mass, acceleration and velocity pitch of the aircraft

[0050]

[0051] is the estimation value of the change rate of the relative earth speed of the aircraft, is the estimation value of the velocity pitch, m is the mass of the aircraft, and g is the gravity acceleration;

[0052] S402, determine the estimation value of the longitudinal component of the aerodynamic lift using the mass, velocity, velocity pitch and its differential of the aircraft, and the geocentric distance

[0053]

[0054] is an estimated value of the rate of change of the velocity inclination angle; is an estimated value of the geocentric distance, is an estimated value of the vehicle relative earth velocity, and

[0055] S403, determining an estimated value of the component of the aerodynamic lift in the lateral direction

[0056]

[0057] is an estimated value of the rate of change of the velocity azimuth angle; is an estimated value of the latitude;

[0058] S404, determining an estimated value of the component of the aerodynamic lift in the longitudinal direction and an estimated value of the component of the aerodynamic lift in the lateral direction

[0059] determining an estimated value of the aerodynamic lift

[0060]

[0061] S405, the aerodynamic force under nominal conditions is:

[0062]

[0063] wherein F aero,d is the aerodynamic drag, F aero,l is the aerodynamic lift, S m is the reference area of the vehicle, C D is the drag coefficient, and C L is the lift coefficient, and p is the atmospheric density, and v is the vehicle relative earth velocity;

[0064] According to the combination of the aerodynamic force estimated value and the nominal value, the aerodynamic force correction coefficient is:

[0065]

[0066] wherein k aero,d is the correction coefficient of the aerodynamic drag, k aero,l is the correction coefficient of the aerodynamic lift; based on the aerodynamic force correction coefficient, the aerodynamic force in the terminal time numerical integral prediction is corrected;

[0067] S406, revising the flight time prediction t p :

[0068]

[0069] wherein LR R is the range L L is the aerodynamic lift D L is the aerodynamic drag Rc L is the current range Rf L is the terminal range c x represents the current flight state in the three-degree-of-freedom motion equation of the aircraft, f represents the terminal state constraint p (PNG) represents the proportional navigation function.

[0070] Compared with the prior art, the beneficial effects of the present application include the following points:

[0071] Roll angle flip optimization: the present application can effectively depress the trajectory by one roll flip, thereby meeting various constraint conditions of the terminal. This feature greatly simplifies the flight path planning, improves the guidance accuracy, and reduces the complexity of the aircraft performing the dive action.

[0072] Synergy of time control and position angle control: the two-stage guidance strategy proposed by the present application effectively combines the lateral maneuver of time control and the optimal guidance of position angle control, realizing four-dimensional coordinated control of time and space. This method solves the contradiction between the two by flexibly adjusting the switching time between lateral maneuver and optimal guidance, ensuring the satisfaction of the terminal constraints.

[0073] Enhanced robustness: by using the inverse solving technique of the dynamic equation, the present application can estimate and compensate for the deviations of the flight environment and the body model in real time during flight, significantly enhancing the robustness of the guidance algorithm, so that the aircraft can better adapt to uncertainties and disturbances.

[0074] Efficient time control: the two-stage guidance switching logic based on terminal time numerical prediction is adopted, improving the accuracy of time control. The prediction accuracy is optimized by numerical integration method, ensuring that the aircraft can accurately reach the target area within the predetermined time, especially suitable for short-range flight in the terminal phase.

[0075] Flexibility and adaptability: the two-stage guidance strategy of the present application meets complex constraints while flexibly adjusting the terminal arrival time through lateral maneuver, improving the flexibility and adaptability of the guidance strategy, so that it can cope with various flight mission requirements.

[0076] In summary, the present application provides an efficient, flexible and robust four-dimensional coordinated guidance scheme for the terminal phase, greatly improving the strike accuracy and mission execution capability of the unpowered high-speed aircraft. By solving the key problems in the terminal phase guidance, the strike accuracy of the aircraft and the robustness of the control system are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0077] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings described below are only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0078] Figure 1 is a schematic diagram of the relative motion of the embodiment of the present application;

[0079] Figure 2 is a two-stage guidance control diagram of the embodiment of the present application;

[0080] Figure 3 is a two-stage guidance schematic diagram of the embodiment of the present application; (a) is when the initial velocity azimuth angle of the dive is less than the terminal velocity azimuth angle constraint, (b) is when the initial velocity azimuth angle of the dive is greater than the terminal velocity azimuth angle constraint;

[0081] Figure 4 is a dive multi-time ITACG trajectory curve of the embodiment of the present application; (a) is an angle of attack-time curve, (b) is a roll angle-time curve, (c) is a velocity angle-time curve, (d) is an azimuth angle-time curve, (e) is a height-time curve, and (f) is a longitude-latitude-height curve;

[0082] Figure 5 is a dive multi-angle ITACG trajectory curve of the embodiment of the present application; (a) is an angle of attack-time curve, (b) is a roll angle-time curve, (c) is a velocity angle-time curve, (d) is an azimuth angle-time curve, (e) is a height-time curve, and (f) is a longitude-latitude-height curve;

[0083] Figure 6 is a dive ITACG random target terminal parameter distribution of the embodiment of the present application; (a) is a terminal position error distribution, (b) is a terminal time distribution, (c) is a terminal velocity angle distribution, and (d) is a terminal azimuth angle distribution. DETAILED DESCRIPTION

[0084] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0085] The embodiment provides a powered high-speed aircraft dive segment space-time four-dimensional coordinated guidance method, and particularly aims at the guidance (ITACG, impact time and angle control guidance) problem of dive terminal time and angle control under complex constraints and full-state high-jet-change conditions, and researches a two-stage guidance strategy based on maneuvering flight and optimal guidance. The first stage is time control lateral maneuvering, and the second stage is position and angle control optimal guidance. The embodiment adopts two-stage guidance switching logic based on terminal time numerical prediction and a maneuvering direction decision method based on the initial heading error of the dive, and realizes the coordination and unification of time control maneuvering flight and optimal guidance. In addition, the embodiment uses inverse solving of the dynamic equation, estimates and compensates the flight environment and body deviation online, so as to enhance the robustness of the guidance algorithm.

[0086] In some specific embodiments, a powered high-speed aircraft dive segment space-time four-dimensional coordinated guidance method comprises the following steps:

[0087] S1, constructing an aircraft dive ITACG guidance model:

[0088] The aircraft motion description adopts a three-degree-of-freedom motion equation established in a ballistic coordinate system. For a high-lift-drag-ratio hypersonic aircraft in the dive segment flight, the flight height is low, and the time and range are relatively short, so the aerodynamic force is small compared with the Coriolis inertial force and the centrifugal inertial force caused by the earth rotation. Therefore, the earth is assumed to be a non-rotating homogeneous sphere in the process of deducing the analytical form of the guidance law.

[0089] The three-degree-of-freedom motion equation of the aircraft is:

[0090]

[0091] Wherein, v is the speed of the aircraft relative to the earth, is the change rate of the speed of the aircraft relative to the earth (· represents the differential of a physical quantity), θ is the speed inclination angle, σ is the speed azimuth angle from north clockwise, r is the geocentric distance, λ and are the longitude and latitude, respectively. ρ is the atmospheric density, m is the mass of the aircraft, S m is the reference area of the aircraft. g = μ M / r 2 is the gravitational acceleration, μ M is the earth gravitational constant, C D and C L are the drag coefficient and the lift coefficient (the functions of the Mach number and the attack angle, for example, CAV-H

[14] ); the control quantity attack angle α is implicit in it, and the other control quantity is the roll angle υ, is the speed inclination angle change rate, This represents the rate of change of the velocity azimuth angle measured clockwise from north. This represents the rate of change of longitude. The rate of change of latitude. This represents the rate of change of distance from the Earth's center.

[0092] The process constraints of an aircraft during the dive phase are mainly reflected in its control capabilities, namely, the control quantities such as the angle of attack and the roll angle, as well as the angular rate, are subject to strict limitations.

[0093]

[0094] Where, α m i n With α max These are the minimum maximum angle of attack constraint values, This represents the maximum rate of change of the angle of attack. The rate of change of the tilt angle; υ is the rate of change of angle of attack; min With υ max The minimum maximum roll angle constraint value. This represents the maximum rate of change of the roll angle. The terminal constraints that dive ITACG guidance needs to satisfy include time. Velocity angle Azimuth longitude latitude and height

[0095]

[0096] Where tar represents the state at the target location, such as t tar Indicates the time at the target location.

[0097] S2. Optimal Dive Guidance Satisfying Angle and Position Constraints

[0098] like Figure 1 As shown, the motion of the aircraft during the dive phase can be decomposed into longitudinal dive plane motion and lateral turning plane motion; wherein, the longitudinal dive plane is defined as the aircraft M, the target O, and the Earth's center O. E The determined plane, the lateral turning plane, is defined as the plane that passes through the target and the center of mass and is perpendicular to the longitudinal diving plane.

[0099] Figure 1 In this context, v is the velocity vector, d is the line-of-sight distance from the aircraft's center of mass to the target, i.e., the length of the line-of-sight MO, and γ... D Let λ be the azimuth angle of the velocity in the dive plane. D η is the viewing angle. D η is the angle between the direction of velocity and the line of sight. T Let γ be the angle between the velocity in the turning plane and the diving plane.T is the direction angle of the velocity in the turn plane (the angle with the north direction), λ TT is the line-of-sight angle in the turn plane (the angle of the line-of-sight with the north direction), λ T is the angle between the line-of-sight direction of the aircraft in the turn plane and the north direction, i.e. the achieved azimuth angle, v d is the projection of the velocity of the aircraft in the dive plane, A is the horizontal plane containing the aircraft M, and O(T) denotes the origin of the target coordinate system O-XYZ, i.e. the target point. The aircraft dive relative motion equation is:

[0100]

[0101] Based on the optimal control theory, the rate of change of the velocity azimuth angle in the line-of-sight coordinate system is obtained as:

[0102]

[0103] where T g is the time to fly calculated in theory:

[0104]

[0105] Since the aircraft motion model is established in the velocity coordinate system, it is necessary to convert the rate of change of the velocity azimuth angle in the line-of-sight coordinate system to the velocity coordinate system:

[0106]

[0107] where and are the required rates of change of the velocity inclination angle and the azimuth angle for guidance, respectively. Further compensation of the earth gravity term is required, and the required overloads N y , N z are:

[0108]

[0109] where, and are the required rates of change of the velocity inclination angle and the azimuth angle for guidance, respectively; g0is the earth gravity acceleration at sea level. Through the control terms of the angular rate and the angle in the above formula, the control of the terminal position and angle is achieved.

[0110] S3, two-stage dive space-time coordinated guidance meeting time constraints

[0111] During the terminal guidance, the aircraft actively changes the magnitude and direction of the aerodynamic force by adjusting the angle of attack and the angle of sideslip, and then controls the flight direction. However, the terminal time control is the magnitude control of the flight velocity in the target direction, so the ITACG guidance of the unpowered high-speed aircraft is a long-period control problem of under-actuation. For example Figure 2 The two-stage terminal dive ITACG guidance of the embodiment includes a constant lateral maneuvering stage and an optimal guidance stage.

[0112] The two-stage guidance strategy is actually to increase the maneuvering flight to change the projection of the velocity vector in the target line-of-sight direction, and then realize the time control. However, the maneuvering flight is a destruction to the original optimal guidance law, and has an adverse effect on the satisfaction of the position and angle constraints, so the coordination of the relationship between the maneuvering flight for time control and the optimal guidance for position and angle control is the core to realize the integrated ITACG guidance task. The longer the maneuvering time of the first stage is, the greater the maneuvering amplitude is, and the longer the flight time is; on the contrary, the shorter the maneuvering time of the first stage is, the smaller the maneuvering amplitude is, and the shorter the flight time is. Therefore, the embodiment achieves the purpose of controlling the terminal time by changing the switching time of the two stages. In the process of diving flight, from the current range L Rc to the terminal range L Rf , the predicted flight time t p is obtained by numerical integration.

[0113]

[0114] where L R is the range, R L is the aerodynamic lift, R D is the aerodynamic drag; x c represents the current flight state in the three-degree-of-freedom motion equation of the aircraft, represents the terminal state constraint in S1. In the prediction process, the current flight state x c of the aircraft is used as the initial value, the guidance command capable of satisfying the terminal constraint is calculated by using the proportional navigation (PNG) method, and the aerodynamic force of the aircraft is calculated by using the bound aerodynamic coefficients C D and C L , through repeated iteration, until the target, and the time at which the numerical integration ends is the predicted flight time t p of the aircraft. In the actual flight process, when the expected flight time is greater than the predicted flight time t p ,

[0115]

[0116] indicates that the aircraft needs to perform the first-stage maneuvering flight to prolong the flight time. The maneuvering command is:

[0117]

[0118] where N zd is the artificial lateral maneuvering overload, is the terminal velocity azimuth constraint, σ v0 is the initial velocity azimuth of the dive; N z is the lateral required overload; sgn() and Sign() are sign functions; the maneuvering flight required by the dive ITACG in the maneuvering command only reflects in the lateral direction, the maneuvering amplitude is given by the human, and the maneuvering direction is determined by the initial line-of-sight azimuth and the terminal velocity azimuth constraint. The decision logic of the maneuvering direction is shown in Figure 3 , such as Figure 3 (a), when σ v0 is less than , the maneuvering overload is negative, and the vehicle velocity azimuth will appear the change rule of first decreasing and then increasing; on the contrary, such as Figure 3 (b), when σ v0 is greater than , the maneuvering overload is positive, and the vehicle velocity azimuth will appear the change rule of first increasing and then decreasing. With the first-stage constant maneuvering, the heading error will become larger and larger, which means that the flight time of the vehicle will be prolonged. In the maneuvering flight, every interval a certain period, the current flight state is taken as the initial condition, the terminal position and angle are taken as the expected value to generate the guidance command, and the numerical prediction method is used to update the predicted flight time t p . When

[0119]

[0120] , the second-stage optimal guidance phase is switched to until the end of the dive guidance. In summary, the dive ITACG guidance law can be expressed as:

[0121]

[0122] For the face-symmetrical aircraft, the attack angle and the roll angle are directly controlled by the guidance command of the dive flight. Therefore, based on the two-direction required overloads N y and N z , the attack angle can be obtained by the aerodynamic parameter back-interpolation:

[0123]

[0124] where represents the back-interpolation calculation based on the lift coefficient, and the other control variable roll angle υ is:

[0125] υ = arctan2(N z , N y )

[0126] Under the effect of the two-stage guidance strategy shown in the diving ITACG guidance law, the bank angle only flips once at the two-stage switching time, and under the effect of the optimal guidance in the second stage, the bank angle presents a monotonic variation law, so the heading error will shrink to zero in a monotonic exponential form. The flipping time is early and the remaining space is large, so as to reduce the influence of frequent flipping of the bank angle under the limited control ability on the guidance accuracy. The optimal guidance method in the second stage controls the aircraft to meet the position and angle constraints with high precision, and the mutual cooperation of the two stages can determine the lateral maneuvering range and then control the terminal arrival time.

[0127] S4, online robustness compensation of environment and ontology deviation

[0128] According to the diving two-stage ITACG strategy, accurate prediction of the terminal time is one of the key factors of time control. In the data integration prediction of the flight time, only the nominal model and data can be used, while the actual flight of the aircraft is inevitably affected by various deviation factors. For the unpowered flight of the diving section, the aircraft is mainly affected by the aerodynamic force and the earth's gravity, and the deviation term is mainly derived from the aerodynamic force. Therefore, the present embodiment uses the flight state parameters to estimate the aerodynamic model and the atmospheric density deviation online, and compensates it to the time prediction link to improve the time prediction accuracy.

[0129] Based on the aircraft mass, acceleration, and velocity bank angle information, the estimated aerodynamic drag is:

[0130]

[0131] is the estimated value of the velocity differential;

[0132] Similarly, using the aircraft mass, velocity, velocity bank angle and its differential, and the geocentric distance, the estimated value of the longitudinal component of the aerodynamic lift is:

[0133]

[0134] is the estimated value of the velocity bank angle differential;

[0135] Correspondingly, the estimated value of the lateral component of the aerodynamic lift is:

[0136]

[0137] is the estimated value of the velocity azimuth angle differential;

[0138] Based on the longitudinal component of the aerodynamic lift and the component of the aerodynamic lift in the lateral direction The estimated value of the aerodynamic lift is:

[0139]

[0140] The measured or estimated value of the parameter x, in which the aerodynamic force estimation is a function of the flight state, can be directly or indirectly given by the navigation system. In addition, the aerodynamic force calculation under the nominal condition is:

[0141]

[0142] Combined with the aerodynamic force estimation and the nominal value, the aerodynamic force correction coefficient is:

[0143]

[0144] wherein k aero,d is the correction coefficient of the aerodynamic drag, and k aero,l is the correction coefficient of the aerodynamic lift.

[0145] Based on the above aerodynamic force correction coefficient, the aerodynamic force in the terminal time numerical integral prediction is corrected.

[0146] Then the flying time prediction equation is revised:

[0147]

[0148] Using the corrected aerodynamic coefficient to calculate the flying time will improve the prediction accuracy of the terminal time, and further provide conditions for accurate control of the arrival time.

[0149] Embodiment 1

[0150] The aircraft adopts BTT control mode, and the control quantities of the attack angle and the roll angle satisfy the following constraints: the minimum attack angle is a min = 0°, the maximum attack angle is a max = 20°, the maximum roll angle is v max = 180° (in the simulation calculation, the change range of the roll angle is converted to the range of [0°, 360°] or [-360°, 0°]); the maximum attack angle change rate is the maximum roll angle change rate is

[0151] The performance of the diving ITACG guidance method is verified in this embodiment. The initial parameters of the diving flight are set as follows: the speed is 1810 m / s, the speed inclination angle is 0°, the longitude is 115°, the latitude is 25.0°, the height is 35.4 km, and the initial azimuth angle is 85°. The terminal parameters are set as follows: the longitude is 116.3°, the latitude is 25.2°, the height is 0 km, the speed inclination angle is -60°, and the speed azimuth angle is 80°. In the diving guidance law, the maximum calculation amount is derived from the numerical prediction of the terminal time, and the rest of the instructions are analytically calculated. Therefore, in order to improve the online calculation efficiency of the guidance instructions, the prediction period is set to 2 s.

[0152] 1. Basic performance verification of diving ITACG

[0153] The performance of the guidance method is verified in this embodiment under three scenarios, i.e., without time control diving guidance (Case 1), the terminal time is 90 s (Case 2), and the terminal time is 95 s (Case 3). As shown in Figure 4 (a)-(f) and Table 1, when there is no time control, the terminal arrival time is 84.06 s, and when the time control is added, the terminal time error is within 0.3 s. The terminal position error is less than 0.7 m, the speed inclination angle error is less than 0.03 deg, and the azimuth angle error is less than 1.3 deg. Taking the terminal time constraint of 90 s as an example, the vehicle performs constant lateral maneuvering for the first 52 s, and then turns into the second stage of optimal guidance with the maximum capability. During the diving flight, the roll angle is only reversed once at the two-stage switching, which creates good conditions for meeting the terminal guidance accuracy. Under the action of the attack angle and the roll angle, the azimuth angle generally shows a trend of first increasing and then decreasing. Comparing Case 2 and Case 3, the longer the terminal time, the longer the maneuvering time in the first stage and the larger the maneuvering range. The above simulation results show that the guidance method can accurately meet the terminal longitude, latitude, height, speed inclination angle, and azimuth angle constraints, and the guidance instructions change smoothly and continuously, which is easy to implement.

[0154] Table 1. Diving multi-time ITACG guidance results

[0155]

[0156] 2. Adaptability verification of diving ITACG

[0157] In order to further verify the performance of the diving ITACG, the terminal time constraint is set to 90 s, the terminal speed azimuth angle is set to 60° (Case 1), 80° (Case 2), and 100° (Case 3), and the other simulation conditions remain unchanged. The simulation results are shown in Table 2 and Figure 5As shown in (a)-(f), the simulation results show that the guidance method researched in the application can meet the terminal position, angle and time constraints with high precision, the terminal time error is within 0.2s, the position error is less than 0.7m, and the angle deviation is less than 0.6deg. In addition, the change law of the inclination side angle in (b) and the azimuth angle in (d) shows that when the terminal azimuth angle is 60deg, the value is less than the initial line-of-sight azimuth angle of the dive, so the aircraft performs the guidance mode of first forward maneuvering and then optimal guidance; on the contrary, when the terminal azimuth angle is 80 and 100deg, the aircraft performs the guidance mode of first negative maneuvering and then optimal guidance. The simulation results show that the dive guidance method researched in the application can autonomously decide the initial maneuvering direction according to the relative motion state, and then meet the terminal constraint conditions with high precision. Figure 5 Figure 5 The change law of the inclination side angle in (b) and the azimuth angle in (d) shows that when the terminal azimuth angle is 60deg, the value is less than the initial line-of-sight azimuth angle of the dive, so the aircraft performs the guidance mode of first forward maneuvering and then optimal guidance; on the contrary, when the terminal azimuth angle is 80 and 100deg, the aircraft performs the guidance mode of first negative maneuvering and then optimal guidance. The simulation results show that the dive guidance method researched in the application can autonomously decide the initial maneuvering direction according to the relative motion state, and then meet the terminal constraint conditions with high precision.

[0158] Table 2 Dive multi-angle ITACG guidance results

[0159]

[0160] 3. Robustness verification of dive ITACG

[0161] To improve the robustness to flight environment and body deviation is an important index of the dive ITACG guidance method. Therefore, in the dynamics simulation, constant deviations are added to the atmospheric density and the aerodynamic coefficient, but the guidance system is unknown to the above deviations, and can only determine the deviation amount through the estimation method, so as to verify the robustness of the dive ITACG method. The terminal parameters are set as follows: longitude is 116.3°, latitude is 25.2°, height is 0km, velocity inclination angle is-60°, velocity azimuth angle is 80°, and the expected reaching time is 90s.

[0162] The present application carries out constant limit deviation test of 15% at most to the atmospheric density and the aerodynamic coefficient respectively, and the guidance results under 27 kinds of deviation combinations are shown in Table 3. The simulation results show that under the condition of constant limit deviation, the time error under all deviation conditions is within 1s, and the position error is less than 3m. In addition, when the atmospheric density and the aerodynamic coefficient are reduced, the control ability of the aircraft is the weakest, which leads to that the terminal position reaches 2.805m, the velocity inclination angle deviation is 1.169deg, and the azimuth angle error reaches 3.214deg. The above results show that the ITACG method proposed in the application can still meet the terminal multiple constraints with high precision, and has strong robustness to the environment and body deviation.

[0163] Table 3 Robustness test results of dive ITACG constant deviation

[0164]

[0165] ​

[0166] The embodiment adds random deviations with mean value of zero and mean square deviation of 3σ=15% to the atmospheric density and the aerodynamic coefficients respectively, and performs 500 times of simulation shooting, and the statistical characteristics and distribution of the terminal parameters are as shown in Table 4 and Figure 6 (a)-(d) shown,

[0167] It can be known from the calculation result that the maximum terminal position error is within 0.7 m, the terminal time error is within 0.3 s, the terminal velocity inclination error is less than 0.1 deg, and the terminal velocity azimuth angle is less than 0.7 deg, further verifying the robustness of the guidance method.

[0168] Table 4 Statistical characteristics of diving ITACG random shooting

[0169]

[0170] The present application is directed to the high dynamic diving ITACG guidance problem under the constraint condition of strong control ability, and a two-stage guidance strategy of combining time control maneuver flight with position angle control optimal guidance is proposed. Firstly, the aircraft motion model and relative motion model are established, and the optimal proportional guidance method is introduced to end the latitude, longitude, height, velocity inclination and azimuth angle constraints; secondly, the lateral maneuver is used to control the terminal arrival time, and the switching logic based on the numerical prediction of the terminal time is proposed, realizing the coordination and unification of time control maneuver flight and optimal guidance; finally, the inverse solution of the dynamics equation is used to estimate and compensate the flight environment and body deviation online, enhancing the robustness of the guidance algorithm.

[0171] Each of the embodiments in the specification is described in a related manner, and the same and similar parts between each of the embodiments can be referred to each other, and each of the embodiments mainly explains the difference from other embodiments. Especially, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0172] The above only describes the preferred embodiments of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for four-dimensional space-time coordinated guidance of an unpowered high-speed vehicle during the reentry phase, characterized in that, The method comprises the following steps: S1, constructing a terminal time and angle control guidance model of the aircraft; S2, optimal dive guidance meeting angle and position constraints; S3, two-stage dive space-time coordination guidance meeting time constraints; wherein the two-stage dive space-time coordination guidance comprises a constant lateral maneuver stage and an optimal guidance stage; Wherein, the S3 controls the terminal time by changing the switching time of the two stages; When expected waiting time Greater than the predicted waiting time t p When necessary, perform constant lateral maneuvering phase to extend flight time; otherwise, switch to optimal guidance phase until dive guidance ends. The predicted flight time t p The determination process of the predicted flight time t is specifically as follows. where L R is the range, R L is the aerodynamic lift, R D is the aerodynamic drag, L Rc is the current range, L Rf is the terminal range, x c denotes the current flight state in the three-degree-of-freedom motion equation of the aircraft, denotes the terminal state constraint, p is the atmospheric density, S m is the reference area of the aircraft, and v is the relative speed of the aircraft to the earth; in the prediction process, the current flight state x c is taken as the initial value, the proportional navigation function f p (PNG) is used to calculate the guidance command that can satisfy the terminal state constraint , and the aerodynamic force of the aircraft is calculated by using the bound drag coefficient C D and the lift coefficient C L , and through repeated iterations, the time at which the numerical integration ends is the predicted flight time t p of the aircraft to the target; Wherein, the maneuver instruction of the constant lateral maneuver stage is: where N zd is the lateral maneuvering overload, is the azimuth constraint, σ v0 is the velocity azimuth at the start of the dive; N z is the lateral required overload; sgn() and Sign() are sign functions; where when σ v0 is less than , the lateral maneuvering overload N zd is negative; when σ v0 is greater than , the maneuvering overload is positive, and when σ v0 is equal to , the lateral maneuvering overload N zd is 0; Wherein, the guidance rate of the two-stage dive space-time coordination guidance of the S3 is: where, and are the required rates of change of the velocity pitch angle and azimuth angle, respectively, v is the vehicle's velocity relative to the earth, g0 is the earth's gravitational acceleration at sea level, N y , N z are the required longitudinal and lateral accelerations of the vehicle, sgn() is the sign function, N zd is the lateral maneuvering acceleration, s v0 is the initial velocity azimuth of the dive, is the azimuth constraint, t p is the predicted loiter time, is the desired loiter time; based on the required longitudinal and lateral accelerations of the vehicle N y , N z and the inverse of the lift coefficient determines the angle of attack a: where m is the aircraft mass, S m is the aircraft reference area; The roll angle υ is: u = arctan2(N z , N y ) S4, online robustness compensation for environmental and body deviations.

2. The unpowered hypersonic vehicle reentry space-time four-dimensional coordinated guidance method according to claim 1, characterized in that, The specific process of the S1 is: S101, establishing an aircraft motion equation: where v is the vehicle's velocity relative to the earth, is the rate of change of the vehicle's velocity relative to the earth, θ is the velocity inclination, σ is the velocity azimuth measured clockwise from north, r is the geocentric range, λ and φ are the longitude and latitude, respectively, ρ is the atmospheric density, m is the vehicle mass, S m is the vehicle's reference area, g = μ M / r 2 is the gravitational acceleration, μ M is the earth's gravitational constant, C D and C L are the drag and lift coefficients, respectively, υ is the bank angle, is the rate of change of the velocity azimuth measured clockwise from north, is the rate of change of the longitude; is the rate of change of the latitude, is the rate of change of the geocentric range, is the rate of change of the velocity inclination; S102, establishing an angle of attack α and roll angle υ constraint of the control quantity: wherein α min and α max are minimum and maximum angle of attack constraint values, respectively, is a maximum rate of change of angle of attack; is a rate of change of bank angle; is a rate of change of angle of attack; υ min and υ max are minimum and maximum bank angle constraint values, respectively, is a maximum bank angle rate of change; S103, determining terminal constraints: is a time constraint, is a speed and tilt constraint, is an azimuth constraint, is a longitude constraint, is a latitude constraint, is an altitude constraint, and tar represents a state at a target.

3. The unpowered hypersonic vehicle reentry space-time four-dimensional coordinated guidance method according to claim 1, characterized in that, The specific process of the S2 is: S201. decompose the aircraft motion in the dive phase into a longitudinal dive plane motion and a lateral turn plane motion, wherein the longitudinal dive plane is defined as the plane passing through the aircraft M, the target O and the Earth center O E the determined plane, the lateral turn plane is defined as the plane passing through the target and the aircraft center of mass and being perpendicular to the longitudinal dive plane; S202, establishing an aircraft dive relative motion equation: wherein is the second derivative of the line-of-sight angle, is the second derivative of the line-of-sight angle in the turn plane, v is the aircraft's velocity relative to the earth, is the rate of change of the aircraft's velocity relative to the earth, d is the line-of-sight distance from the aircraft's center of mass to the target, is the rate of change of the line-of-sight distance from the aircraft's center of mass to the target, is the rate of change of the line-of-sight angle, is the rate of change of the line-of-sight angle in the turn plane, is the rate of change of the azimuth angle of the velocity in the dive plane, is the direction angle of the velocity in the turn plane; S203, determining a velocity azimuth rate of change in a line-of-sight coordinate system: where, is the velocity bank angle constraint, is the position angle constraint, λ T is the real azimuth angle, is the real azimuth angle rate of change, λ D is the line of sight angle, T g is the theoretical calculated time on station: Converting the velocity azimuth rate of change in the line-of-sight coordinate system to a velocity coordinate system: where and are the required rates of change of the velocity inclination and azimuth, respectively; and σ is the velocity azimuth measured clockwise from north, compensated for the earth's gravitational term, so that the required longitudinal and lateral accelerations N y , N z are: Wherein, g0 is the earth's gravitational acceleration at sea level, and θ is the velocity inclination angle.

4. The unpowered hypersonic vehicle reentry space-time four-dimensional coordinated guidance method according to claim 1, wherein, The specific process of the S4 is: S401, determine an aerodynamic drag estimate based on the aircraft mass, acceleration, and velocity pitch angle : is an estimate of the rate of change of the vehicle's velocity relative to the earth, is an estimate of the velocity inclination, m is the mass of the vehicle, and g is the acceleration of gravity. S402, determine the estimate of the longitudinal component of the aerodynamic lift using the aircraft mass, velocity, velocity pitch angle and their derivatives, and the geodetic distance : is an estimate of the rate of change of the velocity inclination; is an estimate of the geocentric range, is an estimate of the vehicle's velocity relative to the earth, and v is the bank angle. S403, determine an estimated value of a component of the aerodynamic lift in the lateral direction : is an estimate of the velocity azimuthal derivative; is a latitude estimate; S404, estimate value of a component of the aerodynamic lift in the longitudinal direction and estimate value of a component of the aerodynamic lift in the lateral direction determining the estimate value of the aerodynamic lift : S405, the aerodynamic force under the nominal condition is: where F aero,d is the aerodynamic drag, F aero,l is the aerodynamic lift, S m is the reference area of the aircraft, C D is the lift coefficient, and p is the atmospheric density, v is the relative velocity of the aircraft to the Earth. L are the drag and lift coefficients of the binding, respectively, and p is the atmospheric density, v is the relative velocity of the aircraft to the Earth. According to the aerodynamic force estimated value and the nominal value, the aerodynamic force correction coefficient is: wherein k aero,d is a correction coefficient of the aerodynamic drag, k aero,l is a correction coefficient of the aerodynamic lift; the aerodynamic force is corrected based on the aerodynamic force correction coefficient in the numerical integration prediction of the terminal time value. S406、t p Revisions made: where L R is the range, R L is the aerodynamic lift, R D is the aerodynamic drag, L Rc is the current range, L Rf is the terminal range, x c denotes the current flight state in the three- degree-of-freedom motion equation of the aircraft, denotes the terminal state constraint, f p (PNG) denotes the proportional navigation function.

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