CN114326813A - Method and system for predicting remaining flight time of unpowered aircraft - Google Patents

Abstract

A method and a system for predicting the residual flight time of an unpowered aircraft are provided, wherein the method comprises the steps of obtaining the target distance, the sight line inclination angle, the sight line deflection angle and the velocity vector of the aircraft at the current moment, calculating the total lead angle, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle; if the flight is turning flight, segmenting according to the total lead angle, wherein the last segment is a straight segment, and the rest segments are turning segments, and predicting the remaining flight time of the turning segments by adopting segmentation iteration; calculating the residual straight-line section range, segmenting the straight-line section according to the residual straight-line section range, and predicting the residual flight time of the straight-line section by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time; and if the straight line section flies linearly, calculating the residual straight line section range, segmenting the straight line section according to the residual straight line section range, and predicting the residual flight time of the straight line section by adopting segmentation iteration, wherein the residual flight time of the straight line section is the predicted total residual flight time.

Description

Method and system for predicting remaining flight time of unpowered aircraft

Technical Field

The invention relates to the technical field of flight time control of unpowered aircrafts, in particular to a method and a system for predicting the remaining flight time of the unpowered aircrafts.

Background

The aircraft attacks the target at a specified time, which is the basis for realizing the cooperative saturation attack of multiple aircraft. To achieve accurate guidance with time constraints, more accurate time-of-flight information is required to form the control feedback. Since the remaining time of flight is often difficult to estimate accurately and the unpowered aircraft varies significantly and uncontrollably in speed during actual flight, the uncertain change in speed in this case presents certain difficulties in predicting the remaining time of flight. Most of the existing methods predict the remaining flight time based on the assumption that the speed of the aircraft is constant and the lead angle is small, however, the constant speed limit is too severe and ideal, the flight speed of the unpowered aircraft at the tail section is remarkably reduced, and the change process is not controlled. If the method is adopted, the problem of inaccurate estimation of the residual flight time is caused, and further attack time control on the aircraft is failed.

Disclosure of Invention

In view of the foregoing analysis, embodiments of the present invention are directed to a method and a system for predicting remaining flight time of an unpowered aircraft, so as to solve the problem of inaccurate estimation of the remaining flight time.

In one aspect, an embodiment of the present invention provides a method for predicting remaining flight time of an unpowered aircraft, including the following steps:

acquiring a target distance, a sight line inclination angle, a sight line deflection angle and a velocity vector of the aircraft at the current moment, calculating a total lead angle based on the sight line inclination angle, the sight line deflection angle and the velocity vector, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle;

if the turning flight is adopted, segmenting the turning section according to the total lead angle, and predicting the remaining flight time of the turning section by adopting segmentation iteration; calculating a residual straight-line segment range according to the total front angle of the starting point of the straight-line segment and the target distance, segmenting the straight-line segment according to the residual straight-line segment range, and predicting the residual flight time of the straight-line segment by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time;

and if the straight line section flies, calculating the residual straight line section flight distance according to the total lead angle and the target distance, segmenting the straight line section according to the residual straight line section flight distance, and predicting the residual flight time of the straight line section by adopting segmentation iteration, wherein the residual flight time of the straight line section is the predicted total residual flight time.

Based on the further improvement of the technical scheme, the method for predicting the residual flight time of the turning section by adopting the segmented iteration or predicting the residual flight time of the straight-line section by adopting the segmented iteration comprises the following steps:

for each segment, acquiring a state variable of a current segment starting point, wherein the state variable comprises a velocity modulus value v_iLine of sight inclination angle theta_L,iView bias angle psi_L,iFront tilt angle eta_z,iLeading deflection angle eta_y,iHeight y of the ground_i；

If the current segment is in the turning segment, the state variable also comprises a total lead angle eta_iAnd a target distance D_tc,i(ii) a If the current segment is in the straight line segment, the state variable further comprises a residual straight line segment range L_i；

If the current segment is in the turning segment, the method is based on

Calculating the predicted value of the initial flight time of the current segment

If the current segment is in a straight line segment, then according to

Calculating the predicted value of the initial flight time of the current segment

Wherein, Δ η_iShowing the variation of the total lead angle of the current subsection, delta L showing the variation of the range of the remaining straight-line segment of the current subsection, K_NRepresenting a navigation ratio;

based on the state variable of the current segment initial point, calculating the initial speed change rate of the current segment according to the kinetic equation of the aircraft centroid motion

Based on the initial rate of change of speed

Predicting the initial flight time of the current segment

Correcting to obtain the corrected value of the current sectional flight time

State variable based on current segment starting point and current segment flight time correction value

Predicting a state variable at the end of a current segment, the current segmentThe state variable at the segment end point is the state variable at the next segment start point;

time of flight correction for all segments

As the predicted turn or straight segment residual time of flight.

Further, based on the initial rate of change of speed

Predicting the initial flight time of the current segment

Correcting to obtain the corrected value of the current sectional flight time

The method comprises the following steps:

based on the initial rate of change of speed

And the initial time-of-flight prediction value

According to the formula

Obtaining a first speed predicted value v of the segmentation end point_p,i；

First velocity prediction value v based on the segment end point_p,i and the initial time-of-flight prediction value

Calculating to obtain a first speed change rate according to a kinetic equation of the mass center motion of the aircraft

According to the formula

Calculating to obtain a first average correction speed

If the current segment is in the turning segment, the method is based on

Calculating current segment flight time correction value

If the current segment is in a straight line segment, then according to

Calculating current segment flight time correction value

Further, a first velocity prediction value v based on the segment end point_p,iAnd the initial time-of-flight prediction value

Calculating to obtain a first speed change rate according to a kinetic equation of the mass center motion of the aircraft

The method comprises the following steps:

predicting value v according to first speed_p,i and the initial time-of-flight prediction value

Correcting the sight line inclination angle and the sight line deflection angle of the current segment to respectively obtain a first corrected sight line inclination angle theta_Lp,iAnd a first corrected sightline declination psi_Lp,i；

If the current segment is in the turning segment, according to the formula y_p,i＝-D_tc,i+1sin(θ_Lp,i) Calculating to obtain a first corrected ground height y_p,i(ii) a If the current segment is in a straight line segment, then according to the formula y_p,i＝-L_i+1sin(θ_Lp,i) Calculating to obtain a first corrected ground height y_p,i(ii) a Wherein D is_tc,i+1Indicating the target distance, L, of the starting point of the i +1 segment_i+1Representing the residual straight-line range of the starting point of the i +1 section;

based on the first corrected sight line inclination angle theta_Lp,iFirst corrected view declination psi_Lp,iAnd a first velocity prediction value v_p,iCalculating the components of the first speed vector in each coordinate axis in the reference coordinate system; calculating to obtain a first correction ballistic inclination angle theta based on the components of the first velocity vector in each coordinate axis in the reference coordinate system_p,i；

Predicting a value v based on the first speed_p,iFirst corrected ground height y_p,iFirst corrected trajectory inclination angle theta_p,iCalculating to obtain a first corrected speed change rate according to a kinetic equation of the mass center motion of the aircraft

Further, a predicted value v is predicted from the first speed_p,iAnd the initial time-of-flight prediction value

Correcting the sight line inclination angle and the sight line deflection angle of the current segment to respectively obtain a first corrected sight line inclination angle theta_Lp,iAnd a first corrected sightline declination psi_Lp,iThe method comprises the following steps:

correcting the sight line inclination angle of the current segment according to the following formula to obtain a first corrected sight line inclination angle theta_Lp,i：

If the current segment is in the turning segment, according to

Calculating initial line of sight inclination angle change rate

And a first modified rate of change of line of sight inclination

If the current segment is in a straight line segment, then according to

Calculating initial line of sight inclination angle change rate

And a first modified rate of change of line of sight inclination

According to the formula

Obtaining a first corrected line-of-sight inclination angle theta_Lp,i；

Correcting the view declination angle of the current segment according to the following formula to obtain a first corrected view declination angle psi_Lp,i：

If the current segment is in the turning segment, the method is based on

Calculating initial rate of change of declination angle

And a first modified rate of change of gaze declination

If the current segment is in a straight line segment, then according to

Calculating initial rate of change of declination angle

And a first modified rate of change of gaze declination

According to the formula

Obtaining a first corrected sightline declination psi_Lp,i。

Further, based on the state variable of the current segment starting point and the current segment flight time correction value

Predicting state variables for the end point of the current segment, including:

initial rate of change of speed according to current segment

And said current segment time-of-flight correction value

According to the formula

Obtaining a second speed predicted value v of the current segmentation end point_q,i；

A second velocity prediction value v based on the segment end point_q,iAnd current segment flight time correction value

Calculating to obtain a second speed change rate according to a kinetic equation of the mass center motion of the aircraft

Rate of change to initial speed

And a second corrected speed change rate

Averaging to obtain a second average correction speed

Correcting the velocity based on the second average

Calculating a third velocity prediction value for an end point of the current segment

The third speed predicted value is the predicted speed v of the end point of the current segment_i+1；

According to the sight line inclination angle theta of the current segmentation starting point_L,iVelocity v of the end point of the current segment_i+1And said current segment time-of-flight correction value

Calculating to obtain the sight line inclination angle theta of the end point of the current segment_L,i+1(ii) a The declination phi of the line of sight according to the starting point of the current segment_L,iVelocity v of the end point of the current segment_i+1And said current segment time-of-flight correction value

Calculating to obtain the view declination phi of the end point of the current segment_L,i+1；

If the current segment is in the turning segment, according to the formula y_i+1＝-D_tc,i+1sinθ_L,i+1Calculating the ground height of the end point of the current segment; if the current segment is in a straight line segment, then according to y_i+1＝-L_i+1sinθ_L,i+1The ground height of the end point of the current segment is calculated.

Further, based on the state variable of the current segment initial point, calculating the initial speed change rate of the current segment according to the dynamic equation of the aircraft centroid motion

The method comprises the following steps:

based on the line of sight inclination angle theta_L,iView bias angle psi_L,iFront tilt angle eta_z,iLeading deflection angle eta_y,iAnd velocity modulus v_iCalculating the component of the velocity vector in each coordinate axis in the reference coordinate system; calculating to obtain the initial ballistic inclination angle theta of the current segment based on the components of the velocity vector on each coordinate axis in the reference coordinate system_i；

If the current subsection is in the turning section, the formula is used

Calculating the component of the acceleration in a ballistic coordinate system; if the current subsection is in the straight line segment, then according to the formula

Calculating the component of the acceleration in a ballistic coordinate system;

according to the ground height y_iObtaining the atmospheric density rho and the sound velocity aT through interpolation, and obtaining the Mach number through calculation according to the atmospheric density rho and the sound velocity aT

And dynamic pressure

The lift coefficient C is calculated according to the following formula_Ld,i：

F_y＝MT·g_tc cosθ_i+MT·a_y,i，F_z＝MT·a_z,i，

Based on the Mach number Mach and the lift coefficient C_Ld,iCalculating an attack angle command alpha by using a Newton iteration method_c,i；

Mach number and attack angle instruction alpha based on the Mach number_c,iCalculating the coefficient of resistance C from the fitting equation_D,i；

According to the formula

The initial rate of change of the speed is calculated,

wherein MT denotes the mass of the aircraft, ST denotes the reference area of the aircraft, g_tcRepresenting the gravitational constant.

Further, after obtaining the state variable of the starting point of the current segment for each segment, the method is based on the initial speed change rate

Predicting the initial flight time of the current segment

Before the correction, the method further comprises the following steps:

if the current subsection is in the turning section, calculating the preposed inclination angle eta of the current subsection end point according to the following formula_z,i+1Leading deflection angle eta_y,i+1And total lead angle η_i+1：

η_y,i+1＝η_y,i+Δη_y,i，η_z,i+1＝η_z,i+Δη_z,i，η_i+1＝arccos(cosη_y,i+1cosη_z,i+1)；

According to the formula

Calculating a target distance D of a current segmentation end point_tc,i+1；

If the current segmentation is in the straight line segment, calculating the remaining straight line segment range L of the current segmentation end point according to the following formula_i+1Front tilt angle eta_z,i+1And a pre-set declination angle eta_y,i+1：

L_i+1＝L_i-ΔL，

Wherein, K_NRepresenting the navigation ratio, Δ_ηDenotes the lead angle segmentation quantity constant and NumP denotes the number of segments of the turnaround segment.

Further, calculating a total lead angle based on the line of sight inclination angle, the line of sight declination angle, and the velocity vector, comprising:

calculating a direction cosine matrix from the reference coordinate system to the sight line coordinate system according to the sight line inclination angle and the sight line deflection angle;

calculating a component of the velocity vector in the line of sight coordinate system based on the direction cosine matrix;

the total lead angle is calculated according to the following formula:

η＝arccos(cosη_ycosη_z)

wherein v is_xL、v_yLAnd v_zLRespectively representing the components, eta, of the velocity vector in three coordinate axes of a line-of-sight coordinate system_zIndicating the angle of advance, eta_yDenotes the lead angle and η denotes the total lead angle.

Compared with the prior art, the method has the advantages that according to a closed-loop aircraft three-dimensional mass center motion equation, turning flight or linear flight of the current flight behavior is judged according to the total lead angle, segmentation is carried out according to the total lead angle when the flight is turning flight, segmentation is carried out according to the residual linear range when the flight is linear flight, the residual flight time is predicted by adopting segmentation iteration, the magnitude of the future speed of the unpowered aircraft is predicted in a segmentation mode and the residual flight time estimation formula is corrected in an iteration mode through iteration solving, the estimation of the residual flight time is more accurate, and therefore the residual flight time can be accurately predicted under the conditions that the total lead angle is greatly changed and the flight speed of the unpowered aircraft is not controlled.

In another aspect, an embodiment of the present invention provides a system for predicting remaining flight time of an unpowered aircraft, including the following modules:

the data acquisition module is used for acquiring a target distance, a sight inclination angle, a sight deflection angle and a velocity vector of the aircraft at the current moment, calculating a total lead angle based on the sight inclination angle, the sight deflection angle and the velocity vector, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle;

the turning flight prediction module is used for segmenting the turning section according to the total lead angle and predicting the remaining flight time of the turning section by adopting segmentation iteration if the turning flight is the turning flight; calculating a residual straight-line segment range according to the total front angle of the starting point of the straight-line segment and the target distance, segmenting the straight-line segment according to the residual straight-line segment range, and predicting the residual flight time of the straight-line segment by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time;

and the linear flight prediction module is used for calculating a residual linear section flight distance according to the total lead angle and the target distance if the linear flight is linear flight, segmenting the linear section according to the residual linear section flight distance, and predicting the residual flight time of the linear section by adopting segmentation iteration, wherein the residual flight time of the linear section is the predicted total residual flight time.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

FIG. 1 is a flow chart of a method for predicting remaining flight time for an unpowered aircraft according to an embodiment of the invention;

FIG. 2 is a block diagram of a system for predicting remaining flight time for an unpowered aircraft according to an embodiment of the invention;

FIG. 3 is a coordinate system diagram of an embodiment of the present invention;

FIG. 4 is a comparison chart of results of different remaining time estimation methods.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

In order to solve the problem that the prediction of the remaining time of the unpowered aircraft is inaccurate under the conditions that the speed changes along with the flight state and the lead angle is large, according to a closed-loop three-dimensional centroid motion equation of the aircraft, the current flight behavior is judged to turn or fly linearly according to the total lead angle, when the current flight behavior is turned, segmentation is carried out according to the total lead angle, when the current flight behavior is flying linearly, segmentation is carried out according to the remaining linear range, the remaining flight time is predicted by adopting segmentation iteration, and through iteration solution, the future speed of the unpowered aircraft is predicted in segments and the remaining flight time estimation formula is corrected in an iteration mode, so that the estimation of the remaining flight time is more accurate, and the remaining flight time can still be accurately predicted under the conditions that the total lead angle changes greatly and the flight speed of the unpowered aircraft is not controlled.

As shown in fig. 3, the coordinate system of the embodiment of the present invention includes a reference coordinate system, a sight line coordinate system, and a ballistic coordinate system.

The reference coordinate system takes the three-dimensional mass center of the aircraft as the origin O, the X-axis direction is parallel to the horizontal plane and points north as positive, and the X-axis direction is taken as_RMeaning that the Y axis is facing vertically upwards, in Y_RIndicating that the Z axis is oriented parallel to the horizontal plane according to the right hand rule, in Z_RAnd (4) showing.

The sight line coordinate system takes the three-dimensional mass center of the aircraft as an origin O, and the X-axis direction points to a target point from the aircraft and takes X as_LIs represented by Z_LThe axial direction is parallel to the horizontal plane and points to X_LThe right is positive, the Y axis is oriented according to the right-hand rule, and Y is used_LAnd (4) showing.

The trajectory coordinate system takes the three-dimensional center of mass of the aircraft as an origin O, and the X-axis direction is along the direction of the velocity vector and takes X as_VIs represented by Y_VThe vertical plane containing velocity vector is vertical to the velocity vector and is positive upwards, the Z axis determines the direction according to the right hand rule, and Z is used_VAnd (4) showing.

The symbols used in the embodiments of the present application are explained in a unified manner: d_tcRepresenting a linear distance between the aircraft and the target; f represents stress; f_LRepresents the total lift; c_LRepresents a lift coefficient; c_DRepresenting a drag coefficient; eta represents the total lead angle, i.e. the aircraft velocity vector and X_LThe included angle of (A); eta_yIndicating the pre-set angle (velocity vector in the line-of-sight coordinate system X)_L-O-Z_LIn-plane projection and X_LThe angle between the axes); eta_zRepresenting the forward tilt (velocity vector and line of sight coordinate system X)_L-O-Z_LThe angle of the plane); Δ η represents the total lead angle variation; Δ η_yRepresenting the amount of change of the lead-out angle; Δ η_zRepresenting the amount of change in the lead inclination; delta_ηIs a leading angle piecewise constant; v represents a velocity modulus;

represents a rate of change of speed;

represents the average speed change rate; y represents the height from the ground; theta_LRepresenting the inclination of the line of sight, i.e. the line of sight vector X_LAnd X_R-O-Z_RThe included angle of the plane; psi^LRepresenting line-of-sight declination, i.e. line-of-sight vector X_LAt X_R-O-Z_RIn-plane projection and X_RThe included angle of the axes;

and

respectively representing the change rate of the inclination angle of the sight line and the change rate of the declination angle of the sight line; theta represents the ballistic inclination angle, i.e. the angle between the velocity vector and the horizontal plane; a is_yAnd a_zRespectively represents acceleration Y in a ballistic coordinate system_vAxis and Z_vThe component of the axis, L represents the range of the residual straight line segment, and Delta L represents the constant of the piecewise quantity of the straight line segment; the index i indicates the current segment and the index i +1 indicates the next segment.

The invention discloses a method for predicting the remaining flight time of an unpowered aircraft, which comprises the following steps as shown in figure 1:

s1, obtaining the target distance, the sight line inclination angle, the sight line deflection angle and the velocity vector of the aircraft at the current moment, calculating a total lead angle based on the sight line inclination angle, the sight line deflection angle and the velocity vector, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle.

S2, if the turning flight is performed, segmenting the turning section according to the total lead angle, and predicting the remaining flight time of the turning section by adopting segmentation iteration; calculating a residual straight-line segment range according to the total front angle of the starting point of the straight-line segment and the target distance, segmenting the straight-line segment according to the residual straight-line segment range, and predicting the residual flight time of the straight-line segment by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time;

and S3, if the straight line section flies, calculating the residual straight line section flight distance according to the total front angle and the target distance, segmenting the straight line section according to the residual straight line section flight distance, and predicting the residual flight time of the straight line section by adopting segmentation iteration, wherein the residual flight time of the straight line section is the predicted total residual flight time.

The current flying behavior is judged to turn or fly linearly according to the total lead angle, segmentation is carried out according to the total lead angle when the current flying behavior is turned, segmentation is carried out according to the residual straight-line flight distance when the current flying behavior is flown linearly, the increment of the lead inclination angle of the aircraft in each segmentation interval is guaranteed to be small angle, and segmentation iteration is adopted to predict the residual flight time, so that the residual flight time can be accurately predicted under the conditions that the total lead angle is greatly changed and the flight speed of the unpowered aircraft is not controlled.

Wherein the obtained velocity vector is a velocity vector in a reference coordinate system, and the components of three coordinate axes in the reference coordinate system can be respectively represented as v_xR、v_yRAnd v_zR。

Specifically, in step S1, calculating a total lead angle based on the line-of-sight inclination angle, the line-of-sight declination angle, and the velocity vector includes:

s11, calculating a direction cosine matrix from the reference coordinate system to the sight line coordinate system according to the sight line inclination angle and the sight line deflection angle;

in particular, according to the formula

Calculating a direction cosine matrix from the reference coordinate system to the sight coordinate system

S12, calculating the component of the velocity vector in the sight line coordinate system based on the direction cosine matrix;

the component of the velocity vector in the line-of-sight coordinate system is

Wherein v is_xL、v_yLAnd v_zLRespectively, represent coordinate components of the velocity vector in the line-of-sight coordinate system.

S13, calculating the total lead angle according to the following formula:

η＝arccos(cosη_ycosη_z)

wherein v is_xL、v_yLAnd v_zLRespectively representing the components, eta, of the velocity vector in three coordinate axes of a line-of-sight coordinate system_zIndicating the angle of advance, eta_yDenotes the lead angle and η denotes the total lead angle.

In practice, the pre-angle fractional constant may take a smaller amount, e.g. Δ_ηAnd 2 degrees can be taken. When total lead angle eta₀＞Δ_ηIf so, judging that the current flight is turning flight, namely judging that the aircraft is turning flight at the moment of predicting the remaining flight currently; otherwise, judging that the current flight behavior is the straight flight.

If the current flight is the turning flight, the turning section is segmented according to the total lead angle and according to a formula

The number of segments in the turn segment is calculated as NumP, and floor (. cndot.) represents rounding down. And sequentially predicting the flight time of each turning section to obtain the residual flight time of the turning section, then calculating the residual straight-line section flight path according to the total front angle of the starting point of the straight-line section and the target distance, segmenting the straight-line section according to the residual straight-line section flight path, and sequentially predicting the flight time of each straight-line section to obtain the residual flight time of the straight-line section, wherein the total residual flight time is the sum of the residual flight time of the turning section and the residual flight time of the straight-line section. Wherein, the starting point of the straight line segment is the end point of the turning segment.

And if the current flight is the straight-line flight, directly segmenting the straight line segment according to the rest straight line segment flight distance. According to the formula

Calculating the range of the rest straight line segment according to a formula

And calculating the number NumL +1 of the sections of the straight line section, and predicting the flight time of each section in sequence to obtain the residual flight time of the straight line section, namely the predicted total residual flight time.

Wherein D is_tcRepresenting the linear distance between the aircraft and the target at the time of prediction of the residual flight, eta representing the total lead angle at the time of prediction of the residual flight, K_NFor the navigation ratio of the proportional guidance method, L represents the remaining straight-line range at the time of performing the remaining flight prediction.

Specifically, the step of predicting the residual flight time of the turning section by adopting segmented iteration or predicting the residual flight time of the straight section by adopting segmented iteration comprises the following steps:

s21, for each segment, obtaining the state variable of the current segment starting point, wherein the state variable comprises a velocity modulus value v_iLine of sight inclination angle theta_L,iView bias angle psi_L,iFront tilt angle eta_z,iLeading deflection angle eta_y,iHeight y of the ground_i；

If the current segment is in the turning segment, the state variable also comprises a total lead angle eta_iAnd a target distance D_tc,i(ii) a If the current segment is in the straight line segment, the state variable further comprises a residual straight line segment range L_i。

If the current flight is the turning flight, for the first segment of the turning segment, the state variable of the starting point is the state value of the residual flight prediction moment, the state variable of the starting point of the first segment of the straight line segment is the state variable of the ending point of the last segment of the turning segment, and the residual straight line segment flight path of the starting point of the first segment of the straight line segment is

D_tc,Nump+1And η_Nump+1Is the distance and total lead angle of the target at the end point of the last segment of the turn.

And if the current flight is the straight-line flight, the state variable of the starting point of the first segment of the straight-line segment is the state value of the residual flight prediction moment.

S22, if the current segment is in the turning segment, according to

Calculating the predicted value of the initial flight time of the current segment

If the current segment is in a straight line segment, then according to

Calculating the predicted value of the initial flight time of the current segment

Wherein, Δ η_iShowing the variation of the total lead angle of the current subsection, delta L showing the variation of the range of the remaining straight-line segment of the current subsection, K_NRepresenting a navigation ratio;

specifically, if the current segment is in the turning segment, the variation Δ η of the total lead angle of the current segment_iCalculated according to the following formula

That is, when i is NumP, that is, the NumP-th segment takes Δ η_i＝-(η_i-NumP·Δ_η) Section 1 to NumP-1, then take Δ η_i＝-Δ_η。

The following process is used to obtain:

to eta_i＝arccos(cosη_y,icosη_z,i) Is differentiated to obtain

And because of

Is provided with

The movement of the aircraft in three-dimensional space thus has the form of movement that

The elimination of a time variable has

Then in the interval t_i,t]Integrate up and simplify to

Thus is provided with

Then on sin eta_tFirst order Taylor expansion, sin η_t＝sinη_i+Δη_t·cosη_tWhen substituted into the former formula have

Then is at

The upper integral can be obtained

According to the formula

Predicting the flight time of the current segment to obtain the initial flight time predicted value of the current segment

If the current segment is in a straight line segment, then according to

Predicting the flight time of the previous segment to obtain the initial flight time predicted value of the current segment

S23, based on the state variable of the current segment initial point, calculating the initial speed change rate of the current segment according to the dynamic equation of the aircraft centroid motion

S24, based on the initial speed change rate

Predicting the initial flight time of the current segment

Correcting to obtain the corrected value of the current sectional flight time

S25, state variable based on current segment starting point and flight time correction value of current segment

Predicting the state variable of the current segmentation end point, wherein the state variable of the current segmentation end point is the state variable of the next segmentation start point;

need to make sure thatIt is noted that if the current segment is the last segment of the straight line segment, the flight time correction value of the current segment is obtained

The total remaining flight time can be obtained and the state variable of the current segment end point is not predicted any more.

Time of flight correction for all segments

As the predicted turn or straight segment residual time of flight.

After step S21, before step S24, the method further includes:

s201, if the current segmentation is in a turning section, calculating a preposed inclination angle eta of a current segmentation end point according to the following formula_z,i+1Leading deflection angle eta_y,i+1And total lead angle η_i+1：

η_y,i+1＝η_y,i+Δη_y,i，η_z,i+1＝η_z,i+Δη_z,i，η_i+1＝arccos(cosη_y,i+1cosη_z,i+1)；

According to the formula

Calculating a target distance D of a current segmentation end point_tc,i+1；

If the current segmentation is in the straight line segment, calculating the remaining straight line segment range L of the current segmentation end point according to the following formula_i+1Front tilt angle eta_z,i+1And a pre-set declination angle eta_y,i+1：

L_i+1＝L_i-ΔL，

Wherein, K_NRepresenting the navigation ratio, Δ_ηRepresenting the lead angle step size constant.

In step S23, based on the state variable of the current segment starting point, calculating the initial speed change rate of the current segment according to the kinetic equation of the aircraft centroid motion, including steps S231-S237:

s231, based on the sight line inclination angle theta_L,iView bias angle psi_L,iFront tilt angle eta_z,iLeading deflection angle eta_y,iAnd velocity modulus v_iCalculating the component of the velocity vector in each coordinate axis in the reference coordinate system; calculating to obtain the ballistic inclination angle theta of the current segment based on the components of the velocity vector on each coordinate axis in the reference coordinate system_i；

Specifically, the ballistic inclination angle θ is calculated according to the following formula:

wherein the content of the first and second substances,

a direction cosine matrix representing the reference coordinate system to the sight coordinate system, v represents the velocity module value, η_zIndicating the angle of advance, eta_zDenotes the lead angle, θ_LIndicating the inclination of the line of sight,. psi_LIndicating declination of line of sight, v_px,v_py,v_pzRespectively representing the components and v of the velocity vector in each axis of the line-of-sight coordinate system_qx,v_qy,v_qzRespectively representing the components of the velocity vector in the respective axes of the reference coordinate system.

The above formula for calculating the ballistic inclination angle θ is expressed as θ ═f_θ(θ_L,ψ_L,η_y,η_z,v)。

The sight line inclination angle theta of the state variable according to the current segment starting point_L,iView bias angle psi_L,iVelocity modulus v_iFront tilt angle eta_z,iAnd a pre-set declination angle eta_y,iWith θ ═ f_θ(θ_L,ψ_L,η_y,η_zV) the initial trajectory inclination angle theta of the current segment can be calculated_i。

S232, if the current subsection is in the turning section, according to a formula

Calculating the component of the current acceleration in a ballistic coordinate system; if the current subsection is in the straight line segment, then according to the formula

Calculating the component of the current acceleration in a ballistic coordinate system;

a_yy representing acceleration in ballistic coordinate system_vComponent of the axis, a_zZ representing acceleration in ballistic coordinate system_vThe component of the axis.

S233, according to the ground height y_iObtaining the atmospheric density rho and the sound velocity aT through interpolation, and obtaining the Mach number through calculation according to the atmospheric density rho and the sound velocity aT

And dynamic pressure

Specifically, according to the American standard atmosphere model, the atmospheric density rho and the speed aT can be obtained through interpolation according to the height of the current subsection from the ground, and according to the method, the atmospheric density rho and the speed aT can be obtained through interpolation

Calculating horseMach number in Hertz, according to

The dynamic pressure is calculated.

S234, calculating the lift coefficient C according to the following formula_Ld,i：

F_y＝MT·g_tc cosθ_i+MT·a_y,i，F_z＝MT·a_z,i

Wherein MT denotes the mass of the aircraft, ST denotes the reference area of the aircraft, g_tcRepresenting the gravitational constant, sign representing a sign function, F_LDenotes total lift, F_yY representing lift in ballistic coordinate system_vComponent of the axis, F_zZ representing lift in ballistic coordinate system_vA component of the axis; according to the calculation principle of the lift force: calculating lift coefficient C_Ld,i。

S235, Mach number and lift coefficient C based on Mach number_Ld,iCalculating an attack angle command alpha by using a Newton iteration method_c,i。

Specifically, the iteration formula of the newton iteration method is:

the initial value of iteration is 5 degrees or alpha₀At 5 deg., the iteration precision meets the precision requirement, e.g., 1e-5, or a maximum number of iterations is reached, e.g., 100, the iteration ends.

Specifically, the function f (α) and the derivative f '(α) used in newton's iteration are as follows:

f(α)＝k_{Cl_00}+k_{Cl_10}α+k_{Cl_01}Mach+k_{Cl_20}α²+k_{Cl_11}α·Mach+k_{Cl_02}Mach²+k_{Cl_30}α³

+k_{Cl_21}α²·Mach+k_{Cl_12}α·Mach²+k_{Cl_03}Mach³+k_{Cl_31}α³·Mach+k_{Cl_22}α²·Mach²

+k_{Cl_13}α·Mach³+k_{Cl_04}Mach⁴+k_{Cl_32}α³·Mach²+k_{Cl_23}α²·Mach³

+k_{Cl_14}α·Mach⁴+k_{Cl_05}Mach⁵-C_Ld

f'(α)＝k_{Cf_00}+k_{Cf_10}α+k_{Cf_01}Mach+k_{Cf_20}α²+k_{Cf_11}α·Mach+k_{Cf_02}Mach²

+k_{Cf_21}α²·Mach+k_{Cf_12}α·Mach²+k_{Cf_03}Mach³+k_{Cf_22}α²·Mach²

+k_{Cf_13}α·Mach³+k_{Cf_04}Mach⁴

wherein k is_{Cl_00}、k_{Cl_10}、k_{Cl_01}、k_{Cl_20}、k_{Cl_11}、k_{Cl_02}、k_{Cl_30}、k_{Cl_21}、k_{Cl_12}、k_{Cl_03}、k_{Cl_31}、k_{Cl_22}、k_{Cl_13}、k_{Cl_04}、k_{Cl_32}、k_{Cl_23}、k_{Cl_14}、k_{Cl_05}，k_{Cf_00}、k_{Cf_10}、k_{Cf_01}、k_{Cf_20}、k_{Cf_11}、k_{Cf_02}、k_{Cf_21}、k_{Cf_12}、k_{Cf_03}、k_{Cf_22}、k_{Cf_13}、k_{Cf_04}Coefficients previously fitted according to the aerodynamic parameters of the aircraft.

Mach number Mach calculated in step S232 and lift coefficient C calculated in step S234_Ld,iSubstituting the above formula to obtain an attack angle instruction alpha through iterative calculation_c,i. The Newton iteration method has high convergence speed, and a relatively accurate numerical solution can be obtained by setting the convergence condition, so that the common calculation is fast and accurateAnd (5) angle of attack instruction.

S236, Mach and attack angle instruction alpha based on Mach number_c,iCalculating the coefficient of resistance C from the fitting equation_D,i；

Specifically, the drag coefficient is calculated according to the following formula:

wherein k is_{tc_00}、k_{tc_10}、k_{tc_01}、k_{tc_20}、k_{tc_11}、k_{tc_02}、k_{tc_30}、k_{tc_21}、k_{tc_12}、k_{tc_03}、k_{tc_40}、k_{tc_31}、k_{tc_22}、k_{tc_13}、k_{tc_04}、k_{tc_50}、k_{tc_}41、k_{tc_32}、k_{tc_23}、k_{tc_14}、k_{tc_05}Coefficients previously fitted according to the aerodynamic parameters of the aircraft. The aerodynamic characteristics of the aircraft are generally described by a large amount of discrete data, and by fitting the data, an approximate fitting relation between a drag coefficient and an attack angle and Mach number can be obtained, so that the method is simple and the calculation speed is high.

Mach number Mach calculated in step S232 and attack angle command alpha calculated in step S236_c,i is substituted into the above formula to obtain a resistance coefficient C by iterative calculation_D,i。

S237, according to the formula

An initial rate of speed change is calculated.

In particular, the kinetic equation according to the movement of the centre of mass of the aircraft

And calculating to obtain an initial speed change rate. The stress of the unpowered aircraft mainly comes from resistance and gravity, so the kinetic equation is expressed as

Wherein

Denotes the influence of resistance on the rate of change of speed, g_tcsinθ_iRepresenting the effect of gravity on the rate of change of speed.

Wherein MT denotes the mass of the aircraft, ST denotes the reference area of the aircraft, g_tcRepresenting the gravitational constant.

The method of calculating the rate of change of speed from step 233 to step 237 is shown as

v denotes the velocity modulus in the reference frame of reference, a_yY representing acceleration in ballistic coordinate system_vComponent of the axis, a_zZ representing acceleration in ballistic coordinate system_vThe component of the axis, θ, represents the ballistic inclination angle and y represents the ground height.

Specifically, step S24 is based on the initial speed change rate

Predicting the initial flight time of the current segment

Correcting to obtain the corrected value of the current sectional flight time

Including steps S241-S244.

S241, based on the initial speed change rate

And the initial time-of-flight prediction value

According to the formula

Get the second of the segment end pointA predicted value v of velocity_p,i；

S242, predicting value v of first speed based on segmentation end point_p,iAnd the initial time-of-flight prediction value

Calculating to obtain a first speed change rate according to a kinetic equation of the mass center motion of the aircraft

Specifically, in step S242, the first speed prediction value v based on the segment end point is_p,iAnd the initial time-of-flight prediction value

Calculating to obtain a first speed change rate according to a kinetic equation of the mass center motion of the aircraft

Includes steps S2421-S2424:

s2421, predicting value v according to first speed_p,iAnd the initial time-of-flight prediction value

Correcting the sight line inclination angle and the sight line deflection angle of the current segment to respectively obtain a first corrected sight line inclination angle theta_Lp,iAnd a first corrected sightline declination psi_Lp,i；

Specifically, a predicted value v is predicted from the first speed_p,iAnd the initial time-of-flight prediction value

Correcting the sight line inclination angle and the sight line deflection angle of the current segment to respectively obtain a first corrected sight line inclination angle theta_Lp,iAnd a first corrected sightline declination psi_Lp,iThe method comprises the following steps:

correcting the sight line inclination angle of the current segment according to the following formula to obtain a first corrected sight line inclination angle theta_Lp,i：

If the current segment is in the turning segment, the method is based on

Calculating initial line of sight inclination angle change rate

And a first modified rate of change of line of sight inclination

If the current segment is in a straight line segment, then according to

Calculating initial line of sight inclination angle change rate

And a first modified rate of change of line of sight inclination

According to the formula

Calculating a first corrected gaze inclination angle θ_Lp,i。

It should be noted that if the current segment is the last segment of the straight line segment, then L is the last segment of the straight line segment _i+10, so the first corrected line-of-sight inclination angle change rate

Directly take 0.

Rate of change of gaze inclination for current segment start point

And a first modified rate of change of line of sight inclination

Averaging to obtain the average inclination angle change rate

Thereby predicting a value based on the initial time of flight

Correcting the sight line inclination angle of the current segment to obtain a first corrected sight line inclination angle theta_Lp,i。

Correcting the view declination angle of the current segment according to the following formula to obtain a first corrected view declination angle psi_Lp,i：

If the current segment is in the turning segment, the method is based on

Calculating initial rate of change of declination angle

And a first modified rate of change of gaze declination

If the current segment is in a straight line segment, then according to

Calculating initial rate of change of declination angle

And a first modified rate of change of gaze declination

According to the formula

Obtaining a first corrected sightline declination psi_Lp,i。

It should be noted that if the current segment is the last segment of the straight line segment, then L is the last segment of the straight line segment _i+10, so the first corrected rate of change of declination

Directly take 0.

S2422, if the current subsection is in the turning section, according to the formula y_p,i＝-D_tc,i+1sin(θ_Lp,i) Calculating to obtain a first corrected ground height y_p,i(ii) a If the current segment is in a straight line segment, then according to the formula y_p,i＝-L_i+1sin(θ_Lp,i) Calculating to obtain a first corrected ground height y_p,i。

S2423, based on the first corrected sight line inclination angle theta_Lp,iFirst corrected view declination psi_Lp,iAnd a first velocity prediction value v_p,iCalculating the components of the first speed vector in each coordinate axis in the reference coordinate system; calculating to obtain a first correction ballistic inclination angle theta based on the components of the first velocity vector in each coordinate axis in the reference coordinate system_p,i；

Specifically, the formula for calculating the ballistic inclination angle θ according to step S231 is expressed as θ ═ f_θ(θ_L,ψ_L,η_y,η_zV) correcting the first line-of-sight inclination angle theta_Lp,iFirst corrected view declination psi_Lp,iFirst speed predicted value v_p,iLeading inclination angle eta of current segmentation end point_z,i+1And the lead angle eta of the current segment end point_y,i+1Carry in f_θCalculating to obtain a first corrected trajectory inclination angle theta_p,i。

Wherein the lead inclination angle eta of the current segment end point_z,i+1And the lead angle eta of the current segment end point_y,i+1May be calculated according to step S201.

S2424, predicting value v based on first speed_p,iFirst corrected ground height y_p,iFirst corrected trajectory inclination angle theta_p,iCalculating to obtain a first corrected speed variation according to a kinetic equation of the mass center motion of the aircraftChemical conversion rate

Specifically, if the current segment is in the turning segment, the formula is followed

Calculating the component of the acceleration in a ballistic coordinate system; if the current subsection is in the straight line segment, then according to the formula

The component of the acceleration in the ballistic coordinate system is calculated.

It should be noted that if the current segment is the last segment of the straight line segment, L is the last segment of the straight line segment_i+1Is 0, so a is not calculated using the above formula_yp,iAnd a_zp,iDirectly connect a to_yp,iAnd a_zp,iIs set to 0.

Wherein the lead inclination angle eta of the current segment end point_z,i+1Leading deflection angle eta of current segmentation end point_y,i+1Target distance D of current segmentation end point_tc,i+1The residual straight-line segment range L of the current segmentation end point_iThe calculation according to step S201 can be obtained according to step S.

Formula for calculating speed change rate in steps S233-S237

The first corrected trajectory inclination angle theta_p,iFirst speed predicted value v_p,i、a_yp,i、a_zp,iAnd a first corrected ground height y_p,iBringing in

Calculating to obtain a first corrected speed change rate

S243, according to the formula

Calculating to obtain a first average correction speed

I.e. the rate of change to the initial speed

And a first corrected speed change rate

Averaging to obtain the average speed change rate

According to the initial velocity v_iAverage rate of change of speed

And initial time-of-flight prediction

Correcting the speed to obtain a first average corrected speed

The accuracy of the estimation is improved by taking the average.

S244, if the current subsection is in the turning section, according to

Calculating current segment flight time correction value

If the current segment is in a straight line segment, then according to

Calculating current segment flight time correction value

According to the obtained first average corrected speed

Recalculating the flight time of the current segment to obtain a current flight time correction value

The line of sight inclination angle, the line of sight deflection angle and the trajectory inclination angle are corrected according to the initial speed change rate, and the predicted value of the flight time is further corrected, so that the prediction is more accurate.

Step S25, based on the state variable of the current segment starting point and the flight time correction value of the current segment

Predicting state variables for the end point of the current segment, including:

s251, according to the initial speed change rate of the current segment

And said current segment time-of-flight correction value

According to the formula

Obtaining a second speed predicted value v of the current segmentation end point_q,i；

And calculating the predicted speed value again according to the corrected estimated flight time value, so that the estimation precision is improved.

S252, second speed predicted value v based on the segment end point_q,iAnd current segment flight time correction value

Calculation from kinetic equations of aircraft centroid motionObtaining a second rate of change of speed

In particular, according to

Calculating a second corrected gaze inclination angle θ_Lq,iAccording to

Calculating to obtain a second declination phi_Lq,i(ii) a According to y_q,i＝-D_tc,i+1sinθ_Lq,iCalculating a second corrected ground height y_q,i；

The formula for calculating the ballistic inclination angle θ according to step S231 is expressed as θ ═ f_θ(θ_L,ψ_L,η_y,η_zV), predicting the second speed v_q,iA second corrected line-of-sight inclination angle theta_Lq,iA second correction of the viewing angle psi_Lq,iLeading inclination angle eta of current segmentation end point_z,i+1And the lead angle eta of the current segment end point_y,i+1Carry in f_θCalculating to obtain a second corrected trajectory inclination angle theta_q,i。

According to the calculation of a in step S2424_yp,iAnd a_zp,iOf formula (a) wherein v_p,iSubstitution to v_q,iCalculating to obtain a_yq,iAnd a_zq,i

Formula for calculating speed change rate in steps S233-S237

Correcting the second trajectory inclination angle theta_q,iThe second speed predicted value v_q,i、a_yq,i、a_zq,iAnd a second corrected ground height y_q,iBringing in

Calculating to obtain a second corrected speed change rate

S253, the initial speed change rate

And a second corrected speed change rate

Averaging to obtain a second average correction speed

S254, correcting the speed based on the second average

Calculating a third velocity prediction value for an end point of the current segment

The third speed predicted value is the predicted speed v of the end point of the current segment_i+1；

S255, according to the sight line inclination angle theta of the current segmentation starting point_L,iVelocity v of the end point of the current segment_i+1And said current segment time-of-flight correction value

Calculating to obtain the sight line inclination angle theta of the end point of the current segment_L,i+1(ii) a The declination phi of the line of sight according to the starting point of the current segment_L,iVelocity v of the end point of the current segment_i+1And said current segment time-of-flight correction value

Calculating to obtain the view declination phi of the end point of the current segment_L,i+1。

Specifically, the current value is calculated according to the following formulaLine of sight inclination theta of segmented end point_L,i+1；

If the current subsection is in the turning section, according to the formula

Calculating a second modified rate of change of gaze inclination

If the current subsection is in the straight line segment, according to the formula

Calculating a second modified rate of change of gaze inclination

According to the formula

Calculating the sight line inclination angle theta of the end point of the current segment_L,i+1。

If the current subsection is in the turning section, according to the formula

Calculating a second modified gaze angle change rate

If the current subsection is in the straight line segment, according to the formula

Calculating a second modified gaze angle change rate

According to the formula

Calculating the gaze offset angle ψ of the end point of the current segment_L,i+1。

S256, if the current subsection is in the turning section, according to the formula y_i+1＝-D_tc,i+1sinθ_L,i+1Calculating the ground height of the end point of the current segment; if the current segment is in a straight line segment, then according to y_i+1＝-L_i+1sinθ_L,i+1Calculating the ground height y of the end point of the current segment_i+1。

By adopting a segmentation mode, the flight time is predicted for each segment, and the time sum of all the segments is the total residual flight time, so that the estimation of the residual flight time under the conditions that the speed of the unpowered aircraft is obviously reduced and the total lead angle is greatly changed is more accurate.

The results of the residual time-of-flight estimation using the prediction method of the present application and other methods are shown in fig. 4. It can be seen that the actual remaining time of flight is a straight line with a slope of-1, and the conventional estimation method and the constant-speed small-angle estimation method obviously estimate that the deviation is large because the speed variation and the large lead angle are not considered. By adopting the residual flight time prediction method provided by the application, the residual flight time estimation curve is approximately superposed with the actual residual flight time curve, the approach degree is higher and higher along with the time lapse, and higher estimation precision is displayed.

In another aspect, an embodiment of the present invention provides a system for predicting remaining flight time of an unpowered aircraft, including the following modules:

the data acquisition module is used for acquiring a target distance, a sight inclination angle, a sight deflection angle and a velocity vector of the aircraft at the current moment, calculating a total lead angle based on the sight inclination angle, the sight deflection angle and the velocity vector, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle;

the turning flight prediction module is used for segmenting the turning section according to the total lead angle and predicting the remaining flight time of the turning section by adopting segmentation iteration if the turning flight is the turning flight; calculating a residual straight-line segment range according to the total front angle of the starting point of the straight-line segment and the target distance, segmenting the straight-line segment according to the residual straight-line segment range, and predicting the residual flight time of the straight-line segment by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time;

and the linear flight prediction module is used for calculating a residual linear section flight distance according to the total lead angle and the target distance if the linear flight is linear flight, segmenting the linear section according to the residual linear section flight distance, and predicting the residual flight time of the linear section by adopting segmentation iteration, wherein the residual flight time of the linear section is the predicted total residual flight time.

The method embodiment and the system embodiment are based on the same principle, and related parts can be referenced mutually, and the same technical effect can be achieved. For a specific implementation process, reference is made to the foregoing embodiments, which are not described herein again.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (10)

1. A method for predicting the remaining flight time of an unpowered aircraft is characterized by comprising the following steps:

acquiring a target distance, a sight line inclination angle, a sight line deflection angle and a velocity vector of the aircraft at the current moment, calculating a total lead angle based on the sight line inclination angle, the sight line deflection angle and the velocity vector, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle;

if the turning flight is adopted, segmenting the turning section according to the total lead angle, and predicting the remaining flight time of the turning section by adopting segmentation iteration; calculating a residual straight-line segment range according to the total front angle of the starting point of the straight-line segment and the target distance, segmenting the straight-line segment according to the residual straight-line segment range, and predicting the residual flight time of the straight-line segment by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time;

and if the straight line section flies, calculating the residual straight line section flight distance according to the total lead angle and the target distance, segmenting the straight line section according to the residual straight line section flight distance, and predicting the residual flight time of the straight line section by adopting segmentation iteration, wherein the residual flight time of the straight line section is the predicted total residual flight time.

2. The unpowered aircraft residual flight time prediction method of claim 1, wherein predicting a turnaround residual flight time using piecewise iteration or predicting a straight line segment residual flight time using piecewise iteration comprises:

for each segment, acquiring a state variable of a current segment starting point, wherein the state variable comprises a velocity modulus value v_iLine of sight inclination angle theta_L,iView bias angle psi_L,iFront tilt angle eta_z,iLeading deflection angle eta_y,iHeight y of the ground_i；

If the current segment is in the turning segment, the state variable also comprises a total lead angle eta_iAnd a target distance D_tc,i(ii) a If the current segment is in the straight line segment, the state variable further comprises a residual straight line segment range L_i；

If the current segment is in the turning segment, the method is based on

Calculating the predicted value of the initial flight time of the current segment

If the current segment is in a straight line segment, then according to

Calculating the predicted value of the initial flight time of the current segment

Wherein, Δ η_iShowing the variation of the total lead angle of the current subsection, delta L showing the variation of the range of the remaining straight-line segment of the current subsection, K_NRepresenting a navigation ratio;

based on the state variable of the current segment initial point, calculating the initial speed change rate of the current segment according to the kinetic equation of the aircraft centroid motion

Based on the initial rate of change of speed

Predicting the initial flight time of the current segment

Correcting to obtain the corrected value of the current sectional flight time

State variable based on current segment starting point and current segment flight time correction value

Predicting the state variable of the current segmentation end point, wherein the state variable of the current segmentation end point is the state variable of the next segmentation start point;

time of flight correction for all segments

As the predicted turn or straight segment residual time of flight.

3. The unpowered aircraft remaining flight time prediction method of claim 2, wherein the initial rate of change of speed is based on

Predicting the initial flight time of the current segment

Correcting to obtain the corrected value of the current sectional flight time

The method comprises the following steps:

based on the initial rate of change of speed

And the initial time-of-flight prediction value

According to the formula

Obtaining a first speed predicted value v of the segmentation end point_p,i；

First velocity prediction value v based on the segment end point_p,iAnd the initial time-of-flight prediction value

Calculating to obtain a first speed change rate according to a kinetic equation of the mass center motion of the aircraft

According to the formula

Calculating to obtain a first average correction speed

If the current segment is in the turning segment, the method is based on

Calculating current segment flight time correction value

If the current segment is in a straight line segment, then according to

Calculating current segment flight time correction value

4. The unpowered aircraft remaining flight time prediction method of claim 3, wherein the first speed prediction value v based on the segment end point is a first speed prediction value v_p,iAnd the initial time-of-flight prediction value

Calculating to obtain a first speed change rate according to a kinetic equation of the mass center motion of the aircraft

The method comprises the following steps:

predicting value v according to first speed_p,iAnd the initial time-of-flight prediction value

Correcting the sight line inclination angle and the sight line deflection angle of the current segment to respectively obtain a first corrected sight line inclination angle theta_Lp,iAnd a first corrected sightline declination psi_Lp,i；

If the current segment is in the turning segment, according to the formula y_p,i＝-D_tc,i+1sin(θ_Lp,i) Calculating to obtain a first corrected ground height y_p,i(ii) a If the current segment is in a straight line segment, then according to the formula y_p,i＝-L_i+1sin(θ_Lp,i) Calculating to obtain a first corrected ground height y_p,i(ii) a Wherein D is_tc,i+1Indicating the target distance, L, of the starting point of the i +1 segment_i+1Representing the residual straight-line range of the starting point of the i +1 section;

based on the first corrected sight line inclination angle theta_Lp,iFirst corrected view declination psi_Lp,iAnd a first velocity prediction value v_p,iCalculating the components of the first speed vector in each coordinate axis in the reference coordinate system; calculating to obtain a first correction ballistic inclination angle theta based on the components of the first velocity vector in each coordinate axis in the reference coordinate system_p,i；

Predicting a value v based on the first speed_p,iFirst corrected ground height y_p,iFirst corrected trajectory inclination angle theta_p,iCalculating to obtain a first corrected speed change rate according to a kinetic equation of the mass center motion of the aircraft

5. The unpowered aircraft remaining flight time prediction method of claim 4, wherein the first velocity prediction value v is based on_p,iAnd the initial time-of-flight prediction value

Correcting the sight line inclination angle and the sight line deflection angle of the current segment to respectively obtain a first corrected sight line inclination angle theta_Lp,iAnd a first corrected sightline declination psi_Lp,iThe method comprises the following steps:

correcting the sight line inclination angle of the current segment according to the following formula to obtain a first corrected sight line inclination angle theta_Lp,i：

If the current segment is in the turning segment, according to

Calculating initial line of sight inclination angle change rate

And a first modified rate of change of line of sight inclination

If the current segment is in a straight line segment, then according to

Calculating initial line of sight inclination angle change rate

And a first modified rate of change of line of sight inclination

According to the formula

Obtaining a first corrected line-of-sight inclination angle theta_Lp,i；

Correcting the view declination angle of the current segment according to the following formula to obtain a first corrected view declination angle psi_Lp,i：

If the current segment is in the turning segment, the method is based on

Calculating initial rate of change of declination angle

And a first modified rate of change of gaze declination

If the current segment is in a straight line segment, then according to

Calculating initial rate of change of declination angle

And a first modified rate of change of gaze declination

According to the formula

Obtaining a first corrected sightline declination psi_Lp,i。

6. The unpowered aircraft remaining flight time prediction method of claim 2, wherein the current segment flight time correction value is based on a state variable of a current segment starting point

Predicting state variables for the end point of the current segment, including:

initial rate of change of speed according to current segment

And said current segment time-of-flight correction value

According to the formula

Obtaining a second speed predicted value v of the current segmentation end point_q,i；

A second velocity prediction value v based on the segment end point_q,iAnd current segment flight time correction value

Calculating to obtain a second speed change rate according to a kinetic equation of the mass center motion of the aircraft

Rate of change to initial speed

And a second corrected speed change rate

Averaging to obtain a second average correction speed

Correcting the velocity based on the second average

Calculating a third velocity prediction for an end point of a current segmentValue of

The third speed predicted value is the predicted speed v of the end point of the current segment_i+1；

According to the sight line inclination angle theta of the current segmentation starting point_L,iVelocity v of the end point of the current segment_i+1And said current segment time-of-flight correction value

Calculating to obtain the sight line inclination angle theta of the end point of the current segment_L,i+1(ii) a The declination phi of the line of sight according to the starting point of the current segment_L,iVelocity v of the end point of the current segment_i+1And said current segment time-of-flight correction value

Calculating to obtain the view declination phi of the end point of the current segment_L,i+1；

If the current segment is in the turning segment, according to the formula y_i+1＝-D_tc,i+1sinθ_L,i+1Calculating the ground height of the end point of the current segment; if the current segment is in a straight line segment, then according to y_i+1＝-L_i+1sinθ_L,i+1The ground height of the end point of the current segment is calculated.

7. The method according to claim 2, wherein the initial speed change rate of the current segment is calculated according to the dynamic equation of the aircraft centroid motion based on the state variable of the current segment starting point

The method comprises the following steps:

based on the line of sight inclination angle theta_L,iView bias angle psi_L,iFront tilt angle eta_z,iLeading deflection angle eta_y,iAnd velocity modulus v_iCalculating velocity vectors at said basisThe component of each coordinate axis in the quasi-reference coordinate system; calculating to obtain the initial ballistic inclination angle theta of the current segment based on the components of the velocity vector on each coordinate axis in the reference coordinate system_i；

If the current subsection is in the turning section, the formula is used

Calculating the component of the acceleration in a ballistic coordinate system; if the current subsection is in the straight line segment, then according to the formula

Calculating the component of the acceleration in a ballistic coordinate system;

according to the ground height y_iObtaining the atmospheric density rho and the sound velocity aT through interpolation, and obtaining the Mach number through calculation according to the atmospheric density rho and the sound velocity aT

And dynamic pressure

The lift coefficient C is calculated according to the following formula_Ld,i：

F_y＝MT·g_tccosθ_i+MT·a_y,i

F_z＝MT·a_z,i

Based on the Mach number Mach and the lift coefficient C_Ld,iCalculating an attack angle command alpha by using a Newton iteration method_c,i；

Mach number and attack angle instruction alpha based on the Mach number_c,iCalculating the coefficient of resistance C from the fitting equation_D,i；

According to the formula

The initial rate of change of the speed is calculated,

wherein MT denotes the mass of the aircraft, ST denotes the reference area of the aircraft, g_tcRepresenting the gravitational constant.

8. The unpowered aircraft remaining flight time prediction method of claim 2, wherein the initial speed change rate is based on after state variables for a current segment starting point are obtained for each segment

Predicting the initial flight time of the current segment

Before the correction, the method further comprises the following steps:

if the current subsection is in the turning section, calculating the preposed inclination angle eta of the current subsection end point according to the following formula_z,i+1Leading deflection angle eta_y,i+1And total lead angle η_i+1：

η_y,i+1＝η_y,i+Δη_y,i

η_z,i+1＝η_z,i+Δη_z,i

η_i+1＝arc cos(cosη_y,i+1cosη_z,i+1)；

According to the formula

Calculating a target distance D of a current segmentation end point_tc,i+1；

If the current segmentation is in the straight line segment, calculating the remaining straight line segment range L of the current segmentation end point according to the following formula_i+1Front tilt angle eta_z,i+1And a pre-set declination angle eta_y,i+1：

L_i+1＝L_i-ΔL

Wherein, K_NRepresenting the navigation ratio, Δ_ηDenotes the lead angle segmentation quantity constant and NumP denotes the number of segments of the turnaround segment.

9. The unpowered aircraft remaining time of flight prediction method of claim 1, wherein calculating a total lead angle based on the line-of-sight inclination, line-of-sight declination, and velocity vector comprises:

calculating a direction cosine matrix from the reference coordinate system to the sight line coordinate system according to the sight line inclination angle and the sight line deflection angle;

calculating a component of the velocity vector in the line of sight coordinate system based on the direction cosine matrix;

the total lead angle is calculated according to the following formula:

η＝arc cos(cosη_ycosη_z)

wherein v is_xL、v_yLAnd v_zLRespectively representing the components, eta, of the velocity vector in three coordinate axes of a line-of-sight coordinate system_zIndicating the angle of advance, eta_yDenotes the lead angle and η denotes the total lead angle.

10. A system for predicting time-of-flight remaining for an unpowered aircraft, comprising:

the data acquisition module is used for acquiring a target distance, a sight inclination angle, a sight deflection angle and a velocity vector of the aircraft at the current moment, calculating a total lead angle based on the sight inclination angle, the sight deflection angle and the velocity vector, and judging whether the current flight behavior is turning flight or straight flight according to the total lead angle;

the turning flight prediction module is used for segmenting the turning section according to the total lead angle and predicting the remaining flight time of the turning section by adopting segmentation iteration if the turning flight is the turning flight; calculating a residual straight-line segment range according to the total front angle of the starting point of the straight-line segment and the target distance, segmenting the straight-line segment according to the residual straight-line segment range, and predicting the residual flight time of the straight-line segment by adopting segmentation iteration; the sum of the turn section residual flight time and the straight section residual flight time is the predicted total residual flight time;

and the linear flight prediction module is used for calculating a residual linear section flight distance according to the total lead angle and the target distance if the linear flight is linear flight, segmenting the linear section according to the residual linear section flight distance, and predicting the residual flight time of the linear section by adopting segmentation iteration, wherein the residual flight time of the linear section is the predicted total residual flight time.

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