CN102139768A - Reentry flight attack angle guiding method of sub-orbital vehicle - Google Patents

Abstract

The invention discloses a reentry flight attack angle guiding method of a sub-orbital vehicle. The method comprises the following steps of: acquiring an attack angle design predicted value through analogue simulation at time intervals; finding the attack angle design predicted value, which keeps a normal overload value of the vehicle always in a fluctuation region of expected normal overload dynamic balance, by using a vehicle homomorphic prediction model in each time interval, so as to realize normal overload dynamic balance at the time interval; acquiring a practical reentry flight attack angle design parameter of the vehicle through the attack angle design predicted value by a fitting method, and determining a reentry flight attack angle design value of the vehicle; and introducing resistance acceleration integration ratio correction at each flight time to make a practical reentry flight resistance acceleration integral value tend to be the same as a predicted resistance acceleration integral value under the attack angle design value, so the reentry flight normal overload of the sub-orbital vehicle is kept to fluctuate in a predetermined region in a dynamic balance section consisting of each time interval and then the aim of reducing the reentry flight normal overload peak value of the sub-orbital vehicle is fulfilled.

Description

A kind of inferior orbital vehicle reenters the angle of attack method of guidance of flight

Technical field

The present invention relates to guide the control technology field, particularly relate to the angle of attack method of guidance that a kind of inferior orbital vehicle reenters flight.

Background technology

The product that inferior orbital vehicle organically combines as aeronautics and space, possessing can either provide regional coverage, helps emergent the delivery and the rapid-action application advantage again, its zone of action---near space both was in can threaten spacecraft, the sensitizing range of aerospace activity be can restrict again, the new focus in aerospace studies field and the growth point of strategic hightech become.

Aircraft reenter flight be meant spacecraft or aerocraft from earth atmosphere outside or the edge reenter earth atmosphere inside until the landing flight course.

The existing similarity of flight that reenters that reenters flight course and space shuttle of inferior orbital vehicle has different qualities again, and resemblance is: all stride the atmospheric flight that reenters, the flight dynamics that reenters is described also basically identical; Difference is: it reenters the characteristic difference of Atmospheric processes.

(speed 3～10Ma) reenters the kinetic energy (speed 25Ma) at initial stage to the flight kinetic energy of inferior orbital vehicle much smaller than space shuttle, make inferior orbital vehicle as space shuttle, not obtain enough lift and realize the balance glide, cause it to reenter flying height and descend rapidly at higher atmosphere edge.Along with highly descending, atmospheric density sharply rises, cause overload, hot-fluid, the dynamic pressure peak value of inferior orbital vehicle to occur simultaneously (with space shuttle elder generation hot-fluid, after carry, the syllogic peak feature of last dynamic pressure is different fully).Wherein, transship particularly evident that normal g-load particularly increases.

Though the reentry velocity of inferior orbital vehicle is low, it reenters the process hot-fluid and reenters hot-fluid less than space shuttle, and transshipping particularly, normal g-load exceeds space shuttle more than one times.When normal g-load was big, the airborne personnel of aircraft and equipment needed to bear bigger overload, and the bearing capacity of airborne personnel and equipment is had relatively high expectations; Simultaneously, the suffered shearing force of the body of aircraft is bigger, is easy to generate distortion, even fractures, and for guaranteeing flight safety, need reinforce or adopt new material to aircraft, causes the research of inferior orbital vehicle and operating cost to increase considerably.

Therefore, the reduction normal g-load is particularly important for inferior orbital vehicle.And the key that reduces the direction overload is that aircraft reenters the design and the guidance of the angle of attack.

Guidance is meant that guiding and controlling aircraft fly to the technology and the method for target or planned orbit according to certain rule.For aircraft reenters angle of attack guidance in the process, make exactly to reenter the angle of attack and adjust according to certain rule, reach the flight requirement of aircraft.Concrete, by angle of attack design being obtained designing angle of attack expected value, according to certain rule this design angle of attack expected value is revised then, obtain angle of attack guidance value.This shows that the design angle of attack guides the angle of attack and plays crucial effects.

At present, the design plan that inferior orbital vehicle is reentered the angle of attack is continued to use space shuttle more and is reentered method of designing when returning, the angle of attack is designed to the linear function of speed or time, by analyzing the reentry corridor among the D-V figure (drag acceleration-velocity diagram) under this angle of attack scheme, determine the design angle of attack.With the angle of attack-speed is example, the functional relation between the two can for:

$\mathrm{\&alpha;}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">V</figure-callout>}}_1\\ {\mathrm{\&alpha;}}_0-\frac{{\mathrm{\&alpha;}}_0-{\mathrm{\&alpha;}}_{\mathrm{end}}}{V_1-V_2}& {\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">V</figure-callout>}}_1\&GreaterEqual;V\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;V_2\end{array}\right.---\left(1\right)$

In the formula (1): α is the design angle of attack; α ₀Be design angle of attack initial value; α _EndBe design angle of attack expected value; V ₁The initial value of aircraft speed when beginning to adjust for the design angle of attack; V ₂For the design angle of attack is adjusted to α _EndThe time aircraft speed value; V is the aircraft flight velocity amplitude.

In the formula (1), when aircraft began to reenter, the design angle of attack kept described design angle of attack initial value α ₀, when aircraft real-time speed value V reaches the initial value V of design angle of attack aircraft speed when beginning to adjust ₁The time, the beginning with

For descending slope is adjusted, reach described design angle of attack expected value α until the design angle of attack _End

The contriver finds in research process, existing angle of attack method of designing, the descending slope of angle of attack adjustment is a fixed value, make the relatively low inferior orbital vehicle of speed reenter that normal g-load is presented as unimodal characteristics or bimodal characteristics in the process, and the normal g-load peak value is bigger.Therefore, the angle of attack method of guidance based on existing angle of attack method of designing has the excessive problem of normal g-load peak value too.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of inferior orbital vehicle to reenter the angle of attack method of guidance of flight, can reduce aircraft and reenter normal g-load peak value in the process.

The angle of attack method of guidance that the embodiment of the invention provides a kind of inferior orbital vehicle to reenter flight may further comprise the steps:

Step 1, the reentering before the flight of aircraft, obtain the design value that reenters the angle of attack, the described design value that reenters the angle of attack is expressed as:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ {\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="h\; V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">h</figure-callout>}}& V_{}{}_1\&GreaterEqual;V\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\end{array}\right.$

Wherein, α _DesFor reentering the design value of the angle of attack; α ₀Be design angle of attack initial value; α _EndBe design angle of attack expected value; V ₁The initial value of aircraft speed when beginning to adjust for the design angle of attack; V ₂For the design angle of attack is adjusted to α _EndThe time aircraft speed value; b ₁, b ₂, b ₃, b ₄Be angle of attack design ratio, V is the aircraft flight velocity amplitude, and h is the aircraft altitude value;

Step 2, utilize aircraft to reenter flight model and aircraft homomorphic predication model, calculate and adopt this to reenter the design value α of the angle of attack _DesWhen reentering flight, each flight is cooresponding drag acceleration predictor constantly

Step 3, reenter in the flight course, measure the drag acceleration D (t) of aircraft current time t in real time, in conjunction with described drag acceleration predictor at aircraft Calculate the coefficient of correction η (t) of the cooresponding design angle of attack of current time t, be specially:

$\mathrm{\&eta;}\left(t\right)=\frac{\underset{t_0}{\overset{t}{\&Integral;}}\hat{D}\left(t\right)\mathrm{dt}}{\underset{t_0}{\overset{t}{\&Integral;}}D\left(t\right)\mathrm{dt}}$

Wherein, t ₀Be meant the initial moment of flying that reenters of aircraft;

Step 4, measure current flying speed v of aircraft (t) and flying height h (t) in real time, utilize the coefficient of correction η (t) of the described current design angle of attack, the design value that reenters the angle of attack that obtains in the step 1 is revised, obtain angle of attack guidance value α _Cmd:

${\mathrm{\&alpha;}}_{\mathrm{cmd}}=({\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v\left(t\right)+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right).$

Preferably, after step 4, also comprise:

Step 5, according to design angle of attack initial value α ₀B1 revises to angle of attack design ratio, makes revised angle of attack design ratio

Satisfy: when aircraft reenters flying speed is V ₁The time,

Wherein, h ₁For aircraft reenters flying speed is V ₁The time cooresponding flying height, t ₁For aircraft reenters flying speed is V ₁The time cooresponding flight constantly;

Concrete, can adopt following formula that angle of attack design ratio b1 is revised:

$b_1^{\&prime;}=\left\{\begin{array}{cc}{b}_1^{\mathrm{start}}& t=t_1\\ b_1^{\mathrm{start}}+{\&Integral;}_{t_1}^{\mathrm{<figure-callout\; id="1"\; label="t\; b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}\frac{b_{}}{}\frac{{}_1\&times;\mathrm{\&eta;}\left(t\right)-{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\mathrm{start}}}{\mathrm{\&Delta;T}-(t-t_1)}\mathrm{<figure-callout\; id="1"\; label="dt\; t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">dt</figure-callout>}& t_{}{}_1<t<{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_1+\mathrm{\&Delta;<figure-callout\; id="1"\; label="T\; b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">T</figure-callout>}& \\ b_{}{}_1\&times;\mathrm{\&eta;}\left(t\right)& t\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_1+\mathrm{\&Delta;T}\end{array}\right.$

Wherein,

Δ T is predefined adjustment time gap;

Step 6, according to described revised angle of attack design ratio

Obtain revised angle of attack guidance value

${\mathrm{\&alpha;}}_{\mathrm{cmd}}^{\&prime;}={\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\&prime;}+({\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v\left(t\right)+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right).$

Preferably, the step 1 in the described method comprises:

Step 11: utilize aircraft to reenter flight model and aircraft homomorphic predication model, each flight angle of attack that reenters constantly that obtains under the aircraft normal g-load kinetic balance condition designs predictor

Step 12: reenter the analog simulation of flight model by aircraft, obtain each flight of aircraft cooresponding flying speed and flying height constantly;

Step 13: utilize method of least square, design predictor according to each flight angle of attack that reenters constantly

Flying speed and flying height, in conjunction with following expression formula, match obtains the expression formula of angle of attack design value:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ {\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="h\; V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">h</figure-callout>}}& V_{}{}_1\&GreaterEqual;V\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\end{array}\right..$

Preferably, the step 11 in the described method comprises:

Set up aircraft and reenter the homomorphic predication model that flight model and aircraft reenter flight, utilize the state of flight that reenters that reenters flight model simulated flight device, reentering flight model is that variable calculates with time; The described initial condition that reenters flight model and forecast model is initial moment t _InitCooresponding aircraft state;

Utilize described aircraft homomorphic predication model, prediction is from initial moment t _InitBeginning, initial value α to preset _InitBe the predictive designs angle of attack Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of the normal g-load that presets N _{N_want}Moment t _{1_ α}

From i=1, α ₀=α _InitRise and carry out following steps:

Step 111: when the individual again flight model of aircraft moves to t _{I_ α}In the time of constantly, from reenter flight model, obtain aircraft and reenter and fly to t _{I_ α}Angle of attack value constantly

Utilize aircraft homomorphic predication model, prediction is with aircraft t _{I_ α}State of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first normal g-load peak value of the i of aircraft

Wherein,

Work as i=1,

k _InitBe angle of attack descending slope initial value, k _Init〉=0;

Step 112: the first normal g-load peak value of more described i

With the dynamically balanced fluctuation of the normal g-load of expectation zone [N _{N_want}± Δ N _n], according to comparative result to the predictive designs angle of attack Descending slope

Adjust, up to the first normal g-load peak value of described i

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding predictive designs angle of attack this moment

Descending slope k _{_ α _ i}Described Δ N _nBe the normal g-load fluctuation limits value that presets;

Step 113: utilize aircraft homomorphic predication model, prediction is with t _{I_ α}Constantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _I-1-k _{_ α _ i}(t-t _{I_ α}) be the predictive designs angle of attack When reentering flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{I+1_ α}

Step 114: set [t _{I_ α}, t _{I+1_ α}] in the time period, angle of attack design predictor

Be α _I-1-k _{_ α _ i}(t-t _{I_ α});

Step 115: as described descending slope k _{_ α _ i}Smaller or equal to default k ₀The time, the normal g-load kinetic balance of aircraft finishes, process ends; Otherwise i adds 1, returns step 111.

Preferably, described method also comprises: when i more than or equal to 2 the time, to t _{I+1_ α}Renewal, be specially:

At [t _{I_ α}, t _{I+1_ α}] in the time period, constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with α _I-1-k _{_ α _ i}(t-t _{I_ α}) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment

With As the t after upgrading _{I+1_ α}

Preferably, during and if only if i=1, setting and adjusting Timing Advance is Δ t _α, at [t _Init, (t _{1_ α}-Δ t _α)] in the time period, aircraft reenters the predictive designs angle of attack of flight

Equal initial value α _Init

When reentering flight model, aircraft moves to t _{1_ α}-Δ t _αIn the time of constantly, utilize aircraft homomorphic predication model, prediction is with aircraft t _{1_ α}-Δ t _αState of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first first normal g-load peak value of aircraft

The more described first first normal g-load peak value

With the dynamically balanced fluctuation of the normal g-load of described expectation zone [N _{N_want}± Δ N _n], according to comparative result to the predictive designs angle of attack

Descending slope k _{_ α}Adjust, up to the described first first normal g-load peak value Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding predictive designs angle of attack this moment

Descending slope k _{_ α _ 1}

Utilize aircraft homomorphic predication model, prediction is with t _{1_ α}-Δ t _αConstantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the described first first normal g-load peak value

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{2_ α}

Set [t _{1_ α}-Δ t _α, t _{2_ α}] in the time period, angle of attack design predictor

Be α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α).

Preferably, described method also comprises: when i=1, to t _{1_ α}Renewal, be specially:

At t _Init≤ t≤(t _{1_ α}-Δ t _α) in, constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with initial value α _InitBe the predictive designs angle of attack

Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}The moment

With As the t after upgrading _{1_ α}

Preferably, in the described method described in the step 112 according to comparative result to the predictive designs angle of attack Descending slope

Adjust, be specially:

If

Increase the predictive designs angle of attack

Descending slope

If

Reduce the predictive designs angle of attack

Descending slope

Preferably, described increase or reduce the predictive designs angle of attack

Descending slope Be specially:

To the described predictive designs angle of attack

Descending slope

Increase or reduce a default adjustment amount Δ k _{_ α}

According to specific embodiment provided by the invention, the invention discloses following technique effect:

The described method of the embodiment of the invention, at first pass through analogue simulation, time segment is to obtaining angle of attack design-calculated predictor, for each time period, utilize aircraft homomorphic predication model, find the interior angle of attack design predictor in the dynamically balanced fluctuation of normal g-load zone that makes the normal g-load value of aircraft be in expectation all the time, realize the normal g-load dynamical equilibrium in this time period; Utilize approximating method subsequently, obtain the angle of attack design parameters that aerocraft real reenters flight, determine that aircraft reenters the flying drilling angle design value by angle of attack design predictor; Constantly introduce the drag acceleration integration than revising in each flight then, make actual reenter the drag acceleration integrated value of flight and the prediction drag acceleration integrated value advolution under the angle of attack design value, and then make aircraft reenter the normal g-load realization dynamical equilibrium of flight, reach the guidance purpose of normal g-load dynamical equilibrium.

Adjusting descending slope with the unique fixing angle of attack of available technology adopting compares, can make normal g-load fluctuation within a narrow range in the fluctuation zone of expectation in each time period, make normal g-load by single/bimodally become flat peak, realized the normal g-load kinetic balance in each time period, reached and reduce the purpose that aircraft reenters the normal g-load peak value in the process.

Description of drawings

Fig. 1 reenters the angle of attack method of guidance diagram of circuit of flight for the inferior orbital vehicle of the embodiment of the invention one;

Fig. 2 reenters the angle of attack method of guidance diagram of circuit of flight for the inferior orbital vehicle of the embodiment of the invention two;

Aircraft reentered the height and the speed evolution diagram of flight when Fig. 3 carried out emulation for adopting the inventive method;

Fig. 4 is the cooresponding design angle of attack of aircraft in the overload kinetic balance time period shown in Figure 3, speed angle of heel and normal g-load evolution diagram;

Fig. 5 is a comparison chart after the cooresponding design angle of attack of aircraft in the overload kinetic balance time period shown in Figure 3, speed angle of heel and the match that designs the angle of attack;

Fig. 6 a to Fig. 6 f is actual flight normal g-load and design normal g-load, the differential chart of the aircraft normal g-load under normal g-load kinetic balance condition of reentering shown in Figure 3.

The specific embodiment

For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

In view of this, the object of the present invention is to provide a kind of inferior orbital vehicle to reenter the angle of attack method of guidance of flight, can reduce aircraft and reenter normal g-load peak value in the process.

Reenter in the flight course at inferior orbital vehicle, but its aerodynamic force approximate expression is:

$\left\{\begin{array}{c}F=\sqrt{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">L</figure-callout>}}^2+D^2}\\ L=\frac{1}{2}\mathrm{\&rho;}{v}^{2}S*\mathrm{cl}\\ D=\frac{1}{2}\mathrm{\&rho;}{v}^{2}S*\mathrm{cd}\end{array}\right.---\left(2\right)$

Wherein, F is the suffered aerodynamic force of aircraft; L is an aerodynamic lift; D is an aerodynamic drag; S is the aircraft reference area; V is an aircraft flight speed; ρ is an atmospheric density; Cl, cd are aerodynamic parameter, are respectively lift coefficient and drag coefficient, all with the positive correlation of angle of attack size.

According to formula (2) as can be known, because aerodynamic parameter cl, cd and angle of attack positive correlation, the reducing of the angle of attack can cause reducing of aerodynamic force F; The reducing of aircraft flight speed V can cause that also aerodynamic force F reduces.And aircraft reenters in the process, and along with the rapid decline of height, atmospheric density ρ is exponential type to be increased, and makes aerodynamic force F increase sharply.

In the existing angle of attack method of designing, the angle of attack is designed to the linear function of speed.When angle of attack descending slope hour because aerodynamic parameter cl and cd be proportionate with the angle of attack, bigger aerodynamic parameter makes aircraft reenter and in earlier stage is subjected to bigger aerodynamic force F, flying speed V reduces rapidly, its normal g-load presents " unimodal " characteristics; When angle of attack descending slope is big, aerodynamic parameter cl and cd reduce rapidly, compensated the influence of the atmospheric density ρ of increase to a certain extent to aerodynamic force F, but, owing to reenter and do not obtain enough velocity attenuations early stage, after aircraft enters dense atmosphere, its normal g-load will increase once more fast, present " bimodal " characteristics.

The described method of the embodiment of the invention, by adjusting the angle of attack, the aerodynamic force F that the aerodynamic force F that the feasible aerodynamic force F that is reduced to cause by the angle of attack reduces, flying speed V decay causes reduces and atmospheric density ρ increase causes is increased on the aircraft body normal direction and reaches balance, make near normal g-load fluctuation within a narrow range a certain setting value, make normal g-load by single/bimodal flat peak, realization normal g-load kinetic balance process of becoming.By prolonging the time length of kinetic balance process, reach and reduce the purpose that aircraft reenters the normal g-load peak value in the process then.

Reentering in the flight course of aircraft, its normal g-load generally can be expressed as:

$N_n=\frac{F_n}{G}=\frac{L\cos \mathrm{\&alpha;}+D\sin \mathrm{\&alpha;}}{G}=\frac{\mathrm{\&rho;}{V}^2(C_l\cos \mathrm{\&alpha;}+C_d\sin \mathrm{\&alpha;})}{2G}---\left(3\right)$

Wherein, N _nBe aircraft normal g-load value; F _nBe the suffered normal component of aerodynamic force F on the aircraft body of aircraft; L is an aerodynamic lift; D is an aerodynamic drag; V is an aircraft flight speed; ρ is an atmospheric density; α is an angle of attack value; G is the suffered gravity of aircraft, equals the product of vehicle mass and local gravitational acceleration.

By formula (3) as seen, influence certain aircraft normal g-load value N constantly _nPrincipal parameter have: angle of attack value α (being proportionate), aircraft flight speed V and atmospheric density ρ with aerodynamic parameter cl and cd.

Wherein, when the flying height of aircraft is in 120km, to atmospheric density ρ differentiate in height:

$\frac{\&PartialD;\mathrm{\&rho;}}{\&PartialD;h}=-\frac{1}{H_s}{e}^{-\frac{h}{H_s}}---\left(4\right)$

Wherein, H _sBeing a steady state value, is 7320.

By formula (4) as seen, along with height h descends, atmospheric density ρ is exponential type to be increased.

For realizing normal g-load value N _nNear fluctuation within a narrow range a certain setting value reaches and reduces the purpose that aircraft reenters the normal g-load peak value in the process, and the present invention is designed to the angle of attack in the angle of attack method of guidance:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ {\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="h\; V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">h</figure-callout>}}& V_{}{}_1\&GreaterEqual;V\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;V_2\end{array}\right.---\left(5\right)$

Wherein, α _DesBe the design angle of attack; α ₀Be design angle of attack initial value; α _EndBe design angle of attack expected value; V ₁The initial value of aircraft speed when beginning to adjust for the design angle of attack; V ₂For the design angle of attack is adjusted to α _EndThe time aircraft speed value; b ₁, b ₂, b ₃, b ₄Be angle of attack design ratio, V is the aircraft flight velocity amplitude, and h is the aircraft altitude value.

In the formula (5), when aircraft begins to reenter flight, the design angle of attack _DesKeep described design angle of attack initial value α ₀, the initial value V of aircraft speed when aircraft flight velocity amplitude V reaches the described design angle of attack and begins to adjust ₁The time, the design angle of attack _DesBeginning with

Adjust, until the design angle of attack _DesReach described design angle of attack expected value α _End

It should be noted that setting: when aircraft reenters flying speed is V ₁, cooresponding flying height is h ₁The time,

When aircraft speed reenters flying speed is V ₂, cooresponding flying height is h ₂The time,

With reference to Fig. 1, reenter the angle of attack method of guidance diagram of circuit of flight for the embodiment of the invention one described inferior orbital vehicle.Said method comprising the steps of:

Step S10:, obtain the design value that reenters the angle of attack reentering before the flight of aircraft; The described design value that reenters the angle of attack can be expressed as:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ {\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="h\; V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">h</figure-callout>}}& V_{}{}_1\&GreaterEqual;V\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;V_2\end{array}\right.---\left(5\right)$

Wherein, α _DesFor reentering the design value of the angle of attack; α ₀Be design angle of attack initial value; α _EndBe design angle of attack expected value; V ₁The initial value of aircraft speed when beginning to adjust for the design angle of attack; V ₂For the design angle of attack is adjusted to α _EndThe time aircraft speed value; b ₁, b ₂, b ₃, b ₄Be angle of attack design ratio, V is the aircraft flight velocity amplitude, and h is the aircraft altitude value.

Concrete, about obtaining angle of attack design ratio b ₁, b ₂, b ₃, b ₄Detailed process, content is introduced in detail in the back.

Step S20: utilize aircraft to reenter flight model and aircraft homomorphic predication model, calculate and adopt this to reenter the design value α of the angle of attack _DesWhen reentering flight, each flight is cooresponding drag acceleration predictor constantly

Described aircraft reenters flight model and the homomorphic predication model mainly comprises: aircraft reenters flight path dynam and kinematical equation; Aircraft body parameter, as vehicle mass, reference area, the mapping table of liter, drag coefficient and the angle of attack and flying speed etc.

Consider that the earth is an ellipsoid, adopt the acoustic velocity value under exponential atmosphere rate and the standard atmosphere, under earth rotating coordinate system, set up aircraft and reenter flight path dynam and kinematical equation:

$\frac{\mathrm{dr}}{\mathrm{dt}}=v\sin \mathrm{\&gamma;}---\left(6\right)$

$\frac{\mathrm{d\&lambda;}}{\mathrm{dt}}=\frac{v\cos \mathrm{\&gamma;}\cos \mathrm{\&xi;}}{r\cos \mathrm{\&psi;}}---\left(7\right)$

$\frac{\mathrm{d\&psi;}}{\mathrm{dt}}=\frac{v\cos \mathrm{\&gamma;}\sin \mathrm{\&xi;}}{r}---\left(8\right)$

$\frac{\mathrm{dv}}{\mathrm{dt}}=-\frac{1}{m}D-g_r\sin \mathrm{\&gamma;}+{\mathrm{\&omega;}}^{2}r\cos \mathrm{\&psi;}(\sin \mathrm{\&gamma;}\cos \mathrm{\&psi;}---\left(9\right)$

$-\cos \mathrm{\&gamma;}\sin \mathrm{\&xi;}\sin \mathrm{\&psi;})$

$v\frac{\mathrm{d\&gamma;}}{\mathrm{dt}}=\frac{1}{m}L\cos \mathrm{\&sigma;}-g_r\cos \mathrm{\&gamma;}+\frac{v^2}{r}\cos \mathrm{\&gamma;}+2\mathrm{\&omega;}v\cos \mathrm{\&xi;}\cos \mathrm{\&psi;}---\left(10\right)$

$+{\mathrm{\&omega;}}^{2}r\cos \mathrm{\&psi;}(\cos \mathrm{\&gamma;}\cos \mathrm{\&psi;}+\sin \mathrm{\&gamma;}\sin \mathrm{\&xi;}\sin \mathrm{\&psi;})$

$v\frac{\mathrm{d\&xi;}}{\mathrm{dt}}=-\frac{1}{m}\&CenterDot;\frac{L\sin \mathrm{\&sigma;}}{\cos \mathrm{\&gamma;}}-\frac{v^2}{r}\cos \mathrm{\&gamma;}\cos \mathrm{\&xi;}\tan \mathrm{\&psi;}$

$+2\mathrm{\&omega;v}(\tan \mathrm{\&gamma;}\sin \mathrm{\&xi;}\cos \mathrm{\&psi;}-\sin \mathrm{\&psi;})---\left(11\right)$

$-\frac{{\mathrm{\&omega;}}^{2}r}{\cos \mathrm{\&gamma;}}\cos \mathrm{\&psi;}\sin \mathrm{\&psi;}\cos \mathrm{\&xi;}-g_{\mathrm{\&psi;}}\frac{\sin \mathrm{\&xi;}\cos \mathrm{\&xi;}}{\cos \mathrm{\&gamma;}}$

Wherein: γ, ξ are respectively flight path angle and flight path drift angle; ψ, λ are respectively geographic latitude and geographic longitude; σ is the aircraft speed angle of heel; L is an aerodynamic lift; D is an aerodynamic drag; M is a vehicle mass; V is an aircraft flight speed; R is the distance in aircraft and the earth's core; g _rBe gravitational acceleration component; ω is a rotational-angular velocity of the earth.

Need to prove, utilize described aircraft to reenter flight model and aircraft homomorphic predication model, calculate the common practise that each cooresponding drag acceleration value of the flight moment is this area when adopting certain angle of attack value to reenter flight, be not described in detail in this.

Step S30: reenter in the flight course at aircraft, measure the drag acceleration D (t) of aircraft current time t in real time, in conjunction with described drag acceleration predictor

Calculate the coefficient of correction η (t) of the cooresponding design angle of attack of current time t.

Wherein, the coefficient of correction η (t) of the current design angle of attack can calculate by following formula:

$\mathrm{\&eta;}\left(t\right)=\frac{\underset{t_0}{\overset{t}{\&Integral;}}\hat{D}\left(t\right)\mathrm{dt}}{\underset{t_0}{\overset{t}{\&Integral;}}D\left(t\right)\mathrm{dt}}---\left(12\right)$

Wherein, t ₀Be meant the initial moment of flying that reenters of aircraft.

Step S40: measure current flying speed v of aircraft (t) and flying height h (t) in real time, utilize the coefficient of correction η (t) of the described current design angle of attack, the design value that reenters the angle of attack that obtains among the step S10 is revised, obtain angle of attack guidance value α _Cmd

${\mathrm{\&alpha;}}_{\mathrm{cmd}}=({\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v\left(t\right)+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right)---\left(13\right)$

The embodiment of the invention one described method, at first by analogue simulation, time segment is to obtaining angle of attack design-calculated predictor, for each time period; Utilize aircraft homomorphic predication model, find the interior angle of attack design predictor in the dynamically balanced fluctuation of normal g-load zone that makes the normal g-load value of aircraft be in expectation all the time, realize the normal g-load dynamical equilibrium in this time period; Utilize approximating method subsequently, obtain the angle of attack design parameters that aerocraft real reenters flight, determine that aircraft reenters the flying drilling angle design value by angle of attack design predictor; Constantly introduce the drag acceleration integration than revising in each flight then, make actual reenter the drag acceleration integrated value of flight and the prediction drag acceleration integrated value advolution under the angle of attack design value, and then make aircraft reenter the normal g-load realization dynamical equilibrium of flight, reach the guidance purpose of normal g-load dynamical equilibrium.

Adjusting descending slope with the unique fixing angle of attack of available technology adopting compares, can make normal g-load fluctuation within a narrow range in the fluctuation zone of expectation in each time period, make normal g-load by single/bimodally become flat peak, realized the normal g-load kinetic balance in each time period, reached and reduce the purpose that aircraft reenters the normal g-load peak value in the process.

In order to satisfy design condition, can also revise angle of attack design ratio b1 in the method for the invention, make revised angle of attack design ratio

Can satisfy the flight design-calculated condition that reenters.With reference to Fig. 2, reenter the angle of attack method of guidance diagram of circuit of flight for the embodiment of the invention two described inferior orbital vehicles.

As shown in Figure 2, in the embodiment of the invention two described methods, step S10 is identical with embodiment one described method to step S40, does not repeat them here.Embodiment two is that with the difference of embodiment one described method after step S40, described method also comprises:

Step S50: according to design angle of attack initial value α ₀B1 revises to angle of attack design ratio, makes revised angle of attack design ratio

Satisfy: when aircraft reenters flying speed is V ₁The time, Wherein, h ₁For aircraft reenters flying speed is V ₁The time cooresponding flying height, t ₁For aircraft reenters flying speed is V ₁The time cooresponding flight constantly.

Concrete, can adopt following formula that angle of attack design ratio b1 is revised:

${\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\&prime;}=\left\{\begin{array}{cc}{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\mathrm{start}}& t=t_1\\ b_1^{\mathrm{start}}+{\&Integral;}_{t_1}^{\mathrm{<figure-callout\; id="1"\; label="t\; b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}\frac{b_{}}{}\frac{{}_1\&times;\mathrm{\&eta;}-{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\mathrm{start}}}{\mathrm{\&Delta;T}-(t-t_1)}\mathrm{<figure-callout\; id="1"\; label="dt\; t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">dt</figure-callout>}& t_{}{}_1<t<{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_1+\mathrm{\&Delta;<figure-callout\; id="1"\; label="T\; b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">T</figure-callout>}& \\ b_{}{}_1\&times;\mathrm{\&eta;}\left(t\right)& t\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_1+\mathrm{\&Delta;T}\end{array}\right.---\left(14\right)$

Wherein,

Δ T is predefined adjustment time gap.Described adjustment time gap Δ T can specifically set according to actual needs.For example, can get 5s.

Step S60: according to described revised angle of attack design ratio Obtain revised angle of attack guidance value

${\mathrm{\&alpha;}}_{\mathrm{cmd}}^{\&prime;}={\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\&prime;}+({\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v\left(t\right)+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right)---\left(15\right)$

The embodiment of the invention two described methods are according to design angle of attack initial value α ₀B1 revises to angle of attack design ratio, makes revised angle of attack design ratio

Can satisfy the flight design-calculated condition that reenters.In the method that each embodiment of the invention described above is provided, the reentering before the flight of aircraft, obtaining the design value that reenters the angle of attack can specifically may further comprise the steps described in the described step S10:

Step S101: utilize aircraft homomorphic predication model, each flight angle of attack that reenters constantly that obtains under the aircraft normal g-load kinetic balance condition designs predictor

Step S102: reenter the analog simulation of flight model by aircraft, obtain each flight of aircraft cooresponding flying speed and flying height constantly;

Step S103: utilize method of least square, according to each flight constantly reenter angle of attack design value, flying speed and flying height, convolution (5), match obtains angle of attack design ratio b ₁, b ₂, b ₃, b ₄, will reenter angle of attack design value and be expressed as:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ {\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="h\; V"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">h</figure-callout>}}& V_{}{}_1\&GreaterEqual;V\&GreaterEqual;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">V</figure-callout>}}_2\end{array}\right..---\left(5\right)$

Concrete, introduce in detail below and utilize aircraft to reenter flight model among the step S101 and type is touched in homomorphic predication, obtain under the aircraft normal g-load kinetic balance condition each flight constantly reenter angle of attack design predictor Process.The embodiment of the invention provides two kinds to obtain aircraft and reenter angle of attack design predictor The specific embodiment.Describe in detail respectively below.

First kind of embodiment:

Step S201: choose the predictive designs angle of attack Initial value α _Init, with initial value α _InitMoment corresponding t _InitFor the angle of attack designs the initial moment.

Wherein, described initial value α _InitCan rule of thumb set in advance; Also can be by obtaining after the free flight of aircraft self-separation point.

Generally, α _InitValue can be 35 ° to 45 °.When adopting bigger design angle of attack initial value α _InitThe time, can make aircraft obtain more velocity attenuation at the initial stage of reentering.

Casehistory obtains initial value α after by the free flight of aircraft self-separation point _InitProcess.Suppose that the separation point inclination angle of aircraft is 20 °, through unpowered rising with reenter when gliding to the separation point height, if attitude of flight vehicle still be the separation point state, then its angle of attack will reach about 40 °, can select initial value α at this moment _InitIt is 40 °.

Step S202: set up aircraft and reenter the homomorphic predication model that flight model and aircraft reenter flight, utilize the state of flight that reenters that reenters flight model simulated flight device, reentering flight model is that variable calculates with time.The described initial condition that reenters flight model and forecast model is initial moment t for the angle of attack designs _InitCooresponding aircraft state.

Described aircraft reenters flight model and the homomorphic predication method for establishing model is the common practise of this area, is not described in detail in this.

Step S203: set the dynamically balanced expectation intermediate value of normal g-load N _{N_want}With normal g-load fluctuation limits value Δ N _n, then the dynamically balanced fluctuation of Qi Wang normal g-load zone is [N _{N_want}± Δ N _n].

Concrete, the dynamically balanced expectation intermediate value of described normal g-load N _{N_want}With normal g-load fluctuation limits value Δ N _nCan specifically set according to actual needs.

For example, can set the dynamically balanced expectation intermediate value of normal g-load N _{N_want}Be the normal g-load binding occurrence that air craft carried personnel and equipment can bear, normal g-load fluctuation limits value Δ N _nBe this expectation intermediate value N _{N_want}2% to 5%.

Step S204: utilize aircraft homomorphic predication model, prediction is from initial moment t _InitThe beginning, with initial value α _InitBe the predictive designs angle of attack

Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}Moment t _{1_ α}

Step S205: set i=1; α ₀=α _Init

Step S206: move to t when aircraft reenters flight _{I_ α}In the time of constantly, from reenter flight model, obtain aircraft and reenter and fly to t _{I_ α}Angle of attack value α constantly _I-1, utilizing aircraft homomorphic predication model, prediction is with aircraft t _{I_ α}State of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first normal g-load peak value of the i of aircraft

Wherein,

Work as i=1,

k _InitBe angle of attack descending slope initial value, k _Init〉=0.

Step S207: the first normal g-load peak value of more described i

With the dynamically balanced fluctuation of the normal g-load of described expectation zone [N _{N_want}± Δ N _n], according to the descending slope of comparative result to the design angle of attack

Adjust, up to the first normal g-load peak value of described i

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding predictive designs angle of attack this moment Descending slope k _{_ α _ i}

Wherein, described according to the descending slope of comparative result to the design angle of attack

Adjust, be specially:

If

Normal g-load N is described _nExcessive, increase the predictive designs angle of attack

Descending slope

If

Need reduce the predictive designs angle of attack

Descending slope

The concrete predictive designs angle of attack

Descending slope

The adjustment mode can for: to the described predictive designs angle of attack Descending slope

Increase or reduce a default adjustment amount Δ k _{_ α}Described adjustment amount Δ k _{_ α}Can specifically set according to actual needs, for example set adjustment amount Δ k _{_ α}Be angle of attack descending slope initial value k _Init1% to 3%.

Step S208: utilize aircraft homomorphic predication model, prediction is with t _{I_ α}Constantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _I-1-k _{_ α _ i}(t-t _{I_ α}) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{I+1_ α}

Integrating step S206 to step S208 as can be known, at [t _{I_ α}, t _{I+1_ α}] in the time period, reenter flight model at aircraft and move to t _{I_ α}In the time of constantly, normal g-load N _nBe the dynamically balanced fluctuation of the normal g-load zone [N that is in described expectation _{N_want}± Δ N _n] in; And moment t _{I+1_ α}Be meant the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment; Simultaneously, at [t _{I_ α}, t _{I+1_ α}] in the time period, by setting to its design angle of attack, can be so that its normal g-load peak value Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in.Therefore, as can be known, at whole [t _{I_ α}, t _{I+1_ α}] time period, the normal g-load value of aircraft is the dynamically balanced fluctuation of the normal g-load zone [N that is in expectation all the time _{N_want}± Δ N _n] in, reached at [t _{I_ α}, t _{I+1_ α}] aircraft reenters the dynamically balanced purpose of flight normal g-load in the time period.

Preferably, described method also comprises: when i more than or equal to 2 the time, to t _{I+1_ α}Renewal, be specially:

At [t _{I_ α}, t _{I+1_ α}] in the time period, constantly with aircraft constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with α _I-1-k _{_ α _ i}(t-t _{I_ α}) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment

With As the t after upgrading _{I+1_ α}

Step S209: set [t _{I_ α}, t _{I+1_ α}] in the time period, angle of attack design predictor

Be α _I-1-k _{_ α _ i}(t-t _{I_ α}).

Step S210: as described descending slope k _{_ α _ i}Smaller or equal to default k ₀The time, the normal g-load kinetic balance of aircraft finishes, process ends; Otherwise i adds 1, returns step S206.

Described default k ₀It is a smaller value.Concrete, can set k ₀Equal the k of adjustment amount Δ described in the step S207 _{_ α}1 to 2 times.

In sum, in the embodiment of the invention, the angle of attack that reenters constantly of each flight under the resulting aircraft normal g-load kinetic balance condition designs predictor

For:

${\widetilde{\mathrm{\&alpha;}}}_{\mathrm{des}}=\left\{\begin{array}{ccc}{\mathrm{\&alpha;}}_{\mathrm{init}}& & t_{\mathrm{init}}\&le;t\&le;{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_{1\_\mathrm{\&alpha;}}\\ & .& \\ & .& \\ & .& \\ {\mathrm{\&alpha;}}_{i-1}-k_{\_\mathrm{\&alpha;}\_i}(t-t_{i\_\mathrm{\&alpha;}})& & t_{i\_\mathrm{\&alpha;}}<t\&le;t_{i+1\_\mathrm{\&alpha;}}\\ & .& \\ & .& \\ & .& \\ {\mathrm{\&alpha;}}_{N-1}-k_{\_\mathrm{\&alpha;}\_N}(t-t_{N-\mathrm{\&alpha;}})& & t_{N-1\_\mathrm{\&alpha;}}<t\&le;t_{\mathrm{end}}\end{array}\right.---\left(16\right)$

First kind of providing of the embodiment of the invention obtains and reenters angle of attack design predictor

Embodiment in, time segment is to the predictive designs angle of attack

Value set.For each time period, utilize aircraft homomorphic predication model, find the interior design angle of attack value in normal g-load dynamically balanced fluctuation zone that makes the normal g-load value of aircraft be in expectation all the time, realize the normal g-load dynamical equilibrium in this time period.

Adjusting descending slope with the unique fixing angle of attack of available technology adopting compares, can make normal g-load fluctuation within a narrow range in the fluctuation zone of expectation in each time period, make normal g-load by single/bimodally become flat peak, realized the normal g-load kinetic balance in each time period, reached and reduce the purpose that aircraft reenters the normal g-load peak value in the process.

Preferably, in the said method, during and if only if i=1, can also comprise: setting and adjusting Timing Advance is Δ t _α, at [t _Init, (t _{1_ α}-Δ t _α)] in the time period, aircraft reenters the predictive designs angle of attack of flight

Equal initial value α _Init

When reentering flight model, aircraft moves to t _{1_ α}-Δ t _αIn the time of constantly, utilize aircraft homomorphic predication model, prediction is with aircraft t _{1_ α}-Δ t _αState of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first first normal g-load peak value of aircraft

The more described first first normal g-load peak value

With the dynamically balanced fluctuation of the normal g-load of described expectation zone [N _{N_want}± Δ N _n], according to comparative result to the predictive designs angle of attack Descending slope k _{_ α}Adjust, up to the described first first normal g-load peak value Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding design angle of attack descending slope k this moment _{_ α _ 1}

Utilize aircraft homomorphic predication model, prediction is with t _{1_ α}-Δ t _αConstantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the described first first normal g-load peak value

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{2_ α}

Set [t _{1_ α}-Δ t _α, t _{2_ α}] in the time period, angle of attack design predictor

Be α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α).

Preferably, described method also comprises: when i=1, to t _{1_ α}Renewal, be specially:

At t _Init≤ t≤(t _{1_ α}-Δ t _α) in, constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with initial value α _InitBe the predictive designs angle of attack Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}The moment

With

As the t after upgrading _{1_ α}

Second kind of embodiment:

Second kind of providing of the embodiment of the invention obtains and reenters angle of attack design predictor

Method can may further comprise the steps:

Step S301: choose the predictive designs angle of attack

Initial value α _Init, with initial value α _InitPairing moment t _InitBe the initial moment.

Step S302: set up aircraft and reenter the homomorphic predication model that flight model and aircraft reenter flight, utilize the state of flight that reenters that reenters flight model simulated flight device, reentering flight model is that variable calculates with time.The described initial condition that reenters flight model and forecast model is initial moment t for the angle of attack designs _InitCooresponding aircraft state.

Step S303: set the dynamically balanced expectation intermediate value of normal g-load N _{N_want}With normal g-load fluctuation limits value Δ N _n, then the dynamically balanced fluctuation of Qi Wang normal g-load zone is [N _{N_want}± Δ N _n].

Step S304: utilize aircraft homomorphic predication model, prediction is from initial moment t _InitThe beginning, with initial value α _InitBe the predictive designs angle of attack

Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}Moment t _{1_ α}

Step S305: setting and adjusting Timing Advance is Δ t _α, at t _Init≤ t≤(t _{1_ α}-Δ t _α) in, the design angle of attack that aircraft reenters flight equals initial value α _Init

Be, at [t _Init, (t _{1_ α}-Δ t _α)] in the time period, the design angle of attack equals initial value α _Init

Because in the specific implementation, have certain delay for the control process of the angle of attack, therefore need keep certain adjustment leeway in time, be Δ t so set the adjustment Timing Advance _α

Preferably, the reentering in the flight course of aircraft since be subjected to effect, the atmosphere of wind-force uneven and influence, may make aerocraft real from initial time t _InitPlay, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}The moment and step S304 in the predictor t that obtains _{1_ α}There is error.

Therefore, the described method of the embodiment of the invention also further comprises described predictor t _{1_ α}Renewal process.Concrete,

At t _Init≤ t≤(t _{1_ α}-Δ t _α) in, can be constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with initial value α _InitBe the predictive designs angle of attack Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}The moment

With The described t of step of updating S305 _Init≤ t≤(t _{1_ α}-Δ t _α) in t _{1_ α}

Step S306: move to t when aircraft reenters flight model _{1_ α}-Δ t _αIn the time of constantly, utilize aircraft homomorphic predication model, prediction with the current state of flight of aircraft be the initial condition of described homomorphic predication model, with α _Init-k _Init(t-t _{1_ α}+ Δ t _α) be the predictive designs angle of attack

When reentering flight, the first first normal g-load peak value of aircraft

Wherein, k _InitBe angle of attack descending slope k _{_ α}Initial value, k _Init〉=0.

Concrete, angle of attack descending slope k _{_ α}Initial value be k _InitCan rule of thumb specifically set.

Step S307: the more described first first normal g-load peak value With the dynamically balanced fluctuation of the normal g-load of described expectation zone [N _{N_want}± Δ N _n], according to comparative result to the predictive designs angle of attack

Descending slope k _{_ α}Adjust.

Concrete, described to the predictive designs angle of attack

Descending slope k _{_ α}Adjust can for:

If

Normal g-load N is described _nExcessive, need to increase the predictive designs angle of attack

Descending slope k _{_ α}If

Need reduce the predictive designs angle of attack

Descending slope k _{_ α}

Concrete, the predictive designs angle of attack

Descending slope k _{_ α}The adjustment mode can for: increase or reduce a default adjustment amount Δ k _{_ α}Described adjustment amount Δ k _{_ α}Can specifically set according to actual needs, for example set adjustment amount Δ k _{_ α}Be angle of attack descending slope initial value k _Init1% to 3%.

Step S308: with adjusted descending slope k _{_ α}α described in the replacement step S306 _Init-k _Init(t_t _{1_ α}+ Δ t _α) in k _Init, repeating step S306 is to step S308, up to the described first first normal g-load peak value

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding design angle of attack descending slope k this moment _{_ α _ 1}

Step S309: utilize aircraft homomorphic predication model, prediction is with t _{1_ α}-Δ t _αConstantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the described first first normal g-load peak value

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{2_ α}

Be, at [t _{1_ α}-Δ t _α, t _{2_ α}] in the time period, angle of attack design predictor

Be α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α).

Preferably, can also comprise described predictor t _{2_ α}Renewal process.Be specially:

At [t _{1_ α}-Δ t _α, t _{2_ α}] in, can be constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α) be the predictive designs angle of attack

Reenter flight, the normal g-load N of aircraft _nThrough the described first first normal g-load peak value

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment

With

Described [the t of step of updating S309 _{1_ α}-Δ t _α, t _{2_ α}] in t _{2_ α}

Step S310: obtain in reentering flight model aircraft and reenter and fly to t _{2_ α}Angle of attack value α constantly ₁, utilizing aircraft homomorphic predication model, prediction is with aircraft t _{2_ α}State of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the second first normal g-load peak value of aircraft

Wherein,

Less than k _{_ α _ 1}Adopt with step S307 to S308 in identical method, right

Adjust, determine the described second first normal g-load peak value

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] cooresponding descending slope k when interior _{_ α _ 2}, adopt the method identical with step S309, obtain the normal g-load N of aircraft _nThrough the described second first normal g-load peak value The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{3_ α}

Be, at [t _{2_ α}, t _{3_ α}] in the time period, angle of attack design predictor

Be α ₁-k _{_ α _ 2}(t-t _{2_ α}).

Preferably, can also comprise described predictor t _{3_ α}Renewal process.Be specially:

At [t _{2_ α}, t _{3_ α}] in, can be constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction from current time, with

Be the predictive designs angle of attack

Reenter flight, the normal g-load N of aircraft _nThrough the described second first normal g-load peak value

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment

With

Described [the t of step of updating S310 _{2_ α}, t _{3_ α}] in t _{3_ α}

Step S311: by that analogy, repeating step S310 obtains aircraft and reenters flight model and move to t _{N_ α}Angle of attack value α constantly _N-1, utilizing aircraft homomorphic predication model, prediction is with aircraft t _{N_ α}State of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first normal g-load peak value of N

Wherein, Less than k _{_ α _ N-1}Obtain the first normal g-load peak value of described N

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] cooresponding descending slope k when interior _{_ α _ N}, and the normal g-load N of aircraft _nThrough behind the described N first normal g-load peak value, break away from the regional [N of the dynamically balanced fluctuation of normal g-load of described expectation _{N_want}± Δ N _n] moment t _{N+1_ α}

Be, at [t _{N_ α}, t _{N+1_ α}] in the time period, angle of attack design predictor

Be α _N-1-k _{_ α _ N}(t-t _{N_ α}).

Preferably, can also comprise described predictor t _{N+1_ α}Renewal process.Be specially:

At [t _{N_ α}, t _{N+1_ α}] in, can be constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction from current time, with Be the predictive designs angle of attack

Reenter flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described N

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment

With Described [the t of step of updating S311 _{N_ α}, t _{N+1_ α}] in t _{N+1_ α}

Step S312: as described α _N-1-k _{_ α _ N}(t-t _{N_ α}) in descending slope k _{_ α _ N}Smaller or equal to default k ₀The time, the normal g-load kinetic balance of aircraft finishes, and jumps out step S311, process ends; Will moment t _{N+1_ α}As dynamically balanced finish time of t _End

Described default k ₀It is a smaller value.Concrete, can set k ₀Equal the k of adjustment amount Δ described in the step S307 _{_ α}1 to 2 times.

In sum, in the embodiment of the invention, reenter angle of attack design predictor by second kind

Each flight under the resulting aircraft normal g-load of acquisition methods kinetic balance condition angle of attack that reenters constantly designs predictor

For:

${\widetilde{\mathrm{\&alpha;}}}_{\mathrm{des}}=\left\{\begin{array}{ccc}{\mathrm{\&alpha;}}_{\mathrm{init}}& & t_{\mathrm{init}}\&le;t\&le;({\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_{1\_\mathrm{\&alpha;}}-\mathrm{\&Delta;}{t}_{\mathrm{\&alpha;}})\\ {\mathrm{\&alpha;}}_{\mathrm{init}}-k_{\_\mathrm{\&alpha;}\_1}(t-{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_{1\_\mathrm{\&alpha;}}+\mathrm{\&Delta;}{t}_{\mathrm{\&alpha;}})& & ({\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_{1\_\mathrm{\&alpha;}}-\mathrm{\&Delta;}{t}_{\mathrm{\&alpha;}})<t\&le;{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">t</figure-callout>}}_{2\_\mathrm{\&alpha;}}\\ {\mathrm{\&alpha;}}_1-k_{\_\mathrm{\&alpha;}\_2}(t-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">t</figure-callout>}}_{2\_\mathrm{\&alpha;}})& & {\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">t</figure-callout>}}_{2\_\mathrm{\&alpha;}}<t\&le;{\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">t</figure-callout>}}_{3\_\mathrm{\&alpha;}}\\ & .& \\ & .& \\ & .& \\ {\mathrm{\&alpha;}}_{N-1}-k_{\_\mathrm{\&alpha;}\_N}(t-t_{N\_\mathrm{\&alpha;}})& & t_{N-1\_\mathrm{\&alpha;}}<t\&le;t_{\mathrm{end}}\end{array}\right.---\left(17\right)$

Second kind that provides in the embodiment of the invention reenters angle of attack design predictor

In the acquisition methods, time segment is to the predictive designs angle of attack

Value set.For each time period, utilize aircraft homomorphic predication model, find the interior design angle of attack value in normal g-load dynamically balanced fluctuation zone that makes the normal g-load value of aircraft be in expectation all the time, realize the normal g-load dynamical equilibrium in this time period.

Adjusting descending slope with the unique fixing angle of attack of available technology adopting compares, can make normal g-load fluctuation within a narrow range in the fluctuation zone of expectation in each time period, make normal g-load by single/bimodally become flat peak, realized the normal g-load kinetic balance in each time period, reached and reduce the purpose that aircraft reenters the normal g-load peak value in the process.

Need to prove that reentering in-flight of inferior orbital vehicle, the factor that influences its normal g-load is not only the angle of attack, also have the speed angle of heel.The suffered aerodynamic force size of described not change of flight of speed angle of heel device, but direction that can the suffered aerodynamic force of variable aircraft.When the speed angle of heel was non-vanishing, the direction of the suffered aerodynamic force of aircraft changed, and with accelerating the descending speed of aircraft, caused the normal g-load of aircraft further to increase.

Reenter the acquisition methods of the design angle of attack in the flight course for the described aircraft of the embodiment of the invention, when not needing to consider the speed angle of heel, only need to set described in step S202 and the S302 that cooresponding aircraft speed angle of heel σ is 0 in the aircraft homomorphic predication model; When needs are considered the speed angle of heel and the angle of attack simultaneously, need pre-establish the design value of each speed angle of heel constantly, the speed angle of heel σ in the model of aircraft homomorphic predication described in step S202 and the S302 is got final product for each corresponding speed angle of heel design value constantly.

In the embodiment of the invention, reentering before the flight of aircraft, obtained and realized the dynamically balanced design value that reenters the angle of attack of normal g-load, and obtained angle of attack design ratio b by least square method with this design value ₁, b ₂, b ₃, b ₄, the angle of attack design value under the angle of attack shown in the formula that obtains thus (5) is expressed can realize the normal g-load dynamical equilibrium.Reenter in the flight course at aircraft, the corrected parameter η (t) of introducing is time dependent integration ratio, and the molecule of ratio is the drag acceleration predictor Integrated value before current time t The denominator of ratio is the integrated value of drag acceleration actual measured value D (t) before current time t

When the drag acceleration predictor

Integration

Integration with drag acceleration actual measured value D (t)

When convergent, illustrate that the state of flight of practical flight just with under the design angle of attack must be predicted the state of flight advolution.From formula (13) as seen, as coefficient of correction η (t)=1, angle of attack guidance value α then _Cmd(t) equal angle of attack design value α _Des(t), this moment the drag acceleration predictor

Integrated value before current time t

Equal the integrated value of drag acceleration actual measured value D (t) before current time t

When coefficient of correction η (t) is not 1, angle of attack guidance value α _Cmd(t) will be at angle of attack design value α _Des(t) adjust, make

With

Convergent.

Below in conjunction with adopting the method for the invention that inferior orbital vehicle is carried out the result that emulation experiment obtains, further specify the purpose that the embodiment of the invention realizes.

In the emulation experiment, set:

Aircraft reenter elemental height (being the peak dot height) H=148km, aircraft is at described cooresponding speed V=2133.5m/s when reentering elemental height.

The velocity peak values that aircraft reenters in the flight course is 2415m/s, and the cooresponding flying height of this velocity peak values is 47.691km.

The effect of the acquisition methods of design angle of attack value of the present invention at first will be described.

Reaching described velocity peak values from aircraft, is purpose with the normal g-load dynamical equilibrium, and the angle of attack is designed, and sets the dynamically balanced expectation intermediate value of described normal g-load N _{N_want}=4.99, normal g-load fluctuation limits value Δ N _n=0.005, the initial value α of design angle of attack _Init=40 °, the speed angle of heel is initially zero, enough adds the back in the flying speed decay.

As shown in Figure 3, when carrying out emulation for employing the method for the invention, aircraft reenters the height and the speed evolution diagram of flight.Wherein, point 1 shown in Figure 3 (peak height point) is corresponding constantly represents the moment of aircraft at the peak dot height to be to reenter initial time also; Point 2 (peak velocity point) are corresponding to reenter the moment that reaches velocity peak values for aircraft constantly; Point 3 (kinetic balance end point) are corresponding to be the kinetic balance finish time constantly.

Point 2 shown in Figure 3 and the time period of putting between 3 are normal g-load dynamical equilibrium section [t _Init, t _End].The evolution of the cooresponding design angle of attack of aircraft, speed angle of heel and normal g-load as shown in Figure 4 in the described overload kinetic balance time period shown in Figure 3.

As seen, keeping design angle of attack initial value α _InitAfter a period of time, normal g-load N _nSharply increase (before the dotted line 1 shown in Figure 4).Leaving certain adjustment lead Δ t _αThe time, the design angle of attack begins to adjust, and normal g-load reaches kinetic balance (dotted line 1 shown in Figure 4 is between the dotted line 2) in presumptive area [4.99 ± 0.005].After flying speed is enough decayed, add speed angle of heel (it is non-vanishing to be the speed angle of heel), and continue to adjust the design angle of attack, make normal g-load N _nIn presumptive area [4.99 ± 0.005], reach dynamical equilibrium (dotted line 2 shown in Figure 4 is between the dotted line 3).This shows that the angle of attack method of designing that the embodiment of the invention is described can more satisfactory realization inferior orbital vehicle reenters the normal g-load kinetic balance of flight.

If with the dynamically balanced expectation intermediate value of described normal g-load N _{N_want}Turn down gradually,, the normal g-load peak value can be forced down to about 3.7～3.8 through the repeatedly interpretation of result of emulation.

For the method for the invention, for the dynamically balanced expectation intermediate value of different normal g-loads N _{N_want}, its track characteristic that reenters process is as shown in table 1:

From table 1, can see, along with the dynamically balanced expectation intermediate value of normal g-load N _{N_want}Reduction, its dynamic pressure peak value and hot-fluid peak value will raise, and illustrate to keep the dynamically balanced expectation intermediate value of higher normal g-load N _{N_want}Help reducing dynamic pressure peak value and hot-fluid peak value.It can also be seen that, normal g-load is dynamically balanced hold time long more, the dynamically balanced expectation intermediate value of its attainable normal g-load N _{N_want}Low more.

Equally for this simulation example, as adopt existing angle of attack method of designing, be employing formula (1) the design angle of attack, wherein design angle of attack initial value α ₀=40 °; Design angle of attack expected value α _End=15 °, the initial value V of aircraft speed when the design angle of attack begins to adjust ₁Correspond to the aircraft reentry velocity peak value in the simulation example, then design the descending slope of the angle of attack

Promptly by different V ₂Unique definite.

For existing method, different angle of attack descending slopes

The track characteristic that reenters process is as shown in table 2:

By contrast table 1 and table 2 as can be known, adopt the method for the invention, can be with the dynamically balanced expectation intermediate value of minimum normal g-load N _{N_want}Force down to 3.7; If have angle of attack method of designing now and adopt, its minimum normal g-load peak value that can reach is also more than 5.9.This shows that the described method of the embodiment of the invention can significantly be forced down aircraft and reenter normal g-load peak value in the flight course.

Secondly angle of attack design ratio b of the present invention will be described ₁, b ₂, b ₃, b ₄The effect of acquisition methods.

Fig. 5 is for designing predictor with the angle of attack that obtains

Match angle of attack design ratio b ₁, b ₂, b ₃, b ₄Design sketch, what fitting method adopted is method of least square.Can be as seen from the figure, for the dynamically balanced expectation intermediate value of different normal g-loads N _{N_want}, the angle of attack design value α after fitting _DesDesign predictor with the angle of attack that reenters that obtains

Well mate.

Guidance effect of the present invention will be described at last.

Fig. 6 a to Fig. 6 f for differ when actual rudders pneumatic power parameter and the described rudders pneumatic power parameter that reenters in flight model and the homomorphic predication model that reenters when flight ± 5%, ± 10%, ± 20% situation under, in described normal g-load kinetic balance section, adopt the actual normal g-load of flight and the difference situation of expectation normal g-load balance intermediate value of reentering of the inventive method guidance.

Among Fig. 6 a to Fig. 6 f, " the whole correction " indication line is under the angle of attack method of guidance of the embodiment of the invention one, the actual normal g-load of flight and the difference situation of expectation normal g-load balance intermediate value of reentering in described normal g-load kinetic balance section.This moment, angle of attack guidance corresponded to formula (13):

${\mathrm{\&alpha;}}_{\mathrm{cmd}}=({\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v\left(t\right)+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right)---\left(13\right)$

Among Fig. 6 a to Fig. 6 f, " b1 revises at correction+integral body " indication line is under the angle of attack method of guidance of the embodiment of the invention two, the actual normal g-load of flight and the difference situation of expectation normal g-load balance intermediate value of reentering in described normal g-load kinetic balance section.This moment, angle of attack guidance corresponded to formula (15):

${\mathrm{\&alpha;}}_{\mathrm{cmd}}^{\&prime;}={\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^{\&prime;}+({\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000322264700031.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\&CenterDot;v\left(t\right)+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000322264700031.png,HSA00000322264700041.png"\; state="\{\{state\}\}">b</figure-callout>}}_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right)---\left(15\right)$

From Fig. 6 to Fig. 6 f as can be seen, when not adopting method of guidance of the present invention, there is error in actual normal g-load in its normal g-load balancing segment with expectation normal g-load balance intermediate value, and adopt method of guidance of the present invention, can effectively reduce aircraft and reenter the influence that the flight deviation is brought, the normal g-load that makes aerocraft real reenter flight reaches unanimity with the normal g-load that designs under the angle of attack, reaches the guidance purpose.

More than a kind of inferior orbital vehicle provided by the present invention is reentered the angle of attack method of guidance of flight, be described in detail, used specific case herein principle of the present invention and embodiment are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, part in specific embodiments and applications all can change.In sum, this description should not be construed as limitation of the present invention.

Claims (9)

1. an inferior orbital vehicle reenters the angle of attack method of guidance of flight, it is characterized in that, comprising:

Step 1, the reentering before the flight of aircraft, obtain the design value that reenters the angle of attack, the described design value that reenters the angle of attack is expressed as:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ b_1+b_2\&CenterDot;v+b_3\&CenterDot;e^{b_4\&CenterDot;h}& V_1\&GreaterEqual;V\&GreaterEqual;V_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;V_2\end{array}\right.$

Wherein, α _DesFor reentering the design value of the angle of attack; α ₀Be design angle of attack initial value; α _EndBe design angle of attack expected value; V ₁The initial value of aircraft speed when beginning to adjust for the design angle of attack; V ₂For the design angle of attack is adjusted to α _EndThe time aircraft speed value; b ₁, b ₂, b ₃, b ₄Be angle of attack design ratio, V is the aircraft flight velocity amplitude, and h is the aircraft altitude value;

Step 2, utilize aircraft to reenter flight model and homomorphic predication model, calculate and adopt this to reenter the design value α of the angle of attack _DesWhen reentering flight, each flight is cooresponding drag acceleration predictor constantly

Step 3, reenter in the flight course, measure the drag acceleration D (t) of aircraft current time t in real time, in conjunction with described drag acceleration predictor at aircraft

Calculate the coefficient of correction η (t) of the cooresponding design angle of attack of current time t, be specially:

$\mathrm{\&eta;}\left(t\right)=\frac{\underset{t_0}{\overset{t}{\&Integral;}}\hat{D}\left(t\right)\mathrm{dt}}{\underset{t_0}{\overset{t}{\&Integral;}}D\left(t\right)\mathrm{dt}}$

Wherein, t ₀Be meant the initial moment of flying that reenters of aircraft;

Step 4, measure current flying speed v of aircraft (t) and flying height h (t) in real time, utilize the coefficient of correction η (t) of the described current design angle of attack, the design value that reenters the angle of attack that obtains in the step 1 is revised, obtain angle of attack guidance value α _Cmd:

${\mathrm{\&alpha;}}_{\mathrm{cmd}}=(b_1+b_2\&CenterDot;v\left(t\right)+b_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right).$

2. method according to claim 1 is characterized in that, also comprises after step 4:

Step 5, according to design angle of attack initial value α ₀B1 revises to angle of attack design ratio, makes revised angle of attack design ratio

Satisfy: when aircraft reenters flying speed is V ₁The time,

Wherein, h ₁For aircraft reenters flying speed is V ₁The time cooresponding flying height, t ₁For aircraft reenters flying speed is V ₁The time cooresponding flight constantly;

Concrete, can adopt following formula that angle of attack design ratio b1 is revised:

$b_1^{\&prime;}=\left\{\begin{array}{cc}{b}_1^{\mathrm{start}}& t=t_1\\ b_1^{\mathrm{start}}+{\&Integral;}_{t_1}^t\frac{b_1\&times;\mathrm{\&eta;}\left(t\right)-b_1^{\mathrm{start}}}{\mathrm{\&Delta;T}-(t-t_1)}\mathrm{dt}& t_1<t<t_1+\mathrm{\&Delta;T}\\ b_1\&times;\mathrm{\&eta;}\left(t\right)& t\&GreaterEqual;t_1+\mathrm{\&Delta;T}\end{array}\right.$

Wherein,

Δ T is predefined adjustment time gap;

Step 6, according to described revised angle of attack design ratio

Obtain revised angle of attack guidance value

${\mathrm{\&alpha;}}_{\mathrm{cmd}}^{\&prime;}=b_1^{\&prime;}+(b_2\&CenterDot;v\left(t\right)+b_3\&CenterDot;e^{b_4\&CenterDot;h\left(t\right)})\&times;\mathrm{\&eta;}\left(t\right).$

3. method according to claim 1 and 2 is characterized in that, described step 1 comprises:

Step 11: utilize aircraft to reenter flight model and aircraft homomorphic predication model, each flight angle of attack that reenters constantly that obtains under the aircraft normal g-load kinetic balance condition designs predictor

Step 12: reenter the analog simulation of flight model by aircraft, obtain each flight of aircraft cooresponding flying speed and flying height constantly;

Step 13: utilize method of least square, design predictor according to each flight angle of attack that reenters constantly Flying speed and flying height, in conjunction with following expression formula, match obtains the expression formula of angle of attack design value:

${\mathrm{\&alpha;}}_{\mathrm{des}}=\left\{\begin{array}{cc}{\mathrm{\&alpha;}}_0& V\&GreaterEqual;V_1\\ b_1+b_2\&CenterDot;v+b_3\&CenterDot;e^{b_4\&CenterDot;h}& V_1\&GreaterEqual;V\&GreaterEqual;V_2\\ {\mathrm{\&alpha;}}_{\mathrm{end}}& V\&le;V_2\end{array}\right..$

4. method according to claim 3 is characterized in that, described step 11 comprises:

Set up aircraft and reenter the homomorphic predication model that flight model and aircraft reenter flight, utilize the state of flight that reenters that reenters flight model simulated flight device, reentering flight model is that variable calculates with time.The described initial condition that reenters flight model and forecast model is initial moment t _InitCooresponding aircraft state;

Utilize described aircraft homomorphic predication model, prediction is from initial moment t _InitBeginning, initial value α to preset _InitBe the predictive designs angle of attack

Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of the normal g-load that presets N _{N_want}Moment t _{1_ α}

From i=1, α ₀=α _InitRise and carry out following steps:

Step 111: move to t when aircraft reenters flight model _{I_ α}In the time of constantly, from reenter flight model, obtain aircraft and reenter and fly to t _{I_ α}Angle of attack value α constantly _I-1, utilizing aircraft homomorphic predication model, prediction is with aircraft t _{I_ α}State of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first normal g-load peak value of the i of aircraft

Wherein,

Work as i=1,

k _InitBe angle of attack descending slope initial value, k _Init〉=0;

Step 112: the first normal g-load peak value of more described i

With the dynamically balanced fluctuation of the normal g-load of expectation zone [N _{N_want}± Δ N _n], according to comparative result to the predictive designs angle of attack

Descending slope

Adjust, up to the first normal g-load peak value of described i

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding predictive designs angle of attack this moment

Descending slope k _{_ α _ i}Described Δ N _nBe the normal g-load fluctuation limits value that presets;

Step 113: utilize aircraft homomorphic predication model, prediction is with t _{I_ α}Constantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _I-1-k _{_ α _ i}(t-t _{I_ α}) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{I+1_ α}

Step 114: set [t _{I_ α}, t _{I+1_ α}] in the time period, angle of attack design predictor

Be α _I-1-k _{_ α _ i}(t-t _{I_ α});

Step 115: as described descending slope k _{_ α _ i}Smaller or equal to default k ₀The time, the normal g-load kinetic balance of aircraft finishes, process ends; Otherwise i adds 1, returns step 111.

5. method according to claim 4 is characterized in that, described method also comprises: when i more than or equal to 2 the time, to t _{I+1_ α}Renewal, be specially:

At [t _{I_ α}, t _{I+1_ α}] in the time period, constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with α _I-1-k _{_ α _ i}(t-t _{I_ α}) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the first normal g-load peak value of described i

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] the moment

With

As the t after upgrading _{I+1_ α}

6. method according to claim 4 is characterized in that, during and if only if i=1, setting and adjusting Timing Advance is Δ t _α, at [t _Init, (t _{1_ α}-Δ t _α)] in the time period, aircraft reenters the predictive designs angle of attack of flight

Equal initial value α _Init

When reentering flight model, aircraft moves to t _{1_ α}-Δ t _αIn the time of constantly, utilize aircraft homomorphic predication model, prediction is with aircraft t _{1_ α}-Δ t _αState of flight constantly be described homomorphic predication model initial condition, with

Be the predictive designs angle of attack

When reentering flight, the first first normal g-load peak value of aircraft

The more described first first normal g-load peak value

With the dynamically balanced fluctuation of the normal g-load of described expectation zone [N _{N_want}± Δ N _n], according to comparative result to the predictive designs angle of attack

Descending slope k _{_ α}Adjust, up to the described first first normal g-load peak value

Be in the dynamically balanced fluctuation of the normal g-load zone [N of described expectation _{N_want}± Δ N _n] in, and determine cooresponding predictive designs angle of attack this moment Descending slope k _{_ α _ 1}

Utilize aircraft homomorphic predication model, prediction is with t _{1_ α}-Δ t _αConstantly the state of flight of aircraft be the initial condition of described homomorphic predication model, with α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α) be the predictive designs angle of attack

When reentering flight, the normal g-load N of aircraft _nThrough the described first first normal g-load peak value

The dynamically balanced fluctuation of the normal g-load of back, the described expectation of disengaging zone [N _{N_want}± Δ N _n] moment t _{2_ α}

Set [t _{1_ α}-Δ t _α, t _{2_ α}] in the time period, angle of attack design predictor

Be α _Init-k _{_ α _ 1}(t-t _{1_ α}+ Δ t _α).

7. method according to claim 6 is characterized in that, described method also comprises: when i=1, to t _{1_ α}Renewal, be specially:

At t _Init≤ t≤(t _{1_ α}-Δ t _α) in, constantly with the initial condition of the current state of flight in reentering flight model of aircraft as the homomorphic predication model, prediction is from current time, with initial value α _InitBe the predictive designs angle of attack

Reenter flight, reach normal g-load N _nMore than or equal to the dynamically balanced expectation intermediate value of normal g-load N _{N_want}The moment

With

As the t after upgrading _{1_ α}

8. method according to claim 4 is characterized in that, described in the step 112 according to comparative result to the predictive designs angle of attack

Descending slope Adjust, be specially:

If

Increase the predictive designs angle of attack

Descending slope

If

Reduce the predictive designs angle of attack Descending slope

9. method according to claim 8 is characterized in that, increases or reduce the predictive designs angle of attack

Descending slope

Be specially:

To the described predictive designs angle of attack

Descending slope

Increase or reduce a default adjustment amount Δ k _{_ α}

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