CN108534785B - A kind of atmosphere enters guided trajectory Adaptive Planning method - Google Patents

A kind of atmosphere enters guided trajectory Adaptive Planning method Download PDF

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CN108534785B
CN108534785B CN201810238228.2A CN201810238228A CN108534785B CN 108534785 B CN108534785 B CN 108534785B CN 201810238228 A CN201810238228 A CN 201810238228A CN 108534785 B CN108534785 B CN 108534785B
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郭敏文
黄翔宇
李茂登
张晓文
魏春岭
徐超
胡锦昌
王晓磊
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Beijing Institute of Control Engineering
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
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    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators
    • G05B13/042—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators in which a parameter or coefficient is automatically adjusted to optimise the performance
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators
    • G05B13/048—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators using a predictor

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Abstract

A kind of atmosphere enters guided trajectory Adaptive Planning method, (1) obtain fly vertical journey and horizontal journey with angle of heel changing rule；(2) it is segmented to the entire process that enters, and determines the Guidance Law in each stage；(3) different inlet points is set and initially indulges journey, judge whether deployed condition meets given constraint under different inlet points, if meeting, then positive initially vertical journey or the negative sense of increasing reduces initially vertical journey, until thering is parachute-opening constraint not to be satisfied, determine that above-mentioned Guidance Law can adjust the limit range of initial vertical journey；(4) during practical flight, judgement initially enter a little vertical journey whether in above-mentioned limit range, if, using step (2) in Guidance Law controlled；If not existing, (5) are thened follow the steps；(5) departure that practical initial vertical journey goes beyond the limit of range is calculated, the vertical journey reference value of nominal trajectory is modified, which is substituted into the Guidance Law in step (2), new Guidance Law is obtained, is controlled using the new Guidance Law.

Description

Self-adaptive planning method for guidance track of atmospheric admission
Technical Field
The invention belongs to the field of guidance of a small-lift-body rarefied atmosphere entering process in a deep space exploration planetary surface landing project, and relates to an analytic prediction correction method based on a nominal track.
Background
The first planet detection task in China implements planet surrounding, landing and patrol detection through one-time launching, and the key of the task is to successfully implement planet surface soft landing. However, 18 planet Landing detection tasks are implemented worldwide, the complete success is only 7 times, and the success rate is less than 39%, so that the difficulty of the planet Landing detection tasks is very high, wherein the entering, descending and Landing processes (EDL, Entry, details, and bonding) are the biggest challenges faced by the planet Landing detection tasks.
The atmospheric admission process is a critical link to the planetary EDL process and has different technical requirements and operating conditions compared to the earth orbiting spacecraft, CE-5 returner task. The planet EDL process time is short (about 8 minutes), the ground measurement and control time delay is long (dozens of minutes), the track precision is limited, and after the forward track maneuver and the separation of two devices (a surround device and a landing patrol device) are completed, the state precision of an initial entry point cannot be ensured; the atmospheric environment on the surface of the planet is complex and changeable, meanwhile, the pneumatic parameters of the detector have larger uncertainty, and the restriction on the parachute opening condition is strong; the main control target of the lift control stage is the parachute opening condition (height, speed and dynamic pressure) and the drop point precision is considered;
at present, the documents published at home and abroad mainly take guidance precision and miss distance as the primary control targets, and little attention is paid to the spreading of the parachute opening height. When the flight capability of the detector is very limited, if the landing accuracy is pursued, the control capability is likely to be used for controlling the landing accuracy completely, and the height adjusting capability is lost. Finally, the parachute opening height cannot meet the parachute opening constraint condition, and the parachute cannot be smoothly unfolded, so that the landing task fails.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the adaptive planning method for the guidance track of the atmospheric admission overcomes the defects of the prior art, and provides an adaptive planning method for the guidance track of the atmospheric admission aiming at the conditions that the lift-drag ratio of a planet detector is small, the flight capability is limited, and the initial admission state has larger deviation.
The technical solution of the invention is as follows: an adaptive planning method for an atmospheric admission guidance track comprises the following steps:
(1) analyzing the flight capability of the detector, and acquiring the change rule of the flight longitudinal and transverse with the roll angle;
(2) segmenting the whole entering process according to the change rule, and determining the atmosphere entering guidance law of each stage; the guidance strategy starts to work when the navigation height is less than 125km, and the guidance strategy is designed based on a nominal track and the nominal value comprises a longitudinal range;
(3) adopting the guidance law of the step (2), and the roll angle satisfies [ -90 degrees, 90 degrees °]Setting different initial longitudinal courses of the entry points, judging whether the parachute opening states under the different entry points meet given constraints, if so, positively increasing the initial longitudinal course or negatively decreasing the initial longitudinal course until the parachute opening constraints are not met, and determining the limit range [ DR ] of the initial longitudinal course which can be adjusted by the guidance lawmin-，DRmax+]；
(4) In the actual flight process, judging whether the longitudinal stroke of the initial entry point is within the limit range, if so, controlling by adopting the guidance law in the step (2) to finish the guidance for atmospheric entry; if not, executing the step (5);
(5) according to the limit range [ DR ]min-，DRmax+]And (3) calculating the deviation amount of the actual initial longitudinal distance exceeding the limit range, correcting the longitudinal distance reference value of the nominal track by using the deviation amount, substituting the corrected value into the guidance law in the step (2) to obtain a new guidance law, and controlling by using the new guidance law to finish the self-adaptive planning of the atmosphere entering the guidance track.
Further, the flight capability of the analysis detector is realized by the following modes:
firstly, determining the positions of landing points which can be flown by a detector under different roll angles;
then, determining an ideal azimuth Az and an actual azimuth Az' according to the landing point position;
cos(s)＝sinφ0sinφf+cosφ0cosφfcos(θf-θ0)
cos(s′)＝sinφ0sinφ′f+cosφ0cosφ′fcos(θ′f-θ0)
finally, the change rule of the flight longitudinal range DR and the flight transverse range CR along with the roll angle is obtained by combining the following formulas:
sinCR＝sins′sin(Az-Az′)
cosDR＝coss′/cosCR
in the above, s is the ideal total voyage, s' is the actual total voyage, (θ)0,φ0)，(θf,φf)，(θ′f,φ′f) Respectively, the latitude and longitude of the ideal initial entry point e, the actual landing site f' and the ideal landing site f.
Further, determining that the atmosphere enters a guidance law in the step (2), firstly, carrying out stage division on an entering process according to flight capacity, and then designing a guidance strategy of each stage; specifically, the method comprises the following steps:
(2.1) judging whether the resistance acceleration is larger than 0.2g, if so, turning to the step (2.2); otherwise, entering a trim attack angle section, and flying by adopting a fixed inclination angle of 0 degree in the trim attack angle section;
(2.2) judging whether the speed is less than a critical speed, if so, entering a course correction segment, and otherwise, entering a main deceleration segment; the navigation direction correction section adopts a course correction and saturation amplitude limiting guidance strategy to fly, and the main deceleration section adopts a guidance strategy based on a nominal track method to fly.
Further, the initial entry point schedule DR in step (4)0Calculated according to the following formula:
sinCR0＝sins0sin(Az-Az′0)
cosDR0＝coss0/cosCR0
cos(s)＝sinφ0sinφf+cosφ0cosφfcos(θf-θ0)
cos(s0)＝sinφ0sinφ′0+cosφ0cosφ′0cos(θ′0-θ0)
s is the ideal total range, s0Voyage, Az 'for actual initial entry point deviating from ideal initial entry point'0Azimuth of the actual initial entry point, (θ)0,φ0)，(θf,φf)，(θ′0,φ′0) Respectively the longitude and latitude of an ideal initial entry point e, an ideal landing point f and an actual initial entry point; CR0Is the initial entry point entry level;
the sign of the initial entry point entry length is determined by:
further, the deviation amount of the actual initial range exceeding the limit range in the step (5) is determined by:
wherein DRerr+，DRerr-The distance needs to be compensated for the deviation.
Further, the deviation amount is used in step (5) to correct the longitudinal reference value of the nominal track, and the longitudinal reference value is determined by the following method:
wherein,is the corrected longitudinal reference value.
Further, the course correction plus saturation amplitude limiting guidance strategy is determined by the following method:
wherein, sigma is a roll angle, K1 is an over-control coefficient, CR represents a transverse path deviation, namely the residual transverse path to be flown, StogoRepresenting the to-be-flown stretch required to reach the ideal landing point, equal to the total to-be-flown stretch StotalThe flight profile is subtracted.
Further, the over-control coefficient K1 is more than 1 and is better within the range of the lift force control capability of the detector.
Further, the critical speed is determined by:
from kinetic equationsDeducing whenVelocity height relationship of time:
wherein r is rm+ h is the distance between the entrance mass and the spark mass, rmIs the Mars radius, the gravitational constant of the MuMars; l and D, the resistance and the lift acceleration of the detectors, and V is the speed of the entrance device relative to the Mars; beta is the ballistic coefficient of the inlet, rho Mars atmospheric density;
the velocity height curve intersects with the velocity height curve in the nominal track, and the velocity at the intersection point is the critical velocity.
Furthermore, the limit value of the roll angle is determined by simulation in consideration of the parachute opening height and the lateral deviation constraint, wherein the constraint mainly comprises the following two aspects: firstly, the method comprises the following steps: in order to improve the parachute opening height, the smaller the amplitude limiting value of the roll angle is; and secondly, the amplitude limiting value of the roll angle is required to ensure the transverse maneuverability of the detector, avoid the over-frequency of reversal and avoid the excessive fuel consumption of attitude excitation.
Compared with the prior art, the invention has the beneficial effects that:
in order to meet the strong parachute opening constraint of the parachute, under the condition that the deviation of the state quantity of an entry point is considered to be large, the correction stage of the deviation of the longitudinal and transverse strokes is reasonably planned according to the flight capability of a detector, and by improving the analysis prediction correction algorithm based on the nominal track method, the invention designs the self-adaptive planning method for the guidance track of the atmosphere entering, so that the height and the dynamic pressure distribution at the parachute opening point are reduced as much as possible while the accuracy of the drop point is comprehensively considered, and the success rate of the parachute opening task is improved.
And calculating the reachable range of the to-be-flown flight according to the flight capability of the detector under the condition of large latitude and longitude deviation of the initial entry point, and subtracting the reachable range from the actual to-be-flown flight under the deviation condition to obtain the deviation value of the to-be-flown flight to be compensated. By compensating the deviation value, the flight capability of the detector can be utilized most fully, the range deviation is reduced as far as possible, meanwhile, the correction of the height is not sacrificed, the height and the dynamic pressure distribution at the parachute opening point are reduced, and the success rate of parachute opening tasks is improved. .
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic illustration of a voyage course;
FIG. 3 is a comparison of guidance instructions for two algorithms;
figure 4 is a comparison of the height versus time curves of the two algorithms,
Detailed Description
The invention is described in detail below with reference to the figures and examples.
An adaptive planning method for an atmospheric admission guidance track is shown in fig. 1, and comprises the following steps:
(1) analyzing the flight capability of the detector;
the flight capability analysis mainly refers to the change rule of the flight longitudinal and transverse courses with the roll angle aiming at a detector with a certain fixed configuration, wherein the longitudinal and transverse courses are defined as shown in the following figure 2. Can be obtained from the longitude and latitude of the initial entry point and the actual landing point. The initial entry point is known, and assuming a constant roll angle, the actual landing point can be obtained by an integral kinetic equation.
Let e be the intersection point of the connecting line of the centroid and the sphere center of the landing patrol instrument and the surface of the planet at the moment of entering, f be the ideal landing point (here, the actual height of the parachute opening point is referred to, e also refers to the intersection point of the sphere concentric with the sphere center at the height, the same applies below), f be the actual landing point, and e be the longitude and latitude of the corresponding e point, f' point (theta is the same as below), respectively0,φ0)，f(θf,φf)，f′(θ′f,φ′f). Defining a large circular arc ef 'passing through the point e and f' as the actual total flight path, an ef 'section circular arc as the flight longitudinal path DR, an f' f section circular arc as the transverse path CR, and ef as the total longitudinal path to be flown, and marking as Stotal. Az and Az' are azimuth angles of the two sections of circular arcs respectively, namely an included angle between the tangential direction of the circular arcs and the true north direction. ef' is the total range s. The longitudinal, transverse and total voyage can be obtained by the longitude and latitude of the initial entry point and the actual landing point, and the specific formula is as follows:
sinCR＝sinssin(Az-Az′)
cosDR＝coss/cosCR
az, Az 'are solved in the same way, and Az' is taken as an example
cos(s)＝sinφ0sinφ′f+cosφ0cosφ′fcos(θ′f-θ0)
(2) According to the flight capability, the entering process is divided into stages: the method comprises a trim attack angle section, a main deceleration section and a course correction section, and a guidance strategy of each stage is designed.
Trimming the attack angle section: when the resistance acceleration is less than 0.2g, the change of the flight distance is slightly influenced by the roll angle due to small aerodynamic force, and the flight adopts a fixed roll angle of 0 degree at the stage;
a main deceleration section: in the stage, an analytic prediction correction algorithm based on a nominal track method is adopted to calculate the roll angle:
in the above formula, h is the flying height,is the rate of change of height; DR is a longitudinal voyage; v is the speed of the inlet relative to the planet; sigma is an inclination angle of the intake device, is used for describing an included angle between a speed vector of the intake device relative to the planet and a longitudinal plane and controlling components of the lift force in the longitudinal plane and the horizontal plane; l and D advancer drag and lift acceleration ·*The reference values for the nominal trajectory are F1, F2 and F3, the feedback coefficient is F1, the overcontrol coefficient is K, the value is generally 5, and the calculation method is shown in the documents G.L.Carman, D.G. Ives, D.K.geller].1998》。
A course correction segment: when the speed is less than a certain critical speed Vt, the range control capability is greatly reduced, the longitudinal guidance law is continuously adopted to exert a remarkable control effect on the range, and the saturation of the controlled quantity is easily caused, so that the transverse deviation is effectively reduced by adopting course correction control. The stage adopts a course correction control and saturation amplitude limiting algorithm:
where σ is the roll angle, K1 is the override coefficient, taken here as 10, CR represents the lateral deviation, i.e. the remaining lateral path to be flown, StogoRepresenting the to-be-flown stretch required to reach the ideal landing point, equal to the total to-be-flown stretch StotalMinus the flight envelope, as shown in figure 2.
The critical speed means that the aircraft flies in the supersonic section, and the lift force can not completely balance the influence of gravity any more when the aircraft finally reaches a certain moment along with the descending of the altitude, namely, the change rate of the flight path angle is also less than 0 when the full lift force is upward. The significance of this transition point is that it defines the efficiency of aerodynamic lift for range control beyond which beyond this time the flight path angle cannot be increased to extend range even with full lift upwards, and the range adjustability becomes limited. The critical speed may be determined by: and deducing a height velocity curve which ensures that the change rate of the flight path angle is 0 from a kinetic equation, and intersecting the height velocity curve of the reference track, wherein the velocity at the intersection point is the critical velocity.
From kinetic equationsDerivation, consideration ofWhen there is
Wherein r is rm+ h is the distance between the entrance mass and the spark mass, rmIs the Mars radius, the gravitational constant of the MuMars; l and D entry drag and lift acceleration, V entry relativeThe magnitude of the velocity of the spark; beta is the ballistic coefficient of the inlet, rho Mars atmospheric density;
from the speed Vt of 1700m/s, there are two purposes to limit the roll angle: firstly, in order to improve the parachute opening height, the smaller the inclination angle amplitude of the section is, the higher the parachute opening height is; secondly, certain transverse maneuvering capability is ensured, the maneuvering capability cannot be overlarge, because the constraint boundary value at the transverse control tail end is small, the overlarge transverse maneuvering capability easily causes unnecessary reversal of the roll angle, the attitude maneuvering consumes redundant fuel, and the limit amplitude is determined to be 30 degrees after analysis.
(3) After the latitude and longitude deviation of the initial entry point is analyzed, the allowable range of the initial longitudinal range is initialized;
and (3) adopting the guidance law of the step (2) under the condition of fully considering the limit deviation atmospheric density, the lift coefficient, the resistance coefficient, the three-axis aerodynamic moment coefficient, the initial entrance angle, the initial speed, the mass and the navigation deviation, wherein the roll angle meets the conditions of [ -90 degrees, and 90 degrees DEG]Setting different entry point initial schedules to DR0(at the nominal entry point, the initial longitudinal length DR should be zero), reversely deducing the longitude and latitude of the initial entry point after deviating from the nominal entry point according to a spherical triangle formula, and judging whether the parachute opening state such as height, dynamic pressure, Mach number, precision and the like meets given constraints or not through integral dynamics to the parachute opening point. If the initial longitudinal distance is satisfied, the initial longitudinal distance can be positively increased or negatively decreased until the parachute opening restriction is not satisfied. The limit range of the initial course which can be adjusted by the guidance law is [ DR ]min-，DRmax+]。
(4) If the initial longitude and latitude deviation is overlarge, adopting a self-adaptive online planning reference track algorithm;
(4.1) calculating an initial longitudinal distance generated after the initial longitude and latitude deviates, and solving a longitudinal distance to be compensated;
first, an initial longitudinal DR is calculated0Initial entry point entry level DR0Calculated according to the following formula:
sinCR0＝sins0sin(Az-Az0′)
cosDR0＝coss0/cosCR0
cos(s)＝sinφ0sinφf+cosφ0cosφfcos(θf-θ0)
cos(s0)＝sinφ0sinφ′0+cosφ0cosφ′0cos(θ′0-θ0)
s is the ideal total range, s0Voyage, Az 'for actual initial entry point deviating from ideal initial entry point'0Azimuth of the actual initial entry point, (θ)0,φ0)，(θf,φf)，(θ′0,φ′0) Respectively the longitude and latitude of an ideal initial entry point e, an ideal landing point f and an actual initial entry point; CR0Is the initial entry point entry level;
note that the sign of the initial entry point entry length is determined by:
limit range [ DR ] according to allowable initial coursemin-，DRmax+]Calculating the deviation amount of the actual longitudinal distance exceeding the limit range, and obtaining:
wherein DRerr+，DRerr-The distance needs to be compensated for the deviation.
And (4.2) adaptively compensating the deviation distance, and correcting the longitudinal stroke quantity of the reference track for generating a new guidance law.
Wherein,is the updated longitudinal reference value.
(5) Solving guidance law
Substituting for the solution obtained in step (4)And updating by adopting an analytic prediction correction algorithm based on a nominal track, and calculating a new guidance law as follows:
the effectiveness of the method is demonstrated by taking an MSL Mars science laboratory as an example and through comparison simulation with an MSL atmospheric admission guidance algorithm. The Mars lander has a mass of 992kg and a maximum cross-sectional area of 16m2Lift-drag ratio of 0.18 and ballistic coefficient of 115kg/m2. The entry procedure initial and terminal condition constraints are shown in table 1.
First, a single latitude bias simulation is set, where only the initial entry point latitude bias is set to-0.4 °. The simulation results of the algorithm of the present invention compared with the MSL guidance method are shown in fig. 3 and 4. As can be seen from fig. 3, due to the large initial latitude deviation, the guidance command of the MSL algorithm is saturated to 90 ° in the initial stage of lift control and lasts for about 50 s. The algorithm of the invention effectively avoids the condition of instruction saturation by the guidance instruction through the online self-adaptive planning of the reference trajectory, thereby effectively improving the parachute opening height, which is improved by about 500 meters as shown in fig. 4.
Table 1 entry procedure initial and terminal condition constraints
Parameter(s) Initial entry point Umbrella opening point
Height (Km) 126.1 /
Longitude (°) 0° 0
Latitude (°) 12.2° 0
Speed (m/s) 6750 /
Angle of incidence (°) -14.4 /
Azimuth of velocity 90 /
Table 2 shooting simulation parameter setting table
The deviation parameter settings of the 1000 times of shooting simulation are shown in table 2, and the statistics of the result data are shown in table 3:
TABLE 3 statistics of targeting results
The results of the targeting simulation show that the spread variance for flight is large (3 σ about 2.5Km) and the spread variance for altitude is small (3 σ about 0.5 Km). Simulation verifies that the method can effectively reduce the height of the parachute opening point and the dispersion of dynamic pressure, and improve the success rate of parachute opening tasks.
The invention has not been described in detail in part of the common general knowledge of those skilled in the art.

Claims (9)

1. An adaptive planning method for an atmospheric admission guidance track is characterized by comprising the following steps:
(1) analyzing the flight capability of the detector, and acquiring the change rule of the flight longitudinal and transverse with the roll angle; the flight capability of the analysis detector is realized by the following modes:
firstly, determining the positions of landing points which can be flown by a detector under different roll angles;
then, determining an ideal azimuth Az and an actual azimuth Az' according to the landing point position;
cos(s)＝sinφ0sinφf+cosφ0cosφfcos(θf-θ0)
cos(s′)＝sinφ0sinφ′f+cosφ0cosφ′fcos(θ′f-θ0)
finally, the change rule of the flight longitudinal range DR and the flight transverse range CR along with the roll angle is obtained by combining the following formulas:
sinCR＝sins′sin(Az-Az′)
cosDR＝coss′/cosCR
in the above, s is the ideal total voyage, s' is the actual total voyage, (θ)0,φ0)，(θf,φf)，(θ′f,φ′f) Respectively the longitude and latitude of an ideal initial entry point e, an actual landing point f' and an ideal landing point f;
(2) segmenting the whole entering process according to the change rule, and determining the atmosphere entering guidance law of each stage; the guidance strategy starts to work when the navigation height is less than 125km, and the guidance strategy is designed based on a nominal track and the nominal value comprises a longitudinal range;
(3) adopting the guidance law of the step (2), and the roll angle satisfies [ -90 degrees, 90 degrees °]Setting different initial longitudinal courses of the entry points, judging whether the parachute opening states under the different entry points meet given constraints, if so, positively increasing the initial longitudinal course or negatively decreasing the initial longitudinal course until the parachute opening constraints are not met, and determining the limit range [ DR ] of the initial longitudinal course which can be adjusted by the guidance lawmin-，DRmax+]；
(4) In the actual flight process, judging whether the longitudinal stroke of the initial entry point is within the limit range, if so, controlling by adopting the guidance law in the step (2) to finish the guidance for atmospheric entry; if not, executing the step (5);
(5) according to the limit range [ DR ]min-，DRmax+]Calculating the deviation of the actual initial course beyond the limit range, and using the deviationAnd (3) correcting the longitudinal stroke reference value of the nominal track, substituting the correction value into the guidance law in the step (2) to obtain a new guidance law, and controlling by using the new guidance law to finish the self-adaptive planning of the atmosphere entering the guidance track.
2. The method of claim 1, wherein: determining an atmospheric guidance entering law in the step (2), firstly, carrying out stage division on an entering process according to flight capacity, and then designing a guidance strategy of each stage; specifically, the method comprises the following steps:
(2.1) judging whether the resistance acceleration is larger than 0.2g, if so, turning to the step (2.2); otherwise, entering a trim attack angle section, and flying by adopting a fixed inclination angle of 0 degree in the trim attack angle section;
(2.2) judging whether the speed is less than a critical speed, if so, entering a course correction segment, and otherwise, entering a main deceleration segment; the navigation direction correction section adopts a course correction and saturation amplitude limiting guidance strategy to fly, and the main deceleration section adopts a guidance strategy based on a nominal track method to fly.
3. The method of claim 1, wherein: initial entry point entry level DR in step (4)0Calculated according to the following formula:
sinCR0＝sins0sin(Az-Az′0)
cosDR0＝coss0/cosCR0
cos(s)＝sinφ0sinφf+cosφ0cosφfcos(θf-θ0)
cos(s0)＝sinφ0sinφ′0+cosφ0cosφ′0cos(θ′0-θ0)
s is the ideal total range, s0For voyages in which the actual initial entry point deviates from the ideal initial entry point, Az0' azimuth of actual initial entry point, ([ theta ])0,φ0)，(θf,φf)，(θ′0,φ′0) Respectively the longitude and latitude of an ideal initial entry point e, an ideal landing point f and an actual initial entry point; CR0Is the initial entry point entry level;
the sign of the initial entry point entry length is determined by:
4. the method of claim 1, wherein: the deviation amount of the actual initial longitudinal distance exceeding the limit range in the step (5) is determined by the following method:
wherein DRerr+，DRerr-The distance needs to be compensated for the deviation.
5. The method of claim 1, wherein: in the step (5), the longitudinal range reference value of the nominal track is corrected by using the deviation amount, and the longitudinal range reference value is determined by the following method:
wherein,and DR is the reference value of the nominal track longitudinal course for the corrected longitudinal course reference value.
6. The method of claim 2, wherein: the course correction and saturation amplitude limiting guidance strategy is determined by the following method:
wherein, sigma is a roll angle, K1 is an over-control coefficient, CR represents a transverse path deviation, namely the residual transverse path to be flown, StogoRepresenting the to-be-flown stretch required to reach the ideal landing point, equal to the total to-be-flown stretch StotalThe flight profile is subtracted.
7. The method of claim 6, wherein: the excessive control coefficient K1 is more than 1 and is better within the range of the lift control capability of the detector.
8. The method of claim 2, wherein: the critical speed is determined by:
from kinetic equationsDeducing whenVelocity height relationship of time:
wherein r is rm+ h is the distance between the entrance mass and the spark mass, rmIs the Mars radius, the gravitational constant of the MuMars; l and D detectorThe resistance and lift acceleration of the device, V is the speed of the entrance relative to the Mars; beta is the ballistic coefficient of the inlet, rho Mars atmospheric density;
the velocity height curve intersects with the velocity height curve in the nominal track, and the velocity at the intersection point is the critical velocity.
9. The method of claim 6, wherein: the limit value of the roll angle considers the parachute opening height and the transverse deviation constraint and is determined through simulation, wherein the constraint mainly comprises the following two aspects: firstly, the method comprises the following steps: in order to improve the parachute opening height, the smaller the amplitude limiting value of the roll angle is; and secondly, the amplitude limiting value of the roll angle is required to ensure the transverse maneuverability of the detector, avoid the over-frequency of reversal and avoid the excessive fuel consumption of attitude excitation.
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