Two-stage prediction, correction and guidance method and system for Mars atmosphere entry

Abstract

The present invention discloses a two-stage prediction and correction guidance method and system for entering the Martian atmosphere. The method includes: establishing a dynamic model of a probe for entering the Martian atmosphere; dividing the Martian atmosphere entry stage into an initial entry stage and a later entry stage, and adopting different guidance strategies according to the characteristics of different stages; in the initial entry stage, the probe flies at a constant roll angle without on-orbit guidance and roll angle adjustment; in the later entry stage, combined with the dynamic model, periodic longitudinal guidance and lateral guidance are implemented, the longitudinal guidance instruction is adjusted according to the error between the predicted longitudinal range and the predicted longitudinal range, and whether to adjust the roll angle sign is determined according to the lateral range error. The present invention does not require an additional roll angle model for specific scenarios. In the first stage, the probe flies at a constant roll angle to adapt to the low atmospheric density and hypersonic characteristics of entering the Martian atmosphere; in the second stage, the probe flies at a fixed roll angle, gradually adjusts the entry trajectory, and improves the guidance accuracy.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and in particular to a two-stage prediction, correction and guidance method and system for entering the atmosphere of Mars. Background Art

[0002] The landing process of Mars exploration is generally divided into three very different parts, namely entry, descent, and landing (EDL). In order to meet the high accuracy and robustness requirements of Mars entry guidance, active guidance algorithms have been successfully applied to Mars exploration missions. This method combines nominal trajectory tracking guidance with predictive correction guidance, divides entry guidance into multiple stages, adds adaptive distance compensation and onboard trajectory planning, and solves the problem of large initial entry state deviation. The guidance law generally believes that in the early and late stages of the entry phase, the roll angle has a weak control ability on the probe's range.

[0003] Therefore, entry guidance is generally divided into three or more stages. The first and final stages mostly use constant roll angle guidance based on experience, and the middle stage uses a combined guidance algorithm that combines the advantages of predictive correction guidance and reference path tracking guidance. However, the more segmentation segments there are, the more prior information such as segmentation thresholds, segmentation flags or nominal roll angles are required, which further increases the complexity of the algorithm and the difficulty of the integral operation. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above existing problems, the present invention is proposed. Therefore, the present invention provides a two-stage prediction and correction guidance method for entering the Martian atmosphere to solve the guidance accuracy and robustness problems of the Martian probe entering the Martian atmosphere, while reducing the algorithm complexity and integration operation difficulty.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a two-stage prediction and correction guidance method for entering the Martian atmosphere, comprising:

[0008] According to the characteristics of the Mars atmosphere entry phase and the motion data of the probe, a dynamic model of the Mars atmosphere entry probe is established;

[0009] Based on speed and drag acceleration, the Mars atmosphere entry phase is divided into the initial entry phase and the final entry phase, and different guidance strategies are adopted according to the characteristics of different phases.

[0010] According to the influence of the roll angle, the probe enters the initial stage and flies at a constant roll angle, without on-orbit guidance and roll angle adjustment;

[0011] Entering the latter stage, the dynamic model is combined to implement periodic longitudinal guidance and lateral guidance, adjust the longitudinal guidance command according to the error between the predicted longitudinal range and the remaining longitudinal range, and determine whether to adjust the sign of the roll angle according to the lateral range error.

[0012] As a preferred solution of the two-stage prediction, correction and guidance method for entering the Martian atmosphere of the present invention, a dynamic model of the probe for entering the Martian atmosphere is established according to the characteristics of the Martian atmosphere entry stage and the motion data of the probe, including:

[0013] Combining dynamic equations with actual measurement data, the altitude, longitude, latitude, speed, track angle and heading angle of the Mars probe when it enters the Martian atmosphere are obtained;

[0014] The three degrees of freedom that ignore the influence of Mars' rotation are determined to enter into the dynamic equation. Taking the influence of uncertainty factors into consideration, the altitude change rate, longitude change rate, latitude change rate, speed change rate, track angle change rate and heading angle change rate are further derived.

[0015] As a preferred solution of the two-stage prediction, correction and guidance method for entering the Martian atmosphere according to the present invention, it also includes:

[0016] The specific formulas for the altitude change rate, longitude change rate, latitude change rate, speed change rate, track angle change rate and heading angle change rate are as follows:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] Among them, h,θ,φ,v,γ, is the probe's altitude, longitude, latitude, speed, track angle, and heading angle from the surface of Mars, k, B c and ρ are lift-to-drag ratio, ballistic coefficient and atmospheric density respectively, σ is the guidance command, g is the gravitational acceleration, R m is the radius of Mars, β is the fitting parameter, C L and C Dare the lift coefficient and drag coefficient of the probe respectively, S is the reference surface area of ​​the probe, and m is the mass of the probe.

[0024] As a preferred solution of the two-stage prediction, correction and guidance method for entering the Martian atmosphere of the present invention, the Martian atmosphere entry stage is divided into an initial entry stage and a later entry stage based on speed and drag acceleration, including:

[0025] The formula for entering the segment is:

[0026]

[0027] Where D is the detector resistance acceleration, C D is the detector drag coefficient, ρ is the atmospheric density, and v is the detector speed;

[0028] When the speed v≥1700m / s or the resistance acceleration D<0.2g, the detector enters the initial section; when the speed v<1700m / s or the resistance acceleration D≥0.2g, the detector enters the latter section.

[0029] As a preferred solution of the two-stage prediction and correction guidance method for entering the Martian atmosphere of the present invention, wherein: according to the influence of the roll angle, the probe entering the initial stage flies at a constant roll angle without performing on-orbit guidance and roll angle adjustment, including:

[0030] The probe performs longitudinal guidance at the entry interface to determine the motion guidance instruction |σ| of the probe in the initial stage of entry. The probe flies at a constant roll angle |σ| for 60 seconds.

[0031] As a preferred solution of the two-stage prediction and correction guidance method for entering the Martian atmosphere of the present invention, wherein: adjusting the longitudinal guidance instruction according to the error between the predicted longitudinal range and the remaining longitudinal range includes:

[0032] Combined with the dynamic model, the longitudinal distance of the Mars atmosphere entry segment is calculated using the formula:

[0033]

[0034] Among them, S is the longitudinal range of the detector, v is the detector speed, and γ is the detector track angle;

[0035] The detector state is numerically integrated using the longitudinal range formula, starting from the current state of the detector until the parachute opening condition is met. The longitudinal range S at the time of parachute opening is f To predict longitudinal course;

[0036] Assume Mars is a star with radius R m The remaining longitudinal range S is calculated based on the current longitude and latitude of the detector and the longitude and latitude of the target parachute opening point. r , the formula is:

[0037]

[0038] Among them, R m is the radius of Mars, θ i and is the current latitude and longitude of the detector, θ f and The latitude and longitude of the target parachute opening point;

[0039] The longitudinal error is calculated. If the longitudinal error is less than the threshold, no longitudinal guidance instruction adjustment is performed. If the longitudinal error is greater than the threshold, the secant method is used to iteratively solve the target longitudinal instruction.

[0040] As a preferred solution of the two-stage prediction correction guidance method for entering the Martian atmosphere of the present invention, wherein: judging whether to adjust the sign of the roll angle according to the traverse error includes:

[0041] Periodic guidance begins after entering the rear section, and the lateral error corridor is defined:

[0042] Λ=a1v+a2

[0043] Among them, Λ is the cross-range error threshold, a1 and a2 are constants, and v is the detector speed;

[0044] When the current traverse error of the detector is within the error corridor, the sign of the roll angle of the current guidance cycle remains unchanged. When the traverse error exceeds the error corridor, the sign of the roll angle of the current guidance cycle flips.

[0045] In a second aspect, the present invention provides a two-stage prediction and correction guidance system for entering the Martian atmosphere, comprising:

[0046] A dynamic model building module is used to build a dynamic model of the probe during the Mars atmosphere entry phase according to the characteristics of the Mars atmosphere entry phase and the motion data of the probe;

[0047] The phase identification module is used to divide the Mars atmospheric entry phase into the initial phase and the final phase based on the speed and drag acceleration, and adopt different guidance strategies according to the characteristics of different phases;

[0048] The initial stage guidance module is used to make the initial stage probe fly at a constant roll angle according to the roll angle, without on-orbit guidance and roll angle adjustment;

[0049] Enter the back-end guidance module, enter the back-end and combine the dynamic model to implement periodic longitudinal guidance and lateral guidance, adjust the longitudinal guidance command according to the error between the predicted longitudinal range and the remaining longitudinal range, and determine whether to adjust the sign of the roll angle according to the lateral range error.

[0050] In a third aspect, the present invention provides a computing device, comprising:

[0051] Memory and processor;

[0052] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the two-stage prediction and correction guidance method for entering the Martian atmosphere are implemented.

[0053] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, can implement the steps of the two-stage prediction and correction guidance method for entering the Martian atmosphere.

[0054] Compared with the prior art, the present invention has the following beneficial effects: the present invention follows the concept of segmentation, only implements the idea of ​​predictive correction guidance, and realizes precise guidance with fewer segmentation stages and a simple algorithm workflow; the proposed guidance method divides the entry stage into two stages, the front entry stage and the back entry stage. In the first stage, the probe flies at a constant roll angle to adapt to the low atmospheric density and hypersonic speed characteristics of entering the Martian atmosphere; the second stage is divided into multiple guidance cycles. In each guidance cycle, the probe flies at a fixed roll angle, gradually adjusts the entry trajectory, and improves the guidance accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0056] Figure 1 A schematic diagram of the overall process of a two-stage prediction, correction and guidance method for entering the Martian atmosphere according to an embodiment of the present invention;

[0057] Figure 2 A schematic diagram of a lateral error corridor of a two-stage prediction-correction-guidance method for entering the Martian atmosphere according to an embodiment of the present invention;

[0058] Figure 3 A schematic diagram of the error band of the two-stage prediction-correction-guidance method for entering the Martian atmosphere according to an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0060] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0061] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0062] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0063] At the same time, in the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0064] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] Example 1

[0066] Reference Figure 1-2, which is an embodiment of the present invention, provides a two-stage prediction and correction guidance method for entering the Martian atmosphere, comprising:

[0067] S1: Establish a dynamic model of the probe during the Mars atmosphere entry phase based on the characteristics of the probe and the motion data of the probe;

[0068] Furthermore, the dynamic equations and actual measurement data are combined to obtain the altitude, longitude, latitude, speed, track angle and heading angle of the Mars probe when it enters the Martian atmosphere;

[0069] Ignoring the influence of Mars' rotation, the three degrees of freedom are determined to enter the dynamic equation, and considering the influence of uncertainty factors, the altitude change rate, longitude change rate, latitude change rate, speed change rate, track angle change rate and heading angle change rate are further derived;

[0070] Furthermore, the specific formulas for the altitude change rate, longitude change rate, latitude change rate, speed change rate, track angle change rate and heading angle change rate are as follows:

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] Among them, h,θ,φ,v,γ, is the probe's altitude, longitude, latitude, speed, track angle, and heading angle from the surface of Mars, k, B c and ρ are lift-to-drag ratio, ballistic coefficient and atmospheric density respectively, σ is the guidance command, g is the gravitational acceleration, R m is the radius of Mars, β is the fitting parameter, C L and C D are the lift coefficient and drag coefficient of the detector respectively, S is the reference surface area of ​​the detector, and m is the mass of the detector;

[0078] Preferably, C L and C D , k, and g are calculated using Curiosity’s fitting model;

[0079] Preferably, the lift-to-drag ratio, ballistic coefficient, atmospheric density and gravitational acceleration are expressed as:

[0080]

[0081]

[0082] ρ=e β(h)

[0083]

[0084] Among them, k,B c and ρ are lift-to-drag ratio, ballistic coefficient and atmospheric density, g is the acceleration due to gravity, R m is the radius of Mars, β is the fitting parameter, C L and C D are the lift coefficient and drag coefficient of the probe, respectively, S is the reference surface area of ​​the probe, m is the mass of the probe, and μ is the Martian gravitational constant;

[0085] It should be noted that a more accurate and reliable dynamic model is established to describe the movement behavior of the probe in the Martian atmosphere, adapt to various uncertainties and interference factors in the process of entering the Martian atmosphere, provide high-precision and robust guidance performance, and ensure that the probe can stably enter the Martian atmosphere; simplify the algorithm workflow to achieve precise guidance, reduce algorithm complexity and the difficulty of integral operations; by solving the guidance accuracy and robustness problems of the Mars probe entering the Martian atmosphere, the success rate of the Mars exploration mission can be improved and the development of Mars exploration technology can be promoted.

[0086] S2: Based on speed and drag acceleration, the Mars atmosphere entry phase is divided into the initial entry phase and the final entry phase, and different guidance strategies are adopted according to the characteristics of different phases;

[0087] Going further, the segment division formula is:

[0088]

[0089] Where D is the detector resistance acceleration, C D is the detector drag coefficient, ρ is the atmospheric density, and v is the detector speed;

[0090] When the speed v≥1700m / s or the drag acceleration D<0.2g, the detector enters the initial stage; when the speed v<1700m / s or the drag acceleration D≥0.2g, the detector enters the latter stage;

[0091] It should be noted that by dividing the entry into the Martian atmosphere into the initial entry stage and the later entry stage based on speed and drag acceleration, and adopting different guidance strategies according to the characteristics of different stages, we can better adapt to the characteristics and needs of different stages, improve the guidance accuracy and robustness; reduce the guidance difficulty and algorithm complexity: by dividing the entry stage into two stages, we can simplify the guidance strategy and algorithm, reduce the guidance difficulty and algorithm complexity, and improve the computing efficiency and real-time performance; through reasonable guidance strategies and algorithms, we can improve the success rate of the probe entering the Martian atmosphere, providing important guarantees for the smooth completion of the Mars exploration mission.

[0092] S3: Based on the influence of the roll angle, the probe enters the initial stage and flies at a constant roll angle without on-orbit guidance or roll angle adjustment;

[0093] Furthermore, the probe is longitudinally guided at the entry interface to determine the motion guidance command |σ| of the probe in the initial stage of entry, and the probe flies at a constant bank angle |σ| for 60 seconds;

[0094] It should be noted that in the first stage, the probe flew at a constant roll angle to adapt to the low atmospheric density and hypersonic characteristics of entering the Martian atmosphere while reducing energy consumption; in the initial stage of entry, the probe flew at a constant roll angle, avoiding guidance errors caused by changes in the roll angle and improving guidance accuracy and stability; the probe did not perform on-orbit guidance and roll angle adjustment, which simplified the guidance process, reduced the requirements for the guidance system, and improved real-time performance; longitudinal guidance at the entry interface can better adapt to unknown factors and interference, and improve the probe's adaptability to unknown factors; through reasonable guidance strategies and algorithms, the success rate of the probe's entry into the Martian atmosphere can be improved, providing important guarantees for the smooth completion of the Mars exploration mission.

[0095] S4: Entering the latter stage and combining with the dynamic model, implementing periodic longitudinal guidance and lateral guidance, adjusting the longitudinal guidance command according to the error between the predicted longitudinal range and the remaining longitudinal range, and judging whether to adjust the sign of the roll angle according to the lateral range error.

[0096] Combined with the dynamic model, the longitudinal distance of the Mars atmosphere entry segment is calculated using the formula:

[0097]

[0098] Among them, S is the longitudinal range of the detector, v is the detector speed, and γ is the detector track angle;

[0099] The detector state is numerically integrated using the longitudinal range formula, starting from the current state of the detector until the parachute opening condition is met. The longitudinal range S at the time of parachute opening is f To predict longitudinal course;

[0100] Assume Mars is a star with radius R m The remaining longitudinal range S is calculated based on the current longitude and latitude of the detector and the longitude and latitude of the target parachute opening point. r , the formula is:

[0101]

[0102] Among them, R m is the radius of Mars, θ i and is the current latitude and longitude of the detector, θ f and The latitude and longitude of the target parachute opening point;

[0103] Calculate the longitudinal error. If the longitudinal error is less than the threshold, no longitudinal guidance instruction adjustment is performed. If the longitudinal error is greater than the threshold, the secant method is used to iteratively solve the target longitudinal instruction.

[0104] Preferably, the formula for calculating the longitudinal error is:

[0105] ΔS=S f -S r

[0106] Among them, ΔS is the longitudinal error value, S f is the predicted vertical range at the time of parachute opening, S r The remaining longitudinal distance between the current longitude and latitude of the detector and the longitude and latitude of the target parachute opening point;

[0107] Preferably, the secant method iteration formula is:

[0108]

[0109] Among them, σ i+1 is the longitudinal instruction, ΔS is the longitudinal error value;

[0110] Preferably, ΔS(σ i+1 )<ΔS threshold ;

[0111] Furthermore, periodic guidance is started after entering the latter stage, and the lateral error corridor is defined:

[0112] Λ=a1v+a2

[0113] Among them, Λ is the cross-range error threshold, a1 and a2 are constants, and v is the detector speed;

[0114] When the current range error of the detector is within the error corridor, the sign of the roll angle of the current guidance cycle remains unchanged. When the range error exceeds the error corridor, the sign of the roll angle of the current guidance cycle flips, such as Figure 2 As shown;

[0115] Preferably, the calculation formula of the detector's lateral range error is:

[0116] ΔΨ=ψ i -ψ e

[0117] Among them, ψ i is the current heading angle of the detector, ψ e is the current desired heading angle of the probe;

[0118] The first choice defines the angle between the line connecting the current position of the detector to the target parachute opening point and the true north direction.

[0119]

[0120] Among them, ψ i is the current heading angle of the detector, ψ e is the current desired heading angle of the detector, and X is the angle between the line connecting the current position of the detector to the target parachute opening point and the true north direction;

[0121] Preferably, the current desired heading angle of the detector is obtained according to the angle between the line from the current position of the detector to the target parachute opening point and the true north direction, and the formula is:

[0122]

[0123] Among them, ψ i is the current heading angle of the detector, ψ e is the current desired heading angle of the detector, and X is the angle between the line connecting the current position of the detector to the target parachute opening point and the true north direction;

[0124] It should be noted that in the later stage of entry, the guidance method better adapts to the complex environment and uncertainty factors in the process of entering the Martian atmosphere, and improves the guidance accuracy and stability; by adopting the secant method to iteratively solve the target longitudinal instructions, the guidance process is simplified, the requirements for the guidance system are reduced, and the real-time performance is improved; at the same time, by calculating the lateral error and the expected heading angle, and judging whether to adjust the sign of the roll angle based on the error, it can better adapt to unknown factors and interference, improve the adaptability of the probe to unknown factors, and improve the success rate of the probe entering the Martian atmosphere, providing important guarantees for the smooth completion of the Mars exploration mission.

[0125] The above is a schematic scheme of the two-stage prediction, correction and guidance method for entering the Martian atmosphere of this embodiment. It should be noted that the technical scheme of the system for two-stage prediction, correction and guidance for entering the Martian atmosphere is the same as the technical scheme of the above-mentioned two-stage prediction, correction and guidance method for entering the Martian atmosphere. For details not described in detail in the technical scheme of the two-stage prediction, correction and guidance system for entering the Martian atmosphere of this embodiment, please refer to the description of the technical scheme of the above-mentioned two-stage prediction, correction and guidance method for entering the Martian atmosphere.

[0126] In this embodiment, the two-stage prediction and correction guidance system for entering the Martian atmosphere includes:

[0127] A dynamic model building module is used to build a dynamic model of the probe during the Mars atmosphere entry phase according to the characteristics of the Mars atmosphere entry phase and the motion data of the probe;

[0128] The phase identification module is used to divide the Mars atmospheric entry phase into the initial phase and the final phase based on the speed and drag acceleration, and adopt different guidance strategies according to the characteristics of different phases;

[0129] The initial stage guidance module is used to make the initial stage probe fly at a constant roll angle according to the roll angle, without on-orbit guidance and roll angle adjustment;

[0130] Enter the back-end guidance module, enter the back-end and combine the dynamic model to implement periodic longitudinal guidance and lateral guidance, adjust the longitudinal guidance command according to the error between the predicted longitudinal range and the remaining longitudinal range, and determine whether to adjust the sign of the roll angle according to the lateral range error.

[0131] This embodiment also provides a computing device, which is applicable to the case of two-stage prediction and correction guidance of Mars atmosphere entry, including:

[0132] A memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the two-stage prediction, correction and guidance method for entering the Martian atmosphere as proposed in the above embodiment.

[0133] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the two-stage prediction, correction and guidance method for entering the Martian atmosphere as proposed in the above embodiment is implemented.

[0134] The storage medium proposed in this embodiment and the two-stage prediction, correction and guidance method for entering the Martian atmosphere proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0135] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0136] Example 2

[0137] Reference Figure 3 Table 1 and Table 1 are an embodiment of the present invention, which provide a two-stage prediction, correction and guidance method for entering the Martian atmosphere. In order to verify its beneficial effects, the comparison results of the two schemes are provided.

[0138] To further evaluate the robustness of the proposed guidance method, we performed a Monte Carlo simulation with 1000 runs in this instance.

[0139] In this simulation experiment, we considered the entry state error, lift-to-drag ratio error, ballistic coefficient error and atmospheric density error. These errors were modeled as random Gaussian distributions, and the mean and standard deviation of the entry state were directly given. The lift-to-drag ratio error, ballistic coefficient error and atmospheric density error were designed to have a disturbance range of ±40%, with the mean value being the nominal value of the corresponding model and the standard deviation being one-third of the disturbance range.

[0140] The proposed guidance method is compared with an uncontrolled method, which uses an optimization algorithm on the entry interface to generate a profile of reference bank angle versus energy according to the current state of the detector and the target parachute opening state.

[0141] During the flight, the detector calculates the current energy based on its current altitude and speed, and selects a roll angle from this fixed reference roll angle profile as a guidance instruction, without the need to recalculate the roll angle online.

[0142] The detector entering the ±3σ error band of longitude and latitude obtained by the uncontrolled method and the Monte Carlo simulation method are as follows: Figure 3As shown in the figure, by statistically analyzing the longitude and latitude of the entry trajectory generated by Monte Carlo simulation, the 3σ deviation of the entry trajectory is calculated, and the ±3σ error band is connected to generate; in the late entry period (after -78° longitude), the error band obtained using the improved prediction correction guidance is significantly smaller than the error band obtained using the uncontrolled method. Compared with the uncontrolled method, the error band area obtained by this method is reduced by 8.17%.

[0143] The spatial distance between the actual parachute opening point generated by the statistical Monte Carlo simulation and the target parachute opening point is the miss distance. The statistical results include the maximum miss distance, the percentage of miss distances less than 5 km and 10 km, and the root mean square value of the miss distance as shown in Table 1.

[0144] Table 1 Statistical results of parachute opening point distribution

[0145] Guidance method Uncontrolled derivative algorithm Improved prediction-correction guidance algorithm Maximum miss distance (km) 36.73 13.47 Percentage of miss distance less than 5km (%) 42.4 92 Percentage of miss distance less than 10km (%) 72.8 100 RMS value of miss distance (km) 9.08 2.84

[0146] As shown in the table above, when the uncontrolled algorithm is used for guidance, the RMS value of the miss distance is 9.08km, and the maximum miss distance is 36.73km. About 42.4% of the parachute opening points are within 5km of the target parachute opening point, and 72.8% are within 10km; when the improved prediction and correction guidance algorithm is used, the RMS value of the miss distance is 9.08km, and the maximum miss distance is 13.47km; about 92% of the parachute opening points are within 5km of the target parachute opening point, and 100% are within 10km.

[0147] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A two-stage prediction and correction guidance method for entering the Martian atmosphere, characterized in that: include: According to the characteristics of the Mars atmosphere entry phase and the motion data of the probe, a dynamic model of the Mars atmosphere entry probe is established; Based on speed and drag acceleration, the Mars atmosphere entry phase is divided into the initial entry phase and the final entry phase, and different guidance strategies are adopted according to the characteristics of different phases. The formula for entering the segment is: Where D is the detector resistance acceleration, C D is the detector drag coefficient, ρ is the atmospheric density, v is the detector speed, and m is the detector mass; When the speed v≥1700m / s or the drag acceleration D<0.2g, the detector enters the initial stage; when the speed v<1700m / s or the drag acceleration D≥0.2g, the detector enters the latter stage; According to the influence of the roll angle, the probe enters the initial stage and flies at a constant roll angle, without on-orbit guidance and roll angle adjustment; The probe performs longitudinal guidance at the entry interface to determine the motion guidance command |σ| of the probe in the initial stage of entry. The probe flies at a constant roll angle |σ| for 60 seconds. Entering the latter stage, combining the dynamic model, implementing periodic longitudinal guidance and lateral guidance, adjusting the longitudinal guidance command according to the error between the predicted longitudinal range and the remaining longitudinal range, and judging whether to adjust the sign of the roll angle according to the lateral range error; Combined with the dynamic model, the longitudinal distance of the Mars atmosphere entry segment is calculated using the formula: Among them, S is the longitudinal range of the detector, v is the detector speed, and γ is the detector track angle; The detector state is numerically integrated using the longitudinal range formula, starting from the current state of the detector until the parachute opening condition is met. The longitudinal range S at the time of parachute opening is f To predict longitudinal course; Assume Mars is a star with radius R m The remaining longitudinal range S is calculated based on the current longitude and latitude of the detector and the longitude and latitude of the target parachute opening point. r , the formula is: Among them, R m is the radius of Mars, θ i and is the current latitude and longitude of the detector, θ f and The latitude and longitude of the target parachute opening point; The longitudinal error is calculated. If the longitudinal error is less than the threshold, no longitudinal guidance instruction adjustment is performed. If the longitudinal error is greater than the threshold, the secant method is used to iteratively solve the target longitudinal instruction.

2. The two-stage prediction, correction and guidance method for entering the Martian atmosphere as claimed in claim 1, characterized in that: According to the characteristics of the Mars atmosphere entry phase and the motion data of the probe, a dynamic model of the Mars atmosphere entry probe is established, including: Combining dynamic equations with actual measurement data, the altitude, longitude, latitude, speed, track angle and heading angle of the Mars probe when it enters the Martian atmosphere are obtained; The three degrees of freedom that ignore the influence of Mars' rotation are determined to enter into the dynamic equation. Taking the influence of uncertainty factors into consideration, the altitude change rate, longitude change rate, latitude change rate, speed change rate, track angle change rate and heading angle change rate are further derived.

3. The two-stage prediction, correction and guidance method for entering the Martian atmosphere as claimed in claim 1 or 2, characterized in that: Also includes, The specific formulas for the altitude change rate, longitude change rate, latitude change rate, speed change rate, track angle change rate and heading angle change rate are as follows: Among them, h,θ,φ,v,γ, is the probe's altitude, longitude, latitude, speed, track angle, and heading angle from the surface of Mars, k, B c and ρ are lift-to-drag ratio, ballistic coefficient and atmospheric density respectively, σ is the guidance command, g is the gravitational acceleration, R m is the radius of Mars and m is the mass of the probe.

4. The two-stage prediction, correction and guidance method for entering the Martian atmosphere as claimed in claim 1, characterized in that: Determine whether to adjust the sign of the roll angle based on the cross-range error, including: Periodic guidance begins after entering the rear section, and the lateral error corridor is defined: Λ=a1v+a2 Among them, Λ is the cross-range error threshold, a1 and a2 are constants, and v is the detector speed; When the current traverse error of the detector is within the error corridor, the sign of the roll angle of the current guidance cycle remains unchanged. When the traverse error exceeds the error corridor, the sign of the roll angle of the current guidance cycle flips.

5. A system for predicting, correcting and guiding the entry of Mars atmosphere in two stages, based on the predicting, correcting and guiding method for the entry of Mars atmosphere in two stages according to any one of claims 1 to 4, characterized in that: include, A dynamic model building module is used to build a dynamic model of the probe during the Mars atmosphere entry phase according to the characteristics of the Mars atmosphere entry phase and the motion data of the probe; The phase identification module is used to divide the Mars atmospheric entry phase into the initial phase and the final phase based on the speed and drag acceleration, and adopt different guidance strategies according to the characteristics of different phases; The initial stage guidance module is used to make the initial stage probe fly at a constant roll angle according to the roll angle, without on-orbit guidance and roll angle adjustment; Enter the back-end guidance module, enter the back-end and combine the dynamic model to implement periodic longitudinal guidance and lateral guidance, adjust the longitudinal guidance command according to the error between the predicted longitudinal range and the remaining longitudinal range, and determine whether to adjust the sign of the roll angle according to the lateral range error.

6. An electronic device comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the two-stage prediction and correction guidance method for entering the Martian atmosphere as described in any one of claims 1 to 4 are implemented.

7. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the two-stage prediction and correction guidance method for entering the Martian atmosphere as described in any one of claims 1 to 4.

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