Soft landing augmented curvature guidance for extraterrestrial bodies

Abstract

The extraterrestrial celestial body soft landing augmented curvature guidance method disclosed by the application belongs to the technical field of deep space exploration. The method for realizing the application is as follows: a dynamic equation of a probe in a planet surface fixed coordinate system is established. According to the trajectory geometric curvature theory, combined with an energy optimal guidance law, a basic form of trajectory curvature guidance is established and an extended form of the curvature guidance is derived. In the trajectory curvature guidance law, whether the probe is in an obstacle influence area and the compensation thrust applied in the obstacle influence area are represented by a thrust compensation term, so that the extraterrestrial celestial body soft landing augmented curvature guidance law is obtained. The compensation thrust only acts on a certain space area near the terrain obstacle, and the energy consumption is closer to the energy optimal guidance law. The acceleration obtained is used for the guidance of the extraterrestrial celestial body soft landing, so as to further improve the relative height of the probe when facing the ground obstacle, and then improve the obstacle avoidance ability of the probe when facing the ground obstacle. The application also has the advantage of high real-time.

Description

Technical Field

[0001] The present invention relates to an augmented curvature guidance method for soft landing of an extraterrestrial body, belonging to the technical field of deep space exploration. Background Art

[0002] Guidance for safe planetary landings is a crucial issue in planetary exploration, crucial to the success of the entire planetary landing mission. With the continuous advancement of aerospace technology and the increasing ambition of space science research, future planetary exploration missions will tend to land in areas of greater scientific interest. These areas often have complex topography and rugged surfaces, with numerous terrain obstacles such as rocks, slopes, depressions, and hills. These obstacles pose a threat to the safety of planetary probes and increase the difficulty of landing on the target celestial body. A trajectory curvature guidance method based on an energy-optimal feedback guidance law controls the sign of the landing trajectory curvature function to guide the probe down along a geometrically convex trajectory. This method improves the probe's terrain obstacle avoidance capability and expands the observable range of the landing area. Summary of the Invention

[0003] The technical problem to be solved by the augmented curvature guidance method for soft landing of extraterrestrial bodies disclosed in the present invention is: to design a compensating thrust in the space near the terrain obstacle, and to design an augmented curvature guidance law for soft landing of extraterrestrial bodies based on the traditional trajectory curvature guidance law by using the compensating thrust, so as to increase the flight trajectory height of the probe, improve the obstacle avoidance capability of the probe and the safety of attachment to the complex terrain environment of the extraterrestrial body. It has the following advantages: (1) It can further increase the relative height of the probe when facing surface obstacles, and ensure the safe landing of the probe when the surface obstacle is higher than the initial height of the probe. (2) Compared with the trajectory curvature guidance method, this method requires lower energy consumption. (3) The guidance law is an analytical guidance law with a simple form and high solution efficiency, which can improve the real-time performance of the guidance law on the onboard computer of the probe.

[0004] The purpose of the present invention is achieved through the following technical solutions.

[0005] The invention discloses an augmented curvature guidance method for soft landing of extraterrestrial objects, which establishes the dynamic equations of the probe in the fixed coordinate system of the planetary surface. According to the trajectory geometric curvature theory and combined with the energy optimal guidance law, the basic form of trajectory curvature guidance is established and the extended form of curvature guidance is derived. In the trajectory curvature guidance law, the thrust compensation term is used to characterize whether the probe is in the obstacle influence area and the compensatory thrust applied to the obstacle influence area, thereby obtaining the augmented curvature guidance law for soft landing of extraterrestrial objects. The obtained acceleration is used to guide the soft landing of extraterrestrial objects, further improving the relative height of the probe when facing surface obstacles, thereby improving the obstacle avoidance capability of the probe facing surface obstacles.

[0006] The invention discloses an augmented curvature guidance method for soft landing of an extraterrestrial object, comprising the following steps:

[0007] Step 1: Establish a surface-fixed rectangular coordinate system for the target planet and establish the probe dynamic equations in this coordinate system.

[0008] A fixed rectangular coordinate system O-XYZ on the planetary surface is established with the target landing point as the origin O, where the Z axis is perpendicular to the local ground plane at the landing point, and its positive direction points to the outside of the target celestial body; the X axis is in the local ground plane at the landing point, and coincides with the cross product vector of the positive direction of the Z axis and the rotation direction of the target celestial body; the Y axis, X axis, and Z axis together form a right-handed coordinate system.

[0009] When the probe moves on the surface fixed connection, the inertial force and other disturbance forces caused by the planet's rotation have a smaller impact on the probe's movement than the control force generated by the engine and the planet's gravity. The inertial force and other disturbance forces caused by the planet's rotation can be ignored. During the landing and obstacle avoidance phase, since the probe's movement time is short, the gravitational acceleration g it experiences is equivalent to a constant vector. The dynamic equation of the probe system is:

[0010]

[0011] Where r = [r x ,r y ,r z ] T and v=[v x ,v y ,v z ] T They represent the position and velocity of the detector under the surface fixed connection, T=[T x ,T y ,T z ] T and a=[a x ,a y ,a z ] T They represent the three-axis components of the detector control force and control acceleration in the surface fixed connection, m represents the mass of the detector, I sp Indicates engine specific impulse, g e is the acceleration due to gravity at sea level.

[0012] Step 2: Calculate the remaining time t required for landing based on the current state of the probe go According to the trajectory geometric curvature theory and combined with the energy optimal guidance law, the basic form of trajectory curvature guidance is established, and the extended form of curvature guidance is derived based on the basic form of trajectory curvature guidance.

[0013] According to the current state of the detector X=[r T ,vT ] T Calculate the remaining time t required for landing go , is the positive real root of the equation shown in formula (2).

[0014]

[0015] In order to make the probe land along a convex trajectory, it is first necessary to determine the concavity and convexity trend of the trajectory in its current state. According to the trajectory geometric curvature theory, the condition for the trajectory to be convex in the XOZ plane is

[0016] v x (r z v x -r x v z )>0 (3)

[0017] The condition for the trajectory to be convex in the YOZ plane is

[0018] v y (r z v y -r y v z )>0 (4)

[0019] For the XOZ or YOZ plane, if the detector initial state satisfies v x (r z v x -r x v z )<0 or v y (r z v y -r y v z )<0, need t c The constant acceleration of the time period transforms the concave state into a convex trajectory state. The superscript "0" indicates the initial moment of the landing phase. If the initial state of the probe satisfies v x (r z v x -r x v z )>0 or v y (r z v y -r y v z )>0 and a turning point appears under the analytical optimal guidance law, it is necessary to apply t from the turning point c constant acceleration over a period of time, and "TP" means turning point, Indicates the remaining flight time at the turning point. If there is no turning point, the trajectory curvature guidance at this time is the analytically optimal guidance.

[0020] Combining formulas (3) and (4) and combining them with the analytical energy optimal guidance law, the basic form of trajectory curvature guidance is constructed as shown in formula (5):

[0021]

[0022] To obtain the extended form of curvature guidance, the magnitude of the constant acceleration is expressed as

[0023] a TP =na OTP (6)

[0024] Where a OTP is the acceleration calculated by analytically analyzing the optimal guidance law at the turning point, and n is a positive real number defined as the acceleration coefficient.

[0025] Step 3: In the trajectory curvature guidance law, the thrust compensation term γa is used com Characterizing whether the probe is in the obstacle influence area and the compensation thrust applied in the obstacle influence area, the augmented curvature guidance method for soft landing of extraterrestrial objects is obtained. By defining the compensation thrust a com The specific form of the on-off function γ for the compensatory thrust and its effect on the probe's range are used to derive the X, Y, and Z-axis components of the augmented curvature guidance method for extraterrestrial soft landings. This augmented curvature guidance method can further increase the probe's relative height when facing surface obstacles, thereby improving the probe's obstacle avoidance capabilities.

[0026] In order to further increase the relative height of the probe when facing surface obstacles and ensure the safe landing of the probe when the surface obstacles are higher than the initial height of the probe, the thrust compensation term γa is used in the trajectory curvature guidance law. com Characterizing whether the probe is in the obstacle influence area and the compensatory thrust applied in the obstacle influence area, the augmented curvature guidance method for soft landing of extraterrestrial objects is obtained as shown in formula (7):

[0027] a=a cur +γa com (7)

[0028] Among them, a cur is the basic form of curvature guidance (n=1) shown in formula (5), a com is the thrust compensation function, and γ is the switching function of the thrust compensation function.

[0029] The augmented curvature guidance method for soft landing on extraterrestrial bodies can further increase the relative height of the probe when facing surface obstacles, thereby improving the probe's obstacle avoidance capability when facing surface obstacles.

[0030] Define a cylinder to wrap the terrain obstacle, and define the cylinder as the inner cylinder, (xjo ,y jo ), z jo and r jo are the horizontal center position, height, and radius of the inner cylinder corresponding to the j-th obstacle. Define another cylinder with the same center as the inner cylinder as the outer cylinder, δ jo and δ jh are the height and radius of the jth outer cylinder, and satisfy δ jo >d jo >0 and δ jh >z jo > 0. When the probe is located in the area between the two cylinders, the compensating thrust takes effect, γ = 1. When the probe is located outside the outer cylinder, the probe performs curvature guidance landing according to the guidance law shown in formula (5), and the compensating thrust does not take effect, γ = 0. The expression of γ is

[0031]

[0032] Among them, ∩ and ∪ represent the intersection and union of state sets respectively, ρ j It represents the distance between the current position of the lander and the center of the j-th obstacle in the horizontal direction, and its expression is:

[0033]

[0034] Compensation thrust a com The expressions in the x-axis, y-axis and z-axis directions are

[0035]

[0036]

[0037]

[0038] Among them, k x ,k y and k z are the weighted coefficients to be designed in the x-axis, y-axis and z-axis directions, and k x ,k y ,k z > 0, in order to ensure that the trajectory curvature of the detector is convex, the compensation thrust coefficient in the z-axis direction should be greater than the compensation thrust coefficient in the horizontal direction, that is, there is

[0039]

[0040] γ x ,γ y and γ z are the switching functions for compensating thrust in the x-axis, y-axis and z-axis directions, respectively, and their expressions are:

[0041]

[0042] γ y =γ x (15)

[0043] γ z =γ (16)

[0044] Substituting formulas (5) and (8)-(12) into formula (7), the components of the augmented curvature guidance method for soft landing of extraterrestrial objects in the X, Y, and Z axes are obtained as shown in formulas (17)-(19):

[0045]

[0046]

[0047] γ z =γ (19)

[0048] Step 4: Use the augmented curvature guidance method for soft landing of extraterrestrial bodies obtained in step 3 to perform planetary landing guidance in the form of components of the x, y, and z axes, further increasing the relative height of the probe when facing surface obstacles, and achieving obstacle avoidance and precise landing when flying in complex areas. In addition, the switching function γ of the compensation thrust constructed in step 3 makes the compensation thrust a com It is only applied in the area affected by the obstacle, thereby shortening the compensating thrust a com action time, and reduce the energy consumption of the probe during the soft landing process of extraterrestrial bodies.

[0049] Beneficial effects:

[0050] 1. The invention discloses an augmented curvature guidance method for soft landing of extraterrestrial objects. In the traditional trajectory curvature guidance law, the thrust compensation term γa is used to com By characterizing whether the probe is in the obstacle influence area and the compensatory thrust applied in the obstacle influence area, the augmented curvature guidance law for soft landing of extraterrestrial objects is obtained, which further increases the relative height of the probe when facing surface obstacles, and ensures the safe landing of the probe when the surface obstacles are higher than the initial height of the probe.

[0051] 2. The augmented curvature guidance method for soft landing of extraterrestrial bodies disclosed in the present invention has a designed compensatory thrust that only acts on a certain spatial area near terrain obstacles. It has a shorter action time and energy consumption that is closer to the energy-optimal guidance law, which has great advantages in fuel consumption.

[0052] 3. The augmented curvature guidance method for soft landing of extraterrestrial objects disclosed in the present invention retains the advantages of the classic curvature guidance law. The designed guidance law is in analytical form and does not contain complex calculations such as integration. It has high settlement efficiency and can improve the real-time performance of the guidance law on the onboard computer of the probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a flow chart of the augmented curvature guidance method for soft landing of an extraterrestrial object according to the present invention.

[0054] Figure 2 shows the simulation analysis results of the augmented curvature guidance method for soft landing of extraterrestrial objects. Figure (a) shows the probe's landing obstacle avoidance trajectory, Figure (b) shows the probe's three-axis position change curve, Figure (c) shows the probe's three-axis velocity change curve, and Figure (d) shows the three-axis acceleration change curve. DETAILED DESCRIPTION

[0055] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0056] Example 1:

[0057] In order to verify the feasibility of the present invention, Mars is used as the target celestial body for landing obstacle avoidance control, and a planetary surface fixed rectangular coordinate system O-XYZ is established with the target landing point as the origin O. In this coordinate system, the initial position of the probe is [40,40,10] T m, the target landing point is [0,0,0] T m, initial velocity is [-1,-1,3] T m / s, the target end speed is [0,0,0] T m / s, initial mass is 2000kg, engine specific impulse is 100s, landing time is 7.77s, k x =0.4, k y =0.4, k z =8, gravitational acceleration at sea level e =9.807m / s 2 , the acceleration of the Martian surface g Mars =3.72m / s 2 .

[0058] like Figure 1 As shown, the analytical obstacle avoidance guidance method for safe soft landing of an extraterrestrial object disclosed in this embodiment is specifically implemented in the following steps:

[0059] Step 1 is implemented as follows:

[0060] A fixed rectangular coordinate system O-XYZ on the planetary surface is established with the target landing point as the origin O, where the Z axis is perpendicular to the local ground plane at the landing point, and its positive direction points to the outside of the target celestial body; the X axis is in the local ground plane at the landing point, and coincides with the cross product vector of the positive direction of the Z axis and the rotation direction of the target celestial body; the Y axis, X axis, and Z axis together form a right-handed coordinate system.

[0061] When the probe moves on the surface fixed connection, the inertial force and other disturbance forces caused by the planet's rotation have a smaller impact on the probe's movement than the control force generated by the engine and the planet's gravity. The inertial force and other disturbance forces caused by the planet's rotation can be ignored. During the landing and obstacle avoidance phase, since the probe's movement time is short, the gravitational acceleration g it experiences is equivalent to a constant vector. The dynamic equation of the probe system is:

[0062]

[0063] Where r = [r x ,r y ,r z ] T and v=[v x ,v y ,v z ] T They represent the position and velocity of the detector under the surface fixed connection, T=[T x ,T y ,T z ] T and a=[a x ,a y ,a z ] T They represent the three-axis components of the detector control force and control acceleration in the surface fixed connection, m represents the mass of the detector, I sp Indicates engine specific impulse, g e is the acceleration due to gravity at sea level.

[0064] Step 2: Calculate the remaining time t required for landing based on the current state of the probe go According to the trajectory geometric curvature theory and combined with the energy optimal guidance law, the basic form of trajectory curvature guidance is established, and the extended form of curvature guidance is derived based on the basic form of trajectory curvature guidance.

[0065] According to the current state of the detector X=[r T ,v T ] T Calculate the remaining time t required for landing go , is the positive real root of the equation shown in formula (21).

[0066]

[0067] In order to make the probe land along a convex trajectory, it is first necessary to determine the concavity and convexity trend of the trajectory in its current state. According to the trajectory geometric curvature theory, the condition for the trajectory to be convex in the XOZ plane is

[0068] v x (r z v x -r x v z )>0 (22)

[0069] The condition for the trajectory to be convex in the YOZ plane is

[0070] v y (r z v y -r y v z )>0 (23)

[0071] For the XOZ or YOZ plane, if the detector initial state satisfies v x (r z v x -r x v z )<0 or v y (r z v y -r y v z )<0, need t c The constant acceleration of the time period transforms the concave state into a convex trajectory state. The superscript "0" indicates the initial moment of the landing phase. If the initial state of the probe satisfies v x (r z v x -r x v z )>0 or v y (r z v y -r y v z )>0 and a turning point appears under the analytical optimal guidance law, it is necessary to apply t from the turning point c constant acceleration over a period of time, and "TP" means turning point, Indicates the remaining flight time at the turning point. If there is no turning point, the trajectory curvature guidance at this time is the analytically optimal guidance.

[0072] Combining equations (22) and (23) and combining them with the analytical energy optimal guidance law, the basic form of trajectory curvature guidance is constructed as shown in equation (24):

[0073]

[0074] To obtain the extended form of curvature guidance, the magnitude of the constant acceleration is expressed as

[0075] a TP =na OTP (25)

[0076] Where a OTP is the acceleration calculated by analytically analyzing the optimal guidance law at the turning point, and n is a positive real number defined as the acceleration coefficient.

[0077] Step 3: In the trajectory curvature guidance law, the thrust compensation term γa is used com Characterizing whether the probe is in the obstacle influence area and the compensation thrust applied in the obstacle influence area, the augmented curvature guidance method for soft landing of extraterrestrial objects is obtained. By defining the compensation thrust a com The specific form of the on-off function γ for the compensatory thrust and its effect on the probe's range are used to derive the X, Y, and Z-axis components of the augmented curvature guidance method for soft landing on extraterrestrial objects. This augmented curvature guidance method can further increase the probe's relative height when facing surface obstacles, thereby improving the probe's obstacle avoidance capabilities.

[0078] In order to further increase the relative height of the probe when facing surface obstacles and ensure the safe landing of the probe when the surface obstacles are higher than the initial height of the probe, the thrust compensation term γa is used in the trajectory curvature guidance law. com Characterizing whether the probe is in the obstacle influence area and the compensatory thrust applied in the obstacle influence area, the augmented curvature guidance method for soft landing of extraterrestrial objects is obtained as shown in formula (26):

[0079] a=a cur +γa com (26)

[0080] Among them, a cur is the basic form of curvature guidance (n=1) shown in formula (21), a com is the thrust compensation function, and γ is the switching function of the thrust compensation function.

[0081] The augmented curvature guidance method for soft landing on extraterrestrial bodies can further increase the relative height of the probe when facing surface obstacles, thereby improving the probe's obstacle avoidance capability when facing surface obstacles.

[0082] Define a cylinder to wrap the terrain obstacle, and define the cylinder as the inner cylinder, (x jo ,y jo ), z jo and r joare the horizontal center position, height, and radius of the inner cylinder corresponding to the j-th obstacle. Define another cylinder with the same center as the inner cylinder as the outer cylinder, δ jo and δ jh are the height and radius of the jth outer cylinder, and satisfy δ jo >d jo >0 and δ jh >z jo > 0. When the probe is located in the area between the two cylinders, the compensating thrust takes effect, γ = 1. When the probe is located outside the outer cylinder, the probe performs curvature guidance landing according to the guidance law shown in formula (21), and the compensating thrust does not take effect, γ = 0. The expression of γ is

[0083]

[0084] Among them, ∩ and ∪ represent the intersection and union of state sets respectively, ρ j It represents the distance between the current position of the lander and the center of the j-th obstacle in the horizontal direction, and its expression is:

[0085]

[0086] Compensation thrust a com The expressions in the x-axis, y-axis and z-axis directions are

[0087]

[0088]

[0089]

[0090] Among them, k x ,k y and k z are the weighted coefficients to be designed in the x-axis, y-axis and z-axis directions, and k x ,k y ,k z > 0, in order to ensure that the trajectory curvature of the detector is convex, the compensation thrust coefficient in the z-axis direction should be greater than the compensation thrust coefficient in the horizontal direction, that is, there is

[0091]

[0092] γ x ,γ y and γ z are the switching functions for compensating thrust in the x-axis, y-axis and z-axis directions, respectively, and their expressions are:

[0093]

[0094] γ y =γ x (34)

[0095] γ z =γ (35)

[0096] Substituting formulas (24) and (27)-(31) into formula (26), the components of the augmented curvature guidance method for soft landing of extraterrestrial objects in the X, Y, and Z axes are obtained as shown in formulas (36)-(38):

[0097]

[0098]

[0099] γ z =γ (38)

[0100] Step 4: Use the augmented curvature guidance method for soft landing of extraterrestrial bodies obtained in step 3 to perform planetary landing guidance in the form of components of the x, y, and z axes, further increasing the relative height of the probe when facing surface obstacles, and achieving obstacle avoidance and precise landing when flying in complex areas. In addition, the switching function γ of the compensation thrust constructed in step 3 makes the compensation thrust a com It is only applied in the area affected by the obstacle, thereby shortening the compensating thrust a com action time, and reduce the energy consumption of the probe during the soft landing process of extraterrestrial bodies.

[0101] The fuel consumption of the entire landing phase is characterized by the propellant mass fraction (PMF).

[0102]

[0103] Where: m0 and Δm represent the initial mass of the probe and the mass consumption during the landing process, respectively.

[0104] A topographic map with information on obstacles and outer cylinders (O zones) as shown in Table 1 was established to perform planetary landing simulations.

[0105] Table 1 Terrain obstacle information of simulated landing area

[0106]

[0107]

[0108] Under given initial and terminal conditions, the lander is controlled using the augmented curvature guidance method for soft landing of extraterrestrial bodies, and lands in a given simulated landing area with terrain obstacles. The final simulation results are shown in Figure 2, indicating that the lander successfully avoids obstacles during the landing process, and both the speed and position converge to the corresponding target values, achieving a precise landing; at the same time, compared with the traditional trajectory convex curvature guidance method, it significantly reduces fuel consumption.

[0109] The above specific description further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An augmented curvature guidance method for soft landing of an extraterrestrial object, characterized by: The following steps are included: Step 1: Establish a surface-fixed rectangular coordinate system for the target planet and establish the probe dynamic equations in this coordinate system; Step 2: Calculate the remaining time t required for landing based on the current state of the probe go According to the trajectory geometric curvature theory and combined with the energy optimal guidance law, the basic form of trajectory curvature guidance is established, and the extended form of curvature guidance is derived based on the basic form of trajectory curvature guidance; Step 3: In the trajectory curvature guidance law, the thrust compensation term γa is used com Characterize whether the probe is in the obstacle influence area and the compensation thrust applied in the obstacle influence area, and obtain the augmented curvature guidance method for soft landing of extraterrestrial objects; by defining the compensation thrust a com , the specific form of the switching function γ of the compensation thrust and the range of action on the detector, and the component forms of the augmented curvature guidance method for soft landing of extraterrestrial objects in the X, Y, and Z axes are obtained; through the augmented curvature guidance method for soft landing of extraterrestrial objects, the relative height of the detector when facing surface obstacles is further increased, thereby improving the obstacle avoidance capability of the detector facing surface obstacles; Step 3 is implemented as follows: In order to further increase the relative height of the probe when facing surface obstacles and ensure the safe landing of the probe when the surface obstacles are higher than the initial height of the probe, the thrust compensation term γa is used in the trajectory curvature guidance law. com Characterizing whether the probe is in the obstacle influence area and the compensatory thrust applied in the obstacle influence area, the augmented curvature guidance method for soft landing of extraterrestrial objects is obtained as shown in formula (7): a=a cur +γa com (7) Among them, a cur is the basic form of curvature guidance (n=1) shown in formula (5), a com is the compensation thrust, γ is the switching function of the compensation thrust; The augmented curvature guidance method for soft landing on extraterrestrial bodies is used to further increase the relative height of the probe when facing surface obstacles, thereby improving the probe's obstacle avoidance capability in the face of surface obstacles; Define a cylinder to wrap the terrain obstacle, and define the cylinder as the inner cylinder, (x jo ,y jo ), z jo and r jo are the horizontal center position, height, and radius of the inner cylinder corresponding to the j-th obstacle; another cylinder with the same center as the inner cylinder is defined outside the inner cylinder as the outer cylinder, δ jo and δ jh are the height and radius of the jth outer cylinder, and satisfy δ jo >d jo >0 and δ jh >z jo >0; when the probe is located in the area between the two cylinders, the compensating thrust takes effect, γ = 1; when the probe is located outside the outer cylinder, the probe performs curvature-guided landing according to the guidance law shown in formula (5), and the compensating thrust does not take effect, γ = 0; the expression of γ is Among them, ∩ and U represent the intersection and union of state sets respectively, ρ j It represents the distance between the current position of the lander and the center of the j-th obstacle in the horizontal direction, and its expression is: Compensation thrust a com The expressions in the x-axis, y-axis and z-axis directions are Among them, k x ,k y and k z are the weighted coefficients to be designed in the x-axis, y-axis and z-axis directions, and k x ,k y ,k z > 0, in order to ensure that the trajectory curvature of the detector is convex, the compensation thrust coefficient in the z-axis direction should be greater than the compensation thrust coefficient in the horizontal direction, that is, there is γ x ,γ y and γ z are the switching functions for compensating thrust in the x-axis, y-axis and z-axis directions, respectively, and their expressions are: c y =c x (15) c z =γ (16) Substituting formulas (5) and (8)-(12) into formula (7), the components of the augmented curvature guidance method for soft landing of extraterrestrial objects in the X, Y, and Z axes are obtained as shown in formulas (17)-(19): c z =γ (19) Step 4: Use the augmented curvature guidance method for soft landing of extraterrestrial bodies obtained in step 3 to perform planetary landing guidance in the form of components of the x, y, and z axes, further improve the relative height of the probe when facing surface obstacles, and achieve obstacle avoidance and precise landing when flying in complex areas; In addition, the switching function γ of the compensation thrust constructed in step 3 makes the compensation thrust a com It is only applied in the area affected by the obstacle, thereby shortening the compensating thrust a com action time, and reduce the energy consumption of the probe during the soft landing process of extraterrestrial bodies.

2. The method for soft landing of an extraterrestrial object using augmented curvature guidance according to claim 1, wherein: Step 1 is implemented as follows: A fixed rectangular coordinate system O-XYZ on the planetary surface is established with the target landing point as the origin O, where the Z axis is perpendicular to the local ground plane at the landing point, with the positive direction pointing outside the target celestial body; the X axis is in the local ground plane at the landing point, and coincides with the cross product vector of the positive direction of the Z axis and the rotation direction of the target celestial body; the Y axis, together with the X and Z axes, forms a right-handed coordinate system; When the probe moves on the surface fixed connection, the inertial force and other disturbance forces caused by the planet's rotation have a smaller impact on the probe's movement than the control force generated by the engine and the planet's gravity. The inertial force and other disturbance forces caused by the planet's rotation can be ignored. During the landing and obstacle avoidance phase, since the probe's movement time is short, the gravitational acceleration g it experiences is equivalent to a constant vector. The dynamic equation of the probe system is: Where r = [r x ,r y ,r z ] T and v=[v x ,v y ,v z ] T They represent the position and velocity of the detector under the surface fixed connection, T=[T x ,T y ,T z ] T and a=[a x ,a y ,a z ] T They represent the three-axis components of the detector control force and control acceleration in the surface fixed connection, m represents the mass of the detector, I sp Indicates engine specific impulse, g e is the acceleration due to gravity at sea level.

3. The method for soft landing of an extraterrestrial object using augmented curvature guidance according to claim 2, wherein: Step 2 is implemented as follows: According to the current state of the detector X=[r T ,v T ] T Calculate the remaining time t required for landing go , is the positive real root of the equation shown in formula (2); In order to make the probe land along a convex trajectory, it is first necessary to determine the concavity and convexity trend of the trajectory in the current state; according to the trajectory geometric curvature theory, the condition for the trajectory to be convex in the XOZ plane is v x (r z v x -r x v z )>0 (3) The condition for the trajectory to be convex in the YOZ plane is v y (r z v y -r y v z )>0 (4) For the XOZ or YOZ plane, if the detector initial state satisfies v x (r z v x -r x v z )<0 or v y (r z v y -r y v z )<0, need t c The constant acceleration of the time period transforms the concave state into a convex trajectory state. The superscript "0" indicates the initial moment of the landing phase. If the initial state of the probe satisfies v x (r z v x -r x v z )>0 or v y (r z v y -r y v z )>0 and a turning point appears under the analytical optimal guidance law, it is necessary to apply t from the turning point c constant acceleration over a period of time, and "TP" means turning point, Indicates the remaining flight time at the turning point. If there is no turning point, the trajectory curvature guidance at this time is the analytically optimal guidance. Combining formulas (3) and (4) and combining them with the analytical energy optimal guidance law, the basic form of trajectory curvature guidance is constructed as shown in formula (5): To obtain the extended form of curvature guidance, the magnitude of the constant acceleration is expressed as a TP =na OTP (6) In the formula, a OTP is the acceleration calculated by analytically analyzing the optimal guidance law at the turning point, and n is a positive real number defined as the acceleration coefficient.

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