Planetary detector preset time trajectory tracking control method under input saturation

Abstract

The invention discloses a planetary detector preset time trajectory tracking control method under input saturation. The method comprises the following steps: establishing an initial kinetic model of a planetary probe in an atmosphere entry section; setting a reference radial distance of the planetary detector; determining an initial height tracking compensation error and a first-order height tracking compensation error of the planetary probe based on an actual radial distance and a reference radial distance in the initial dynamic model; obtaining a second-order height tracking compensation error based on the initial kinetic model, the initial height tracking compensation error and the first-order height tracking compensation error; setting an initial sliding mode variable, and processing the initial sliding mode variable to obtain a first-order sliding mode variable; according to the invention, the technical problem that the planetary probe cannot realize high-precision landing within the preset time in a complex space environment is solved.

Description

Technical Field

[0001] The present invention relates to the field of planetary detection control technology, and in particular to a planetary detector preset time trajectory tracking control method under input saturation. Background Art

[0002] With the development of planetary exploration missions, future planetary probes will be expected to provide fast and precise landing accuracy under uncertain factors and external interference. In complex space environments, trajectory tracking control methods are more suitable for entry guidance of planetary probes. Previously, most of them used finite-time sliding mode control methods, but this method caused the finite time of system convergence to be constrained by initial conditions, and the initial conditions are generally difficult to know in advance. In order to solve this problem, a fixed-time sliding mode control scheme was proposed, but because the fixed time of system convergence is related to the system structure parameters, it is difficult for users to independently adjust the system convergence time. Summary of the invention

[0003] An embodiment of the present invention provides a preset time trajectory tracking control method for a planetary probe under input saturation, so as to at least solve the technical problem that the planetary probe cannot achieve high-precision landing within the preset time in a complex space environment.

[0004] According to one aspect of an embodiment of the present invention, a method for tracking and controlling a preset time trajectory of a planetary probe under input saturation is provided. The method may include: establishing an initial dynamic model of a planetary probe in an atmospheric entry phase; setting a reference radial distance of the planetary probe; determining an initial altitude tracking compensation error and a first-order altitude tracking compensation error of the planetary probe based on an actual radial distance and a reference radial distance in the initial dynamic model; obtaining a second-order altitude tracking compensation error based on the initial dynamic model, the initial altitude tracking compensation error and the first-order altitude tracking compensation error; setting an initial sliding mode variable, processing the initial sliding mode variable, and obtaining a first-order sliding mode variable; when a control input of a planetary probe system is saturated, setting an auxiliary system model, and obtaining an updated second-order altitude tracking compensation error based on the auxiliary system model; obtaining an updated first-order sliding mode variable based on the updated second-order altitude tracking compensation error and the first-order sliding mode variable; obtaining a first Lyapunov function and a second Lyapunov function; and determining that the trajectory tracking convergence of the planetary probe within a target preset time under control input saturation based on the updated first-order sliding mode variable, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variable, and the initial altitude tracking compensation error, wherein the target preset time is determined based on the first preset time of the initial sliding mode variable and the second preset time in the auxiliary system model.

[0005] Optionally, determining the initial height tracking compensation error of the planetary probe based on the actual radial distance and the reference radial distance in the initial dynamic model includes: determining the difference between the actual radial distance and the reference radial distance in the initial dynamic model as the initial height tracking compensation error of the planetary probe.

[0006] Optionally, the process of determining the first-order height tracking compensation error is: differentiating the initial height tracking compensation error to obtain the first-order height tracking compensation error.

[0007] Optionally, the processing the initial sliding mode variable to obtain the first-order sliding mode variable includes: taking a derivative of the initial sliding mode variable to obtain the first-order sliding mode variable.

[0008] Optionally, obtaining an updated second-order altitude tracking compensation error based on the auxiliary system model includes: replacing a control input of the planetary probe system with the auxiliary system model to obtain an updated second-order altitude tracking compensation error.

[0009] Optionally, determining that the trajectory tracking of the planetary probe converges within a target preset time under control input saturation based on the updated first-order sliding mode variable, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variable and the initial altitude tracking compensation error includes: determining that the initial sliding mode variable converges to zero within the first preset time based on the updated first-order sliding mode variable and the first Lyapunov function; when the initial sliding mode variable converges to zero within the first preset time, determining that the initial altitude tracking compensation error converges to zero within the second preset time based on the initial sliding mode variable and the second Lyapunov function; when the initial altitude tracking compensation error converges to near zero within the second preset time, the trajectory tracking of the planetary probe converges within the target preset time under control input saturation.

[0010] Beneficial effects of the present invention: The present invention proposes a preset time trajectory tracking control method for a planetary probe under input saturation. Firstly, a dynamic model of the entry segment of the planetary probe is established. On this basis, a terminal sliding mode variable is designed. A continuous function is used in the design of the controller to eliminate the chattering phenomenon. In addition, in order to obtain a faster convergence rate and allow users to customize the convergence time, a preset time convergence method is adopted. Finally, an input saturation auxiliary function is used to limit the control input, which ensures that the present invention can be applied in practice. The present invention combines sliding mode control, input saturation and preset time convergence methods, which not only ensures precise guidance under interference, but also can converge the tracking error to the vicinity of the origin within the user preset time, thereby improving the landing accuracy of the planetary probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a flow chart of a preset time trajectory tracking control method for a planetary probe under input saturation according to an embodiment of the present invention; Figure 2 is a schematic diagram of the relationship between the planetary inertial coordinate system, the fixed coordinate system and the geographic coordinate system according to an embodiment of the present invention; Figure 3 is a schematic diagram of a trajectory tracking error and a height curve under a target preset time control input according to an embodiment of the present invention; Figure 4 is a schematic diagram of a control input curve under a preset target time control input according to an embodiment of the present invention; Figure 5 4 is a schematic diagram of a convergence curve of a downward sliding mode variable of an input under a preset target time control according to an embodiment of the present invention. DETAILED DESCRIPTION

[0012] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0013] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0014] Example 1 According to an embodiment of the present invention, a method for tracking and controlling a preset time trajectory of a planetary probe under input saturation is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system comprising at least one set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0015] Figure 1 is a flow chart of a preset time trajectory tracking control method for a planetary probe under input saturation according to an embodiment of the present invention. Figure 1 As shown, the method may include the following steps: Step S101, establishing an initial dynamic model of the planetary probe during the atmospheric entry phase.

[0016] In the technical solution provided in the above step S101 of the present invention, the working time of the planetary probe in the atmospheric entry phase is very short, and the accuracy requirement of the gravitational field is not high, so the simplified gravitational field model is: (1) Among them, in formula (1) is the planet's gravitational acceleration, is the planetary gravitational constant, is the distance from the center of mass of the planet probe to the center of mass of the planet, and the simplified atmospheric density model is: (2) Among them, in formula (2) is the atmospheric density at the location of the detector, is the atmospheric density at atmospheric altitude, is the planet radius, is the atmospheric height, Figure 2 It is a schematic diagram of the relationship among the planetary inertial coordinate system, the fixed coordinate system and the geographic coordinate system according to an embodiment of the present invention.

[0017] Assume that the planetary probe is a rigid body and only consider the motion of its center of mass. In addition, the planet can be regarded as an approximate standard sphere without rotation during the entire entry process, and the planetary atmosphere is assumed to be uniformly distributed. Based on the above reasonable assumptions, the initial dynamic model of the planetary probe during the atmospheric entry phase is established: (3) (4) (5) (6) (7) (8) in, is the radial distance between the center of mass of the planet probe and the center of mass of the planet, is the longitude of the planet probe, is the latitude of the planet probe, is the flying speed of the planetary probe, is the flight path angle, is the heading angle, is the tilt angle, For lift, For resistance, is the gravitational acceleration of the planet, is the mass of the planetary probe, and the expressions for lift and drag are: (9) in is the reference area of ​​the planetary probe, and are the lift coefficient and the drag coefficient respectively.

[0018] Step S102, setting a reference radial distance of the planetary probe.

[0019] In the technical solution provided in step S102 of the present invention, it is defined as is the second-order differentiable reference radial distance of the planetary probe.

[0020] Step S103, determining the initial altitude tracking compensation error and the first-order altitude tracking compensation error of the planetary probe based on the actual radial distance and the reference radial distance in the initial dynamics model.

[0021] In the technical solution provided in the above step S103 of the present invention, is the actual radial distance, then the initial height tracking compensation error of the planetary probe can be expressed as , the first-order height tracking compensation error can be expressed as .

[0022] Step S104, obtaining a second-order height tracking compensation error based on the initial dynamics model, the initial height tracking compensation error and the first-order height tracking compensation error.

[0023] In the technical solution provided in step S104 of the present invention, based on the initial dynamic model (3)-(8) of the planetary probe during the atmospheric entry phase, the uncertainty of the atmospheric density, drag coefficient and lift coefficient during the entry phase is considered. The atmospheric density, drag coefficient and lift coefficient in the above formula can be respectively expressed as , , .in, , and are the nominal atmospheric density, drag coefficient, and lift coefficient, respectively. , and is the uncertainty of atmospheric density, drag coefficient and lift coefficient. Therefore, the second-order altitude tracking compensation error can be expressed as: (10) in, represents the control input, and the rest are:

[0024] in, is a bounded uncertain disturbance, satisfying , F(t) represents the conventional state function of the planetary probe system, and H(t) represents the control state gain function of the planetary probe system. , F(t), H(t), and The state of the planetary probe system is briefly recorded as , , and .

[0025] Step S105, setting initial sliding mode variables, processing the initial sliding mode variables, and obtaining first-order sliding mode variables.

[0026] In the technical solution provided in the above step S105 of the present invention, the expression for defining the initial sliding mode variable is: (11) in, is a parameter related to the scheduled time, satisfying and is an even number, It is an odd number. represents the sliding mode surface gain, represents the gain after the sliding surface, both of which are positive constants, is the parameter of the sliding surface related to the predetermined time, where is the parameter before conversion, is the converted parameter, It is a positive constant given by the user, representing the time constant of the sliding surface.

[0027] The initial sliding mode variables are differentiated to obtain the first-order sliding mode variables.

[0028] Step S106, when the control input of the planetary probe system is saturated, an auxiliary system model is set, and based on the auxiliary system model, an updated second-order altitude tracking compensation error is obtained.

[0029] In the technical solution provided in the above step S106 of the present invention, since input saturation occurs in practical applications, the control input is nonlinear, and the control input saturation is expressed as follows: (12) in, represents the ideal control action, and are the upper and lower bounds of the input saturation limit; The auxiliary system model is defined as follows: (13) in, is the state of the auxiliary planetary probe system, To assist the planetary probe system gain, is the auxiliary state segment value, is the bounded control input error. Definition (14) represents the preset time-related quantity of the auxiliary planetary probe system, where Indicates the pre-set time gain of the auxiliary planetary probe system, Indicates the gain of the auxiliary planetary probe system after preset time, Preset time parameters for auxiliary planetary probe systems and is an even number, which is a preset time even parameter for the auxiliary planetary probe system. is an odd number, which is a preset time odd parameter for the auxiliary planetary probe system. The total time gain is predetermined for the auxiliary planetary probe system and To assist the planetary probe system in converting the pre-parameters, To assist the conversion of the planetary probe system parameters, It is a positive constant given by the user, representing the time constant of the auxiliary planetary probe system state.

[0030] The control input in formula (10) is replaced by the auxiliary system model to obtain the updated second-order height tracking compensation error.

[0031] Step S107, obtaining an updated first-order sliding mode variable based on the updated second-order height tracking compensation error and the first-order sliding mode variable.

[0032] In the technical solution provided in step S107 of the present invention, the expression of the first-order sliding mode variable is: (15) Substituting equation (10) into equation (15), that is, according to the updated second-order height tracking compensation error and the first-order sliding mode variable, the expression of the updated first-order sliding mode variable is obtained as follows: (16) in, It is a new state variable of the planetary probe system model.

[0033] Theorem 1: For a planetary probe with unknown disturbances, in order to achieve accurate trajectory tracking during the entry phase, the following ideal control input is designed: (17) in, is the hyperbolic tangent function used to offset the total uncertainty and is a positive constant representing a small range of boundaries.

[0034] Step S108, obtaining a first Lyapunov function and a second Lyapunov function.

[0035] Step S109, based on the updated first-order sliding mode variables, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variables and the initial altitude tracking compensation error, determine that the trajectory tracking convergence of the planetary probe within the target preset time under control input saturation, wherein the target preset time is determined based on the first preset time of the initial sliding mode variables and the second preset time in the auxiliary system model.

[0036] In the technical solution provided in the above step S109 of the present invention, based on the updated first-order sliding mode variables, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variables and the initial height tracking compensation error, the trajectory tracking convergence of the planetary probe within the target preset time under control input saturation is obtained.

[0037] The above method of this embodiment is further introduced below.

[0038] As an optional implementation method, step S103, determining the initial height tracking compensation error of the planetary probe based on the actual radial distance and the reference radial distance in the initial dynamic model, includes: determining the difference between the actual radial distance and the reference radial distance in the initial dynamic model as the initial height tracking compensation error of the planetary probe.

[0039] In this embodiment, the difference between the actual radial distance and the reference radial distance in the initial dynamic model is determined as the initial height tracking compensation error of the planetary probe. The expression is:

[0040] in, Compensate for errors in initial altitude tracking of planetary probes.

[0041] As an optional implementation manner, in step S103, the process of determining the first-order height tracking compensation error is: derivating the initial height tracking compensation error to obtain the first-order height tracking compensation error.

[0042] In this embodiment, the expression of the first-order height tracking compensation error obtained by derivation of the initial height tracking compensation error is:

[0043] in, is the first-order height tracking compensation error.

[0044] As an optional implementation manner, step S105, processing the initial sliding mode variable to obtain the first-order sliding mode variable, includes: taking the derivative of the initial sliding mode variable to obtain the first-order sliding mode variable.

[0045] As an optional implementation method, step S106, obtaining an updated second-order altitude tracking compensation error based on the auxiliary system model, includes: replacing the control input of the planetary probe system with the auxiliary system model to obtain an updated second-order altitude tracking compensation error.

[0046] In this embodiment, the control input of the planetary probe system is replaced by the auxiliary system model to obtain an updated second-order altitude tracking compensation error.

[0047] As an optional implementation method, step S109, based on the updated first-order sliding mode variable, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variable and the initial height tracking compensation error, determining that the trajectory tracking converges of the planetary probe within the target preset time under control input saturation includes: based on the updated first-order sliding mode variable and the first Lyapunov function, determining that the initial sliding mode variable converges to zero within the first preset time; when the initial sliding mode variable converges to zero within the first preset time, based on the initial sliding mode variable and the second Lyapunov function, determining that the initial height tracking compensation error converges to zero within the second preset time; when the initial height tracking compensation error converges to near zero within the second preset time, the trajectory tracking converges of the planetary probe within the target preset time under control input saturation.

[0048] In this embodiment, the Lyapunov stability of the planetary probe system for the target preset time is proved below. Before giving the proof, the following lemma is introduced: Lemma 1: If a nonlinear planetary probe system exists a Lyapunov function that satisfies: (18) in, is the time constant, To preset time parameters, is the gain before the function, is the post-function gain and ε is a positive constant representing the small boundary value of the function, then the trajectory of the planetary probe system converges to the actual preset time. And the convergence time is ,in The parameters related to the planetary probe system are adjusted, and the convergence domain is expressed as follows: (19) In particular, when ε=0, the state of the planetary probe system at time tends to 0.

[0049] Lemma 2: For the state ,parameter and ,have Established.

[0050] Lemma 3: When the sliding mode variable satisfies , planetary probe system status At the second preset time Converges to 0 internally.

[0051] Lemma 4: For any state is the power parameter, n represents the state order, and the following inequality holds:

[0052] Substituting (17) into (16), we get the first-order derivative of the sliding mode variable: (20) Among them, the total uncertainty of the planetary probe system is .

[0053] Choose a suitable first Lyapunov function as: (twenty one) when When the auxiliary planetary probe system comes into play, according to (20) and (13), the derivative of the above Lyapunov function is (twenty two) Among them, the small error And Lemma 2 and Lemma 4 are used in the above derivation. is bounded, and from Lemma 1 we can see that the state and At the first preset time ( ) converges within, where is a and The parameters of the planetary probe system are constants. Therefore, the Lyapunov function of the planetary probe system will converge to (twenty three) when When , the input saturation problem does not occur, that is, , we can get the same result as in (22).

[0054] According to Lemma 3, we choose a suitable second Lyapunov function as (twenty four) From the above, we can deduce the known sliding mode variables It will remain constant in a domain, let this domain be the sliding mode variable convergence domain , under this condition, the following equation holds: (25) After taking the derivative of (24), substituting (25) into it, the derivative of the second Lyapunov function is (26) From Lemma 1, we can see that the state of the planet probe system is At the second preset time ( ) converges to the vicinity of the origin within a certain period of time. Therefore, the planetary probe system will converge to the vicinity of the origin within a certain period of time. Internal stability.

[0055] Figure 3 is a schematic diagram of a trajectory tracking error and a height curve under a target preset time control input according to an embodiment of the present invention; Figure 3 It can be seen that the tracking error of the planetary probe system can be successfully converged within 200s.

[0056] Figure 4 is a schematic diagram of a control input curve under a preset target time control input according to an embodiment of the present invention; Figure 4 It can be seen that the control input of the planetary probe system is limited between the upper and lower limits, achieving control under input saturation.

[0057] Figure 5 is a schematic diagram of a convergence curve of a downward sliding mode variable under a preset target time control input according to an embodiment of the present invention, Figure 5 It can be seen that the sliding mode variables of the planetary probe system converge within 200s.

[0058] In an embodiment of the present invention, an initial dynamic model of a planetary probe in an atmospheric entry phase is established; a reference radial distance of the planetary probe is set; an initial altitude tracking compensation error and a first-order altitude tracking compensation error of the planetary probe are determined based on the actual radial distance and the reference radial distance in the initial dynamic model; a second-order altitude tracking compensation error is obtained based on the initial dynamic model, the initial altitude tracking compensation error and the first-order altitude tracking compensation error; an initial sliding mode variable is set, and the initial sliding mode variable is processed to obtain a first-order sliding mode variable; when the control input of the planetary probe system is saturated, an auxiliary system model is set, and an updated second-order altitude tracking compensation error is obtained based on the auxiliary system model; an updated first-order sliding mode variable is obtained based on the updated second-order altitude tracking compensation error and the first-order sliding mode variable. Quantity; obtain the first Lyapunov function and the second Lyapunov function; based on the updated first-order sliding mode variable, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variable and the initial height tracking compensation error, determine the trajectory tracking convergence of the planetary probe within the target preset time under control input saturation, wherein the target preset time is determined based on the first preset time of the initial sliding mode variable and the second preset time in the auxiliary system model, which solves the technical problem that the planetary probe cannot achieve high-precision landing within the preset time in a complex space environment, and achieves the technical effect of designing a non-singular terminal sliding mode variable with a preset time, combining a continuous function, and introducing an input saturation auxiliary system in the control input, so that the planetary probe can land with high precision within the preset time in a complex space environment.

[0059] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0060] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0061] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0062] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed over multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0063] In addition, each functional unit in each embodiment of the present invention may be integrated into a first processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0064] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A planetary probe preset time trajectory tracking control method under input saturation, characterized in that: include: Establish the initial dynamics model of the planetary probe during the atmospheric entry phase; Set the reference radial distance of the planetary probe; Based on the actual radial distance and the reference radial distance in the initial dynamics model, an initial height tracking compensation error and a first-order height tracking compensation error of the planetary probe are determined; Based on the initial dynamics model, the initial height tracking compensation error and the first-order height tracking compensation error, a second-order height tracking compensation error is obtained; Set the initial sliding mode variable, process the initial sliding mode variable, and obtain the first-order sliding mode variable; When the control input of the planetary probe system is saturated, an auxiliary system model is set, and an updated second-order height tracking compensation error is obtained based on the auxiliary system model; Based on the updated second-order height tracking compensation error and the first-order sliding mode variable, an updated first-order sliding mode variable is obtained; Get the first Lyapunov function and the second Lyapunov function; Based on the updated first-order sliding mode variables, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variables and the initial height tracking compensation error, it is determined that the trajectory tracking convergence of the planetary probe within the target preset time under control input saturation, wherein the target preset time is determined based on the first preset time of the initial sliding mode variables and the second preset time in the auxiliary system model.

2. The method according to claim 1, characterized in that The step of determining the initial height tracking compensation error of the planetary probe based on the actual radial distance and the reference radial distance in the initial dynamics model comprises: The difference between the actual radial distance and the reference radial distance in the initial dynamic model is determined as the initial height tracking compensation error of the planetary probe.

3. The method according to claim 1, characterized in that The process of determining the first-order height tracking compensation error is as follows: the initial height tracking compensation error is derived to obtain the first-order height tracking compensation error.

4. The method according to claim 1, characterized in that The processing of the initial sliding mode variables to obtain the first-order sliding mode variables includes: The initial sliding mode variable is differentiated to obtain the first-order sliding mode variable.

5. The method according to claim 1, characterized in that The updated second-order height tracking compensation error is obtained based on the auxiliary system model, including: The auxiliary system model is used to replace the control input of the planetary probe system to obtain the updated second-order altitude tracking compensation error.

6. The method according to claim 1, characterized in that The method of determining the trajectory tracking convergence of the planetary probe within a target preset time under control input saturation based on the updated first-order sliding mode variable, the first Lyapunov function, the second Lyapunov function, the initial sliding mode variable and the initial height tracking compensation error comprises: Based on the updated first-order sliding mode variable and the first Lyapunov function, determining that the initial sliding mode variable converges to zero within a first preset time; When the initial sliding mode variable converges to zero within the first preset time, based on the initial sliding mode variable and the second Lyapunov function, determining that the initial height tracking compensation error converges to zero within the second preset time; When the initial height tracking compensation error converges to near zero within the second preset time, the trajectory tracking of the planetary probe converges within the target preset time under control input saturation.

7. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method of claim 1.

8. A computer-readable storage medium, characterized in that Computer executable instructions are stored, and when the instructions are executed, they are used to implement the method of claim 1.

9. A computer program product, characterized in that The invention comprises computer executable instructions, which are used to implement the method of claim 1 when being executed.

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