Trajectory tracking guidance system and method for Mars atmosphere entry process

Abstract

The trajectory tracking guidance system and method for entering the Mars atmosphere solves the problem of how to achieve the anti-saturation effect while minimizing the rapidity of the guidance law, and belongs to the field of Mars exploration technology. The invention includes: the controller obtains the desired control quantity u according to the height tracking error e and the anti-saturation auxiliary variable χ in combination with the guidance law c , the controlled variable y=e+χ in the guidance law, according to u c The actual control quantity u is calculated based on the control constraints, and the guidance is performed according to the reference trajectory based on the actual control quantity u; the anti-saturation auxiliary system is based on the expected control quantity u at the previous moment. c And the actual control quantity u obtains Δu, Δu=u‑u c , obtain the anti-saturation auxiliary variable χ: #imgabs0# The present invention enables the guidance system to quickly exit the saturation working area, and when the saturation disappears, the compensation amount can quickly converge to 0 within a limited time.

Description

Technical Field

[0001] The invention relates to a trajectory tracking and guidance system and method for a Mars atmosphere entry process, belonging to the technical field of Mars exploration. Background Art

[0002] The probe is flying without power during the process of entering the Martian atmosphere. During the whole process, it can only adjust the aerodynamic direction by changing the probe's tilt angle, thereby changing the probe's flight trajectory. Since the Martian atmosphere is thin, with an atmospheric density of about 1% of the Earth's, and changes approximately exponentially with altitude, the probe's ability to correct its trajectory through aerodynamic forces is very limited, and control saturation problems are very likely to occur. If not properly handled, it will not only reduce the accuracy of trajectory tracking longitude, but also cause control instability.

[0003] The most common and practical anti-saturation solution is to consider saturation of the control law as a whole, which can be summarized as follows: first, design the guidance law without considering input saturation, and then constrain the desired control quantity generated by the guidance law to meet the requirements of input saturation. Specifically, it can be divided into two types: directly imposing saturation constraints on the control quantity and designing an anti-saturation auxiliary system. Imposing saturation constraints directly on the control quantity will cause a deviation between the actual control input and the desired control input, and this deviation cannot be directly felt by the controller, which will cause the controller to work in the saturation area for a long time and the control ability will degrade; designing an anti-saturation auxiliary system can make the controller exit the saturation working area when saturation occurs, so that the controller can work in the non-saturation area as much as possible to preserve the controller performance, but this method cannot fully exert the actual ability of the actuator and will actually reduce the rapidity of the guidance law.

[0004] Taking into account the short duration of the Martian atmosphere entry process, there is a strong demand for the rapidity of the guidance law. However, the actual characteristics of the Martian atmosphere entry process require that the guidance law must be designed to resist saturation. It is urgent to propose a method that can achieve the anti-saturation effect while minimizing the damage to the rapidity of the guidance law. Summary of the invention

[0005] In order to solve the problem of how to achieve the anti-saturation effect while minimizing the damage to the rapidity of the guidance law, the present invention provides a trajectory tracking guidance system and method for entering the Martian atmosphere.

[0006] The present invention provides a trajectory tracking and guidance system for entering the Martian atmosphere, including a controller and an anti-saturation auxiliary system;

[0007] The controller is used to obtain the desired control quantity u according to the height tracking error e and the anti-saturation auxiliary variable χ combined with the guidance law c , the controlled variable y=e+χ in the guidance law, according to u cThe actual control quantity u is calculated in combination with the control constraints, and guidance is performed according to the reference trajectory based on the actual control quantity u;

[0008] Anti-saturation auxiliary system, used to control the expected control quantity u at the previous moment c And the actual control amount u to obtain Δu, Δu = uu c , obtain the anti-saturation auxiliary variable χ:

[0009]

[0010] are the gain coefficients of the anti-saturation auxiliary system. are the index coefficients of the anti-saturation auxiliary system,

[0011] As a preference, the guidance law in the controller is:

[0012]

[0013] K d , K i are proportional, differential and integral gains respectively, g e =L cosγ,

[0014] L represents lift acceleration, γ represents the flight track angle, D represents drag acceleration, g represents the Martian gravity acceleration, V represents the relative speed between the probe and the Martian atmosphere, r represents the radial distance from the probe's center of mass to the center of Mars, and r represents the radial distance from the probe's center of mass to the center of Mars. c Indicates the expected detector fire center distance.

[0015] As a preferred embodiment, in the controller, according to u c Combined with the control constraints, the actual control quantity u is calculated as:

[0016] The actual control quantity u∈[u min ,u max ],u max 、u min are the upper and lower bounds of the actual controlled quantity respectively;

[0017]

[0018] As a preferred embodiment, in the controller, according to the desired atmospheric entry point state r0, V0, θ0, φ0, γ0, ψ0 and the desired terminal state r f ,V f ,θ f ,φ f ,γ f ,ψ f Design the reference trajectory to obtain the desired detector state at each moment, including the reference height h r, the current state of the detector includes the detector height h, and the height tracking error e = hh is obtained r ;

[0019] r0, V0, θ0, φ0, γ0, ψ0 represent the distance from the center of fire, velocity, longitude, latitude, track angle and heading angle of the detector at the expected atmospheric entry point, respectively;

[0020] r f ,V f ,θ f ,φ f ,γ f ,ψ f They respectively represent the fire center distance, speed, longitude, latitude, track angle and heading angle of the expected terminal detector.

[0021] As a preference,

[0022] V is the relative speed between the probe and the Martian atmosphere.

[0023] Preferably, the controller determines the flight bank angle σ according to the actual control variable u=cosσ, and performs atmospheric entry trajectory tracking and guidance of the probe in combination with the longitudinal dynamics equation of the probe.

[0024] Preferably, the longitudinal dynamic equation of the detector is:

[0025]

[0026] r is the radial distance from the probe's center of mass to the center of Mars, V is the relative speed between the probe and the Martian atmosphere, γ is the flight track angle, ψ is the flight heading angle, θ and φ represent longitude and latitude respectively, and g m =μ / r 2 is the Martian gravitational acceleration, μ is the Martian gravitational constant, L = ρV 2 C L S r / (2m) and D=ρV 2 C D S r / (2m) represent lift acceleration and drag acceleration respectively, m is the mass of the probe, S r is the aerodynamic area of ​​the detector, C D , C L are the drag coefficient and lift coefficient of the Martian atmosphere respectively, and ρ is the density of the Martian atmosphere; the atmospheric density ρ satisfies:

[0027]

[0028] Where ρ0 and h represent the standard atmospheric density of Mars and the height of the probe from the surface of Mars, respectively. h = r-R0, r is the distance between the probe and the center of Mars, R0 is the radius of Mars, and r s is the reference altitude of the Martian atmosphere.

[0029] The present invention also provides a trajectory tracking and guidance method for entering the Martian atmosphere, comprising:

[0030] Step 1: Determine the control constraints of the detector guidance system;

[0031] Step 2: Determine the reference trajectory and the current state of the detector, and calculate the height tracking error e;

[0032] Step 3: Design the guidance law. The controlled variable in the guidance law is y=e+χ, where χ represents the anti-saturation auxiliary variable. The output of the guidance law is the desired controlled variable u c , calculate the actual control quantity u in combination with the control constraints, and guide according to the reference trajectory based on the actual control quantity u;

[0033] The method for obtaining the anti-saturation auxiliary variable χ is:

[0034]

[0035] are the gain coefficients of the anti-saturation auxiliary system. are the index coefficients of the anti-saturation auxiliary system,

[0036] According to the expected control quantity u at the previous moment c And the actual control amount u obtains Δu, Δu=uu c .

[0037] Beneficial effects of the present invention: The present invention designs an anti-saturation auxiliary system for the trajectory tracking guidance system for entering the Martian atmosphere, which can provide compensation when the control is saturated, so that the guidance system can quickly exit the saturated working area, and the compensation can quickly converge to 0 within a limited time when the saturation disappears. The system of the present invention can effectively maintain the stability of the guidance system when control saturation occurs, and can well maintain the working performance of the original guidance system such as rapidity, so that the guidance system can fully utilize the working capacity of the detector actuator during the atmospheric entry process, and ensure that the detector quickly and accurately tracks the reference trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the principle of the method of the present invention;

[0039] Figure 2 It is the state change curve of the guidance process without finite time anti-saturation;

[0040] Figure 3 It is the state change curve of the guidance process with limited time anti-saturation. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0044] During the atmospheric entry process, the detector's ability to correct trajectory deviations through aerodynamic forces varies with atmospheric density and detector speed. It is extremely weak in some stages of the process and relatively strong in some stages. The detector's limited aerodynamic force is the real reason for control saturation, which is difficult to optimize through controller design. In this case, it is a more reasonable choice to correct the error through an anti-saturation auxiliary system. On the one hand, when control saturation occurs, the auxiliary system can maintain system stability; on the other hand, if the auxiliary variable can decay quickly when saturation disappears, the detector can maximize its aerodynamic correction capability. Based on the above ideas, an anti-saturation auxiliary system is designed in combination with the finite time theorem. In order to facilitate the design and analysis of the auxiliary system, some definitions and lemmas are first given.

[0045] Definition 1 Consider a nonlinear system Where f(x)=(f1(x),...f n (x) T :R n →R n is a vector function, and f(0) = 0, x∈R n . If for any ε>0, there exists (r1,...r n )∈R n , where r i >0,i=1,2,...n, so that f(x) satisfies where k≥-max{r i ,i=1,2,...,n}, then f(x) is said to be related to (r1,r2,...,r n ) has homogeneity k.

[0046] Lemma 1 Consider the nonlinear system where f(0) = 0, x∈R n , f(x) is a homogeneous vector function with respect to (r1,r2,...,r n ) has homogeneity k<0. Assume that the system is asymptotically stable to x=0. At this time, if i=1,2...,n, If x=0 is established, then x=0 is a local finite-time stable equilibrium point of the system. In addition, if the system is globally asymptotically stable, then the system is globally finite-time stable.

[0047] Lemma 2 Assume that the function f(t) is differentiable, there exists a finite limit as t→∞, and Uniformly continuous, then when t→∞

[0048] Lemma 3 Assume that the function f(t):R + →R is differentiable and satisfies 1) exists and is finite; 2) there exist functions g1(t) and g1(t) that satisfy If g1(t) is uniformly continuous and So Established.

[0049] The main content of this implementation method is to design the following finite time anti-saturation auxiliary steps. Let the anti-saturation auxiliary variable be χ, and the system can be expressed as

[0050]

[0051] In the formula, Δu=uu c , where u is the actual output of the actuator, u c is the desired output of the controller, and Δu=0 when saturation does not occur.

[0052] Theorem 1. When saturation does not occur, the auxiliary variable χ in system (2) converges to 0 in a finite time.

[0053] Proof. When the controller is not saturated, Δu=0, that is,

[0054]

[0055] make Then there is

[0056]

[0057] Select the Lyapunov function as

[0058]

[0059] Taking its derivative, we get

[0060]

[0061] Obviously, the function V χ Non-increasing and has a finite limit, which also means that the state and It is bounded, as shown by the theorem conditions. At this time Derivation can be verified There is a boundary, so Uniformly continuous, Lemma 2 shows that tends to 0, that is, x χ2 tends to 0. From formula (3), we can know is bounded, so and Consistent and continuous. Observation The equation of motion is

[0062]

[0063] make

[0064]

[0065] Can be verified Consistently continuous, It tends to 0. tends to 0. According to Lemma 3, tends to zero, then there must be tends to zero, so the closed-loop system is asymptotically stable.

[0066] Further, take Considering formula (3), according to definition 1, we can know that the homogeneity of the system is Lemma 1 shows that the system is finite-time stable. That is, when saturation disappears, the anti-saturation auxiliary variable χ converges to 0 in a finite time.

[0067] The trajectory tracking and guidance system for entering the Martian atmosphere of this embodiment includes a controller and an anti-saturation auxiliary system;

[0068] The controller is used to obtain the desired control quantity u according to the height tracking error e and the anti-saturation auxiliary variable χ combined with the guidance law c , the controlled variable y=e+χ in the guidance law, according to u c The actual control quantity u is calculated in combination with the control constraints, and guidance is performed according to the reference trajectory based on the actual control quantity u;

[0069] Anti-saturation auxiliary system, used to control the expected control quantity u at the previous moment c And the actual control amount u obtains Δu, Δu=uu c , obtain the anti-saturation auxiliary variable χ:

[0070]

[0071] k χ1 , k χ2 are the gain coefficients of the anti-saturation auxiliary system. are the index coefficients of the anti-saturation auxiliary system,

[0072] This implementation method designs an anti-saturation auxiliary system in combination with the finite-time control theory. The system can provide compensation when control saturation occurs, so that the controller can quickly exit the saturation working area. When saturation disappears, the compensation amount can quickly converge to 0 within a finite time. This method can effectively reduce the impact of the anti-saturation system on the rapidity of guidance, give full play to the performance of the guidance law during the guidance process, and ensure that the detector accurately and quickly tracks the reference trajectory.

[0073] In this embodiment, the probe height is used as the control variable. During the Martian atmosphere entry process, the probe tracks the desired height trajectory to achieve trajectory tracking guidance. The height tracking error is defined as e = hh r , where h r As the reference height, taking the derivative of e, we can get

[0074]

[0075]

[0076] In the formula

[0077]

[0078] g e =L cosγ

[0079] d e =d γ V cosγ+d v sinγ

[0080] Due to the physical condition of the actuator, during the atmospheric entry process, the control amount is constrained to u∈[u min ,u max ]Inside.

[0081] In this embodiment, in the guidance design work, it is necessary to design u in equation (8) so that the trajectory error e can converge to 0.

[0082] If a PID controller is used, u can be designed as

[0083] In order to combine the anti-saturation auxiliary system with the guidance law so that the guidance law has anti-saturation performance, the controlled variable in the guidance law is y = e + χ. At this time, under the action of the controller, the expected output of the controller is

[0084]

[0085] From formula (1) and Δu=uu c It can be seen that when control saturation occurs, u≠u c , that is, Δu≠0, at this time, the amplitude of χ increases, and the amplitude of y decreases, and the desired control amount output by the controller decreases until the controller leaves the saturated working area; when the controller enters the unsaturated area from the saturated area, χ decays to zero in a finite time, and the controlled amount recovers to y=e, at this time the controller can perform guidance work according to its pre-designed performance.

[0086] In this embodiment, the controller is based on u c Combined with the control constraints, the actual control quantity u is calculated as:

[0087] The actual control quantity u∈[u min ,u max ],u max 、u min are the upper and lower bounds of the actual controlled quantity respectively;

[0088]

[0089] In this embodiment, the controller is based on the desired atmospheric entry point state r0, V0, θ0, φ0, γ0, ψ0 and the desired terminal state r f ,V f ,θ f ,φ f ,γ f ,ψ f Design the reference trajectory to obtain the desired detector state at each moment, including the reference height h r , the current state of the detector includes the detector height h, and the height tracking error e = hh is obtained r ;

[0090] r0, V0, θ0, φ0, γ0, ψ0 represent the distance from the center of fire, velocity, longitude, latitude, track angle and heading angle of the detector at the expected atmospheric entry point, respectively;

[0091] r f ,V f ,θ f ,φ f ,γ f ,ψ fThey respectively represent the fire center distance, speed, longitude, latitude, track angle and heading angle of the expected terminal detector.

[0092] Summary of symbol definitions

[0093]

[0094]

[0095]

[0096] Note: The lower right corner of the variable symbol is marked with 0, indicating the initial value; the lower right corner is marked with f, indicating the terminal moment value; the lower right corner is marked with r, indicating the expected value. f ,r c They represent the initial time, terminal time and expected detector fire center distance respectively.

[0097] Simulation conditions: 1. The probe has a height deviation of 1 km at the initial entry point, and the guidance law shown in formula (11) is used to track and guide the entry trajectory into the Martian atmosphere:

[0098]

[0099] In the formula, K p ,K d ,K i They are proportional term, differential term, and integral term gains respectively. At this time:

[0100]

[0101] Formula (12) is asymptotically stable.

[0102] Hard saturation is used to constrain the desired control quantity, that is,

[0103]

[0104] 2. The probe has a height deviation of 1 km at the initial entry point. The guidance law shown in formula (9) is used to track and guide the entry trajectory into the Martian atmosphere. The guidance law incorporates the anti-saturation auxiliary system of this embodiment.

[0105] The Martian atmospheric environment parameters used in the simulation are shown in Table 1, the physical parameters of the probe are shown in Table 2, and the initial and final states of the probe are shown in Table 3. Based on the data shown in Table 3 and the principle of maximizing the terminal height, the reference trajectory used in the simulation is generated by the Gpops software. The controller parameters and anti-saturation auxiliary system parameters are shown in Table 4.

[0106] Table 1 Nominal Martian environmental parameters

[0107]

[0108] Table 2 Nominal detector physical parameters

[0109]

[0110] Table 3 Nominal detector initial and final states

[0111]

[0112] Table 4 Gain coefficients of guidance law and path constraint processing module

[0113]

[0114]

[0115] The simulation is terminated when the probe speed is lower than 550m / s or the altitude is lower than 11.8766km.

[0116] The simulation results corresponding to working condition 1 and working condition 2 are plotted on Figure 2 and Figure 3 .

[0117] Depend on Figure 2 It can be seen that when the atmospheric entry guidance law does not include anti-saturation design, the actual control output always remains in the saturation state. At this time, the controller performance is degraded, the guidance law cannot drive the detector to track the desired trajectory, and the tracking error diverges;

[0118] Depend on Figure 3 It can be seen that when the atmosphere entry guidance law includes an anti-saturation design, that is, the anti-saturation auxiliary system designed in this embodiment is attached, the controller can quickly exit the saturation working area after saturation occurs, and the controller performance is well maintained, and the trajectory tracking error converges at an early stage.

[0119] At the same time, by Figure 3 The control input curve and the local enlarged diagram in the figure clearly show the working process of the anti-saturation auxiliary system: when the control is saturated, the controller is driven to exit the saturation zone; the finite time characteristics of the anti-saturation auxiliary variable change curve and the local enlarged diagram can be clearly seen.

[0120] The above results show that the anti-saturation auxiliary system designed in this embodiment can effectively deal with the control saturation problem. At the same time, since the anti-saturation auxiliary variables can converge quickly when saturation disappears, the guidance system can still make full use of the control capability of the detector, and adding the anti-saturation auxiliary system will not significantly affect the rapidity of the original guidance system. Since the Mars atmosphere entry trajectory tracking guidance process requires the guidance law to fully utilize the ability of the actuator and have sufficient rapidity, the anti-saturation auxiliary system designed in this embodiment is particularly suitable for this process and is a solution that fully considers the application background and characteristics.

[0121] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. The trajectory tracking and guidance system for Mars atmosphere entry is characterized by: The system includes a controller and an anti-saturation auxiliary system; The controller is used to obtain the desired control quantity u according to the height tracking error e and the anti-saturation auxiliary variable χ combined with the guidance law c , the controlled variable y=e+χ in the guidance law, according to u c The actual control quantity u is calculated in combination with the control constraints, and guidance is performed according to the reference trajectory based on the actual control quantity u; Anti-saturation auxiliary system, used to control the expected control quantity u at the previous moment c And the actual control amount u to obtain Δu, Δu = uu c , obtain the anti-saturation auxiliary variable χ: k χ1 , k χ2 are the gain coefficients of the anti-saturation auxiliary system, k χ1 ,k χ2 >0,α χ1 , α χ2 All are index coefficients of the anti-saturation auxiliary system, 0<α χ1 <1, α χ2 =2α χ1 / (1+α χ1 ); The guidance law in the controller is: K p , K d , K i are proportional, differential and integral gains respectively, g e =L cosγ, L represents lift acceleration, γ represents the flight track angle, D represents drag acceleration, g represents the Martian gravity acceleration, V represents the relative speed between the probe and the Martian atmosphere, r represents the radial distance from the probe's center of mass to the center of Mars, and r represents the radial distance from the probe's center of mass to the center of Mars. c represents the expected detector fire center distance; In the controller, according to u c Combined with the control constraints, the actual control quantity u is calculated as: The actual control quantity u∈[u min ,u max ],u max 、u min are the upper and lower bounds of the actual controlled quantity respectively; 2. The trajectory tracking and guidance system for entering the Mars atmosphere according to claim 1, characterized in that: In the controller, according to the desired atmospheric entry point state r0, V0, θ0, φ0, γ0, ψ0 and the desired terminal state r f ,V f ,θ f ,φ f ,γ f ,ψ f Design the reference trajectory to obtain the desired detector state at each moment, including the reference height h r , the current state of the detector includes the detector height h, and the height tracking error e = hh is obtained r ; r0, V0, θ0, φ0, γ0, ψ0 represent the distance from the center of fire, velocity, longitude, latitude, track angle and heading angle of the detector at the expected atmospheric entry point, respectively; r f ,V f ,θ f ,φ f ,γ f ,ψ f They respectively represent the fire center distance, speed, longitude, latitude, track angle and heading angle of the expected terminal detector.

3. The trajectory tracking and guidance system for entering the Mars atmosphere according to claim 2, characterized in that: V is the relative speed between the probe and the Martian atmosphere.

4. The trajectory tracking and guidance system for entering the Mars atmosphere according to claim 1, characterized in that: The controller determines the flight bank angle σ according to the actual control variable u=cosσ, and performs atmospheric entry trajectory tracking and guidance based on the longitudinal dynamic equation of the probe.

5. The trajectory tracking and guidance system for entering the Mars atmosphere according to claim 4, characterized in that: The longitudinal dynamic equation of the detector is: r is the radial distance from the probe's center of mass to the center of Mars, V is the relative speed between the probe and the Martian atmosphere, γ is the flight track angle, ψ is the flight heading angle, θ and φ represent longitude and latitude respectively, and g m =μ / r 2 is the Martian gravitational acceleration, μ is the Martian gravitational constant, L = ρV 2 C L S r / (2m) and D=ρV 2 C D S r / (2m) represent lift acceleration and drag acceleration respectively, m is the mass of the probe, S r is the aerodynamic area of ​​the detector, C D , C L are the drag coefficient and lift coefficient of the Martian atmosphere respectively, and ρ is the density of the Martian atmosphere; the atmospheric density ρ satisfies: Where ρ0 and h represent the standard atmospheric density of Mars and the height of the probe from the surface of Mars, respectively. h = r-R0, r is the distance between the probe and the center of Mars, R0 is the radius of Mars, and r s is the reference altitude of the Martian atmosphere.

6. A trajectory tracking and guidance method for entering the Martian atmosphere, characterized in that: The method comprises: Step 1: Determine the control constraints of the detector guidance system; Step 2: Determine the reference trajectory and the current state of the detector, and calculate the height tracking error e; Step 3: Design the guidance law. The controlled variable in the guidance law is y=e+χ, where χ represents the anti-saturation auxiliary variable. The output of the guidance law is the desired controlled variable u c , calculate the actual control quantity u in combination with the control constraints, and guide according to the reference trajectory based on the actual control quantity u; The method for obtaining the anti-saturation auxiliary variable χ is: k χ1 , k χ2 are the gain coefficients of the anti-saturation auxiliary system, k χ1 ,k χ2 >0,α χ1 , α χ2 All are index coefficients of the anti-saturation auxiliary system, 0<α χ1 <1, α χ2 =2α χ1 / (1+α χ1 ); According to the expected control quantity u at the previous moment c And the actual control amount u to obtain Δu, Δu = uu c ; The guidance law is: K p , K d , K i are proportional, differential and integral gains respectively, g e =L cosγ, L represents lift acceleration, γ represents the flight track angle, D represents drag acceleration, g represents the Martian gravity acceleration, V represents the relative speed between the probe and the Martian atmosphere, r represents the radial distance from the probe's center of mass to the center of Mars, and r represents the radial distance from the probe's center of mass to the center of Mars. c represents the expected detector fire center distance; According to u c Combined with the control constraints, the actual control quantity u is calculated as: The actual control quantity u∈[u min ,u max ],u max 、u min are the upper and lower bounds of the actual controlled quantity respectively; 7. A computer-readable storage device storing a computer program, characterized in that: When the computer program is executed, the trajectory tracking and guidance method for entering the Martian atmosphere as claimed in claim 6 is implemented.

8. A trajectory tracking and guidance system for Mars atmosphere entry, comprising a storage device, a processor, and a computer program stored in the storage device and executable on the processor, characterized in that: The processor executes the computer program to implement the trajectory tracking and guidance method for entering the Martian atmosphere as described in claim 6.

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