A dual-channel angle tracking guidance method for aerodynamically assisted orbit descent

Abstract

This invention provides a dual-channel angle tracking guidance method for aerodynamically assisted descent, including: establishing a dynamic model of a spacecraft's aerodynamically assisted descent under angle-of-attack-sideslip angle modulation, considering the effects of J2 perturbation and celestial rotation; selecting the lift coefficient and lateral force coefficient as control variables for the longitudinal and lateral channels respectively, and using the track angle and heading angle as tracking variables respectively; comprehensively considering the uncertainties of aerodynamic parameters and atmospheric environment, and combining the aerodynamically assisted descent dynamic model of the spacecraft, obtaining a model of the aerodynamically assisted descent tracking guidance problem under angle-of-attack-sideslip angle modulation, and constructing lumped uncertainty terms; using an extended state observer to approximate the tracking variables and lumped uncertainty terms; and designing tracking guidance laws for the longitudinal and lateral channels based on linear state error feedback. Therefore, using the above method, the tracking guidance performance under parameter disturbances and uncertainties can be guaranteed, achieving high-precision tracking of the nominal trajectory of aerodynamically assisted descent.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and in particular to a dual-channel angle tracking guidance method for aerodynamically assisted orbit descent. Background Technology

[0002] Aerodynamic-assisted landing (AART) achieves orbital changes by traversing planetary atmospheres, saving significant fuel compared to simple space orbital maneuvers and reserving more space for payloads. Considering the highly dynamic environment and aerodynamic parameter uncertainties encountered during AART, spacecraft need flight control capabilities to adjust their trajectory promptly and proactively. Currently, in AART maneuvers, lift-driven spacecraft primarily adjust their trajectory profile through lift modulation, using the lift vector to influence the spacecraft's motion. A traditional lift modulation strategy is tilt angle modulation, which uses the tilt angle to rotate the lift vector relative to the incoming velocity vector, achieving longitudinal and lateral control by adjusting the magnitude and sign of the tilt angle. A second lift modulation method is angle-of-attack-slip angle modulation, which adjusts the spacecraft's angle of attack and sideslip angle to control the magnitude and direction of aerodynamic lift (L), drag (D), and lateral force (Q). Adjusting the angle of attack and sideslip angle can decompose the horizontal, lateral, and vertical motion relative to the spacecraft's body axis. In some scenarios, angle-of-attack-slip angle modulation offers superior performance compared to tilt angle control.

[0003] Currently, in 2020, Daniel and Christopher studied a numerical prediction-correction guidance method under angle-of-attack-slip angle modulation (AOA-SM) for a Mars aerodynamic descent mission set. Also in 2020, Rohan et al., based on a linearized aerodynamic model, modified a full numerical prediction-correction guidance method originally used for tilt angle modulation (TAP-SM) for AOA-SM, demonstrating that AOA-SM is a feasible technique for achieving aerodynamic descent of blunt-body spacecraft on Neptune. Although the decoupled flight control strategy of AOA-SM has potential advantages, research on its application in aerodynamic descent is still in its early stages. Furthermore, research on AOA-SM in aerodynamic descent focuses primarily on prediction-correction guidance methods, requiring continuous online prediction of trajectory states and iterative correction of guidance commands, while research on tracking guidance methods is still limited.

[0004] Therefore, there is an urgent need for a tracking and guidance method that can perform high-precision tracking of the nominal trajectory of aerodynamic assisted descent under angle of attack-side slip angle modulation, while having lower requirements for equipment computing power and being more in line with the requirements of engineering practice. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-channel angle tracking guidance method for aerodynamic assisted descent, ensuring tracking and guidance performance under parameter disturbances and uncertainties, and achieving high-precision tracking of the nominal trajectory of aerodynamic assisted descent under angle of attack-side slip angle modulation.

[0006] To achieve the above objectives, the present invention provides a dual-channel angle tracking guidance method for pneumatically assisted orbit descent, comprising the following steps:

[0007] S1. Considering the effects of J2 perturbation and celestial body rotation, establish a spacecraft aerodynamic-assisted orbit descent dynamics model under angle of attack-side slip angle modulation;

[0008] S2. Select the lift coefficient and lateral force coefficient as the control variables for the longitudinal and lateral channels respectively, and use the track angle and heading angle as the tracking variables respectively;

[0009] S3. Taking into account the uncertainties of aerodynamic parameters and atmospheric environment, and combining the aerodynamic assisted descent dynamics model of the spacecraft, a model of aerodynamic assisted descent tracking guidance problem under angle of attack-side slip angle modulation is obtained, and lumped uncertainty terms are constructed.

[0010] S4. Use an extended state observer to approximate the tracking variables and lumped uncertainty terms;

[0011] S5. Based on linear state error feedback, tracking guidance laws are designed in both longitudinal and lateral dual channels.

[0012] Preferably, the aerodynamically assisted orbit descent dynamic model of the spacecraft is a three-degree-of-freedom dynamic equation, as follows:

[0013]

[0014] In the formula, and Let r, θ, φ, V, γ, and ψ be the derivatives of the spacecraft's state variables r, θ, φ, V, γ, and ψ with respect to time, r be the radial distance from the Earth's center to the spacecraft's center of mass, θ be the longitude, φ be the latitude, V be the spacecraft's velocity relative to the celestial body, γ be the trajectory angle of the velocity vector relative to the celestial body, ψ be the heading angle, σ be the roll angle, L, D, and Q be the aerodynamic lift acceleration, drag acceleration, and lateral force acceleration, respectively, and g be the derivative of the spacecraft's state variables r, θ, φ, V, γ, and ψ with respect to time. r g φ These are the radial and latitudinal components of gravitational acceleration, respectively, and ω is the angular velocity of the celestial body's rotation.

[0015] in,

[0016]

[0017] In the formula, ρ is the atmospheric density, S is the spacecraft reference area, m is the spacecraft mass, and C is the atmospheric density. L C D CQ These represent the lift coefficient, drag coefficient, and lateral force coefficient, respectively; μ is the gravitational parameter of the celestial body; R0 is the equatorial radius of the celestial body; and J2 is the dynamic flattening of the celestial body.

[0018] Preferably, in step 2, the lift coefficient is determined using the track angle as the tracking variable, and the lateral force coefficient is determined using the heading angle as the tracking variable, as detailed below:

[0019] Define the tracking variable as:

[0020] x1=γ

[0021] x2=ψ

[0022] Considering that the roll angle remains at 0 degrees during angle-of-attack-slip angle modulation, and combining this with the three-degree-of-freedom dynamic equations, by differentiating x1 and x2 with respect to time, we obtain:

[0023]

[0024] In the formula, These are the derivatives of the tracking variables x1 and x2, respectively.

[0025] The lift coefficient and lateral force coefficient are determined based on the derivatives of the tracking variables x1 and x2.

[0026] The control values ​​for the longitudinal and lateral channels are respectively taken as u. c1 =C L u c2 =C Q Considering the limited attitude control capabilities of spacecraft, attitude angles α and β should be controlled within a reasonable range, and the corresponding aerodynamic coefficient inputs should also be within a certain range. Input saturation can be described as:

[0027] u 1min ≤u c1 ≤u 1max

[0028] u 2min ≤u c2 ≤u 2max

[0029] The preferred model for the aerodynamic descent tracking guidance problem under angle-of-attack-sideslip angle modulation is as follows:

[0030]

[0031] in,

[0032]

[0033] In the formula, H1, H2, N1, and N2 are model-based terms, and δ1 and δ2 are lumped uncertainty terms.

[0034] Preferably, the extended state observer used in step S4 is as follows:

[0035]

[0036] in,

[0037] z lon =[z lon1 ,z lon2 ] T

[0038] z lat =[z lat1 ,z lat2 ] T

[0039] u lon =u c1 +N1 / H1

[0040] u lat =u c2 +N2 / H2

[0041] The values ​​of the coefficient matrix are:

[0042]

[0043] In the formula, Let z be the derivatives of the longitudinal and lateral estimation vectors with respect to time, respectively. lon1 z lon2 z lat1 z lat2 These are estimates of γ, δ1, ψ, and δ2, respectively. These represent the observer's estimates of the tracking amount in the longitudinal and lateral channels, respectively; L lon L lat These are the error feedback gain vectors of the observer in the longitudinal and lateral channels, respectively.

[0044] Preferably, step S5 includes designing linear state error feedback to control the system, as follows:

[0045] u′ c1 =K P1 (γ d -z lon1 )

[0046] u′ c2 =K P2 (ψ d -z lat1 )

[0047] In the formula, u′ c1 u′ c2These are the longitudinal and lateral linear state error feedback control laws, respectively, K P1 K P2 These are the proportional coefficients for longitudinal and lateral state error feedback, respectively, γ d , ψ d These represent the expected track angle and expected heading angle corresponding to the nominal trajectory, respectively.

[0048] Preferably, tracking guidance laws are designed for both longitudinal and lateral channels, as follows:

[0049] When the extended state observer correctly estimates the tracking variable and the lumped uncertainty, let

[0050]

[0051] The guidance system is simplified to a single integrator system:

[0052]

[0053] Based on linear state error feedback, the control command expression is obtained:

[0054]

[0055] According to the commanded value u of the lift coefficient c1 The commanded value u of the lateral force coefficient c2 By combining the aerodynamic model of a specific spacecraft, commands for angle of attack and sideslip angle are obtained.

[0056] Therefore, the present invention employs the above-mentioned dual-channel angle tracking guidance method for pneumatically assisted orbit descent, which has the following technical advantages:

[0057] (1) The longitudinal and lateral channels can be controlled simultaneously by the angle of attack-side slip angle modulation, and the channels can be decoupled.

[0058] (2) Using the angle of attack as the control variable in the longitudinal channel, the lift-to-drag ratio of the spacecraft can be changed, which has strong control capability;

[0059] (3) The derived aerodynamic-assisted descent dual-channel angle tracking guidance model is a first-order model with a relatively simple structure. The corresponding tracking guidance law has low requirements for the equipment's computing power, which meets the actual requirements of engineering.

[0060] (4) Taking into account the uncertainties of atmospheric environment and aerodynamic parameters, a lumped uncertainty term is constructed and an extended state observer is introduced to estimate and compensate for it, so that the guidance method has strong robustness.

[0061] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0062] Figure 1 This is a block diagram of a dual-channel angle tracking guidance method for pneumatic assisted descent under angle of attack-side slip angle modulation in an embodiment of a pneumatic assisted descent method.

[0063] Figure 2 This is an example of a dual-channel angle tracking guidance method for aerodynamic assisted orbit descent, showing the tracking of the velocity-elevation profile in a Mars aerodynamic assisted orbit descent scenario.

[0064] Figure 3 This is an example of a dual-channel angle tracking guidance method for aerodynamically assisted orbit descent, illustrating the tracking of orbital inclination in a Mars aerodynamically assisted orbit descent scenario. Detailed Implementation

[0065] The present invention will be explained in more detail through the following embodiments. The purpose of disclosing the present invention is to protect all changes and modifications within the scope of the present invention. The present invention is not limited to the following embodiments.

[0066] This embodiment simulates and analyzes a Mars aerodynamic assisted descent tracking and guidance problem. The target orbit is an elliptical orbit with an altitude of 300×3000km and an inclination of 89deg. The parameter model of the spacecraft is taken as the Mars Science Laboratory (MSL) spacecraft. The initial entry conditions under the Mars aerodynamic assisted descent scenario are shown in Table 1.

[0067] Table 1. Inertial entry conditions under the Mars aerodynamic-assisted orbit descent scenario.

[0068] Entering the state value high 128km longitude -116.5deg latitude -46.67deg speed 5.9km / s track angle -11deg Heading angle 0.00deg

[0069] like Figure 1 As shown, the present invention provides a dual-channel angle tracking guidance method for pneumatically assisted orbit descent, comprising the following steps:

[0070] S1. Considering the effects of J2 perturbation and celestial rotation, a spacecraft aerodynamic-assisted orbit descent dynamic model is established under angle of attack-side slip angle modulation. The spacecraft aerodynamic-assisted orbit descent dynamic model is a three-degree-of-freedom dynamic equation.

[0071] The three-degree-of-freedom dynamic equations of the spacecraft during the aerodynamically assisted orbit descent maneuver are as follows:

[0072]

[0073] In the formula, and Let r, θ, φ, V, γ, and ψ be the derivatives of the spacecraft's state variables r, θ, φ, V, γ, and ψ with respect to time, where r is the radial distance from the Earth's center to the spacecraft's center of mass; θ is the longitude; φ is the latitude; V is the spacecraft's velocity relative to the celestial body; γ is the trajectory angle of the velocity vector relative to the celestial body, i.e., the ballistic inclination angle; ψ is the heading angle, i.e., the ballistic deflection angle; the projection of the relative velocity vector to the celestial body clockwise from true north onto the local horizontal plane is positive; σ is the tilt angle, which is set to 0 in the angle-of-attack-sideslip modulation mode, thereby decoupling the longitudinal and lateral control; L, D, and Q are the aerodynamic lift acceleration, drag acceleration, and lateral force acceleration, respectively; g is the velocity vector of the spacecraft relative to the celestial body; φ is the velocity vector of the spacecraft relative to the celestial body; γ is the velocity vector of the spacecraft relative to the celestial body; φ is the velocity vector of the spacecraft relative to the celestial body; γ is the velocity vector of the spacecraft relative to the celestial body; ψ is the velocity vector of the spacecraft relative to the celestial body; σ is the tilt angle, which is set to 0 in the angle-of-attack-sideslip modulation mode, thereby decoupling the longitudinal and lateral control; L, D, and Q are the aerodynamic lift acceleration, drag acceleration, and lateral force acceleration, respectively; g is the velocity vector of the spacecraft relative to the celestial body; φ ... r g φ ω represents the radial and latitudinal components of gravitational acceleration, respectively, and ω is the angular velocity of celestial body rotation.

[0074] in,

[0075]

[0076] In the formula, ρ is the atmospheric density; S is the spacecraft reference area; m is the spacecraft mass; C L C D C Q These are the lift coefficient, drag coefficient, and lateral force coefficient, respectively. For the MSL model in this embodiment, the lift coefficient and drag coefficient are mainly determined by the angle of attack α, and the lateral force coefficient is mainly determined by the sideslip angle β, as shown in the following formulas:

[0077]

[0078] In the formula, C Lα C Dα C Q,β These are the derivatives of the lift coefficient, drag coefficient, and lateral force coefficient, respectively. C D0 This represents the drag coefficient at zero angle of attack. In other embodiments, the relationship between the aerodynamic coefficient and the angle of attack α and sideslip angle β can be adjusted based on existing spacecraft aerodynamic models, according to actual conditions.

[0079] g r g φ The specific expression is as follows:

[0080]

[0081] In the formula, μ is the gravitational parameter of the celestial body, R0 is the equatorial radius of the celestial body, and J2 is the dynamic flattening of the celestial body.

[0082] S2. Select the lift coefficient and lateral force coefficient as the control variables for the longitudinal and lateral channels, respectively, and the track angle and heading angle as the tracking variables.

[0083] Considering the different aerodynamic models and varying mapping relationships between aerodynamic coefficients and attitude angles across different spacecraft, the aerodynamic coefficients of the spacecraft are chosen as the control variables to avoid loss of generality. The control variables for the longitudinal and lateral channels are selected as the lift coefficients CL. L Lateral force coefficient C Q And C is determined using the track angle γ as the tracking variable. L Choosing the heading angle ψ as the tracking variable to determine C Q The details are as follows:

[0084] First, define the tracking variable as follows:

[0085] x1=γ

[0086] x2=ψ

[0087] Secondly, considering that the roll angle remains at 0 degrees during angle-of-attack-sideslip modulation, and combining this with the three-degree-of-freedom dynamic equations, by differentiating x1 and x2 with respect to time, we obtain:

[0088]

[0089] The control values ​​for the longitudinal and lateral channels are respectively taken as u. c1 =C L u c2 =C Q Considering the limited attitude control capabilities of spacecraft, attitude angles α and β should be controlled within a reasonable range, and the corresponding aerodynamic coefficient inputs should also be within a certain range. Input saturation can be described as:

[0090] u 1min ≤u c1 ≤u 1max

[0091] u 2min ≤u c2 ≤u 2max

[0092] S3. Taking into account the uncertainties of aerodynamic parameters and atmospheric environment, and combining the aerodynamic assisted descent dynamics model of spacecraft, a model of aerodynamic assisted descent tracking guidance problem under angle of attack-side slip angle modulation is derived, and lumped uncertainty terms are constructed.

[0093] Due to the complex atmospheric environment of planets, spacecraft are inevitably affected by uncertainties in aerodynamic coefficients and atmospheric density. When these uncertainties are taken into account, the aerodynamic coefficients (including control inputs) and planetary atmospheric density can be expressed as:

[0094]

[0095] In the formula, C L- nom, CQ- nom、ρ nm These are the nominal aerodynamic lift coefficient, lateral force coefficient, and atmospheric density, respectively; ΔC L ΔC Q Δρ and Δρ represent the uncertainties in aerodynamic lift coefficient, lateral force coefficient, and atmospheric density, respectively; u c1 u c2 These are the command values ​​for the lift coefficient and the lateral force coefficient, respectively; Δu1 and Δu2 are the corresponding control disturbances.

[0096] Combining the above formulas, we obtain the aerodynamic-assisted descent dual-channel angle tracking guidance model under angle of attack-side slip angle modulation:

[0097]

[0098] In the formula, H1, H2, N1, and N2 are model-based terms, and δ1 and δ2 are lumped uncertainty terms.

[0099] in,

[0100]

[0101] S4. Use an extended state observer to approximate the tracking variable and the lumped uncertainty term.

[0102] Considering the existence of lumped uncertainties and the measurement errors of tracking variables (track angle, heading angle) during spacecraft flight, an extended state observer is used to approximate the tracking variables and lumped uncertainties.

[0103]

[0104] in,

[0105] z lon =[z lon1 ,z lon2 ] T

[0106] z lat =[z lat1 ,z lat2 ] T

[0107] u lon =u c1 +N1 / H1

[0108] u lat =u c2 +N2 / H2

[0109] The values ​​of the coefficient matrix are:

[0110]

[0111] In the formula, Let z be the derivatives of the longitudinal and lateral estimation vectors with respect to time, respectively. lon1 z lon2 z lat1 z lat2 These are estimates of γ, δ1, ψ, and δ2, respectively. These represent the observer's estimates of the tracking amount in the longitudinal and lateral channels, respectively; L lon L lat β and t are the error feedback gain vectors of the observer in the longitudinal and lateral channels, respectively, where β lon1 β lon2 β lat1 β lat2 The value can be adjusted using existing bandwidth methods or trial-and-error methods.

[0112] S5. Based on linear state error feedback, tracking guidance laws are designed in both longitudinal and lateral dual channels.

[0113] When the observer can correctly estimate the tracking variable and the lumped uncertainty, let

[0114]

[0115] In the formula, u′ c1 u′ c2 These are the longitudinal and lateral linear state error feedback control laws, respectively.

[0116] The system is then simplified to a single integrator system.

[0117]

[0118] Design a linear state error feedback mechanism to control the system:

[0119] u′ c1 =K P1 (γ d -z lon1 )

[0120] u′ c2 =K P2 (ψ d -z lat1 )

[0121] In the formula, γ d , ψ d K represents the expected track angle and expected heading angle corresponding to the nominal trajectory, respectively. P1 K P2 These are the proportional coefficients for longitudinal and lateral state error feedback, respectively.

[0122] Combining the above formulas, the final expression of the control command is:

[0123]

[0124] Based on the commanded values ​​of the lift coefficient and lateral force coefficient, and combined with existing spacecraft aerodynamic models, the relationship between the aerodynamic coefficients and the angle of attack and sideslip angle is obtained according to the actual situation. This allows for the acquisition of corresponding angle of attack and sideslip angle commands, thereby achieving aerodynamic-assisted orbit descent tracking guidance under angle-of-attack-sideslip angle modulation. For example... Figure 2 and Figure 3 As shown, this embodiment can drive the spacecraft to track the nominal trajectory with high precision in both longitudinal and lateral channels, and successfully complete the aerodynamic assisted orbit descent mission; and the velocity increment required for the spacecraft to insert into the target orbit after exiting the atmosphere is 56.3 m / s, and the orbital inclination deviation is 0.0055 deg.

[0125] Therefore, the present invention adopts the above-mentioned dual-channel angle tracking guidance method for pneumatic assisted descent, which can realize the tracking guidance of pneumatic assisted descent under the angle of attack-side slip angle modulation mode, ensure the tracking guidance performance under parameter disturbance and uncertainty, and achieve high-precision tracking of the nominal trajectory of pneumatic assisted descent.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dual-channel angle tracking guidance method for pneumatically assisted orbit descent, characterized in that, Includes the following steps: S1. Considering J2 perturbation and celestial body rotation, establish a spacecraft aerodynamic-assisted orbit descent dynamics model under angle of attack-side slip angle modulation; S2. Select the lift coefficient and lateral force coefficient as the control variables for the longitudinal and lateral channels respectively, and use the track angle and heading angle as the tracking variables respectively; S3. Based on the uncertainties of aerodynamic parameters and atmospheric environment, and combined with the aerodynamic assisted descent dynamics model of spacecraft, a model of aerodynamic assisted descent tracking guidance problem under angle of attack-side slip angle modulation is obtained, and lumped uncertainty terms are constructed. S4. Use an extended state observer to approximate the tracking variables and lumped uncertainty terms; S5. Based on linear state error feedback, tracking guidance laws are designed in both longitudinal and lateral dual channels.

2. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 1, characterized in that, In step S1, the aerodynamic-assisted descent dynamic model of the spacecraft is a three-degree-of-freedom dynamic equation, as follows: ； In the formula, , , , , , These are spacecraft state quantities. , , , , , The derivative with respect to time, The radial distance from the Earth's center to the spacecraft's center of mass. Longitude Latitude The velocity of the spacecraft relative to the celestial body. The trajectory angle is the velocity vector relative to the celestial body. For heading angle, The tilt angle, , and These are aerodynamic lift acceleration, drag acceleration, and lateral force acceleration, respectively. , These are the radial and latitudinal components of gravitational acceleration, respectively. This refers to the angular velocity of a celestial body's rotation. in, ； ； ； ； ； In the formula, Atmospheric density, For spacecraft reference area, For spacecraft mass, , , These are the lift coefficient, drag coefficient, and lateral force coefficient, respectively. For celestial gravitational parameters, The radius of the celestial body's equator. It represents the celestial dynamics flattening.

3. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 2, characterized in that, In step S2, the lift coefficient is determined using the track angle as the tracking variable, and the lateral force coefficient is determined using the heading angle as the tracking variable, as detailed below: Define the tracking variable as: ； ； In angle-of-attack-sideslip modulation, the roll angle is kept at 0 degrees. Combined with the three-degree-of-freedom dynamic equations, for... , Taking the derivative with respect to time, we get: ； ； In the formula, Tracking variables , The derivative; Based on tracking variables , The derivative of the coefficient is used to determine the lift coefficient and the lateral force coefficient.

4. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 3, characterized in that, In step S3, the uncertainties in aerodynamic parameters and the atmospheric environment include the aerodynamic lift coefficient, the lateral force coefficient, and the atmospheric density, as detailed below: ； In the formula, These are the nominal aerodynamic lift coefficient, lateral force coefficient, and atmospheric density, respectively. , , These are the uncertainties in aerodynamic lift coefficient, lateral force coefficient, and atmospheric density, respectively. , These are the commanded values ​​for the lift coefficient and the lateral force coefficient, respectively. , These are the corresponding control disturbances.

5. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 4, characterized in that, The obtained model for the aerodynamic-assisted trajectory descent tracking guidance problem under angle-of-attack-slip angle modulation is as follows: ； ； in, ； ； In the formula, , , , It is a model-based item. , It is a lumped uncertain term.

6. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 5, characterized in that, In step S4, the extended state observer used is as follows: ； ； in, ； ； ； ； The values ​​of the coefficient matrix are: ； In the formula, These are the derivatives of the longitudinal and lateral estimation vectors with respect to time, respectively. , , , They are respectively for , , , The estimate; , These represent the observer's estimates of the tracking amount in the longitudinal and lateral channels, respectively. These are the error feedback gain vectors of the observer in the longitudinal and lateral channels, respectively.

7. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 6, characterized in that, Step S5 includes designing linear state error feedback to control the system, as detailed below: ； ； In the formula, , These are the longitudinal and lateral linear state error feedback control laws, respectively. , These are the proportional coefficients for longitudinal and lateral state error feedback, respectively. , These represent the expected track angle and expected heading angle corresponding to the nominal trajectory, respectively.

8. The dual-channel angle tracking guidance method for pneumatically assisted orbit descent according to claim 7, characterized in that, The tracking guidance law is designed for both longitudinal and lateral dual channels, as follows: When the extended state observer correctly estimates the tracking variable and the lumped uncertainty, let ； ； The guidance system is simplified to a single integrator system: ； ； Based on linear state error feedback, the control command expression is obtained: ； ； According to the commanded value of the lift coefficient Command value of lateral force coefficient By combining the specific aerodynamic-assisted orbit descent dynamics model of the spacecraft, commands for angle of attack and sideslip angle are obtained.

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