Parachute six-degree-of-freedom mathematical model construction method for mars landing

Abstract

The invention discloses a parachute six-degree-of-freedom mathematical model construction method for mars landing. The method comprises the following steps: establishing a Mars atmosphere environment parameter model, initializing a density function, a gravitational acceleration function and a temperature function of the Mars atmosphere, and taking the tail end height, speed and attack angle data of a Mars entering section as input to obtain initial state parameters; active anti-interference control is executed based on the initial state parameters, towing acceleration tracking control is conducted on the flight path of the entering section, and corrected parachute opening point state data are output; establishing a Mars surface inertial coordinate system and a parachute system body coordinate system, constructing a fire transformation matrix by using parachute opening point state data, and determining an attitude angle and a velocity component of the system based on the transformation matrix to obtain a coordinate system initialization result; and based on a coordinate system initialization result, establishing a six-degree-of-freedom dynamic model by using a parachute-aircraft system with an additional mass item. According to the invention, the technical problem of inaccurate mars landing is solved.

Description

Technical Field

[0001] This invention relates to the field of mathematics, and more specifically, to a method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars landing. Background Technology

[0002] The entry, descent, and landing (EDL) process is a crucial phase in Mars exploration missions, with the parachute system playing a central role in the deceleration and stable descent of the spacecraft. To analyze and verify the kinematic characteristics of the parachute-spacecraft system in the Martian atmosphere, it is typically necessary to establish a corresponding dynamic mathematical model to describe the system's velocity, attitude, and position changes during the descent phase. Current modeling methods for Mars parachute systems are mostly based on simplified dynamic assumptions, often employing three-degree-of-freedom or quasi-static models, or neglecting aerodynamic unsteady effects and added mass changes in six-degree-of-freedom modeling. These methods fail to fully reflect the true dynamic characteristics of the translational and rotational coupling during parachute deployment and descent.

[0003] On the other hand, the Martian atmosphere is characterized by low density, large scale, and rapid changes in aerodynamic environment with altitude. When a parachute moves in the thin atmosphere, the acceleration effect of the surrounding airflow introduces significant unsteady added mass and damping changes. Existing six-degree-of-freedom models typically approximate this with constant added mass or empirical damping coefficients, resulting in insufficient simulation accuracy during the parachute deployment transient phase and attitude oscillations. Furthermore, some modeling methods fail to effectively correct for the end state of the entry phase, directly using the calculated entry trajectory as the initial condition for parachute deployment. This easily transmits entry phase disturbance errors to the parachute descent model, thus affecting the overall simulation stability and reliability.

[0004] Therefore, there is an urgent need for a mathematical modeling method for parachute systems that can combine the characteristics of the Martian atmospheric environment, consider disturbance corrections during the entry phase, and simultaneously describe the coupling effects of translational and angular motion within a six-degree-of-freedom framework, in order to improve the accuracy and stability of dynamic simulations of the Mars landing process. Summary of the Invention

[0005] This invention provides a method and system for constructing a six-degree-of-freedom mathematical model of a parachute for Mars landing, in order to at least solve the technical problems of Mars.

[0006] According to one aspect of the present invention, a method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing is provided, comprising: establishing a Martian atmospheric environment parameter model, initializing the density function, gravitational acceleration function, and temperature function of the Martian atmosphere, and obtaining initial state parameters by taking the terminal altitude, velocity, and angle of attack data of the Martian approach phase as input; executing an active disturbance rejection control algorithm based on the initial state parameters to perform drag acceleration tracking control on the flight trajectory of the approach phase, and outputting corrected parachute deployment point state data; establishing a Martian surface inertial coordinate system and a parachute system volume coordinate system, constructing a transformation matrix between the Martian surface inertial coordinate system and the parachute system volume coordinate system using the parachute deployment point state data, and determining the attitude angle and velocity components of the system based on the transformation matrix to obtain coordinate system initialization results; and establishing a six-degree-of-freedom dynamic model of the parachute-spacecraft system with added mass terms based on the coordinate system initialization results.

[0007] According to another aspect of the present invention, a system for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing is also provided, comprising: a model establishment module configured to establish a Martian atmospheric environment parameter model, initialize the density function, gravitational acceleration function, and temperature function of the Martian atmosphere, and obtain initial state parameters using the terminal altitude, velocity, and angle of attack data of the Martian entry phase as input; a state determination module configured to execute an active disturbance rejection control algorithm based on the initial state parameters, perform drag acceleration tracking control on the flight trajectory of the entry phase, and output corrected parachute deployment point state data; a transformation module configured to establish a Martian surface inertial coordinate system and a parachute system volume coordinate system, construct a transformation matrix between the Martian surface inertial coordinate system and the parachute system volume coordinate system using the parachute deployment point state data, and determine the attitude angle and velocity components of the system based on the transformation matrix to obtain coordinate system initialization results; and an establishment module configured to establish a six-degree-of-freedom dynamic model of the parachute-spacecraft system with an added mass term based on the coordinate system initialization results.

[0008] In this embodiment of the invention, a method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing is provided, comprising: establishing a Martian atmospheric environment parameter model, initializing the density function, gravitational acceleration function, and temperature function of the Martian atmosphere, and obtaining initial state parameters using the terminal altitude, velocity, and angle of attack data of the Mars approach phase as input; executing an active disturbance rejection control algorithm based on the initial state parameters to perform drag acceleration tracking control on the flight trajectory of the approach phase, and outputting corrected parachute deployment point state data; establishing a Martian surface inertial coordinate system and a parachute system volume coordinate system, constructing a transformation matrix between the Martian surface inertial coordinate system and the parachute system volume coordinate system using the parachute deployment point state data, and determining the system's attitude angles and velocity components based on the transformation matrix to obtain coordinate system initialization results; and establishing a six-degree-of-freedom dynamic model of the parachute-spacecraft system with added mass terms based on the coordinate system initialization results. This solves the technical problems of Mars. Attached Figure Description

[0009] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0010] Figure 1 This is a flowchart of an optional method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars landing, according to an embodiment of the present invention;

[0011] Figure 2 This is a flowchart of another optional method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach landing according to an embodiment of the present invention;

[0012] Figure 3 This is an optional force diagram of an aircraft according to an embodiment of the present invention;

[0013] Figure 4 This is a schematic diagram of the volume coordinate system of an optional parachute system according to an embodiment of the present invention;

[0014] Figure 5 This is a flowchart of an optional method for establishing a six-degree-of-freedom dynamic model according to an embodiment of the present invention;

[0015] Figure 6 This is a schematic diagram of an optional six-degree-of-freedom mathematical model construction system for Mars landing according to an embodiment of the present invention;

[0016] Figure 7 A schematic diagram of the structure of a computer device suitable for implementing embodiments of the present disclosure is shown. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0018] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0019] According to an embodiment of the present invention, a method embodiment for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach landing is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0020] Figure 1 This is a method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing according to an embodiment of the present invention, such as... Figure 1 As shown, the method includes the following steps:

[0021] Step S102: Establish a Martian atmospheric environment parameter model, initialize the density function, gravitational acceleration function, and temperature function of the Martian atmosphere, and obtain the initial state parameters by taking the end-of-Mars entry phase altitude, velocity, and angle of attack data as input.

[0022] For example, the Martian atmospheric density distribution function is obtained, and the gravitational acceleration is calculated based on the Martian radius and the surface gravity constant to obtain a set of coupled parameters of atmospheric density and gravitational acceleration; the set of coupled parameters is matched with the input initial altitude to calculate the set of local atmospheric characteristics parameters of the Martian entry segment, wherein the set of local atmospheric characteristics parameters includes local density, pressure and temperature.

[0023] Step S104: Based on the initial state parameters, execute the active disturbance rejection control algorithm to perform drag acceleration tracking control on the flight trajectory of the entry segment, and output the corrected parachute opening point state data.

[0024] For example, based on the initial state parameters, the total disturbance is estimated in real time using an extended state observer; the total disturbance is used to compensate for unknown disturbances, so that the drag acceleration tracks the reference drag acceleration, and the real-time trajectory deviation is obtained; based on the real-time trajectory deviation, the updated parachute deployment point height, velocity, and attitude angle are calculated to obtain the corrected parachute deployment point state data.

[0025] Step S106: Establish the Mars surface inertial coordinate system and the parachute system volume coordinate system. Construct a transformation matrix between the Mars surface inertial coordinate system and the parachute system volume coordinate system using the parachute deployment point state data. Determine the system's attitude angles and velocity components based on the transformation matrix to obtain the coordinate system initialization results.

[0026] For example, the origin is determined based on the Martian surface directly below the parachute deployment point, the Z-axis is determined based on the direction of the Martian center, the X-axis is determined based on the initial flight direction, and the Y-axis is determined according to the right-hand rule, thus establishing the Martian surface inertial coordinate system; the origin is determined based on the center of mass of the parachute-spacecraft system, the X-axis is determined based on the instantaneous motion direction of the system, and the Z-axis is determined based on the direction along the parachute's principal axis of symmetry, thus establishing the parachute system volume coordinate system; using the parachute deployment point state data, a coordinate transformation matrix is ​​established between the Martian surface inertial coordinate system and the parachute system volume coordinate system, wherein the coordinate transformation matrix satisfies a composite rotation relationship with a three-axis rotation sequence.

[0027] Step S108: Based on the coordinate system initialization results, a six-degree-of-freedom dynamic model is established using the parachute-aircraft system with added mass terms. The six-degree-of-freedom dynamic model includes translational dynamic equations and angular motion equations.

[0028] First, using a time-adaptive damping correction coefficient, the calculation error of the added mass is corrected to obtain an equivalent added mass term. Based on this equivalent added mass term, a translational dynamic equation is constructed. For example, the local atmospheric density at the parachute deployment altitude is calculated based on a Martian atmospheric environment parameter model, and a basic added mass model of the system is constructed according to the parachute reference area coefficient. Using the time-adaptive damping correction coefficient, the equivalent added mass term, which varies with time, is constructed. This equivalent added mass term characterizes the transient influence of unsteady airflow in the thin Martian atmosphere on the parachute system. The spacecraft mass, parachute mass, and the equivalent added mass term are superimposed to obtain the total equivalent mass of the parachute-spacecraft system. Based on this total equivalent mass, the translational dynamic equation is established in the volume coordinate system of the parachute system. Then, based on the positional relationship between the aerodynamic components and the parachute center of mass relative to the system center of mass, the aerodynamic moments in the roll, pitch, and yaw directions are calculated, and the angular motion equation is established in conjunction with the system's moment of inertia.

[0029] This application also provides a method for constructing a six-degree-of-freedom mathematical model of a parachute system for Mars entry, descent, and landing. This method can be executed by a computer program and is used to accurately describe the dynamic characteristics of the parachute-spacecraft system during the descent phase in the Martian atmosphere. By establishing a coordinate system, constructing equations of motion, and introducing additional mass and adaptive damping correction terms, dynamic simulation of the system's velocity, altitude, and attitude angles over time can be achieved. The method specifically proposed in this embodiment utilizes a time-adaptive damping coefficient. Correcting the transient effects of unsteady airflow in the thin Martian atmosphere on the parachute system improves modeling accuracy and simulation stability.

[0030] like Figure 2 As shown, the method includes the following steps:

[0031] Step S202: Establish a Martian atmospheric environment parameter model.

[0032] The Martian atmospheric environment parameter model includes atmospheric density. ,temperature ,pressure With gravitational acceleration The distribution function. The above function can be approximated by an empirical formula:

[0033]

[0034] in, For surface density, This is a scale for the elevation of the Martian atmosphere. Indicates altitude. Gravitational acceleration. Determined by the following formula:

[0035]

[0036] in The radius of Mars. is the Earth's surface gravity constant.

[0037] These parameters are used as environmental inputs, and the state at the end of the entry segment (i.e., the parachute deployment point) is read, including the speed. ,high Flight path angle and angle of attack . Figure 3 The force diagram of the aircraft is shown.

[0038] Step S204: Proceed to segment disturbance rejection control modeling.

[0039] To obtain the precise parachute deployment point, trajectory tracking calculations are first performed based on active disturbance rejection control. This control algorithm compensates for unknown disturbances through an observer, ensuring trajectory stability during the entry phase and achieving precise tracking of the target's drag acceleration.

[0040] The controller output variable is the roll angle. It corrects its flight trajectory by controlling the lift-to-drag ratio. Assume the reference drag acceleration is... The actual drag acceleration is Then the tracking error According to the Extended State Observer (ESO) principle of ADRC, the dynamic equations of the system can be approximated as:

[0041]

[0042] in For the known part of the system, To control the gain, To control the input, Total disturbance. ESO real-time estimation. The drag acceleration is then compensated for in the control law, thereby achieving stable tracking.

[0043] The terminal state parameters after this control are used as the initial values ​​for parachute deployment.

[0044] Step S206: Establish the coordinate transformation matrix.

[0045] To describe the relationship between the Martian surface reference frame and the parachute system volume coordinate system, this embodiment defines two main coordinate systems:

[0046] First, the Martian surface inertial coordinate system Its origin is located on the Martian surface directly below the point of parachute deployment. The axis points towards the center of Mars. The axis is along the initial direction of flight. The axis is determined according to the right-hand rule.

[0047] Second, the volume coordinate system of the parachute system .like Figure 4 As shown, its origin is at the center of mass of the parachute-aircraft system. The shaft is along the instantaneous direction of the system's motion. The axis points downwards along the principal axis of symmetry of the parachute. The axis is perpendicular to the first two.

[0048] To achieve quantization transformation between coordinates, a coordinate transformation matrix is ​​established. It uses Euler angles (Roll) (Looking up and down) and (Yaw) defines the rotation order. The matrix expression is:

[0049]

[0050] In this way, by updating the trigonometric function terms in real time at each time step to obtain the changes in the system attitude angle, a two-way mapping between the ground inertial frame and the volume coordinate system can be achieved.

[0051] Step S208: Establish a six-degree-of-freedom dynamic model.

[0052] The goal of this phase is to establish a six-degree-of-freedom (6DOF) nonlinear dynamic model that can simultaneously reflect the coupling effects of translation and rotation, in order to describe the changes in velocity, attitude, and position of the parachute-aircraft system during descent.

[0053] The model consists of two types of equations of motion: linear equations and angular equations. The linear equations reflect the translational characteristics of the system's center of mass, while the angular equations characterize the rotational changes in the system's attitude. For ease of computer solution, both types of equations are implemented in volume coordinates. Chinese expression.

[0054] like Figure 5 As shown, the method for establishing a six-degree-of-freedom dynamic model includes the following steps:

[0055] Step S2081, add quality modeling.

[0056] As the parachute moves through the thin Martian atmosphere, the surrounding fluid accelerates, creating unsteady additional drag on the system. To accurately characterize this effect, this embodiment employs the equivalent mass method, which equates the unsteady aerodynamic effects to the system's added mass. The basic expression is as follows:

[0057]

[0058] in, For local atmospheric density, This is the reference area factor for the parachute. An additional mass coefficient is added. To further improve model accuracy, this embodiment introduces a time-adaptive damping correction coefficient. Construct an improved formula:

[0059]

[0060] in This is a time-dependent function used to characterize the coupling effect between atmospheric disturbances and the parachute oscillation frequency. The computer dynamically adjusts this function based on the rate of change of velocity and the intensity of airflow fluctuations during the simulation. This corrects the bias of traditional models under unsteady flow conditions.

[0061] In this embodiment, the time-adaptive damping correction coefficient To correct the errors of traditional mass-added models in unsteady flow fields, specifically, it can be:

[0062]

[0063] in For the rate of change of velocity, Indicates the standard deviation of velocity fluctuation. The angular frequency of the parachute structure oscillation. These are weighting coefficients calibrated through experiments or simulations.

[0064] First item The second term reflects the sensitivity of the system's instantaneous acceleration to changes in added mass. This reflects the influence of flow field unsteadiness on damping characteristics; the third item This is used to simulate the periodic fluctuations caused by the elasticity of parachute materials. The three terms are superimposed to form an overall correction coefficient, allowing the added mass to adaptively adjust with time and environment.

[0065] In other embodiments, in the additional mass modeling, the time-adaptive damping coefficient It can be further extended to a multidimensional function. ,in For the overall angle of attack, Let be the Mach number. This not only takes into account the time factor but also reflects changes in the flow state. The formula can be written as:

[0066]

[0067] The program automatically switches when the computer detects a transition in Mach number from the supersonic to the subsonic region. The functional form of the response was adjusted from exponential decay to sinusoidal to better simulate the reattachment effect. This multi-parameter adaptive design significantly improves the simulation continuity across the Mach range.

[0068] Step S2082: Establish the linear equation of motion.

[0069] According to Newton's second law, in a local inertial reference frame on the surface of Mars, the force balance of the system's center of mass can be expressed as:

[0070]

[0071] in This represents the total equivalent mass of the system, including the mass of the aircraft. Parachute quality and added quality ; This represents the component of the system's center-of-mass velocity in the volume coordinate system. Aerodynamic force Let gravitational force be the force. Decomposing the above equation into three components, we get:

[0072]

[0073] Here These represent the roll, pitch, and yaw angular velocity components, respectively. The aerodynamic terms on the right-hand side of the equation... It is determined by the aerodynamic characteristics of the parachute.

[0074] Step S2083, aerodynamic modeling.

[0075] The force characteristics of a parachute mainly include normal force and tangential force. To simplify calculations and maintain accuracy, a method based on the total angle of attack is used. Empirical coefficient model:

[0076]

[0077] In the formula For parachute reference area, These are the normal, tangential, and lateral force coefficients, all determined by wind tunnel testing or numerical simulation. To ensure the model's stability in a rarefied atmosphere, the computer adjusts the coefficients based on the local Mach number in each iteration. Automatic correction and The value of .

[0078] Step S2084: Establish the equations of angular motion.

[0079] The system's rotational motion is driven by external torques, primarily originating from the aerodynamic torque at the center of mass and the gravitational torque. According to Euler's equations, the equations of angular motion can be obtained as follows:

[0080]

[0081] in Let be the rotational inertia of the system in the three principal axis directions. These are the external moments in the roll, pitch, and yaw directions, respectively.

[0082] The aerodynamic moment is determined by the force distribution of the parachute at its center of mass. According to the definition of moment:

[0083]

[0084] in Here are the position coordinates of the parachute's center of mass relative to the system's center of mass. To eliminate high-frequency oscillations caused by parachute oscillation, this embodiment introduces a smoothing factor during numerical calculations. The angular velocity is updated recursively:

[0085]

[0086] Step S2085: Update coordinate transformation.

[0087] attitude angle The change is due to the angular velocity vector Integrating, we obtain the following relation:

[0088]

[0089] The computer integrates and updates the above differential equation at each time step to obtain the system attitude angles in real time. After obtaining the new Euler angles, the coordinate transformation matrix is ​​updated using the formula. This is then substituted back into the linear equations of motion, thus forming a fully coupled recursive solution loop.

[0090] Step S2086: Establish the navigation and position integral equations.

[0091] The change in the position of the system's center of mass needs to be obtained by integrating the velocity in the inertial coordinate system. This can be achieved through the inverse transformation of the coordinate transformation matrix. The volume coordinate velocity components can be... Converted to linear velocity in an inertial frame The relationship is as follows:

[0092]

[0093] After unfolding, we get:

[0094]

[0095] Numerical integration yields the spatial location change of the system. Since wind fluctuations are relatively small in the Martian atmosphere, the model assumes no lateral airflow; the computer will... The item is used to evaluate lateral drift, while the main descent height is determined by... control.

[0096] To achieve high-precision solution with limited computing resources, this embodiment employs an adaptive time-step integration algorithm in its computer implementation. The initial step size is set to... When the rate of change of attitude angle is detected or rate of change of velocity When the set threshold is exceeded, the program automatically reduces the step size to improve solution accuracy. Time integration uses the fourth-order Runge-Kutta scheme.

[0097]

[0098] in The state vector includes Equal components. Four slopes. The results are obtained from the system's differential equations. This integral method combines stability and computational efficiency, and is suitable for highly nonlinear six-degree-of-freedom systems.

[0099] Meanwhile, to prevent numerical oscillations caused by Mars' thin atmosphere, this embodiment introduces a correction mechanism based on energy conservation during the solution process: when the change in total kinetic energy exceeds a threshold... At that time, the program automatically corrects the velocity component, so that the kinetic energy returns to the physically reasonable range, thereby ensuring the stability of the calculation.

[0100] Once the computer completes the integral solution of the six-degree-of-freedom equations, it can generate time-varying outputs of the system's motion state, including altitude, velocity, acceleration, attitude angles, angular velocity, and force curves. The output data is stored in time-series format and can be used to verify the descent characteristics of the parachute-spacecraft system under different Martian atmospheric conditions.

[0101] Due to the extremely low atmospheric density on Mars, parachute systems are prone to rapid velocity changes and attitude jitter in the initial stages. To avoid energy drift caused by the accumulation of integration errors, this embodiment introduces an automatic correction module based on energy conservation. The total energy of the system is calculated in each integration cycle:

[0102]

[0103] When detected Automatically adjust the speed component scaling factor. ,make:

[0104]

[0105] in The value range is usually in to The energy feedback correction ensures the balance between the total kinetic and potential energy during long-term simulations, preventing trajectory drift caused by numerical errors.

[0106] This embodiment provides a method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing. Through modeling the Martian atmospheric environment, calculating disturbance rejection control during the approach phase, establishing the coordinate transformation matrix, correcting for added mass and adaptive damping, and solving the six-degree-of-freedom dynamic equations, it achieves a comprehensive description of the parachute-spacecraft system's motion characteristics during the descent phase. This method can be executed on a computer platform, supports multi-scenario simulation and parameter optimization, and provides a foundation for the design of guidance and control algorithms for Mars landers.

[0107] This application provides a method for Mars approach and landing control, which uses a six-degree-of-freedom mathematical model to determine the motion characteristics of a spacecraft; then, based on these motion characteristics, it controls the spacecraft's Mars approach and landing. The six-degree-of-freedom mathematical model construction method in this method has been described above and will not be repeated here.

[0108] This application also provides a system for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing, such as... Figure 6 As shown, the system includes: a model establishment module 62, configured to establish a Martian atmospheric environment parameter model, initialize the density function, gravitational acceleration function, and temperature function of the Martian atmosphere, and obtain initial state parameters using the terminal altitude, velocity, and angle of attack data of the Martian entry phase as input; a state determination module 64, configured to execute an active disturbance rejection control algorithm based on the initial state parameters, perform drag acceleration tracking control on the flight trajectory of the entry phase, and output corrected parachute deployment point state data; a transformation module 66, configured to establish a Martian surface inertial coordinate system and a parachute system volume coordinate system, construct a transformation matrix between the Martian surface inertial coordinate system and the parachute system volume coordinate system using the parachute deployment point state data, and determine the system's attitude angle and velocity components based on the transformation matrix to obtain coordinate system initialization results; and an establishment module 68, configured to establish a six-degree-of-freedom dynamic model of the parachute-spacecraft system with added mass terms based on the coordinate system initialization results.

[0109] It should be noted that the six-degree-of-freedom mathematical model construction system for parachutes for Mars approach and landing provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the equipment can be divided into different functional modules to complete all or part of the functions described above. In addition, the six-degree-of-freedom mathematical model construction system for parachutes for Mars approach and landing provided in the above embodiments and the method embodiment of the method for constructing a six-degree-of-freedom mathematical model for parachutes for Mars approach and landing belong to the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0110] Figure 7 A schematic diagram of a computer device suitable for implementing embodiments of the present disclosure is shown. It should be noted that... Figure 7 The computer device shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments disclosed herein.

[0111] like Figure 7 As shown, the computer device includes a central processing unit (CPU) 1001, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage section 1008 into a random access memory (RAM) 1003. The RAM 1003 also stores various programs and data required for system operation. The CPU 1001, ROM 1002, and RAM 1003 are interconnected via a bus 1004. An input / output (I / O) interface 1005 is also connected to the bus 1004.

[0112] The following components are connected to I / O interface 1005: an input section 1006 including a keyboard, mouse, etc.; an output section 1007 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers, etc.; a storage section 1008 including a hard disk, etc.; and a communication section 1009 including a network interface card such as a LAN card, modem, etc. The communication section 1009 performs communication processing via a network such as the Internet. A drive 1010 is also connected to I / O interface 1005 as needed. A removable medium 1011, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on drive 1010 as needed so that computer programs read from it can be installed into storage section 1008 as needed.

[0113] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing, characterized in that, include: A Martian atmospheric environment parameter model was established, and the density function, gravitational acceleration function, and temperature function of the Martian atmosphere were initialized. The initial state parameters were obtained by taking the terminal altitude, velocity, and angle of attack data of the Martian entry phase as input. Based on the initial state parameters, an active disturbance rejection control algorithm is executed to perform drag acceleration tracking control on the flight trajectory during the entry phase, and the corrected parachute deployment point state data is output. Establish the Mars surface inertial coordinate system and the parachute system volume coordinate system. Use the parachute deployment point state data to construct the transformation matrix between the Mars surface inertial coordinate system and the parachute system volume coordinate system. Based on the transformation matrix, determine the system's attitude angles and velocity components to obtain the coordinate system initialization results. Based on the coordinate system initialization results, a six-degree-of-freedom dynamic model is established using the parachute-aircraft system with added mass terms.

2. The method according to claim 1, characterized in that, Establish a model of Martian atmospheric environmental parameters, including: Obtain the Martian atmospheric density distribution function, and calculate the gravitational acceleration based on the Martian radius and the surface gravity constant to obtain the coupled parameter set of atmospheric density and gravitational acceleration; The set of coupling parameters is matched with the input initial altitude to calculate the set of local atmospheric characteristic parameters for the Mars entry phase, wherein the set of local atmospheric characteristic parameters includes local density, pressure and temperature.

3. The method according to claim 1, characterized in that, Based on the initial state parameters, an active disturbance rejection control algorithm is executed to perform drag acceleration tracking control on the flight trajectory during the entry phase, and the corrected parachute deployment point state data is output, including: Based on the initial state parameters, the total disturbance is estimated in real time using an extended state observer; The total disturbance is used to compensate for the unknown disturbance, so that the drag acceleration tracks the reference drag acceleration, and the real-time trajectory deviation is obtained. Based on the real-time trajectory deviation, the updated parachute deployment point height, velocity, and attitude angle are calculated to obtain the corrected parachute deployment point state data.

4. The method according to claim 1, characterized in that, Establish a Martian surface inertial coordinate system and a parachute system volumetric coordinate system. Construct a transformation matrix between the Martian surface inertial coordinate system and the parachute system volumetric coordinate system using the parachute deployment point state data, including: The origin is determined based on the Martian surface directly below the parachute deployment point, the Z-axis is determined based on the direction of the Martian center, the X-axis is determined based on the initial flight direction, and the Y-axis is determined according to the right-hand rule, thus establishing the Martian surface inertial coordinate system. The origin is determined based on the center of mass of the parachute-aircraft system, the X-axis is determined based on the instantaneous motion direction of the system, and the Z-axis is determined based on the direction along the main axis of symmetry of the parachute. The volume coordinate system of the parachute system is then established. Using the parachute deployment point state data, a coordinate transformation matrix is ​​established between the Martian surface inertial coordinate system and the parachute system volume coordinate system, wherein the coordinate transformation matrix satisfies a composite rotation relationship with a three-axis rotation sequence.

5. The method according to claim 1, characterized in that, Based on the coordinate system initialization results, a six-degree-of-freedom dynamic model is established using the parachute-aircraft system with added mass terms, including: The time-adaptive damping correction coefficient is used to correct the error in the calculation of the additional mass, and the equivalent additional mass term is obtained. Based on the equivalent additional mass term, the translational dynamic equation is constructed. Based on the positional relationship between the aerodynamic components and the parachute's center of mass relative to the system's center of mass, the aerodynamic moments in the roll, pitch, and yaw directions are calculated, and the angular motion equations are established in conjunction with the system's moment of inertia. The six-degree-of-freedom dynamic model includes translational dynamics equations and angular motion equations.

6. The method according to claim 5, characterized in that, Using a time-adaptive damping correction coefficient, the calculation error of the added mass is corrected to obtain an equivalent added mass term. Based on the equivalent added mass term, a translational dynamic equation is constructed, including: The local atmospheric density at the parachute deployment altitude was calculated based on the Martian atmospheric environment parameter model, and the basic additional mass model of the system was constructed based on the parachute reference area coefficient. Using a time-adaptive damping correction coefficient, an equivalent additional mass term that varies with time is constructed, wherein the equivalent additional mass term is used to characterize the transient effects of unsteady airflow in the thin Martian atmosphere on the parachute system. The mass of the aircraft, the mass of the parachute, and the equivalent additional mass term are superimposed to obtain the total equivalent mass of the parachute-aircraft system, and the translational dynamic equations are established in the volume coordinate system of the parachute system based on the total equivalent mass.

7. A method for Mars landing and descent control, characterized in that, include: The motion characteristics of the aircraft are determined based on the method of any one of claims 1 to 6; Based on the aforementioned motion characteristics, the Mars landing and descent of the spacecraft are controlled.

8. A system for constructing a six-degree-of-freedom mathematical model of a parachute for Mars approach and landing, characterized in that, include: The model building module is configured to build a Martian atmospheric environment parameter model, initialize the density function, gravitational acceleration function, and temperature function of the Martian atmosphere, and obtain the initial state parameters by taking the end altitude, velocity, and angle of attack data of the Martian entry phase as input. The state determination module is configured to execute an active disturbance rejection control algorithm based on the initial state parameters, perform drag acceleration tracking control on the flight trajectory during the entry phase, and output corrected parachute deployment point state data. The transformation module is configured to establish the Martian surface inertial coordinate system and the parachute system volume coordinate system, construct the transformation matrix between the Martian surface inertial coordinate system and the parachute system volume coordinate system using the parachute deployment point state data, and determine the system's attitude angles and velocity components based on the transformation matrix to obtain the coordinate system initialization results. The module is configured to establish a six-degree-of-freedom dynamic model of the parachute-aircraft system with an added mass term based on the initialization results of the coordinate system.

9. A computer device, characterized in that, include: Memory and processor The memory stores computer programs; The processor is configured to execute a computer program stored in the memory, wherein when the computer program is executed, the processor performs the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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