Round parachute airdrop system and prediction method, device and program product of airdrop landing point

Abstract

The present invention provides a method, device and program product for predicting a circular parachute airdrop system and its airdrop drop point. The method comprises: establishing a fluid-solid coupling model of a circular parachute opening process; establishing an unsteady aerodynamic model of the circular parachute using an unsteady aerodynamic coefficient of the circular parachute; establishing a dynamic model of the circular parachute airdrop system; establishing a first constraint on speed and a second constraint on force between the circular parachute dynamic model and the load dynamic model; predicting the airdrop drop point of the circular parachute airdrop system according to the circular parachute dynamic model, the load dynamic model, the constraint conditions of the circular parachute airdrop system, the predetermined circular parachute basic parameters, the mass of the load, the airdrop height and the current wind speed. By performing a fluid-solid coupling numerical simulation on the inflation process of the circular parachute system, the prediction accuracy of the airdrop drop point of the circular parachute airdrop system is improved.

Description

Technical Field

[0001] The present invention relates to the field of aircraft dynamics and control technology, and in particular to a round parachute airdrop system and a prediction method, device and program product of an airdrop landing point thereof. Background Art

[0002] The dome airdrop system is widely used in the aerospace field, mainly to reduce the descent speed of objects to ensure their safe landing. Unlike the controllable parafoil system, the dome airdrop system relies on the aerodynamic drag generated by the canopy inflation to slow down the descent speed. It is of great significance to study the dynamic behavior and landing point prediction of this type of system.

[0003] The canopy inflation process of the circular parachute system is complex and highly nonlinear. Especially in actual operation, there is a strongly coupled aerodynamic effect between the airflow and the canopy, which makes it particularly difficult to accurately model the system. Summary of the invention

[0004] The embodiments of the present invention provide a circular parachute airdrop system and a prediction method, device and program product for the airdrop landing point thereof, which improves the prediction accuracy of the airdrop landing point of the circular parachute airdrop system by performing fluid-solid coupling numerical simulation on the inflation process of the circular parachute system.

[0005] In order to achieve the above object, on the one hand, a prediction method for the airdrop point of a round parachute airdrop system is provided, wherein the round parachute airdrop system comprises: a round parachute and a load carried by the round parachute, wherein the round parachute comprises: a parachute body, wherein the parachute body comprises parachute ropes and parachute canopy, wherein the prediction method comprises:

[0006] S1, establish the fluid-solid coupling model of the circular parachute opening process, including:

[0007] S11, establishing a flow field model of the flow field where the round umbrella is located, wherein the flow field is a wind field, wherein:

[0008] The differential form of the continuity equation in the steady-state flow field is expressed as:

[0009]

[0010] in, is the velocity vector of the fluid, is the air density, is the vector differential operator;

[0011] In the fluid domain In the paper, the momentum and mass conservation laws of the fluid are expressed using the Navier-Stokes equations and the continuity equation as follows:

[0012]

[0013] ;

[0014] In the formula is the volume force, is the stress tensor, where:

[0015]

[0016] in is the pressure of the fluid, is the identity matrix, is the dynamic viscosity of the fluid;

[0017] S12, using two-dimensional membrane shell elements to model the canopy structure of the round umbrella, where:

[0018] The domain where the canopy is located Discretize, through the reference coordinate system The movement of the canopy film unit in the structural domain is expressed as:

[0019]

[0020] in, is the displacement of the canopy film unit in the structural domain; X represents the position of the canopy film unit in the structural domain; t is the time;

[0021] Among them, the control equation of the canopy film structure is:

[0022]

[0023] in: represents the material density, is the speed of the canopy membrane structure movement, is the Cauchy stress tensor, It is the structural domain force acting on the canopy membrane structure;

[0024] Among them, the interface between the wind field fluid domain and the umbrella canopy structure domain is The displacement and traction conditions on are defined as:

[0025]

[0026]

[0027] is the outer normal of the fluid domain boundary, and are the displacement and traction functions exerted by the fluid on the canopy structure;

[0028] The canopy of the circular umbrella is meshed using a three-node two-dimensional shell element, and its stress-strain relationship is expressed as:

[0029]

[0030]

[0031]

[0032] in: , , and denote Poisson's ratio, stress, strain and elastic modulus, respectively. When represents radial direction, : indicates the latitude direction; and denote shear strain and shear stress, respectively, represents the shear modulus, is a predetermined nonlinear coefficient;

[0033] The parachute line dynamics model is expressed as a discretized model:

[0034]

[0035]

[0036]

[0037] in, represents the initial force of the parachute line, represents the stiffness of the paracord material, is the change in the length of the parachute line, is the initial length of the parachute line, is the offset from the initial length of the cell, is the elastic modulus, is the cross-sectional area of ​​the paracord, represents the tension of the parachute line, Indicates the actual length of the parachute rope at the current moment;

[0038] S13, using the flow field model and the modeling of the canopy structure, simulating the fluid-solid coupling process of the round canopy and the flow field, wherein the fluid-solid interface in the fluid-solid coupling process The following kinematic and dynamic equilibrium conditions are met:

[0039]

[0040]

[0041] in, Represents the fluid domain at the fluid-solid interface stress; Indicates that the domain is at the fluid-solid interface stress;

[0042] S2, unsteady aerodynamic coefficient using circular parachute The following unsteady aerodynamic model of the circular parachute is established, where the unsteady aerodynamic coefficient of the circular parachute is Determine according to the fluid-solid coupling model established in step S1:

[0043]

[0044] in, is the aerodynamic force of the circular parachute, is the air density, is the incoming flow velocity, is the characteristic area of ​​the canopy;

[0045] S3, establish the dynamic model of the circular parachute airdrop system, including:

[0046] S31, establish the dynamic model of the load:

[0047] Based on the pre-established load coordinate system , establish the load dynamics model; where the origin of the load coordinate system At the intersection of the parachute lines, the load coordinate system The axis points to the center of mass of the load, The axis points to the right of the load, Axis and Axis and The axes together form a right-handed coordinate system;

[0048] Among them, in the load dynamics model, the momentum of the load and angular momentum In the load coordinate system it is expressed as:

[0049]

[0050] in, is the speed of the load, is the angular velocity of the load, is the generalized mass matrix of the load;

[0051] in,

[0052]

[0053] in, For The amount of

[0054] According to the momentum theorem and angular momentum theorem:

[0055] ;

[0056]

[0057] in, is the gravity acting on the load, is the tension of the parachute line, for The torque, for The torque;

[0058] S32, establish a circular parachute dynamics model, including:

[0059] According to the pre-established circular umbrella coordinate system , establish the circular parachute dynamic model; among them, the origin of the circular parachute coordinate system At the intersection of the parachute lines, the circular parachute coordinate system The axis is vertically downward, The axis points to the right side of the canopy and Axis vertical, Axis and Axis and The axes together form a right-handed coordinate system;

[0060] Among them, in the round umbrella dynamics model, the momentum of the round umbrella is and angular momentum In the circular umbrella coordinate system, it is expressed as:

[0061]

[0062] in, is the mass of the round umbrella itself, is the additional mass generated by the environment during the descent of the parachute, is the mass center velocity of the round umbrella in the round umbrella coordinate system, is the angular velocity of the round umbrella in the round umbrella coordinate system, , , and is the mass matrix;

[0063] According to the momentum theorem and angular momentum theorem, we can get:

[0064] ;

[0065]

[0066] in, is the weight of the parachute, is the tension of the parachute rope on the canopy, , and They are , and The corresponding torque;

[0067] S4, establishing a first constraint on speed and a second constraint on force between the circular parachute dynamic model and the load dynamic model, and obtaining constraint conditions of the circular parachute airdrop system, wherein:

[0068] The first constraint is: ;

[0069] The second constraint is: ;

[0070] in, is a rotation matrix from a predetermined inertial coordinate system to the circular umbrella coordinate system;

[0071] is a rotation matrix from a predetermined inertial coordinate system to the load coordinate system;

[0072] Wherein, the predetermined point in space is taken as the origin of the inertial coordinate system , The axis is vertically downward, The axis points north, The axis points east;

[0073] S5, predicting the airdrop point of the round parachute airdrop system according to the round parachute dynamics model, the load dynamics model, the constraints of the round parachute airdrop system, the predetermined round parachute basic parameters, the mass of the load, the airdrop height and the current wind speed; the round parachute basic parameters include the size of the round parachute, the number of fluid grids corresponding to the canopy, the descent speed of the round parachute during the inflation stage and the mass of the round parachute itself.

[0074] Preferably, the prediction method is used for the structural domain where the canopy is located. Discretization involves:

[0075] Lagrangian operator shell element based on Belytschko-Lin-Tsay algorithm for the structural domain where the canopy is located Discretize.

[0076] Preferably, in the prediction method, the size of the round umbrella includes: the diameter of the round umbrella, the diameter of the top hole of the round umbrella, the projection diameter of the round umbrella and the umbrella length of the round umbrella.

[0077] Preferably, the method, wherein

[0078]

[0079] in, is the roll angle of the circular parachute in the inertial coordinate system, is the pitch angle of the circular parachute in the inertial coordinate system, is the yaw angle of the circular parachute in the inertial coordinate system.

[0080] On the other hand, a circular parachute airdrop system is provided for predicting an airdrop landing point using the method for predicting an airdrop landing point of a circular parachute airdrop system as described in any one of the above items.

[0081] On the other hand, a device for predicting the airdrop landing point of a circular parachute airdrop system is provided, comprising a memory and a processor, wherein the memory stores at least one program, and the at least one program is executed by the processor to implement a method for predicting the airdrop landing point of a circular parachute airdrop system as described above.

[0082] On the other hand, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the steps of the method for predicting the airdrop landing point of a circular parachute airdrop system as described in any one of the above.

[0083] The above technical solution has the following technical effects:

[0084] The embodiment of the present invention establishes a fluid-solid coupling model of the circular parachute opening process, and can determine the deformation of the parachute under the current wind speed, thereby accurately simulating the system motion trajectory after the canopy is inflated, thereby improving the landing point prediction accuracy and prediction performance of the circular parachute airdrop system. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 A schematic diagram of a flow chart of a method for predicting an airdrop landing point of a round parachute airdrop system according to an embodiment of the present invention;

[0086] Figure 2 It is a schematic diagram of the solution process of fluid-solid coupling calculation in one embodiment of the present invention;

[0087] Figure 3 A schematic diagram of a coordinate system used in a method for predicting an airdrop landing point of a round parachute airdrop system according to an embodiment of the present invention;

[0088] Figure 4 The present invention is a schematic structural diagram of an exemplary disc-strap parachute used in a method for predicting the airdrop landing point of a round parachute airdrop system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0089] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0090] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0091] Embodiment 1:

[0092] Figure 1 The flowchart of the method for predicting the airdrop point of a round parachute airdrop system according to an embodiment of the present invention is shown in FIG. The round parachute airdrop system includes a round parachute (i.e., a parachute) and a load carried by the round parachute. The round parachute includes a parachute body, which includes parachute ropes and parachute canopy. Figure 1 The method for predicting the airdrop landing point of a round parachute airdrop system according to an embodiment of the present invention comprises the following steps:

[0093] S1, establish the fluid-solid coupling model of the circular parachute opening process, including:

[0094] S11, establish a flow field model of the flow field where the round umbrella is located, the flow field is a wind field, wherein:

[0095] The differential form of the continuity equation in the steady-state flow field is expressed as:

[0096]

[0097] in, is the velocity vector of the fluid, is the air density, is the vector differential operator;

[0098] In the fluid domain In the equation, the momentum and mass conservation laws of the fluid are expressed using the Navier-Stokes equation and the continuity equation as follows:

[0099]

[0100] ; In the formula is the volume force, is the stress tensor, where:

[0101]

[0102] in is the pressure of the fluid, is the identity matrix, is the dynamic viscosity of the fluid;

[0103] S12, using two-dimensional membrane shell elements to model the canopy structure of the round umbrella, where:

[0104] The domain where the canopy is located Discretize, through the reference coordinate system The movement of the canopy film unit in the structural domain is expressed as:

[0105]

[0106] in, is the displacement of the canopy film unit in the structural domain; X represents the position of the canopy film unit in the structural domain; t is the time;

[0107] Among them, the control equation of the canopy film structure is:

[0108]

[0109] in: represents the material density, is the speed of the canopy membrane structure movement, is the Cauchy stress tensor, It is the domain force acting on the canopy membrane structure; preferably, the Lagrangian shell element based on the Belytschko-Lin-Tsay algorithm is used to calculate the domain force of the parachute. Discretize

[0110] Among them, the interface between the wind field fluid domain and the umbrella canopy structure domain is The displacement and traction conditions on are defined as:

[0111]

[0112]

[0113] is the outer normal of the fluid domain boundary, and are respectively the displacement and traction functions exerted by the fluid on the canopy structure; in a specific implementation, the traction boundary here represents the pressure exerted by the fluid on the canopy fabric structure;

[0114] The canopy of the circular umbrella is meshed using a three-node two-dimensional shell element, and its stress-strain relationship is expressed as:

[0115]

[0116]

[0117]

[0118] in: , , and denote Poisson's ratio, stress, strain and elastic modulus, respectively. When represents radial direction, : indicates the latitude direction; and denote shear strain and shear stress, respectively, represents the shear modulus, is a predetermined nonlinear coefficient; in a specific implementation, the above parameter value is obtained in advance through an experiment of stress-strain relationship;

[0119] The parachute line dynamics model is expressed as a discretized model:

[0120]

[0121]

[0122]

[0123] in, represents the initial force of the parachute line, represents the stiffness of the paracord material, is the change in the length of the parachute line, is the initial length of the parachute line, is the offset from the initial length of the cell, is the elastic modulus, is the cross-sectional area of ​​the paracord, represents the tension of the parachute line, Indicates the actual length of the parachute rope at the current moment;

[0124] S13, using the flow field model and the modeling of the canopy structure, simulating the fluid-solid coupling process of the circular canopy and the flow field, wherein the fluid-solid interface in the fluid-solid coupling process The following kinematic and dynamic equilibrium conditions are met:

[0125]

[0126]

[0127] in, Represents the fluid domain at the fluid-solid interface stress; Indicates that the domain is at the fluid-solid interface stress;

[0128] Figure 2 FIG. 1 is a schematic diagram of a solution process of a fluid-structure coupling calculation in one embodiment of the present invention. Figure 2 The solution process of the fluid-structure coupling calculation of this embodiment includes the following steps:

[0129] 1) Determine the boundary conditions and initial conditions of the flow field;

[0130] 2) Calculate the flow field;

[0131] 3) Map the pressure of the fluid grid points to the structural nodes;

[0132] 4) Calculate the movement of the canopy structure;

[0133] 5) Fluid domain mesh items;

[0134] 6) Flow field solution;

[0135] 7) Determine whether convergence has occurred; if so, end the process; otherwise, proceed to step 3) and repeat iterations 3)-7) until convergence.

[0136] In summary, the calculation principles of fluid-solid coupling include: determining the boundary conditions and initial conditions of the flow field as well as the shape and movement of the canopy structure; solving the fluid domain and transferring the calculated aerodynamic force to the structural domain; calculating the structural deformation of the structural domain under the action of aerodynamic force and transmitting it to the fluid domain as a displacement boundary condition, while the fluid domain solves the pressure on the new canopy boundary and transmits it to the structural domain; under the change of external force, the structure further deforms, and the new displacement boundary condition is calculated and transmitted to the fluid; repeating the above steps iteratively until the solutions of the two solution domains reach the convergence conditions.

[0137] S2, unsteady aerodynamic coefficient using circular parachute The unsteady aerodynamic model of the circular parachute is established, where the unsteady aerodynamic coefficients of the circular parachute are It is determined according to the fluid-solid coupling model established in step S1, where the unsteady aerodynamic model of the circular parachute is:

[0138]

[0139] in, is the aerodynamic force of the circular parachute, is the air density, is the incoming flow velocity, is the characteristic area of ​​the canopy;

[0140] In a specific implementation, according to the model established in step S1, the aerodynamic coefficients of the circular parachute are obtained using existing explicit dynamic simulation software such as Ansys LS-DYNA. ;

[0141] Specifically, the round parachute is flexible. When the structure of the round parachute is deformed, the aerodynamic force of the round parachute changes accordingly. The unsteady aerodynamic force of any motion of the round parachute is calculated by the above-mentioned fluid-solid coupling model, thereby establishing the influence relationship of the structural deformation of the round parachute on the aerodynamic force; when the aerodynamic force of the round parachute changes, the force acting on the canopy changes. The structural deformation vector of the canopy is calculated based on the film structure dynamics equation, thereby establishing the influence relationship of the aerodynamic force of the round parachute on the structural deformation: the structural deformation and aerodynamic force of the round parachute affect each other, thereby establishing a coupling model of the structural deformation and aerodynamic force of the round parachute, and obtaining the unsteady aerodynamic coefficient of the round parachute. , and the above-mentioned unsteady aerodynamic model of the circular parachute is established.

[0142] S3, establish the dynamic model of the circular parachute airdrop system, including:

[0143] S31, establish the dynamic model of the load:

[0144] Based on the pre-established load coordinate system , establish the load dynamics model; where the origin of the load coordinate system At the intersection of the above parachute lines, the load coordinate system The axis points to the center of mass of the load, The axis points to the right of the load, Axis and Axis and The axes together form a right-handed coordinate system;

[0145] in, Figure 3 It is a schematic diagram of a coordinate system of a circular parachute airdrop system, i.e., a circular parachute-load system, established in one embodiment of the present invention; Figure 3 middle is the center of mass of the circular umbrella; is the center of mass of the load; Figure 3 The established circular parachute coordinate system, load coordinate system and inertial coordinate system are shown in FIG. 1 ; the forces acting on the circular parachute are analyzed in the circular parachute coordinate system, and the forces acting on the load are analyzed in the load coordinate system; wherein the load coordinate system and the inertial coordinate system will be described below; in the embodiment of the present invention, the circular parachute is regarded as a fluid for modeling analysis in the circular parachute coordinate system, and the load is regarded as a solid for modeling analysis in the load coordinate system;

[0146] Among them, in the above load dynamics model, the momentum of the load and angular momentum In the load coordinate system it is expressed as:

[0147]

[0148] in, is the speed of the load, is the angular velocity of the load, is the generalized mass matrix of the load;

[0149] in,

[0150]

[0151] in, , , For The amount of

[0152] According to the momentum theorem and angular momentum theorem:

[0153] ;

[0154] in, is the gravity acting on the load, is the tension of the parachute line, for The torque, for The torque;

[0155] In one specific implementation, the load is a mass , the bottom radius is , the height is A rigid cylinder with uniform mass distribution;

[0156] S32, establish a circular parachute dynamics model, including:

[0157] According to the pre-established circular umbrella coordinate system , establish the circular parachute dynamic model; among them, the origin of the circular parachute coordinate system At the intersection of the parachute lines, the circular parachute coordinate system The axis is vertically downward, The axis points to the right side of the canopy and Axis vertical, Axis and Axis and The axes together form a right-handed coordinate system;

[0158] Among them, in the above round umbrella dynamics model, the momentum of the round umbrella is and angular momentum In the circular umbrella coordinate system, it is expressed as:

[0159]

[0160] in, is the mass of the round umbrella itself, is the additional mass generated by the environment during the descent of the parachute, is the mass center velocity of the round umbrella in the above round umbrella coordinate system, is the angular velocity of the round umbrella in the above round umbrella coordinate system, , , and is the mass matrix;

[0161] According to the momentum theorem and angular momentum theorem, we can get:

[0162] ;

[0163]

[0164] in, is the weight of the parachute, is the tension of the parachute rope on the canopy, , and They are , and The corresponding torque;

[0165] S4, establishing a first constraint on speed and a second constraint on force between the circular parachute dynamics model and the load dynamics model, and obtaining the constraint conditions of the circular parachute airdrop system, wherein:

[0166] The first constraint mentioned above is: ;

[0167] The second constraint above is: ;

[0168] in, is the rotation matrix from the predetermined inertial coordinate system to the above circular umbrella coordinate system;

[0169] is the rotation matrix from the predetermined inertial coordinate system to the above load coordinate system;

[0170] Among them, the predetermined point in space is taken as the origin of the above inertial coordinate system , The axis is vertically downward, The axis points north, The axis points east;

[0171] In a specific implementation,

[0172]

[0173] in, is the roll angle of the circular parachute in the inertial coordinate system, is the pitch angle of the circular parachute in the inertial coordinate system, is the yaw angle of the circular parachute in the inertial coordinate system;

[0174] is the rotation matrix from the predetermined inertial coordinate system to the load coordinate system; when the corresponding coordinate system is determined, the determination of the rotation matrix is ​​a prior art and will not be repeated here;

[0175] Among them, the predetermined point in space is taken as the origin of the inertial coordinate system , The axis is vertically downward, The axis points north, The axis points east; the inertial coordinate system is Figure 3 shown.

[0176] S5, predicting the airdrop point of the round parachute airdrop system according to the round parachute dynamics model, the load dynamics model, the constraints of the round parachute airdrop system, the predetermined round parachute basic parameters, the mass of the load, the airdrop height and the current wind speed; the round parachute basic parameters include the size of the round parachute, the number of fluid grids corresponding to the canopy, the descent speed of the round parachute during the inflation phase and the mass of the round parachute itself. In a specific implementation, the size of the round parachute includes: the diameter of the round parachute, the top hole diameter of the round parachute, the projection diameter of the round parachute and the parachute length of the round parachute.

[0177] In a specific implementation of an embodiment of the present invention, basic parameters of a round parachute, i.e., an airdrop parachute, and the mass of a load are preset, wherein the basic parameters of the round parachute include: the size of the round parachute, the number of fluid grids corresponding to the canopy, the descent speed of the round parachute during the inflation phase, and the mass of the round parachute itself; in a specific implementation, the size of the round parachute includes: the diameter of the round parachute, the top hole diameter of the round parachute, the projection diameter of the round parachute, and the parachute length of the round parachute; Figure 4 The present invention is a schematic structural diagram of an exemplary disc-strap parachute used in a method for predicting the airdrop landing point of a round parachute airdrop system according to an embodiment of the present invention. Figure 4 middle, is the top hole diameter of the round umbrella; is the projection diameter of the circular umbrella.

[0178] After obtaining the dynamic model of the round parachute airdrop system, the dynamic model of the round parachute airdrop system, i.e. the round parachute-load system, can be used to predict the airdrop landing point according to the corresponding round parachute information and load information in the actual test of the round parachute airdrop system to be predicted.

[0179] In one example, the set circular parachute information and load information are: the parachute diameter is 2.7m, the top hole diameter is 0.56m, the projection diameter is 1.6m, the parachute length is 2.72m, the number of fluid grids is 121,350, of which the number of grids on the canopy surface is 6,425, the descent speed in the inflation stage is set to 50 m / s, the mass of the parachute is 2.5 kg, and the mass of the load carried is 180 kg.

[0180] The above parameter values ​​are only exemplary and can be adaptively adjusted according to different actual conditions.

[0181] Embodiment 2:

[0182] An embodiment of the present invention also provides a circular parachute airdrop system that uses the method for predicting the airdrop landing point of the circular parachute airdrop system described in any one of the above items to predict the airdrop landing point.

[0183] Embodiment three:

[0184] The present invention also provides a device for predicting the airdrop landing point of a circular parachute airdrop system, comprising a memory and a processor, wherein the memory stores at least one program, and the at least one program is executed by the processor to implement a method for predicting the airdrop landing point of a circular parachute airdrop system as described above.

[0185] Further, as an executable solution, the prediction device may be a computer unit, which may be a computing device such as a desktop computer, a notebook, a PDA, and a cloud server. The computer unit may include, but is not limited to, a processor and a memory. Those skilled in the art may understand that the composition structure of the above-mentioned computer unit is only an example of a computer unit and does not constitute a limitation on the computer unit. It may include more or less components than the above-mentioned components, or a combination of certain components, or different components. For example, the computer unit may also include input and output devices, network access devices, buses, etc., which are not limited in the embodiments of the present invention.

[0186] Further, as an executable solution, the processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the computer unit, and various interfaces and lines are used to connect various parts of the entire computer unit.

[0187] The memory can be used to store the computer program and / or module, and the processor realizes various functions of the computer unit by running or executing the computer program and / or module stored in the memory, and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system and at least one application required for a function; the data storage area can store data created according to the use of the mobile phone, etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (SecureDigital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0188] Embodiment 4:

[0189] The present invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above method in the embodiment of the present invention are implemented.

[0190] If the module / unit integrated in the computer unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory) and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction.

[0191] Embodiment five:

[0192] The present invention also provides a computer program product, comprising a computer program, which, when executed by a processor, implements the steps of the method for predicting the airdrop landing point of the circular parachute airdrop system as described above.

[0193] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A method for predicting the airdrop point of a round parachute airdrop system, the round parachute airdrop system comprising: A round parachute and the load carried by the round parachute, the round parachute comprising: a parachute body, the parachute body comprising parachute ropes and parachute canopy, characterized in that the prediction method comprises: S1, establish the fluid-solid coupling model of the circular parachute opening process, including: S11, establishing a flow field model of the flow field where the round umbrella is located, wherein the flow field is a wind field, wherein: The differential form of the continuity equation in the steady-state flow field is expressed as: in, is the velocity vector of the fluid, is the air density, is the vector differential operator; In the fluid domain In the paper, the momentum and mass conservation laws of the fluid are expressed using the Navier-Stokes equations and the continuity equation as follows: In the formula is the volume force, is the stress tensor, where: in is the pressure of the fluid, is the identity matrix, is the dynamic viscosity of the fluid; S12, using two-dimensional membrane shell elements to model the canopy structure of the round umbrella, where: The domain where the canopy is located Discretize, through the reference coordinate system The movement of the canopy film unit in the structural domain is expressed as: in, is the displacement of the canopy film unit in the structural domain; X represents the position of the canopy film unit in the structural domain; t is the time; Among them, the control equation of the canopy film structure is: in: represents the material density, is the speed of the canopy membrane structure movement, is the Cauchy stress tensor, It is the structural domain force acting on the canopy membrane structure; Among them, the interface between the wind field fluid domain and the canopy structure domain is The displacement and traction conditions on are defined as: is the external normal of the fluid domain boundary, D(t) and T(t) are the displacement and traction functions exerted by the fluid on the canopy structure, respectively; The canopy of the circular umbrella is meshed using a three-node two-dimensional shell element, and its stress-strain relationship is expressed as: in: , , and denote Poisson's ratio, stress, strain and elastic modulus, respectively. When represents radial direction, : indicates the latitude direction; and denote shear strain and shear stress, respectively, represents the shear modulus, is a predetermined nonlinear coefficient; The parachute line dynamics model is expressed as a discretized model: in, represents the initial force of the parachute line, represents the stiffness of the parachute rope material, is the change in the length of the parachute line, is the initial length of the parachute line, is the offset from the initial length of the cell, is the elastic modulus, is the cross-sectional area of ​​the paracord, represents the tension of the parachute line, Indicates the actual length of the parachute rope at the current moment; S13, using the flow field model and the modeling of the canopy structure, simulating the fluid-solid coupling process of the circular canopy and the flow field, wherein the fluid-solid interface in the fluid-solid coupling process The following kinematic and dynamic equilibrium conditions are met: in, Represents the fluid domain at the fluid-solid interface stress; Indicates that the domain is at the fluid-solid interface stress; S2, unsteady aerodynamic coefficient using circular parachute An unsteady aerodynamic model of a circular parachute is established, wherein the unsteady aerodynamic coefficient of the circular parachute is According to the fluid-solid coupling model established in step S1, the unsteady aerodynamic model of the circular parachute is: in, is the aerodynamic force of the circular parachute, is the air density, is the incoming flow velocity, is the characteristic area of ​​the canopy; S3, establish the dynamic model of the circular parachute airdrop system, including: S31, establish the dynamic model of the load: Based on the pre-established load coordinate system , establish the load dynamics model; where the origin of the load coordinate system At the intersection of the parachute lines, the load coordinate system The axis points to the center of mass of the load, The axis points to the right of the load, Axis and Axis and The axes together form a right-handed coordinate system; In the load dynamics model, the momentum of the load and angular momentum In the load coordinate system it is expressed as: in, is the speed of the load, is the angular velocity of the load, is the generalized mass matrix of the load; in, in, for The amount of According to the momentum theorem and angular momentum theorem: in, is the gravity acting on the load, is the tension of the parachute line, for The torque, for The torque; S32, establish a circular parachute dynamics model, including: According to the pre-established circular umbrella coordinate system , establish the circular parachute dynamic model; among them, the origin of the circular parachute coordinate system At the intersection of the parachute lines, the circular parachute coordinate system The axis is vertically downward, The axis points to the right side of the canopy and Axis vertical, Axis and Axis and The axes together form a right-handed coordinate system; Among them, in the round umbrella dynamics model, the momentum of the round umbrella is and angular momentum In the circular umbrella coordinate system, it is expressed as: in, is the mass of the round umbrella itself, is the additional mass generated by the environment during the descent of the parachute, is the mass center velocity of the round umbrella in the round umbrella coordinate system, is the angular velocity of the round umbrella in the round umbrella coordinate system, , , and is the mass matrix; According to the momentum theorem and angular momentum theorem, we can get: in, is the weight of the parachute, is the tension of the parachute rope on the canopy, They are The corresponding torque; S4, establishing a first constraint on speed and a second constraint on force between the circular parachute dynamic model and the load dynamic model, and obtaining constraint conditions of the circular parachute airdrop system, wherein: The first constraint is: ; The second constraint is: ; in, is a rotation matrix from a predetermined inertial coordinate system to the circular umbrella coordinate system; is a rotation matrix from a predetermined inertial coordinate system to the load coordinate system; Wherein, the predetermined point in space is taken as the origin of the inertial coordinate system , The axis is vertically downward, The axis points north, The axis points east; S5, predicting the airdrop point of the round parachute airdrop system according to the round parachute dynamics model, the load dynamics model, the constraints of the round parachute airdrop system, the predetermined round parachute basic parameters, the mass of the load, the airdrop height and the current wind speed; the round parachute basic parameters include the size of the round parachute, the number of fluid grids corresponding to the canopy, the descent speed of the round parachute during the inflation stage and the mass of the round parachute itself.

2. The method for predicting the airdrop point of the round parachute airdrop system according to claim 1 is characterized in that: The domain where the canopy is located Discretization involves: Lagrangian operator shell element based on Belytschko-Lin-Tsay algorithm for the structural domain where the canopy is located Discretize.

3. The method for predicting the airdrop point of the round parachute airdrop system according to claim 1, characterized in that: The dimensions of the round umbrella include: the diameter of the round umbrella, the diameter of the top hole of the round umbrella, the projection diameter of the round umbrella and the umbrella length of the round umbrella.

4. The method for predicting the airdrop point of the circular parachute airdrop system according to claim 1, characterized in that: in, is the roll angle of the circular parachute in the inertial coordinate system, is the pitch angle of the circular parachute in the inertial coordinate system, is the yaw angle of the circular parachute in the inertial coordinate system.

5. A circular parachute airdrop system that uses the method for predicting the airdrop landing point of a circular parachute airdrop system according to any one of claims 1 to 4 to predict the airdrop landing point.

6. A device for predicting the airdrop point of a round parachute airdrop system, characterized in that: The method comprises a memory and a processor, wherein the memory stores at least one program, and the at least one program is executed by the processor to implement the method for predicting the airdrop landing point of the round parachute airdrop system as described in any one of claims 1 to 4.

7. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for predicting the airdrop landing point of a circular parachute airdrop system as described in any one of claims 1 to 4 are implemented.

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