Adapter multi-rigid-body dynamic modeling method based on pre-pressing and flexibility characteristics

Abstract

The invention discloses an adapter multi-rigid-body dynamic modeling method based on pre-pressing and flexibility characteristics. According to the invention, an adapter model is dispersed in a multi-rigid-body dynamic framework, and a nonlinear spring-torsion spring unit is introduced to realize flexible deformation, so that the nonlinear mechanical response of an adapter body in a launching process is effectively simulated; based on a nonlinear rigidity curve calibrated by an experiment or simulation, the compression and torsion response of the adapter is accurately reproduced; through the spring original length offset correction technology, the actual assembly pre-compression state is directly mapped, and the initial condition accuracy is improved. According to the invention, the pre-pressing of the adapter and the nonlinear mechanical response of the adapter in the launching process can be effectively simulated, and the large subsample calculation and rapid iteration requirements of a rocket launching system are met.

Description

Technical Field

[0001] The present invention relates to the field of space launch technology, and in particular to a modeling and simulation method that integrates the pre-compression state and dynamic flexible deformation characteristics of an adapter, which is suitable for dynamic analysis of a rocket launch system and optimized design of an adapter structure. Background Art

[0002] The adapter is tightly pressed between the rocket and the launcher, and its supporting and vibration-damping properties reduce the initial disturbances during launch. During launch, complex environmental disturbances, such as vibrations from the vehicle-mounted launch platform and the shaking of the offshore launch platform due to waves, can cause the rocket to undergo attitude changes such as pitch and yaw within the launcher. These attitude changes within the launcher cause the adapter to deform. Preload on each side of the rocket helps dampen these changes. Therefore, both adapter deformation and preload during launch are not negligible.

[0003] In launch dynamics simulation, simulating the dynamic behavior of adapters has become an integral part of launch system design and optimization. Using virtual prototype simulation models, the rocket's attitude changes and the forces acting on the adapter during launch are studied, and the initial disturbances of the rocket launch are determined, providing a scientific basis for the design and improvement of rocket launch systems. As a key component connecting the rocket to the launch device, the adapter directly impacts the stability and safety of the rocket launch. However, the preload introduced during installation and the highly nonlinear mechanical response exhibited by its composite structure pose significant challenges to simulation modeling.

[0004] Launch dynamics research typically utilizes methods such as multi-rigid-body dynamics simulation and finite element rigid-flexible coupling simulation. Finite element simulation, by meticulously dividing structural elements and establishing precise constitutive models, can simulate the complex deformation behavior of the adapter during installation and launch. However, finite element simulation relies on refined meshing, making the simulation process time-consuming. Furthermore, capturing the adapter's computational complexity is high, requiring significant computational power, particularly when the launch model requires large-scale sample calculations or high-frequency iterations. Finite element simulation requires dozens or even hundreds of CPU cores to calculate a single operating condition, making it difficult to quickly obtain large-scale sample results for application in engineering practice. Furthermore, when the gap between the rocket and the rail / barrel wall is small, the adapter is thinner. In finite element simulations, the solid mesh of thinner structures is subject to compression, which can lead to mesh distortion, resulting in reduced accuracy and even calculation errors. Furthermore, pre-stressing the adapter typically requires initial penetration through methods such as dynamic relaxation, increasing the number of calculation steps and the difficulty of simulation. For example, patent CN115618605A discloses a preload modeling method for adapters based on an interference fit. This method establishes an interference fit model between the adapter and the guide rail and solves the model using a dynamic relaxation method to achieve static equilibrium under preload. However, methods such as finite element methods that simulate flexible deformation require long computational time, and the dynamic relaxation process added to the interference fit balance increases the total computational effort, resulting in high computational cost and time, making it unsuitable for rapid iterative calculations.

[0005] Although multi-rigid-body dynamics simulation has fast calculation speed and high iteration efficiency, and is suitable for the complex system design stage where parameters need to be frequently adjusted to seek the optimal solution, it uses the rigidity assumption and ignores nonlinear deformation, which cannot characterize the nonlinear mechanical behavior of the adapter. The simulation results deviate greatly from the actual dynamic response. Summary of the Invention

[0006] In view of this, the present invention provides a multi-rigid body dynamic modeling method of the adapter based on pre-stress and flexibility characteristics, which can effectively simulate the pre-stress of the adapter and the nonlinear mechanical response of the adapter during the launch process, and meet the large sample calculation and rapid iteration requirements of the rocket launch system.

[0007] The adapter multi-rigid body dynamic modeling method based on preload and flexibility characteristics of the present invention includes:

[0008] S1, extract the key bearing area of ​​the adapter body and discretize it into the inner aptamer and outer aptamer; construct the rigid structure model of the inner and outer aptamers respectively;

[0009] S2, selecting characteristic points corresponding to several positions on the rigid structure models of the inner and outer aptamers;

[0010] S3, experimentally obtain the nonlinear compression stiffness curve and torsional stiffness curve at different positions of the adapter body;

[0011] S4, establishing a nonlinear spring model and a nonlinear torsion spring model between the characteristic points corresponding to the rigid structure models of the inner and outer adapters; the spring force is the nonlinear compression stiffness curve at the corresponding position of the adapter body measured in S3, and the torque is the nonlinear torsional stiffness curve at the corresponding position of the adapter body measured in S3;

[0012] S5, build the rocket and launch tube / rail model;

[0013] S6, set constraints:

[0014] The rigid structure model of the internal aptamer is fixedly connected to the rocket model;

[0015] The middle feature points of the rigid structure model of the inner and outer aptamers are restricted to move only along the line connecting them;

[0016] A dynamic contact force model is defined between the rigid structure model of the external adapter and the launch tube / guide rail. When the rigid structure model of the external adapter leaves the launch tube / guide rail, the spring and torsion spring return to their original lengths and then fail.

[0017] S7, adjust the initial displacement of the spring according to the actual assembly pre-compression amount to simulate the pre-compression of the adapter body.

[0018] Preferably, in S2, several boundary points on the contact surface between the external adapter and the launch tube / guide rail 4, as well as the midpoint of the contact surface, are selected as feature points; the feature points on the internal adapter correspond one-to-one with the feature point positions on the external adapter.

[0019] Preferably, in S3, a universal testing machine is used to obtain a nonlinear compression stiffness curve.

[0020] Preferably, a nonlinear compression stiffness curve is obtained by testing at a rate close to the actual compression condition.

[0021] Preferably, in S3, a nonlinear torsional stiffness curve is obtained by using a torsion testing machine experiment.

[0022] Preferably, in S3, a spline curve is used to fit the nonlinear compression stiffness curve and the torsional stiffness curve.

[0023] Preferably, in S5, the step of restricting the middle feature points of the rigid structure models of the inner and outer aptamers to move only along the line connecting the two is replaced by restricting the middle feature points of the rigid structure models of the inner and outer aptamers to be on the intersection line of two vertical planes.

[0024] Preferably, a damping term is added to the nonlinear spring model and the nonlinear torsion spring model.

[0025] Beneficial effects:

[0026] The present invention uses the multi-rigid body dynamics method to discretize the adapter body into two pieces, and introduces nonlinear springs and torsion spring units to realize compression and flexible deformation, effectively simulating the nonlinear mechanical response of the adapter body during the launch process; based on the nonlinear stiffness curve calibrated by experiments or simulations, the compression and torsion responses of the adapter are accurately reproduced; through the spring original length offset correction technology, the actual assembly pre-compression state is directly mapped to improve the accuracy of the initial conditions.

[0027] This model adopts the multi-body dynamics method for calculation. Usually, one working condition only occupies one CPU thread, and multiple working conditions can be calculated in parallel. It has the characteristics of low resource consumption and feasibility of large-sample calculation. In addition, the pre-pressurized parameterized modeling of the present invention can realize rapid model generation, and the simple operation significantly improves the calculation efficiency and supports large-scale parameter rapid iteration. The present invention has high calculation efficiency and high simulation accuracy, and is adaptable to various complex working conditions. It provides an innovative solution for the modeling of rocket launch system adapters and flexible connectors in other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the adapter simulation part, rocket, launch tube / guide rail of the present invention.

[0029] Figure 2 This is a flow chart of the adapter multi-rigid body dynamics modeling method of the present invention.

[0030] Figure 3 : The feature point distribution diagram of the nine-feature point adapter; among them, (a) is the feature point distribution of the outer adapter, and (b) is the feature point distribution of the inner adapter.

[0031] Figure 4 This is the force variation curve of an adapter during simulation.

[0032] Among them, 1-external adapter, 2-internal adapter, 3-rocket, 4-launch tube / rail. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0034] The present invention provides an adapter multi-rigid body dynamics modeling method based on pre-compression and flexibility characteristics.

[0035] During the launch process, the change in the rocket's attitude angle causes the adapter to not only be axially compressed in a single direction, but also to have a certain degree of angular deflection on the inner and outer surfaces. Therefore, the present invention first discretizes the adapter body to be analyzed into two rigid body models: the outer adapter 1 and the inner adapter 2. The inner surface of the inner adapter 2 is fixedly connected to the rocket 3, and the outer surface of the outer adapter 1 is in contact with the launch tube wall or guide rail 4. The inner adapter 2 and the outer adapter 1 are constrained by the center collinearity, that is, the two can be axially compressed and angularly deflected in three directions, such as Figure 1 shown.

[0036] Next, the present invention uses nonlinear spring and torsion spring units to further constrain the rigid body models of the outer adapter 1 and inner adapter 2, accurately characterizing the nonlinear mechanical responses of the adapter bodies in compression, torsion, and preload. A nonlinear spring model is established by selecting several corresponding feature points on the inner and outer adapters to simulate the compression characteristics of the adapter bodies. The original spring length offset is adjusted based on the actual assembly preload to achieve precise preload application. A nonlinear torsion spring model is established at the corresponding central feature points of the inner and outer adapters to simulate the torsion characteristics of the adapter bodies. The collinear constraints established by the central feature points of the inner and outer adapters are used to connect the inner and outer adapters, ensuring computational efficiency and simulation accuracy without affecting the flexible deformation characteristics of the adapters. A contact constraint is established between the outer adapter and the launch tube wall or guide rail to simulate the actual sliding and separation behavior of the adapter body during launch.

[0037] Then, based on the experimental data of the adapter body, the force-displacement curve of the constructed spring model and the torque-angle curve of the torsion spring model were calibrated. By adjusting the initial offset of the original length of the spring, the pre-compression amount in the actual assembly is directly reflected, avoiding the complex iterative calculation of the preload force in the traditional method.

[0038] Finally, spline curves are used to realize dynamic mapping of stiffness curves to ensure the continuity of mechanical response.

[0039] The flow chart of the present invention is as follows Figure 2 As shown below. Figure 3 The nine selected feature points are described in detail:

[0040] (1) 3D geometric modeling and feature point selection

[0041] Create simplified 3D geometric models of the inner and outer adapter structures:

[0042] After ignoring chamfers and other irrelevant geometric features, the key load-bearing areas of the adapter body are extracted and discretized, and the rigid structural models of the inner and outer adapters are constructed respectively;

[0043] Select several feature points on the rigid structure model of the inner and outer adapters, such as Figure 3As shown, on the external adapter, 8 boundary points on the contact surface with the launch tube / guide rail 4 and 1 midpoint of the contact surface are selected; the characteristic points on the internal adapter correspond one-to-one with the characteristic points on the external adapter.

[0044] (2) Determination of nonlinear stiffness characteristics

[0045] The nonlinear compression stiffness curve (force-displacement relationship) and torsional stiffness curve (torque-angle relationship) of the adapter body are obtained through experiments. Among them, the nonlinear compression stiffness curve can be obtained by using a universal testing machine, etc. to compress the specimen at a certain rate, and simultaneously record the load (F) and displacement (δ). The nonlinear torsional stiffness curve can be obtained by using a torsion testing machine, etc. to twist the specimen to the target angle at a certain angular velocity, and simultaneously record the torque (T) and relative torsion angle (θ). It should be pointed out that the modulus of polyurethane, a commonly used material for adapters, increases with increasing strain rate. It is necessary to test the compression conditions at a rate similar to that of actual working conditions and use spline curves to fit the nonlinear compression and torsional stiffness curves.

[0046] (3) Nonlinear spring and torsion spring modeling

[0047] Compression parameters: A nonlinear spring model is established between the eight contact surface boundary points of the inner and outer adapters (①-①′, ②-②′, ③-③′, ... ⑨-⑨′ except ⑤-⑤′). The spring force is the nonlinear compression stiffness curve at the corresponding position of the adapter body measured in step (2).

[0048] Pre-compression correction: Adjust the original spring length offset according to the actual assembly pre-compression, that is, adjust the initial displacement (δ0) to ensure that the initial force state is consistent with the actual working conditions and realize the adapter pre-compression simulation.

[0049] Here, both the stiffness parameters and preload can be parameterized and modeled, and the stiffness parameters or bias parameters can be dynamically adjusted to adapt to different working conditions. Adapter stiffness design and preload optimization can be performed.

[0050] Torsion parameters: A nonlinear torsion spring model is established between the central characteristic points (⑤-⑤′) of the inner and outer adapters, and the torque is the torsional stiffness curve at the center point of the adapter body measured in step (2).

[0051] (4) Build the rocket and launch tube / rail, and set constraints and contacts

[0052] Binding constraint: The inner adapter is fixedly connected to the rocket body to ensure that the inner adapter is always in the corresponding position of the rocket during the launch process, and the force transmission position of the adapter is accurate.

[0053] Collinearity constraint: This method restricts the relative freedom of motion between the center points of the inner and outer adapters. The two center points can only move along the line connecting them, while the remaining pairs of points are unrestricted. This method maintains the flexible deformation characteristics of the adapter while ensuring the kinetic movement of the outer adapter during launch, thus avoiding non-physical displacement. Alternatively, the collinearity constraint between the center points of the inner and outer adapters can be replaced with two perpendicular planar pairs, constrained to the intersection of the two planes. If the intersection coincides with the line defined by the collinearity constraint, the result is equivalent.

[0054] Contact Setup: Define a dynamic contact force model between the external adapter and the launch tube / rail to simulate sliding friction and separation during launch. As the external adapter leaves the rail, the spring and torsion spring return to their original lengths, ultimately failing.

[0055] In addition, if factors such as damping are considered, damping terms can also be added to the spring model and torsion spring model.

[0056] (5) Set the simulation boundary conditions according to the working conditions being studied, such as setting wave and vibration excitation on the launch tube / guide rail, setting the corresponding launch load on the rocket and the bottom of the launch tube, etc., and set the appropriate calculation step size to start the simulation calculation.

[0057] This paper utilizes multibody dynamics to discretize the adapter into two pieces. The nonlinear dynamic characteristics of the launch process are characterized using springs, torsion springs, constraints, and contacts. By setting precise load (F) displacement (δ) and torque (T) relative torsion angle (θ) curves, the complex deformation behavior of the adapter during installation and launch is simulated. Preload simulation is achieved by setting an initial displacement (δ0) to simulate the preload. After setting the boundary conditions and calculation step size, the simulation can begin.

[0058] The adapter simulation model constructed by the present invention is such that during the launch process, the inner and outer adapters can move together with the rocket without restricting the rotational freedom of the inner and outer adapters in three directions. The rigid compression characteristics are represented by a nonlinear spring, and the flexible characteristics are represented by a central torsion spring, thereby realizing fast and high-precision simulation of the mechanical properties of the adapter.

[0059] Figure 4This is the force change curve of a certain adapter simulation process, in which no action is applied from 0 to 3s, which is the static balance stage. Different wave excitations are applied at 3s and 6s to cause the rocket to deflect, which in turn causes the force change of the adapter. Due to the use of penalty functions to determine contact in the multi-body dynamics software model, as well as model geometric errors, a certain initial force may appear, and the static equilibrium initial contact force needs to be calculated and observed for the first time. Taking this simulation as an example, the preload in this calculation is 4450N, and the initial force of the model is 180N, so a compression offset of about 4270N is set. The calculation step size of this simulation calculation is set to 0.005s. It can be seen from the data that the static balance has been completed smoothly in the 0.06s data. At this time, the calculation time is about 30s, the equilibrium preload is 4437N, and the error is only 0.3%, which meets the adapter's requirements for fast and high-precision calculation considering preload and flexibility.

[0060] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-rigid body dynamic modeling method for an adapter based on preload and flexibility features, characterized in that: include: S1, extract the key bearing regions of the adapter body and discretize them into internal and external aptamers; The rigid structural models of the inner and outer aptamers were constructed separately; S2, selecting characteristic points corresponding to several positions on the rigid structure models of the inner and outer aptamers; S3, experimentally obtain the nonlinear compression stiffness curve and torsional stiffness curve at different positions of the adapter body; S4, establishing a nonlinear spring model and a nonlinear torsion spring model between the characteristic points corresponding to the rigid structure models of the inner and outer adapters; the spring force is the nonlinear compression stiffness curve at the corresponding position of the adapter body measured in S3, and the torque is the nonlinear torsional stiffness curve at the corresponding position of the adapter body measured in S3; S5, build the rocket and launch tube / rail model; S6, set constraints: The rigid structure model of the internal aptamer is fixedly connected to the rocket model; The middle feature points of the rigid structure model of the inner and outer aptamers are restricted to move only along the line connecting them; A dynamic contact force model is defined between the rigid structure model of the external adapter and the launch tube / guide rail. When the rigid structure model of the external adapter leaves the launch tube / guide rail, the spring and torsion spring return to their original lengths and then fail. S7, adjust the initial displacement of the spring according to the actual assembly pre-compression amount to simulate the pre-compression of the adapter body.

2. The method according to claim 1, wherein In S2, several boundary points on the contact surface between the outer adapter and the launch tube / guide rail 4, as well as the midpoint of the contact surface, are selected as feature points; the feature points on the inner adapter correspond one-to-one to the feature point positions on the outer adapter.

3. The method according to claim 1, wherein In S3, a nonlinear compression stiffness curve is obtained by using a universal testing machine.

4. The method according to claim 3, wherein The nonlinear compression stiffness curve is obtained by testing at a rate close to the actual working compression condition.

5. The method according to claim 1, wherein In S3, a nonlinear torsional stiffness curve is obtained by using a torsion testing machine experiment.

6. The method according to any one of claims 1 to 5, characterized in that: In S3, a nonlinear compression stiffness curve and a torsional stiffness curve are obtained by spline curve fitting.

7. The method according to claim 1, wherein In said S5, the restriction that the middle feature points of the rigid structure models of the inner and outer aptamers can only move along the line connecting them is replaced by restricting the middle feature points of the rigid structure models of the inner and outer aptamers to be on the intersection line of two vertical planes.

8. The method according to claim 1, wherein Add damping terms to the nonlinear spring model and the nonlinear torsion spring model.

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