A fast modeling method for rigid-flexible-sloshing coupling model of launch vehicle

Abstract

The application discloses a kind of fast modeling methods of launch vehicle rigid-elastic-slosh coupling model, the motion equation of launch vehicle is established: the motion equation of launch vehicle is established; Force, torque and its generalized force are solved; Propellant sloshing is analyzed using spring-mass-damper equivalent model; The nonlinear full-quantity dynamic model of launch vehicle six degrees of freedom is established: the inertia force, inertia torque and generalized force generated by propellant sloshing are substituted into the motion equation of launch vehicle, and the motion equation of centroid, the motion equation around centroid, the elastic vibration equation of rocket in pitch, yaw and roll three directions are obtained; Launch vehicle rigid-elastic-slosh coupling model is solved.The application can realize the fast numerical simulation of launch vehicle rigid-elastic-slosh coupling model, and analyze the influence of solution result on the attitude change of launch vehicle, and lay the foundation for the navigation and attitude control design of launch vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerospace technology, in particular to a rapid modeling method of a rigid-elastic-sloshing coupled model of a launch vehicle. BACKGROUND

[0002] The attitude control system of a launch vehicle is one of the key components to ensure the required flight attitude and stability during the flight process. The system must be able to cope with various complex external and internal motion factors, including rigid body motion, elastic vibration, and liquid sloshing.

[0003] Rigid body motion control is the basis of the attitude control system, which is mainly achieved through the adjustment of the thrust direction of the rocket's thrusters. The controller calculates the required engine swing angle based on the attitude information obtained by the sensor and the target attitude requirements provided by the guidance system, and then adjusts the working state of the engine swing angle through the actuator, thereby achieving the control of the translational and rotational motion of the rocket. During the flight of the rocket, the shell may be affected by the airflow and other external factors, which may cause elastic vibration. In order to maintain flight stability and structural integrity, the attitude control system needs to control this vibration. This is usually achieved by installing vibration dampers in the rocket structure or using active vibration control technology, which applies appropriate forces through the actuator to suppress vibration. The liquid sloshing in the rocket propellant tank is also an important factor that needs to be considered by the attitude control system. Liquid sloshing can cause changes in the center of mass and inertia moment of the rocket, which in turn affects the flight attitude and stability of the rocket. In order to solve this problem, the controller will execute appropriate forces through the actuator to actively control the liquid sloshing based on the center of mass information collected by the sensor, in order to maintain the flight stability of the rocket.

[0004] In summary, the attitude control system of a launch vehicle is a complex and critical component that directly affects the flight stability and mission execution capability of the rocket. Therefore, establishing a high-fidelity rigid-elastic-sloshing coupled dynamics model of a launch vehicle and performing rapid simulation calculation can effectively achieve the attitude control of the rocket and ensure its safe and reliable completion of various flight tasks. SUMMARY

[0005] The purpose of the present application is to provide a rapid modeling method of a rigid-elastic-sloshing coupled model of a launch vehicle, to establish a rigid-elastic-sloshing coupled model of a launch vehicle, to analyze its dynamic characteristics, and to provide a state description of the system motion as a foundation for navigation and attitude control design.

[0006] The technical solution to achieve the purpose of the present application is a rapid modeling method of a rigid-elastic-sloshing coupled model of a launch vehicle, comprising the following steps:

[0007] Step one, determine the appropriate coordinate system to describe the motion of the launch vehicle, in the half-speed coordinate system, the establishment of the launch vehicle center of mass motion equation; in the body coordinate system, the establishment of the launch vehicle around the center of mass motion equation; in the elastic coordinate system, the launch vehicle is simplified as a one-dimensional beam model, the establishment of the launch vehicle elastic vibration equation;

[0008] Step two, in the case of considering elastic deformation, respectively solve the various forces, moments and generalized forces acting on the body, including gravity, the force, moment and generalized force generated by the swing of the launch force, the inertia force, moment and generalized force related to the swing angle when the engine swings, the combined force of the aerodynamic force, lift and aerodynamic damping force, the combined force of the lateral force and aerodynamic damping force, the combined moment of the aerodynamic damping moment, the aerodynamic stability moment and the damping force moment, the generalized force of the aerodynamic force and the aerodynamic damping force in the pitch direction and the yaw direction;

[0009] Step three, the propellant in the tank of the launch vehicle is equivalent to a spring-mass-damper system for equivalent modeling, the analysis of the propellant shaking with the motion of the launch vehicle, and the establishment of the motion equation of the propellant shaking through the equivalent model;

[0010] Step four, the forces, moments and generalized forces obtained in step two are substituted into the center of mass motion equation, the motion equation around the center of mass and the elastic vibration equation in step one, and the obtained launch vehicle motion equation constitutes the six-degree-of-freedom nonlinear full-quantity dynamic model of the rocket;

[0011] Step five, the six-degree-of-freedom nonlinear full-quantity dynamic model in step four and the propellant shaking model in step three are integrated to form a launch vehicle rigid-elastic-shaking coupled dynamic model, and the equation set is solved by using a numerical method according to the given initial conditions to obtain the motion state of the launch vehicle at different times.

[0012] Further, the motion equation of the launch vehicle includes: the center of mass motion equation, the motion equation around the center of mass and the elastic vibration equation. The forces, moments and generalized forces to be solved include: gravity, the force, moment and generalized force generated by the swing of the launch force, the inertia force, moment and generalized force related to the swing angle when the engine swings, the combined force of the aerodynamic force, lift and aerodynamic damping force, the combined force of the lateral force and aerodynamic damping force, the combined moment of the aerodynamic damping moment, the aerodynamic stability moment and the damping force moment, the generalized force of the aerodynamic force and the aerodynamic damping force in the pitch direction and the yaw direction.

[0013] Further, according to the spring-mass-damper equivalent model in step three, the propellant shaking equations in the pitch direction and the yaw direction of the launch vehicle are established, and the inertia force, moment and generalized force generated by the additional propellant shaking are established.

[0014] Further, in step four, the various forces, moments and their generalized forces obtained in step two and step three are substituted into the rocket motion equations in step one to obtain the equations of motion of the center of mass, the equations of motion around the center of mass, the equations of elastic vibration of the rocket in the three directions of pitch, yaw and roll.

[0015] The platform for solving and analyzing in step five includes but is not limited to: Matlab.

[0016] Therefore, compared with the prior art, the following beneficial effects can be achieved by adopting the present application:

[0017] 1) The rigid-elastic-sloshing coupling model of the launch vehicle can be quickly modeled, the model is universal, reusable and expandable, and the modeling efficiency is greatly improved.

[0018] 2) The state description and mathematical description of the system can be provided, which lays a foundation for subsequent navigation and control design. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a flow chart of the rigid-elastic-sloshing coupling model quick modeling method of the launch vehicle of the present application.

[0020] Figure 2 is a rocket engine layout diagram of the present application.

[0021] Figure 3 is an elastic arrow in the roll, pitch and yaw planes.

[0022] Figure 4 is a liquid sloshing equivalent model and a sloshing diagram in the pitch and yaw planes.

[0023] Figure 5 is the position and velocity vector of the rocket in the launch coordinate system.

[0024] Figure 6 is the yaw angle and roll angle of the rocket relative to the launch system.

[0025] Figure 7 The projection of the rotation angle of the arrow body around the center of mass in the arrow system is given.

[0026] Figure 8 is the velocity inclination angle, track yaw angle and tilt angle of the velocity coordinate system relative to the launch system.

[0027] Figure 9 is the attack angle and side slip angle of the velocity coordinate system relative to the arrow body coordinate system.

[0028] Figure 10 is the equivalent pitch angle, yaw angle and roll angle of the rocking engine.

[0029] Figure 11is the comparison of the pitch angle of the rocket relative to the launch system and the program angle. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0031] A fast modeling method of a rigid-flexible-vibration coupling model of a launch vehicle includes the following steps:

[0032] Step one, establishing the motion equation of the launch vehicle, specifically:

[0033] According to Newton's second law, the mass center motion equation in the half-velocity coordinate system is

[0034]

[0035] where m is the total mass of the rocket, is the component of all external forces acting on the rocket body in the h-axis of the half-velocity coordinate system under the condition of elastic deformation.

[0036] If the b-axis of the rocket system is taken as the principal axis of inertia of the rocket body, the mass center motion equation is obtained according to the momentum theorem relative to the mass center as

[0037]

[0038] where is the moment of inertia of the rocket body around the b-axis of the rocket system. is the moment of the external forces acting on the rocket body around the mass center under the condition of elastic deformation.

[0039] When studying elastic vibration, the rocket is usually simplified as a one-dimensional beam model, and the elastic vibration equation is

[0040]

[0041] where is the i-th order vibration circular frequency and damping ratio in the corresponding direction, are the i-th order generalized mass and generalized force, respectively.

[0042] Step two, solving the force, moment and generalized force, specifically:

[0043] The component expression of the gravity in the half-velocity coordinate system h is

[0044]

[0045] where g is the acceleration of gravity. Since the mass center position is assumed to be unchanged before and after elastic deformation, the gravity does not produce a moment of force on the mass center of the rocket, and the corresponding generalized force of elastic vibration is also zero.

[0046] The engine swing will make the thrust produce a lateral component as a control force, and the four swing engine thrust forces in the b-frame of the rocket body are Figure 2

[0047]

[0048] where P1 is the thrust of a single engine. The moment of force of the thrust on the mass center in the b-frame of the rocket body is

[0049]

[0050] where x R and x T are the distances from the engine swing point and the mass center of the rocket body to the theoretical tip point of the rocket. In the elastic coordinate system E, the generalized forces of the thrust in the torsion, pitch bending vibration and yaw bending vibration directions are respectively

[0051]

[0052] The expression of the combined force of the swing inertia forces of the four engines in the b-frame of the rocket body is

[0053]

[0054] where m R and l R are the mass and swing length of a single engine, respectively. The expression of the combined moment of the swing inertia moment of force in the b-frame of the rocket body is

[0055]

[0056] where is the axial apparent acceleration. The generalized forces of the inertia force and moment of force related to the swing angle are

[0057]

[0058] The aerodynamic drag in the O1X c axis direction of the speed system c is

[0059]

[0060] The combined force of the lift and aerodynamic damping force in the O1Y c axis direction is

[0061]

[0062] The aerodynamic drag in the O1Z c ​The resultant of the lateral force and the aerodynamic damping force in the axial direction is

[0063]

[0064] In O1X c The aerodynamic drag moment in the axial direction is

[0065]

[0066] Where m dx is the rolling damping moment coefficient.

[0067] In O1Y c The resultant moment of the aerodynamic stability moment and the damping moment in the axial direction is

[0068]

[0069] Where m dy is the yaw aerodynamic damping moment coefficient derivative.

[0070] In O1Z c The resultant moment of the aerodynamic stability moment and the damping moment in the axial direction is

[0071]

[0072] Where m dz is the pitch aerodynamic damping moment coefficient derivative.

[0073] The generalized force of the aerodynamic force and the aerodynamic damping force in the pitch direction and the yaw direction is

[0074]

[0075]

[0076] Step three, analyze the propellant sloshing by using a spring-mass-damper equivalent model, specifically:

[0077] The propellant sloshing equation in the pitch direction and the yaw direction is

[0078]

[0079] The additional propellant sloshing inertia force is

[0080]

[0081] Where m p is the tank sloshing mass.

[0082] The additional inertia moment due to sloshing is

[0083]

[0084] The generalized force corresponding to the inertia force and moment related to the sway is

[0085]

[0086] Step four, a six-degree-of-freedom nonlinear full-quantity dynamic model is established, specifically:

[0087] The above obtained various forces, moments and their generalized forces are substituted into equations (1), (2) and (3), and the equations of motion of the center of mass in the semi-velocity coordinate system are represented in a matrix form as

[0088]

[0089] Where F BX , F BY and F BZ are additional structural disturbance forces, and N P is the number of storage tanks.

[0090] The equation of motion of the rocket in the arrow system is

[0091]

[0092]

[0093] Where F and F are additional structural disturbance forces. In the elastic coordinate system E, the elastic vibration equations of the rocket in the pitch, yaw and roll directions are

[0094]

[0095] Where i = 1, 2, …, n γ .

[0096]

[0097]

[0098] Step five, the rigid-elastic-sway coupled model of the launch vehicle is solved.

[0099] Embodiment

[0100] In order to verify the effectiveness of the present application, the above rigid-elastic-sway coupled model of the launch vehicle is simulated as follows. Figure 5 The position and velocity vector diagram of the launch vehicle in the launch coordinate system is given; Figure 6 The yaw angle and roll angle of the rocket relative to the launch system are given; Figure 7 The projection of the rotation angle of the arrow body around the center of mass in the arrow system is given; Figure 8The velocity coordinate system relative to the launching system's velocity inclination, track yaw angle, and tilt angle are given. Figure 9 The attack angle and side slip angle of the velocity coordinate system relative to the rocket body coordinate system are given. Figure 10 The equivalent pitch angle, yaw angle, and roll angle of the wobbling engine are given. Figure 11 The comparison of the pitch angle and the program angle of the rocket relative to the inertial system is given, and it can be seen from the figure that the change of the pitch angle is in good agreement with the designed program angle. According to the motion description of the carrier rocket given by the figure, it can be illustrated that the rigid-flexible-sway coupling model of the carrier rocket established by the present application can well lay a foundation for the subsequent navigation and attitude control design of the carrier rocket.

[0101] The technical features of the above embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered that it is within the scope of the present application.

[0102] The above embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it should not be understood as the limitation of the patent scope of the present application. It should be pointed out that, for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

[0103] The unexplained part in the present application belongs to the known technology in the art.

Claims

1. A fast modeling method of rigid-flex-oscillation coupling model of launch vehicle, characterized in that, The method comprises the following steps: Step one, determining a suitable coordinate system to describe the motion of the launch vehicle, establishing the center of mass motion equation of the launch vehicle in the half-speed coordinate system, and establishing the motion equation of the launch vehicle around the center of mass in the rocket body coordinate system; In the elastic coordinate system, the launch vehicle is simplified as a one-dimensional beam model, and the elastic vibration equation of the launch vehicle is established; Step two, in the case of considering elastic deformation, the various forces, torques and generalized forces acting on the rocket body are solved respectively, including gravity, force and torque generated by engine swing, inertia force, torque and generalized force related to swing angle, aerodynamic force, lift and aerodynamic damping force, lateral force and aerodynamic damping force, aerodynamic damping torque, aerodynamic stability torque and damping torque, and generalized force of the aerodynamic force and aerodynamic damping force in the pitch and yaw directions; Step three, the propellant in the storage tank of the launch vehicle is equivalent to a spring-mass-damper system for equivalent modeling, the shaking of the propellant caused by the motion of the launch vehicle is analyzed, and the motion equation of the propellant shaking is established through the equivalent model; Step four, the forces, torques and generalized forces obtained in step two are substituted into the center of mass motion equation, the motion equation around the center of mass and the elastic vibration equation in step one respectively, and the obtained motion equation of the launch vehicle constitutes a six-degree-of-freedom nonlinear full-quantity dynamic model of the rocket; Step five, the six-degree-of-freedom nonlinear full-quantity dynamic model in step four and the propellant shaking model in step three are integrated to form a rigid-elastic-shaking coupled dynamic model of the launch vehicle, and the equation set is solved by using a numerical method according to the given initial conditions to obtain the motion state of the launch vehicle at different times.

2. The quick modeling method of rigid-elastic-slosh coupling model of launch vehicle according to claim 1, characterized in that: The gravity in step two is established in the half-speed coordinate system, and the gravity does not generate torque on the center of mass of the rocket because it is assumed that the center of mass position is unchanged before and after the elastic deformation, and the corresponding elastic vibration generalized force is also zero.

3. The quick modeling method of rigid-elastic-slosh coupling model of launch vehicle of claim 1, wherein: The force, torque and generalized force generated by the engine swing in step two include the thrust, control force and inertia force related to the swing angle, wherein the force and torque are established in the rocket body coordinate system, and the generalized force is established in the elastic coordinate system.

4. The quick modeling method of rigid-elastic-slosh coupling model of launch vehicle of claim 1, wherein: The aerodynamic force, lift and aerodynamic damping force, lateral force and aerodynamic damping force, aerodynamic damping torque, aerodynamic stability torque and damping torque in step two are established in the speed coordinate system, the forces and torques are converted to the rocket body coordinate system through a coordinate conversion matrix, and the generalized forces of the aerodynamic force and aerodynamic damping force in the pitch and yaw directions are established in the elastic coordinate system.

5. The quick modeling method of rigid-elastic-slosh coupling model of launch vehicle of claim 1, wherein: According to the spring-mass-damper equivalent model, the propellant shaking equations in the pitch and yaw directions of the launch vehicle are established, and the inertia force, inertia torque and generalized force generated by the propellant shaking are established, wherein the inertia force and inertia torque generated by the propellant shaking are established in the rocket body coordinate system, and the generalized force is established in the elastic coordinate system.

6. The quick modeling method of rigid-elastic-slosh coupling model of launch vehicle of claim 1, wherein: The solving platform includes but is not limited to Matlab.

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