A method for simulating the correlation between space and ground in a two-degree-of-freedom support mechanism

Abstract

A method for simulating the relationship between the flight dynamics and the ground coordinates of a two-degree-of-freedom support mechanism is presented. This method combines the three-degree-of-freedom flight dynamics equations in the aircraft's body coordinate system with the motion equations of the two-degree-of-freedom support mechanism. Appropriate motion quantities are selected for simulation based on these equations, establishing a correspondence between the flight dynamics equations and the mechanism's motion equations. Based on this correspondence, the motion quantities of the support mechanism are inversely solved, and the motion trajectories of the mechanism's degrees of freedom are planned using the inverse solution. This support mechanism can simulate the flight response of an aircraft in the longitudinal plane, measure unsteady aerodynamic forces of the aircraft during flight simulation, and serve as a verification platform for flight control laws.

Description

Technical Field

[0001] This invention relates to a method for simulating the correlation between the ground and space in a two-degree-of-freedom support mechanism, belonging to the field of aerodynamics research. Background Technology

[0002] The capture trajectory test technology is a special wind tunnel test technology for studying the separation characteristics of aircraft. As an advanced and effective test technology for studying the separation characteristics of aircraft, it has been widely used to study the separation characteristics of various aircraft, providing test basis for the safe and efficient separation of aircraft and the design of flight control systems.

[0003] During wind tunnel testing, a scaled-down model or component of an aircraft is installed within the wind tunnel test section. Based on the principle of similarity, the wind tunnel system is driven to generate simulated flight airflow within the test section. Simultaneously, a control system manages and measures the airflow to study the interaction between the flow field and the model, and to understand the aerodynamic characteristics of an actual aircraft. Wind tunnel testing is characterized by relatively low cost and relatively accurate data. Although wind tunnel testing is subject to many interfering factors that can affect data accuracy, after data correction, the obtained data can provide a reliable basis for the development and control of aircraft.

[0004] Cruise missiles are generally used in shore-to-ship, ship-to-ship, and air-to-ground missiles. Their motion control often employs a planned flight method, typically controlling the missile to fly within a fixed vertical plane. The level flight phase is the main flight phase of a cruise missile. This phase is characterized by the missile not performing large maneuvers and flying at a constant speed and altitude.

[0005] Under typical initial conditions, a two-degree-of-freedom support mechanism is used to simulate the trim process and steady-state flight state through rudder deflection trim. Under steady-state flight state, disturbances are applied in different ways, and the trim process and steady-state flight state are simulated through rudder deflection trim. During the trim process, aerodynamic loads, structural loads, deformation, and flow field are measured. Based on the above, a new phenomenon of fluid-structure interaction is explored.

[0006] Compared to the quasi-steady results of traditional trajectory capture tests, which are influenced by the motion frequency and static force measurement method, the results of traditional trajectory capture tests are quasi-steady and ignore the influence of the model's motion velocity term on unsteady aerodynamic forces. Therefore, the test results deviate from the actual flight test data. Summary of the Invention

[0007] The technical problem solved by this invention is: addressing the issues of difficulty in simulating velocity terms and insufficient consideration of unsteady aerodynamic forces in existing technologies, a ground-space correlation simulation method for a two-degree-of-freedom support mechanism is proposed.

[0008] The present invention solves the above-mentioned technical problem through the following technical solution:

[0009] A method for simulating the geostationary correlation of a two-degree-of-freedom support mechanism includes:

[0010] Construct the three-degree-of-freedom dynamic equations of the aircraft in the longitudinal plane;

[0011] Construct the equations of motion for the two-degree-of-freedom support mechanism;

[0012] The motion quantities are selected to characterize the correspondence between the three-degree-of-freedom dynamic equations of the aircraft and the motion equations of the two-degree-of-freedom support mechanism;

[0013] Based on the obtained correspondence, the motion quantities of each degree of freedom of the two-degree-of-freedom support mechanism are solved inversely.

[0014] Based on the inverse kinematics results, the degrees of freedom in each direction of the two-degree-of-freedom support mechanism are calculated and planned to complete the simulation of the aircraft response.

[0015] The three-degree-of-freedom dynamic equations of the aircraft are established in the aircraft's body coordinate system, specifically as follows:

[0016]

[0017]

[0018]

[0019]

[0020]

[0021] F a =[F ax ,F ay ,0]F d =[F dx ,F dy ,0]

[0022] M a =[0,0,M az M d =[0,0,M dz ]

[0023] f = [f x ,f y ,0]ω=[0,0,ω z ]

[0024] r t =[x t ,y t ,0]

[0025] In the formula, r t This represents the position vector of the aircraft in the volume coordinate system. This represents the relative velocity of the aircraft in the body coordinate system. ω z The pitch angle and pitch rate represent the pitch angle and pitch velocity of the aircraft system relative to the inertial frame, respectively, where m is the mass of the aircraft, and I is the velocity. z F is the moment of inertia of the aircraft's pitch axis. a The aerodynamic force acting on the aircraft can be measured by a force balance, F. d M represents other external forces acting on the aircraft, f represents the entrainment acceleration and Coriolis acceleration in the moving coordinate system, and M represents the other external forces acting on the aircraft. a The aerodynamic torque acting on the aircraft can be measured by a force balance, M. d This represents other external torques acting on the aircraft.

[0026] The coordinate transformation is performed on the three-degree-of-freedom dynamic equations of the aircraft to obtain the state quantities in the inertial frame relative to the coordinate system of the flight mechanical body. Specifically:

[0027] A T r t =r i

[0028] r i =[x i ,y i ,0]

[0029]

[0030]

[0031] In the formula, the transformation matrix from the inertial frame to the volume coordinate system is A, r i This represents the position vector of the aircraft in an inertial frame. Let θ represent the velocity of the aircraft in the inertial frame, θ be the ballistic ground velocity inclination angle, and α be the angle of attack of the aircraft. To measure unsteady aerodynamic forces, wind tunnel tests need to simulate the angle of attack α and the pitch rate ω. z Two motion quantities. To simulate flight response, the normal displacement y is simulated through wind tunnel testing. i Pitch angle Two levels of exercise.

[0032] The dual-degree-of-freedom support mechanism includes a floating platform, a pitching platform, and a horizontal slider. The floating platform and the pitching platform are connected to the horizontal slider via a rotating shaft and a connecting rod. The movement of the horizontal slider causes the connecting rod and the pitching platform to rotate around the rotating shaft of the floating platform. The relevant parameters are as follows:

[0033] l1 is the distance between the horizontal slider axis and the pitch stage axis, l2 is the distance between the pitch stage connecting rod axis and the pitch axis, l3 is the connecting rod length, l4 is the distance from the model's center of mass to the pitch stage axis, l5 is the length of the floating platform, l6 is the vertical distance from the horizontal slider axis to the floating platform, ΔX and ΔY are the horizontal displacement of the pitch slider and the vertical displacement of the floating platform, which are the two movable degrees of freedom of the two-degree-of-freedom support mechanism.

[0034] The aircraft body coordinate system coincides with the wind tunnel model body coordinate system, the inertial frame coincides with the wind tunnel frame, and the position vector R of the two-degree-of-freedom support mechanism model in the wind tunnel frame is... k Represented as:

[0035]

[0036] The velocity V of the two-degree-of-freedom support mechanism model in the wind tunnel system k Represented as:

[0037]

[0038] The wind tunnel wind speed V D In the wind tunnel system, it is represented as:

[0039] V D =[V w ,0,0]

[0040] The two-degree-of-freedom support mechanism model is represented in the wind tunnel system as follows:

[0041]

[0042] The ballistic airspeed tilt angle θ of the two-degree-of-freedom support mechanism model in the wind tunnel system s The calculation formula is:

[0043]

[0044] For a specific wind tunnel dynamic support mechanism, the motion equations for each degree of freedom of the two-degree-of-freedom support mechanism are established as follows:

[0045]

[0046]

[0047]

[0048]

[0049] In the formula, Let y be the pitch angle of the model under the support mechanism. sThe normal displacement of the model is given by the function f, which is solved numerically and then linearly fitted. The horizontal displacement ΔX of the pitch slider is related to the model's pitch angle. The relationship is linear within the specified angular range.

[0050] Select the angle of attack α and the pitch angular velocity ω z Pitch angle With normal displacement y i Flight state simulation and flight response simulation were performed respectively, and the correspondence between the three-degree-of-freedom dynamic equations of the aircraft and the motion equations of the two-degree-of-freedom support mechanism was established as follows:

[0051]

[0052] The angle of attack α is simulated as an equivalent quantity to the ballistic ground velocity inclination angle θ.

[0053] θ s =θ

[0054] Specifically, the inverse solution is performed on the motion quantities of each degree of freedom of the two-degree-of-freedom support mechanism, as follows:

[0055] By calculating the three-degree-of-freedom dynamics of the aircraft Perform inverse kinematics to obtain the motion commands of the support mechanism.

[0056]

[0057] The motion equations of each degree of freedom of the two-degree-of-freedom support mechanism are determined by inverse solving the correspondence between the aircraft dynamics equations and the motion equations of the support mechanism.

[0058] The support mechanism movement command For unsteady aerodynamic measurement and flight response simulation, a cubic polynomial fitting method is used to simulate the displacement and velocity of a two-degree-of-freedom support mechanism, specifically:

[0059] ΔX=a0+a1t+a2t 2 +a3t 3

[0060] ΔY = b0 + b1t + b2t 2 +b3t 3

[0061] Specifically, the coefficients of the polynomial are obtained by differentiating the displacements and velocities at both ends of the actuation step.

[0062]

[0063]

[0064] In the formula, t represents the actuation time, t0 is the initial time, t1 is the terminal time, and the actuation time t∈[t0,t1]. After the calculation is completed, the trajectory solution of the model is calculated.

[0065] The motion calculation of the three-degree-of-freedom dynamic equations of the aircraft is based on the force balance and inertial navigation system installed on the two-degree-of-freedom support mechanism model. At the same time, the inertial force of the two-degree-of-freedom support mechanism model is measured and the aerodynamic force is calculated. The two-degree-of-freedom support mechanism model is also equipped with servo motors to realize flight response control.

[0066] The advantages of this invention compared to the prior art are:

[0067] This invention provides a two-degree-of-freedom support mechanism ground-to-ground correlation simulation method, which can simultaneously simulate displacement and velocity, and simulate unsteady flight response. Utilizing a real-time active actuator system and solution program, the model only needs to satisfy geometric similarity, not mass and moment of inertia similarity, greatly reducing the difficulty of model manufacturing. It can ensure flight response simulation and unsteady aerodynamic force measurement, reducing the difficulty of model design. Through the two-degree-of-freedom support mechanism ground-to-ground correlation simulation method, the displacement and velocity of the model in the wind tunnel can be made continuous, enabling the simulation of unsteady flight response. Attached Figure Description

[0068] Figure 1 Flowchart of the method for simulating the geo-orbit correlation of a two-degree-of-freedom support mechanism provided for the invention;

[0069] Figure 2 A schematic diagram of the two-degree-of-freedom support mechanism and a schematic diagram of the inertial coordinate system and the volume coordinate system provided for the invention;

[0070] Figure 3 A conceptual diagram of a two-degree-of-freedom support mechanism provided for the invention; Detailed Implementation

[0071] A method for simulating the relationship between the flight dynamics and the ground coordinates of a two-degree-of-freedom support mechanism is presented. This method combines the three-degree-of-freedom flight dynamics equations in the aircraft's body coordinate system with the motion equations of the two-degree-of-freedom support mechanism. Appropriate motion quantities are selected for simulation based on these equations, establishing a correspondence between the flight dynamics equations and the mechanism's motion equations. Based on this correspondence, the motion quantities of the support mechanism are inversely solved, and the motion trajectories of the mechanism's degrees of freedom are planned using the inverse solution. This support mechanism can simulate the flight response of an aircraft in the longitudinal plane, measure unsteady aerodynamic forces of the aircraft during flight simulation, and serve as a verification platform for flight control laws.

[0072] The specific steps are as follows:

[0073] Construct the three-degree-of-freedom dynamic equations of the aircraft in the longitudinal plane;

[0074] Construct the equations of motion for the two-degree-of-freedom support mechanism;

[0075] The motion quantities are selected to characterize the correspondence between the three-degree-of-freedom dynamic equations of the aircraft and the motion equations of the two-degree-of-freedom support mechanism;

[0076] Based on the obtained correspondence, the motion quantities of each degree of freedom of the two-degree-of-freedom support mechanism are solved inversely.

[0077] Based on the inverse kinematics results, the degrees of freedom in each direction of the two-degree-of-freedom support mechanism are calculated and planned to complete the simulation of the aircraft response.

[0078] The dual-degree-of-freedom support mechanism includes a floating platform, a pitching platform, and a horizontal slider. The floating platform and the pitching platform are connected to the horizontal slider via a rotating shaft and a connecting rod. The movement of the horizontal slider drives the connecting rod and the pitching platform to rotate around the rotating shaft of the floating platform. The specific parameters are as follows:

[0079] l1 is the distance between the horizontal slider axis and the pitch stage axis, l2 is the distance between the pitch stage connecting rod axis and the pitch axis, l3 is the connecting rod length, l4 is the distance from the model's center of mass to the pitch stage axis, l5 is the length of the floating platform, l6 is the vertical distance from the horizontal slider axis to the floating platform, ΔX and ΔY are the horizontal displacement of the pitch slider and the vertical displacement of the floating platform, which are the two movable degrees of freedom of the two-degree-of-freedom support mechanism;

[0080] The three-degree-of-freedom dynamic equations of the aircraft are established in the aircraft's body coordinate system, specifically as follows:

[0081]

[0082]

[0083]

[0084]

[0085]

[0086] F a =[F ax ,F ay ,0]F d =[F dx ,F dy ,0]

[0087] M a =[0,0,M az M d =[0,0,Mdz ]

[0088] f = [f x ,f y ,0]ω=[0,0,ω z ]

[0089] r t =[x t ,y t ,0]

[0090] In the formula, r t This represents the position vector of the aircraft in the volume coordinate system. This represents the relative velocity of the aircraft in the body coordinate system. ω z The pitch angle and pitch rate represent the pitch angle and pitch velocity of the aircraft system relative to the inertial frame, respectively, where m is the mass of the aircraft, and I is the velocity. z F is the moment of inertia of the aircraft's pitch axis. a The aerodynamic force acting on the aircraft can be measured by a force balance, F. d M represents other external forces acting on the aircraft, f represents the entrainment acceleration and Coriolis acceleration in the moving coordinate system, and M represents the other external forces acting on the aircraft. a The aerodynamic torque acting on the aircraft can be measured by a force balance, M. d This represents other external torques acting on the aircraft.

[0091] The coordinate transformation is performed on the three-degree-of-freedom dynamic equations of the aircraft to obtain the state quantities in the inertial frame relative to the coordinate system of the flight mechanical body. Specifically:

[0092] A T r t =r i

[0093] r i =[x i ,y i ,0]

[0094]

[0095]

[0096] In the formula, the transformation matrix from the inertial frame to the volume coordinate system is A, r i This represents the position vector of the aircraft in an inertial frame. Let θ represent the velocity of the aircraft in the inertial frame, θ be the ballistic ground velocity inclination angle, and α be the angle of attack of the aircraft. To measure unsteady aerodynamic forces, wind tunnel tests need to simulate the angle of attack α and the pitch rate ω. zTwo motion quantities. To simulate flight response, the normal displacement y is simulated through wind tunnel testing. i Pitch angle Two levels of exercise.

[0097] The aircraft's body coordinate system coincides with the wind tunnel test model's body coordinate system, and the inertial frame coincides with the wind tunnel system. The position vector R of the two-degree-of-freedom support mechanism model in the wind tunnel system is... k Represented as:

[0098]

[0099] The velocity V of the two-degree-of-freedom support mechanism model in the wind tunnel system k Represented as:

[0100]

[0101] The wind tunnel wind speed V D In the wind tunnel system, it is represented as:

[0102] V D =[V w ,0,0]

[0103] The two-degree-of-freedom support mechanism model is represented in the wind tunnel system as follows:

[0104]

[0105] The ballistic airspeed tilt angle θ of the two-degree-of-freedom support mechanism model in the wind tunnel system s The calculation formula is:

[0106]

[0107] For a specific wind tunnel dynamic support mechanism, the motion equations for each degree of freedom of the two-degree-of-freedom support mechanism are established as follows:

[0108]

[0109]

[0110]

[0111]

[0112] In the formula, Let y be the pitch angle of the model under the support mechanism. s The normal displacement of the model is given by the function f, which is solved numerically and then linearly fitted. The horizontal displacement ΔX of the pitch slider is related to the model's pitch angle. The relationship is linear within the specified angular range.

[0113] Select the angle of attack α and the pitch angular velocity ω z Pitch angle With normal displacement y i Flight state simulation and flight response simulation were performed respectively, and the correspondence between the three-degree-of-freedom dynamic equations of the aircraft and the motion equations of the two-degree-of-freedom support mechanism was established as follows:

[0114]

[0115] The angle of attack α is simulated as an equivalent quantity to the ballistic ground velocity inclination angle θ:

[0116] θ s =θ

[0117] Specifically, the inverse solution is performed on the motion quantities of each degree of freedom of the two-degree-of-freedom support mechanism, as follows:

[0118] By calculating the three-degree-of-freedom dynamics of the aircraft Perform inverse kinematics to obtain the motion commands of the support mechanism.

[0119]

[0120] The inverse kinematics method yields the equations of motion for each degree of freedom of the two-degree-of-freedom support mechanism, which are obtained through the inverse kinematics method based on the correspondence between the aircraft dynamics equations and the support mechanism's equations of motion.

[0121] Support mechanism movement commands For unsteady aerodynamic measurement and flight response simulation, a cubic polynomial fitting method is used to simulate the displacement and velocity of a two-degree-of-freedom support mechanism, specifically:

[0122] ΔX=a0+a1t+a2t 2 +a3t 3

[0123] ΔY = b0 + b1t + b2t 2 +b3t 3

[0124] Specifically, the coefficients of the polynomial are obtained by differentiating the displacements and velocities at both ends of the actuation step.

[0125]

[0126]

[0127] In the formula, t represents the actuation time, t0 is the initial time, t1 is the terminal time, and the actuation time t∈[t0,t1]. After the solution is completed, the trajectory solution result of the wind tunnel model is calculated.

[0128] The motion quantity calculation of the three-degree-of-freedom dynamic equations of the aircraft is achieved based on the force balance and inertial navigation system installed on the two-degree-of-freedom support mechanism model. At the same time, the inertial force of the two-degree-of-freedom support mechanism model is measured and the aerodynamic force is calculated. The two-degree-of-freedom support mechanism model is also equipped with servo motors to realize flight response control.

[0129] The following description, in conjunction with the accompanying drawings and preferred embodiments, provides further details:

[0130] In the current embodiment, the method for simulating the geostationary correlation of a two-degree-of-freedom support mechanism is as follows: Figure 1 As shown in the diagram, the two-degree-of-freedom support mechanism is as follows: Figure 3 As shown, the steps are as follows:

[0131] (1) Construct the three-degree-of-freedom dynamic equations of the aircraft in the longitudinal plane. Where r t This represents the position vector of the aircraft in the volume coordinate system. This represents the relative velocity of the aircraft in the body coordinate system. ω z The pitch angle and pitch rate represent the pitch angle and pitch velocity of the aircraft system relative to the inertial frame, respectively, where m is the mass of the aircraft, and I is the velocity. z F is the moment of inertia of the aircraft's pitch axis. a The aerodynamic force acting on the aircraft can be measured by a force balance, F. d M represents other external forces acting on the aircraft, f represents the entrainment acceleration and Coriolis acceleration in the moving coordinate system, and M represents the other external forces acting on the aircraft. a The aerodynamic torque acting on the aircraft can be measured by a force balance, M. d This represents other external torques acting on the aircraft.

[0132]

[0133]

[0134]

[0135]

[0136]

[0137] F a =[F ax ,F ay ,0]F d =[F dx ,F dy ,0]

[0138] M a =[0,0,M azM d =[0,0,M dz ]

[0139] f = [f x ,f y ,0]ω=[0,0,ω z ]

[0140] r t =[x t ,y t ,0]

[0141] To establish the correspondence between the space and ground coordinate systems, coordinate transformation is used to convert the state quantities in the flight mechanical body coordinate system into state quantities in the inertial frame:

[0142] A T r t =r i

[0143] r i =[x i ,y i ,0]

[0144]

[0145]

[0146] Wherein, the transformation matrix from the inertial frame to the volume coordinate system is A, r i This represents the position vector of the aircraft in an inertial frame. Let θ represent the velocity of the aircraft in the inertial frame, θ be the ballistic ground velocity inclination angle, and α be the angle of attack of the aircraft. To measure unsteady aerodynamic forces, wind tunnel tests need to simulate the angle of attack α and the pitch rate ω. z Two motion quantities. To achieve flight response simulation, wind tunnel testing is needed to simulate the normal displacement y. i Pitch angle Two levels of exercise.

[0147] (2) Construct the equations of motion for the two-degree-of-freedom support mechanism. For example... Figure 2As shown, the model's coordinate system coincides with the aircraft's coordinate system, and the inertial frame coincides with the wind tunnel frame. The mechanism consists of two parts: a floating platform and a pitching platform. The floating platform and the pitching platform are connected to a horizontal slider via a rotating shaft and connecting rod. The horizontal movement of the slider can drive the connecting rod and the pitching platform to rotate around the floating platform's rotating shaft. l1 is the distance between the horizontal slider's rotating shaft and the pitching platform's rotating shaft, l2 is the distance between the pitching platform's connecting rod's rotating shaft and the pitching rotating shaft, l3 is the length of the connecting rod, l4 is the distance from the model's center of mass to the pitching platform's rotating shaft, l5 is the length of the floating platform, and l6 is the vertical distance from the horizontal slider's rotating shaft to the floating platform. ΔX and ΔY are the horizontal displacement of the pitching slider and the vertical displacement of the floating platform, respectively, representing the two movable degrees of freedom of the support mechanism.

[0148] Position vector R of the model in the wind tunnel k In a wind tunnel system, this can be represented as:

[0149]

[0150] The model's velocity V in the wind tunnel k In a wind tunnel system, this can be represented as:

[0151]

[0152] Wind speed V in the wind tunnel D In a wind tunnel system, this can be represented as:

[0153] V D =[V w ,0,0]

[0154] Therefore, the airspeed of the model in the wind tunnel can be expressed as:

[0155]

[0156] The model's airspeed tilt angle θ in the wind tunnel s The calculation formula is:

[0157]

[0158] For a specific wind tunnel dynamic support mechanism, the motion equations for each degree of freedom of the two-degree-of-freedom support mechanism are established:

[0159]

[0160]

[0161]

[0162]

[0163] in, Let y be the pitch angle of the model under the support mechanism.s Let be the normal displacement of the model. Since the function f is relatively complex, it can be solved numerically (Newton's method) and linearly fitted. The fitting results show that under small-angle motion, ΔX and... There is an approximately linear relationship.

[0164] (3) Select appropriate motion quantities to establish the correspondence between flight dynamics and the kinematics of the support mechanism's degrees of freedom. To achieve flight state simulation and unsteady aerodynamic force measurement, the angle of attack α and pitch angular velocity ω should be simulated. z To meet the requirements of flight response simulation, pitch angle should be simulated. With normal displacement y i Based on simulation criteria, the correspondence between flight dynamics quantities and the degrees of freedom of the support mechanism is constructed:

[0165]

[0166] α s =αy s =y i

[0167] Based on the correspondence between the flight dynamics equations and the mechanism motion equations, the simulation of the angle of attack α can be equivalent to the simulation of the ballistic ground velocity inclination angle θ, that is:

[0168] θ s =θ

[0169] (4) Based on the correspondence between the motion quantities of flight dynamics and the motion quantities of the support mechanism, the motion quantities of each degree of freedom of the support mechanism are solved inversely. Based on the correspondence, the four simulated quantities of flight mechanics are solved: It can be solved in reverse.

[0170]

[0171]

[0172] (5) Based on the inverse kinematics solution, the trajectory of the mechanism's degrees of freedom is calculated and planned to simulate the flight response. This is achieved through the inverse kinematics solution. The motion commands of the support mechanism are obtained, thereby enabling the simulation of unsteady aerodynamic forces and flight response. To ensure continuity of displacement and velocity in two degrees of freedom, a cubic polynomial fitting method can be used.

[0173] ΔX=a0+a1t+a2t 2 +a3t 3

[0174] ΔY = b0 + b1t + b2t 2 +b3t3

[0175] By taking the first and second derivatives of the time term in the above equation, and given the displacements and velocities of the two endpoints of the actuation step, the coefficients of the polynomial can be solved.

[0176]

[0177]

[0178] Where t represents the actuation time, t0 is the initial time, and t1 is the final time. After calculating the coefficients, the trajectory solution can be obtained. Where the actuation time t∈[t0,t1].

[0179] By combining different experimental similarity criteria, it can be fully applied to various fields suitable for this invention. To satisfy the similarity of projectile dynamics, the similarity law of the experimental model can be designed according to the above conditions. Since the gas compressibility is ignored in low-speed wind tunnel tests, the aerodynamic coefficients and aerodynamic moment coefficients of the experimental and real states are equal.

[0180] To ensure similar projectile attitude and motion, each scaling factor must satisfy the following:

[0181]

[0182]

[0183] To ensure similarity in the linear motion of the projectile's attitude, each scaling factor must satisfy the following:

[0184]

[0185]

[0186] The advantages of the principle and method designed in this patent are mainly reflected in the fact that the model is always in motion in the wind tunnel, and inertial force deduction and force measurement, inverse solution command calculation and motion trajectory planning are carried out. The influence of the model's motion velocity term on unsteady aerodynamic forces is fully considered, the simulated flight process is more realistic, and the correlation between space and ground is carried out based on similarity relationship. It is applicable to a variety of fluid-structure interaction dynamic tests.

[0187] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0188] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for simulating the correlation between space and ground in a two-degree-of-freedom support mechanism, characterized in that... include: Construct the three-degree-of-freedom dynamic equations of the aircraft in the longitudinal plane; Construct the equations of motion for the two-degree-of-freedom support mechanism; The dual-degree-of-freedom support mechanism includes a floating platform, a pitching platform, and a horizontal slider. The floating platform and the pitching platform are connected to the horizontal slider via a rotating shaft and a connecting rod. The movement of the horizontal slider causes the connecting rod and the pitching platform to rotate around the rotating shaft of the floating platform. The relevant parameters are as follows: This is the distance between the horizontal slider axis and the pitch stage axis. This represents the distance between the pitch stage linkage axis and the pitch axis. The length of the link. Let be the distance from the model's center of mass to the axis of rotation of the pitch stage. The length of the floating platform. This is the vertical distance from the horizontal slider's pivot to the floating platform. and The horizontal displacement of the pitch slider and the vertical displacement of the floating platform are the two movable degrees of freedom of the two-degree-of-freedom support mechanism. For a specific wind tunnel dynamic support mechanism, the motion equations for each degree of freedom of the two-degree-of-freedom support mechanism are established as follows: In the formula, The pitch angle of the model under the support mechanism. For the normal displacement of the model, the function The horizontal displacement of the pitch slider is solved numerically and linearly fitted. With model pitch angle The relationship is linear within the specified angular range; The motion quantities are selected to characterize the correspondence between the three-degree-of-freedom dynamic equations of the aircraft and the motion equations of the two-degree-of-freedom support mechanism; Based on the obtained correspondence, the motion quantities of each degree of freedom of the two-degree-of-freedom support mechanism are solved inversely. Based on the inverse kinematics results, the degrees of freedom in each direction of the two-degree-of-freedom support mechanism are calculated and planned to complete the simulation of the aircraft response; Select angle of attack With pitch angular velocity Pitch angle With normal displacement Flight state simulation and flight response simulation were performed separately, and the correspondence between the three-degree-of-freedom dynamic equations of the aircraft and the motion equations of the two-degree-of-freedom support mechanism was established as follows: ； The angle of attack The simulation is equivalent to the ballistic ground velocity inclination angle. Analog quantity: Specifically, the inverse solution is performed on the motion quantities of each degree of freedom of the two-degree-of-freedom support mechanism, as follows: By calculating the three-degree-of-freedom dynamics of the aircraft Perform inverse kinematics to obtain the motion commands of the support mechanism. : ： The motion equations of each degree of freedom of the two-degree-of-freedom support mechanism are determined by inverse solving the correspondence between the aircraft dynamics equations and the motion equations of the support mechanism.

2. The method for simulating the correlation between Earth and space in a two-degree-of-freedom support mechanism according to claim 1, characterized in that: The three-degree-of-freedom dynamic equations of the aircraft are established in the aircraft's body coordinate system, specifically as follows: In the formula, This represents the position vector of the aircraft in the volume coordinate system. This represents the relative velocity of the aircraft in the body coordinate system. Represents the pitch angle and pitch rate of the aircraft system relative to the inertial frame. For the mass of the aircraft, Let the moment of inertia be the pitch axis of the aircraft. The aerodynamic forces acting on the aircraft can be measured using a force balance. Other external forces acting on the aircraft Represents the entrainment acceleration and Coriolis acceleration in the moving coordinate system. The aerodynamic torque acting on the aircraft can be measured using a force balance. This represents other external torques acting on the aircraft.

3. The method for simulating the correlation between Earth and space in a two-degree-of-freedom support mechanism according to claim 2, characterized in that: The coordinate transformation is performed on the three-degree-of-freedom dynamic equations of the aircraft to obtain the state quantities in the inertial frame relative to the coordinate system of the flight mechanical body. Specifically: In the formula, the transformation matrix from the inertial frame to the volume coordinate system is: , This represents the position vector of the aircraft in an inertial frame. Represents the speed of the aircraft in an inertial frame. The ballistic ground velocity inclination angle, To measure the angle of attack of an aircraft and to achieve the measurement of unsteady aerodynamic forces, wind tunnel testing requires simulating the angle of attack. Pitch angular velocity To simulate flight response, two motion quantities were used, and the normal displacement was simulated through wind tunnel testing. Pitch angle Two levels of exercise.

4. The method for simulating the correlation between Earth and space in a two-degree-of-freedom support mechanism according to claim 3, characterized in that: The aircraft body coordinate system coincides with the wind tunnel model body coordinate system, the inertial frame coincides with the wind tunnel system, and the position vector of the two-degree-of-freedom support mechanism model in the wind tunnel system is... Represented as: Velocity of a two-degree-of-freedom support mechanism model in a wind tunnel Represented as: The wind tunnel wind speed In the wind tunnel system, it is represented as: The two-degree-of-freedom support mechanism model is represented in the wind tunnel system as follows: 。 5. The method for simulating the correlation between Earth and space in a two-degree-of-freedom support mechanism according to claim 4, characterized in that: The ballistic airspeed inclination angle of the two-degree-of-freedom support mechanism model in the wind tunnel system The calculation formula is: 。 6. The method for simulating the correlation between Earth and space in a two-degree-of-freedom support mechanism according to claim 5, characterized in that: The support mechanism movement command For unsteady aerodynamic measurement and flight response simulation, a cubic polynomial fitting method is used to simulate the displacement and velocity of a two-degree-of-freedom support mechanism, specifically: Specifically, the coefficients of the polynomial are obtained by differentiating the displacements and velocities at both ends of the actuation step. In the formula, Represents the time of action. At the initial moment, Terminal time, actuation time After the solution is completed, the trajectory solution result of the calculation model is obtained.

7. The method for simulating the correlation between Earth and space in a two-degree-of-freedom support mechanism according to claim 6, characterized in that: The motion calculation of the three-degree-of-freedom dynamic equations of the aircraft is based on the force balance and inertial navigation system installed on the two-degree-of-freedom support mechanism model. At the same time, the inertial force of the two-degree-of-freedom support mechanism model is measured and the aerodynamic force is calculated. The two-degree-of-freedom support mechanism model is also equipped with servo motors to realize flight response control.

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