A multi-dimensional force and position information perception method for simulated motion of aircraft model in dynamic derivative test

Abstract

The present invention belongs to the field of wind tunnel dynamic derivative tests of aircraft models, and discloses a multi-dimensional force and position information perception method for simulated motion of aircraft models in dynamic derivative tests. The method aims at high-frequency measurement of multi-dimensional transient forces under complex flow fields, proposes a force measurement and solution model based on a multi-dimensional force piezoelectric balance, and characterizes the instantaneous force state of the aircraft through the mapping relationship between multi-directional force and charge; considers the multi-size optimization method of the angle encoder positioner with spatial size constraints and positioning accuracy tolerance, and designs a three-degree-of-freedom angle monitoring layout with the positioner structure and the angle encoder-component transmission unit integrated; assembles a piezoelectric balance and an angle encoder, and builds a combined measurement integrated layout of the force and position state of the aircraft model; studies the force and position integrated calibration method of the measurement system, and constructs a force and position solution model of the measurement center-center of mass of the aircraft model, so as to realize the real-time and accurate characterization of the spatial force and position state of the aircraft.

Description

Technical Field

[0001] The invention belongs to the field of wind tunnel dynamic derivative tests of aircraft models, and relates to a multi-dimensional force and position information perception method for simulated motion of an aircraft model in a dynamic derivative test. Background Art

[0002] The high-speed wind tunnel dynamic derivative test is the main means of evaluating the dynamic stability of highly maneuverable aircraft. Its core is to measure the aerodynamic force of the model with high reliability and high precision when the scaled model simulates the motion state. However, the allowable test space of the high-speed aircraft model is small, the high-speed flow field duration is short, the aerodynamic force / angular displacement to be measured has many dimensions and high frequency, which makes the aerodynamic force / angular displacement difficult or even impossible to measure, and it is difficult to ensure the accuracy and reliability of the dynamic derivative test data. Therefore, in order to ensure the accurate evaluation of the dynamic stability of highly maneuverable aircraft, it is of great significance to study the multi-degree-of-freedom force and position information perception method in the dynamic derivative test.

[0003] In the paper "Analysis of Unsteady Thrust Generation in Pulse Detonation Engines", Joshi et al. from the Aerodynamics Research Center of the University of Arlington proposed a piezoelectric balance force measurement system that compensates for the inertial effect, aiming at the problem of low measurement accuracy of aerodynamic load measurement in hypersonic pulse wind tunnels due to the influence of inertial effects. This force measurement system achieves high-precision measurement of single-dimensional dynamic forces in hypersonic environments, but it still has deficiencies in comprehensive force and position measurement. In the paper "Investigation on dynamic derivative test technique in hypersonic wind tunnel", Liu Jin et al. from the China Academy of Aerospace Aerodynamics (CAAA) proposed a combined force and position information measurement method based on a strain balance and a flexible hinge in order to meet the needs of studying the unsteady state and longitudinal / lateral coupled aerodynamic characteristics of aerospace vehicles. This measurement system can realize the integrated measurement of force and position information. However, obtaining the attitude angle through the hinge results in high mechanical damping, which affects the measurement accuracy.

[0004] At present, the force and position measurements in dynamic derivative tests are mostly measured independently using existing finished products. However, the existing force measuring devices are unable to achieve high-frequency transient multi-dimensional aerodynamic force measurement under the constraints of limited installation geometric space (mm level) and limited test time (ms level). The existing attitude measurement devices require a large-scale space to be implemented, and the sensor response of the measuring elements is low and is not suitable for multi-dimensional transient attitude measurement occasions. Therefore, there is an urgent need for a small and highly intensive multi-dimensional force and position state measurement method for aircraft models. Summary of the invention

[0005] The present invention overcomes the shortcomings of existing methods and proposes a method for sensing multi-dimensional force and position information under simulated motion of an aircraft. First, the method aims at high-frequency measurement of multi-dimensional transient forces under complex flow fields, proposes a force measurement and solution model based on a multi-dimensional force piezoelectric balance, and characterizes the instantaneous force state of the aircraft through the mapping relationship between multi-directional force and charge; secondly, a multi-size optimization method of the angle encoder positioner is used to consider the spatial size constraints and positioning accuracy tolerance, and a three-degree-of-freedom angle monitoring layout integrating the positioner structure and the angle encoder-component transmission unit is designed; then, the piezoelectric balance and the angle encoder are assembled to build a combined measurement integrated layout of the force and position state of the aircraft model; finally, the force and position integrated calibration method of the measurement system is studied, and a force and position solution model of the measurement center-the center of mass of the aircraft model is constructed to realize real-time and accurate characterization of the spatial force and position state of the aircraft. This method can ensure high-reliability and high-precision measurement of the model force and position state information in high-speed wind tunnel dynamic derivative tests, and accurately evaluate the dynamic stability of highly maneuverable aircraft.

[0006] Technical solution of the present invention:

[0007] A method for sensing multi-dimensional force and position information of simulated motion of an aircraft model in a dynamic derivative test. First, a multi-dimensional force calibration platform is built, and a multi-directional excitation test is carried out on a multi-dimensional force piezoelectric balance to collect and obtain multi-directional force-charge time-frequency domain data; a force measurement and solution model is obtained by a polynomial fitting method to characterize the instantaneous force state of the aircraft; an angle monitoring layout is designed to form an angle encoder positioner structure and an integrated layout of an angle encoder-component transmission unit, and key dimensions and tolerances are designed; a welding fixture for an angle encoder is designed to form a multi-degree-of-freedom angle monitoring layout; a combined measurement integrated layout of the model force and position state is constructed, and a force and position integrated calibration method is studied to realize the conversion from the measurement axis coordinate system to the model axis coordinate system, and to obtain a real-time and accurate representation of the space force and position state of the aircraft;

[0008] The specific steps are as follows:

[0009] 1) Build a multi-dimensional force calibration platform, conduct multi-directional excitation tests on multi-dimensional force piezoelectric balances, collect time-frequency domain data of multi-directional force-charge, and draw time-domain mapping curves and frequency-domain response curves; select multiple fixed-frequency loading signals for parameter fitting, and obtain the frequency variation function of the parameters through polynomial fitting; select the swept frequency loading function, conduct wide-frequency domain continuous excitation tests, obtain multi-directional charge responses, and optimize the parameters of the fitting polynomial;

[0010] 1.1) Build a multi-dimensional force calibration platform, conduct multi-directional excitation tests on the multi-dimensional force piezoelectric balance, and collect multi-directional force-charge time-frequency domain data; fix the multi-dimensional force test adapter to the multi-dimensional force piezoelectric balance through a cone surface; install the multi-dimensional force piezoelectric balance to the adapter of the dynamic derivative testing machine; connect the other end of the dynamic derivative testing machine to the mechanism mobile horizontal fixture, and then install the mechanism mobile horizontal fixture on the vibration table base through a slide rail and push it to the force measurement area; install multiple exciters to the vibration table base, and fit the spherical arc of the exciter with the spherical arc of the multi-dimensional force test adapter. The construction of the multi-dimensional force calibration platform is now completed. Its structural diagram is shown in the figure below. Figure 2 As shown;

[0011] Multiple exciters apply loads in different directions. By comparing the force signal feedback from the exciter with the multi-channel charge signals collected by the multi-dimensional force piezoelectric balance, a multi-directional force-charge time domain fixed-frequency data set is obtained; the function form of the load is shown in the following formula:

[0012]

[0013] Among them, F represents the load, A and f are the amplitude and frequency of the load, and t is the time variable;

[0014] 1.2) Draw the time domain mapping curve and frequency domain response curve based on the time-frequency domain data of multi-directional force-charge. Based on the time-domain fixed-frequency data set of multi-directional force-charge, linearly fit the curve in a single direction to determine the various coefficients; the coefficient matrix is ​​as follows:

[0015] F = [ F x F y F z M x M y M z ] = [ a 1 x a 2 x a 3 x a 4 x a 5 x a 6 x a 1 y a 2 y a 3 y a 4 y a 5 y a 6 y a 1 z a 2 z a 3 z a 4 z a 5 z a 6 z b 1 x b 2 x b 3 x b 4 x b 5 x b 6 x b 1 y b 2 y b 3 y b 4 y b 5 y b 6 y b 1 z b 2 z b 3 z b 4 z b 5 z b 6 z ] [ C 1 C 2 C 3 C 4 C 5 C 6 ] = BC

[0016] Among them, the subscripts x, y, and z represent the yaw, roll, and pitch directions respectively; , , , , , Respectively represent the load force and moment in the yaw, roll and pitch directions; C 1~6 represents the six-way charge; a, b are the coefficients of load force and torque respectively; F is the multidimensional force vector; B is the coefficient matrix; C is the charge vector;

[0017] 1.3) Select loads of multiple frequencies to perform isotropic coefficient fitting respectively, and obtain the isotropic coefficient matrix at different frequencies. The function of the coefficient changing with frequency is fitted by polynomial:

[0018]

[0019] in, is the parameter matrix of the polynomial, and its dimension is the same as the coefficient matrix; is the isotropic coefficient matrix of the polynomial output; f is the frequency of the load;

[0020] Thus, a multi-directional force-charge mapping function is formed, which can realize the solution of the multi-dimensional force on the multi-dimensional force piezoelectric balance at different frequencies. The mapping function form is shown in the following formula (4):

[0021]

[0022] 1.4) Select the frequency domain continuous excitation test of the swept frequency loading signal to obtain the time domain data of the multi-directional charge signal and the load data of multiple exciters, and establish a time domain swept frequency data set. The form of the swept frequency loading signal is shown in the following formula:

[0023]

[0024] Where A represents the load amplitude, is the rate of frequency change;

[0025] 1.5) Based on the above-mentioned time-domain frequency sweep data set, a frequency identification window with a length of ξ is established, the collected multi-directional charge signal is tracked online, and the multi-directional charge signal in the window is subjected to a fast Fourier transform to calculate the frequency of the multi-directional charge signal stage time. The frequency and the multi-directional charge signal are substituted into the mapping function of formula (4). By comparing the load data of the exciter in the time-domain frequency sweep data set with the output F of the mapping function, the parameter matrix is ​​optimized. , ensuring the high adaptability of the mapping relationship under real-time variable frequency load;

[0026] 2) Design an angle monitoring layout to meet the needs of high-precision measurement of multi-DOF angular displacement in narrow spaces, and form an integrated layout of angle encoder-positioner-component transmission unit; consider the measurement and positioning requirements, determine the positioning form, and design key dimensions and tolerances; design a welding fixture to ensure the positioning accuracy of the photosensitive element in the reading head during circuit welding, and weld the reading head; finally install the reading head and grating code disk to achieve real-time measurement of multi-DOF angular displacement;

[0027] 2.1) Design the angle monitoring layout for the needs of high-precision measurement of multi-degree-of-freedom angular displacement in narrow space, and design the integrated layout of the positioner and angle encoder-component transmission unit. The main view, side view and bottom view of the pitch and yaw layout are respectively Figure 6 , 7 , 8, the main view and the bottom view of the rolling layout are Fig. 9 , Fig.10 As shown;

[0028] The angle encoder adopts a split grating encoder, which includes a reading head and a grating code disk. The reading head is composed of a photosensitive element and a PCB board. The reading head and the grating code disk need to be installed separately; the positioner includes a limit frame, a positioning pin and a pre-tightening bolt. The right-angle side of the reading head is positioned by the edge line of the limit frame, and it is fixed to the limit frame by screws. The positioning pin on the positioner is inserted into the positioning installation hole and tightened by the pre-tightening bolt, thereby fixing the reading head in the working position; for the reading heads in the three directions of pitch, yaw and roll, two positioners are designed, wherein the roll side positioner is used to position the reading head in the roll direction, and the yaw and pitch side positioners are used to position the reading heads in the yaw and pitch directions;

[0029] Three groups of angle encoders are used to monitor the pitch, yaw and roll directions respectively. The grating code disks of the three groups of angle encoders are fixed to the rotor end of roll, the rotor end of yaw and the stator end of pitch respectively. The positioning and mounting holes and pre-tightening holes of the roll side positioner are processed to the back side of the yaw bow axis, and the positioning and mounting holes and pre-tightening holes of the yaw and pitch directions are processed to the inner side of the vibration cylinder. The positioning pins on the two positioners are respectively installed in the corresponding positioning and mounting holes, and are tightened by pre-tightening bolts.

[0030] 2.2) Taking into account the measurement and positioning requirements, the positioning form is determined by plane limit, and the key dimensions and tolerances are designed based on the positioning form to ensure that the positioning error is within the tolerance range; the accuracy mapping model is shown in the following formula (6):

[0031] ( Δ d 1 Δ d 2 Δ d 3 cot Δ α cot Δ β ) = [ 0 0 0 1 − 1 0 0 0 0 0 − 1 1 0 0 1 0 0 0 1 0 0 0 0 0 − 1 0 0 0 0 0 0 0 0 0 1 / d 2 0 0 0 0 0 0 0 0 0 1 / d 1 ] ( Δ X 1 Δ X 2 Δ X 3 Δ X 4 Δ X 5 Δ X 6 Δ X 7 x 1 x 2 )

[0032] in, is the positioning dimension between the photosensitive element and the grating code disk, is the required positioning tolerance between the photosensitive element and the grating code disk in three directions, α and β are the required skew angle tolerances of the photosensitive element and the grating code disk respectively; To monitor the positioning dimension tolerance in the layout for angles; is the verticality tolerance; the specific positioning relationship of the angle encoder is as follows Figure 4 , 5 As shown;

[0033] 2.3) Obtain the reading head by welding the PCB board and the photosensitive element, design the welding fixture and dimensional tolerance. The welding fixture includes a welding positioning fixture and a fixture base. During the welding process, place the PCB board on the fixture base, and align its right-angled edge with the fixture limit block inside the fixture base. Then align the welding positioning fixture to the fixture limit block outside the fixture base and fix it with screws. Then fit the right-angled edge of the photosensitive element to the inner right-angled edge of the welding positioning fixture and weld it. By designing the dimensional tolerance of the welding positioning fixture and the fixture base, the welding positioning accuracy is ensured. Finally, the welded reading head is installed on the locator to form a three-degree-of-freedom angle monitoring layout;

[0034] 3) By installing a multi-dimensional force piezoelectric balance at the front end of the dynamic derivative test mechanism and a three-degree-of-freedom angular displacement monitoring layout at the middle rotation center of the dynamic derivative test mechanism, a combined measurement layout of the force and position state of the aircraft model is formed, and a force-position integrated calibration method is constructed to realize the conversion from the measurement value of the dynamic derivative test mechanism to the measurement value of the force and position state of the aircraft model;

[0035] 3.1) Install the angle encoder at the rotation center of the dynamic derivative test mechanism, and together with the multi-dimensional force piezoelectric balance at the front end of the dynamic derivative test mechanism, form a combined measurement layout of the force and position state of the aircraft model; install the combined measurement layout on the multi-dimensional force calibration platform to form a force and position calibration test system;

[0036] 3.2) Construct a force-position integrated calibration method, and conduct a multi-degree-of-freedom loading excitation test on the dynamic derivative test mechanism. The excitation point is selected as the front end of the multi-dimensional force piezoelectric balance. Since the measurement center is coaxial with the rotation axis, it is considered that the measurement and rotation centers are concentric. The geometric error between the measurement center and the actual center of mass is e = [ e x , e y , e z ] T , through the moment balance formula, the geometric error is quantitatively solved and the formula is as follows:

[0037]

[0038] in, is the torque measurement value of the i-th degree of freedom, is the actual value of the rotational acceleration torque of the aircraft model. is the moment of inertia of the ith degree of freedom about the centroid axis, is the rotational angular acceleration of the i-th degree of freedom, is the actual aircraft model mass, is the geometric error between the measured center and the actual center of mass in the i-th degree of freedom;

[0039] 3.3) Based on the obtained The force and position state of the aircraft model measured by the force and position calibration test system is corrected to obtain the solution model of the force and position state of the aircraft model, so as to realize the accurate perception of the force and position information; the solution model is shown in the following formula:

[0040]

[0041] in, is the torque measuring aerodynamic moment of the ith degree of freedom, is the angular velocity of the measured i-th degree of freedom, is the rotation angular velocity of the i-th degree of freedom; the force and position state of the aircraft model is obtained through the rotation angle and torque measurement value of the dynamic derivative test mechanism, and the perception of multi-dimensional force and position information is realized.

[0042] The beneficial effects of the present invention are to provide a method for sensing multi-dimensional force and position information of coupled motion of an aircraft model, taking into account the narrow closed test space, multi-dimensional high dynamics of measurement force, and high-frequency time-varying attitude angle in the dynamic derivative experiment. Compared with the problems of insufficient dynamic measurement capability and low spatial integration of traditional methods, the method proposed in the present invention can form a combined measurement integrated layout of the force and position state of the aircraft model in the narrow closed space of the high-speed wind tunnel dynamic derivative test mechanism, and solve the dynamic information of the multi-dimensional force and position of the aircraft model in real time. In the multi-degree-of-freedom dynamic derivative test in the high-speed wind tunnel, the measurement response is fast, the accuracy is high, and the dynamic derivative solution effect is good, which can ensure reliable evaluation of dynamic stability and can be applied to many types of wind tunnel tests and aircraft model support systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flowchart of the multi-dimensional force position information perception method in the dynamic derivative test of the present invention.

[0044] Figure 2 It is a structural schematic diagram of the multi-dimensional force calibration platform in the present invention.

[0045] Figure 3 It is a schematic diagram of the layout of the three-degree-of-freedom angular displacement monitoring system of the present invention.

[0046] Figure 4 It is a front view showing the positioning relationship of the angle encoder of the present invention.

[0047] Figure 5 It is a side view of the positioning relationship of the angle encoder of the present invention.

[0048] Figure 6 It is a front view of the pitch and yaw angle monitoring arrangement of the present invention.

[0049] Figure 7 It is a side view of the pitch and yaw angle monitoring arrangement of the present invention.

[0050] Figure 8 This is a bottom view of the pitch and yaw angle monitoring arrangement of the present invention.

[0051] Fig. 9 It is a side view of the roll angle monitoring arrangement of the present invention.

[0052] Fig.10 This is the front view of the roll angle monitoring layout of the present invention.

[0053] Fig.11 A top view of the geometric positioning layout of the angle encoder photosensitive element and the PCB board of the present invention

[0054] Fig.12 This is the front view of the geometric positioning layout of the angle encoder photosensitive element and the PCB board of the present invention

[0055] Fig.13 The figure is a schematic diagram of the structure of the auxiliary welding locator between the angle encoder photosensitive element and the PCB board of the present invention.

[0056] Fig.14 This is a diagram showing the measurement results of the three-dimensional torque of the present invention.

[0057] Fig.15 This is a diagram showing the measurement results of the three-dimensional force of the present invention.

[0058] Fig.16 This is a diagram showing the measurement results of the three-dimensional angle quantity of the present invention.

[0059] In the figure: 1-exciter, 2-excitation table base, 3-multi-dimensional force test adapter, 4-dynamic derivative test mechanism, including multi-dimensional force piezoelectric balance, 5-mechanism moving horizontal fixture, 6-multi-dimensional force piezoelectric balance, 7-pitch angle encoder, 8-roll angle encoder, 9-yaw angle encoder, 10-yaw bow axis, 11-vibration cylinder, 12-roll axis rotor, 13-yaw pitch side positioner, 14-pitch side reading head, 15-pitch side grating code disk, 16-yaw side reading head, 17-yaw side grating code disk, 18-roll side positioner, 19-roll side reading head, 20-roll side grating code disk, 21-angle encoder photosensitive element, 22-PCB circuit board, 23-welding positioning fixture, 24-fixture limit block, 25-fixture base. DETAILED DESCRIPTION

[0060] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments and drawings.

[0061] Example

[0062] Considering that the wind tunnel model is subjected to single-degree-of-freedom excitation for the three degrees of freedom of pitch, yaw and roll, a multi-degree-of-freedom force and position state perception experiment is carried out based on a combined measurement scheme of a front six-dimensional force piezoelectric balance and a central three-degree-of-freedom angular displacement monitoring layout. The specific steps are as follows:

[0063] Step 1: Multi-dimensional calibration platform construction and calibration

[0064] Based on the laboratory environment, a multi-dimensional force calibration platform is built, including a multi-dimensional force piezoelectric balance, a dynamic derivative testing machine, a mobile horizontal fixture, and a vibration table base. Firstly, a multi-directional excitation test is carried out on the multi-dimensional force piezoelectric balance. Three orthogonal excitation directions of X, Y and Z are set. Single-degree-of-freedom loading is performed on the three degrees of freedom of pitch, yaw and roll respectively. A fixed-frequency loading signal is set in each direction, and the time-frequency signal of the output charge is collected. The signal function form is shown in formula (1). Based on the time domain analysis results, the mapping relationship between force and charge in different directions at the same frequency is determined, and the coefficient matrix in formula (2) is fitted. Then, based on the frequency domain signal, the change of the coefficient matrix at different frequencies is determined to ensure that the force-charge mapping relationship at different frequencies is still accurate. The functional relationship of the coefficient matrix with frequency is shown in formula (3). In order to prevent overfitting, a wide-band continuous excitation test is carried out. The signal function form is shown in formula (5). By establishing a frequency identification window and updating the frequency information through Fourier transform fixed samples, the frequency and multi-directional charge signal are substituted into the mapping function of formula (4), and the parameter matrix in formula (3) is further optimized to improve the frequency domain applicability of the mapping relationship.

[0065] Step 2: Positioning design and calibration of three-degree-of-freedom angular displacement monitoring system

[0066] In order to achieve high-precision angular position monitoring in a narrow space, first of all, facing the small size demand, based on the angle encoder, which is composed of a grating code disk, a photosensitive element and a PCB board, the angle encoder-locator-component transmission unit is integrated to achieve an overall miniaturized and intensive layout; the guide groove on the locator is designed to cooperate with the limit block / limit pin and other limit elements to locate the angle measurement system, and the dimension chain analysis of the relevant dimensions of all components is performed to ensure that the cumulative error of all parts is within the allowable range, and the manufacturing tolerance of each dimension is reasonably allocated to ensure the overall positioning accuracy; finally, in order to meet the requirements of high-precision measurement of the angle monitoring device, the alignment accuracy between the photosensitive element and the PCB is set to be at least less than 5 microns, and the size and tolerance of the welding fixture are designed to achieve high positioning accuracy welding processing. After the processing is completed, the angle encoders are installed in the pitch, yaw and roll directions of the angular displacement measurement locator to form a three-degree-of-freedom angle monitoring layout to ensure multi-degree-of-freedom measurement in a narrow space.

[0067] Step 3: Overall calibration of the multi-dimensional force measurement system

[0068] An integrated layout for combined measurement of the force and position state of the aircraft model is constructed, with the angle encoder installed at the rotation center of the dynamic derivative test mechanism, and the multidimensional force piezoelectric balance installed at the front end of the dynamic derivative test mechanism; the combined measurement layout is installed on the multidimensional force calibration platform to form a force and position calibration test system; a multi-degree-of-freedom loading and vibration test is carried out on the mechanism, and the force and position measurement data and loading signals are recorded. By comparing the measured torque value with the theoretical value under a single degree of freedom, the geometric error from the measurement center to the model center of mass under this degree of freedom is calculated, and the conversion from the measurement center to the model center of mass is completed; the force and position state data of the aircraft model is obtained, and high-frequency perception of the aircraft space force and position information is realized.

[0069] The present invention provides a multi-dimensional force and position information perception method for the coupled motion of an aircraft model in a wind tunnel experiment in a small space. Compared with the traditional method, the present invention overcomes the shortcomings of insufficient dynamic measurement capability and low spatial integration. Through the combined measurement integrated layout, the multi-dimensional force and position dynamic information of the model can be solved in real time in the limited space of a high-speed wind tunnel dynamic derivative test mechanism. In the multi-degree-of-freedom high-speed wind tunnel dynamic derivative test, the present invention has the characteristics of fast response, high measurement accuracy, and excellent dynamic derivative solution effect, ensuring a reliable evaluation of dynamic stability, and is applicable to a variety of wind tunnel tests and model support systems.

Claims

1. A method for sensing multi-dimensional force and position information of simulated motion of an aircraft model in a dynamic derivative test, characterized in that: Here are the steps: 1) Build a multi-dimensional force calibration platform, conduct multi-directional excitation tests on multi-dimensional force piezoelectric balances, collect time-frequency domain data of multi-directional force-charge, and draw time-domain mapping curves and frequency-domain response curves; select multiple fixed-frequency loading signals for parameter fitting, and obtain the frequency variation function of the parameters through polynomial fitting; select the swept frequency loading function, conduct wide-frequency domain continuous excitation tests, obtain multi-directional charge responses, and optimize the parameters of the fitting polynomial; 1.1) Build a multi-dimensional force calibration platform, conduct multi-directional excitation tests on multi-dimensional force piezoelectric balances, and collect multi-directional force-charge time-frequency domain data; The multi-dimensional force test adapter is fixedly connected to the multi-dimensional force piezoelectric balance through a conical surface; Install the multi-dimensional force piezoelectric balance to the adapter of the dynamic derivative testing machine; connect the other end of the dynamic derivative testing machine to the mechanism mobile horizontal fixture, then install the mechanism mobile horizontal fixture on the vibration table base through the slide rail, and push it to the force measurement area; install multiple exciters to the vibration table base, fit the ball arc of the exciter with the ball arc of the multi-dimensional force test adapter, and the multi-dimensional force calibration platform is completed; Multiple exciters apply loads in different directions. By comparing the force signal feedback from the exciter with the multi-channel charge signals collected by the multi-dimensional force piezoelectric balance, a multi-directional force-charge time-domain fixed-frequency data set is obtained; the function form of the load is shown in the following formula: Among them, F represents the load, A and f are the amplitude and frequency of the load, and t is the time variable; 1.2) Draw the time domain mapping curve and frequency domain response curve based on the time-frequency domain data of multi-directional force-charge. Based on the time-domain fixed-frequency data set of multi-directional force-charge, linearly fit the curve in a single direction to determine the various coefficients; the coefficient matrix is ​​as follows: Among them, the subscripts x, y, and z represent the yaw, roll, and pitch directions respectively; , , , , , Respectively represent the load force and moment in the yaw, roll and pitch directions; C 1~6 represents the six-way charge; a, b are the coefficients of load force and torque respectively; F is the multidimensional force vector; B is the coefficient matrix; C is the charge vector; 1.3) Select loads of multiple frequencies to perform isotropic coefficient fitting respectively, and obtain the isotropic coefficient matrix at different frequencies. The function of the coefficient changing with frequency is fitted by polynomial: in, is the parameter matrix of the polynomial, and its dimension is the same as the coefficient matrix; is the isotropic coefficient matrix of the polynomial output; f is the frequency of the load; Thus, a multi-directional force-charge mapping function is formed, which can realize the solution of the multi-dimensional force on the multi-dimensional force piezoelectric balance at different frequencies. The mapping function form is shown in the following formula (4):

1. 4) Select the frequency domain continuous excitation test of the swept frequency loading signal to obtain the time domain data of the multi-directional charge signal and the load data of multiple exciters, and establish the time domain swept frequency data set. The form of the swept frequency loading signal is shown in the following formula: Where A represents the load amplitude, is the rate of frequency change; 1.5) Based on the above-mentioned time-domain frequency sweep data set, a frequency identification window with a length of ξ is established, the collected multi-directional charge signal is tracked online, and the multi-directional charge signal in the window is subjected to a fast Fourier transform to calculate the frequency of the multi-directional charge signal stage time. The frequency and the multi-directional charge signal are substituted into the mapping function of formula (4). By comparing the load data of the exciter in the time-domain frequency sweep data set with the output F of the mapping function, the parameter matrix is ​​optimized. , ensuring the high adaptability of the mapping relationship under real-time variable frequency load; 2) Design an angle monitoring layout to meet the needs of high-precision measurement of multi-DOF angular displacement in narrow spaces, and form an integrated layout of angle encoder-positioner-component transmission unit; consider the measurement and positioning requirements, determine the positioning form, and design key dimensions and tolerances; design a welding fixture to ensure the positioning accuracy of the photosensitive element in the reading head during circuit welding, and weld the reading head; finally install the reading head and grating code disk to achieve real-time measurement of multi-DOF angular displacement; 2.1) Design an angle monitoring layout to meet the needs of high-precision measurement of angular displacements in narrow spaces and with multiple degrees of freedom, and design an integrated layout of the angle encoder-positioner-component transmission unit. The angle encoder adopts a split grating encoder, which includes a reading head and a grating code disk. The reading head consists of a photosensitive element and a PCB board, and the reading head and the grating code disk need to be installed separately; the positioner includes a limit frame, a positioning pin and a pre-tightening bolt. The right-angle side of the reading head is positioned by the edge line of the limit frame, and it is fixed to the limit frame by screws. The positioning pin on the positioner is inserted into the positioning mounting hole and tightened by the pre-tightening bolt, thereby fixing the reading head in the working position; two positioners are designed for the reading heads in the three directions of pitch, yaw and roll, of which the roll side positioner is used to position the reading head in the roll direction, and the yaw and pitch side positioners are used to position the reading heads in the yaw and pitch directions; Three groups of angle encoders are used to monitor the pitch, yaw and roll directions respectively. The grating code disks of the three groups of angle encoders are fixed to the roll rotor end, the roll rotor end and the pitch stator end respectively. The positioning and mounting holes and pre-tightening holes of the roll side positioner are processed to the back side of the yaw bow axis, and the positioning and mounting holes and pre-tightening holes of the yaw and pitch directions are processed to the inner side of the vibration cylinder. The positioning pins on the two positioners are respectively installed in the corresponding positioning and mounting holes, and are tightened by pre-tightening bolts. 2.2) Taking into account the measurement and positioning requirements, the positioning form is determined by plane limit, and the key dimensions and tolerances are designed based on the positioning form to ensure that the positioning error is within the tolerance range; the accuracy mapping model is shown in the following formula (6): in, is the positioning dimension between the photosensitive element and the grating code disk, The required positioning tolerances in three directions between the photosensitive element and the grating code disk; α and β are the required skew angle tolerances of the photosensitive element and the grating code disk respectively; To monitor the positioning dimension tolerance in the layout for angles; is the verticality tolerance; 2.3) Obtain the reading head by welding the PCB board and the photosensitive element, design the welding fixture and dimensional tolerance. The welding fixture includes a welding positioning fixture and a fixture base. During the welding process, place the PCB board on the fixture base, and align its right-angled edge with the fixture limit block inside the fixture base. Then align the welding positioning fixture to the fixture limit block outside the fixture base and fix it with screws. Then fit the right-angled edge of the photosensitive element to the inner right-angled edge of the welding positioning fixture and weld it. By designing the dimensional tolerance of the welding positioning fixture and the fixture base, the welding positioning accuracy is ensured. Finally, the welded reading head is installed on the locator to form a three-degree-of-freedom angle monitoring layout; 3) By installing a multi-dimensional force piezoelectric balance at the front end of the dynamic derivative test mechanism and a three-degree-of-freedom angular displacement monitoring layout at the middle rotation center of the dynamic derivative test mechanism, a combined measurement layout of the force and position state of the aircraft model is formed, and a force-position integrated calibration method is constructed to realize the conversion from the measurement value of the dynamic derivative test mechanism to the measurement value of the force and position state of the aircraft model; 3.1) Install the angle encoder at the rotation center of the dynamic derivative test mechanism, and together with the multi-dimensional force piezoelectric balance at the front end of the dynamic derivative test mechanism, form a combined measurement layout of the force and position state of the aircraft model; install the combined measurement layout on the multi-dimensional force calibration platform to form a force and position calibration test system; 3.2) Construct a force-position integrated calibration method, and conduct a multi-degree-of-freedom loading excitation test on the dynamic derivative test mechanism. The excitation point is selected as the front end of the multi-dimensional force piezoelectric balance. Since the measurement center is coaxial with the rotation axis, it is considered that the measurement and rotation centers are concentric. The geometric error between the measurement center and the actual center of mass is , through the moment balance formula, the geometric error is quantitatively solved and the formula is as follows: in, is the torque measurement value of the i-th degree of freedom, is the actual value of the rotational acceleration torque of the aircraft model. is the moment of inertia of the ith degree of freedom about the centroid axis, is the rotational angular acceleration of the i-th degree of freedom, is the actual aircraft model mass, is the geometric error between the measured center and the actual center of mass in the i-th degree of freedom; 3.3) Based on the obtained The force and position state of the aircraft model measured by the force and position calibration test system is corrected to obtain the solution model of the force and position state of the aircraft model, so as to realize the accurate perception of the force and position information; the solution model is shown in the following formula: in, is the torque measuring aerodynamic moment of the ith degree of freedom, is the angular velocity of the measured i-th degree of freedom, is the rotation angular velocity of the i-th degree of freedom; the force and position state of the aircraft model is obtained through the rotation angle and torque measurement value of the dynamic derivative test mechanism, and the perception of multi-dimensional force and position information is realized.

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