A piezoelectric-driven high-frequency forced vibration dynamic derivative test method in a tail strut cavity

Abstract

The present invention belongs to the field of dynamic stability derivative measurement, and discloses a tail strut-type cavity high-frequency forced vibration dynamic derivative test method based on piezoelectric drive. Based on the test technical indicators and according to the power matching principle, the driver is selected; a high-frequency anti-backlash actuation mode with symmetrical distribution of actuators and bidirectional alternating actuation is proposed, which greatly reduces the gap in the transmission process and has the ability to continuously adjust the excitation amplitude and frequency; based on the piezoelectric actuation mode design and optimization of the rotary excitation transmission structure, it is realized that the linear micro-displacement is converted into a reciprocating swing of a single degree of freedom in a confined space; a high-frequency excitation module, a low-damping angular displacement monitoring module and a multi-dimensional force measurement module are built in the cavity of a high-speed aircraft model, which improves the accuracy of the dynamic derivative test data measurement; by collecting the angular displacement and multi-dimensional aerodynamic data of the model, the solution of multiple types of dynamic derivative data is realized, and the dynamic derivative test of the aircraft model is completed.

Description

Technical Field

[0001] The invention belongs to the field of dynamic stability derivative measurement, and relates to a tail strut type cavity high frequency forced vibration dynamic derivative test method based on piezoelectric drive. Background Art

[0002] With the development of aircraft, modern flight missions have put forward higher requirements for flight quality. For example, advanced fighters are required to have high maneuverability, while civil aircraft focus on comfort. As an important indicator of aircraft performance, dynamic stability requires accurate quantitative analysis in the design stage to ensure the effectiveness of the design. The dynamic derivative test solves various dynamic derivatives through wind tunnel tests, and has the ability to accurately evaluate the dynamic stability of the aircraft shape. It has become an indispensable test link in the model development process. The precise measurement of the dynamic derivatives of the aircraft model has a profound impact on the effectiveness of the design and has become an increasingly important issue.

[0003] However, in the current field of high-speed dynamic derivative tests, the existing dynamic derivative test technology has gradually failed to meet the needs. First, traditional test devices often combine motors with cams or various transmission rod groups to convert rotational motion into reciprocating motion of the model. During high-frequency actuation, the gap between the rods will cause deformation and lag in motion, affecting the accuracy of dynamic derivative tests; second, traditional test technology often uses flexible hinges as an angle measurement method. If the test Mach number is high, its mechanical damping will reduce the accuracy of aerodynamic damping measurement, thereby affecting the test accuracy; finally, if this type of excitation method wants to adjust the amplitude, the test can only be suspended to replace the rods, which seriously affects the test efficiency. Especially with the development of continuous wind tunnel technology, traditional test technology has become the main factor restricting the efficiency of dynamic stability assessment. Therefore, there is an urgent need for a small gap, low damping, and amplitude-adjustable test device that can be used in high-speed wind tunnels. It can drive the model to achieve a variety of vibration conditions under high-speed complex flow fields, and accurately obtain the model vibration angular displacement and aerodynamic force at the same time, obtain accurate and effective dynamic derivatives, and provide reliable characteristic data feedback for the aerodynamic shape design of cutting-edge aircraft.

[0004] In 2017, Liu Jin's team from the China Academy of Aerospace Aerodynamics published a paper titled "Hypersonic Wind Tunnel Dynamic Derivative Test Technology", which proposed a forced vibration experimental device for aircraft dynamic derivatives used in the FD-07 hypersonic wind tunnel. The device is driven by an electric motor, transmitted through a crank rocker, and measures angular displacement with a flexible hinge. It can be used for dynamic derivative tests under Mach 5-8 conditions. However, the device has a low actuation frequency, a fixed actuation amplitude, and large mechanical damping. Different amplitude tasks require manual replacement of transmission components, and the test efficiency and accuracy need to be improved. In 2013, Marija Samardžić of the Military Technical Institute of Serbia published a paper entitled "Apparatus for measurement of pitch and yaw damping derivatives in high Reynolds number blowdown wind tunnel" (Marija Samardžić, Pitch and yaw damping derivative measurement device in high Reynolds number wind tunnel. Measurement 46 (2013) 2457-2466). It proposed a single-degree-of-freedom oscillating dynamic derivative test device for use in the tail strut of a high Reynolds number wind tunnel. It uses elastic suspension support, hydraulic drive, and flexible hinges to measure angular displacement. It can carry out dynamic derivative tests under 0.3-3 Mach conditions. However, the hydraulic drive device is difficult to achieve high-frequency actuation, and the mechanical damping of the system is large. There is still much room for improvement in the test accuracy.

[0005] In summary, in high-speed wind tunnel tests, traditional test devices face high-frequency actuation conditions, and their motion quality is difficult to guarantee, the device damping is high, and the test efficiency is low. There is an urgent need for a high-frequency forced vibration dynamic derivative test method with high-precision and low damping, accurate force and position measurement, and adaptability to a variety of amplitude conditions. Summary of the invention

[0006] The main technical problem solved by the present invention is to overcome the shortcomings of the existing technology. In view of the fact that the existing dynamic derivative test device cannot effectively solve the problems of long time consumption for transmission parts replacement, difficulty in high-frequency actuation in a narrow space, small gap required for mechanical transmission, and small damping required for angular displacement measurement, a high-frequency forced vibration dynamic derivative test method based on piezoelectric drive is invented. The technology is based on the test technical indicators and the principle of power registration to select the driver; a high-frequency anti-backlash actuation mode with symmetrical distribution of actuators and alternating actuation in both directions is proposed, which greatly reduces the gap in the transmission process and has the ability to continuously adjust the excitation amplitude and frequency; based on the piezoelectric actuation mode design and optimization of the rotary excitation transmission structure, the linear micro-displacement is converted into a reciprocating swing of a single degree of freedom in a confined space; a high-frequency excitation module, a low-damping angular displacement monitoring module and a multi-dimensional force measurement module are built in the cavity of a high-speed aircraft model, which improves the accuracy of the dynamic derivative test data measurement; by collecting the angular displacement and multi-dimensional aerodynamic data of the model, the solution of multiple types of dynamic derivative data is realized, and the dynamic derivative test of the aircraft model is completed. The invention can ensure single-degree-of-freedom dynamic derivative tests of aircraft models under high-speed flow fields, which not only ensures the precise calculation of dynamic derivative criteria, but also takes into account the continuity and efficiency of the test.

[0007] The technical solution of the present invention:

[0008] A piezoelectric-driven tail strut-type intracavity high-frequency forced vibration dynamic derivative test method, first based on the test technical indicators, according to the power matching principle, the driver is selected; secondly, a high-frequency anti-backlash actuation mode with symmetrical distribution of actuators and bidirectional alternating actuation is proposed to reduce the gap in the transmission process; based on the actuation mode, the rotary excitation transmission structure is designed and optimized to realize the conversion of linear micro-displacement into single-degree-of-freedom reciprocating swing in a confined space; a high-frequency excitation module, a low-damping angular displacement monitoring module and a multi-dimensional force measurement module are built in the cavity of a high-speed aircraft model to form a tail strut-type intracavity high-frequency forced vibration dynamic derivative test system; wind tunnel tests are carried out to collect aerodynamic load and angular displacement data to solve the dynamic derivatives required for the model test. The specific steps are as follows:

[0009] Step 1: To align the drive power with the load power, a transient analysis is performed based on the given load and the required motion target to select the piezoelectric actuator 4;

[0010] According to the D'Alembert principle, the piezoelectric driving torque is equal to the sum of the wind load torque, the rotational inertia torque and the friction torque of the mechanism transmission. Therefore, the torque balance equation of the aircraft model is as follows:

[0011]

[0012] in, is the piezoelectric driving torque, is the wind load moment, J is the moment of inertia, α is the angular acceleration of the aircraft, is the friction torque of the mechanism transmission;

[0013] Since the target motion is a periodic reciprocating swing, the wind load torque, the transmission inertia torque and the friction torque of the mechanism transmission all change periodically with the motion angle and have a maximum value. It is known that the piezoelectric actuator 4 needs to satisfy the torque balance, so it is necessary to ensure that the piezoelectric driving torque is greater than the maximum load torque, and the driving instantaneous power is greater than the maximum load power; the details are as follows:

[0014]

[0015] in, is the driving instantaneous power, is the load power, is the angular velocity of the aircraft model, represents the friction force of the i-th revolving pair, is the diameter of the i-th revolving pair, is the relative angular velocity of the i-th rotating pair; the maximum load power is obtained based on the above formula, and the piezoelectric actuator 4 is selected based on the obtained maximum load power to ensure that the driving instantaneous power of the piezoelectric actuator 4 is greater than the maximum load power and the size should meet the space constraints of the dynamic derivative test mechanism;

[0016] Step 2: In order to reduce the influence of the transmission gap on the rotational vibration stability during the driving process of the piezoelectric actuator 4, a high-frequency anti-backlash actuation mode of bidirectional piezoelectric drive is proposed based on the linear drive characteristics of the piezoelectric actuator 4;

[0017] The piezoelectric actuators 4 are arranged symmetrically on both sides of the rotary excitation transmission mechanism. When one side of the piezoelectric actuator 4 is extended, the other side is contracted in the opposite phase with the same displacement. The two actuators are actuated alternately, and the conversion from the linear drive amount to the angular rotation is realized through the rotary excitation transmission mechanism. During the driving process of the piezoelectric actuators 4 on both sides, the displacement of the expansion and contraction is equal, thereby ensuring the compression state in the rotary excitation transmission mechanism, so that the gap is minimized and the excitation is relatively stable.

[0018] Step 3: Design a rotational excitation transmission mechanism with a bidirectional symmetrical layout, and adapt the high-frequency anti-backlash actuation mode of bidirectional piezoelectric drive by arranging the piezoelectric actuator 4 and the transmission structure symmetrically up and down, which includes a device base 1, a pre-tightening wedge block 2, a rear convex block 3, a piezoelectric actuator 4, a base adapter 5, a front vibration cylinder 6, a front articulated seat 12, a transmission long rod 13, a transmission short rod 14, a rotating shaft 15 and a rear articulated seat 16;

[0019] The device base 1 and the base adapter 5 are tightened with bolts; arc grooves are symmetrically opened on the upper and lower sides of the base adapter 5, and the axis of the arc groove is in the same vertical plane as the circular hole in the center of the base adapter 5; the central circular hole of the front vibration cylinder 6 is coaxially aligned with the central circular hole of the base adapter 5, and the rotating shaft 15 is inserted into the two central circular holes. The rotating shaft 15 is fixedly connected with the central circular hole of the base adapter 5 by interference fit, and is clearance-matched with the central circular hole of the front vibration cylinder 6, so that the front vibration cylinder 6 can rotate around the rotating shaft 15; arc grooves are symmetrically opened on the upper and lower sides of the front vibration cylinder 6, and the axis of the arc groove of the front vibration cylinder 6 is in the same vertical plane as the axis of the rotating shaft 15; two transmission long rods 13 are cross-placed in the cavity of the base adapter 5, and the arc surfaces of the forked ends of the transmission long rods 13 match the upper and lower arc grooves of the front vibration cylinder 6, and the two transmission short rods 14 are placed respectively On the upper and lower sides of the cavity of the base adapter 5, one end of the transmission short rod 14 is matched with the arc grooves on the upper and lower sides of the base adapter 5, and the other end is placed in the arc groove at one end of the transmission long rod 13; the two front hinge seats 12 and the two rear protrusions 3 are respectively installed on the front and rear sides of the two piezoelectric actuators 4, and placed in the semicircular grooves on the upper and lower sides of the device base 1; the arc grooves on the front sides of the two front hinge seats 12 are respectively matched with the cylindrical arc surfaces of the two transmission long rods 13, and the arc grooves of the two rear hinge seats 16 are matched with the cylindrical arc surfaces of the two rear protrusions 3; the pre-tightening wedge 2 is pressed between the rear hinge seat 16 and the device base 1 to play an axial pre-tightening role; through the linear displacement of the piezoelectric actuator 4, the two transmission short rods 14 are pushed to produce angular swing, and the rotation is transmitted through the two transmission long rods 13, thereby realizing the rotation of the front vibration cylinder 6;

[0020] Step 4: Build a piezoelectric-driven intracavity high-frequency forced vibration dynamic derivative test system, which includes a balance adapter 7, a piezoelectric multi-dimensional force measurement balance 8, an angular displacement encoder 9, an encoder positioner 10, and a grating code disk 11 in addition to a bidirectionally symmetrically arranged rotary excitation transmission mechanism;

[0021] On the basis of the rotary excitation transmission mechanism, the grating code disk 11 is fixed to the rotating shaft 15 by gluing, the encoder positioner 10 is fixed to the front vibration cylinder 6 by pin positioning and bolt tightening, the angular displacement encoder 9 is fitted along the limit block of the positioner and tightened by screws to form a low-damping angular displacement monitoring layout;

[0022] Fix the balance adapter 7 to the front vibration cylinder 6 by bolts, and fix the piezoelectric multi-dimensional force measurement balance 8 to the front vibration cylinder 6 by conical surface matching; connect the piezoelectric actuator 4 to the power amplifier, and the power amplifier to the voltage output card to form an actuator control module; connect the piezoelectric multi-dimensional force measurement balance 8 to the multi-dimensional force acquisition card, and connect the angular displacement encoder 9 to the angular displacement detection card to form a physical quantity measurement acquisition module; connect the actuator control module and the physical quantity measurement acquisition module to the real-time controller and the host computer in turn, and finally form an actuator control loop and a physical quantity measurement acquisition loop to realize the output control of the piezoelectric actuator and the real-time measurement of the angular displacement output by the rotary excitation transmission mechanism and the multi-dimensional force received, and finally tighten the aircraft model with the conical surface of the piezoelectric multi-dimensional force measurement balance 8. At this point, the tail support type intra-cavity high-frequency forced vibration dynamic derivative test system is completed;

[0023] Step 5: According to the test requirements, the piezoelectric actuators 4 on the upper and lower sides are controlled to drive alternately in opposite phases, axially push the front hinge seat 12, drive the transmission long rod 13 and the transmission short rod 14 to rotate, and push the front vibration cylinder 6 and the motion base to rotate, thereby driving the aircraft model to produce simple harmonic motion; wherein the driving signal is expressed as formula (3):

[0024]

[0025] Among them, k i 、h i is the bias and driving amount of the i-th piezoelectric actuator 4, A and f are the excitation amplitude and frequency of the piezoelectric actuator 4, and t is the time variable;

[0026] Step 6: The aircraft model performs simple harmonic motion in the flow field, and the time history data of aerodynamic force and angular displacement are obtained through the piezoelectric multi-dimensional force measurement balance 8 and the angular displacement encoder 9. The data are collected and recorded, and substituted into equation (4) to solve the dynamic derivative required for the test;

[0027]

[0028] Wherein, the subscripts w and v respectively indicate the results of wind and vacuum calibration conditions, M is the amplitude of the forcing moment, ω is the circular frequency of vibration, , are the vibration circular frequencies under wind and vacuum calibration conditions, ϕ is the phase lag angle, θ0 is the motion amplitude, is the aerodynamic damping, is the aerodynamic static damping, is the direct derivative, is the time difference derivative, is the aerodynamic derivative, is the inertia moment of the aircraft model, q∞ 、V ∞ are the fluid density and characteristic velocity respectively, A is the reference area, and d is the reference length.

[0029] The beneficial effect of the present invention is to provide a piezoelectric-driven tail strut-type intra-cavity high-frequency forced vibration dynamic derivative test method, which can realize the high-frequency reciprocating swing of the aircraft model in a single degree of freedom under a complex high-speed flow field. Compared with traditional devices, the test device has a small gap and a high movement frequency during the actuation process, and can achieve stepless adjustment of the amplitude and frequency, which greatly shortens the test interval time of the replacement of transmission components and improves efficiency. The angular displacement detection system adopts a non-contact measurement solution, does not generate additional mechanical damping, and improves the test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is an overall flow chart of a piezoelectric-driven tail strut-type intra-cavity high-frequency forced vibration dynamic derivative test method.

[0031] Figure 2 The figure is a schematic diagram of a rotary vibration transmission mechanism with a bidirectional symmetrical layout according to the present invention.

[0032] Figure 3 The present invention is a schematic diagram of a bidirectional symmetrical layout rotary excitation transmission mechanism.

[0033] Figure 4 The figure is a schematic diagram of the overall assembly of a tail support type intracavity high frequency forced vibration device of the present invention.

[0034] Figure 5 It is a cross-sectional view of the assembly of the intracavity high-frequency forced vibration device of the present invention.

[0035] Figure 6 This is the assembly diagram of the intracavity angular displacement monitoring layout of the present invention.

[0036] Figure 7 It is a cross-sectional view of the transmission mechanism assembly of the intracavity high-frequency forced vibration device of the present invention.

[0037] Figure 8 It is a schematic diagram of the intracavity high-frequency forced vibration dynamic derivative test system based on piezoelectric drive of the present invention.

[0038] In the figure: 1 device base, 2 preload wedge, 3 rear bump, 4 piezoelectric actuator, 5 base adapter, 6 front vibration cylinder, 7 balance adapter, 8 piezoelectric multi-dimensional force measurement balance, 9 angular displacement encoder, 10 encoder positioner, 11 grating code disk, 12 front articulated seat, 13 transmission long rod, 14 transmission short rod, 15 rotation axis, 16 rear articulated seat. DETAILED DESCRIPTION

[0039] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings and technical solutions.

[0040] The embodiment takes the tail strut type cavity high frequency forced vibration dynamic derivative test designed for a 2.4m wind tunnel as an example, the case load is 59Nm, the excitation amplitude is ±1°, and the frequency is 5Hz, and the following is explained in conjunction with the accompanying drawings:

[0041] Figure 4 The overall assembly diagram of a tail strut type intracavity high frequency forced vibration device of the present invention is shown in FIG. The tail strut type intracavity high frequency forced vibration dynamic derivative test method based on piezoelectric drive of the present invention is used, and the specific steps are as follows:

[0042] (1) From formula (1), we can know the model moment balance equation. By theoretically analyzing each term, we can get

[0043] The formulas are shown in equation (5):

[0044]

[0045] Among them, the subscripts w, J, and f represent wind load, inertia, and friction terms, respectively. is the moment of inertia, P is the wind pressure, x is the moment per unit area from the center of rotation, s is the unit area, is the density distribution, the subscript i is the serial number of each rotation pair, n is the number of rotation pairs, represents the friction force of the i-th revolving pair, is the radius of the rotation pair. Therefore, the moment balance equation of the aircraft model can be obtained as shown in the following formula (6):

[0046]

[0047] in, is the driving torque. Calculate the values ​​of each factor and substitute them into formula (2) to obtain the required power of the driver. Based on the required power and the limited size, the driver selection can be completed.

[0048] (2) A high-frequency anti-backlash actuation mode of bidirectional piezoelectric drive is proposed. In this mode, when the piezoelectric actuator on one side is extended, the actuator on the other side is contracted synchronously in the opposite direction, and the displacement of the two is kept consistent. The core of this design is that during the driving process of the piezoelectric actuators 4 on both sides, the displacement of the extension and contraction is equal, which ensures that the transmission parts are always in a compressed state, minimizing the gap. Through bidirectional coordinated motion, the accuracy of the model motion can be effectively improved, thereby improving the accuracy of the dynamic derivative measurement.

[0049] (3) Based on the transmission mode and motion requirements, a bidirectional symmetrical layout of the rotation excitation transmission structure is designed and optimized. The linear displacement of the piezoelectric actuator 4 drives the two transmission short rods 14 to produce angular swing, and the rotation is transmitted through the two transmission long rods 13, thereby realizing the rotation of the front vibration cylinder 6. The schematic diagram of the mechanism is shown in Figure 2 shown.

[0050] On this basis, considering the space size limitation and load constraint, the transmission structure is optimized. The design goal is to ensure that the transmission structure can provide sufficient strength and rigidity in a small space and convert the linear displacement of the driver into stable rotational motion. The efficiency and reliability of the transmission system are ensured through reasonable structural layout and material selection.

[0051] The device base 1 is fastened to the base adapter 5 by bolts. Arc grooves are symmetrically provided on the upper and lower sides of the base adapter 5, and the axis of the arc groove is in the same vertical plane as the center circular hole of the base adapter 5. The center circular hole of the front vibration cylinder 6 is coaxially aligned with the center circular hole of the base adapter 5, and the rotating shaft 15 is inserted to ensure the fit of the two center circular holes. The rotating shaft 15 is fixedly connected to the center circular hole of the base adapter 5 by an interference fit, while maintaining a clearance fit with the center circular hole of the front vibration cylinder 6, so that the front vibration cylinder 6 can rotate around the rotating shaft 15. Symmetrical arc grooves are also provided on the upper and lower sides of the front vibration cylinder 6, and the axis of the arc groove is in the same vertical plane as the axis of the rotating shaft 15. Two transmission long rods 13 are placed crosswise in the cavity of the base adapter 5, and the arc surface of the forked end thereof matches the upper and lower arc grooves of the front vibration cylinder 6. At the same time, the two short transmission rods 14 are respectively placed on the upper and lower sides of the cavity of the base adapter 5, one end of which cooperates with the arc grooves on the upper and lower sides of the base adapter 5, and the other end is placed in the arc groove at one end of the long transmission rod 13. The two front hinge seats 12 and the two rear protrusions 3 are respectively installed on the front and rear sides of the two piezoelectric actuators 4, and placed in the semicircular grooves on the upper and lower sides of the device base 1. The arc grooves on the front sides of the two front hinge seats 12 cooperate with the cylindrical arc surfaces of the two long transmission rods 13, and the arc grooves of the two rear hinge seats 16 cooperate with the cylindrical arc surfaces of the two rear protrusions 3. The preload wedge 2 is pressed between the rear hinge seat 16 and the device base 1 to achieve axial preload. The final structure of a bidirectional symmetrical layout rotary excitation transmission mechanism is as shown in FIG. Figure 3 shown.

[0052] (4) Build a piezoelectric-driven intracavity high-frequency forced vibration dynamic derivative test device. In addition to the bidirectional symmetrical layout of the rotary excitation transmission mechanism, the design and assembly process of the test device can be divided into the following key parts:

[0053] Angular displacement monitoring system: On the basis of the rotary excitation transmission mechanism, the grating code disk 11 is firmly fixed to the rotating shaft 15 by gluing technology. The encoder positioner 10 is firmly installed on the front vibration cylinder 6 by means of pin positioning and bolt tightening. The angular displacement encoder 9 fits tightly with the limit block of the positioner and is tightened by screws to form a low-damping angular displacement monitoring layout. The balance adapter 7 is firmly fixed to the front vibration cylinder 6 by bolts, and the piezoelectric multi-dimensional force measurement balance 8 is fixedly connected to the front vibration cylinder 6 by conical surface matching. The piezoelectric actuator 4 is connected to the power amplifier, and the power amplifier is connected to the voltage output card to form an actuator control module. At the same time, the piezoelectric multi-dimensional force measurement balance 8 is connected to the multi-dimensional force acquisition card, and the angular displacement encoder 9 is connected to the angular displacement detection card to form a physical quantity measurement and acquisition module. The actuator control module and the physical quantity measurement and acquisition module are connected to the real-time controller and the host computer in turn, and finally form an actuator control loop and a physical quantity measurement and acquisition loop to control the output of the piezoelectric actuator and the real-time measurement of the angular displacement and multi-dimensional force output by the rotary excitation transmission mechanism. Finally, the aircraft model is closely matched with the cone surface of the piezoelectric multi-dimensional force measurement balance 8. At this point, the construction of the tail support type intracavity high-frequency forced vibration dynamic derivative test system is completed, which can realize the real-time measurement of the piezoelectric actuator output control, the angular displacement and multi-dimensional force of the test device, thereby completing the high-precision test and verification of the test device.

[0054] (5) According to the test requirements, the actuators 4 on the upper and lower sides are controlled to drive alternately in opposite phases to generate axial displacement. By driving the front hinge seat 12, the transmission long rod 13 and the short rod 14 rotate, thereby driving the front vibration cylinder 6 to rotate together with the motion base, and finally driving the model to generate simple harmonic motion. The driving signal is shown in formula (3).

[0055] (6) When the model performs simple harmonic motion in the flow field, the time history data of the aerodynamic force and angular displacement of the model when it moves in the flow field can be obtained through the piezoelectric multi-dimensional force measurement balance 8 and the angular displacement encoder 9. These data can be used to solve the dynamic derivatives required for the experiment, as shown in formula (4).

[0056] Compared with the traditional dynamic derivative test method, the dynamic derivative test method based on high-frequency forced vibration in the tail strut cavity proposed in this invention can realize high-frequency reciprocating excitation of a single degree of freedom in a complex high-speed flow field. The test device has a smaller gap and a higher movement frequency during the actuation process, and can realize stepless adjustment of amplitude and frequency, thereby significantly shortening the test interval of transmission component replacement and improving work efficiency. In addition, the angular displacement detection system adopts a non-contact measurement scheme, avoiding the introduction of additional mechanical damping, and further improving the accuracy of the test.

Claims

1. A piezoelectric-driven tail-braced cavity high-frequency forced vibration dynamic derivative test method, characterized in that: Here are the steps: Step 1: To align the drive power with the load power, a transient analysis is performed based on the given load and the required motion target to select the piezoelectric actuator (4); According to the D'Alembert principle, the piezoelectric driving torque is equal to the sum of the wind load torque, the rotational inertia torque and the friction torque of the mechanism transmission. Therefore, the torque balance equation of the aircraft model is as follows: in, is the piezoelectric driving torque, is the wind load moment, J is the moment of inertia, α is the angular acceleration of the aircraft, is the friction torque of the mechanism transmission; Since the target motion is a periodic reciprocating swing, the wind load torque, the transmission inertia torque and the friction torque of the mechanism transmission all change periodically with the motion angle and have a maximum value. It is known that the piezoelectric actuator (4) needs to satisfy the torque balance, so it is necessary to ensure that the piezoelectric driving torque is greater than the maximum load torque, and the driving instantaneous power is greater than the maximum load power; the details are as follows: in, is the driving instantaneous power, is the load power, is the angular velocity of the aircraft model, represents the friction force of the i-th revolving pair, is the diameter of the i-th revolving pair, is the relative angular velocity of the i-th rotating pair; the maximum load power is obtained based on the above formula, and the piezoelectric actuator (4) is selected based on the obtained maximum load power to ensure that the driving instantaneous power of the piezoelectric actuator (4) is greater than the maximum load power and the size should meet the space constraints of the dynamic derivative test mechanism; Step 2: In order to reduce the influence of the transmission gap on the rotational vibration stability during the driving process of the piezoelectric actuator (4), a high-frequency anti-backlash actuation mode of bidirectional piezoelectric drive is proposed based on the linear drive characteristics of the piezoelectric actuator (4); The piezoelectric actuators (4) are arranged symmetrically on both sides of the rotary excitation transmission mechanism. When one side of the piezoelectric actuators (4) is extended, the other side is contracted in an opposite phase with the same displacement. The two actuators are actuated alternately, and the conversion from the linear drive amount to the angular rotation is realized through the rotary excitation transmission mechanism. During the driving process of the piezoelectric actuators (4) on both sides, the displacement of the extension and contraction is equal, thereby ensuring the compression state in the rotary excitation transmission mechanism, minimizing the gap and making the excitation more stable. Step 3: Design a rotational excitation transmission mechanism with a bidirectional symmetrical layout, and adapt the high-frequency anti-backlash actuation mode of bidirectional piezoelectric drive by arranging the piezoelectric actuator (4) and the transmission structure symmetrically in the upper and lower parts, which includes a device base (1), a pre-tightening wedge block (2), a rear convex block (3), a piezoelectric actuator (4), a base adapter (5), a front vibration cylinder (6), a front hinge seat (12), a transmission long rod (13), a transmission short rod (14), a rotation axis (15) and a rear hinge seat (16); The device base (1) and the base adapter (5) are tightened with bolts; arc grooves are symmetrically opened on the upper and lower sides of the base adapter (5), and the arc groove axis and the circular hole in the center of the base adapter (5) are in the same vertical plane; the central circular hole of the front vibration cylinder (6) and the central circular hole of the base adapter (5) are coaxially aligned, and a rotating shaft (15) is inserted into the two central circular holes. The rotating shaft (15) is fixedly connected to the central circular hole of the base adapter (5) by interference fit, and is connected to the central circular hole of the front vibration cylinder (6). The central circular hole is gap-matched, and the front vibration cylinder (6) can rotate around the rotation axis (15); arc grooves are symmetrically opened on the upper and lower sides of the front vibration cylinder (6), and the arc groove axis of the front vibration cylinder (6) and the axis of the rotation axis (15) are in the same vertical plane; two transmission long rods (13) are cross-placed in the cavity of the base adapter (5), and the arc surface of the forked end of the transmission long rod (13) is matched with the upper and lower arc grooves of the front vibration cylinder (6), and two transmission short rods (14) are respectively placed At the upper and lower sides of the cavity of the base adapter (5), one end of the transmission short rod (14) is matched with the arc grooves on the upper and lower sides of the base adapter (5), and the other end is placed in the arc groove at one end of the transmission long rod (13); two front hinge seats (12) and two rear protrusions (3) are respectively installed on the front and rear sides of the two piezoelectric actuators (4) and placed in the semicircular grooves on the upper and lower sides of the device base (1); the arc grooves on the front sides of the two front hinge seats (12) are respectively connected to the two piezoelectric actuators. The cylindrical arc surface of the movable long rod (13) cooperates with the arc grooves of the two rear hinge seats (16) and the cylindrical arc surfaces of the two rear protrusions (3); the preload wedge (2) is pressed between the rear hinge seat (16) and the device base (1) to play an axial preload role; the two transmission short rods (14) are driven to produce angular swing through the linear displacement of the piezoelectric actuator (4), and the rotation is transmitted through the two transmission long rods (13), thereby realizing the rotation of the front vibration cylinder (6); Step 4: Build a piezoelectric-driven intracavity high-frequency forced vibration dynamic derivative test system, which includes a balance adapter (7), a piezoelectric multi-dimensional force measurement balance (8), an angular displacement encoder (9), an encoder positioner (10) and a grating code disk (11) in addition to a bidirectionally symmetrically arranged rotary excitation transmission mechanism; On the basis of the rotary excitation transmission mechanism, the grating code disk (11) is fixed to the rotating shaft (15) by gluing, the encoder positioner (10) is fixed to the front vibration cylinder (6) by pin positioning and bolt tightening, the angular displacement encoder (9) is fitted along the limit block of the positioner, and is tightened by screws to form a low-damping angular displacement monitoring layout; The balance adapter (7) is fixed to the front vibration cylinder (6) by bolts, and the piezoelectric multi-dimensional force measurement balance (8) is fixed to the front vibration cylinder (6) by matching the conical surface; the piezoelectric actuator (4) is connected to the power amplifier, and the power amplifier is connected to the voltage output card to form an actuator control module; the piezoelectric multi-dimensional force measurement balance (8) is connected to the multi-dimensional force acquisition card, and the angular displacement encoder (9) is connected to the angular displacement detection card to form a physical quantity measurement acquisition module; the actuator control module and the physical quantity measurement acquisition module are connected to the real-time controller and the host computer in sequence, and finally an actuator control loop and a physical quantity measurement acquisition loop are formed to realize the output control of the piezoelectric actuator and the real-time measurement of the angular displacement output by the rotary excitation transmission mechanism and the multi-dimensional force received, and finally the aircraft model is tightened and matched with the conical surface of the piezoelectric multi-dimensional force measurement balance (8), and thus the tail support type cavity high-frequency forced vibration dynamic derivative test system is completed; Step 5: According to the test requirements, the piezoelectric actuators (4) on the upper and lower sides are controlled to drive alternately in opposite phases, axially push the front hinge seat (12), drive the transmission long rod (13) and the transmission short rod (14) to rotate, and push the front vibration cylinder (6) and the motion base to rotate, thereby driving the aircraft model to produce simple harmonic motion; wherein the driving signal is expressed as formula (3): Among them, k i 、h i are the bias and drive quantities of the i-th piezoelectric actuator (4), A and f are the excitation amplitude and frequency of the piezoelectric actuator (4), and t is the time variable; Step 6: The aircraft model performs simple harmonic motion in the flow field, and the time history data of aerodynamic force and angular displacement are obtained through the piezoelectric multi-dimensional force measurement balance (8) and the angular displacement encoder (9), which are collected and recorded, and substituted into equation (4) to solve the dynamic derivative required for the test; Wherein, the subscripts w and v respectively indicate the results of wind and vacuum calibration conditions, M is the amplitude of the forcing moment, ω is the circular frequency of vibration, , are the vibration circular frequencies under wind and vacuum calibration conditions, ϕ is the phase lag angle, θ0 is the motion amplitude, is the aerodynamic damping, is the aerodynamic static damping, is the direct derivative, is the time difference derivative, is the aerodynamic derivative, is the inertia moment of the aircraft model, q ∞ 、V ∞ are the fluid density and characteristic velocity respectively, A is the reference area, and d is the reference length.

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