A three-degree-of-freedom forced vibration dynamic derivative test method based on piezoelectric drive

Abstract

The present invention belongs to the field of dynamic stability derivative measurement, and discloses a three-degree-of-freedom forced vibration dynamic derivative test method based on piezoelectric drive. The method adopts a three-degree-of-freedom excitation mechanism layout of yaw-roll bidirectional parallel + pitch unidirectional series, which can accommodate the three-degree-of-freedom excitation mechanism in a narrow and long space; by designing and optimizing the bidirectional excitation parallel mechanism, the displacement mapping of the four actuators from linear telescopic to the two-degree-of-freedom swing of the model is realized, and the bidirectional excitation parallel mechanism is connected in series with the existing single-degree-of-freedom excitation mechanism to form a three-degree-of-freedom excitation device; an angular encoder and a piezoelectric balance are combined to form a force-position state monitoring system, and the actuation angular displacement and multi-dimensional aerodynamic force of the model under the whole process are collected, and then multiple types of dynamic derivative data are obtained. The invention can ensure that the aircraft model is tested for three-degree-of-freedom dynamic derivatives in a continuous wind tunnel and a high-speed flow field, which not only ensures the precise measurement of multiple types of dynamic derivatives under multi-degree-of-freedom motion, but also takes into account the continuous and efficient test.

Description

Technical Field

[0001] The invention belongs to the field of dynamic stability derivative measurement, and relates to a three-degree-of-freedom forced vibration dynamic derivative test method based on piezoelectric drive. Background Art

[0002] With the development of high-speed aircraft, missiles, rockets and reentry vehicles, ultra-high-speed performance and high-maneuverability flight capabilities have become the strategic direction of aircraft design. Modern flight missions place higher demands on the aerodynamic performance of aircraft to ensure that the aircraft has sufficient dynamic stability under such conditions. As an aerodynamic performance prediction technology, dynamic derivative testing can judge the stability of aircraft during maneuvering flight during the design stage. It has become an indispensable test link in the model development process. The precise determination of dynamic derivatives of aircraft models has a profound impact on the effectiveness of the design and has become an increasingly important issue.

[0003] However, the existing dynamic derivative test technology has gradually failed to match the advancedness required for such aircraft tests. For cutting-edge aircraft with ultra-high speed, high maneuverability, and post-stall maneuverability, the high-angle-of-attack aerodynamic characteristics under extreme flight conditions are coupled with the aircraft state variables and their rates of change. The cross-coupling of aerodynamic forces in different directions may produce movements in different directions. Therefore, it is necessary for the high-speed wind tunnel dynamic derivative test to have multi-degree-of-freedom actuation capabilities, so as to obtain accurate, reliable, and complete cross- and cross-coupled dynamic derivative criteria. However, the traditional high-speed wind tunnel forced vibration test technology mostly considers single-degree-of-freedom tests, or combines forced vibration with free vibration tests to form multi-degree-of-freedom tests. The correctness and confidence of the cross / cross-coupled dynamic derivatives obtained by such tests still need to be improved. Therefore, there is an urgent need for a multi-degree-of-freedom dynamic derivative test device that can be used in high-speed wind tunnels, which can control the model to achieve a variety of vibration conditions under high-speed complex flow fields, and accurately obtain the model vibration curve and the multi-dimensional aerodynamic forces it receives, so as to solve and obtain accurate and effective dynamic derivative criteria, and provide reliable characteristic data feedback for the aerodynamic shape design of cutting-edge aircraft.

[0004] In 2014, Dan D. Vicroy's team from NASA published a paper titled "Low-speed Dynamic Wind Tunnel Test Analysis of a Generic 53° ​​Swept UCAV Configuration with Controls" (Dan D. Vicroy, NASA. AIAA 2014-23). ​​It proposed a multi-degree-of-freedom dynamic derivative excitation device for low-speed wind tunnels with external belly struts. Based on the Stewart platform, the six-degree-of-freedom motion of the model can be achieved. However, the actuation frequency of the device is low, the actuation accuracy is not high, and it is limited to low-speed wind tunnel tests. In 2019, Shen Lin's team from Nanjing University of Aeronautics and Astronautics published a paper entitled "Effects of yaw-rollcoupling ratio on lateral-directional aerodynamic characteristics" (Shen, Lin, Effects of yaw-roll coupling ratio on lateral-directional aerodynamic characteristics. CHINESE JOURNAL OF AERONAUTICS 2019-272). It proposed a dual-degree-of-freedom dynamic derivative excitation device for use in the tail strut of a low-speed wind tunnel. The device can realize the coupled motion of yaw and roll of the model. However, the device uses hydraulic actuation with a low actuation frequency. The achievable vibration conditions are limited to yaw-roll coupled motion, and there are few types of criteria that can be accurately solved.

[0005] The following factors need to be considered when implementing multi-degree-of-freedom dynamic derivative tests of aircraft in high-speed wind tunnels. First, it is necessary to ensure that the driving mechanism meets the multi-degree-of-freedom excitation capability under complex flow fields; second, it is necessary to ensure the stability and accuracy of the multi-degree-of-freedom motion output of the model's composite motion; and finally, it is necessary to ensure that the test support method has the least impact on the near-wake flow pattern of the spoiler. This poses several major challenges to the dynamic derivative test device from an objective level: first, in order to minimize the interference of the support rod on the flow field around the model and ensure the accurate measurement of the dynamic derivative, a cantilever support rod tail support structure is often used. However, the inner cavity space of the model is narrow and limited, which limits the design configuration and placement space of the composite excitation mechanism and the driving parts; second, the transient multi-dimensional large loads generated by the complex flow field of the wind tunnel will have a serious impact on the reliability and precision of the model movement; finally, the measurement task conditions of various dynamic derivatives are different. In order to enhance the adaptability of the test mechanism, the excitation device needs to have high load-bearing, high stiffness, gapless transmission, wide-band response and other capabilities. Conventional dynamic derivative test mechanisms are no longer applicable. 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 three-degree-of-freedom composite excitation in a narrow space, transient multi-dimensional continuous large load interference, and high adaptability to multiple working conditions, a three-degree-of-freedom forced vibration dynamic derivative test method based on piezoelectric actuator drive is invented. This technology adopts a three-degree-of-freedom excitation mechanism layout of yaw-roll bidirectional parallel + pitch unidirectional series, which can accommodate the excitation mechanism in a narrow and long space; by designing and optimizing the bidirectional excitation parallel mechanism, the displacement mapping of the four actuators from linear telescopic to the two-degree-of-freedom swing of the model is realized, and the bidirectional excitation parallel mechanism is connected in series with the existing single-degree-of-freedom excitation mechanism to form a three-degree-of-freedom excitation device; an angular encoder and a piezoelectric balance are combined to form a force-position state monitoring system to collect the actuation angular displacement and multi-dimensional aerodynamic force of the model under the whole process, and then obtain multiple types of dynamic derivative data. This invention can ensure that the aircraft model can be tested for three-degree-of-freedom dynamic derivatives in a continuous wind tunnel and high-speed flow field, which not only ensures the precise calculation of the 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 three-degree-of-freedom forced vibration dynamic derivative test method, based on established experimental indicators, designs size and load constraints to form a three-degree-of-freedom excitation mechanism layout of yaw-roll bidirectional parallel + pitch unidirectional series; designs a parallel mechanism configuration for two-degree-of-freedom excitation in a narrow space to enable it to have a bidirectional composite high-frequency excitation capability, and connects the bidirectional excitation parallel mechanism in series with the existing single-degree-of-freedom excitation mechanism to form a three-degree-of-freedom excitation device; builds a force-position state monitoring system based on an angular displacement encoder and a piezoelectric balance, and integrates them to form a three-degree-of-freedom dynamic derivative forced vibration test system; drives the system to perform three-degree-of-freedom actuation under wind tunnel conditions, collects multi-dimensional aerodynamic load and multi-dimensional angular displacement data, and solves the dynamic derivatives required for model testing.

[0009] The specific steps are as follows:

[0010] Step 1: Determine the task volume constraints based on the given load and space size requirements;

[0011] Since the space inside the aircraft model cavity is long and narrow, when facing the large aspect ratio aircraft model, the loads in the yaw and roll directions are close and much smaller than the load in the pitch direction. Therefore, a three-degree-of-freedom excitation mechanism layout of a yaw-roll bidirectional parallel mechanism + a pitch unidirectional excitation mechanism in series is proposed; the yaw-roll bidirectional parallel mechanism is placed on the front side of the three-degree-of-freedom excitation mechanism layout and is directly connected to the aircraft model to drive the aircraft model to perform yaw-roll bidirectional compound motion; the pitch unidirectional excitation mechanism is placed on the rear side of the three-degree-of-freedom excitation mechanism layout and is connected in series with the yaw-roll bidirectional parallel mechanism to drive the yaw-roll bidirectional parallel mechanism and the aircraft model to realize pitch direction excitation together;

[0012] Step 2: Design the yaw-roll bidirectional parallel mechanism

[0013] The yaw-roll bidirectional parallel mechanism includes four branches, each of which includes a linear drive mechanism and a displacement amplification mechanism, and each branch is ultimately connected in parallel to a parallel end;

[0014] Four yaw and roll piezoelectric actuators 5 are used as linear actuators to output linear displacement; the front and rear sides of the yaw and roll piezoelectric actuator 5 are connected to two yaw and roll movable bases 4 as axial protection for the yaw and roll piezoelectric actuator 5; the yaw and roll movable base 4 at the rear end is spherically matched with the yaw and roll rear hinged seat 8 to facilitate automatic centering after force is applied; the yaw and roll pre-tightening wedge block 9 is tightened between the rear end wedge surface of the yaw and roll rear hinged seat 8 and the outer wall of the yaw and roll vibration cylinder 1 by bolts to play an axial fixing role; the yaw and roll front hinged seat 3 serves as a one-way rotating pair on the front side of the yaw and roll piezoelectric actuator 5, one side of which is spherically matched with the yaw and roll movable base 4 to achieve relative rotation, and the other side It is hinged with the yaw roll transmission lever 17 to transmit displacement; the four yaw roll transmission levers 17 are used as displacement amplification mechanisms to amplify linear displacement. A single yaw roll transmission lever 17 includes two cylindrical shafts and a ball, one of which cooperates with the cylindrical surface of the yaw roll front hinge seat 3 to form a rotation pair, and the other cylindrical shaft cooperates with the cylindrical hole in the yaw roll vibration cylinder 1 to form a rotation pair. The ball at the end of the yaw roll transmission lever 17 contacts with the matching plane of the roll shaft 16 to form a high pair of point-to-surface contact, which can generate relative displacement along the two degrees of freedom tangentially of the matching plane; the roll shaft 16 and the yaw shaft 18 are parallel ends, wherein the yaw shaft 18 is hinged with the yaw roll vibration cylinder 1 to form a yaw rotation axis O. z The roll axis 16 is hinged with the yaw axis 18 to form a roll rotation axis O x , the piezoelectric balance 2 is fastened with the roll axis 16 through a conical surface; when the two yaw roll piezoelectric actuators 5 on the left are driven linearly, the two yaw roll piezoelectric actuators 5 on the right are driven in reverse phase, driving the yaw roll transmission lever 17 to swing in the same direction, driving the ball to slide on the matching plane, and at the same time driving the yaw axis to rotate around O z When the two diagonal yaw roll piezoelectric actuators 5 are driven linearly, the remaining two yaw roll piezoelectric actuators 5 are driven in reverse phase, driving the upper and lower yaw roll transmission levers 17 to swing in opposite directions, driving the ball to slide in the matching plane, while driving the roll axis around O x Rotation; thereby realizing the motion conversion of the linear displacement drive of the four yaw roll piezoelectric actuators 5 to the yaw roll rotational angular displacement; wherein the linear drive mechanism and the displacement amplification mechanism are symmetrically arranged around the roll axis 16 and the piezoelectric balance 2, ensuring that the yaw-roll bidirectional parallel mechanism can work in a narrow and long space, achieving a higher space utilization rate;

[0015] Step 3: Build a three-degree-of-freedom dynamic derivative excitation device, which includes a pitch front articulated seat 6, a pitch moving base 7, a pitch piezoelectric actuator 10, a pitch rear articulated seat 11, a pitch preload wedge 12, a pitch body 13, a positioning pin 14, a split cone block 15, a pitch transmission long rod 19, a pitch transmission short rod 20, a grating code disk 21, an angular displacement encoder 22, a pitch yaw encoder fixture 23, a roll encoder fixture 24 and a pitch axis 25 in addition to the yaw-roll bidirectional parallel mechanism;

[0016] A cylindrical groove is formed at the rear end of the pitch body 13 for assembly with the split cone block 15. During assembly, the pitch body 13 is aligned with the pin holes on the split cone block 15, and the positioning pin 14 is installed to ensure that the circumferential angles of the two are aligned. Then, the bolts are installed and tightened to ensure that the pitch body 13 is firmly connected with the split cone block 15.

[0017] The front end of the pitch body 13 is provided with a groove, the end cylindrical surface of the pitch transmission short rod 20 matches with the groove at the front end of the pitch body 13, the end cylindrical surface of the pitch transmission long rod 19 matches with the groove on the yaw roll vibration cylinder 1, the pitch transmission short rod 20 and the first end cylindrical surface of the pitch transmission long rod 19 are matched and installed in the pitch front hinge seat 6, forming a set of pitch displacement amplification mechanism, realizing the motion transmission of the pitch excitation mechanism; the upper and lower surfaces of the pitch body 13 are respectively provided with a long cylindrical groove, and the pitch rear hinge seat 11 and the pitch pre-tightening wedge 12 are installed at the rear end of the long cylindrical groove, and the two are matched through the inclined surface; the pitch moving base 7 is assembled on the pitch piezoelectric actuator 1 0 at both ends to form a combination, which is installed in the long cylindrical groove of the pitch body 13, the pitch moving base 7 at the front end of the combination cooperates with the spherical surface of the pitch front hinge seat 6, and the pitch moving base 7 at the rear end cooperates with the spherical surface of the pitch rear hinge seat 11; a pre-tightening bolt is installed in the threaded hole of the pitch pre-tightening wedge 12, and through the pre-tightening of the bolt, the pitch rear hinge seat 11 cooperates with the pitch pre-tightening wedge 12 inclined surface to ensure that the output of the pitch piezoelectric actuator 10 is aligned, and the reliable output of the pitch piezoelectric actuator 10 is ensured; the components installed in the two long cylindrical grooves of the pitch body 13 are the same and the installation method is the same, completing the construction of the pitch excitation structure;

[0018] There is a cylindrical hole on each of the two side planes at the front end of the pitch body 13, which is used to install the pitch axis 25, and the yaw-roll bidirectional parallel mechanism is connected to the pitch body 13 through the pitch axis 25, so as to realize the series connection of the yaw-roll bidirectional parallel mechanism and the pitch unidirectional excitation mechanism; a grating code disk 21 is installed on the inner side of the pitch axis 25 to measure the angular displacement in the pitch direction; a grating code disk 21 is installed on the cylindrical boss of the yaw axis 18 to measure the angular displacement in the yaw direction; a grating code disk 21 is installed at the connection between the roll axis 16 and the yaw axis 18 to measure the angular displacement in the roll direction; the two angular position disks are connected to each other. The pitch encoder 22 is installed on the pitch yaw encoder fixture 23 by screws, and is installed on the yaw roll vibration cylinder 1 through the positioning pins on the pitch yaw encoder fixture 23, and is fastened with bolts. At the same time, an angular displacement encoder 22 is installed on the roll encoder fixture 24 by screws, and is installed on the yaw axis 18 through the positioning pins on the roll encoder fixture 24, and is fastened with screws; the yaw axis 18 is installed in the corresponding installation hole of the yaw roll vibration cylinder 1, and the installation of the yaw-roll bidirectional parallel mechanism three-degree-of-freedom angular displacement monitoring device is completed;

[0019] The pitch piezoelectric actuator 10 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 balance 2 is connected to the multi-dimensional force acquisition card, and the angular displacement encoder 22 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 to form an actuator control loop and a physical quantity measurement acquisition loop, so as to realize the output control of the piezoelectric ceramic and the real-time measurement of the angular displacement and multi-dimensional force of the excitation device, and finally the aircraft model is tightened and matched with the conical surface of the piezoelectric balance 2 to form a three-degree-of-freedom dynamic derivative forced vibration test system;

[0020] Step 4: Under the wind tunnel flow field, the three-degree-of-freedom excitation mechanism is driven by two pitch piezoelectric actuators 10 and four yaw and roll piezoelectric actuators 5 to perform three-degree-of-freedom compound motion; wherein, the driving signal of the two pitch piezoelectric actuators 10 is expressed as formula ( ):

[0021] ( )

[0022] The driving signal of the four yaw and roll piezoelectric actuators 5 is expressed as the formula ( ):

[0023] ( )

[0024] in, , is the bias and drive amount of the i-th pitch piezoelectric actuator 10, , are respectively the excitation amplitude and frequency of the pitch piezoelectric actuator 10 in the j-th degree of freedom transmission chain, and t is the time variable;

[0025] The pitch piezoelectric actuators 10 on both sides extend and retract in anti-phase according to the driving signal, and the output displacement axially pushes the pitch front hinge seat 6, drives the pitch transmission long rod 19 and the pitch transmission short rod 20, and uses the pitch body 13 as the base to pry the yaw roll vibration cylinder 1 to achieve pitch movement. The yaw roll vibration cylinder 1 drives the piezoelectric balance 2 to pitch, and the conical connection of the piezoelectric balance 2 drives the aircraft model to achieve pitch movement; in the yaw roll vibration cylinder 1, according to the second step, the rotation drive of the yaw axis 18 and the roll axis 16 is realized, and then the piezoelectric balance 2 is driven to perform yaw roll movement through the conical connection at the roll axis 16, thereby driving the aircraft model to achieve yaw roll movement;

[0026] Step 5: The aircraft model is excited with three degrees of freedom in the flow field, and the multi-dimensional aerodynamic force is transmitted to the piezoelectric balance 2 through the cone surface, so as to obtain the aerodynamic load data; the rotation is monitored by the angular displacement encoder 22 inside the three-degree-of-freedom excitation mechanism, so as to obtain the three-degree-of-freedom angular displacement data of the test model; the angular velocity of the model is obtained, and substituted into the dynamic derivative formula ( )、( ) Solve the direct derivatives, cross derivatives and cross-coupled derivatives required for the experiment;

[0027] ( )

[0028] ( )

[0029] Where w and v are the results of wind and vacuum calibration conditions, respectively, M is the amplitude of the forcing moment, ω is the circular frequency of vibration, , are the circular frequencies of vibration under wind and vacuum calibration conditions, is the phase lag angle, θ0 is the motion amplitude, is the moment of inertia of the aircraft model, is the aerodynamic damping, is the aerodynamic static damping, q ∞ 、V ∞ are the fluid density and characteristic velocity respectively, A is the reference area, d is the reference length, is the direct derivative, is the time difference derivative, is the aerodynamic derivative, , Represent the movement angles in the main direction and the secondary direction respectively, , are the angular velocities in the primary and secondary directions, The aerodynamic torque in the main direction, , are the aerostatic moment and aerodynamic moment in the secondary direction, is the small phase difference between the primary motion and the secondary torque, and α is the angle of attack of the aircraft.

[0030] The beneficial effect of the present invention is to provide a three-degree-of-freedom dynamic derivative test method based on piezoelectric ceramic drive, which can realize the three-degree-of-freedom movement of the aircraft model under a complex high-speed flow field. Compared with traditional devices, the tail strut excitation device has less interference with the flow under high-speed flow fields, and can ensure the multi-degree-of-freedom composite movement capability. The present invention adopts an embedded tail strut design, and multiple groups of piezoelectric ceramics are alternately actuated and driven in coordination to realize three-degree-of-freedom forced vibration in the narrow and long cavity of the model; a force-position state monitoring system based on an angular displacement encoder and a piezoelectric balance is built to collect the angular displacement and multi-dimensional aerodynamic data of the model, effectively ensuring the solution of multiple types of dynamic derivative data. The invention can ensure the three-degree-of-freedom dynamic derivative test of the aircraft model under high-speed flow fields, and ensure the accuracy of dynamic derivative measurement, greatly improving the efficiency of dynamic derivative tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is an overall flow chart of a three-degree-of-freedom dynamic derivative test method based on piezoelectric drive.

[0032] Figure 2 It is a simplified structural diagram of the yaw-roll bidirectional parallel mechanism of the present invention.

[0033] Figure 3 It is a schematic structural diagram of the yaw-roll bidirectional parallel mechanism of the present invention.

[0034] Figure 4 It is an overall schematic diagram of a three-degree-of-freedom excitation device of the present invention.

[0035] Figure 5 This is an external assembly diagram of the three-degree-of-freedom excitation device of the present invention.

[0036] Figure 6 It is an assembly cross-sectional view of the three-degree-of-freedom exciting device of the present invention.

[0037] Figure 7 It is an assembly side sectional view of the three-degree-of-freedom angular displacement monitoring arrangement of the present invention.

[0038] Figure 8 It is a cross-sectional view of the parallel end assembly of the yaw and roll excitation mechanism of the present invention.

[0039] Fig. 9 It is a front cross-sectional view of the assembly of the three-degree-of-freedom angular displacement monitoring arrangement of the present invention.

[0040] Fig.10 It is a schematic diagram of the three-degree-of-freedom dynamic derivative forced vibration test system of the present invention.

[0041] In the figure: 1 yaw and roll vibration cylinder; 2 piezoelectric balance; 3 yaw and roll front articulated seat; 4 yaw and roll moving base; 5 yaw and roll piezoelectric actuator; 6 pitch front articulated seat; 7 pitch moving base; 8 yaw and roll rear articulated seat; 9 yaw and roll pre-tightening wedge; 10 pitch piezoelectric actuator; 11 pitch rear articulated seat; 12 pitch pre-tightening wedge; 13 pitch body; 14 positioning pin; 15 split cone block; 16 roll axis; 17 lever; 18 yaw axis; 19 pitch transmission long rod; 20 pitch transmission short rod; 21 grating code disk; 22 angular displacement encoder; 23 pitch yaw encoder fixture; 24 roll encoder fixture; 25 pitch axis. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments and drawings.

[0043] The embodiment takes a three-degree-of-freedom forced vibration dynamic derivative test system designed for a 2.4m wind tunnel as an example. The pitch load is 59Nm, the yaw and roll load is 13Nm, the excitation amplitude is ±1°, and the frequency is 5Hz. The following is a description with reference to the accompanying drawings:

[0044] Figure 4 The following is a schematic diagram of the assembly of a tail strut embedded three-degree-of-freedom excitation device according to the present invention. The three-degree-of-freedom forced vibration dynamic derivative test method based on piezoelectric drive according to the present invention is used. The specific steps are as follows:

[0045] (1) Based on the given load and space size requirements, determine the task constraints, where the aerodynamic load requirements are as follows:

[0046] ( )

[0047] Among them, M x , M y , M z are the aerodynamic torque loads in the rolling, pitching and yaw directions, L x , L y , L zThey are the space limitations of the roll, pitch, and yaw axes. Since the space inside the aircraft model cavity is long and narrow, the space size of the roll axis is much larger than the other two directions. At the same time, the loads in the yaw and roll directions are similar, and significantly smaller than the load in the pitch direction. Therefore, a three-degree-of-freedom excitation layout in which a yaw-roll bidirectional parallel mechanism and a pitch unidirectional excitation mechanism are connected in series is proposed. In this layout, the yaw-roll bidirectional parallel mechanism is located at the front side of the three-degree-of-freedom excitation system and is directly connected to the aircraft model. It is responsible for driving the aircraft model to achieve the compound motion of yaw and roll. The pitch unidirectional excitation mechanism is placed at the back side of the three-degree-of-freedom excitation layout and is connected in series with the yaw-roll bidirectional parallel mechanism to drive the yaw-roll bidirectional parallel mechanism and the exciting motion of the aircraft in the pitch direction. This design aims to effectively improve the multi-dimensional excitation capability of the aircraft model to meet the experimental needs.

[0048] (2) Design a yaw-roll bidirectional parallel mechanism. Its motion principle and mechanism diagram are shown in the following figure. Figure 2 As shown. The yaw-roll bidirectional parallel mechanism consists of four branches, each of which includes a linear drive mechanism and a displacement amplification mechanism, and is finally connected in parallel to the end actuator. The four yaw-roll piezoelectric actuators 5 in the mechanism are used as linear drivers to output linear displacement. Both ends of each yaw-roll piezoelectric actuator 5 are connected to the yaw-roll moving base 4 to play an axial protection role. The yaw-roll moving base 4 at the tail end is connected to the yaw-roll rear hinge seat 8 through a spherical fit so that it can be automatically centered after being stressed. The yaw-roll preload wedge 9 is tightened between the wedge surface at the rear end of the yaw-roll rear hinge seat 8 and the outer wall of the yaw-roll vibration cylinder 1 by bolts, playing an axial fixing role. The front yaw-roll hinge seat 3 serves as a one-way rotating pair at the front end of the yaw-roll piezoelectric actuator 5, relying on one side to achieve relative rotation with the spherical fit of the yaw-roll moving base 4, and the other side is hinged with the yaw-roll transmission lever 17 to achieve displacement transmission.

[0049] The four yaw and roll transmission levers 17 are used as displacement amplification mechanisms to amplify the linear displacement. A single yaw and roll transmission lever 17 contains two cylindrical shafts and a ball, one of which forms a rotation pair with the cylindrical surface of the yaw and roll front hinge seat 3, and the other cylindrical shaft forms a rotation pair with the cylindrical hole in the yaw and roll vibration cylinder 1; the ball at the end of the lever contacts the matching plane of the roll shaft 16 to form a high pair of point-to-surface contact, with two tangential degrees of freedom along the plane. The roll shaft 16 and the yaw shaft 18 are parallel ends, and the yaw shaft 18 is hinged to the yaw and roll vibration cylinder 1 to form a yaw rotation axis. The roll axis 16 is hinged with the yaw axis 18 to form a roll rotation axis and is fixed to the piezoelectric balance 2 through a conical fastening connection.

[0050] When the two yaw and roll piezoelectric actuators 5 on the left perform linear driving and the two actuators on the right perform reverse driving, the yaw and roll transmission levers 17 swing in the same direction, driving the balls to slide on the matching plane and drive the yaw axis to rotate around If the two diagonal yaw and roll piezoelectric actuators 5 are driven linearly and the other two actuators are driven in the opposite direction, the upper and lower yaw and roll transmission levers 17 will swing in different directions, driving the ball bearings to slide on the matching plane, driving the roll axis to rotate around Rotation. Thus, the linear displacement of the four yaw-roll piezoelectric actuators 5 is converted into yaw and roll rotational angular displacement. All linear drive mechanisms and displacement amplification mechanisms are symmetrically arranged around the roll axis 16 and the piezoelectric balance 2, thereby ensuring that the yaw-roll bidirectional parallel mechanism works in a narrow and long space to achieve efficient space utilization.

[0051] (3) Build a three-degree-of-freedom dynamic derivative excitation device. In addition to the yaw-roll bidirectional parallel mechanism, the device also involves a pitch front articulated seat 6, a pitch moving base 7, a pitch piezoelectric actuator 10, a pitch rear articulated seat 11, a pitch preload wedge 12, a pitch body 13, a positioning pin 14, a split cone block 15, a pitch transmission long rod 19, a pitch transmission short rod 20, a grating code disk 21, an angular displacement encoder 22, a pitch yaw encoder fixture 23, a roll encoder fixture 24 and a pitch axis 25. The three-degree-of-freedom dynamic derivative excitation device is assembled in sequence, and the final structure is as follows: Figures 4 to 9 As shown, the pitch piezoelectric actuator 10 is connected to the power amplifier, and the power amplifier is connected to the voltage output card, thereby forming an actuator control module. At the same time, the piezoelectric balance 2 is connected to the multi-dimensional force acquisition card, and the angular displacement encoder 22 is connected to the angular displacement detection card, forming a physical quantity measurement acquisition module. Then, the actuator control module and the physical quantity measurement acquisition module are connected to the real-time controller and the host computer in turn to form an actuator control loop and a physical quantity measurement acquisition loop to achieve output control of the piezoelectric ceramics and real-time measurement of the angular displacement and multi-dimensional force of the excitation device. Finally, the aircraft model is fastened to the conical surface of the piezoelectric balance 2 to form a three-degree-of-freedom dynamic derivative forced vibration test system, as shown in FIG. Fig.10 shown.

[0052] (4) Under the wind tunnel flow field, for different angles of attack, according to the pitch and yaw and roll motion requirements, the actuator control signal is designed. The driving signal of the two ceramics in the pitch group can be expressed as follows: ), the driving signal of the four ceramics of the yaw and roll group can be expressed as the formula ( ).

[0053] (5) The model is excited with three degrees of freedom in the flow field, and the multi-dimensional aerodynamic force is transmitted through the cone surface and the piezoelectric balance 2, thereby obtaining the aerodynamic load data; the rotation of the model is monitored by the angular displacement encoder 22 inside the model, thereby obtaining the three-degree-of-freedom angular displacement data of the test model; thus, the angular velocity of the model can be obtained and substituted into the dynamic derivative formula ( )、( ) Solve the direct derivatives and cross and cross-coupled derivatives required for the test; Compared with the traditional dynamic derivative test method, the three-degree-of-freedom dynamic derivative test method based on piezoelectric drive proposed in the present invention adopts multiple groups of piezoelectric actuators for collaborative driving, and realizes the three-degree-of-freedom excitation of the wind tunnel aircraft model in a narrow and long cavity through multiple series and parallel rod groups. Compared with the traditional method, the present invention realizes the high-speed wind tunnel multi-degree-of-freedom forced excitation vibration derivative test in the form of a model tail support, forms a force-position state monitoring system based on an angular displacement encoder and a piezoelectric balance, collects the model angular displacement and multi-dimensional aerodynamic force, and then reliably obtains multiple types of dynamic derivative data, solving the problems of low excitation freedom of traditional high-speed wind tunnel dynamic derivative devices, low test Mach number of multi-degree-of-freedom dynamic derivative devices, and large interference with the model flow, thereby greatly improving the accuracy of dynamic derivative measurement and improving the efficiency of dynamic derivative tests.

Claims

1. A three-degree-of-freedom forced vibration dynamic derivative test method based on piezoelectric actuation, characterized in that: Here are the steps: Step 1: Determine the task volume constraints based on the given load and space size requirements; Since the space inside the aircraft model cavity is long and narrow, when facing the large aspect ratio aircraft model, the loads in the yaw and roll directions are close and much smaller than the load in the pitch direction. Therefore, a three-degree-of-freedom excitation mechanism layout of a yaw-roll bidirectional parallel mechanism + a pitch unidirectional excitation mechanism in series is proposed; the yaw-roll bidirectional parallel mechanism is placed on the front side of the three-degree-of-freedom excitation mechanism layout and is directly connected to the aircraft model to drive the aircraft model to perform yaw-roll bidirectional compound motion; the pitch unidirectional excitation mechanism is placed on the rear side of the three-degree-of-freedom excitation mechanism layout and is connected in series with the yaw-roll bidirectional parallel mechanism to drive the yaw-roll bidirectional parallel mechanism and the aircraft model to realize pitch direction excitation together; Step 2: Design the yaw-roll bidirectional parallel mechanism The yaw-roll bidirectional parallel mechanism includes four branches, each of which includes a linear drive mechanism and a displacement amplification mechanism, and each branch is ultimately connected in parallel to a parallel end; Four yaw roll piezoelectric actuators (5) are used as linear actuators to output linear displacement; the front and rear sides of the yaw roll piezoelectric actuator (5) are connected to two yaw roll movable bases (4) as axial protection for the yaw roll piezoelectric actuator (5); the yaw roll movable base (4) at the rear end is spherically matched with the yaw roll rear hinge seat (8) to facilitate automatic centering after force is applied; the yaw roll preload wedge block (9) is tightened between the rear end wedge surface of the yaw roll rear hinge seat (8) and the outer wall of the yaw roll vibration cylinder (1) by bolts to play an axial fixing role; the yaw roll front hinge seat (3) serves as a one-way rotation pair on the front side of the yaw roll piezoelectric actuator (5), one side of which is spherically matched with the yaw roll movable base (4) to achieve relative rotation, and the other side of which is spherically matched with the yaw roll movable base (4) to achieve relative rotation. The side is hinged with the yaw roll transmission lever (17) to transmit displacement; the four yaw roll transmission levers (17) are used as displacement amplification mechanisms to amplify linear displacement, and a single yaw roll transmission lever (17) comprises two cylindrical shafts and a ball bearing, wherein one cylindrical shaft cooperates with the cylindrical surface of the yaw roll front hinge seat (3) to form a rotation pair, and the other cylindrical shaft cooperates with the cylindrical hole in the yaw roll vibration cylinder (1) to form a rotation pair, and the ball bearing at the end of the yaw roll transmission lever (17) contacts with the matching plane of the roll shaft (16) to form a high pair of point-to-surface contact, which can generate relative displacement along the two degrees of freedom tangential to the matching plane; the roll shaft (16) and the yaw shaft (18) are used as parallel ends, wherein the yaw shaft (18) is hinged with the yaw roll vibration cylinder (1) to form a yaw rotation axis O z The roll axis (16) is hinged with the yaw axis (18) to form a roll rotation axis O x The piezoelectric balance (2) and the roll axis (16) are fastened together through a conical surface; when the two yaw roll piezoelectric actuators (5) on the left are linearly driven, the two yaw roll piezoelectric actuators (5) on the right are driven in reverse phase, driving the yaw roll transmission lever (17) to swing in the same direction, driving the ball bearing to slide on the matching plane, and at the same time driving the yaw axis to rotate around O z Rotation; when the two diagonal yaw roll piezoelectric actuators (5) are driven linearly and the other two yaw roll piezoelectric actuators (5) are driven in reverse phase, the upper and lower yaw roll transmission levers (17) are driven to swing in different directions, driving the ball bearings to slide on the matching plane, and at the same time driving the roll axis to rotate around O x Rotation; thereby realizing the motion conversion of the linear displacement drive of the four yaw-roll piezoelectric actuators (5) into the yaw-roll rotational angular displacement; wherein the linear drive mechanism and the displacement amplification mechanism are symmetrically arranged around the roll axis (16) and the piezoelectric balance (2), ensuring that the yaw-roll bidirectional parallel mechanism can work in a narrow and long space, thereby achieving a high space utilization rate; Step 3: construct a three-degree-of-freedom dynamic derivative excitation device, which includes, in addition to the yaw-roll bidirectional parallel mechanism, a pitch front hinge seat (6), a pitch moving base (7), a pitch piezoelectric actuator (10), a pitch rear hinge seat (11), a pitch preload wedge (12), a pitch body (13), a positioning pin (14), a split cone block (15), a pitch transmission long rod (19), a pitch transmission short rod (20), a grating code disk (21), an angular displacement encoder (22), a pitch yaw encoder fixture (23), a roll encoder fixture (24) and a pitch axis (25); A cylindrical groove is formed at the rear end of the pitch body (13) for assembly with the split cone block (15). During assembly, the pin holes on the pitch body (13) and the split cone block (15) are aligned, a positioning pin (14) is inserted to ensure that the circumferential angles of the two are aligned, and then a bolt is inserted and tightened to ensure that the pitch body (13) and the split cone block (15) are connected and fastened. The front end of the pitch body (13) is provided with a groove, the end cylindrical surface of the pitch transmission short rod (20) matches with the groove at the front end of the pitch body (13), the end cylindrical surface of the pitch transmission long rod (19) matches with the groove on the yaw roll vibration cylinder (1), the pitch transmission short rod (20) and the front end cylindrical surface of the pitch transmission long rod (19) are matched and installed in the pitch front hinge seat (6), forming a set of pitch displacement amplification mechanism, realizing the motion transmission of the pitch excitation mechanism; the upper and lower surfaces of the pitch body (13) are respectively provided with a long cylindrical groove, the rear end of the long cylindrical groove is installed with the pitch rear hinge seat (11) and the pitch preload wedge (12), and the two are matched through the inclined surface; the pitch moving base (7) is assembled on the pitch piezoelectric actuator ( 10) at both ends, forming a combination, and installing the combination into the long cylindrical groove of the pitch main body (13), the pitch moving base (7) at the front end of the combination cooperates with the spherical surface of the pitch front hinge seat (6), and the pitch moving base (7) at the rear end cooperates with the spherical surface of the pitch rear hinge seat (11); a pre-tightening bolt is installed in the threaded hole of the pitch pre-tightening wedge block (12), and through the pre-tightening of the bolt, the pitch rear hinge seat (11) and the pitch pre-tightening wedge block (12) cooperate with the inclined surface to ensure that the output of the pitch piezoelectric actuator (10) is aligned, and the reliable output of the working force of the pitch piezoelectric actuator (10) is ensured; the components installed in the two long cylindrical grooves of the pitch main body (13) are the same and the installation method is the same, and the construction of the pitch excitation structure is completed; The front end of the pitch body (13) is provided with a cylindrical hole on both side planes for installing a pitch axis (25), and the yaw-roll bidirectional parallel mechanism is connected to the pitch body (13) via the pitch axis (25), so as to realize the series connection of the yaw-roll bidirectional parallel mechanism and the pitch unidirectional excitation mechanism; a grating code disk (21) is installed on the inner side of the pitch axis (25) for measuring the angular displacement in the pitch direction; a grating code disk (21) is installed on the cylindrical boss of the yaw axis (18) for measuring the angular displacement in the yaw direction; a grating code disk (21) is installed at the connection between the roll axis (16) and the yaw axis (18) for measuring the angular displacement in the roll direction; and the two angular The displacement encoder (22) is mounted on the pitch-yaw encoder fixture (23) by means of screws, and is mounted on the yaw-roll vibration cylinder (1) by means of positioning pins on the pitch-yaw encoder fixture (23), and is fastened by means of bolts; at the same time, an angular displacement encoder (22) is mounted on the roll encoder fixture (24) by means of screws, and is mounted on the yaw axis (18) by means of positioning pins on the roll encoder fixture (24), and is fastened by means of screws; the yaw axis (18) is mounted in a corresponding mounting hole of the yaw-roll vibration cylinder (1), and the installation of the yaw-roll bidirectional parallel mechanism three-degree-of-freedom angular displacement monitoring device is completed; The pitch piezoelectric actuator (10) is connected to a power amplifier, and the power amplifier is connected to a voltage output card to form an actuator control module; the piezoelectric balance (2) is connected to a multi-dimensional force acquisition card, and the angular displacement encoder (22) is connected to an 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 a real-time controller and a host computer in sequence to form an actuator control loop and a physical quantity measurement acquisition loop, so as to realize the output control of the piezoelectric ceramic and the real-time measurement of the angular displacement and multi-dimensional force of the excitation device, and finally the aircraft model is tightened and matched with the conical surface of the piezoelectric balance (2) to form a three-degree-of-freedom dynamic derivative forced vibration test system; Step 4: Under the wind tunnel flow field, the three-degree-of-freedom excitation mechanism is driven by two pitch piezoelectric actuators (10) and four yaw and roll piezoelectric actuators (5) to perform three-degree-of-freedom compound motion; wherein the driving signals of the two pitch piezoelectric actuators (10) are expressed as formula ( ): ( ) The driving signal of the four yaw and roll piezoelectric actuators (5) is expressed as follows: ): ( ) in, , are the bias and drive values ​​of the i-th pitch piezoelectric actuator (10), , are respectively the excitation amplitude and frequency of the pitch piezoelectric actuator (10) in the j-th degree of freedom transmission chain, and t is a time variable; The pitch piezoelectric actuators (10) on both sides extend and retract in anti-phase according to the driving signal, and the output displacement axially pushes the pitch front hinge seat (6), drives the pitch transmission long rod (19) and the pitch transmission short rod (20), and uses the pitch body (13) as a base to pry the yaw roll vibration cylinder (1) to achieve pitch movement. The yaw roll vibration cylinder (1) drives the piezoelectric balance (2) to pitch, and the conical connection of the piezoelectric balance (2) drives the aircraft model to achieve pitch movement; in the yaw roll vibration cylinder (1), according to the second step, the rotation drive of the yaw axis (18) and the roll axis (16) is achieved, and then the piezoelectric balance (2) is driven to perform yaw roll movement through the conical connection at the roll axis (16), thereby driving the aircraft model to achieve yaw roll movement; Step 5: The aircraft model is subjected to three-degree-of-freedom excitation in the flow field, and the multi-dimensional aerodynamic force is transmitted to the piezoelectric balance (2) through the cone surface, thereby obtaining aerodynamic load data; the rotation of the aircraft model is monitored by the angular displacement encoder (22) inside the three-degree-of-freedom excitation mechanism, thereby obtaining the three-degree-of-freedom angular displacement data of the aircraft model; the angular velocity of the model is obtained, and substituted into the dynamic derivative formula ( )、( ) Solve the direct derivatives, cross derivatives and cross-coupled derivatives required for the experiment; ( ) ( ) Where w and v are the results of wind and vacuum calibration conditions, respectively, 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 moment of inertia of the aircraft model, is the aerodynamic damping, is the aerodynamic static damping, q ∞ 、V ∞ are the fluid density and characteristic velocity respectively, A is the reference area, d is the reference length, is the direct derivative, is the time difference derivative, is the aerodynamic derivative, , Represent the movement angles in the main direction and the secondary direction respectively, , are the angular velocities in the primary and secondary directions, The aerodynamic torque in the main direction, , are the aerostatic moment and aerodynamic moment in the secondary direction, is the small phase difference between the primary motion and the secondary torque, and α is the angle of attack of the aircraft.

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