Piezoelectric balance and method for measuring propeller exciting force

Abstract

The application provides a piezoelectric balance and a measuring method thereof suitable for propeller exciting force measurement. The piezoelectric balance suitable for propeller exciting force measurement comprises a multi-component piezoelectric balance system 22, a propeller and a transmission shaft 1, the propeller is arranged at the upper end of the transmission shaft 1; a hollow structure is arranged inside the upper end of the transmission shaft 1, the multi-component piezoelectric balance system 22 is arranged inside the hollow structure, and the upper end of the multi-component piezoelectric balance system 22 is attached to the propeller and can measure the propeller exciting force. The application facilitates the measurement of the propeller exciting force, can estimate the propeller unsteady exciting force through the multi-component piezoelectric balance in a complex environment, can inversely solve the exciting force through the actual sensor measurement result, can reconstruct the dynamic exciting force in multiple directions, the multi-component piezoelectric balance system 22 arranged inside the transmission shaft 1 can avoid damage caused by extreme environment, and the carrying capacity for high static thrust and torque is improved.

Description

Technical Field

[0001] This invention relates to the field of propeller measurement technology, specifically to a piezoelectric balance and its measurement method suitable for measuring propeller excitation force, and more particularly to a shaft-end embedded multi-force piezoelectric balance and its measurement method suitable for measuring propeller excitation force. Background Technology

[0002] Vibration and noise caused by propellers have always been a major component of ship system noise. Accurately measuring the unsteady hydrodynamic forces of rotating propellers is of great significance for vibration and noise control. Therefore, it is necessary to design a force balance for measuring the excitation force of underwater propellers.

[0003] Existing force meters for ship propellers are large, complex in structure, and difficult to install. Furthermore, most of them directly measure static thrust and torque, failing to accurately measure the unsteady hydrodynamic forces acting on the propeller. Devices capable of estimating these forces entirely through experimentation are almost nonexistent. This is primarily because the unsteady excitation forces on propellers are complex, with amplitudes much smaller than static thrust, making them difficult to distinguish. The directions of these forces are also complex, with a wide dynamic range and rich spectral components.

[0004] Patent document CN105021337A discloses a propeller-driven rotary force measuring device and method. Developing a synchronous rotary force measuring device for propellers is of significant importance. The device comprises: a drive motor, which is a variable frequency AC motor; the output shaft of the variable frequency AC motor is connected to a torque sensor, which is fixed on a mounting platform; the torque sensor is connected to the propeller via a high-speed coupling B; the propeller is connected to a slip ring actuator; the other end of the slip ring actuator is connected to a six-component rotating shaft balance; and the six-component rotating shaft balance is connected to the propeller hub. This invention is applied to propeller-driven rotary force measuring devices. However, in this design, the sensor is not close to the propeller, resulting in a lower signal-to-noise ratio. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a piezoelectric balance and its measurement method suitable for measuring propeller excitation force.

[0006] The piezoelectric balance for measuring propeller excitation force according to the present invention includes a multi-force piezoelectric balance system, a propeller, and a drive shaft, wherein the propeller is disposed at the upper end of the drive shaft;

[0007] The upper end of the drive shaft has a hollow structure inside, and the multi-component piezoelectric balance system is set inside the hollow structure. The upper end of the multi-component piezoelectric balance system is attached to the propeller and can measure the propeller excitation force.

[0008] Preferably, the multi-component piezoelectric balance system includes an upper multi-component force measuring plate, a lower multi-component force measuring plate, a piezoelectric force sensor group, and a lead screw and slider preload mechanism;

[0009] The upper end face of the upper multi-component force measuring disk is connected to the propeller, the lower end face of the lower multi-component force measuring disk is attached to the inner end face of the hollow structure, and the piezoelectric force sensor group is arranged between the upper multi-component force measuring disk and the lower multi-component force measuring disk.

[0010] The lead screw and slider preload mechanism is connected to the upper multi-component force measuring plate, the lower multi-component force measuring plate, and the piezoelectric force sensor group, and can adjust the parallelism between the upper and lower multi-component force measuring plates. The piezoelectric force sensor group includes multiple piezoelectric force sensors.

[0011] Preferably, the propeller includes a hollow hub, a hub cap, and blades. The upper end face of the drive shaft is fastened to the lower end face of the hollow hub. The upper multi-component force measuring disk is close to the hollow hub, and the lower multi-component force measuring disk is clearance-fitted with the inner end face of the hollow structure.

[0012] Preferably, the piezoelectric force sensor group includes multiple piezoelectric force sensors mounted symmetrically on an axis.

[0013] Preferably, the lead screw and slider preload mechanism is configured in a one-to-one correspondence with the piezoelectric force sensor;

[0014] The lead screw and slider preload mechanism includes a worm gear, a worm, a wedge-shaped slider, a tensioning screw, an adjusting base, a stepped shaft, a base, and a base support plate. The base support plate is connected to the adjusting base and is longitudinally arranged on one side of the wedge-shaped slider. The lower end face of the adjusting base is fastened to a piezoelectric force sensor, and the lower end face of the piezoelectric force sensor is connected to a lower multi-component force measuring disk.

[0015] The upper end face of the wedge-shaped slider is in contact with the lower end face of the upper multi-component force measuring disk, and the lower end face of the wedge-shaped slider is in contact with the upper end face of the adjusting base. The upper end face of the adjusting base is a wedge-shaped surface.

[0016] The wedge-shaped slider is provided with a threaded hole along the horizontal direction. The tensioning screw passes through the threaded hole. One end of the tensioning screw is connected to the base plate, and the other end of the tensioning screw is fixedly connected to the worm wheel. The worm wheel meshes with the longitudinally arranged worm. The worm is fixedly connected to the stepped shaft. One end of the stepped shaft is rotatably connected to the base. The base is fixedly installed on the lower multi-component force measuring plate.

[0017] When the lead screw and slider preload mechanism is adjusting the parallelism, the other end of the stepped shaft is connected to an external rod. After the hub cap is opened, the external rod can pass through the hollow hub and drive the worm to rotate through the stepped shaft, thereby driving the wedge slider to slide on the wedge surface in sequence through the worm wheel and the tensioning screw.

[0018] Preferably, a hole is provided on the upper multi-component force measuring disk at a position corresponding to the stepped shaft, and the size of the hole is larger than the diameter of the external rod;

[0019] When the lead screw and slider preload mechanism completes the parallelism adjustment, the external rod is disassembled, and a sealing plug is provided inside the hole.

[0020] Preferably, one end of the tensioning screw is connected to the base plate via a coupling device;

[0021] The base plate is provided with a through hole, the connecting device passes through the through hole and is clearance-fitted with the through hole, one end of the connecting device has a diameter larger than the through hole, and the other end of the connecting device is connected to the tensioning screw.

[0022] When the lead screw and slider preload mechanism completes the parallelism adjustment, a positioning stop pin is provided on the base plate. The positioning stop pin can limit the longitudinal position of the wedge slider, thereby preventing the wedge slider from sliding on the wedge surface.

[0023] Preferably, a rolling bearing is provided between the stepped shaft and the base.

[0024] Preferably, both the lower multi-component force measuring disk and the transmission shaft are provided with through holes along the axial direction, and the through holes are provided with wiring.

[0025] The measurement method of the piezoelectric balance for measuring propeller excitation force according to the present invention, using the aforementioned piezoelectric balance for measuring propeller excitation force, includes the following steps:

[0026] Step 1: Adjust the parallelism by controlling the external rod to drive the wedge slider to slide on the wedge surface, thereby adjusting the parallelism between the upper and lower multi-component force measuring plates.

[0027] Step 2: Calculate the equivalent longitudinal stiffness, equivalent transverse stiffness, equivalent torsional stiffness, and equivalent bending stiffness of the combined effect of the multi-force piezoelectric balance system and the hollow tube wall on the drive shaft, and retain them as parameters.

[0028] Step 3: Disassemble the external rod and control the propeller to start working. The propeller is subjected to dynamic excitation force.

[0029] Step 4: The dynamic excitation force is converted into a response signal by a piezoelectric force sensor group, and the response signal is input into the PC through the LMS data acquisition system;

[0030] Step 5: The PC processes the input signal based on the parameters obtained in Step 2 using the decoupling equivalent formula and the torque inverse formula, thereby reconstructing the dynamic excitation force.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention has a simple structure and is easy to operate, which facilitates the measurement of propeller excitation force. It enables the estimation of unsteady propeller excitation force in complex environments through a multi-component piezoelectric balance. The excitation force can be solved inversely based on the measurement results of the multi-component piezoelectric balance system, and the dynamic excitation force in multiple directions can be reconstructed.

[0033] 2. The present invention employs a multi-component piezoelectric balance system installed inside the drive shaft, which avoids damage caused by extreme environments. By connecting it in parallel with the hollow tube wall of the drive shaft, it improves the load-bearing capacity for high static thrust and torque.

[0034] 3. The present invention adopts the technical means of setting a lead screw and slider pre-tightening mechanism in the multi-force piezoelectric balance system. By fine adjustment, the parallelism of the upper and lower contact planes is ensured, so that the piezoelectric force sensor group is basically uniformly stressed, which facilitates force estimation. Attached Figure Description

[0035] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0036] Figure 1 This is a schematic diagram of the structure of the present invention;

[0037] Figure 2 For the present invention Figure 1 Cross-sectional view along the AA direction;

[0038] Figure 3 This is a schematic diagram of the main structure of the lead screw and slider preload mechanism in this invention;

[0039] Figure 4 This is a side view of the lead screw and slider preload mechanism in this invention.

[0040] Figure 5 This is a schematic diagram illustrating the calculation principle of step 2 in the measurement method of a piezoelectric balance applicable to propeller excitation force measurement in this invention.

[0041] Figure 6 This is a flowchart of the measurement method of the piezoelectric balance applicable to the measurement of propeller excitation force in this invention;

[0042] The diagram shows:

[0043] Drive shaft 1, worm gear 10

[0044] Hollow propeller hub 2 Wedge-shaped slider 11

[0045] Hub cap 3, tension screw 12

[0046] Blade 4, engagement device 13

[0047] Multi-component force measuring plate 5 Adjustment base 14

[0048] Upper multi-component force measuring plate 51, stepped shaft 15

[0049] Lower multi-component force measuring plate 52, rolling bearing 16

[0050] Piezoelectric force sensor assembly 6, base 17

[0051] First piezoelectric force sensor 61 Base plate 18

[0052] Second piezoelectric force sensor 62, positioning stop pin 19

[0053] Third piezoelectric force sensor 63 wedge surface 20

[0054] Fourth piezoelectric force sensor 64 External rod 21

[0055] Sealing plug 7 Multi-component piezoelectric balance system 22

[0056] Lead screw and slider preload mechanism 8 holes 23

[0057] worm gear 9 Detailed Implementation

[0058] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0059] In view of the deficiencies in the prior art, this invention proposes a piezoelectric balance and its measurement method suitable for measuring the excitation force of a propeller. The piezoelectric balance is located at the shaft end, close to the propeller, so that the measured signal has a high signal-to-noise ratio. At the same time, the force-measuring piezoelectric balance is mainly composed of multiple axisymmetric piezoelectric force sensors, which can accurately and stably measure the dynamic force response of the system. The input force is reconstructed by decoupling the equivalent force of the measurement results and inverse calculation of the torque. The lead screw and slider preload mechanism is used to facilitate the adjustment of the force uniformity of the multiple piezoelectric force sensors.

[0060] The piezoelectric balance for measuring propeller excitation force provided by the present invention, such as Figure 1As shown, the device includes a multi-component piezoelectric balance system 22, a propeller, and a drive shaft 1. The propeller consists of a hollow hub 2, a hub cap 3, and blades 4, and is positioned at the upper end of the drive shaft 1. The upper end of the drive shaft 1 has a hollow structure inside, and the upper surface of the drive shaft 1 is connected to the lower surface of the hollow hub 2 by multiple bolts. The multi-component piezoelectric balance system 22 is located inside the hollow structure, and its upper end is attached to the propeller and can measure the propeller's excitation force.

[0061] like Figure 3 , Figure 4 As shown, the multi-component piezoelectric balance system 22 includes an upper multi-component force measuring plate 51, a lower multi-component force measuring plate 52, a piezoelectric force sensor group 6, and a lead screw and slider pre-tensioning mechanism 8. The upper end face of the upper multi-component force measuring plate 51 is close to the hollow propeller hub 2, and the lower end face of the lower multi-component force measuring plate 52 is in contact with the inner end face of the hollow structure. The piezoelectric force sensor group 6 is disposed between the upper multi-component force measuring plate 51 and the lower multi-component force measuring plate 52. The lead screw and slider pre-tensioning mechanism 8 is connected to the upper multi-component force measuring plate 51, the lower multi-component force measuring plate 52, and the piezoelectric force sensor group 6, and can adjust the parallelism between the upper and lower multi-component force measuring plates 51 and 52. The piezoelectric force sensor group 6 includes multiple piezoelectric force sensors. The upper multi-component force measuring plate 51 is close to the hollow propeller hub 2, and the lower multi-component force measuring plate 52 is in clearance fit with the inner end face of the hollow structure. The piezoelectric force sensor group 6 includes multiple axisymmetrically mounted piezoelectric force sensors, a distribution that facilitates data decoupling. Both the lower multi-component force measuring disk 52 and the transmission shaft 1 have axially arranged through holes, with wiring installed inside the through holes.

[0062] like Figure 3 , Figure 4As shown, the lead screw and slider pre-tensioning mechanism 8 is configured in a one-to-one correspondence with the piezoelectric force sensor; the lead screw and slider pre-tensioning mechanism 8 includes a worm gear 9, a worm 10, a wedge-shaped slider 11, a tensioning spiral lead screw 12, a connecting device 13, an adjusting base 14, a stepped shaft 15, a rolling bearing 16, a base 17, a base support plate 18, and a positioning stop pin 19. The base support plate 18 is connected to the adjusting base 14 and is longitudinally arranged on one side of the wedge-shaped slider 11. The lower end face of the adjusting base 14 is connected to the piezoelectric force sensor by bolts, and the lower end face of the piezoelectric force sensor is connected to the lower multi-component force measuring disk 52. The upper end face of the wedge-shaped slider 11 is in contact with the lower end face of the upper multi-component force measuring disk 51, and the lower end face of the wedge-shaped slider 11 is in contact with the upper end face of the adjusting base 14. The upper end face of the adjusting base 14 is a wedge-shaped surface 20. A threaded hole is provided along the transverse side of the wedge-shaped slider 11. The tensioning screw 12 passes through the threaded hole. One end of the tensioning screw 12 is connected to the base support plate 18, and the other end of the tensioning screw 12 is fixedly connected to the worm gear 9. The worm gear 9 meshes with the longitudinally arranged worm 10. Rod 10 is fixedly connected to stepped shaft 15. One end of stepped shaft 15 is rotatably connected to base 17, which is fixedly mounted on lower multi-component force measuring disk 52. When the lead screw slider pre-tightening mechanism 8 adjusts the parallelism, the other end of stepped shaft 15 is connected to external rod 21. After opening the propeller hub cap 3, external rod 21 can pass through the hollow propeller hub 2 and drive the worm gear 10 to rotate via stepped shaft 15, thereby driving the wedge slider 11 to slide on wedge surface 20 in sequence through worm wheel 9 and tensioning screw 12. Adjustment base 14 is fixed to piezoelectric force sensor group 6 by bolts.

[0063] like Figure 1 As shown, a hole 23 is provided on the upper multi-component force measuring disk 51 at a position corresponding to the stepped shaft 15. The size of the hole 23 is larger than the diameter of the external rod 21. When the lead screw slider preload mechanism 8 completes the parallelism adjustment, the external rod 21 is disassembled, and a sealing plug 7 is provided inside the hole 23. The external rod 21 is relatively long axially and can extend to the outside through the hole 23 in the upper multi-component force measuring disk 51, facilitating the adjustment of the device. After adjustment, it is sealed by the sealing plug 7 to prevent the measurement system from failing due to extreme environments.

[0064] like Figure 4As shown, one end of the tensioning screw 12 is connected to the base plate 18 via a connecting device 13. The base plate 18 has a through hole, through which the connecting device 13 passes and is clearance-fitted. One end of the connecting device 13 has a diameter larger than the through hole, and the other end is connected to the tensioning screw 12. When the screw-slider pre-tensioning mechanism 8 completes parallelism adjustment, a positioning stop pin 19 is provided on the base plate 18. The positioning stop pin 19 can limit the longitudinal position of the wedge-shaped slider 11, thereby preventing the wedge-shaped slider 11 from sliding on the wedge-shaped surface 20. A rolling bearing 16 is provided between the stepped shaft 15 and the base 17.

[0065] Example 1:

[0066] This embodiment provides a shaft-end embedded multi-component piezoelectric balance for measuring propeller excitation force, including an embedded multi-component piezoelectric balance system 22, a hollow propeller hub 2, propeller blades 4, a hub cap 3, and a drive shaft 1. The multi-component piezoelectric balance system 22 is installed inside the propeller drive shaft 1 and is used to reconstruct the unsteady hydrodynamic or unsteady aerodynamic forces experienced by the propeller. In order to avoid damage from extreme environments, the embedded multi-component piezoelectric balance system 22 is located inside the drive shaft 1, with one end close to the hollow propeller hub 2, hub cap 3, and propeller blades 4, and has a high signal-to-noise ratio; the other end is in contact with the drive shaft 1 with a hollow structure at the shaft end.

[0067] The propeller blades 4 are mounted on the hollow hub 2 and fixed by the hub cap 3. The embedded multi-component piezoelectric balance system 22 is installed between the hollow hub 2 and the drive shaft 1 with a hollow structure at the shaft end. By connecting in parallel with the tube wall of the hollow structure of the drive shaft 1, the system improves the load-bearing capacity for high static thrust and torque.

[0068] The embedded multi-force piezoelectric balance system 22 consists of a multi-force measuring disk 5, a piezoelectric force sensor group 6, and a lead screw and slider preload mechanism 8. The piezoelectric force sensor group 6 is corrosion-resistant, provides stable measurement data, and can measure dynamic force response. It includes a first piezoelectric force sensor 61, a second piezoelectric force sensor 62, a third piezoelectric force sensor 63, and a fourth piezoelectric force sensor 64, arranged in a "U" shape and installed symmetrically along the axis. This distribution facilitates data decoupling. The drive shaft 1 and the multi-force measuring disk 5 are clearance-fitted. The upper end face of the drive shaft 1 is connected to the end face of the hollow propeller hub 2 by multiple bolts.

[0069] The multi-component force measuring disk 5 is used for the fixed installation of the piezoelectric force sensor assembly 6 and the lead screw slider preload mechanism 8. The piezoelectric force sensor assembly 6 does not contact the drive shaft 1 and is evenly distributed between the upper multi-component force measuring disk 51 and the lower multi-component force measuring disk 52. The lower surface of the lower multi-component force measuring disk 52 is in contact with the inner end face of the drive shaft 1, and there is a hollow space in the middle to facilitate the entry and exit of the experimental connection wire. The upper surface of the upper multi-component force measuring disk 51 is in contact with the lower end face of the hollow paddle hub 2. Due to the piezoelectric force sensor... Group 6 has high sensitivity, so even if the mating surface of the multi-component force measuring disk 5 is made as close to the machining accuracy as possible, it is still difficult to ensure that each sensor in the piezoelectric force sensor group 6 is subjected to uniform force. To solve this problem, a lead screw and slider preload mechanism 8 is designed, which is located between the piezoelectric force sensor group 6 and the upper multi-component force measuring disk 51. By fine adjustment, the parallelism of the mating plane is ensured so that the four piezoelectric force sensors in the piezoelectric force sensor group 6 are subjected to basically uniform force, so as to facilitate force estimation.

[0070] The lead screw and slider preload mechanism 8 is adjusted by a wedge-shaped slider 11 with a horizontal upper surface. The upper surface of the wedge-shaped slider 11 is close to the upper multi-component force measuring disk 51, and the lower surface is in contact with the adjusting base 14. A threaded hole is provided in the middle for installing the tensioning screw 12. The tensioning screw 12 is connected to the engaging device 13 near the base plate 18, and the other end is fixedly connected to the worm gear 9. The worm gear 9 meshes with the worm 10. The worm 10 is fixedly connected to the stepped shaft 15, which is connected to the base 17 through a rolling bearing 16. The base 17 is fixedly installed to the lower multi-component force measuring disk 52 by screws. The engaging device 13 passes through the base plate 18 and leaves a certain gap when the shaft system is engaged. One end engages with the tensioning screw 12, and the other end is used to limit the axial position of the shaft system. The base plate 18 is provided with a positioning stop pin 19 to limit the position of the wedge-shaped slider 11 and prevent it from sliding on the wedge surface 20.

[0071] The stepped shaft 15 has a hollow hexagonal hole at its upper end. An external rod 21 passes through the upper multi-component force measuring disk 51 for adjusting the position of the wedge-shaped slider 11. The external rod 21 is relatively long axially and can extend to the outside through the hole 23 in the upper multi-component force measuring disk 51, facilitating device adjustment. After adjustment, the measurement system is sealed with a sealing plug 7 to prevent measurement system failure caused by extreme environments. The lead screw slider preload mechanism 8 is respectively matched with the first piezoelectric force sensor 61, the second piezoelectric force sensor 62, the third piezoelectric force sensor 63, and the fourth piezoelectric force sensor 64. Preload is applied manually for fine adjustment to ensure the parallelism of the mating surfaces and make the force on each piezoelectric force sensor basically uniform.

[0072] The measurement method of the piezoelectric balance for measuring propeller excitation force according to the present invention, using the aforementioned piezoelectric balance for measuring propeller excitation force, includes the following steps:

[0073] Step 1: Adjust the parallelism by controlling the external rod 21 to drive the wedge slider 11 to slide on the wedge surface 20, thereby adjusting the parallelism between the upper multi-component force measuring disk 51 and the lower multi-component force measuring disk 52.

[0074] Step 2: Calculate the equivalent longitudinal stiffness, equivalent transverse stiffness, equivalent torsional stiffness, and equivalent bending stiffness of the combined effect of the multi-force piezoelectric balance system 22 and the hollow tube wall on the drive shaft 1, and retain them as parameters.

[0075] Step 3: Disassemble the external rod 21 and control the propeller to start working. The propeller is subjected to dynamic excitation force.

[0076] Step 4: The dynamic excitation force is converted into a response signal by the piezoelectric force sensor group 6, and the response signal is input into the PC through the LMS data acquisition system; preferably, the response signal enters the LMS data acquisition system through a charge amplifier.

[0077] Step 5: The PC processes the input signal based on the parameters obtained in Step 2 using the decoupling equivalent formula and the torque inverse formula, thereby reconstructing the dynamic excitation force.

[0078] Example 2:

[0079] This embodiment provides the calculation process for steps 2 and 5 of the measurement method of the piezoelectric balance applicable to propeller excitation force measurement.

[0080] Taking the piezoelectric force sensor group 6, which includes a first piezoelectric force sensor 61, a second piezoelectric force sensor 62, a third piezoelectric force sensor 63, and a fourth piezoelectric force sensor 64, arranged in a "U" shape and axially symmetrically mounted, as an example:

[0081] In step 2, the multi-force piezoelectric balance system 22 is connected in parallel with the hollow tube wall of the drive shaft 1. The equivalent longitudinal stiffness of the combined action of the embedded multi-force piezoelectric balance system 22 and the tube wall of the drive shaft 1 is calculated. This is equivalent to the longitudinal stiffness of the hollow thin-walled stiffness of the drive shaft 1 combined with the longitudinal stiffness of the piezoelectric force sensor group 6. The equivalent longitudinal stiffness of the hollow thin-walled stiffness of the drive shaft 1 is:

[0082]

[0083] Among them, E t Let A be the elastic modulus of drive shaft 1. t Let l be the cross-sectional area of ​​the hollow shaft of drive shaft 1. t The length of the hollow part in drive shaft 1.

[0084] The total longitudinal equivalent stiffness of the piezoelectric force sensor group 6 is:

[0085] k z1 =4k s1

[0086] Where k s1 Let k be the longitudinal stiffness of a piezoelectric force sensor. z1 The longitudinal stiffness of the parallel piezoelectric force sensor group 6.

[0087] Therefore, the total equivalent longitudinal stiffness of the embedded adjustable dynamic instrument system 22 and the tube wall is:

[0088]

[0089] And k z1 With k s1 The magnitudes are similar, so the hollow part of drive shaft 1 will help distribute the force on the sensor.

[0090] The embedded multi-force piezoelectric balance system 22 is connected in parallel with the hollow tube wall of the drive shaft 1. Calculating the equivalent lateral stiffness of the combined effect of the embedded multi-force piezoelectric balance system 22 and the tube wall of the drive shaft 1 is relatively complex. First, the four piezoelectric force sensors are connected in both parallel and series connections, and their equivalent stiffness is:

[0091]

[0092] Where k s2 Let k be the lateral stiffness of a piezoelectric force sensor. z2 The lateral stiffness of the parallel piezoelectric force sensor group 6.

[0093] At the same time, it is connected in parallel with the tube wall of drive shaft 1. Therefore, the total lateral stiffness of the embedded multi-force piezoelectric balance system 22 and the tube wall is...

[0094]

[0095] Where k t2 This is the equivalent lateral stiffness of the thin-walled hollow shaft of drive shaft 1.

[0096] Similarly, the equivalent bending stiffness and equivalent torsional stiffness of the embedded multi-force piezoelectric balance system 22 under the combined action of the drive shaft 1 and the tube wall are represented by k3 and k4 respectively. The equivalent bending stiffness and equivalent torsional stiffness of the piezoelectric force sensor group 6 are k z3 k z4 .

[0097] In step 5, the response signal is input into the MATLAB program on the PC via the LMS data acquisition system. The input signal is processed using the decoupling equivalent formula and the torque inverse formula. The decoupling equivalent formula and the torque inverse formula are as follows:

[0098] Longitudinal force:

[0099]

[0100] Lateral force (taking the y-direction as an example):

[0101]

[0102] Bending moment (taking the direction about y as an example):

[0103]

[0104] Torque:

[0105]

[0106] Among them, f x1 f x2 f x3 f x4 f y1 f y2 f y3 f y4 f z1 f z2 f z3 f z4 The values ​​are the measurement results of the first piezoelectric force sensor 61, the second piezoelectric force sensor 62, the third piezoelectric force sensor 63, and the fourth piezoelectric force sensor 64 in the piezoelectric force sensor group 6, respectively. 'a' represents the distance from the first piezoelectric force sensor 61, the second piezoelectric force sensor 62, the third piezoelectric force sensor 63, and the fourth piezoelectric force sensor 64 to the center of the circle in the x and y directions. The solutions for the lateral force and bending moment in the x and z axes are similar.

[0107] The method for reconstructing dynamic excitation force in this invention is also applicable to piezoelectric force sensor groups 6 with different installation schemes. When the same or similar principle is used in piezoelectric force sensor groups 6 with different installation schemes, they should be equally protected.

[0108] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0109] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A piezoelectric balance suitable for measuring the excitation force of a propeller, characterized in that, It includes a multi-force piezoelectric balance system (22), a propeller and a drive shaft (1), the propeller being disposed at the upper end of the drive shaft (1); The upper end of the drive shaft (1) is provided with a hollow structure, and the multi-force piezoelectric balance system (22) is provided inside the hollow structure. The upper end of the multi-force piezoelectric balance system (22) is attached to the propeller and can measure the propeller excitation force. The multi-component piezoelectric balance system (22) includes an upper multi-component force measuring plate (51), a lower multi-component force measuring plate (52), a piezoelectric force sensor group (6), and a lead screw and slider preload mechanism (8). The upper end face of the upper multi-component force measuring disk (51) is close to the propeller, and the lower end face of the lower multi-component force measuring disk (52) is attached to the inner end face of the hollow structure. The piezoelectric force sensor group (6) is arranged between the upper multi-component force measuring disk (51) and the lower multi-component force measuring disk (52). The lead screw and slider preload mechanism (8) is connected to the upper multi-component force measuring plate (51), the lower multi-component force measuring plate (52) and the piezoelectric force sensor group (6) respectively, and can adjust the parallelism between the upper multi-component force measuring plate (51) and the lower multi-component force measuring plate (52). The piezoelectric force sensor group (6) includes multiple piezoelectric force sensors. The lead screw and slider preload mechanism (8) is configured in a one-to-one correspondence with the piezoelectric force sensor; The lead screw and slider preload mechanism (8) includes a worm gear (9), a worm (10), a wedge slider (11), a tensioning screw (12), an adjusting base (14), a stepped shaft (15), a base (17), and a base support plate (18). The base support plate (18) is connected to the adjusting base (14) and is longitudinally arranged on one side of the wedge slider (11). The lower end face of the adjusting base (14) is fastened to a piezoelectric force sensor, and the lower end face of the piezoelectric force sensor is connected to a lower multi-component force measuring disk (52). The upper end face of the wedge slider (11) is in contact with the lower end face of the upper multi-component force measuring disk (51), and the lower end face of the wedge slider (11) is in contact with the upper end face of the adjusting base (14). The upper end face of the adjusting base (14) is a wedge-shaped surface (20). The wedge-shaped slider (11) has a threaded hole along its horizontal direction. The tensioning screw (12) passes through the threaded hole. One end of the tensioning screw (12) is connected to the base plate (18), and the other end of the tensioning screw (12) is fixedly connected to the worm wheel (9). The worm wheel (9) meshes with the longitudinally arranged worm (10). The worm (10) is fixedly connected to the stepped shaft (15). One end of the stepped shaft (15) is rotatably connected to the base (17). The base (17) is fixedly installed on the lower multi-component force measuring disk (52). When the lead screw and slider preload mechanism (8) adjusts the parallelism, the other end of the stepped shaft (15) is connected to the external rod (21). After the hub cap (3) is opened, the external rod (21) can pass through the hollow hub (2) and drive the worm (10) to rotate through the stepped shaft (15), thereby driving the wedge slider (11) to slide on the wedge surface (20) in sequence through the worm wheel (9) and the tensioning screw (12).

2. The piezoelectric balance for measuring propeller excitation force according to claim 1, characterized in that, The propeller also includes blades (4), the upper end face of the drive shaft (1) is fastened to the lower end face of the hollow propeller hub (2), the upper multi-component force measuring disk (51) is close to the hollow propeller hub (2), and the lower multi-component force measuring disk (52) is clearance-fitted with the inner end face of the hollow structure.

3. The piezoelectric balance for measuring propeller excitation force according to claim 1, characterized in that, The piezoelectric force sensor group (6) includes multiple piezoelectric force sensors mounted symmetrically on an axis.

4. The piezoelectric balance for measuring propeller excitation force according to claim 1, characterized in that, The upper multi-component force measuring disk (51) has a hole (23) at a position corresponding to the stepped shaft (15), and the size of the hole (23) is larger than the diameter of the external rod (21); When the lead screw and slider preload mechanism (8) completes the parallelism adjustment, the external rod (21) is disassembled, and a sealing plug (7) is provided inside the hole (23).

5. The piezoelectric balance for measuring propeller excitation force according to claim 1, characterized in that, One end of the tensioning screw (12) is connected to the base plate (18) via a coupling device (13). The base plate (18) is provided with a through hole, the connecting device (13) passes through the through hole and is in clearance fit with the through hole, one end of the connecting device (13) has a diameter larger than the through hole, and the other end of the connecting device (13) is connected to the tensioning screw (12). When the lead screw and slider preload mechanism (8) completes the parallelism adjustment, a positioning stop pin (19) is provided on the base plate (18). The positioning stop pin (19) can limit the longitudinal position of the wedge slider (11), thereby preventing the wedge slider (11) from sliding on the wedge surface (20).

6. The piezoelectric balance for measuring propeller excitation force according to claim 1, characterized in that, A rolling bearing (16) is provided between the stepped shaft (15) and the base (17).

7. The piezoelectric balance for measuring propeller excitation force according to claim 1, characterized in that, Both the lower multi-component force measuring disk (52) and the transmission shaft (1) are provided with through holes along the axial direction, and the through holes are provided with wiring.

8. A method for measuring the excitation force of a propeller using a piezoelectric balance, characterized in that, The piezoelectric balance for measuring propeller excitation force according to any one of claims 1-7 comprises the following steps: Step 1: Adjust the parallelism by controlling the external rod (21) to drive the wedge slider (11) to slide on the wedge surface (20), thereby adjusting the parallelism between the upper multi-component force measuring disk (51) and the lower multi-component force measuring disk (52); Step 2: Calculate the equivalent longitudinal stiffness, equivalent transverse stiffness, equivalent torsional stiffness and equivalent bending stiffness of the combined action of the multi-force piezoelectric balance system (22) and the hollow tube wall on the drive shaft (1) and retain them as parameters; Step 3: Disassemble the external rod (21) and control the propeller to start working. The propeller is subjected to dynamic excitation force. Step 4: The dynamic excitation force is converted into a response signal by the piezoelectric force sensor group (6), and the response signal is input into the PC through the LMS data acquisition system; Step 5: The PC processes the input signal based on the parameters obtained in Step 2 using the decoupling equivalent formula and the torque inverse formula, thereby reconstructing the dynamic excitation force.

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