Patch type spherical rotor multi-degree-of-freedom ultrasonic motor and excitation method thereof

Abstract

The application discloses a patch type spherical rotor multi-degree-of-freedom ultrasonic motor and an excitation method thereof. The ultrasonic motor comprises a piezoelectric vibrator, a base, a spherical rotor and a pre-tightening module. The piezoelectric vibrator comprises a stator and a piezoelectric ceramic sheet. The stator comprises a first base body, a second base body and first to fourth driving feet. The base comprises a fixing cylinder and a web. The pre-tightening module comprises a threaded rod, a bearing, a bearing seat, a clamping hemisphere, a spring, a pre-tightening nut and a gasket. Different excitation signals are applied to the piezoelectric ceramic sheet, so as to excite two modes of an axial symmetric bending mode and two orthogonal axial bending modes of the stator, thereby coupling to form a micro-elliptical motion on the four driving feet, and the spherical rotor is driven by friction to rotate in three degrees of freedom. The application can realize three degrees of freedom rotation, has the advantages of adjustable pre-pressure, simple and compact structure, no electric self-locking, easy miniaturization and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultrasonic motor, in particular to a patch type spherical rotor multi-degree-of-freedom ultrasonic motor and an excitation method thereof. BACKGROUND

[0002] The development of precision driving technology is constantly promoting the development of aerospace, optical instruments, intelligent robots and other fields. As the actuator of precision driving technology, the actuator is the most important part of the precision driving system, which is the most difficult and has the most design requirements. With the development of frontier fields and special environment fields, more restrictions and requirements are put forward for the actuator. The traditional electromagnetic motor has been difficult to meet the requirements. The ultrasonic motor is a new type of actuator which uses the inverse piezoelectric effect of piezoelectric material to drive through friction effect. The ultrasonic motor uses the inverse piezoelectric effect of piezoelectric ceramic to convert electrical energy into mechanical energy. By applying a specific excitation signal to the piezoelectric ceramic, the piezoelectric vibrator generates a micro-elliptical motion at the driving foot which is beneficial to the driving rotor. The interface friction effectively transmits kinetic energy to the rotor, so as to realize mechanical energy output. The ultrasonic motor has the advantages of flexible structure, simple and compact structure, high positioning accuracy, no electromagnetic interference and no electric self-locking, and is suitable for application in precision driving fields such as space pointing mechanism and optical tracking system.

[0003] The traditional multi-degree-of-freedom motor is realized by using multiple single-degree-of-freedom rotary motors in series. The multiple motors and complex transmission mechanism will inevitably lead to complex structure, large volume and error out of control of the motor, affecting the stability of the motor. The multi-degree-of-freedom ultrasonic motor has high mechanical integration. While meeting the multi-degree-of-freedom driving, it still retains the characteristics and advantages of single-degree-of-freedom ultrasonic motor. The patch type stator structure can simplify the motor structure and effectively reduce the volume of the motor. The proposed pre-tightening module can provide uniform and adjustable pre-tightening force between the stator and the spherical rotor, increasing the stability of the motor. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a patch type spherical rotor multi-degree-of-freedom ultrasonic motor and an excitation method thereof.

[0005] The present application adopts the following technical solutions to solve the above technical problems:

[0006] The patch type spherical rotor multi-degree-of-freedom ultrasonic motor comprises a piezoelectric vibrator, a base, a spherical rotor and a pre-tightening module.

[0007] The piezoelectric vibrator comprises a stator and a piezoelectric ceramic sheet.

[0008] The stator comprises a first base, a second base, and first to fourth driving feet, wherein the first base is a hollow cylinder with an upper and lower opening; the second base is a cylinder with a cylindrical first groove on its lower end face; the center of the first groove is provided with a through hole with a diameter equal to the inner diameter of the first base; the lower end face of the first base and the upper end face of the second base are coaxially fixed; the first to fourth driving feet are uniformly arranged on the upper end face of the first base in a circumferential direction;

[0009] The piezoelectric ceramic sheet is a ring-shaped piezoelectric ceramic sheet comprising first to fourth sub-zones arranged uniformly in a circumferential direction and connected in sequence end to end, the first to fourth sub-zones are polarized along a thickness direction, the first and fourth sub-zones have the same polarization direction, the second and third sub-zones have the same polarization direction, and the first and second sub-zones have opposite polarization directions;

[0010] The piezoelectric ceramic sheet has an outer diameter equal to the diameter of the second base and an inner diameter greater than the outer diameter of the first base, is sleeved on the first base and is coaxially attached to the upper end face of the second base, and the four boundary lines of the piezoelectric ceramic sheet correspond to the first to fourth driving feet one by one;

[0011] The base comprises a fixing cylinder and a web plate;

[0012] The fixing cylinder is a hollow cylinder with an upper and lower opening, has an outer diameter smaller than the diameter of the first groove and an inner diameter greater than the inner diameter of the first base, and has an upper end face coaxially fixed to the bottom surface of the first groove of the second base;

[0013] The web plate is a circular plate with a diameter equal to the inner diameter of the fixing cylinder, is arranged in the fixing cylinder and is coaxially fixed to the fixing cylinder, and has a circular limiting hole in the center;

[0014] The spherical rotor is a spherical crown shell with a circular through hole in the center of its outer wall along its axis;

[0015] The pre-tightening module comprises a threaded rod, a bearing, a bearing seat, a clamping hemisphere, a spring, a pre-tightening nut, and a gasket;

[0016] The threaded rod comprises a nut and a screw rod;

[0017] The clamping hemisphere is a spherical segment with a height greater than a radius and a diameter greater than the diameter of the limiting hole, has a second groove in the center of its bottom surface for cooperating with the pre-tightening spring, and has a through hole in the center of the second groove for the screw rod to pass through;

[0018] The bearing seat is a hollow cylinder with an upper and lower opening, has a lower end coaxially fixed to the center of the outer wall of the spherical rotor, and contains the circular through hole in the center of the spherical rotor;

[0019] The bearing is arranged in the bearing seat, and an outer ring thereof is coaxially fixed to the inner wall of the bearing seat;

[0020] The nut of the threaded rod is located inside the bearing housing and abuts against the inner ring of the bearing. The threaded rod passes through the inner ring of the bearing, the circular through hole at the center of the spherical rotor, the through hole on the clamping hemisphere, the spring, the washer, and is then threadedly connected to the preload nut, so that the center of the clamping hemisphere coincides with the center of the spherical rotor.

[0021] The circular through hole at the center of the screw and the spherical rotor, the inner ring of the bearing, and the through hole on the clamping hemisphere are all clearance fit;

[0022] The spring is sleeved on the screw between the washer and the bearing, and is in a compressed state to provide preload; the adjusting nut is used to adjust the preload.

[0023] As a further optimization of the patch-type spherical rotor multi-degree-of-freedom ultrasonic motor of the present invention, the bearing adopts a deep groove ball bearing.

[0024] As a further optimization of the patch-type spherical rotor multi-degree-of-freedom ultrasonic motor of the present invention, a first clamping mechanism and a second clamping mechanism are symmetrically provided on both sides of the fixed cylinder;

[0025] The first clamping mechanism and the second clamping mechanism have the same structure, both including a first connecting rod, a second connecting rod and a flexible hinge. One end of the first connecting rod is fixedly connected to the side wall of the bearing part, and the other end is fixedly connected to one end of the flexible hinge. One end of the second connecting rod is fixedly connected to the other end of the flexible hinge, and the other end is used to be fixedly connected to the outside.

[0026] As a further optimization of the patch-type spherical rotor multi-degree-of-freedom ultrasonic motor of the present invention, the top of the nut is provided with a countersunk cross groove, so that the screw can easily engage with the threaded engagement of the adjusting nut.

[0027] As a further optimization of the patch-type spherical rotor multi-degree-of-freedom ultrasonic motor of the present invention, the connection between the base and the second substrate is located at the pitch circle of the piezoelectric vibrator's working mode.

[0028] The present invention also discloses an excitation method for the patch-type spherical rotor multi-degree-of-freedom ultrasonic motor, comprising the following steps;

[0029] Let the line containing the angle bisectors of the first and third sections of the piezoelectric ceramic sheet be the X-axis, the line containing the angle bisectors of the second and fourth sections be the Y-axis, and the line passing through the center of the piezoelectric ceramic sheet and perpendicular to the piezoelectric ceramic sheet be the Z-axis.

[0030] If it is necessary to drive the spherical rotor to rotate around the positive X-axis:

[0031] The first excitation signal is applied to the second and fourth sub-zones of the piezoelectric ceramic sheet, the second excitation signal is applied to the first sub-zone of the piezoelectric ceramic sheet, and the third excitation signal is applied to the third sub-zone of the piezoelectric ceramic sheet; the first to third excitation signals are all AC harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, and the third excitation signal is opposite in phase to the second excitation signal, so that the axial bending mode B(1, 1) and the axial symmetric bending mode B(1, 0) are simultaneously excited on the piezoelectric vibrator; through the coupling of the modes B(1, 1) and B(1, 0), a micro-amplitude elliptical motion perpendicular to the X-axis is formed on the surface particles of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the X-axis through friction;

[0032] If the spherical rotor needs to rotate reversely around the X-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference;

[0033] If the spherical rotor needs to be driven to rotate forwardly around the Y-axis:

[0034] The first excitation signal is applied to the first and third sub-zones of the piezoelectric ceramic sheet, the second excitation signal is applied to the fourth sub-zone of the piezoelectric ceramic sheet, and the third excitation signal is applied to the second sub-zone of the piezoelectric ceramic sheet; the first to third excitation signals are all AC harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, and the third excitation signal is opposite in phase to the second excitation signal, so that the axial bending mode B(1, 1)' and the axial symmetric bending mode B(1, 0) are simultaneously excited on the piezoelectric vibrator; the modes B(1, 1)' and B(1, 1)' are axial bending modes with the same frequency and orthogonal to each other; through the coupling of the modes B(1, 1)' and B(1, 0), a micro-amplitude elliptical motion perpendicular to the Y-axis is formed on the surface particles of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the Y-axis through friction;

[0035] If the spherical rotor needs to rotate reversely around the Y-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference;

[0036] If the spherical rotor needs to be driven to rotate forwardly around the Z-axis:

[0037] The first excitation signal is applied to the second sub-area and the fourth sub-area of the piezoelectric ceramic sheet, and the second excitation signal is applied to the first sub-area and the third sub-area of the piezoelectric ceramic sheet; the first excitation signal and the second excitation signal are both AC harmonic signals of the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, so that the axial bending mode B(1,1) and the axial bending mode B(1,1)' are excited on the piezoelectric vibrator at the same time; through the coupling of the mode B(1,1) and the mode B(1,1)', a micro-amplitude elliptical motion perpendicular to the Z-axis is formed on the surface particle of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the Z-axis through friction;

[0038] If the spherical rotor needs to rotate reversely around the Z-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference.

[0039] Compared with the prior art, the above technical scheme has the following technical effects:

[0040] The patch type stator structure avoids the problem of excessive longitudinal size caused by the use of longitudinal vibration mode, and realizes simple and compact structure and easy miniaturization; the piezoelectric driving technology is used to directly drive the spherical rotor to realize three-degree-of-freedom rotation, and the pre-tightening module can make the motor realize uniform pre-tightening force without being limited by the installation position, which is suitable for robot joint technology, precision positioning platform, optical target tracking and laser communication fields. DETAILED DESCRIPTION

[0041] Figure 1 is a structural schematic diagram of the application;

[0042] Figure 2 is a sectional view schematic diagram of the application;

[0043] Figure 3 is a structural schematic diagram of the piezoelectric vibrator in the application;

[0044] Figure 4 is a polarization mode schematic diagram of the piezoelectric ceramic in the application;

[0045] Figure 5 is a structural schematic diagram of the cooperation of the spherical rotor and the bearing seat in the application;

[0046] Figure 6 is a structural schematic diagram of the clamped hemisphere in the application;

[0047] Figure 7 is a contrast modal schematic diagram of the axial symmetric bending of the piezoelectric vibrator in the application in the positive and negative directions of the Z-axis;

[0048] Figure 8 is a contrast schematic diagram of the axial bending B(1,1) mode of the piezoelectric vibrator in the application in the positive and negative directions of the Y-axis;

[0049] Figure 9 This is a comparative schematic diagram of the axial bending B(1,1)' mode of the piezoelectric vibrator in the present invention in the positive and negative X-axis directions;

[0050] Figure 10 This is a schematic diagram of the working state of the piezoelectric vibrator when it rotates around the X-axis according to the present invention;

[0051] Figure 11 This is a schematic diagram of the working state of the piezoelectric vibrator when it rotates around the Y-axis according to the present invention;

[0052] Figure 12 This is a schematic diagram of the working state of the piezoelectric vibrator when it rotates around the Z-axis according to the present invention.

[0053] In the figure, 1-stator, 2-spherical rotor, 3-threaded rod, 4-bearing, 5-piezoelectric ceramic plate, 6-base, 7-clamping hemisphere, 8-spring, 9-washer, 10-preload nut, 11-second drive foot, 12-first base, 13-second base, 14-spherical rotor, 15-circular through hole on spherical rotor, 16-bearing seat, 17-through hole on clamping hemisphere, 18-second groove. Detailed Implementation

[0054] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0055] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0056] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, and / or parts, these elements, components, and / or parts are not limited by these terms. These terms are merely used to distinguish elements, components, and / or parts from one another. Therefore, the first element, component, and / or part discussed below may be a second element, component, or part without departing from the teachings of this invention.

[0057] like Figure 1 , Figure 2 As shown, the present invention discloses a patch-type spherical rotor multi-degree-of-freedom ultrasonic motor, comprising a piezoelectric vibrator, a base, a spherical rotor, and a pre-tightening module;

[0058] The piezoelectric vibrator comprises a stator and a piezoelectric ceramic sheet;

[0059] like Figure 3As shown, the stator includes a first base, a second base, and first to fourth drive feet. The first base is a hollow cylinder with openings at the top and bottom. The second base is a cylinder with a cylindrical first groove on its lower end face. The center of the first groove has a through hole with a diameter equal to the inner diameter of the first base. The lower end face of the first base and the upper end face of the second base are coaxially fixedly connected. The first to fourth drive feet are circumferentially and uniformly arranged on the upper end face of the first base.

[0060] like Figure 4 As shown, the piezoelectric ceramic sheet is an annular piezoelectric ceramic sheet, comprising first to fourth sections that are uniformly arranged circumferentially and connected end to end in sequence. The first to fourth sections are all polarized along the thickness direction. The polarization directions of the first and fourth sections are the same, the polarization directions of the second and third sections are the same, and the polarization directions of the first and second sections are opposite.

[0061] The outer diameter of the piezoelectric ceramic sheet is equal to the diameter of the second substrate, and the inner diameter is greater than the outer diameter of the first substrate. It is fitted outside the first substrate and coaxially attached to the upper surface of the second substrate. The four dividing lines of the piezoelectric ceramic sheet correspond one-to-one with the first to fourth driving feet.

[0062] The base includes a fixed cylinder and a web plate;

[0063] The fixed cylinder is a hollow cylinder with openings at the top and bottom. Its outer diameter is smaller than the diameter of the first groove, and its inner diameter is larger than the inner diameter of the first base. Its upper end face is coaxially fixed to the bottom surface of the first groove in the second base.

[0064] The web is a circular plate with a diameter equal to the inner diameter of the fixed cylinder. It is set inside the fixed cylinder and coaxially fixed to the fixed cylinder. A circular limiting hole is provided at the center of the web.

[0065] like Figure 5 As shown, the spherical rotor is a spherical crown-shaped shell, and a circular through hole is provided at the center of its outer wall along its axis;

[0066] The preload module includes a threaded rod, a bearing, a bearing housing, a clamping hemisphere, a spring, a preload nut, and a washer;

[0067] The threaded rod includes a nut and a screw;

[0068] like Figure 6 As shown, the clamping hemisphere is a spherical notch with a height greater than its radius, and its diameter is greater than the diameter of the limiting hole. The bottom surface has a second groove at its center for cooperating with the pre-tightening spring, and the center of the second groove has a through hole for the screw to pass through.

[0069] The bearing housing is a hollow cylinder with openings at both ends. Its lower end is coaxially fixed to the center of the outer wall of the spherical rotor, and the circular through hole at the center of the spherical rotor is included inside.

[0070] The bearing is arranged in the bearing seat, and the outer ring is coaxially connected with the inner wall of the bearing seat;

[0071] As shown in the figure, the nut of the threaded rod is arranged in the bearing seat and abuts against the inner ring of the bearing, the screw rod of the threaded rod is sequentially connected with the inner ring of the bearing, the circular through hole in the center of the spherical rotor, the through hole on the clamping hemisphere, the spring, the gasket and the pre-tightening nut through threads, so that the ball center of the clamping hemisphere coincides with the ball center of the spherical rotor; Figure 2 The screw rod and the circular through hole in the center of the spherical rotor, the inner ring of the bearing and the through hole on the clamping hemisphere are all clearance fit;

[0072] The spring is sleeved outside the screw rod between the gasket and the bearing and is in a compressed state, and is used for providing pre-tightening force; the adjusting nut is used for adjusting the pre-tightening force.

[0073] The bearing preferably adopts a deep groove ball bearing.

[0074] The first clamping mechanism and the second clamping mechanism are symmetrically arranged on both sides of the fixed cylinder.

[0075] The first clamping mechanism and the second clamping mechanism are the same in structure and each include a first connecting rod, a second connecting rod and a flexible hinge, wherein one end of the first connecting rod is fixedly connected with the side wall of the bearing part, and the other end is fixedly connected with one end of the flexible hinge; one end of the second connecting rod is fixedly connected with the other end of the flexible hinge, and the other end is used for being fixedly connected with the outside.

[0076] The top of the nut is provided with a countersunk cross recess, so that the screw rod is convenient for threadedly cooperating with the adjusting nut.

[0077] As shown in the figure, the connecting position of the base and the second base is located at the pitch circle of the working mode of the piezoelectric vibrator.

[0078] Figures 7-9 The connecting position of the base and the second base is located at the pitch circle of the working mode of the piezoelectric vibrator.

[0079] The application further discloses an excitation method of the patch type spherical rotor multi-degree-of-freedom ultrasonic motor, which comprises the following steps.

[0080] The straight line where the angle bisectors of the first and third subareas of the piezoelectric ceramic sheet are located is defined as the X axis, the straight line where the angle bisectors of the second and fourth subareas are located is defined as the Y axis, and the straight line passing through the center of the piezoelectric ceramic sheet and being perpendicular to the piezoelectric ceramic sheet is defined as the Z axis.

[0081] If it is required to drive the spherical rotor to rotate in the positive direction around the X axis:

[0082] ​The first excitation signal is applied to the second and fourth sub-zones of the piezoelectric ceramic sheet, the second excitation signal is applied to the first sub-zone of the piezoelectric ceramic sheet, and the third excitation signal is applied to the third sub-zone of the piezoelectric ceramic sheet; the first to third excitation signals are all AC harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, and the third excitation signal is opposite in phase to the second excitation signal, so that the axial bending mode B(1, 1) and the axial symmetric bending mode B(1, 0) are simultaneously excited on the piezoelectric vibrator, as shown in Figure 8 and Figure 7 The coupling of the modes B(1, 1) and B(1, 0) forms a micro-elliptical motion perpendicular to the X-axis on the surface particles of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the X-axis by friction, as shown in Figure 10 ;

[0083] If the spherical rotor needs to rotate reversely around the X-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference;

[0084] If the spherical rotor needs to be driven to rotate forwardly around the Y-axis:

[0085] The first excitation signal is applied to the first and third sub-zones of the piezoelectric ceramic sheet, the second excitation signal is applied to the fourth sub-zone of the piezoelectric ceramic sheet, and the third excitation signal is applied to the second sub-zone of the piezoelectric ceramic sheet; the first to third excitation signals are all AC harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, and the third excitation signal is opposite in phase to the second excitation signal, so that the axial bending mode B(1, 1)' and the axial symmetric bending mode B(1, 0) are simultaneously excited on the piezoelectric vibrator, as shown in Figure 9 and Figure 7 The coupling of the modes B(1, 1) and B(1, 1)' forms a micro-elliptical motion perpendicular to the Y-axis on the surface particles of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the Y-axis by friction, as shown in Figure 8 and Figure 9 ; Figure 11

[0086] If the spherical rotor needs to rotate reversely around the Y-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference;

[0087] If the spherical rotor needs to be driven to rotate forwardly around the Z-axis:

[0088] ​The first excitation signal is applied to the second and fourth sub-zones of the piezoelectric ceramic sheet, and the second excitation signal is applied to the first and third sub-zones of the piezoelectric ceramic sheet; the first and second excitation signals are both AC harmonic signals of the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, so that the axial bending mode B(1,1) and the axial bending mode B(1,1)' are simultaneously excited on the piezoelectric vibrator, as shown in Figure 8 and Figure 9 As shown; through the coupling of the modes B(1,1) and B(1,1)', a micro-amplitude elliptical motion perpendicular to the Z-axis is formed on the surface particle of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the Z-axis through friction, as shown in Figure 12 As shown;

[0089] If the spherical rotor needs to rotate in the opposite direction around the Z-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference.

[0090] It can be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and should not be interpreted with idealized or overly formal meanings unless defined as such.

[0091] The above specific embodiments further illustrate the purposes, technical solutions and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A patch-type spherical rotor multi-degree-of-freedom ultrasonic motor, characterized by, The piezoelectric vibrator, the base, the spherical rotor and the pre-tightening module are included. The piezoelectric vibrator includes a stator and a piezoelectric ceramic sheet. The stator includes a first base, a second base and first to fourth driving feet, wherein the first base is a hollow cylinder with upper and lower openings; the second base is a cylinder with a first cylindrical groove on its lower end face; the first groove has a through hole at its center with a diameter equal to the inner diameter of the first base; the lower end face of the first base and the upper end face of the second base are coaxially fixed; the first to fourth driving feet are uniformly arranged on the upper end face of the first base; The piezoelectric ceramic sheet is an annular piezoelectric ceramic sheet including first to fourth sub-zones arranged uniformly and connected in sequence, all of which are polarized along the thickness direction, the first and fourth sub-zones have the same polarization direction, the second and third sub-zones have the same polarization direction, and the first and second sub-zones have opposite polarization directions; The piezoelectric ceramic sheet has an outer diameter equal to the diameter of the second base and an inner diameter greater than the outer diameter of the first base, and is coaxially pasted on the upper end face of the second base outside the first base; and the four dividing lines of the piezoelectric ceramic sheet correspond to the first to fourth driving feet one by one; The base includes a fixed cylinder and a web; The fixed cylinder is a hollow cylinder with upper and lower openings, and has an outer diameter smaller than the diameter of the first groove and an inner diameter greater than the inner diameter of the first base; the upper end face of the fixed cylinder is coaxially fixed with the bottom face of the first groove of the second base; The web is a circular plate with a diameter equal to the inner diameter of the fixed cylinder, and is coaxially fixed in the fixed cylinder; and the center of the web is provided with a circular limiting hole; The spherical rotor is a spherical crown shell with a circular through hole at the center of its outer wall along its axis; The pre-tightening module includes a threaded rod, a bearing, a bearing seat, a clamping hemisphere, a spring, a pre-tightening nut and a washer; The threaded rod includes a nut and a screw rod; The clamping hemisphere is a spherical segment with a height greater than the radius, and has a diameter greater than the diameter of the limiting hole; the center of the bottom face of the clamping hemisphere is provided with a second groove for cooperating with the pre-tightening spring, and the center of the second groove is provided with a through hole for the screw rod to pass through; The bearing seat is a hollow cylinder with open ends, and is coaxially fixed with the center of the outer wall of the spherical rotor at the lower end, so that the circular through hole at the center of the spherical rotor is included; The bearing is arranged in the bearing seat, and the outer ring of the bearing is coaxially fixed with the inner wall of the bearing seat; The nut of the threaded rod is arranged in the bearing seat and abuts against the inner ring of the bearing; the screw rod passes through the inner ring of the bearing, the circular through hole at the center of the spherical rotor, the through hole on the clamping hemisphere, the spring and the washer in sequence, and is then threadedly connected with the pre-tightening nut, so that the spherical center of the clamping hemisphere coincides with the spherical center of the spherical rotor; The screw rod and the circular through hole at the center of the spherical rotor, the inner ring of the bearing and the through hole on the clamping hemisphere are all clearance fitted; The spring is in a compressed state and is sleeved outside the screw rod between the washer and the bearing, and is used to provide a pre-tightening force; and the pre-tightening nut is used to adjust the pre-tightening force.

2. The patch spherical rotor multi-degree-of-freedom ultrasonic motor according to claim 1, characterized in that, The bearing is a deep groove ball bearing.

3. The patch spherical rotor multi-degree-of-freedom ultrasonic motor according to claim 1, characterized in that, First and second clamping mechanisms are symmetrically arranged on both sides of the fixed cylinder; The first clamping mechanism and the second clamping mechanism are identical in structure and each comprises a first connecting rod, a second connecting rod and a flexible hinge, wherein one end of the first connecting rod is fixedly connected with a side wall of the bearing part, the other end of the first connecting rod is fixedly connected with one end of the flexible hinge, one end of the second connecting rod is fixedly connected with the other end of the flexible hinge, and the other end of the second connecting rod is used for being fixedly connected with the outside.

4. The patch spherical rotor multi-degree-of-freedom ultrasonic motor according to claim 1, characterized in that, The top of the nut is provided with a countersunk cross recess, so that the screw rod is convenient to be screwed with the pre-tightening nut.

5. The patch spherical rotor multi-degree-of-freedom ultrasonic motor according to claim 1, characterized in that, The connecting position of the base and the second base is located at a nodal circle of the working mode of the piezoelectric vibrator.

6. The method of claim 1, wherein the patch-type spherical rotor multi-degree-of-freedom ultrasonic motor is characterized by Comprise the following steps: Let the straight line where the angle bisector of the first subarea and the third subarea of the piezoelectric ceramic sheet is located be the X axis, the straight line where the angle bisector of the second subarea and the fourth subarea is located be the Y axis, and the straight line passing through the center of the piezoelectric ceramic sheet and perpendicular to the piezoelectric ceramic sheet be the Z axis; If it is needed to drive the spherical rotor to rotate in a positive direction around the X axis: The second subarea and the fourth subarea of the piezoelectric ceramic sheet are applied with a first excitation signal, the first subarea of the piezoelectric ceramic sheet is applied with a second excitation signal, and the third subarea of the piezoelectric ceramic sheet is applied with a third excitation signal; the first to third excitation signals are all alternating harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, and the third excitation signal is opposite to the second excitation signal in phase, so that the axial bending mode B(1, 1) and the axial symmetric bending mode B(1, 0) are simultaneously excited on the piezoelectric vibrator; through the coupling of the mode B(1, 1) and the mode B(1, 0), a micro-amplitude elliptical motion perpendicular to the X axis is formed on the surface particle of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the X axis through friction; If it is needed to rotate the spherical rotor in a reverse direction around the X axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference; If it is needed to drive the spherical rotor to rotate in a positive direction around the Y axis: The first subarea and the third subarea of the piezoelectric ceramic sheet are applied with a first excitation signal, the fourth subarea of the piezoelectric ceramic sheet is applied with a second excitation signal, and the second subarea of the piezoelectric ceramic sheet is applied with a third excitation signal; the first to third excitation signals are all alternating harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, and the third excitation signal is opposite to the second excitation signal in phase, so that the axial bending mode B(1, 1)' and the axial symmetric bending mode B(1, 0) are simultaneously excited on the piezoelectric vibrator; the mode B(1, 1) and the mode B(1, 1)' are axial bending modes with the same frequency and orthogonal to each other; through the coupling of the mode B(1, 1)' and the mode B(1, 0), a micro-amplitude elliptical motion perpendicular to the Y axis is formed on the surface particle of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the Y axis through friction; If it is needed to rotate the spherical rotor in a reverse direction around the Y axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference; If it is needed to drive the spherical rotor to rotate in a positive direction around the Z axis: The first excitation signal is applied to the second and fourth sub-zones of the piezoelectric ceramic sheet, and the second excitation signal is applied to the first and third sub-zones of the piezoelectric ceramic sheet; the first and second excitation signals are AC harmonic signals with the same frequency and amplitude, wherein the first excitation signal leads the second excitation signal by π / 2 in time phase difference, so that the axial bending mode B(1,1) and the axial bending mode B(1,1)' are simultaneously excited on the piezoelectric vibrator; through the coupling of the modes B(1,1) and B(1,1)', a micro-amplitude elliptical motion perpendicular to the Z-axis is formed on the surface particle of the driving foot of the piezoelectric vibrator, and the piezoelectric vibrator drives the spherical rotor to rotate around the Z-axis through friction; If the spherical rotor needs to rotate in the opposite direction around the Z-axis, the first excitation signal can be changed so that the first excitation signal lags behind the second excitation signal by π / 2 in time phase difference.

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