Normal quasi-zero stiffness, tangential high stiffness clamping mechanism

Abstract

The application discloses a normal quasi-zero stiffness and tangential high stiffness clamping mechanism, which comprises a base, a stator, a bearing, a positioning column and a bolt. The first flexible clamping beams on both sides of the stator are respectively installed on the two positioning columns, and a certain displacement is applied to the stator during installation to make the first flexible clamping beams deform; the second flexible clamping beam at the bottom of the stator is in contact with the base and is installed and positioned by the bolt; the top of the stator is in abutment with the bearing and drives the bearing to rotate. The application has compact structure, and the side mounting part of the stator is designed as a flexible beam, the normal total stiffness of the stator and the bearing is close to zero stiffness; due to the quasi-zero stiffness performance, the pre-pressing force in the vertical direction can be basically unchanged within a certain deformation range, thereby avoiding the influence of installation errors and motor wear; due to the high-frequency impact of the motor and the bearing in the vertical direction, the quasi-zero stiffness performance can reduce the transmission of the vibration; and the tangential high stiffness ensures the positioning accuracy of the motor drive.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic motor clamping mechanisms, specifically a clamping mechanism with quasi-zero normal stiffness and high tangential stiffness. Background Technology

[0002] An ultrasonic motor is a miniature actuator, mainly composed of a metallic elastic matrix, a mover, piezoelectric ceramics, and friction materials. It utilizes the inverse piezoelectric effect of piezoelectric ceramics to convert electrical energy into mechanical energy, effectively avoiding the shortcomings of traditional electromagnetic motors such as electromagnetic interference and low efficiency. It can cause the stator to vibrate slightly through the vibration of the piezoelectric material in the ultrasonic frequency band, and under specific excitation methods, it can generate elliptical motion with driving capability on the stator, thereby driving the mover pressed against the stator surface to move, transforming microscopic motion into macroscopic motion. This motion can be circular or linear.

[0003] Compared to traditional electromagnetic motors, ultrasonic motors have a greater potential advantage in terms of size and are widely used in various micro-miniature devices. New Scale in the US has developed a drive component with a motor diameter of M3, which can be used for micro-flow control, optical focusing, and micro-motion platforms. Raytheon in the US uses a plate-type ultrasonic motor to drive the opening and closing of an aperture. However, as the motor size decreases, the processing and clamping of the substrate becomes more difficult. Currently, the development of 3D printing technology makes the processing of various micro-miniature devices much easier.

[0004] Meanwhile, ultrasonic motors are driven by friction, so a certain preload needs to be applied between the stator and mover. This preload is usually applied using flexible components such as disc springs or springs. However, changes in ambient temperature, wear between the stator and mover, and assembly errors can alter the preload, affecting the motor's output performance. Furthermore, the high-frequency impact collisions between the stator and mover of an ultrasonic motor can generate vibrations at specific frequencies, which is unacceptable in applications requiring high precision and stability. Therefore, this paper considers designing a clamping mechanism for ultrasonic motors with quasi-zero stiffness in the normal direction and high stiffness in the tangential direction. The motor stator and clamping mechanism are integrated using 3D printing. This clamping mechanism exhibits quasi-zero stiffness in the normal direction, providing constant preload to ensure stable motor output performance. Simultaneously, the quasi-zero stiffness isolates vibrations caused by impact collisions between the stator and mover, improving the stability of the ultrasonic motor's operation; the high stiffness in the tangential direction ensures positioning accuracy during stator drive. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a clamping mechanism with quasi-zero stiffness in the normal direction and high stiffness in the tangential direction. The motor stator and the clamping mechanism are integrated and manufactured using 3D printing. This clamping mechanism has quasi-zero stiffness in the normal direction, which can provide constant preload and isolate the vibration of the ultrasonic motor. It also has high stiffness in the tangential direction, which facilitates the driving and positioning of the motor.

[0006] The present invention provides a clamping mechanism with quasi-zero normal stiffness and high tangential stiffness, including a base, a stator (with first and second flexible clamping beams), bearings, positioning columns and bolts.

[0007] The bearing is mounted on a positioning pin above the stator, and the bearing is driven to rotate along the positioning pin above the stator.

[0008] The stator is located in the center of the base, and the positioning columns are fixed on the base and distributed on the left, right and top sides of the stator.

[0009] The stator has a first flexible clamping beam on both the left and right sides, and the first flexible clamping beam is fixedly connected to the positioning columns on both sides respectively; the first flexible clamping beam is initially an inclined straight beam, and during installation, the stator is applied to the bottom with displacement pressure, causing the flexible beam to buckle and deform.

[0010] The stator has a second flexible clamping beam at its bottom, which is in contact with the base. When the stator is displaced to the bottom, the second flexible beam will also deform.

[0011] The bolts are installed at the bottom of the base for fixing the second flexible clamping beam.

[0012] In a further improvement, a drive foot and several piezoelectric ceramic plates are provided above the stator. The drive foot abuts against the bearing, driving the bearing to rotate along the positioning pin.

[0013] In a further improvement, when the first flexible clamping beam is displaced in the vertical direction, the structural stiffness will experience a sudden change from positive stiffness to negative stiffness and back to positive stiffness; by adjusting the displacement, its stiffness is kept at negative stiffness.

[0014] When the second flexible clamping beam is displaced in the vertical direction, it has linear positive stiffness. Therefore, the total stiffness in the vertical direction is the sum of the stiffnesses of the first and second flexible beams.

[0015] By rationally designing the dimensions of the flexible beam so that its negative stiffness is consistent with its positive stiffness, the total stiffness is increased. Approaching zero, i.e., near-zero stiffness.

[0016] Within a certain deformation range, the total stiffness approaches zero, and the magnitude of the total restoring force remains essentially unchanged. Further improvements include ensuring that the tangential stiffness of the first flexible clamping beam is similar to that of the second flexible beam after deformation, providing linear positive stiffness; thereby ensuring high tangential stiffness and guaranteeing the positioning of the motor.

[0017] The beneficial effects of this invention are as follows: 1. This invention integrates the flexible beam and motor stator using 3D printing, and achieves near-zero stiffness performance by superimposing positive and negative stiffness, which has the advantages of simple structure and convenient installation.

[0018] 2. Considering installation errors and motor wear, the spring compression can vary to a certain extent, and the preload between the stator and bearing can remain basically unchanged, thus avoiding the influence of installation and wear.

[0019] 3. Because the stator vibrates at high frequencies (>20 kHz), the stator and bearing will undergo a contact-disengagement reciprocating process, which will generate vibration impact on the bearing in the vertical direction; quasi-zero stiffness performance can effectively reduce the transmission of this vibration. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is an installation diagram of the present invention; Figure 3 Force and displacement curves of the flexible beam in this invention; Figure 4 The pre-pressure and displacement curve described in this invention.

[0022] In the figure, 1-base, 2-first positioning post, 3-second positioning post, 4-bearing, 5-first flexible clamping beam, 6-third positioning post, 7-bolt, 8-second flexible clamping beam. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] One specific embodiment of the present invention is as follows: Figure 1 As shown, a mounting method for a plate-type ultrasonic motor is provided, including a base 1, a stator, a first positioning post 2, a second positioning post 3, a bearing 4, a first flexible clamping beam 5, a third positioning post 6, bolts 7, and a second flexible clamping beam 8.

[0025] The bearing is mounted on a positioning pin above the stator, and the stator abuts against the bearing, driving the bearing to rotate along the positioning pin.

[0026] The stator is located in the center of the base, and the positioning posts are fixed on the base and distributed on the left, right and top sides of the stator.

[0027] The stator has a flexible clamping beam and is manufactured using an integrated 3D printing design.

[0028] The stator has first flexible clamping beams on both the left and right sides, which are fixedly connected to positioning posts on both sides. The first flexible clamping beams are initially inclined straight beams. During installation, a displacement pressure is applied to the stator towards the bottom, causing the flexible beams to buckle and deform. Figure 2 As shown.

[0029] The stator has a second flexible clamping beam at the bottom, which is in contact with the base. When the stator is displaced to the bottom, the second flexible beam will also deform.

[0030] Bolts are installed at the bottom of the base for mounting and securing the second flexible clamping beam.

[0031] The stator is provided with a drive foot and several piezoelectric ceramic plates. The drive foot abuts against the bearing and drives the bearing to rotate along the positioning pin.

[0032] When the first flexible clamping beam is displaced in the vertical direction, the structural stiffness will experience a sudden change from positive stiffness to negative stiffness and back to positive stiffness, such as... Figure 3 As shown; Vertical restoring force provided by the flexible beam: ; in L Let P be the initial length of the flexible beam, and P be the critical buckling load. and It is a system constant.

[0033] For ease of analysis and calculation, a linear fit of the restoring force yields the following: 4625 , -630 , 5286 ; in E The Young's modulus of the material. I Let be the moment of inertia of the beam. θ The angle between the initial state of the flexible beam and the horizontal direction.

[0034] By adjusting the displacement This keeps its stiffness at a negative stiffness.

[0035] When the second flexible clamping beam undergoes displacement in the vertical direction, it exhibits linear positive stiffness: Its stiffness can be expressed as: ; in α These are dimensionless coefficients related to the material, which can be calibrated through experimental measurement; E The Young's modulus of the material. I Let be the moment of inertia of the beam. d The distance between the two ends is denoted as .

[0036] Therefore, the total stiffness in the vertical direction is the sum of the stiffnesses of the first and second flexible beams.

[0037] By rationally designing the dimensions of the flexible beam so that its negative stiffness is consistent with its positive stiffness, the total stiffness is increased. Approaching zero, i.e., near-zero stiffness.

[0038] Within a certain deformation range, the total stiffness approaches zero, and the magnitude of the total restoring force remains essentially unchanged.

[0039] The curve of total restoring force versus displacement in the vertical direction is as follows: Figure 4 As shown.

[0040] After the first flexible clamping beam deforms, its tangential stiffness is similar to that of the second flexible clamping beam, providing linear positive stiffness; its high tangential stiffness ensures the positioning of the motor.

[0041] Considering installation errors and motor wear, the first and second flexible clamping beams can vary to a certain extent, and the preload between the stator and the bearing can remain basically unchanged, thus avoiding the influence of installation and wear. Since the stator vibrates at high frequencies (>20 kHz), the stator and the bearing will undergo a contact-disengagement reciprocating process, which will generate vibration impact on the bearing in the vertical direction. The quasi-zero stiffness performance can effectively reduce the transmission of this vibration.

[0042] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, for the device embodiments, the above descriptions are merely preferred embodiments of the present invention. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple, and relevant parts can be referred to the descriptions of the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, without departing from the principle of the present invention, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A clamping mechanism with quasi-zero normal stiffness and high tangential stiffness, characterized in that: Includes base, stator, bearings, and positioning pins; The bearing is mounted on a positioning post above the stator, and the bearing is driven to rotate along the positioning post by the stator above it. The stator is located in the center of the base, and the positioning posts are fixed on the base and distributed on the left, right and top sides of the stator. The stator has first flexible clamping beams on both the left and right sides, and the first flexible clamping beams are fixedly connected to the positioning columns on both sides respectively. The first flexible clamping beams are initially inclined straight beams. During installation, the stator is subjected to displacement pressure at the bottom, causing the first flexible beams on both the left and right sides to buckle and deform. After the first flexible clamping beams deform, they provide linear positive stiffness and have high stiffness in the tangential direction to ensure the positioning of the motor. The stator has a second flexible clamping beam at the bottom, which is fixed to the base. When the stator is displaced to the bottom, the second flexible beam deforms. The linear stiffness of the second flexible clamping beam and the stiffness of the first flexible clamping beam in the normal direction are added together and approach zero. The first flexible clamping beam is designed to be inclined, making an angle θ with the horizontal direction. Let the initial length of the beam be... L Moment of inertia is I E is the Young's modulus of the material. When a displacement is applied along the vertical direction, the stiffness of the flexible beam will exhibit three stages as the displacement changes: positive-negative-positive stiffness. , , By adjusting the displacement This ensures that the stiffness of the first flexible beam remains in the negative stiffness stage after the motor is installed and fixed.

2. The clamping mechanism with quasi-zero normal stiffness and high tangential stiffness according to claim 1, characterized in that: The second flexible clamping beam is fixedly connected to the base by bolts.

3. The clamping mechanism with quasi-zero normal stiffness and high tangential stiffness according to claim 1, characterized in that: The stator is provided with a drive foot and several piezoelectric ceramic plates above it. The drive foot abuts against the bearing and drives the bearing to rotate along the positioning column.

4. The clamping mechanism with quasi-zero normal stiffness and high tangential stiffness according to claim 1, characterized in that: The stator is manufactured entirely using 3D printing, with integrated design and processing.

5. The clamping mechanism with quasi-zero normal stiffness and high tangential stiffness according to claim 1, characterized in that: The second flexible clamping beam is in a compressed state after the motor is installed and fixed, and its stiffness is expressed as follows: ;in α The dimensionless coefficients related to the material are calibrated through experimental measurement; E The Young's modulus of the material. I Let be the moment of inertia of the beam. d The distance between the two ends is denoted as ; at this point, the stiffness changes almost linearly and can be considered a constant.

6. The clamping mechanism with quasi-zero normal stiffness and high tangential stiffness according to claim 1, characterized in that: The first flexible clamping beam deforms into a semi-circular arch shape, and its stiffness in the tangential direction is similar to that of the second flexible clamping beam, with the stiffness changing linearly.

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