A curved beam variable stiffness fast tool servo device and its use method

Abstract

The present invention belongs to the technical field of precision machining equipment, and discloses a curved beam variable stiffness fast tool servo device and a method for using the same, comprising: three flexible mechanisms, namely a single straight circular flexible hinge that serves as a guide, a straight beam flexible hinge, and a flexible curved beam that serves as a variable stiffness function; a driving component, which is three groups of piezoelectric ceramics that serve to drive the flexible mechanism to produce deformation; a magnetorheological elastomer that mainly serves to change the stiffness of the structure; and a tool holder seat and a rigid base that mainly serve to place the tool; the present invention can simultaneously achieve a change in the stiffness of the magnetorheological elastomer through an external magnetic field and a pre-tightening force provided to the curved beam by the left and right piezoelectric ceramics, thereby changing the stiffness of the flexible curved beam, and the stiffness of the flexible curved beam and the core layer magnetorheological elastomer are connected in parallel, so that the stiffness of the device can be changed individually or in a coordinated manner.

Description

Technical Field

[0001] The invention belongs to the technical field of precision machining equipment and relates to a curved beam variable stiffness fast tool servo device and a use method thereof. Background Art

[0002] A fast tool servo mechanism, also known as a fast tool servo, is a commonly used auxiliary mechanism in ultra-precision machining, primarily used in turning processes. It controls fast tools through a combination of macro- and micro-scale methods, enabling the machining of complex surfaces at higher frequencies to achieve more precise optical surfaces. In the complex surface machining process, achieving different machining objectives requires the use of different structures and control methods, making the design of different fast tool servo structures essential.

[0003] Flexible hinge units, also known as flexible hinges, are usually used in fast tool servo mechanisms to guide input displacements and decouple multi-directional displacement inputs. They have both structural characteristics and material properties brought by the selected materials. However, once the material parameter characteristics are determined, their stiffness is also determined.

[0004] Stiffness parallel means that when multiple springs or elastic elements are connected together in parallel, their total stiffness is equal to the sum of the stiffness of each spring or elastic element. At this time, the deformation of each spring or elastic element is the same.

[0005] The Euler flexible curved beam structure is mostly used in shock absorption systems. According to existing data, the Euler flexible curved beam has different sensitivities to the output stiffness in the diameter direction as the preload force in the axial direction varies. That is, the output force corresponding to different displacements at the output end is different, and the output stiffness of the structure changes.

[0006] In the prior art, patent application number 2018105880330, titled "A Cam-Tensioned Fast Tool Servo System with Adjustable Stiffness," incorporates a cam mechanism to control the stiffness of a flexible mechanism. This mechanical adjustment is subject to impact and vibration. Patent application number 2020111854449, titled "A Self-Adjusting Fast Tool Servo Device with Stiffness," proposes a magnetorheological elastomer, but relies solely on changes in the elastic modulus of the magnetorheological elastomer to control the stiffness of the structure, resulting in a very limited controllable range. Patent application number 2024109945378, titled "A Magnetorheological Stiffness Fast Tool Servo Device," achieves continuous dynamic variation of the overall stiffness of the fast tool servo, but the magnetorheological fluid suffers from inherent shortcomings: low performance; prone to leakage and difficulty sealing during operation; poor solid-phase particle settling stability, resulting in unstable device operation; and unsatisfactory heat dissipation.

[0007] Therefore, a curved beam variable stiffness fast tool servo device and a method of using the same are provided to solve the above problems. Summary of the Invention

[0008] In order to solve the technical problems that the stiffness of traditional fast tool servo mechanisms is usually a constant value and cannot be adjusted, and that the working performance of magnetorheological fluid is unstable when magnetorheological fluid is used to achieve the effect of structural variable stiffness, the present invention proposes a curved beam variable stiffness fast tool servo device and a method of using the same. In this structure, the flexible curved beam and the core layer magnetorheological elastomer are in a parallel relationship, that is, the two structures are in a parallel relationship in spatial distribution, that is, the total output stiffness of the device is the sum of the stiffness contributed by the curved beam structure to the output end and the stiffness contributed by the magnetorheological elastomer to the output end. By independently controlling the stiffness of the flexible curved beam and the core layer magnetorheological elastomer, they are adjusted independently or coordinated to achieve dynamic adjustment of the stiffness of the structural output end, that is, the stiffness of the turning tool.

[0009] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions, which are described as follows in conjunction with the accompanying drawings:

[0010] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0011] A curved beam variable stiffness fast tool servo device comprises a single straight circular flexible hinge 1, a fine adjustment component 2, a driving component 3, and a variable stiffness mechanism 4;

[0012] The fine-tuning component 2 includes a straight beam flexible hinge 201 and a pre-tightening bolt 202;

[0013] The straight beam flexible hinge 201 is located at the rear side of the driving component 3;

[0014] The straight beam flexible hinge 201 is fine-tuned and driven by the pre-tightening bolt 202, thereby fine-tuning the pre-tightening driving component 3;

[0015] The variable stiffness mechanism 4 is composed of a rigid structure 401, a flexible curved beam 402, and a magnetorheological elastomer 403;

[0016] The single straight circular flexible hinge 1 is directly connected to the rigid structure 401;

[0017] The flexible curved beam 402 and the magnetorheological elastomer 403 are directly fixedly connected to the tool holder 5 as a whole.

[0018] Furthermore, the driving component 3 is composed of three groups of piezoelectric ceramics, which are divided into two categories; the first group of piezoelectric ceramics 301 and the second group of piezoelectric ceramics 302 together constitute the first type of piezoelectric ceramics, which are located on the rigid structure 401 and play a role in pre-tightening the flexible curved beam 402; the third group of piezoelectric ceramics 303 are the second type of piezoelectric ceramics, which are located on the tool holder 5 and play a role in driving the tool holder 5 and the tool installed on the tool holder to a predetermined position.

[0019] Furthermore, the single straight circular flexible hinge 1 is symmetrically distributed on both sides relative to the central axis of the tool holder 5, and plays a role in guiding the displacement input by the driving component 3 and uncoupling the front-to-back and left-to-right displacement input.

[0020] Furthermore, the variable stiffness mechanism 4 is symmetrically distributed on both sides relative to the central axis of the tool holder 5.

[0021] The flexible curved beam 402 in the unilateral variable stiffness mechanism 4 is provided with two pieces, which sandwich the magnetorheological elastomer 403 without a gap.

[0022] Furthermore, the magnetorheological elastomer is formed by closely stacking magnetorheological elastic sheets formed by solidifying polydimethylsiloxane (PDMS) mixed with carbonyl iron particles, and the shape of the magnetorheological elastomer is consistent with the shape of the flexible curved beam.

[0023] Furthermore, the fine-tuning components 2 are located on the rigid base frame 6 and are provided in three groups.

[0024] Furthermore, three straight beam flexible hinges 201 are provided, all located at the rear side of the driving component 3 and at the front end of the pre-tightening bolt 202 .

[0025] Furthermore, the rigid base frame 6 constitutes the structural basis of the variable stiffness fast tool servo device, and the construction of the single straight circular flexible hinge 1, fine-tuning component 2, driving component 3, and variable stiffness mechanism 4 components are adapted to the design distribution position and size of the rigid base frame 6.

[0026] A method for using a curved beam variable stiffness fast tool servo device, characterized by:

[0027] The first type of piezoelectric ceramics on both sides generate corresponding elongation due to the application of external voltage, giving the flexible curved beam 402 a corresponding preload displacement;

[0028] After the flexible curved beam 402 is pre-tightened, the second type of piezoelectric ceramic located at the rear side of the tool holder generates a corresponding extension due to the application of the external voltage, so that the tool installed at the tool mounting hole 501 on the tool holder 5 reaches the predetermined processing position;

[0029] By applying different external voltages to the first type of piezoelectric ceramics, the flexible curved beam 402 will be preloaded to different degrees; the second type of piezoelectric ceramics on the rear side of the tool holder will produce the same elongation when the same external voltage is applied; the forces acting on the output end of the tool are different; different output displacements at the output end of the structure correspond to different output forces, and the output stiffness changes;

[0030] The flexible curved beam 402 and the magnetorheological elastomer 403 are in a parallel relationship, and the output stiffness is regulated by the coordinated changes of the flexible curved beam 402 and the magnetorheological elastomer 403 .

[0031] Furthermore, a slight pre-tightening force is applied to the straight beam flexible hinge 201 by fine-tuning the pre-tightening bolt 202, thereby fine-tuning the pre-tightening of the first type piezoelectric ceramic.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The flexible curved beam structure used in the present invention has the advantages of small size, high precision and easy realization of variable stiffness characteristics. Due to the buckling deformation, the flexible curved beam is highly sensitive to the preload displacement in the axial direction, that is, only a micron-level displacement input is required to cause significant deformation of the flexible curved beam. This will cause the flexible curved beam to have significantly different displacements in the direction perpendicular to its axis under the same force conditions, that is, the stiffness changes significantly.

[0034] The present invention utilizes a magnetorheological elastomer structure to ensure that the structure has a magnetorheological effect, thereby avoiding the shortcomings of the magnetorheological fluid itself, such as low performance; easy leakage during operation and difficulty in sealing; poor sedimentation stability of solid phase particles in the components, which leads to unstable device operation; and unsatisfactory heat dissipation effect of the device.

[0035] In the variable stiffness mechanism of the present invention, the stiffness of the magnetorheological elastomer itself can be changed through a magnetic field; and the flexible curved beam can be pre-tightened by a driving component to cause deformation of the flexible curved beam structure, thereby changing the output stiffness of the turning tool. The two can work together or change the output stiffness of the turning tool independently, and the output stiffness of the fast tool servo mechanism can be dynamically adjusted, so that the working bandwidth of the structure can be expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with the accompanying drawings:

[0037] Figure 1 This is a front view of a curved beam variable stiffness fast tool servo device according to the present invention;

[0038] Figure 2 It is a top and bottom isometric drawing of a curved beam variable stiffness fast tool servo device of the present invention;

[0039] Figure 3This is a schematic structural diagram of a single straight circular flexible hinge component of a curved beam variable stiffness fast tool servo device of the present invention;

[0040] Figure 4 This is a structural diagram of a fine-tuning component of a curved beam variable-rigidity fast-tool servo device according to the present invention;

[0041] Figure 5 This is a schematic diagram of a variable stiffness structure of a curved beam variable stiffness fast tool servo device of the present invention;

[0042] Among them, 1-single straight circular flexible hinge, 2-fine-tuning component, 201-straight beam flexible hinge, 202-pre-tightening bolt, 301-first group of piezoelectric ceramics, 302-second group of piezoelectric ceramics, 303-third group of piezoelectric ceramics, 4-variable stiffness mechanism, 401-rigid structure, 402-flexible curved beam, 403-magnetorheological elastomer, 5-turning tool holder, 501-turning tool mounting hole, 6-rigid base frame. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the implementation of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below in conjunction with the drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present invention, and should not be understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The embodiments of the present invention are described in detail below in conjunction with the drawings.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present invention.

[0045] The present invention will be described in detail below with reference to the accompanying drawings:

[0046] The present invention provides an embodiment of a curved beam variable stiffness fast tool servo device, comprising:

[0047] Reference Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 The present invention provides a curved beam variable stiffness fast tool servo device using a magnetorheological elastomer as a core layer, comprising:

[0048] The present invention employs three types of flexible mechanisms: 1. a single straight circular flexible hinge 1, 2. a straight beam flexible hinge 201, and 3. a flexible curved beam 402. The three flexible mechanisms are arranged as follows: the single straight circular flexible hinge 1, which serves as a guide, is directly connected to the rigid structure 401 included in the variable stiffness mechanism 4 and is symmetrically distributed with respect to the central axis of the tool holder. There are three straight beam flexible hinges 201 in the device, all located behind the drive component 3 and at the front end of the fine-tuning component 2. In the device, the flexible curved beam 402, which functions as a variable stiffness mechanism, is directly connected to the rigid structure 401 included in the variable stiffness mechanism 4 and is also directly connected to the tool holder 5.

[0049] The fine-tuning components 2 are located on the rigid base frame 6. There are three of them, all located behind the driving component 3, that is, behind the first and second piezoelectric ceramics. The straight beam flexible hinges 201 in the fine-tuning components are driven by the pre-tightening bolts 202 for fine-tuning and pre-tightening the driving component 3.

[0050] The pre-tightening bolt hole in the fine-tuning component is used to install the pre-tightening bolt. Its function is to pre-tighten the straight beam flexible hinge in the fine-tuning component by adjusting the pre-tightening bolt, and then pre-tighten the piezoelectric ceramics in the driving component. By fine-tuning and pre-tightening on both sides at the same time, it can be ensured that the central axis of the tool holder always coincides with the central axis of the rigid base frame, that is, the structure has good concentricity.

[0051] The piezoelectric ceramic driving components are divided into two categories according to their distribution positions. The two types of driving components have different functions for the variable stiffness fast tool servo device. Among them, the one at one end of which is located on the rigid structure mainly provides pre-tightening displacement for the flexible curved beam structure, while the one at one end of which is located on the tool holder mainly provides displacement input for the movement of the tool along the central axis of the tool holder.

[0052] Specifically, the driving component 3 is composed of three groups of piezoelectric ceramics, which can be divided into two categories. The first group of piezoelectric ceramics 301 and the second group of piezoelectric ceramics 302 together constitute the first type of piezoelectric ceramics. One end of the first type of piezoelectric ceramics is located on the rigid structure 401, and the other end is located on the fine-tuning component, which plays a role in pre-tightening the flexible curved beam 402. The third group of piezoelectric ceramics 303 is the second type of piezoelectric ceramics. One end of the second type of piezoelectric ceramics is located on the turning tool holder, and the other end is located on the fine-tuning component. It plays a role in driving the turning tool holder 5 and the turning tool mounted on the turning tool holder to a predetermined position for further processing of the workpiece.

[0053] The variable stiffness mechanism 4 is mainly composed of two flexible curved beams 402 and a core magnetorheological elastic body 403, and is fixedly connected to the rigid structure 401 as a whole;

[0054] The utility model also includes a turning tool, which is installed on the turning tool holder. To ensure that the turning tool is firmly fixed on the turning tool holder, at least two screws are used to press the turning tool on the turning tool holder.

[0055] The tool holder 5 and the two parts of the variable stiffness mechanism 4, namely the two flexible curved beams 402 and the core magnetorheological elastomer 403, are directly connected. There are four tool mounting holes 501 on the tool holder 5 for mounting the tool.

[0056] The rigid base frame 6 mainly constitutes the structural basis of the variable-rigidity fast tool servo device, and the construction of other components is based on the design distribution position and size of the rigid base frame 6.

[0057] The single straight circular flexible hinge 1 is symmetrically distributed on both sides relative to the central axis of the tool holder 5. There are two groups of four on one side and eight on both sides. It mainly guides the displacement input by the driving component 3 and decouples the front-to-back and left-to-right displacement inputs; its role is to guide the displacement input by the piezoelectric ceramic and decouple the inputs of the two types of driving components.

[0058] The variable stiffness mechanism consists of two flexible curved beams 402 seamlessly sandwiching a magnetorheological elastomer 403. The magnetorheological elastomer is composed of five tightly stacked magnetorheological elastic sheets, each made by mixing and curing polydimethylsiloxane (PDMS) with carbonyl iron particles. The shape of the magnetorheological elastomer matches that of the flexible curved beams. The magnetorheological elastomer is composed of five tightly stacked 1mm magnetorheological elastic sheets. The magnetorheological elastomer is made by mixing polydimethylsiloxane (PDMS) with carbonyl iron particles, thoroughly stirring, vacuum defoaming, pouring into a mold, and finally heating and curing.

[0059] An external magnetic field is used to control the transformation of randomly dispersed carbonyl iron particles in the core magnetorheological elastomer from isotropy to anisotropy, that is, the magnetic particles in the magnetorheological elastomer will form a chain structure along the direction of the solidified magnetic field, thereby changing the stiffness of the magnetorheological elastomer.

[0060] In the embodiment, a method for using a curved beam variable stiffness fast tool servo device using a magnetorheological elastomer as a core layer is as follows:

[0061] 1. The piezoelectric ceramics of the first type of driving components located on both sides produce corresponding elongation due to the application of external voltage, thereby giving the flexible curved beam 402 a corresponding pre-tightening displacement. In order to ensure that the center axis of the tool holder and the center axis of the rigid base have good coincidence, a small pre-tightening force can be applied to the straight beam flexible hinge 201 through the pre-tightening bolt 202 of the fine-tuning component 2, thereby pre-tightening and fine-tuning the piezoelectric ceramics to ensure that the structure has good concentricity.

[0062] 2. After the flexible curved beam 402 is pre-tightened, the piezoelectric ceramic of the second type of driving component located at the rear side of the tool holder generates corresponding elongation due to the application of external voltage, so that the tool installed at the tool mounting hole 501 on the tool holder 5 reaches the predetermined processing position.

[0063] 3. By applying different voltages to the piezoelectric ceramics of the first-type drive components, the flexible curved beam 402 is also preloaded to varying degrees. At this point, the piezoelectric ceramics of the second-type drive components on the rear side of the toolholder produce the same elongation under the same applied voltage, but the forces acting on the tool output are different. In other words, different output displacements at the output end of the structure correspond to different output forces, resulting in changes in the structure's output stiffness and expanding the device's operating bandwidth.

[0064] 4. In order to further increase the output stiffness in step 3 and further broaden the output stiffness of the device, based on the principle that stiffness parallel connection can expand stiffness, the flexible curved beam 402 and the magnetorheological elastomer 403 are connected in parallel, that is, a variable stiffness mechanism 4 is formed. Under the control of an external magnetic field, the stiffness of the magnetorheological elastomer 403 is changed, thereby affecting the output stiffness of the structure.

[0065] 5. Since the flexible curved beam 402 and the magnetorheological elastomer 403 described in the above steps 3 and 4 are in a parallel relationship, the adjustment of the output stiffness of the structure can rely on both the flexible curved beam 402 and the magnetorheological elastomer 403, or on the coordinated changes of the two at the same time, so the output stiffness of the structure can be controlled in real time.

[0066] The foregoing description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by any person skilled in the art within the technical scope disclosed herein and within the spirit and principles of the present invention shall be covered by the scope of protection of the present invention. Furthermore, any matters not described in detail in this specification constitute prior art known to those skilled in the art.

Claims

1. A curved beam variable stiffness fast tool servo device, characterized by: It comprises a single straight circular flexible hinge (1), a fine-tuning component (2), a driving component (3), and a variable stiffness mechanism (4); The fine-tuning component (2) includes a straight beam flexible hinge (201) and a pre-tightening bolt (202); The straight beam flexible hinge (201) is located at the rear side of the driving component (3); The straight beam flexible hinge (201) is fine-tuned and driven by the pre-tightening bolt (202), thereby fine-tuning the pre-tightening driving component (3); The variable stiffness mechanism (4) is composed of a rigid structure (401), a flexible curved beam (402), and a magnetorheological elastomer (403); The single straight circular flexible hinge (1) is directly connected to the rigid structure (401); The flexible curved beam (402) and the magnetorheological elastic body (403) are integrally and directly fixedly connected to the turning tool holder (5); The driving component (3) is composed of three groups of piezoelectric ceramics, which are divided into two categories; the first group of piezoelectric ceramics (301) and the second group of piezoelectric ceramics (302) together constitute the first type of piezoelectric ceramics, the first type of piezoelectric ceramics are located on the rigid structure (401), and play a role in pre-tightening the flexible curved beam (402); the third group of piezoelectric ceramics (303) are the second type of piezoelectric ceramics, the second type of piezoelectric ceramics are located on the turning tool holder (5), and play a role in driving the turning tool holder (5) and the turning tool installed on the turning tool holder to a predetermined position; The single straight circular flexible hinge (1) is symmetrically distributed on both sides relative to the central axis of the tool holder (5), and plays a role in guiding the displacement input by the driving component (3) and releasing the coupling of the front-back and left-right displacement inputs; The variable stiffness mechanism (4) is symmetrically distributed on both sides relative to the central axis direction of the tool holder (5). The flexible curved beam (402) in the unilateral variable stiffness mechanism (4) is provided with two pieces, which sandwich the magnetorheological elastomer (403) without a gap.

2. The curved beam variable stiffness fast tool servo device according to claim 1, characterized in that: The magnetorheological elastomer is formed by closely stacking magnetorheological elastic sheets formed by solidifying polydimethylsiloxane (PDMS) mixed with carbonyl iron particles, and the shape of the magnetorheological elastomer is consistent with the shape of the flexible curved beam.

3. The curved beam variable stiffness fast tool servo device according to claim 1, characterized in that: The fine-tuning components (2) are located on a rigid base frame (6) and are provided in three groups.

4. The curved beam variable stiffness fast tool servo device according to claim 1, characterized in that: Three straight beam flexible hinges (201) are provided, all located at the rear side of the driving component (3) and at the front end of the pre-tightening bolt (202).

5. The curved beam variable stiffness fast tool servo device according to claim 3, characterized in that: The rigid base frame (6) forms the structural basis of the variable stiffness fast tool servo device, and the construction of the single straight circular flexible hinge (1), the fine-tuning component (2), the driving component (3), and the variable stiffness mechanism (4) components are adapted to the design distribution position and size of the rigid base frame (6).

6. The method for using the curved beam variable stiffness fast tool servo device according to claim 1, characterized in that: The first type of piezoelectric ceramics on both sides generate corresponding elongation due to the application of external voltage, giving the flexible curved beam (402) a corresponding preload displacement; After the flexible curved beam (402) is pre-tightened, the second type of piezoelectric ceramic located at the rear side of the tool holder generates a corresponding extension due to the application of an external voltage, so that the tool installed at the tool mounting hole (501) on the tool holder (5) reaches a predetermined processing position; By applying different external voltages to the first type of piezoelectric ceramic, the flexible curved beam (402) will be preloaded to different degrees; The second type of piezoelectric ceramics on the rear side of the tool holder produce the same elongation when the same external voltage is applied; the forces acting on the output end of the tool are different; different output displacements at the output end of the structure correspond to different output forces, and the output stiffness changes; The flexible curved beam (402) and the magnetorheological elastic body (403) are in a parallel relationship, and the output stiffness is regulated by the coordinated changes of the flexible curved beam (402) and the magnetorheological elastic body (403).

7. The method of use according to claim 6, characterized in that: A slight pre-tightening force is applied to the straight beam flexible hinge (201) by fine-tuning the pre-tightening bolt (202), thereby fine-tuning the pre-tightening of the first type of piezoelectric ceramic.

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