A six-degree-of-freedom adjustable dynamic variable stiffness device based on concentric circles

Abstract

The present invention discloses a concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device, comprising an upper platform, an upper mounting angle seat, an adjustable dynamic variable stiffness mechanism, a lower mounting angle seat and a lower platform. The upper end of the adjustable dynamic variable stiffness mechanism is connected to the upper platform via the upper mounting angle seat, and the lower end of the adjustable dynamic variable stiffness mechanism is connected to the lower platform via the lower mounting angle seat. The device is based on a multi-degree-of-freedom parallel configuration and is composed of six identical adjustable dynamic variable stiffness mechanisms. The adjustable dynamic variable stiffness mechanism can be adjusted to two states: adjustable dynamic low stiffness and adjustable dynamic high stiffness, thereby forming an adjustable dynamic variable stiffness mechanism.

Description

Technical Field

[0001] The present invention relates to the technical field of variable stiffness, in particular to a concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device. Background Art

[0002] With the development of science and technology and the emergence of emerging disciplines, many fields such as industrial production, medical equipment, and space exploration have placed higher demands on the field of variable stiffness. For example, variable stiffness devices have gradually become a hot research area in the field of robotics. Because they can change their own stiffness according to different needs, they can improve the safety of human-computer interaction, especially in situations with close human contact, such as the service industry and the medical industry. Due to its broad prospects, more and more people have begun to study variable stiffness devices. Therefore, a more powerful and adaptable variable stiffness device has an irreplaceable role. Devices with adjustable dynamic variable stiffness can achieve support, limit, and protection of objects in a high stiffness state, and can also achieve vibration reduction of objects in a low stiffness state.

[0003] Adjustable stiffness mechanisms currently exist in two forms: passive and active. Active stiffness mechanisms typically employ an additional driver to control a stiffness-adjusting switch, achieving real-time stiffness adjustment. Passive stiffness mechanisms primarily employ magnetic attraction and manual adjustment. However, these methods lack the ability to control the stiffness of the device in real time. Furthermore, stiffness-adjusting devices are typically large, requiring significant additional energy and complex control mechanisms. Consequently, their widespread application is less widespread than passive stiffness mechanisms.

[0004] The patent specification with publication number CN109968397B discloses an adaptive passive variable stiffness joint, which is mainly used to solve the problems of large joint size and slow response in current variable stiffness joints. Its structure is that the arm and the joint are connected, and the inside of the arm is a four-bar linkage. The joint includes a joint shell and a lever and slider moving mechanism inside the shell. The lever is connected to the connecting rod through the slider. The connecting rod transmits gravity information to the slider to display its position information. The movement of the slider changes the force distribution information at both ends of the lever, thereby changing the overall stiffness of the joint and realizing adjustable stiffness. Summary of the Invention

[0005] The purpose of the present invention is to provide a six-degree-of-freedom adjustable dynamic variable stiffness device based on concentric circles to solve the problems existing in the above-mentioned prior art. The structure of the variable stiffness device is based on a multi-degree-of-freedom parallel configuration, and utilizes the principle of superposition of the stiffness of a positive stiffness leaf spring and a V-shaped leaf spring. By controlling the stiffness switch, the conversion between the positive stiffness and the negative stiffness of the V-shaped leaf spring is realized, thereby changing the stiffness of the system and ensuring that the system forms two stiffness structural forms. When the stiffness switch is closed, the system realizes an adjustable dynamic high-stiffness structural form, which can realize the support, limitation and protection of the object; when the stiffness switch is turned on, the system realizes an adjustable dynamic low-stiffness structural form, which can realize the vibration reduction effect on the object.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a six-degree-of-freedom adjustable dynamic variable stiffness device based on concentric circles, comprising

[0007] an upper platform, the upper platform being configured to contact a load, the bottom surface of the upper platform being provided with three first grooves and three second grooves, wherein the circumference of the inner three first grooves and the circumference of the outer three second grooves are concentric; and

[0008] A mounting angle seat, the mounting angle seat comprising an upper mounting angle seat and a lower mounting angle seat of identical structure, each of the first groove and the second groove being connected to the upper mounting angle seat by a countersunk bolt, and the bottom of the upper mounting angle seat being connected to the bearing column of the adjustable dynamic variable stiffness mechanism; and

[0009] The adjustable dynamic variable stiffness mechanism comprises a bearing column, an upper cover, a positive stiffness leaf spring, an auxiliary mounting block, a support beam mounting plate 1, a support beam, a support beam mounting plate 2, a connecting rod, a stiffness switch, a V-shaped leaf spring, a cylindrical shell and a lower cover, wherein the upper cover and the lower cover are respectively mounted on both ends of the cylindrical shell, and the bearing column passes through the upper cover and is arranged in the inner cavity of the cylindrical shell; the positive stiffness leaf spring, the V-shaped leaf spring and the positive stiffness leaf spring are sequentially connected to the bearing column located in the inner cavity of the cylindrical shell; the other end of the positive stiffness leaf spring is connected to the cylindrical shell through the auxiliary mounting block; the other end of the V-shaped leaf spring is fixedly connected to the connecting rod; the lower end of the connecting rod is connected to the stiffness switch, and the support beam mounting plate 2 is mounted on both sides of the connecting rod, and the two ends of the support beam are respectively welded to the support beam mounting plate 1 and the support beam mounting plate 2, and the lower end of the support beam mounting plate 1 is fixedly connected to the cylindrical shell by bolts; and

[0010] The lower platform is used to contact the foundation. The top surface of the lower platform is provided with three third grooves and three fourth grooves. The circumference of the three inner third grooves and the circumference of the three outer fourth grooves are concentric circles. Each of the third grooves and the fourth grooves is connected to the lower mounting angle seat by a countersunk bolt.

[0011] In one embodiment, the centers of the upper platform and the lower platform are on a vertical line, the diameter of the circle where the first groove is located is the same as the diameter of the circle where the third groove is located, and the diameter of the circle where the second groove is located is the same as the diameter of the circle where the fourth groove is located.

[0012] In one embodiment, the main body of the upper platform includes a central platform, a connecting plate and a hexagonal platform. The central platform and the hexagonal platform are concentrically arranged, and a plurality of connecting plates are evenly distributed around the central platform. The other end of the connecting plate is fixedly connected to the inner side of the hexagonal platform; the outer edge line of the hexagonal platform is hexagonal, and the inner edge is circular.

[0013] In one embodiment, the main body of the lower platform includes a central platform, a connecting plate and a hexagonal platform. The central platform and the hexagonal star platform are concentrically arranged, and a plurality of connecting plates are evenly distributed around the central platform. The other end of the connecting plate is fixedly connected to the inner side of the hexagonal star platform; the outer edge line of the hexagonal star platform is a regular hexagonal star, and the inner edge is circular.

[0014] In one embodiment, the upper mounting angle seat includes a cylinder and an oblique cut surface located on one side of the top of the cylinder, and threaded holes are formed on both the cylinder and the oblique cut surface.

[0015] In one embodiment, each of the first grooves and the second grooves is connected to the cylinder of the upper mounting angle seat through a countersunk bolt, and the beveled surface of the upper mounting angle seat is connected to the bearing column of the adjustable dynamic variable stiffness mechanism through a stud; each of the third grooves and the fourth groove is connected to the cylinder of the lower mounting angle seat through a countersunk bolt, and the beveled surface of the lower mounting angle seat is connected to the lower cover of the adjustable dynamic variable stiffness mechanism through a stud.

[0016] In one embodiment, the upper end of the upper cover is provided with a through hole having a diameter larger than that of the supporting column; the lower end of the upper cover is provided with four threaded holes on its circumference, and the four threaded holes are connected to the cylindrical shell by screws respectively.

[0017] In one embodiment, both ends of the positive stiffness leaf spring are welded to the auxiliary mounting blocks, and the auxiliary mounting blocks at both ends of the positive stiffness leaf spring are provided with through holes for connecting to the bearing column and the cylindrical shell respectively; the upper end of the V-shaped leaf spring is welded to the auxiliary mounting block, and the auxiliary mounting block at the upper end of the V-shaped leaf spring is connected to the bearing column by screws, and the lower end of the V-shaped leaf spring is fixedly connected by bolts and a connecting rod.

[0018] In one embodiment, when the stiffness switch is closed, the V-shaped leaf spring is in a straight line state, and the V-shaped leaf spring provides positive stiffness to the adjustable dynamic variable stiffness mechanism. The stiffness analytical formula is:

[0019]

[0020] The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle, so the adjustable dynamic variable stiffness mechanism is in an adjustable dynamic high stiffness structure form;

[0021] When the stiffness switch is turned on, the V-shaped leaf spring is in a bent state. The V-shaped leaf spring provides negative stiffness in the direction of the bearing column axis to the adjustable dynamic variable stiffness mechanism. The stiffness analytical formula is:

[0022]

[0023] The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle, so the adjustable dynamic variable stiffness mechanism is in an adjustable dynamic low stiffness structural form.

[0024] In one embodiment, the adjustable dynamic variable stiffness mechanism includes adjustable dynamic variable stiffness mechanism one, adjustable dynamic variable stiffness mechanism two, adjustable dynamic variable stiffness mechanism three, adjustable dynamic variable stiffness mechanism four, adjustable dynamic variable stiffness mechanism five and adjustable dynamic variable stiffness mechanism six, and any two adjustable dynamic variable stiffness mechanisms are parallel or perpendicular to each other in space; the first groove includes first groove one, first groove two and first groove three, the second groove includes second groove one, second groove two and second groove three, the third groove includes third groove one, third groove two and third groove three, the fourth groove includes fourth groove one, fourth groove two and third groove three, and the upper and lower ends of the adjustable dynamic variable stiffness mechanism one are respectively assembled in the first groove one and the first groove three through the upper mounting angle seat and the lower mounting angle seat. In the fourth groove one, the upper and lower ends of the adjustable dynamic variable stiffness mechanism two are respectively assembled in the second groove one and the third groove one through the upper mounting angle seat and the lower mounting angle seat, the upper and lower ends of the adjustable dynamic variable stiffness mechanism three are respectively assembled in the first groove two and the fourth groove two through the upper mounting angle seat and the lower mounting angle seat, the upper and lower ends of the adjustable dynamic variable stiffness mechanism four are respectively assembled in the second groove two and the third groove two through the upper mounting angle seat and the lower mounting angle seat, the upper and lower ends of the adjustable dynamic variable stiffness mechanism five are respectively assembled in the first groove three and the fourth groove three through the upper mounting angle seat and the lower mounting angle seat, and the upper and lower ends of the adjustable dynamic variable stiffness mechanism six are respectively assembled in the second groove three and the third groove three through the upper mounting angle seat and the lower mounting angle seat.

[0025] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0026] The six-degree-of-freedom adjustable dynamic variable stiffness device based on concentric circles of the present invention includes an upper platform, an upper mounting angle seat, an adjustable dynamic variable stiffness mechanism, a lower mounting angle seat and a lower platform. The upper end of the adjustable dynamic variable stiffness mechanism is connected to the upper platform through the upper mounting angle seat, and the lower end of the adjustable dynamic variable stiffness mechanism is connected to the lower platform through the lower mounting angle seat. The device is based on a multi-degree-of-freedom parallel configuration and is composed of six identical adjustable dynamic variable stiffness mechanisms. The adjustable dynamic variable stiffness mechanism can be adjusted to two states: adjustable dynamic low stiffness and adjustable dynamic high stiffness, thereby forming an adjustable dynamic variable stiffness mechanism.

[0027] The variable stiffness device described in the present invention is an adjustable dynamic variable stiffness device based on a multi-degree-of-freedom parallel configuration. It has two adjustable dynamic stiffness structural forms. The adjustable dynamic high stiffness structure is mainly used for supporting, limiting and protecting objects, and the adjustable dynamic low stiffness structure is mainly used to suppress the influence of external disturbances on the normal operation of the equipment.

[0028] The adjustable dynamic variable stiffness mechanism described in this invention utilizes a concentric mounting structure, enabling symmetrical mounting of each mechanism. This ensures uniform loading of each mechanism when the device is loaded. The positive and V-shaped leaf springs in the adjustable dynamic variable stiffness mechanism adhere to the principle of stiffness superposition. While maintaining system stiffness, the leaf springs also serve as vibration dampers, attenuating vibration-transmitted energy.

[0029] The positive stiffness leaf spring, V-shaped leaf spring and support beam described in the present invention are all connected to the load-bearing column and the cylindrical shell by bolts using auxiliary mounting blocks, so they are easy to replace. The stiffness of the components can be adjusted by changing the size and material of the components, thereby changing the stiffness of the system and achieving an adjustable stiffness effect.

[0030] In the adjustable dynamic variable stiffness structure described in the present invention, the first stiffness structure is an adjustable dynamic high stiffness structure. In this state, when the stiffness switch is closed, the V-shaped leaf spring is not loaded and provides positive stiffness. The positive stiffness leaf spring provides support. The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle. The positive stiffness provided by the V-shaped leaf spring is superimposed on the positive stiffness provided by the positive stiffness leaf spring, thereby realizing a high stiffness state of the entire device. This state can realize the functions of supporting, limiting and protecting objects.

[0031] In the adjustable dynamic variable stiffness structure described in the present invention, the second stiffness structure is an adjustable dynamic low stiffness structure. In this state, when the stiffness switch is turned on, the V-shaped leaf spring bends under load, providing negative stiffness, and the positive stiffness leaf spring provides support. The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle. The negative stiffness provided by the V-shaped leaf spring and the positive stiffness provided by the positive stiffness leaf spring are superimposed, thereby reducing the stiffness of the mechanism and reaching a quasi-zero stiffness state. This state mainly realizes the vibration reduction effect on the object.

[0032] The connection parts of the variable stiffness device of the present invention are all fixedly connected by bolts and screws, thereby ensuring the reliability of the entire device.

[0033] The adjustable dynamic variable stiffness device of the present invention has a simple structure, stable operation, low manufacturing and maintenance costs, and convenient structural replacement, and can effectively achieve the functions of fixed support, position limiting, protection and suppression of natural frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 Schematic diagram of the overall structure of the present invention;

[0036] Figure 2(a) is a schematic diagram of the upper platform structure of the present invention;

[0037] Figure 2(b) is a schematic diagram of the lower platform structure of the present invention;

[0038] Figure 3 (a) is a schematic diagram of the installation angle seat in the present invention;

[0039] FIG3( b ) is a cross-sectional view of the installation angle seat in the present invention;

[0040] FIG4( a ) is a schematic diagram of an adjustable dynamic variable stiffness mechanism of the present invention;

[0041] FIG4( b ) is a cross-sectional view of the adjustable dynamic variable stiffness mechanism of the present invention;

[0042] FIG5( a ) is a schematic diagram of the stiffness switch in the present invention in a closed state;

[0043] FIG5( b ) is a schematic diagram of the stiffness switch in the present invention in an open state;

[0044] FIG6( a ) is a schematic diagram of the V-shaped leaf spring state in the adjustable dynamic high stiffness structure of the present invention;

[0045] FIG6( b ) is a schematic diagram of the V-shaped leaf spring state in the adjustable dynamic low stiffness structure of the present invention;

[0046] Figure 7 A comparison diagram of the force-displacement curves of the V-shaped leaf spring under two stiffness conditions in the present invention;

[0047] Among them, the figure markings are: 1-upper platform; 2-upper mounting angle seat; 3-double-headed stud; 4-adjustable dynamic variable stiffness mechanism; 41-adjustable dynamic variable stiffness mechanism one; 42-adjustable dynamic variable stiffness mechanism two; 43-adjustable dynamic variable stiffness mechanism three; 44-adjustable dynamic variable stiffness mechanism four; 45-adjustable dynamic variable stiffness mechanism five; 46-adjustable dynamic variable stiffness mechanism six; 5-lower mounting angle seat; 6-lower platform; 7-bearing column; 8-upper cover; 9-positive stiffness leaf spring; 10-auxiliary mounting block; 11-support beam mounting plate one; 12-support beam; 13-support beam mounting plate two, 14 connecting rod; 15-stiffness switch; 16-V-shaped leaf spring; 17-cylindrical shell; 18-lower cover. DETAILED DESCRIPTION

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] The purpose of the present invention is to provide a six-degree-of-freedom adjustable dynamic variable stiffness device based on concentric circles to solve the problems existing in the above-mentioned prior art. The structure of the variable stiffness device is based on a multi-degree-of-freedom parallel configuration, and utilizes the principle of superposition of the stiffness of a positive stiffness leaf spring and a V-shaped leaf spring. By controlling the stiffness switch, the conversion between the positive stiffness and the negative stiffness of the V-shaped leaf spring is realized, thereby changing the stiffness of the system and ensuring that the system forms two stiffness structural forms. When the stiffness switch is closed, the system realizes an adjustable dynamic high-stiffness structural form, which can realize the support, limitation and protection of the object; when the stiffness switch is turned on, the system realizes an adjustable dynamic low-stiffness structural form, which can realize the vibration reduction effect on the object.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] like Figure 1-Figure 7 As shown, the present invention provides a concentric circle-based, six-degree-of-freedom, dynamically adjustable, variable stiffness device comprising an upper platform 1, an upper mounting angle seat 2, a stud 3, an adjustable dynamically variable stiffness mechanism 4, a lower mounting angle seat 5, and a lower platform 6. The overall structure is relatively compact, occupies a small area, has low manufacturing and maintenance costs, and facilitates component replacement, allowing the device system stiffness to be adjusted based on actual application scenarios. The adjustable dynamically variable stiffness device described in the present invention has two stiffness structures: an adjustable dynamic high stiffness structure and an adjustable dynamic low stiffness structure. Switching between the two stiffness structures is achieved by controlling a stiffness switch.

[0052] Figure 2(a) is a schematic diagram of the upper platform structure of the present invention. The upper platform 1 described in the present invention is an unequal-sided hexagonal prism, which is used to contact the load. Six grooves are opened on the bottom surface of the upper platform 1. The circumference of the three grooves near the center and the circumference of the three grooves near the outside are concentric circles. The threaded holes opened in the middle of the six grooves are connected to the upper mounting angle seat 2 through countersunk bolts; the lower platform 6 described in the present invention is shaped like a hexagonal star. The plane of the lower platform 6 is the same as that of the upper platform 1 and has six grooves. The circumference of the grooves is also concentric circles. A threaded through hole is opened in the middle of each groove of the upper and lower platforms, which is used to fix the adjustable dynamic variable stiffness mechanism 4 to the upper platform 1 and the lower platform 6 respectively through the mounting angle seats. The concentric circle mounting structure can make the adjustable dynamic variable stiffness mechanism 4 symmetrical in pairs, ensuring that each adjustable dynamic variable stiffness mechanism is evenly loaded when the device is loaded.

[0053] Figures 3(a)-(b) are schematic and cross-sectional views of the mounting angle seat according to the present invention. The mounting angle seat according to the present invention features a beveled surface, which deflects the force transmission direction in the adjustable dynamic variable stiffness mechanism 4 from the vertical, achieving natural decoupling of the spatial cube. The mounting angle seat has threaded holes on both the beveled surface and the upper end surface. The beveled surface of the upper mounting angle seat 2 is connected to the support column 7 in the adjustable dynamic variable stiffness mechanism 4 via studs 3, and the upper end surface is connected to the upper platform 1 via countersunk bolts. The beveled surface of the lower mounting angle seat 5 is connected to the lower cover 18 via studs 3, and the upper end surface is connected to the lower platform 6 via countersunk bolts. The upper and lower mounting angle seats are interchangeable.

[0054] There are six adjustable dynamic variable stiffness mechanisms 4, namely adjustable dynamic variable stiffness mechanism 1 41, adjustable dynamic variable stiffness mechanism 2 42, adjustable dynamic variable stiffness mechanism 3 43, adjustable dynamic variable stiffness mechanism 4 44, adjustable dynamic variable stiffness mechanism 5 45 and adjustable dynamic variable stiffness mechanism 6 46. The first groove includes the first groove 1, the first groove 2 and the first groove 3, the second groove includes the second groove 1, the second groove 2 and the second groove 3, the third groove includes the third groove 1, the third groove 2 and the third groove 3, and the fourth groove includes the fourth groove 1, the fourth groove 2 and the third groove 3. The upper and lower ends of the adjustable dynamic variable stiffness mechanism 1 41 are respectively assembled in the first groove 1 and the fourth groove 1 through the upper mounting angle seat 2 and the lower mounting angle seat 5. The upper and lower ends of the second variable stiffness mechanism 42 are respectively mounted in the second groove 1 and the third groove 1 via the upper mounting angle seat 2 and the lower mounting angle seat 5. The upper and lower ends of the third adjustable dynamic variable stiffness mechanism 43 are respectively mounted in the first groove 2 and the fourth groove 2 via the upper mounting angle seat 2 and the lower mounting angle seat 5. The upper and lower ends of the fourth adjustable dynamic variable stiffness mechanism 44 are respectively mounted in the second groove 2 and the third groove 2 via the upper mounting angle seat 2 and the lower mounting angle seat 5. The upper and lower ends of the fifth adjustable dynamic variable stiffness mechanism 45 are respectively mounted in the first groove 3 and the fourth groove 3 via the upper mounting angle seat 2 and the lower mounting angle seat 5. The upper and lower ends of the sixth adjustable dynamic variable stiffness mechanism 46 are respectively mounted in the second groove 3 and the third groove 3 via the upper mounting angle seat 2 and the lower mounting angle seat 5. The six adjustable dynamic variable stiffness mechanisms 4 are fixedly connected to the upper and lower mounting angle seats via studs 3. Each adjustable dynamic variable stiffness mechanism 4 is parallel or perpendicular to each other in space.

[0055] Figures 4(a)-(b) are schematic and cross-sectional views of the adjustable dynamic variable stiffness mechanism of the present invention. The adjustable dynamic variable stiffness mechanism 4 comprises a bearing column 7, an upper cover 8, a positive stiffness leaf spring 9, an auxiliary mounting block 10, a support beam mounting plate 1 11, a support beam 12, a support beam mounting plate 2 13, a connecting rod 14, a stiffness switch 15, a V-shaped leaf spring 16, a cylindrical housing 17, and a lower cover 18. The bearing column 7 is cylindrical, with threaded holes on its outer side for secure connection to the V-shaped leaf spring 16 and the positive stiffness leaf spring 9 via bolts. The upper end of the bearing column 7 also has a threaded hole for secure connection to the upper mounting angle seat 2 via a stud 3.

[0056] The positive stiffness leaf spring 9 is welded to the auxiliary mounting block 10 at both ends. The auxiliary mounting block 10 has through holes for connecting to the support column 7 and the cylindrical housing 17, respectively. The upper end of the V-shaped leaf spring 16 is welded to the auxiliary mounting block 10, which has through holes for connecting to the support column 7 via screws. The lower end of the V-shaped leaf spring 16 has through holes for bolting the V-shaped leaf spring 16 to the connecting rod 14. The positive stiffness leaf spring 9 and the V-shaped leaf spring 16 are easy to disassemble and replace. By replacing the positive stiffness leaf spring 9 and the V-shaped leaf spring 16, the stiffness of the device can be easily adjusted. The cylindrical housing 17 has four threaded holes on each side, which are used to connect to the upper cover 8 and the lower cover 18 via screws, respectively. The outer side of the cylindrical housing 17 has several through holes for screwing to the positive stiffness leaf spring 9 and the support beam mounting plate 11, and for installing the stiffness switch 15. The upper end of the upper cover 8 is provided with a through hole with a diameter larger than that of the supporting column 7, which is used to install the supporting column 7 and limit it. The lower end is provided with four threaded holes on the circumference, which are connected to the cylindrical shell 17 by screws.

[0057] Figures 5(a)-(b) are schematic diagrams of the closed and open states of the stiffness switch 15 of the present invention. The stiffness switch 15 of the present invention is used to control the stiffness structure of the device. When the stiffness switch 15 is closed, the device is in an adjustable dynamic high stiffness structure. When the stiffness switch 15 is open, the device is in an adjustable dynamic low stiffness structure. The two steel plates extending from the upper side of the stiffness switch 15 are each provided with two threaded holes, which are connected to the connecting rod 14 by bolts. The connecting rod 14 has a total of four threaded holes, the two lower ones are connected to the stiffness switch 15, and the two upper ones are connected to the support beam mounting plate 2 13. The two sides of the support beam 12 are welded to the support beam mounting plate 1 11 and the support beam mounting plate 2 13 respectively. The lower end of the support beam mounting plate 11 is welded to the auxiliary mounting block 10 and is fixed to the cylindrical shell 17 by bolts. The support beam mounting plate 2 13 has threaded holes on the upper and lower sides, which are fixed to the connecting rod 14 by bolts. The function of support beam 12 is to prevent the stiffness switch 15 from automatically closing when the load-bearing column 7 is loaded after the stiffness switch 15 is opened, thereby providing a self-locking effect. Support beam 12, along with support beam mounting plate 11 and support beam mounting plate 2 13, form a support beam structural module. This module is replaceable, thus achieving the self-locking condition of the stiffness switch of the adjustable dynamic variable stiffness mechanism at different stiffness levels.

[0058] Specifically, there are six positive leaf springs 9, which are primarily used to provide positive stiffness to the adjustable dynamic variable stiffness mechanism 4. Each group of two positive leaf springs 9 is evenly distributed at a 120° angle outside the support column 7. Both sides of the positive leaf springs 9 are welded to auxiliary mounting blocks 10, each with threaded holes. One side of the auxiliary mounting block 10 is bolted to the support column 7, while the other side is bolted to the cylindrical housing 17. Therefore, the positive leaf springs 9 are easily replaceable, thereby achieving adjustable stiffness of the adjustable dynamic variable stiffness mechanism 4.

[0059] There are six V-shaped leaf springs 16 in total, and they have two configurations. When the stiffness switch 15 is closed, they assume a straight shape, providing positive stiffness and placing the adjustable dynamic variable stiffness mechanism 4 in a high-stiffness configuration, supporting, limiting, and protecting the object. When the stiffness switch 15 is open, they assume a curved shape, providing negative stiffness and placing the adjustable dynamic variable stiffness mechanism 4 in a low-stiffness configuration, providing vibration damping. The V-shaped leaf springs 16 are arranged in groups of two, with the two V-shaped leaf springs 16 in each group forming a 45° angle, and the remaining groups forming a 120° angle, evenly distributed around the outer side of the support column 7. The upper sides of the V-shaped leaf springs 16 are welded to the auxiliary mounting block 10, which has threaded holes for bolted connection to the support column 7. The lower sides of the V-shaped leaf springs 16 also have threaded holes for bolted connection to the connecting rod 14. The V-shaped leaf springs 16 are replaceable, thus achieving adjustable stiffness for the adjustable dynamic variable stiffness mechanism.

[0060] There are three connecting rods 14 in total, and each connecting rod 14 has four through holes. The first through hole on the upper side connects the support beam mounting plates 13 on both sides and the V-shaped leaf springs 16 on both sides through bolts; the second through hole is connected to the support beam mounting plates 13 on both sides through bolts; and the two through holes on the lower side are fixedly connected to the stiffness switch 15 through bolts.

[0061] There are 18 support beams 12 in total. Each support beam 12 is thin at the ends and thick in the middle to increase its tensile strength. Three support beams are grouped together, and each group of support beams is welded to support beam mounting plate 11 and support beam mounting plate 2 13 on both sides. Support beam mounting plate 2 13 has through-holes on its top and bottom, and is bolted to connecting rod 14. Auxiliary mounting blocks 10 are welded to the underside of support beam mounting plate 11. Auxiliary mounting blocks 10 have through-holes and are bolted to cylindrical housing 17. When the stiffness switch 15 is turned on, the support beams 12 prevent the load-bearing column 7 from automatically closing when the switch is loaded, thereby providing a self-locking effect. The support beam structure is interchangeable, thus achieving self-locking conditions for the adjustable dynamic variable stiffness mechanism 4 at different stiffness levels.

[0062] There are three stiffness switches 15 , which are mainly used to control the stiffness state of the shock absorbing mechanism, thereby controlling different functions. Four through holes are opened on the upper side of the stiffness switch 15 , which are fixedly connected to the connecting rod 14 through bolts.

[0063] The lower cover 18 and upper cover 8 are primarily used to connect to the cylindrical housing 17. Each of the upper and lower covers 8 and 18 has four threaded holes around them for connection to the cylindrical housing 17. The lower cover 18 has a threaded hole on its underside for connection to the lower mounting angle seat 5 via a stud. The upper end of the upper cover 8 has a circular through-hole that serves as a limiter for the bearing column 7. The outer side of the cylindrical housing 17 has 24 circular through-holes for bolt connection to the positive stiffness leaf spring 9 and support beam mounting plate 11. Three square through-holes are also provided on the outer side of the cylinder for mounting a bistable switch. Four threaded holes are provided at each end of the cylindrical housing 17 for fixed connection to the upper and lower covers 8 and 18, respectively.

[0064] Figures 6(a)-(b) illustrate the V-shaped leaf spring in the adjustable dynamic high stiffness and adjustable dynamic low stiffness configurations of the present invention. The upper end of the V-shaped leaf spring is welded to an auxiliary mounting block, which has a through hole and is bolted to the support column. The lower end of the V-shaped leaf spring has a through hole and is bolted to the connecting rod. Figure 6(a) shows the V-shaped leaf spring in a straight position when the stiffness switch is off. In this state, it provides positive stiffness to the adjustable dynamic variable stiffness mechanism. The analytical formula for its stiffness is:

[0065]

[0066] The V-shaped leaf spring and the positive stiffness leaf spring satisfy the principle of stiffness superposition, so the adjustable dynamic variable stiffness mechanism is in an adjustable dynamic high stiffness structure. Figure 6(b) shows that when the stiffness switch is turned on, the V-shaped leaf spring is in a bent state. In this state, it provides negative stiffness to the adjustable dynamic variable stiffness mechanism in the direction of the bearing column axis. Its stiffness analytical formula is:

[0067]

[0068] The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle, so the adjustable dynamic variable stiffness mechanism is in an adjustable dynamic low stiffness structural form.

[0069] Attachment Figure 7The figure below compares the force-displacement curves of the V-shaped leaf spring under two stiffness conditions in the present invention. The slope of the force-displacement curve represents the stiffness, so the force-displacement curves of the V-shaped leaf spring described in the present invention represent the stiffness of the V-shaped leaf spring under two stiffness conditions. Curve 1 shows when the stiffness switch is closed. By observing the curve, it can be seen that when the load-bearing column is loaded and displaced, and when U changes, the slope of the curve continuously increases, that is, the stiffness of the V-shaped leaf spring continuously increases. At this time, it provides positive stiffness, and the device meets the high stiffness state. Curve 2 shows when the stiffness switch is open. By observing the curve, it can be seen that when the load-bearing column is near the equilibrium position and -1<U<1, the slope of the curve is negative, that is, the stiffness of the V-shaped leaf spring is negative, and it provides negative stiffness. By superimposing the negative stiffness provided by the V-shaped leaf spring with the positive stiffness of the positive stiffness leaf spring, the load-bearing column near the equilibrium position can be adjusted to a quasi-zero stiffness state, and the device meets the low stiffness state.

[0070] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all changes that fall within the meaning and range of equivalents of the claims be included in the present invention, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0071] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A six-degree-of-freedom adjustable dynamic variable stiffness device based on concentric circles, characterized by: The upper platform comprises an upper platform, a lower platform and an adjustable dynamic variable stiffness mechanism, wherein the upper platform is used to contact the load and is connected to the adjustable dynamic variable stiffness mechanism via a mounting angle seat, and the lower platform is used to contact the foundation and is connected to the adjustable dynamic variable stiffness mechanism via a mounting angle seat; The adjustable dynamic variable stiffness mechanism includes a bearing column, an upper cover, a positive stiffness leaf spring, an auxiliary mounting block, a support beam mounting plate 1, a support beam, a support beam mounting plate 2, a connecting rod, a stiffness switch, a V-shaped leaf spring, a cylindrical shell and a lower cover, the upper cover and the lower cover being respectively mounted on both ends of the cylindrical shell, the bearing column passing through the upper cover is arranged in the inner cavity of the cylindrical shell; the positive stiffness leaf spring, the V-shaped leaf spring and the positive stiffness leaf spring are sequentially connected on the bearing column located in the inner cavity of the cylindrical shell, the other end of the positive stiffness leaf spring is connected to the cylindrical shell through the auxiliary mounting block; the other end of the V-shaped leaf spring is fixedly connected to the connecting rod; the lower end of the connecting rod is connected to the stiffness switch, and the support beam mounting plate 2 is mounted on both sides of the connecting rod, the two ends of the support beam are respectively welded to the support beam mounting plate 1 and the support beam mounting plate 2, and the lower end of the support beam mounting plate 1 is fixedly connected to the cylindrical shell by bolts.

2. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 1, characterized in that: The bottom surface of the upper platform is provided with three first grooves and three second grooves, and the circumference of the three inner first grooves is concentric with the circumference of the three outer second grooves; the top surface of the lower platform is provided with three third grooves and three fourth grooves, and the circumference of the three inner third grooves is concentric with the circumference of the three outer fourth grooves, and each of the third grooves and the fourth grooves is connected to the mounting angle seat by a countersunk bolt; the centers of the upper platform and the lower platform are on a vertical line, the diameter of the circumference of the first groove is the same as the diameter of the circumference of the third groove, and the diameter of the circumference of the second groove is the same as the diameter of the circumference of the fourth groove.

3. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 2, characterized in that: The main body of the upper platform includes a central platform, a connecting plate and a hexagonal platform. The central platform and the hexagonal platform are concentrically arranged. A plurality of connecting plates are evenly distributed around the central platform. The other end of the connecting plate is fixedly connected to the inner side of the hexagonal platform. The outer edge line of the hexagonal platform is hexagonal, and the inner edge is circular.

4. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 2, characterized in that: The main body of the lower platform includes a central platform, a connecting plate and a hexagonal platform. The central platform and the hexagonal star platform are concentrically arranged. A plurality of connecting plates are evenly distributed around the central platform. The other end of the connecting plate is fixedly connected to the inner side of the hexagonal star platform. The outer edge line of the hexagonal star platform is a regular hexagonal star, and the inner edge is circular.

5. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 2, characterized in that: The mounting angle seat includes an upper mounting angle seat and a lower mounting angle seat with the same structure. Each of the first groove and the second groove is connected to the upper mounting angle seat by a countersunk bolt respectively. The bottom of the upper mounting angle seat is connected to the bearing column of the adjustable dynamic variable stiffness mechanism; the upper mounting angle seat includes a cylinder and an oblique section located on one side of the top of the cylinder, and threaded holes are provided on the cylinder and the oblique section.

6. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 5, characterized in that: Each of the first grooves and the second grooves is connected to the cylinder of the upper mounting angle seat through a countersunk bolt, and the beveled surface of the upper mounting angle seat is connected to the bearing column of the adjustable dynamic variable stiffness mechanism through a stud; each of the third grooves and the fourth groove is connected to the cylinder of the lower mounting angle seat through a countersunk bolt, and the beveled surface of the lower mounting angle seat is connected to the lower cover of the adjustable dynamic variable stiffness mechanism through a stud.

7. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 1, characterized in that: The upper end of the upper cover is provided with a through hole with a diameter larger than that of the bearing column; the lower end of the upper cover is provided with four threaded holes on its circumference, and the four threaded holes are connected to the cylindrical shell through screws respectively.

8. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 1, characterized in that: The two ends of the positive stiffness leaf spring are welded to the auxiliary mounting blocks, and the auxiliary mounting blocks at both ends of the positive stiffness leaf spring are provided with through holes for connecting to the bearing column and the cylindrical shell respectively; the upper end of the V-shaped leaf spring is welded to the auxiliary mounting block, and the auxiliary mounting block at the upper end of the V-shaped leaf spring is connected to the bearing column by screws, and the lower end of the V-shaped leaf spring is fixedly connected by bolts and a connecting rod.

9. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 1, characterized in that: When the stiffness switch is closed, the V-shaped leaf spring is in a straight line state. The V-shaped leaf spring provides positive stiffness to the adjustable dynamic variable stiffness mechanism. The stiffness analytical formula is: The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle, so the adjustable dynamic variable stiffness mechanism is in an adjustable dynamic high stiffness structure form; When the stiffness switch is turned on, the V-shaped leaf spring is in a bent state. The V-shaped leaf spring provides negative stiffness in the direction of the bearing column axis to the adjustable dynamic variable stiffness mechanism. The stiffness analytical formula is: The V-shaped leaf spring and the positive stiffness leaf spring satisfy the stiffness superposition principle, so the adjustable dynamic variable stiffness mechanism is in an adjustable dynamic low stiffness structural form.

10. The concentric circle-based six-degree-of-freedom adjustable dynamic variable stiffness device according to claim 5, characterized in that: The adjustable dynamic variable stiffness mechanism includes adjustable dynamic variable stiffness mechanism one, adjustable dynamic variable stiffness mechanism two, adjustable dynamic variable stiffness mechanism three, adjustable dynamic variable stiffness mechanism four, adjustable dynamic variable stiffness mechanism five and adjustable dynamic variable stiffness mechanism six, and any two adjustable dynamic variable stiffness mechanisms are parallel or perpendicular to each other in space; the first groove includes first groove one, first groove two and first groove three, the second groove includes second groove one, second groove two and second groove three, the third groove includes third groove one, third groove two and third groove three, the fourth groove includes fourth groove one, fourth groove two and third groove three, the upper and lower ends of the adjustable dynamic variable stiffness mechanism one are respectively assembled in the first groove one and the fourth groove one through the upper mounting angle seat and the lower mounting angle seat. The upper and lower ends of the adjustable dynamic variable stiffness mechanism two are respectively assembled in the second groove one and the third groove one through the upper mounting angle seat and the lower mounting angle seat; the upper and lower ends of the adjustable dynamic variable stiffness mechanism three are respectively assembled in the first groove two and the fourth groove two through the upper mounting angle seat and the lower mounting angle seat; the upper and lower ends of the adjustable dynamic variable stiffness mechanism four are respectively assembled in the second groove two and the third groove two through the upper mounting angle seat and the lower mounting angle seat; the upper and lower ends of the adjustable dynamic variable stiffness mechanism five are respectively assembled in the first groove three and the fourth groove three through the upper mounting angle seat and the lower mounting angle seat; the upper and lower ends of the adjustable dynamic variable stiffness mechanism six are respectively assembled in the second groove three and the third groove three through the upper mounting angle seat and the lower mounting angle seat.

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