A three-degree-of-freedom parallel motion platform with adjustable preload and large stroke

Abstract

A preload adjustable large stroke three-degree-of-freedom parallel motion platform, which includes a preload table, a stage, a flexible bracket, a patch-type piezoelectric drive mechanism and a base; the preload table is connected to the base, the stage and the patch-type piezoelectric drive mechanism are arranged in the flexible bracket, multiple groups of patch-type piezoelectric drive mechanisms are evenly arranged along the circumference and installed on the base, the stage is preloaded by the preload table, when working, the stage and the top output end of the patch-type piezoelectric drive mechanism are in static friction contact, the preload table is supported on the base by the flexible bracket, and the top output end of the patch-type piezoelectric drive mechanism generates output when the patch-type piezoelectric drive mechanism is powered on, which can drive the stage to move horizontally or rotate around the axis. The motion platform of the present invention is based on stick-slip motion, the adjustment range of the preload force is large, and back-off can be prevented. The overall structure is compact and the output control accuracy is high.

Description

Technical Field

[0001] The present invention belongs to the field of piezoelectric precision driving, and specifically relates to a preload-adjustable large-stroke three-degree-of-freedom parallel motion platform, which can be widely used in high-precision machining, ultra-precision displacement control and other precision positioning output fields. Background Art

[0002] Existing micro-manipulation platforms use ultrasonic motors, vacuum motors, piezoelectric drives, etc. The principle of piezoelectric drive is the piezoelectric effect, an effect in which applied stress can generate electric charge and applied electric field can generate dimensional deformation, that is, converting electrical energy and mechanical energy into each other. The piezoelectric effect is divided into positive piezoelectric effect and inverse piezoelectric effect. The positive piezoelectric effect is generally used in piezoelectric sensors, that is, converting mechanical energy into electrical energy. Most piezoelectric actuators are inverse piezoelectric effects, which are made using magnetic effects. Piezoelectric drive directly applies deformation to the driven part to achieve mechanical drive, which is different from traditional actuators that need to form rotation first and then convert it into target power. The use of flexible hinge mechanism realizes functions that traditional mechanisms cannot achieve. It has the characteristics of relying on its own small deformation and recovery after being driven and easy replacement.

[0003] Publication No. CN110148436A discloses a large-stroke, rotatable three-degree-of-freedom parallel flexible micro-motion platform. The platform uses a connecting rod amplification mechanism to achieve three-degree-of-freedom movement. The overall preload adjustment range is uncontrollable, and it cannot carry or adapt to heavy workpieces. The inertia of the piezoelectric drive is not taken into account, and the retraction of the stage cannot be guaranteed. The actual output accuracy is not ideal.

[0004] Publication No. CN209774584U discloses a planar three-degree-of-freedom fully flexible parallel positioning platform, which uses a voice coil motor to drive a distributed flexibility hinge to transmit displacement and force, and uses a series-parallel hybrid method to increase the working stroke. The overall preload adjustment range is uncontrollable and cannot carry or adapt to workpieces of larger weight. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a three-degree-of-freedom parallel motion platform with adjustable preload and large stroke. The platform is based on stick-slip motion, has a large adjustment range of preload force, can prevent backlash, has a compact overall structure, and has high output control accuracy.

[0006] A preload-adjustable large-stroke three-degree-of-freedom parallel motion platform comprises a preload platform, a stage, a flexible bracket, a patch-type piezoelectric drive mechanism and a base; the preload platform is connected to the base, the stage and the patch-type piezoelectric drive mechanism are arranged in the flexible bracket, a plurality of groups of patch-type piezoelectric drive mechanisms are arranged in an angle along the circumferential direction and installed on the base, the stage is preloaded by the preload platform, when working, the stage and the top output end of the patch-type piezoelectric drive mechanism are in static friction contact, the preload platform is supported on the base by the flexible bracket, and the top output end of the patch-type piezoelectric drive mechanism generates output when power is supplied, which can drive the stage to move in the x-direction or the y-direction or rotate around the axis.

[0007] Each group of the patch-type piezoelectric drive mechanism includes a positioning seat, an inner flexible arc mechanism, an outer flexible arc mechanism and a piezoelectric sheet; the positioning seat is installed on the base, the inner flexible arc mechanism and the outer flexible arc mechanism are arranged on the positioning seat from the inside out, the inner flexible arc mechanism and the outer flexible arc mechanism are perpendicular to each other and flexibly connected to the positioning seat, and piezoelectric sheets are attached to the outer sides of the inner flexible arc mechanism and the outer flexible arc mechanism.

[0008] The flexible bracket includes an integrally formed upper frame, an arc-shaped flexible plate, a lower frame, a flexible diamond frame inside the frame, and a flexible fork-shaped support frame; the corners of the upper frame and the lower frame are connected by multiple arc-shaped flexible plates, the middle parts of the upper frame and the lower frame are connected by a flexible diamond frame inside the frame, the flexible fork-shaped support frame is arranged in the flexible diamond frame inside the frame, and the corners of the upper frame and the lower frame are respectively connected to the preload table and the base.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. For stick-slip motion, the adjustment of the preload force has an important influence on the motion effect. Therefore, the present invention can expand the adjustment range of the preload force by adding a flexible bracket, so that the load range is wider.

[0011] 2. Due to inertia, piezoelectric drive will produce backlash during the movement process. Use multiple sets of patch-type piezoelectric drive mechanisms to coordinate with each other to offset the backlash.

[0012] 3. The flexible bracket of the present invention is processed by wire cutting, and the flexible bracket has the advantages of no mechanical friction, high processing precision, and one-time molding.

[0013] 4. The present invention has a compact overall structure, light weight, convenient processing, high control accuracy, and is suitable for robot systems and micro-electromechanical systems of micro-operating systems.

[0014] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a schematic diagram of the three-dimensional structure of the preload-adjustable large-stroke three-degree-of-freedom parallel motion platform of the present invention;

[0016] Figure 2 It is an exploded view of the preload-adjustable, long-stroke, three-degree-of-freedom parallel motion platform of the present invention;

[0017] Figure 3 It is a schematic diagram of the structure of the present invention after removing the preload platform and the loading platform;

[0018] Figure 4 It is a three-dimensional diagram of a patch-type piezoelectric drive mechanism;

[0019] Figure 5 is a stereogram of a flexible stent;

[0020] Figure 6 A perspective view of a preload table with a bull's eye bearing;

[0021] Figure 7 It is a schematic diagram of the movement of the stage along the y direction in the embodiment;

[0022] Figure 8 is a schematic diagram of the movement of the stage along the x-direction in the embodiment;

[0023] Fig. 9 Schematic diagram of the rotation of the stage along the z direction in the embodiment.

[0024] Wherein: 1. preload table, 2. loading table, 3. flexible bracket, 3-1. upper frame, 3-2. arc-shaped flexible plate, 3-3. lower frame, 3-4. flexible diamond frame in the frame, 3-5. flexible fork-shaped support frame, 4. patch-type piezoelectric drive mechanism, 4-1. positioning seat, 4-2. inner flexible arc mechanism, 4-2-1. stick-slip top plate A, 4-2-2. two arc-shaped flexible shells A, 4-2-3. H-shaped flexible frame, 4-3. outer flexible arc mechanism, 4-3-1. stick-slip top plate B, 4-3-2. two arc-shaped flexible shells B, 4-3-3. diamond-shaped flexible frame, 4-4. piezoelectric sheet, 5. base, 6. preload bolts, 7. bull's eye bearing. DETAILED DESCRIPTION

[0025] The embodiments of the technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings. Unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0026] Embodiment 1, as Figure 1-Figure 2As shown, a preload-adjustable large-stroke three-degree-of-freedom parallel motion platform comprises a preload platform 1, a stage 2, a flexible bracket 3, a patch-type piezoelectric drive mechanism 4 and a base 5; the preload platform 1 is connected to the base 5, the stage 2 and the patch-type piezoelectric drive mechanism 4 are arranged in the flexible bracket 3, a plurality of groups of patch-type piezoelectric drive mechanisms 4 are evenly arranged along the circumferential direction and installed on the base 5, the stage 2 is preloaded by the preload platform 1, and when working, the stage 2 and the top output end of the patch-type piezoelectric drive mechanism 4 are in static friction contact, the preload platform 1 is supported on the base 5 by the flexible bracket 3, and the top output end of the patch-type piezoelectric drive mechanism 4 generates output when power is supplied, which can drive the stage 2 to move in the x-direction or the y-direction or rotate around the axis.

[0027] The patch-type piezoelectric drive mechanism 4 is connected to the base 5 by bolts, and the stage 2 is placed on the patch-type piezoelectric drive mechanism 4 and directly contacts, thereby driving the stage 2 to move (translationally or vertically) through static friction. The preload platform 1 is connected to the base 5 by four bolts 6. An elastic flexible bracket 3 is installed between the preload platform 1 and the base 5 to facilitate the adjustment of the preload effect on the stage 2 and increase the range of the preload force; when working, the preload platform 1 contacts the stage 2, thereby applying a preload force to increase the positive pressure between the stage 2 and the patch-type piezoelectric drive mechanism 4 and increase the friction. In order to improve the contact between the preload platform 1 and the stage 2 and reduce the resistance caused, a universal bearing is installed on the contact surface so that the eight universal bearings are evenly distributed on the preload platform 1.

[0028] Embodiment 2, as Figure 1-Figure 3 As shown, each group of the patch-type piezoelectric drive mechanism 4 comprises a positioning seat 4-1, an inner flexible arc mechanism 4-2, an outer flexible arc mechanism 4-3 and a piezoelectric sheet 4-4; the positioning seat 4-1 is installed on the base 5, the inner flexible arc mechanism 4-2 and the outer flexible arc mechanism 4-3 are arranged on the positioning seat 1 by the inner and outer sides, the inner flexible arc mechanism 4-2 and the outer flexible arc mechanism 4-3 are perpendicular to each other and flexibly connected to the positioning seat 4, and the outer sides of the inner flexible arc mechanism 4-2 and the outer flexible arc mechanism 4-3 are both affixed with piezoelectric sheets 4-4;

[0029] The patch-type piezoelectric drive mechanism 4 in this embodiment preferably uses three groups, such as Figure 3 and Figure 4 As shown, they are evenly arranged in a triangular manner. Any group of patch-type piezoelectric drive mechanisms 4 can be arranged along the y direction, and the other two groups of patch-type piezoelectric drive mechanisms 4 are arranged at equal angles to them in the circumferential direction. Preferably, the three groups of patch-type piezoelectric drive mechanisms 4 are arranged at 120 degrees to each other.

[0030] Furthermore, the inner flexible arc mechanism 4-2 and the outer flexible arc mechanism 4-3 are flexibly connected to the positioning seat 4-1, for example, using flexible hinges. The bottom of the inner flexible arc mechanism 4-2 and the outer flexible arc mechanism 4-3 are respectively connected to the positioning seat 4-1 through flexible hinges, thereby increasing the load range of the loading platform 2.

[0031] The structural operation based on the above arrangement is that when the stage 2 moves in the y-direction, the voltage of the piezoelectric fiber sheets 4-4 of the multiple groups (for example, 3 groups) of inner flexible arc mechanisms 4-2 is increased at the same time, and the top output end generates output to form a y-direction resultant force, which can drive the stage 2 to move along the y-direction, while the piezoelectric fiber sheets 4-4 of the multiple groups (for example, 3 groups) of outer flexible arc mechanisms 4-3 are not energized; when retreating, the piezoelectric fiber sheets 4-4 of the multiple groups (for example, 3 groups) of outer flexible arc mechanisms 4-3 are energized at the same time to increase the voltage, the top output end rests on the stage 2, and the piezoelectric fiber sheets 4-4 of the multiple groups (3 groups) of inner flexible arc mechanisms 4-2 are energized to reduce the voltage until it is zero.

[0032] When the stage 2 moves in the x-direction, the voltage of the piezoelectric fiber sheets 4-4 of the flexible arc mechanisms 4-2 in any two adjacent groups (2 groups) is increased at the same time, and the top output end generates an output to form an x-direction resultant force, which can drive the stage 2 to move along the x-direction, while the piezoelectric fiber sheets 4-4 of the flexible arc mechanisms 4-2 in the remaining group (1 group) are not energized; when retreating, the piezoelectric fiber sheets 4-4 of the flexible arc mechanisms 4-3 in multiple groups (for example, 3 groups) are energized at the same time to increase the voltage, and the top output end rests on the stage 2, while the piezoelectric fiber sheets 4-4 of the flexible arc mechanisms 4-2 in multiple groups (for example, 3 groups) are energized to reduce the voltage until it is zero.

[0033] When the stage 2 rotates around the axis, the piezoelectric fiber sheets 4-4 of multiple groups (for example, 3 groups) of the outer flexible arc-shaped mechanisms 4-3 increase the voltage at the same time, and the top output end generates output to form a combined force around the z-axis, which can drive the stage 2 to rotate around the axis, while the piezoelectric fiber sheets 4-4 of multiple groups (for example, 3 groups) of the inner flexible arc-shaped mechanisms 4-2 are not powered; when retreating, the piezoelectric fiber sheets 4-4 of multiple groups (for example, 3 groups) of the inner flexible arc-shaped mechanisms 4-2 increase the voltage at the same time, and the top output end abuts against the stage 2, while the piezoelectric fiber sheets 4-4 of multiple groups (for example, 3 groups) of the outer flexible arc-shaped mechanisms 4-3 reduce the voltage until it is zero. The rest is the same as the specific embodiment 2.

[0034] Embodiment 3, based on embodiment 1 and / or embodiment 2, as Figure 4As shown, the inner flexible arc mechanism 4-2 includes a stick-slip top plate A4-2-1, two arc-shaped flexible shells A4-2-2 and an H-shaped flexible frame 4-2-3; the inner arc surfaces of the two arc-shaped flexible shells A4-2-2 are arranged opposite to each other and butted together to form a hollow structure, the stick-slip top plate A4-2-1 is arranged on the top of the hollow structure, and the H-shaped flexible frame 4-2-3 is also connected to the hollow structure, and the bottom of the hollow structure is flexibly connected to the positioning seat 4-1.

[0035] Alternatively, the outer flexible arc-shaped mechanism 4-3 includes a stick-slip top plate B4-3-1, two arc-shaped flexible shells B4-3-2 and a diamond-shaped flexible frame 4-3-3; the inner arc surfaces of the two arc-shaped flexible shells B4-3-2 are arranged opposite to each other and butted together to form a hollow structure, the stick-slip top plate B4-3-1 is arranged on the top of the hollow structure, and the diamond-shaped flexible frame 4-3-3 is also connected to the hollow structure, and the bottom of the hollow structure is flexibly connected to the positioning seat 4-1.

[0036] In this embodiment, the inside of the hollow structure is in contact with the diamond-shaped flexible frame 4-3-3 and the arc-shaped flexible shell B4-3-2, and the diamond-shaped flexible frame 4-3-3 is also connected with a flexible fork-shaped support frame (such as a χ-shaped flexible structure) for support; the H-shaped flexible frame 4-2-3 of the inner flexible arc-shaped mechanism 4-2 is connected with the arc-shaped flexible shell A4-2-2, and both structures increase the toughness of the patch-type piezoelectric drive mechanism 4. The bottom of the patch-type piezoelectric drive mechanism 4 adopts a flexible structure (such as a double-leaf flexible hinge) to increase the load range of the stage 2. The piezoelectric sheet 4-3 is attached to both sides of the symmetrical arc surface, and the deformation generated by the movement of the inner flexible arc-shaped mechanism 4-2 and the outer flexible arc-shaped mechanism 4-3 driven by the piezoelectric action is contacted with the lower surface of the stage 2 through the outer surface of the stick-slip top plate A4-2-1 or the stick-slip top plate B4-3-1, and the stage 2 is driven to move through static friction, and the three groups of patch-type piezoelectric drive mechanisms 4 cooperate with each other to achieve three degrees of freedom. The rest is different from any one of Embodiments 2 to 3.

[0037] Embodiment 4: Based on any of the above embodiments, a plurality of bull's eye bearings 7 are arranged circumferentially on the edge of the center hole on the lower surface of the preload platform 1. A through hole 1-1 for installing a preload bolt 6 is provided on the edge of the preload platform 1. Figure 6 As shown, the purpose of such a setting is to improve the resistance caused by friction. Optionally, eight bull's eye bearings are installed at equal angles on the lower surface of the preload table 1 to solve the problem of excessive friction with the stage 2. The flexible bracket 3 is integrally formed by wire cutting or 3D printing. The positioning seat 4-1, the inner flexible arc mechanism 4-2 and the outer flexible arc mechanism 4-3 are integrally formed by wire cutting or 3D printing. It is cut on the base platform 1 by wire cutting, does not require assembly, is light in weight, and is suitable for use in micro-motion platforms.

[0038] Embodiment 5, based on any one of the above embodiments, Figure 5 As shown, the flexible bracket 3 includes an upper frame 3-1, an arc-shaped flexible plate 3-2, a lower frame 3-3, an inner-frame flexible diamond frame 3-4 and a flexible fork-shaped support frame 3-5; the corners of the upper frame 3-1 and the lower frame 3-3 are connected via a plurality of arc-shaped flexible plates 3-2, the middle of the upper frame 3-1 and the lower frame 3-3 are connected via an inner-frame flexible diamond frame 3-4, the flexible fork-shaped support frame 3-5 is arranged in the inner-frame flexible diamond frame 3-4, and the corners of the upper frame 3-1 and the lower frame 3-3 are respectively connected to the preload table 1 and the base 5. The preload table 1 and the base 5 are supported by the flexible bracket 3, which is formed by integrated processing and has the characteristics of no mechanical friction, no mating idle travel, no need for lubrication, and high motion sensitivity. Figure 5 The completely symmetrical structure of the flexible support 3 ensures the balance of elasticity.

[0039] Figure 5 The upper frame 3-1 and the lower frame 3-3 are respectively connected with the pre-tightening bolts 6 and the pre-tightening platform 1, so that the flexible bracket 3 is respectively fixed with the base 5 and the pre-tightening platform 1. The upper frame 3-1 and the lower frame 3-3 structure in the figure ensure the rigidity of the whole structure; the arc-shaped flexible plate 3-2, the flexible diamond frame 3-4 in the frame and the flexible fork-shaped support frame 3-5 give full play to the micro-elastic deformation and recovery characteristics of the metal.

[0040] The working principle of the present invention is described below with a specific embodiment: define a three-axis coordinate system x, y, and z. The following involves the definitions of the first, second, ... only for the convenience of explanation and understanding, and is not limiting.

[0041] Embodiment 6: Based on any one of the above embodiments, Figure 7-Figure 9 As shown,

[0042] Y axis movement Figure 7It is explained that the second piezoelectric sheet 4.2.3 and the third piezoelectric sheet 4.3.3 act on the second inner flexible arc mechanism 4-2 and the third inner flexible arc mechanism 4-2 respectively, so that the second stick-slip top plate 4.2.1 and the third stick-slip top plate 4.3.1 generate Z-axis upward and horizontal forces, and the two generate a combined force in the Y-axis direction in the XY plane, and the force in the Z-axis direction increases the positive pressure between the stage 2. The first piezoelectric sheet 4.1.3 acts on the first inner flexible arc mechanism 4-2, and the first stick-slip top plate 4.1.1 generates a Y-axis horizontal force and a Z-axis upward force, and cooperates with the second inner stick-slip top plate 4.2.1 and the third inner stick-slip top plate 4.3.1 to generate a Y-axis combined force. When the first inner stick-slip top plate 4.1.1, the second inner stick-slip top plate 4.2.1 and the third inner stick-slip top plate 4.3.1 of the patch-type piezoelectric drive mechanism 4 retreat within the signal period, the first right piezoelectric sheet 4.1.a and the first left piezoelectric sheet 4.1.b on the first outer flexible arc-shaped mechanism 4-3, the second left piezoelectric sheet 4.2.a and the second right piezoelectric sheet 4.2.b on the second outer flexible arc-shaped mechanism 4-3 and the third left piezoelectric sheet 4.3.a and the third right piezoelectric sheet 4.3.b on the third outer flexible arc-shaped mechanism 4-3 act simultaneously to cause their respective first outer stick-slip top plate 4.1.c, the second outer stick-slip top plate 4.2.c and the third outer stick-slip top plate 4.3.c to generate an upward force to prevent the worktable 2 from retreating.

[0043] X-axis movement Figure 8 It is explained that the second piezoelectric sheet 4.2.3 and the third upper piezoelectric sheet 4.3.5 act on the second inner flexible arc mechanism 4-2 and the third inner flexible arc mechanism 4-2 respectively, so that the second stick-slip top plate 4.2.1 generates a centripetal force and a Z-axis force, and the third stick-slip top plate 4.3.1 generates a centripetal force and a Z-axis force. The two generate a resultant force in the X-axis direction in the XY plane, and the force in the Z-axis direction increases the positive pressure between the stage 2. In this process, the first inner flexible arc mechanism 4-2 is not energized and does not act. When the second inner stick-slip top plate 4.2.1 and the third inner stick-slip top plate 4.3.1 of the patch-type piezoelectric drive mechanism 4 retreat within the signal period, the first right piezoelectric sheet 4.1.b and the first left piezoelectric sheet 4.1.a on the first outer flexible arc-shaped mechanism 4-3, the second left piezoelectric sheet 4.2.a and the second right piezoelectric sheet 4.2.b on the second outer flexible arc-shaped mechanism 4-3 and the third left piezoelectric sheet 4.3.a and the third right piezoelectric sheet 4.3.b on the third outer flexible arc-shaped mechanism 4-3 act simultaneously to cause their respective first outer stick-slip top plate 4.1.c, the second stick-slip top plate 4.2.c and the third outer stick-slip top plate 4.3.c to generate an upward force to prevent the worktable 2 from retreating.

[0044] Rotate around the Z axis Fig. 9It is explained that the first right piezoelectric sheet 4.1.b, the second left piezoelectric sheet 4.2.a and the third left piezoelectric sheet 4.3.a act on the first outer flexible arc mechanism 4-3, the second outer flexible arc mechanism 4-3 and the third outer flexible arc mechanism 4-3 respectively, the first outer stick-slip top plate 4.1.c, the second outer stick-slip top plate 4.2.c and the third outer stick-slip top plate 4.3.c generate a force toward the Z axis and a force perpendicular to themselves, and the three generate a torque around the Z axis in the XY plane. The force in the Z axis direction increases the positive pressure between the stage 2 and the stage 2, causing the stage 2 to rotate around the Z axis. During the whole process, the first inner flexible arc mechanism 4-2 is not energized and does not act. When the first outer stick-slip top plate 4.1.c, the second outer stick-slip top plate 4.2.c and the third outer stick-slip top plate 4.3.c retreat within the signal period; the first piezoelectric sheet 4.1.3, the first lower piezoelectric sheet 4.1.5, the second piezoelectric sheet 4.2.3, the second upper piezoelectric sheet 4.2.5, the third piezoelectric sheet 4.3.3 and the third upper piezoelectric sheet 4.3.5 act simultaneously to cause the first inner stick-slip top plate 4.1.1, the second inner stick-slip top plate 4.2.1 and the third inner stick-slip top plate 4.3.1 to generate an upward force to prevent the stage from retreating.

[0045] The present invention has been disclosed as above with preferred implementation cases, but it is not used to limit the present invention. Any technician familiar with the profession can make slight changes or modifications to equivalent implementation cases with equivalent changes by using the above-disclosed structures and technical contents without departing from the scope of the technical solution of the present invention, which still fall within the scope of the technical solution of the present invention.

Claims

1. A preload-adjustable, long-stroke, three-DOF parallel motion platform, characterized by: The invention comprises a pre-tightening platform (1), a stage (2), a flexible bracket (3), a patch-type piezoelectric drive mechanism (4) and a base (5); the pre-tightening platform (1) is connected to the base (5); the stage (2) and the patch-type piezoelectric drive mechanism (4) are arranged in the flexible bracket (3); a plurality of groups of patch-type piezoelectric drive mechanisms (4) are evenly arranged along the circumference and installed on the base (5); the stage (2) is pre-tightened by the pre-tightening platform (1); when working, the stage (2) and the top output end of the patch-type piezoelectric drive mechanism (4) are in static friction contact; the pre-tightening platform (1) is supported on the base (5) by the flexible bracket (3); when the patch-type piezoelectric drive mechanism (4) is energized, the top output end generates an output, which can drive the stage (2) to move in the x-direction or the y-direction or rotate around the axis; The flexible bracket (3) comprises an integrally formed upper frame (3-1), an arc-shaped flexible plate (3-2), a lower frame (3-3), an inner flexible diamond frame (3-4) and a flexible fork-shaped support frame (3-5); the corners of the upper frame (3-1) and the lower frame (3-3) are connected via a plurality of arc-shaped flexible plates (3-2); the middle parts of the upper frame (3-1) and the lower frame (3-3) are connected via an inner flexible diamond frame (3-4); the flexible fork-shaped support frame (3-5) is arranged in the inner flexible diamond frame (3-4); the corners of the upper frame (3-1) and the lower frame (3-3) are respectively connected to the preload table (1) and the base (5); when working, the preload table (1) contacts the stage (2), thereby applying a preload force to increase the positive pressure between the stage (2) and the patch-type piezoelectric drive mechanism (4).

2. According to claim 1, a preload-adjustable, long-stroke, three-degree-of-freedom parallel motion platform, characterized in that: Each group of the patch-type piezoelectric drive mechanism (4) comprises a positioning seat (4-1), an inner flexible arc-shaped mechanism (4-2), an outer flexible arc-shaped mechanism (4-3) and a piezoelectric sheet (4-4); the positioning seat (4-1) is mounted on a base (5); the inner flexible arc-shaped mechanism (4-2) and the outer flexible arc-shaped mechanism (4-3) are arranged on the positioning seat (4-1) from the inside to the outside; the inner flexible arc-shaped mechanism (4-2) and the outer flexible arc-shaped mechanism (4-3) are perpendicular to each other and flexibly connected to the positioning seat (4-1); and the outer side surfaces of the inner flexible arc-shaped mechanism (4-2) and the outer flexible arc-shaped mechanism (4-3) are both affixed with piezoelectric sheets (4-4); When the stage (2) moves in the y direction, the piezoelectric sheets (4-4) of the multiple groups of inner flexible arc-shaped mechanisms (4-2) simultaneously increase the voltage, and the top output end generates an output to form a y-direction resultant force, which can drive the stage (2) to move in the y direction, while the piezoelectric sheets (4-4) of the multiple groups of outer flexible arc-shaped mechanisms (4-3) are not energized; when retreating, the piezoelectric sheets (4-4) of the multiple groups of outer flexible arc-shaped mechanisms (4-3) are energized at the same time to increase the voltage, while the piezoelectric sheets (4-4) of the multiple groups of inner flexible arc-shaped mechanisms (4-2) are energized to reduce the voltage; When the stage (2) moves in the x-direction, the piezoelectric sheets (4-4) of any two adjacent groups of inner flexible arc mechanisms (4-2) simultaneously increase the voltage, and the top output end generates an output to form an x-direction resultant force, which can drive the stage (2) to move along the x-direction, while the piezoelectric sheets (4-4) of the remaining groups of inner flexible arc mechanisms (4-2) are not energized; when retreating, the piezoelectric sheets (4-4) of multiple groups of outer flexible arc mechanisms (4-3) are energized at the same time to increase the voltage, while the piezoelectric sheets (4-4) of multiple groups of inner flexible arc mechanisms (4-2) are energized to reduce the voltage; When the stage (2) rotates around the axis, the piezoelectric sheets (4-4) of the multiple groups of outer flexible arc-shaped mechanisms (4-3) increase the voltage at the same time, and the top output end generates an output to form a combined force around the z-axis, which can drive the stage (2) to rotate around the axis, while the piezoelectric sheets (4-4) of the multiple groups of inner flexible arc-shaped mechanisms (4-2) are not powered; when retreating, the piezoelectric sheets (4-4) of the multiple groups of inner flexible arc-shaped mechanisms (4-2) increase the voltage at the same time, while the piezoelectric sheets (4-4) of the multiple groups of outer flexible arc-shaped mechanisms (4-3) reduce the voltage.

3. According to claim 2, a preload-adjustable, long-stroke, three-DOF parallel motion platform, characterized in that: The inner flexible arc-shaped mechanism (4-2) comprises a sticky top plate A (4-2-1), two arc-shaped flexible outer shells A (4-2-2) and an H-shaped flexible frame (4-2-3); The inner arc surfaces of the two arc-shaped flexible shells A (4-2-2) are arranged opposite to each other and butted together to form a hollow structure. The sticky top plate A (4-2-1) is arranged on the top of the hollow structure. An H-shaped flexible frame (4-2-3) is also connected inside the hollow structure. The bottom of the hollow structure is flexibly connected to the positioning seat (4-1).

4. According to claim 2, a preload-adjustable, long-stroke, three-DOF parallel motion platform, characterized in that: The outer flexible arc-shaped mechanism (4-3) comprises a sticky top plate B (4-3-1), two arc-shaped flexible outer shells B (4-3-2) and a diamond-shaped flexible frame (4-3-3); the inner arc surfaces of the two arc-shaped flexible outer shells B (4-3-2) are arranged opposite to each other and butted together to form a hollow structure, the sticky top plate B (4-3-1) is arranged on the top of the hollow structure, the diamond-shaped flexible frame (4-3-3) is also connected in the hollow structure, and the bottom of the hollow structure is flexibly connected to the positioning seat (4-1).

5. According to claim 4, a preload-adjustable, long-stroke, three-DOF parallel motion platform, characterized in that: A flexible fork-shaped support frame is also connected inside the diamond-shaped flexible frame (4-3-3).

6. According to claim 2, a preload-adjustable, long-stroke, three-DOF parallel motion platform, characterized in that: The bottoms of the inner flexible arc-shaped mechanism (4-2) and the outer flexible arc-shaped mechanism (4-3) are respectively connected to the positioning seat (4-1) through flexible hinges.

7. According to claim 1, a preload-adjustable, long-stroke, three-DOF parallel motion platform, characterized in that: A plurality of bull's eye bearings (7) are arranged along the circumferential direction on the edge of the central hole on the lower surface of the preload platform (1).

8. The preload-adjustable, long-stroke, three-DOF parallel motion platform according to claim 1, characterized in that: The flexible support (3) is formed by one-piece wire cutting or 3D printing.

9. The preload-adjustable, long-stroke, three-DOF parallel motion platform according to claim 2 or 6, characterized in that: The positioning seat (4-1), the inner flexible arc-shaped mechanism (4-2) and the outer flexible arc-shaped mechanism (4-3) are integrally formed by wire cutting or 3D printing.

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