A planar two-degree-of-freedom compliant precision positioning platform

Abstract

The present invention relates to a planar two-degree-of-freedom compliant precision positioning platform, comprising a carrier and a plurality of compliant hinges; four five-bar displacement amplification mechanisms are evenly distributed around the carrier; each five-bar displacement amplification mechanism comprises a driving source, a symmetrical lever displacement amplification mechanism driven by the driving source, and a semi-rhombus displacement amplification mechanism connected in series to the symmetrical lever displacement amplification mechanism; the semi-rhombus displacement amplification mechanism is connected to the carrier via a compliant hinge. The output of the driving source can be amplified by the symmetrical lever displacement amplification mechanism and the semi-rhombus displacement amplification mechanism, and then transmitted to the carrier via the compliant hinge to drive the carrier's movement. Combined with a symmetrical configuration layout with push-pull output without a guide beam, the overall size of the precision positioning platform can be controlled to be relatively small, the structure more compact, and the motion inertia very small, thereby achieving decoupled two-degree-of-freedom motion, relatively high output displacement, and a high motion bandwidth.

Description

Technical Field

[0001] The present invention relates to the technical field of precision positioning platforms, in particular to a planar two-degree-of-freedom compliant precision positioning platform. Background Art

[0002] Currently, precision positioning platforms based on piezoelectrically driven compliant mechanisms are widely used in various fields of science and technology, including atomic force scanning microscopy, micro-nano manipulation, micro-nano processing, and fiber optic docking. The performance of a compliant precision positioning platform is primarily measured by the following indicators: travel range, bandwidth, dimensions, and motion decoupling. Compliant mechanisms transmit the force and displacement of piezoelectric ceramic actuators through compliant elastic units such as compliant beams or compliant hinges. Therefore, they offer the advantages of being frictionless, free of backlash, easy to manufacture, with minimal assembly error and high positioning accuracy. Piezoelectric ceramic actuators also offer advantages such as fast response, nanometer-level displacement resolution, and compact size. Therefore, piezoelectric ceramic-driven compliant mechanisms can achieve nanometer-level positioning accuracy and microsecond-level response speeds.

[0003] However, piezoelectric ceramics also have the disadvantage of small output displacement, which is generally only tens of microns. In order to achieve higher output displacement, various compliant displacement amplification mechanisms such as lever-type displacement amplification mechanisms, bridge-type displacement amplification mechanisms, diamond-type displacement amplification mechanisms, and Scott-Russell displacement amplification mechanisms are needed to amplify the output displacement. However, using too many compliant units to transmit motion will increase the motion inertia that needs to be driven, thereby reducing the platform's natural frequency, that is, the bandwidth. To increase the platform's bandwidth, researchers will use methods such as increasing the stiffness of the compliant units and reducing the load mass. This can increase the platform's natural frequency, but will lead to a reduction in the platform's output displacement and the reduction in the load space. In general, a key design issue for precision positioning platforms based on piezoelectric-driven compliant mechanisms is to achieve a reasonable distribution of equivalent stiffness and equivalent mass, so that the two conflicting indicators of output displacement and motion bandwidth can be optimized as much as possible, thereby improving the platform's travel and bandwidth, making it suitable for different application scenarios. In addition, the motion decoupling of the compliant platform is also a very important indicator. If the platform's motion cannot be decoupled, the difficulty of designing the control algorithm will increase significantly. In order to achieve a specific motion, complex kinematic inverse solutions are required, which greatly increases the complexity of the algorithm and the performance requirements for the controller. If the design is improper, the repeatability of the compliant platform will be reduced. In order to achieve motion decoupling of the compliant platform from the structural design, various guide beams and complex parasitic displacement elimination mechanisms will be used. Although these mechanisms can effectively realize the motion structure, their large use of compliant rods will also bring about the problems of large space occupation and reduced motion bandwidth. Therefore, designing a compliant precision positioning platform with a compact structure, motion decoupling, relatively large displacement stroke, and high motion bandwidth is a challenge and a problem that the academic and engineering communities urgently need to solve.

[0004] The prior art discloses a paper: Ling M. Optimal design of apiezo-actuated 2-DOF millimeter-range monolithic flexure mechanism with a pseudo-static model [J]. Mechanical Systems and Signal Processing, 2018, 115: 120-131. This paper designs a planar two-DOF compliant precision positioning platform with millimeter-level travel and motion decoupling. The platform utilizes a three-stage displacement amplification mechanism consisting of a rhombus-shaped displacement amplification mechanism, a semi-rhombus-shaped displacement amplification mechanism, and a lever-type displacement amplification mechanism to achieve displacement amplification. A symmetrical configuration driven by a push-pull piezoelectric ceramic actuator is employed, and a compliant beam guide mechanism is used to achieve motion decoupling in the X and Y directions. The platform ultimately achieves a 30x displacement amplification ratio, an output displacement of up to 1.2 mm, and a natural frequency of 130 Hz.

[0005] It has the following technical problems: in order to amplify the micron-level displacement output of piezoelectric ceramics into millimeter-level displacement output, a three-stage displacement amplification mechanism is used. This amplification mechanism has too many flexible rods, low stiffness and large motion inertia (large mass), which ultimately leads to an overall size that is too large, at least 120mm, which is not suitable for integration into precision measuring instruments. In addition, the motion bandwidth is low, only 130Hz, and fast and precise positioning cannot be achieved. Summary of the Invention

[0006] In response to the problems existing in the prior art, the purpose of the present invention is to provide a planar two-degree-of-freedom flexible precision positioning platform with a compact structure and small motion inertia, which can achieve decoupled two-degree-of-freedom motion, relatively high output displacement and high motion bandwidth.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A planar two-degree-of-freedom compliant precision positioning platform comprises a stage and a plurality of compliant hinges;

[0009] There are four five-rod displacement amplification mechanisms evenly distributed around the stage;

[0010] Each five-bar displacement amplification mechanism includes a driving source, a symmetrical lever displacement amplification mechanism driven by the driving source, and a semi-rhombus displacement amplification mechanism connected in series to the symmetrical lever displacement amplification mechanism;

[0011] The semi-rhombus displacement amplification mechanism is connected to the stage through a flexible hinge.

[0012] Furthermore, the stage and the four five-bar displacement amplification mechanisms are located in the same plane.

[0013] Furthermore, the loading platform is provided with a load mounting hole.

[0014] Furthermore, the symmetrical lever displacement amplification mechanism includes a base, two symmetrically arranged driving source input ends and two symmetrically arranged lever arms, the two ends of the driving source are respectively abutted against the two driving source input ends, the input ends of the two lever arms are respectively connected to the two driving source input ends through flexible hinges, the fulcrum ends of the two lever arms are respectively connected to the two ends of the base through flexible hinges, and the output ends of the two lever arms are respectively rigidly connected to the two ends of the semi-rhombus displacement amplification mechanism.

[0015] Furthermore, the semi-rhombus displacement amplification mechanism includes two symmetrically arranged flexible beams, the output ends of the two lever arms are rigidly connected to one end of the two flexible beams, and the other ends of the two flexible beams intersect and are connected to the worktable through a flexible hinge at the intersection.

[0016] Furthermore, the base is provided with a base mounting hole.

[0017] Furthermore, the flexible hinge is leaf-shaped, straight-circular-shaped or V-shaped.

[0018] Furthermore, the compliant beam is a straight compliant beam or a rigid beam with compliant hinges at both ends.

[0019] Furthermore, the driving source is a piezoelectric ceramic actuator.

[0020] In general, the present invention has the following advantages:

[0021] The output of the drive source is amplified through a two-stage process, using a symmetrical lever-type displacement amplification mechanism and a semi-rhombus-shaped displacement amplification mechanism. This is then transmitted to the stage via a compliant hinge, driving the stage's motion. Combined with the symmetrical layout of the push-pull output without a guide beam, the overall dimensions of the precision positioning platform can be kept relatively small, resulting in a more compact structure. Furthermore, the symmetrical structure ensures decoupling of motion. Because the lever-type displacement amplification mechanism connects the five-bar displacement amplification mechanism to the drive source, the drive source essentially only experiences telescopic deformation. During the entire motion of the precision positioning platform, no other inertial motion, such as rotation or translation, occurs. Consequently, the moment of inertia is minimal, thereby increasing the bandwidth of the precision positioning platform. This allows the platform to achieve relatively high output displacement and a high motion bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the three-dimensional structure of the planar two-degree-of-freedom compliant precision positioning platform of this embodiment.

[0023] Figure 2 Schematic diagram of the planar structure of the planar two-degree-of-freedom compliant precision positioning platform of this embodiment.

[0024] Figure 3 Schematic diagram of the three-dimensional structure of the five-bar displacement amplification mechanism of this embodiment.

[0025] Figure 4 Schematic diagram of the planar structure of the five-bar displacement amplification mechanism of this embodiment.

[0026] In the picture:

[0027] 1-stage, 2-piezoelectric ceramic actuator, 3-five-bar displacement amplification mechanism, 301 (302, 303)-compliant hinge, 304-lever arm, 305-compliant beam, 306-piezoelectric ceramic actuator input end, 307-base, 4-load mounting hole, 5-base mounting hole. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below.

[0029] like Figures 1-4 As shown, a planar two-degree-of-freedom flexible precision positioning platform has a loading platform 1 in the middle of the positioning platform for mounting various types of loads. Load mounting holes 4 for fixing the loads are distributed on the loading platform. Connected to the loading platform 1 are four five-rod displacement amplification mechanisms 3 distributed at the four corners of the positioning platform.

[0030] Each five-bar displacement amplification mechanism 3 is internally provided with a piezoelectric ceramic actuator 2 that provides driving force. A base mounting hole 5 is provided at the end of the five-bar mechanism for mounting and fixing the precision positioning platform on other devices.

[0031] In this embodiment, the symmetrical layout of the push-pull output displacement amplification mechanisms directly connected to the periphery of the intermediate loading platform 1, driven by piezoelectric ceramic actuators 2 without guide beams, is referred to as a symmetrical push-pull output configuration without guide beams. Push-pull output specifically refers to the situation where two displacement amplification mechanisms, either left or right, drive the loading platform 1 left or right or up and down, with one displacement amplification mechanism providing a push action and the other providing a pull action. In this layout, the displacement amplification mechanisms not only drive the loading platform 1 but also provide guidance. For example, when the left or right displacement amplification mechanism pulls the loading platform left or right, the compliant beams 305 of the upper and lower displacement amplification mechanisms swing. Due to their symmetry, the upper and lower displacement amplification mechanisms restrain each other, ensuring that the loading platform 1 only translates leftward or rightward, rather than upward or downward. This layout decouples the motion of the precision positioning platform. Furthermore, by eliminating complex guide beams and decoupling mechanisms, the number of compliant units required for driving and their moment of inertia are reduced, resulting in a compact layout and minimal space usage.

[0032] Existing precision positioning platforms typically use a piezoelectric ceramic actuator 2 to directly output displacement, resulting in a small displacement range. Alternatively, they employ a single-stage amplification diamond displacement amplification mechanism, a bridge displacement amplification mechanism, or a combination of these hybrid displacement amplification mechanisms. These mechanisms, due to the large number of rods, increase size and reduce bandwidth. Furthermore, the inertial motion generated by the piezoelectric ceramic actuator in addition to telescopic motion also reduces bandwidth. The compliant precision positioning platform of this embodiment utilizes a five-rod displacement amplification mechanism 3 as the displacement amplification mechanism. The advantages of the five-rod displacement amplification mechanism 3 include low moment of inertia, a large displacement amplification ratio, good output displacement and bandwidth, a relatively compact structure, and a small overall size. Its overall performance is superior to that of bridge and diamond displacement amplification mechanisms.

[0033] like Figure 3 、 Figure 4 Specifically, the five rods in the five-rod displacement amplification mechanism 3 refer to two lever arms 304, two compliant beams 305, and a base 307. The five-rod displacement structure is bilaterally symmetrical and can be viewed as a two-stage displacement amplification mechanism consisting of a symmetrical lever displacement amplification mechanism and a semi-rhombus displacement amplification mechanism connected in series.

[0034] The specific structure of the lever-type displacement amplification mechanism includes: a symmetrical piezoelectric ceramic actuator input terminal 306 connected to a compliant hinge 302, which is directly connected to a lever arm 304. Lever arm 304 is connected to a base 307 via a compliant hinge 301. The end of lever arm 304 is directly connected to the compliant beam 305 of the semi-rhombus-shaped displacement amplification mechanism. The specific functions of these components are: the compliant hinge 301 and base 307 serve as the fulcrum of the lever-type displacement amplification mechanism; the compliant hinge 302 and piezoelectric ceramic actuator input terminal 306 serve as the input of the lever-type displacement amplification mechanism; and the output of the lever-type displacement amplification mechanism is connected to the compliant beam 305.

[0035] The semi-rhombus displacement amplification mechanism includes two symmetrical flexible beams 305. The input end is the output end of the lever-type displacement amplification mechanism, and the output end of the semi-rhombus displacement amplification mechanism is the intersection of the flexible beams 305, which is connected to the flexible hinge 303. Finally, the five-bar displacement amplification mechanism 3 composed of the lever-type displacement amplification mechanism and the semi-rhombus displacement amplification mechanism is connected to the worktable 1 through the flexible hinge 303.

[0036] The piezoelectric ceramic actuator 2 will be installed between the symmetrical piezoelectric ceramic actuator input ends 306 through interference fit, and then the driving force of the piezoelectric ceramic actuator 2 will directly act on the piezoelectric ceramic actuator input end 306, transmitting force and displacement through the five-bar mechanism, and finally driving the worktable 1 to move.

[0037] Since the five-bar displacement amplification mechanism 3 is actually a two-stage displacement amplification mechanism, it can achieve a larger displacement amplification ratio than a single lever displacement amplification mechanism, a diamond displacement amplification mechanism, or other displacement amplification mechanisms, and thus can achieve a relatively large output displacement. Furthermore, the five-bar displacement amplification mechanism 3 is compact in structure, and its symmetrical configuration layout with a push-pull output without a guide beam can keep the overall size of the precision positioning platform relatively small. Since the portion connecting the five-bar displacement amplification mechanism 3 and the piezoelectric ceramic actuator 2 is a lever-type displacement amplification mechanism, the piezoelectric ceramic actuator 2 essentially only produces telescopic deformation. During the entire movement of the precision positioning platform, no other inertial motions such as rotation or translation are generated. Therefore, the motion inertia is very small, thereby increasing the bandwidth of the precision positioning platform, allowing the precision positioning platform to have a relatively high bandwidth.

[0038] In addition to leaf-shaped flexible hinges, the flexible hinges 301 (302, 303) in the five-bar displacement amplification mechanism 3 can also use other types of notch-shaped flexible hinges such as straight circular, V-shaped, etc., and the specific form is not limited; the straight flexible beam 305 in the five-bar displacement amplification mechanism 3 can be replaced by other types of flexible beam rods such as rigid beams with flexible hinges at both ends, and the specific form is not limited, as long as it remains the five-bar displacement amplification mechanism 3.

[0039] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A planar two-degree-of-freedom compliant precision positioning platform, characterized by: including a stage and multiple compliant hinges; There are four five-rod displacement amplification mechanisms evenly distributed around the stage; Each five-bar displacement amplification mechanism includes a driving source, a symmetrical lever displacement amplification mechanism driven by the driving source, and a semi-rhombus displacement amplification mechanism connected in series to the symmetrical lever displacement amplification mechanism; The semi-rhombus displacement amplification mechanism is connected to the stage via a compliant hinge; The stage and the four five-rod displacement amplification mechanisms are located in the same plane; The symmetrical lever displacement amplification mechanism includes a base, two symmetrically arranged drive source input ends, and two symmetrically arranged lever arms, wherein the two ends of the drive source are respectively abutted against the two drive source input ends, the input ends of the two lever arms are respectively connected to the two drive source input ends via flexible hinges, the fulcrum ends of the two lever arms are respectively connected to the two ends of the base via flexible hinges, and the output ends of the two lever arms are respectively rigidly connected to the two ends of the semi-rhombus displacement amplification mechanism; The semi-rhombus displacement amplification mechanism includes two symmetrically arranged flexible beams. The output ends of the two lever arms are rigidly connected to one end of the two flexible beams respectively. The other ends of the two flexible beams intersect and the intersection is connected to the worktable through a flexible hinge.

2. A planar two-degree-of-freedom compliant precision positioning platform according to claim 1, characterized in that: The loading platform is provided with load mounting holes.

3. The planar two-degree-of-freedom compliant precision positioning platform according to claim 1, characterized in that: The base is provided with a base mounting hole.

4. The planar two-degree-of-freedom compliant precision positioning platform according to claim 1, characterized in that: The flexible hinge is a notch type flexible hinge.

5. The planar two-degree-of-freedom compliant precision positioning platform according to claim 1, characterized in that: The compliant beam is a straight compliant beam or a rigid beam with compliant hinges at both ends.

6. The planar two-degree-of-freedom compliant precision positioning platform according to claim 1, characterized in that: The driving source is a piezoelectric ceramic actuator.

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