Z-axis piezoelectric lifting platform

Abstract

The invention provides a Z-axis piezoelectric lifting platform and a piezoelectric nanometer positioning table. The Z-axis piezoelectric lifting platform comprises an objective table; the base is arranged below the objective table, the base comprises a partition plate and a bottom plate arranged below the partition plate, and a containing cavity is further formed between the partition plate and the bottom plate; the pre-tightening mechanism is arranged in the containing cavity, the two ends of the pre-tightening mechanism are connected with the bottom plate and the objective table, and the pre-tightening mechanism applies first pre-tightening force in the z-axis direction to the objective table; the decoupling mechanisms comprise decoupling modules and connecting rods, the two connecting rods are orthogonally distributed on the decoupling modules, the two decoupling mechanisms are arranged in a central symmetry mode relative to the partition plate, and the other ends of the connecting rods are connected with the partition plate; the two ends of the amplifying mechanism are connected with the decoupling mechanism and the bottom plate, the amplifying mechanism amplifies the small displacement of the piezoelectric ceramic into the needed displacement and can achieve load supporting, and the pre-tightening mechanism not only plays a pre-tightening role in the amplifying mechanism outputting the displacement, but also plays a remarkable role in counteracting in the loading process and decoupling in the non-motion direction.

Description

Technical Field

[0001] The present invention relates to a piezoelectric nano-positioning stage, and particularly to a Z-axis piezoelectric lifting platform. Background Art

[0002] A piezoelectric nano-positioning stage is a mechanical structure that uses piezoelectric ceramics to drive for ultra-high-precision positioning and movement. Utilizing the inverse piezoelectric effect of piezoelectric ceramics, it generates a tiny displacement after being energized. In recent years, a composite micro-displacement device composed of a piezoelectric ceramic drive unit and a flexible guiding mechanism has gradually become the mainstream technical solution. Such a device has both sub-micron positioning accuracy, high structural stiffness, and millisecond-level response speed, and has been widely used in cutting-edge scientific and technological fields such as semiconductor lithography and biological micromanipulation.

[0003] Currently, the Z-axis piezoelectric lifting platform has disadvantages such as poor stiffness, small magnification, low drive efficiency, poor replaceability of the assembly of the magnification mechanism and the working platform, weak load-bearing capacity of the working platform, poor anti-interference ability, and high processing difficulty. The magnification mechanisms currently used in the Z-axis piezoelectric lifting platform are usually of two types, triangular magnification and lever magnification. Lever magnification depends on the rod length ratio and has high design requirements for stress concentration and load, while the triangular magnification mechanism magnifies a small displacement to the required displacement through bridge magnification, which can not only ensure rigidity and displacement but also better meet the load. At the same time, the stability of the Z-axis piezoelectric lifting platform is also a key factor affecting the use performance. The coupling error in the movement direction and the non-movement direction is a problem that the current Z-axis piezoelectric lifting platform needs to solve. Currently, generally four symmetric magnification mechanisms are used for work, which not only increases the cost but also makes it difficult to ensure the control accuracy and the consistency of the magnification mechanism. Summary of the Invention

[0004] The present invention provides a Z-axis piezoelectric lifting platform, and its purpose is to solve the problems that the existing Z-axis piezoelectric lifting platform has defects in stability and accuracy.

[0005] In order to achieve the above purpose, an embodiment of the present invention provides a Z-axis piezoelectric lifting platform, including:

[0006] A stage;

[0007] A base, arranged below the stage, the base includes a partition and a bottom plate arranged below the partition, and there is also an accommodation cavity between the partition and the bottom plate;

[0008] A pre-tightening mechanism, arranged in the accommodation cavity, one end of the pre-tightening mechanism is connected to the bottom plate, and the other end is connected to the stage, and the pre-tightening mechanism applies a first pre-tightening force along the z-axis direction to the stage;

[0009] The decoupling mechanism includes a decoupling module connected to the stage and a connecting rod disposed on the decoupling module. The two connecting rods are orthogonally distributed on the decoupling module. The two decoupling mechanisms are centrosymmetrically arranged with respect to the partition board, and the other end of the connecting rod is connected to the partition board;

[0010] The amplifying mechanism is disposed in the accommodating cavity, with one end connected to the decoupling mechanism and the other end connected to the bottom plate. The amplifying mechanism is used to amplify the displacement generated by the piezoelectric ceramics installed in the amplifying mechanism.

[0011] Preferably, the pre-tightening mechanism is a helical spring. One end of the helical spring is connected to the bottom plate, and the other end is connected to the stage. The helical spring is in a compressed or telescopic state.

[0012] Preferably, the pre-tightening mechanism is a special-shaped spring. The special-shaped spring includes a first connecting section and a second connecting section. The first connecting section and the second connecting section are located in the same plane. An S-shaped intermediate part is also disposed in the plane. Two ends of the intermediate part are respectively connected to the first connecting section and the second connecting section. One end of the first connecting section, which is far from the intermediate part, is also connected with a bending section perpendicular to the plane. The bending section is fixed on the stage, and the other end is connected to the bottom plate. The special-shaped spring is in a compressed or telescopic state.

[0013] Preferably, the first end of the connecting rod connected to the decoupling module is lower than the second end of the connecting rod connected to the partition board, so that the first end applies a second pre-tightening force downward along the z-axis to the decoupling module.

[0014] Preferably, the two connecting rods are orthogonally arranged on the decoupling module, and the angular bisector direction of the two connecting rods coincides with the Y axis.

[0015] Preferably, a decoupling window is provided on the partition board, and the decoupling module is located in the decoupling window.

[0016] Preferably, an installation position for installing a capacitance sensor is reserved on the partition board.

[0017] Preferably, the decoupling mechanism can also be provided with four connecting rods, and the four connecting rods are arranged in a cross on the decoupling module.

[0018] The above solution of the present invention has the following beneficial effects:

[0019] In the present application, the amplifying mechanism amplifies the tiny displacement of the piezoelectric ceramics into the required displacement and can realize load support. The pre-tightening mechanism not only plays a pre-tightening role for the amplifying mechanism that outputs displacement, but also plays a significant role in offsetting during loading and decoupling in non-moving directions. The connecting rod of the decoupling mechanism connects the amplifying mechanism and the partition board, restricts the non-moving direction, and reduces the coupling error.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed implementation section. Description of the Drawings

[0021] Figure 1 is an exploded view of the present invention;

[0022] Figure 2 is a schematic structural diagram of the present invention (hiding the loading platform);

[0023] Figure 3 is a decoupling principle diagram;

[0024] Figure 4 is a schematic diagram of a special-shaped spring;

[0025] Figure 5 is a schematic diagram of another decoupling mechanism;

[0026] Figure 6a is a schematic diagram of the time and output displacement of a conventional lifting platform;

[0027] Figure 6b is a schematic diagram of the time and output displacement of the present application;

[0028] Figure 7a is the working curve under no-load and low spring stiffness conditions;

[0029] Figure 7b is the working curve under no-load and constant mass conditions;

[0030] Figure 8a is the load-bearing capacity result diagram of a conventional lifting platform without a decoupling mechanism and a pre-tightening mechanism;

[0031] Figure 8b is the load-bearing capacity result diagram of the present application;

[0032] Figure 9a is the stress result diagram of a conventional lifting platform;

[0033] Figure 9b is the stress result diagram of the present application.

[0034]

Description of the Reference Numerals

[0035] 10 - Loading platform,

[0036] 20 - Partition board, 21 - Decoupling window, 22 - Installation position,

[0037] 30 - Main body,

[0038] 40 - Bottom plate,

[0039] 50 - Pre - tightening mechanism, 51 - First connection segment, 52 - Second connection segment, 53 - Intermediate part, 54 - Bending segment, 60 - Decoupling mechanism, 61 - Decoupling module, 62 - Link

[0040] 70 - Amplification mechanism. Detailed implementation manner

[0041] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0042] As Figures 1-5 shown, an embodiment of the present invention provides a Z - axis piezoelectric lifting platform, including a load platform 10. A base is provided below the load platform 10. The base includes a partition 20 and a bottom plate 40. The load platform 10, the partition 20 and the base are arranged from top to bottom in the z - axis direction (i.e., the longitudinal direction). A main body 30 is also provided between the partition 20 and the base. The main body 30 penetrates in the z - axis direction to form an accommodation cavity. The partition 20 is arranged at the upper end of the main body 30, and the bottom plate 40 is arranged at the lower end of the main body 30. The pre - tightening mechanism 50 is arranged in the accommodation cavity. One end of the pre - tightening mechanism 50 is connected to the base, and the other end is connected to the load platform 10. The pre - tightening mechanism 50 is in a non - natural elongation state, so that a first pre - tightening force in the z - axis direction can be applied to the load platform 10. A decoupling mechanism 60 is also provided on the partition 20. The decoupling mechanism 60 includes a decoupling module 61 and a link 62. The decoupling module 61 is fixed below the load platform 10. One end of the link 62 is fixedly connected to the decoupling module 61, and the other end is fixedly connected to the partition 20. Each link 62 is orthogonally distributed on the decoupling module 61, and the two structural units are centrosymmetrically arranged about the center of the partition 20.

[0043] The amplification mechanism 70 is also arranged in the accommodation cavity, and one end of the amplification mechanism 70 is connected to the decoupling mechanism 60, and the other end is connected to the bottom plate 40. The amplification mechanism 70 adopts a bridge - type amplification mechanism, and the amplification mechanism 70 amplifies the displacement generated by the piezoelectric ceramics installed in the amplification mechanism 70.

[0044] In this application, the decoupling mechanism 60 is assembled with the load platform 10 to ensure that the displacement output by the amplification mechanism 70 is transmitted to the load platform 10 without interference, ensuring the stable operation of the load platform 10.

[0045] The decoupling mechanism 60 is installed through the link 62. When the amplification mechanism 70 connected to the decoupling mechanism 60 outputs displacement in the z - axis direction, it is intervened by the decoupling mechanism in the X and Y directions, so as to ensure that the amplification mechanism 70 can stably output in the z - axis direction.

[0046] In one embodiment of the present application, the preloading mechanism 50 is a helical spring. One end of the helical spring is fixedly connected to the bottom plate 40, and the other end is fixedly connected to the load platform 10. The helical spring is in a compressed or telescopic state.

[0047] In another embodiment of the present application, the preloading mechanism 50 is a special-shaped spring. The special-shaped spring includes a first connecting section 51 and a second connecting section 52. The first connecting section 51 and the second connecting section 52 are located in the same plane. An S-shaped middle part 53 is also arranged in this plane. Both ends of the middle part 53 are respectively connected to the first connecting section 51 and the second connecting section 52. One end of the first connecting section 51 far from the middle part 53 is also connected with a bent section 54. The bent section 54 is perpendicular to the plane where the middle part 53 is located. The bent section 54 is fixed below the load platform 10, and the other end is connected to the bottom plate 40. The special-shaped spring is in a compressed or telescopic state.

[0048] In the above two preloading mechanisms 50, when in a compressed state, they can provide an upward first preloading force for the load platform 10, and when in a telescopic state, they can provide a downward first preloading force for the load platform 10. Applying the first preloading force is beneficial to improving the service life and stability of the piezoelectric ceramic.

[0049] It should be particularly noted that when using a special-shaped spring, not only the first preloading force is generated, but also due to the shape of the special-shaped spring, there is a certain constraint in the X and Y directions. The flexibility of the special-shaped spring enables the load platform 10 to have little damping in the moving direction (z-axis direction), while having a certain rigidity in the non-moving directions (X and Y directions) for constraint.

[0050] Refer to Figure 3 As shown, the figure is the decoupling principle of the decoupling mechanism 60. It can be seen from this figure that under the action of the connecting rod 62, a traction force F generated by the load on the decoupling mechanism 60 can be decomposed into F X and F Y in the X-axis direction and the Y-axis direction. When the present application is affected by unstable factors, it can offset the interference in the non-moving direction and also has a preloading effect in the z-axis direction.

[0051] When the decoupling mechanism 60 cooperates with the helical spring, under the action of the decoupling mechanism 60, a single decoupling effect can be achieved in the X and Y axis directions. When the decoupling mechanism 60 cooperates with the special-shaped spring, the decoupling mechanism 60 and the special-shaped unit are decoupled simultaneously, realizing double decoupling, and its effect is better than that of the helical spring, and the lifting platform is more stable.

[0052] To further improve the stability of the stage 10, the connecting rod 62 has a first end and a second end. The first end is the end where the connecting rod 62 is connected to the decoupling module 61, and the second end is the end where the connecting rod 62 is connected to the partition 20. The first end is lower than the second end, so that the connecting rod 62 presents a certain arc, thereby enabling the first end to apply a second pre-tightening force downward along the z-axis to the decoupling module 61.

[0053] In the decoupling mechanism 60, the two connecting rods 62 are orthogonally arranged on the decoupling module 61, and the angular bisector direction of the two connecting rods 62 coincides with the Y-axis. The straight lines where the two connecting rods 62 are located form connection points, and the connection points of the two decoupling mechanisms 60 are arranged oppositely.

[0054] Preferably, a decoupling window 21 penetrating the partition 20 is provided on the partition 20. The decoupling module 61 is located within the decoupling window 21, and the amplification mechanism 70 is located below the structural module.

[0055] Preferably, an installation position 22 for installing a capacitance sensor is reserved on the partition 20.

[0056] In some embodiments of the present application, the decoupling mechanism 60 is further provided with four connecting rods 62. The straight lines where the four connecting rods 62 are located are arranged in a cross shape on the decoupling module 61.

[0057] Compared with the existing piezoelectric micro-displacement platform, the present application has the advantages of simple structure, low cost, strong replaceability, large load-bearing capacity, and small coupling error, and the pre-tightening is applied in advance to extend the service life and stability.

[0058] The COMSOL MultiphYsics simulation software is used to simulate the Z-axis piezoelectric lifting platform with the decoupling mechanism 60 and the pre-tightening mechanism 50. At the same time, a conventional Z-axis piezoelectric lifting platform without the decoupling mechanism 60 and the pre-tightening mechanism 50 is used as a comparison.

[0059] Refer to Figure 6a and Figure 6b as shown, Figure 6a is a schematic diagram of time and output displacement of a conventional Z-axis piezoelectric lifting platform, Figure 6b is a schematic diagram of time and output displacement of the present application. As can be seen from the Figure 6a image shown, in the case of no constraints of the decoupling mechanism 60 and the pre-tightening mechanism 50, using a sine excitation signal will cause overshoot and instability. This is because the piezoelectric ceramic will generate inertia through the amplification mechanism, making the displacement unstable. Combining Figure 6bFor the shown image, after adding the constraints of the decoupling mechanism 60 and the preloading mechanism 50, the output displacement curve is closer to a sine wave. When working, if a stable sine excitation signal is given, the output displacement does not follow well, resulting in unstable operation. As shown in Fig. 6A, there will be offset and overshoot phenomena, and the maximum displacement is not reached at the theoretical maximum point (the peaks and valleys of the sine excitation signal should correspond to the maximum displacement of the output displacement). After adding the corresponding structures and optimizing, the output displacement is significantly smoother and more stable, more compliant and better, and the stable working state is more beneficial to the service life of the piezoelectric ceramic.

[0060] The installation of the decoupling mechanism 60 and the preloading mechanism 50 in this application has a slight impact on the output of the piezoelectric ceramic, but does not affect the load capacity.

[0061] Refer to Figure 7a 、 Figure 7b and Figure 8a 、 8b as shown, where Figure 7a is the working curve under no-load and low spring stiffness conditions, Figure 7b is the working curve under no-load and constant mass conditions, Figure 8a is the load capacity result diagram of the conventional Z-axis piezoelectric lifting platform without the decoupling mechanism 60 and the preloading mechanism 50, Figure 8b is the load capacity result diagram of this application.

[0062] Among them Figure 7a 、 Figure 7b , the abscissa V is the applied voltage, V0 is the maximum voltage, the ordinate Δl is the displacement change of the piezoelectric ceramic actuator, ΔL0 is the displacement change of the output displacement under no-load, ΔL is the displacement change under low spring stiffness, ΔL FS is the free stroke, F block is the blocking force, k A is the stiffness of the piezoelectric ceramic, k L is the load stiffness, F eff is the effective force, F maX is the maximum force, ΔL0’ is the displacement change of the output displacement after offset, F maX ’ is the maximum force after offset.

[0063] The stiffness of the amplification mechanism 70 helps to determine the performance of the piezoelectric ceramic and select an appropriate preload force, and to examine the effect of the preload and the performance of the amplification mechanism 70 by testing the two systems. Figure 7a On the right side of L <<k A A ) is the working curve of an amplification mechanism 70 under no-load and low stiffness load (k

[0064]

[0065] where ΔL FS is the free stroke, F block is the blocking force, k A is the stiffness of the piezoelectric ceramic, and k L is the load stiffness.

[0066] It can be seen from Figure 7a that the stroke of this application is slightly reduced. This is because the force applied by the preloading mechanism 50 returns to the piezoelectric ceramic, causing "self-compression" of the piezoelectric ceramic and reducing the overall stroke of the amplification mechanism 70. If the stroke and force are regarded as complementary properties of the amplification mechanism 70, it can be concluded that the low-stiffness spring produces a displacement close to the free stroke, but the effective force is much smaller than the blocking force. The performance of the high-stiffness spring (k L >> k A ) is just the opposite. In this case, the effective force is given by the following formula:

[0067]

[0068] On the right side of the Figure 7b figure is the working curve of an amplification mechanism 70 without load and with a constant mass. Among them, A is the no-load condition and B is the constant mass.

[0069] When the constant mass is used as the load on the amplification mechanism 70, the force (m×g) applied to the amplification mechanism 70 is independent of the stroke. Its working curve is as shown on the right side of Figure 7b . The force of the stable mass offsets the zero point on the amplification mechanism 70, but since the force is constant, the working curve is approximately the same as that of the no-load amplification mechanism 70. Therefore, the stroke remains close to the free stroke. The constant mass load only offsets the zero point by providing initial compression and maintains the same stroke range.

[0070] As shown in Figure 8a and 8b , comparing the load-bearing capacity of the conventional Z-axis piezoelectric lifting platform with that of this application will have a certain impact on the load and output force. After comparing the simulation results, it is found that using the decoupling mechanism and the preloading mechanism will improve the corresponding load-bearing capacity. When the same displacement is output, using the decoupling mechanism and the preloading mechanism will increase the response load and also have a good effect on the service life.

[0071] Referring to Figure 9a and Figure 9b shown, Figure 9a is the stress result diagram of the conventional Z-axis piezoelectric lifting platform, Figure 9b is the stress result diagram of this application. Combining Figure 9a and Figure 9b, it can be seen that after using the preloading mechanism 50 and the decoupling mechanism 60, the stress concentration can be significantly reduced, and the reliability and service life can be improved.

[0072] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A Z-axis piezoelectric lifting platform, characterized in that, Comprising: A stage (10); A base, disposed below the stage (10), the base includes a partition (20) and a bottom plate (40) disposed below the partition (20), and there is also a receiving cavity between the partition (20) and the bottom plate (40); A pre-tightening mechanism (50), disposed in the receiving cavity, one end of the pre-tightening mechanism (50) is connected to the bottom plate (40), and the other end is connected to the stage (10), and the pre-tightening mechanism (50) applies a first pre-tightening force in the z-axis direction to the stage (10); A decoupling mechanism (60), including a decoupling module (61) connected to the stage (10) and a connecting rod (62) disposed on the decoupling module (61), the two connecting rods (62) are orthogonally distributed on the decoupling module (61), and the two decoupling mechanisms (60) are symmetrically arranged about the partition (20), and the other end of the connecting rod (62) is connected to the partition (20); An amplifying mechanism (70), disposed in the receiving cavity, and one end is connected to the decoupling mechanism (60), and the other end is connected to the bottom plate (40), and the amplifying mechanism (70) is used to amplify the displacement generated by the piezoelectric ceramics installed in the amplifying mechanism (70).

2. The Z-axis piezoelectric lifting platform according to claim 1, wherein: The pre-tightening mechanism (50) is a helical spring, one end of the helical spring is connected to the bottom plate (40), and the other end is connected to the stage (10), and the helical spring is in a compressed or telescopic state.

3. The Z-axis piezoelectric lifting platform according to claim 1, wherein: The pre-tightening mechanism (50) is a special-shaped spring, the special-shaped spring includes a first connecting section (51) and a second connecting section (52), the first connecting section (51) and the second connecting section (52) are in the same plane, and an s-shaped middle part (53) is also disposed in the plane, and both ends of the middle part (53) are respectively connected to the first connecting section (51) and the second connecting section (52), and the first connecting section (51) is also connected with a bending section (54) perpendicular to the plane at the end far from the middle part (53), the bending section (54) is fixed on the stage (10), and the other end is connected to the bottom plate (40), and the special-shaped spring is in a compressed or telescopic state.

4. The Z-axis piezoelectric lifting platform according to claim 2 or 3, characterized in that: The first end of the connecting rod (62) connected to the decoupling module (61) is lower than the second end of the connecting rod (62) connected to the partition (20) so that the first end applies a second pre-tightening force in the downward z-axis direction to the decoupling module (61).

5. The Z-axis piezoelectric lifting platform according to claim 1, wherein: The two connecting rods (62) are orthogonally arranged on the decoupling module (61), and the angular bisector direction of the two connecting rods (62) coincides with the Y axis.

6. The Z-axis piezoelectric lifting platform according to claim 1, wherein: A decoupling window (21) is disposed on the partition (20), and the decoupling module (61) is located in the decoupling window (21).

7. The Z-axis piezoelectric lifting platform according to claim 1, wherein: An installation position (22) for installing a capacitance sensor is also reserved on the partition (20).

8. The Z-axis piezoelectric lifting platform according to claim 1, characterized in that: The decoupling mechanism (60) may also be provided with four connecting rods (62), and the four connecting rods (62) are arranged in a cross on the decoupling module (61).

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