Piezoelectric actuator, working method thereof and driving mechanism

Abstract

The invention belongs to the technical field of piezoelectric driving, and relates to a piezoelectric driver, a working method thereof and a driving mechanism. The piezoelectric actuator is mainly composed of a driving body, a driving foot, a pre-tightening force mechanism and a bolt. The driving body generates a non-resonance induction mode and brings first direction displacement and second direction displacement to be generated near a resonance mode under the excitation of a plurality of paths of driving electric signals due to the synergistic strain effect of a plurality of piezoelectric bodies, and the tail end of the driving foot forms an elliptical motion track through the synergistic effect of the displacements in two orthogonal directions. The driving mechanism comprises a piezoelectric actuator, a sliding block, a carrying platform and a fixing mechanism, the piezoelectric actuator is fixed to the sliding block and moves together with the sliding block during driving, a fixed piezoelectric actuator in a traditional scheme is converted into a moving part, and the advantages of being long in stroke and large in thrust are achieved. According to the invention, the beneficial effects of wide frequency band, large output and high-precision driving can be achieved, and miniaturization of a driving system is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric drive technology, specifically relating to a piezoelectric actuator, its working method, and a drive mechanism. Background Technology

[0002] Currently, micro-drive systems, as the core carrier of high-precision positioning and drive technologies, have demonstrated enormous application potential in fields such as aerospace precision instruments, microelectronic manufacturing equipment, biological micromanipulation, microrobots, and high-end consumer electronics. However, the continuous miniaturization of drive systems poses a severe challenge to traditional drive components. Taking electromagnetic motors as an example, they rely on the principle of electromagnetic induction and generally suffer from inherent defects such as complex structures and susceptibility to electromagnetic interference. More importantly, there is an irreconcilable contradiction between size reduction and energy efficiency improvement, making it difficult for miniaturized electromagnetic motors to simultaneously achieve key performance indicators such as large stroke, large driving force, and fast response. Piezoelectric actuators, based on the inverse piezoelectric effect of piezoelectric materials, directly drive mechanical deformation with electrical energy and achieve macroscopic displacement output through frictional coupling between the stator and actuator. This principle endows them with significant characteristics such as fast response, high power density, nanometer-level displacement resolution, resistance to electromagnetic interference, and power-off self-locking. Therefore, piezoelectric drive technology is considered an ideal solution to overcome the performance bottleneck of micro-drive systems, especially suitable for high-precision micromanipulation scenarios with stringent space constraints and the need for multi-functional integration.

[0003] However, current mainstream resonant piezoelectric actuators generally rely on the coupling of two orthogonal vibration modes to achieve their driving function. This design architecture inevitably subjectes them to dual technical constraints: on the one hand, it must meet strict requirements for multiple modal coupling to amplify the stator end vibration displacement; on the other hand, it is highly sensitive to the resonant frequency, meaning that even a small frequency shift can lead to a significant decrease in driving efficiency. Especially when environmental factors (such as temperature fluctuations and external interference) intervene, it is very easy to cause modal decoupling failure or resonant frequency shift. Such parameter drifts significantly increase the risk of driving performance degradation. Specifically, environmental disturbances break the modal orthogonality coupling condition or cause the operating frequency to deviate from the resonant peak range, ultimately leading to a significant decrease in the actuator's output efficiency.

[0004] To address the above issues, existing technologies have attempted various approaches: adopting a non-resonant driving mode avoids the sensitivity issues of modes and resonant frequencies, but sacrifices the resonant amplification effect, resulting in a significant decrease in output speed and load capacity; using a single-resonant mode drive simplifies mode control, but still cannot effectively avoid the negative impact of resonant frequency shift.

[0005] Furthermore, at the drive mechanism design level, existing solutions generally adopt a fixed piezoelectric actuator configuration. This design suffers from two technical constraints: firstly, the fixed support structure itself occupies considerable space, directly hindering the miniaturization process of the system; secondly, the stroke of the piezoelectric actuator requires a guide rail space structure twice the stroke length, which further compresses the integrated design margin, and the actuator must additionally bear the inertial load generated by the weight of the long slider during movement. Therefore, the aforementioned structural defects not only limit the miniaturization scale of the drive system, but also cause a significant deterioration in drive load capacity due to the accumulation of self-weight load during long-stroke operation. Summary of the Invention

[0006] The purpose of this invention is to provide a piezoelectric actuator and its working method and driving mechanism to solve the following problems of existing actuators: insufficient driving motion stability at resonant frequency, difficulty in miniaturization, and significant deterioration of driving load capacity due to the accumulation of self-weight load in long-stroke conditions.

[0007] This invention is achieved through the following technical solution: This invention discloses a piezoelectric actuator, comprising a driving body, a preload mechanism, and a driving foot; The preload mechanism is fixed to one side of the drive body, and the drive foot is fixed to the other side of the drive body; The preload mechanism is used to provide elastic preload to the drive body, so that the drive foot maintains adaptive elastic contact with the friction interface; The driving foot serves as a displacement amplification and output mechanism; The driving body adopts a dual-piezoelectric driving body configuration or a quad-piezoelectric driving body configuration.

[0008] Furthermore, when the actuator adopts a dual piezoelectric actuator configuration, it includes a first variant and a second variant; The first variant includes a two-layer structure, with the first layer consisting of two piezoelectric elements and the second layer being an elastomer; The second variant is formed by combining two piezoelectric elements.

[0009] Furthermore, when the actuator adopts a four-piezoelectric actuator configuration, it includes a third variant and a fourth variant; The third variant includes a three-layer structure, with the first and third layers each composed of two piezoelectric elements; the second layer is an elastomer. The fourth variant consists of a two-layer structure, each layer consisting of two piezoelectric elements.

[0010] Furthermore, both opposite sides of the piezoelectric body are covered with an electrode layer, and the electrode layer is made of a conductive material.

[0011] Furthermore, the preload mechanism employs a spring or a spring sheet.

[0012] Furthermore, the drive foot is installed at the crest of the vibration wave of the drive body.

[0013] Furthermore, the cross-sectional profile of the driving foot can be rectangular, circular, semi-circular, triangular, or irregular.

[0014] Furthermore, the drive feet are made of wear-resistant materials.

[0015] The present invention also discloses a method for operating the piezoelectric actuator, comprising the following steps: In the non-resonant operating state, by applying a specific waveform electrical signal to the driving body, the inverse piezoelectric effect is used to excite the driving body to generate a displacement output in the first direction. At the same time, a resonant mode with a displacement orthogonal to the first direction is selected, and the frequency of the driving electrical signal is set to be close to the resonant frequency of the resonant mode, so that the driving body generates orthogonal bidirectional displacement in a wide frequency range. The combined motion of the two displacements forms an elliptical trajectory, and then the sliding component is driven to move through friction coupling.

[0016] The present invention also discloses a driving mechanism, including a slider, a loading platform, a fixing mechanism, and the piezoelectric actuator; the piezoelectric actuator and the loading platform are both fixed on the slider; The fixing mechanism includes a guide mechanism, a fixed slide rail, and a fixed friction plate; The guiding mechanism is used to guide the sliding of the cargo platform; the slider is mounted on a fixed slide rail. The driving foot contacts and engages with the fixed friction plate, which provides a friction interface for the driving foot to make frictional contact and drive the slider and the platform to move.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a piezoelectric actuator that induces a first-direction displacement in the driven body through multiple driving signals, and combines this with a second-direction displacement orthogonal to the resonant mode to synthesize the driving motion. This method effectively avoids the mode decoupling and resonant frequency drift problems of traditional dual-resonant mode piezoelectric actuators, and significantly widens the operating frequency range while ensuring output performance.

[0018] This invention also discloses a method for operating a piezoelectric actuator, in which the electrode surfaces of each piezoelectric element are excited by a driving electrical signal to generate a synergistic strain effect among multiple piezoelectric elements. Specifically, in the non-resonant operating state, by applying a specific waveform electrical signal, the inverse piezoelectric effect is used to excite the actuator to generate a displacement output in the first direction. Furthermore, by selecting a resonant mode orthogonal to the first direction and setting the frequency of the driving electrical signal to be close to the resonant frequency of this mode, the actuator can generate orthogonal bidirectional displacement over a wide frequency range. That is, the composite motion of the two-direction displacement forms an elliptical trajectory, which is then used to drive the sliding component to achieve motion through frictional coupling.

[0019] The aforementioned multi-piezoelectric synergistic strain effect refers to inducing orthogonal composite deformations (such as bending, stretching, and torsion) by applying an electrical signal that matches the resonant frequency of the driving body's bending / stretching / torsion deformations. For example, when the excitation signal matches the bending resonant frequency of the driving body, it can synchronously induce orthogonal stretching deformations, achieving displacement output optimization through orthogonal deformation coupling. Here, the matching resonant frequency refers to applying an electrical signal within a wide frequency band near the resonant frequency.

[0020] The non-resonant operating state refers to the vibration mode in which multiple piezoelectric bodies are excited by multiple driving signals, causing them to produce coordinated strain, thereby generating a vibration mode with displacement in a specific direction. The resonant mode is an inherent vibration mode that depends on the geometry of the body, and each mode corresponds to its characteristic frequency (e.g., first-order bending resonant mode, second-order bending resonant mode, first-order elongation resonant mode, etc.).

[0021] This invention also discloses a driving mechanism that fixes a piezoelectric actuator onto a slider, transforming it from a fixed stator in traditional solutions into a moving component, thus realizing the conversion between stator and mover roles. In traditional solutions, the piezoelectric actuator is fixedly mounted as a stator, and the length of space required to drive the slider must be at least twice the driving stroke. This driving mechanism avoids this limitation, requiring only that the sliding displacement of the slider equals the required driving displacement. Furthermore, this mechanism can theoretically achieve unlimited stroke driving. In traditional fixed piezoelectric stator solutions, the actuator must overcome the gravity of the long slider during long stroke driving; however, this mechanism, for long stroke driving, only needs to overcome the mass of the piezoelectric actuator itself and the small slider, thereby significantly improving the load capacity. Attached Figure Description

[0022] Figure 1 This is a structural diagram of a drive mechanism according to a preferred embodiment of the present invention; Figure 2 This is a structural diagram of the drive mechanism according to another preferred embodiment of the present invention; Figure 3 This is an exploded view of a piezoelectric actuator structure according to a preferred embodiment of the present invention; Figure 4 Figure 1 is a schematic diagram of the driving body configuration of the dual piezoelectric element according to the present invention; wherein, Figure 2a is the first variant; and Figure 3b is the second variant. Figure 5 Figure 1 is a schematic diagram of the driving body configuration of the four piezoelectric elements according to the present invention; wherein, Figure 2a is the third variant; and Figure 3b is the fourth variant. Figure 6 This is a schematic diagram of the electrical signal required to be applied to the drive body according to some preferred embodiments of the present invention; Figure 7This is a schematic diagram illustrating the working principle of a drive unit according to a preferred embodiment of the present invention; Figure 8 This is a schematic diagram illustrating the working principle of the drive body according to another preferred embodiment of the present invention; In the diagram: 1. Piezoelectric actuator; 2. Slider; 3. Loading platform; 4. First guide mechanism; 5. Fixed slide rail; 6. Fixed friction plate; 7. Second guide mechanism; 11. Drive body; 12. Drive foot; 13. Preload mechanism; 14. Bolt; 71. Guide rail; 72. Ball bearing; 111. Piezoelectric material; 112. Elastomer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0024] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0025] It should be noted that the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus. Furthermore, the terms "horizontal" and "vertical" are based on the orientation and positional relationship of the devices or components shown in the accompanying drawings and are used only for better description of the invention, not to require that the shown devices, components, or apparatus must have that specific orientation, and therefore should not be construed as limiting the invention.

[0026] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0027] This invention provides a piezoelectric actuator, its operating method, and a driving mechanism, which can save space in miniaturized applications while achieving high-precision output under wide bandwidth and high load.

[0028] Example 1 like Figure 1As shown, this embodiment discloses a driving mechanism, including a piezoelectric actuator 1, a slider 2, a loading platform 3, and a fixing mechanism. The fixing mechanism is divided into three parts: a first guide mechanism 4, a fixed slide rail 5, and a fixed friction plate 6.

[0029] The piezoelectric actuator 1 and the platform 3 are fixed to the slider 2, forming an integral unit. This unit can reciprocate on the fixed slide rail 5 under the drive of the piezoelectric actuator 1. The guide mechanism 4, as a fixed component, provides guiding constraints for the movement of the platform 3, which can significantly reduce the tilt angle generated during the movement, thereby improving the driving accuracy.

[0030] The loading platform 3 is not limited to various forms such as square, round, or polygonal, and mainly provides a motion platform for the required driving components.

[0031] Guiding mechanism is Figure 1 The first guide mechanism 4, which is shown in the guide rod structure form, is installed through the mounting hole of the guide rod on one side of the loading platform 3.

[0032] It should be noted that the stroke of the drive mechanism in this embodiment can theoretically be infinite, and its specific size can be adjusted by the length of the three fixed mechanisms (first guide mechanism 4, fixed slide rail 5, and fixed friction plate 6). Since the piezoelectric actuator 1 is fixedly connected to the slider 2 and moves during the drive process, compared with the traditional fixed piezoelectric actuator scheme, this mechanism does not require a guide rail length twice the drive stroke, saving space for the micro device. At the same time, when the piezoelectric actuator 1 moves, it only needs to overcome its own mass and the mass of the slider 2, avoiding the burden of overcoming the weight of the long slider in the long stroke drive of the traditional fixed piezoelectric actuator, thus significantly improving its load capacity.

[0033] For piezoelectric drives, the piezoelectric element 111 itself is relatively small. To further reduce the system space in practical applications, it is necessary to consider the issue of the length of the slider 2's running space occupying the entire system space.

[0034] Example 2 Unlike Embodiment 1, the guiding mechanism is... Figure 2 The second guide mechanism 7 shown is in the form of ball bearings and guide rails.

[0035] The second guiding mechanism 7 includes a guide rail 71 with a semi-circular groove, and a semi-circular groove is pre-made on one side of the loading platform 3. The two semi-circular grooves form a mounting hole, in which a plurality of balls 72 are installed.

[0036] The specific structure of the piezoelectric actuator 1 described above is as follows: Figure 3As shown, it mainly includes a drive body 11, a drive foot 12, a pre-tightening mechanism 13, and bolts 14. The drive foot 12 is fixed to the drive body 11; the side of the drive body 11 opposite to the drive foot 12 is fixed to the pre-tightening mechanism 13, which is further fixed to the slider 2 by bolts 14.

[0037] The drive foot 12 is fixed to the drive body 11 and is used to amplify and output its displacement. The cross-sectional profile of the drive foot 12 can be designed as a rectangle, circle, semicircle, triangle or irregular shape, and is preferably located at the vibration crest of the drive body 11. In addition, the number of drive feet 12 is not limited, but depends on the vibration mode of the drive body 11.

[0038] The driving foot 12 contacts and engages with the fixed friction plate 6, converting the micro-displacement of the driving body 11 into macro-motion through the friction interface.

[0039] To extend the service life of the drive mechanism, the drive foot 12 and the fixed friction plate 6 should be made of wear-resistant materials, such as ceramics like zirconium oxide, alumina, and silicon carbide, or high-wear-resistant metals and carbon fiber composites. The selection of materials is not limited to these.

[0040] The preload mechanism 13 applies an elastic force to the drive body 11, ensuring elastic contact between the drive foot 12 and the fixed friction plate 6. This design provides the piezoelectric actuator 1 with adaptive capability, effectively compensating for assembly and manufacturing errors, and contributing to improved consistency of the manufactured piezoelectric actuator 1. The preload mechanism 13 may employ, but is not limited to, a spring or spring sheet structure.

[0041] The specific structure of the aforementioned driving body 11 is as follows: Figure 4 The driving body configuration of the dual piezoelectric element shown or Figure 5 The diagram shows the driving configuration of the four piezoelectric elements.

[0042] like Figure 4 The first variant shown in Figure a has a two-layer structure, with the first layer consisting of two piezoelectric bodies 111 and the second layer being an elastomer 112.

[0043] like Figure 4 The second variant shown in Figure b has a drive body 11 composed of two piezoelectric bodies 111.

[0044] like Figure 5 The third variant shown in Figure a has a piezoelectric-elastomer composite structure for the driving body 11, which specifically includes a three-layer structure. The first and third layers are each composed of two piezoelectric bodies 111, and the second layer is an elastomer 112.

[0045] like Figure 5The fourth variant shown in Figure b has a piezoelectric composite structure for the actuator 11, which specifically includes a two-layer structure, each layer consisting of two piezoelectric elements 111.

[0046] in, Figure 4 The drive body 11 structure in the middle can be applied as follows: Figure 6 The two preferred driving signals are CH1 and CH2. Figure 5 The drive body 11 structure in the middle can be applied as follows: Figure 6 The four preferred driving signals are CH1, CH2, CH3 and CH4.

[0047] The piezoelectric body 111 has an electrode layer on both opposite sides. The material of the electrode layer is not limited to conductive materials such as gold, silver, platinum, palladium, copper, nickel, and aluminum. The shape of the electrode layer is not limited to square, circular, or irregular shapes.

[0048] Under the excitation of a preferred driving signal, the driving body 11 can induce a specific vibration mode. In one embodiment, the induced vibration mode may be: Figure 7 The diagram shows either Mode 1 or Mode 2; Mode 1 is a bending mode in which the displacement output point can generate displacement in the Z direction, and Mode 2 is another bending mode in which the displacement output point can generate displacement in the X direction. By combining the two modes, displacements with two orthogonal directions can be generated through the displacement output point. Further selection of a resonant mode orthogonal to the direction of the induced mode output displacement (such as...) Figure 7 (Corresponding to Mode 2 or Mode 1); by adjusting the frequency of the preferred driving signal to near the resonant frequency of the resonant mode (in some embodiments, this can be within a 20kHz frequency band near the resonant frequency), the driving body 11 can output displacements in two orthogonal directions within a wider frequency band. By adjusting the driving signal (such as phase, amplitude, etc.), an elliptical motion trajectory can be synthesized to achieve the driving function.

[0049] In another embodiment, the induced vibration mode may be Figure 8 The diagram shows either Mode 1 or Mode 2; Mode 1 is a bending mode where the displacement output point can generate displacement in the X direction, and Mode 2 is a stretching mode where the displacement output point can generate displacement in the Z direction. By combining these two modes, displacements with two orthogonal directions can be generated through the displacement output point. Further selection of a resonant mode orthogonal to the output displacement direction of the induced mode (such as...) Figure 8 (corresponding to mode two or mode one); and by adjusting the frequency of the preferred driving signal to near the resonant frequency of the resonant mode, the driving body 11 can output displacements in two orthogonal directions within a wide frequency band. By adjusting the driving signal (such as phase, amplitude, etc.), an elliptical motion trajectory can be synthesized to achieve the driving function.

[0050] The configuration of the preferred driving signals must be adapted to the driving body configuration: a dual-piezoelectric driving body requires two driving signals, while a quad-piezoelectric driving body requires four; the phase difference, amplitude, and waveform parameters of the multiple signals are determined by the target induced vibration mode; and the driving frequency must match the eigenfrequency of the selected resonant mode. Matching the resonant frequency refers to applying an electrical signal within a wide frequency band near the resonant frequency. This driving mode not only eliminates the modal decoupling problem faced by traditional coupled-mode piezoelectric actuators 1, but its wideband design also more effectively avoids the significant performance degradation problem caused by resonant frequency shift.

[0051] The piezoelectric element 111 may be a single-layer or multi-layer structure, and the material may include, but is not limited to, piezoelectric ceramics or piezoelectric single crystals, such as: lead zirconate titanate (PZT) ceramics, bismuth scandate-lead titanate (BS-PT) ceramics, barium titanate (BaTiO3) ceramics, potassium sodium niobate (KNN) ceramics, lead magnesium niobate-lead titanate (PMN-PT) single crystals, lead zinc niobate-lead titanate (PZN-PT) single crystals, and one or more combinations thereof. Furthermore, the polarization direction of the piezoelectric element 111 is not limited to its length, width, or thickness direction.

[0052] The elastomer 112 can be made of materials with high fatigue strength, excellent vibration transmission efficiency, and good durability, such as beryllium bronze, aluminum alloy, and titanium alloy.

[0053] In summary, this invention proposes an innovative piezoelectric actuator and a drive mechanism comprising the same. This method significantly broadens the operating bandwidth while maintaining output performance by synergistically controlling induced vibration modes and resonant modes. Simultaneously, the designed compact drive mechanism effectively saves space and improves load capacity, providing a new approach for the development of miniaturized high-precision drive technology.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A piezoelectric actuator, characterized in that, It includes a drive body (11), a preload mechanism (13), and a drive foot (12). The preload mechanism (13) is fixed to one side of the drive body (11), and the drive foot (12) is fixed to the other side of the drive body (11); The preload mechanism (13) is used to provide elastic preload to the drive body (11) so that the drive foot (12) maintains adaptive elastic contact with the friction interface; The driving foot (12) serves as a displacement amplification and output mechanism; The driving body (11) adopts a dual piezoelectric driving body configuration or a quad piezoelectric driving body configuration.

2. The piezoelectric actuator according to claim 1, characterized in that, When the actuator (11) adopts a dual piezoelectric actuator configuration, it includes a first variant and a second variant; The first variant includes a two-layer structure, the first layer consisting of two piezoelectric elements (111) and the second layer being an elastomer (112). The second variant is formed by combining two piezoelectric elements (111).

3. A piezoelectric actuator according to claim 1, characterized in that, When the actuator (11) adopts a four-piezoelectric actuator configuration, it includes the third variant and the fourth variant; The third variant includes a three-layer structure, with the first and third layers each consisting of two piezoelectric elements (111); the second layer is an elastomer (112). The fourth variant comprises a two-layer structure, each consisting of two piezoelectric elements (111).

4. A piezoelectric actuator according to claim 2 or 3, characterized in that, The piezoelectric material (111) has an electrode layer on both opposite sides, and the electrode layer is made of a conductive material.

5. A piezoelectric actuator according to claim 1, characterized in that, The preload mechanism (13) uses a spring or a spring sheet.

6. A piezoelectric actuator according to claim 1, characterized in that, The driving foot (12) is installed at the vibration crest of the driving body (11).

7. A piezoelectric actuator according to claim 1, characterized in that, The cross-sectional profile of the driving foot (12) is rectangular, circular, semi-circular, triangular or irregular.

8. A piezoelectric actuator according to claim 1, characterized in that, The drive foot (12) is made of wear-resistant material.

9. The method of operating the piezoelectric actuator according to any one of claims 1-8, characterized in that, Includes the following processes: In the non-resonant working state, by applying a specific waveform electrical signal to the driving body (11), the driving body (11) is excited to generate a first direction displacement output by utilizing the inverse piezoelectric effect; at the same time, a resonant mode with an orthogonal displacement to the first direction is selected, and the frequency of the driving electrical signal is set to be close to the resonant frequency of the resonant mode, so that the driving body (11) generates an orthogonal bidirectional displacement in a wide frequency range. The combined motion of the two directions of displacement forms an elliptical trajectory, and then the sliding component is driven to move through friction coupling.

10. A driving mechanism, characterized in that, Includes a slider (2), a loading platform (3), a fixing mechanism, and a piezoelectric actuator (1) as described in any one of claims 1-8; the piezoelectric actuator (1) and the loading platform (3) are both fixed on the slider (2); The fixing mechanism includes a guide mechanism, a fixed slide rail (5), and a fixed friction plate (6); The guiding mechanism is used to guide the sliding of the cargo platform (3); the slider (2) is mounted on the fixed slide rail (5); The driving foot (12) contacts and engages with the fixed friction plate (6). The fixed friction plate (6) provides a friction interface for the driving foot (12) so that the driving foot (12) can make friction contact to drive the slider (2) and the platform (3) to move.

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