Stick-slip-inching hybrid trans-scale piezoelectric actuator and method of operation thereof

Abstract

The application discloses a stick-slip-inching composite cross-scale piezoelectric driver and a working method thereof, and belongs to the technical field of precise piezoelectric driving. In view of the problem that the existing piezoelectric composite driver has a complex structure and limited mode switching due to the separated setting of the driving and clamping units, the integrated scheme of the driving and clamping is provided. The driver comprises a base, a slider guide rail, a slider, a piezoelectric driving module, a connecting plate, a sliding table and a pre-pressing mechanism. The piezoelectric driving module comprises a symmetrical compliant mechanism and two piezoelectric stacks embedded on both sides of the compliant mechanism. The two piezoelectric stacks share the same displacement amplification system and drive two driving legs to frictionally contact the slider, respectively. By changing the voltage excitation signal, the three modes of stick-slip stepping, inching motion and precise positioning can be independently switched on the same driver. The application has a compact structure, realizes the comprehensive performance of non-backstep, nanometer positioning and large-stroke rapid motion, and is suitable for cross-scale precise positioning of optical instrument posture adjustment, biological microscopic operation and wafer detection.

Description

Technical Field

[0001] This invention relates to the field of precision piezoelectric drive technology, and in particular to a stick-slippery-inchworm composite multi-scale piezoelectric actuator and its working method. Background Technology

[0002] Piezoelectric actuation is a precision driving technology that utilizes the inverse piezoelectric effect of piezoelectric materials to convert electrical energy into mechanical energy, thereby achieving motion displacement output. Based on this technology, piezoelectric actuators, with their high positioning accuracy, fast response speed, and power-off self-locking characteristics, have been widely applied in cutting-edge fields such as microstructure fabrication, cell micromanipulation, micro / nano-manipulated robots, and precision equipment attitude adjustment. In cross-scale precision positioning fields such as optical instrument attitude adjustment, biological cell micromanipulation, and wafer inspection, which require simultaneous macroscopic rapid movement, non-backtracking stepping, and microscopic precision positioning, the technical performance of piezoelectric actuators directly determines the upper limit of the system's achievable accuracy and efficiency. Therefore, developing piezoelectric actuators that combine large-stroke rapid movement, non-backtracking stepping, and nanometer-level positioning accuracy is of great significance for expanding the large-scale application of precision piezoelectric actuation technology in high-end equipment.

[0003] The current development status and existing technical routes of composite drive technology.

[0004] (I) The basic principles of piezoelectric drive technology and the limitations of a single drive mode.

[0005] Piezoelectric actuators can be classified into ultrasonic resonant, inertial stick-slip, and inchworm types according to their driving principle. Among them, stick-slip actuators have a simple structure and relatively high speed, but they suffer from displacement backlash and have low driving force.

[0006] The inchworm actuator uses a clamping mechanism to achieve non-retractable motion and high output force, but its structure is complex and its driving frequency and speed are limited.

[0007] To overcome the limitations of a single drive principle, a composite drive technology combining inchworm-like and stick-slip drive principles has been developed in this field, aiming to achieve comprehensive performance such as large stroke, high load capacity, and non-reverse motion.

[0008] (II) The development path from complete separation to functional separation.

[0009] In the field of composite drive technology, the piezoelectric positioning platform that couples the biomimetic and parasitic motion principles of inchworms, disclosed in 2018 (see CN108111052A), adopts a completely separate structure in which the clamping unit, the moving unit, and the driving unit are connected to the base by screws. The clamping and driving functions are realized by the clamping flexible hinge claw and the driving flexible hinge claw, respectively. The coupling of the biomimetic and parasitic motion of inchworms is realized by the timing control of periodic square waves and sawtooth waves.

[0010] A inchworm-type piezoelectric linear actuator disclosed in 2020 (see CN111327228A) adopts a separate drive component and a clamping component. The drive component amplifies the displacement a second time through the first and second bridge amplification structures, while the clamping component amplifies the clamping displacement through the lever structure, so as to solve the problem of small output displacement of the inchworm-type actuator.

[0011] A piezoelectric linear actuator for inchworms with a sticky-slip hybrid drive (see CN112271953A) disclosed in 2021 integrates the drive mechanism 3 and the clamping mechanism 4 with the support rib 401 via a connecting block 304. However, the first piezoelectric stack 305 and the second piezoelectric stack 404 independently drive their respective flexible hinge mechanisms, failing to achieve the sharing of the same displacement amplification system between the drive leg and the clamping foot.

[0012] (III) The inherent logic of existing technical routes.

[0013] The aforementioned prior art all follows the technical assumption of "functional separation," which assumes that the driving function (generating displacement and amplifying it) and the clamping function (fixing the mover to prevent retraction) must be undertaken by independent mechanical units. Therefore, the driving unit and the clamping unit are physically separated and installed on the base respectively. This assumption is reflected in the prior art as follows: in prior art 2 (i.e., CN108111052A), the clamping unit and the driving unit are connected to the base by screws respectively; in prior art 3 (i.e., CN111327228A), the driving component and the clamping component are set separately; in prior art 1 (i.e., CN112271953A), the driving mechanism and the clamping mechanism are driven independently by the first piezoelectric stack and the second piezoelectric stack respectively, and are installed in their respective independent flexible hinge structures.

[0014] Existing technologies achieve composite actuation through the sequential coordination of separate units. The rationale for this approach lies in the fact that each unit can be independently designed and optimized to meet the needs of displacement amplification and friction clamping. However, this comes at the cost of complex structure, large size, and high assembly precision requirements. From the perspective of natural technological evolution, the technological progress in this field has consistently followed the "functional separation" paradigm, from completely separate units to side-connected integrated molding with functional separation, never breaking through the cognitive boundary that the drive unit and clamping unit must be independently designed.

[0015] The shortcomings of existing technologies are described below.

[0016] (i) It has a complex structure, large volume, and high assembly precision requirements.

[0017] In this field, when introducing flexible hinges and piezoelectric stack timing control technology to balance large-stroke rapid motion and non-returning motion, the technical approach is to use new technologies such as flexible hinge displacement amplification and independent piezoelectric stack drive to implement the old method of functionally separated composite drive. The new technology is used to construct independent drive units and clamping / clamping units and install them on the base, and then use the timing coordination of the drive unit and the clamping / clamping unit to achieve composite drive motion.

[0018] Existing technologies focus on the functional separation and correlation between "discrete drive units generating displacement and amplifying it" and "discrete clamping / locking units fixing the mover to prevent retraction." Correspondingly, this application changes the traditional discrete module design, adopting an integrated composite drive module with a symmetrical compliant mechanism integrating dual piezoelectric stacks to replace the discrete drive units and clamping / locking units. Furthermore, it sets the first and second flexible hinges to share the same displacement amplification system, adapting to the new design concept where displacement amplification and force transmission can share the same mechanism in piezoelectric stack inverse piezoelectric effect and frictional coupling drive.

[0019] (ii) It is not possible to independently and flexibly switch between the three drive modes of stick-slipping stepping, inchworm motion and precision positioning on the same set of hardware.

[0020] In this field, when introducing piezoelectric stack multi-channel voltage signal timing control technology to achieve cross-scale precision positioning, the technical approach is to use a new technology of multiple independent voltage signals to implement the old method of periodic alternating mixed motion. The new technology controls the periodic alternating cooperation of the separate drive unit and the clamping / clamping unit, and then uses the periodic alternation of inchworm motion and stick-slip motion to achieve mixed drive motion.

[0021] Existing technologies focus on the relationship between "the periodic alternation and timing coordination of separate drive units and clamping / locking units" and "composite drive motion". Accordingly, this application changes the traditional periodic alternation mixed motion mode, and adopts three modes of stick-slip stepping, inchworm motion and precision positioning by independently switching voltage signals on the same integrated symmetrical compliant mechanism. The first piezoelectric stack and the second piezoelectric stack are respectively controlled by independent voltage signals to drive the first drive leg and the second drive leg, so as to adapt to the new design concept of the two drive legs in the same displacement amplification system that can act as both drive feet and clamping feet.

[0022] (iii) Lack of precise means of adjusting pre-pressure.

[0023] In this field, when introducing piezoelectric stack installation technology to achieve frictional coupling, the technical approach is to use new technologies (interference fit installation of piezoelectric stacks, adjusting screws) to implement old methods (fixed preload or position adjustment). The new technology is used to fix the piezoelectric stack or adjust the distance between the friction plate and the moving platform, and then the frictional coupling effect is obtained by utilizing the correlation between the fixed preload or the position of the friction plate and the frictional coupling performance.

[0024] Existing technologies focus on the relationship between "fixed preload or friction plate position" and "friction coupling performance." Accordingly, this application changes the traditional fixed preload or position adjustment mode, replacing the interference fit or adjusting screw with a micrometer-spring adjustable preload mechanism. It also sets up a system where the compression of the preload spring is changed by screwing in the micrometer to precisely adjust the preload between the drive module and the slider according to Hooke's Law, thus adapting to the physical laws governing the differentiated preload requirements of static and sliding friction conversion under different drive modes.

[0025] In summary, existing technologies, based on the assumption of "functional separation," result in complex structures, large volumes, and limited mode switching. Therefore, it is necessary to develop a piezoelectric actuator capable of flexibly switching between multiple drive modes in an integrated, compact structure, and possessing precise pre-pressure adjustment capabilities to meet the comprehensive requirements of cross-scale precision positioning. Summary of the Invention

[0026] The purpose of this invention is to provide a piezoelectric actuator that can integrate the driving function and the clamping function mechanism, so as to overcome the problems of complex structure, large size and inability to flexibly switch between multiple driving modes on the same hardware due to the separate setting of the driving unit and the clamping unit in the prior art by following the functional separation technical route.

[0027] To achieve the above objectives, the stick-slippery looper-inchworm composite multi-scale piezoelectric actuator of the present invention includes a base 1, a slider guide rail 2, a slider 3, a piezoelectric drive module, a connecting plate 6, a slide table 5, and a pre-pressing mechanism; the slider guide rail 2 is fixed on the base 1, the slider 3 is slidably assembled on the slider guide rail 2 and outputs linear displacement, and the piezoelectric drive module is fixed on the slide table 5 through the connecting plate 6; The piezoelectric drive module includes a symmetrical compliant mechanism 8, a first piezoelectric stack 11, a second piezoelectric stack 12, a gasket 10, and a preload bolt 9. The symmetrical compliant mechanism 8 includes a first flexible hinge 84, a second flexible hinge 83, a first drive leg 81, a second drive leg 82, an amplifying lever formed by the flexible hinge and the drive leg, and a piezoelectric stack pre-reserved frame. The first piezoelectric stack 11 and the second piezoelectric stack 12 are respectively embedded in the left and right sides of the piezoelectric stack pre-reserved frame. The outer ends of the first piezoelectric stack 11 and the second piezoelectric stack 12 abut against the preload bolt 9 through the gasket 10, and the inner ends abut against the lever portion on the corresponding side of the symmetrical compliant mechanism 8. The first piezoelectric stack 11 and the second piezoelectric stack 12 are controlled by independent voltage signals and drive the first drive leg 81 and the second drive leg 82 respectively. The first drive leg 81 and the second drive leg 82 contact the friction plate 4 attached to one side of the slider 3 and drive the slider 3 to move linearly through friction.

[0028] The first flexible hinge 84 is the rotation fulcrum of the amplifying lever. After the output displacement of the piezoelectric stack is amplified by the amplifying lever, it drives the corresponding driving leg to output displacement through the second flexible hinge 83. The first piezoelectric stack 11 and the second piezoelectric stack 12 share a displacement amplification system composed of the first flexible hinge 84 and the second flexible hinge 83.

[0029] By applying different voltage excitation signals to the first piezoelectric stack 11 and / or the second piezoelectric stack 12, the switching between three driving modes—stick-slip stepping mode, inchworm motion mode, and precision positioning mode—can be independently realized on the same stick-slip-inchworm composite multi-scale piezoelectric actuator. When a triangular wave voltage signal with a rise time greater than a fall time is applied to the first piezoelectric stack 11 or the second piezoelectric stack 12, it operates in stick-slip step mode. When a trapezoidal voltage signal with a phase difference is applied to the first piezoelectric stack 11 and the second piezoelectric stack 12 respectively, it operates in inchworm motion mode; When a monotonically increasing voltage signal is applied to the first piezoelectric stack 11 or the second piezoelectric stack 12, it operates in precision positioning mode.

[0030] The bottom of the symmetrical compliant mechanism 8 (if the direction towards the slider 3 is taken as the forward direction, then "bottom" here refers to "rear part") is provided with two symmetrical connecting plate bolt through holes 86 on both sides. The connecting plate 6 is provided with threaded holes 62 that correspond one-to-one with the connecting plate bolt through holes 86. The symmetrical compliant mechanism 8 is fixedly connected to the connecting plate 6 by mounting bolts 13 that pass through the connecting plate bolt through holes 86 and the threaded holes 62. The surface of the connecting plate 6 is provided with a T-shaped groove, which is used to prevent the first piezoelectric stack 11, the second piezoelectric stack 12 and the amplified lever portion of the symmetrical compliant mechanism 8 from contacting and interfering with the connecting plate 6; the upper two ends of the connecting plate 6 are provided with countersunk holes 61, and the connecting plate 6 is fixed to the slide table 5 by mounting bolts 7 passing through the countersunk holes 61; the first drive leg 81 and the second drive leg 82 extend forward from the slide table 5.

[0031] The pre-compression mechanism includes a micrometer 16, a micrometer fixing seat 15, and a pre-compression spring 14; the micrometer fixing seat 15 is fixedly installed on the slide table fixing base plate 17, the slide table fixing base plate 17 is a fixed support plate independent of the base 1, fixed on the base 1 and located on the side of the slide table 5; the micrometer fixing seat 15 is provided with a mounting hole for mounting the micrometer 16, and the micrometer 16 is fixed in the mounting hole; One end of the preload spring 14 is connected to the micrometer 16, and the other end acts on the piezoelectric drive module. By screwing in the micrometer 16, the compression of the preload spring 14 is changed. The elastic force generated by the preload spring 14 acts on the piezoelectric drive module and drives the slide table 5 to move towards the slider 3, thereby adjusting the preload between the piezoelectric drive module and the slider 3. The preload is determined according to Hooke's law F=kx, where k is the elastic constant of the preload spring 14 and x is the compression of the preload spring 14.

[0032] The base 1 is an L-shaped plate with countersunk threaded holes; the slide 5 is guided and engaged with the base 1 along the preload direction, and the guiding engagement is achieved by a planar guide surface or guide groove between the slide 5 and the base 1 to constrain the slide 5 to move along the preload direction.

[0033] The present invention also provides a method for operating the stick-slip-inchworm composite multi-scale piezoelectric actuator described above. By applying different voltage excitation signals to the first piezoelectric stack 11 and / or the second piezoelectric stack 12, three driving modes—stick-slip stepping mode, inchworm motion mode, and precision positioning mode—are switched on the same stick-slip-inchworm composite multi-scale piezoelectric actuator. When the slider 3 needs to move forward, the first piezoelectric stack 11 is excited; when the slider 3 needs to move in the reverse direction, the second piezoelectric stack 12 is excited or the phase difference of the voltage signal is reversed.

[0034] The stick-slip stepping mode includes the following steps: S1: Adjust the micrometer 16 of the preload mechanism so that the first drive leg 81 and the second drive leg 82 apply a preload Fn to the slider 3, where Fn represents the normal preload between the drive leg and the slider 3; S2: Apply a triangular wave voltage signal with a rise time greater than the fall time to the first piezoelectric stack 11, and the second piezoelectric stack 12 is not excited; the voltage is zero at the initial time t0, the first piezoelectric stack 11 maintains its original length, and the slider 3 remains stationary. S3: The period from t0 to t1 is the viscous stage. The driving voltage rises, the first piezoelectric stack 11 elongates, and after being transmitted and amplified by the symmetrical compliant mechanism 8, the first driving leg 81 produces an oblique movement. Under the action of static friction, the slider 3 is driven to move forward by a displacement d1, where d1 represents the positive displacement of the slider 3 in the viscous stage. S4: The period from t1 to t2 is the sliding stage. The driving voltage decreases, the first piezoelectric stack 11 shrinks to its initial length, the first driving leg 81 returns to its initial position, and the first driving leg 81 and the slider 3 slide relative to each other due to inertia. The sliding friction causes the slider 3 to move backward by a displacement d2, and d2 is less than d1. The step displacement of the slider 3 in one driving cycle is Δd = d1 - d2. S5: Under the excitation of a continuous triangular wave voltage signal, steps S3 and S4 are executed cyclically to drive the slider 3 to make continuous linear motion in the positive direction, and the moving speed of the slider 3 is adjusted by changing the frequency of the triangular wave voltage signal. When slider 3 needs to move in the opposite linear direction, a triangular wave voltage signal is applied to the second piezoelectric stack 12 instead, and the first piezoelectric stack 11 is not excited.

[0035] The inchworm's movement pattern includes the following steps: S1: Adjust the micrometer 16 of the preload mechanism so that the first drive leg 81 and the second drive leg 82 apply preload Fn to the slider 3; S2: Apply trapezoidal voltage signals V1 and V2 with a phase difference to the first piezoelectric stack 11 and the second piezoelectric stack 12 respectively. V1 represents the driving voltage of the first piezoelectric stack 11 and V2 represents the driving voltage of the second piezoelectric stack 12. At the initial time t0, both voltages V1 and V2 are zero. The first piezoelectric stack 11 and the second piezoelectric stack 12 maintain their original lengths, and the slider 3 remains stationary. t0 to t4 are five consecutive times within one driving cycle. S3: During the period from t0 to t1, the voltage V1 rises, the voltage V2 remains zero, the first piezoelectric stack 11 elongates, the first driving leg 81 generates an oblique motion and drives the slider 3 to move a displacement d1 in the positive direction under the action of static friction, and the second driving leg 82 remains stationary. S4: During the period from t1 to t2, the voltage V1 remains constant, the voltage V2 increases, the first piezoelectric stack 11 maintains a constant elongation, the first driving leg 81 remains stationary, the second piezoelectric stack 12 elongates, and the second driving leg 82 further presses the slider 3 on the basis of the existing pre-pressure contact, thereby clamping the slider 3. S5: During the period from t2 to t3, the voltage V1 decreases while the voltage V2 remains unchanged. The first piezoelectric stack 11 contracts, the first drive leg 81 returns to its initial position, and the second drive leg 82 maintains its clamping on the slider 3, so the slider 3 does not retract. S6: During the period from t3 to t4, voltage V1 remains zero, voltage V2 decreases, the second piezoelectric stack 12 contracts, the second driving leg 82 returns to its initial position and drives the slider 3 to move forward by a displacement d2 under the action of static friction; the step displacement Δd of the slider 3 within one driving cycle is d1+d2. S7: Repeat steps S3 to S6 to drive slider 3 to make continuous non-reverse stepping motion in the positive direction; When the slider 3 needs to move in the reverse linear direction, the phase difference between voltage V1 and voltage V2 is changed to be the opposite of the phase difference during forward movement.

[0036] The precise positioning mode includes the following steps: S1: Adjust the micrometer 16 of the pre-compression mechanism so that the first drive leg 81 and the second drive leg 82 apply a pre-compression force Fn to the slider 3; S2: Apply a voltage signal that increases monotonically and remains constant to the first piezoelectric stack 11, while the second piezoelectric stack 12 is not excited; at the initial time t0, the voltage is zero, the first piezoelectric stack 11 maintains its original length, and the slider 3 remains stationary; S3: During the period from t0 to t1, the driving voltage rises, the first piezoelectric stack 11 elongates, and after being transmitted and amplified by the symmetrical compliant mechanism 8, the first driving leg 81 produces an oblique movement. Under the action of static friction, it directly drives the slider 3 to move a small displacement d1 in the positive direction. After the voltage remains constant, the position of the slider 3 remains unchanged, realizing the precise positioning of the slider 3. When slider 3 needs to be precisely positioned in reverse, a voltage signal that increases monotonically and remains constant is applied to the second piezoelectric stack 12, and the first piezoelectric stack 11 is not excited.

[0037] The present invention has the following main advantages: 1. The driving function and clamping function are integrated at the mechanism level, resulting in a compact structure and eliminating secondary assembly errors.

[0038] The symmetrical compliant mechanism 8 integrates the first piezoelectric stack 11, the second piezoelectric stack 12, and two sets of flexible hinge levers into the same mechanism. The first drive leg 81 and the second drive leg 82 share a displacement amplification system composed of the first flexible hinge 84 (rotation fulcrum) and the second flexible hinge 83 (displacement output point). The single mechanism simultaneously undertakes the "displacement amplification output" (driving function) and "static friction locking" (clamping function).

[0039] Theoretically speaking, the deformation of a flexible hinge is bidirectionally reversible. When the same lever system is subjected to positive force, it can amplify the displacement, and when subjected to reverse force, it can transmit the clamping force. The displacement amplification and force transmission share the same transmission path in mechanics. Therefore, the requirement that "the drive and clamping must be set up as two separate mechanical units" is not a physical necessity, but rather a design convention of "functional separation" in existing technology.

[0040] From the perspective of existing technologies, the evolution of technology—from fully separable in 2018, to bridge-type amplified separable in 2020, and side-connected but functionally separated in 2021—has consistently failed to break through the design convention of "functional separation." This invention embeds two piezoelectric stacks into the same reserved frame, representing a paradigm shift from "separate" to "integrated." This fundamentally avoids secondary assembly errors and axial misalignment caused by bolted connections between separate modules, resulting in a simultaneous reduction in assembly accuracy requirements and volume.

[0041] 2. The three driving modes can be switched independently and flexibly on the same set of hardware, and the "independent switching capability" is an inevitable technical effect of the integrated structure.

[0042] The first piezoelectric stack 11 and the second piezoelectric stack 12 are controlled by independent voltage signals, which drive the first driving leg 81 and the second driving leg 82 respectively. Each piezoelectric stack can be separated from the other piezoelectric stack and output a complete driving waveform independently.

[0043] Theoretically speaking: Since each driving leg has an independent "stack-lever-driving leg" excitation chain, a single stack can independently complete the "static friction synchronization-inertial slip" stick-slip stepping cycle by applying a triangular wave. Applying a voltage that increases monotonically and then remains constant can independently complete pure static micro-displacement positioning without the need for another unit to cooperate.

[0044] In contrast, in the prior art 1, the rapid drop of PZT1 must occur after the release of PZT2 (clamping mechanism). Its so-called "stick-slip" is only one link in the inchworm-like "clamping-drive-release-reset" process, not an independent mode. The independent switching capability of the present invention is a direct mapping of the "integrated dual excitation chain" structure at the control level, which is beyond the reach of unconventional waveform combinations.

[0045] 3. The precision positioning mode breaks through the functional boundaries of existing technologies and realizes a complete closed loop of cross-scale positioning capabilities.

[0046] By applying a monotonically increasing and then constant voltage to a single piezoelectric stack, the slider 3 is directly driven by static friction to produce a small displacement and maintain its position, achieving a positioning accuracy at the nanometer level.

[0047] Theoretically speaking, within the linear operating region of a piezoelectric stack, elongation is approximately proportional to voltage; the smaller the voltage increment, the higher the displacement resolution. This mode is a non-periodic, purely static micro-displacement mode, which belongs to a different category in terms of physical mechanism from the periodic stepping mode. Existing technologies 1, 2, and 3 all remain within the paradigm of "intermittent cooperation between inchworm and stick-slip." The precision positioning mode is a third independent mode that has not been disclosed in existing technologies. It, along with the stick-slip stepping mode (macroscopic centimeter-level rapid movement) and the inchworm movement mode (stepping without backtracking), constitute a complete cross-scale positioning chain of "macro-meso-micro" on the same hardware.

[0048] 4. The inchworm motion mode achieves true non-retrograde stepping, and the stepping displacement is the sum of two driving displacements. Under the control of the phase difference trapezoidal voltage signals V1 and V2, when the first driving leg 81 drives the slider 3 forward by d1, the second driving leg 82 clamps to prevent retrograde. When the second driving leg 82 retracts, it drives the slider 3 forward by d2 again. The stepping displacement Δd = d1 + d2 in one cycle.

[0049] Theoretically: Both drive legs share the same amplification system, and the roles of clamping and driving can be instantly interchanged between the two drive legs. At any given moment, one drive leg is always in the clamping state. The retraction path is mechanically closed; therefore, the absence of retraction is an inevitable result of the structural timing, not a result of debugging. This effect has been verified through prototype experiments (tested with a laser displacement sensor LK-G10, under conditions of 120 V driving voltage and 1 Hz operating frequency, stable stepping with no retraction).

[0050] 5. The preload can be precisely and linearly adjusted to meet the diverse needs of multi-mode friction coupling.

[0051] The pre-compression mechanism consists of a micrometer 16, a micrometer fixing base 15, and a pre-compression spring 14. The compression of the pre-compression spring 14 is changed by screwing in the micrometer 16, and the pre-compression force is precisely linearly adjusted according to Hooke's law F=kx. The slide table fixing base plate 17 provides an independent mounting foundation for the pre-compression mechanism, and the mating surface between the slide table 5 and the base 1 provides guidance for the pre-compression direction.

[0052] Theoretically speaking: the static friction / sliding friction conversion in stick-slip mode, the clamping reliability in inchworm mode, and the static friction drive in precision positioning mode all take the normal preload Fn as the key boundary condition, and the requirements of the three are different; the linear correspondence between the spring compression x and the advance of the micrometer 16 makes the preload quantifiable and reproducible, which is different from the interference fit (non-adjustable) and adjusting screw of the existing technology (the adjustment object is the position of the friction plate rather than the preload itself).

[0053] The present invention also has the following incidental technical advantages: The control system is simple. The three modes can be switched simply by changing the voltage signal waveform, without the need for displacement sensor feedback or complex closed-loop control circuits.

[0054] The stick-slip stepping mode enables rapid motion with a large stroke. The rise time of the triangular wave is longer than the fall time, which satisfies the mechanical conditions of static friction synchronization in the viscous stage and inertial slip in the sliding stage. The high-frequency band can achieve continuous and rapid motion at the macroscopic centimeter level.

[0055] The split design allows for expansion. The piezoelectric drive module and slider are separate units, and the number of modules and the slider guide 2 stroke can be selected according to the application, allowing for flexible adjustment of speed, thrust, and stroke.

[0056] In summary, this invention breaks through the evolutionary paradigm of "functional separation" in existing technologies by integrating a dual piezoelectric stack with an integrated symmetrical compliant mechanism. It achieves independent and flexible switching between three modes—stick-slip stepping, inchworm movement, and precise positioning—on the same compact hardware. It also features comprehensive performance with non-backtracking stepping, nanometer-level positioning accuracy, and precisely adjustable pre-pressure. Moreover, the ability to switch between the above modes independently and the non-backtracking effect are inevitable technical effects brought about by the integrated structure. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the overall appearance structure of the present invention; Figure 2 This is a schematic diagram of the piezoelectric drive module of the present invention; Figure 3 This is a schematic diagram of the symmetrical compliant mechanism of the present invention; Figure 4 This is a schematic diagram of the connecting plate of the present invention; Figure 5 This is a schematic diagram illustrating the working principle of the stick-slip stepping mode of the present invention; Figure 6 This is a schematic diagram illustrating the working principle of the inchworm's movement mode in this invention; Figure 7 This is a schematic diagram illustrating the working principle of the precision positioning mode of the present invention; Figure 8 This is a physical diagram of the prototype of the driver of this invention; Figure 9 This is a step displacement curve diagram of the inchworm / stick-slip drive mode of the driver described in this invention; Figure 10 This is a frequency-velocity characteristic curve of the stick-slip stepping mode of the present invention; Figure 11 This is a displacement curve diagram in the precision positioning mode of the present invention.

[0058] In the diagram: 1-Base, 2-Slider guide rail, 3-Slider, 4-Friction plate, 5-Slide table, 6-Connecting plate, 61-Counterhead hole, 62-Threaded hole, 7-Mounting bolt, 8-Symmetrical compliant mechanism, 81-First drive leg, 82-Second drive leg, 83-Second flexible hinge, 84-First flexible hinge, 85-Threaded hole of piezoelectric stack preload bolt, 86-Through hole of connecting plate bolt, 9-Preload bolt, 10-Washer, 11-First piezoelectric stack, 12-Second piezoelectric stack, 13-Mounting bolt, 14-Preload spring, 15-Micrometer fixing seat, 16-Micrometer, 17-Slide table fixing base plate. Detailed Implementation

[0059] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The present invention can be implemented in many different forms and should not be considered limited to the embodiments described herein; rather, these embodiments are provided to make this disclosure thorough and complete, and to fully convey the scope of the invention to those skilled in the art. In the drawings, the dimensions of some components are enlarged for clarity.

[0060] like Figure 1 As shown, the stick-slippery-inchworm composite multi-scale piezoelectric actuator of this embodiment includes a base 1, a slider guide rail 2, a slider 3, a piezoelectric drive module, a connecting plate 6, a slide table 5, and a preload mechanism. The slider guide rail 2 is fixed to the base 1 by bolts, and the slider 3 is slidably assembled on the slider guide rail 2 for outputting linear displacement. A friction plate 4 made of ceramic material is attached to one side of the slider 3 to reduce friction and wear during the operation of the actuator. The piezoelectric drive module is fixed to the slide table 5 by the connecting plate 6. The piezoelectric drive module and the slider 3 adopt a separate design, and a specific number of piezoelectric drive modules can be selected and placed in parallel according to different applications, and cooperate with the slider guide rail 2 with a specific stroke, thereby flexibly adjusting the drive speed, output thrust, and output stroke.

[0061] like Figure 2 As shown, the piezoelectric drive module consists of a symmetrical compliant mechanism 8, a first piezoelectric stack 11, a second piezoelectric stack 12, a gasket 10, and a preload bolt 9. The piezoelectric stack utilizes the inverse piezoelectric effect of the piezoelectric material, elongating and deforming when voltage is applied, and returning to its original length after power is cut off. Based on the overall dimensions of the piezoelectric drive and the reserved frame dimensions in the symmetrical compliant mechanism 8, the first piezoelectric stack 11 and the second piezoelectric stack 12 are selected from the PST150 / 5×5 / 20L model manufactured by Xinmingtian Company, with dimensions of 6×6×18mm. 3 The maximum output displacement is 20 μm under 150V driving voltage, the maximum thrust is 1600 N, and the resonant frequency is approximately 50 kHz. This meets the motion requirements of the piezoelectric actuator described in this invention.

[0062] like Figure 3As shown, the symmetrical compliant mechanism 8 is an integrated flexible structure, including a first flexible hinge 84, a second flexible hinge 83, a first drive leg 81, a second drive leg 82, an amplifying lever composed of the flexible hinge and the drive leg, a piezoelectric stack pre-reserved frame, and piezoelectric stack pre-compression bolt threaded holes 85 located at both ends. The first piezoelectric stack 11 and the second piezoelectric stack 12 are respectively embedded in the piezoelectric stack pre-reserved frames on the left and right sides of the symmetrical compliant mechanism 8. The outer ends of the two piezoelectric stacks abut against the pre-compression bolts 9 screwed into the piezoelectric stack pre-compression bolt threaded holes 85 through the washers 10, and the inner ends abut against the lever portions on the corresponding sides of the symmetrical compliant mechanism 8. By tightening the pre-compression bolts 9, the piezoelectric stacks can be fixed in the piezoelectric stack pre-reserved frames through the washers 10 and a pre-compression force can be applied to the piezoelectric stacks. The pre-compression bolts 9 are also used to adjust the pre-compression force of the first piezoelectric stack 11 and the second piezoelectric stack 12 during operation. The symmetrical compliant mechanism 8 is made of 7075 aluminum alloy, wherein the first flexible hinge 84 has a minimum thickness of 1 mm and the second flexible hinge 83 has an arc radius of 1 mm.

[0063] The displacement amplification and transmission principle of the symmetrical compliant mechanism 8 is as follows: the first flexible hinge 84 serves as the rotation fulcrum of the amplifying lever, the output end of the piezoelectric stack serves as the force point of the amplifying lever, and the second flexible hinge 83 serves as the displacement output point. When the piezoelectric stack is energized and elongates, its minute output displacement is amplified by the amplifying lever and then drives the corresponding driving leg to output displacement through the second flexible hinge 83. Specifically, the first piezoelectric stack 11 drives the first driving leg 81 through the corresponding amplifying lever and the second flexible hinge 83, and the second piezoelectric stack 12 drives the second driving leg 82 through the corresponding amplifying lever and the second flexible hinge 83. The first driving leg 81 and the second driving leg 82 are in contact with the friction plate 4 attached to one side of the slider 3, and drive the slider 3 to move linearly through friction. The first piezoelectric stack 11 and the second piezoelectric stack 12 are controlled by independent voltage signals, so the two driving legs can act independently or in coordination according to a set timing sequence.

[0064] It should be noted that, compared to the existing technology where the drive unit and clamping unit are separately installed on the base, the symmetrical compliant mechanism 8 of this invention integrates two piezoelectric stacks and two sets of flexible hinge levers into a single mechanism. This allows the first drive leg 81 and the second drive leg 82 to share the same displacement amplification system, achieving integration of drive and clamping functions in a single structure. In inchworm motion mode, the two drive legs can alternately act as drive feet and clamping feet; in stick-slip stepping mode and precision positioning mode, a single piezoelectric stack can work independently. This integrated structure fundamentally avoids secondary assembly errors and axial deflection caused by bolted connections between separate modules, improving displacement transmission accuracy and resulting in a compact structure. Furthermore, it is this integrated structure that enables a single piezoelectric stack to independently output the drive waveforms required for stick-slip stepping or precision positioning. The ability to independently switch between the three drive modes is a direct technical effect of the integrated structure, rather than simply a change in waveform.

[0065] like Figure 3 and Figure 4 As shown, the symmetrical compliant mechanism 8 has two symmetrical connecting plate bolt through holes 86 on both sides of its bottom. The connecting plate 6 has threaded holes 62 that correspond one-to-one with the connecting plate bolt through holes 86. The symmetrical compliant mechanism 8 is fixedly connected to the connecting plate 6 by mounting bolts 13 that pass through the connecting plate bolt through holes 86 and threaded holes 62. The surface of the connecting plate 6 is provided with T-shaped grooves to prevent the first piezoelectric stack 11, the second piezoelectric stack 12 and the amplified lever part of the symmetrical compliant mechanism 8 from contacting and interfering with the connecting plate 6. The upper two ends of the connecting plate 6 are provided with countersunk holes 61. The connecting plate 6 is fixed to the slide table 5 by mounting bolts 7 that pass through the countersunk holes 61. The first drive leg 81 and the second drive leg 82 extend forward from the slide table 5 to form frictional contact with the friction plate 4 on one side of the slider 3.

[0066] like Figure 1As shown, the pre-compression mechanism consists of a micrometer 16, a micrometer mounting base 15, and a pre-compression spring 14. The slide table mounting base 17 is a fixed support plate independent of the base 1, fixed to the vertical mounting surface of the base 1 by mounting bolts, located on the side of the slide table 5, and used to provide a mounting base for the pre-compression mechanism; the micrometer mounting base 15 is bolted to the slide table mounting base 17, and has mounting holes for mounting the micrometer 16. The mounting holes have internal threads that match the external threads of the micrometer 16, and the micrometer 16 is fixed in the mounting holes; one end of the pre-compression spring 14 is connected to the micrometer 16, and the other end acts on the piezoelectric drive module. The compression of the preload spring 14 can be changed by screwing in the micrometer 16, causing the preload spring 14 to generate elastic force and act on the piezoelectric drive module. Since the piezoelectric drive module is fixedly connected to the slide table 5 through the connecting plate 6 and mounting bolts 7, the elastic force of the preload spring 14 drives the piezoelectric drive module, together with the slide table 5, to move slightly towards the slider 3, thereby providing and adjusting the preload between the piezoelectric drive module and the slider 3. The guide of the slide table 5 in the preload direction is provided by the mating surface (planar guide surface or guide groove) between the slide table 5 and the base 1, so as to constrain the movement of the slide table 5 in the preload direction without deflection. According to Hooke's Law, the preload applied by the preload mechanism can be calculated using F=kx, where F is the preload in N; k is the elastic constant of the preload spring 14 in N / m, obtained from the technical parameters provided by the spring manufacturer or measured through spring testing experiments; and x is the compression of the preload spring 14 in mm, generated by the advance of the micrometer scale 16. In the initial free state of the spring, x is equal to the advance of the micrometer scale 16. The advance of the micrometer scale 16 can be accurately read. Combined with the linear relationship of Hooke's Law, precise linear adjustment of the preload can be achieved, thereby adapting to the differentiated requirements of friction coupling in different driving modes: too little preload will lead to insufficient friction coupling and drive failure; too much preload will aggravate the wear of the friction plate 4 and increase the load on the piezoelectric stack. This invention compares the speed, thrust, and load characteristics of the actuator under different preloads. After experimental debugging, the preload is adjustable in the range of 5 N to 15 N. For example, the actuator's motion is more stable in three driving modes at approximately 9 N.

[0067] like Figure 1 As shown, the base 1 is an L-shaped plate with countersunk threaded holes, and the slide table fixing base plate 17 and the slider guide rail 2 are respectively fixed to the base 1 by mounting bolts.

[0068] This embodiment also provides a method for operating the aforementioned stick-slip-inchworm composite multi-scale piezoelectric actuator. By applying different voltage excitation signals to the first piezoelectric stack 11 and / or the second piezoelectric stack 12, the three driving modes—stick-slip stepping mode, inchworm motion mode, and precision positioning mode—can be independently switched on the same actuator: When a triangular wave voltage signal with a rise time greater than a fall time is applied to a single piezoelectric stack, it operates in stick-slip stepping mode; when trapezoidal voltage signals with a phase difference are applied to both piezoelectric stacks, it operates in inchworm motion mode; and when a voltage signal with a monotonically rising and then constant voltage is applied to a single piezoelectric stack, it operates in precision positioning mode. The three driving modes can be switched simply by changing the waveform of the voltage signal, without the need for additional displacement sensor feedback or complex closed-loop control circuits, resulting in a simple control system. The specific driving principle is as follows: Figures 5 to 7 As shown.

[0069] The working principle of the stick-slip stepping mode is as follows: Figure 5 As shown, it utilizes the conversion between static friction and sliding friction, as well as the difference in inertial force, to achieve step displacement, specifically including the following steps: S1: Adjust the micrometer 16 of the preload mechanism so that the first drive leg 81 and the second drive leg 82 apply a preload Fn to the slider 3, where Fn represents the normal preload between the drive leg and the slider 3.

[0070] S2: When slider 3 needs to move in a positive linear direction, a triangular wave voltage signal is applied to the first piezoelectric stack 11, while the second piezoelectric stack 12 is not excited. The rise time of the triangular wave voltage signal is longer than the fall time to satisfy the mechanical conditions that the static friction force in the viscous stage is sufficient to drive slider 3 to move synchronously, and the inertial force in the sliding stage causes the driving leg and slider 3 to slide relative to each other. At the initial time t=t0, the voltage is 0 V, the first piezoelectric stack 11 maintains its original length, and slider 3 remains stationary. During the experiment, the duty cycle of the applied triangular wave voltage signal is usually selected as 90%, the amplitude is 120 V, and the frequency range is 1-2000 Hz.

[0071] S3: The period from t0 to t1 is the viscous stage. The driving voltage rises, and the first piezoelectric stack 11 elongates as the voltage rises. After being transmitted and amplified by the symmetrical compliant mechanism 8, it generates oblique motion at the first driving leg 81. Under the action of static friction, it drives the slider 3 to move forward by a displacement d1, where d1 represents the positive displacement of the slider 3 in the viscous stage.

[0072] S4: During the period from t1 to t2, the sliding phase occurs. The driving voltage decreases, and the first piezoelectric stack 11 synchronously contracts to its initial length. The first driving leg 81 quickly returns to its initial position. Due to the inertial force, the first driving leg 81 and the slider 3 slide relative to each other. The sliding friction between them causes the slider 3 to move backward by a displacement d2, and d2 is less than d1. Therefore, the step displacement of the driver in one driving cycle is Δd = d1 - d2.

[0073] S5: Under the excitation of a continuous triangular wave voltage signal, steps S3 and S4 are repeated cyclically, thereby driving slider 3 to move continuously in a straight line in the positive direction. The moving speed of slider 3 can be changed by changing the frequency of the triangular wave voltage signal: the higher the frequency of the triangular wave voltage signal, the greater the moving speed of slider 3; in the high-frequency range, continuous rapid motion with a macroscopic centimeter-level stroke can be achieved, and in the low-frequency range, continuous stepping motion with a micrometer-level stroke can be achieved. The high-frequency range and low-frequency range are relative to the mechanical response characteristics of the driver, and the criteria for judgment are the achievement of continuous rapid motion or continuous stepping motion. In the stick-slip drive mode, when the drive frequency is in the range of 1-100Hz, the driver usually exhibits micrometer-level stepping motion, so this frequency range is defined as the low-frequency range; while when the drive frequency is greater than 100 Hz, the output displacement of the driver exhibits continuous and smooth linear motion in a macroscopic manner, so this frequency range is set as the high-frequency range.

[0074] When slider 3 needs to make a reverse linear motion, a triangular wave voltage signal is applied to the second piezoelectric stack 12, and the first piezoelectric stack 11 is not excited.

[0075] The working principle of the inchworm's movement pattern is as follows: Figure 6 As shown, it utilizes alternating clamping and driving of dual driving legs to achieve non-retrograde stepping; the clamping refers to the state in which one driving leg keeps the slider 3 in a fixed position and prevents it from regressing through static friction in the inchworm movement mode. The inchworm movement mode specifically includes the following steps: S1: Adjust the micrometer 16 of the preload mechanism so that the first drive leg 81 and the second drive leg 82 apply preload Fn to the slider 3.

[0076] S2: When slider 3 needs to move in a forward, non-reverse linear motion, trapezoidal voltage signals V1 and V2 with a phase difference are applied to the first piezoelectric stack 11 and the second piezoelectric stack 12, respectively. V1 represents the driving voltage of the first piezoelectric stack 11, and V2 represents the driving voltage of the second piezoelectric stack 12. At the initial time t=t0, both voltages V1 and V2 are 0 V, the first piezoelectric stack 11 and the second piezoelectric stack 12 maintain their original lengths, and slider 3 remains stationary. t0 to t4 are five consecutive moments within one driving cycle. During the experiment, the amplitude of the two applied trapezoidal voltage signals is 120 V, and the phase difference is 90°. The frequency and the duration of each stage are determined according to the mechanical response characteristics of the actuator and the target step displacement.

[0077] S3: During the period from t0 to t1, the voltage V1 rises while the voltage V2 remains constant at 0 V. The first piezoelectric stack 11 extends synchronously with the voltage V1, driving the first driving leg 81 to move obliquely to the right. Under the action of static friction, it drives the slider 3 to move a displacement d1 in the positive direction. The second piezoelectric stack 12 and the second driving leg 82 remain stationary.

[0078] S4: During the period from t1 to t2, the voltage V1 remains unchanged, and the voltage V2 rises to the same value as V1. The first piezoelectric stack 11 maintains a constant elongation, and the first driving leg 81 remains stationary. The second piezoelectric stack 12 elongates synchronously with the voltage V2, and the second driving leg 82 further generates a left-side oblique movement on the basis of the existing pre-pressure contact, increasing the contact positive pressure with the slider 3 until the slider 3 is clamped.

[0079] S5: During the period from t2 to t3, the voltage V1 decreases while the voltage V2 remains constant. The first piezoelectric stack 11 contracts synchronously with the voltage V1, and the first driving leg 81 returns to its initial position. The second piezoelectric stack 12 maintains its elongation, and the second driving leg 82 maintains its clamping on the slider 3. Therefore, the slider 3 will not retract.

[0080] S6: During the period from t3 to t4, voltage V1 remains constant at 0 V, while voltage V2 decreases. The first piezoelectric stack 11 and the first driving leg 81 remain stationary. The second piezoelectric stack 12 contracts synchronously with voltage V2, and the second driving leg 82 returns to its initial position. Under the action of static friction, the second driving leg 82 drives the slider 3 to move forward by a displacement d2. Therefore, within one driving cycle, the step displacement of the actuator is Δd = d1 + d2, and the slider 3 is driven twice within one motion cycle without any retraction.

[0081] S7: Under the excitation of continuous voltage signals V1 and V2, steps S3 to S6 are repeated in a cycle, thereby driving slider 3 to make continuous non-reverse stepping motion in the positive direction.

[0082] When slider 3 needs to make a reverse linear motion, simply change the phase difference between voltages V1 and V2 so that it is the opposite of the phase difference when moving in the forward direction.

[0083] The working principle of precision positioning mode is as follows: Figure 7 As shown, it utilizes static friction to directly drive slider 3 to generate a small displacement and maintain its position, specifically including the following steps: S1: Adjust the micrometer 16 of the preload mechanism so that the first drive leg 81 and the second drive leg 82 apply preload Fn to the slider 3.

[0084] S2: When slider 3 needs to be precisely positioned in the forward direction, a monotonically increasing and then constant voltage is applied to the first piezoelectric stack 11, while the second piezoelectric stack 12 is not excited. At the initial time t=t0, the voltage is 0 V, the first piezoelectric stack 11 maintains its original length, and slider 3 remains stationary. The voltage amplitude and rise rate in the precision positioning mode are determined based on the target positioning accuracy and the linear operating region of the piezoelectric stack. For example, when the voltage slowly rises from 0 V to 4 V, the positioning resolution is approximately 69 nm.

[0085] S3: During the period from t0 to t1, the driving voltage rises, and the first piezoelectric stack 11 elongates as the voltage rises. After being transmitted and amplified by the symmetrical compliant mechanism 8, it generates an oblique motion at the first driving leg 81. Under the action of static friction, it directly drives the slider 3 to move a small displacement d1 in the positive direction. After the voltage remains constant, the position of the slider 3 remains unchanged, thereby achieving precise positioning of the slider 3.

[0086] When slider 3 needs to be precisely positioned in reverse, a voltage that increases monotonically and remains constant is applied to the second piezoelectric stack 12, so that the first piezoelectric stack 11 is not excited.

[0087] Based on the inverse piezoelectric effect of piezoelectric materials, within the linear operating region of the piezoelectric stack, the elongation of the piezoelectric stack is approximately proportional to the applied voltage. The smaller the voltage increment, the smaller the corresponding elongation increment, and the higher the displacement resolution of slider 3. When the elongation increment caused by the voltage increment is lower than the target positioning resolution, the elongation of the piezoelectric stack can theoretically reach the picometer level, meaning that slider 3 can theoretically achieve picometer-level positioning accuracy. However, the output thrust of the piezoelectric stack decreases as the input voltage decreases. If the thrust is too small, it cannot overcome the deformation resistance of the symmetrical compliant mechanism 8, and the drive leg will not be able to drive slider 3 to move. Therefore, the positioning accuracy of the actuator in precision positioning mode is generally at the nanometer level. Precision positioning mode is a non-periodic, purely static micro-displacement mode, which, together with stick-slip stepping mode and inchworm motion mode, constitutes a complete cross-scale positioning capability.

[0088] To verify the technical effects of the present invention, a prototype piezoelectric actuator was fabricated, such as... Figure 8 As shown, the stepping displacement characteristics of the driver were tested using a laser displacement sensor. The experimental results show that under a driving voltage of 120 V and an operating frequency of 1 Hz, the driver can achieve stable stepping displacement. Compared with the stick-slip stepping mode, in the inchworm motion mode, slider 3 is driven twice within one motion cycle, and there is no backlash. The single-step displacement is adjustable in the sub-micron to micron range according to the pre-pressure and voltage parameters, verifying the reliability of the alternating clamping and driving of the dual-drive legs in the integrated structure. In the stick-slip stepping mode, the driver output speed first increases and then decreases with increasing frequency, reaching a peak of 34.9 mm / s at 1400 Hz. Figure 10 As shown. In precision positioning mode, as the voltage slowly increases from 0 V to 4 V, the driver's positioning resolution is approximately 69 nm, as... Figure 11 As shown.

[0089] The three driving modes of this invention can be used in two levels. Level one is the primary usage mode: on the same actuator, the three driving modes can be switched between each other according to the current task requirements. For example, the stick-slip stepping mode is selected for large-stroke rapid coarse positioning, the inchworm motion mode is selected for fine adjustment without backlash, and the precision positioning mode is selected for nanometer-level precise positioning. After switching between the three modes, the actuator can achieve comprehensive performance such as large-stroke rapid movement, backlash-free stepping, and nanometer-level positioning accuracy. Level two is the auxiliary application mode: in complex precision positioning systems, multiple piezoelectric actuators of this invention can be configured for multiple moving parts with different scales and accuracy requirements. Each actuator selects the corresponding working mode according to the needs of its location. For example, a actuator working in stick-slip stepping mode is configured for large-stroke coarse adjustment parts, an actuator working in inchworm motion mode is configured for fine adjustment without backlash, and an actuator working in precision positioning mode is configured for nanometer-level positioning parts. Multiple actuators cooperate to meet the overall multi-scale movement requirements of the system.

[0090] The meanings of the English units appearing in this application are explained as follows: V is the unit of voltage (volt); Hz is the unit of frequency (hertz); N is the unit of force (newton); N / m is the unit of elastic constant (newton per meter); mm is the unit of length (millimeter).

[0091] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. 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 present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A stick-slippery-inchworm composite trans-scale piezoelectric actuator, characterized in that: It includes a base (1), a slider guide rail (2), a slider (3), a piezoelectric drive module, a connecting plate (6), a slide table (5), and a pre-pressing mechanism; the slider guide rail (2) is fixed on the base (1), the slider (3) is slidably assembled on the slider guide rail (2) and outputs linear displacement, and the piezoelectric drive module is fixed on the slide table (5) through the connecting plate (6); The piezoelectric drive module includes a symmetrical compliant mechanism (8), a first piezoelectric stack (11), a second piezoelectric stack (12), a gasket (10), and a preload bolt (9); the symmetrical compliant mechanism (8) includes a first flexible hinge (84), a second flexible hinge (83), a first drive leg (81), a second drive leg (82), an amplifying lever composed of the flexible hinge and the drive leg, and a piezoelectric stack pre-reserved frame; the first piezoelectric stack (11) and the second piezoelectric stack (12) are respectively embedded on the left and right sides of the piezoelectric stack pre-reserved frame, and the first piezoelectric stack (11) and the second piezoelectric stack (12) are respectively embedded on the left and right sides of the piezoelectric stack pre-reserved frame. The outer ends of the piezoelectric stack (12) abut against the preload bolt (9) through the gasket (10), and the inner ends abut against the lever portion on the corresponding side of the symmetrical compliant mechanism (8); the first piezoelectric stack (11) and the second piezoelectric stack (12) are controlled by independent voltage signals and drive the first drive leg (81) and the second drive leg (82) respectively; the first drive leg (81) and the second drive leg (82) are in contact with the friction plate (4) attached to one side of the slider (3) and drive the slider (3) to move linearly through friction.

2. The stick-slippery inchworm composite trans-scale piezoelectric actuator according to claim 1, characterized in that: The first flexible hinge (84) is the rotation fulcrum of the amplifying lever. After the output displacement of the piezoelectric stack is amplified by the amplifying lever, it drives the corresponding driving leg to output displacement through the second flexible hinge (83). The first piezoelectric stack (11) and the second piezoelectric stack (12) share the displacement amplification system composed of the first flexible hinge (84) and the second flexible hinge (83).

3. The stick-slippery inchworm composite trans-scale piezoelectric actuator according to claim 1 or 2, characterized in that: By applying different voltage excitation signals to the first piezoelectric stack (11) and / or the second piezoelectric stack (12), the switching between three driving modes—stick-slip stepping mode, inchworm motion mode, and precision positioning mode—can be independently realized on the same stick-slip-inchworm composite multi-scale piezoelectric actuator. When a triangular wave voltage signal with a rise time greater than a fall time is applied to the first piezoelectric stack (11) or the second piezoelectric stack (12), it operates in stick-slip step mode. When a trapezoidal voltage signal with a phase difference is applied to the first piezoelectric stack (11) and the second piezoelectric stack (12), the operation is in inchworm motion mode; When a voltage signal that rises monotonically and remains constant is applied to the first piezoelectric stack (11) or the second piezoelectric stack (12), it operates in precision positioning mode.

4. The stick-slippery inchworm composite trans-scale piezoelectric actuator according to claim 1, characterized in that: The symmetrical compliant mechanism (8) has two symmetrical connecting plate bolt through holes (86) on both sides of its bottom. The connecting plate (6) has threaded holes (62) that correspond one-to-one with the connecting plate bolt through holes (86). The symmetrical compliant mechanism (8) is fixedly connected to the connecting plate (6) by mounting bolts (13) that pass through the connecting plate bolt through holes (86) and the threaded holes (62). The surface of the connecting plate (6) is provided with a T-shaped groove, which is used to prevent the first piezoelectric stack (11), the second piezoelectric stack (12) and the amplified lever part of the symmetrical compliant mechanism (8) from contacting and interfering with the connecting plate (6); the upper two ends of the connecting plate (6) are provided with countersunk holes (61), and the connecting plate (6) is fixed to the slide (5) by mounting bolts (7) passing through the countersunk holes (61); the first drive leg (81) and the second drive leg (82) extend forward out of the slide (5).

5. The stick-slippery inchworm composite trans-scale piezoelectric actuator according to claim 1, characterized in that: The preload mechanism includes a micrometer (16), a micrometer mounting base (15), and a preload spring (14); the micrometer mounting base (15) is fixedly installed on the slide table mounting base (17), the slide table mounting base (17) is a fixed support plate independent of the base (1), fixed on the base (1) and located on the side of the slide table (5); the micrometer mounting base (15) is provided with mounting holes for mounting the micrometer (16), and the micrometer (16) is fixed in the mounting holes; One end of the preload spring (14) is connected to the micrometer (16), and the other end acts on the piezoelectric drive module. By rotating the micrometer (16) to change the compression of the preload spring (14), the elastic force generated by the preload spring (14) acts on the piezoelectric drive module and drives the slide (5) to move towards the slider (3) to adjust the preload between the piezoelectric drive module and the slider (3). The preload is determined according to Hooke's law F=kx, where k is the elastic constant of the preload spring (14) and x is the compression of the preload spring (14).

6. The stick-slippery inchworm composite trans-scale piezoelectric actuator according to claim 1, characterized in that: The base (1) is an L-shaped plate with countersunk threaded holes; the slide (5) is guided and engaged with the base (1) in the pre-pressure direction. The guiding engagement is achieved by the planar guide surface or guide groove between the slide (5) and the base (1) to constrain the slide (5) to move in the pre-pressure direction.

7. A method for operating a stick-slippery-inchworm composite multi-scale piezoelectric actuator according to any one of claims 1 to 6, characterized in that: By applying different voltage excitation signals to the first piezoelectric stack (11) and / or the second piezoelectric stack (12), three driving modes—stick-slip stepping mode, inchworm motion mode, and precision positioning mode—are switched on the same stick-slip-inchworm composite cross-scale piezoelectric actuator. When the slider (3) needs to move forward, the first piezoelectric stack (11) is excited; when the slider (3) needs to move in the opposite direction, the second piezoelectric stack (12) is excited or the phase difference of the voltage signal is reversed.

8. The working method according to claim 7, characterized in that: The stick-slip stepping mode includes the following steps: S1: Adjust the micrometer (16) of the preload mechanism so that the first drive leg (81) and the second drive leg (82) apply a preload Fn to the slider (3), where Fn represents the normal preload between the drive leg and the slider (3); S2: Apply a triangular wave voltage signal with a rise time greater than the fall time to the first piezoelectric stack (11), and the second piezoelectric stack (12) is not excited; the voltage is zero at the initial time t0, the first piezoelectric stack (11) maintains its original length, and the slider (3) remains stationary; S3: The period from t0 to t1 is the viscous stage. The driving voltage rises and the first piezoelectric stack (11) elongates. After being transmitted and amplified by the symmetrical compliant mechanism (8), the first driving leg (81) produces an oblique motion. Under the action of static friction, the slider (3) is driven to move in the positive direction by a displacement d1. d1 represents the positive displacement of the slider (3) in the viscous stage. S4: The period from t1 to t2 is the sliding stage. The driving voltage decreases, the first piezoelectric stack (11) shrinks to the initial length, the first driving leg (81) returns to the initial position, and the first driving leg (81) and the slider (3) slide relative to each other due to inertia. The sliding friction causes the slider (3) to move backward by a displacement d2, and d2 is less than d1. The step displacement of the slider (3) in one driving cycle is Δd = d1 - d2. S5: Under the excitation of a continuous triangular wave voltage signal, steps S3 and S4 are executed cyclically to drive the slider (3) to make continuous linear motion in the positive direction, and the moving speed of the slider (3) is adjusted by changing the frequency of the triangular wave voltage signal. When the slider (3) needs to move in the opposite direction, a triangular wave voltage signal is applied to the second piezoelectric stack (12), and the first piezoelectric stack (11) is not excited.

9. The working method according to claim 7, characterized in that: The inchworm's movement pattern includes the following steps: S1: Adjust the micrometer (16) of the preload mechanism so that the first drive leg (81) and the second drive leg (82) apply preload Fn to the slider (3); S2: Apply trapezoidal voltage signals V1 and V2 with a phase difference to the first piezoelectric stack (11) and the second piezoelectric stack (12), respectively. V1 represents the driving voltage of the first piezoelectric stack (11) and V2 represents the driving voltage of the second piezoelectric stack (12). At the initial time t0, both voltages V1 and V2 are zero. The first piezoelectric stack (11) and the second piezoelectric stack (12) maintain their original lengths, and the slider (3) remains stationary. t0 to t4 are five consecutive times within one driving cycle. S3: During the period from t0 to t1, the voltage V1 rises, the voltage V2 remains zero, the first piezoelectric stack (11) elongates, the first driving leg (81) generates oblique motion and drives the slider (3) to move a displacement d1 in the positive direction under the action of static friction, and the second driving leg (82) remains stationary; S4: During the period from t1 to t2, the voltage V1 remains unchanged, the voltage V2 increases, the first piezoelectric stack (11) maintains a constant elongation, the first driving leg (81) remains stationary, the second piezoelectric stack (12) elongates, and the second driving leg (82) further presses the slider (3) on the basis of the existing pre-pressure contact, thereby clamping the slider (3); S5: During the period from t2 to t3, the voltage V1 decreases while the voltage V2 remains constant. The first piezoelectric stack (11) contracts, the first drive leg (81) returns to its initial position, and the second drive leg (82) maintains its clamping on the slider (3). The slider (3) does not retract. S6: During the period from t3 to t4, the voltage V1 remains zero, the voltage V2 decreases, the second piezoelectric stack (12) contracts, the second driving leg (82) returns to the initial position and drives the slider (3) to move a displacement d2 in the positive direction under the action of static friction; the step displacement Δd of the slider (3) in one driving cycle is d1+d2; S7: Repeat steps S3 to S6 to drive slider (3) to make continuous non-returning stepping motion in the positive direction; When the slider (3) needs to move in the opposite direction, the phase difference between voltage V1 and voltage V2 is changed so that it is opposite to the phase difference during forward movement.

10. The working method according to claim 7, characterized in that: The precise positioning mode includes the following steps: S1: Adjust the micrometer (16) of the preload mechanism so that the first drive leg (81) and the second drive leg (82) apply preload Fn to the slider (3); S2: Apply a voltage signal that increases monotonically and remains constant to the first piezoelectric stack (11), while the second piezoelectric stack (12) is not excited; at the initial time t0, the voltage is zero, the first piezoelectric stack (11) maintains its original length, and the slider (3) remains stationary; S3: During the period from t0 to t1, the driving voltage rises, the first piezoelectric stack (11) elongates, and after being transmitted and amplified by the symmetrical compliant mechanism (8), the first driving leg (81) produces an oblique motion. Under the action of static friction, the slider (3) is directly driven to move a small displacement d1 in the positive direction. After the voltage remains constant, the position of the slider (3) remains unchanged, realizing the precise positioning of the slider (3). When the slider (3) needs to be precisely positioned in the reverse direction, a voltage signal that increases monotonically and remains constant is applied to the second piezoelectric stack (12), and the first piezoelectric stack (11) is not excited.

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