A planar motion device

Abstract

The application discloses a planar motion device, belonging to the technical field of precise positioning and driving control, which comprises a stator unit, a mover unit and a driving unit. The driving unit comprises a driving frame and a motion foot, the motion foot comprises a foot tip and three piezoelectric elements connected between the foot tip and the driving frame, the three piezoelectric elements drive the foot tip to move in parallel along two mutually orthogonal extension directions, and the piezoelectric element perpendicular to a preset plane drives the foot tip to abut against or separate from the stator unit. The application adopts the parallel driving of the full-axial stacked piezoelectric elements, the single-step stroke reaches dozens of microns, and the demand of large-stroke fast positioning is met. Meanwhile, the tangential stacked sliding contact mode is abandoned, the processing requirement of the contact surface is reduced, the cost is reduced, and the long-term reliability is improved. The displacement output of the three orthogonal piezoelectric elements is essentially decoupled, the motion coupling interference is avoided, and the multi-degree-of-freedom trajectory control precision is improved.

Description

Technical Field

[0001] This invention relates to the field of precision positioning and drive control equipment technology, and in particular to a planar motion device. Background Technology

[0002] In cutting-edge fields such as semiconductor precision manufacturing, ultra-precision machining, micro-nano detection, and high-end optical instruments, planar motion devices, as core positioning and transmission mechanisms, need to achieve nanometer-level resolution over a large stroke range. Piezoelectric-driven micro-displacement mechanisms, due to their high resolution, lack of electromagnetic interference, and fast response speed, have become the mainstream power source for such equipment.

[0003] However, existing planar motion devices based on piezoelectric elements mostly adopt a structure of axial and tangential stacks in series. This structure has the following inherent shortcomings: First, due to the limitations of piezoelectric material properties and manufacturing processes, tangential stacks are difficult to manufacture in long dimensions, resulting in a single-step motion stroke of only a few micrometers, which cannot meet the requirements for large-stroke rapid positioning; Second, in the series structure, the tangential stacks are in direct contact with the guide rail surface, which places extremely stringent requirements on the flatness, roughness, and other processing quality of the guide rail surface, significantly increasing the difficulty of manufacturing and assembly; Third, during long-term operation, the contact surfaces suffer severe friction and wear, and coupled with the coupling effect between multiple stacks, the long-term reliability and stability of the equipment are significantly reduced. Summary of the Invention The purpose of this invention is to provide a planar motion device to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0004] The technical solution adopted to solve the above-mentioned technical problems is as follows: This invention provides a planar motion device, comprising: Stator unit; The moving subunit is configured to be able to perform planar motion relative to the stator unit in a preset plane; At least one drive unit, each drive unit including a drive frame and at least one moving foot, the drive frame being fixedly mounted on the moving subunit, the moving foot including a toe and three piezoelectric elements connected between the toe and the drive frame, the three piezoelectric elements driving the toe to move relative to the drive frame in parallel along their respective extension and retraction directions; the extension and retraction directions of the three piezoelectric elements are mutually orthogonal, wherein the extension and retraction directions of two piezoelectric elements are parallel to the preset plane and perpendicular to each other, the extension and retraction direction of the other piezoelectric element is perpendicular to the preset plane, and the piezoelectric element perpendicular to the preset plane is configured to drive the toe to move in a direction perpendicular to the preset plane, thereby causing the toe to abut or separate from the stator unit.

[0005] The beneficial effects of the planar motion device of the present invention are: This invention effectively overcomes the technical bottlenecks of existing series structures by employing a structural innovation of parallel drive using axially stacked piezoelectric elements. On the one hand, the axial stack can be made long enough and avoids displacement loss in series transmission, increasing the single-step stroke from several micrometers to tens of micrometers, greatly meeting the needs of large-stroke rapid positioning of motion platforms. On the other hand, this invention abandons the transmission method of sliding contact between tangential stack and guide rail surface, and instead adopts static contact between the foot and stator unit, significantly reducing the dependence on the processing accuracy such as flatness and roughness of stator contact surface, thereby reducing manufacturing costs and improving the maintainability and long-term operational reliability of the equipment in industrial environments. At the same time, the three orthogonal piezoelectric elements drive the foot in parallel, and their displacement output is essentially decoupled in the three orthogonal directions, avoiding the complex motion coupling interference in traditional series structures, and greatly improving the accuracy and simplicity of multi-degree-of-freedom trajectory control.

[0006] As a further improvement to the above technical solution, each piezoelectric element is provided with a flexible mechanism at at least one end, and each piezoelectric element is connected between the drive frame and the toe through the flexible mechanism. The flexible mechanism is configured to be rigid along the extension and retraction direction of the corresponding piezoelectric element to transmit displacement, and can produce compliant deformation in other directions.

[0007] As a further improvement to the above technical solution, each piezoelectric element is provided with a flexible mechanism at both ends, and the piezoelectric element is connected to the drive frame and the toe respectively through two flexible mechanisms.

[0008] As a further improvement to the above technical solution, the flexible mechanism includes a first connector, a first flexible hinge, a second connector, a second flexible hinge, and a third connector arranged sequentially along the extension and retraction direction corresponding to the piezoelectric element; the first flexible hinge and the second flexible hinge are respectively perpendicular to the extension and retraction direction corresponding to the piezoelectric element, and an angle is formed between the first flexible hinge and the second flexible hinge; the first connector is hinged to the second connector through the first flexible hinge, and the third connector is hinged to the second connector through the second flexible hinge; the first connector is connected to the piezoelectric element, and the third connector is connected to the drive frame or the toe.

[0009] As a further improvement to the above technical solution, the sports foot also includes an elastomer connected between the toe and the drive frame, and the elastomer is configured to provide the toe with a restoring elastic force and a preload force.

[0010] As a further improvement to the above technical solution, the elastic body is disposed on one side of the toe that is opposite to one of the piezoelectric elements parallel to the preset plane and extends along the extension and retraction direction of the piezoelectric element. One end of the elastic body is fixed to the toe and the other end is fixed to the drive frame. The elastic body is configured to provide the toe with a reset elastic force and a preload force along the extension and retraction direction of the piezoelectric element.

[0011] As a further improvement to the above technical solution, two moving feet are provided, and the two moving feet are arranged at intervals along a direction parallel to the preset plane.

[0012] As a further improvement to the above technical solution, an elastomer is connected between the two toes, and the elastomer is configured to provide the two toes with a restoring elastic force and a preload force along the interval direction.

[0013] As a further improvement to the above technical solution, the drive unit is provided with at least three, and the at least three drive units are distributed between the stator unit and the moving unit along a plane parallel to the preset plane, and the directions of the two moving feet on two adjacent drive units are arranged at an angle.

[0014] Furthermore, the present invention also proposes a planar motion control method applicable to the aforementioned planar motion device, the control method comprising: The driving voltages of the two piezoelectric elements in the two moving feet that are perpendicular to the preset plane are energized in opposite phases, so that the two toes alternately contact or separate from the stator unit; With one of the toes abutting against the stator unit, the two piezoelectric elements corresponding to the toes and parallel to the preset plane are energized, driving the drive frame to move the moving subunit relative to the stator unit in a preset direction and a preset amplitude. In another state where the toe is separated from the stator unit, the two piezoelectric elements corresponding to the toe and parallel to the preset plane are energized to drive the toe to reset.

[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram of the planar motion device provided by the present invention, specifically embodiment one. Figure 2This is an exploded view of Embodiment 1 of the planar motion device provided by the present invention; Figure 3 This is a schematic diagram of an embodiment of the flexible mechanism provided by the present invention; Figure 4 This is a schematic diagram of the planar motion device provided by the present invention, specifically embodiment two. Figure 5 This is an exploded view of Embodiment 2 of the planar motion device provided by the present invention; Figure 6 This is a flowchart of the planar motion control method provided by the present invention; Icon labels: Stator unit 100; Moving unit 200; Drive unit 300; drive frame 310; side plate 311; top plate 312; First foot 400; First toe 401; First piezoelectric element 411; Second piezoelectric element 412; Third piezoelectric element 413; First elastic body 431; First support base 432; Second foot 500; Second toe 501; Fourth piezoelectric element 511; Fifth piezoelectric element 512; Sixth piezoelectric element 513; Second elastic body 531; Second support base 532; Flexible mechanism 600; first connector 610; first flexible hinge 620; second connector 630; second flexible hinge 640; third connector 650; Third elastomer 700. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0018] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0019] In the description of this invention, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features or their sequential relationship.

[0020] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of the present invention, not all embodiments.

[0022] Reference Figures 1-5 The planar motion device of the present invention is implemented in the following embodiment. For ease of description, the X-axis, Y-axis and Z-axis are defined as mutually orthogonal, wherein the X-axis and Y-axis together define a preset plane (i.e., the XY plane) and the Z-axis is perpendicular to the preset plane.

[0023] Example 1: like Figures 1 to 3 As shown, a planar motion device in this embodiment mainly includes a stator unit 100, a mover unit 200, and a drive unit 300.

[0024] like Figure 1 As shown, the stator unit 100 is a frame structure that extends on a predetermined XY plane. It typically serves as the stationary base of the entire device, providing a supporting foundation for the planar movement of the mover unit 200. The mover unit 200 is positioned above the stator unit 100 along the Z-axis. It is also a frame structure and is configured to perform planar movement relative to the stator unit 100 within a predetermined plane, which is another XY plane parallel to the extension plane of the stator unit 100.

[0025] It should be noted that, in use, the upper part of the moving unit 200 is used to support external workpieces or loads. The combined weight of the moving unit 200 and the load it supports provides a natural preload force along the Z-axis (i.e., vertical direction) between the drive unit 300 and the stator unit 100. This gravity preload mechanism has the following significant advantages: Compared to traditional solutions that require additional auxiliary mechanisms such as magnetic preload or spring preload to achieve contact preload between the foot and the stator unit, this invention does not require any additional preload components. It can rely on its own weight to ensure that the contact friction between the foot and the stator unit meets the requirements of stepper drive. This simplifies the overall structure of the device, reduces the number of parts and assembly processes, and lowers manufacturing costs. On the other hand, it reduces potential failure points introduced by fatigue, aging, or loosening of auxiliary preload mechanisms, effectively avoiding the adverse effects of preload fluctuations on motion accuracy and stability, thereby significantly improving the consistency and reliability of the equipment under long-term continuous operation.

[0026] like Figure 1As shown, the drive unit 300 includes a drive frame 310 and a moving foot, with the drive frame 310 fixedly mounted below the moving subunit 200. In this embodiment, as... Figure 2 As shown, the drive frame 310 has a closed frame structure, specifically including four side plates 311 and a top plate 312 connecting the moving sub-unit 200, to form an internal space to accommodate the moving foot and related components. It is understood that in other embodiments, the drive frame 310 and the moving sub-unit 200 may adopt an integral molding structure to further reduce assembly steps and improve overall rigidity.

[0027] The locating foot is highly integrated within the drive frame 310. Regarding the number of locating feet, in some other embodiments, only one locating foot may be provided to achieve a single-leg hopping stepping movement mode; such as... Figure 2 As shown, in this embodiment, to improve the smoothness of the movement and driving efficiency, two moving feet are preferably provided, namely the first moving foot 400 and the second moving foot 500. The parallel configuration of the two feet enables high-speed, continuous alternating walking. While one foot abuts against the stator unit 100 and pushes the actuator unit 200 forward, the other foot lifts up and returns to its original position, thus ensuring uninterrupted movement and significantly improving the efficiency and continuity of large-stroke motion. Of course, in other embodiments, three or more moving feet can be provided and divided into two groups to work alternately, further improving load capacity and movement stability.

[0028] In this embodiment, as Figure 2 As shown, the first moving foot 400 and the second moving foot 500 are arranged at intervals along a direction parallel to a preset plane, specifically at intervals along the X-axis. In some other embodiments, they may also be arranged at intervals along the Y-axis, etc.

[0029] The specific structure of each foot is described in detail below. Each foot includes a toe and three piezoelectric elements connected between the toe and the drive frame 310. The three piezoelectric elements drive the corresponding toe to move relative to the drive frame 310 in parallel along their respective extension and retraction directions. The extension and retraction directions of the three piezoelectric elements are mutually orthogonal, with two piezoelectric elements having extension and retraction directions parallel to a preset plane and perpendicular to each other, and the extension and retraction direction of the third piezoelectric element perpendicular to the preset plane. This configuration of three piezoelectric elements driving the same toe in parallel with mutually orthogonal extension and retraction directions is the core foundation for achieving large stroke, high precision, and approximately decoupled motion in this invention. The principle is that each of the three piezoelectric elements independently outputs displacement along orthogonal directions. Since the displacement directions are orthogonal, the displacement components in each direction are independent and do not interfere with each other kinematically. Therefore, it is possible to achieve accurate synthesis and control of displacement in any direction in three-dimensional space without complex decoupling algorithms, fundamentally avoiding motion coupling errors caused by the intersection of displacement transmission paths in traditional series structures.

[0030] Specifically, such as Figure 2 As shown, in the first moving foot 400, the first piezoelectric element 411 extends along the Z-axis and connects the first foot tip 401 to the drive frame 310. When energized, it generates displacement along the Z-axis and is configured to drive the first foot tip 401 to move along the Z-axis, thereby causing the first foot tip 401 to abut (contact and generate pressure) or separate (disengage) from the stator unit 100. The second piezoelectric element 412 extends along the Y-axis and connects the first foot tip 401 to the drive frame 310. When energized, it generates displacement along the Y-axis. The third piezoelectric element 413 extends along the X-axis and connects the first foot tip 401 to the drive frame 310. When energized, it generates displacement along the X-axis. The second piezoelectric element 412 and the third piezoelectric element 413 together drive the first foot tip 401 to position and step in the XY plane.

[0031] like Figure 2 As shown, in the second moving foot 500, the fourth piezoelectric element 511 extends along the Z-axis and connects the second foot tip 501 to the drive frame 310. When energized, it generates displacement along the Z-axis and is configured to drive the second foot tip 501 to move along the Z-axis, thereby causing the second foot tip 501 to abut or separate from the stator unit 100. The fifth piezoelectric element 512 extends along the Y-axis and connects the second foot tip 501 to the drive frame 310. When energized, it generates displacement along the Y-axis. The sixth piezoelectric element 513 extends along the X-axis and connects the second foot tip 501 to the drive frame 310. When energized, it generates displacement along the X-axis. Similarly, the fifth piezoelectric element 512 and the sixth piezoelectric element 513 jointly drive the second foot tip 501 to position and step in the XY plane.

[0032] Through the above structure, the first piezoelectric element 411 and the fourth piezoelectric element 511 independently control the lifting and lowering of the first toe 401 and the second toe 501 in the Z-axis direction, so as to achieve alternating contact and separation with the stator unit 100. When the first toe 401 contacts the stator unit 100, the second piezoelectric element 412 and the third piezoelectric element 413 are energized to generate telescopic displacement. Due to the static friction between the first toe 401 and the stator unit 100, it cannot slide relative to the stator unit 100. This displacement drives the drive frame 310 (along with the moving sub-unit 200) to move forward, thereby achieving a large stride forward. At the same time, the fourth piezoelectric element 511 in the second moving foot 500 drives the second toe 501 to lift and separate, and the fifth piezoelectric element 512 and the sixth piezoelectric element 513 are energized to drive the second toe 501 to return to its original position, preparing for the next step. This alternation achieves continuous walking.

[0033] Furthermore, such as Figure 2 As shown, to achieve the aforementioned parallel driving effect of primary rigidity and lateral flexibility, each piezoelectric element has a flexible mechanism 600 at at least one end, and each piezoelectric element is connected between the drive frame 310 and the toe via the flexible mechanism 600. The flexible mechanism 600 is configured to be rigid along the extension and retraction direction of the corresponding piezoelectric element to efficiently transmit displacement and thrust, while it can produce compliant deformation (including yaw and slight rotation) in other directions (i.e., in the plane perpendicular to the extension and retraction direction). The setting of this flexible mechanism 600 plays a crucial role: since the three piezoelectric elements are connected in parallel on the same toe in a spatially orthogonal orientation, when one of the piezoelectric elements actively extends or shortens along its extension and retraction direction, the toe will inevitably generate displacement along that direction. At this time, the other two piezoelectric elements, as follower branches, need to passively adapt their effective length to the displacement change of the toe; otherwise, geometric interference will occur, causing the brittle piezoelectric ceramic to be subjected to destructive shear force and bending moment and damaged. By incorporating anisotropic stiffness flexible mechanisms 600 at the ends of each piezoelectric element, these mechanisms maintain high stiffness in their principal direction (the extension and contraction direction of the piezoelectric element) to ensure displacement transmission efficiency, while exhibiting low stiffness in the lateral and rotational directions. This allows for automatic compliant deformation to release geometric constraints, effectively protecting the piezoelectric elements from lateral force damage. While the lateral compliant deformation of the flexible mechanism 600 inevitably introduces a small second-order parasitic displacement in the follower branch, the output stroke of the piezoelectric element is only on the order of tens of micrometers, far smaller than its physical size. Therefore, the impact of this parasitic displacement on the actual toe trajectory is extremely small and negligible. Thus, this device approximately eliminates parallel interference stress through the compliant deformation of the flexible mechanism 600, while suppressing motion coupling to a very low range. It achieves approximately orthogonal decoupling output of three-dimensional displacement within a single moving foot, significantly improving motion accuracy.

[0034] In this embodiment, the flexible mechanism 600 is specifically an orthogonal flexible hinge structure. Taking the flexible mechanism 600 installed at one end of the third piezoelectric element 413 (with the extension direction along the X-axis) as an example, as follows... Figure 3As shown, the flexible mechanism 600 includes a first connector 610, a first flexible hinge 620, a second connector 630, a second flexible hinge 640, and a third connector 650 arranged sequentially along the X-axis. The first flexible hinge 620 extends along the Z-axis, and the second flexible hinge 640 extends along the Y-axis. That is, the first flexible hinge 620 and the second flexible hinge 640 are perpendicular to the extension / retraction direction (X-axis) of their respective piezoelectric elements, and form a 90° angle between them (along the Z-axis and Y-axis, respectively). The first connector 610 is hinged to the second connector 630 via the first flexible hinge 620, and the third connector 650 is hinged to the second connector 630 via the second flexible hinge 640. The first connector 610 is connected to the third piezoelectric element 413, and the third connector 650 is connected to the drive frame 310 or the first foot 401. More specifically, the second connector 630 has V-groove structures formed on both ends of its X-axis face. The V-groove structure on one end face of the second connector 630 extends through the second connector 630 along the Y-axis, and the V-groove structure on the other end face extends through the second connector 630 along the Z-axis. The end of the first connector 610 near the second connector 630 has a V-shaped platform structure that matches the V-groove structure. The first flexible hinge 620 is located at the tip of the V-shaped platform structure, and arc-shaped structures are respectively provided on both sides along the Z-axis, forming cylindrical cavities. There is sufficient gap between the first connector 610 and the second connector 630, that is, there is space required for the first connector 610 to rotate relative to the second connector 630 around the Z-axis. Similarly, the end of the third connector 650 near the second connector 630 is formed with a V-shaped platform structure that matches the V-groove structure. The second flexible hinge 640 is located at the tip of the V-shaped platform structure, and arc-shaped structures are respectively provided on both sides along the Y-axis, forming cylindrical cavities. There is sufficient gap between the second connector 630 and the third connector 650 to meet the space required for the third connector 650 to rotate relative to the second connector 630 around the Y-axis.

[0035] Understandably, the first flexible hinge 620 and the second flexible hinge 640 enable the entire flexible mechanism 600 to form a segmented rotational structure. Both flexible hinges are located at the tips of the corresponding V-shaped platform structures, where the cross-sectional thickness is small and stress is concentrated, thereby significantly reducing the offset of the rotation center and improving the motion accuracy and fatigue life of the flexible mechanism 600. Meanwhile, the first connecting member 610, the first flexible hinge 620, the second connecting member 630, the second flexible hinge 640, and the third connecting member 650 are preferably integrally formed using wire cutting, resulting in a compact overall structure with no assembly gaps, avoiding the backlash error introduced by gaps in traditional hinged structures.

[0036] In terms of mechanical properties, the flexible mechanism 600 exhibits significant anisotropy: in its principal direction (i.e., the axial displacement output direction of the connected piezoelectric element), due to the continuous material and large cross-section, it exhibits solid rigidity and extremely high tensile and compressive stiffness, ensuring that the large stroke displacement and thrust generated by the piezoelectric element can be transmitted to the toe with almost no loss; while in other non-driving directions, especially in the rotational directions around the Y-axis and Z-axis, due to the extremely low bending stiffness of the thin-walled hinge structure, the mechanism is allowed to produce slight yaw rotation in these two directions. This "principal rigidity and lateral flexibility" characteristic means that when the first piezoelectric element 411 is energized and generates active displacement along the Z-axis, the second piezoelectric element 412 and the third piezoelectric element 413 connected in parallel with it act as follower branches, and the flexible mechanism 600 at both ends of them will undergo corresponding yaw deformation to adapt to the Z-direction displacement of the first toe 401, effectively releasing the spatial over-constraint caused by the parallel connection of multiple branches. Although this bias introduces a minute lateral parasitic displacement in terms of geometry, it is a second-order infinitesimal quantity and its impact on motion accuracy is negligible. Therefore, this device achieves high-precision approximate decoupled output of three-dimensional displacement without requiring complex active compensation algorithms.

[0037] The second moving foot 500 has the same parallel structure, flexible mechanism 600 configuration and decoupling principle as the first moving foot 400, which will not be described in detail here.

[0038] Preferably, such as Figure 2 As shown, in order to further improve the protection effect of the flexible mechanism 600 on the piezoelectric element and the symmetry of displacement transmission, the flexible mechanism 600 is provided at both ends of each piezoelectric element. That is, the piezoelectric element is connected to the drive frame 310 and the foot tip through two flexible mechanisms 600 respectively, so that the piezoelectric element is flexibly constrained and released at both ends in the extension and retraction direction, further reducing the risk of the piezoelectric element bearing lateral force.

[0039] In some alternative embodiments, the flexible mechanism 600 may also employ a spherical flexible hinge structure. Specifically, the spherical flexible hinge includes a spherical connector and a fixed connector. The fixed connector has a hemispherical groove, and the spherical connector has a spherical structure and a rod-like structure. The spherical structure is connected to the end of the rod-like structure and is rotatably mounted within the hemispherical groove. During linkage, the spherical structure can achieve micro-rotation in any direction within the hemispherical groove, which also serves to release geometric constraints and protect the piezoelectric element from lateral forces. Compared to orthogonal flexible hinges, spherical flexible hinges offer higher degrees of freedom, but are slightly inferior in terms of rotational accuracy and fatigue life. The choice between these options depends on the specific operating conditions required in practical applications.

[0040] Furthermore, to improve the motion stability and displacement recovery reliability of the foot under high-frequency alternating stepping conditions, this device incorporates multiple elastic bodies, such as... Figure 2 As shown, each foot also includes a first elastic body 431, which is connected between the toe and the drive frame 310 and is configured to provide the toe with a restoring elastic force and a preload force.

[0041] Specifically, let's take the first movement, foot 400, as an example for explanation, such as... Figure 2 As shown, the first elastic body 431 is disposed on the side of the first toe 401 facing away from the second piezoelectric element 412 (i.e., the other side opposite to the second piezoelectric element 412 along the Y-axis). The first elastic body 431 extends along the Y-axis, with one end fixedly connected to the first toe 401 and the other end fixedly connected to the first support base 432, which is fixedly mounted on the drive frame 310. The first elastic body 431 can elastically deform along the Y-axis, and its functions include at least two aspects: First, it provides axial preload to the second piezoelectric element 412, ensuring that the piezoelectric element is in a stable pressurized working state in the initial state, eliminating stroke backflow caused by gaps or installation errors, and improving the response sensitivity and displacement output consistency of the piezoelectric element; Second, after the second piezoelectric element 412 is de-energized or retracted, the first elastic body 431 uses its own elastic restoring force to pull the first toe 401 back to the initial equilibrium position along the Y-axis, thereby realizing the rapid and accurate reset of the toe and preparing for the next stepping action.

[0042] The technical principle is as follows: the first elastic body 431 and the second piezoelectric element 412 form a push-pull arrangement along the Y-axis. When the second piezoelectric element 412 actively extends to push the first toe 401 to move along the positive Y-axis, the first elastic body 431 is stretched and stores elastic potential energy. When the second piezoelectric element 412 is de-energized and contracts, the first elastic body 431 releases the stored elastic potential energy, pulling the toe back to its initial position. This collaborative mechanism of active drive and passive recovery eliminates the need for additional reverse drive piezoelectric elements for the reciprocating motion of the first toe 401 in the Y-axis direction, thereby reducing the number of piezoelectric elements and control channels, and simplifying the control strategy. Simultaneously, the first elastic body 431 also acts as a damper during movement, effectively suppressing toe oscillations and inertial impacts caused by high-frequency alternating steps, further improving the stability and positioning accuracy of the movement, making it particularly suitable for continuous stepping motion scenarios with large strokes and high speeds. It is worth noting that the elastic coefficient and preload of the first elastic body 431 need to be matched and designed according to the output force of the second piezoelectric element 412 and the load mass of the toe, so as to ensure the best balance between rapid recovery and avoiding overdamping.

[0043] Furthermore, it is understood that in some alternative embodiments, the first elastic body 431 is not limited to being disposed on the side opposite to the second piezoelectric element 412. It can also be configured according to the degree of freedom of movement of the toe in the plane, and disposed on the opposite side of the X-axis direction corresponding to the third piezoelectric element 413, serving as a pre-tensioning and reset element for the third piezoelectric element 413. Even more specifically, when the toe needs to achieve bidirectional active drive in the plane, a combination of piezoelectric elements and elastic bodies can be disposed on both sides of the toe in the X-axis direction and / or on both sides of the toe in the Y-axis direction, thereby achieving precise drive and reset control of the toe in all directions within a preset plane. In other embodiments, the first elastic body 431 can also be in the form of a coil spring, leaf spring, gas spring, or magnetic spring, as long as it can provide elastic restoring force and pre-tensioning force in the desired direction.

[0044] Similarly, as Figure 2 As shown, in the second moving foot 500, the second elastic body 531 is disposed on the side of the second foot tip 501 facing away from the fifth piezoelectric element 512 in the same manner, extending along the Y-axis. One end of the elastic body 531 is fixedly connected to the second foot tip 501, and the other end is fixedly connected to the second support base 532. The elastic body 531 is mounted on the drive frame 310 by the second support base 532, providing preload force for the fifth piezoelectric element 512 and providing Y-axis reset force for the second foot tip 501. Its working principle is completely consistent with that of the first elastic body 431, and will not be described in detail here.

[0045] Furthermore, such as Figure 2 As shown, a third elastomer 700 is connected between the two toes. The third elastomer 700 is configured to provide the two toes with a restoring elastic force and a preload force along their spacing direction (i.e., the X-axis).

[0046] Specifically, such as Figure 2 As shown, the first foot tip 401 and the second foot tip 501 are arranged at intervals along the X-axis. A third elastic body 700 extends along the X-axis and connects between the first foot tip 401 and the second foot tip 501, and the third elastic body 700 is disposed on the side where the first foot tip 401 and the second foot tip 501 face each other. The third elastic body 700 can elastically deform along the X-axis, and its function is to provide axial preload for the third piezoelectric element 413 and the sixth piezoelectric element 513, and at the same time provide a restoring force for the displacement of the first foot tip 401 and the second foot tip 501 in the X-axis.

[0047] Its working principle is as follows: In the bipedal alternating stepping mode, when the first foot tip 401 abuts against the stator unit 100 and the third piezoelectric element 413 is energized and extends to push the actuator unit 200 to step along the X-axis, the second foot tip 501 is in a suspended state. At this time, the third elastic body 700 is stretched (or compressed) and stores elastic potential energy. When the first foot tip 401 is lifted, the second foot tip 501 falls and begins the next stepping action, the third elastic body 700 releases the stored elastic potential energy, assisting the first foot tip 401 to reset to the initial position along the X-axis, preparing for the next stepping cycle. Through the above-mentioned coordinated action, the third elastic body 700 plays a key role in force transmission and displacement coordination during the bipedal alternating stepping process. It ensures the continuity of displacement of the two feet during the alternation process and avoids the cumulative stepping error caused by insufficient restoring force of the piezoelectric element itself, thereby significantly improving the positioning accuracy and motion consistency of the device in long-term continuous stepping motion.

[0048] The third elastic body 700, together with the aforementioned first elastic body 431 and second elastic body 531, constitutes a complete elastic preload and reset network. Specifically, the first elastic body 431 provides a Y-axis reset force for the first moving foot 400, the second elastic body 531 provides a Y-axis reset force for the second moving foot 500, and the third elastic body 700 provides an X-axis reset force for both moving feet. The synergistic effect of these three components ensures that each toe has reliable reset capability in both horizontal degrees of freedom (X and Y directions) within the preset plane. This allows the toe to quickly and accurately return to its initial equilibrium position after the piezoelectric element is de-energized or contracted, effectively eliminating positioning drift caused by multiple step accumulations.

[0049] It is worth noting that the elastic coefficient of the third elastic body 700 needs to be designed to match the output force of the third piezoelectric element 413 and the sixth piezoelectric element 513, the distance between the two moving feet, and the operating frequency. This ensures that sufficient restoring force is provided during alternating stepping without generating excessive resistance to the active forward movement of the toes. In other embodiments, the third elastic body 700 can be in the form of a helical spring, leaf spring, gas spring, or magnetic spring. Multiple elastic bodies can also be connected in parallel or series, as long as they can provide elastic restoring force along the distance between the two toes. In embodiments with more than two moving feet, similar elastic bodies can be placed between the toes of adjacent moving feet to form a multi-foot cooperative restoring network.

[0050] Example 2: like Figure 4 and Figure 5As shown, the main difference between this embodiment and Embodiment 1 lies in the number and distribution of the drive units 300. In this embodiment, there are at least three drive units 300 (three are shown in the figure). The at least three drive units 300 are distributed between the stator unit 100 and the moving sub-unit 200 along a direction parallel to the preset plane. That is, the drive frame 310 of each drive unit 300 is fixedly installed below the moving sub-unit 200, and the drive units 300 are distributed in a dispersed manner within the preset plane.

[0051] Furthermore, the two moving feet on two adjacent drive units 300 are arranged at an angle to each other. Figure 4 Taking the three-drive unit layout shown as an example, the three drive units 300 are arranged in a triangle within a preset plane. The two moving legs of the first drive unit 300 are spaced apart along the X-axis; the two moving legs of the second drive unit 300 are spaced apart at an angle of approximately 120° to the X-axis; and the two moving legs of the third drive unit 300 are spaced apart at an angle of approximately 240° to the X-axis. In other words, the stepping directions of each of the three drive units 300 are at certain angles to each other within the preset plane, forming a spatially symmetrical drive layout. Of course, the angles between the drive units 300 are not limited to a uniform 120° distribution. In practical applications, the orientation and angle of each drive unit 300 can be flexibly adjusted according to the required degrees of freedom and control precision, for example, set to 90°, 60°, or other non-uniform angles.

[0052] The technical principle is as follows: a single drive unit 300 achieves two-dimensional step displacement in a preset plane. When multiple drive units 300 are arranged at different azimuth angles between the moving subunit 200 and the stator unit 100, the linear step displacement output by each drive unit 300 forms displacement vectors in different directions within the preset plane. By independently and coordinately controlling the amplitude, phase, and timing of the drive voltage of all piezoelectric elements in each drive unit 300 through a host computer or centralized controller, these displacement vectors can be vector synthesized: when the displacement vectors output by each drive unit 300 are in the same direction, the moving subunit 200 achieves pure translational motion within the preset plane; when the displacement vectors output by each drive unit 300 are in different directions, the synthesized result generates a rotational torque around the Z-axis within the preset plane, thereby realizing the rotational motion of the moving subunit 200 around the Z-axis.

[0053] This invention also proposes a planar motion control method applicable to any of the aforementioned planar motion devices, particularly planar motion devices with two moving feet (a first moving foot 400 and a second moving foot 500). The control method is used to achieve large-stroke, high-precision continuous stepping motion of the moving subunit 200 relative to the stator unit 100 within a preset plane. The planar motion control method of this invention will be described in detail below with reference to the bipedal alternating walking structure of Embodiment 1.

[0054] like Figure 6 As shown, the planar motion control method specifically includes the following steps: Step S100: Control the driving voltages of the two piezoelectric elements perpendicular to the preset plane in the two moving feet to be energized in opposite phases, so that the two toes alternately contact or separate from the stator unit.

[0055] This step controls the first piezoelectric element 411 of the first moving foot 400 and the fourth piezoelectric element 511 of the second moving foot 500 to be energized respectively. The first piezoelectric element 411 and the fourth piezoelectric element 511 are both piezoelectric elements whose extension and contraction directions are perpendicular to the preset plane (i.e., along the Z-axis). Their function is to drive the corresponding toe to move along the Z-axis so that the toe abuts (contacts and generates positive pressure, anchored by static friction) or separates (lifts up and breaks contact) from the stator unit 100.

[0056] More specifically, when driving voltages are applied to the first piezoelectric element 411 and the fourth piezoelectric element 511, their driving voltages are out of phase. That is, when the first piezoelectric element 411 is extended by a positive voltage, the first foot 401 moves downward along the Z-axis and abuts against the stator unit 100; at the same time, the fourth piezoelectric element 511 is shortened by a reverse voltage (or is in a de-energized contraction state), and the second foot 501 moves upward along the Z-axis and separates from the stator unit 100. Conversely, when the first piezoelectric element 411 is de-energized and contracts, the first foot 401 lifts up and separates, while the fourth piezoelectric element 511 is energized and extends, and the second foot 501 falls down to abut against the stator unit 100. Through this phase-opposite voltage control, the first foot 401 and the second foot 501 can alternately abut or separate from the stator unit 100, laying the foundation for subsequent alternating stepping motion.

[0057] The opposite phase means that in a complete step cycle, the voltage changes of the first piezoelectric element 411 and the fourth piezoelectric element 511 are opposite. When the first piezoelectric element 411 is at a high level (elongation), the fourth piezoelectric element 511 is at a low level (contraction); when the first piezoelectric element 411 is at a low level (contraction), the fourth piezoelectric element 511 is at a high level (elongation). The phase difference of the voltage waveform is 180°.

[0058] It is understandable that the frequency and timing of the alternating contact and separation of the two toes are determined by the waveform frequency and duty cycle of the driving voltage. In actual control, the magnitude of the contact force between the toes and the stator unit 100 can be adjusted by regulating the amplitude of the driving voltage, thereby regulating the maximum value of the static friction force; the stepping speed can be adjusted by regulating the frequency of the driving voltage; and the contact time ratio of each toe within one stepping cycle can be adjusted by regulating the duty cycle of the driving voltage to adapt to different load conditions and motion requirements.

[0059] By driving the two Z-axis piezoelectric elements with opposite phases, the two feet alternately lift and drop, so that at least one foot of the moving unit 200 always keeps in contact with the stator unit 100 during the movement, thereby ensuring the continuity and stability of the movement process and avoiding the interruption or loss of control of the movement due to both feet being suspended in the air at the same time.

[0060] Step S200: When one of the foot tips is in contact with the stator unit, control the two piezoelectric elements corresponding to the foot tip and parallel to the preset plane to be energized, drive the drive frame to move the moving sub-unit relative to the stator unit in a preset direction and preset amplitude.

[0061] Specifically, the example is taken with the first foot tip 401 abutting against the stator unit 100 and the second foot tip 501 separating from the stator unit 100. In this state, the first foot tip 401 is in close contact with the stator unit 100 by the natural preload generated by the gravity of the moving sub-unit 200 and the load, and the static friction between the two is sufficient to resist the driving reaction force.

[0062] At this time, the second piezoelectric element 412 (along the Y-axis) and the third piezoelectric element 413 (along the X-axis), corresponding to the first foot tip 401, are energized according to preset voltage amplitude and polarity. The second piezoelectric element 412 and the third piezoelectric element 413 generate telescopic displacement along the Y-axis and X-axis, respectively. Due to the static friction between the first foot tip 401 and the stator unit 100, it cannot slide relative to the stator unit 100. The displacement generated by this axial stacking cannot be released by the sliding of the first foot tip 401, and thus reacts on the drive frame 310. That is, the first foot tip 401 serves as a fixed anchor point, and the drive frame 310, together with the moving subunit 200 fixed thereon, moves relative to the stator unit 100 in a direction opposite to the displacement direction of the second piezoelectric element 412 and the third piezoelectric element 413.

[0063] More specifically, a desired forward direction vector for the moving sub-unit 200 within a preset plane is defined, which can be decomposed into X-axis and Y-axis components. The required voltage amplitude and polarity (extension or contraction) for the third piezoelectric element 413 are determined based on the X-axis component; the required voltage amplitude and polarity (extension or contraction) for the second piezoelectric element 412 are determined based on the Y-axis component. The second and third piezoelectric elements 412 and 413 are simultaneously energized, each outputting a corresponding extension or contraction displacement. The vector combination of these two orthogonal displacements constitutes the actual forward direction and amplitude of the moving sub-unit 200 within the preset plane. By controlling the magnitude and polarity of the voltage applied to the second and third piezoelectric elements 412 and 413, the direction and step size of each step of the moving sub-unit 200 can be precisely controlled.

[0064] In a complete bipedal stepping cycle, step S200 is executed once for each foot in an alternating contact state. Specifically, when the first toe 401 contacts the ground, the second piezoelectric element 412 and the third piezoelectric element 413 drive the moving subunit 200 forward one step; when the second toe 501 contacts the ground, the fifth piezoelectric element 512 and the sixth piezoelectric element 513 similarly drive the moving subunit 200 forward one step. The alternating contact of the two toes and each driving a forward movement constitutes a complete stepping cycle, with the moving subunit 200 advancing two steps.

[0065] The axial stacking of piezoelectric elements can be made long enough that the extension and retraction displacement of a single energization can reach tens of micrometers, far exceeding the several micrometers of the traditional tangential stacking. This significantly increases the step distance during each abutment drive, thereby greatly reducing the number of steps required to complete the same total stroke and greatly improving the large-stroke movement efficiency of the motion platform. At the same time, since the X-axis and Y-axis drives are independent of each other, high-precision, approximately decoupled control of movement in any direction within the plane is achieved.

[0066] Step S300: In the state where the other foot is separated from the stator unit, control the two piezoelectric elements corresponding to the foot and parallel to the preset plane to be energized, and drive the foot to reset.

[0067] Specifically, taking the state where the first foot tip 401 is in contact with the stator unit 100 and the second foot tip 501 is separated from the stator unit 100 as an example. While the first foot tip 401 is in contact with the driving sub-unit 200 and moving forward, the second foot tip 501 is in a separated and suspended state. At this time, the fourth piezoelectric element 511 is kept energized to keep the second foot tip 501 in a raised state.

[0068] Simultaneously, the fifth piezoelectric element 512 (along the Y-axis) and the sixth piezoelectric element 513 (along the X-axis) corresponding to the second foot tip 501 are energized. The driving voltage amplitude and polarity of the fifth piezoelectric element 512 and the sixth piezoelectric element 513 are opposite to or set according to the reset path of the voltage values ​​of the second piezoelectric element 412 and the third piezoelectric element 413 when driving forward in step S200. Since the second foot tip 501 is in a separated state from the stator unit 100, there is no static friction constraint between them. The extension and retraction displacement generated by the energization of the fifth piezoelectric element 512 and the sixth piezoelectric element 513 will directly drive the second foot tip 501 to reset relative to the drive frame 310 along the X-axis and Y-axis in the preset plane, that is, to move one step in the opposite direction to the forward direction of the moving sub-unit 200 in step S200, so that the second foot tip 501 returns to the initial position relative to the moving sub-unit 200.

[0069] In a complete bipedal walking cycle, the resetting actions of the two toes are completed within the half-cycle when they are in the separated state. That is, when the first toe 401 contacts and moves forward, the second toe 501 separates and resets; when the second toe 501 contacts and moves forward, the first toe 401 separates and resets. Through this parallel control strategy of "simultaneous contact and forward movement and separation and reset," there is no time loss of waiting for reset during bipedal walking, thus achieving high-speed continuous motion.

[0070] In the aforementioned control process, the elastic restoring forces of the first elastic body 431, the second elastic body 531, and the third elastic body 700 can synergistically assist in toe reset. Taking the Y-axis reset of the second toe 501 as an example: when the fifth piezoelectric element 512 is de-energized or contracts, the second elastic body 531 relies on its own elastic restoring force to pull the second toe 501 back to its initial equilibrium position along the Y-axis, thereby reducing the need for reverse energization of the piezoelectric element, reducing energy consumption and control complexity. Similarly, the third elastic body 700 assists in the X-axis reset coordination between the two toes.

[0071] By controlling the toes to reset in the suspended state, it is ensured that each moving foot is in its initial position relative to the drive frame 310 when it makes contact again. This guarantees consistent step distance and accurate direction, avoiding cumulative step distance errors caused by toe position deviation. Simultaneously, the reset action is performed in parallel with the forward movement, without consuming additional movement time, ensuring the device's high-speed continuous stepping capability.

[0072] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A planar motion device, characterized in that, include: Stator unit; The moving subunit is configured to be able to perform planar motion relative to the stator unit in a preset plane; At least one drive unit, each drive unit including a drive frame and at least one moving foot, the drive frame being fixedly mounted on the moving subunit, the moving foot including a toe and three piezoelectric elements connected between the toe and the drive frame, the three piezoelectric elements driving the toe to move relative to the drive frame in parallel along their respective extension and retraction directions; the extension and retraction directions of the three piezoelectric elements are mutually orthogonal, wherein the extension and retraction directions of two piezoelectric elements are parallel to the preset plane and perpendicular to each other, the extension and retraction direction of the other piezoelectric element is perpendicular to the preset plane, and the piezoelectric element perpendicular to the preset plane is configured to drive the toe to move in a direction perpendicular to the preset plane, thereby causing the toe to abut or separate from the stator unit.

2. The planar motion device according to claim 1, characterized in that: At least one end of each of the piezoelectric elements is provided with a flexible mechanism, and each of the piezoelectric elements is connected between the drive frame and the toe via the flexible mechanism. The flexible mechanism is configured to be rigid in the extension and retraction direction of the corresponding piezoelectric element to transmit displacement, and to produce compliant deformation in other directions.

3. The planar motion device according to claim 2, characterized in that: Each piezoelectric element has a flexible mechanism at both ends, and the piezoelectric element is connected to the drive frame and the toe respectively through two of the flexible mechanisms.

4. The planar motion device according to claim 2, characterized in that: The flexible mechanism includes a first connector, a first flexible hinge, a second connector, a second flexible hinge, and a third connector arranged sequentially along the extension / retraction direction corresponding to the piezoelectric element. The first flexible hinge and the second flexible hinge are perpendicular to the extension / retraction direction corresponding to the piezoelectric element, and an angle is formed between the first flexible hinge and the second flexible hinge. The first connector is hinged to the second connector via the first flexible hinge, and the third connector is hinged to the second connector via the second flexible hinge. The first connector is connected to the piezoelectric element, and the third connector is connected to the drive frame or the toe.

5. The planar motion device according to claim 1, characterized in that: The foot also includes an elastomer connected between the toe and the drive frame, the elastomer being configured to provide a restoring elastic force and a preload force to the toe.

6. The planar motion device according to claim 5, characterized in that: The elastic body is disposed on one side of the toe, which is opposite to one of the piezoelectric elements and parallel to the preset plane, and extends along the extension and retraction direction of the piezoelectric element. One end of the elastic body is fixed to the toe, and the other end is fixed to the drive frame. The elastic body is configured to provide the toe with a reset elastic force and a preload force along the extension and retraction direction of the piezoelectric element.

7. The planar motion device according to any one of claims 1 to 6, characterized in that: The device has two legs, which are arranged at intervals along a direction parallel to the preset plane.

8. The planar motion device according to claim 7, characterized in that: An elastomer is connected between the two toes, the elastomer being configured to provide the two toes with a restoring elastic force and a preload force in the spaced direction.

9. The planar motion device according to claim 7, characterized in that: The drive unit is provided with at least three units, which are distributed between the stator unit and the mover unit along a plane parallel to the preset plane, and the two moving feet on two adjacent drive units are arranged at an angle to each other.

10. A planar motion control method, characterized in that, The control method, applicable to any one of claims 7 to 9, comprises: The driving voltages of the two piezoelectric elements in the two moving feet that are perpendicular to the preset plane are energized in opposite phases, so that the two toes alternately contact or separate from the stator unit; With one of the toes abutting against the stator unit, the two piezoelectric elements corresponding to the toes and parallel to the preset plane are energized, driving the drive frame to move the moving subunit relative to the stator unit in a preset direction and a preset amplitude. In another state where the toe is separated from the stator unit, the two piezoelectric elements corresponding to the toe and parallel to the preset plane are energized to drive the toe to reset.

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