A stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning

Abstract

This invention discloses a stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning, comprising a compliant unit, a pre-tensioning member, and a piezoelectric ceramic. The compliant unit has a slot containing a friction material. The piezoelectric ceramic is disposed on the compliant unit, and the piezoelectric ceramic and the compliant unit are connected via the pre-tensioning member. Pre-tensioning of the piezoelectric ceramic is achieved by adjusting the torque of the pre-tensioning member. The compliant unit can be designed as a first compliant unit, a second compliant unit, a third compliant unit, and a fourth compliant unit. The input and output stiffness performance can be altered by changing the physical characteristics of the first, second, third, and fourth compliant units to better adapt to different output environments.

Description

Technical Field

[0001] This invention relates to the field of precision positioning and its applications, and in particular to a stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning. Background Technology

[0002] For kinematic pairs composed of traditional mechanical structures, such as the rack-driven prismatic joints in gear and rack mechanisms and the revolute joints at the connection points of multi-link mechanisms, slide rails, sliders, and bearings are the main components of the kinematic pair. However, for precision positioning technology, these components have significant shortcomings: First, these mechanisms are composed of separate parts, and the machining and assembly accuracy of these parts has a huge impact on the accuracy of the final kinematic pair. Improving these accuracies requires significant costs. Second, due to the limitations of their own mechanical motion principles, these mechanisms are bulky and difficult to integrate. The driving parts of traditional kinematic pairs often use motors, cylinders, hydraulic cylinders, etc., but due to the limitations of the driving principles of these components, manufacturing driving components that are both small in size and high in precision faces significant cost and feasibility issues. In contrast, the compliant part of the stick-slip piezoelectric compliant unit adopts an integrated design, combining the kinematic pair into the compliant unit. It features high precision, zero backlash, simple structure, no friction and wear, no assembly required, large load capacity, and easy miniaturization. Furthermore, it can be integrally formed using machining methods such as wire cutting, overcoming the cost and size problems of kinematic pairs composed of traditional mechanical structures. The piezoelectric ceramic in the drive section of the stick-slip piezoelectric compliant unit utilizes the inverse piezoelectric effect to convert input electrical energy into mechanical force and mechanical displacement, achieving displacement output at the micron to nanometer level.

[0003] Among the existing piezoelectric compliant actuators, there are many design precedents for large stroke and high precision, but few designs compare stiffness adjustment using different compliant unit structures. Therefore, it is necessary to explore the influence of different structures on stiffness in order to analyze the impact on input stiffness and output stiffness.

[0004] Ren Zhisheng et al. disclosed a "compliant parallel four-bar linkage amplification mechanism piezoelectric stick-slip linear platform" in Chinese invention patent CN114567200A. The compliant unit disclosed therein consists of a linkage and a compliant circular arc hinge, realizing the change in force and displacement between the input of the piezoelectric ceramic driving device and the output of the driving foot. Not only is its structure simple, but the driving foot is also made of a material integrated with the compliant unit, which can cause significant wear due to friction, and even permanent damage to the mechanism. Summary of the Invention

[0005] To address at least one of the problems existing in the prior art, this invention provides a stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning. This structure can change the input stiffness and output stiffness performance by varying the physical characteristics of the first compliant unit, the second compliant unit, the third compliant unit, and the fourth compliant unit proposed in this invention, so as to better adapt to different output environments.

[0006] To achieve the objective of this invention, the present invention provides a stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning, comprising a compliant unit, a pre-tightening member, and a piezoelectric ceramic. The compliant unit is provided with a slot, and a friction material is disposed in the slot. The piezoelectric ceramic is disposed on the compliant unit, and the piezoelectric ceramic and the compliant unit are connected through the pre-tightening member, and the pre-tightening of the piezoelectric ceramic is achieved by adjusting the torque of the pre-tightening member.

[0007] By properly pre-tightening the piezoelectric ceramic in the compliant unit through the pre-tightening screw, the piezoelectric ceramic can be controlled by the voltage signal to achieve output performance with different characteristics. It has the advantages of simple structure, strong interchangeability and low cost.

[0008] The input voltage signal of the piezoelectric ceramic is a sawtooth wave. The elongation of the piezoelectric ceramic is positively correlated with the voltage. The voltage signal of the piezoelectric ceramic is a sawtooth wave input, which is converted into an output at the slot through the physical structure of the compliant unit. This causes the slot to drive the friction material to move slowly in a certain direction in the horizontal direction and then quickly retract. When the sawtooth wave signal is slowly increasing, static friction is generated between the friction material in the slot and the object in frictional contact. The friction material and the object in frictional contact move together along the elongation direction of the piezoelectric ceramic. When the sawtooth wave signal is rapidly decreasing, the slot drives the friction material to move rapidly. Due to the inertia of the object in frictional contact, there is a certain frictional contact between the friction material in the slot and the external object, which can move a certain distance parallel to the elongation direction of the piezoelectric ceramic. The friction material drives the object in frictional contact to retract a small displacement along the shortening direction of the piezoelectric ceramic. Through the periodic change of the sawtooth wave signal, linear motion output is achieved through the stick-slip motion principle.

[0009] Furthermore, the compliant unit is a first compliant unit, which includes a first fixed rigid part and a first rhomboid amplification mechanism, a first movable rigid part, a first rotary compliant hinge, a second movable rigid part, a parallel contact lever, and a lever-type amplification mechanism rotary hinge located on the first fixed rigid part. The slot provided on the first compliant unit is a first slot.

[0010] The first rhomboid amplification mechanism, the first movable rigid part, the first compliant rotary hinge, and the second movable rigid part are connected in sequence. The piezoelectric ceramic is disposed in the first rhomboid amplification mechanism and the elongation of the piezoelectric ceramic can cause the first rhomboid amplification mechanism to deform in order to store elastic energy. The second movable rigid part is connected to the first slot above by a parallel contact lever and to the first fixed rigid part below by a lever-type amplification mechanism rotary hinge.

[0011] The first compliant unit, through the cooperation of the first rhomboid amplification mechanism, the first rotary compliant hinge, the parallel contact lever, the lever-type amplification mechanism rotary hinge, and other structures, can flexibly amplify and reduce the output force and output displacement of the piezoelectric compliant actuator. The first compliant unit can independently design the output force, output speed, resolution, etc. of the stiffness optimization compliant drive mechanism used for piezoelectric stick-slip positioning by changing its internal geometric features.

[0012] Furthermore, the compliant unit is a second compliant unit, which includes a second fixed rigid part and a second rhomboid amplification mechanism, a third movable rigid part, a first flexible contact cantilever beam, a parallelogram pre-tensioning compliant beam, and a pre-tensioning force adjustment seat located on the second fixed rigid part. The slot provided on the second compliant unit is a second slot.

[0013] The second rhombic amplification mechanism, the third movable rigid part, the first flexible contact cantilever beam and the second slot are connected in sequence. The piezoelectric ceramic is set in the second rhombic amplification mechanism and the elongation of the piezoelectric ceramic can cause the second rhombic amplification mechanism to deform in order to store elastic energy.

[0014] The parallelogram pre-tightened compliant beam includes at least two support beams, one of which connects to the second slot and the second fixed rigid part, and the other support beam is provided with the pre-tightening force adjustment seat. A pre-tightening hole is provided on the second fixed rigid part at a position opposite to the pre-tightening force adjustment seat.

[0015] Furthermore, the input and output stiffness can be adjusted by changing the number of support beams connecting the second slot and the second fixed rigid part.

[0016] Furthermore, the compliant unit is a third compliant unit, which includes a third fixed rigid part and a third rhomboid amplification mechanism, a fourth movable rigid part, a second flexible contact guide beam, a fifth movable rigid part, a vertical pre-tensioned compliant beam, and a horizontal pre-tensioned compliant beam located on the third fixed rigid part. The slot provided on the third compliant unit is a third slot.

[0017] The third rhomboid amplification mechanism, the fourth movable rigid part, the second flexible contact guide beam, the fifth movable rigid part, and the third slot are connected in sequence. The piezoelectric ceramic is set in the third rhomboid amplification mechanism and the elongation of the piezoelectric ceramic can cause the third rhomboid amplification mechanism to deform in order to store elastic energy.

[0018] The vertical pre-tensioned compliant beam and the horizontal pre-tensioned compliant beam are perpendicular to each other and connected in series. The vertical pre-tensioned compliant beam is connected to both the fifth movable rigid part and the third fixed rigid part. The vertical pre-tensioned compliant beam is used to generate deformation displacement in the left-right direction of the third compliant unit, and the horizontal pre-tensioned compliant beam is used to generate deformation displacement in the up-down direction of the third compliant unit.

[0019] Furthermore, the input stiffness can be increased or decreased by changing the span, width, and number of parallel beams of the vertical prestressed compliant beam.

[0020] Furthermore, the output stiffness can be increased or decreased by changing the span, width, and number of parallel beams of the horizontal prestressed compliant beam.

[0021] Furthermore, the compliant unit is a fourth compliant unit, which includes a fourth fixed rigid part and a fourth rhomboid amplification mechanism, a sixth movable rigid part, a third flexible contact guide beam, a fourth slot, and a "Z"-shaped pre-tightening compliant beam located on the fourth fixed rigid part. The slot provided on the fourth compliant unit is the fourth slot.

[0022] The fourth rhomboid amplification mechanism, the sixth movable rigid part, the third flexible contact guide beam, the fourth slot, and the "Z"-shaped pre-tightening compliant beam are connected in sequence, and the end of the "Z"-shaped pre-tightening compliant beam is connected to the fourth fixed rigid part. The piezoelectric ceramic is set in the fourth rhomboid amplification mechanism, and the elongation of the piezoelectric ceramic can cause the fourth rhomboid amplification mechanism to deform in order to store elastic energy. The beam direction in the "Z"-shaped pre-tightening compliant beam is at a certain angle to the input force direction of the piezoelectric ceramic and the pressure direction of the friction material on the fourth slot.

[0023] Furthermore, the input stiffness and output stiffness can be adjusted by changing the angle between the beam direction in the "Z"-shaped pre-tightened compliant beam and the input force direction of the piezoelectric ceramic and the pressure direction of the friction material in the fourth slot.

[0024] The first compliant unit, the second compliant unit, the third compliant unit, and the fourth compliant unit are designed with similar functions to avoid the piezoelectric ceramic actuator being subjected to shear force.

[0025] The various configurations of the compliant unit have rigid parts to ensure the rigidity of the matrix and provide rigid support for other flexible parts.

[0026] The various configurations of the compliant unit are designed with preload screw mounting holes on the side. The preload of the piezoelectric ceramic is adjusted by adjusting the torque of the preload screw to change the magnitude of the input force.

[0027] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0028] (1) The compliant unit proposed in this invention can be designed as a first compliant unit, a second compliant unit, a third compliant unit, and a fourth compliant unit configuration. The four configurations can have the same installation size. By replacing these four compliant unit structures, the same design of the stick-slip positioning platform can be driven. Different driving effects can be achieved by installing different compliant units under the same installation method and installation space.

[0029] (2) The first compliant unit, the second compliant unit, the third compliant unit, and the fourth compliant unit proposed in this invention have different stiffness characteristics. By comparing the driving characteristics of these four compliant unit structures, the influence of compliant unit structures with different stiffness characteristics on stick-slip motion can be analyzed.

[0030] (3) The compliant unit structure proposed in this invention uses a first slot, a second slot, a third slot or a fourth slot with similar structure and the same function to drive the friction material, and can generate stick-slip motion through sawtooth wave drive. The friction is consumed on the friction material rather than on the compliant unit integral material. By selecting the friction material, the service life can be improved, and the worn friction material can be replaced to avoid directly replacing the entire compliant unit after wear, thus reducing costs. Attached Figure Description

[0031] Figure 1 This is a structural schematic diagram of a stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning provided in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of the first compliant unit in the stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning in an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the second compliant unit in the stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning in an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the third compliant unit in the stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the fourth compliant unit in the stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning in an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0037] The present invention proposes embodiments 1-4 of the overall structure of the stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning and four compliant unit structures with different physical characteristics. Other piezoelectric compliant actuators can also achieve corresponding functions through this configuration and the corresponding principle.

[0038] See Figure 1 The present invention proposes a stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning, comprising a pre-tightening component, a piezoelectric ceramic 2, and a compliant unit 3. The pre-tightening component is a screw, defined as a pre-tightening screw 1. The compliant unit 3 is provided with a slot in which friction material can be embedded. The side of the compliant unit 3 is provided with a threaded hole. The piezoelectric ceramic 2 is assembled into the threaded hole of the compliant unit 3 by the pre-tightening screw 1. The pre-tightening of the piezoelectric ceramic 2 is achieved by adjusting the torque of the pre-tightening screw 1.

[0039] By changing the internal geometric features of the compliant unit 3, the input stiffness and output stiffness can be altered. The compliant unit 3 can be designed as any one of the following structures: a first compliant unit, a second compliant unit, a third compliant unit, and a fourth compliant unit. The slots on the corresponding compliant units are defined as the first slot, the second slot 16, the third slot 24, and the fourth slot 31.

[0040] The stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning utilizes the stick-slip drive principle to achieve motion. The elongation of the piezoelectric ceramic 2 is positively correlated with the voltage. The voltage signal of the piezoelectric ceramic 2 is a sawtooth wave input, which is converted into a motion output at the first slot 6, the second slot 16, the third slot 24, or the fourth slot 31 through the physical structure of the compliant unit 3. This causes the first slot 6, the second slot 16, the third slot 24, or the fourth slot 31 to drive the friction material to move slowly in a certain direction in the horizontal direction and then quickly retract. When the sawtooth wave signal is slowly increasing, there is a certain frictional contact between the friction material in the first slot 6 and the external friction material, and the material can move a certain distance parallel to the elongation direction of the piezoelectric ceramic 2. Static friction is generated between objects (such as guide rails), and the friction material and the object in frictional contact move together along the elongation direction of the piezoelectric ceramic 2. When the sawtooth wave signal is rapidly decreasing, the first slot 6, the second slot 16, the third slot 24, or the fourth slot 31 drives the friction material to move rapidly. Due to the inertia of the object in frictional contact, relative motion and a certain amount of dynamic friction are generated between the friction material in the first slot 6, the second slot 16, the third slot 24, or the fourth slot 31 and the object in frictional contact. The friction material drives the object in frictional contact to move backward along the shortening direction of the piezoelectric ceramic 2 by a displacement smaller than the forward motion. Through the periodic change of the sawtooth wave signal, the linear motion output is achieved through the stick-slip motion principle.

[0041] The final output part of this drive mechanism is a slot. By embedding friction materials with different properties within the slot, different output effects are achieved through stick-slip motion. For example, if zirconia ceramic friction material is embedded in the slot, the low coefficient of friction and high wear resistance of zirconia ceramic can provide a large range of preload while achieving output force at the slot, reducing adjustment difficulty. Alternatively, if bearing steel friction material is embedded in the slot and welded and fixed within it, the thermal stability of the output stick-slip motion can be improved, resulting in low thermal decay of the piezoelectric stick-slip positioning based on the compliant unit 3, reducing the thermal attenuation of the friction material caused by long-term frictional heating.

[0042] Example 1

[0043] See Figure 2 The compliant unit 3 can be configured as the first compliant unit through the design of its physical characteristics.

[0044] The first compliant unit includes a first fixed rigid part 12, a first rhomboid amplification mechanism 4, a first movable rigid part 5, a first rotary compliant hinge 11, a second movable rigid part 8, a parallel contact lever 7, and a lever-type amplification mechanism rotary hinge 10. The rigid parts ensure the rigidity of the base. The first rhomboid amplification mechanism 4, the first rotary compliant hinge 11, the parallel contact lever 7, and the lever-type amplification mechanism rotary hinge 10 flexibly amplify and reduce the output force and displacement of the piezoelectric ceramic 2. The first movable rigid part 5 and the second movable rigid part 8 change the direction of force and displacement transmission.

[0045] The first fixed rigid part 12 serves as the base of the compliant unit 3, and is considered a rigid body due to its minimal deformation. A first rhomboid amplification mechanism 4, symmetrically positioned vertically, is located on the left side of the first fixed rigid part 12. This mechanism 4 is connected to the first movable rigid part 5. The piezoelectric ceramic 2 is assembled within the symmetrically positioned rhomboid amplification mechanism 4, between the movable rigid part 5 and the first fixed rigid part 12. The left end of the piezoelectric ceramic 2 abuts against the first fixed rigid part 12, and the right end abuts against the left end of the movable rigid part 5. The elongation of the piezoelectric ceramic 2 causes deformation of the first rhomboid amplification mechanism 4, thereby storing elastic energy. The presence of the first rhomboid amplification mechanism 4 prevents the piezoelectric ceramic 2 from being subjected to shear forces. The first movable rigid part 5 is connected to the second movable rigid part 8 on its right side via a first rotary compliant hinge 11, allowing for a flexible connection between the two parts. The upper part of the second movable rigid part 8 is connected to the first slot 6 via a parallel contact lever 7 to optimize the vertical rigidity of the first slot 6. Friction material is provided inside the first slot 6. The lower part of the second movable rigid part 8 is connected to the first fixed rigid part 12 via a lever-type amplification mechanism rotating hinge 10. The lever-type amplification mechanism rotating hinge 10 generates relative rotational motion, thereby achieving amplified output at the first slot 6.

[0046] The stick-slip driving method is as follows: the voltage signal of the piezoelectric ceramic 2 is a sawtooth wave input. The sawtooth wave signal causes the first slot 6 to drive the friction material to move slowly in a certain direction in the horizontal direction and then quickly retract. The physical structure of the first compliant unit itself is converted into the output at the first slot 6. Stick-slip motion with constantly changing sliding friction and static friction is generated on the object in frictional contact parallel to the first slot 6, so as to realize the output of linear motion.

[0047] Example 2

[0048] See Figure 3The compliant unit 3 can be designed into the configuration of a second compliant unit by changing its physical characteristics. The driving method and preload adjustment method of the second compliant unit are the same as those of the first compliant unit. It has the same space for embedding the piezoelectric ceramic 2 located between the second fixed rigid part 19 and the third movable rigid part 14. The second compliant unit includes the second fixed rigid part 19, the second rhomboid amplification mechanism 13, the third movable rigid part 14, the first flexible contact cantilever beam 15, the parallelogram preload compliant beam 17, and the preload adjustment seat 18.

[0049] The output force and displacement of the piezoelectric ceramic 2 are flexibly amplified and reduced by the second rhomboid amplification mechanism 13, the first flexible contact cantilever beam 15, and the parallelogram pre-tightened compliant beam 17, and the direction of force and displacement transmission is changed by the third movable rigid part 14.

[0050] A second rhomboid amplification mechanism 13, symmetrically arranged vertically, is positioned on the left side of the second fixed rigid portion 19. This second rhomboid amplification mechanism 13 is connected to the third movable rigid portion 14. The piezoelectric ceramic 2 is located between the second fixed rigid portion 19 and the third movable rigid portion 14, within the second rhomboid amplification mechanism 13. The left side of the piezoelectric ceramic 2 abuts against the second fixed rigid portion 19, and the right side abuts against the left end of the third movable rigid portion 14. The design of the second rhomboid amplification mechanism 13 prevents the piezoelectric ceramic 2 from being subjected to shear force and allows it to store its elastic energy through elastic deformation. The design of the second fixed rigid portion 19 ensures the stiffness of the second compliant unit matrix.

[0051] The third movable rigid part 14 is connected to the second slot 16 via the first flexible contact cantilever beam 15. The second slot 16 is provided with friction material. In the space below the second slot 16 and facing the second fixed rigid part 19, an inclined parallelogram pre-tightening flexible beam 17 is provided. The parallelogram pre-tightening flexible beam 17 includes two parallel support beams. The right support beam of the parallelogram pre-tightening flexible beam 17 is connected to the second fixed rigid part 19, and the left support beam of the parallelogram pre-tightening flexible beam 17 is connected to the pre-tightening force adjustment seat 18.

[0052] The second compliant unit alters the output characteristics, such as input stiffness, output stiffness, and amplification ratio, at the second slot 16 through the cooperation of the second rhomboid amplification mechanism 13, the first flexible contact guide beam 15, and the parallelogram pre-tightening compliant beam 17. The first flexible contact guide beam 15 provides weak stiffness contact between the output and input, reducing the influence of input stiffness. The parallelogram pre-tightening compliant beam 17 partially compensates for the weakening of output stiffness through parallel rods, improving pre-tightening displacement. It is understandable that the method of the parallelogram pre-tightening compliant beam 17 is not limited to... Figure 3 The structure shown, with two supporting beams connected in parallel, without changing... Figure 3The input and output stiffness can be approximately proportionally changed by changing the number of the support beams on the right side of the parallelogram pre-tensioned flexible beam 17, that is, the support beams located on the right side of the support beam on the left side of the parallelogram pre-tensioned flexible beam 17 and parallel to the second slot 16 and the second fixed rigid part 19.

[0053] See Figure 3 The second compliant unit is designed with a preload adjustment seat 18 between the second fixed rigid part 19 and the left support beam of the parallelogram preload compliant beam 17. A screw is screwed in from bottom to top through a threaded hole (i.e., preload hole) opened on the second rigid part 19 and located directly below the preload adjustment seat 18. The screw passes through the threaded hole and abuts against the preload adjustment seat 18. By tightening the screw, the preload adjustment seat 18 moves axially toward the screw, thereby causing flexible deformation of the parallelogram preload compliant beam 17 and the first flexible contact guide beam 15. The vertical displacement at the second slot 16 can be indirectly adjusted through the screw.

[0054] Example 3

[0055] See Figure 4 The compliant unit 3 can be designed into the configuration of a third compliant unit by changing its physical characteristics. The driving method and the method of adjusting the preload of the third compliant unit are the same as those of the first compliant unit.

[0056] The third compliant unit includes a third fixed rigid part 27, a third rhomboid amplification mechanism 20, a fourth movable rigid part 21, a second flexible contact guide beam 22, a fifth movable rigid part 23, a vertical pre-tensioned compliant beam 25, and a horizontal pre-tensioned compliant beam 26. The third rhomboid amplification mechanism 20, the second flexible contact guide beam 22, the vertical pre-tensioned compliant beam 25, and the horizontal pre-tensioned compliant beam 26 flexibly amplify and reduce the output force and output displacement of the piezoelectric ceramic 2, while the fourth movable rigid part 21 and the fifth movable rigid part 23 change the direction of force and displacement transmission.

[0057] See Figure 4A symmetrical third rhomboid amplification mechanism 20 is provided on the left side of the third fixed rigid part 27 of the third compliant unit. The third rhomboid amplification mechanism 20 is connected to the fourth movable rigid part 21. The piezoelectric ceramic 2 is located between the third fixed rigid part 27 and the fourth movable rigid part 21 and is located within the third rhomboid amplification mechanism 20. The piezoelectric ceramic 2 abuts against the third fixed rigid part 27 on its left side and against the left end of the fourth movable rigid part 21 on its right side. The design of the third rhomboid amplification mechanism 20 avoids the piezoelectric ceramic 2 from being subjected to shear force and can store its elastic energy through elastic deformation, thereby improving the input stiffness. The fourth movable rigid part 21 is connected to the fifth movable rigid part 23 through the second flexible contact guide beam 22. The fifth movable rigid part 23 is rigidly connected to the third slot 24, on which friction material is embedded. The second flexible contact guide beam 22 flexibly transmits power between the input and output parts, improving the vertical output stiffness of the third compliant unit and making the amplification ratio of the third compliant unit close to 1.

[0058] In this embodiment, the third rhomboid amplification mechanism 20 prevents the piezoelectric ceramic 2 from being subjected to shear force. The third fixed rigid part 27 ensures the rigidity of the third compliant unit matrix.

[0059] See Figure 4 The vertical pre-tensioning compliant beam 25 and the horizontal pre-tensioning compliant beam 26 are perpendicular to each other and connected in series. The leftmost part of the vertical pre-tensioning compliant beam 25 is connected to the fifth movable rigid part 23, and the rightmost part of the vertical pre-tensioning compliant beam 25 is connected to the third fixed rigid part 27. The vertical pre-tensioning compliant beam 25 generates deformation displacement in the left-right direction of the third compliant unit, affecting the input stiffness; the horizontal pre-tensioning compliant beam 26 generates deformation displacement in the up-down direction of the third compliant unit, affecting the output stiffness and providing pre-tension displacement. The input stiffness can be increased or decreased by changing the span, width, and number of parallel beams of the vertical pre-tensioning compliant beam 25. The horizontal pre-tensioning compliant beam 26 is perpendicular to the pressure direction of the friction material on the third slot 24. The output stiffness can be increased or decreased by changing the span, width, and number of parallel beams of the horizontal pre-tensioning compliant beam 26.

[0060] Example 4

[0061] See Figure 5 The compliant unit 3 can be designed into the configuration of the fourth compliant unit by changing its physical characteristics. The driving method and the method of adjusting the preload of the fourth compliant unit are the same as those of the first compliant unit.

[0062] The fourth compliant unit includes a fourth fixed rigid part 33, a fourth rhomboid amplification mechanism 28, a sixth movable rigid part 29, a third flexible contact guide beam 30, a fourth slot 31, and a "Z"-shaped pre-tightening compliant beam 32. The fourth rhomboid amplification mechanism 28, the sixth movable rigid part 29, the third flexible contact guide beam 30, and the "Z"-shaped pre-tightening compliant beam 32 flexibly amplify and reduce the output force and displacement of the piezoelectric ceramic 2, while the sixth movable rigid part 29 changes the direction of force and displacement transmission.

[0063] See Figure 5 A fourth rhomboid amplification mechanism 28, symmetrically arranged vertically, is positioned on the left side of the fourth fixed rigid part 33 of the fourth compliant unit. This fourth rhomboid amplification mechanism 28 is connected to the sixth movable rigid part 29. The piezoelectric ceramic 2 is located between the fourth fixed rigid part 33 and the sixth movable rigid part 29, within the fourth rhomboid amplification mechanism 28. The piezoelectric ceramic 2 abuts against the fourth fixed rigid part 33 on its left side and against the left end of the sixth movable rigid part 29 on its right side. The fourth rhomboid amplification mechanism 28 prevents the piezoelectric ceramic 2 from being subjected to shear force and allows it to store its elastic energy through elastic deformation, thus improving input stiffness. Between the right side of the sixth movable rigid part 29 and the right side of the fourth fixed rigid part 33, a third flexible contact guide beam 30, a fourth slot 31, and a "Z"-shaped pre-tightening compliant beam 32 are connected in series. Friction material is embedded in the fourth slot 2.

[0064] In this embodiment, the third flexible contact guide beam 30 mainly affects the input stiffness of the portion between the sixth movable rigid part 29 and the fourth slot 31, and also indirectly affects the amplification ratio. The beam direction in the "Z"-shaped pre-tightening compliant beam 32 is at a certain angle to the input force direction of the piezoelectric ceramic 2 and the pressure direction of the friction material on the fourth slot 31. By changing these angles, the purpose of adjusting the input stiffness and output stiffness in a certain proportion can be achieved by changing the beam span and width inside the "Z"-shaped pre-tightening compliant beam 32 at a certain angle.

[0065] See Figure 5 The fourth rhomboid amplification mechanism 23 is designed to prevent the piezoelectric ceramic 2 from being subjected to shear forces. The fourth rigid part 26 is designed to ensure the rigidity of the fourth compliant unit matrix.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning, characterized in that, The device includes a compliant unit, a pre-tightening element, and a piezoelectric ceramic. The compliant unit has a slot, and a friction material is disposed in the slot. The piezoelectric ceramic is disposed on the compliant unit, and the piezoelectric ceramic and the compliant unit are connected by the pre-tightening element. The pre-tightening of the piezoelectric ceramic is achieved by adjusting the torque of the pre-tightening element. The compliant unit is a first compliant unit, a second compliant unit, a third compliant unit, or a fourth compliant unit. The first compliant unit includes a first fixed rigid part and a first rhomboid amplification mechanism, a first movable rigid part, a first rotary compliant hinge, a second movable rigid part, a parallel contact lever, and a lever-type amplification mechanism rotary hinge located on the first fixed rigid part. The slot provided on the first compliant unit is the first slot. The first rhomboid amplification mechanism, the first movable rigid part, the first rotary compliant hinge, and the second movable rigid part are connected in sequence. The piezoelectric ceramic is disposed in the first rhomboid amplification mechanism and the elongation of the piezoelectric ceramic can cause the first rhomboid amplification mechanism to deform in order to store elastic energy. The second movable rigid part is connected to the first slot above by a parallel contact lever and to the first fixed rigid part below by a lever-type amplification mechanism rotary hinge. The second compliant unit includes a second fixed rigid part and a second rhomboid amplification mechanism located on the second fixed rigid part, a third movable rigid part, a first flexible contact cantilever beam, a parallelogram pre-tensioned compliant beam, and a pre-tension force adjustment seat. The slot provided on the second compliant unit is the second slot. The second rhombic amplification mechanism, the third movable rigid part, the first flexible contact cantilever beam and the second slot are connected in sequence. The piezoelectric ceramic is set in the second rhombic amplification mechanism and the elongation of the piezoelectric ceramic can cause the second rhombic amplification mechanism to deform in order to store elastic energy. The parallelogram pre-tightened compliant beam includes at least two support beams, one of which connects to the second slot and the second fixed rigid part, and the other support beam is provided with the pre-tightening force adjustment seat. A pre-tightening hole is provided on the second fixed rigid part at a position opposite to the pre-tightening force adjustment seat. The third compliant unit includes a third fixed rigid part and a third rhomboid amplification mechanism located on the third fixed rigid part, a fourth movable rigid part, a second flexible contact guide beam, a fifth movable rigid part, a vertical pre-tensioned compliant beam, and a horizontal pre-tensioned compliant beam. The slot provided on the third compliant unit is the third slot. The third rhomboid amplification mechanism, the fourth movable rigid part, the second flexible contact guide beam, the fifth movable rigid part, and the third slot are connected in sequence. The piezoelectric ceramic is set in the third rhomboid amplification mechanism and the elongation of the piezoelectric ceramic can cause the third rhomboid amplification mechanism to deform in order to store elastic energy. The vertical pre-tensioned compliant beam and the horizontal pre-tensioned compliant beam are perpendicular to each other and connected in series. The vertical pre-tensioned compliant beam is connected to both the fifth movable rigid part and the third fixed rigid part. The vertical pre-tensioned compliant beam is used to generate deformation displacement in the left-right direction of the third compliant unit, and the horizontal pre-tensioned compliant beam is used to generate deformation displacement in the up-down direction of the third compliant unit. The fourth compliant unit includes a fourth fixed rigid part and a fourth rhomboid amplification mechanism located on the fourth fixed rigid part, a sixth movable rigid part, a third flexible contact guide beam, a fourth slot, and a "Z"-shaped pre-tensioned compliant beam. The slot provided on the fourth compliant unit is the fourth slot. The fourth rhomboid amplification mechanism, the sixth movable rigid part, the third flexible contact guide beam, the fourth slot, and the "Z"-shaped pre-tightening compliant beam are connected in sequence, and the end of the "Z"-shaped pre-tightening compliant beam is connected to the fourth fixed rigid part. The piezoelectric ceramic is set in the fourth rhomboid amplification mechanism, and the elongation of the piezoelectric ceramic can cause the fourth rhomboid amplification mechanism to deform in order to store elastic energy. The beam direction in the "Z"-shaped pre-tightening compliant beam is at a certain angle to the input force direction of the piezoelectric ceramic and the pressure direction of the friction material on the fourth slot.

2. The stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning according to claim 1, characterized in that, The elongation of piezoelectric ceramics is positively correlated with voltage. During operation, the voltage signal of the piezoelectric ceramic is a sawtooth wave input, which is converted into an output at the slot through the physical structure of the compliant unit. This causes the slot to drive the friction material to move slowly in a certain direction in the horizontal direction and then quickly retract. When the sawtooth wave signal is slowly increasing, static friction is generated between the friction material in the slot and the object in parallel friction contact with it. The friction material and the object in friction contact move together along the elongation direction of the piezoelectric ceramic. When the sawtooth wave signal is rapidly decreasing, the slot drives the friction material to move rapidly. The friction material drives the object in friction contact to retract along the shortening direction of the piezoelectric ceramic by a displacement smaller than the forward movement. Through the periodic change of the sawtooth wave signal, linear motion output is achieved through the stick-slip motion principle.

3. The stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning according to claim 1, characterized in that, In the second compliant unit, the input and output stiffness are adjusted by changing the number of support beams connecting the second slot and the second fixed rigid part.

4. The stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning according to claim 1, characterized in that, In the third compliant element, the input stiffness is increased or decreased by changing the span, width, and number of parallel beams of the vertical prestressed compliant beam.

5. The stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning according to claim 1, characterized in that, In the third compliant unit, the output stiffness is increased or decreased by changing the span, width, and number of parallel beams of the horizontal prestressed compliant beam.

6. The stiffness-optimized compliant drive mechanism for piezoelectric stick-slip positioning according to claim 1, characterized in that, In the fourth compliant unit, the input stiffness and output stiffness are adjusted by changing the angle between the beam direction in the "Z"-shaped pre-tightened compliant beam and the input force direction of the piezoelectric ceramic and the pressure direction of the friction material in the fourth slot.

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