A flexible manipulator with variable clamping force and constant force kneading and its usage method

Abstract

This invention discloses a flexible manipulator with variable clamping force and constant force rubbing motion, and its usage method, belonging to the field of micromanipulator technology. It includes a first driving mechanism, a second driving mechanism, a variable stiffness clamping mechanism, and a constant force rubbing motion mechanism. The variable stiffness clamping mechanism is constructed by connecting a guide beam assembly, a variable stiffness beam assembly, and a decoupling beam assembly in series, with a first clamping end at its end. The stiffness of the first clamping end can be adjusted by embedding a shape memory alloy. The constant force rubbing motion mechanism consists of a positive stiffness structure and a negative stiffness structure, with a second clamping end opposite to the first clamping end at its end. The decoupling beam assembly connects the two mechanisms, achieving structural decoupling. This invention solves the problems of non-adjustable clamping stiffness, slow constant force response, and mutual interference between functions in existing flexible manipulators, achieving adaptive gripping and stable rubbing motion of micro-scale objects.

Description

Technical Field

[0001] This invention relates to the field of micromanipulator technology, specifically to a flexible manipulator with variable clamping force and constant force rubbing, and its method of use. Background Technology

[0002] In the fields of micromanipulation, microassembly, and precision gripping, micromanipulators need to simultaneously possess high compliance, stable force output, and the ability to manipulate fragile targets with minimal damage. Traditional rigid grippers, due to limitations in transmission clearance, friction, and force control precision, struggle to meet the requirements of micro-scale operations. Therefore, flexible gripping systems are gradually becoming an important development direction for micromanipulation fixtures. However, existing flexible gripping systems still have certain problems in practical use:

[0003] First, existing flexible clamping systems cannot adjust their stiffness once manufactured and assembled. Furthermore, their output clamping force is significantly affected by the inherent stiffness of their structure. When dealing with objects of different sizes, stiffnesses, or extremely fragile objects, the fixed stiffness severely limits clamping force adjustment. It cannot coordinate with the drive source to adjust the clamping force, lacks the ability to adaptively adjust based on the object being manipulated, and has poor versatility. Second, in precision operations, to improve target positioning or separation capabilities, a constant force mechanism is typically used to output additional auxiliary force to push, rub, or lift the object. However, existing constant force mechanisms often require large drive displacements to trigger their nonlinear segments in order to achieve a stable constant force output range. This makes it difficult to provide constant force immediately within the small displacement range of micro-operations. This results in discontinuous activation and slow response of the auxiliary force, failing to meet the demands for instantaneous and stable auxiliary force in precision operations.

[0004] When existing fixed-stiffness flexible clamping systems are simply combined with independent constant-force mechanisms, structural interference and mechanical coupling occur within the limited installation space. The forces and displacements generated by the clamping action disturb the output state of the constant-force mechanism, and conversely, the actions of the constant-force mechanism also affect the stability of the clamping. This functional coupling problem makes system control complex and makes it difficult to achieve high-precision independent control and coordinated operation of clamping and kneading actions. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a flexible manipulator with variable clamping force and constant force rubbing, and its usage method. By integrating a variable stiffness clamping mechanism and a constant force rubbing mechanism and decoupling the two, the invention solves the problems of non-adjustable structural stiffness and limited clamping force adjustment, slow constant force output response, and mutual interference during functional integration in the prior art. This enables adaptive safe gripping and stable and precise rubbing of micro-scale objects.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a flexible manipulator with variable clamping force and constant force rubbing is provided, comprising a first driving mechanism, a second driving mechanism, a variable stiffness clamping mechanism and a constant force rubbing mechanism, wherein the variable stiffness clamping mechanism is provided with a guide beam assembly, the output end of the first driving mechanism is mounted to the guide beam assembly, a variable stiffness beam assembly is mounted at the end of the guide beam assembly away from the first driving mechanism, a decoupling beam assembly is mounted at the end of the variable stiffness beam assembly away from the guide beam assembly, and a first clamping end is provided at one end of the variable stiffness beam assembly;

[0008] The constant force rubbing mechanism includes a positive stiffness structure and a negative stiffness structure. The output end of the second drive mechanism is installed with the negative stiffness structure, and the negative stiffness structure is installed with the positive stiffness structure. The end of the positive stiffness structure away from the negative stiffness structure is provided with a second clamping end. The second clamping end and the first clamping end are arranged relative to each other at a set distance.

[0009] The decoupling beam assembly is installed on the positive stiffness structure and the negative stiffness structure, respectively.

[0010] In some embodiments of the present invention, the guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly are arranged parallel to each other, and the geometric centers of the guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly are arranged collinearly to form a center line. The driving force output direction of the first driving mechanism is arranged along the center line and perpendicular to the guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly. The driving force output directions of the first driving mechanism and the second driving mechanism are perpendicular to each other.

[0011] In some embodiments of the present invention, the guide beam assembly is provided with a plurality of guide flexible straight beams, which are symmetrically arranged on both sides of the center line; the variable stiffness beam assembly is provided with a plurality of variable stiffness flexible straight beams, which are symmetrically arranged on both sides of the center line; the decoupling beam assembly is provided with a plurality of decoupling flexible straight beams, which are symmetrically arranged on both sides of the center line.

[0012] The axial lengths of the guiding flexible straight beam and the decoupling flexible straight beam are the same, and the axial lengths of the variable stiffness flexible straight beams are all greater than those of the guiding flexible straight beam and the decoupling flexible straight beam.

[0013] In some embodiments of the present invention, the middle part of the guiding flexible straight beam is provided with a guiding beam connecting block and is installed with the first driving mechanism, the middle part of the variable stiffness flexible straight beam is provided with a variable stiffness beam connecting block, and the middle part of the decoupled flexible straight beam is provided with a decoupled beam connecting block.

[0014] A first connecting beam assembly is provided between the guide beam connecting block and the variable stiffness beam connecting block, and a second connecting beam assembly is provided between the variable stiffness beam connecting block and the decoupling beam connecting block. The first connecting beam assembly extends along the driving force output direction of the first driving mechanism, and the second connecting beam assembly extends along the force transmission direction of the first connecting beam assembly.

[0015] In some embodiments of the present invention, the two ends of the guiding flexible straight beam are respectively provided with first connecting members, and the first connecting members are respectively fixedly connected to the variable stiffness flexible straight beams at both ends.

[0016] The two ends of the decoupled flexible straight beam are respectively provided with second connecting members. One end of the two second connecting members is fixedly connected to the two variable stiffness flexible straight beams respectively, and the other end of the two second connecting members is fixedly connected to the positive stiffness structure and the negative stiffness structure respectively.

[0017] In some embodiments of the present invention, the variable stiffness flexible straight beam includes an intermediate layer plate, with clamping plates on both sides of the intermediate layer plate, and shape memory alloy wires disposed in the clamping plates. The shape memory alloy wires are connected to an external power supply device via wires. The intermediate layer plate is made of thermoplastic plastic, and the clamping plates are made of silicone polymer material.

[0018] In some embodiments of the present invention, a third connecting member is provided between the positive stiffness structure and the negative stiffness structure. The negative stiffness structure includes a negative stiffness connecting block, which is connected to the output end of the second drive mechanism. Two inclined flexible straight beams are symmetrically arranged on both sides of the negative stiffness connecting block to form a bistable inclined beam assembly. One end of the bistable inclined beam assembly is fixedly connected to the decoupling beam assembly, and the other end of the bistable inclined beam assembly is fixedly connected to the third connecting member.

[0019] A negative stiffness hexagonal component is installed at the end of the negative stiffness connecting block away from the second drive mechanism.

[0020] In some embodiments of the present invention, the positive stiffness structure includes a positive stiffness hexagonal component, the positive stiffness hexagonal component is disposed on the outer periphery of the negative stiffness hexagonal component, one end of the positive stiffness hexagonal component is fixedly connected to the negative stiffness connecting block, the other end of the positive stiffness hexagonal component is provided with a positive stiffness connecting block, one end of the positive stiffness connecting block is fixedly connected to the negative stiffness hexagonal component, and the other end of the positive stiffness connecting block is fixedly connected to a second clamping end;

[0021] The positive stiffness connecting block has two parallel flexible straight beams symmetrically arranged on both sides to form a double parallel beam assembly. One end of the double parallel beam assembly is fixedly connected to the decoupling beam assembly, and the other end of the double parallel beam assembly is fixedly connected to the third connecting member.

[0022] In some embodiments of the present invention, the negative stiffness connecting block extends along the driving force output direction of the second driving mechanism, and the positive stiffness connecting block extends along the force transmission direction of the negative stiffness connecting block.

[0023] In a second aspect of the invention, a method of using a flexible manipulator with variable clamping force and constant force rubbing is provided, comprising:

[0024] According to the actual working conditions, power is supplied to the shape memory alloy wire in the variable stiffness flexible straight beam to adjust the phase state of the variable stiffness flexible straight beam, so as to set the stiffness of the variable stiffness beam assembly and make the clamping stiffness of the variable stiffness clamping mechanism match the target workpiece.

[0025] The second driving mechanism applies a pre-displacement to the constant force rubbing mechanism, so that the elastic forces of the positive stiffness structure and the negative stiffness structure cancel each other out, and the constant force is output in the constant force range of the force-displacement curve.

[0026] The clamping stiffness of the variable stiffness clamping mechanism is controlled to make the first clamping end move closer to the second clamping end to clamp the target workpiece.

[0027] The second drive mechanism is controlled to cause the second clamping end to reciprocate, applying a constant rubbing force to the target workpiece.

[0028] One or more technical solutions of the present invention have the following beneficial effects:

[0029] By adjusting the phase state of the shape memory alloy through external power supply, the overall equivalent stiffness of the variable stiffness beam assembly can be directly adjusted. This solves the problem of limited clamping force adjustment range caused by the non-adjustable stiffness of the manipulator structure in the prior art. By adjusting the stiffness of the variable stiffness beam assembly and coordinating with the output force control of the first drive mechanism, the clamping force output by the first clamping end can be adjusted in real time, reversibly, and flexibly according to the size and stiffness characteristics of the object being manipulated. This fundamentally overcomes the limitation that the stiffness of traditional flexible grippers cannot be adjusted once they are manufactured, and achieves adaptive gripping of the target workpiece, greatly improving the versatility of the manipulator.

[0030] The bistable inclined beam assembly and the negative stiffness hexagonal assembly work together to quickly generate a significant negative stiffness effect under relatively small driving displacement. At the same time, the double parallel beam assembly and the positive stiffness hexagonal assembly provide linear restoring force. The two can achieve force balance within a specific pre-displacement range, allowing the second clamping end to quickly enter and maintain a constant force output state. This ensures that a stable and continuous rubbing force can be quickly provided within the fine displacement range required for micro-operation, effectively meeting the requirements of precision operation for rapid and stable response of auxiliary force.

[0031] The variable stiffness clamping mechanism and the constant force rubbing mechanism are arranged side by side and independently in space. They are mainly structurally connected by a decoupling beam assembly. This layout and connection method allows the force and motion generated when the first drive mechanism drives the first clamping end to grasp to be buffered and isolated by the decoupling beam assembly, which has minimal impact on the balance state of the positive and negative stiffness structure inside the constant force rubbing mechanism. Similarly, when the constant force rubbing mechanism is working, its action has a negligible impact on the stiffness setting and clamping stability of the variable stiffness beam assembly. This effectively suppresses the mutual interference between the functions of the variable stiffness clamping mechanism and the constant force rubbing mechanism, enabling the clamping and rubbing operations to be independently controlled and precisely coordinated, simplifying the system control complexity and improving the overall operational stability and reliability. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of a flexible manipulator with variable clamping force and constant force rubbing provided in Embodiment 1 of the present invention. Figure 1 ;

[0033] Figure 2 This is a schematic diagram of the overall structure of a flexible manipulator with variable clamping force and constant force rubbing provided in Embodiment 1 of the present invention. Figure 2 ;

[0034] Figure 3 This is a schematic diagram of the variable stiffness flexible straight beam provided in Embodiment 1 of the present invention;

[0035] Figure 4 This is a schematic diagram of the force-displacement curve of the constant force rubbing mechanism provided in Embodiment 1 of the present invention;

[0036] Figure 5 This is a schematic diagram illustrating the deformation principle of a flexible manipulator with variable clamping force and constant force rubbing, as provided in Embodiment 1 of the present invention. Figure 1 ;

[0037] Figure 6 This is a schematic diagram illustrating the deformation principle of a flexible manipulator with variable clamping force and constant force rubbing, as provided in Embodiment 1 of the present invention. Figure 2 .

[0038] In the diagram: 1. First driving mechanism; 2. Second driving mechanism; 3. Guide flexible straight beam; 4. Guide beam connecting block; 5. Variable stiffness flexible straight beam; 6. Variable stiffness beam connecting block; 7. Decoupled flexible straight beam; 8. Decoupled beam connecting block; 9. First connecting beam assembly; 10. Second connecting beam assembly; 11. First connector; 12. Second connector; 13. Third connector; 14. Intermediate layer plate; 15. Clamping plate; 16. Shape memory alloy wire; 17. Negative stiffness connecting block; 18. Inclined flexible straight beam; 19. Negative stiffness hexagonal assembly; 20. Positive stiffness hexagonal assembly; 21. Positive stiffness connecting block; 22. Parallel flexible straight beam; 23. First clamping end; 24. Second clamping end. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] In a typical embodiment of the present invention, such as Figures 1 to 6 As shown, a flexible manipulator with variable clamping force and constant force rubbing is proposed, including a first driving mechanism 1, a second driving mechanism 2, a variable stiffness clamping mechanism and a constant force rubbing mechanism. The variable stiffness clamping mechanism is provided with a guide beam assembly. The output end of the first driving mechanism 1 is installed with the guide beam assembly. A variable stiffness beam assembly is installed at the end of the guide beam assembly away from the first driving mechanism 1. A decoupling beam assembly is installed at the end of the variable stiffness beam assembly away from the guide beam assembly. A first clamping end 23 is provided at one end of the variable stiffness beam assembly.

[0042] The constant force rubbing mechanism includes a positive stiffness structure and a negative stiffness structure. The output end of the second drive mechanism 2 is installed with the negative stiffness structure, and the negative stiffness structure is installed with the positive stiffness structure. The end of the positive stiffness structure away from the negative stiffness structure is provided with a second clamping end 24. The second clamping end 24 and the first clamping end 23 are set relative to each other at a set distance.

[0043] The decoupled beam assembly is installed on both the positive stiffness structure and the negative stiffness structure.

[0044] By integrating the variable stiffness clamping mechanism and the constant force rubbing mechanism into the same manipulator and using a decoupling beam assembly to connect the two, the two functions are integrated into a single compact manipulator, enabling the manipulator to simultaneously have the ability to adjust the variable stiffness clamping force and provide stable constant force rubbing.

[0045] The variable stiffness clamping mechanism, through the series arrangement of the guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly, forms a force transmission and motion guidance path from the first drive mechanism 1 to the first clamping end 23, ensuring the accuracy and stability of the clamping action. The combination of positive stiffness and negative stiffness structures in the constant force rubbing mechanism lays the foundation for achieving constant force output within a specific displacement range. The first clamping end 23 and the second clamping end 24 are arranged at intervals relative to each other, clarifying the points of action for clamping and rubbing. As a connector between the two core functional mechanisms, the decoupling beam assembly not only achieves structural integration but also plays a certain role in isolating and buffering force transmission, helping to reduce mutual interference between the variable stiffness clamping mechanism and the constant force rubbing mechanism during operation, and providing a guarantee for achieving coordinated and independent control of clamping and rubbing.

[0046] The guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly are arranged parallel to each other, and their geometric centers are collinear to form a centerline. The driving force output direction of the first drive mechanism 1 is arranged along the centerline and perpendicular to the guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly. The driving force output directions of the first drive mechanism 1 and the second drive mechanism 2 are perpendicular to each other.

[0047] The guide beam assembly, variable stiffness beam assembly, and decoupling beam assembly are parallel to each other and have their geometric centers collinear. This ensures that the driving force or deformation force can be transmitted efficiently and without eccentricity along a preset centerline, greatly reducing lateral force components or motion jamming caused by structural asymmetry, and improving force transmission efficiency and motion accuracy. The driving force output direction of the first drive mechanism 1 is along this centerline and perpendicular to each beam assembly, so that the driving force can be directly converted into the axial deformation of the beam assembly, resulting in high driving efficiency and low energy loss. The driving force output directions of the first drive mechanism 1 and the second drive mechanism 2 are set perpendicular to each other. This layout allows the driving of the two functional mechanisms to be spatially independent and can be controlled and operated independently, further strengthening the decoupling and independence of functions at the drive level, which is beneficial for the execution of complex and precise operation sequences.

[0048] The guide beam assembly has multiple guide flexible straight beams 3, which are symmetrically arranged on both sides of the center line; the variable stiffness beam assembly has multiple variable stiffness flexible straight beams 5, which are symmetrically arranged on both sides of the center line; the decoupling beam assembly has multiple decoupling flexible straight beams 7, which are symmetrically arranged on both sides of the center line.

[0049] The axial lengths of the guiding flexible straight beam 3 and the decoupled flexible straight beam 7 are the same, and the axial lengths of the variable stiffness flexible straight beam 5 are all greater than those of the guiding flexible straight beam 3 and the decoupled flexible straight beam 7.

[0050] The guiding flexible straight beam 3, the variable stiffness flexible straight beam 5, and the decoupling flexible straight beam 7 are all arranged symmetrically on both sides of the centerline. This symmetrical layout allows for a more uniform force distribution, effectively offsetting the torque or bending effects caused by asymmetrical deformation, thereby significantly enhancing the stability and linearity of the entire clamping mechanism under load. The guiding flexible straight beam 3 and the decoupling flexible straight beam 7 have the same axial length, which helps maintain consistency in deformation coordination between the guiding and decoupling sections. The variable stiffness flexible straight beam 5 has a longer axial length than the other two, meaning that the variable stiffness beam has a larger elastic deformation range. This provides sufficient deformation space for stiffness changes induced by the phase transformation of the shape memory alloy wire 16, resulting in a wider stiffness adjustment range, higher sensitivity, and the ability to adapt to a wider range of operating object stiffness requirements.

[0051] like Figure 2 As shown, the guide flexible straight beam 3 is provided with a guide beam connecting block 4 in the middle and is installed with the first drive mechanism 1; the variable stiffness flexible straight beam 5 is provided with a variable stiffness beam connecting block 6 in the middle; and the decoupled flexible straight beam 7 is provided with a decoupled beam connecting block 8 in the middle.

[0052] A first connecting beam assembly 9 is provided between the guide beam connecting block 4 and the variable stiffness beam connecting block 6, and a second connecting beam assembly 10 is provided between the variable stiffness beam connecting block 6 and the decoupling beam connecting block 8. The first connecting beam assembly 9 extends along the driving force output direction of the first driving mechanism 1, and the second connecting beam assembly 10 extends along the force transmission direction of the first connecting beam assembly 9.

[0053] Corresponding connecting blocks are respectively installed in the middle sections of the guiding flexible straight beam 3, the variable stiffness flexible straight beam 5, and the decoupled flexible straight beam 7, providing stable mounting points for the drive mechanism and other connecting components. The guiding beam connecting block 4 and the variable stiffness beam connecting block 6 are connected by a first connecting beam assembly 9, which extends along the driving force output direction of the first drive mechanism 1, ensuring that the driving force can be directly and losslessly transmitted from the drive point to the variable stiffness beam assembly, which is key to efficient power transmission. Similarly, the second connecting beam assembly 10 extends along the force transmission direction of the first connecting beam assembly 9, connecting the variable stiffness beam connecting block 6 and the decoupled beam connecting block 8, ensuring the continuity and consistency of the force transmission path. This modular connection method not only enhances the overall integrity and rigidity of the structure, but also makes the force transmission path clear and controllable, reducing energy dissipation and motion errors caused by loose connections or unclear paths.

[0054] The flexible straight beam 3 is provided with first connecting parts 11 symmetrically at both ends, and the first connecting parts 11 are fixedly connected to the variable stiffness flexible straight beams 5 at both ends respectively.

[0055] The two ends of the decoupled flexible straight beam 7 are symmetrically provided with second connecting members 12. One end of the two second connecting members 12 is fixedly connected to the two variable stiffness flexible straight beams 5 respectively, and the other end of the two second connecting members 12 is fixedly connected to the positive stiffness structure and the negative stiffness structure respectively.

[0056] The guide flexible straight beam 3 is fixedly connected to the variable stiffness flexible straight beam 5 at both ends via the first connector 11. This end fixing method provides a reliable interface for the force and displacement transmission between beam components, ensuring that the deformation of the guide section can effectively drive the coordinated action of the variable stiffness section. The decoupled flexible straight beam 7 is connected to the variable stiffness flexible straight beam 5 at one end via the second connector 12, and the other end is fixedly connected to the positive stiffness structure and the negative stiffness structure respectively. This ensures that when the entire device is under force, the load or deformation at the clamping end is buffered by the decoupled beam and will not be transmitted to the constant force mechanism. The action of the constant force mechanism can also be constrained to a certain extent through this path, thereby establishing an isolated mechanical interaction relationship between the two main functional units.

[0057] The variable stiffness flexible straight beam 5 includes an intermediate layer plate 14, with clamping plates 15 on both sides of the intermediate layer plate 14. Shape memory alloy wires 16 are provided in the clamping plates 15, and the shape memory alloy wires 16 are connected to external power supply equipment through wires. The intermediate layer plate 14 is made of thermoplastic plastic, and the clamping plates 15 are made of silicone polymer material.

[0058] The intermediate layer 14 provides basic support and shape, while the side plates 15 embed shape memory alloy wires 16. The shape memory alloy wires 16 are connected to an external power supply via wires, allowing for precise control of their phase transformation, such as the transformation from martensite to austenite, through electrical heating, thereby significantly altering their elastic modulus. Since the shape memory alloy wires 16 are embedded in the load-bearing path of the variable stiffness flexible straight beam 5, changes in their modulus directly lead to changes in the equivalent bending stiffness of the entire variable stiffness flexible straight beam 5.

[0059] like Figure 3 As shown, the intermediate layer 14 is made of thermoplastic, which may provide good machinability and a certain degree of toughness. The clamping plate 15 is made of silicone polymer material, such as polydimethylsiloxane, whose high elasticity and insulation protect the internal shape memory alloy wire 16 while allowing the beam to undergo large deformations without damage. This composite structure enables active, reversible, continuous, or graded electrified adjustment of the clamping stiffness of the variable stiffness clamping mechanism, completely solving the fundamental defect of fixed stiffness in traditional flexible clamps and greatly improving the versatility and adaptability of the operator.

[0060] A third connector 13 is provided between the positive stiffness structure and the negative stiffness structure. The negative stiffness structure includes a negative stiffness connecting block 17, which is connected to the output end of the second drive mechanism 2. Two inclined flexible straight beams 18 are symmetrically arranged on both sides of the negative stiffness connecting block 17 to form a bistable inclined beam assembly. One end of the bistable inclined beam assembly is fixedly connected to the decoupling beam assembly, and the other end of the bistable inclined beam assembly is fixedly connected to the third connector 13.

[0061] A negative stiffness hexagonal component 19 is installed at the end of the negative stiffness connecting block 17 away from the second drive mechanism 2.

[0062] The negative stiffness structure is connected to the second drive mechanism 2 via a negative stiffness connecting block 17, which is the input end of the constant force rubbing mechanism. When the bistable inclined beam assembly, composed of two inclined flexible straight beams 18, is under compression, its force-displacement relationship exhibits nonlinearity. After reaching a specific critical point, a negative stiffness effect may occur where the force decreases with increasing displacement. One end of the bistable inclined beam assembly is connected to the decoupling beam assembly, and the other end is connected to the subsequent structure via a third connector 13. This arrangement integrates it into the overall force chain.

[0063] The negative stiffness hexagonal component 19 installed at the other end of the negative stiffness connecting block 17 is a linkage mechanism composed of four flexible straight beams, two connecting rods, and a central connecting straight beam. Its geometry helps to generate or adjust specific nonlinear mechanical behavior, working in conjunction with the bistable inclined beam to jointly shape the required negative stiffness force-displacement curve. This configuration allows for the rapid generation of a significant negative stiffness effect under relatively small driving displacement. Combined with the positive stiffness structure, this enables the entire constant force actuation mechanism to enter the constant force equilibrium range without a large pre-displacement, thereby achieving a fast-response stable constant force output and meeting the requirements of micro-operations for instantaneous and smooth auxiliary force.

[0064] The positive stiffness structure includes a positive stiffness hexagonal component 20, which is disposed on the outer periphery of the negative stiffness hexagonal component 19. One end of the positive stiffness hexagonal component 20 is fixedly connected to the negative stiffness connecting block 17, and the other end of the positive stiffness hexagonal component 20 is provided with a positive stiffness connecting block 21. One end of the positive stiffness connecting block 21 is fixedly connected to the negative stiffness hexagonal component 19, and the other end of the positive stiffness connecting block 21 is fixedly connected to the second clamping end 24.

[0065] Two parallel flexible straight beams 22 are symmetrically arranged on both sides of the positive stiffness connecting block 21 to form a double parallel beam assembly. One end of the double parallel beam assembly is fixedly connected to the decoupling beam assembly, and the other end of the double parallel beam assembly is fixedly connected to the third connecting piece 13.

[0066] The positive stiffness structure includes a positive stiffness hexagonal component 20, which consists of four flexible straight beams and two connecting rods. It is positioned on the outer periphery of the negative stiffness hexagonal component 19. This nested arrangement saves space and achieves compact integration. The double-parallel beam assembly, formed by two parallel flexible straight beams 22, provides linear or near-linear positive stiffness, meaning its reaction force is proportional to the displacement. Furthermore, the arrangement of the double-parallel beam assembly also serves a guiding function, constraining the direction of motion. The positive stiffness connecting block 21 ultimately connects to the second clamping end 24, providing a stable and predictable positive stiffness force output.

[0067] When the second drive mechanism 2 applies displacement, the negative stiffness structure generates a nonlinearly decreasing force, while the positive stiffness structure mainly generates a linearly increasing force through the double parallel beam assembly and the positive stiffness hexagonal assembly 20, so that the resultant force of the two remains constant within a certain displacement range, thereby outputting the required constant force as the rubbing force at the second clamping end 24.

[0068] like Figure 4 As shown, the horizontal segment of the curve represents the constant force range of the force-displacement curve reached when the elastic forces of the positive stiffness structure and the negative stiffness structure cancel each other out.

[0069] The negative stiffness connecting block 17 extends along the driving force output direction of the second driving mechanism 2, and the positive stiffness connecting block 21 extends along the force transmission direction of the negative stiffness connecting block 17.

[0070] The negative stiffness connecting block 17 extends along the driving force output direction of the second driving mechanism 2, ensuring that the input direction of the driving force is consistent with the core deformation direction of the negative stiffness structure, resulting in the highest driving efficiency. The positive stiffness connecting block 21 extends along the force transmission direction of the negative stiffness connecting block 17, indicating that the force transmission path of the positive stiffness structure and the force output path of the negative stiffness structure are coordinated in direction. This ensures that the forces from the positive stiffness structure and the negative stiffness structure can be synthesized along the designed direction vector, avoiding component force loss or mutual cancellation due to directional deviation. This makes the directionality of the constant force output clearer, and the efficiency and accuracy of the synthesized force higher, further ensuring the stability and reliability of the constant force rubbing effect.

[0071] In this embodiment, as Figure 1As shown, the first and second drive mechanisms employ voice coil motors, which are supported by mounting bases adapted to the voice coil motors. The guide beam assembly, decoupling beam assembly, and third connector are supported by fixing blocks and secured to each other with screws. This arrangement ensures uniform load transfer over a large mounting contact area. The fixing blocks are positioned at the same height as the mounting bases, effectively ensuring the overall manipulator remains stable and tilt-free during use. The manipulator as a whole utilizes flexible mechanisms, and the beam itself is manufactured in a single 3D print, reducing assembly errors and improving output consistency. Through these features, the manipulator possesses excellent flexibility, buffering, and self-adaptive capabilities. Faced with minor positional deviations, vibrations, or impacts, it can absorb energy through structural deformation, maintaining a stable constant force output.

[0072] Figure 5 This demonstrates the deformation state of the flexible manipulator. When the first drive mechanism 1 outputs driving force to the right, the guide beam assembly, the variable stiffness beam assembly, and the decoupling beam assembly undergo corresponding deformations. The first clamping end 23 moves to the right and smoothly approaches the second clamping end 24. At this time, the driving force output by the first drive mechanism 1 will not affect the constant force rubbing mechanism. When the second drive mechanism 2 outputs driving force upward, the negative stiffness structure and the positive stiffness structure undergo corresponding deformations. The second clamping end 24 moves upward a set distance relative to the first clamping end 23.

[0073] Figure 6 The deformation process of the flexible manipulator is shown. The dashed line represents the state of the flexible manipulator when it is not in use, and the solid line represents the corresponding deformation states of the guide beam assembly, variable stiffness beam assembly, decoupling beam assembly, negative stiffness structure and positive stiffness structure after the first drive mechanism 1 and the second drive mechanism 2 output driving forces respectively.

[0074] In a second aspect of the invention, a method of using a flexible manipulator with variable clamping force and constant force rubbing is provided, comprising:

[0075] According to the actual working conditions, power is supplied to the shape memory alloy wire 16 inside the variable stiffness flexible straight beam 5 to adjust the phase state of the variable stiffness flexible straight beam 5, so as to set the stiffness of the variable stiffness beam assembly and make the clamping stiffness of the variable stiffness clamping mechanism match the target workpiece.

[0076] The second drive mechanism 2 applies a pre-displacement to the constant force rubbing mechanism, so that the elastic forces of the positive stiffness structure and the negative stiffness structure cancel each other out, and the constant force is output in the constant force range of the force-displacement curve.

[0077] The first drive mechanism 1 is controlled according to the clamping stiffness of the variable stiffness clamping mechanism to bring the first clamping end 23 close to the second clamping end 24 to clamp the target workpiece.

[0078] The second drive mechanism 2 is controlled to cause the second clamping end 24 to reciprocate, applying a constant rubbing force to the target workpiece.

[0079] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A flexible manipulator with variable clamping force and constant force rubbing, characterized in that, It includes a first driving mechanism, a second driving mechanism, a variable stiffness clamping mechanism, and a constant force rubbing mechanism. The variable stiffness clamping mechanism is provided with a guide beam assembly. The output end of the first driving mechanism is installed with the guide beam assembly. A variable stiffness beam assembly is installed at the end of the guide beam assembly away from the first driving mechanism. A decoupling beam assembly is installed at the end of the variable stiffness beam assembly away from the guide beam assembly. A first clamping end is provided at one end of the variable stiffness beam assembly. The constant force rubbing mechanism includes a positive stiffness structure and a negative stiffness structure. The output end of the second drive mechanism is installed with the negative stiffness structure, and the negative stiffness structure is installed with the positive stiffness structure. The end of the positive stiffness structure away from the negative stiffness structure is provided with a second clamping end. The second clamping end and the first clamping end are arranged relative to each other at a set distance. The decoupling beam assembly is installed on the positive stiffness structure and the negative stiffness structure, respectively; The guide beam assembly, variable stiffness beam assembly, and decoupling beam assembly are arranged parallel to each other, and their geometric centers are collinear to form a centerline. The driving force output direction of the first driving mechanism is arranged along the centerline and perpendicular to the guide beam assembly, variable stiffness beam assembly, and decoupling beam assembly. The driving force output directions of the first driving mechanism and the second driving mechanism are perpendicular to each other. The guide beam assembly has multiple guide flexible straight beams, which are symmetrically arranged on both sides of the center line; the variable stiffness beam assembly has multiple variable stiffness flexible straight beams, which are symmetrically arranged on both sides of the center line; the decoupling beam assembly has multiple decoupling flexible straight beams, which are symmetrically arranged on both sides of the center line. The axial lengths of the guiding flexible straight beam and the decoupling flexible straight beam are the same, and the axial lengths of the variable stiffness flexible straight beams are all greater than those of the guiding flexible straight beam and the decoupling flexible straight beam. The variable stiffness flexible straight beam includes an intermediate layer plate, with clamping plates on both sides of the intermediate layer plate. Shape memory alloy wires are provided in the clamping plates, and the shape memory alloy wires are connected to an external power supply device through wires. The intermediate layer plate is made of thermoplastic plastic, and the clamping plates are made of silicone polymer material. A third connector is provided between the positive stiffness structure and the negative stiffness structure. The negative stiffness structure includes a negative stiffness connecting block, which is connected to the output end of the second drive mechanism. Two inclined flexible straight beams are symmetrically arranged on both sides of the negative stiffness connecting block to form a bistable inclined beam assembly. One end of the bistable inclined beam assembly is fixedly connected to the decoupling beam assembly, and the other end of the bistable inclined beam assembly is fixedly connected to the third connector. A negative stiffness hexagonal component is installed at the end of the negative stiffness connecting block away from the second drive mechanism; The positive stiffness structure includes a positive stiffness hexagonal component, which is disposed on the outer periphery of the negative stiffness hexagonal component. One end of the positive stiffness hexagonal component is fixedly connected to the negative stiffness connecting block, and the other end of the positive stiffness hexagonal component is provided with a positive stiffness connecting block. One end of the positive stiffness connecting block is fixedly connected to the negative stiffness hexagonal component, and the other end of the positive stiffness connecting block is fixedly connected to the second clamping end. The positive stiffness connecting block has two parallel flexible straight beams symmetrically arranged on both sides to form a double parallel beam assembly. One end of the double parallel beam assembly is fixedly connected to the decoupling beam assembly, and the other end of the double parallel beam assembly is fixedly connected to the third connecting member.

2. The flexible manipulator with variable clamping force and constant force rubbing as described in claim 1, characterized in that, The guide flexible straight beam has a guide beam connecting block installed in the middle and the first drive mechanism is installed in the middle; the variable stiffness flexible straight beam has a variable stiffness beam connecting block in the middle; and the decoupled flexible straight beam has a decoupled beam connecting block in the middle. A first connecting beam assembly is provided between the guide beam connecting block and the variable stiffness beam connecting block, and a second connecting beam assembly is provided between the variable stiffness beam connecting block and the decoupling beam connecting block. The first connecting beam assembly extends along the driving force output direction of the first driving mechanism, and the second connecting beam assembly extends along the force transmission direction of the first connecting beam assembly.

3. The flexible manipulator with variable clamping force and constant force rubbing as described in claim 1, characterized in that, The guide flexible straight beam is provided with first connecting members symmetrically at both ends, and the first connecting members are fixedly connected to the variable stiffness flexible straight beams at both ends respectively. The two ends of the decoupled flexible straight beam are respectively provided with second connecting members. One end of the two second connecting members is fixedly connected to the two variable stiffness flexible straight beams respectively, and the other end of the two second connecting members is fixedly connected to the positive stiffness structure and the negative stiffness structure respectively.

4. The flexible manipulator with variable clamping force and constant force rubbing as described in claim 1, characterized in that, The negative stiffness connecting block extends along the driving force output direction of the second driving mechanism, and the positive stiffness connecting block extends along the force transmission direction of the negative stiffness connecting block.

5. A method of using a flexible manipulator with variable clamping force and constant force rubbing as described in any one of claims 1-4, characterized in that, include: According to the actual working conditions, power is supplied to the shape memory alloy wire in the variable stiffness flexible straight beam to adjust the phase state of the variable stiffness flexible straight beam, so as to set the stiffness of the variable stiffness beam assembly and make the clamping stiffness of the variable stiffness clamping mechanism match the target workpiece. The second driving mechanism applies a pre-displacement to the constant force rubbing mechanism, so that the elastic forces of the positive stiffness structure and the negative stiffness structure cancel each other out, and the constant force is output in the constant force range of the force-displacement curve. The clamping stiffness of the variable stiffness clamping mechanism is controlled to make the first clamping end move closer to the second clamping end to clamp the target workpiece. The second drive mechanism is controlled to cause the second clamping end to reciprocate, applying a constant rubbing force to the target workpiece.

Images