Continuous multi-stroke constant-force compliant mechanism

Abstract

The invention relates to a flexible multistable mechanism in the fields of precision assembly, micro electro mechanical systems, biomedical engineering and the like, in particular to a continuous multi-stroke constant-force compliant mechanism which is characterized by at least comprising a base, parallel cosine beams with negative stiffness characteristics are connected to the base, and the parallel cosine beams are connected to the base. The parallel cosine beams comprise a first cosine beam and a second cosine beam which have different buckling critical pressures, the first cosine beam is connected with the guide beam, the guide beam is connected with the composite beam and receives displacement input by the outside through the displacement input end, the first cosine beam is connected with the composite beam through the rigid guide beam, the guide beam is provided with the displacement input end, and the second cosine beam is connected with the composite beam through the rigid guide beam. The third-order buckling critical pressure of the second cosine beam is lower than that of the first cosine beam, and negative stiffness deformation occurs preferentially during displacement input; after the second cosine beam completes the stroke, the rigid end of the second cosine beam and the rigid cross beam of the base form contact constraint, the second cosine beam is converted into a constant bearing reaction output state, and meanwhile the first cosine beam is triggered to enter second-section negative stiffness deformation; the positive stiffness characteristic of the composite beam and the negative stiffness characteristic of the parallel cosine beam achieve stiffness coupling offset through the guide beam, and therefore the double-stroke constant force output platform is formed. According to the design, the dynamic stability of wide-area constant force output is realized through sequential triggering and constraint state conversion of double-beam buckling modes.

Description

Technical Field

[0001] The present invention relates to a flexible multi-stable mechanism in the fields of precision assembly, microelectromechanical systems, biomedical engineering, etc., and in particular to a continuous multi-stroke constant-force compliant mechanism. Background Art

[0002] As a core functional component in the fields of robotics technology and precision equipment, a compliant mechanism realizes energy transfer and motion control through the controllable deformation of elastic elements. Compared with traditional rigid mechanisms, it has significant advantages such as no friction loss, no assembly clearance, and integrated kinematic pairs. In scenarios such as micro-nano operations, biomedical medical devices, and aerospace precision docking, the compliant mechanism can effectively avoid the wear and error accumulation problems of traditional hinges / bearings and improve the system reliability.

[0003] Currently, the design research of compliant constant-force mechanisms mainly focuses on the design problems of compliant constant-force mechanisms with a single stroke. For example, a passive flexible constant-force mechanism designed by Wang Nianfeng et al. has a simple structure. When the input displacement at the input end is within a certain range, the mechanism can still provide an approximately constant output reaction force (Patent No.: CN209504113U). However, such a passive flexible constant-force mechanism still has problems such as limited compliant stroke, non-linear fluctuation of the output force, and is limited to a single constant-force range with a relatively single negative stiffness structure form, and cannot meet the requirements of multi-segment constant-force ranges of constant-force mechanisms in practical applications.

[0004] In recent years, multi-stroke compliant mechanisms have extended the compliant domain through parallel elastic units or hierarchical deformation strategies. Although approximate constant-force output is achieved in specific stroke segments, their coupled deformation paths lead to sudden changes in stiffness in each stroke segment, making it difficult to meet the dynamic stability requirements under continuous variable working conditions. Therefore, the present invention proposes a continuous multi-stroke constant-force compliant mechanism based on a parallel negative stiffness structure, which uses a composite beam with positive stiffness characteristics and a parallel cosine beam with negative stiffness characteristics to achieve stiffness coupling cancellation through a guiding beam, thereby forming a double-stroke constant-force output platform. At the same time, it meets the dynamic stability of achieving wide-range constant-force output. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-stroke constant-force compliant mechanism with a parallel negative stiffness structure that is simple in structure and good in processability.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A continuous multi-stroke constant force compliant mechanism, which at least includes a base, and a parallel cosine beam with negative stiffness characteristics is connected to the base. The parallel cosine beam includes a cosine beam one and a cosine beam two with different buckling critical pressures. Among them, the cosine beam one is connected to a guiding beam, and the guiding beam is connected to a composite beam, and receives the displacement input from the outside through a displacement input end. The cosine beam one is connected to the composite beam through the guiding beam, and the guiding beam is provided with a displacement input end.

[0008] The parallel cosine beam is composed of a cosine beam one and a cosine beam two with negative stiffness characteristics.

[0009] The parallel cosine beam is composed of a cosine beam one and a cosine beam two with negative stiffness characteristics. After the cosine beam two completes the stroke, its rigid end forms a contact constraint with the rigid cross beam of the base and turns into a constant reaction force output state, while triggering the cosine beam one to enter the second-stage negative stiffness deformation.

[0010] The composite beam has a force-displacement relationship with positive linear correlation (i.e., positive stiffness characteristics), and the negative stiffness characteristics of the parallel cosine beam are used to achieve stiffness coupling cancellation, thereby forming a double-stroke constant force output platform.

[0011] In the parallel cosine beam, the thickness of the cosine beam one is 1.07 mm, the thickness of the cosine beam two is 1 mm, and the thickness of each beam of the composite beam is 1.7 mm.

[0012] The parallel cosine beam and the composite beam are connected to each other through the guiding beam to form an integral body.

[0013] The base plays a role of support and fixation.

[0014] The parallel cosine beam is a bistable flexible mechanism with negative stiffness characteristics.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) Compared with the traditional single-stroke constant force compliant mechanism, the present invention realizes double-stroke constant force output by adopting the bistable flexible mechanism of the parallel cosine beam, and broadens the constant force stroke of the compliant mechanism.

[0017] (2) Compared with the general multi-stroke constant force compliant mechanism, the present invention adopts a negative stiffness cosine beam one and a cosine beam two with different buckling critical pressures, and realizes the dynamic stability of wide-range constant force output through the sequential triggering of the double-beam buckling mode and the conversion of the constraint state. Description of the Drawings

[0018] The following further describes the present invention with reference to the accompanying drawings of the embodiments.

[0019] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention;

[0020] Figure 2 Yes Figure 1 The mechanism in the middle is in a stable equilibrium state at Stroke 1;

[0021] Figure 3 Yes Figure 1 The mechanism in the middle is in a stable equilibrium state at Stroke 2;

[0022] Figure 4 This is a partial enlarged view of the parallel cosine beam in the embodiment of the present invention;

[0023] Figure 5 This is the force-displacement curve of the theoretical model and finite element simulation of the composite beam when a fixed constraint is applied to the base of the composite beam structure and a displacement of 16 mm in the Y direction is applied to the rigid guiding beam;

[0024] Figure 6 This is the theoretical model and finite element simulation results of the force-displacement curve of the parallel cosine beam when a fixed constraint is applied to the base and displacement constraints in the x and z directions are applied to the sides of the left and right guiding beams;

[0025] Figure 7 This is the force-displacement relationship of the constant force mechanism formed by the superposition of the stiffness of the composite beam and the parallel cosine beam obtained according to the theoretical model and finite element simulation respectively;

[0026] Figure 8 This is the force-displacement relationship of the constant force mechanism, composite beam, and parallel cosine beam respectively as the length of the composite beam changes.

[0027] In the figure: 1. Base; 2. Displacement input end; 3. Guiding beam; 4. Composite beam; 5. Cosine beam 1; 6. Parallel cosine beam; 7. Cosine beam 2. Detailed implementation manners

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will describe the specific implementation manners of the present invention with reference to the accompanying drawings. Obviously, the accompanying drawings only show some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can still be derived based on these drawings, and other implementation manners can be obtained therefrom.

[0029] See Figures 1 to 4 , this example discloses a constant force compliant mechanism with continuous multi-strokes, which at least includes a base 1, and a parallel cosine beam 6 with negative stiffness characteristics is connected to the base 1. The parallel cosine beam 6 includes a cosine beam 1 5 and a cosine beam 2 7 with different buckling critical pressures. Among them, the cosine beam 1 5 is connected to the guiding beam 3, the guiding beam 3 is connected to the composite beam 4, and receives the displacement input from the outside through the displacement input end 2.

[0030] SeeFigure 2 Since the parallel cosine beam 6 includes a first cosine beam 5 and a second cosine beam 7 with different buckling critical pressures, when in the working state, the second cosine beam 7 with a smaller buckling critical pressure first undergoes buckling deformation until the mechanism reaches a stable equilibrium state in the first stroke.

[0031] See Figure 3 Since the parallel cosine beam 6 includes a first cosine beam 5 and a second cosine beam 7 with different buckling critical pressures, after the stroke of the second cosine beam 7 ends, the rigid end of the guiding beam 3 contacts the rigid crossbeam of the base 1. At this time, the second cosine beam 7 no longer deforms and only provides a constant reaction force. The first cosine beam 5 starts to deform and undergoes a second-stage buckling deformation until the mechanism reaches a stable equilibrium state in the second stroke.

[0032] See Figure 4 The parallel cosine beam 6 includes a first cosine beam 5 and a second cosine beam 7 with different buckling critical pressures, and the parallel cosine beam 6 is a bistable flexible mechanism with negative stiffness characteristics.

[0033] See Figures 5 to 7 Since the theoretical models of the composite beam, parallel cosine beam, and constant-force mechanism have been idealized and simplified in terms of boundary conditions compared to actual simulations, and factors such as the simplification of dynamic inertial forces and damping dissipation in theoretical analysis, there will be slight errors between each part of the theoretical model and the actual simulation. The error values are all less than 8% and all conform to the changing trend of the force-displacement relationship in the theoretical model.

[0034] See Figure 8 As the length of the composite beam gradually decreases, the positive stiffness value of the composite beam increases, causing the force-displacement curve of the constant-force mechanism to tend towards positive stiffness characteristics, thereby enhancing the load-bearing capacity of the mechanism. The change in the length of the composite beam has a more significant impact on the load-bearing capacity of the second-stage constant force, but has a smaller impact on the constant-force range.

[0035] Working principle: The first cosine beam 5 is connected to the composite beam 4 through the guiding beam 3, and the guiding beam 3 is provided with a displacement input end. The third-order buckling critical pressure of the second cosine beam 7 is lower than that of the first cosine beam 5. During displacement input, the second cosine beam 7 preferentially undergoes negative stiffness deformation. When the second cosine beam 7 completes its stroke, its rigid end contacts the rigid crossbeam of the base 1 and forms a constraint, entering the state of outputting a constant reaction force, and at the same time triggering the first cosine beam 5 to enter the second-stage negative stiffness deformation. The positive stiffness characteristics of the composite beam 4 and the negative stiffness characteristics of the parallel cosine beam 6 achieve stiffness coupling through the guiding beam 3, so that the stiffness of the two cancels each other out, thereby forming a double-stroke constant-force output platform.

[0036] One application of the present invention is used in the assembly of precision parts. In industries such as electronics, automotive, and semiconductors, when assembling tiny or fragile parts, it is necessary to avoid damage caused by excessive or uneven force. The present invention can ensure stable contact force and adapt to the tolerance or position deviation of the parts. The above is only used to illustrate the technical solution of the present invention, rather than limiting it. It can be fully applicable to the fields suitable for the present invention. For those of ordinary skill in the art, modifications or substitutions can still be made to the technical solutions and technical features in the foregoing description and embodiments. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A continuous multi-stroke constant force compliant mechanism, comprising a base (1), a guiding beam (3), a composite beam (4) and a parallel cosine beam (6), characterized in that: It includes at least a base (1), and a parallel cosine beam (6) with negative stiffness characteristics is connected to the base (1). The parallel cosine beam (6) is composed of a cosine beam one (5) and a cosine beam two (7) with different buckling critical pressures. Among them, the cosine beam one (5) is connected to a guiding beam (3), and the guiding beam (3) is connected to a composite beam (4), and receives the displacement input from the outside through a displacement input end (2). Based on its lower third-order buckling critical load, the cosine beam two (7) preferentially enters the negative stiffness buckling stage when the displacement is input. When it completes the predetermined stroke, the rigid end forms a contact constraint with the rigid cross beam of the base (1), and the system switches to a constant reaction force output mode, and simultaneously activates the second-stage negative stiffness deformation of the cosine beam one (5). The positive stiffness of the composite beam (4) and the negative stiffness characteristics of the parallel cosine beam (6) achieve stiffness coupling balance through the guiding beam (3), and finally a double-stroke constant force output mechanism is constructed.

2. The continuously multi-trip constant-force compliant mechanism according to claim 1, wherein: The parallel cosine beam (6) is composed of a cosine beam one (5) and a cosine beam two (7) with negative stiffness characteristics.

3. A continuous multi-stroke constant force compliant mechanism according to claim 1, characterized in that: The cosine beam one (5) and the cosine beam two (7) with negative stiffness characteristics have different buckling critical pressures.

4. A continuous multi-stroke constant force compliant mechanism according to claim 1, characterized in that When the cosine beam two (7) completes the stroke, its rigid end forms a contact constraint with the rigid cross beam of the base (1), and switches to a constant reaction force output state, and simultaneously triggers the cosine beam one (5) to enter the second-stage negative stiffness deformation.

5. A continuous multi-stroke constant-force compliant mechanism according to claim 1, characterized in that: The composite beam (4) has a force-displacement relationship with positive linear correlation (i.e., positive stiffness characteristics), and the negative stiffness characteristics of the parallel cosine beam (6) achieve stiffness coupling cancellation through the guiding beam (3), so as to form a double-stroke constant force output platform.

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