A compliant constant force mechanism and a clamping mechanism and a clamping method thereof

Abstract

The present application relates to a kind of compliant constant force mechanism and a kind of clamping mechanism and its clamping method, compliant constant force mechanism includes base, double-beam coupling type constant force mechanism, bridge type displacement amplifier and piezoelectric driver;Bridge type displacement amplifier is connected to base, piezoelectric driver is arranged in bridge type displacement amplifier, bridge type displacement amplifier is equipped with output port;Double-beam coupling type constant force mechanism is connected to base and the output port of bridge type displacement amplifier respectively, and the end of double-beam coupling type constant force mechanism is equipped with mechanism output end face;Wherein, the output of piezoelectric driver generates the displacement of first stage amplification at output port by bridge type displacement amplifier;The displacement at output port is obtained second stage amplification at mechanism output end face by double-beam coupling type constant force mechanism.It is realized that the periodic shift of part is arranged in compliant clamping mechanism, and the adaptive alignment assembly of misaligned part is realized by this active, controllable periodic motion, with stronger engineering application value.

Description

Technical Field

[0001] This invention relates to the fields of compliant mechanism technology and micro-part assembly technology, specifically to a compliant constant force mechanism and a clamping mechanism and clamping method thereof. Background Technology

[0002] Compliant mechanisms transmit force and energy through elastic deformation, thereby transmitting part or all of the motion. This is why compliant mechanisms have the ability to sense and control force.

[0003] Compliant clamping mechanisms are among the most commonly used micro-assembly actuators. Micro-assembly often requires the precise assembly of a series of heterogeneous and dissimilar tiny parts with micron-level accuracy. However, existing micro-assembly technologies have not yet achieved a good balance between ensuring operational safety, reliability, and system convenience.

[0004] [1] Xu H, Zhang X, Zang H, et al. AnSMA-based compliant adjustable constant force gripper for microassembly[J]. International Journal of Mechanical Sciences, 2024, 278: 109430. This paper constructs an asymmetric constant force mechanism, which achieves constant force clamping by mirroring two constant force mechanisms. By replacing the beams in the constant force mechanism with shape memory alloy beams, the output constant force can be adjusted, avoiding the introduction of a complex force control system during operation. However, it has the disadvantages of slow execution speed and poor pose control capability. The reason for the slow execution speed of this mechanism is that it uses shape memory alloy sheets for driving, and the slow heating-cooling rate restricts the reaction rate of the mechanism; while the reason for the lack of pose control capability is that this study did not carry out relevant optimization work, and still has a strong dependence on the visual servo positioning system.

[0005] [2] Baksys B, Baskutiene J, and Baskutis S. The vibratory alignment of the parts in robotic assembly[J]. Industrial Robot: An International Journal.2017, 44(6):720-729. This study introduces a method for aligning parts by applying periodic vibration signals to the parts to be assembled using a robotic arm and a telecentric flexible gripper during macroscopic part assembly. The study shows that appropriate vibration signals can effectively improve the alignment efficiency of parts and reduce assembly force to a certain extent. However, this work falls within the scope of macroscopic operations and uses a robotic arm and a large fixed base. In this study, the research object, research content, and configuration used are all difficult to directly apply to the field of micro-part assembly. In addition, the device built in this work still heavily relies on the multidimensional force sensing system, because the system does not have components that can achieve force adjustment. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a compliant constant force mechanism and a clamping mechanism and clamping method thereof, which can effectively reduce the control difficulty of micro-assembly systems and improve the efficiency of precision assembly of micro parts.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A compliant constant force mechanism includes a base, a double-beam connected constant force mechanism, a bridge displacement amplifier, and a piezoelectric actuator; The bridge displacement amplifier is connected to the base, the piezoelectric driver is located inside the bridge displacement amplifier, and the bridge displacement amplifier has an output port; The double-beam connected constant force mechanism is connected to the base and the output port of the bridge displacement amplifier respectively, and the end of the double-beam connected constant force mechanism is provided with a mechanism output end face; The piezoelectric actuator output generates a first-stage amplified displacement at the output port through a bridge displacement amplifier; the displacement at the output port is amplified a second stage at the output end face of the mechanism through a double-beam connected constant force mechanism.

[0008] Furthermore, the double-beam connected constant force mechanism includes a first beam, a flexible beam connector, and a second beam. The first beam and the second beam are arranged at intervals. One end of the first beam is connected to the base, and one end of the second beam is connected to the output port of the bridge displacement amplifier. The other ends of the first beam and the second beam are both connected to the flexible beam connector. The output end face of the mechanism is located at the end of the flexible beam connector.

[0009] Furthermore, both beams No. 1 and No. 2 are compliant leaf-shaped beams.

[0010] Furthermore, the bridge displacement amplifier includes a short flexible beam, an output port and a fixed port arranged opposite to each other; the fixed port is connected to the base; equivalent rigid connecting bodies are provided on both sides of the output port and the fixed port, and the output port and the fixed port are both connected to the equivalent rigid connecting bodies through the short flexible beam, and the piezoelectric actuator is located between the two equivalent rigid connecting bodies.

[0011] Furthermore, the base is provided with a short straight groove through hole, which is used to connect with the interface of the external guide mechanism.

[0012] A clamping mechanism includes two guide mechanisms and two compliant constant force mechanisms. The two compliant constant force mechanisms are respectively connected to the two guide mechanisms. The guide mechanisms are used to provide opening and closing movements between the two compliant constant force mechanisms. A clamping opening for clamping parts is formed between the mechanism output end faces of the two compliant constant force mechanisms.

[0013] A clamping method includes the following steps: When the two compliant constant force mechanisms are driven to close by the guide mechanism, the output end faces of the two compliant constant force mechanisms contact the parts and complete the constant force clamping.

[0014] Furthermore, when an equal and constant voltage signal is provided to the piezoelectric actuators of the two compliant constant force mechanisms, the two compliant constant force mechanisms produce equal deformation, and the constant force value changes synchronously, thereby realizing adjustable constant force clamping.

[0015] Furthermore, when the piezoelectric actuators of the two compliant constant force mechanisms are supplied with varying voltage signals of the same amplitude but with a phase difference, the output end faces of the two compliant constant force mechanisms produce asynchronous displacements, causing the clamped parts to shift periodically.

[0016] In summary, the present invention has the following advantages: 1. By arranging a drive structure within a compliant clamping mechanism, periodic offset of parts is achieved through the transmission of the compliant mechanism. This active and controllable periodic motion enables adaptive alignment and assembly of misaligned parts, demonstrating greater engineering application value. Existing compliant micro-clamping mechanisms do not consider arranging additional actuators within the mechanism to generate similar periodic motions in parts, thus lacking the capability for automatic alignment in micro-assemblies. Existing strategies for achieving part alignment by providing periodic vibrations remain at a macroscopic scale, and the source of the periodic vibrations is a robotic arm or vibration generator, rather than the clamping mechanism. This results in insufficiently direct and controllable periodic motion of the parts. Furthermore, existing technologies do not include strategies for protecting parts during periodic motion using constant force mechanisms.

[0017] 2. The proposed asymmetric compliant constant force structure incorporates a bridge-type displacement amplification mechanism and a piezoelectric actuator, possessing high-frequency active displacement output and passively adjustable constant force capability, making it directly usable as a gripper for micro-parts. Existing constant force mechanism technologies generally use symmetrical compliant structure configurations, which are not suitable for direct application as micro-gripping mechanisms; existing adjustable constant force structures only have simple constant force value adjustment capabilities, but due to the use of too many external structures or reliance on material stiffness changes to achieve constant force adjustment, they suffer from slow adjustment speeds; existing piezoelectric ceramic driven compliant mechanisms mostly only have displacement and force output capabilities, have not yet considered the problem of adjustable constant force clamping, and lack force self-adaptation capabilities.

[0018] 3. A novel structure integrating a bridge-type displacement amplification mechanism with a double-beam connection is proposed. This structure not only utilizes the constant force output function of the double-beam connection constant force mechanism but also leverages its displacement amplification capability at specific locations, achieving a miniaturized, high-amplification-ratio compliant structure. Conventional solutions mostly rely on repetitive and bulky displacement amplification mechanisms to amplify the mechanism's output, making miniaturization difficult. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the planar structure of a compliant constant force mechanism with an embedded piezoelectric actuator.

[0020] Figure 2 This is a three-dimensional structural diagram of a compliant constant force mechanism with an embedded piezoelectric actuator.

[0021] Figure 3 This is a schematic diagram of the planar structure of a bridge displacement amplifier.

[0022] Figure 4 This is a three-dimensional structural diagram of the clamping mechanism.

[0023] Figure 5 This is a schematic diagram of the planar structure of the clamping mechanism.

[0024] In the picture: 1-Base, 2-Short straight groove through hole, 3-Beam No. 1, 4-Flexible beam connector, 5-Mechanism output end face, 6-Beam No. 2, 7-Output port, 8-Bridge displacement amplifier, 9-Ceramic output end face, 10-Piezoelectric actuator, 11-Short flexible beam, 12-Equivalent rigid connector, 13-Fixed port, 14-Guide mechanism, 15-Adapter plate, 16-Parts. Detailed Implementation

[0025] The present invention will now be described in further detail.

[0026] like Figure 1 , Figure 2As shown, a compliant constant force mechanism with an embedded piezoelectric actuator includes a base 1, a double-beam connected constant force mechanism, a bridge displacement amplifier 8, and a piezoelectric actuator 10.

[0027] For details, please refer to Figures 1 to 4 The components include: base 1, beam 3, flexible beam connector 4, beam 6, bridge displacement amplifier 8, and piezoelectric actuator 10.

[0028] The base 1 has two short straight groove through holes 2 for connecting to the external guide mechanism 14 via the adapter plate 15; the short straight groove through holes 2 can also be used to slightly adjust the relative position of the base 1 and the guide mechanism 14.

[0029] Both beam 3 and beam 6 are compliant leaf-shaped beams. Their left sides are connected to the base 1 and the output port 7 of the bridge displacement amplifier 8, respectively, and their right sides are connected to the flexible beam connector 4. The end of the flexible beam connector 4 is the mechanism output end face 5. The piezoelectric driver 10 is placed inside the bridge displacement amplifier 8, specifically in the area designated by the two ceramic output faces 9.

[0030] Beam 3, the flexible beam connector 4, and beam 6 together constitute a double-beam connected constant force mechanism. Assuming that the left sides of beams 3 and 6 are both fixed constraints, and the structure is subjected to an external displacement load at the output end face 5, beams 3 and 6 will experience buckling during bending deformation, thus generating constant force motion characteristics at the output end face 5, thereby achieving the constant force function of the mechanism.

[0031] In the design, a bridge displacement amplifier 8 with an embedded piezoelectric actuator 10 is arranged at the left port of beam 6.

[0032] The detailed structure of the bridge displacement amplifier 8 is as follows: Figure 3 As shown, it includes an output port 7, four short flexible beams 11, an equivalent rigid connector 12, and a fixed port 13.

[0033] The fixed port 13 is integrally connected to the base 1. The piezoelectric actuator 10 outputs force / displacement to the ceramic output end face 9, and then, through the transmission of the equivalent rigid connector 12, causes the short flexible beam 11 to deform, thereby driving the output port 7 to move downward. The output of the piezoelectric actuator 10, through the bridge displacement amplifier 8, will generate a first-stage amplified displacement at the output port 7; the displacement at the output port 7 will be amplified a second time at the mechanism output end face 5 through the double-beam connected constant force mechanism. The amplified displacement direction is as follows: Figure 1 As indicated by the middle arrow. This achieves the active offset function of the compliant constant force mechanism.

[0034] Furthermore, after the piezoelectric actuator 10 generates an output, causing the output end face 5 of the mechanism to shift, the mechanical properties of beam 3 and beam 6 will change. If an external displacement load is applied to the output end face 5 of the mechanism at this time, the constant force characteristics will also change, specifically manifested as changes in the constant force value and the constant force movement range. Thus, the active constant force value adjustment function of the compliant constant force mechanism is realized.

[0035] When using the designed compliant constant force mechanism to build a clamping mechanism or other actuator, simply connect the clamping mechanism or other actuator to the external guide mechanism 14 via the adapter plate 15 to complete the construction of the required system, for example. Figure 4 , Figure 5 As shown. It should be noted that the guide mechanism 14 can be of any type, as long as it can provide the opening and closing motion of the designed mechanism relative to the axis. A hypothetical part 16 is placed between the output end faces 5 of the two constant force mechanisms. When the compliant constant force mechanism of the embedded actuator is driven to close towards the center by the external guide mechanism 14, the output end face 5 gradually exhibits a constant force effect after contacting part 16, thus completing constant force clamping. When equal and constant voltage signals are provided to the two piezoelectric actuators 10, the compliant constant force mechanisms of the embedded actuators on both sides will produce equal deformation, and the constant force value will change synchronously, thereby achieving adjustable constant force clamping.

[0036] When the piezoelectric actuators 10 on both sides are supplied with varying voltage signals of the same amplitude but with a phase difference, the output end faces 5 of the mechanism on both sides will produce asynchronous displacements, thereby causing the clamped part 16 to periodically offset relative to both sides of the clamping mechanism axis. In particular, providing part 16 with a single degree of freedom periodic offset allows part 16 to have additional motion capability during assembly. When part 16 becomes stuck during assembly due to inaccurate alignment, this additional motion capability will help part 16 to disengage from the stuck state and thus re-align. In addition, the constant force characteristic of the mechanism can also protect the operated part 16 from damage during periodic offset.

[0037] This invention redesigns a double-beam connected constant force mechanism, innovatively placing the bridge amplification mechanism at the end of one of the beams, thus creating a compact and novel compliant constant force mechanism. This compliant mechanism also possesses the advantages of miniaturization, active end offset, and passively adjustable constant force output. By configuring the same compliant constant force mechanism, a usable compliant constant force clamping mechanism can be constructed. By applying different voltage signals to the piezoelectric actuator 10 in the mechanism, the opening and closing of the clamping jaws, the adjustment of the output constant force, and the periodic offset of the component 16 can be achieved respectively.

[0038] Existing technologies achieve safe operation and pose adjustment of part 16 by adding force sensors, micro-vision servo systems, and precision positioning platforms to the micro-assembly system. This invention, however, controls the operating force through a constant force effect provided by a mechanism, and achieves automatic alignment of the micro-part 16 by providing controllable periodic offsets through part 16. The solution provided by this invention effectively reduces the dependence of the micro-part 16 assembly system on force feedback systems and precision positioning servo systems.

[0039] In summary, the compliant constant force mechanism provided by this invention is not only compact in size and can provide active offset and constant force adjustment functions, but also can achieve adaptive adjustment of the position and angle of part 16 during micro-assembly through a special loading method, thereby effectively improving the performance of operation.

[0040] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A compliant constant force mechanism, characterized in that: Includes a base, a double-beam connected constant force mechanism, a bridge displacement amplifier, and a piezoelectric actuator; The bridge displacement amplifier is connected to the base, the piezoelectric driver is located inside the bridge displacement amplifier, and the bridge displacement amplifier has an output port. The double-beam connected constant force mechanism is connected to the base and the output port of the bridge displacement amplifier respectively, and the end of the double-beam connected constant force mechanism is provided with a mechanism output end face; The double-beam connected constant force mechanism includes a first beam, a flexible beam connector, and a second beam. The first beam and the second beam are arranged at intervals. One end of the first beam is connected to the base, and one end of the second beam is connected to the output port of the bridge displacement amplifier. The other ends of the first beam and the second beam are both connected to the flexible beam connector. The output end face of the mechanism is located at the end of the flexible beam connector. Both beam No. 1 and beam No. 2 are compliant leaf-shaped beams; The piezoelectric actuator output generates a first-stage amplified displacement at the output port through a bridge displacement amplifier; the displacement at the output port is amplified a second stage at the output end face of the mechanism through a double-beam connected constant force mechanism. The bridge displacement amplifier includes a short flexible beam, an output port and a fixed port arranged opposite to each other; the fixed port is connected to the base; equivalent rigid connecting bodies are provided on both sides of the output port and the fixed port, and the output port and the fixed port are connected to the equivalent rigid connecting bodies through the short flexible beam. The piezoelectric actuator is located between the two equivalent rigid connecting bodies.

2. The compliant constant force mechanism according to claim 1, characterized in that: The base is provided with a short straight groove through hole, which is used to connect with the interface of the external guide mechanism.

3. A clamping mechanism, characterized in that: It includes two guiding mechanisms and two compliant constant force mechanisms as described in claim 1 or 2. The two compliant constant force mechanisms are respectively connected to the two guiding mechanisms in a one-to-one correspondence. The guiding mechanisms are used to provide opening and closing movements between the two compliant constant force mechanisms. A clamping opening for clamping parts is formed between the mechanism output end faces of the two compliant constant force mechanisms.

4. A clamping method, characterized in that: The clamping mechanism according to claim 3 includes the following steps: When the two compliant constant force mechanisms are driven to close by the guide mechanism, the output end faces of the two compliant constant force mechanisms contact the parts and complete the constant force clamping.

5. The clamping method according to claim 4, characterized in that: When equal and constant voltage signals are provided to the piezoelectric actuators of the two compliant constant force mechanisms, the two compliant constant force mechanisms produce equal deformations, and the constant force values ​​change synchronously, thereby achieving adjustable constant force clamping.

6. The clamping method according to claim 4, characterized in that: When a piezoelectric actuator of two compliant constant force mechanisms is supplied with a voltage signal of the same amplitude but with a phase difference, the output end faces of the two compliant constant force mechanisms will produce asynchronous displacements, causing the clamped parts to shift periodically.

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