Compliant constant force mechanism, clamping mechanism and clamping method of clamping mechanism

Abstract

The invention relates to a compliant constant force mechanism, a clamping mechanism and a clamping method of the clamping mechanism. The compliant constant force mechanism comprises a base, a double-beam connection type constant force mechanism, a bridge type displacement amplifier and a piezoelectric actuator. The bridge type displacement amplifier is connected to the base, the piezoelectric actuator is arranged in the bridge type displacement amplifier, and the bridge type displacement amplifier is provided with an output port; the double-beam connection type constant force mechanism is connected to the base and an output port of the bridge type displacement amplifier, and a mechanism output end face is arranged at the tail end of the double-beam connection type constant force mechanism. Wherein the output of the piezoelectric actuator generates first-stage amplified displacement at an output port through the bridge type displacement amplifier; and the displacement at the output port is subjected to second-stage amplification at the output end face of the mechanism through the double-beam connection type constant force mechanism. The driving structure is arranged in the flexible clamping mechanism, periodic offset of parts is achieved, self-adaptive alignment assembly of misaligned parts can be achieved by means of the active and controllable periodic movement, and higher engineering application value is achieved.

Description

Technical Field

[0001] The present invention relates to the technical fields of compliant mechanism technology and micro-component assembly technology, and specifically provides a compliant constant force mechanism, a clamping mechanism and a clamping method thereof. Background Art

[0002] A compliant mechanism transfers force and energy through elastic deformation to transfer part or all of the motion. Therefore, the compliant mechanism has the ability to sense and control force.

[0003] A compliant clamping mechanism is one of the most commonly used micro-assembly actuators. Micro-assembly often requires precise assembly of a series of heterogeneous and different micro-components with micron-level accuracy. However, the existing micro-assembly technical solutions have not achieved a good balance in ensuring the safety, reliability of operations, and the convenience of the system.

[0004] [1] Xu H, Zhang X, Zang H, et al. An SMA-based compliant adjustable constant force gripper for microassembly[J]. International Journal of Mechanical Sciences, 2024, 278: 109430. In this paper, an asymmetric constant force mechanism was constructed. Constant force clamping was achieved by mirror-arranging two constant force mechanisms. The output constant force was adjusted by replacing the beam in the constant force mechanism with a shape memory alloy beam, avoiding the introduction of a complex force control system during the operation. However, it has the disadvantages of slow execution speed and lack of pose adjustment ability. The reason for its slow execution speed is that a shape memory alloy sheet is used for driving, and the slow heating-cooling rate restricts the reaction rate of the mechanism. The reason for the lack of pose adjustment ability is that no relevant optimization work has been carried out in this research, and it still has a strong dependence on the visual servo positioning system.

[0005] [2]Baksys B, Baskutiene J, and Baskutis S. The vibratory alignment ofthe parts in roboticassembly[J]. Industrial Robot: An International Journal.2017, 44(6):720-729. This study introduced a method for aligning parts during macro-scale part assembly. By applying periodic vibration signals to the parts to be assembled using a robotic arm and a telecentric flexible gripper, the parts can be aligned. The study showed that appropriate vibration signals can effectively improve the alignment efficiency of parts and reduce the assembly force to a certain extent. However, this work belongs to the scope of macro-scale operations and uses a robotic arm and a large fixed base during the operation. In this study, it is difficult to directly apply the research object, research content, or the configuration used to the field of micro-part assembly. In addition, the device built in this work still heavily relies on the multi-dimensional force sensing system included because there are no components in the involved system that can achieve the force adjustment function. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the object of the present invention is to provide a compliant constant force mechanism, a clamping mechanism and a clamping method thereof, which can effectively reduce the control difficulty of the micro-assembly system and improve the precision assembly efficiency of micro-parts.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A compliant constant force mechanism includes a base, a double-beam connection type constant force mechanism, a bridge type displacement amplifier, and a piezoelectric actuator; The bridge type displacement amplifier is connected to the base, the piezoelectric actuator is arranged inside the bridge type displacement amplifier, and the bridge type displacement amplifier is provided with an output port; The double-beam connection type constant force mechanism is respectively connected to the base and the output port of the bridge type displacement amplifier, and the end of the double-beam connection type constant force mechanism is provided with an end face of the mechanism output; Wherein, the output of the piezoelectric actuator generates a first-stage amplified displacement at the output port through the bridge type displacement amplifier; the displacement at the output port obtains a second-stage amplification at the end face of the mechanism output through the double-beam connection type constant force mechanism.

[0008] Further, the double-beam connection type constant force mechanism includes a first beam, a flexible beam connection body, 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, one end of the second beam is connected to the output port of the bridge type displacement amplifier, and the other ends of the first beam and the second beam are both connected to the flexible beam connection body. The end face of the mechanism output is located at the end of the flexible beam connection body.

[0009] Further, both the first beam and the second beam are compliant leaf-shaped beams.

[0010] Further, the bridge-type displacement amplifier includes a short flexible beam, output ports and fixed ports arranged oppositely; the fixed ports are connected to the base; equivalent rigid connectors are respectively arranged on both sides of the output ports and the fixed ports, and both the output ports and the fixed ports are connected to the equivalent rigid connectors through the short flexible beam, and the piezoelectric actuator is arranged between the two equivalent rigid connectors.

[0011] Further, a short straight groove-shaped through hole is provided in the base, and the short straight groove-shaped through hole is used to connect with an external guiding mechanism interface.

[0012] A clamping mechanism includes two guiding mechanisms and two compliant constant-force mechanisms. 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 an opening and closing movement between the two compliant constant-force mechanisms, and a clamping opening for clamping a part 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 guiding mechanisms, after the mechanism output end faces of the two compliant constant-force mechanisms contact the part, constant-force clamping is completed.

[0014] Further, 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 generate equal deformations, and the constant-force values change synchronously, thereby realizing adjustable constant-force clamping.

[0015] Further, when changing voltage signals with the same amplitude but a phase difference are provided to the piezoelectric actuators of the two compliant constant-force mechanisms, the mechanism output end faces of the two compliant constant-force mechanisms generate asynchronous displacements, causing the clamped part to generate periodic offsets.

[0016] Generally speaking, the present invention has the following advantages: 1. By arranging a driving structure in the compliant clamping mechanism and relying on the transmission of the compliant mechanism, periodic offset of the part is realized. With this active and controllable periodic movement, adaptive alignment assembly of misaligned parts can be achieved, which has stronger engineering application value. Existing compliant micro-clamping mechanisms have not considered arranging additional actuators in the mechanism to make the part generate a similar periodic movement and do not have the ability of micro-assembly automatic alignment; existing strategies for achieving part alignment by providing periodic vibrations still remain at the macroscopic scale, and the source of periodic vibrations is the robotic arm or the vibration generator rather than the clamping mechanism, and the periodic movement generated for the part is not direct and controllable enough. In addition, the existing technology does not include a strategy for protecting the part during the periodic movement by using a constant-force mechanism.

[0017] 2. The proposed asymmetric compliant constant force structure is additionally embedded with a bridge-type displacement amplification mechanism and a piezoelectric actuator, which has high-frequency active displacement output and passive adjustable constant force capabilities, and can be directly used as a micro part gripper. In the existing constant force mechanism technologies, symmetric compliant structure configurations are generally used, which are not convenient for direct application as micro gripper mechanisms; the existing adjustable constant force structures only have simple constant force value adjustment capabilities, but have the disadvantage of slow adjustment speed because they utilize too many external structures or rely on the stiffness change of materials to achieve constant force adjustment; most of the existing piezoelectric ceramic-driven compliant mechanisms only have displacement and force output capabilities, have not considered the problem of adjustable constant force gripping, and do not have force self-adaptive capabilities.

[0018] 3. The novel structure of the double-beam connection type constant force mechanism integrated with a bridge-type displacement amplification mechanism not only utilizes the constant force output function of the double-beam connection type constant force mechanism, but also utilizes its displacement amplification ability at special sites to achieve a miniaturized and high amplification ratio compliant structure. Most of the conventional schemes only utilize repetitive and bulky displacement amplification mechanisms to achieve the amplification of the mechanism output, and it is difficult to miniaturize the volume. Brief Description of the Drawings

[0019] Figure 1 It is a schematic plan view of a compliant constant force mechanism embedded with a piezoelectric actuator.

[0020] Figure 2 It is a schematic three-dimensional view of a compliant constant force mechanism embedded with a piezoelectric actuator.

[0021] Figure 3 It is a schematic plan view of a bridge-type displacement amplifier.

[0022] Figure 4 It is a schematic three-dimensional view of a gripping mechanism.

[0023] Figure 5 It is a schematic plan view of a gripping mechanism.

[0024] In the figure: 1 - Base, 2 - Short straight groove-shaped through hole, 3 - First beam, 4 - Flexible beam connection body, 5 - Mechanism output end face, 6 - Second beam, 7 - Output port, 8 - Bridge-type displacement amplifier, 9 - Ceramic output end face, 10 - Piezoelectric actuator, 11 - Short flexible beam, 12 - Equivalent rigid connection body, 13 - Fixed port, 14 - Guide mechanism, 15 - Adapter plate, 16 - Part. Detailed Description of the Invention

[0025] The following will further elaborate on the present invention in detail.

[0026] As shown in Figure 1 、 Figure 2As shown in the figure, a compliant constant force mechanism embedded with a piezoelectric actuator includes a base 1, a double-beam connection type constant force mechanism, a bridge type displacement amplifier 8, and a piezoelectric actuator 10.

[0027] Specifically, referring to Figures 1 to 4 , the constituent units are: a base 1, a first beam 3, a flexible beam connector 4, a second beam 6, a bridge type displacement amplifier 8, and a piezoelectric actuator 10.

[0028] Among them, two short straight groove through-holes 2 are provided in the base 1 for connecting to an external guiding mechanism 14 through an 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 guiding mechanism 14.

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

[0030] The first beam 3, the flexible beam connector 4, and the second beam 6 together constitute a double-beam connection type constant force mechanism. When it is assumed that both the left sides of the first beam 3 and the second beam 6 are fixed constraints, and the structure is subjected to an external displacement load at the mechanism output end face 5, the first beam 3 and the second beam 6 will produce a buckling effect during the bending deformation process, and then a constant force motion characteristic will be generated at the mechanism output end face 5, thereby realizing the constant force function of the mechanism.

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

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

[0033] Among them, 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, the short flexible beams 11 are deformed, and then the output port 7 is driven to move downward. The output of the piezoelectric actuator 10 will generate a first-stage amplified displacement at the output port 7 with the help of the bridge type displacement amplifier 8; the displacement at the output port 7 will be second-stage amplified at the mechanism output end face 5 with the help of the double-beam connection type constant force mechanism. The direction of the amplified displacement is as Figure 1 indicated by the arrow in the figure. Thus, the active offset function of the compliant constant force mechanism is realized.

[0034] In addition, after the piezoelectric actuator 10 generates an output and causes the output end face 5 of the mechanism to deflect, the mechanical properties of the first beam 3 and the second beam 6 will change. If an external displacement load is applied at the output end face 5 of the mechanism at this time, the generated constant force characteristics will also change, specifically manifested as changes in the constant force value and the constant force motion 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 actuating mechanisms, only by connecting the clamping mechanism or other actuating mechanisms to the external guiding mechanism 14 through the adapter plate 15 can the construction of the required system be completed. For example Figure 4 、 Figure 5 as shown. It should be noted that the guiding 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. There is a hypothetical part 16 between the output end faces 5 of the two constant force mechanisms. When the compliant constant force mechanism with an embedded actuator is driven by the external guiding mechanism 14 to close towards the center, the constant force effect will gradually appear after the output end face 5 of the mechanism contacts the part 16, that is, the constant force clamping is completed. When equal and constant voltage signals are provided to the two piezoelectric actuators 10, the compliant constant force mechanisms with embedded actuators on both sides will produce equal deformations, and the constant force values will also change synchronously. Thus, adjustable constant force clamping can be achieved.

[0036] When changing voltage signals with the same amplitude but a phase difference are provided to the piezoelectric actuators 10 on both sides, the output end faces 5 on both sides will produce asynchronous displacements, and then the clamped part 16 will produce periodic offsets on both sides of the axis of the clamping mechanism. In particular, providing a single-degree-of-freedom periodic offset to the part 16 can endow the part 16 with additional motion capabilities during the assembly process. When the part 16 gets stuck during the assembly process due to inaccurate pose alignment, such additional motion capabilities will help the part 16 get out of the stuck state and then complete the alignment again. In addition, the constant force characteristics of the mechanism can also protect the part 16 being operated from being damaged during the periodic offset process.

[0037] The present invention redesigned the double-beam connection type constant force mechanism, innovatively arranged the bridge amplification mechanism at the port of one of the beams of the double-beam connection type constant force mechanism, and constituted a new type of compliant constant force mechanism with a compact structure. Therefore, this compliant mechanism also has the advantages of miniaturization, active end offset, and passive adjustable constant force output at the same time. By configuring the same compliant constant force mechanism, a usable compliant constant force clamping mechanism can be built. By giving different voltage signals to the piezoelectric actuator 10 in the mechanism, the opening and closing of the jaws of the clamping mechanism, the adjustment of the output constant force, and the periodic offset of the part 16 can be realized respectively.

[0038] The existing technical means achieve the safe operation and pose adjustment of part 16 by adding a force sensor, a micro-vision servo system, and a precision positioning platform in the micro-assembly system. However, the present invention realizes the control of the operating force through the constant force effect provided by the mechanism, and realizes the automatic alignment of the micro part 16 by providing a controllable periodic offset through part 16. The solution provided by the present invention can effectively reduce the dependence of the micro part 16 assembly system on the force feedback system and the precision positioning servo system.

[0039] In summary, the compliant constant force mechanism provided by the present invention, in addition to being small in size and capable of providing functions of active offset and constant force adjustment, can also realize the adaptive adjustment of the position and angle of part 16 during the micro-assembly process through a special loading method, thereby effectively improving the performance of the operation.

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

Claims

1. A compliant constant force mechanism, characterized in that: It includes a base, a double-beam connection type constant force mechanism, a bridge type displacement amplifier, and a piezoelectric actuator; The bridge type displacement amplifier is connected to the base, the piezoelectric actuator is arranged inside the bridge type displacement amplifier, and the bridge type displacement amplifier is provided with an output port; The double-beam connection type constant force mechanism is respectively connected to the base and the output port of the bridge type displacement amplifier, and the end of the double-beam connection type constant force mechanism is provided with a mechanism output end face; Among them, the output of the piezoelectric actuator generates a first-stage amplified displacement at the output port through the bridge type displacement amplifier; the displacement at the output port obtains a second-stage amplification at the mechanism output end face through the double-beam connection type constant force mechanism.

2. The compliant constant force mechanism according to claim 1, wherein: The double-beam connection type constant force mechanism includes a first beam, a flexible beam connection body, 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, one end of the second beam is connected to the output port of the bridge type displacement amplifier, and the other ends of the first beam and the second beam are both connected to the flexible beam connection body. The mechanism output end face is located at the end of the flexible beam connection body.

3. The compliant constant force mechanism according to claim 2, characterized in that: Both the first beam and the second beam are compliant leaf-shaped beams.

4. A compliant constant force mechanism according to claim 1, characterized in that: The bridge type displacement amplifier includes a short flexible beam, an output port and a fixed port arranged oppositely; the fixed port is connected to the base; equivalent rigid connection bodies are respectively arranged on both sides of the output port and the fixed port, and both the output port and the fixed port are connected to the equivalent rigid connection bodies through the short flexible beam, and the piezoelectric actuator is arranged between the two equivalent rigid connection bodies.

5. A compliant constant force mechanism according to claim 1, characterized in that: A short straight groove type through hole is provided in the base, and the short straight groove type through hole is used to be connected with an external guiding mechanism interface.

6. A clamping mechanism, characterized in that: It includes two guiding mechanisms and two compliant constant force mechanisms according to any one of claims 1-5. The two compliant constant force mechanisms are respectively and correspondingly connected to the two guiding mechanisms. The guiding mechanism is used to provide an opening and closing movement between the two compliant constant force mechanisms, and a clamping port for clamping parts is formed between the mechanism output end faces of the two compliant constant force mechanisms.

7. A clamping method, characterized in that: Adopting a clamping mechanism according to claim 6, it includes the following steps: When the two compliant constant force mechanisms are driven to close by the guiding mechanism, the mechanism output end faces of the two compliant constant force mechanisms contact the part and then complete constant force clamping.

8. The clamping method according to claim 7, wherein: 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 generate equal deformations, and the constant force values change synchronously, thereby realizing adjustable constant force clamping.

9. The clamping method according to claim 7, characterized in that: When changing voltage signals with the same amplitude but a phase difference are provided to the piezoelectric actuators of the two compliant constant force mechanisms, the mechanism output end faces of the two compliant constant force mechanisms generate asynchronous displacements, causing the clamped part to generate periodic offsets.

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