Hybrid driven compliant microgripping mechanism and method thereof

Abstract

The application relates to a hybrid driving compliant micro-gripping mechanism and a method thereof, which comprises a guide mechanism and two jaw structures; the guide mechanism is provided with a shape memory alloy wire and two output ports, the distance between the two output ports is adjusted by the shape memory alloy wire; one end of each of the two jaw structures is connected to the two output ports of the guide mechanism one by one, and the other end of each of the two jaw structures is provided with a part clamping end face; the jaw structure is provided with a piezoelectric driver, and the distance between the two part clamping end faces is adjusted by the piezoelectric driver. The mechanism inherits the advantages of the shape memory alloy wire, such as small volume, large output stroke, and the piezoelectric ceramic, such as fast response speed and high motion precision, and can realize high-precision adjustment of the position of a part, has large output stroke and fast response speed, and can ensure that the micro-gripping mechanism has large compatibility and controllability in the operation of a micro part.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compliant mechanism and micro parts assembly, in particular to a hybrid-driven compliant micro-gripping mechanism and method thereof. BACKGROUND

[0002] Compliant mechanisms transfer force and energy through elastic deformation, and thus transfer part or all of the motion. Compliant mechanisms, coupled with actuators that are also easily miniaturized, such as piezoelectric actuators, shape memory alloys, magnetic actuators, voice coil motors, etc., can exhibit great application potential in precision engineering, biological engineering, micro-electro-mechanical systems, etc.

[0003] Compliant gripping mechanisms are the most commonly used micro-assembly actuators. Piezoelectric ceramics are often used as actuators in research, coupled with various types of displacement amplification mechanisms designed by compliant mechanisms, such as bridge-type displacement amplification mechanisms, lever-type displacement amplification mechanisms, Scott-Russell mechanisms, etc., to generate closing or opening motion of the mechanism end relative to the axis of the part, and thus complete the gripping of micro parts. For compliant gripping mechanisms, on the one hand, it is necessary to have a large enough gripping stroke to meet the needs of different size parts, and on the other hand, it is necessary to have enough motion accuracy to facilitate the control of gripping force. However, existing solutions have not achieved these two goals well, such as the following two papers.

[0004] [1] Wang R, Zhang X, Zhu B, et al. A Topology-Optimized Compliant Microgripper With Replaceable Modular Tools for Cross-Scale Microassembly[J]. IEEE / ASME Transactions on Mechatronics, 2023, 1-12.

[0005] In this paper, a compliant amplification mechanism is generated using topology optimization, coupled with two piezoelectric actuators to achieve a good balance of structure size, large stroke, and high bandwidth. The study also designs replaceable jaw structures, which to some extent expands the application of a single gripper. However, the mechanism shown in this paper has the shortcomings of insufficient output stroke and insufficient compatibility, although it has fast response speed and small mechanism size.

[0006] [2]Xu H, Zhang X, Wang R, et al. Design of an SMA-driven compliant constant-force gripper based on a modified chained pseudo-rigid-body model[J]. Mechanism and Machine Theory. 2023, 187:105371.

[0007] In this paper, a compliant gripper with high stroke is constructed by using shape memory alloy wire to drive the compliant mechanism. In addition, an asymmetric constant force mechanism is constructed in this paper, and two constant force mechanisms are arranged by mirror image to realize constant force clamping, which avoids the introduction of complex force control system in the process of operation. However, it has the disadvantages of slow execution speed and lack of pose control ability. SUMMARY

[0008] In view of the problems existing in the prior art, the purpose of the present application is to provide a hybrid driving compliant micro-gripping mechanism and method, which has a large output stroke and a fast response speed, and can ensure that the micro-gripping mechanism has a large compatibility and controllability in the operation of micro parts.

[0009] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0010] A hybrid driving compliant micro-gripping mechanism, comprising a guide mechanism and two jaw structures;

[0011] The guide mechanism is provided with a shape memory alloy wire and two output ports, and the distance between the two output ports is adjusted by the shape memory alloy wire;

[0012] One end of each of the two jaw structures is connected to the two output ports of the guide mechanism one by one, and the other end of each of the two jaw structures is provided with a part clamping end face;

[0013] The jaw structure is provided with a piezoelectric actuator, and the distance between the two part clamping end faces is adjusted by the piezoelectric actuator.

[0014] Further, the guide mechanism comprises a guide base, the guide base is provided with a U groove bearing, the shape memory alloy wire is wound on the U groove bearing, and the two ends of the shape memory alloy wire are fixed to the two output ports of the guide mechanism.

[0015] Further, a guide beam is arranged between each of the two output ports and the guide base, one end of each guide beam is connected to the guide base, and the other end is connected to the output port.

[0016] Further, the distance between the two ends of the two guide beams is greater than the distance between the other two ends of the two guide beams.

[0017] Further, the guide beam comprises a guide No. 1 beam and a guide No. 2 beam, and the guide No. 1 beam and the guide No. 2 beam are arranged in a spaced and non-parallel manner.

[0018] Further, a long straight slot-shaped through hole is arranged on the guide base, and the long straight slot-shaped through hole is used for adapting to the installation of the U-shaped groove bearing.

[0019] Further, the jaw structure comprises a jaw base, a flexible gap-shaped hinge and an equivalent rigid component connected in sequence, the jaw base is connected to the output port of the guide mechanism, the mounting cavity of the piezoelectric driver is formed between the jaw base and the equivalent rigid component, and the part clamping end face is located at the end of the equivalent rigid component.

[0020] A hybrid driving flexible micro-clamping method comprises the following steps,

[0021] The shape memory alloy wire is used to drive and adjust the distance between the two output ports of the guide mechanism, so as to adjust the distance between the two jaw structures.

[0022] The piezoelectric driver is used to drive and adjust the distance between the part clamping end faces of the two jaw structures, so as to clamp the workpiece by the two part clamping end faces.

[0023] Further, the implementation manner of adjusting the distance between the two output ports of the guide mechanism by the shape memory alloy wire is that,

[0024] When the shape memory alloy wire is powered and heated to generate a contraction effect, equal driving forces are generated on both sides of the guide mechanism, the guide beam is correspondingly deformed and transmits force and movement to the output port, there is a certain angle between the force direction and the displacement direction of the output port, so that the two output ports are respectively opened to both sides and the displacement amount is greater than the contraction amount of the shape memory alloy wire; after the shape memory alloy wire is powered off, the deformation potential energy of the guide beam drives the shape memory alloy wire to restore the original length, and the two output ports are reset.

[0025] Further, the implementation manner of clamping the workpiece by the two part clamping end faces is that,

[0026] The same voltage signal is provided to the two piezoelectric drivers to clamp the workpiece by the two part clamping end faces, or different voltage signals are provided to the two piezoelectric drivers to make the clamped workpiece produce a deviation.

[0027] In general, the present application has the following advantages:

[0028] 1. The mixed drive is adopted, the mixed drive compliant micro-gripping mechanism inherits all the advantages of the selected driver, and further realizes the required gripping mechanism performance, and has stronger engineering application value. In the prior art, only a single type of driver is generally selected, and the compliant mechanism is configured to only consider the optimization of a single index, and the overall improvement of the gripper function is not considered, and the mechanism performance is seriously limited by the performance of the single driver.

[0029] 2. The proposed compliant double-sided guide structure more reasonably utilizes the characteristics of the shape memory alloy wire, and the shape memory alloy wire is wound in the guide mechanism according to the specified path, and the compact structure and the amplified displacement are realized. In the prior art, the shape memory alloy wire is often directly arranged in the direction required by the mechanism to move, so that the displacement amplification characteristic is not realized, and the size of the mechanism is difficult to reduce.

[0030] 3. The compliant micro-gripping mechanism is designed by combining the shape memory alloy wire and the piezoelectric ceramic, so that the designed mechanism inherits the advantages of small volume, large output stroke of the shape memory alloy wire and fast response speed and high motion precision of the piezoelectric ceramic, and can realize high-precision adjustment of the position of the part. The prior art does not integrate the advantages of the two driving technologies, and the designed gripper still has defects in mechanism size, stroke, and motion precision, in addition, the existing compliant gripper mostly only has the gripping function, and does not have the function of simultaneously realizing gripping and part position adjustment through mixed driving.

[0031] In summary, the present application has a large output stroke and a fast response speed, and can ensure that the micro-gripping mechanism has greater compatibility and controllability in the operation of small parts. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a schematic diagram of the three-dimensional structure of the mixed drive compliant micro-gripping mechanism.

[0033] Figure 2 It is a schematic diagram of the top view of the mixed drive compliant micro-gripping mechanism.

[0034] Figure 3 It is a schematic diagram of the plane structure of the jaw structure.

[0035] Figure 4 It is a schematic diagram of the plane structure of the guide mechanism.

[0036] In the figure:

[0037] 1-Guiding mechanism, 2-Shape memory alloy wire, 3-U-groove bearing, 4-Adapter plate, 5-Piezoelectric actuator, 6-Jaw structure, 7-Screw and nut, 13-Jaw base, 14-Compliant notch hinge, 15-Equivalent rigid component, 16-Part clamping end face, 17-Output end face, 18-Guiding base, 19-Long straight groove through hole, 20-Round hole, 21-Guiding beam 1, 22-Guiding beam 2, 23-Output port, 24-Connecting hole, 25-Equivalent loading point, 26-Base fixing hole. Detailed Implementation

[0038] The present invention will now be described in further detail.

[0039] like Figure 1 , Figure 2 As shown, a hybrid driven compliant micro-gripping mechanism includes a guide mechanism 1 and two jaw structures 6;

[0040] The guide mechanism 1 is provided with a shape memory alloy wire 2 and two output ports 23. The distance between the two output ports 23 is adjusted by the shape memory alloy wire 2.

[0041] One end of each of the two jaw structures 6 is connected to one of the two output ports 23 respectively, and the other end of each of the two jaw structures 6 is provided with a part clamping end face 16.

[0042] Each jaw structure 6 is equipped with a piezoelectric actuator 5, and the distance between the two part clamping end faces 16 is adjusted by the piezoelectric actuator 5.

[0043] When clamping a workpiece, the distance between the two output ports 23 is first adjusted by the shape memory alloy wire 2, thereby opening the two jaw structures 6; then the distance between the two part clamping end faces 16 is adjusted by the piezoelectric actuator 5 in the jaw structure 6, so that the workpiece can be clamped by the two part clamping end faces 16.

[0044] Specifically, the guide mechanism 1 includes a guide base 18, the guide base 18 is provided with a U-groove bearing 3, the shape memory alloy wire 2 is wound around the U-groove bearing 3, and the two ends of the shape memory alloy wire 2 are respectively fixed to the two output ports 23 of the guide mechanism 1.

[0045] refer to Figure 4In this embodiment, the guide base 18 is provided with four through holes for mounting the U-groove bearings 3, and both surfaces of the guide base 18 are provided with four U-groove bearings 3. On each surface, four U-groove bearings 3 are sequentially wound with a shape memory alloy wire 2. The four through holes for mounting the U-groove bearings 3 include two round holes 20 and two long straight slot-shaped through holes 19. The two long straight slot-shaped through holes 19 are used to adjust the positions of the two U-groove bearings 3 fixed thereon, so as to keep the shape memory alloy wire 2 in a tensioned state. The guide base 18 is further provided with three base fixing holes 26. The two output ports 23 are provided with four connecting holes 24 for connecting with the jaw structure 6 through the adapter plate 4.

[0046] Two guide beams are respectively arranged between the two output ports 23 and the guide base 18. One end of each guide beam is connected to the guide base 18, and the other end is connected to the output port 23. When the shape memory alloy wire 2 outputs a drive, the guide beams will deform correspondingly, and transmit the force and movement to the output port 23 after amplification, so as to generate an output with a larger stroke.

[0047] The distance between one end of the two guide beams is greater than the distance between the other end of the two guide beams.

[0048] The guide beams include a guide No. 1 beam 21 and a guide No. 2 beam 22, which are arranged in a spaced and non-parallel manner.

[0049] By adopting such a configuration, compared with the conventional parallel beam type guide mechanism, the non-parallel beam type guide mechanism can effectively reduce the parasitic displacement and parasitic rotation of the output port 23 under the action of the output force of the shape memory alloy wire 2, which is conducive to improving the clamping stability of the micro-gripping mechanism and maintaining higher clamping precision.

[0050] Reference Figure 3 The jaw structure 6 includes a jaw base 13, a compliant notched hinge 14, and an equivalent rigid component 15. The jaw base 13 has two jaw through holes for connecting with the output port 23 of the guide mechanism 1 through the adapter plate 4 and the screw nut 7; the compliant notched hinge 14 is the main flexible deformation component in the jaw structure 6, and is used to transmit the displacement and force output by the piezoelectric driver 5; the end of the equivalent rigid component 15 is a part clamping end face 16; the jaw base 13 and the equivalent rigid component 15 enclose to form a mounting cavity for the piezoelectric driver 5, i.e., the area specified by the two ceramic output end faces 17. When the piezoelectric driver 5 generates displacement / force at the ceramic output end face 17, the compliant notched hinge 14 will deform, and the output of the driver will generate an amplified displacement at the part clamping end face 16 by means of the lever effect, and the displacement direction is upward. Since the piezoelectric ceramic has the advantages of fast driving frequency and high movement precision, the jaw structure 6 has the ability to generate fast and high-precision short-range displacement output at the part clamping end face 16.

[0051] Reference Figure 2 With the shape memory alloy wire 2 being heated to generate a contraction effect by connecting the electric current, the equivalent load points 25 on both sides of the guide mechanism 1 will generate the same driving force, and the two guide beams will correspondingly generate deformation to transmit the movement, so as to make the two output ports 23 respectively open to both sides. At this time, the force direction and the displacement direction of the output port 23 have a certain angle (for example, the force direction is indicated by the arrow), which constitutes a normal displacement amplification configuration, so that the output port 23 has a larger displacement than the contraction of the shape memory alloy wire 2. The amplified displacement will eventually make the jaw structure 6 open to both sides, so as to realize the opening of the clamping mechanism. Correspondingly, when the shape memory alloy wire 2 is disconnected from the electric current, the clamping mechanism will automatically return to the initial position by relying on the internal energy stored in the guide beam. Due to the large deformation and large structure flexibility of the shape memory alloy wire 2, the guide mechanism 1 has the characteristics of compact structure and the ability to generate long-range displacement output at the output port 23 by means of the shape memory alloy wire 2 in the bending configuration. Figure 4

[0052] A hybrid driving compliant micro-clamping method, comprising the following steps,

[0053] Adjusting the distance between the two output ports 23 of the guide mechanism 1 by the shape memory alloy wire 2, and then adjusting the distance between the two jaw structures 6.

[0054] Adjusting the distance between the part clamping end faces 16 of the two jaw structures 6 by the piezoelectric driver 5, and then clamping the workpiece by the two part clamping end faces 16.

[0055] Further, the implementation manner of adjusting the distance between the two output ports 23 of the guide mechanism 1 by the shape memory alloy wire 2 is that,

[0056] When the shape memory alloy wire 2 is heated to generate a contraction effect by connecting the electric current, the equivalent load points 25 on both sides of the guide mechanism 1 will generate the same driving force, and the guide beams will correspondingly generate deformation and transmit the force and movement to the output ports 23. The force direction and the displacement direction of the output port 23 have a certain angle, so as to make the two output ports 23 respectively open to both sides and the displacement is greater than the contraction of the shape memory alloy wire 2. When the shape memory alloy wire 2 is disconnected from the electric current, the elastic potential energy of the guide beam will drive the shape memory alloy wire 2 to restore the original length, and the two output ports 23 will be reset.

[0057] Further, the implementation manner of clamping the workpiece by the two part clamping end faces 16 is that,

[0058] The same voltage signal is provided to the two piezoelectric drivers 5 to realize the clamping of the workpiece by the two part clamping end faces 16, or different voltage signals are provided to the two piezoelectric drivers 5 to make the clamped workpiece produce a deviation.​

[0059] In summary, the hybrid driving compliant clamping mechanism of the present application combines the advantages of different drivers, effectively achieving the balance of small size, large stroke, high execution precision / speed of the mechanism, and also realizing the adjustment of the position of the parts in the micro-assembly process, thereby effectively improving the performance of the clamping mechanism in the clamping of cross-scale micro-parts, and ensuring that the micro-clamping mechanism has greater compatibility and controllability in the operation of micro-parts.

[0060] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A hybrid-driven compliant micro-gripping mechanism, characterized in that: Includes a guiding mechanism and two jaw structures; The guiding mechanism is equipped with a shape memory alloy wire and two output ports, and the distance between the two output ports is adjusted by the shape memory alloy wire. One end of each of the two jaw structures is connected to one of the two output ports of the guide mechanism, and the other end of each of the two jaw structures is provided with a part clamping end face. Each jaw structure is equipped with a piezoelectric actuator, and the distance between the two clamping end faces of the parts is adjusted by the piezoelectric actuator. The guiding mechanism includes a guiding base, which is equipped with a U-groove bearing. A shape memory alloy wire is wound around the U-groove bearing, and the two ends of the shape memory alloy wire are respectively fixed to the two output ports of the guiding mechanism. Guide beams are provided between the two output ports and the guide base, with one end of each guide beam connected to the guide base and the other end connected to the output port; The distance between one end of the two guide beams is greater than the distance between the other ends of the two guide beams; The guide base is provided with a long straight groove through hole, which is used to accommodate the installation of U-groove bearings; The jaw structure includes a jaw base, a compliant notch hinge, and an equivalent rigid component connected in sequence. The jaw base is connected to the output port of the guide mechanism. The jaw base and the equivalent rigid component enclose and form a mounting cavity for the piezoelectric actuator. The part clamping end face is located at the end of the equivalent rigid component.

2. The hybrid-driven compliant micro-gripping mechanism according to claim 1, characterized in that: The guide beams include guide beam 1 and guide beam 2, which are arranged alternately and not in parallel.

3. A hybrid-driven compliant micro-gripping method, characterized in that: The hybrid-driven compliant micro-gripping mechanism according to claim 1 or 2 includes the following steps: The distance between the two output ports of the guide mechanism is adjusted by using a shape memory alloy wire to drive the adjustment mechanism, thereby adjusting the distance between the two jaw structures. The distance between the two clamping end faces of the two jaw structures is adjusted by using a piezoelectric actuator, thereby enabling the two clamping end faces to clamp the workpiece.

4. The hybrid-driven compliant micro-gripping method according to claim 3, characterized in that: The method for achieving the adjustment of the distance between the two output ports of the guide mechanism using a shape memory alloy wire is as follows: When the shape memory alloy wire is heated by electricity and produces a contraction effect, an equal driving force is generated on both sides of the guide mechanism. The guide beam deforms accordingly and transmits force and movement to the output port. There is a certain angle between the force direction and the displacement direction of the output port, which causes the two output ports to open to both sides and the displacement is greater than the contraction of the shape memory alloy wire. When the shape memory alloy wire is de-energized, the deformation energy of the guide beam drives the shape memory alloy wire to return to its original length and resets the two output ports.

5. The hybrid-driven compliant micro-gripping method according to claim 3, characterized in that: The method for clamping the workpiece using the two clamping end faces is as follows: The same voltage signal can be provided to two piezoelectric actuators to achieve clamping of the workpiece by the clamping ends of the two parts, or different voltage signals can be provided to two piezoelectric actuators to cause the clamped workpiece to shift.

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