Lockable linear motion joint based on a compliant mechanism and shape memory alloy

Abstract

The application relates to a lockable linear motion joint based on a compliant mechanism and a shape memory alloy, which comprises an outer tube, an inner rod, a pre-tightening screw, a compliant mechanism and a shape memory alloy composite actuator; the pre-tightening screw is installed at one end of the inner rod, and the compliant mechanism and the shape memory alloy composite actuator are both installed inside the inner rod; the inner rod is provided with a hole on the opposite surface of the output end of the compliant mechanism, which is used for the contact between the output end of the compliant mechanism and the outer tube; in a non-powered state, the motion joint is in a locked state; in a powered state, the shape memory alloy composite actuator is axially contracted, the pressure on both sides of the shaft is released, the deformation is recovered, and the motion joint is switched to an unlocked state. Compared with the prior art, the application has the advantages of simple structure, modularization and rapid installation, friction locking through the deformation of the compliant mechanism, simple and reliable control mode, and application to more reconfigurable mechanism application scenarios.

Description

Technical Field

[0001] This invention relates to the field of lockable joint mechanism technology, and in particular to a lockable linear motion joint based on a compliant mechanism and a shape memory alloy. Background Technology

[0002] Lockable joint mechanisms are widely used in reconfigurable robots and adaptive deformable mechanisms to achieve energy management or system motion reconfiguration. Modularly constructed reconfigurable robots can achieve various combinations of deformable structures using locking joints, while increasing the overall load-bearing capacity of the mechanism to adapt to more complex working environments and complete specialized tasks. Furthermore, lockable joint mechanisms can be applied in many other related fields, such as the system motion reconfiguration of small robots and space mechanisms in the aerospace field.

[0003] Numerous achievements have been made both domestically and internationally in the field of reconfigurable robots. Current research on reconfigurable robots is beginning to explore lightweight and high-load-bearing capabilities. Lockable joint mechanisms can provide good load-bearing capacity and stiffness during the deformation of reconfigurable robots while meeting dimensional and weight requirements, and can also minimize the overall structural and control complexity of the robot. However, existing locking mechanisms suffer from problems such as complex structure, large size and mass, difficulty in locking at any position, and significant application limitations.

[0004] Therefore, there is a lack of research and design on locking mechanisms for reconfigurable robots and related fields. There is an urgent need to study a lockable joint mechanism that is small in size, simple in structure, can adapt to deformation, and has load-bearing capacity. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a lockable linear motion joint based on a compliant mechanism and a shape memory alloy. By setting a compliant mechanism and a shape memory alloy composite actuator, the invention achieves a compact size of the motion joint, a simple and reliable control method, and excellent locking performance.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a lockable linear motion joint based on a compliant mechanism and a shape memory alloy, comprising an outer tube, an inner rod, a preload screw, a compliant mechanism, and a shape memory alloy composite actuator;

[0008] The inner rod, preload screw, compliant mechanism, and shape memory alloy composite actuator are all located inside the outer tube;

[0009] The preload screw is installed at one end of the inner rod, and the compliant mechanism and the shape memory alloy composite actuator are both installed inside the inner rod;

[0010] The inner rod has a hole on its surface opposite to the output end of the compliant mechanism, and the hole is used for the output end of the compliant mechanism to contact the outer tube.

[0011] In the normal state, i.e., without power, the joint is locked, the preload screw is tightened, and the compliant mechanism and the shape memory alloy composite actuator are axially compressed, causing the compliant mechanism to expand outward at both ends and contact the inner wall of the outer tube, resulting in compression and generating friction to keep the joint locked. In the energized state, the shape memory alloy composite actuator contracts axially, releasing the pressure on both sides of the compliant mechanism, thereby restoring the deformation of the compliant mechanism. The compliant mechanism separates from the inner wall of the outer tube at both ends, and the joint switches to the unlocked state.

[0012] Furthermore, the shape memory alloy composite actuator includes a custom-made gasket, a disc spring assembly, and a hollow guide tube;

[0013] The hollow guide tube passes through the disc spring assembly, and the customized gaskets pass through both ends of the hollow guide tube. The hollow guide tube is used for axial constraint.

[0014] Furthermore, the shape memory alloy composite actuator also includes a shape memory alloy wire bundle and a wire bundle crimping member, wherein the shape memory alloy wire bundle passes through the hollow guide tube;

[0015] The wire bundle crimping members are respectively disposed at both ends of the shape memory alloy wire bundle, and the wire bundle crimping members are used to press the shape memory alloy wire bundle.

[0016] Furthermore, the shape memory alloy wire bundle is composed of several shape memory alloy wires arranged in parallel;

[0017] The crimping surface of the wire bundle crimping member is serrated to improve the wire bundle crimping effect;

[0018] The disc spring assembly includes several disc springs, which are stacked in the same or opposite directions.

[0019] Furthermore, the inner rod includes an inner rod body and an inner rod side cover;

[0020] The inner rod body has pre-tightening screw mounting holes and ventilation and heat dissipation holes at both ends.

[0021] The inner rod side cover is provided with a power-conducting wire groove and a screw countersunk hole. The power-conducting wire groove is used to arrange power-conducting wires that energize the shape memory alloy actuator inside the inner rod side cover.

[0022] The countersunk screw hole is used to fully embed the head of the preloaded screw into the hole, ensuring that the surface of the inner rod side cover is flat after assembly.

[0023] Furthermore, the inner rod body is provided with a mounting groove for mounting the compliant mechanism and the shape memory alloy composite actuator.

[0024] Furthermore, the compliant mechanism is an integral structure, and a flexible hinge is provided in the compliant mechanism, through which the compliant mechanism transmits motion.

[0025] Furthermore, the outer tube and the inner rod are fitted with a clearance to facilitate bidirectional sliding.

[0026] Furthermore, one end of the inner rod body is provided with a hinge joint, which is used to connect with the hinge support of the external device.

[0027] Furthermore, one end of the outer tube is provided with a quick-release structure for quickly disassembling the hinge joint.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. The present invention has a simple structure and can be modularly and quickly installed. Friction locking is achieved by controlling the deformation of the compliant mechanism, and the control method is simple and reliable.

[0030] 2. The shape memory alloy composite actuator in this invention has the advantages of short stroke, high rigidity and compact structure, and achieves the miniaturization and lightweighting of the joint under the condition of meeting the locking load.

[0031] 3. The compliant mechanism in this invention has high stiffness and small deformation characteristics after optimization design. The high stiffness characteristic can transmit large loads, thereby obtaining excellent locking performance; the small deformation characteristic complements the small stroke characteristic of the shape memory alloy composite actuator.

[0032] 4. This invention can achieve locking at any position, making it suitable for more application scenarios of reconfigurable mechanisms.

[0033] 5. This invention is in a locked state under normal conditions when not powered on, and the unlocking power consumption is small. When arranged in a mechanism system, it can effectively save system energy consumption. Attached Figure Description

[0034] Figure 1 A cross-sectional view of a lockable linear motion joint based on a compliant mechanism and shape memory alloy;

[0035] Figure 2 for Figure 1 Schematic diagram of the structure of the inner and outer tubes;

[0036] Figure 3 for Figure 1 Schematic diagram of the inner rod:

[0037] Figure 4 This is a schematic diagram of a lockable linear motion joint based on a compliant mechanism and shape memory alloy in a locked working state.

[0038] Figure 5 for Figure 4 Enlarged structural diagram at point A;

[0039] Figure 6 for Figure 1 Schematic diagram of the compliant mechanism;

[0040] Figure 7 for Figure 1 Front view of the compliant mechanism;

[0041] Figure 8 for Figure 1 A schematic diagram of a shape memory alloy composite actuator;

[0042] Figure 9 for Figure 4 A three-dimensional structural diagram of the main body of the inner rod;

[0043] Figure 10 for Figure 4 A sectional view of the main body of the inner rod.

[0044] Figure 1 Explanation of Chinese markings:

[0045] 1-Outer tube, 2-Inner rod, 3-Preload screw, 4-Compliant mechanism, 5-Shape memory alloy composite actuator;

[0046] Figure 2 Explanation of Chinese markings:

[0047] 1-Outer tube;

[0048] Figure 3 Explanation of Chinese markings:

[0049] 2-Inner rod, 3-Preload screw;

[0050] Figure 4 Explanation of Chinese markings:

[0051] 21-Inner rod main body, 22-Inner rod side cover, 4-Compliant mechanism, 5-Shape memory alloy composite actuator;

[0052] Figure 5 Explanation of Chinese markings:

[0053] 1-Outer tube;

[0054] Figure 6 Explanation of Chinese markings:

[0055] 4-Compliance mechanism;

[0056] Figure 7 Explanation of Chinese markings:

[0057] 6- Flexible hinge;

[0058] Figure 8 Explanation of Chinese markings:

[0059] 7-Shape memory alloy wire bundle, 8-Wire bundle crimping piece, 9-Custom gasket, 10-Disc spring assembly, 11-Hollow guide tube;

[0060] Figure 9 Explanation of Chinese markings:

[0061] 21-Inner rod main body component;

[0062] Figure 10 Explanation of Chinese markings:

[0063] 21-Inner rod main body component. Detailed Implementation

[0064] The following examples illustrate specific implementations of the present invention. These examples are carried out based on the solution described in the present invention, and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following examples.

[0065] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0066] Example 1

[0067] This embodiment provides a lockable linear motion joint based on a compliant mechanism and a shape memory alloy, such as Figure 1 As shown, it includes an outer tube 1, an inner rod 2, a preload screw 3, a compliant mechanism 4, and a shape memory alloy composite actuator 5. Figure 2 and Figure 3 As shown, the outer tube 1 and the inner rod 2 are fitted with a clearance and have surface contact, facilitating bidirectional sliding. One end of the outer tube 1 is equipped with a quick-release structure for quickly disassembling the hinge joint to adjust the preload screw. The hinge joint is used to connect with the hinge support of an external device and allows rotational movement.

[0068] The inner rod 2, preload screw 3, compliant mechanism 4, and shape memory alloy composite actuator 5 are all located inside the outer tube 1. The outer tube and inner rod are made lightweight by removing or replacing materials while ensuring strength.

[0069] A preload screw 3 is installed at one end of the inner rod 2. The compliant mechanism 4 and the shape memory alloy composite actuator 5 are both installed inside the inner rod 2. A hole is provided on the inner rod 2 on the surface opposite the output end of the compliant mechanism 4. (See attached image) Figure 5 The hole is used for the output end of the compliant mechanism 4 to contact the outer tube 1. For example... Figure 4 As shown, the inner rod 2 includes an inner rod main body 21 and an inner rod side cover 22; Figure 9 This is a three-dimensional structural diagram of the main inner rod component. Figure 10 This is a sectional view of the main body of the inner rod, consisting of... Figure 9 and Figure 10 It is known that the inner rod main body 21 has pre-tightening screw 3 mounting holes and ventilation holes at both ends; the inner rod side cover 22 has a power wire groove and a screw countersunk hole. The power wire groove is used to arrange the power wire for energizing the shape memory alloy composite actuator 5 inside the inner rod side cover, and the screw countersunk hole is used to ensure that the screw head is fully embedded in the hole, ensuring that the surface of the inner rod side cover is flat after assembly. The inner rod main body 21 has a mounting groove for mounting the compliant mechanism 4 and the shape memory alloy composite actuator 5. One end of the inner rod main body 21 also has a hinge joint, which is used to connect with the hinge support of the external device and allows rotational movement.

[0070] Figure 8 This is a schematic diagram of a shape memory alloy composite actuator, as shown below. Figure 8 As shown, the shape memory alloy composite actuator 5 includes a shape memory alloy wire bundle 7, a wire bundle crimping member 8, a custom-made gasket 9, a disc spring assembly 10, and a hollow guide tube 11. The hollow guide tube 11 passes through the disc spring assembly 10, and the custom-made gasket 9 passes through both ends of the hollow guide tube 11 for axial constraint. The shape memory alloy wire bundle 7 passes through the center of the hollow guide tube 11; the wire bundle crimping member 8 is respectively disposed at both ends of the shape memory alloy wire bundle 7, and the wire bundle crimping member 8 is used to press the shape memory alloy wire bundle 7, and to axially slightly press the custom-made gasket 5 and the disc spring assembly 6 to eliminate axial gap. The crimping surface of the wire bundle crimping member 8 is serrated to improve the wire bundle pressing effect; the shape memory alloy wire bundle 7 is composed of several shape memory alloy wires arranged in parallel; the disc spring assembly 10 includes several disc springs, which are stacked in the same or opposite directions, and the disc spring assembly 10 has high axial stiffness.

[0071] When the shape memory alloy composite actuator 5 is energized, the shape memory alloy wire bundle 3 contracts, pulling the wire bundle crimping member 4 and compressing the disc spring assembly 6, causing the shape memory alloy composite actuator 5 to contract axially. After de-energization, the disc spring assembly 6 recovers its deformation and indirectly stretches the shape memory alloy wire bundle 3 through the wire bundle crimping member 4, causing the shape memory alloy composite actuator 5 to recover its axial deformation. The shape memory alloy composite actuator 5 consists of the active contraction of the shape memory alloy wire bundle 3 and the passive deformation of the disc spring assembly 6, forming a repetitive driving function.

[0072] like Figure 6 and Figure 7 As shown, the compliant mechanism 4 is designed with a flexible hinge 6, which is integrally formed by electrical discharge machining. The compliant mechanism 4 transmits motion through the flexible hinge 6. Its structure is compact. When the compliant mechanism 4 is compressed in one direction, it can expand outward in another orthogonal direction and transmit the load. The compliant mechanism 4 can be matched with different actuators, and various locking modes can be achieved by designing different structures. The shape memory alloy composite actuator 5 can be replaced with a piezoelectric actuator or an electric drive mechanism with micro-motion contraction function. Such actuators need to be able to actuate under high load conditions.

[0073] In its normal state, the joint is locked. That is, when no power is applied, after the pre-tightening screw 3 is tightened, the compliant mechanism 4 and the shape memory alloy composite actuator 5 are axially compressed. The compliant mechanism 4 transmits axial deformation to the sides via the flexible hinge 6. The two sides of the compliant mechanism 4 contact and compress the inner wall of the outer tube 1. When there is a relative movement tendency between the surfaces, static friction is generated to resist the relative movement, thus achieving friction locking. At this time, the joint is in the locked state. When powered on, the shape memory alloy composite actuator 5 contracts axially, releasing the pressure on both sides of the compliant mechanism 4, allowing it to recover its deformation. Its two lateral ends separate from the inner wall of the outer tube 1, and the joint is in the unlocked state. When the power is deactivated, the shape memory alloy composite actuator 5 recovers its axial deformation and compresses the compliant mechanism 4, causing its two lateral ends to contact and compress the inner wall of the outer tube 1. At this time, the joint switches to the locked state.

[0074] The shape memory alloy composite actuator 5 undergoes axial deformation as the energized state changes, enabling the contact and separation between the compliant mechanism 4 and the inner wall of the outer tube 1. This, in turn, achieves bidirectional locking and releasing of the linear motion joint. It features small size, lightweight construction, and high load capacity, making it suitable for adaptive deformation and reconfigurable systems in small robots or deformable truss systems, improving the system's structural stability and load-bearing capacity. Furthermore, this motion joint requires few parts, has a simple and reliable structure, and is easy to assemble modularly, meeting the application requirements of modular, reconfigurable mechanisms with high repeatability.

[0075] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A lockable linear motion joint based on a compliant mechanism and a shape memory alloy, characterized in that, It includes an outer tube (1), an inner rod (2), a preload screw (3), a compliant mechanism (4), and a shape memory alloy composite actuator (5); The inner rod (2), preload screw (3), compliant mechanism (4) and shape memory alloy composite actuator (5) are all located inside the outer tube (1); The preload screw (3) is installed at one end of the inner rod (2), and the compliant mechanism (4) and the shape memory alloy composite actuator (5) are both installed inside the inner rod (2); The inner rod (2) has a hole on its surface opposite to the output end of the compliant mechanism (4), and the hole is used for the output end of the compliant mechanism (4) to contact the outer tube (1); In the normal state, i.e., without power, the joint is locked, the pre-tightening screw (3) is tightened, and the compliant mechanism (4) and the shape memory alloy composite actuator (5) are axially compressed, causing the compliant mechanism (4) to expand outward at both ends and contact the inner wall of the outer tube (1), resulting in compression and friction, which keeps the joint locked. In the energized state, the shape memory alloy composite actuator (5) contracts axially, releasing the pressure on both sides of the compliant mechanism (4), thereby restoring the deformation of the compliant mechanism (4), separating the compliant mechanism (4) from the inner wall of the outer tube (1) at both ends, and switching the joint to the unlocked state. The shape memory alloy composite actuator (5) includes a custom-made gasket (9), a disc spring assembly (10), and a hollow guide tube (11). The hollow guide tube (11) passes through the disc spring assembly (10), and the two ends of the hollow guide tube (11) pass through the custom gasket (9) respectively. The hollow guide tube (11) is used for axial constraint. The shape memory alloy composite actuator (5) further includes a shape memory alloy wire bundle (7) and a wire bundle crimping member (8), wherein the shape memory alloy wire bundle (7) passes through the hollow guide tube (11). The wire bundle crimping member (8) is respectively disposed at both ends of the shape memory alloy wire bundle (7), and the wire bundle crimping member (8) is used to press the shape memory alloy wire bundle (7). The shape memory alloy wire bundle (7) is composed of several shape memory alloy wires arranged in parallel; The crimping surface of the wire bundle crimping member (8) is serrated to improve the wire bundle crimping effect; The disc spring assembly (10) includes a plurality of disc springs, which are stacked in the same or opposite directions. The compliant mechanism (4) is an integral structure, and a flexible hinge (6) is provided in the compliant mechanism (4). The compliant mechanism (4) transmits motion through the flexible hinge (6).

2. The lockable linear motion joint based on a compliant mechanism and shape memory alloy according to claim 1, characterized in that, The inner rod (2) includes an inner rod body (21) and an inner rod side cover (22). The inner rod body (21) has pre-tightening screw mounting holes and ventilation and heat dissipation holes at both ends; The inner rod side cover (22) is provided with a power-conducting wire groove and a screw countersunk hole. The power-conducting wire groove is used to arrange power-conducting wires that energize the shape memory alloy actuator (5) inside the inner rod side cover (22). The countersunk screw hole is used to fully embed the head of the preloaded screw (3) into the hole, ensuring that the surface of the inner rod side cover (22) is flat after assembly.

3. A lockable linear motion joint based on a compliant mechanism and shape memory alloy according to claim 2, characterized in that, The inner rod body (21) is provided with a mounting groove, which is used to install the compliant mechanism (4) and the shape memory alloy composite actuator (5).

4. A lockable linear motion joint based on a compliant mechanism and shape memory alloy according to claim 1, characterized in that, The outer tube (1) and the inner rod (2) are fitted with a clearance to facilitate bidirectional sliding.

5. A lockable linear motion joint based on a compliant mechanism and shape memory alloy according to claim 2, characterized in that, One end of the inner rod body (21) is also provided with a hinge joint, which is used to connect with the hinge support of the external device.

6. A lockable linear motion joint based on a compliant mechanism and shape memory alloy according to claim 1, characterized in that, One end of the outer tube (1) is provided with a quick-release structure for quick disassembly of the hinge joint.

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