Soft robotic arm and robot based on conductive twisted fiber and shape memory alloy

Abstract

The application discloses a soft robot arm based on conductive twisted fiber and shape memory alloy, which comprises a robot arm, a bottom plate installed at the top end of the robot arm, and an end effector installed at the center of the bottom plate; a plurality of annular grooves are formed in the side wall of the robot arm towards the central axis and are uniformly distributed along the length direction of the robot arm; a plurality of first through holes and third through holes are formed in each annular groove, and the first through holes and the third through holes in all the annular grooves are kept corresponding; the first through holes and the third through holes are also formed in the bottom plate; the soft robot arm further comprises a plurality of shape memory alloy springs and conductive twisted fibers; the shape memory alloy springs and the conductive twisted fibers pass through all the first through holes and the third through holes and then penetrate through the robot arm from the head to the tail and are connected with the bottom plate; different currents are applied to each of the shape memory alloy springs and the conductive twisted fibers so that the soft robot arm reaches a target bending angle. The scheme can improve the rigidity of the soft robot arm and has a simple structure and is easy to control.

Description

Technical Field

[0001] This invention belongs to the field of soft robotics, specifically relating to a soft robotic arm and robot based on conductive twisted fibers and shape memory alloys. Background Technology

[0002] Since the introduction of robotics into the medical field in the 1980s, breakthroughs have been continuously achieved in medical robot research. While traditional rigid robots offer advantages in precision and stability, their limited flexibility makes them unsuitable for certain special situations. However, with the development of soft robots, it has been discovered that they can overcome the shortcomings of traditional rigid robots in the medical field. For example, in minimally invasive surgery, due to the limited operating space, traditional rigid robots, with their limited degrees of freedom, require extremely precise control and pre-judgment to successfully complete the surgery. Furthermore, their high Young's modulus poses a potential risk of damaging organs during surgery. Soft robots, on the other hand, possess unlimited degrees of freedom, strong continuous deformation capabilities, and excellent environmental adaptability. They can flexibly change their shape to work in complex, unstructured spaces, and because they are made of flexible materials, they exhibit good adaptability and safety when interacting with the internal environment of the human body.

[0003] However, existing soft robots are typically made of flexible materials with low Young's modulus, such as silicone rubber and fiber fabrics. While achieving low stiffness, this also significantly reduces stability. The end effector may exhibit tremors, vibrations, and weak force, which to some extent reduces the precision of soft robot surgery and increases surgical risks. Therefore, achieving compliance while ensuring stability and precision is an important research direction for variable stiffness soft surgical robots. For example, the paper "Tendon-based stiffening for a pneumatically actuated soft manipulator," published in IEEE ROBOTICS AND AUTOMA TION LETTERS, January 2016, Volume 1, Issue 2, pp. 632-637, introduces a variable stiffness manipulator that combines tendon-driven and pneumatic-driven actuation using the principle of resistance. Its principle involves inflating three pairs of internal pressure chambers to achieve bending in any direction. After the manipulator reaches the target position at its tip, the internal tendons are tensioned to increase stiffness.

[0004] Chinese invention patent CN105945930A discloses a line-driven, variable stiffness soft robot. The robot's drive arm is driven by three drive cables. The drive arm is a soft drive arm filled with solid particles. When the drive arm reaches a designated position, a vacuum pump creates a negative pressure inside the drive arm, utilizing the vacuum particle blocking effect to achieve variable stiffness. This method not only enables the robot to withstand high-strength compressive forces but also allows for flexible adjustment of both compliance and stiffness.

[0005] However, most variable stiffness soft robots currently achieve stiffness adjustment by regulating air pressure and applying magnetic fields. Although this method can achieve both compliance and stiffness adjustment, the required structure is relatively complex and has certain control difficulties. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a soft robotic arm and robot based on conductive twisted fibers and shape memory alloys. This solution adjusts the bending angle of the soft robotic arm by applying different magnitudes of current to the conductive twisted fibers and shape memory alloys. Since the conductive twisted fibers and shape memory alloys are arranged oppositely inside the robotic arm and their stiffness increases during the electrothermal drive process, the stiffness of the soft robotic arm is increased. This structure is simple and easy to control.

[0007] Technical Solution: This invention includes a robotic arm, a base plate mounted at the top of the robotic arm, and an end effector mounted at the center of the base plate. The robotic arm is cylindrical in shape, with multiple annular grooves evenly distributed along the length of the robotic arm from its sidewalls towards its central axis. Each annular groove contains multiple first and third through holes, and the first and third through holes in all annular grooves correspond to each other. Corresponding first and third through holes are also formed on the base plate. The invention also includes multiple shape memory alloy springs and conductive twisted fibers. The shape memory alloy springs pass through all the first through holes and then through the beginning and end of the robotic arm, connecting to the base plate. The conductive twisted fibers pass through all the third through holes and then through the beginning and end of the robotic arm, connecting to the base plate. By applying different magnitudes of current to each of the shape memory alloy springs and conductive twisted fibers, the soft robotic arm achieves a target bending angle.

[0008] The first and third through holes inside the annular groove are arranged in opposition. The conductive twisted fibers and shape memory alloy springs inside bend in opposite directions during the electrothermal drive process, generating counterforce, which enables the soft robotic arm to obtain higher stiffness.

[0009] The conductive twisted fiber double helix structure is made by twisting and winding fiber materials. When electricity is applied to both ends, Joule heat is generated, causing the fiber materials to heat up, twist, and shrink, thereby fine-tuning the posture of the soft robotic arm and improving the accuracy of position adjustment.

[0010] Both the robotic arm and the base plate have central through holes for assembling end effectors, which improves overall stability.

[0011] The end effector can be replaced with a soft gripper or endoscope as needed.

[0012] The soft gripper includes a base, an upper plate mounted on the base, and a shape memory alloy spring connected to the center of the base and the upper plate; multiple fingers are arranged along the top edge of the upper plate to grasp objects.

[0013] The fingers have a hollow structure inside, which allows them to move flexibly under external force, making them fit the object more closely when gripping it.

[0014] The robotic arm is made of silicone rubber, which is prone to deformation.

[0015] The present invention also includes a robot comprising a plurality of variable stiffness soft robotic arms based on conductive twisted fibers and shape memory alloys, the plurality of variable stiffness soft robotic arms being connected in series through a central through hole, thereby controlling each variable stiffness soft robotic arm to bend at a different angle.

[0016] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] (1) Both the conductive twisted fiber and the shape memory alloy spring are driven by electrothermal energy. By passing different currents to both ends of each conductive twisted fiber and each shape memory alloy spring, the soft robotic arm can achieve the target bending angle. During the energization process, the stiffness of the conductive twisted fiber and the shape memory alloy will increase, which will lead to an increase in the stiffness of the soft robotic arm.

[0018] (2) The soft robotic arm has a compact structure, does not require complex and redundant equipment, and can be easily integrated into a variable stiffness soft robot system.

[0019] (3) The conductive twisted fiber and the shape memory alloy spring are in an antagonistic configuration. The counterforce obtained by simultaneously electrothermally driving both will further increase the stiffness of the soft robotic arm. The conductive twisted fiber can also effectively improve the hysteresis characteristics of the shape memory alloy. Attached Figure Description

[0020] Figure 1 This is an isometric view of a soft robotic arm.

[0021] Figure 2 This is the front view of the soft robotic arm;

[0022] Figure 3 This is a schematic diagram of the robotic arm structure of the present invention;

[0023] Figure 4This is a schematic diagram of the top of the robotic arm of the present invention;

[0024] Figure 5 This is a schematic diagram of the shape memory alloy spring structure of the present invention;

[0025] Figure 6 This is a schematic diagram of the conductive twisted fiber structure of the present invention;

[0026] Figure 7 This is a comparison diagram of the effects of the variable stiffness soft robotic arm of the present invention at different stiffnesses;

[0027] Figure 8 Schematic diagram of a variable stiffness soft surgical robot;

[0028] Figure 9 This is a schematic diagram of the driving principle when the end effector is a software gripper. Detailed Implementation

[0029] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0030] like Figure 1-4 As shown, the soft robotic arm of the present invention comprises five parts: a robotic arm 1, a shape memory alloy spring (SMA) 2, a base plate 3, an end effector 4, and conductive twisted fiber (SCP) 5. The robotic arm 1 is cylindrical in shape and can bend and deflect at any angle in three-dimensional space. Multiple annular grooves are formed from the side wall of the robotic arm 1 towards the central axis. The multiple annular grooves are evenly distributed along the length of the robotic arm 1. The annular grooves can reduce the stiffness of the robotic arm 1 when bending and improve its flexibility. Each annular groove has three first through holes 11 and three third through holes 13, which are arranged opposite to each other. The actual number of first through holes 11 and third through holes 13 is not limited to three in this embodiment, but can be determined as needed, as long as the rule of opposite arrangement is met. In order to better position the first through holes 11 and third through holes 13, a stepped structure is first formed inside each annular groove. Three first through holes 11 and three third through holes 13 are evenly formed inside the stepped structure, and each first through hole 11 and each third through hole 13 are arranged opposite to each other. Both the center of the robotic arm 1 and the center of the base plate 3 have a central through hole 12 for mounting end effectors, such as endoscopes, robotic grippers, etc. The top of the robotic arm 1 has a hexagonal slot for mounting the base plate 3, and the end effector 4 is mounted in the center of the base plate 3.

[0031] The first through hole 11 and the third through hole 13 on the next annular groove are aligned, meaning that the first through hole 11 and the third through hole 13 inside all annular grooves are aligned, and the first through hole 11 and the third through hole 13 are also aligned on the base plate 3. The shape memory alloy spring 2 passes through all the first through holes 11 and then through the beginning and end of the robotic arm 1, and is connected to the base plate 3. The conductive twisted fiber 5 passes through all the third through holes 13 and then through the beginning and end of the robotic arm 1, and is connected to the base plate 3. Each conductive twisted fiber 5 and the shape memory alloy spring 2 are arranged opposite each other, and the opposing force generated during the thermal contraction process when the two ends are energized further increases the stiffness of the soft robotic arm.

[0032] The robotic arm 1 is made of silicone rubber and, due to the annular grooves around its perimeter, can bend at large angles in any direction under external force. The base plate 3 is made of resin and can be obtained through 3D printing or injection molding with commercial silicone solution. The robotic arm 1 and base plate 3 are manufactured by casting, forming a single piece that is soft and easy to use. First, the molds for the robotic arm and base plate are designed using 3D drawing software. Silicone solution and resin solution are then injected into the molds, and after curing, the robotic arm and base plate are obtained. Twisted fiber is an artificial muscle made from highly twisted fibers; the shape memory alloy spring is made of a special material.

[0033] like Figure 5 As shown, the shape memory alloy spring 2 can contract when heated by electricity and recover when cooled by power-off, and is used to control the bending deformation of the soft robotic arm.

[0034] like Figure 6 As shown, the conductive twisted fiber 5 is an artificial muscle made from highly twisted fibers. The conductive twisted fiber 5 has a double-helix structure, made by twisting and winding fiber materials. Utilizing the principle of electrothermal drive, Joule heat is generated when electricity is applied to both ends, causing the fiber material to heat up, twist, and contract, pulling the robotic arm 1 to bend, thereby fine-tuning the posture of the soft robotic arm. During the energizing process, the stiffness of the conductive twisted fiber 5 and the shape memory alloy spring 2 increases, thus increasing the stiffness of the soft robotic arm.

[0035] like Figure 7 As shown, a heavy object is attached to the end effector of the soft robotic arm. When the soft robotic arm is in a high-stiffness state, the variable-stiffness soft robotic arm undergoes a slight deformation, with the end effector sinking by a distance of l1, as shown. Figure 7 As shown in Figure (a); when the variable stiffness soft robot arm is in a high stiffness state, the variable stiffness soft robot arm undergoes large deformation, with the end effector sinking by l2, as shown in Figure (a). Figure 7 As shown in Figure (b), l1 is much smaller than l2.

[0036] like Figure 8As shown, the present invention also includes a robot comprising multiple variable stiffness soft robotic arms based on conductive twisted fibers and shape memory alloys. These multiple variable stiffness soft robotic arms are connected in series via a central through-hole 12. Each variable stiffness soft robotic arm is controlled to bend at different angles to achieve complex posture changes of the end effector 4, adapting to different working environment requirements. In this solution, the robot includes three series-connected soft robotic arms. Complex robotic arm postures are obtained by applying different magnitudes of current to each conductive twisted fiber 5 and shape memory alloy spring 2. Because the conductive twisted fibers 5 and shape memory alloy spring 2 are configured in opposite directions, they bend in opposite directions when current is applied, giving the soft robotic arm variable stiffness capability.

[0037] Shape memory alloy springs are used to drive the robot, while conductive twisted fibers are used to fine-tune the robot's position and posture. In actual operation, while pushing the soft robotic arm towards the target, different magnitudes of current are applied to the three shape memory alloy springs 2 to obtain the target bending angle. After the soft robotic arm reaches the designated position, the conductive twisted fibers 5 are then energized. Because the twisted fibers and shape memory alloy springs are configured in opposite directions, they bend in opposite directions to obtain higher stiffness. Finally, the final position of the end effector can be fine-tuned by adjusting the magnitude of the current, achieving a more accurate function of manipulating the instrument to the target position.

[0038] like Figure 8 and Figure 9 As shown, the end effector 4 can be replaced with a soft gripper or an endoscope as needed. The soft gripper includes a base 41, an upper plate 43 mounted above the base 41, and a shape memory alloy spring 2 connecting the center of the base 41 and the upper plate 43. Three fingers 44 are arranged along the edge of the top surface of the upper plate 43. The fingers 44 have a hollow internal structure. The soft gripper adopts a fin-like structure based on the fin-ray effect, which enhances its applicability when gripping objects. The hollow internal structure of the fingers 44 allows them to flexibly change under external force, making them fit the object more closely when gripping it, improving object containment and providing protection for the gripped object. The soft gripper body is manufactured using 3D printing in one piece and is driven by the shape memory alloy spring 2. The soft gripper is connected to the robotic arm 1 via the base 41. When the variable stiffness soft robotic arm reaches the designated position and posture, it energizes the shape memory alloy spring 2 connected to the center of the base 41 and the upper plate 43. The shape memory alloy spring 2 heats up and contracts, pulling the upper plate 43 to make the fingers 44 bend and complete the gripping action.

Claims

1. A soft robotic arm based on conductive twisted fibers and shape memory alloys, characterized in that: Includes a robotic arm (1), a base plate (3) mounted on the top of the robotic arm (1), and an end effector (4) mounted on the center of the base plate (3). The robotic arm (1) is cylindrical in shape. Multiple annular grooves are opened from the side wall of the robotic arm (1) toward the central axis. The multiple annular grooves are evenly distributed along the length of the robotic arm (1). Multiple first through holes (11) and third through holes (13) are opened inside each annular groove. The first through holes (11) and third through holes (13) opened inside all annular grooves are consistent. The first through holes (11) and third through holes (13) are also opened on the bottom plate (3). It also includes multiple shape memory alloy springs (2) and conductive twisted fibers (5). The shape memory alloy springs (2) pass through all the first through holes (11) and then through the beginning and end of the robotic arm (1), and are connected to the base plate (3). The conductive twisted fibers (5) pass through all the third through holes (13) and then through the beginning and end of the robotic arm (1), and are connected to the base plate (3). By applying different currents to each of the shape memory alloy springs (2) and conductive twisted fibers (5), the soft robotic arm can achieve the target bending angle. The first through hole (11) and the third through hole (13) inside the annular groove are arranged oppositely, and the conductive twisted fiber (5) and the shape memory alloy spring (2) in them bend in opposite directions during the electrothermal drive process, generating opposing forces.

2. The soft robotic arm based on conductive twisted fibers and shape memory alloys according to claim 1, characterized in that: The conductive twisted fiber (5) has a double helix structure and is made by twisting and winding fiber materials. When the two ends are energized, Joule heat is generated, which causes the fiber materials to heat up and twist and shrink, thereby finely adjusting the posture of the soft robotic arm.

3. The soft robotic arm based on conductive twisted fibers and shape memory alloys according to claim 1, characterized in that: Both the robotic arm (1) and the base plate (3) have central through holes (12) for assembling end effectors.

4. The soft robotic arm based on conductive twisted fibers and shape memory alloys according to claim 1, characterized in that: The end effector (4) can be replaced with a soft gripper or endoscope as needed.

5. The soft robotic arm based on conductive twisted fibers and shape memory alloys according to claim 4, characterized in that: The soft gripper includes a base (41), an upper plate (43) mounted above the base (41), and a shape memory alloy spring (2) connected at the center of the base (41) and the upper plate (43); multiple fingers (44) are arranged along the top edge of the upper plate (43).

6. The soft robotic arm based on conductive twisted fibers and shape memory alloys according to claim 5, characterized in that: The finger (44) has a hollow structure inside.

7. The soft robotic arm based on conductive twisted fibers and shape memory alloys according to claim 1, characterized in that: The robotic arm (1) is made of silicone rubber.

8. A robot, characterized in that: The invention includes multiple soft robotic arms based on conductive twisted fibers and shape memory alloys as described in claim 1, wherein the multiple soft robotic arms are connected in series through a central through hole (12) thereon, and each soft robotic arm is controlled to bend at a different angle.

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