Variable stiffness robotic arm based on fluid heat exchange and control method thereof, robot

Abstract

The application discloses a variable stiffness mechanical arm based on fluid heat exchange and a control method and robot thereof, and the variable stiffness mechanical arm comprises a base and an execution part arranged at the end of the base; the execution part comprises a first silica gel pipe, a second silica gel pipe is arranged in the first silica gel pipe, a spiral heat exchange pipe is arranged in the second silica gel pipe, and low-melting-point alloy is filled between the second silica gel pipe and the spiral heat exchange pipe; by inputting heat exchange fluid with a temperature lower than or higher than the phase transition temperature of the low-melting-point alloy into the spiral heat exchange pipe, heat exchange is carried out between the heat exchange fluid in the spiral heat exchange pipe and the low-melting-point alloy, so that the low-melting-point alloy is switched between a solid state and a liquid state, and the switching between a rigid state and a flexible state of the execution part is realized.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more particularly to a variable stiffness robotic arm based on fluid heat exchange, its control method, and a surgical robot. Background Technology

[0002] Knee cartilage defects are a common degenerative disease of the musculoskeletal system, affecting a large global population. Their symptoms severely reduce patients' quality of life and increase the societal burden of healthcare. Because articular cartilage is avascular, its self-repair capacity is extremely limited. Therefore, effective intervention in the early stages of the disease is crucial to preventing its progression to end-stage osteoarthritis. Current early treatments (such as intra-articular injections) often have limited effectiveness, and once the condition progresses to the end stage, patients typically require knee replacement surgery to implant an artificial joint.

[0003] In recent years, although surgical robots for knee joints have made significant progress in the field of joint replacement, their design concepts and functional configurations are mainly aimed at large-scale bone resection and prosthesis implantation, and are not suitable for the refined, localized repair treatment of early cartilage defects. In addition, existing surgical robot systems are usually large in size, and often require relatively large incisions during surgery, making it difficult to meet the clinical needs for minimally invasive and complex operations that can be performed deep into the joint cavity through a single-port incision.

[0004] The knee joint cavity is a narrow, unstructured environment containing complex anatomical structures such as ligaments and menisci. When performing cartilage repair tasks, this places conflicting demands on the mechanical characteristics of the surgical robot's end effector: on the one hand, the instrument needs high flexibility during navigation to navigate around obstacles and reach the target location without damaging healthy tissue; on the other hand, after reaching the lesion, the instrument needs sufficient rigidity to apply the necessary surgical force and maintain postural stability when performing physical operations such as debridement and subchondral bone drilling. Traditional rigid instruments alone cannot flexibly reach complex locations, while flexible instruments alone cannot provide sufficient maneuvering force; neither can simultaneously meet these requirements.

[0005] To address the aforementioned contradictions, variable stiffness technology has emerged, which can controllably alter the structural stiffness of robot components according to task requirements. Currently, the mainstream variable stiffness technologies mainly include the following categories: 1. Jamming-based methods: stiffness changes are achieved by altering the constraint state of internal particles or layered media, but these methods suffer from slow response speed, limited range of stiffness changes, and easy coupling between rigid and flexible states. 2. Methods based on structural deformation: stiffness changes are achieved by changing the contact area through mechanical rotation or by using special geometric configurations, but this often leads to complex structures, making it difficult to achieve miniaturization within the extremely small size required for minimally invasive surgical instruments; 3. Phase Change Material-based methods: These methods utilize the significant difference in modulus of materials (such as low-melting-point alloys) during solid-liquid phase transitions to achieve stiffness switching. They have the inherent advantages of fast response speed and suitability for miniaturization.

[0006] However, existing variable stiffness solutions based on phase change materials mostly employ simple internal fluid heat exchange or electric heating to control the phase change. Within miniaturized surgical instruments, limited by extremely small spaces and fluid channels, achieving efficient, rapid, and uniform heat exchange to significantly shorten stiffness transition time (i.e., shorten surgical waiting time) remains a key bottleneck restricting the clinical application of this technology.

[0007] In summary, there is still a lack of surgical robot end effectors that can balance flexibility and rigidity, have high thermal response speed, and be suitable for early minimally invasive repair of knee cartilage. Summary of the Invention

[0008] To address the shortcomings of existing technologies, embodiments of the present invention provide a variable stiffness robotic arm based on fluid heat exchange, its control method, and a surgical robot.

[0009] In a first aspect, embodiments of the present invention provide a variable stiffness robotic arm based on fluid heat exchange, the variable stiffness robotic arm comprising: Base; and, An actuator is located at the end of the base; the actuator includes a first silicone tube, a second silicone tube is disposed inside the first silicone tube, a spiral heat exchange tube is disposed inside the second silicone tube, and a low melting point alloy is filled between the second silicone tube and the spiral heat exchange tube. By introducing a heat exchange fluid with a temperature lower or higher than the phase transformation temperature of the low-melting-point alloy into the spiral heat exchange tube, heat exchange occurs between the heat exchange fluid and the low-melting-point alloy, thereby controlling the switching of the low-melting-point alloy between solid and liquid states, and thus realizing the switching of the actuator between rigid and flexible states.

[0010] Furthermore, a number of drive motors are installed in the base, and each drive motor is connected to a cable via a motor flange. The cable is installed in the actuator through a cable management groove located between the first silicone tube and the second silicone tube to drive the actuator.

[0011] Furthermore, a cable retainer is provided between the first silicone tube and the second silicone tube. The cable retainer is used to guide and constrain the cable to control the movement of the actuator.

[0012] Furthermore, the low-melting-point alloy is made of Field metal.

[0013] Furthermore, an end effector is installed at the end of the actuator; the end effector includes one or more combinations of cutting tools, additive manufacturing tools, hemostasis and cutting tools, and sensing and measuring tools.

[0014] Furthermore, the spiral heat exchange tube is a spiral hollow copper tube, and the spiral structure of the spiral heat exchange tube is configured as a turbulence element to enhance the turbulence effect between the fluid inside the tube and the low melting point alloy in order to improve the heat exchange efficiency.

[0015] Furthermore, a vision unit is provided at the end of the base; the vision unit includes a monocular camera and a light source.

[0016] Secondly, embodiments of the present invention provide a control method for a variable stiffness robotic arm based on fluid heat exchange, the method comprising: When the low-melting-point alloy is in a liquid state and the actuator is in a flexible state, the drive motor moves the actuator to the target position by pulling or releasing the corresponding cable. A cryogenic liquid is introduced into the spiral heat exchange tube, and heat exchange occurs between the cryogenic liquid and the low-melting-point alloy in the spiral heat exchange tube. The low-melting-point alloy is controlled to cool down and condense, thereby switching the actuator to a rigid state and performing the operation task. Once the operation is completed, a high-temperature liquid is introduced into the spiral heat exchange tube. Heat exchange occurs between the high-temperature liquid and the low-melting-point alloy in the spiral heat exchange tube, controlling the low-melting-point alloy to heat up and melt, thereby switching the actuator to a flexible state.

[0017] Furthermore, the process by which the drive motor moves the actuator to the target position by pulling or releasing the corresponding cable includes: Based on geometric relationships, construct the mapping relationship between the bending plane angle, bending angle, bending radius and cable length in the task space; Based on the coordinates of the target location, the bending plane angle, bending angle, and bending radius in the task space are calculated, and the target length of the cable is obtained according to the mapping relationship. Based on the target length of the cable, the drive motor is controlled to move the actuator to the target position by changing the length of the cable.

[0018] Thirdly, embodiments of the present invention provide a surgical robot, including the aforementioned variable stiffness robotic arm based on fluid heat exchange.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention innovatively employs a spiral heat exchange tube in a variable stiffness motion actuator. This spiral structure, acting as a turbulence element, significantly enhances the turbulence effect of the circulating fluid (high-temperature or low-temperature liquid) within the tube, thereby greatly improving the heat exchange efficiency between the fluid inside the spiral heat exchange tube and the low-melting-point alloy body. Compared to traditional straight tubes or natural cooling methods, this invention can greatly shorten the phase transition time of the low-melting-point alloy between the solid (rigid) and liquid (flexible) states, solving the problems of slow response speed and long surgical waiting time in existing minimally invasive instruments based on phase change materials.

[0020] (2) This invention perfectly solves the contradictory requirements of "flexibility" and "rigidity" in minimally invasive knee joint surgery through the phase transformation mechanism of low-melting-point alloys. In the flexible state, combined with the wire-driven method, the robotic arm has extremely high degrees of freedom and compliance, and can safely bypass sensitive tissues such as the infrapatellar fat pad and ligaments, and penetrate deep into the narrow area of ​​the knee joint cavity, avoiding unintentional damage to healthy tissues. In the rigid state, the solidified alloy provides sufficient structural rigidity and support for the end effector, ensuring posture stability and force output capability when performing contact physical operations such as grinding and drilling, thus guaranteeing surgical precision.

[0021] (3) This invention utilizes the physical properties of phase change materials to achieve variable stiffness, eliminating the need for complex mechanical locking mechanisms or bulky hydraulic / pneumatic devices, resulting in a simple and compact structure. Combined with the slender continuous structure design, this device is easily miniaturized, making it ideal for minimally invasive treatments that can be performed inside the human body through a single hole or natural cavity.

[0022] (4) The system of the present invention integrates the execution unit and the vision unit in a compact structure. Through the coordinated drive of the same base, it can simultaneously acquire surgical field images and perform operations without the need for multi-hole puncture. At the same time, the end effector supports the replacement of various actuators such as grinding head, drill bit, and printing head, so that a single robot can complete the entire surgical process from lesion cleaning, subchondral bone treatment to in-situ repair and filling, without the need to repeatedly change surgical instruments, which significantly improves surgical efficiency. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the overall structure of a variable stiffness robotic arm based on fluid heat exchange provided in an embodiment of the present invention; Figure 2This is a schematic diagram of the internal structure of the base provided in an embodiment of the present invention; Figure 3 A schematic diagram of the structure of the execution unit provided in an embodiment of the present invention; Figure 4 This is a schematic cross-sectional view of the execution unit along line AA provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the liquid inlet and outlet structure of the heat exchange tube of the actuator provided in an embodiment of the present invention; Figure 6 A partial enlarged view of the execution unit provided in an embodiment of the present invention; Figure 7 A schematic diagram of the vision section provided in an embodiment of the present invention; Figure 8 This is a geometrical schematic diagram of the kinematic model provided in an embodiment of the present invention.

[0025] In the diagram, 100 is the base unit; 110 is the drive motor; 120 is the end cap; 130 is the motor mounting bracket; 140 is the motor flange; 150 is the cable management trough; 200 is the actuator; 210 is the end effector; 220 is the first silicone tube; 230 is the cable tray; 240 is the cable; 250 is the spiral heat exchange tube; 260 is the low melting point alloy; 270 is the second silicone tube; 280 is the quick-connect interface; 300 is the vision unit; 310 is the camera; and 320 is the light source. Detailed Implementation

[0026] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0028] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0029] The present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features of the following embodiments and implementations can be combined with each other.

[0030] like Figure 1 As shown, this embodiment of the invention provides a variable stiffness robotic arm based on fluid heat exchange. This robotic arm employs a linearly driven continuum structure and incorporates the phase transformation characteristics of low-melting-point alloys, aiming to solve the challenges of minimally invasive surgery in narrow, unstructured environments such as the knee joint cavity. The variable stiffness robotic arm includes: A base 100, within which are mounted a plurality of drive motors 110 arranged circumferentially. Each drive motor 110 is connected to a cable 240 via a motor flange 140. The cable 240 is installed within an actuator 200 via a cable management groove 150 located between a first silicone tube 220 and a second silicone tube 270 to drive the actuator 200; and... An execution unit 200 is disposed at the end of the base 100; the execution unit 200 includes a first silicone tube 220, a second silicone tube 270 disposed inside the first silicone tube 220, a spiral heat exchange tube 250 disposed inside the second silicone tube 270, and a low melting point alloy 260 filling the space between the second silicone tube 270 and the spiral heat exchange tube 250. By introducing a heat exchange fluid with a temperature lower or higher than the phase change temperature of the low-melting-point alloy 260 into the spiral heat exchange tube 250, heat exchange occurs between the heat exchange fluid in the spiral heat exchange tube 250 and the low-melting-point alloy 260, thereby controlling the switching of the low-melting-point alloy 260 between solid and liquid states, and thus realizing the switching of the actuator 200 between rigid and flexible states.

[0031] Furthermore, such as Figure 2 As shown, the drive motor 110 is mounted on the base 100 via a motor mounting bracket 130. The base 100 is also provided with an end cap 120 for encapsulating and protecting internal components, preventing liquid splashing during surgery from entering the motor cavity. Figure 3 and Figure 4As shown, a plurality of cable retainers 230 are also provided between the first silicone tube 220 and the second silicone tube 270. Each cable retainer 230 has a through hole for guiding and constraining the cable 240 to control the multi-degree-of-freedom bending motion of the actuator 200 and the vision unit 300 in a flexible state. The first silicone tube 220 is used for heat insulation, and the second silicone tube 270 is used for inner layer encapsulation. The presence of the cable retainers 230 not only prevents the cable from experiencing radial runout (bowlstring effect) when bending, but also acts as a support similar to a spine, ensuring that the actuator 200 can achieve controllable multi-degree-of-freedom bending motion in a flexible state.

[0032] Furthermore, such as Figure 5 As shown, the spiral heat exchange tube 250 is connected to two quick-connect ports 280 at its end. One quick-connect port 280 serves as a liquid inlet, and the other quick-connect port 280 serves as a liquid outlet. The other end of the two quick-connect ports 280 is used to connect to a pump or an external circulation pipeline to realize the input, output, and circulation flow control of the heat exchange liquid.

[0033] Furthermore, the low-melting-point alloy 260 uses Field metal (indium: 51%, bismuth: 32.5%, tin: 16.5%), which has a melting point of approximately 62°C. This is higher than human body temperature to prevent accidental melting. Simultaneously, through inner encapsulation, outer insulation, and temperature-controlled fluid control, the phase change material is isolated from human tissue, reducing the risk of heat leakage. Figure 6 As shown, the spiral heat exchange tube 250 is a spiral hollow copper tube. The spiral structure of the spiral heat exchange tube 250 is configured as a turbulence element. This structure can enhance the turbulence effect of the fluid inside the tube, thereby enhancing the turbulence effect between the fluid inside the tube and the low melting point alloy 260 to improve the heat exchange efficiency, and enabling the actuator 200 to switch between a rigid state and a flexible state. When the low melting point alloy 260 is solid, the actuator 200 is in a rigid state and has the ability to resist external forces. When the low melting point alloy 260 is liquid, the actuator 200 is in a flexible state and can be bent freely.

[0034] Furthermore, an end effector 210 is installed at the end of the execution unit 200; the end effector 210 can be replaced according to surgical needs, including one or more combinations of cutting tools (such as grinding heads, bone drills, milling cutters), additive manufacturing tools (such as bioprinting nozzles, injection needles), clamping tools (such as grippers, needle holders), hemostasis and cutting tools (such as electrosurgical knives, ultrasonic scalpels) and sensing and measuring tools (such as probes, force sensors).

[0035] Furthermore, the variable stiffness robotic arm based on fluid heat exchange provided in this embodiment of the invention further includes: a vision unit 300 is also provided at the end of the base 100; as shown in the figure. Figure 7As shown, the vision unit 300 includes a monocular camera 310 and a light source 320, used to acquire image information within the narrow surgical cavity in real time to assist the doctor in navigation and operation. The line-driven method of the vision unit 300 is the same as that of the execution unit 200.

[0036] In an exemplary manufacturing method, the actuator 200 in a variable stiffness robotic arm based on fluid heat exchange can be prepared by the following steps: Step S101: Melt the low-melting-point alloy 260 and pour it into the second silicone tube 270.

[0037] In step S102, while the low-melting-point alloy 260 is still in a molten or semi-molten state, the spiral heat exchange tube 250 is inserted into the molten low-melting-point alloy 260.

[0038] Step S103: After the low melting point alloy 260 cools and solidifies, the assembly of the cable 240 and the cable tray 230 is completed.

[0039] On the other hand, embodiments of the present invention also provide a control method for a variable stiffness robotic arm based on fluid heat exchange, the method comprising: In step S1, when the low-melting-point alloy 260 is in a liquid state and the actuator 200 is in a flexible state, the drive motor 110 pulls or releases the corresponding cable 240 to move the actuator 200 and the vision unit 300 to the target position.

[0040] Specifically, such as Figure 8 As shown, step S1 includes: Based on the assumption of constant curvature, the bending plane angles in the task space are constructed according to geometric relationships. Bending angle Bending radius With cable length The mapping relationship between them is expressed as follows: Task space coordinates With the angle of the curved plane Bending angle Bending radius The expression for the mapping relationship between them is as follows: In the formula, .

[0041] Based on the coordinates of the target location Solve for the bending plane angle, bending angle, and bending radius in the task space. And based on the mapping relationship, the target length of the cable is obtained; Based on the target length of the cable The drive motor is controlled to move to the target position by changing the length of the cable.

[0042] In step S2, a cryogenic liquid is pumped into the quick-connect interface 280. Heat exchange occurs between the cryogenic liquid and the low-melting-point alloy 260 within the spiral heat exchange tube 250, controlling the cooling and condensation of the low-melting-point alloy 260. This switches the actuator 200 to a rigid state, enabling it to perform operational tasks. In this state, the robot can perform stable and precise operations such as debridement, drilling, or in-situ printing.

[0043] Step S3: After the operation task is completed, high-temperature liquid is pumped into the quick-connect interface 280. Heat exchange occurs between the high-temperature liquid in the spiral heat exchange tube 250 and the low-melting-point alloy 260, and the low-melting-point alloy 260 is heated and melted, thereby switching the actuator 200 to a flexible state.

[0044] In summary, this invention provides a variable stiffness robotic arm based on fluid heat exchange. Employing a spiral heat exchange tube as a turbulence element, it significantly improves heat exchange efficiency by enhancing the turbulence effect of the fluid within the tube. This enables the robotic arm to rapidly complete the solid-liquid phase transition of low-melting-point alloys, solving the problems of slow response and long surgical waiting times associated with traditional variable stiffness instruments. Simultaneously, this invention resolves the operational challenges in the narrow environment of the knee joint cavity: in its flexible state, it can flexibly navigate around obstacles to the lesion; in its rigid state, it provides sufficient support for grinding or drilling, ensuring the safety and precision of minimally invasive surgery.

[0045] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A variable stiffness robotic arm based on fluid heat exchange, characterized in that, The variable stiffness robotic arm includes: Base (100); and, An actuator (200) is disposed at the end of the base (100); the actuator (200) includes a first silicone tube (220), a second silicone tube (270) is disposed inside the first silicone tube (220), a spiral heat exchange tube (250) is disposed inside the second silicone tube (270), and a low melting point alloy (260) is filled between the second silicone tube (270) and the spiral heat exchange tube (250). By introducing a heat exchange fluid with a temperature lower than or higher than the phase change temperature of the low melting point alloy (260) into the spiral heat exchange tube (250), heat exchange occurs between the heat exchange fluid in the spiral heat exchange tube (250) and the low melting point alloy (260), thereby controlling the switching of the low melting point alloy (260) between solid and liquid states, and thus realizing the switching of the actuator (200) between rigid and flexible states.

2. The variable stiffness robotic arm based on fluid heat exchange according to claim 1, characterized in that, The base (100) is equipped with a plurality of drive motors (110). Each drive motor (110) is connected to a cable (240) via a motor flange (140). The cable (240) is installed in the actuator (200) via a cable management groove (150) located between the first silicone tube (220) and the second silicone tube (270) to drive the actuator (200).

3. A variable stiffness robotic arm based on fluid heat exchange according to claim 2, characterized in that, A cable retainer (230) is also provided between the first silicone tube (220) and the second silicone tube (270). The cable retainer (230) is used to guide and constrain the cable (240) to control the movement of the actuator (200).

4. A variable stiffness robotic arm based on fluid heat exchange according to claim 1, characterized in that, The low-melting-point alloy (260) is made from Field Metals.

5. A variable stiffness robotic arm based on fluid heat exchange according to claim 1, characterized in that, The end of the actuator (200) is equipped with an end function actuator (210); the end function actuator (210) includes one or more combinations of cutting tools, additive manufacturing tools, hemostasis and cutting tools, and sensing and measuring tools.

6. A variable stiffness robotic arm based on fluid heat exchange according to claim 1, characterized in that, The spiral heat exchange tube (250) is a spiral hollow copper tube. The spiral structure of the spiral heat exchange tube (250) is configured as a turbulence element to enhance the turbulence effect between the fluid inside the tube and the low melting point alloy (260) to improve the heat exchange efficiency.

7. A variable stiffness robotic arm based on fluid heat exchange according to claim 1, characterized in that, The base (100) is further provided with a vision unit (300) at its end; the vision unit (300) includes a monocular camera (310) and a light source (320).

8. A control method for a variable stiffness robotic arm based on fluid heat exchange according to any one of claims 1-7, characterized in that, The method includes: When the low-melting-point alloy (260) is in a liquid state and the actuator (200) is in a flexible state, the drive motor (110) pulls or releases the corresponding cable (240) to move the actuator (200) to the target position; Low-temperature liquid is introduced into the spiral heat exchange tube (250), and heat exchange occurs between the low-temperature liquid in the spiral heat exchange tube (250) and the low-melting-point alloy (260). The low-melting-point alloy (260) is controlled to cool down and condense, thereby switching the actuator (200) to a rigid state and performing the operation task. When the operation task is completed, high-temperature liquid is input into the spiral heat exchange tube (250). Heat exchange occurs between the high-temperature liquid in the spiral heat exchange tube (250) and the low-melting-point alloy (260), and the low-melting-point alloy (260) is heated and melted, thereby switching the actuator (200) to a flexible state.

9. The control method for a variable stiffness robotic arm based on fluid heat exchange according to claim 8, characterized in that, The process by which the drive motor (110) moves the actuator (200) to the target position by pulling or releasing the corresponding cable (240) includes: Based on geometric relationships, construct the mapping relationship between the bending plane angle, bending angle, bending radius and cable length in the task space; Based on the coordinates of the target location, the bending plane angle, bending angle, and bending radius in the task space are calculated, and the target length of the cable is obtained according to the mapping relationship. Based on the target length of the cable, the drive motor is controlled to move the actuator to the target position by changing the length of the cable.

10. A surgical robot, characterized in that, Including the variable stiffness robotic arm based on fluid heat exchange as described in any one of claims 1-7.

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