Rigidity adjusting structure for continuum robot joint and continuum robot joint
By using first and second direction stiffness adjustment components and thermal isolation components made of nickel-titanium alloy, the coupling problem of joint stiffness adjustment in continuum robots is solved, realizing independent and precise stiffness control of joints, which is suitable for multi-scale applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIMEI UNIV
- Filing Date
- 2026-02-09
- Publication Date
- 2026-04-24
AI Technical Summary
Existing technologies struggle to achieve independent, decoupled, and continuous control of the longitudinal and lateral stiffness of joints in continuum robots at the level of a single joint, and existing solutions are complex and difficult to miniaturize.
The first and second directional stiffness adjustment components, made of nickel-titanium alloy, utilize the phase transformation characteristics of the alloy under temperature changes or stress. Through the physical barrier of the thermal isolation component, the axial and radial stiffness of the joint can be independently controlled, and precise adjustment can be achieved in combination with an external electronic control system.
It achieves independent adjustment of the axial and radial stiffness of the joint, with a stiffness variation ratio of 1:2 to 1:3 and a response time in the range of milliseconds to hundreds of milliseconds. The system is simplified and miniaturized, making it suitable for a variety of application scenarios.
Smart Images
Figure CN121912428A_ABST
Abstract
Description
Technical Field
[0001] This application relates to continuum robot technology, and in particular to a stiffness adjustment structure for a continuum robot joint and a continuum robot joint. Background Technology
[0002] Continuum robots are a class of robots with a continuous, flexible skeleton. Unlike traditional rigid linkage robots, continuum robots can bend and twist along their entire length. They are typically composed of multiple identical or similar structures strung together, and their shape is changed by controlling these strung structures to achieve maneuvering objectives. Due to their inherent compliance and continuous deformation capabilities, continuum robots have significant application advantages in key areas such as minimally invasive surgery, confined space exploration, and human-robot interaction, and have enormous market potential.
[0003] The ability to actively adjust joint stiffness is one of the core indicators determining the performance of continuum robots, directly affecting the robot's adaptability to different load conditions, accuracy requirements, and safety standards. Currently, mainstream variable stiffness technologies in the industry are mainly developed based on the following principles: antagonistic actuation (such as tendon actuation), particle blockage effect, interlayer friction adjustment, and the controllable characteristics of electrorheological / magnetorheological fluids. These technologies have been initially applied in specific scenarios, but have not yet formed universally applicable high-performance solutions.
[0004] For example, existing technology discloses a biomimetic rigid-flexible coupled variable stiffness continuum robot. This continuum robot includes a body, a continuum mechanism, a main skeleton, a stiffness adjustment mechanism, a drive mechanism, a sensor unit, a control processing module, and a power module. Its continuum mechanism includes three parts: continuum mechanism one, continuum mechanism two, and continuum mechanism three, each composed of multiple circular rigid segments, elastic rods, and compression springs. The stiffness adjustment mechanism consists of multiple sets of friction sliders, springs, pressure blocks, pull rods, connecting rods, connecting shafts, turntables, torsion springs, and pull ropes. This technical solution uses a method of adding a stiffness adjustment mechanism to the circular rigid segments of the continuum mechanism and using a motor to adjust the posture and stiffness, which has the advantage of a compact structure. Simultaneously, the tension of the pull ropes in the stiffness adjustment mechanism is used to adjust the friction force between the friction sliders and elastic rods, achieving controllable stiffness. However, this technical solution typically only allows for global, coarse adjustments to the robot as a whole, whether "soft" or "hard," and stiffness changes are often coupled with robot deformation. It is not possible to achieve independent, decoupled, and continuous control of longitudinal and lateral stiffness at the level of a single joint.
[0005] Existing technology also discloses a variable stiffness rigid-flexible coupled super-redundant continuum robot, including a head unit continuum, an intermediate unit continuum, a tail unit continuum, and drive lines. The head unit continuum includes a head segment and multiple structural segments connected in sequence. The upper surface of the head segment is flat and used to connect to the end effector. The intermediate unit continuum is connected to the head unit continuum and includes multiple structural segments connected in sequence. The tail unit continuum is connected to the intermediate unit continuum and includes a tail segment and multiple structural segments connected in sequence. The lower surface of the tail segment is flat and used to fix it to a work platform or base. Multiple drive lines pass through the tail segment and structural segments and connect to the head segment, used to transmit driving force to the head segment, structural segments, and tail segment. This technical solution "manifests" stiffness changes by tightening the drive lines to change the mechanical constraints between segments, which falls under the category of macroscopic structural mechanics. This technical solution solves the problems of poor structural stability caused by insufficient drive line tension in traditional continuum robots and the inability to actively adjust structural stiffness. However, it relies on a drive cable running through the entire system and complex inter-segment fit, making the system complex and difficult to miniaturize. Summary of the Invention
[0006] To address at least one of the aforementioned problems, this application provides a stiffness adjustment structure and a joint for a continuous robot, which can achieve independent control of stiffness in different directions (such as axial and radial) at the level of a single joint without relying on drive cables.
[0007] This application provides a stiffness adjustment structure for the joint of a continuum robot, employing the following technical solution: A stiffness adjustment structure for a joint of a continuum robot includes a first-direction stiffness adjustment component, a second-direction stiffness adjustment component, and a thermal isolation component. The first-direction stiffness adjustment component and the second-direction stiffness adjustment component are made of nickel-titanium alloy. The first-direction stiffness adjustment component extends along a preset first direction and surrounds a through space along a preset second direction. The second-direction stiffness adjustment component is sleeved on the first-direction stiffness adjustment component along the preset second direction. The thermal isolation component is disposed between the first-direction stiffness adjustment component and the second-direction stiffness adjustment component.
[0008] By adopting the above technical solution, utilizing the phase transformation mechanism of nickel-titanium alloy under temperature changes or stress—that is, the unique property of reversible transformation between austenite and martensite—the first and second direction stiffness adjustment components are designed to be made of nickel-titanium alloy. Through the physical barrier of the thermal isolation component, thermal decoupling between the first and second direction stiffness adjustment components is achieved. Therefore, when the stiffness adjustment structure for a continuous robot joint of this application is applied to a continuous robot joint, with the first direction pre-defined as the axial direction of the joint and the second direction pre-defined as the circumferential direction, only external temperature changes or stress are needed to adjust the stiffness of the joint along the desired direction using the first and second direction stiffness adjustment components (the first direction stiffness adjustment component can adjust the axial stiffness of the joint, and the second direction stiffness adjustment component can adjust the radial stiffness of the joint), thus achieving independent stiffness adjustment in two different directions of the joint.
[0009] Preferably, the first directional stiffness adjustment component includes at least two first directional stiffness adjustment units, which are arranged along a preset second direction to form the through space. The at least two first directional stiffness adjustment units are distributed at intervals along a preset first direction, and the through spaces formed by adjacent first directional stiffness adjustment units are interconnected.
[0010] By adopting the above technical solution, as a specific structural example, the first direction stiffness adjustment component can adopt a design of multiple first direction stiffness adjustment units. Each first direction stiffness adjustment unit is arranged along a preset second direction to form a through space. The through spaces formed by each first direction stiffness adjustment unit are interconnected. Multiple first direction stiffness adjustment units are distributed sequentially at intervals along the preset first direction (i.e., they are not connected to each other).
[0011] Preferably, the first directional stiffness adjustment unit is a ring structure, and at least two first directional stiffness adjustment units are arranged in parallel.
[0012] By adopting the above technical solution, as a specific structural example, the first directional stiffness adjustment unit is a ring structure, such as a circular ring structure. Among the multiple first directional stiffness adjustment units of the circular ring structure, their diameters can be the same or different. As another specific structural example, the multiple first directional stiffness adjustment units are distributed in parallel. The multiple first directional stiffness adjustment units can be distributed at equal distances or at different distances. As another specific structural example, the circumferential center of the through space formed by the first directional stiffness adjustment unit of each circular ring structure is distributed along the central axis of the joint, or the circumferential center of the through space formed by the first directional stiffness adjustment unit is staggered around the central axis of the joint.
[0013] As another structural example, the first direction stiffness adjustment unit is a filament or strip structure (i.e., nickel-titanium alloy wire or nickel-titanium alloy strip). In a single first direction stiffness adjustment unit, the two ends of the filament or strip structure are connected along a preset second direction to form a ring structure. Multiple ring structures of first direction stiffness adjustment units are then distributed in parallel at intervals along a preset first direction to form a first direction stiffness adjustment component.
[0014] Preferably, the first directional stiffness adjustment component includes at least two first directional stiffness adjustment units, the at least two first directional stiffness adjustment units are arranged sequentially along a preset first direction, and two adjacent first directional stiffness adjustment units are connected end to end to form a spiral structure, and the through space is provided within the spiral structure.
[0015] By adopting the above technical solution, as a structural example, the first-direction stiffness adjustment component can be designed with multiple first-direction stiffness adjustment units. These units are arranged sequentially along a preset first direction, and adjacent units are connected end-to-end along the preset first direction and rotated and bent to form a spiral structure, penetrating the space within the spiral structure. The spiral structure formed by the multiple first-direction stiffness adjustment units is preferably a regular spiral structure, such as an equidistant spiral, a logarithmic spiral, or a cylindrical spiral.
[0016] As another structural example, the first direction stiffness adjustment unit is a filamentous or strip-shaped structure (i.e., nickel-titanium alloy wire or nickel-titanium alloy strip). Multiple filamentous or strip-shaped first direction stiffness adjustment units are arranged sequentially along a preset first direction. Each first direction stiffness adjustment unit is rotated and bent along the preset first direction. Two adjacent filamentous or strip-shaped first direction stiffness adjustment units are connected end to end along the two ends of the preset first direction to form a spiral structure first direction stiffness adjustment component.
[0017] Preferably, the second directional stiffness adjustment component is a two-dimensional mesh structure or a three-dimensional mesh structure.
[0018] By adopting the above technical solution, as a structural example, the second-direction stiffness adjustment component adopts a two-dimensional mesh structure or a three-dimensional mesh structure, such as a regular hexagonal (i.e., honeycomb mesh), square, equilateral triangle, or an irregular pentagonal, hexagonal, or other mesh structure.
[0019] Preferably, the second directional stiffness adjusting member is arranged along a preset second direction to form a cylindrical structure.
[0020] By adopting the above technical solution as a structural example, for a first direction stiffness adjustment component formed by parallel and spaced first direction stiffness adjustment units of multiple ring structures, the second direction stiffness adjustment component can be designed as a cylindrical structure formed along a preset second direction, and then fits onto the outer circumferential surface of the first direction stiffness adjustment component.
[0021] As another structural example, the second-direction stiffness adjustment component is a sheet-like structure (i.e., a nickel-titanium alloy sheet) with a grid structure. The sheet-like second-direction stiffness adjustment component is connected along two sides of a preset second direction, thus forming an overall cylindrical structure.
[0022] Preferably, the second-direction stiffness adjustment member is provided with at least two stiffness adjustment areas in sequence along a preset second direction.
[0023] By adopting the above technical solution, as a structural example, the second direction stiffness adjustment component is provided with multiple stiffness adjustment areas in sequence along the preset second direction. The stiffness adjustment areas are corresponding to the control of applying different temperature changes and stresses, thereby dividing the second direction stiffness adjustment component into multiple independent control areas distributed along the joint circumference, realizing local radial stiffness differential adjustment.
[0024] Preferably, the second directional stiffness adjusting element is a negative Poisson's ratio structure.
[0025] By adopting the above technical solution, as a structural example, the second-direction stiffness adjustment component is selected with a negative Poisson's ratio structure, such as a typical concave honeycomb structure, which can further improve the radial deformation capacity and stiffness response sensitivity.
[0026] Preferably, it further includes a first heating element and a second heating element. The first heating element is disposed on the first directional stiffness adjusting member and is used to provide heat to the first directional stiffness adjusting member to enable the first directional stiffness adjusting member to achieve the transformation between austenite and martensite. The second heating element is disposed on the second directional stiffness adjusting member and is used to provide heat to the second directional stiffness adjusting member to enable the second directional stiffness adjusting member to achieve the transformation between austenite and martensite.
[0027] By adopting the above technical solution as a structural example, the design of the first and second heating elements facilitates the supply of heat to the first and second directional stiffness adjusting components.
[0028] Preferably, the first thermal element is an electrothermal excitation electrode, and the second thermal element is an electrothermal excitation circuit.
[0029] By adopting the above technical solution, as a structural example, the first thermal element can be an electrothermal excitation electrode. For the first directional stiffness adjustment unit of the annular structure, an independent electrothermal excitation electrode can be provided at each of the two ends of each first directional stiffness adjustment unit along the preset first direction. For the first directional stiffness adjustment member of the spiral structure, an independent electrothermal excitation electrode can be provided at each of the two ends of each first directional stiffness adjustment unit along the preset first direction.
[0030] The second thermal element can be an electrothermal excitation circuit. For a first-direction stiffness adjustment component with a two-dimensional or three-dimensional mesh structure, the electrothermal excitation circuit (such as a serpentine copper thin-film heating circuit) can be fabricated on the surface of its mesh structure using microelectromechanical processing (MEMS). Furthermore, for multiple stiffness adjustment regions, a separate electrothermal excitation circuit can be fabricated on the surface of the mesh structure within each stiffness adjustment region using MEMS, thus dividing the area into multiple independent control regions distributed along the circumference.
[0031] An external electrical control system or current drive module can be used to connect multiple electrothermal excitation circuits in the first and second thermal elements to the external electrical control system or current drive module. Under the control of the external electrical control system or current drive module, heat can be conveniently provided to the first and second direction stiffness adjustment components through Joule heating.
[0032] This application also provides a continuum robot joint, which adopts the following technical solution: A continuum robot joint includes a hollow joint body and the aforementioned stiffness adjustment structure for the continuum robot joint. The stiffness adjustment structure for the continuum robot joint is disposed within the hollow structure of the joint body. The preset first direction is the axial direction of the joint body, the preset second direction is the circumferential direction of the joint body, and the through space is connected to the hollow structure of the joint body.
[0033] By adopting the above technical solution, in the joint of the continuum robot of this application, the first directional stiffness adjustment component is distributed along the axial direction of the joint body and surrounds the joint body to form a through space, and the second directional stiffness adjustment component is sleeved on the outer peripheral surface of the first directional stiffness adjustment component along the circumference of the joint body. As a specific structural example, the first directional stiffness adjustment component and the second directional stiffness adjustment component are coaxially arranged with the joint body.
[0034] Preferably, the thermal insulation element is disposed on the joint body, or the thermal insulation element is integrally formed with the joint body.
[0035] By adopting the above technical solution, as a specific structural example, the thermal insulation component is disposed on the joint body or integrally formed with the joint body. Specifically, the thermal insulation component uses a low thermal conductivity material, for example, a thermal conductivity of less than 0.05 W / m. Low thermal conductivity materials of K, such as silica aerogel and porous polymer foam, are used to better isolate the heat transfer between the first-direction stiffness adjustment component and the second-direction stiffness adjustment component, thereby achieving thermal coupling for joint axial and radial stiffness adjustment.
[0036] Preferably, it further includes a power element and a connector, wherein the power element is connected to the connector and is used to drive the connector to rotate, and the connector is connected to the first directional stiffness adjusting element.
[0037] By adopting the above technical solution, as a specific structural example, the power element drives the first direction stiffness adjustment component to rotate via the connecting member and the first direction stiffness adjustment component through the connecting member. Specifically, the power element can be an existing motor, and the connecting member adopts a shaft structure.
[0038] Preferably, it also includes a displacement sensor connected to the power element, used to detect the joint position and the rotational speed of the power element, and to provide a position feedback signal.
[0039] By adopting the above technical solution, as a specific structural example, a displacement sensor is added to detect the rotational speed and joint position of the power element in real time, while providing position feedback signals to the external control system. More specifically, the displacement sensor can be an existing encoder, which can be coaxially set with the power output shaft of the power element.
[0040] Preferably, it also includes a speed reducer connected to the power element, which is used to reduce the rotational speed of the power element and increase the output torque.
[0041] By adopting the above technical solution as a specific structural example, the reducer is connected to the power output shaft of the power element to reduce the speed of the power element and realize the precision drive of the joint.
[0042] Preferably, it also includes a sensing module and a control module. The sensing module is used to provide feedback signals on the strain state and phase change process of the joint, and the control module is connected to the sensing module, displacement sensor, power element, and reducer respectively.
[0043] Preferably, the control module includes a temperature / strain signal demodulation module, a central processing unit, and a multi-channel current drive module. The sensing module, the temperature / strain signal demodulation module, the central processing unit, and the multi-channel current drive module are sequentially connected by signals. The multi-channel current drive module is used to apply current signals to the first directional stiffness adjustment component and the second directional stiffness adjustment component.
[0044] By adopting the above technical solution, as a specific structural example, the sensing module can be a fiber optic grating sensor (e.g., 0.15 mm in diameter) integrated inside the joint and / or a "self-sensing" circuit based on the resistance change of nickel-titanium alloy, used to provide real-time feedback on the strain state and phase transformation process of the joint; the control module includes a temperature / strain signal demodulation module, a central processing unit, and a multi-channel current drive module. The sensing module (fiber optic grating sensor and "self-sensing" circuit) is used to provide real-time feedback of strain signals. The temperature / strain signal demodulation module is used to receive the feedback signal from the sensing module. The central processing unit is used to receive the upper-level target stiffness command and independently control the excitation signals applied to the first and second direction stiffness adjustment components. The central processing unit receives the signal from the temperature / strain signal demodulation module and applies a control signal to the multi-channel current drive module. The multi-channel current drive module receives the control signal from the central processing unit and outputs a current signal. The current signal passes through the electrothermal excitation electrode and the electrothermal excitation circuit to perform Joule heating on the first and second direction stiffness adjustment components and control the phase transformation ratio of austenite (A phase) and martensite (M phase) of the alloy.
[0045] Preferably, the joint body further includes a first cover and a second cover, with a first opening and a second opening respectively at both ends along the axial direction, the first cover being located at the first opening and the second cover being located at the second opening.
[0046] By adopting the above technical solution, as a specific structural example, the joint body is a hollow structure with openings at both ends. The two ends of the joint body along the axial direction are provided with a first opening and a second opening respectively. The first directional stiffness adjustment component is arranged along the direction from the first opening to the second opening. The sealing of the entire joint structure is achieved through the first cover and the second cover.
[0047] In summary, this application has at least the following beneficial effects: (1) The stiffness adjustment structure for the joint of the continuum robot of this application solves the coupling problem of stiffness adjustment in different directions in the joint of the continuum robot by the cooperative design of the first direction stiffness adjustment component, the second direction stiffness adjustment component and the thermal isolation component. It can independently control the axial and radial stiffness of the joint. At the same time, it can cooperate with the control system of the peripheral device to provide a structural basis for the precise control of stiffness adjustment in different directions. (2) The stiffness adjustment structure for the joint of the continuum robot in this application relies on the reversible phase transformation characteristics of NiTi alloy. The stiffness in both directions can be continuously adjusted in both directions from "soft" (high martensite ratio) to "hard" (high austenite ratio), with a stiffness change ratio of 1:2 to 1:3, covering the stiffness requirements of most application scenarios. (3) The first and second direction stiffness adjustment components are core structures made of only NiTi material and have no complex auxiliary mechanisms. They can be miniaturized through micro-machining processes (photolithography, etching) and are suitable for a wide range of scales, from industrial robots (macro) to intravascular surgical instruments (micro, diameter <3mm). They have the technical advantages of compact structure and multi-scale applicability. Attached Figure Description
[0048] Figure 1 This is a schematic diagram of the overall structure of the joint of the continuum robot according to an embodiment of this application; Figure 2 This is an exploded view of the joint structure of a continuum robot according to an embodiment of this application; Figure 3 This is a three-dimensional structural diagram of the first-direction stiffness adjustment component in the joint of a continuum robot according to an embodiment of this application; Figure 4 This is a schematic diagram of the structure of the second-direction stiffness adjustment component in the joint of the continuum robot according to an embodiment of this application; Figure 5 This is a planar unfolded view of the second-direction stiffness adjustment member in the joint of a continuum robot according to an embodiment of this application; Figure 6 This is a schematic diagram of the structure of a continuum robot joint after assembly of the joint body, the first direction stiffness adjustment component, the second direction stiffness adjustment component, and the thermal insulation component, according to an embodiment of this application. Figure 7 This is an exploded view of the joint body and the first direction stiffness adjustment component in the joint of the continuum robot according to an embodiment of this application; Figure 8 This is an exploded view of the joint of the continuum robot according to an embodiment of this application, omitting the joint body and the first direction stiffness adjustment component; Figure 9 This is a cross-sectional view of the joint of the continuum robot in an embodiment of this application, omitting the second-direction stiffness adjustment component.
[0049] Label Explanation: 1. First direction stiffness adjustment component; 11. First direction stiffness adjustment unit; 2. Second direction stiffness adjustment component; 21. Stiffness adjustment area; 3. Thermal insulation component; 4. Through space; 5. Joint body; 6. Power element; 7. Connector; 8. Displacement sensor; 91. First cover; 92. Second cover; 10. Reducer. Detailed Implementation
[0050] Although the invention can be readily embodied in various forms, only some specific embodiments are shown in the accompanying drawings and will be described in detail in this specification. It is understood that this specification should be regarded as an exemplary illustration of the principles of the invention and is not intended to limit the invention to what is described herein.
[0051] Therefore, a feature pointed out in this specification is used to illustrate one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. While certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.
[0052] In the embodiments shown in the accompanying drawings, the directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of the various elements of the invention are relative rather than absolute. These descriptions are appropriate when these elements are in the positions shown in the drawings. If the descriptions of the positions of these elements change, these directional indications also change accordingly.
[0053] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.
[0054] Abbreviations: NiTi: Nickel-Titanium alloy; A phase: Austenite phase, which refers to the austenite phase; M phase: Martensite phase, which refers to the martensitic phase.
[0055] Example According to one embodiment shown in this example, the construction can be referred to as [example]. Figure 1-9 Throughout this view, the same reference numerals denote corresponding components. It should be understood that the continuum robot joint according to this embodiment can be used in fields such as minimally invasive surgery, confined space exploration, and human-computer interaction, improving the performance and application expansion of continuum robots.
[0056] like Figure 1-9 As shown, the joint of the continuum robot in this embodiment includes a first cover, a second cover, a joint body, a stiffness adjustment structure, a power element, a connector, a displacement sensor, a reducer, a sensing module, and a control module.
[0057] See Figure 6 In this embodiment, the joint body is a hollow structure and is cylindrical in shape. It has a first opening and a second opening at both ends along its axial direction, such as... Figure 1 As shown, the first cover and the second cover are respectively installed at the first opening and the second opening, achieving a seal for the overall structure and protecting the internal components. Furthermore, each of the first and second covers has a wire through-hole for the input and output of electrical thermal excitation and sensor signals.
[0058] See Figure 6 The stiffness adjustment structure includes a first-direction stiffness adjustment component, a second-direction stiffness adjustment component, and a thermal isolation component. The first-direction stiffness adjustment component and the second-direction stiffness adjustment component are made of nickel-titanium alloy, respectively. The thermal isolation component is made of a material with a thermal conductivity of less than 0.05 W / m. K is composed of materials with low thermal conductivity.
[0059] See Figure 3 The first-direction stiffness adjustment component includes 16 first-direction stiffness adjustment units, each made of nickel-titanium alloy wire, which forms a ring around the joint circumference. Each nickel-titanium alloy wire has independent electrothermal excitation electrodes at both ends, achieving austenite-martensite phase transformation through Joule heating, thereby independently adjusting the joint's axial stiffness. The 16 first-direction stiffness adjustment units are evenly spaced and parallel along the joint axis, and the 16 ring-shaped first-direction stiffness adjustment units are coaxially arranged with the joint. Furthermore, the center of each of the 16 ring-shaped first-direction stiffness adjustment units forms a through space communicating with the hollow structure of the joint body. In other words, the 16 equally spaced, parallel, and coaxially distributed ring-shaped first-direction stiffness adjustment units form the first-direction stiffness adjustment component of this embodiment. Specifically, this embodiment uses 16 NiTi alloy wires with a diameter of 0.5 mm, which are pre-stretched to achieve superelasticity; in the miniaturized embodiment (joint diameter < 3 mm), single or multiple NiTi alloy microwires with a diameter of 50 μm can be used.
[0060] See Figure 4 and Figure 8 In this embodiment, the second-direction stiffness adjustment component is a nickel-titanium alloy sheet with a negative Poisson's ratio grid structure, which is arranged in a cylindrical shape around the joint circumference. Specifically, in this embodiment, a 0.2 mm thick NiTi alloy sheet is laser-cut into a two-dimensional concave hexagonal negative Poisson's ratio grid. In the miniaturized embodiment, a 10 μm thick NiTi thin film can be used to create a micro-grid through photolithography and etching processes.
[0061] See Figure 5 The second-direction stiffness adjustment component has three stiffness adjustment zones arranged sequentially along the joint circumference. Each stiffness adjustment zone is equipped with an independent electrothermal excitation circuit. By locally heating the stiffness adjustment zone, the martensitic variant can be reset or preferentially oriented, thereby independently adjusting the radial stiffness of the joint.
[0062] See Figure 6 and Figure 7 The thermal insulator is fixedly connected to the joint body and forms an annular receiving space distributed along the circumference of the joint body. The second-direction stiffness adjustment component is fitted within this annular receiving space. Fourteen annular first-direction stiffness adjustment units are located within the hollow structure of the joint body, and the thermal insulator is positioned precisely between the cylindrical second-direction stiffness adjustment component and the 14 annular first-direction stiffness adjustment units. See also... Figure 2 , Figure 8 and Figure 9 The second directional stiffness adjustment component is supported within the joint body by the second cover.
[0063] See also Figure 2 , Figure 8 and Figure 9 In this embodiment, the connector is a cylindrical shaft structure, the power element is a motor, the displacement sensor is an encoder, and the reducer is a harmonic reducer. The harmonic reducer, motor, and encoder are arranged sequentially and coaxially. The motor is fixed on the joint body, and its power output shaft is connected to the reducer to provide the rotational power required for the overall joint drive. The encoder is coaxially mounted with the motor to detect the motor speed and joint position in real time and provide position feedback signals to the control module. The harmonic reducer is connected to the output shaft of the motor to reduce the motor speed and increase the output torque, thereby achieving precise joint drive. One end of the connector is connected to the encoder, and the other end of the connector passes through the output ends of the motor and the harmonic reducer in sequence, and is fixedly connected to the longitudinal stiffness adjustment layer to transmit the drive torque and support the internal structure.
[0064] In this embodiment, the sensing module is a fiber optic grating sensor integrated inside the joint, used for real-time feedback of the joint's strain state and phase transition process. The control module includes a temperature / strain signal demodulation module, a central processing unit, and a multi-channel current drive module. The sensing module, temperature / strain signal demodulation module, central processing unit, and multi-channel current drive module are sequentially signal-connected. The multi-channel current drive module is independently connected to the electrothermal excitation electrode in the first direction stiffness adjustment component and the electrothermal excitation circuits in the three stiffness adjustment areas of the second direction stiffness adjustment component, respectively, for applying current signals to the first and second direction stiffness adjustment components.
[0065] The working principle of the control module and sensing module in this embodiment is as follows: the sensing module provides real-time feedback on the strain state and phase transition process of the joint; the temperature / strain signal demodulation module receives the signal fed back by the sensing module and identifies and demodulates it; the central processing unit receives the demodulated signal from the temperature / strain signal demodulation module and outputs a control signal to the multi-channel current drive module; the multi-channel current drive module independently controls the excitation signal applied to the first direction stiffness adjustment component and the second direction stiffness adjustment component according to the control signal, thereby completing the stiffness adjustment.
[0066] Based on the above structural description, the working principle of adjusting the axial and radial stiffness of the joints of the continuum robot in this embodiment is as follows: The central processing unit in the control module receives the target stiffness command from the upper level. It connects to the electrothermal excitation electrode in the first directional stiffness adjustment component via a multi-channel current drive module, applying pulsed current to control the phase transformation ratio of austenite (A phase) to martensite (M phase) in the alloy, thereby independently adjusting the axial stiffness of the joint. Simultaneously, the multi-channel current drive module independently controls three electrothermal excitation circuits in the second directional stiffness adjustment component. Based on the target stiffness requirement, it controls heating at least one of the three stiffness adjustment regions in the second directional stiffness adjustment component. Depending on the actual situation, the target stiffness requirements of the three stiffness adjustment regions can be the same or different. This allows for localized heating to reset or preferentially orient the martensite variants, thereby independently adjusting the radial stiffness of the joint. For radial stiffness adjustment, external clamps or micro-actuators can be added inside the joint body. These micro-actuators or external clamps apply the same or different radial preloads to the three stiffness adjustment regions in the second directional stiffness adjustment component to induce preferential radial orientation of the martensite variants.
[0067] In addition, this embodiment can also be used with a dedicated control algorithm to improve the phase change control accuracy requirements of the first direction stiffness adjustment component and the second direction stiffness adjustment component. For example, a control algorithm combining feedforward compensation and closed-loop feedback (such as PID combined with Preisach hysteresis compensation model) can be used to overcome phase change hysteresis nonlinearity.
[0068] The specific adjustment methods and steps for adjusting the axial and radial stiffness of the joints of the continuum robot in this embodiment are as follows: 1. Bidirectional adjustment of axial stiffness: (1) Stiffening process: The control module calculates the required austenite volume fraction based on the target longitudinal stiffness Kz through the pre-stored "phase transformation ratio-stiffness-temperature" mapping model, generates a corresponding current pulse sequence to act on the first direction stiffness adjustment component, and raises the wire temperature through Joule heating to induce the alloy to transform into austenite, thereby achieving stiffness enhancement. (2) Stiffness reduction process: Stop applying current, use ambient heat dissipation to reduce the temperature of the first direction stiffness adjustment component, and the alloy transforms into martensite to achieve stiffness reduction; (3) Closed-loop correction: The fiber optic grating sensor provides real-time feedback of strain signals, and the control algorithm corrects the current output based on the feedback to achieve accurate tracking of axial stiffness.
[0069] 2. Bidirectional adjustment of radial stiffness: (1) Stiffening process: Ensure that the second direction stiffness adjustment component is in a state of full martensite or high martensite ratio, apply radial preload through the built-in micro actuator of the joint or external clamp, induce the martensite variant to preferentially orient in the radial direction, and significantly improve the radial stiffness; (2) Stiffness reduction process: The heating circuit of the target stiffness adjustment area in the second direction stiffness adjustment component is energized to heat the target stiffness adjustment area to the austenitic state. After cooling, it is transformed into non-oriented martensite or the variant orientation is directly reset to restore low stiffness. Local radial stiffness differential adjustment can be achieved by selecting different stiffness adjustment areas. 3. Decoupling control: Through the physical isolation of thermal isolation components and the independent excitation channel design of the first direction stiffness adjustment component and the second direction stiffness adjustment component by the control module, the spatial and temporal decoupling of the thermal excitation process in the two directions is achieved, ensuring that the adjustment does not interfere with each other.
[0070] In this embodiment, the ratio of longitudinal stiffness to transverse stiffness can reach 1:2 to 1:3, and the phase change response time is on the order of milliseconds to hundreds of milliseconds; the miniaturized embodiment can achieve excitation and sensing integration through the same pair of wires, simplifying system integration.
[0071] The joint of the continuum robot in this embodiment has the following advantages: 1. Achieve true stiffness decoupling adjustment: Through the design of the first direction stiffness adjustment component, the second direction stiffness adjustment component, and the thermal isolation component, the coupling problem of stiffness adjustment in different directions in the existing technology is completely solved. Axial and radial stiffness can be controlled independently and precisely, and the adjustment accuracy is improved by more than 30%. 2. Two-way wide-range adjustment: Relying on the reversible phase transformation characteristics of NiTi alloy, the stiffness in both directions can be continuously adjusted in both directions from "soft" (high martensite ratio) to "hard" (high austenite ratio), with a stiffness change ratio of 1:2 to 1:3, covering the stiffness requirements of most application scenarios. 3. Fast response and low steady-state power consumption: The phase transition is directly triggered by Joule heating, with a response time in the range of milliseconds to hundreds of milliseconds, which is more than 10 times faster than the existing solutions (seconds); after the phase transition is completed, the stiffness state is maintained autonomously by the material phase state, without the need for continuous energy input, and the steady-state power consumption is reduced by more than 80%. 4. Compact structure and applicable to multiple scales: The core functional layer is made of only NiTi material and has no complex auxiliary structures. It can be miniaturized through microfabrication processes (photolithography, etching) and is suitable for a wide range of scales, from industrial robots (macro) to intravascular surgical instruments (micro, diameter <3mm). 5. Self-sensing potential: Self-sensing can be achieved by utilizing the resistance change during the phase transformation process of NiTi alloy, which can reduce dependence on external sensors, further simplify the system structure, and reduce integration costs.
[0072] When the joint of the continuum robot in this embodiment is applied to a continuum robot, it has the following technical advantages in terms of economic benefits: 1. Industrial sector: It can improve the operating accuracy and load adaptability of continuous robots, reduce equipment maintenance costs, and extend service life. It is estimated that the overall efficiency of a single unit will increase by 20%-40%. 2. Medical field: Adapting to the miniaturization and high precision requirements of minimally invasive surgical instruments, reducing surgical trauma, improving surgical safety, and reducing the cost of treating postoperative complications, it has significant medical and economic benefits and social value; 3. Industrial value: It promotes the miniaturization and low power consumption of variable stiffness technology, drives the technological upgrading of upstream and downstream industries such as NiTi alloy processing and microelectromechanical systems, and forms new technological growth points.
[0073] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A stiffness adjustment structure for a joint of a continuum robot, characterized in that, The device includes a first directional stiffness adjusting component, a second directional stiffness adjusting component, and a thermal isolation component. The first directional stiffness adjusting component and the second directional stiffness adjusting component are made of nickel-titanium alloy. The first directional stiffness adjusting component extends along a preset first direction and surrounds a through space along a preset second direction. The second directional stiffness adjusting component is sleeved on the first directional stiffness adjusting component along the preset second direction. The thermal isolation component is disposed between the first directional stiffness adjusting component and the second directional stiffness adjusting component.
2. The stiffness adjustment structure for a joint of a continuum robot according to claim 1, characterized in that, The first directional stiffness adjustment component includes at least two first directional stiffness adjustment units. The first directional stiffness adjustment units are arranged along a preset second direction to form the through space. The at least two first directional stiffness adjustment units are distributed at intervals along a preset first direction, and the through spaces formed by adjacent first directional stiffness adjustment units are interconnected.
3. The stiffness adjustment structure for a joint of a continuum robot according to claim 2, characterized in that, The first directional stiffness adjustment unit is a ring structure, and at least two first directional stiffness adjustment units are arranged in parallel.
4. The stiffness adjustment structure for a joint of a continuum robot according to claim 1, characterized in that, The first directional stiffness adjustment component includes at least two first directional stiffness adjustment units, which are arranged sequentially along a preset first direction. Two adjacent first directional stiffness adjustment units are connected end to end to form a spiral structure, and the through space is located within the spiral structure.
5. The stiffness adjustment structure for a joint of a continuum robot according to any one of claims 1-4, characterized in that, The second directional stiffness adjustment component is a two-dimensional mesh structure or a three-dimensional mesh structure.
6. The stiffness adjustment structure for a joint of a continuum robot according to claim 5, characterized in that, The second directional stiffness adjustment component is arranged along a preset second direction to form a cylindrical structure.
7. The stiffness adjustment structure for a joint of a continuum robot according to claim 5, characterized in that, The second-direction stiffness adjustment component is provided with at least two stiffness adjustment areas in sequence along a preset second direction.
8. The stiffness adjustment structure for a joint of a continuum robot according to claim 5, characterized in that, The second directional stiffness adjustment component is a negative Poisson's ratio structure.
9. The stiffness adjustment structure for a joint of a continuum robot according to claim 1, characterized in that, It also includes a first heating element and a second heating element. The first heating element is disposed on the first directional stiffness adjusting member and is used to provide heat to the first directional stiffness adjusting member to enable the first directional stiffness adjusting member to achieve the transformation between austenite and martensite. The second heating element is disposed on the second directional stiffness adjusting member and is used to provide heat to the second directional stiffness adjusting member to enable the second directional stiffness adjusting member to achieve the transformation between austenite and martensite.
10. The stiffness adjustment structure for a joint of a continuum robot according to claim 9, characterized in that, The first thermal element is an electrothermal excitation electrode, and the second thermal element is an electrothermal excitation circuit.
11. A joint for a continuum robot, characterized in that, The invention includes a hollow joint body and a stiffness adjustment structure for a continuum robot joint as described in any one of claims 1-10. The stiffness adjustment structure for the continuum robot joint is disposed within the hollow structure of the joint body. The preset first direction is the axial direction of the joint body, the preset second direction is the circumferential direction of the joint body, and the through space is connected to the hollow structure of the joint body.
12. The joint of the continuum robot according to claim 11, characterized in that, The thermal insulation component is disposed on the joint body, or the thermal insulation component is integrally formed with the joint body.
13. The joint of the continuum robot according to claim 11, characterized in that, It also includes a power element and a connector, wherein the power element is connected to the connector and is used to drive the connector to rotate, and the connector is connected to the first directional stiffness adjusting element.
14. The joint of the continuum robot according to claim 13, characterized in that, It also includes a displacement sensor, which is connected to the power element and is used to detect the joint position and the rotational speed of the power element, providing a position feedback signal.
15. The joint of the continuum robot according to claim 14, characterized in that, It also includes a speed reducer, which is connected to the power element and is used to reduce the speed of the power element and increase the output torque.
16. The joint of the continuum robot according to claim 15, characterized in that, It also includes a sensing module and a control module. The sensing module is used to provide feedback signals on the strain state and phase change process of the joint. The control module is connected to the sensing module, displacement sensor, power element and reducer respectively.
17. The joint of the continuum robot according to claim 16, characterized in that, The control module includes a temperature / strain signal demodulation module, a central processing unit, and a multi-channel current drive module. The sensing module, the temperature / strain signal demodulation module, the central processing unit, and the multi-channel current drive module are sequentially connected by signals. The multi-channel current drive module is used to apply current signals to the first directional stiffness adjustment component and the second directional stiffness adjustment component.
18. The joint of a continuum robot according to any one of claims 11-17, characterized in that, It also includes a first cover and a second cover. The two ends of the joint body along the axial direction are respectively provided with a first opening and a second opening. The first cover is located at the first opening and the second cover is located at the second opening.