A continuous variable stiffness control platform based on concentric tube rotating mechanism

Abstract

The application relates to a continuous variable stiffness control platform based on a concentric tube rotating mechanism and belongs to the technical field of medical minimally invasive surgery robots.The application is used for solving the problems of response lag, large structure size and difficulty in realizing continuous and accurate stiffness control of existing continuous body mechanical arm variable stiffness technologies such as intelligent materials and particle blockage.The application comprises a driving shell assembly, a power transmission assembly and a variable stiffness concentric tube assembly; the power transmission assembly is installed in the inside of the driving shell assembly, the variable stiffness concentric tube assembly is connected with the power transmission assembly, and the variable stiffness concentric tube assembly extends to the outside of the driving shell assembly; the control platform controls the same direction or reverse rotation of the inner and outer nested tubes of the variable stiffness concentric tube assembly through the double-motor independent driving synchronous pulley of the power transmission assembly, so that the equivalent bending stiffness of the whole variable stiffness concentric tube assembly is changed. The application is used for medical minimally invasive surgery.

Description

Technical Field

[0001] This invention relates to the field of continuous robot technology in minimally invasive medical surgery, specifically to a continuously variable stiffness control platform based on a concentric tube rotation mechanism. Background Technology

[0002] Flexible continuous robotic arms are characterized by high compliance and flexibility, with telescopic flexible continuous robotic arms exhibiting even greater flexibility. However, their high compliance leads to a lower load capacity, which limits their application in certain scenarios. To improve the load capacity of flexible continuous robotic arms, it is necessary to endow them with variable stiffness capabilities. Existing technologies for variable stiffness mainly include blocking, phase transition, antagonism, and structural variation.

[0003] Existing variable stiffness technologies for continuum robotic arms (such as smart materials and particle blockage technologies) suffer from drawbacks such as slow response, large structural dimensions, and difficulty in achieving continuous and precise stiffness control. This invention proposes a rotatable kaleidoscope-shaped variable stiffness continuum nested robot (VS-CNR) drive platform to address the problem that traditional variable stiffness mechanisms cannot simultaneously achieve high flexibility and high stiffness. By introducing additional rotational degrees of freedom and utilizing the relative rotation between concentric nested tubes with specific patterned cuts, the moment of inertia of the cross-section is instantaneously changed, enabling continuous and rapid adjustment of stiffness in the radial force direction. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing continuous body manipulator variable stiffness technology, such as response lag, large structural size, and difficulty in achieving continuous and precise stiffness control. Variable stiffness mechanisms cannot simultaneously achieve high flexibility and high stiffness. Therefore, this invention provides a continuously variable stiffness control platform based on a concentric tube rotation mechanism.

[0005] The technical solution adopted by the present invention to solve the above problems is: a continuously variable stiffness control platform based on a concentric tube rotation mechanism, comprising a drive housing assembly, a power transmission assembly, and a variable stiffness concentric tube assembly; the power transmission assembly is installed inside the drive housing assembly, the variable stiffness concentric tube assembly is connected to the power transmission assembly, and the variable stiffness concentric tube assembly extends outside the drive housing assembly; the control platform independently drives the synchronous pulleys through the dual motors of the power transmission assembly to control the same-direction or opposite-direction rotation of the inner and outer nested tubes of the variable stiffness concentric tube assembly, thereby changing the overall equivalent bending stiffness of the variable stiffness concentric tube assembly.

[0006] Furthermore, the variable stiffness concentric tube assembly includes an inner tube and an outer tube, with the outer tube sleeved outside the inner tube; the inner tube wall is uniformly provided with multiple sets of symmetrical cut features along the axial direction; the outer tube wall is uniformly provided with multiple sets of symmetrical cut features along the axial direction.

[0007] Furthermore, the power transmission assembly includes an inner tube motor, an outer tube motor, an inner tube active synchronous pulley, an outer tube active synchronous pulley, an inner tube driven synchronous pulley, an outer tube driven synchronous pulley, and a synchronous belt; both the inner tube motor and the outer tube motor are mounted on a fixed motor frame of the drive housing assembly; the inner tube active synchronous pulley is connected to the inner tube motor, the inner tube driven synchronous pulley is connected to the inner tube, and the inner tube active synchronous pulley and the inner tube driven synchronous pulley are driven by a synchronous belt; the outer tube active synchronous pulley is connected to the outer tube motor, the outer tube driven synchronous pulley is connected to the outer tube, and the outer tube active synchronous pulley and the outer tube driven synchronous pulley are driven by a synchronous belt.

[0008] Furthermore, the inner tube is a hollow structure comprising an inner tube head end and an inner tube tail end; a stepped surface is provided at the connection position between the inner tube head end and the inner tube tail end; the outer tube is sleeved outside the inner tube head end; the inner tube tail end is rotatably connected to the inner tube fixing seat; the inner tube driven synchronous pulley is fixedly connected to the inner tube tail end; the outer tube is rotatably connected to the concentric tube fixing frame of the drive housing assembly via bearings; the outer tube is rotatably connected to the outer tube fixing seat; both the inner tube fixing seat and the outer tube fixing seat are fixedly connected to the concentric tube fixing frame.

[0009] Furthermore, the drive housing assembly also includes a base plate, a lower housing, and an upper housing; the fixed motor frame and the concentric tube fixing frame are both mounted on the base plate, the base plate is located inside the lower housing and is fixedly connected to the lower housing, and the upper housing is provided on the top of the lower housing.

[0010] Furthermore, both the inner tube motor and the outer tube motor are stepper motors or servo motors.

[0011] Furthermore, each set of the notch features includes two tube wall notches symmetrically arranged on the axial cross sections of the relatively variable stiffness concentric tube assembly.

[0012] Furthermore, each set of cut features on the inner tube and the outer tube is correspondingly provided, and when the inner tube and the outer tube rotate in the same direction or in opposite directions, the center lines of the tube wall cuts on the inner tube and the outer tube fall within the same radial cross section of the variable stiffness concentric tube assembly.

[0013] Furthermore, the shape of the pipe wall cut is a straight groove structure, and the diameter of the circular structures at both ends of the straight groove is greater than the width of the rectangular structure in the middle.

[0014] Furthermore, both the inner tube and the outer tube are nickel-titanium alloy tubes, and the tube wall cuts are processed by laser cutting.

[0015] The present invention has the following beneficial technical effects:

[0016] When the inner and outer tubes of the motor-driven variable stiffness concentric tube assembly of the present invention rotate in the same or opposite directions, the effective cross-sectional inertial tensor of the composite tube changes due to the mutual misalignment and overlap of the cuts on the surface tube walls. The continuous stiffness is adjustable, and the stiffness can be continuously and steplessly adjusted from low to high by changing the rotation angle between the concentric tubes. The maximum stiffness can be increased many times over from the original state, balancing compliance and load-bearing capacity.

[0017] This invention features a compact structure and is easy to integrate. As a drive platform, its output variable stiffness concentric tube is embedded in the distal end of an existing single-hole continuous robot, resulting in a small size that does not increase the external dimensions of the original interventional surgical instruments. This invention offers a fast response speed, abandoning traditional smart materials that rely on temperature changes. The purely mechanical structure, combined with direct motor drive, achieves millisecond-level transient stiffness response. By introducing additional rotational degrees of freedom and utilizing the relative rotation between concentric nested tubes with patterned cuts, this invention instantaneously changes the moment of inertia of the cross-section, enabling continuous and rapid adjustment of stiffness in the radial force direction. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the internal structure of the present invention;

[0020] Figure 3 This is the left view of the present invention;

[0021] Figure 4 yes Figure 3 CC section view;

[0022] Figure 5 This is a structural schematic diagram of a variable stiffness concentric tube assembly;

[0023] Figure 6 yes Figure 5 The left view;

[0024] Figure 7 This is a schematic diagram of the power transmission component;

[0025] Figure 8 yes Figure 7 A magnified view of a portion of the image;

[0026] Figure 9 This is a schematic diagram of the cut in the tube wall of a concentric tube assembly;

[0027] Figure 10 This is a schematic diagram illustrating the change in the overlap of tube wall cuts when the concentric tube assembly rotates relative to each other.

[0028] In the diagram, 1000 is the drive housing assembly; 1100 is the base plate; 1200 is the lower housing; 1300 is the upper housing; 1400 is the motor mounting bracket; and 1500 is the concentric tube mounting bracket.

[0029] 2000, Power transmission assembly; 2101, Inner tube motor; 2102, Outer tube motor; 2201, Inner tube drive synchronous pulley; 2202, Outer tube drive synchronous pulley; 2301, Inner tube driven synchronous pulley; 2302, Outer tube driven synchronous pulley; 2400, Bearing; 2500, Inner tube mounting base; 2600, Outer tube mounting base;

[0030] 3000, Variable stiffness concentric tube assembly; 3100, Tube wall cut; 3200, Inner tube; 3201, Inner tube head; 3202, Inner tube tail; 3300, Outer tube. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0032] Specific implementation method one: Combining Figures 1 to 10 This embodiment describes a continuously variable stiffness control platform based on a concentric tube rotation mechanism, comprising a drive housing assembly 1000, a power transmission assembly 2000, and a variable stiffness concentric tube assembly 3000. The power transmission assembly 2000 is installed inside the drive housing assembly 1000, and the variable stiffness concentric tube assembly 3000 is connected to the power transmission assembly 2000 and extends outside the drive housing assembly 1000. The control platform independently drives the synchronous pulleys via dual motors of the power transmission assembly 2000 to control the unidirectional or counter-directional rotation of the inner and outer nested tubes of the variable stiffness concentric tube assembly 3000, thereby changing the overall equivalent bending stiffness of the variable stiffness concentric tube assembly 3000.

[0033] In a preferred embodiment, the variable stiffness concentric tube assembly 3000 includes an inner tube 3200 and an outer tube 3300, with the outer tube 3300 sleeved outside the inner tube 3200; the inner tube 3200 has multiple sets of symmetrical cut features uniformly arranged along the axial direction on its wall; the outer tube 3300 has multiple sets of symmetrical cut features uniformly arranged along the axial direction on its wall.

[0034] In a preferred embodiment, the power transmission assembly 2000 includes an inner tube motor 2101, an outer tube motor 2102, an inner tube driving synchronous pulley 2201, an outer tube driving synchronous pulley 2202, an inner tube driven synchronous pulley 2301, an outer tube driven synchronous pulley 2302, and a synchronous belt; the inner tube motor 2101 and the outer tube motor 2102 are both mounted on the fixed motor frame 1400 of the drive housing assembly 1000; the inner tube driving synchronous belt... The inner tube motor 2101 is connected to the inner tube driven synchronous belt pulley 2301 and the inner tube 3200. The inner tube driven synchronous belt pulley 2201 and the inner tube driven synchronous belt pulley 2301 are driven by a synchronous belt. The outer tube driven synchronous belt pulley 2202 is connected to the outer tube motor 2102. The outer tube driven synchronous belt pulley 2302 and the outer tube 3300 are driven by a synchronous belt. The outer tube driven synchronous belt pulley 2202 and the outer tube driven synchronous belt pulley 2302 are driven by a synchronous belt.

[0035] In a preferred embodiment, the inner tube 3200 is a hollow structure comprising an inner tube head end 3201 and an inner tube tail end 3202; a stepped surface is provided at the connection position between the inner tube head end 3201 and the inner tube tail end 3202; the outer tube 3300 is sleeved outside the inner tube head end 3201; the inner tube tail end 3202 is rotatably connected to the inner tube fixing seat 2500; the inner tube driven synchronous pulley 2301 is fixedly connected to the inner tube tail end 3202; the outer tube 3300 is rotatably connected to the concentric tube fixing frame 1500 of the drive housing assembly 1000 via a bearing 2400; the outer tube 3300 is rotatably connected to the outer tube fixing seat 2600; both the inner tube fixing seat 2500 and the outer tube fixing seat 2600 are fixedly connected to the concentric tube fixing frame 1500.

[0036] In a preferred embodiment, the drive housing assembly 1000 further includes a base plate 1100, a lower housing 1200, and an upper housing 1300; the fixed motor frame 1400 and the concentric tube fixing frame 1500 are both mounted on the base plate 1100, the base plate 1100 is disposed inside the lower housing 1200 and fixedly connected to the lower housing 1200, and the upper housing 1300 is disposed on the top of the lower housing 1200.

[0037] In a preferred embodiment, both the inner tube motor 2101 and the outer tube motor 2102 are stepper motors or servo motors.

[0038] In a preferred embodiment, each set of the cut features includes two pipe wall cuts 3100 symmetrically arranged in the cross-section of the relatively variable stiffness concentric tube assembly 3000.

[0039] In a preferred embodiment, each set of cut features on the inner tube 3200 and the outer tube 3300 is correspondingly provided. When the inner tube 3200 and the outer tube 3300 rotate in the same direction or in opposite directions, the center lines of the tube wall cuts 3100 on the inner tube 3200 and the outer tube 3300 all fall within the same radial cross section of the variable stiffness concentric tube assembly 3000.

[0040] In a preferred embodiment, the shape of the pipe wall cut 3100 is a straight groove structure, and the diameter of the circular structures at both ends of the straight groove is greater than the width of the rectangular structure in the middle.

[0041] In a preferred embodiment, both the inner tube 3200 and the outer tube 3300 are nickel-titanium alloy tubes, and the tube wall cut 3100 is processed by laser cutting.

[0042] Specific Implementation Method Two: Combining Figures 1 to 10 This embodiment of the invention addresses the dual requirements of compliance and high load-bearing capacity for continuum robots operating within narrow cavities by providing a continuously variable stiffness control platform based on a concentric tube rotation mechanism. In this embodiment, the coaxial stiffness control platform mainly includes a drive housing assembly 1000, a power transmission assembly 2000, and a variable stiffness concentric tube assembly 3000. Its main function is to precisely control the unidirectional or counter-directional rotation of the inner and outer nested tubes by independently driving synchronous pulleys with dual motors, thereby changing the overall equivalent bending stiffness of the concentric tube assembly.

[0043] In a preferred embodiment, the drive housing assembly 1000 serves as the support base for the entire mechanism and is formed by the snap-fitting of a base plate 1100, a lower housing 1200, and an upper housing 1300, resulting in high internal space utilization. A fixed motor frame 1400 and an outer tube fixing frame 1500 are fixedly connected inside the housing, providing a stable mechanical reference for power transmission and pipeline rotation.

[0044] In a preferred embodiment, the power transmission assembly 2000 is used to precisely transmit the rotational motion of the motors to the concentric tube. This assembly includes two high-precision DC motors 2100, a driving synchronous pulley 2200, a driven synchronous pulley 2300, and a synchronous belt. The two motors are respectively fixed to a motor frame 1400, and power is transmitted via the synchronous belt to the driven synchronous pulley 2300, which is connected to the base of the concentric tube. To ensure smooth rotation, the driven pulley is partially nested in an inner bearing 2400, which is fixed between the base plate and the mounting frame. This dual-motor configuration allows the system to achieve two sets of independent or coordinated rotational motions.

[0045] In a preferred embodiment, the variable stiffness concentric tube assembly 3000 is the core actuator for stiffness adjustment. It consists of two nested nickel-titanium alloy tubes with uniformly symmetrical tube wall cutouts 3100, including an inner tube 3200 and an outer tube 3300. The inner tube 3200 has 20 sets of tube wall cutouts 3100, which are driven to rotate by a first motor 2101. The outer tube 3300 has 24 sets of tube wall cutouts 3100, which are driven to rotate independently by a second motor 2102. In addition to the 20 sets of tube wall cutouts 3100 corresponding to those of the inner tube 3200, the proximal end of the outer tube 3300 also has multiple sets of symmetrical tube wall cutouts 3100.

[0046] The other components and connections are the same as in Specific Implementation Method 1.

[0047] Specific implementation method three: Combining Figures 1 to 10 This embodiment describes the working principle of the continuously variable stiffness control platform for the concentric tube rotation mechanism: When the inner tube 3200 and outer tube 3300 of the variable stiffness concentric tube assembly 3000 are driven by the motor to rotate relative to each other in the same or opposite directions, the effective cross-sectional inertia tensor of the composite tube changes due to the mutual misalignment and overlap of the surface tube wall cuts 3100. According to the Euler-Bernoulli beam theory and the principle of flexibility superposition, this redistribution of the cut layout directly changes the bending stiffness of the composite tube in a specific force direction, and integrating it into a continuous robotic arm enables continuous adjustment of the device from flexible to rigid.

[0048] The other components and connections are the same as in Specific Implementation Method 1.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A continuously variable stiffness control platform based on a concentric tube rotation mechanism, characterized in that: It includes a drive housing assembly (1000), a power transmission assembly (2000), and a variable stiffness concentric tube assembly (3000). The power transmission assembly (2000) is installed inside the drive housing assembly (1000), the variable stiffness concentric tube assembly (3000) is connected to the power transmission assembly (2000), and the variable stiffness concentric tube assembly (3000) extends to the outside of the drive housing assembly (1000); The control platform independently drives the synchronous pulleys via the dual motors of the power transmission component (2000), controlling the rotation of the inner and outer nested tubes of the variable stiffness concentric tube assembly (3000) in the same or opposite directions, thereby changing the overall equivalent bending stiffness of the variable stiffness concentric tube assembly (3000).

2. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 1, characterized in that: The variable stiffness concentric tube assembly (3000) includes an inner tube (3200) and an outer tube (3300), wherein the outer tube (3300) is sleeved on the outside of the inner tube (3200); The inner tube (3200) has multiple sets of symmetrical cut features evenly arranged along the axial direction on its wall; the outer tube (3300) has multiple sets of symmetrical cut features evenly arranged along the axial direction on its wall.

3. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 1, characterized in that: The power transmission assembly (2000) includes an inner tube motor (2101), an outer tube motor (2102), an inner tube driving synchronous pulley (2201), an outer tube driving synchronous pulley (2202), an inner tube driven synchronous pulley (2301), an outer tube driven synchronous pulley (2302), and a synchronous belt; both the inner tube motor (2101) and the outer tube motor (2102) are mounted on the fixed motor frame (1400) of the drive housing assembly (1000); The inner tube active synchronous pulley (2201) is connected to the inner tube motor (2101), the inner tube driven synchronous pulley (2301) is connected to the inner tube (3200), and the inner tube active synchronous pulley (2201) and the inner tube driven synchronous pulley (2301) are driven by a synchronous belt. The outer tube active synchronous pulley (2202) is connected to the outer tube motor (2102), the outer tube driven synchronous pulley (2302) is connected to the outer tube (3300), and the outer tube active synchronous pulley (2202) and the outer tube driven synchronous pulley (2302) are driven by a synchronous belt.

4. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 2, characterized in that: The inner tube (3200) is a hollow structure, including the inner tube head end (3201) and the inner tube tail end (3202). The connection position between the first end (3201) and the last end (3202) of the inner tube is provided with a stepped surface. The outer tube (3300) is sleeved outside the first end (3201) of the inner tube. The last end (3202) of the inner tube and the inner tube fixing seat (2500) are rotatably connected. The driven synchronous belt pulley (2301) of the inner tube and the last end (3202) of the inner tube are fixedly connected. The outer tube (3300) is rotatably connected to the concentric tube fixing bracket (1500) of the drive housing assembly (1000) via the bearing (2400), and the outer tube (3300) and the outer tube fixing seat (2600) are rotatably connected; Both the inner tube fixing seat (2500) and the outer tube fixing seat (2600) are fixedly connected to the concentric tube fixing frame (1500).

5. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 1, characterized in that: The drive housing assembly (1000) also includes a base plate (1100), a lower housing (1200), and an upper housing (1300); the fixed motor frame (1400) and the concentric tube fixing frame (1500) are both mounted on the base plate (1100), the base plate (1100) is located inside the lower housing (1200) and is fixedly connected to the lower housing (1200), and the upper housing (1300) is provided on the top of the lower housing (1200).

6. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 3, characterized in that: Both the inner tube motor (2101) and the outer tube motor (2102) are stepper motors or servo motors.

7. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 2, characterized in that: Each group of cut features includes two tube wall cuts (3100) symmetrically arranged in the cross-section of two relatively variable stiffness concentric tube assemblies (3000).

8. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 2, characterized in that: Each set of cut features on the inner tube (3200) and the outer tube (3300) is provided accordingly. When the inner tube (3200) and the outer tube (3300) rotate in the same direction or in opposite directions, the center lines of the tube wall cuts (3100) on the inner tube (3200) and the outer tube (3300) all fall within the radial cross section of the same variable stiffness concentric tube assembly (3000).

9. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 7, characterized in that: The shape of the pipe wall cut (3100) is a straight groove structure, and the diameter of the circular structure at both ends of the straight groove is greater than the width of the rectangular structure in the middle.

10. The continuously variable stiffness control platform based on the concentric tube rotation mechanism according to claim 2, characterized in that: Both the inner tube (3200) and the outer tube (3300) are nickel-titanium alloy tubes, and the tube wall cut (3100) is processed by laser cutting.

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