A torsion-resistant continuum robot with shape sensing function and a control method thereof

Abstract

The application discloses a torsion-resistant continuum robot with shape sensing function and a control method thereof, which is composed of two continuum robot arms and a middle rigid section. A hinge interface is arranged on a mechanical arm subunit and a connecting piece, a buckle structure is formed by a reserved cutout of a wire coil and an interface unit, and the overall torsion resistance is realized through the buckle structure and a hinge configuration formed by each unit. Structural reconstruction is realized through the number and structure rearrangement of two subunits. The rigidity of the mechanical arm is changed by increasing the tension of the rope. The bending angle of the mechanical arm is measured by a method for measuring passive rope displacement through a high-integration displacement sensor. According to a robot kinematics model and a Jacobian matrix, a closed-loop control method based on shape information is proposed. The overall outer diameter is less than 5 mm, and there is a central channel. The proposed continuum robot is compact, torsion-resistant, rigidity-adjustable and low in cost. The high-precision closed-loop control of the micro robot is realized without using expensive sensors, and the continuum robot is used for medical operations.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more specifically, to an anti-torsion continuum robot with shape perception capabilities and its control method. Background Technology

[0002] In recent years, natural orifice surgery has gained widespread popularity due to its advantages over traditional surgery, including less trauma, no scarring, less patient discomfort, and faster recovery. It aligns with the development philosophy of minimally invasive surgery in modern medicine. For example, the larynx, esophagus, and nasal cavity are complex areas of the human body with a wide variety of lesions, and these areas have gradually become important surgical access routes for treating these conditions.

[0003] Current natural orifice surgeries often employ rigid instruments, which are prone to collision with tissues, resulting in high surgical risks, significant difficulty, and challenging operation for surgeons. They require a high level of technical skill, have a long learning curve, and are difficult to completely remove diseased tissue, making certain complex surgeries unsuitable for natural orifice procedures. While some surgical robots exist for nasal endoscopy and laryngoscopy, their flexibility and rigidity are limited. Due to inherent structural design flaws, they are prone to torsional deformation, restricting their application in nasal or transoral larynx surgeries. Therefore, there is an urgent need for a new torsional-resistant, flexible surgical robot.

[0004] Existing surgical robots are often limited by their outer diameter, making it impossible to integrate sensors to detect their bending angles. Consequently, they generally employ open-loop control methods, resulting in limited accuracy. Therefore, there is an urgent need for novel shape perception and closed-loop control methods. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a torsion-resistant continuum robot with shape-sensing capabilities and its control method. Its structural design achieves torsion resistance, and its bending can be controlled by adjusting the rope length, enabling surgical operations in complex and curved surgical environments. The overall stiffness is adjusted by controlling the tension of the drive rope, meeting the stiffness requirements of different surgical procedures. The bending angle of the micro-robotic arm is measured by using a highly integrated, dedicated, low-cost displacement sensor to measure the passive rope displacement, thereby achieving closed-loop control of the robotic arm.

[0006] The anti-torsion continuum robot with shape-sensing function proposed in this invention can adopt the following technical solutions:

[0007] An anti-torsion continuum robot with shape perception function includes a dedicated displacement sensor, a passive displacement measuring rope, a second section of the distal manipulator drive rope, a first section of the proximal manipulator drive tube, a bottom connector, a top connector, a guide reel fixed to a central support spring, a first proximal manipulator interface unit and a second proximal manipulator interface unit, a proximal manipulator subunit, an intermediate rigid transition section, a distal manipulator interface unit, a distal manipulator subunit, and a central support spring;

[0008] The fixed wire tray is fixed to the central spring, wherein one end of the first section of the proximal manipulator drive tube is fixed to the end of the proximal manipulator, and one end of the second section of the distal manipulator drive rope is fixed to the top of the robot.

[0009] Four slits are set in the circumferential direction of the fixed guide plate. The shape of the slits is complementary to the shape of the bottom column of the proximal manipulator interface unit. During the assembly of the continuum robot, the bottom column of the proximal manipulator interface unit crosses and is inserted into the slits of the fixed guide plate to form an anti-torsion structure.

[0010] The first near-segment robotic arm interface unit, the second near-segment robotic arm interface unit, the far-segment robotic arm interface unit, the near-segment robotic arm subunit, the far-segment robotic arm subunit, and the middle rigid segment are all provided with an annular boss. The boss has a central hole for the central support spring to pass through, and a wire hole is provided around the circumference of the boss for guiding the drive rope.

[0011] Each proximal robotic arm subunit has two symmetrically arranged inclined surfaces convex from the outside to the inside on both its back and front ends. One end face of the robotic arm subunit has two protruding first arc-shaped rotating shafts, and the other end face has two first arc-shaped notch grooves. The shapes of the first arc-shaped rotating shafts and the first arc-shaped notch grooves are complementary. The axial directions of the first arc-shaped rotating shafts and the first arc-shaped notch grooves are parallel to each other. Each proximal robotic arm subunit is nested on the central support spring in sequence through the central hole. The first arc-shaped rotating shaft portions of adjacent proximal robotic arm subunits are embedded in the first arc-shaped notch grooves to form a rotational bending hinge configuration.

[0012] One end face of the distal continuum subunit is symmetrically provided with two inclined surfaces convex from the outside to the inside, and two protruding second arc-shaped rotating shafts are provided on this end face. The other end face of the distal continuum subunit is symmetrically provided with two inclined surfaces convex from the outside to the inside, and two second arc-shaped notch grooves are provided on this other end face. The second arc-shaped rotating shafts and the second arc-shaped notch grooves are complementary in shape. The axial direction of the second arc-shaped rotating shafts on the same distal continuum subunit is perpendicular to the axial direction of the second arc-shaped notch grooves. The second arc-shaped rotating shafts of each adjacent distal continuum subunit are partially embedded in the second arc-shaped notch grooves to form a curved hinge configuration.

[0013] Furthermore, the system's bending drive rope is made of super-elastic nickel-titanium alloy. The near-segment robotic arm sub-units are arranged in sequence to form the near-segment robotic arm, which is driven to bend by two nickel-titanium alloy tubes. The far-segment robotic arm sub-units are arranged in sequence to form the far-segment robotic arm, which is driven to bend by four nickel-titanium alloy wires.

[0014] Furthermore, the bending stiffness of the central support spring is approximately expressed as K. EI =a θ ×F axis +b θ F axis a is the axial force borne by the spring. θ and b θ The coefficient is related to the bending angle; the bending stiffness of the central support spring is related to the axial force, and the stiffness of the continuous robotic arm is adjusted by changing the axial tension of the nickel-titanium alloy while simultaneously tensioning or relaxing all the drive ropes of the single-section robotic arm.

[0015] Furthermore, by changing the size and number of the near and far robotic arm sub-units, as well as the length of the intermediate rigid section, the overall rigidity, flexibility, and workspace of the robotic arm can be adjusted.

[0016] Furthermore, by changing the structural form of a single robot sub-unit to rearrange the combination of the multiple degrees of freedom of the robot or to achieve non-uniform bending of a single robotic arm, or by using a robotic arm interface unit to expand the number of robotic arm segments, the high adaptability and reconfigurability requirements of the robotic arm can be achieved.

[0017] Furthermore, it also includes four passive displacement measuring ropes. The bending angle of the two robotic arms can be detected by measuring the passive displacement of one and three of the ropes when the robot bends. One end of the passive displacement measuring rope is fixed, and the other end is connected to a dedicated displacement measuring sensor. The other end of the sensor is fixed. The sensor is a soft elastic tube with liquid metal inside. The displacement of the passive measuring rope is calculated by measuring the change in resistance of the liquid metal inside the soft elastic tube. The bending angle of the robotic arm is calculated from the displacement data of the passive measuring rope.

[0018] The control method for the above-mentioned anti-torsion continuum robot provided by this invention can adopt the following technical solution: The robot arm bends in different directions by changing the length of the drive rope; high-precision closed-loop control of the robot is achieved based on the measured bending angle information. Assuming the bending parameter angles of the near and far segments of the robot arm are θ1, α1 and θ2, α2 respectively, where θ represents the magnitude of the bending angle and α represents the bending direction, α being the angle between the bending direction and the location of the nickel-titanium alloy tube, then the change in the length of the nickel-titanium alloy tube of the near segment of the robot arm is as follows:

[0019] l 11=θ1r + θ1a / 2 - r1θ1cos(α1)

[0020] l 12 =θ1r+θ1a / 2-r1θ1cos(π-α1)

[0021] The changes in the length of the nickel-titanium alloy wire rope in the remote robotic arm are expressed as follows:

[0022]

[0023] Among them l 11 and l 12 Indicates the change in the nickel-titanium alloy tube of the near-segment robotic arm, l 21 ~l 24 This indicates the change in the second section of the drive rope at the far end; r represents the inner radius of the central spring, r1 is the distance between the drive rope and the center line of the spring, and a represents the spring wire diameter; a positive value of l indicates release, and a negative value indicates pull.

[0024] Four dedicated displacement sensors measure the displacement changes of four passive ropes. The angles corresponding to the positions of the four passive displacement measuring ropes are 0°, 0°, 0°, and 0° respectively. π, For the first section of the near-arm, the bending angle is determined by the change in the passive rope at the 0-degree position: l' 11 =θ1r+θ1a / 2-r1θ1cos(α1), if l' 11 If >0, then α1=0. If l' 11 If < 0, then α1 = π.

[0025] The remote robotic arm, on the other hand, uses... π, The bending angle of the passive rope due to its position change is calculated. Given the bending angle of the near-end robotic arm, the change in passive rope length caused by the bending of the far-end robotic arm is determined.

[0026] l″ 21 =θ2r + θ2a / 2 - r1θ2sin(α2)

[0027] l″ 22 =θ2r + θ2a / 2 + r1θ2cos(α2)

[0028] l″ 23 =θ2r + θ2a / 2 + r1θ2sin(α2)

[0029] and then:

[0030] The displacement of the passive displacement measuring rope is obtained using a low-cost dedicated displacement sensor; the relationship between the sensor resistance and strain is expressed as follows: Where L l The initial length of the liquid metal channel is represented by ρ, the resistivity of the liquid metal is represented by r2, and the initial radius of the channel inside the silicone tube is represented by μ. l The ratio is Poisson's ratio; the sensor strain is obtained based on the resistance change, and then the passive displacement measurement rope displacement is obtained. Based on this, the shape perception of the robotic arm can be realized.

[0031] Furthermore, a closed-loop controller for the robotic arm is established based on the detected bending angle; the relationship between the robot drive rope length and joint space is expressed as: Δq=J qψ Δψ, Δψ1=[Δθ1 Δα1] T ,Δψ2=[Δθ1 Δα1Δθ2 Δα2] T , Δq1=[l 11 l 12 ], Δq2=[l 21 l 22 l 23 l 24 ] T The change in rope length is represented by the Jacobian matrix of the two sections, which are then expressed as follows:

[0032]

[0033] Based on the real-time measured bending shape of the robotic arm and its ideal shape, the angular deviation of the robotic arm is calculated. Using the calculated Jacobian matrix, the change in the drive rope is then calculated to achieve closed-loop control of the robotic arm.

[0034] Compared with the prior art, the present invention has the following advantages and effects:

[0035] 1. The matching structures, such as the arc-shaped protruding rotating shafts and arc-shaped grooves on both ends of the robotic arm sub-unit and interface unit, the protruding column on the end face of the interface unit, and the circumferential cut of the guide plate, can achieve axial anti-torsion of the overall structure of the robotic arm.

[0036] 2. Since the robotic arm is fixed to the guide rail and the central spring, the axial force of the robotic arm caused by the drive rope is entirely applied to the central spring frame, preventing excessive friction between the continuous sub-units from affecting the system accuracy.

[0037] 3. The two robotic arms are driven by nickel-titanium alloy tubes and nickel-iron alloy drive wires respectively, which can realize the adjustment of the bending angle of the two sections.

[0038] 4. By changing the size and number of robotic arm sub-units and the length of the intermediate rigid transition section, the robot's workspace, flexibility, and rigidity can be adjusted to meet the operational requirements of different types of surgeries.

[0039] 5. The axial force of the spring affects the system stiffness. The stiffness of the robotic arm can be adjusted by changing the resultant force of the drive rope in the axial direction of the robotic arm, so as to adapt it to different surgical operations.

[0040] 6. The robot of the present invention has one bending degree of freedom and two bending degrees of freedom in its two sections respectively. The number of robot sections can be expanded through the interface unit. By changing the structural form of a single robot sub-unit, the combination of degrees of freedom of multiple robot sections can be rearranged, thereby changing the overall degrees of freedom of the robot. Alternatively, non-uniform bending of a single robotic arm can be achieved, meeting the high adaptability and reconfigurability requirements of surgical operations.

[0041] 7. This invention uses a highly integrated, low-cost displacement sensor to measure the passive displacement of a measuring rope to detect its bending angle. The structure is compact, and the angle measurement information is used to achieve closed-loop control of the robotic arm, meeting the high precision requirements of surgery for the robotic arm.

[0042] This invention provides a torsion-resistant continuum robot with shape-sensing capabilities, offering greater flexibility, versatility, easier stiffness adjustment, and higher control precision. It can be reconfigured according to surgical tasks. The technology employed better meets the precision and stiffness requirements of natural orifice surgery, reduces surgical risks, improves surgical safety, and expands the indications for natural orifice surgery. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the overall structure of the anti-torsion continuum robot of the present invention;

[0044] Figure 2 This is a magnified view of a portion of the drive end and passive rope displacement measurement section of a continuum robot.

[0045] Figure 3 This is a partial cross-sectional view of the robot's two robotic arms;

[0046] Figure 4 It is a fixed wire guide plate that is fixedly connected to the central spring frame in the robot;

[0047] Figure 5 It is the interface unit connecting the bottom of the near-segment continuous robotic arm to the fixed guide wire disk;

[0048] Figure 6 It is a sub-unit of the near-segment continuum robotic arm;

[0049] Figure 7 It is the interface unit that connects the top of the near-segment continuous robotic arm to the fixed guide wire disk;

[0050] Figure 8 It is the rigid transition section in the middle of the continuous robotic arm;

[0051] Figure 9 It is a sub-unit of the long-range continuum robotic arm;

[0052] Figure 10 It is the central spring frame of the continuous robotic arm;

[0053] Figure 11 This is a cross-sectional view of a displacement sensor;

[0054] Figure 12 It is a closed-loop control method for robotic arms.

[0055] Labels in the diagram: 1. End-effector displacement sensor, 1-1 to 1-4 correspond to four different displacement sensors; 1-5. Flexible silicone tube; 1-6. Liquid metal; 1-7. Measuring lead wire; 2. Passive displacement measuring rope, 2-1 to 2-4 correspond to four different passive displacement measuring ropes; 3. Second-section distal robotic arm drive rope, 3-1 to 3-4 correspond to four different second-section distal robotic arm drive ropes; 4. First-section proximal robotic arm drive tube, 4-1 to 4-2 correspond to two different first-section proximal robotic arm drive tubes; 5. Bottom connector; 6. Fixed lead wire reel, 6-1. Lead wire reel notch; 6-2. Lead wire reel center hole; 6-3. Lead wire reel lead wire hole; 7. Proximal robotic arm bottom. 7-1. Interface unit protruding column; 8. Proximal robotic arm subunit; 8-1. Proximal robotic arm subunit annular boss; 8-2. Proximal robotic arm subunit center hole; 8-3. Proximal robotic arm subunit arc-shaped groove; 8-4. Proximal robotic arm subunit arc-shaped pivot; 8-5. Proximal robotic arm subunit inclined surface; 9. Proximal top interface unit; 10. Intermediate rigid transition section; 11. Distant robotic arm subunit; 11-1. Distant robotic arm subunit arc-shaped pivot; 11-2. Distant robotic arm subunit arc-shaped groove; 11-3. Distant robotic arm subunit inclined surface; 12. Distant robotic arm top interface unit; 13. Robot top connector; 14. Central spring. Detailed Implementation

[0056] The following is in conjunction with the appendix Figures 1 to 12 The present invention will be explained and described in detail.

[0057] See also Figure 1As shown, this invention proposes a torsion-resistant continuum robot with shape perception capabilities. The robotic arm includes a dedicated displacement sensor 1, a passive displacement measuring rope 2, a second-section distal robotic arm drive rope 3, a first-section proximal robotic arm drive tube 4, a bottom connector 5, a top connector 13, a guide rail 6 fixed to a central support spring, proximal robotic arm interface units 7 and 9, a proximal robotic arm sub-unit 8, a middle rigid transition section 10, a distal robotic arm interface unit 12, a distal robotic arm sub-unit 11, and a central support spring 14. The robotic arm includes two bendable sections and a middle rigid transition section. The first bendable section can be bent in a plane, while the second section can be bent in space. Both sections are driven to bend by nickel-titanium alloy wires.

[0058] like Figure 2 The diagram shows a partial enlarged view of the drive end and passive rope displacement measurement section of the continuum robot. 1-1 to 1-4 correspond to four different displacement sensors, one end of which is fixed, and the other end is connected to the passive displacement measurement rope. 2-1 to 2-4 correspond to four different passive displacement measurement ropes. Rope 2-1 has one end fixed to the end-effector guide rail of the proximal manipulator, and the other end connected to the displacement sensor, enabling shape measurement of the proximal manipulator. Ropes 2-2 to 2-4 have one end fixed to the end-effector guide rail of the distal manipulator, and the other end connected to the displacement sensor, enabling bending shape measurement of the distal manipulator. The specific layout of the drive mechanism for the proximal and distal manipulators and the two sections of the passive measurement rope can be seen in the diagram. Figure 3 The image shows a partial cross-sectional view of two sections of the robot.

[0059] like Figure 4 The diagram shows a robot-attached guide rail, which includes a central channel 6-2, fixed to a central spring 14 by welding or bonding. Circular holes 6-3 are evenly distributed around the circumference of the guide rail, serving as channels for the drive rope. Circularly distributed cutouts 6-1 are reserved for interface units or robot connector interfaces.

[0060] Figure 5 The lower interface unit of the near-end robotic arm has a protruding column structure 7-1 that is fixed in the reserved cut of the wire guide plate 6 to prevent the overall structure from twisting.

[0061] Figure 6This is a sub-unit of the near-end bending robotic arm, featuring a central annular boss structure 8-1, a central hole 8-2 for threading through the central spring support, and circumferentially distributed circular holes for guiding ropes. Two inclined surfaces 8-5 are symmetrically arranged on both ends of the unit, and arc-shaped protruding pivots 8-4 and notched grooves 8-3 are respectively located at the top and bottom, their shapes complementary and their layout consistent. The near-end robotic arm is interconnected with multiple units on the central spring support. The pivot 8-4 of the next unit is embedded in the notched groove 8-3 of the previous unit, allowing them to rotate relative to each other to form a rotating hinge structure. A spindle-shaped gap is formed between the inclined surfaces of adjacent units to prevent interference.

[0062] Figure 7 The upper interface unit of the lower bending robotic arm has a protruding column that can be inserted into the cut of the fixed wire tray to prevent twisting between the interface unit and the wire tray.

[0063] Figure 8 The lower part of the rigid transition section of the robotic arm is fitted into the cut of the fixed wire guide plate, and the upper part of the arc-shaped protruding rotating shaft cooperates with the groove notch of the upper far section of the robotic arm sub-unit to form a rotating hinge.

[0064] Figure 9 The upper bending robotic arm subunit has two symmetrically arranged inclined surfaces at each end. The upper part has a pair of arc-shaped protruding pivots 11-1, and the lower part has a pair of arc-shaped grooves 11-2, whose shape is complementary to 11-1. The line connecting the two grooves is perpendicular to the line connecting the two 11-1 pivots. The subunits are connected in series on a spring via a central channel. The rotational hinges formed by three adjacent units are perpendicular to each other, enabling the distal robotic arm to bend in any direction in space.

[0065] Figure 10 The central spring core is formed by adjacent spring wires in contact with each other to prevent axial compression of the core under axial force. The fixed guide coil is also fixed to the central spring core, so the axial force generated by pulling the drive rope acts on the central spring core, preventing excessive friction between the bending segment units and thus affecting the bending of the segment. The bending stiffness of the central spring frame can be approximately expressed as K. EI =a θ ×F axis +b θ F axis For the axial force of the spring, a θ and b θ This is a coefficient related to the bending angle. The bending stiffness of the spring is related to the axial force. The stiffness of the central spring core increases under the action of axial force, so the stiffness of the robot system can be improved by increasing the tension of the drive rope.

[0066] Figure 11This is a dedicated displacement sensor, where 1-5 are soft elastic tubes, 1-6 are liquid metal inside the elastic tubes, and 1-7 are measuring wires. Sensor data is obtained through the wires.

[0067] The near-end robotic arm is driven by two nickel-titanium alloy tubes, 4-1 and 4-2, while the far-end robotic arm is driven by four nickel-titanium alloy wires, 3-1 to 3-4. The layout is shown in [reference needed]. Figure 2 and Figure 3 As shown, the near-segment bending robotic arm performs in-plane bending, while the far-segment robotic arm can be bent in any direction in space. The two robotic arms can meet different stiffness requirements by changing the thickness of the nickel-titanium alloy wire and tube. The stiffness of each segment of the robotic arm can be adjusted separately by using different drive configurations for the two segments.

[0068] The robotic arm consists of two curved robotic arms and a rigid transition section in the middle. The length of each robotic arm can be changed by altering the number and size of the fixed guide wire disk and the intermediate curved sub-unit, thereby changing the bendable angle of each section and adjusting the system's flexibility, workspace, and overall rigidity.

[0069] The robot of this invention has one bending degree of freedom in its two segments and two bending degrees of freedom in its other segment, respectively. The number of segments can be expanded through the connecting components of the robotic arm. By changing the structural form of a single robot sub-unit, the combination of degrees of freedom of multiple robot segments can be rearranged, or non-uniform bending of a single robotic arm segment can be achieved, meeting the high adaptability and reconfigurability requirements of surgical operations. The cable-driven robotic arm proposed in this invention has a compact structure, facilitating miniaturization, with an outer diameter of less than 5mm. It can be reconfigured according to different operational needs by changing the size and number of sub-units. The structural design of the bending sub-unit, the fixed guide rail, the connecting unit, and the intermediate rigid section achieves overall anti-torsion. The stiffness of the robotic arm can be adjusted by changing the tension of the drive cable. The robot's central channel facilitates integration with standard or customized surgical instruments.

[0070] The present invention proposes a torsion-resistant continuum robot with shape perception function. By changing the length of the drive rope, different bending angles are controlled in the proximal and distal sections of the robotic arm. The kinematic model is inferred considering the change in the robot's centerline length. Assuming the bending angle parameters of the proximal and distal sections of the robotic arm are θ1, α1 and θ2, α2 respectively, where θ represents the magnitude of the bending angle and α represents the bending direction, i.e., the angle between the bending direction and the 4-1 drive tube, the change in the length of the nickel-titanium alloy tube of the proximal section of the robotic arm is as follows:

[0071] l 11 =θ1r + θ1a / 2 - r1θ1cos(α1)

[0072] l 12=θ1r+θ1a / 2-r1θ1cos(π-α1)

[0073] The changes in the length of the nickel-titanium alloy wire rope in the remote robotic arm can be expressed as follows:

[0074]

[0075] Among them l 11 and l 12 This indicates the variation in the nickel-titanium alloy tubes 4-1 and 4-2 of the near-section of the robotic arm, l 21 -l 24 This indicates the variation in the second section of the drive rope, from 3-1 to 3-4. 'r' represents the inner radius of the central spring, 'r1' is the distance between the drive rope and the spring's centerline, and 'a' represents the spring wire diameter. A positive value for 'l' indicates release, and a negative value indicates tension.

[0076] This invention relates to an anti-torsion continuum robot with shape perception capabilities. It can calculate the bending angle based on the displacement of the passive drive ropes. Four low-cost dedicated displacement sensors can correspondingly calculate the displacement changes of the four passive ropes. The angular positions corresponding to the positions of the four passive displacement measurement ropes are 0°, 0°, and 0° respectively. π,

[0077] For the first section of the near-arm, the bending angle is determined by the change in the passive rope at the 0-degree position: l' 11 =θ1r+θ1a / 2-r1θ1cos(α1), if l' 11 If α > 0, then α1 = 0. If l' 11 If < 0, then α1 = π.

[0078] For remote robotic arms, through π, The bending angle is determined by the change in position of the passive rope. The bending angle of the second section must be determined by removing the coupling effect of the bending in the first section.

[0079]

[0080] Knowing the bending angle of the first section, we can calculate:

[0081] l″ 21 =θ2r + θ2a / 2 - r1θ2sin(α2)

[0082] l″ 22 =θ2r + θ2a / 2 + r1θ2cos(α2)

[0083] l″ 23 =θ2r + θ2a / 2 + r1θ2sin(α2)

[0084] and then: At this point, the bending angles of the near and far sections of the robotic arm can be determined.

[0085] The displacement of the passive displacement measuring rope is acquired using a low-cost dedicated displacement sensor. The relationship between the sensor's resistance and strain can be expressed as: Where L l The initial length of the liquid metal portion is represented by ρ, the resistivity of the liquid metal is represented by r2, and the initial radius of the internal channel of the silicone tube is represented by μ. l Poisson's ratio. Based on the change in resistance, the strain of the sensor can be obtained, and thus the passive displacement measurement rope can be derived. Based on this, the shape sensing of the robotic arm can be realized.

[0086] Based on the detected bending angles of the two segments of the robotic arm, a closed-loop controller for the robotic arm can be established, such as... Figure 12 As shown. The relationship between the robot's drive rope length and joint space can be expressed as: Δq = J qψ Δψ, Δψ1=[Δθ1 Δα1] T , Δψ2=[Δθ1 Δα1 Δθ2 Δα2] T , Δq1=[l 11 l 12 ], Δq2=[l 21 l 22 l 23 l 24 ] T This indicates the change in rope length.

[0087] The Jacobian matrices of the two sections are expressed as follows:

[0088]

Claims

1. A torsion-resistant continuum robot with shape sensing function, characterized in that: it comprises a dedicated displacement sensor (1), a passive displacement measurement cable (2), a second section distal manipulator driving cable (3), a first section proximal manipulator driving tube (4), a bottom connector (5), a top connector (13), a wire reel (6) fixed with a center spring (14), a first proximal manipulator interface unit (7) and a second proximal manipulator interface unit (9), a proximal manipulator sub-unit (8), an intermediate rigid transition section (10), a distal manipulator interface unit (12), a distal continuum sub-unit (11), and a center spring (14); the wire reel (6) is fixed with the center spring (14), one end of the first section proximal manipulator driving tube (4) is fixed with the proximal manipulator end, and one end of the second section distal manipulator driving cable (3) is fixed with the robot top; the wire reel (6) is provided with four notches (6-1) in the circumferential direction, the shape of the notches is complementary to the shape of the bottom cylinder (7-1) of the first proximal manipulator interface unit (7), and in the assembly process of the continuum robot, the bottom cylinder (7-1) of the first proximal manipulator interface unit (7) is cross-coupled into the notches (6-1) to form a torsion-resistant structure; the first proximal manipulator interface unit (7), the second proximal manipulator interface unit (9), the distal manipulator interface unit (12), the proximal manipulator sub-unit (8), the distal continuum sub-unit (11), and the intermediate rigid transition section (10) are all provided with annular bosses in the middle, the bosses are provided with center holes for passing through the center spring (14), and the bosses are provided with wire holes in the circumferential direction for guiding the second section distal manipulator driving cable (3) and the first section proximal manipulator driving tube (4); the end faces of the proximal manipulator sub-unit (8) are both symmetrically provided with two outwardly convex inclined surfaces (8-5), one end face of the proximal manipulator sub-unit (8) is provided with two convex first arc-shaped rotating shafts (8-4), and the other end face is provided with two first arc-shaped notched grooves (8-3), the first arc-shaped rotating shafts (8-4) and the first arc-shaped notched grooves (8-3) are complementary in shape, the axial directions of the first arc-shaped rotating shafts (8-4) and the first arc-shaped notched grooves (8-3) are parallel to each other, the proximal manipulator sub-units (8) are sequentially nested on the center spring (14) through the center holes, and the first arc-shaped rotating shafts (8-4) of the adjacent proximal manipulator sub-units (8) are partially embedded in the first arc-shaped notched grooves (8-3) to form a rotating and bending hinge configuration. ​ The one end face of the far segment continuum subunit (11) is symmetrically provided with two outwardly convex inclined surfaces (11-3), and the end face is provided with two convex second arc-shaped rotating shafts (11-1); the other end face of the far segment continuum subunit (11) is symmetrically provided with two outwardly convex inclined surfaces, and the other end face is provided with two second arc-shaped notch grooves (11-2); the second arc-shaped rotating shaft (11-1) and the second arc-shaped notch groove (11-2) are complementary in shape; the axial directions of the second arc-shaped rotating shaft (11-1) and the second arc-shaped notch groove (11-2) on the same far segment continuum subunit (11) are perpendicular to each other; and the second arc-shaped rotating shaft (11-1) of each adjacent far segment continuum subunit (11) is partially embedded in the second arc-shaped notch groove (11-2) to form a curved hinge configuration.

2. The torsion-resistant continuum robot of claim 1, wherein: The second segment far segment mechanical arm driving rope (3) and the first segment near segment mechanical arm driving tube (4) are made of super-elastic nickel-titanium alloy; the near segment mechanical arm subunits (8) are sequentially arranged to form a near segment mechanical arm; the first segment near segment mechanical arm driving tube (4) includes two nickel-titanium alloy tubes (4-1, 4-2), and the near segment mechanical arm is driven to bend by the two nickel-titanium alloy tubes (4-1, 4-2); the far segment continuum subunits (11) are sequentially arranged to form a far segment mechanical arm; the second segment far segment mechanical arm driving rope (3) includes four nickel-titanium alloy wires (3-1, 3-2, 3-3, 3-4), and the far segment mechanical arm is driven to bend by the four nickel-titanium alloy wires (3-1, 3-2, 3-3, 3-4).

3. The torsion-resistant continuum robot of claim 2, wherein: The bending stiffness of the center spring (14) is approximately expressed as K EI = a θ × F axis + b θ , F axis is the axial force experienced by the spring, a θ and b θ are coefficients related to the bending angle; the bending stiffness of the center spring (14) is related to the axial force, and the stiffness of the continuum manipulator is adjusted by changing the axial tension of the nitinol alloy while tensioning or relaxing all the drive cords of the single-joint manipulator.

4. The torsion-resistant continuum robot of claim 1, wherein: The stiffness, flexibility and working space of the whole mechanical arm can be adjusted by changing the size and number of the near segment and far segment mechanical arm subunits and the length of the intermediate rigid transition segment.

5. The torsion-resistant continuum robot of claim 1, wherein: The high adaptability and reconfigurability of the mechanical arm can be realized by changing the structure of the single-segment robot subunit to rearrange the degree of freedom combination of the multi-segment robot or realize the non-uniform bending of the single-segment mechanical arm, or by using a mechanical arm interface unit to expand the number of mechanical arm segments.

6. The twist-resistant continuum robot of claim 1, wherein: The passive displacement measuring ropes have four ropes, and the passive displacement of one and three measuring ropes when the robot bends respectively realizes the detection of the bending angles of the two-segment mechanical arms; one end of the passive displacement measuring rope is fixed, and the other end is connected with a displacement sensor, and the other end of the displacement sensor is fixed; the displacement sensor is a soft elastic tube with a liquid metal in the internal passage, and the displacement of the passive measuring rope is calculated by measuring the resistance change of the liquid metal in the soft elastic tube; the bending angle of the mechanical arm is calculated by the displacement data of the passive measuring rope.

7. A control method of a torsionally-stiff continuum robot according to claim 2, characterized by: The bending of the mechanical arm in different directions is realized by changing the length change amount of the nickel-titanium alloy tube and the length change amount of the nickel-titanium alloy wire, and the high-precision closed-loop control of the robot is realized based on the measured bending angle information; assuming that the bending parameters angles of the near segment and far segment mechanical arms are θ1, α1 and θ2, α2 respectively, wherein θ represents the size of the bending angle, and α represents the bending direction, and α is the included angle between the bending direction and the position of the nickel-titanium alloy tube (4-1), then the length change of the nickel-titanium alloy tube is: l 11 = θ1r+ θ1a / 2- r1θ1cos(α1) l 12 = θ1r+ θ1a / 2- r1θ1cos(π- α1) The length change amount of the nickel-titanium alloy wire is represented as: wherein l 11 and l 12 represents the length change amount of the nickel-titanium alloy tube (4-1, 4-2), l 21 ~ l 24 represents the rope length change amount of the nickel-titanium alloy wire (3-1, 3-2, 3-3, 3-4); r represents the inner radius of the center spring, r1 is the distance from the driving rope to the center line of the spring, and a represents the wire diameter of the spring; a positive value of l indicates release, and a negative value indicates pull. Four displacement sensors correspond to measure the displacement change of four passive displacement measurement ropes, the angles corresponding to the positions of the four passive displacement measurement ropes are 0, π, For the first section near the mechanical arm, the bending angle is solved by the change of the passive displacement measurement rope at 0 degree position: l' 11 = θ1r+ θ1a / 2- r1θ1cos(α1), if l' 11 > 0, then α1= 0, If l' 11 < 0, then α1= π, The far segment robot arm then moves the passive displacement measurement rope π, The passive displacement measurement rope length change due to the far segment robot arm bending is solved in the case of knowing the near segment robot arm bending angle: l" 21 = θ2r + θ2a / 2 - r1θ2sin(α2) l" 22 = θ2r+ θ2a / 2+ r1θ2cos(α2) l" 23 = θ2r + θ2a / 2 + r1θ2sin(α2) Further: The displacement of the passive displacement measuring rope is acquired by a displacement sensor; a relationship between the resistance of the displacement sensor and the strain is represented as: Wherein L l represents an initial length of a liquid metal channel, p represents a liquid metal resistivity, r2 represents an initial radius of an internal channel of a silica gel tube, mu l represents a Poisson's ratio; a displacement of the passive displacement measuring rope is obtained based on resistance change, a strain of the displacement sensor, and further a shape sensing of the mechanical arm.

Images