Tubular thin-walled continuum structure and flexible robotic arm

Abstract

The application discloses a tubular continuum structure and a flexible mechanical arm. The continuum structure is mainly composed of a fiber material and includes an inner woven tube, an outer woven tube and an end connecting structure. The inner woven tube is embedded in the outer woven tube, and the surfaces of the two are tightly attached. The spiral angle of the outer woven tube is smaller than that of the inner woven tube, so that the radial expansion deformation of the inner tube under the axial driving force can be limited. The ends of the inner and outer woven tubes are fixed together by the end connecting structure. One end of an axial wire or other driver can be fixed to the surface of the woven tube, and the bending deformation of the continuum structure can be realized by pulling. A plurality of groups of driving wires are connected at different axial and circumferential positions of the structure, so that the complex spatial movement required by the flexible mechanical arm can be realized. The radial deformation interference between the inner and outer woven tubes can realize large curvature bending under large axial driving force. Meanwhile, the structure is compact, hollow inside, easy to realize and has high environmental adaptability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of minimally invasive surgery, environmental exploration, and the like, and in particular to a thin-walled, hollow, and large-curvature-bendable flexible continuum structure and a flexible manipulator based on the flexible continuum structure. BACKGROUND

[0002] The continuum structure can achieve large-curvature bending to adapt to complex environments, and is commonly used as a flexible tip of an instrument (a small manipulator) and a long handle structure of a flexible instrument system (a large manipulator) in the field of minimally invasive surgery. According to the rigidity level of the structural material, the continuum structure can be divided into two categories.

[0003] One category is to use discrete or hollow rigid parts, and this category of continuum structure is mainly driven by wire pulling; the rigid structural material can withstand the driving tension, and the discrete configuration makes the overall structure have low bending stiffness. In the surgical environment and other conditions with high safety requirements, this method is limited because the rigid material used may cause serious damage to human tissues if the wire breaks.

[0004] The second category is based entirely on soft materials, and this category of continuum structure is commonly made of a cavity structure made of silicone material and driven by applying positive air pressure. This type of structure has a large air cavity volume and is difficult to make into a compact and small structure. Due to the low material rigidity, the structure cannot withstand excessive tension and cannot use the wire driving method suitable for complex environments.

[0005] In summary, it is necessary to design a continuum structure that uses soft materials to fully ensure safety and can withstand the tension of the axial driving wire to achieve motion driving.

[0006] To solve the above problems, the present application is born. SUMMARY

[0007] (I) Technical problems solved

[0008] To overcome the contradiction between the soft structure and the ability to withstand large axial driving force of the existing continuum structure, a continuum structure based on a multi-layer braided tube with bending compliance is designed, and the radial motion interference of different layers of braided tubes is used to solve the problems raised in the background technology.

[0009] (II) Technical solutions

[0010] To achieve the above object, the present application is implemented by the following technical scheme: A tubular thin-wall continuum structure, comprising an inner layer braided tube and an outer layer braided tube, both having the characteristics of high bending compliance, thin wall and hollow inside, the inner layer braided tube is embedded inside the outer layer braided tube, and the surfaces of the two are closely attached; further comprising two end connection structures, respectively located at the proximal end and the distal end of the braided tube, fixing the two ends of the double-layer braided tube to prevent axial relative sliding.

[0011] In some exemplary embodiments of the present application, the outer layer braided tube adopts a smaller spiral angle than the inner layer braided tube, which can constrain the radial expansion of the inner layer braided tube under the driving of the axial eccentric pressure. Thus, the disclosed continuum structure has high axial stiffness and low bending stiffness, and realizes approximate pure bending motion under the axial eccentric force.

[0012] In some exemplary embodiments of the present application, a flexible wire can be used as a driver, and one end thereof is fixed to the surface of the braided tube and the other end is dragged by a motor or the like driver to form the axial eccentric force, so that the continuum structure undergoes bending motion (approximately pure bending motion in actual application).

[0013] In some exemplary embodiments of the present application, a shape memory alloy wire can be used as a driver, and is fixed to the surface of the braided tube, and one end thereof is excited by heating or the like to form the axial eccentric force, so that the continuum structure undergoes bending motion.

[0014] In some exemplary embodiments of the present application, a pneumatic muscle or the like can be used as a driver, and is fixed to the surface of the braided tube, and one end thereof is controlled by a pneumatic pump or the like to control the extension and contraction of the pneumatic muscle to form the axial eccentric force, so that the continuum structure undergoes bending motion.

[0015] In some exemplary embodiments of the present application, a plurality of groups of axial driving wires can be used, and the fixed ends are connected to different axial and circumferential positions of the braided tube, and combined driving is realized to achieve more complex spatial motion, serving as a flexible mechanical arm.

[0016] As a preferred scheme, further, an additional passive wire can be additionally provided on the surface of the braided structure, and a locking mechanism is additionally provided at the proximal end, the passive wire is clamped and its motion is limited by the locking mechanism, the overall stiffness of the mechanical arm is increased, and the deformation resistance is improved.

[0017] In this scheme, the mechanical arm has two uses:

[0018] 1. Make it small, as the end of a surgical instrument, which is a "finger" similar to, as a part of the surgical tool. Figure 11

[0019] ​2. Make it larger as a supporting catheter, then the tool is another structure to make it, it comes to support another structure to make the surgical tool, such as Figure 12 .

[0020] That is, the application scenarios of the surgical tools in the drawings of the specification Figure 11 and Figure 12 are all application scenarios of surgical tools, only the roles of the actual application structures are different.

[0021] Exemplarily, the flexible mechanical arm of the continuum structure of the present application can be made in the range of 3-5mm in outer diameter as a flexible end of a flexible surgical instrument in the field of minimally invasive surgery, or can be made in the range of about 20mm in outer diameter as a long handle for surgery, and the internal cavity thereof can be used to guide and support internal surgical tools, thereby improving the stability and force output capacity of the system.

[0022] The specific application method of the hollow thin-walled continuum structure and the flexible mechanical arm thereof comprises the following steps:

[0023] a. Motion driving step: complex spatial motion is realized by controlling the combined driving wire, and the position and attitude meeting the working condition requirements are realized;

[0024] b. Rigidity improving step: the passive wire is clamped by the locking mechanism, so that the structure presents higher rigidity, and the stability and external force output capacity of the system are improved;

[0025] c. Operation step: the rigidity of the proximal end of the mechanical arm can be improved, and the flexible end of the distal end is driven to operate; or the rigidity can be improved as a whole, and other flexible tools are passed through the inside of the mechanical arm to operate, at this time, the flexible mechanical arm mainly provides a rigid passage to guarantee the force output and stability;

[0026] d. Operation completion withdrawal step: the clamping function of the locking mechanism is cancelled, the passive wire is relaxed, the mechanical arm returns to a flexible state, and is moved under the driving of the wire and safely withdrawn from the operation environment.

[0027] (Three) beneficial effects

[0028] After the above technical scheme is adopted, the continuum structure provided by the present application can be used for operation in a narrow and complex space such as minimally invasive surgery, and compared with the prior art, has the following beneficial effects:

[0029] 1. The continuum structure of the present application is made of flexible fiber material, and has higher safety when contacting the human body.

[0030] 2. The continuum structure of the present application is hollow and thin-walled inside, which is beneficial to reduce the outer contour size of the structure, and has higher adaptability to narrow and small spaces such as body cavities.

[0031] 3、The continuum structure of the present application has good flexibility, can bear large driving force to realize large curvature bending, and has stronger adaptability to complex geometric morphology of body cavity environment, etc.

[0032] 4、The continuum structure of the present application can embed passive wires into the net structure, and does not need additional guide wire structure, so that the structure design is simpler.

[0033] 5、The multiple mesh holes of the continuum structure of the present application distributed along the axial direction can be used for fixing driving wires, the connection position arrangement mode of the driving wires is richer, and more complex spatial motion postures can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is the overall assembly relationship of the continuum structure of the embodiment of the present application;

[0035] Figure 2 It is a schematic diagram of the inner layer braided tube of the continuum structure of the embodiment of the present application;

[0036] Figure 3 It is a schematic diagram of the outer layer braided tube of the continuum structure of the embodiment of the present application;

[0037] Figure 4 It is a schematic diagram of bending deformation of the single layer braided tube of the continuum structure of the embodiment of the present application;

[0038] Figure 5 It is a schematic diagram of radial expansion deformation of the single layer braided tube of the continuum structure of the embodiment of the present application;

[0039] Figure 6 It is a schematic diagram of driving of the continuum structure of the embodiment of the present application by driving wires;

[0040] Figure 7 It is a schematic diagram of driving of the continuum structure of the embodiment of the present application by shape memory alloy;

[0041] Figure 8 It is a schematic diagram of driving of the continuum structure of the embodiment of the present application by gas pressure;

[0042] Figure 9 It is a schematic diagram of complex spatial motion of the continuum structure of the embodiment of the present application under the arrangement of multiple driving wires;

[0043] Figure 10 It is a schematic diagram of improvement of rigidity of the continuum structure of the embodiment of the present application by locking driving wires;

[0044] Figure 11 It is a schematic diagram of use of the continuum structure of the embodiment of the present application as a main body of a surgical flexible mechanical arm;

[0045] Figure 12This is a schematic diagram illustrating the use of a continuous structure as the end of a flexible surgical instrument according to an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0047] This invention provides a flexible continuum structure mainly composed of flexible inner and outer braided tube structures, end connection structures, and axial actuators; it achieves radial profile stability by means of asynchronous radial expansion of the inner and outer braided tubes, thereby realizing pure bending motion driven by axial eccentric force.

[0048] Figure 1 This is a schematic diagram of the overall structure of the continuum according to an embodiment of the present invention. Figure 1 As shown, the continuum structure includes an inner braided tube 1-1, an outer braided tube 1-2, a distal end connection structure 1-3, a proximal end connection structure 1-4, and an axial actuator 1-5. The distal end connection structure 1-3 connects the distal ends of the inner braided tube 1-1 and the outer braided tube 1-2 together; the proximal end connection structure 1-4 connects the proximal ends of the inner braided tube 1-1 and the outer braided tube 1-2 together; the axial relative movement between the inner braided tube 1-1 and the outer braided tube 1-2 is locked, thereby forming a double-layer configuration.

[0049] like Figure 2 The diagram shows the specific structural form of the inner braided tubing; the specific structural form of the outer braided tubing is as follows. Figure 3 As shown, both the inner and outer braided tubes are made of multiple threads spirally wound and intersected. The threads include multiple left-handed and right-handed spirals of equal quantity. Multiple left-handed spirals are arranged in sequence, and multiple right-handed spirals are arranged in sequence. The left-handed and right-handed spirals intersect and intertwine to form the braided tube structure.

[0050] Braided tubing has good flexibility, and its bending shape is as follows: Figure 4 As shown, large curvature bending can be achieved. The braided tube structure has radial expansion properties; under axial force, it undergoes radial expansion deformation, and its radial expansion shape is as follows... Figure 5 As shown.

[0051] like Figure 2 and Figure 3 As shown, the outer braided tube has a smaller helix angle, and its radial expansion is smaller compared to the inner braided tube under the same axial displacement. The deformation incompatibility between the two tubes prevents the structure from expanding radially. Therefore, under the action of the axial actuators 1-5 added to its surface, the continuous structure of this embodiment can maintain a stable cross-sectional profile and only undergo pure bending deformation that is conducive to forming complex spatial postures.

[0052] In some embodiments of the present invention, the bending motion of the designed continuum structure can be driven by an axial wire, and the control method is as follows: Figure 6 As shown, one end of the drive wire 6-2 is connected to the grid cell of the continuous structure 6-1, and the other end is connected to the stepper motor 6-3. The controller 6-4 controls the driver 6-5, which in turn controls the number of rotations of the stepper motor 6-3, thus controlling the stretching of the drive wire and causing the continuous structure to bend towards the stretched drive wire. With three drive wires 6-2 evenly distributed circumferentially, bending of the continuous structure in any direction can be achieved.

[0053] In some embodiments of the present invention, the bending motion of the designed continuum structure can be driven by a shape memory alloy actuator, and the control method is as follows: Figure 7 As shown, the shape memory alloy actuator 7-2 is spiral-shaped and fixed to the surface of the continuum structure 7-1. It is connected to a power supply 7-3, a switch 7-4, and a rheostat 7-5 via wires, forming an electrical circuit. When switch 7-4 is closed, the shape memory alloy actuator 7-2 contracts, driving the continuum structure to bend towards the heated shape memory alloy actuator. By controlling the resistance of the rheostat 7-5, the current is changed, controlling the driving force of the shape memory alloy actuator 7-2, and thus controlling the degree of bending of the continuum structure. With three shape memory alloy actuators 7-2 evenly distributed circumferentially, bending of the continuum structure in any direction can be achieved.

[0054] In some embodiments of the present invention, the bending motion of the designed continuum structure can be driven by a pneumatic actuator, and the control method is as follows: Figure 8 As shown. The pneumatic actuator 8-2 can be composed of silicone-fiber, such as McKibben pneumatic muscles, and is fixed to the surface of the continuous structure 8-1. It is connected to the air pump 8-3 and the air pressure valve 8-4 through an air guide tube, forming an air circuit. When the air pump 8-3 is turned on, the pneumatic actuator 8-2 contracts or extends, driving the continuous structure to bend in the direction of the contracting pneumatic muscle or in the opposite direction of the extending pneumatic actuator. By controlling the air pressure valve 8-4 to change the air pressure, the deformation of the pneumatic actuator 8-2 is controlled, thereby controlling the degree of bending of the continuous structure. With three pneumatic actuators 8-2 evenly distributed circumferentially, bending of the continuous structure in any direction can be achieved.

[0055] When the continuum structure of this invention employs a wire-driven method, more complex spatial motions can be achieved through multiple sets of axial drive wires and different end connection combinations. Examples of connections for multiple sets of drive wires are shown below. Figure 9The driving wire 9-2 and the driving wire 9-3 are connected at different circumferential positions of the continuum structure 9-1, and multi-directional bending of the structure can be achieved. The driving wire 9-2 and the driving wire 9-4 are connected at different axial positions of the continuum structure, and non-constant curvature bending of the structure at different axial positions can be achieved. Meanwhile, pulling the driving wire 9-3 and the driving wire 9-4 can achieve a more complex spatial pose of the structure.

[0056] When the continuum structure of the present application is driven by the wire, passive wires can be added inside the structure. The stiffness of the structure can be increased by locking the proximal end of the passive wire. The principle is shown in Figure 10 The passive wire 10-2 is connected to the surface of the continuum structure 10-1 at one end and passes through the locking mechanism 10-3 at the other end. When the locking mechanism 10-3 is closed, the passive wire 10-2 is clamped and the ability of the continuum structure to deform in the opposite circumferential direction of the passive wire is limited, thereby increasing the stiffness. Using multiple sets of passive wires 10-2 and locking mechanisms 10-3 can improve the stiffness of the continuum structure in multiple different directions.

[0057] Figure 11 The continuum structure of the present application is used as a flexible end of a minimally invasive surgical instrument. The functional end of the instrument (surgical forceps, etc.) 11-2 is connected to the distal end of the continuum structure 11-1, and the tool long rod 11-3 is connected to the proximal end of the continuum structure 11-1. The driving wire inside the tool long rod 11-3 drives the movement of the continuum structure 11-1, forming a spatial pose of the functional end 11-2 of the surgical instrument for easy operation.

[0058] Figure 12 The continuum structure of the present application is used as a flexible mechanical arm for minimally invasive surgery.

[0059] 12-1 is a surgical tool, and all surgical tools enter the human body for surgical operation through the continuum structure flexible mechanical arm 12-2 of the present application. The outer wall of the surgical tool 12-1 is attached to the inner wall of the mechanical arm 12-2, and the mechanical arm 12-2 can increase the stiffness by clamping the passive wire. Furthermore, the mechanical arm 12-2 can play a role in isolating tools and protecting tissues when the surgical tool enters the human body, and can play a role in supporting multiple tools during surgical operation.

[0060] As can be seen from the above embodiments, the present application based on flexible fiber material can obtain higher human-machine contact safety, and the radial expansion of the inner and outer woven tubes is not coordinated to ensure stable cross-sectional profile under axial driving force. Compared with existing flexible continuum structures, the present application has the advantages of high safety, flexible structure, small size, simple design and driving, and is more suitable for high safety requirements, space.

[0061] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above-described specific embodiments are merely examples of the present application and are not intended to limit the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A hollow thin-walled continuous structure, comprising: The inner and outer braided tube structures are made of fine threads and are flexible, thin-walled and hollow. The inner braided tube is embedded inside the outer braided tube and the surfaces of the two are tightly attached. The braided tube structure is formed by multiple braided threads spirally wound and crossed. The proximal and distal end connection structures fix the two ends of the inner and outer braided tubes respectively to form a continuous structure and prevent axial relative sliding. An axial actuator is fixed on the surface of the continuum structure, and several axial actuators are arranged on the axial and circumferential surfaces of the continuum structure. The outer braided tube has a smaller helix angle than the inner braided tube. Under axial eccentric pressure, it can constrain the radial expansion of the inner braided tube, so that the continuous structure has high axial stiffness and low bending stiffness. Under axial eccentric force, the radial profile is stabilized by the asynchronous radial expansion of the inner and outer braided tubes, thereby realizing pure bending motion driven by axial eccentric force.

2. The hollow thin-walled continuous structure according to claim 1, characterized in that: A flexible drive wire is fixed on the surface of the braided tube as an actuator. The other end of the drive wire is dragged by a motor to form an axial eccentric force, causing the continuous structure to bend.

3. The hollow thin-walled continuous structure according to claim 1, characterized in that: A shape memory alloy wire is fixed on the surface of the braided tube as an actuator. The other end of the shape memory alloy wire is excited by electrothermal means to form an axial eccentric force, causing the continuous structure to bend.

4. The hollow thin-walled continuous structure according to claim 1, characterized in that: The surface of the braided tube is connected to a pneumatic muscle as an actuator. The other end of the pneumatic muscle is controlled by an air pump to extend and retract, thereby generating an axial eccentric force that causes the continuous structure to bend.

5. A flexible robotic arm, employing the hollow thin-walled continuous structure as described in claim 2, characterized in that: Multiple sets of axial drive wires are used, with their fixed ends connected to different axial and circumferential positions of the inner and outer braided tubes. Under combined drive, more complex spatial movements can be achieved, thus serving as a flexible robotic arm.

6. The flexible robotic arm according to claim 5, characterized in that: A passive wire is embedded in the surface of the braided tube outside the drive. The near end of the passive wire is not connected to the motor, but is connected to a locking mechanism added to the near end. The locking mechanism clamps the passive wire and restricts its movement, thereby increasing the overall rigidity of the robotic arm and improving its resistance to deformation.

7. A hollow thin-walled continuous structure and its application method with a flexible robotic arm, characterized in that, The flexible robotic arm described in claim 5 or 6 comprises the following steps: a. Motion driving steps: By controlling the combined drive wires, complex spatial motions are achieved to realize the position and attitude that meet the working conditions. b. Stiffness enhancement step: The driven wire is clamped by the locking mechanism to make the structure exhibit higher stiffness, thereby improving the system's stability and ability to output external forces; c. Operation steps: The rigidity of the proximal end of the robotic arm can be increased to drive the flexible end of the distal end to perform the operation; or the overall rigidity can be increased to insert other flexible tools into the robotic arm for operation. In this case, the flexible robotic arm mainly provides a rigid path to ensure force output and stability. d. Withdrawal procedure after completion of the operation: cancel the clamping function of the locking mechanism, release the passive wire, the robotic arm returns to a flexible state, moves under the drive of the wire, and safely withdraws from the work environment.

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