Snake robot and joint thereof

Abstract

A snake-arm robot assembly can include a first link and a second link with a joint formed therebetween, the joint including a first contact portion and a second contact portion that rollingly contact one another to allow the first link and the second link to pivot relative to one another. The first contact portion and the second contact portion are configured to mutually contact at a first contact point and a second contact point corresponding to a first orientation and at a third contact point and a fourth contact point corresponding to a second orientation. The joint can be configured such that, when the links are in the first orientation, a line of action of a net force acting on the joint intersects a first reference line extending between the first contact point and the second contact point, and, when the links are in the second orientation, the line of action intersects a second reference line extending between the third contact point and the fourth contact point.

Description

Technical Field

[0001] This subject matter generally relates to a robotic arm for inspecting an environment and / or performing maintenance operations on components within that environment (e.g., components within the space inside a turbine engine), and more particularly to a snake-arm robot and its joints. Background Technology

[0002] Confined environments, such as gas turbine engines, require specialized inspection and maintenance tools. At least some gas turbine engines include, in a cross-flow arrangement, a compressor section comprising a low-pressure compressor and a high-pressure compressor for compressing air flowing through the engine, a combustor for mixing fuel with compressed air to make the mixture ignitable, and a turbine section comprising a high-pressure turbine and a low-pressure turbine for powering the compressor section.

[0003] Within one or more sections, at least certain gas turbine engines define openings that allow for the insertion of tools such as pipe endoscopes and robotic arms. These openings may vary in size, so each annular opening must be accommodated using a specialized insertion tool that extends around and through these openings. Attached Figure Description

[0004] By providing the snake-arm robot and its joints as described in the following detailed description, various needs are at least partially met, especially when studied in conjunction with the accompanying drawings. The complete and enabling disclosure of this invention, including its best mode, is set forth in the specification with reference to the accompanying drawings for those skilled in the art, wherein:

[0005] Figure 1 Perspective views of robotic arm assemblies constructed according to various embodiments of these teachings;

[0006] Figure 2 Including various embodiments constructed based on these teachings Figure 1 A perspective view of the robotic arm assembly, in which the outer skin of the robotic arm has been removed to show multiple sequentially arranged and hinged links in a neutral construction;

[0007] Figure 3 Including various embodiments constructed based on these teachings Figure 2 An enlarged elevation view of a segment of the proximal portion of a robotic arm assembly, including adjacent proximal and distal links;

[0008] Figure 4 Including various embodiments constructed based on these teachings Figure 3 A perspective view of a proximal link of a section of a robotic arm assembly;

[0009] Figure 5 Including various embodiments constructed based on these teachings Figure 4The plan view of the connecting rod shown illustrates a tensioning member extending axially in a through-hole extending through the connecting rod.

[0010] Figure 6 Including various embodiments constructed based on these teachings Figure 2 A perspective view of the link in the smaller distal portion of the robotic arm assembly;

[0011] Figure 7 The perspective view includes a portion of another robotic arm constructed according to various embodiments of these teachings, comprising a lower proximal joint formed by a proximal first link and an intermediate second link in a first orientation, and an upper distal joint formed by an intermediate second link and a distal third link in a second orientation.

[0012] Figure 8 It is constructed based on various embodiments of these teachings. Figure 7 A front view of a portion of the robotic arm;

[0013] Figure 9 It is constructed based on various embodiments of these teachings. Figure 8 The cross-sectional view of the robotic arm section through line 9-9;

[0014] Figure 10 It is constructed based on various embodiments of these teachings. Figure 7 Another front view of a portion of the robotic arm;

[0015] Figure 11 It is constructed based on various embodiments of these teachings. Figure 10 The cross-sectional view of the robotic arm through line 11-11;

[0016] Figure 12 This is a perspective view of the optional links constructed based on these teachings;

[0017] Figure 13 It is a geometric structure representing a segment of a snake-arm robot constructed based on these teachings, including adjacent links in neutral, aligned positions;

[0018] Figure 14 It is constructed based on these teachings Figure 13 A pivotally oriented geometric structure is used to visualize the trajectory of the contact point p at the end of the line of action of the net force F;

[0019] Figure 15 It is a plan view representing a linkage, with four equally spaced ropes terminating within it;

[0020] Figure 16 It is a plan view representing a linkage, with three equally spaced ropes terminating within it.

[0021] The elements in the figures are drawn for simplicity and clarity and are not necessarily drawn to scale. For example, the size and / or relative positioning of some elements in the figures may be exaggerated relative to other elements to aid in understanding the various embodiments of this teaching. Furthermore, common but easily understood elements that are useful or necessary in commercially viable embodiments are generally not described to minimize obscuring these various embodiments of this teaching. Certain actions and / or steps may be depicted or described in a specific sequence of occurrence, while those skilled in the art will understand that such specificity of the sequence is not actually necessary. Detailed Implementation

[0022] Robots (such as snake-arm robots) have long, thin arms with articulated joints along their length, allowing them to bend in a snake-like manner. Typical features associated with snake-arm robots include self-supporting arms driven by tensioning components such as control lines, tendons, or ropes. At least some snake-arm robot components include multiple links joined together at various joints. Furthermore, multiple control lines or ropes may extend through the arm, with one or more ropes terminating at individual links to move such links relative to rear-adjacent or near-adjacent links. The ropes may be coupled to one or more motors within the base of the snake-arm assembly, allowing the assembly to control the arm's movement by selectively increasing and / or decreasing the tension on one or more of the control lines. Due to their shape and control characteristics, snake-arm robots are commonly used to access confined spaces and perform tasks.

[0023] Snake-arm robots are typically used in conjunction with an introduction device that guides the arm into a confined space. For example, a snake-arm robot can be mounted on a remotely operated vehicle or on an industrial robot that can serve as the introduction device. In this case, the shape of the arm is coordinated with the linear movement of the introduction device's axis, allowing the operator to control the snake-arm robot's arm and head to guide it along a path into the work area or confined space to perform its function and / or tasks.

[0024] The ability of serpentine robots to pass through small openings and move through cluttered environments and / or reach into confined spaces enables such robots to be used in many applications involving access problems. For example, serpentine robots can be used to work in confined spaces in industrial or hazardous environments. Furthermore, serpentine robots can carry or be equipped with various types of tools and / or robot heads designed for the work. Therefore, serpentine robots can be used to inspect, repair, and / or maintain components in a variety of environments.

[0025] A snake-arm robot is a long, thin robotic arm operated by multiple tensioning members, also known as control lines, wires, ropes, cables, tendons, threads, etc., terminating at points along the length of the robotic arm. These tensioning members are tensioned or pulled using actuators (such as motors at the base of the arm). The number of tensioning members is typically 1.5 to 2 times the number of degrees of freedom of the arm. For lightweight arms, the tension and preload in the tensioning members may be similar for all tensioning members in the arm. The compressive force at the base of the link columns that make up the arm is the sum of the tensions in each tensioning member. For some snake-arm robots, the compressive force can exceed 500 times the arm's payload.

[0026] Snake-arm robots capable of bending in multiple directions typically consist of Hooke joints or universal joints between links, with tensioning members arranged in loops around the ends of each link to span the joints. The line of compressive action at the base of the arm due to tension in the tensioning members, coupled with the elastic instability of the link columns, gives rise to load limits and corresponding stiffness and load limits. These load limits are calculable and are considered limiting factors in known snake-arm robots, posing significant challenges, including in aerospace and industrial environments.

[0027] By studying the action line trajectory of the tensioning component in the snake-arm robot during joint bending, the inventors discovered that the contact surface of a roughly cylindrical or spherical rolling joint can be sized and constructed such that the action line of the compressive force acting on the joint coincides with the contact point between the contact surface, or, if there are multiple contact points, a reference line extending between or through the contact points along the entire range of motion of the joint.

[0028] Generally, various aspects of this disclosure can be used with a robotic arm including a first proximal link and a second distal link, and a joint therebetween. The joint includes convex contact portions that roll against each other to allow the first and second links to pivot relative to each other. The convex contact portions are configured to contact each other at first and second contact points corresponding to a first orientation of the first and second links. The first and second convex contact portions are also configured to contact each other at third and fourth contact points corresponding to a second orientation of the first and second links. The joint is configured such that when the first and second links are in the first orientation, the line of action of the net force acting on the joint intersects a first reference line extending between the first and second contact points, and when the first and second links are in the second orientation, the line of action of the net force acting on the joint intersects a second reference line extending between the third and fourth contact points.

[0029] In some embodiments, a first tensioning member and a second tensioning member each extend through at least a portion of a first link and a second link. The first and second tensioning members are fixed relative to the second link to allow the second link to pivot relative to the first link by pulling one of the first and second tensioning members proximally in and releasing the other of the first and second tensioning members distally. Both the first and second tensioning members have a free length spanning a joint between the first and second links. When the first and second links are in a first orientation, a first reference line extending between a first contact point and a second contact point is equidistant from each free length of the first and second tensioning members, and when the first and second links are in a second orientation, a second reference line extending between a third contact point and a fourth contact point is also equidistant from each free length of the first and second tensioning members. In some embodiments, the size and construction of a through-hole in the joint through which the tensioning member extends can be designed to control how the tensioning member bends as it extends from one joint to another. In some embodiments, the through-hole has proximal and distal portions that are enlarged relative to an intermediate portion extending therebetween. In some forms, the middle portion has a constant diameter. In some forms, the proximal portion of the through-hole gradually widens along the proximal direction, while the distal portion of the through-hole gradually widens along the distal direction.

[0030] By constructing the robotic arm in the above manner, elastic instability is reduced or eliminated. Furthermore, the payload capacity and stiffness of the robotic arm are improved. Further, the complexity of the robotic arm can be reduced and it can be further miniaturized to allow entry into smaller or more enclosed environments. The range of motion of each joint can also be increased compared to Hooke joints of similar size.

[0031] The terms and expressions used herein have the general technical meaning as attributed to them by one of ordinary skill in the art, unless otherwise specified herein. The term “or” as used herein should be interpreted as having a disjunctive structure rather than a conjunctive structure, unless specifically stated otherwise. The terms “connection,” “fixation,” “attachment,” etc., refer to direct connection, fixation, or attachment, as well as indirect connection, fixation, or attachment through one or more intermediate parts or features, unless otherwise specified herein.

[0032] Unless the context clearly indicates otherwise, the singular forms “a,” “one,” and “the” include plural references.

[0033] The approximate language used in this specification and claims is intended to modify any quantitative representation, which may be altered without changing its associated essential function. Accordingly, values ​​modified by terms such as “approximately,” “approximately,” and “substantially” are not limited to the specified precise values. In at least some instances, approximate language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to construct or manufacture the component and / or system. For example, approximate language may refer to a margin of 10%.

[0034] The above and other benefits become clearer through a comprehensive review and study of the following detailed description. Refer now to the accompanying drawings, especially... Figure 1 and Figure 2 Now we will present an illustrative snake-arm robot 100 that is compatible with many of these teachings.

[0035] The snake-arm robot 100 is shown in a neutral, aligned position, having an elongated body extending from a base 102 along a longitudinal axis L. The body of the snake-arm robot 100 is formed by columns of sequentially arranged and hinged segments 104. Figure 2 (Two of them are cited in the text), each segment consists of a pair of adjacent links 105 ( Figure 2 (Two of them are cited in the text) Formation, a pair of adjacent links 105 including a relative proximal link 106 and a relative distal link 108, with a joint 110 between them allowing the links 106, 108 to move, pivot, or bend relative to each other. Each link 105 may have a body formed by separate proximal and distal link portions 112, 114 connected or fixed to each other, or may have a monolithic, integral body, such as Figure 7-12 As shown. In some embodiments, the connecting rod 105 can be manufactured by electrical discharge machining (EDM), machining, and additive manufacturing processes, such as direct metal laser melting (DMLM) and direct metal laser sintering (DMLS). Figure 2 As shown, adjacent segments 104 overlap and share links, such that the proximal link 106 of one segment 104 can be the distal link 108 of the adjacent segment, and the distal link 108 of the same segment 104 can form the proximal link 106 of the adjacent distal segment 104. Accordingly, links 106 and 108 can be referred to here as first, second, third, proximal, distal, etc.

[0036] Movement of the links 105 is controlled by tensioning members or ropes 126 extending through and terminating at each link 105. In some embodiments, at least two ropes 126 terminate at or within each distal link 108 of segment 104 for moving the link 108 relative to the corresponding proximal link 106. In some embodiments, four ropes 126 terminate at each second link 108, such that each other link 105 may be without a rope attached thereto. In other embodiments, three ropes 126 may terminate at each second link 108. In some embodiments, the ropes 126 terminating at each link 105 are spaced approximately equal apart. In some embodiments, two ropes 126 terminate at a link 105, with the ropes 126 radially opposite each other.

[0037] Rope 126 extends from base 102 and is selectively released or pulled in via one or more actuators 103 (e.g., electric motors and / or linear actuators) to tension or relax the rope. Rope 126 may be coupled to pulleys, drums, spools, drums, and / or reels to change the path of the rope within base 102. In some embodiments, a pair of ropes 126 terminating at link 105 may be a rope portion of a single rope 126 extending around a pulley driven by a single motor. Controller 101 is operatively coupled to one or more actuators 103 for controlling the operation of the snake-arm robot 100. Furthermore, controller 101 may be operatively coupled to head portion 124 and / or attached to one or more links 105 of the snake-arm robot 100 and / or head portion 124, or to one or more sensors, cameras, tools, or devices (not shown) embedded therein.

[0038] exist Figure 2 In the illustrated embodiment, the snake-arm robot 100 includes 16 joints 110, each with a single degree of freedom, although in other forms the number of joints may vary, and each joint may have one or two degrees of freedom. Figure 1 and Figure 2 As shown, the arm of the snake-arm robot 100 includes a larger diameter proximal portion 164 and a smaller diameter distal portion 166. The larger diameter proximal portion 164 (see...) Figure 3-5 The connecting rod 105 and the smaller diameter distal portion 166 (see) Figure 6Similar to link 105, except for having a larger size and an increased number of through holes 132 to allow additional ropes 126 (including ropes attached to link 105 of the smaller diameter distal portion 166) to extend beyond link 105. At the transition between the larger diameter proximal portion 164 and the smaller diameter distal portion 166, transition link 107 includes a larger proximal link portion 112 connected to the smaller distal link portion 114. As just an example to illustrate the relatively small size of one embodiment of the snake-arm robot 100, link 105 of the smaller diameter distal portion 166 can have a diameter of approximately 6 mm, for example, 6.2 mm, and link 105 of the larger diameter proximal portion 164 can have a diameter of approximately 8 mm. The arm portion of this form of snake-arm robot 100 can have a length of approximately 98 mm or less than 4 inches.

[0039] In some embodiments, such as Figure 4 and Figure 5 As shown, the link 105 of the larger diameter proximal portion 164 includes a plurality of through holes 132 arranged in a pattern of two concentric rings, while the link 105 of the smaller diameter distal portion 166, as shown... Figure 6 As shown, the through-hole 132 has only a single-ring pattern. Typically, the rope 126, which extends through the inner ring pattern of the through-hole 132 of the link 105 through the larger diameter proximal portion 164, continues to the link through the smaller diameter distal portion 166.

[0040] Rope 126 can be secured relative to a single link 105 in various ways. In some embodiments, a crimp member, such as a cylindrical crimp sleeve, is attached to rope 126 by plastically deforming the crimp member as the rope extends through it. In some embodiments, a countersunk hole may be formed as part of a through-hole 132 in link 105 to receive the crimp member. In other embodiments, link 105 itself may be locally deformed adjacent to through-hole 132 to reduce the diameter of through-hole 132, thereby clamping rope 126 extending therein. In other embodiments, rope 126 may be thermally brazed within through-hole 132 using a filler metal such as bronze. In some embodiments, rope 126 may be wrapped within through-hole 132 to create sufficient friction with the sidewalls of through-hole 132 to hold the end of rope 126 in place. Specifically, the rope 126 has sufficient rigidity such that the U-shaped bend of the rope within the closely sized through-hole 132 generates a reaction force due to rotation, and the friction from the surrounding winch increases the available holding force. In other embodiments, the rope 126 may be bonded to the sidewall of the through-hole 132 using an adhesive. In other embodiments, the end of the rope 126 may be inserted through the through-hole 132, such that the rope end is slightly untied. The rope end may then be coated with an adhesive, brazing filler, or solder to build up the monofilaments of the rope 126, and then the rope end may be pulled back into the through-hole 132 to create a wedging action. In other forms, a pointed object may be driven into the rope end in the through-hole 132 to wed the end of the rope 126 into the through-hole 132. In other embodiments, a tapered chuck may be fitted onto the rope 126 and inserted into the through-hole 132, such that the tension on the rope 126 pulls the chuck, which engages with the sidewall of the through-hole, and weds the components together.

[0041] exist Figure 1 In some embodiments shown, the link 105 is surrounded by an outer sheath 130, which may be formed of a flexible material, such as an elastic sleeve made of silicone rubber or other synthetic rubber, a natural rubber compound or other elastomer with a large strain capacity, a corrugated thin-walled sleeve made of a thin metal such as copper, beryllium copper, or stainless steel (in such a way that it has a similar flexibility to a gaiter when bent), or a woven jacket made of finely woven fibers in different directions made of metals or polymers such as stainless steel, nickel-titanium alloy, and beryllium copper. The outer sheath 130 is configured to protect and prevent components of the snake-arm robot 100, including joint 110 and rope 126, from contamination by foreign objects in the environment and to allow segment 104 to bend.

[0042] like Figure 2As shown, the snake-arm robot 100 includes a plurality of links 105, including a base link 116 located proximally to the robot arm assembly, a distal end link 122 located distally to the robot arm assembly, and a plurality of intermediate links 128 located between the base link 116 and the distal end link 122. The base link 116 includes a distal rolling contact portion 118 for engaging with a proximal rolling contact portion 120 immediately adjacent to the link 105. The intermediate links 128 have both a distal rolling contact portion 118 and a proximal rolling contact portion 120. The distal end link 122 includes a single proximal rolling contact portion 120. A head portion 124 at the distal end of the snake arm 100 is positioned adjacent to the distal end link 122 at the distal end and may include an end effector, a tool such as a rotary tool for grinding or drilling, a sensor such as an eddy current sensor, a camera, a light source, a nozzle for introducing fluid, etc.

[0043] At the distal rolling contact portion 118 of the first proximal link 106 and the proximal rolling contact portion 120 of the second distal link 108, adjacent first and second links 106 and 108 form a joint 110. For example... Figure 7 As shown, the distal rolling contact portion 118 includes at least a first convex contact surface 140 of the first link 106, and the proximal rolling contact portion 120 includes at least a second convex contact surface 142 of the second link 108. The first convex contact surface 140 and the second convex contact surface 142 are configured to roll into contact with each other to allow the first and second links 106 and 108 to pivot relative to each other. Figure 6 As shown, for intermediate link 128, convex contact surfaces 140, 142 are formed at each distal end 136 and proximal end 134 of each link 105. In some forms, such as Figure 4-6 As shown, the rolling contact portions 118 and 120 of the first and second connecting rods 106 and 108 each include a plurality of convex contact surfaces 140 and 142. In some embodiments, the contact portions 118 and 120, including their first and second contact surfaces 140 and 142, are convex in their entirety, such that no portion or any part of their surface is concave. The contact portions 118 and 120 may be formed from a single continuous convex contact surface 140 and 142, as shown. Figure 12 As shown, or the contact portions 118, 120 can be formed by multiple discontinuous convex contact surfaces 140, 142, such as Figure 4-6 As shown.

[0044] Now for reference Figure 7-11The diagram shows three links 105 forming two joints 110, an upper or distal joint 110B, and a lower or proximal joint 110A. The intermediate link 105 forms the distal link 108A of the lower joint 110A and the proximal link 106B of the upper joint 110B. Links 106 and 108 forming the lower joint 110A are shown in a first pivot orientation, and links 106 and 108 forming the upper joint 110B are positioned relative to each other in a second pivot orientation. Referring now to the lower joint 110A, the first and second convex contact surfaces 140 and 142 of the first and second contact portions 118 and 120 are configured to contact each other at first and second contact points 144 and 146 at the first and second convex contact surfaces 140 and 142 corresponding to the first orientation of the first and second links 106 and 108. The first contact point 144 and the second contact point 146 are positioned opposite each other on both sides of the central opening 138, as shown... Figure 8 As shown. In some embodiments, the first contact point 144 and the second contact point 146 can be arbitrarily positioned on the line contact, especially when the first and second convex contact surfaces 140 and 142 are part of corresponding cylindrical convex contact surfaces. In some embodiments, although the distribution of contact pressure between the convex contact surfaces 140 and 142 is nominally linear, in reality, due to the effects of pressure and the elasticity of the materials including the connecting rod, as well as the deformation generated by the contact surfaces, the line will have some smaller actual width, and due to surface roughness, tolerances in any manufacturing process employed, and elastic deformation of the connecting rod 105, the distribution of contact pressure in the nominal contact line direction will be non-uniform.

[0045] In some embodiments, such as Figure 7-11As shown, the second or intermediate link 108A of joints 110A, 110B includes a third contact portion 118 having a third convex contact surface 140 opposite to the second convex contact surface 142. The third convex contact portion is configured to roll into contact with a fourth convex contact portion 120 of the third link 108B having a fourth convex contact surface 142. The third link 108B is positioned distally from the second link 108 along a longitudinal axis. The second and third links 108A, 108B correspondingly form a second distal joint 110B. The third contact portion 118 rotates 90 degrees about the longitudinal axis. However, in other forms, the third contact portion 118 may rotate at least 30 degrees or more about the longitudinal axis L, for example, 30 degrees, 45 degrees, 60 degrees, or 75 degrees, to allow the third links 105, 108 to pivot in a direction different from the direction in which the second link 108A pivots relative to the first link 106A. In some embodiments, the link 105 may have the same size and construction. Thus, the first and third contact portions 118 of adjacent links may have the same construction, and the second and fourth contact portions 120 of adjacent links may have the same construction, except that they are rotated relative to each other about a longitudinal axis, for example, rotated about the longitudinal axis L by at least 30 degrees or more, such as 30 degrees, 45 degrees, 60 degrees, 75 degrees or 90 degrees about the longitudinal axis.

[0046] Link 105 includes a plurality of through holes or apertures 132 that generally extend longitudinally between a proximal end 134 and a distal end 136 of link 105. Rope 126 may extend through the openings or apertures 132 to connect adjacent links 105 together and to move the orientation of links 105 relative to each other. In some embodiments, the through holes 132 are arranged in a generally annular pattern around a larger central opening 138 that extends along its longitudinal axis between the proximal end 134 and the distal end 136 of link 105 to allow fluid, electrical and / or data lines, as well as flexible drive shafts and / or other components, to pass from base 102 to other links and / or head portions 124.

[0047] It should be understood that bending of joint 110 is achieved by pulling a length of rope 126 into one side of the joint while simultaneously releasing a length of rope 126 out the other side. When the length of rope 126 fixed to the distal link 108A of joint 110A is adjusted to move the distal link 108 relative to the adjacent end link 106, links 106A and 108A will move to a second orientation different from the first orientation, such as the orientation of links 106B and 108B forming the upper joint 110B, as... Figure 10 and Figure 11As shown. Now referring to the upper joint 110B, the first and second convex contact surfaces 140, 142 of the first and second contact portions 118, 120 are configured to contact each other at third and fourth contact points 148, 150 at the first and second convex contact surfaces 140, 142 corresponding to the second orientation of the first and second connecting rods 106, 108. Figure 9 As shown, the third and fourth contact points 148 and 150 are positioned opposite each other on either side of the central opening 138. In some forms, the first and second contact portions 118 and 120 each include a plurality of convex contact surface portions 140 and 142, such as... Figure 4-6 As shown, the contact point pairs can be located at individual convex contact surface portions 140 and 142 of each contact portion 118 and 120.

[0048] like Figure 8-11 As shown, each of joints 110A and 110B is configured such that when the arm 100 is stationary, and when the first and second links 106 and 108 are in a first orientation, the line of action of the net force F acting on the joint intersects a first reference line R1, which extends between the first and second contact points. When the first and second links 106 and 108 are in a second orientation, the line of action of the net force acting on the joint intersects a second reference line R2, which extends between the third and fourth contact points 148 and 150. The net force F acting on the joint includes all compressive forces acting on the joint, including the net tension of the rope 126 terminating at the distal end of the joint, and the forces exerted by the payload and weight of the robotic arm 100. It will be apparent to those skilled in the art that when the arm moves under acceleration, the line of action of the net force F may cease to coincide with reference lines R1 and R2.

[0049] In some embodiments, the first and second contact portions 118, 120 each include a plurality of convex contact surfaces 140, 142, wherein the plurality of convex contact surfaces of each link extend along a cylindrical profile to allow the first and second links to move relative to each other with only a single degree of freedom. In other embodiments, the convex contact surfaces 140, 142 may extend along a spherical profile, such that the joint 110 has two degrees of freedom.

[0050] In some embodiments, each link 105 includes a plurality of through holes 132 extending between its proximal and distal ends 134, 136 to allow a rope 126 to extend through the link for connection with other links 105. Accordingly, contact portions 118, 120 and their convex contact surfaces 140, 142 may be interrupted by distal and proximal holes 158, 160 of the through holes 132. Figure 9 and Figure 11As shown, at least one of the plurality of through holes 132 includes proximal and distal portions 152, 154, which are enlarged relative to an intermediate portion 156 of the through hole 132 extending between the proximal and distal portions 152, 154. In some embodiments, the intermediate portion 156 is sized to fit snugly to a rope 126 extending through the intermediate portion 156 while allowing the rope 126 to move within the through hole 132. In some embodiments, the dimensions of at least the intermediate portion 156 of the through hole 132 may be designed to an H8 tolerance based on manufacturing tolerances for cylindrical holes drilled or reamed. For example, the diameter gap between the rope 126 and the through hole 132 may be about 25 to 50 micrometers, or 1 / 1000 to 2 / 1000 of an inch, or less than about 1% or less than about 2% of the diameter of the rope 126.

[0051] In some embodiments, link 105 includes at least one alignment feature configured to inhibit sliding of the first contact portion 118 and the second contact portion 120 relative to each other. In one form, the alignment feature includes one or more protrusions, such as teeth 162 of the first link 106 and corresponding teeth 162 of the second link 108, configured to engage with each other when the first and second links move relative to each other between different orientations or joint angles. In some embodiments, such as... Figure 3-6 As shown, tooth 162 is an involute gear tooth. In some embodiments, the gear teeth or teeth of each of the first and second links are disposed along the outer periphery of the first and second links 106, 108, for example, on opposite sides of each of the proximal ends 134 and distal ends 136. Other alignment features may be utilized, such as belts and / or elastic members extending longitudinally between the links.

[0052] In some embodiments, the snake-arm robot 100 includes a proximal first link 106A and a distal second link 108A that are adjacent to each other along the longitudinal axis of the robot arm, such as... Figure 7-11 As shown. A proximal joint 110A is formed between the first and second links 106A and 108A. This proximal joint includes a first contact portion 118 and a second contact portion 120. The first contact portion includes a first convex contact surface 140 of the first link 106A, and the second contact portion includes a second convex contact surface 142 of the second link 108A. The first convex contact surface 140 and the second convex contact surface 142 are configured to roll contact with each other to allow the first link 106A and the second link 108A to pivot relative to each other. Figure 8 and Figure 9 As shown, the first convex contact surface 140 and the second convex contact surface 142 are configured to contact each other at a first contact point 144 and a second contact point 146 at the first convex contact surface 140 and the second convex contact surface 142 corresponding to the first orientation of the first link 106A and the second link 108A. Now refer to Figure 10 and Figure 11 For illustrative purposes, in particular, the upper joint 110B formed by the intermediate link 106B and the distal link 108B, including the first and first contact portions 118, 120 of the first and second convex contact surfaces 140, 142 of the links 106B and 108B, are configured to contact each other at third contact points 148 and fourth contact points 150 at the first convex contact surfaces 140 and 142 corresponding to the second orientation of the first link 106B and the second link 108B, wherein the second orientation differs from the first orientation. It should be understood that the three links 105 forming joints 110A and 110B are capable of similar rotational movements relative to the other links of each joint, except that the direction of rotation of the distal link is oriented differently relative to the longitudinal axis in each case, for example, as... Figure 7-11 The 90 degrees shown in the embodiment.

[0053] Refer again Figure 8 and Figure 9 A first tensioning member 126A extends through at least a portion of a first link 106A and a second link 108A. A second tensioning member 126B extends through at least a portion of a first link 106A and a second link 108A. The first and second tensioning members 126A and 126B are fixed relative to the second link 108A to allow the second link 108A to pivot relative to the first link 106A by pulling one of the first and second tensioning members 126A proximally and releasing the other of the first and second tensioning members 126A distally.

[0054] In some embodiments, a first through-hole 132A and a second through-hole 132B extend through each of a first link 106A and a second link 108A. A first tensioning member 126A extends through the first through-hole 132A of the first link 106A and at least partially through the first through-hole 132A of the second link 108A. A second tensioning member 126B extends through the second through-hole 132B of the first link 106A and at least partially through the second through-hole 132B of the second link 108A. The first and second tensioning members 126A, 126B are fixed relative to the second link 108A to allow the second link 108A to pivot relative to the first link 106A by pulling one of the first and second tensioning members 126A proximally and releasing the other of the first and second tensioning members 126B. Specifically, as Figure 9 As shown, the first tensioning member 126A is pulled in proximally, and the second tensioning member 126B is released distally, causing the intermediate link 108A to pivot to the right, as... Figure 9As shown. In some embodiments, the length by which one of the first and second tensioning members 126A is pulled in is equal to the length by which the other of the first and second tensioning members 126B is released. In some embodiments, a third tensioning member 126C extends through the first and second links 106A, 108A and at least partially through a third link 108B adjacent at its distal end to the second intermediate links 108A, 106B, wherein the third tensioning member 126C is fixed relative to the third link 108B to allow the third link 108B to be oriented relative to the second link 106B.

[0055] In some embodiments, each of the first and second tensioning members 126A, 126B has a free length 168 that does not contact the first and second links and spans the joint between the first and second links 106, 108. Figure 8 and Figure 9 As shown, when the first link 106A and the second link 108A are in the first orientation, the first reference line R1 extends between the first contact point 144 and the second contact point 146, and the first reference line R1 is equidistant from each free length 168 of the first and second tensioning members 126A and 126B. Similarly, now referring to... Figure 10 and Figure 11 When the first and second links 106B and 108B, i.e., the intermediate and upper links for illustrative purposes, are in the second orientation, the second reference line R2 extends between the third and fourth contact points 148 and 150. The second reference line R2 is also equidistant from each free length 168 of the first and second tensioning members 126C and 126D.

[0056] In some embodiments, a 1-DOF joint 110 is formed between each link 105. In other embodiments, the snake-arm robot 100 may be equipped with 1-DOF and 2-DOF joints 110, or only with 2-DOF joints. In some embodiments, such as a snake-arm robot 100 with two-DOF joints, four cables 126 terminate at one link 105 between every two joints 110. In other embodiments, two cables 126 terminate at each link 105, i.e., at each distal link 108 of each 1-DOF joint 110. In some embodiments, the axis of rotation of each joint 110 is rotated relative to the adjacent joint 110 such that the axis of rotation from each cable 126 to the centerline C of each joint is rotated. L (See Figure 5The distance is maximized to minimize rope load. Minimizing rope load is useful in many ways, including reducing the size of the rope 126 required for a given material choice and construction, reducing the required volume of the rope termination and supporting links 105, and reducing structural compression of the snake-arm robot 100. Structural compression of the arm determines the required strength of each link 105 and joint 110, but also affects the elastic stability of the columns of the snake-arm robot 100.

[0057] In some embodiments, including the above-described embodiments, it has been found that by constructing joint 110 such that the instantaneous rotation center of joint 110 coincides with the effective line of action of the compressive load F on joint 110, the snake-arm robot 100 can be made neutrally stable, i.e., the tendency of the arm to bend can be eliminated. Figure 9 , Figure 11 and Figure 14 As shown.

[0058] Another motivation for designing a multi-DOF snake arm robot is to provide ease of control. It should be understood that in the rigid-link snake arm robot 100, bending a joint 110 is achieved by pulling a length of rope into one side of the joint while simultaneously releasing a length of rope into the other side. If the length of the released rope is equal to the length of the pulled rope and in opposite directions, the sum of the two lengths remains constant. This allows for simplified control of the movement of joint 110 because it allows two ropes (or sections of a single rope) to be controlled by a single motor and coupled to a drum or reel, or a linear actuator, etc.

[0059] The inventors discovered that the following two criteria can be met: 1) the reference line extending from the contact point of each joint, or between multiple contact points of each joint, intersects the line of action of the net force acting on the joint; and 2) the amount of rope 126 released is equal to the amount of rope pulled in. This solution can be constructed graphically or analytically and results in a generally cylindrical rolling contact surface for a single-degree-of-freedom (2-D) joint, or a generally spherical rolling contact surface for a two-degree-of-freedom (3-D) joint as shown and described herein.

[0060] The above two criteria are satisfied when the center of the approximately convex cylindrical or spherical surface and the inflection point of rope 126 are in the same plane. When the joint bending angle 9 changes, the contact point p between the convex contact surfaces 140 and 142 moves laterally relative to the contact surfaces by an amount equal to the radius of the convex contact surface multiplied by the sine of half the joint bending angle 9. This keeps the contact point on a line between the centers of the convex contact surfaces 140 and 142. Furthermore, since the centers of the two convex contact surfaces 140 and 142 are always separated by a distance equal to the sum of the radii of the two convex contact surfaces, the sum of the lengths of the released and pulled ropes remains constant. This joint model is applicable to very flexible ropes, where the bending of the rope itself occurs over a very short distance when it transitions from a straight length within the link to a straight length between the links, assumed to be zero length in the above description using idealized rope characteristics.

[0061] In some embodiments, the rope is selected to be rigid under tension, such as a stranded wire rope. These ropes can be made of various materials, including steel, stainless steel, or tungsten. The repeatable bending capability of a stranded wire rope is limited by the strain of the rope strands or filaments. A stranded structure using smaller filaments allows for tighter bending than a simpler rope with larger filaments, but at the cost of higher cost, lower abrasion resistance, and more complex failure modes. The filaments in a wire rope are typically cold-drawn and work-hardened to produce a material with few defects and high tensile strength. One criterion for determining the minimum permissible bending radius of a moving wire rope is to limit the reverse or repeated stress in each filament to less than the fatigue limit or durability limit of the material. This radius can be used to redefine the bending pattern of the rope. Thus, in some embodiments, the radii of the opposing sidewalls of the proximal and distal portions 152 of the through-hole 132 can be selected to be equal to or greater than the minimum bending radius of the rope 126.

[0062] In some embodiments, the proximal portion 152 of at least one through-hole 132 expands along a first direction transverse to the longitudinal axis, and the distal portion 154 of at least one through-hole 132 expands along a second direction transverse to the longitudinal axis, the second direction being different from the first direction. Typically, the first and second directions are perpendicular to the axis of rotation of the joint 110. In some embodiments, the first and second directions are oriented at an angle of 30 degrees or greater around the longitudinal axis L, for example, 30, 45, 60, 75, or 90 degrees around the longitudinal axis L. Figure 7 As shown. In some embodiments, the proximal portion 152 of at least one through hole 132 gradually widens in the proximal direction, and the distal portion 154 of at least one through hole 132 gradually widens in the distal direction. The proximal and distal portions 152 and 154 of the through hole may be funnel-shaped, such that the opposite sidewalls or sidewall portions of the through hole 132 have an arcuate or circular arcuate structure that diverges from each other.

[0063] Introducing the rope bending radius into the rolling joint arrangement can cause the line of action of the net force on the joint to shift away from the rolling contact point between the links, or from a reference line extending between multiple contact points. Therefore, the inventors have discovered that the convex contact portions 118, 120 and the surface or its surface can be designed such that the line of action of the net force on the joint remains intersecting the contact point or the reference line extending between multiple contact points. In some forms, the convex contact portions and the surface or its surface have a non-circular profile, as further described below.

[0064] As a way of explanation, Figure 13 A simplified representation of the central cross-section of joint 110 is shown, wherein joint 110 includes a proximal link 106 and a distal link 108 aligned in a neutral position. The xy coordinate system is located at the contact point p in the straight neutral position of the link, at a height H from the end of the straight section of rope 126, and has a length L at the proximal end of the middle portion 156 of the through hole 132 within the upper distal link 108. Figure 14 The constructed geometry for visualizing the trajectory of contact point p is shown, defined at the bottom of the straight line length L, outlining the contact portions 118, 120 (e.g., surfaces 140, 142) at the ends of the line of action of the net force between links 106, 108 at joint 110. Similarly, if multiple contact points exist between rolling contact surfaces, contact point p is located at the intersection of a reference line and the line of action of the net force acting on the joint, with the reference line extending between the contact points. The imaginary radius R corresponds to the rope bending radius, which is translated on the link so that its upper end aligns with the centerline of the straight link. If 9 is expressed in radians, the length of the bending segment is R9.

[0065] To satisfy the criterion of constant rope length, L = H - Rθ.

[0066] To keep the position of the contact point p in the xy coordinate system on the center line between the two rope lines, the xy coordinates of the contact point p as a function of angle θ can be parameterized as follows:

[0067] x=R(1-cosθ)+L sinθ

[0068] y = H - (R sinθ + L cosθ)

[0069] Without compensation, errors in rope length can be significant and may lead to variations in the tension and angle errors of the snake-arm robot, variations large enough to significantly affect position control. However, within a reasonable range of angular deflection within the arm's joints, the shape of the aforementioned ideal contact point curve, while not an arc, is sufficiently close to one. Therefore, for manufacturing purposes, it is preferable to use an arc form instead of the more complex ideal contact point curve without causing functional problems. However, the radius of the arc differs from the radius of the original circle. The simplest way to choose an approximate circle is to fit a circle centered at x=0 and tangent to the horizontal x-axis at y=0, and fit the point at the end of the ideal contact point arc, i.e., the contact point at the maximum deflection angle of the joint. Other optimization strategies can also be employed, such as minimizing the theoretical area between the non-circular and circular approximations.

[0070] Figure 15 and Figure 16 Two different embodiments of the cable spacing 126 for the distal link of a two-degree-of-freedom joint are shown. Figure 15 Four equally spaced ropes 126 are shown arranged in a circular pattern of radius r and fixed to the connecting rod 105. Figure 16 Three equally spaced ropes 126 are shown arranged in a ring pattern of radius r and fixed within the connecting rod 105. Figure 15 The four-rope structure shown reduces the available cross-sectional space of the linkage, but remains simple to design, construct, and control. Furthermore, the four-rope structure offers advantages in load capacity. Specifically, in the four-rope structure, the minimum distance (radius r / √2) from the hinge center to the line of action 170 of the rope pair is greater than that in the three-rope structure (radius r / 2).

[0071] Other fixing patterns for the ropes 126 are possible, and the ropes 126 do not need to be equidistant as shown in the figure. If the ropes 126 are not equidistant, the load on each rope will be different from the load on each rope in the equidistant example. In the snake-arm robot 100 for general applications without biased loads, equidistant tendons can provide the most uniform load capacity. However, in other applications where the snake-arm robot 100 is intended to load along a specific direction, it may be advantageous to space the ropes unevenly in the links.

[0072] Further aspects of this disclosure are provided by the subject matter of the following clauses:

[0073] A robotic arm includes: a first link and a second link, the first link and the second link being positioned adjacent to each other along a longitudinal axis of the robotic arm; a joint formed by the first link and the second link, the joint including a first convex contact portion of the first link and a second convex contact portion of the second link, the first convex contact portion and the second convex contact portion being configured to roll contact with each other to allow the first link and the second link to pivot relative to each other; wherein the first convex contact portion and the second convex contact portion are configured to contact each other at a first contact point and a second contact point at the first contact portion and the second convex contact portion corresponding to a first orientation of the first link and the second link; wherein the first convex contact portion and The second convex contact portion is configured to contact each other at a third contact point and a fourth contact point at the first convex contact portion and the second convex contact portion corresponding to the second orientation of the first link and the second link, wherein the second orientation is different from the first orientation; and wherein the joint is configured such that when the first link and the second link are in the first orientation, the line of action of the net force acting on the joint intersects a first reference line extending between the first contact point and the second contact point, and when the first link and the second link are in the second orientation, the line of action of the net force acting on the joint intersects a second reference line extending between the third contact point and the fourth contact point.

[0074] The robotic arm according to any of the foregoing clauses, wherein the first convex contact portion and the second convex contact portion are convex in their entirety.

[0075] The robotic arm according to any of the foregoing clauses, wherein the first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein at least one of the plurality of convex contact surfaces is discontinuous with another of the plurality of convex contact surfaces.

[0076] The robotic arm according to any of the foregoing clauses, wherein the first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein the plurality of convex contact surfaces of each link extend along a cylindrical profile to allow the first link and the second link to move relative to each other with only a single degree of freedom.

[0077] According to any of the preceding clauses of the robotic arm, wherein the second link includes a third convex contact portion opposite to the second convex contact portion, the third convex contact portion being configured to roll into contact with a fourth convex contact portion of the third link, the third link being positioned distally from the second link along the longitudinal axis, wherein the third convex contact portion is rotated at least 30 degrees about the longitudinal axis to allow the third link to pivot in a direction different from the direction in which the second link pivots relative to the first link.

[0078] The robotic arm according to any of the foregoing clauses, wherein each of the first link and the second link includes a plurality of through holes extending between its proximal and distal ends, wherein at least one of the plurality of through holes includes a proximal portion and a distal portion, the proximal portion and the distal portion being enlarged relative to a middle portion of the through hole extending between the proximal portion and the distal portion.

[0079] The robotic arm according to any of the foregoing clauses, wherein the proximal portion of the at least one through hole expands along a first direction transverse to the longitudinal axis, and the distal portion of the at least one through hole expands along a second direction transverse to the longitudinal axis, the second direction being different from the first direction.

[0080] The robotic arm according to any of the foregoing clauses, wherein the first direction is perpendicular to the second direction.

[0081] The robotic arm according to any of the foregoing clauses, wherein the proximal portion of the at least one through hole gradually widens in the proximal direction, and the distal portion of the at least one through hole gradually widens in the distal direction.

[0082] The robotic arm according to any of the foregoing clauses further includes at least one alignment feature configured to inhibit sliding of the first convex contact portion and the second convex contact portion relative to each other.

[0083] The robotic arm according to any of the foregoing clauses, wherein the at least one alignment feature includes a tooth of the first link and a corresponding tooth of the second link, the tooth of the first link and the corresponding tooth of the second link being configured to engage with each other when the first link and the second link move between the first orientation and the second orientation.

[0084] The robotic arm according to any of the foregoing clauses, wherein the teeth of each of the first link and the second link are arranged along the outer periphery of the first link and the second link.

[0085] The robotic arm according to any of the foregoing clauses further includes a first through-hole and a second through-hole extending through each of the first link and the second link; a first tensioning member extending through the first through-hole of the first link and at least partially through the first through-hole of the second link; a second tensioning member extending through the second through-hole of the first link and at least partially through the second through-hole of the second link; wherein the first tensioning member and the second tensioning member are fixed relative to the second link to allow the second link to pivot relative to the first link by pulling one of the first tensioning member and the second tensioning member proximally in and releasing the other of the first tensioning member and the second tensioning member; and wherein the length by which said one of the first tensioning member and the second tensioning member is pulled in is equal to the length by which said one of the first tensioning member and the second tensioning member is released.

[0086] The robotic arm according to any of the foregoing clauses further includes a third tensioning member that extends at least partially through a third link adjacent to the second link at its distal end, wherein the third tensioning member is fixed relative to the third link for moving the orientation of the third link relative to the second link.

[0087] The robotic arm according to any of the foregoing clauses, wherein the first tensioning member and the second tensioning member each have a free length spanning the joint between the first link and the second link; wherein, when the first link and the second link are in the first orientation, a first reference line extending between the first contact point and the second contact point is equidistant from each of the free lengths of the first tensioning member and the second tensioning member, and when the first link and the second link are in the second orientation, a second reference line extending between the third contact point and the fourth contact point is also equidistant from each of the free lengths of the first tensioning member and the second tensioning member.

[0088] A robotic arm includes: a first link and a second link, the first link and the second link being positioned adjacent to each other along a longitudinal axis of the robotic arm; a joint formed between the first link and the second link, including a first convex contact portion of the first link and a second convex contact portion of the second link, the first convex contact portion and the second convex contact portion being configured to roll contact with each other to allow the first link and the second link to pivot relative to each other; wherein the first convex contact portion and the second convex contact portion are configured to contact each other at a first contact point and a second contact point at the first convex contact portion and the second convex contact portion corresponding to a first orientation of the first link and the second convex contact portion; wherein the first convex contact portion and the second convex contact portion are configured to contact each other at a third contact point and a fourth contact point at the first convex contact portion and the second convex contact portion corresponding to a second orientation of the first link and the second link, wherein the second orientation is different from the first orientation; and a first tensioning member extending through the first link and the second link. At least a portion of the first link and the second link; a second tensioning member extending through at least a portion of the first link and the second link; wherein the first tensioning member and the second tensioning member are fixed relative to the second link to allow the second link to pivot relative to the first link by pulling one of the first tensioning member and the second tensioning member proximally in and releasing the other of the first tensioning member and the second tensioning member distally; wherein the first tensioning member and the second tensioning member each have a free length spanning the joint between the first link and the second link; and wherein, when the first link and the second link are in the first orientation, a first reference line extending between the first contact point and the second contact point is equidistant from each of the free lengths of the first tensioning member and the second tensioning member, and when the first link and the second link are in the second orientation, a second reference line extending between the third contact point and the fourth contact point is also equidistant from each of the free lengths of the first tensioning member and the second tensioning member.

[0089] The robotic arm according to any of the foregoing clauses further includes at least one alignment feature configured to inhibit sliding of the first convex contact portion and the second convex contact portion relative to each other.

[0090] The robotic arm according to any of the foregoing clauses, wherein the at least one alignment feature includes a tooth of the first link and a corresponding tooth of the second link, the tooth of the first link and the corresponding tooth of the second link being configured to engage with each other when the first link and the second link move between different joint angles.

[0091] The robotic arm according to any of the foregoing clauses, wherein the gear teeth are arranged along the outer periphery of the first link and the second link.

[0092] According to any of the preceding clauses, in the robotic arm, for each of the first and second orientations of the first and second links, the length by which the first tensioning member and the second tensioning member are pulled proximally is equal to the length by which the other tensioning member is released distally.

[0093] The robotic arm according to any of the foregoing clauses, wherein the first convex contact portion and the second convex contact portion are convex in their entirety.

[0094] The robotic arm according to any of the foregoing clauses, wherein the first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein at least one of the plurality of convex contact surfaces is discontinuous with another of the plurality of convex contact surfaces.

[0095] The robotic arm according to any of the foregoing clauses, wherein the first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein the plurality of convex contact surfaces of each link extend along a cylindrical profile to allow the first link and the second link to move relative to each other with only a single degree of freedom.

[0096] According to any of the preceding clauses of the robotic arm, wherein the second link includes a third convex contact portion opposite to the second convex contact portion, the third convex contact portion being configured to roll into contact with a fourth convex contact portion of the third link, the third link being positioned distally from the second link along the longitudinal axis, wherein the third convex contact portion is rotated at least 30 degrees about the longitudinal axis to allow the third link to pivot in a direction different from the direction in which the second link pivots relative to the first link.

[0097] The robotic arm according to any of the foregoing clauses, wherein each of the first link and the second link includes a plurality of through holes extending between its proximal and distal ends, wherein at least one of the plurality of through holes includes a proximal portion and a distal portion, the proximal portion and the distal portion being enlarged relative to a middle portion of the through hole extending between the proximal portion and the distal portion.

[0098] The robotic arm according to any of the foregoing clauses, wherein the proximal portion of the at least one through hole expands along a first direction transverse to the longitudinal axis, and the distal portion of the at least one through hole expands along a second direction transverse to the longitudinal axis, the second direction being different from the first direction.

[0099] The robotic arm according to any of the foregoing clauses, wherein the first direction is perpendicular to the second direction.

[0100] The robotic arm according to any of the foregoing clauses, wherein the proximal portion of the at least one through hole gradually widens in the proximal direction, and the distal portion of the at least one through hole gradually widens in the distal direction.

[0101] The robotic arm according to any of the foregoing clauses further includes a third tensioning member that extends at least partially through a third link adjacent to the second link at its distal end, wherein the third tensioning member is fixed relative to the third link for moving the orientation of the third link relative to the second link.

[0102] A robotic arm includes: a first link and a second link positioned adjacent to each other along a longitudinal axis of the robotic arm; a joint formed between the first link and the second link, including a first convex contact portion of the first link and a second convex contact portion of the second link, the first convex contact portion and the second convex contact portion being configured to roll contact with each other to allow the first link and the second link to pivot relative to each other; a first tensioning member extending through the first link and the second link; and a second tensioning member extending through the first link and the second link; wherein the first tensioning member and the second tensioning member are fixed relative to the second link to be pulled proximally into the first tensioning member and the second tensioning member. One of the first tensioning members and the other of the second tensioning member is extended distally, allowing the second link to pivot relative to the first link at one of a plurality of different joint angles measured between the first link and the second link; wherein the first tensioning member and the second tensioning member each have an inflection point corresponding to each of the plurality of different joint angles located between the first link and the second link, except when the first link and the second link are aligned along the longitudinal axis such that the joint angle is zero; wherein the first convex contact portion and the second convex contact portion are configured such that at each of the plurality of different joint angles, the center of rotation between the first convex contact portion and the second convex contact portion lies in a reference plane containing the inflection point of the first tensioning member and the second tensioning member.

Claims

1. A robot arm, characterized in that, include: A proximal first link and a distal second link, the first link and the second link being positioned adjacent to each other along the longitudinal axis of the robot arm; A joint formed by the first link and the second link, including a first convex contact portion of the first link and a second convex contact portion of the second link, the first convex contact portion and the second convex contact portion being configured to roll contact with each other to allow the first link and the second link to pivot relative to each other; The first convex contact portion and the second convex contact portion are configured to contact each other at a first contact point and a second contact point at the first convex contact portion and the second convex contact portion corresponding to a first orientation of the first link and the second link. Wherein, the first convex contact portion and the second convex contact portion are configured to contact each other at a third contact point and a fourth contact point at the first convex contact portion and the second convex contact portion corresponding to the second orientation of the first link and the second link, wherein the second orientation is different from the first orientation; The joint is configured such that when the first link and the second link are in the first orientation, the line of action of the net force acting on the joint intersects a first reference line extending between the first contact point and the second contact point; and when the first link and the second link are in the second orientation, the line of action of the net force acting on the joint intersects a second reference line extending between the third contact point and the fourth contact point; and Each of the first and second links includes a plurality of through holes extending between its proximal and distal ends. At least one of the plurality of through holes in each of the first and second links includes a proximal portion and a distal portion, the proximal portion and the distal portion being enlarged relative to a middle portion of the through hole extending between the proximal portion and the distal portion. A first tensioning member extends through at least one of the plurality of through holes in the first link and at least partially through at least one of the plurality of through holes in the second link; A second tensioning member extends through another of the plurality of through holes in the first link and at least partially through another of the plurality of through holes in the second link; Wherein, the first contact surface and the second contact surface have non-circular contours, and in a given direction of the joint, in the central cross-section of the joint extending through the first tensioning member and the second tensioning member, the xy coordinates of the reference contact point trajectory at the intersection of the reference line extending between the contact point pairs and the line of action of the net force between the connecting rods are described by x = R(1-cosθ) + L sinθ and y = H - (R sinθ + L cosθ), where: R is the bending radius of the rope; θ is half the bending angle between the first link and the second link in the central cross-section, in radians; H is the height from the end of the straight section of the rope; L is the length of the second link at the distal end near the middle portion of the through hole.

2. The robot arm according to claim 1, characterized in that, in, The first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein at least one of the plurality of convex contact surfaces is discontinuous with another of the plurality of convex contact surfaces.

3. The robot arm of claim 1, wherein, in, The first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein the plurality of convex contact surfaces of each link extend along a cylindrical profile to allow the first link and the second link to move relative to each other with only a single degree of freedom.

4. The robot arm of claim 1, wherein, in, The second link includes a third convex contact portion opposite to the second convex contact portion, the third convex contact portion being configured to roll into contact with a fourth convex contact portion of the third link, the third link being positioned distally from the second link along the longitudinal axis, wherein the third convex contact portion is rotated at least 30 degrees about the longitudinal axis to allow the third link to pivot in a direction different from the direction in which the second link pivots relative to the first link.

5. The robot arm of claim 1, wherein, in, The proximal portion of the at least one through hole expands along a first direction transverse to the longitudinal axis, and the distal portion of the at least one through hole expands along a second direction transverse to the longitudinal axis, the second direction being different from the first direction.

6. The robot arm of claim 1, wherein, in, The proximal portion of the at least one through hole gradually widens in the proximal direction, and the distal portion of the at least one through hole gradually widens in the distal direction.

7. The robotic arm according to claim 1, characterized in that, The first link and the second link are further included with gear teeth and corresponding gear teeth, which are configured to engage with each other and inhibit the sliding of the first and second convex contact portions relative to each other when the first and second links move between the first and second orientations, wherein the gear teeth of each of the first and second links are arranged along the outer periphery of the first and second links.

8. The robotic arm according to claim 1, characterized in that, It further includes a first through hole and a second through hole, the first through hole and the second through hole extending through each of the first link and the second link; A first tensioning member extends through the first through-hole of the first link and at least partially through the first through-hole of the second link; A second tensioning member extends through the second through hole of the first link and at least partially through the second through hole of the second link; Wherein, the first tensioning member and the second tensioning member are fixed relative to the second link, such that by pulling one of the first tensioning member and the second tensioning member proximally in and releasing the other of the first tensioning member and the second tensioning member, the second link is allowed to pivot relative to the first link; and Wherein, the length by which one of the first tensioning member and the second tensioning member is pulled in is equal to the length by which the other of the first tensioning member and the second tensioning member is released.

9. The robotic arm according to claim 8, characterized in that, It further includes a third tensioning member that extends at least partially through a third link adjacent to the second link at its distal end, wherein the third tensioning member is fixed relative to the third link for moving the orientation of the third link relative to the second link.

10. The robotic arm according to claim 8, characterized in that, in, The first tensioning member and the second tensioning member each have a free length spanning the joint between the first link and the second link; Wherein, when the first link and the second link are in the first orientation, the first reference line extending between the first contact point and the second contact point is equidistant from each of the free lengths of the first tensioning member and the second tensioning member, and when the first link and the second link are in the second orientation, the second reference line extending between the third contact point and the fourth contact point is also equidistant from each of the free lengths of the first tensioning member and the second tensioning member.

11. A robotic arm, characterized in that, include: A proximal first link and a distal second link, the first link and the second link being positioned adjacent to each other along the longitudinal axis of the robot arm; A joint is formed between the first link and the second link, including a first convex contact portion of the first link and a second convex contact portion of the second link, the first convex contact portion and the second convex contact portion being configured to roll contact with each other to allow the first link and the second link to pivot relative to each other; The first convex contact portion and the second convex contact portion are configured to contact each other at a first contact point and a second contact point at the first convex contact portion and the second convex contact portion corresponding to a first orientation of the first link and the second link. Wherein, the first convex contact portion and the second convex contact portion are configured to contact each other at a third contact point and a fourth contact point at the first convex contact portion and the second convex contact portion corresponding to the second orientation of the first link and the second link, wherein the second orientation is different from the first orientation; A first tensioning member extends through at least a portion of the first link and the second link; A second tensioning member extends through at least a portion of the first link and the second link; Wherein, the first tensioning member and the second tensioning member are fixed relative to the second link to allow the second link to pivot relative to the first link by pulling one of the first tensioning member and the second tensioning member into the proximal end and releasing the other of the first tensioning member and the second tensioning member into the distal end; Wherein, the first tensioning member and the second tensioning member each have a free length spanning the joint between the first link and the second link; Wherein, when the first link and the second link are in the first orientation, a first reference line extending between the first contact point and the second contact point is equidistant from each of the free lengths of the first tensioning member and the second tensioning member; and when the first link and the second link are in the second orientation, a second reference line extending between the third contact point and the fourth contact point is also equidistant from each of the free lengths of the first tensioning member and the second tensioning member; and Each of the first and second links includes a plurality of through holes extending between its proximal and distal ends. At least one of the plurality of through holes in each of the first and second links includes a proximal portion and a distal portion, the proximal portion and the distal portion being enlarged relative to a middle portion of the through hole extending between the proximal portion and the distal portion. A first tensioning member extends through at least one of the plurality of through holes in the first link and at least partially through at least one of the plurality of through holes in the second link; A second tensioning member extends through another of the plurality of through holes in the first link and at least partially through another of the plurality of through holes in the second link; Wherein, the first contact surface and the second contact surface have non-circular contours, and in a given direction of the joint, in the central cross-section of the joint extending through the first tensioning member and the second tensioning member, the xy coordinates of the reference contact point trajectory at the intersection of the reference line extending between the contact point pairs and the line of action of the net force between the connecting rods are described by x = R(1-cosθ) + L sinθ and y = H - (R sinθ + L cosθ), where: R is the bending radius of the rope; θ is half the bending angle between the first link and the second link in the central cross-section, in radians; H is the height from the end of the straight section of the rope; L is the length of the second link at the distal end near the middle portion of the through hole.

12. The robotic arm according to claim 11, characterized in that, in, For each of the first and second orientations of the first and second links, the length by which one of the first and second tensioning members is pulled proximally is equal to the length by which the other of the first and second tensioning members is released distally.

13. The robotic arm according to claim 11, characterized in that, in, The first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein at least one of the plurality of convex contact surfaces is discontinuous with another of the plurality of convex contact surfaces.

14. The robotic arm according to claim 11, characterized in that, in, The first convex contact portion and the second convex contact portion each include a plurality of convex contact surfaces, wherein the plurality of convex contact surfaces of each link extend along a cylindrical profile to allow the first link and the second link to move relative to each other with only a single degree of freedom.

15. The robotic arm according to claim 11, characterized in that, in, The second link includes a third convex contact portion opposite to the second convex contact portion, the third convex contact portion being configured to roll into contact with a fourth convex contact portion of the third link, the third link being positioned distally from the second link along the longitudinal axis, wherein the third convex contact portion is rotated at least 30 degrees about the longitudinal axis to allow the third link to pivot in a direction different from the direction in which the second link pivots relative to the first link.

16. The robotic arm according to claim 11, characterized in that, in, The proximal portion of the at least one through hole expands along a first direction transverse to the longitudinal axis, and the distal portion of the at least one through hole expands along a second direction transverse to the longitudinal axis, the second direction being different from the first direction.

17. The robotic arm according to claim 11, characterized in that, in, The proximal portion of the at least one through hole gradually widens in the proximal direction, and the distal portion of the at least one through hole gradually widens in the distal direction.

18. The robotic arm according to claim 11, characterized in that, It further includes a third tensioning member that extends at least partially through a third link adjacent to the second link at its distal end, wherein the third tensioning member is fixed relative to the third link for moving the orientation of the third link relative to the second link.

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