A cable-driven bionic robot arm based on spherical cable-driven joint

Abstract

A kind of cable-driven bionic mechanical arm based on spherical cable-driven joint, including sequentially connected shoulder joint, elbow joint, wrist joint and the driving rope distributed in various positions;The shoulder joint belongs to spherical cable-driven joint, internally provided with double-layer spherical hinge constrained by single cable loop and three degrees of freedom rope parallel driving module;The elbow joint is internally provided with single degree of freedom rope parallel driving module;The wrist joint belongs to spherical cable-driven joint, internally provided with spherical hinge and three degrees of freedom rope parallel driving module.The present application realizes the centralized arrangement of driving unit, joint structure is simple and stable, motion range is large, with the advantages of high load self-weight ratio, flexible motion, suitable for application scenarios facing man-machine cooperation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of robots, in particular to a cable-driven bionic robot arm based on a spherical cable-driven joint. BACKGROUND

[0002] With the development of modern industry, mechanical arms have been widely used in many fields. Bionic robot arms, with their similar characteristics to human arms, have shown high interaction and learning performance with humans, and are favored in fields such as medical treatment, human-computer interaction and entertainment that require high interaction with humans. Research on bionic robot arms has high practical value and great development potential.

[0003] A human arm has seven degrees of freedom, three in the shoulder joint, one in the elbow joint, one in the forearm, and two in the wrist joint. It has the characteristics of high degrees of freedom, low inertia, large workspace and high dynamic characteristics. The cable has the characteristics of high strength, low inertia and high compliance. Cable-driven has natural advantages in miniaturization, lightness, flexibility and precision. And due to the characteristics of cable transmission, the driving end can be placed almost anywhere desired. At the same time, the cable and human tendon have high similarity in force transmission and motion transmission. Starting from the basic structure of the human upper limb, it is expected to achieve similarity in driving mechanism and kinematics with humans, greatly improving the overall performance of the bionic robot arm.

[0004] In the existing design of cable-driven bionic robot arms, there are two design directions. One treats the cable as human muscle and imitates human muscle to lay the cable. Since human muscles are usually directly pulled for driving, straight cable configurations are usually used in such designs. This configuration has a simple mechanical structure design, but due to the interference between the cables and between the cables and the mechanism, the joint is difficult to have a workspace similar to that of the human body.

[0005] The other treats the cable as a medium for remote transmission, designs a transmission structure, and realizes a rotary joint with the same degrees of freedom as the human body. This type of joint can achieve a workspace similar to that of the human body, but usually has a complex mechanical structure and cable routing, and does not have similar kinematics and driving mechanism to the human body.

[0006] Therefore, how to balance simple structure design, large workspace, and kinematics and driving mechanism similar to the human body is one of the research problems of bionic robot arms. SUMMARY

[0007] In order to solve the problems existing in the prior art, the present application aims to provide a cable-driven bionic robot arm based on spherical cable-driven joints, which has simple structure, large workspace and similar kinematics and driving mechanism to human body. It is noted that the deep muscles in the human joints are mostly attached to the joint surface, so the spherical cable-driven joint is designed according to this mechanism. In the spherical cable-driven joint, the driving rope is wrapped on the surface of the ball, and is attached to the spherical surface and forms a stable rope path by the internal tension of the rope, and is driven along the spherical surface.

[0008] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A cable-driven bionic robot arm based on spherical cable-driven joints, comprising shoulder joint, elbow joint, wrist joint and driving rope distributed at various positions connected in sequence; the shoulder joint belongs to spherical cable-driven joint, and is internally provided with double-layer spherical hinge constrained by single cable ring and three-degree-of-freedom rope parallel driving module; the elbow joint is internally provided with single-degree-of-freedom rope parallel driving module; the wrist joint belongs to spherical cable-driven joint, and is internally provided with spherical hinge and three-degree-of-freedom rope parallel driving module;

[0010] The spherical cable-driven joint, the driving rope is wrapped on the surface of the ball, and is attached to the spherical surface and forms a stable rope path by the internal tension of the driving rope, and is driven along the spherical surface;

[0011] The double-layer spherical hinge constrained by single cable ring of the shoulder joint is composed of outer base, middle shell, inner ball head and closed rope ring, the closed rope ring passes through the rope passing holes located on the outer base and the middle shell one by one, and is always wrapped on the surface of the middle shell when the middle shell is deflected in two degrees of freedom, forming a constraint structure;

[0012] The three-degree-of-freedom rope parallel driving module of the shoulder joint includes rope fixed to the middle shell and rope fixed to the inner ball head; the rope fixed to the middle shell is led out from the rope outlet hole located on the outer base, arranged along the surface of the middle shell, fixed to the edge of the middle shell, and drives the middle shell; the rope fixed to the inner ball head is led out from the rope outlet hole located on the outer base, passes through the rope passing hole located on the middle shell along the surface of the middle shell and the inner ball head, and is wound and fixed on the shaft body of the inner ball head, driving the inner ball head;

[0013] The single-degree-of-freedom rope parallel driving module of the elbow joint includes dynamic pulley force enhancement structure and straight cable driving module;

[0014] The dynamic pulley force enhancement structure is composed of large arm connecting rod, pulley one, pulley two, dynamic pulley and small arm base, wherein the large arm connecting rod, pulley one, pulley two and small arm base are coaxial, and the center plane of the dynamic pulley is tangent to the edges of pulley one and pulley two;

[0015] The straight cable driving module is composed of a large arm connecting rod, a pulley three, a pulley four and a small arm base, wherein the pulley three is fixedly connected to the large arm connecting rod, the pulley four is fixedly connected to the small arm base, and the pulley three and the pulley four are located on the ventral side of the elbow joint; the elbow part of the small arm base is driven by elbow cable one and elbow cable two; the elbow cable one is led out from the cable hole in the outer base, connected to the cable hole in the large arm connecting rod through the Bowden cable, and sequentially passes through the pulley one, the movable pulley in the small arm base and the pulley two, and is fixedly connected to the large arm connecting rod; the elbow cable two is led out from the cable hole in the outer base, connected to the cable hole in the large arm connecting rod through the Bowden cable, passes through the pulley three in the large arm connecting rod, and is fixedly connected to the pulley four in the small arm base.

[0016] The spherical hinge of the wrist joint is composed of a wrist shell and a wrist ball head in the wrist shell.

[0017] The three-degree-of-freedom cable parallel driving module of the wrist joint comprises a small arm connecting rod and four cables fixedly connected to the wrist ball head; the cables are led out from the cable hole in the outer base, connected to the small arm connecting rod through the Bowden cable, arranged along the surface of the wrist ball head, wound and fixed on the shaft body of the wrist ball head, and drive the wrist ball head; the driving principle is that the same side cable pulls to make the wrist ball head deflect, and the opposite side cable pulls to make the wrist ball head spin.

[0018] The inner layer ball head is fixedly connected to the large arm connecting rod, and the small arm base is fixedly connected to the small arm connecting rod, so that the shoulder joint, the elbow joint and the wrist joint are sequentially connected to form the whole bionic mechanical arm.

[0019] Preferably, the edges of the outer base and the middle layer shell are respectively uniformly distributed with four cable holes, and the closed cable rings are staggered into the eight cable holes one by one, wrapped on the surface of the middle layer shell, and form a constraint structure. When the wrap angles of the outer base and the middle layer shell are 45° and 103° respectively, the middle layer shell is constrained, and approximately has two degrees of freedom of deflection, thereby expanding the deflection angle range of the inner layer spherical hinge.

[0020] Preferably, in the shoulder joint, the four cables fixedly connected to the middle layer shell and the four cables fixedly connected to the inner layer ball head have the following driving principle: the same side cable pulls to make the inner layer ball head deflect, and the deflection angle is greater than 100°; the opposite side cable pulls to make the inner layer ball head spin, and the spin angle is greater than 360°, so that the inner layer ball head can reach another posture from one posture with any trajectory in the working space.

[0021] Preferably, in the wrist joint, the same side cable pulls to make the wrist ball head deflect, and the deflection angle is greater than 50°; the opposite side cable pulls to make the wrist ball head spin, and the spin angle is greater than 360°, so that the wrist ball head can reach another posture from one posture with any trajectory in the working space.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] 1. The middle shell, inner spherical head and wrist spherical head simultaneously serve as rotating pairs in the structure and rope guide mechanisms in the transmission, thus reducing mechanical design and simplifying the arm structure;

[0024] 2. The ropes of the wrist joint and shoulder joint are wrapped around the spherical surface, and the friction between the ropes and the spherical surface serves as damping, so the ropes are not prone to vibration and the rope path is more stable;

[0025] 3. Under the same driving torque, the ropes wrapped around the spherical surface are smaller in volume than straight ropes, so the arm is smaller in size.

[0026] 4. All joints of the robot arm are driven by ropes at the distal end, and the arm does not have any driver, so it is light in weight and good in mobility.

[0027] In summary, the arm structure of the rope-driven bionic robot arm based on the spherical cable-driven joint is simple in structure, small in size, light in weight, large in load, good in mobility, large in working space, and the ropes arranged along the spherical surface are more stable and less susceptible to external environmental interference. It is suitable for human-machine cooperation application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0028] To more clearly illustrate the embodiments of the present application and / or the prior art solutions, the following briefly introduces the drawings needed in the embodiments and / or prior art descriptions. Obviously, the drawings in the following description are only some embodiments of the present application.

[0029] Figure 1 Fig. 1 is a schematic diagram of the overall assembly structure of the rope-driven bionic robot arm of the present application;

[0030] Figure 2 Fig. 2 is a schematic diagram of the shoulder joint assembly structure of the present application;

[0031] Figure 3 Fig. 3 is a schematic diagram of the elbow joint assembly structure of the present application;

[0032] Figure 4 Fig. 4 is a schematic diagram of the wrist joint assembly structure of the present application;

[0033] Explanation of reference signs:

[0034]

[0035]

[0036] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0037] The following describes embodiments of the present application in detail with reference to the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0038] like Figure 1 The cable-driven bionic robotic arm based on a spherical cable-driven joint shown in the figure comprises a shoulder joint S, an elbow joint E and a wrist joint W which are fixedly connected in sequence.

[0039] The shoulder joint S comprises an outer base 1, a middle shell 4, an inner ball head 7, and a closed rope loop 2. The outer base 1, middle shell 4, and inner ball head 7 sequentially contact each other in a spherical sliding manner, with their sphere centers coinciding. The closed rope loop 2 passes through the cable holes located on the edges of the outer base 1 and middle shell 4, wrapping around the surface of the middle shell 4 to form a restraining structure. Constrained by the closed rope loop 2, the middle shell 4 has two deflection degrees of freedom relative to the outer base 1, and the inner ball head 7 has three rotational degrees of freedom relative to the middle shell 2.

[0040] The middle shell 4 of the shoulder joint S is driven by middle ropes 1 5, 2 8, 3 10, and 4 11. These ropes are drawn from the outer base 1 and wrapped around the middle shell 4. The basic driving principle is that when one rope is pulled, the middle shell 4 deflects in the corresponding direction.

[0041] The inner ball 7 of the shoulder joint S is driven by inner ropes 1 3, 2 6, 3 9, and 4 12. These ropes are drawn from the outer base 1, pass through the rope holes in the middle shell 4, and wind around and wrap around the surface of the inner ball 7. The basic driving principle is that the inner ball 7 deflects when the ipsilateral rope is pulled, and spins when the contralateral rope is pulled.

[0042] The elbow joint E includes an arm connecting rod 13, pulley 15, pulley 2 16, pulley 3 14, pulley 4 19, a movable pulley 18, and an arm base 17. The arm connecting rod 13, pulley 15, pulley 2 16, and arm base 17 are coaxial. The movable pulley 18 is located on the arm base 17, with its center plane tangent to the edges of pulley 15 and pulley 2 16. Pulley 3 14 is fixedly connected to the arm connecting rod 13, and pulley 4 19 is fixedly connected to the arm base 17. Pulleys 3 14 and 4 19 are located on the ventral side of the elbow joint. The arm base 17 has one degree of rotational freedom relative to the arm connecting rod 13.

[0043] The forearm base 17 of the elbow joint E is driven by the elbow rope 1 20 and the elbow rope 2 21, the elbow rope 1 20 is led out from the rope hole of the upper arm connecting rod 13, sequentially passes through the pulley 1 15, the movable pulley 18 and the pulley 2 16, and is fixed on the upper arm connecting rod 13; the elbow rope 2 21 is led out from the rope hole of the upper arm connecting rod 13, passes through the pulley 3 14, and is fixed on the pulley 4 19. The basic driving principle is that when the one side rope is pulled, the forearm base 17 rotates to the corresponding direction.

[0044] The wrist joint W includes the forearm connecting rod 26, the wrist shell 27 and the wrist ball head 28, wherein the wrist shell 27 is fixedly connected to the end of the forearm connecting rod 26, and the wrist ball head 28 and the wrist shell 27 are in contact in the form of spherical sliding. The wrist ball head 28 has three rotational degrees of freedom relative to the wrist shell 27.

[0045] The wrist ball head 28 of the wrist joint W is driven by the wrist rope 1 22, the wrist rope 2 23, the wrist rope 3 24 and the wrist rope 4 25, which are all led out from the rope hole of the forearm connecting rod 26, and are wound and covered on the surface of the wrist ball head 28. The basic driving principle is that when the same side rope is pulled, the wrist ball head 28 is deflected, and when the opposite side rope is pulled, the wrist ball head 28 is spun.

[0046] The working process of the sprocket-driven bionic mechanical arm based on the spherical sprocket-driven joint is as follows: according to the kinematic geometric relationship, the middle layer rope 1 5, the middle layer rope 2 8, the middle layer rope 3 10, the middle layer rope 4 11, the inner layer rope 1 3, the inner layer rope 2 6, the inner layer rope 3 9 and the inner layer rope 4 12 are driven, so that the shoulder joint S is rotated to the required posture; the elbow rope 1 20 and the elbow rope 2 21 are driven to make the elbow joint E flex to the required angle; the wrist rope 1 22, the wrist rope 2 23, the wrist rope 3 24 and the wrist rope 4 25 are driven to make the wrist joint W rotate to the required posture.

[0047] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made under the concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A cable-driven bionic robotic arm based on a spherical cable-driven joint, characterized by: It includes the shoulder joint, elbow joint, wrist joint and drive ropes distributed at various positions connected in sequence; the shoulder joint is a spherical cable-driven joint, with a double-layer spherical joint constrained by a single cable ring and a three-degree-of-freedom rope parallel drive module inside; the elbow joint is equipped with a single-degree-of-freedom rope parallel drive module inside; the wrist joint is a spherical cable-driven joint, with a spherical joint and a three-degree-of-freedom rope parallel drive module inside; The spherical cable-driven joint has a driving rope wrapped around the surface of the sphere. The driving rope relies on the inherent tension of the driving rope to fit the sphere and form a stable rope path, thereby driving along the sphere. The double-layer ball joint constrained by a single cable ring of the shoulder joint is composed of an outer base, a middle shell, an inner ball head and a closed cable ring. The closed cable ring passes through the cable holes on the outer base and the middle shell one by one, and always covers the surface of the middle shell when the middle shell performs two-degree-of-freedom deflection, forming a constrained structure. The three-degree-of-freedom cable parallel drive module of the shoulder joint includes a cable fixed to the middle shell and a cable fixed to the inner ball head; the cable fixed to the middle shell is led out from the cable outlet hole located on the outer base, arranged along the surface of the middle shell, and fixedly connected to the edge of the middle shell to drive the middle shell; the cable fixed to the inner ball head is led out from the cable outlet hole located on the outer base, passes through the cable hole located on the middle shell along the surface of the middle shell and the inner ball head, is wound around and fixed on the shaft of the inner ball head to drive the inner ball head; The single-degree-of-freedom cable parallel drive module of the elbow joint includes a movable pulley force-amplifying structure and a straight-pull cable drive module; The movable pulley force-increasing structure is composed of a boom connecting rod, pulley 1, pulley 2, a movable pulley and a small arm base, wherein the boom connecting rod, pulley 1, pulley 2 and the small arm base are coaxial, and the movable pulley is located on the small arm base, and its central plane is tangent to pulley 1 and pulley 2; The straight-pull cable drive module consists of a boom connecting rod, pulley three, pulley four and a forearm base, wherein pulley three is fixedly connected to the boom connecting rod, pulley four is fixedly connected to the forearm base, and pulleys three and four are located on the ventral side of the elbow; the forearm base elbow is driven by elbow rope one and elbow rope two, elbow rope one is led out from the rope outlet hole located on the outer base, connected to the rope outlet hole of the boom connecting rod through a Bowden cable, passes through pulley one, the movable pulley and pulley two located on the forearm base in sequence, and is fixed to the boom connecting rod; elbow rope two is led out from the rope outlet hole located on the outer base, connected to the rope outlet hole of the boom connecting rod through a Bowden cable, passes through pulley three located on the boom connecting rod, and is fixed to pulley four located on the forearm base; The ball joint of the wrist joint consists of a wrist shell and a wrist ball head located in the wrist shell; The three-degree-of-freedom cable parallel drive module of the wrist joint includes a forearm link and four cables fixed to the wrist ball head. The cables are led out from the cable outlet holes located on the outer base, connected to the forearm link through Bowden cables, arranged along the surface of the wrist ball head, wound around and fixed on the shaft of the wrist ball head, and drive the wrist ball head. The driving principle is that when the ipsilateral rope is pulled, the wrist ball head deflects, and when the contralateral rope is pulled, the wrist ball head rotates. The inner ball head is fixedly connected to the upper arm connecting rod, and the lower arm base is fixedly connected to the lower arm connecting rod, so that the shoulder joint, elbow joint and wrist joint are connected in sequence to form a bionic mechanical arm as a whole.

2. The cable-driven bionic robotic arm based on a spherical cable-driven joint according to claim 1, characterized in that: There are four rope holes evenly distributed on the edges of the outer base and the middle shell respectively. Closed rope loops are staggered through the eight rope holes one by one and wrapped around the surface of the middle shell to form a constraint structure; when the wrap angles of the outer base and the middle shell are 45° and 103° respectively, the middle shell is constrained and has two deflection degrees of freedom, which expands the deflection angle range of the inner ball joint.

3. The cable-driven bionic robotic arm based on a spherical cable-driven joint according to claim 1, characterized in that: In the shoulder joint, there are four ropes fixed to the middle shell and four ropes fixed to the inner ball head. The driving principle is: when the rope on the same side is pulled, the inner ball head is deflected, and the deflection angle is greater than 100°; when the rope on the opposite side is pulled, the inner ball head is rotated, and the rotation angle is greater than 360°.

4. The cable-driven bionic robotic arm based on a spherical cable-driven joint according to claim 1, characterized in that: In the wrist joint, when the ipsilateral rope is pulled, the wrist ball head deflects, and the deflection angle is greater than 50°; when the contralateral rope is pulled, the wrist ball head rotates, and the rotation angle is greater than 360°.

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