A rope-driven joint and rope-driven mechanical arm for realizing flexible buffering

Abstract

The present invention discloses a rope-driven joint for realizing flexible buffering, comprising a fixed platform, a moving platform that rotates in a first plane relative to the fixed platform, and an intermediate platform that can rotate in the first plane is provided between the fixed platform and the moving platform; when the intermediate platform rotates clockwise relative to the fixed platform, a first rigid rope for limiting rotation is provided, and when it rotates counterclockwise, a first elastic rope for rotation buffer is provided; when the moving platform rotates clockwise relative to the intermediate platform, a second elastic rope for rotation buffer is provided, and when it rotates counterclockwise, a second rigid rope for limiting rotation is provided. The present invention combines a plurality of rope-driven joints for realizing flexible buffering in series into a rope-driven mechanical arm, so that the rope-driven mechanical arm realizes the function of flexible buffering, is in a high rigidity state when the external load is small to ensure the motion accuracy and control accuracy, and exhibits flexibility to ensure intrinsic safety when subjected to a large external load such as external force impact.

Description

Technical Field

[0001] The invention relates to robot joint design and mechanical arm configuration design, in particular to a rope-driven joint and a rope-driven mechanical arm capable of realizing flexible buffering. Background Art

[0002] In recent years, the market demand for service robots has been growing, and the application of service robots has gradually become more widespread. However, due to a series of technical problems that have not been solved, service robots still have problems such as poor flexibility and poor safety, and cannot achieve intrinsically safe human-machine interaction. Therefore, the application of service robots is limited and the popularity is still low. Therefore, the lack of safety of service robots is an important issue that needs to be solved urgently.

[0003] Traditional industrial robots have high motion accuracy, but due to their high rigidity, it is difficult to achieve intrinsically safe operation, so they cannot be directly applied to the market as service robots. In order to achieve reliable and safe operation, improving the flexibility of the robot arm is an effective solution. There are two existing methods to achieve the flexibility of the robot arm:

[0004] One method is to achieve the flexibility of the robot arm through a compliant control algorithm. By selecting control parameters or using a compliant control model, the robot arm has the performance similar to that of a flexible arm. Commonly used methods include impedance control and admittance control. The disadvantage of this method is that it has high requirements on the performance of the controller, and the control algorithm is prone to divergence when subjected to external force impact. Therefore, the flexibility of this method is not reliable enough and it is difficult to apply to service robots.

[0005] Another approach is to achieve intrinsic compliance of the robot arm by designing flexible elements. Add elastic elements to the robot arm and control the stiffness of the elastic elements to achieve stiffness control of the robot arm. This approach implements compliance directly on the robot arm hardware, so it can achieve intrinsically safe operation.

[0006] The flexible manipulator has the characteristics of intrinsic safety. The rope-driven robot is a special hybrid mechanism that is driven by a rope to move the motion platform (7), and is composed of a number of single-degree-of-freedom or multi-degree-of-freedom rope-driven joints. The rope-driven robot has the advantages of light weight, small inertia, strong load-bearing capacity, good flexibility, etc., so it is very suitable for application in service robots and has high research value.

[0007] However, lower stiffness often leads to insufficient precision in the movement of the robot arm. In some cases, the robot arm needs to achieve high-stiffness movement while ensuring safety. Although the robot arm can achieve conversion control between high and low stiffness, it still takes time to switch between different stiffnesses, making it difficult to cope with emergencies such as collisions. Therefore, it is difficult for existing robot arms to achieve both high precision and safety at the same time.

[0008] In order to ensure the safety of the rope-driven manipulator, the stiffness of the rope-driven joint needs to be adjusted and controlled. There is no technical solution for controlling the stiffness of the rope-driven joint in the prior art.

[0009] Therefore, we need to design a robotic arm that can always maintain a high stiffness state when completing normal operations to ensure sufficient motion accuracy, and can also show flexibility when subjected to large external force impact to achieve buffering protection and ensure safety. Summary of the invention

[0010] In view of the above-mentioned status of the prior art, the present invention provides a rope-driven joint and a rope-driven robotic arm that realize flexible buffering. Such rope-driven joint and rope-driven robotic arm have high stiffness under low load and low stiffness under high load, thereby solving the technical problem that the existing rope-driven joint and rope-driven robotic arm are difficult to achieve both high precision and safety at the same time.

[0011] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a rope-driven joint for realizing flexible buffering, comprising a fixed platform, a moving platform rotating in a first plane relative to the fixed platform, and an intermediate platform capable of rotating in the first plane is provided between the fixed platform and the moving platform; when the intermediate platform rotates clockwise relative to the fixed platform, a first rigid rope for limiting rotation is provided, and when it rotates counterclockwise, a first elastic rope for rotation buffer is provided; when the moving platform rotates clockwise relative to the intermediate platform, a second elastic rope for rotation buffer is provided, and when it rotates counterclockwise, a second rigid rope for limiting rotation is provided.

[0012] As a further improvement of the above technical solution, the intermediate platform is connected to the fixed platform via a first rotating pair; the intermediate platform is connected to the movable platform via a second rotating pair.

[0013] As a further improvement of the above technical solution, the first rotation pair and the second rotation pair have the same rotation axis.

[0014] As a further improvement of the above technical solution, the first rotating pair has a first rotating axis, and the second rotating pair has a second rotating axis; the first rotating axis and the second rotating axis are parallel and arranged separately up and down.

[0015] As a further improvement of the above technical solution, the fixed platform has a first connecting arm and a second connecting arm extending to both sides in a first plane; the intermediate platform has a third connecting arm and a fourth connecting arm extending to both sides in the first plane; the movable platform has a fifth connecting arm and a sixth connecting arm extending to both sides in the first plane; the first connecting arm, the third connecting arm and the fifth connecting arm are located on the same side; the second connecting arm, the fourth connecting arm and the sixth connecting arm are located on the same side.

[0016] As a further improvement of the above technical solution, the first rigid rope is located between the first connecting arm and the third connecting arm; the first elastic rope is located between the second connecting arm and the fourth connecting arm; the second elastic rope is located between the third connecting arm and the fifth connecting arm; and the second rigid rope is located between the fourth point connecting arm and the sixth connecting arm.

[0017] As a further improvement of the above technical solution, the first rigid rope and the second rigid rope are steel wire ropes.

[0018] As a further improvement of the above technical solution, the first elastic rope and the second elastic rope are steel wire ropes connected in series with springs.

[0019] The present invention combines a plurality of rope-driven joints for realizing flexible buffering in series to form a rope-driven mechanical arm, so that the rope-driven mechanical arm realizes the function of flexible buffering.

[0020] Compared with the prior art, the rope-driven joint and rope-driven robot arm of the present invention are in a high-rigidity state when the external load is small to ensure motion accuracy and control accuracy, and show flexibility to ensure inherent safety when subjected to a large external load such as external force impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a schematic diagram of the structure of a rope-driven joint in an embodiment of the present invention.

[0022] Figure 2a Schematic diagram of the deformation of the rope and the joint when the rope-driven joint is subjected to a rightward external force in the embodiment of the present invention Figure 1 .

[0023] Figure 2b 2 is a schematic diagram of the deformation of the rope and the joint when the rope-driven joint is subjected to a rightward external force in an embodiment of the present invention.

[0024] Figure 2c 3 is a schematic diagram of the deformation of the rope and the joint when the rope-driven joint is subjected to a rightward external force in an embodiment of the present invention.

[0025] Figure 3a Schematic diagram of the deformation of the rope and the joint when the rope-driven joint is subjected to a leftward external force in the embodiment of the present invention Figure 1 .

[0026] Figure 3b 2 is a schematic diagram of the deformation of the rope and the joint when the rope-driven joint is subjected to an external force to the left in the embodiment of the present invention.

[0027] Figure 3c 3 is a schematic diagram of the deformation of the rope and the joint when the rope-driven joint is subjected to a leftward external force in an embodiment of the present invention.

[0028] Figure 4 Schematic diagram of external force-dynamic platform displacement curve according to an embodiment of the present invention.

[0029] Figure 5 1 is a schematic diagram of the structure of a rope-driven mechanical arm in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Figures 1 to 5 Shown is a schematic diagram of the structure and a schematic diagram of the external force-displacement curve of this embodiment.

[0031] The reference numerals in the drawings are: fixed platform 1 , first rigid rope 2 , intermediate platform 3 , rotating shaft 4 , second rigid rope 5 , first elastic rope 6 , movable platform 7 , second elastic rope 8 .

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on it.

[0033] The purpose of this design is to achieve a high stiffness state for the manipulator when the external load is small, and a low stiffness state when the external load is large. The innovation of this design is to make full use of the redundant drive characteristics of the rope drive mechanism. When the moving platform 7 is not subjected to external force, the tension of all driving ropes is greater than 0, that is, the ropes are in a tensioned state, so that the manipulator is in a balanced state. When the end is subjected to an external load, if the external load is small, it will only cause a change in the rope tension and will not cause the movement of the rope drive joint.

[0034] like Figure 1 As shown, the rope-driven joint for realizing flexible buffering includes a fixed platform 1 and a moving platform 7 that rotates in a first plane relative to the fixed platform 1. An intermediate platform 3 that can rotate in the first plane is provided between the fixed platform 1 and the moving platform 7. When the intermediate platform 3 rotates clockwise relative to the fixed platform 1, a first rigid rope 2 for limiting rotation is provided, and when it rotates counterclockwise, a first elastic rope 6 for rotation buffer is provided. When the moving platform 7 rotates clockwise relative to the intermediate platform 3, a second elastic rope 8 for rotation buffer is provided, and when it rotates counterclockwise, a second rigid rope 5 for limiting rotation is provided.

[0035] The intermediate platform 3 is connected to the fixed platform 1 through a first rotation pair, and the intermediate platform 3 is connected to the movable platform 7 through a second rotation pair. In this embodiment, the first rotation pair and the second rotation pair preferably use the same rotation axis, which has the effect of simplifying the structure.

[0036] The fixed platform 1 has a first connecting arm and a second connecting arm extending to both sides in the first plane; the intermediate platform 3 has a third connecting arm and a fourth connecting arm extending to both sides in the first plane; the moving platform 7 has a fifth connecting arm and a sixth connecting arm extending to both sides in the first plane; the first connecting arm, the third connecting arm and the fifth connecting arm are located on the same side; the second connecting arm, the fourth connecting arm and the sixth connecting arm are located on the same side.

[0037] The first rigid rope 2 is located between the first connecting arm and the third connecting arm; the first elastic rope 6 is located between the second connecting arm and the fourth connecting arm; the second elastic rope 8 is located between the third connecting arm and the fifth connecting arm; the second rigid rope 5 is located between the fourth connecting arm and the sixth connecting arm.

[0038] Among them, the first rigid rope 2 and the second rigid rope 5 can be regarded as ideal ropes with very large stiffness. In this embodiment, a steel wire rope is preferably taken as an example.

[0039] The first elastic rope 6 and the second elastic rope 8 can be regarded as ropes whose stiffness increases with the increase of tension. In this embodiment, a steel wire rope with a series spring is preferably taken as an example.

[0040] Since the cable-driven joint is a mechanism with driving redundancy, internal forces exist in the ropes. The first rigid rope 2 and the first elastic rope 6 between the intermediate platform 3 and the fixed platform 1, and the second elastic rope 8 and the second rigid rope 5 between the moving platform 7 and the intermediate platform 3 are arranged alternately to achieve buffer protection. The working principle is as follows:

[0041] As Figure 2a shown, if the moving platform 7 is subjected to a clockwise moment w and w < fl, the cable-driven joint will remain in its original position, the tension of the second rigid rope 5 will decrease, and the moment of the tension of the second rigid rope 5 on the cable-driven joint is equal to w, and the cable-driven joint always remains balanced. As Figure 2b shown, when w = fl, the cable-driven joint is in a critical state, and the tension of the second rigid rope 5 is 0. As Figure 2c shown, when w > fl and the external moment continues to increase, the second elastic rope 8 is stretched, the moving platform 7 rotates clockwise, and the second rigid rope 5 fails. The second elastic rope 8 is stretched, and its tension generates a moment opposite to w on the cable-driven joint, and the cable-driven joint achieves balance at a new position.

[0042] As Figure 3a shown, if the moving platform 7 is subjected to a counterclockwise moment w and w < fl, the cable-driven joint will remain in its original position, the tension of the first rigid rope 2 will decrease, and the moment of the tension of the first rigid rope 2 on the cable-driven joint is equal to w, and the cable-driven joint always remains balanced. As Figure 3b shown, when w = fl, the cable-driven joint is in a critical state, and the tension of the first rigid rope 2 is 0. As Figure 3cAs shown in FIG. 1 , when w>fl, the external torque continues to increase, the first elastic rope 6 is stretched, the moving platform 7 rotates counterclockwise, and the first rigid rope 2 fails. The first elastic rope 6 is stretched, and its tension generates a torque in the opposite direction of w on the rope-driven joint, and the rope-driven joint achieves balance in the new position.

[0043] From the above, it can be seen that when the external torque on the moving platform 7 is small, the rope-driven joint has almost no displacement, and the rope-driven joint has a very large stiffness. When the external torque on the moving platform 7 exceeds a critical value, the rope-driven joint will rotate, and the rope-driven joint has a small stiffness. In the first case, the rope-driven joint has a large stiffness and can perform high-precision movements; in the second case, the rope-driven joint can achieve buffer protection.

[0044] A plurality of rope-driven joints are combined to form a rope-driven robotic arm. When the external load is small, the rope-driven robotic arm is in a high-rigidity state to ensure the motion accuracy and control accuracy. When the rope-driven robotic arm is subjected to a large external load, such as when it is impacted by an external force, it can show flexibility to ensure intrinsic safety.

[0045] like Figure 5 As shown, in this embodiment, four of the above-mentioned rope-driven joints are connected in series to form a rope-driven mechanical arm, which also has a flexible buffering function.

[0046] The rotation planes where the rope-driven joints in the rope-driven manipulator are located are independently cross-arranged. When the moving platform 7 of the fourth rope-driven joint is subjected to a clockwise torque w in the rotation plane, the tension of the second rigid rope 5 decreases and the tension of the first rigid rope 2 increases. When w is small, the joint torque caused by w is completely offset by the change in the tension of the first rigid rope 2 and the second rigid rope 5. Therefore, the rope-driven manipulator will not move, and the rope-driven manipulator can be regarded as being in a high-rigidity state. When w increases until the tension of the second rigid rope 5 decreases to 0, the rope-driven manipulator reaches a critical state. At this time, if the external force w continues to increase, the tension of the second rigid rope 5 cannot continue to decrease, and the tension of the second elastic rope 8 connected in series with the spring begins to increase. Therefore, the fourth rope-driven joint begins to rotate clockwise, and the rope-driven manipulator can be regarded as being in a flexible state.

[0047] Similarly, when the moving platform 7 at the end of the fourth rope-driven joint is subjected to a counterclockwise torque w in the rotation plane, the tension of the first rigid rope 2 decreases and the tension of the second rigid rope 5 increases. When w is small, the joint torque caused by w is completely offset by the change in the tension of the first rigid rope 2 and the second rigid rope 5. Therefore, the rope-driven robotic arm will not move, and the rope-driven robotic arm can be regarded as being in a high-rigidity state at this time. When w increases until the force of the first rigid rope 2 decreases to 0, the rope-driven robotic arm reaches a critical state. At this time, if the external force w continues to increase, the tension of the first rigid rope 2 cannot continue to decrease, and the force of the first elastic rope 6 where the spring is connected in series begins to increase. Therefore, the fourth rope-driven joint begins to rotate counterclockwise, and the rope-driven robotic arm can be regarded as being in a flexible state at this time.

[0048] like Figure 4 As shown, the external force-moving platform displacement curve presents nonlinear characteristics. When the external load applied to the rope-driven manipulator is small, the moving platform 7 will not be displaced; when the external load reaches a critical value and continues to increase, the slope of the external force-moving platform 7 displacement curve increases with the increase of the external load. Therefore, the flexible rope-driven manipulator of the present invention can adjust its own state according to the size of the external load, that is, it can achieve high-rigidity movement when the external load is small, and achieve flexibility when the load is large.

[0049] In addition to the structure of the rope-driven joint in the above embodiment, the rope-driven joint may also have other implementation structures. For example, the first rotation pair between the intermediate platform 3 and the fixed platform 1 has a first rotation axis, and the second rotation pair between the intermediate platform 3 and the movable platform 7 has a second rotation axis. The first rotation axis and the second rotation axis are parallel and arranged separately up and down.

[0050] The best embodiment of the present invention has been described, and various changes or modifications made by those skilled in the art will not depart from the scope of the present invention.

Claims

1. A rope-driven joint for achieving flexible buffering, comprising a fixed platform (1), and a moving platform (7) rotating in a first plane relative to the fixed platform (1), characterized in that: An intermediate platform (3) that can rotate within a first plane is provided between the fixed platform (1) and the movable platform (7); a first rigid rope (2) for limiting the clockwise rotation of the intermediate platform (3) relative to the fixed platform (1) and a first elastic rope (6) for buffering the rotation of the intermediate platform (3) when it rotates counterclockwise relative to the fixed platform (1) are provided between the intermediate platform (3) and the fixed platform (1); a second elastic rope (8) for buffering the rotation of the movable platform (7) when it rotates clockwise relative to the intermediate platform (3) and a second rigid rope (5) for limiting the counterclockwise rotation of the movable platform (7) relative to the intermediate platform (3) are provided between the movable platform (7) and the intermediate platform (3); The first rigid rope (2) and the second rigid rope (5) are steel wire ropes.

2. The rope-driven joint according to claim 1, characterized in that: The intermediate platform (3) is connected to the fixed platform (1) via a first rotation pair; and the intermediate platform (3) is connected to the movable platform (7) via a second rotation pair.

3. The rope-driven joint according to claim 2, characterized in that: The first rotating pair and the second rotating pair have the same rotating axis.

4. The rope-driven joint according to claim 2, characterized in that: The first rotating pair has a first rotating axis, and the second rotating pair has a second rotating axis; the first rotating axis and the second rotating axis are parallel and arranged separately up and down.

5. The rope-driven joint according to claim 1, characterized in that: The fixed platform (1) has a first connecting arm and a second connecting arm extending to both sides in a first plane; the intermediate platform (3) has a third connecting arm and a fourth connecting arm extending to both sides in the first plane; the movable platform (7) has a fifth connecting arm and a sixth connecting arm extending to both sides in the first plane; the first connecting arm, the third connecting arm and the fifth connecting arm are located on the same side; the second connecting arm, the fourth connecting arm and the sixth connecting arm are located on the same side.

6. The rope-driven joint according to claim 5, characterized in that: The first rigid rope (2) is located between the first connecting arm and the third connecting arm; the first elastic rope (6) is located between the second connecting arm and the fourth connecting arm; the second elastic rope (8) is located between the third connecting arm and the fifth connecting arm; and the second rigid rope (5) is located between the fourth point connecting arm and the sixth connecting arm.

7. The rope-driven joint according to claim 1, characterized in that: The first elastic rope (6) and the second elastic rope (8) are steel wire ropes with springs connected in series.

8. A rope-driven mechanical arm for realizing flexible buffering, characterized in that: The invention is composed of a plurality of rope-driven joints as claimed in claim 1 connected in series.

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