A cable-driven robotic arm joint device capable of 360° rotation

Abstract

This invention discloses a rope-driven robotic arm joint device capable of 360° rotation, comprising a 360° rotating joint, a drive device, a tensioning device, an arm, a mast, a rope, and a guide wheel device. The drive device and tensioning device are respectively built into the outer ends of the two arms, connected by ropes to drive the robotic arm. The inner ends of the two arms are connected to the two ends of the rotating joint. The mast is connected to the rotating joint via a pin. The drive device connects to the rope and controls its extension and retraction length. The tension of the rope is transmitted to the ends of the arms through the mast, thereby driving the rotating joint and the arms to rotate. This invention's rope-driven robotic arm joint device uses an anti-parallelogram mechanism to connect adjacent arms, achieving 360° rotation of the robotic arm. The parallelogram mechanism connecting the arms and mast ensures that the mast always bisects the joint angle of the robotic arm during joint movement, while also improving the overall bending resistance and load-bearing capacity of the robotic arm.

Description

Technical Field

[0001] This invention relates to the field of space large-scale rope-driven robotic arm design technology, specifically to a rope-driven robotic arm joint device capable of 360° rotation. Background Technology

[0002] Space robotic arms are crucial for space missions such as spacecraft capture and docking, payload transportation, on-orbit assembly and maintenance, and space station construction. As deep space exploration and on-orbit servicing systems become increasingly large, stringent quality and cost requirements for aerospace products limit the development of large-size space robotic arms. Therefore, the design of large-size, high-ratio, lightweight space robotic arms is of significant research importance.

[0003] Traditional large-scale space robotic arms typically consist of one or more rigid arms connected by rotary joints. These rotary joints integrate various devices such as motors, gear reducers, controllers, sensors, and electrical harnesses, resulting in complex structures and large volumes, accounting for 85%-90% of the robotic arm's mass. Secondly, due to positional interference between robotic arms and interference from the wiring harness, traditional robotic arms struggle to achieve large-angle movements and high aspect ratios, leading to extremely high transportation costs for large robotic arms. Furthermore, because the torque applied by the motor in the rotary joint is located in the middle of the robotic arm, long-distance space tasks require the use of larger and heavier motors and gear reducers. The increased mass resulting from the increased length of the robotic arm limits its operating distance.

[0004] Patent document CN115488871A discloses a lightweight, high-torque tendon-driven single-degree-of-freedom mechanical joint device, including a rotary joint, a boom, two arms, a drive module, and a drive rope. This mechanical joint device helps reduce structural complexity, improve control precision, weaken or avoid motion coupling between joints, and has a large range of motion. The boom can increase the drive arm and improve the output torque. Rope antagonistic control can change the joint stiffness characteristics. Its ultra-light weight and excellent extension / retraction ratio enable rapid deployment and application. Specifically, the joint device includes a pivot offset mechanism, two pivots, and four gears. Each pivot has a rotation range of ±90°. By applying the same control to the two pivots, the pivot angles are made consistent, thereby achieving 360° movement of the robotic arm within a plane. The joint device is quite complex, requiring joint control of two rotating shafts, which increases the control complexity. The structure of the rotating shafts and gears results in lower bending resistance and load-bearing capacity of the joint. Furthermore, when the boom cross-section is large, larger gears are needed to achieve 360° rotation of the joint in order to ensure that the boom and boom do not restrict the rotation range of the joint, thus increasing the mass of the structure. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to simplify the joint structure, reduce the complexity of joint control, improve the stiffness and load-bearing capacity of the joint while achieving 360° joint rotation, and make the rotary joint have good dimensional adaptability when facing changes in the cross-sectional dimensions of the boom.

[0006] The technical solution adopted by this invention to solve its technical problem is: a rope-driven robotic arm joint device capable of 360° rotation, characterized in that it includes a drive device 1, an arm 2, a 360° rotating joint 3, a mast 4, a rope 5, a tensioning device 6, and a guide wheel device 7. The drive device 1 and the tensioning device 6 are respectively built into the outer ends of the two arms 2. The inner ends of the arms 2 are respectively connected to the two ends of the 360° rotating joint 3. The mast 4 is connected to the 360° rotating joint 3 through a pin. The two ends of the rope 5 are connected to the tensioning device 6 at the end of the arm 2 after being wound by the drive device 1. The motor 12 in the drive device 1 drives the winch 13 to control the length of the rope 5, and the tension is transmitted to the two ends of the arm 2 through the mast 4 and the guide wheel device 7, thereby driving the 360° rotating joint 3 to drive the robotic arm to rotate.

[0007] The driving device includes a base 11, a motor 12, a winch 13, a first pulley 14, and a second pulley 15. The rope 5 enters the winch 13 through the first pulley 14 and winds around once. It exits the driving device 1 through the second pulley 15. This special winding method generates friction, which is then used by the motor 12 to drive the winch 13 to control the length of the rope 5, circulating the rope 5 from one side of the robotic arm to the other.

[0008] The arm 2 is a lightweight truss structure composed of spliced ​​carbon fiber plates.

[0009] The 360° rotating joint 3 includes an anti-parallelogram mechanism 31, a parallelogram mechanism 32, a planar thrust ball bearing 33, a stop bolt 34, and a lock nut 35. The planar thrust ball bearing 33 is installed between the connecting rods of the anti-parallelogram mechanism 31 and the parallelogram mechanism 32, and they are connected by the stop bolt 34 and the lock nut 35. The anti-parallelogram mechanism 31 is used to realize the 360° rotation of the joint. The distance between the rotation axes of the hinge rods on the diagonal of the parallelogram mechanism 32 can be varied to adapt to the change in the distance between the center points of the inner ends of the two arm rods 2 during the movement of the robotic arm. The mast 4 is connected to the rotation center of the fourth hinge rod 322 in the parallelogram mechanism 32 by the stop bolt, ensuring that the distance between the mast 4 and the arm rods 2 on both sides of the 360° rotating joint 3 is always equal. Therefore, the mast 4 always bisects the included angle between the two adjacent arm rods of the robotic arm during the movement of the 360° rotating joint 3.

[0010] The mast 4 includes two horizontal plates 41, a first support block 42, a second support block 43, and a roller 44. The two horizontal plates 41 are connected by bolts through the first support block 42 and the second support block 43.

[0011] The rope 5 can be a steel wire rope, nylon rope, polyester rope, etc., and its material and size can be selected according to actual needs.

[0012] The tensioning device 6 includes a base 61, a coil spring 62, and a drum 63, which are installed at one end of the robotic arm and are used to tension the rope 5 and compensate for changes in the length of the rope 5.

[0013] The guide wheel device 7 includes a pulley seat 71 and a pulley 72, which are arranged at the transition position where the rope 5 enters and exits the drive device 1 and the tensioning device 6, to ensure that the rope 5 is always in the same plane and does not interfere with the position of the arm 2.

[0014] The size of the winch 13 and the number of turns of the rope 5 can be adjusted according to the actual load requirements to ensure adaptability to different task needs.

[0015] The robotic arm of the present invention further includes one or more of a power supply, a controller, and a torque sensor disposed with the motor 12.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] The joint device of the present invention achieves 360° rotation of the joint through an anti-parallelogram mechanism, using only four lightweight connecting rods, which simplifies the joint structure, improves the layout and support of the rotation axis, thereby improving the stiffness and load-bearing capacity of the joint, and the anti-parallelogram mechanism has good dimensional adaptability when facing changes in the cross-sectional size of the arm.

[0018] The joint device of the present invention ensures that the mast always bisects the angle between two adjacent arms of the robotic arm during the rotational joint movement through a parallelogram mechanism, thus preventing the mast from being misaligned during movement.

[0019] The joint device of the present invention is driven by a single motor, which reduces the weight of the robotic arm, and the joint rotation does not require joint control of the rotating shaft, thus reducing the complexity of control.

[0020] In this invention, the robotic arm employs a guide wheel device to ensure that the rope remains on the same plane and does not interfere with the arm's position, thereby improving the reliability and smoothness of the transmission. Furthermore, the robotic arm can be modularly arranged. For long-distance spatial tasks, multiple joint modules and arms can be connected in series to form a large robotic arm with a large size and high aspect ratio, enabling rapid deployment and use for future space missions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the rope-driven robotic arm in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the 360° rotating joint device in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the motion range of the 360° rotating joint device in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the boom structure in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the mast structure in an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the drive device in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the tensioning device in an embodiment of the present invention;

[0028] Figure 8 This is a schematic diagram of the guide wheel device in an embodiment of the present invention; Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] See appendix Figure 1 The rope-driven robotic arm includes a drive unit 1, arms 2, a 360° rotating joint 3, a mast 4, a rope 5, a tensioning device 6, and a guide wheel device 7. The drive unit 1 and the tensioning device 6 are respectively built into the outer ends of the two arms 2. The inner ends of the two arms 2 are respectively connected to the anti-parallelogram mechanism 31 in the 360° rotating joint 3. The mast 4 is connected to the parallelogram mechanism 32 in the 360° rotating joint 3 through a pin. During the movement of the 360° rotating joint 3, it always bisects the included angle between the two adjacent arms 2 of the robotic arm. The guide wheel device 7 is arranged at the transition position where the rope 5 enters and exits the drive unit 1 and the tensioning device 6. After the two ends of the rope 5 are wound by the drive unit 1, they pass through the two ends of the mast 4 and are respectively connected to the two tensioning devices 6 at the ends of the arms 2. The motor 12 in the drive unit 1 drives the winch 13 to control the length of the rope 5, and the tension of the rope 5 is transmitted to the two ends of the arms 2 through the mast 4 and the guide wheel device 7, thereby driving the 360° rotating joint 3 to drive the robotic arm to rotate.

[0031] See appendix Figure 2 The 360° rotating joint 3 device includes an anti-parallelogram mechanism 31, a parallelogram mechanism 32, a planar thrust ball bearing 33, a stop bolt 34, and a lock nut 35. More specifically, the anti-parallelogram mechanism 31 consists of two first hinge rods 311 and two second hinge rods 312, and the parallelogram mechanism 32 consists of two third hinge rods 321 and two fourth hinge rods 322. The first hinge rods 311 have a special shape, with a square boss for connecting to the arm 2. A circular boss is provided on the square boss for connecting to the third hinge rods 321, and has a certain height. To prevent the parallelogram mechanism 32 from interfering with the arm 2 during movement, the hinge rod has grooves and through holes for mounting the planar thrust ball bearing 33, allowing the head of the plug bolt 34 and the nut to be inserted, thus avoiding interference with other components. The planar thrust ball bearing 33 bears the pressure between the hinge rods and ensures smooth rotation between them. The plug bolt 34 connects the hinge rods and acts as a pivot. The distance between the two pivots 34 on the diagonal of the parallelogram mechanism 32 can vary to adapt to the change in distance between the center points of the inner ends of the two arms 2 during the movement of the robotic arm.

[0032] The 360° rotating joint 3 uses a four-bar linkage to connect the truss arm 2 and the mast 4, which increases the support components and improves the overall rigidity and load-bearing capacity of the rotating joint.

[0033] See appendix Figure 3The schematic diagram of the motion range of the 360° rotating joint device shows that the rotating joint takes the two rotating axes of the anti-parallelogram mechanism 31 as the rotation center. In the range of 0-180°, the joint takes the upper rotating axis as the rotation center, and in the range of 180°-360°, the joint takes the lower rotating axis as the rotation center. The 360° motion range of the robotic arm is achieved by changing the rotation center.

[0034] See appendix Figure 4 The boom 2 includes two horizontal plates 21, side plates 22, and vertical plates 23. Each plate has fixing and limiting grooves. One horizontal plate 21 is connected to the other horizontal plate 21 via the two side plates 22 and the two vertical plates 23, forming a mortise and tenon connection. L-shaped angle irons 24 secure the plates together, creating a stable connection and forming the overall frame structure of the boom. Both the horizontal plates 21 and the side plates 22 have numerous perforations to reduce the weight of the boom.

[0035] See appendix Figure 5 The mast 4 includes two horizontal plates 41, a first support block 42, a second support block 43, and a roller 44. The two horizontal plates 41 are connected by bolts through the first support block 42 and the second support block 43.

[0036] See appendix Figure 6 The drive device 1 includes a base 11, a motor 12, a winch 13, a first pulley 14, and a second pulley 15. The base 11 is composed of aluminum alloy plates connected by screws. The motor 12, winch 13, first pulley 14, and second pulley 15 are all fixed to the horizontal plate in the middle of the base 11 by bolts. The horizontal plate in the middle of the base 11 is offset from the center plane to ensure that the rope 5 is always located in the middle plane of the arm 2 when entering and exiting the drive device 11. The winch 13 includes two symmetrical columns at the front and rear to limit the rope 5. The rope 5 enters the winch 13 through the first pulley 14 and winds around once. It exits the drive device 1 through the second pulley 15. Friction is generated by this special winding method, and then the motor 12 drives the winch 13 to control the length of the rope 5, circulating the rope 5 from one side of the robotic arm to the other side.

[0037] Traditional motor and drum drive systems increase the effective diameter of the drum and cannot be driven using only one motor and one rope. By adopting a drive system with the winch 13 and two pulleys arranged on the same plane, the number of drive motors and ropes is reduced, and the problems of rope displacement and entanglement that are prone to occur when the winch is arranged vertically are avoided, thus improving the stability of the robotic arm.

[0038] See appendix Figure 7The tensioning device 6 includes a base 61, a coil spring 62, and a drum 63. The drum 63 is fixed to the base 61 by a pin. One end of the coil spring 62 is fixed to the threaded hole of the drum 63 by two bolts, and the other end has a through hole for connecting to the rope 5. The two tensioning devices are installed on the side plate of one end of the robotic arm to tension the rope 5 and compensate for changes in the length of the rope 5 on both sides. In the initial state, the coil springs 62 of both tensioning devices 6 are in a stretched state, providing passive tension to keep the rope 5 in a taut state. During the movement of the robotic arm, when the rate at which the rope length on one side of the robotic arm shortens is greater than the rate at which the rope length on the other side increases, the coil spring 62 causes one side of the rope to contract, accumulating the excess rope length and preventing the rope from slack. When the rate at which the rope length on one side of the robotic arm increases is greater than the rate at which the rope length on the other side shortens, the rope causes one side of the coil spring 62 to stretch, compensating for the required length of the rope.

[0039] See appendix Figure 8 The guide wheel device 7 includes a pulley seat 71 and a pulley 72. The pulley 72 is fixed on the pulley seat 71 by bolts and nuts. It is arranged as a whole at the transition position where the rope 5 enters and exits the drive device 1 and the tensioning device 6, so as to ensure that the rope 5 is always in the same plane and does not interfere with the position of the arm 2.

[0040] It should be noted that the size of the winch 13 and the number of turns of the rope 5 on the winch 13 can be adjusted according to the actual load requirements to ensure that it can adapt to different task needs.

[0041] Furthermore, to improve control accuracy, the rope-driven robotic arm also includes one or more of a power supply, controller, encoder, and torque sensor connected to the motor 12 and the rotary joint 3.

[0042] In use, the overall length of the robotic arm can be determined according to the specific application scenario and design requirements. Multiple single-degree-of-freedom rotary joints can be selected and connected in series with the joint arm to form a large robotic arm with a large size and high folding ratio, so as to realize the rapid deployment and use of future space missions.

[0043] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, the specific implementation of the present invention will be readily apparent without departing from this description.

[0044] Under the premise of the inventive concept, modifications can still be made to the technical solutions described above, or some of the technical features can be equivalently replaced or significantly modified, and if the performance or use is the same, they should all be considered to fall within the protection scope of this invention.

Claims

1. A cable-driven robotic arm joint device capable of 360° rotation, characterized in that, The system includes a drive unit (1), a boom (2), a 360° rotating joint (3), a mast (4), a rope (5), a tensioning device (6), and a guide wheel device (7). The drive unit (1) and the tensioning device (6) are respectively built into the outer ends of the two booms (2). The inner ends of the two booms (2) are respectively connected to the two ends of the 360° rotating joint (3). The mast (4) is connected to the 360° rotating joint (3) through a pin. The two ends of the rope (5) are connected to the tensioning device (6) at the end of the boom (2) after being wound by the drive unit (1). The motor (12) in the drive unit (1) drives the winch (13) to control the length of the rope (5) and transmits the rope tension to the two ends of the boom (2) through the mast (4) and the guide wheel device (7), thereby driving the 360° rotating joint (3) to drive the robotic arm to rotate. The 360° rotating joint (3) includes an anti-parallelogram mechanism (31), a parallelogram mechanism (32), a planar thrust ball bearing (33), a stop bolt (34), and a lock nut (35). The planar thrust ball bearing (33) is installed between the connecting rods of the anti-parallelogram mechanism (31) and the parallelogram mechanism (32), and is connected by the stop bolt (34) and the lock nut (35). The anti-parallelogram mechanism (31) is used to realize the 360° rotation of the joint, and the parallelogram mechanism (32) is used to ensure that the mast (4) always bisects the included angle between the two adjacent arms (2) of the robotic arm during the movement of the 360° rotating joint (3). The anti-parallelogram mechanism (31) consists of two first hinge rods (311) and two second hinge rods (312), and the parallelogram mechanism (32) consists of two third hinge rods (321) and two fourth hinge rods (322). The first hinge rod (311) has a special shape and is provided with a square boss for connecting the arm (2). A circular boss is provided on the square boss for connecting the third hinge rod (321) and has a certain height to avoid positional interference between the parallelogram mechanism (32) and the arm (2) during the movement.

2. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 1, characterized in that, The drive device includes a base (11), a motor (12), a winch (13), a first pulley (14), and a second pulley (15). The rope (5) enters the winch (13) through the first pulley (14) and is wound around once. It exits the drive device (1) through the second pulley (15). Friction is generated through this special winding method. The motor (12) drives the winch (13) to control the length of the rope (5) and circulate the rope (5) from one side of the robotic arm to the other side.

3. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 1, characterized in that, The boom (2) is a lightweight truss structure made of spliced ​​carbon fiber plates.

4. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 1, characterized in that, The mast (4) includes two horizontal plates (41), a first support block (42), a second support block (43), and a roller (44). The two horizontal plates (41) are connected by bolts through the first support block (42) and the second support block (43).

5. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 1, characterized in that, The rope (5) is a wire rope, nylon rope or polyester rope.

6. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 1, characterized in that, The tensioning device (6) includes a base (61), a coil spring (62), and a drum (63), which is installed at one end of the robotic arm to keep the rope (5) taut during the movement of the robotic arm and to compensate for changes in the length of the rope (5) when the configuration of the robotic arm changes.

7. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 1, characterized in that, The guide wheel device (7) includes a pulley seat (71) and a pulley (72), which are arranged at the transition position between the rope (5) entering and exiting the drive device (1) and the tensioning device (6) to ensure that the rope (5) is always in the same plane and does not interfere with the position of the arm (2).

8. The cable-driven robotic arm joint device capable of 360° rotation as described in claim 2, characterized in that, The size of the winch (13) and the number of turns of the rope (5) can be adjusted according to the actual load requirements to ensure that they can meet different task requirements.

9. A cable-driven robotic arm joint device capable of 360° rotation as described in any one of claims 1 to 8, characterized in that, It also includes one or more of a power supply, a controller, and a torque sensor that are disposed with the motor (12).

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