A multi-degree-of-freedom robot arm imitating human shoulder and elbow joint movement

Abstract

This invention relates to the field of humanoid robots, specifically a multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints. The aim is to provide a multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints, possessing high rigidity, high motion accuracy, and strong load-bearing capacity in its overall structure, capable of achieving multi-degree-of-freedom composite motion in three-dimensional space. The technical solution is a multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints, characterized in that: the multi-degree-of-freedom robotic arm includes a base assembly equipped with four planetary gears, two Hooke hinge assemblies arranged in parallel below the base assembly and driven by two planetary gears respectively, two connecting rods driven by the two Hooke hinge assemblies respectively, and an output actuator driven by the two connecting rods together.

Description

Technical Field

[0001] This invention relates to the field of humanoid robots, specifically a multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints. Background Technology

[0002] Humanoid robots, with their human-like mobility and environmental adaptability, have demonstrated profound application potential in service, medical, and industrial collaboration fields. As the core unit for performing tasks, the robotic arm connects the torso and the end effector (hand) via joints, serving as a crucial vehicle for the robot to achieve spatial positioning, force transmission, and precision operations. Its kinematic and dynamic performance is not only related to the accuracy of operation but is also paramount to achieving intelligent operation of the entire robot.

[0003] CN117584110A discloses a highly integrated seven-DOF humanoid robotic arm design, which simulates the physiological structure of a human arm by connecting the upper arm module and the forearm module. Its core feature lies in its highly integrated drive and control scheme. The shoulder joint uses a reduction gear set to offset the motor rotor, integrating a dual-axis power system within a very small space. The main control microcontroller is built into the upper arm housing, completely eliminating the limitations of external controllers or electrical control cabinets. However, this design still has some shortcomings. First, the wrist-cutting motion relies on a linkage system, which has limited rigidity compared to a direct-drive configuration, making it more prone to mechanical backlash and reduced accuracy over long-term operation. Furthermore, some non-hollow wiring designs (such as the wrist rotation module) still pose a risk of cable wear during frequent joint rotation, and due to the tight stacking of internal components, disassembly and maintenance are extremely difficult in the event of a failure in a lower-level component. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology. This invention proposes a multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints. This multi-degree-of-freedom robotic arm has high rigidity, high motion accuracy and strong load-bearing capacity in its overall structure, and can realize multi-degree-of-freedom compound motion in three-dimensional space.

[0005] The technical solution provided by this invention is: A multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints is characterized in that: the multi-degree-of-freedom robotic arm includes a base assembly with four planetary gears, two Hooke hinge assemblies arranged in parallel below the base assembly and driven by two planetary gears respectively, two connecting rods driven by the two Hooke hinge assemblies respectively, and an output actuator driven by the two connecting rods together. The base assembly includes two symmetrically arranged connecting bodies and two symmetrically fixed housings on the two connecting bodies; two planetary carriers of planetary gears are coaxially mounted on the two connecting bodies respectively, and four sun gear motors that drive the sun gears are fixed in the two housings respectively, and the four planetary gears output power through rotating rings connected by gear rings respectively; The two Hooke hinge assemblies are structurally identical, namely a first Hooke hinge assembly and a second Hooke hinge assembly. Each Hooke hinge assembly includes two cylindrical drive structures disposed at both ends of the shaft seat, a motor disposed on the shaft seat to drive the rotary joint, and a limiting structure for limiting the position of the Hooke hinge assembly. The cylindrical drive structure includes a cylindrical pair and a Hooke hinge connected in sequence. The main shaft is vertically arranged and rotatably positioned in the middle of the two shaft seats. The bottom ends of the two main shafts are horizontally fixed with a first rotary joint and a second rotary joint for hinged connecting rods. The rotating shaft connected to the cylindrical pair slider in the cylindrical pair is hinged to the hinge lug on the rotating ring; or... The two Hooke hinge assemblies are structurally identical, namely the third and fourth Hooke hinge assemblies. Each Hooke hinge assembly includes two horizontally arranged rotating rods, one end of which is hinged to the main shaft, and two cylindrical pair transmission structures connecting the other ends of the two rotating rods. The cylindrical pair transmission structure includes a cylindrical pair and a Hooke hinge connected in sequence. The two main shafts are arranged vertically, and the bottom ends are respectively horizontally fixed with a first rotary joint and a second rotary joint for hinged connecting rods. The cylindrical pair includes a sliding member and a sliding rod that cooperate with each other, and the sliding rod is connected to the rotating ring.

[0006] In the first and second Hooke hinge assemblies, the first and second bearing seats are both symmetrically bent rods with both sides curving upwards. The two hinge seats are respectively fixed on the mounting rings at both ends of the bearing seats, and the axes of the two mounting rings intersect at one point. The first and second cantilever arms are both bent rods with bushings at both ends. One end of each cantilever arm is fixed to the middle of the bearing seat, while the other end extends upwards at an angle and is hinged to the lower end of the handle of the auxiliary hinge lug. The distance between the hinged end and the hinge seats at both ends of the bearing seat is the same.

[0007] In the first and second Hooke hinge assemblies, the top end of the cylindrical sub-slider is horizontally connected to a rotating shaft that engages with the hinge lug of the rotating ring, and the axis of the rotating shaft is perpendicular to the axis of the cylindrical sub-slider; the hinge seat, the cross shaft, and the hinge seat fixed on the shaft seat at the bottom end of the cylindrical sub-slider cooperate to form a Hooke hinge.

[0008] The limiting structure includes a sliding groove coaxially disposed on each connecting body, an auxiliary hinge lug that mates with the sliding groove, and a cantilever that connects the bearing seat and the auxiliary hinge lug at both ends respectively; the sliding groove is formed by two fixing rings coaxially disposed on the outer circumferential surface of the connecting body and spaced apart.

[0009] In the third and fourth Hooke hinge assemblies, one end of each of the two rotating rods of each Hooke hinge assembly is hinged to a vertically arranged main shaft, the bottom end of which is horizontally fixed with a rotating joint; the other ends of the two rotating rods are respectively connected to a sliding member through the Hooke hinge, and the sliding member cooperates with the slide rod to form a cylindrical pair.

[0010] The first rotary joint has an axis perpendicular to the axis of the connected main shaft. The first rotary joint has two hinge ears with shaft holes respectively, and a cylindrical protrusion with the shaft hole is provided on the outer side of one of the hinge ears. The axis of the second rotary joint is perpendicular to the axis of the connected main shaft.

[0011] The hinge shaft fixed at the top of the first connecting rod is hinged to the hinge ear of the first rotary joint. The first connecting rod motor is mounted on the cylindrical protrusion of the hinge ear of the first rotary joint and coaxially connected to the hinge shaft at the top of the first connecting rod to drive the first connecting rod. The bottom end of the first connecting rod is hinged to another bushing of the first connecting member.

[0012] The top end of the second connecting rod is hinged to the second rotary joint via a hinge lug; the bottom end of the second connecting rod has two hinge lugs with shaft holes respectively, and one of the hinge lugs has a cylindrical protrusion with the shaft hole on its outer side. The hinge shaft that mates with the shaft hole is inserted and fixed in the bushing of the second connecting member; the second connecting rod motor is mounted on the cylindrical protrusion of the hinge lug of the second connecting rod and is coaxially connected and fixed to the hinge shaft of the second connecting member to drive the actuator shaft.

[0013] The output actuator includes a second connector fixed to one end of the actuator shaft and a first connector hinged to the same end of the actuator shaft via a bushing; the first connector is a double bushing structure with mutually perpendicular axes; the second connector is a bushing with a fixed hinge shaft, the outside of which is fixed to the rear end of the actuator shaft, and the axis of the hinge shaft is perpendicular to the axis of the actuator shaft.

[0014] The beneficial effects of this invention are: This invention, with high rigidity, high motion accuracy and strong load-bearing capacity, introduces the Hooke joint assembly and cylindrical pair in the joint of the robotic arm, enabling the robotic arm to simultaneously realize multi-degree-of-freedom compound motion such as spatial rotation and posture adjustment, effectively simulating the natural motion characteristics of the human arm during extension, contraction and swinging.

[0015] Compared to traditional robotic arm structures that achieve multiple degrees of freedom by connecting multiple independently driven rotary joints in series, this invention integrates linear motion and omnidirectional rotation degrees of freedom into the same joint module, reducing the number of independent joints, making the overall structure more compact, and the transmission path more rational.

[0016] When the posture of the robotic arm changes, the Hooke hinge assembly can adaptively adjust the spatial angle, and the linear translating pair can dynamically compensate for the axial displacement, so that the power transmission process remains continuous and smooth, reducing parasitic motion and sudden force changes caused by posture changes.

[0017] The intermediate transmission structure of the present invention can be either a cylindrical pair or a guide rail type sliding pair. Different embodiments maintain the same degree of freedom of motion and functional effect, which facilitates flexible selection in terms of load-bearing capacity, stroke length or structural layout according to actual application requirements. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of Embodiment 1 of the present invention.

[0019] Figure 2 for Figure 1 One of the structural schematic diagrams of the middle base assembly (viewing direction is) Figure 1 (To the left front).

[0020] Figure 3 for Figure 1 Schematic diagram of the middle base assembly, part two (viewing direction is) Figure 1 (Right rear).

[0021] Figure 4 for Figure 2 Exploded view of the central base assembly.

[0022] Figure 5 for Figure 1 A three-dimensional structural diagram of the first Hooke hinge assembly.

[0023] Figure 6 for Figure 1 A three-dimensional structural diagram of the second Hooke hinge assembly.

[0024] Figure 7 for Figure 5 A three-dimensional structural diagram of the first bearing seat.

[0025] Figure 8 for Figure 6 A three-dimensional structural diagram of the second bearing seat (partial cross-section).

[0026] Figure 9 for Figure 1 A three-dimensional structural diagram of the output actuator.

[0027] Figure 10 This is a three-dimensional structural diagram of Embodiment 2 of the present invention.

[0028] Figure 11 for Figure 10 One of the structural schematic diagrams of the middle base assembly (viewing direction is) Figure 10 (To the left front).

[0029] Figure 12 for Figure 10 Schematic diagram of the middle base assembly, part two (viewing direction is) Figure 10 (Right rear).

[0030] Figure 13 for Figure 10 A three-dimensional structural diagram of the third Hooke hinge assembly.

[0031] Figure 14 for Figure 10 A three-dimensional structural diagram of the fourth Hooke hinge assembly.

[0032] Figure label: Detailed Implementation

[0033] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0034] Example 1 Figure 1 The multi-degree-of-freedom robotic arm shown, which mimics the movement of the human shoulder and elbow joints, includes, from top to bottom: a base assembly 1, a first Hooke hinge assembly 2, a second Hooke hinge assembly 3, a first link 4, a second link 5, and an output actuator 6.

[0035] The base assembly 1 serves as the connection interface between the robotic arm and the robot's torso or main structure, and is used to bear the forces and torques generated during the robotic arm's movement. The first Hooke hinge assembly 2 and the second Hooke hinge assembly 3 are arranged in parallel below the base assembly. The top ends of the first link 4 and the second link 5 are respectively connected to the bottom ends of the first Hooke hinge assembly and the second Hooke hinge assembly, and the bottom ends of the first link 4 and the second link 5 are connected to the output actuator 6, thereby forming a complete multi-degree-of-freedom robotic arm kinematic chain.

[0036] The above structural arrangement enables the robotic arm to maintain a compact structure while possessing excellent spatial movement capabilities and load adaptability.

[0037] like Figures 2 to 4As shown: The base assembly 1 includes a cylindrical first connecting body 17 and a second connecting body 18 with identical structures. Two fixing rings 135 with a spacing (forming a groove on the outer circumference of the connecting body) are fixed to the center of the outer circumference of each connecting body. Several through holes are evenly distributed on the fixing rings, and screws are provided. The first outer shell 11 and the second outer shell 12 each have two cylindrical cavities (one lower end of each cylindrical cavity is open to the outside). The two cavities of each outer shell are parallel to each other and arranged side-by-side. The inner diameter of each cavity is compatible with the outer diameter of the connecting body. The two cavities of the first outer shell are simultaneously inserted into the same end of the two bodies and then fastened to the screw holes on the end faces of the two cavities by the screws. The second outer shell faces the first outer shell and is inserted into and fastened to the other end of the two bodies in the same manner, thereby connecting the first connecting body 17, the second connecting body, the first outer shell 11, and the second outer shell 12 into a single unit.

[0038] To provide driving power, four identical planetary gears and four sun gear motors are mounted on the base assembly; two planetary gears are each mounted in the first and second housings; each planetary gear is equipped with a sun gear motor 134. Figure 4 It can be seen that: in the first outer shell, two sun gears are installed in two cylindrical cavities, and two planetary carriers 132 are fixed in the two connecting bodies and located on one side near the second outer shell. Several planetary teeth 133 are rotatably positioned on the planetary carriers. Two sun gear motors 134 are fixed to the outer end faces of the other side of the two cylindrical cavities. The sun gears are coaxially fixed with the sun gear motor shafts and mesh with the gear ring 136. The gear ring also meshes with the planetary teeth 133 and is oscillatingly positioned in the track of the cylindrical cavity. The transmission ring 137 is clamped and fixed on the outside of the gear ring. The two sun gears and two sun gear motors in the second outer shell are also symmetrically installed in the same way (details omitted), so that the four sun gear motors are symmetrically arranged on the axial exterior of the two connecting bodies, and a planetary carrier is fixed on each axial side of each connecting body.

[0039] The base assembly serves as the connection interface between the robotic arm and the robot's torso or main structure, providing a mounting reference for the entire robotic arm and bearing the loads and torques generated during its movement. In terms of motion mechanism, the first Hooke hinge assembly 2 and the second Hooke hinge assembly 3 are located below the base assembly, providing the robotic arm with not only three-dimensional orientation deflection degrees of freedom but also ensuring stable power transmission under different spatial orientations. Through their orthogonally arranged revolute joints, the Hooke hinge assembly enables the downstream linkage mechanism to swing flexibly in multiple directions, significantly enhancing the robotic arm's spatial motion capabilities.

[0040] like Figure 4As shown; in the planetary gears, the sun gear is coaxially connected to the motor shaft of the sun gear motor 134, the planet carrier 132 is fixed to the connecting body, and the rotating ring 137 is coaxially fixed to the outside of the gear ring. The rotating ring has a pair of hinged ears that extend outward from the open end on the lower side of the housing to facilitate power output; when the sun gear motor starts, it drives the rotating ring 137 to rotate at a certain angle relative to the base assembly, thereby outputting power. All four planetary gears have the same structural configuration. In one connecting body, a planet carrier with two planetary gears is mounted and the two sun gears are coaxially arranged; in another connecting body, two planetary gears are also mounted and the two sun gears are also coaxially arranged.

[0041] like Figure 5 and Figure 6 As shown: a first Hooke hinge assembly 2 driven by two planetary gears connected to the same connecting body, and a second Hooke hinge assembly 3 driven by two planetary gears connected to another connecting body; the two Hooke hinge assemblies have the same structure, both of which integrate two first cylindrical pair transmission structures, a rotary joint driven by a motor, and a limiting structure for limiting the position of the Hooke hinge assembly on the shaft seat.

[0042] In the two cylindrical pair transmission structures of the first Hooke hinge assembly, each first cylindrical pair transmission structure includes a first cylindrical pair and a Hooke hinge connected in sequence; wherein, the first cylindrical pair includes a first cylindrical pair slider 22 and a first cylindrical pair slide rail 27 that cooperate with each other; the top end of the first cylindrical pair slider is connected to a rotating shaft, the axis of the rotating shaft is perpendicular to the axis of the cylindrical pair slide rail, and the rotating shaft is hinged to a pair of hinge ears on the rotating ring 137; the hinge ears at the bottom end of the first cylindrical pair slide rail 27, the cross shaft, and the hinge ears on the first hinge seat 220 cooperate to form the first Hooke hinge; the first hinge seat 220 is fixed on the mounting ring at one end of the first shaft seat 23. Another second cylindrical pair transmission structure is the same as the first cylindrical pair transmission structure. Its second cylindrical pair includes a second cylindrical pair slider 25 and a second cylindrical pair slide rail 28 that cooperate with each other. The axis of the rotating shaft connected to the top of the second cylindrical pair slider is perpendicular to the axis of the second cylindrical pair slide rail, and the rotating shaft also cooperates with a pair of hinge ears on the rotating ring. The hinge ears at the bottom of the second cylindrical pair slide rail 28, the cross shaft, and the hinge ears on the second hinge seat 221 cooperate to form a second Hooke hinge. The second hinge seat 221 is fixed on the mounting ring at the other end of the first shaft seat 23. The second Hooke hinge assembly has the same structure; wherein: the hinge lug at the bottom of the third cylindrical secondary slide rail 36, the cross shaft, and the hinge lug on the third hinge seat 320 cooperate to form the third Hooke hinge, and the third hinge seat 320 is fixed on the mounting ring at one end of the second shaft seat 33; the hinge lug at the bottom of the fourth cylindrical secondary slide rail 37, the cross shaft, and the fourth hinge seat 321 cooperate to form the fourth Hooke hinge, and the fourth hinge seat 321 is fixed on the mounting ring at the other end of the second shaft seat 33; the rest will not be described in detail.

[0043] When the robotic arm undergoes spatial deflection, the Hooke joint assembly is responsible for attitude adjustment, while the cylindrical joint compensates for the length changes caused by the attitude change through its axial sliding and rotation functions, thereby ensuring the continuity of power transmission and the smoothness of movement.

[0044] In addition, such as Figure 4 As shown: The first Hooke hinge assembly 2 and the second Hooke hinge assembly 3 are respectively provided with a first auxiliary hinge ear 21 and a second auxiliary hinge ear 31. The two auxiliary hinge ears (similar in structure to a badminton racket) cooperate with the sliding grooves on the outer circumferential surface of the first connecting body and the sliding grooves on the outer circumferential surface of the second connecting body to form a rotating pair respectively; the lower ends of the handles of the two auxiliary hinge ears are rotatably connected to the first hinge seat and the second hinge seat respectively, thereby forming a limiting structure, which can limit the maximum swing angle of the Hooke hinge assembly, and at the same time play a role in auxiliary support and reducing local stress concentration under load.

[0045] like Figure 5 , Figure 7 As shown: In the first Hooke hinge assembly, the first hinge seat 220 and the second hinge seat 221 are respectively fixed to the mounting rings at both ends of the first bearing seat 23. The first bearing seat is a symmetrically curved rod with both sides bending upwards, and the middle part is horizontal; the first hinge seat 220 and the second hinge seat 221 are fixed to two mounting rings at both ends of the first bearing seat, and the extended lines of the axes of these two mounting rings intersect at a point (this point is located above the first bearing seat; see [reference]). Figure 7 The first cantilever 20 is a curved rod, with one end fixed to the upper side of the middle part of the first bearing seat; the other end extends upward at an incline and forms a bushing at the end, which is then hinged to the lower end of the handle of the first auxiliary hinge ear 21 to form a rotating pair, thereby forming the aforementioned limiting structure; moreover, the distance from the hinge end to the first hinge seat 220 is the same as the distance from the hinge end to the second hinge seat 221. A through shaft hole is vertically opened in the middle position of the first bearing seat, and the first main shaft 29 is rotatably positioned in the shaft hole; the first rotary joint 24 fixed to the lower end of the first main shaft has two hinge ears, and the two hinge ears are respectively provided with horizontally corresponding and correspondingly connected shaft holes (the axes of the two shaft holes are perpendicular to the axis of the first main shaft), and a cylindrical protrusion is fixed on the outer side of one of the hinge ears, and the aforementioned shaft hole is horizontally opened in the cylindrical protrusion. The first motor 26 is fixedly mounted on the upper side of the first shaft seat. The motor shaft is coaxially arranged with the first main shaft and connected to the first main shaft through a coupling. Thus, when the power is turned on, the motor drives the first main shaft, thereby realizing the rotation of the first rotary joint 24 around the first main shaft.

[0046] like Figure 6 , Figure 8As shown: In the second Hooke hinge assembly, the third hinge seat 320 and the fourth hinge seat 321 are respectively fixed to the mounting rings at both ends of the second bearing seat 33; the second bearing seat is a symmetrically bent rod with both sides curving upwards, and the middle part is horizontal; the third hinge seat 320 and the fourth hinge seat 321 are fixed to the two mounting rings at both ends of the second bearing seat, and the axes of these two mounting rings intersect at one point (this point is located above the second bearing seat); the second cantilever 38 is a bent rod, one end of which is fixed to the lower side of the middle part of the second bearing seat, and the other end extends upwards at an angle to form a bushing, and then is hinged to the lower end of the handle of the second auxiliary hinge lug 31 to form a rotating pair; and Furthermore, the distance from the hinge end to the third hinge seat 320 is the same as the distance from the hinge end to the fourth hinge seat 321; a shaft hole is vertically opened in the middle position of the second shaft seat, and the second main shaft 30 is rotatably positioned in the shaft hole; a horizontally arranged second rotary joint 34 (the second rotary joint is a joint shaft, and the axis of the second main shaft is perpendicular to the axis of the joint shaft) is fixed at the lower end of the second main shaft; the second motor 39 is fixedly installed on the upper side of the second shaft seat, and the motor shaft is coaxially arranged with the first main shaft and connected to the first main shaft through a coupling; thus, when the power is turned on, the second main shaft 30 is driven, thereby realizing the rotation of the second rotary joint 34 around the second main shaft.

[0047] Obviously, the first Hooke hinge assembly 2 and the second Hooke hinge assembly 3 have basically the same structure; the only difference is that in the first Hooke hinge assembly, one end of the first cantilever 20 is fixed to the upper side of the middle part of the first shaft seat, and the lower end of the first main shaft 29 is horizontally mounted with the first rotary joint 24 through the hinge frame; while in the second Hooke hinge assembly, one end of the second cantilever 38 is fixed to the lower side of the middle part of the second shaft seat, and the lower end of the second main shaft 30 is directly fixed with the second rotary joint 34.

[0048] When the robotic arm undergoes spatial deflection, the Hooke joint assembly is responsible for attitude adjustment, while the cylindrical joint compensates for the length changes caused by the attitude change through its axial sliding and rotation functions, thereby ensuring the continuity of power transmission and the smoothness of movement.

[0049] like Figure 9 As shown, in the output actuator 6, the second connector 63 is a bushing with a fixed hinge shaft. The bushing is externally fixed to the rear end of the actuator 62, and the axis of the hinge shaft is perpendicular to the axis of the actuator. The first connector 61 is a double bushing structure, and the axes of the two bushings are perpendicular to each other; one bushing is movably sleeved on the rear end of the actuator 62 (adjacent to the second connector 63), and the other bushing is hinged to the shaft hole at the bottom end of the first connecting rod 4 through the hinge shaft.

[0050] like Figure 1As shown: the shaft hole at the top of the first connecting rod 4 is perpendicular to the shaft hole at its bottom, and a hinge shaft is fixed in the shaft hole at the top. The two ends of the hinge shaft fixed at the top of the first connecting rod 4 are respectively inserted into the shaft holes of the two protrusions of the first rotary joint, thereby realizing the hinge connection between the first connecting rod and the first rotary joint. The first connecting rod motor is installed at the end of the cylindrical protrusion of the first rotary joint. The motor shaft of the first connecting rod motor extends into the shaft hole of the protrusion and is connected to the hinge shaft through a coupling, thereby driving the first connecting rod to swing when the first connecting rod motor is started.

[0051] Both ends of the second connecting rod 5 are provided with a pair of hinge ears. The two pairs (four) of hinge ears at both ends extend outward in the same direction to avoid motion interference with the first connecting rod, and the axes of the hinge ears are parallel to each other. The two hinge ears at the top of the second connecting rod 5 are hinged to the second rotating joint 34 of the second Hooke hinge assembly 3. The two hinge ears at the bottom of the second connecting rod 5 are respectively provided with horizontally corresponding and connected shaft holes (the axes of the two shaft holes are perpendicular to the axis of the second main shaft). A cylindrical protrusion is provided on the outer side of one of the hinge ears, and the shaft hole is horizontally provided in the cylindrical protrusion. The hinge shaft is inserted and fixed in the bushing of the second connecting member 63 and rotates with the two shaft holes. The second connecting rod motor is fixedly installed at the end of the cylindrical protrusion. The motor shaft of the second connecting rod motor extends into the shaft hole of the protrusion and is connected to the hinge shaft through a coupling, thereby driving the second connecting rod to swing when energized.

[0052] Therefore, the first link 4 and the second link 5 can work together through the two link motors during the movement to stably transmit the displacement and posture changes output by the two transmission rings to the output actuator 6, so as to simulate the movement characteristics of muscle contraction and bone extension in the human arm. This enables the robotic arm to have a spatial deflection ability similar to the human shoulder or elbow joint during the movement, thereby realizing multi-degree-of-freedom compound movements such as extension, retraction and spatial swing of the robotic arm to adapt to different working postures and complex spatial environments.

[0053] Example 2 like Figure 10As shown: The differences between this embodiment and Embodiment 1 are as follows: First, the structure of the first Hooke hinge assembly 2 and the second Hooke hinge assembly 3 has been changed, and they have been replaced by the third Hooke hinge assembly 7 and the fourth Hooke hinge assembly 8. Second, the two auxiliary hinge ears in Embodiment 1 have been removed, and the four rotating rings fixed to the outside of the four planetary gear rings in Embodiment 1 have also been modified: the pair of hinge ears on each rotating ring has been changed to a slide bar, and each slide bar cooperates with a sliding member to form a cylindrical pair; that is: the first slide bar 111 and the second slide bar 121 driven by the two planetary gears at both ends of the first connecting body cooperate with the first sliding member 214 and the second sliding member 215 respectively to form two cylindrical pairs; the third slide bar 131 and the fourth slide bar 141 driven by the two planetary gears at both ends of the second connecting body cooperate with the third sliding member 314 and the fourth sliding member 315 respectively to also form two cylindrical pairs.

[0054] Example 2 continues the design concept of Example 1, and provides a multi-degree-of-freedom robotic arm that is equivalent to Example 1 in terms of motion freedom, operation function and overall motion effect.

[0055] like Figure 13 As shown: The third Hooke hinge assembly 7 includes a horizontally arranged first rotating rod 212 and a second rotating rod 216. One end of these two rotating rods is hinged to a vertically arranged third main shaft 211. The bottom end of the third main shaft 211 is fixed to a first rotating joint 24 with a horizontally arranged axis. The bottom end of the third joint shaft 215 is connected to the first rotating joint 24. The other end of the first rotating rod 212 is connected to the first sliding member 214 through a fifth Hooke hinge 213 (the two rotating shafts of the fifth Hooke hinge are arranged perpendicularly to each other). The first sliding member is a sliding sleeve structure, which cooperates with the first sliding rod 111 to form a cylindrical pair, thereby forming a cylindrical pair transmission structure. The other end of the second rotating rod 216 is connected to the second sliding member 215 through a sixth Hooke hinge 217 (the two rotating shafts of the sixth Hooke hinge are arranged perpendicularly to each other). The second sliding member is a sliding sleeve structure, which cooperates with the second sliding rod 121 to form a cylindrical pair, thereby forming another cylindrical pair transmission structure.

[0056] The upper ends of the first slide bar 111 and the second slide bar 121 are respectively fixed to the rotating rings on the two planetary gear rings at both ends of the first connecting body, thereby introducing driving force.

[0057] like Figure 14As shown: The fourth Hooke hinge assembly 7 includes a horizontally arranged third rotating rod 312 and a fourth rotating rod 316. One end of these two rotating rods is hinged to a vertically arranged fourth main shaft 311. The bottom end of the fourth main shaft 311 is fixed to a horizontally arranged second rotary joint 34. The other end of the third rotating rod 312 is connected to a third sliding member 314 via a seventh Hooke hinge 313. The third sliding member 314 is a sliding sleeve structure, which cooperates with the third sliding rod 131 to form a cylindrical pair, thereby forming the third cylindrical pair transmission structure. The other end of the fourth rotating rod 316 is connected to a fourth sliding member 315 via an eighth Hooke hinge 317. The fourth sliding member is a sliding sleeve structure, which cooperates with the fourth sliding rod 141 to form a cylindrical pair, thereby forming the fourth cylindrical pair transmission structure.

[0058] The upper ends of the third slide bar 131 and the fourth slide bar 141 are respectively fixed to the rotating rings on the two planetary gear rings at both ends of the second connecting body, thereby introducing driving force.

[0059] Obviously, the fourth Hooke hinge assembly 8 is basically the same as the third Hooke hinge assembly 7; the only difference is that the bottom end of the third spindle 215 is connected to the first rotary joint 24, and the bottom end of the fourth spindle 311 is connected to the second rotary joint 34, which is the same as in embodiment 1.

[0060] The first rotary joint 24 and the second rotary joint 34 drive the output actuator 6 through the first connecting rod 4 and the second connecting rod 5, which are hinged in sequence, respectively; this is the same as in Embodiment 1, and will not be described in detail again.

[0061] The above structure ensures that when the sliding component moves and rotates, the first Hooke hinge assembly 2 and the second Hooke hinge assembly 3 can still perform spatial deflection motion, forming a composite kinematic chain of "cylindrical pair + Hooke hinge". This composite kinematic chain organically combines linear motion and rotational motion, enabling the robotic arm to achieve high-precision and flexible spatial operations when performing complex tasks.

[0062] The cylindrical pair formed by the sliding rod and sliding component connecting the rotating ring, and the cylindrical pair transmission structure formed by combining with the Hooke's joint, are equivalent to the transmission structure in Example 1 in terms of degree of freedom, motion form, and output effect. Through this design, the robotic arm can achieve stable and continuous reciprocating motion output while maintaining its original spatial deflection capability, meeting the usage requirements of multi-degree-of-freedom robotic arms in industrial assembly, material handling, and complex path tracking.

[0063] Furthermore, the multi-degree-of-freedom robotic arm in this embodiment features a compact structure and uniform force distribution. Simultaneously, the modular assembly of the base assembly 1, the third Hooke hinge assembly 7, and the fourth Hooke hinge assembly 8 facilitates the maintenance and functional expansion of the robotic arm.

[0064] By combining a cylindrical joint with a Hooke's hinge assembly, this embodiment achieves flexible coupling in the power transmission path, enabling the robotic arm to perform multi-plane and multi-angle composite movements in space. For example, when performing grasping, handling, or assembly tasks, the transmission ring in the robotic arm base assembly can move and rotate through sliding components. Combined with the rotational deflection provided by the third and fourth Hooke's hinge assemblies 7 and 8, this allows the robotic arm's output actuator 6 to achieve precise positioning and attitude adjustment in three-dimensional space. This design balances operational freedom with structural compactness, providing reliable support for the efficient operation of multi-degree-of-freedom robotic arms in confined space environments.

[0065] Working principle: The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joint, as described in this invention, achieves composite movements of the robotic arm in different spatial postures through the synergistic effect of the cylindrical joint and the Hooke hinge assembly during operation.

[0066] In the initial state of the robotic arm, the base assembly is fixed to the robot's torso or main body and serves as the power input and intermediate transmission node for the entire robotic arm. When the rotating ring of the base assembly outputs power, the intermediate transmission structure begins to operate. In Embodiment 1, the intermediate transmission structure adopts a cylindrical pair form. Under driving action, the cylindrical pair reciprocates linearly along the main axis of the cylindrical pair slider, while also allowing rotation around this axis at a certain angle. In Embodiment 2, the intermediate transmission structure also adopts a cylindrical pair form, enabling the transmission shaft in the transmission ring to not only move linearly along the sliding member, forming a stable linear displacement output, but also to achieve relative rotation. Although the two implementations have different structural forms, both provide equivalent linear motion components to the downstream mechanism.

[0067] While the linear translating joint is displaced, the two Hooke joints provide spatial attitude adjustment for the intermediate transmission unit and the lower linkage mechanism. The Hooke joints enable the linear translating joint to maintain continuous and smooth power transmission when the robotic arm undergoes spatial deflection, pitch, or lateral swing, thereby avoiding jamming or additional stress caused by attitude changes.

[0068] As the base assembly rotates, the power output is transmitted to the output actuator through the first and second links. Under the constraint of the Hooke joint, the linkage mechanism converts linear displacement into the extension or retraction motion of the end effector, while simultaneously adjusting the spatial attitude of the end effector in conjunction with the Hooke joint.

[0069] Throughout the entire motion process, the linear prismatic joint provides the main axial displacement motion, while the Hooke joint provides the necessary spatial rotational degrees of freedom. The various kinematic joints form a compound kinematic chain through geometric constraints, enabling the robotic arm to perform complex movements such as extension, retraction, and swinging, similar to those of a human arm, under multi-degree-of-freedom conditions. Due to the rational configuration of the Hooke joint and prismatic joint, the robotic arm can maintain the continuity, stability, and rational force distribution of its motion in different spatial postures.

[0070] This invention integrates the Hooke joint with the cylindrical joint, enabling the robotic arm to achieve spatial posture adjustment while possessing axial displacement compensation capabilities. This effectively reduces the additional load and parasitic displacement generated during complex posture changes, improves overall motion stability and environmental adaptability, and makes it particularly suitable for applications such as humanoid robots that have high requirements for motion coordination and reliability.

Claims

1. A multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints, characterized in that: The multi-degree-of-freedom robotic arm includes a base assembly (1) with four planetary gears, two Hooke hinge assemblies arranged in parallel below the base assembly and driven by two planetary gears respectively, two links driven by the two Hooke hinge assemblies respectively, and an output actuator driven by the two links together. The two Hooke hinge assemblies are a first Hooke hinge assembly (2) and a second Hooke hinge assembly (3) with identical structures. Each Hooke hinge assembly includes two cylindrical pair transmission structures disposed at both ends of the shaft seat, a motor disposed on the shaft seat to drive the rotary joint, and a limiting structure for limiting the position of the Hooke hinge assembly. The cylindrical pair transmission structure includes a cylindrical pair and a Hooke hinge connected in sequence. The main shaft is vertically arranged and rotatably positioned in the middle of the two shaft seats. The bottom ends of the two main shafts are horizontally fixed with a first rotary joint (24) and a second rotary joint (34) for hinged connecting rods. The rotating shaft connected to the cylindrical pair slider in the cylindrical pair is hinged to the hinge lug on the rotating ring; or... The two Hooke hinge assemblies are a third Hooke hinge assembly (7) and a fourth Hooke hinge assembly (8) with identical structures. Each Hooke hinge assembly includes two horizontally arranged rotating rods with one end hinged to the main shaft and two cylindrical pair transmission structures connecting the other ends of the two rotating rods. The cylindrical pair transmission structure includes a cylindrical pair and a Hooke hinge connected in sequence. The two main shafts are arranged vertically and the bottom ends are respectively fixed with a first rotating joint (24) and a second rotating joint (34) for hinged connecting rods. The cylindrical pair includes a sliding member and a sliding rod that cooperate with each other. The sliding rod is connected to the rotating ring.

2. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 1, characterized in that: The base assembly includes two symmetrically arranged connecting bodies and two symmetrically fixed housings on the two connecting bodies; two planetary carriers of planetary gears are coaxially mounted on the two connecting bodies respectively, and four sun gear motors that drive the sun gears are fixed in the two housings respectively, and the four planetary gears output power through rotating rings connected by gear rings respectively.

3. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 2, characterized in that: In the first Hooke hinge assembly (2) and the second Hooke hinge assembly (3), the first bearing seat (23) and the second bearing seat (33) are both symmetrically bent rods with both sides bending upwards. The two hinge seats are respectively fixed on the mounting rings at both ends of the bearing seat, and the axes of the two mounting rings intersect at one point. The first cantilever (20) and the second cantilever (38) are both bent rods with bushings at both ends. One end of each cantilever is fixed in the middle of the bearing seat, while the other end extends upwards at an angle and is hinged to the lower end of the handle of the auxiliary hinge ear. The distance between the hinge end and the hinge seats at both ends of the bearing seat is the same.

4. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 3, characterized in that: In the first Hooke hinge assembly (2) and the second Hooke hinge assembly (3), the top end of the cylindrical sub-slider is horizontally connected to a rotating shaft that engages with the hinge lug of the rotating ring, and the axis of the rotating shaft is perpendicular to the axis of the cylindrical sub-slider; the hinge seat, the cross shaft and the hinge seat fixed on the shaft seat at the bottom end of the cylindrical sub-slider cooperate to form a Hooke hinge.

5. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 4, characterized in that: The limiting structure includes a sliding groove coaxially disposed on each connecting body, an auxiliary hinge lug that mates with the sliding groove, and a cantilever that connects the bearing seat and the auxiliary hinge lug at both ends respectively; the sliding groove is formed by two fixing rings (135) coaxially disposed on the outer circumferential surface of the connecting body and spaced apart from each other.

6. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 5, characterized in that: In the third Hooke hinge assembly (7) and the fourth Hooke hinge assembly (8), one end of each of the two rotating rods of each Hooke hinge assembly is hinged to a vertically arranged main shaft, and the bottom end of the main shaft is horizontally fixed with a rotating joint; the other ends of the two rotating rods are respectively connected to a sliding member through the Hooke hinge, and the sliding member cooperates with the slide rod to form a cylindrical pair.

7. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 6, characterized in that: The first rotary joint (24) has an axis perpendicular to the axis of the main shaft to which it is connected. The first rotary joint has two hinge ears with shaft holes respectively. A cylindrical protrusion with the shaft hole is provided on the outer side of one of the hinge ears. The second rotary joint (34) has an axis perpendicular to the axis of the main shaft to which it is connected.

8. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 7, characterized in that: The hinge shaft fixed at the top of the first link (4) is hinged to the hinge ear of the first rotary joint (24). The first link motor (41) is mounted on the cylindrical protrusion of the hinge ear of the first rotary joint and coaxially connected to the hinge shaft at the top of the first link to drive the first link. The bottom end of the first link is hinged to another bushing of the first connector (61).

9. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 8, characterized in that: The top end of the second connecting rod (5) is hinged to the second rotary joint (34) through a hinge ear; the two hinge ears at the bottom end of the second connecting rod are respectively provided with shaft holes, and a cylindrical protrusion with the shaft hole is provided on the outer side of one of the hinge ears. The hinge shaft that mates with the shaft hole is inserted and fixed in the bushing of the second connecting member (63); the second connecting rod motor (51) is installed on the cylindrical protrusion of the hinge ear of the second connecting rod (61) and is coaxially connected to the hinge shaft fixed to the second connecting member (63) to drive the actuator shaft (62).

10. The multi-degree-of-freedom robotic arm that mimics the movement of the human shoulder and elbow joints according to claim 9, characterized in that: The output actuator (6) includes a second connector (63) fixed to one end of the actuator shaft (62) and a first connector (61) hinged to the same end of the actuator shaft via a bushing; the first connector is a double bushing structure with mutually perpendicular axes; the second connector (63) is a bushing with a fixed hinge shaft, the outside of the bushing is fixed to the rear end of the actuator shaft (62), and the axis of the hinge shaft is perpendicular to the axis of the actuator shaft.

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