Multi-drive staged output and spherical center rotation three-degree-of-freedom joint driver

Abstract

This invention discloses a three-degree-of-freedom joint actuator with multi-drive, graded output and spherical rotation, comprising: a motor section, a gear section, and an output shaft. The motor section includes a left motor, a middle motor, and a right motor; the gear section includes a differential bevel gear assembly and a spherical gear assembly, with the differential bevel gear assembly connected to the left and right motors, and the spherical gear assembly connected to the middle motor; one end of the output shaft is coupled to the differential bevel gear assembly and the spherical gear assembly. The input power of the left and right motors is transmitted to the output shaft through the differential bevel gear assembly, and the input power of the middle motor is transmitted to the output shaft through the spherical gear assembly, thereby achieving graded power output, and the motion trajectory surface of the output shaft is spherical. This invention achieves high energy density and high mechanical efficiency in a compact form, a spherical actuator motion trajectory, and three-degree-of-freedom rotational motion without mechanical structural compromises, thus mimicking hip joint movement.

Description

Technical Field

[0001] This invention relates to the field of joint actuator technology, and in particular to a three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation. Background Technology

[0002] Joint actuators, as core power devices, are widely used in powered exoskeletons, humanoid robots, and mechanical hip joints. A feasible research approach is to abandon the traditional approach to hip joint actuator research and instead propose a completely new form of joint actuator based on bionics, in order to achieve an artificial joint actuator that closely resembles the human hip joint in terms of driving performance, motion performance, and control logic.

[0003] Based on existing research findings on actuators, high-performance joint actuators are a necessary prerequisite for researching high-performance prostheses, powered exoskeletons, humanoid robots, and mechanical hip joints. Only by achieving breakthroughs in core components can the performance of intelligent equipment based on these components be significantly improved. Taking existing actuator research as an example, the current academic focus on joint actuators mainly includes: high power density and mechanical efficiency output, high mechanical structural compactness and modularity, wide range of motion capabilities, and high dynamic response. The human hip joint currently maintains the optimal performance in these aspects. If the core factors of the biomechanical advantages of the human hip joint can be extracted, it will be possible to realize the engineering practice of biomimetic model-driven systems, thereby providing new ideas for proposing biomimetic motion modes and control methods suitable for novel actuators.

[0004] The current research and development focus and challenges of hip joints mainly include: high power density and mechanical efficiency output, high mechanical structural compactness and modularity, high dynamic response, and wide range of motion. Currently, artificial hip joint actuators are still primarily based on traditional series-connected actuators, and their form has not seen fundamental breakthroughs for a long time. Furthermore, they still differ significantly from human hip joints in key performance indicators. Existing joint actuators mainly suffer from the following three problems:

[0005] Firstly, in terms of drive power (dynamics), current artificial hip joints are basically three-axis individually driven, with each motor only driving its corresponding rotational degree of freedom. Even in medical robots and surgical arms, the output power required for each degree of freedom, like that of human joints, is not uniform or constant. This means that when using a mid-range power motor, there may be power redundancy in light-load rotational degrees of freedom, while insufficient power may occur in heavy-load rotational degrees of freedom, making it impossible to achieve high energy density output and maintain high mechanical efficiency. In order to cover the degree of freedom with the largest load, the engineering community generally selects motors based on the highest load, which may lead to wasted power density in some degrees of freedom. Furthermore, since the motor does not work during all motion periods, the motion mechanism must carry the "dead weight" of the non-working joints to complete the movement. This not only increases the overall motion inertia of the mechanism but also greatly reduces mechanical efficiency, which is particularly unfavorable for applications such as medical robots that have high requirements for motion precision and energy efficiency.

[0006] Secondly, in terms of drive control (cybernetics), current medical robot rotary mechanisms primarily rely on the series rotation of multiple single-degree-of-freedom joints. Each joint is sequentially connected by a linkage frame, and the rotation centers of the three degrees of freedom are not at a single point. This increases the motion space required to complete the rotation and complicates the inverse kinematics control calculations, necessitating the calculation of the Jacobian matrix and the addition of offset components to the rotation matrix. In this mechanical structure, the axes of the series actuators are not fixed during compound motions, and the paths to the same coordinate are not unique, making inverse kinematics solutions complex and creating control challenges. Furthermore, due to the superposition of the series stages, each joint introduces transmission errors. The accumulation of these errors can lead to increased deviations in the position and orientation of the end effector, reducing execution accuracy.

[0007] Finally, regarding rotational form (kinematics), traditional artificial powered hip joints primarily use series transmission, achieving rotational motion around three axes through simple superposition of single-axis actuators. This achieves a three-degree-of-freedom rotational motion effect in space only through mechanical compromise, but the actuator's motion trajectory is not spherical, failing to biomimeticly simulate the ball-joint-like motion effect of the human hip joint. Furthermore, series robotic arms place high demands on the mechanical properties of each link, and their load-bearing capacity is affected by the strength and stiffness of each arm. Due to the limitations of the actuators and transmission devices on each joint, the total load capacity of a series robotic arm may be limited. Larger loads may lead to joint torque imbalance, even exceeding the system's load-bearing capacity. Summary of the Invention

[0008] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, one objective of this invention is to propose a three-degree-of-freedom joint actuator with multi-drive hierarchical output and spherical center rotation, which can achieve high energy density and high mechanical efficiency in a compact shape, spherical actuator motion trajectory, and three-degree-of-freedom rotational motion without mechanical structural compromises. This enables the key performance indicators of the artificial joint actuator to be close to those of the human hip joint as a whole, and at a low manufacturing cost.

[0009] The multi-drive, graded output, and ball-center rotation three-degree-of-freedom joint actuator of the present invention includes:

[0010] The motor section includes a left motor, a middle motor, and a right motor arranged side by side in the same direction;

[0011] The gear section includes a differential bevel gear assembly and a spherical gear assembly. The differential bevel gear assembly is connected to the left motor and the right motor, and the spherical gear assembly is connected to the intermediate motor.

[0012] An output shaft, one end of which is coupled to the differential bevel gear assembly and the spherical gear assembly;

[0013] The input power of the left motor and the right motor is transmitted to the output shaft through the differential bevel gear assembly, and the input power of the intermediate motor is transmitted to the output shaft through the spherical gear assembly, thereby realizing graded power output, and the motion trajectory surface of the output shaft is a sphere.

[0014] In use, the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator of this invention uses the left motor, right motor and middle motor in the motor part to control the movement of the output shaft by controlling the differential bevel gear assembly and spherical gear assembly in the gear module. The output shaft will make spherical motion around a fixed point, which imitates the movement characteristics of the greater trochanter of the femur in the acetabulum and achieves a ball-joint-like constraint effect.

[0015] In summary, the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator of the present invention can achieve high energy density and high mechanical efficiency in a compact shape, spherical actuator motion trajectory, and three-degree-of-freedom rotational motion without mechanical structural compromise. This makes the key performance indicators of the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator close to those of the human hip joint as a whole, and the manufacturing cost is low.

[0016] In some embodiments, different load degrees of freedom are used to grade the output power. The motion state of the output shaft is controlled by a combination of the left motor, the middle motor and the right motor. The low load degree of freedom is driven by the middle motor only, the medium load degree of freedom is driven by the left motor and the right motor, and the high load degree of freedom is driven by the left motor, the right motor and the middle motor together.

[0017] In some embodiments, the rotation state of the output shaft is controlled by the speed coupling of the left motor, the right motor, and the intermediate motor. If the left motor and the right motor rotate in opposite directions, and the intermediate motor rotates in the same direction as the left motor or the right motor, the output shaft rotates around the axis of the intermediate motor. At this time, the left motor, the right motor, and the intermediate motor work simultaneously and output maximum load power. When the intermediate motor does not rotate, if the left motor and the right motor rotate in the same direction, the output shaft rotates around the axis of the differential bevel gear assembly. The axis of the differential bevel gear assembly is perpendicular to the axes of the left motor, the right motor, and the intermediate motor. At this time, the left motor and the right motor work and output medium load power. When the left motor and the right motor do not rotate, and the intermediate motor rotates, the output shaft rotates on its own axis. The rotation direction of the output shaft is the same as the rotation direction of the intermediate motor. At this time, only the intermediate motor works and outputs low load power.

[0018] In some embodiments, the intersection points of the rotation axes of the three degrees of freedom of the output shaft coincide at a fixed point in space, and the output shaft rotates on a spatial spherical surface with the fixed point as the center.

[0019] In some embodiments, the motor portion further includes a mounting bracket on which the left motor, the middle motor, and the right motor are mounted.

[0020] In some embodiments, the differential bevel gear assembly includes a left motor bevel gear, a left bidirectional bevel gear, a differential output bevel gear, a right motor bevel gear, a right bidirectional bevel gear, and a C-shaped coupling plate; the left motor bevel gear is fixed on the output shaft of the left motor; the left bidirectional bevel gear meshes with the left motor bevel gear; the right motor bevel gear is fixed on the output shaft of the right motor; the right bidirectional bevel gear meshes with the right motor bevel gear; the differential output gear meshes with the left bidirectional bevel gear and the right bidirectional bevel gear respectively; the C-shaped coupling plate is fixed to one end of the differential output bevel gear and the output shaft respectively.

[0021] In some embodiments, the differential bevel gear assembly further includes a left spindle, a right spindle, and a bevel gear retainer. The left spindle and the right spindle are coaxially arranged and perpendicular to the output shaft of the left motor, the output shaft of the intermediate motor, and the output shaft of the right motor. The left bidirectional bevel gear is fixed on the left spindle, and the left end of the left spindle and the left bidirectional bevel gear are rotatably supported on the mounting bracket. The right bidirectional bevel gear is fixed on the right spindle, and the right end of the right spindle and the right bidirectional bevel gear are rotatably supported on the mounting bracket. The bevel gear retainer is fixedly installed on the left spindle and the right spindle to limit the differential output bevel gear. The C-shaped coupling plate is installed on the bevel gear retainer and is rotatable relative to the bevel gear retainer.

[0022] In some embodiments, the mounting bracket includes a left mounting ear, a left support plate, a right mounting ear, and a right support plate; the left end of the left spindle is rotatably mounted on the left mounting ear, and the left bidirectional bevel gear is rotatably supported on the concave arc top of the left support plate; the right end of the right spindle is rotatably mounted on the right mounting ear, and the right bidirectional bevel gear is rotatably supported on the concave arc top of the right support plate.

[0023] In some embodiments, the differential bevel gear assembly further includes a left lubrication sleeve and a right lubrication sleeve; the left lubrication sleeve is sleeved on the left bidirectional bevel gear and located between the left support plate and the left bidirectional bevel gear; the right lubrication sleeve is sleeved on the right bidirectional bevel gear and located between the right support plate and the right bidirectional bevel gear.

[0024] In some embodiments, the spherical gear assembly includes a fixed-end spherical gear coupling, a fixed-end spherical gear, an output-end spherical gear coupling, an output-end spherical gear, and a spherical gear center connecting plate; wherein, the fixed-end spherical gear coupling is coaxially connected to the output shaft of the intermediate motor; the fixed-end spherical gear is disposed in the fixed-end spherical gear coupling; the output-end spherical gear coupling is coaxially connected to one end of the output shaft; the output-end spherical gear is disposed in the output-end spherical gear coupling and meshes with the fixed-end spherical gear; there are two spherical gear center connecting plates, and the two ends of the two spherical gear center connecting plates are respectively hinged to the two sides of the fixed-end spherical gear coupling and the fixed-end spherical gear coupling.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0027] Figure 1 This is a schematic diagram of the overall structure of a three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to an embodiment of the present invention.

[0028] Figure 2 This is an exploded view of the details of a three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the spherical gear assembly of a three-degree-of-freedom joint actuator with multi-drive hierarchical output and spherical center rotation according to an embodiment of the present invention.

[0030] Reference numerals: 1000, a three-DOF joint actuator with multi-drive graded output and ball center rotation; Motor section 1; Left motor 101; Middle motor 102; Right motor 103; Mounting bracket 104; Left mounting ear 10401; Left support plate 10402; Right mounting ear 10403; Right support plate 10404; Gear section 2; Differential bevel gear assembly 201; Left motor bevel gear 20101; Left bidirectional bevel gear 20102; Differential output bevel gear 20103; Right motor bevel gear 20 104; Right bidirectional bevel gear 20105; C-shaped coupling plate 20106; Left spindle 20107; Right spindle 20108; Bevel gear fastening limiter 20109; Left lubrication sleeve 20110; Right lubrication sleeve 20111; Spherical gear assembly 202; Fixed end spherical gear coupling 20201; Fixed end spherical gear 20202; Output end spherical gear coupling 20203; Output end spherical gear 20204; Spherical gear center connecting plate 20205; Output shaft 3. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] refer to Figures 1 to 3 This invention proposes a three-degree-of-freedom joint actuator 1000 with multi-drive hierarchical output and ball center rotation.

[0033] refer to Figures 1 to 3The multi-drive, graded output, and spherical rotation three-degree-of-freedom joint actuator 1000 of this invention includes: a motor part 1, a gear part 2, and an output shaft 3. The functions of the motor part 1 and the gear part 2 are similar to those of the human acetabulum and femur, respectively. The motor part 1 includes a left motor 101, a middle motor 102, and a right motor 103 arranged side by side and in the same direction. The gear part 2 includes a differential bevel gear assembly 201 and a spherical gear assembly 202. The differential bevel gear assembly 201 is connected to the left motor 101 and the right motor 103, and the spherical gear assembly 202 is connected to the middle motor 102. One end of the output shaft 3 is coupled to the differential bevel gear assembly 201 and the spherical gear assembly 202. The input power of the left motor 101 and the right motor 103 is transmitted to the output shaft 3 through the differential bevel gear assembly 201, and the input power of the middle motor 102 is transmitted to the output shaft 3 through the spherical gear assembly 202, thereby realizing graded power output, and the motion trajectory surface of the output shaft 3 is a sphere.

[0034] Specifically, motor section 1 is the fixed part of the entire actuator, mimicking the structure of the human hip acetabulum. Motor section 1 includes a left motor 101, a middle motor 102, and a right motor 103 arranged side by side and in the same direction. The left motor 101, the middle motor 102, and the right motor 103 are three identical brushless DC geared motors. The three motors are coupled and drive in a hierarchical manner, achieving the driving effect of a high-torque motor. Unlike traditional multi-degree-of-freedom joint actuators, there is no need to configure a high-load, high-torque motor for each rotational degree of freedom, thus saving manufacturing costs.

[0035] Gear section 2 is the moving part of the entire actuator, mimicking the structure of the human femur. Gear section 2 includes a differential bevel gear assembly 201 and a spherical gear assembly 202. The differential bevel gear assembly 201 is connected to the left motor 101 and the right motor 103, and the spherical gear assembly 202 is connected to the intermediate motor 102. Thus, the power input from the left motor 101 and the right motor 103 can be transmitted through the differential bevel gear assembly 201, and the power input from the intermediate motor 102 can be transmitted through the spherical gear assembly 202, achieving double coupling through the differential bevel gear assembly 201 and the spherical gear assembly 202. One end of the output shaft 3 is coupled to the differential bevel gear assembly 201 and the spherical gear assembly 202. The power input from the left motor 101 and the right motor 103 is transmitted to the output shaft 3 through the differential bevel gear assembly 201, and the power input from the middle motor 102 is transmitted to the output shaft 3 through the spherical gear assembly 202. Since both the differential bevel gear assembly 201 and the spherical gear assembly 202 are coupled to one end of the output shaft 3, the output shaft 3 can rotate freely within a certain range in three rotational directions, thereby realizing the output of power at different angles. By controlling the left motor 101, right motor 103, and middle motor 102, and under the coupling action of the differential bevel gear assembly 201 and spherical gear assembly 202, graded power output is achieved. For example, power is output in stages with different load degrees of freedom. The motion state of the output shaft 3 is controlled by the combination of the left motor 101, middle motor 102, and right motor 103. The low load degree of freedom (inward rotation and outward rotation) is driven only by the middle motor 103, the medium load degree of freedom (inward retraction and outward extension) is driven by the left motor 101 and right motor 103, and the high load degree of freedom (bending and extension) is driven by the left motor 101, right motor 102, and middle motor 103. This greatly simplifies the motion algorithm design and mechanical structure design, and also provides convenience for exploring more application scenarios. Because a spherical gear assembly 202 is used and the spherical gear assembly 202 is connected to one end of the output shaft 3, the motion trajectory surface of the output shaft 3 is guaranteed to be spherical, that is, the output shaft 3 will perform spherical motion centered on a fixed point, which imitates the motion characteristics of the greater trochanter of the femur in the acetabulum and achieves a ball joint-like constraint effect.

[0036] In terms of dynamic characteristics, the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator 1000 of this invention uses three motors with identical parameters arranged side-by-side: a left motor 101, a middle motor 102, and a right motor 103. For different load degrees of freedom such as flexion / extension, adduction / abduction, and internal / external rotation, 3, 2, and 1 motors are used respectively. This power arrangement completely simulates the driving mechanism of the human hip joint, increasing motor reuse, reducing the power requirement of individual motors, and decreasing the overall size of the actuator. The multi-drive graded coupling output principle of the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator 1000 mimics the time-sharing multiplexed coupling drive of multiple muscles in the human body, achieving graded output for different load degrees of freedom to improve the utilization rate of each drive unit and increase overall energy density and mechanical efficiency.

[0037] In terms of control characteristics, the multi-drive, hierarchical output, and spherical rotation three-degree-of-freedom joint actuator 1000 of this invention uses three motors that mesh in multiple stages through a differential bevel gear assembly 201 and a spherical gear assembly 202 to drive the output shaft 3. This eliminates the need for cascaded hinges, enabling three-degree-of-freedom rotational motion within space, significantly reducing the workspace required for three-degree-of-freedom rotation, and mechanically simplifying the joint actuator control algorithm. The spherical motion centered on a fixed point ensures that any point in space has unique coordinates. The hierarchical coupling control of the motor part 1 to the output shaft 3 ensures that the path to any point in space has a unique solution, reducing the difficulty of solving inverse kinematics. The spherical trajectory design provides precise workspace control. By controlling the angle and motion trajectory of each joint, precise position and attitude control can be achieved.

[0038] In terms of kinematic characteristics, the multi-drive, graded output, and ball-center rotation three-degree-of-freedom joint actuator 1000 of this invention places the rotation centers of the three rotational degrees of freedom at the same ball center, rather than a series connection of multiple single-degree-of-freedom joints. Through the meshing of the differential bevel gear assembly 201 and the spherical gear assembly 202, the multi-drive, graded output, and ball-center rotation three-degree-of-freedom joint actuator 1000 can transmit power at different angles, causing the intersection of the rotation axes to coincide at a single point in space, mimicking the motion characteristics of the greater trochanter of the femur in the acetabulum, and achieving a ball-joint-like constraint effect. This structure eliminates the need for the length of the links in conventional multi-bar hinge joint structures, allowing the end effector to complete three-degree-of-freedom rotation simply by controlling the motor to drive the rotating ball head. This significantly reduces the overall size of the joint actuator and simplifies the control of the joint actuator from the core design level of the rotation mechanism, achieving a wide range of rotation without structural compromises. Because its motion trajectory is similar to that of the human hip joint, it can achieve a more natural gait when applied to prostheses, exoskeletons, and humanoid robots. With the dual coupling of the differential bevel gear assembly 201 and the spherical gear assembly 202, the three-degree-of-freedom joint actuator 1000 with multi-drive hierarchical output and spherical center rotation can achieve unimpeded rotation from 0 to 120 degrees in three rotational directions, which greatly simplifies motion algorithm design and mechanical structure design, and also provides convenience for exploring more application scenarios.

[0039] In terms of manufacturing cost, the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator 1000 of this invention uses three motors coupled with graded power drive, which can achieve the driving effect of a high-torque motor by using three small-torque motors, without the need to configure a high-load, high-torque motor for each rotational degree of freedom as in traditional multi-degree-of-freedom joint actuators, thus saving manufacturing costs. This provides a lower-cost and higher-performance drive configuration option for existing joint actuator designs.

[0040] In summary, the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator 1000 of the present invention can achieve high energy density and high mechanical efficiency in a compact shape, spherical actuator motion trajectory, and three-degree-of-freedom rotational motion without mechanical structural compromise. This makes the key performance indicators of the multi-drive graded output and ball-center rotation three-degree-of-freedom joint actuator 1000 close to those of the human hip joint as a whole, and the manufacturing cost is low.

[0041] In some embodiments, different load degrees of freedom are used to output power in stages. The motion state of the output shaft 3 is controlled by a combination of the left motor 101, the middle motor 102 and the right motor 103. The low load degree of freedom is driven only by the middle motor 102, the medium load degree of freedom is driven by the left motor 101 and the right motor 103, and the high load degree of freedom is driven by the left motor 101, the right motor 103 and the middle motor 102.

[0042] Specifically, when using low-load degree-of-freedom output power, the left motor 101 and the right motor 103 do not rotate, only the middle motor 102 rotates, and the output shaft 3 will maintain the same rotation direction and rotation speed as the middle motor 102, thereby simulating the internal and external rotation movements of the hip joint.

[0043] When the output power is at medium load degrees of freedom, the middle motor 102 does not rotate, while the left motor 101 and the right motor 103 rotate. When the left motor 101 and the right motor 103 rotate in the same direction, the output shaft 3 will rotate together with the C-shaped coupling plate 20106 around the bevel gear fastening limiter 20109. When the left motor 101 and the right motor 103 rotate in different directions, the output shaft 3 will rotate together with the C-shaped coupling plate 20106 around the coaxially set left main shaft 20107 and right main shaft 20108, thereby simulating the adduction and abduction movements of the hip joint.

[0044] When high-load, degree-of-freedom output power is used, the left motor 101, right motor 103, and middle motor 102 rotate simultaneously, and the output shaft 3 maintains the same rotation direction and speed as the middle motor 102. When the left motor 101 and right motor 103 rotate in the same direction, the output shaft 3, together with the C-shaped coupling plate 20106, rotates around the bevel gear fastening limiter 20109. When the left motor 101 and right motor 103 rotate in different directions, the output shaft 3, together with the C-shaped coupling plate 20106, rotates around the coaxially set left main shaft 20107 and right main shaft 20108, thereby simulating hip joint flexion and extension movements.

[0045] This power arrangement simulates the driving mechanism of the human hip joint, which can increase the reuse rate of motors, reduce the power requirements of individual motors, and reduce the overall size of the actuator. The multi-drive hierarchical output and ball-center rotation three-degree-of-freedom joint actuator 1000 of this invention mimic the time-sharing multiple-multiplexed coupling drive of multiple muscles in the human body, realizing hierarchical output of different load degrees of freedom to improve the utilization rate of each drive unit and improve the overall energy density and mechanical efficiency.

[0046] In some embodiments, the output shaft 3 achieves rotation from 0 to 120° in three degrees of freedom. With the dual coupling of the differential bevel gear assembly 201 and the spherical gear assembly 202, the output shaft 3 can achieve unimpeded rotation from 0 to 120° in three rotational directions, which greatly simplifies the design of motion algorithms and mechanical structures, and also provides convenience for exploring more application scenarios.

[0047] In some embodiments, the rotation state of the output shaft 3 is controlled by the speed coupling of the left motor 101, the right motor 103, and the intermediate motor 102. If the left motor 101 and the right motor 103 rotate in opposite directions, and the intermediate motor 102 rotates in the same direction as the left motor 101 or the right motor 103, the output shaft 3 rotates around the axis of the intermediate motor 102. At this time, the left motor 101, the right motor 103, and the intermediate motor 102 work simultaneously and output maximum load power. When the intermediate motor 102 does not rotate, if the left motor 101 and the right motor 103 rotate in the same direction, the output shaft 3 rotates around the axis of the differential bevel gear assembly 201. The axis of the differential bevel gear assembly 201 is perpendicular to the axes of the left motor 101, the right motor 103, and the intermediate motor 102. That is, the axis of the differential bevel gear assembly 201 can be understood as... Figure 2 The left bidirectional bevel gear 20102 and the right bidirectional bevel gear 20105 are on the same axis. At this time, the left motor 101 and the right motor 103 work and output medium-load power. If the left motor 101 and the right motor 103 rotate in opposite directions, the output shaft 3 rotates around the axis of the middle motor 102. When the left motor 101 and the right motor 103 do not rotate and the middle motor 102 rotates, the output shaft 3 rotates on its own, and the rotation direction of the output shaft 3 is the same as the rotation direction of the middle motor 102. At this time, only the middle motor 102 works and outputs low-load power.

[0048] In some embodiments, the intersection points of the rotation axes of the three degrees of freedom of the output shaft 3 coincide at a fixed point in space, and the output shaft 3 rotates on a spatial spherical surface with the fixed point as the center.

[0049] In some embodiments, the motor part 1 further includes a mounting bracket 104, on which the left motor 101, the middle motor 102 and the right motor 103 are mounted, and the mounting bracket 104 provides fixed support for the left motor 101, the middle motor 102 and the right motor 103.

[0050] In some embodiments, the differential bevel gear assembly 201 includes a left motor bevel gear 20101, a left bidirectional bevel gear 20102, a differential output bevel gear 20103, a right motor bevel gear 20104, a right bidirectional bevel gear 20105, and a C-shaped coupling plate 20106; the left motor bevel gear 20101 is fixed on the output shaft 3 of the left motor 101; the left bidirectional bevel gear 20102 meshes with the left motor bevel gear 20101; the right motor bevel gear 20104 is fixed on the output shaft 3 of the right motor 103; the right bidirectional bevel gear 20105 meshes with the right motor bevel gear 20104; the differential output gear meshes with the left bidirectional bevel gear 20102 and the right bidirectional bevel gear 20105 respectively; and the C-shaped coupling plate 20106 is fixed to one end of the differential output bevel gear 20103 and the output shaft 3 respectively. The left bidirectional bevel gear 20102 and the right bidirectional bevel gear 20105 are both designed by connecting a pair of bevel gears facing opposite directions, which is equivalent to two coaxially fixed bevel gears. The left bidirectional bevel gear 20102 can mesh with the left motor bevel gear 20101 and the differential output bevel gear 20103 at the same time, and the right bidirectional bevel gear 20105 can mesh with the right motor bevel gear 20104 and then the differential output bevel gear 20103 at the same time.

[0051] It is understandable that the power input from the left motor 101 is transmitted to the differential output bevel gear 20103 through the left motor bevel gear 20101 and the left bidirectional bevel gear 20102, and the power input from the right motor 103 is transmitted to the differential output bevel gear 20103 through the right motor bevel gear 20104 and the right bidirectional bevel gear 20105. The power transmitted by the left bidirectional bevel gear 20102 and the right bidirectional bevel gear 20105 is coupled through the differential output bevel gear, and then transmitted to the output shaft 3 through the C-shaped coupling plate 20106.

[0052] In some embodiments, the differential bevel gear assembly 201 further includes a left main shaft 20107, a right main shaft 20108, and a bevel gear fastening limiter 20109. The left main shaft 20107 and the right main shaft 20108 are coaxially arranged and perpendicular to the output shaft 3 of the left motor 101, the output shaft 3 of the middle motor 102, and the output shaft 3 of the right motor 103. The left bidirectional bevel gear 20102 is fixed on the left main shaft 20107, and the left end of the left main shaft 20107 and the left bidirectional bevel gear 20102 are rotatably supported on the left main shaft 20107. Mounting bracket 104; right bidirectional bevel gear 20105 is fixed on right spindle 20108, and the right end of right spindle 20108 and right bidirectional bevel gear 20105 are rotatably supported on mounting bracket 104 respectively; bevel gear fastening limiter 20109 is fixedly installed on left spindle 20107 and right spindle 20108 to limit differential output bevel gear 20103; C-shaped coupling plate 20106 is installed on bevel gear fastening limiter 20109 and is rotatable relative to bevel gear fastening limiter 20109.

[0053] Understandably, the differential output bevel gear 8 meshes simultaneously with both the left bidirectional bevel gear 20102 and the right bidirectional bevel gear 20105, allowing it to rotate around the left main shaft 20107 and the right main shaft 20108, as well as around the main shaft of the intermediate motor 102. The bevel gear retaining limiter 20109 is fixedly mounted on the left main shaft 20107 and the right main shaft 20108, limiting the displacement of the differential output bevel gear 20103. The C-shaped coupling plate 20106 can be tightly connected to the differential output bevel gear 20103 via bolts and is mounted on the bevel gear retaining limiter 20109. Its movement is the same as that of the differential output bevel gear 20103, allowing it to rotate around the left main shaft 20107 and the right main shaft 20108, as well as around the main shaft of the intermediate motor 102. The C-shaped coupling plate 20106 is directly and tightly connected to the output shaft 3, which allows the output shaft 3 to rotate around the left main shaft 20107 and the right main shaft 20108, as well as around the main shaft of the middle motor 102.

[0054] In some embodiments, the mounting bracket 104 includes a left mounting ear 10401, a left support plate 10402, a right mounting ear 10403, and a right support plate 10404; the left end of the left main shaft 20107 is rotatably mounted on the left mounting ear 10401, and the left double-bevel gear 20102 is rotatably supported on the concave arc top of the left support plate 10402; the right end of the right main shaft 20108 is rotatably mounted on the right mounting ear 10403, and the right double-bevel gear 20105 is rotatably supported on the concave arc top of the right support plate 10404, and the structural layout is reasonable and reliable.

[0055] In some embodiments, the differential bevel gear assembly 201 further includes a left lubrication sleeve 20110 and a right lubrication sleeve 20111; the left lubrication sleeve 20110 is sleeved on the left double-bevel gear 20102 and located between the left support plate 10402 and the left double-bevel gear 20102; the right lubrication sleeve 20111 is sleeved on the right double-bevel gear 20105 and located between the right support plate 10404 and the right double-bevel gear 20105. It is understood that the left lubrication sleeve 20110, sleeved on the left double-bevel gear 20102, serves as a buffer lubricant to facilitate the rotation of the left double-bevel gear 20102; the right lubrication sleeve 20111, sleeved on the right double-bevel gear 20105, also serves as a buffer lubricant to facilitate the rotation of the right double-bevel gear 20105.

[0056] In some embodiments, the spherical gear assembly 202 includes a fixed-end spherical gear coupling 20201, a fixed-end spherical gear 20202, an output-end spherical gear coupling 20203, an output-end spherical gear 20204, and a spherical gear center connecting plate 20205; wherein, the fixed-end spherical gear coupling 20201 is coaxially connected to the output shaft 3 of the intermediate motor 102; the fixed-end spherical gear 20202 is disposed on the fixed-end spherical gear coupling 20202. In section 01; the output end spherical gear coupling 20203 is coaxially connected to one end of the output shaft 3; the output end spherical gear 20204 is set in the output end spherical gear coupling 20203 and meshes with the fixed end spherical gear 20202; there are two spherical gear center connecting plates 20205, and the two ends of the two spherical gear center connecting plates 20205 are respectively hinged to the two sides of the fixed end spherical gear coupling 20201 and the fixed end spherical gear coupling 20201.

[0057] Understandably, a pair of unrestricted meshing spherical gears can perform three-degree-of-freedom rotational motion in space. Constrained by the spherical gear center connecting plate 20205, the fixed-end spherical gear coupling 20201, and the output-end spherical gear coupling 20203, the output-end spherical gear 20204 loses one degree of freedom. The output-end spherical gear 20204 can then perform two-degree-of-freedom motion around the fixed-end spherical gear 20202: one is rotation about the connecting hole on the fixed-end spherical gear coupling 20201, moving with the C-shaped coupling plate 20106; the other is rotation about the axis of the output-end spherical gear 20204, rotating with the fixed-end spherical gear coupling 20201 around its own axis. Among them, the spherical gear center connecting plate 20205 ensures that the distance between the center of the fixed end spherical gear 20202 and the center of the output end spherical gear 20204 remains unchanged, ensuring that the motion trajectory surface of the output shaft 3 is spherical, that is, the output shaft 3 will perform spherical motion centered on a fixed point, mimicking the motion characteristics of the greater trochanter of the femur in the acetabulum, and achieving a ball joint-like constraint effect.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball-center rotation, characterized in that, include: The motor section includes a left motor, a middle motor, and a right motor arranged side by side in the same direction; The gear section includes a differential bevel gear assembly and a spherical gear assembly. The differential bevel gear assembly is connected to the left motor and the right motor, and the spherical gear assembly is connected to the intermediate motor. An output shaft, one end of which is coupled to the differential bevel gear assembly and the spherical gear assembly; The input power of the left motor and the right motor is transmitted to the output shaft through the differential bevel gear assembly, and the input power of the middle motor is transmitted to the output shaft through the spherical gear assembly, thereby realizing graded power output, and the motion trajectory surface of the output shaft is a sphere; The output power is graded with different load degrees of freedom. The motion state of the output shaft is controlled by a combination of the left motor, the middle motor and the right motor. The low load degree of freedom is driven by the middle motor only, the medium load degree of freedom is driven by the left motor and the right motor, and the high load degree of freedom is driven by the left motor, the right motor and the middle motor together. The rotation state of the output shaft is controlled by the speed coupling of the left motor, the right motor, and the intermediate motor. If the left motor and the right motor rotate in opposite directions, and the intermediate motor rotates in the same direction as the left motor or the right motor, the output shaft rotates around the axis of the intermediate motor. At this time, the left motor, the right motor, and the intermediate motor work simultaneously and output maximum load power. When the intermediate motor does not rotate, if the left motor and the right motor rotate in the same direction, the output shaft rotates around the axis of the differential bevel gear assembly. The axis of the differential bevel gear assembly is perpendicular to the axes of the left motor, the right motor, and the intermediate motor. At this time, the left motor and the right motor work and output medium load power. When the left motor and the right motor do not rotate, and the intermediate motor rotates, the output shaft rotates on its own axis in the same direction as the intermediate motor. At this time, only the intermediate motor works and outputs low load power.

2. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to claim 1, characterized in that, The three degrees of freedom of the output shaft's rotation axes intersect at a fixed point in space, and the output shaft rotates on a spherical surface with the fixed point as its center.

3. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to any one of claims 1-2, characterized in that, The motor section also includes a mounting bracket, on which the left motor, the middle motor, and the right motor are mounted.

4. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to claim 3, characterized in that, The differential bevel gear assembly includes a left motor bevel gear, a left bidirectional bevel gear, a differential output bevel gear, a right motor bevel gear, a right bidirectional bevel gear, and a C-shaped coupling plate; the left motor bevel gear is fixed on the output shaft of the left motor; the left bidirectional bevel gear meshes with the left motor bevel gear; the right motor bevel gear is fixed on the output shaft of the right motor; the right bidirectional bevel gear meshes with the right motor bevel gear; the differential output gear meshes with the left bidirectional bevel gear and the right bidirectional bevel gear respectively; the C-shaped coupling plate is fixed to one end of the differential output bevel gear and the output shaft respectively.

5. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to claim 4, characterized in that, The differential bevel gear assembly further includes a left main shaft, a right main shaft, and a bevel gear fastening limiter. The left and right main shafts are coaxially arranged and perpendicular to the output shafts of the left motor, the middle motor, and the right motor. The left bidirectional bevel gear is fixed on the left main shaft, and the left end of the left main shaft and the left bidirectional bevel gear are rotatably supported on the mounting bracket. The right bidirectional bevel gear is fixed on the right main shaft, and the right end of the right main shaft and the right bidirectional bevel gear are rotatably supported on the mounting bracket. The bevel gear fastening limiter is fixedly installed on the left and right main shafts to limit the differential output bevel gear. The C-shaped coupling plate is installed on the bevel gear fastening limiter and is rotatable relative to the bevel gear fastening limiter.

6. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to claim 5, characterized in that, The mounting bracket includes a left mounting ear, a left support plate, a right mounting ear, and a right support plate; the left end of the left spindle is rotatably mounted on the left mounting ear, and the left bidirectional bevel gear is rotatably supported on the concave arc top of the left support plate; the right end of the right spindle is rotatably mounted on the right mounting ear, and the right bidirectional bevel gear is rotatably supported on the concave arc top of the right support plate.

7. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to claim 6, characterized in that, The differential bevel gear assembly further includes a left lubrication sleeve and a right lubrication sleeve; the left lubrication sleeve is fitted onto the left bidirectional bevel gear and located between the left support plate and the left bidirectional bevel gear; the right lubrication sleeve is fitted onto the right bidirectional bevel gear and located between the right support plate and the right bidirectional bevel gear.

8. The three-degree-of-freedom joint actuator with multi-drive hierarchical output and ball center rotation according to any one of claims 1-2, characterized in that, The spherical gear assembly includes a fixed-end spherical gear coupling, a fixed-end spherical gear, an output-end spherical gear coupling, an output-end spherical gear, and a spherical gear center connecting plate. The fixed-end spherical gear coupling is coaxially connected to the output shaft of the intermediate motor. The fixed-end spherical gear is housed within the fixed-end spherical gear coupling. The output-end spherical gear coupling is coaxially connected to one end of the output shaft. The output-end spherical gear is housed within the output-end spherical gear coupling and meshes with the fixed-end spherical gear. There are two spherical gear center connecting plates, each hinged at both ends to the fixed-end spherical gear coupling and the two sides of the fixed-end spherical gear coupling, respectively.

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