Miniature servo joint actuator module

Abstract

This invention relates to the field of robotics and discloses a miniature servo motor joint execution module. The functional components include a drive control board, a capacitor board, an encoder disk assembly, a hollow brushless motor, a reducer, and an output flange, all coaxially and sequentially nested outside the mounting shaft. All functional components adopt a coaxial nested integrated structure design, significantly reducing the overall size of the miniature servo motor joint execution module and adapting it to the limited installation space of miniature robots. Multiple functional components are connected to electrical signals via a ribbon cable, optimizing the wiring structure, saving space, and improving the overall integration and reliability of the joint. The drive control board, capacitor board, and encoder disk assembly are integrally assembled, improving signal transmission stability, balancing integration and drive efficiency, simplifying assembly processes, ensuring assembly coaxiality, shortening the tolerance chain, reducing cumulative errors, improving consistency in mass production, and reducing the difficulty and cost of assembly and subsequent maintenance.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more particularly to a miniature servo joint actuator module. Background Technology

[0002] In the field of small automated equipment such as industrial robots, collaborative robots, and service robots, joint actuators (servo motors) are core functional components. Their performance parameters directly determine the load capacity, motion accuracy, response speed, and overall size of the equipment's joints. Furthermore, they are a key bottleneck restricting the miniaturization and precision development of some robots using servo motor joints. Currently, small joint actuators cannot meet the stringent application requirements of miniature devices such as the fingers of small quadruped robots or humanoid robots.

[0003] In existing technologies, joint actuators, taking small robot joints as an example, are assembled from multiple independent components. Each component is independently designed and assembled, using an axial or radial stacking layout. This results in a large overall length and radial diameter of the joint actuator, making it unsuitable for the narrow installation spaces of humanoid robot fingers and ankles. This leads to problems such as scattered layout, cumbersome connections, large volume redundancy, and low integration, making it difficult to adapt to micro-installation spaces. The tolerance chain formed by the assembly of multiple components is long, resulting in a large cumulative error, affecting the stability of joint operation, increasing operating noise and component wear, and making assembly and maintenance difficult. The assembly process of multiple independent components is cumbersome, with a large number of parts and a long tolerance chain, making it difficult to ensure consistency in mass production. Later maintenance requires disassembling multiple components, which is complex and costly. Power transmission and position feedback are achieved through mechanical connectors, resulting in low torque density and position feedback accuracy that is difficult to meet the requirements of precision operations. Signal and power transmission between components relies on wiring harnesses, which are complex and need to pass through the moving parts of the joint. This not only occupies additional installation space but is also prone to wear and breakage during joint movement, significantly reducing the reliability of joint operation. The aforementioned problems severely restrict the performance improvement and application scenario expansion of small robots, making it impossible to meet the needs of miniaturization and precision. Summary of the Invention

[0004] The purpose of this invention is to provide a miniature servo joint actuator module that optimizes the wiring structure, reduces the assembly volume, and is suitable for the limited installation space of miniature robots; it has low assembly error, high overall joint integration and reliability, stable signal transmission, and is easy to assemble and maintain.

[0005] To achieve this objective, the present invention adopts the following technical solution: The miniature servo joint actuator module includes multiple functional components, a mounting shaft, and a wiring board. The functional components include a drive control board, a capacitor board, an encoder disk assembly, a hollow brushless motor, a reducer, and an output flange, which are coaxially and sequentially nested outside the mounting shaft. All of the functional components are connected to electrical signals through the wiring board. The drive control board, the capacitor board, and the encoder disk assembly are integrally assembled.

[0006] As an optional technical solution for the micro servo joint actuator module, the encoder disk assembly includes an input absolute encoder and an output absolute encoder arranged coplanarly. The input absolute encoder is connected to the outer end ring of the hollow brushless motor, and the output absolute encoder is connected to the inner end ring of the hollow brushless motor.

[0007] As an optional technical solution for the micro servo joint actuator module, the encoder disk assembly also includes an encoder signal acquisition board. The encoder signal acquisition board is located on the side of the input absolute encoder and the output absolute encoder near the capacitor plate. A bushing is provided between the mounting shaft and the hollow brushless motor. One end of the output flange can pass through the bushing and connect to the encoder signal acquisition board.

[0008] As an optional technical solution for the micro servo joint actuator module, the ribbon cable is a flexible printed circuit board.

[0009] As an optional technical solution for the micro servo joint actuator module, the mounting shaft is hollow, and the wiring between the ribbon cable and the functional component passes through the mounting shaft.

[0010] As an optional technical solution for the micro servo joint actuator module, the reducer is configured as a micro harmonic reducer.

[0011] As an optional technical solution for a micro servo joint actuator module, the hollow brushless motor includes a motor stator and a motor rotor. The motor stator and the motor rotor can rotate relative to each other, and the motor stator is connected to the mounting shaft through a bearing.

[0012] As an optional technical solution for a micro servo motor joint actuator module, the motor rotor is rigidly connected to the input end of the reducer.

[0013] As an optional technical solution for the micro servo joint actuator module, the micro servo joint actuator module also includes a housing, and the motor stator is integrally assembled with the housing.

[0014] As an optional technical solution for the micro servo joint actuator module, the housing is made of high-strength aluminum alloy.

[0015] The beneficial effects of this invention are: The micro servo joint actuator module provided by this invention includes multiple functional components, a mounting shaft, and a wiring board. The functional components include a drive control board, a capacitor board, an encoder disk assembly, a hollow brushless motor, a reducer, and an output flange, all coaxially and sequentially nested outside the mounting shaft. All functional components share the same central axis, employing a coaxial nested integrated structure design. This breaks away from the existing independent layout of components, significantly reducing the overall size of the micro servo joint actuator module and adapting it to the limited installation space of micro robots. Multiple functional components are connected to electrical signals via the wiring board, optimizing the wiring structure, saving space, and improving the overall integration and reliability of the joint. The drive control board, capacitor board, and encoder disk assembly are integrally assembled, improving signal transmission stability, balancing integration and drive efficiency, significantly reducing the number of parts and assembly steps. The coaxial structure ensures the coaxiality of each component, shortening the tolerance chain and reducing cumulative errors, improving the consistency of mass production, and simultaneously reducing the difficulty and cost of assembly and subsequent maintenance. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of the overall structure of the micro servo joint actuator module provided in a specific embodiment of the present invention.

[0017] In the picture: 1. Drive end cover; 2. Cable board; 3. Drive control board; 4. Capacitor board; 5. Encoder signal acquisition board; 6. Housing; 7. Input absolute encoder; 8. Output absolute encoder; 9. Motor rotor; 10. Motor stator; 11. Bushing; 12. Reducer; 13. Bearing retaining ring; 14. Mounting shaft; 15. Bearing cover; 16. Output flange; 17. First threaded connector; 18. Second threaded connector; 19. Four-point contact bearing; 20. Second deep groove ball bearing; 21. First deep groove ball bearing. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0019] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0021] In the description of this embodiment, the terms "upper," "lower," "right," and "left," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0022] like Figure 1 As shown, this invention discloses a micro servo joint execution module, including multiple functional components, a mounting shaft 14, and a cable board 2. The functional components include a drive control board 3, a capacitor board 4, an encoder disk assembly, a hollow brushless motor, a reducer 12, and an output flange 16, which are coaxially and nested sequentially outside the mounting shaft 14. All functional components share the same central axis and adopt a coaxial nested integrated structure design, breaking the pattern of independent layout of each component in the prior art. This significantly reduces the overall volume of the micro servo joint execution module, making it suitable for the narrow installation space of micro robots. It simplifies the assembly process, shortens the tolerance chain, reduces cumulative errors, ensures the consistency of mass production, and reduces production costs and later maintenance difficulty.

[0023] In this embodiment, multiple functional components are connected to electrical signals via a ribbon cable board 2, which can be a flexible printed circuit board, i.e., an FPC ribbon cable board. All wiring connections use a single FPC ribbon cable board to replace traditional multi-wire harness connections, minimizing redundant space between components and achieving compact integration. This achieves the dual goals of miniaturization and high integration from a structural perspective, while also facilitating the cascading use of multiple servos. Simultaneously, the mounting shaft 14 is hollow, with wiring between the ribbon cable board 2 and functional components passing through it. The FPC ribbon cable board integrates all wiring, and combined with the hollow internal wiring design of the mounting shaft 14, optimizes the wiring structure, completely eliminating the risk of external wiring wear and breakage, resolving the space-consuming drawbacks, improving reliability, saving space, and enhancing the overall integration of the joint.

[0024] Specifically, the drive control board 3, capacitor board 4, and encoder disk assembly are integrally assembled using a single circular PCB design, eliminating the need for additional mounting brackets and further reducing installation space. Simultaneously, it integrates with an FPC cable board for wiring integration, simplifying cabling and improving signal transmission stability. It integrates all control components, including the MCU, drive chip, power management module, and signal processing module, optimizing the layout and balancing integration and drive efficiency. A drive end cover 1 is located at the end of the drive control board 3 furthest from the capacitor board 4, connected to the mounting shaft 14 via a first deep groove ball bearing 21. This integrated design significantly reduces the number of parts and assembly steps, while the coaxial structure ensures coaxiality of all components, improving consistency in mass production and reducing the difficulty and cost of assembly and subsequent maintenance.

[0025] Furthermore, the encoder disk assembly includes an input absolute encoder 7 and an output absolute encoder 8 arranged coplanarly. The input absolute encoder 7 is connected to the outer ring of the hollow brushless motor's end, used to accurately acquire the motor's speed and angle, realizing closed-loop control of the motor's speed and providing precise data for power output adjustment. The output absolute encoder 8 is connected to the inner ring of the hollow brushless motor's end, synchronously linked with the output flange 16, directly acquiring the actual position of the joint output flange 16, providing real-time feedback on the output position deviation, effectively compensating for errors in the transmission process of the reducer 12, and ensuring joint positioning accuracy. The input absolute encoder 7 and the output absolute encoder 8 are coplanar and share a single signal receiving element, which significantly reduces axial space while ensuring feedback accuracy, further improving integration, simplifying the signal processing path, and improving feedback response speed. The coplanar dual encoder design with full closed-loop control is adopted. The output absolute encoder 8 directly feeds back the actual position, while the input absolute encoder 7 and the output absolute encoder 8 provide synchronous feedback. This achieves high-precision position feedback, effectively compensates for transmission errors, significantly improves joint positioning accuracy, repeatability, and control stability, completely eliminates redundant space between components, optimizes feedback accuracy and space utilization, and enables joint miniaturization.

[0026] For example, the encoder code disk assembly also includes an encoder signal acquisition board 5, which is located on the side of the input absolute encoder 7 and the output absolute encoder 8 near the capacitor plate 4. A bushing 11 is provided between the mounting shaft 14 and the hollow brushless motor. The output flange 16 is connected to the bearing retaining ring 13 on its outer side through a four-point contact bearing 19. One end of the output flange 16 can pass through the bearing cover 15 and the bushing 11 to connect with the encoder signal acquisition board 5. The bearing cover 15 is fixedly assembled by a first threaded connector 17, while the output flange 16 is fixedly assembled by a second threaded connector 18. Multiple motor series wires can be arranged inside the bushing 11, further avoiding the design of external wiring. This saves space and avoids wear of the wiring harness during joint movement, greatly improving operational reliability.

[0027] Traditional planetary reducers require multiple stages to achieve a large reduction ratio, which not only occupies extra space but also causes power transmission losses, resulting in low torque output per unit volume. In this embodiment, reducer 12 is set as a miniature harmonic reducer, replacing the traditional multi-stage planetary reducer. Utilizing the characteristics of harmonic drive, a large reduction ratio can be achieved in a single stage, eliminating the need for multi-stage stacking, significantly reducing the size of the reduction mechanism, and simultaneously reducing power transmission losses and improving torque transmission efficiency. The miniature harmonic reducer is coaxially assembled with the hollow brushless motor and output flange 16, resulting in a compact structure that increases the output torque per unit volume by more than 40%. This allows it to meet the load requirements of small robots and micro-automation equipment within a miniature size. Furthermore, harmonic drive has the advantages of high rigidity and low backlash error, which can significantly improve the smoothness of joint operation and positioning accuracy. Under the same volume specifications, it significantly increases the joint output torque, improves torque density, and achieves the core advantage of "small volume, high torque".

[0028] Compared to traditional servo motor solutions with the same torque, the axial length of the micro servo motor joint actuator module in this solution is shortened by more than 30%, and the radial diameter is reduced by more than 25%. Combined with the integration of coplanar dual encoders and FPC wiring boards, true miniaturization is achieved. It can be flexibly applied to humanoid robot fingers, small quadruped robot ankles, micro collaborative robots, and other applications in confined installation spaces. It is also easy to use multiple servo motors in series.

[0029] Optionally, the hollow brushless motor adopts a hollow shaft external rotor brushless DC motor with an outer diameter typically of 20mm-30mm, providing basic power output for the joint. The hollow brushless motor includes a motor stator 10 and a motor rotor 9, which can rotate relative to each other. The motor stator 10 is connected to the mounting shaft 14 via a second deep groove ball bearing 20, and the motor rotor 9 is rigidly connected to the input end of the reducer 12 without the need for additional connecting parts. This effectively utilizes radial space, while simultaneously increasing the motor torque constant, enhancing power output efficiency, and reducing power transmission losses.

[0030] Understandably, the micro servo joint actuator module also includes a housing 6. The motor stator 10 is integrally assembled with the housing 6. The housing 6 is made of high-strength aluminum alloy and is used to install and fix each independent component, provide mechanical protection and structural support. The motor stator 10 is in direct contact with the aluminum alloy housing 6, which can achieve efficient heat dissipation, avoid the performance degradation caused by overheating during long-term operation of the motor, solve the heat dissipation problem of miniaturized equipment, effectively extend the service life of the joint, and reduce the failure rate. The housing 6 also serves as the mounting carrier for each component, with a compact structure that combines protection and support functions, further reducing the overall size.

[0031] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A miniature servo joint actuator module, characterized in that, It includes multiple functional components, a mounting shaft (14) and a ribbon cable board (2). The functional components include a drive control board (3), a capacitor board (4), an encoder code disk assembly, a hollow brushless motor, a reducer (12) and an output flange (16) that are coaxially and nested in sequence outside the mounting shaft (14). All of the functional components are connected to electrical signals through the ribbon cable board (2). The drive control board (3), the capacitor board (4) and the encoder code disk assembly are integrally assembled.

2. The miniature servo joint actuator module according to claim 1, characterized in that, The encoder disk assembly includes an input absolute encoder (7) and an output absolute encoder (8) arranged on the same plane. The input absolute encoder (7) is connected to the outer end ring of the hollow brushless motor, and the output absolute encoder (8) is connected to the inner end ring of the hollow brushless motor.

3. The miniature servo joint actuator module according to claim 2, characterized in that, The encoder code disk assembly also includes an encoder signal acquisition board (5), which is located on the side of the input absolute encoder (7) and the output absolute encoder (8) near the capacitor plate (4). A bushing (11) is provided between the mounting shaft (14) and the hollow brushless motor. One end of the output flange (16) can pass through the bushing (11) and connect to the encoder signal acquisition board (5).

4. The miniature servo joint actuator module according to claim 1, characterized in that, The ribbon cable board (2) is a flexible printed circuit board.

5. The miniature servo joint actuator module according to claim 1, characterized in that, The mounting shaft (14) is hollow, and the wiring between the cable board (2) and the functional component passes through the mounting shaft (14).

6. The miniature servo joint actuator module according to claim 1, characterized in that, The reducer (12) is configured as a miniature harmonic reducer.

7. The miniature servo joint actuator module according to claim 1, characterized in that, The hollow brushless motor includes a motor stator (10) and a motor rotor (9). The motor stator (10) and the motor rotor (9) can rotate relative to each other. The motor stator (10) and the mounting shaft (14) are connected by bearings.

8. The miniature servo joint actuator module according to claim 7, characterized in that, The motor rotor (9) is rigidly connected to the input end of the reducer (12).

9. The miniature servo joint actuator module according to claim 7, characterized in that, The micro servo joint actuator module also includes a housing (6), and the motor stator (10) is integrally assembled with the housing (6).

10. The micro servo joint actuator module according to claim 9, characterized in that, The outer shell (6) is made of high-strength aluminum alloy.

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