Double differential type robot joint

Abstract

The invention discloses a double differential type robot joint which comprises a structural assembly, a driving module, a sensing module, a control module and a testing module, the control module, the sensing module and the driving module are connected through the structural assembly, and integrated design is achieved. A double-differential speed reducer, an outer rotor motor, double encoders and a control module are integrated through integrated design, the bidirectional power flow characteristic and a dynamic rigidity adjusting mechanism of a double-differential transmission system are combined, and the rigid transmission limitation of a traditional speed reducer is broken through; the problems that a traditional joint is large in size, lack of energy regulation and management, poor in reverse driving performance, poor in dynamic anti-interference capacity, low in transmission efficiency and insufficient in control precision are solved, and rigidity flexibility, energy circulation and dynamic response improvement are achieved.

Description

Technical Field

[0001] The present invention relates to the field of robot joint technology, and in particular to an integrated robot joint structure that integrates a dual differential reducer, an outer rotor motor and multiple sensors, which is suitable for high-precision and high-dynamic driving scenarios such as humanoid robots, quadruped robot dogs, collaborative robots, and industrial robotic arms. Background Art

[0002] As the core execution unit of robot movement, robot joints must have the characteristics of high torque density, high precision and compact layout. Traditional robot joints mostly adopt a separate design of motor and reducer, which has problems such as large size, complex transmission chain, and insufficient dynamic response. In the existing reducer technology, although the planetary reducer has high torque density, the reduction ratio and transmission stiffness are fixed, and the impact resistance is weak; although the harmonic reducer has high precision, the reverse drive performance is poor and it is easily damaged by impact. When traditional reducers encounter external impacts, they need to rely on external damping elements to absorb energy, which increases the complexity of the system. In addition, most existing joints use a single encoder feedback, which makes it difficult to eliminate the cumulative transmission error, resulting in limited positioning accuracy.

[0003] Some robot joints use algorithms to compensate for transmission errors or introduce elastic elements to absorb shocks, but fail to achieve dynamic energy regulation from the mechanical structure level. Therefore, there is an urgent need for an integrated joint solution that is highly integrated, compact, has high reduction ratio adjustability, shock resistance, and multi-closed-loop control. Summary of the invention

[0004] In view of the current gap in robot electric-driven joints with explosive and impact resistance, the present invention provides a new dual-differential robot joint, which integrates a dual-differential reducer, an outer rotor motor, a dual encoder and a control module through an integrated design, and combines the bidirectional power flow characteristics and dynamic stiffness adjustment mechanism of the dual-differential transmission system to break through the rigid transmission limitations of traditional reducers, solve the problems of large size, lack of energy regulation and management, poor back-drive performance, poor dynamic anti-interference ability, low transmission efficiency, and insufficient control accuracy of traditional joints, and achieves flexible stiffness, energy circulation, and improved dynamic response.

[0005] The present invention adopts the following technical solution:

[0006] In order to solve the above problems, the present invention provides a dual differential robot joint, including: a structural component, a driving module, a sensor module, a control module and a test module. The control module, the sensor module and the driving module are connected by the structural component to achieve an integrated design. The structural component is used to integrate various modules of the joint, including: a front shell, an outer shell, a rear shell, a motor output assembly, and an input shaft. The outer shell is respectively fixedly connected to the front shell and the rear shell. The stator in the motor output assembly is fixedly connected to the internal structure of the outer shell. The input shaft is fixedly connected to the motor output assembly. The dual differential reducer in the driving module provides a power source; the driving module is used for power transmission and power output of the joint. The driving module includes: an outer rotor motor, a dual differential reducer, and the motor rotor is fixedly connected to the motor output assembly; the sensor module is used to sense the angle changes of the input and output ends of the joint in real time, and provide feedback in real time. The sensor module includes an input end encoder and an output end encoder The encoder has a universal structure and is not described here. The input encoder magnetic ring is fixedly connected to the motor output component, the input encoder signal acquisition board is fixedly connected to the control bracket, the output encoder magnetic ring is fixedly connected to the shell, and the output encoder signal acquisition board is fixedly connected to the output flange; the control module is used for real-time control adjustment, feedback adjustment, self-disturbance rejection adjustment, and current position speed loop adjustment. The control module includes: a PCB board and a control board. The control board is fixedly connected to the control bracket, and the PCB board is superimposed on the control board and fixedly connected; the test module is used to perform a hysteresis test on the joint. The test module includes a hysteresis test locking assembly, which is fixedly connected to the shell and can lock the input shaft.

[0007] As a further optimization of the technical solution, the front shell 6, the outer shell 8, and the rear shell 19 are provided with threaded holes and fixed shaft sections for fixing the motor stator 11, the control bracket 15, the positioning end cover 21, and the output end encoder 27. The outer rotor motor includes a stator 11 and a motor rotor 12. The stator 11 is embedded in the outer shell 8. The motor rotor 12 is bonded to the motor output assembly 13 by anaerobic adhesive, and the motor output assembly 13 is fastened to the input shaft 22. The dual differential reducer includes eight bevel gears, a planetary shaft 9, and an output shaft 1; the motor rotor 12 is fixedly connected to the motor output assembly 13, the input end encoder magnetic ring is fixedly connected to the motor output assembly 13, the input end encoder signal acquisition board is fixedly connected to the control bracket 15, the output end encoder magnetic ring is fixedly connected to the outer shell 8, the output end encoder signal acquisition board is fixedly connected to the output flange 2, the control board 16 is fixedly connected to the control bracket 15, and the PCB board 17 is superimposed on the control board 16 and fixedly connected.

[0008] As a further optimization of the technical solution, the input shaft 22 drives the input bevel gear 23 by connecting with the input bevel gear 23 including but not limited to the spline connection, and the input bevel gear 23 meshes with the planetary large bevel gear A7 and the planetary large bevel gear B25 to form the first stage differential, and the planetary large bevel gears A7 and B25 are connected to the planetary small bevel gear A10 and the planetary small bevel gear B26 through the planetary shaft 9, and mesh with the support bevel gear 24 and the output bevel gear 4, and finally drive the output shaft 1, and the reduction ratio is expanded by replacing the tooth number difference of the planetary gear set, and the outer dimensions remain unchanged. The input end encoder 14 is coaxially installed with the input end encoder magnetic ring 18, and the resolution can reach 0.005°. The output end encoder 27 is coaxially installed with the output end encoder magnetic ring 3, and the resolution can reach 0.005°. The PCB board 17 is installed on the control bracket 15, and the integrated signal conditioning circuit supports CAN FD communication. The control board 16 is installed on the control bracket 15, and cooperates with the PCB board to perform self-disturbance control and feedback adjustment.

[0009] As a further optimization of this technical solution, an integrated joint with an integrated dual differential reducer is proposed. The structure is designed to greatly reduce the axial size while ensuring transmission accuracy, with a transmission error of ≤1 arcmin and a backlash of ≤1 arcmin. The planetary bevel gear A7, the planetary bevel gear A10, the planetary bevel gear B25, and the planetary bevel gear B26 are symmetrically distributed, with a load balance of ≥95%.

[0010] As a further optimization of this technical solution, an integrated joint with self-disturbance rejection control and real-time compensation of transmission error is proposed. The self-disturbance rejection control is coordinated by the control board, PCB board, and double-end encoder. The extended state observer estimates the internal / external disturbance of the joint in real time and compensates through nonlinear feedback. The response time is ≤2ms. The real-time compensation of transmission error collects angle information in real time through encoders at both ends and feeds it back to the control module for real-time input compensation to improve transmission accuracy.

[0011] As a further optimization of this technical solution, an integrated joint with dynamic energy management is proposed. The structure can absorb external impact. When the external impact force drives the output shaft 1 to move in the opposite direction, the planetary gears 7 and 25 rotate differentially, storing the kinetic energy in the system inertia. The structural shell is driven instantaneously, and the motor is instantaneously overloaded to drive the planetary gears to revolve synchronously, releasing the stored kinetic energy, and the peak torque is increased by 50%.

[0012] As a further optimization of the technical solution, a modularly expandable integrated joint is proposed. The structure can be expanded into a multi-degree-of-freedom joint or adjust the torque-speed characteristics by adjusting the difference in the number of teeth at each level or replacing the gear set, and can achieve dual output capabilities. The dual output capabilities are based on the modified structure and can be expanded to planetary gear revolution output and large bevel gear output. The multi-degree-of-freedom output capabilities achieved by adjusting the structure are all within the protection scope of the present invention.

[0013] As a further optimization of the present technical solution, a hysteresis test locking device is proposed, which can lock the joint input end by fixing the hysteresis test locking assembly to the housing, thereby providing conditions for the joint hysteresis test. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is an isometric illustration of the overall appearance of the integrated joint.

[0015] Figure 2 It is a cross-sectional view of the overall structure of the integrated joint, showing the meshing relationship of the dual differential gears and the motor-encoder layout.

[0016] Figure 3 This is the overall structure assembly diagram of the integrated joint.

[0017] Figure 4 This is a front view of the overall appearance of the integrated joint.

[0018] Figure 5 This is the front view of the overall appearance of the integrated joint.

[0019] Figure 6 This is the rear view of the overall appearance of the integrated joint.

[0020] Figure 7 This is a diagram of the integrated joint backlash test locking device.

[0021] Markings in the figure: 1. Output shaft; 2. Output flange; 3. Output encoder magnetic ring; 4. Output bevel gear; 5. Large bevel gear; 6. Front shell; 7. Planetary large bevel gear A; 8. Shell; 9. Planetary shaft; 10. Planetary small bevel gear A; 11. Motor stator; 12. Motor rotor; 13. Motor output assembly; 14. Input encoder; 15. Control bracket; 16. Control board; 17; PCB board; 18. Input encoder magnetic ring; 19. Back shell; 20. Bracket; 21. Positioning end cover; 22. Input shaft; 23. Input bevel gear; 24. Support bevel gear; 25. Planetary large bevel gear B; 26. Planetary small bevel gear B; 27 Output encoder; 28. Backlash test locking assembly. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art can understand that in the various embodiments of the present invention, many technical details are provided to enable readers to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can be implemented.

[0023] To avoid repetitive language, the "fixed connection" mentioned in the text can be a fixed connection through bolts, rivets, welding, interference fit and spline fit, and technical personnel in this field can choose according to their own needs.

[0024] like Figures 1 to 6 As shown, a planetary dual differential robot joint of the present invention includes a housing, a gear transmission system, a motor, an encoder, a controller, a driver and other fixed parts. The gear transmission system, the motor, the encoder, the controller and the driver are integrated through the housing.

[0025] The front shell 6, the rear shell 19 and the outer shell 8 are fixed by bolts, and the joint surface is coated with silicone-based sealant. The bearing seat hole is reserved inside the shell for installing the support shaft, gears and bearings. The motor stator 11 is fixed to the inner wall of the outer shell 8 by interference fit or bonding. The stator winding adopts H-class insulating enameled wire with a slot fill rate of ≥85%. The motor rotor 12 is fixed to the motor output component 13 by interference fit or bonding, and the motor output component 13 is fixed to the input shaft 22 by interference fit or bonding.

[0026] The input bevel gear 23 is connected to the input shaft 22 through a spline, and is fixed axially by a retaining ring, with a radial runout of ≤0.02mm. The input bevel gear 23 is meshed with the planetary large bevel gear A7 and the planetary large bevel gear B25 at the same time, and the tooth side clearance is controlled at 0.06-0.08mm by adjusting the gasket. The planetary large bevel gear A7 is fixed to the planetary small bevel gear A10, and the planetary large bevel gear B25 is fixed to the planetary small bevel gear B26. The planetary large bevel gear A7, the planetary small bevel gear A10, the planetary large bevel gear B25 and the planetary small bevel gear B26 are connected in series through the planetary shaft 9, and can disturb the rotation of the planetary shaft 9. The planetary small bevel gears 10 and 26 are meshed with the supporting bevel gear 24 and the output bevel gear 4, and the output bevel gear is fixed to the output shaft 1 through an expansion sleeve, and the end face flatness of the output flange 2 is ≤0.01mm.

[0027] The input encoder magnetic ring 18 is bolted to the motor output assembly 13, with a radial spacing of 0.5mm from the encoder and a resolution of 0.005° (17-bit absolute encoder). The input encoder 14 is fixed to the control bracket 15. The output encoder magnetic ring 3 is fixed to the output flange 2, with a radial spacing of 0.5mm from the encoder and a resolution of 0.005° (17-bit absolute encoder). The output encoder 27 is fixed to the front shell 6.

[0028] The control board 16 and the PCB board 17 are fixed to the control bracket 15 by screws. The control board is equipped with an ARM Cortex-M7 processor, runs an ADRC algorithm, and has a sampling frequency of 10kHz. The signal line uses a shielded twisted pair cable and supports CAN FD communication (baud rate 10Mbps). The control module can be waterproofed with glue.

[0029] The bevel gear can adjust the reduction ratio by adjusting the difference in the number of teeth of the mutually meshing gears and adjusting the basic parameters of the gears, and the reduction ratio range can reach 0-300. The joint transmission structure is extensible, and the external motor can be connected to the large bevel gear 5 to achieve dual input; the external output shaft can be connected to the supporting bevel gear 24 to achieve dual output.

[0030] The output shaft 1 is suddenly subjected to a reverse torque of 10 N·m through a hydraulic servo cylinder, and the planetary large bevel gear (7, 25) and the planetary small bevel gear (10, 26) rotate differentially and revolve around the planetary shaft 9 and the supporting bevel gear 24 to store kinetic energy. The output shaft 1 speed is reduced to 0, and the impact energy absorption efficiency is ≥85%.

[0031] The hysteresis test locks the input shaft, uses the hysteresis test locking assembly 28 to fix the input shaft 22, and performs hysteresis measurement of angular displacement at the output end, and the measured hysteresis is ≤1 arcmin.

[0032] According to the above embodiments, the integration, high precision and high dynamic performance of the robot joints can be well realized. Based on the above technical scheme, in order to solve the same technical problem, even if some non-substantial changes or improvements are made to the present invention, the essence of the technical scheme adopted is still the same as the present invention, so it should also be within the protection scope of the present invention.

Claims

1. A dual differential robot joint, characterized in that: include: Structural components, driving module, sensor module, control module and test module. The structural components connect the control module, sensor module and driving module to achieve an integrated design. The structural component is used to integrate various modules of the joint, including: a front shell, an outer shell, a rear shell, a motor output component, and an input shaft. The outer shell is respectively fixedly connected to the front shell and the rear shell, the stator in the motor output component is fixedly connected to the internal structure of the outer shell, and the input shaft is fixedly connected to the motor output component. The double differential reducer in the drive module provides a power source; the drive module is used for power transmission and power output of the joint, and the drive module includes: an outer rotor motor, a double differential reducer, and the motor rotor is fixedly connected to the motor output component; the sensor module is used to sense the angle changes of the input and output ends of the joint in real time, and provide real-time feedback, and the sensor module includes an input end encoder The encoder, the output end encoder, the input end encoder magnetic ring and the motor output component are fixedly connected, the input end encoder signal acquisition board is fixedly connected to the control bracket, the output end encoder magnetic ring is fixedly connected to the shell, and the output end encoder signal acquisition board is fixedly connected to the output flange; the control module is used for real-time control adjustment, feedback adjustment, self-disturbance rejection adjustment, and current position speed loop adjustment. The control module includes: a PCB board and a control board. The control board is fixedly connected to the control bracket, and the PCB board is superimposed on the control board and fixedly connected; the test module is used to perform a hysteresis test on the joint, and the test module includes a hysteresis test locking assembly, which is fixedly connected to the shell to lock the input shaft.

2. A dual differential robot joint according to claim 1, characterized in that: The front shell, the outer shell and the rear shell are provided with threaded holes and fixed shaft sections for fixing the motor stator, the control bracket, the positioning end cover and the output end encoder; the outer rotor motor comprises a stator and a motor rotor, the stator is embedded in the outer shell, the motor rotor and the motor output assembly are bonded by anaerobic adhesive, and the motor output assembly is tightly connected to the input shaft; the dual differential reducer comprises eight bevel gears, a planetary shaft and an output shaft; the motor rotor is fixedly connected to the motor output assembly, the input end encoder magnetic ring is fixedly connected to the motor output assembly, the input end encoder signal acquisition board is fixedly connected to the control bracket, the output end encoder magnetic ring is fixedly connected to the outer shell, the output end encoder signal acquisition board is fixedly connected to the output flange, the control board is fixedly connected to the control bracket, and the PCB board is superimposed on the control board and fixedly connected.

3. A dual differential robot joint according to claim 1, characterized in that: The input shaft drives the input bevel gear by connecting with the input bevel gear including a spline. The input bevel gear meshes with the planetary large bevel gear A and the planetary large bevel gear B to form a first-stage differential. The planetary large bevel gear A and the planetary large bevel gear B are connected to the planetary small bevel gear A and the planetary small bevel gear B through the planetary shaft, mesh with the supporting bevel gear and the output bevel gear, and finally drive the output shaft. By replacing the difference in the number of teeth of the planetary gear set, the reduction ratio is expanded without changing the overall dimensions. The input encoder is coaxially installed with the input encoder magnetic ring, with a resolution of 0.005°; the output encoder is coaxially installed with the output encoder magnetic ring, with a resolution of 0.005°; the PCB board is installed on the control bracket, integrated with the signal conditioning circuit, and supports CAN FD communication; the control board is installed on the control bracket, and cooperates with the PCB board to perform self-disturbance rejection control and feedback adjustment.

4. A dual differential robot joint according to claim 1, characterized in that: Transmission error ≤ 1 arcmin, backlash ≤ 1 arcmin; planetary large bevel gear A, planetary small bevel gear A, planetary large bevel gear B, planetary small bevel gear B are symmetrically distributed, and load balance ≥ 95%.

5. The dual differential robot joint according to claim 1, characterized in that: The anti-disturbance control is coordinated through the control board, PCB board, and double-end encoder. The extended state observer estimates the internal / external disturbance of the joint in real time and compensates through nonlinear feedback. The response time is ≤2ms. The real-time compensation of transmission error collects angle information in real time through the encoders at both ends, and feeds it back to the control module for real-time input end compensation to improve transmission accuracy.

6. A dual differential robot joint according to claim 1, characterized in that: When the external impact force drives the output shaft 1 to move in the opposite direction, the planetary gears rotate differentially and store the kinetic energy in the system inertia; the structural shell is driven instantaneously, and the motor is instantaneously overloaded to drive the planetary gears to revolve synchronously, releasing the stored kinetic energy, and the peak torque is increased by 50%.

7. A dual differential robot joint according to claim 1, characterized in that: By adjusting the difference in the number of teeth at each level or replacing the gear set, it can be expanded into a multi-degree-of-freedom joint or the torque-speed characteristics can be adjusted, and dual output capacity can be achieved. The dual output capacity is based on changing the structure and is expanded to planetary gear revolution output and large bevel gear output; the multi-degree-of-freedom output capacity is achieved by adjusting the structure.

8. The dual differential robot joint according to claim 1, characterized in that: The joint input end can be locked by fixing the hysteresis test locking assembly to the housing, providing conditions for the joint hysteresis test.

Images