Customized multi-motor driven robot joint and motor double-loop control method

Abstract

The invention discloses a customized multi-motor driven robot joint and a motor double-loop control method, and belongs to the technical field of robots, the customized multi-motor driven robot joint comprises a shell, a hollow shaft and a driving assembly, the driving assembly comprises gears and motors, and the output end of each motor is provided with a gear; the hollow shaft is rotatably arranged in the shell, and inner teeth meshed with the gear are arranged on the inner wall of the hollow shaft; the output disc is connected with the hollow shaft. The control method is used for controlling the robot joint and comprises the steps of initializing a system, recognizing the number of motors and ports, switching modes according to needs, automatically switching multi-motor control modes, receiving instruction positions by the dynamic bias torque controller, dynamically calculating bias currents of all paths and controlling rotation programs of all the motors. According to the method, the change of the joint quality and the output torque is realized by customizing the number of the motors under the condition of not changing the boundary dimension of the joint, the transmission back clearance can be eliminated based on the position-current double-loop control method, and the dynamic following performance and the control precision of the joint are improved.

Description

Technical Field

[0001] The present invention relates to a robot joint and a control method, and more particularly to a customized multi-motor driven robot joint and a dual-loop control method for motors, belonging to the technical field of robots. Background Art

[0002] With the continuous development of robot technology, robot joints, as key components for motion and control, carry important functions, especially in the fields of industrial robots, service robots, and medical robots. As the most common robot joint, the rotary joint is used to output torque and rotation angle, and generally consists of a motor, a reducer, a controller, etc. Most traditional robot joint drive methods rely on single-motor drive, which is technically mature, but there are certain limitations in terms of accuracy, load adaptability, response speed, and reliability.

[0003] A large number of joints are required in robots, and the requirements for load, response speed, accuracy, etc. of joints at different positions may vary. In view of this characteristic, in traditional robot research and development, robot joints with different structural dimensions are designed to match the requirements.

[0004] At the same time, since traditional robot joints are driven by a single motor, additional planetary reducers, harmonic reducers, etc. are required to reduce the speed and amplify the torque, which further increases the size and mass of the joints. Especially in the miniaturized design of robot joints, it is difficult to balance the size and performance. There is still a certain market gap in small-sized, desktop-level robot joints, which has great market potential.

[0005] In summary, how to achieve small size, large torque, zero transmission backlash, and high transmission accuracy has become an urgent problem for those skilled in the art. Summary of the Invention

[0006] To overcome the deficiencies of the prior art, the present invention proposes a customized multi-motor driven robot joint and a dual-loop control method for motors. Under the condition of ensuring the same external dimension of the joint, by customizing the number of motors and the adaptive control method, the mechanical difficulty of the robot body design is greatly simplified, and more targeted performance advantages are provided, which can achieve small size, large torque, zero transmission backlash, and high transmission accuracy.

[0007] A customized multi-motor driven robot joint includes:

[0008] A housing for accommodating the drive assembly;

[0009] The drive assembly includes N gears and N motors, where N≥2, and a gear is installed at the output end of each motor;

[0010] The hollow shaft is rotatably arranged inside the housing, and internal teeth meshing with the gear are provided on the inner wall of the hollow shaft;

[0011] The output disk is connected to the hollow shaft and is used to configure robots with different configurations.

[0012] A dual-loop control method for motors is used to control the robot joints. The method includes the following steps: system initialization, identifying the number of motors and ports, automatically switching the multi-motor control mode, the dynamic bias torque controller receiving the command position, dynamically calculating the bias current of each path, and controlling the rotation of each motor.

[0013] The reduction ratio of the internal teeth to the gear is 1:4.

[0014] Further, in the dual-loop control method for motors:

[0015] The input quantity of the current loop is calculated in the position loop, and the output quantity of the current loop is calculated in the current loop;

[0016] In the position loop, the difference between the command position and the actual position obtained through the position feedback module is calculated, which is the position following error. The position following error passes through the position PID control to output a voltage to the dynamic bias torque controller, and the dynamic bias torque controller calculates the input quantity of the current loop;

[0017] In the current loop, the difference between the input quantity of the current loop and the torque obtained through the current feedback module is calculated, which is the torque following error. The torque following error passes through the current PID adjustment and is converted into a signal that can be accepted by the drive chip, and is converted into a current by the drive chip and sent to the motor to control the operation of the motor.

[0018] The beneficial effects of the present invention compared with the prior art:

[0019] 1. The joint structure is compact and has a high integration degree. A planetary gear transmission with a reduction ratio of 1:4 is designed, and multi-motor drive is introduced to achieve a small size and a large output torque.

[0020] 2. The joint can also customize the number of drive motors to achieve dynamic adjustment of the rated output torque and mass of the joint.

[0021] 3. By adjusting the number of internal motors of the joint, the consistency of the external dimensions is ensured, the reuse of the housing is realized, and the design and manufacturing costs are reduced.

[0022] 4. The multi-motor dual-loop control strategy of the joint realizes the adaptability of the number of motors and the dynamic bias torque control based on the position-current dual loop, can eliminate the transmission backlash, and improves the dynamic following performance and control accuracy of the joint.

[0023] The following further illustrates the solution of the present application with reference to the drawings and embodiments: Description of the Drawings

[0024] Figure 1 This is a perspective view of a customized multi-motor driven robot joint of the present application;

[0025] Figure 2 is Figure 1 a sectional view of;

[0026] Figure 3 is a dual-motor drive mode diagram;

[0027] Figure 4 is a three-motor drive mode diagram;

[0028] Figure 5 is a four-motor drive mode diagram;

[0029] Figure 6 is a six-motor drive mode diagram;

[0030] Figure 7 is a multi-motor dual-loop control flow diagram;

[0031] Figure 8 is a dynamic bias torque control system diagram based on a position-current dual loop. Detailed implementation manners

[0032] The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the technical terms or scientific terms used in the present application have the ordinary meanings understood by those skilled in the art.

[0033] Traditional robot joints are driven by a single motor, and additional planetary reducers, harmonic reducers, etc. are required to reduce the rotational speed and amplify the torque, further increasing the size and mass of the joints. Especially in the miniaturized design of robot joints, it is difficult to balance the size and performance. There is still a certain market gap in small, desktop-level robot joints, which has great market potential.

[0034] In view of this, a customized multi-motor driven robot joint and a multi-motor dual-loop control method for controlling the position of the joint are provided.

[0035] Referring to Figure 1 and Figure 2 , a customized multi-motor driven robot joint provided by this embodiment includes a housing 1, a gear 4, a motor 5, an output disk 7, and a hollow shaft 9;

[0036] A middle partition platform is arranged inside the housing 1. N gears 4 and N motors 5 are respectively arranged on both sides of the middle partition platform, where N > 1. The hollow shaft 9 is rotatably arranged inside the housing 1. The hollow shaft 9 is connected with an internal gear ring. The output end of each motor 5 is equipped with a gear 4, and the gear 4 meshes with the internal gear ring. The output end of the hollow shaft 9 is connected with an output disc 7.

[0037] This embodiment makes full use of the advantages of planetary gear transmission, provides motors for the gears, and realizes multi-motor parallel drive. The middle partition platform is used to arrange the gears 4 and motors 5. The gears 4 are located on one side of the middle partition platform to achieve rotation, and the motors 5 are fixed on the other side of the middle partition platform for driving.

[0038] The robot joint of this embodiment realizes drive and control integration, has high integration and a compact structure. The output disc 7 can be configured with different configurations of robots to form various configurations such as robotic arms, snake-like robots, and biped robots.

[0039] Preferably, the housing 1 is a cylindrical housing (such as a cylindrical shell). Upper end covers 2 and bottom end covers 3 are arranged at the relatively two axial ends of the housing 1. Relative rotation between the upper end cover 2 and the hollow shaft 9 is realized through a bearing 8. The outside of the bearing 8 (such as a crossed roller bearing) is fixed to the upper end cover 2 through the cylindrical shell. The output disc 7 and the output shaft 9 are fixed inside the bearing 8 to realize relative rotation of the joint.

[0040] The control board 6 is located below the motor and fixed on the bottom end cover 3, and is used to control the rotation of the gears driven by multiple motors to realize precise adjustment of the joint position.

[0041] Optionally, referring to Figures 3 - 6 , the number N of the gears 4 or motors 5 is three, four, five or six. With such a setting, the miniaturized design is ensured, and the output torque and motion accuracy are greatly improved.

[0042] Optionally, the number of teeth of the internal gear ring and the gear 4 are 80 and 20 respectively, the module is 0.5, and the reduction ratio is 1:4 to realize multi-motor parallel drive. By customizing the number of motors, various configurations such as single-motor, dual-motor, triple-motor, quadruple-motor, and six-motor can be realized, so as to change the joint mass and output torque without changing the external dimensions of the joint.

[0043] Mounting holes for assembling robots are distributed on the upper end cover 2 and the bottom end cover 3. It is convenient to form various configurations of robots, such as forming various configurations such as robotic arms, snake-like robots, and biped robots.

[0044] Based on the robot joint with the above structure, a set of parameters of the robot joint of an embodiment is provided:

[0045] Joint mass: 230 - 380 g, varying with the number of motors;

[0046] Envelope size: 60×60×60mm 3

[0047] Operating voltage: 12V

[0048] Rated load: 2 - 12 Nm, varying with the number of motors.

[0049] Refer to Figure 7 , a multi - motor double - loop control method is provided for controlling the robot joint. The method includes the following steps: system initialization, identifying the number of motors and ports, automatically switching the multi - motor control mode according to the mode to be switched, the dynamic bias torque controller receiving the command position, dynamically calculating the bias current of each path, and controlling the rotation of each motor.

[0050] Further, as Figure 8 shown, in the multi - motor double - loop control method,

[0051] The input quantity of the current loop is calculated in the position loop, and the output quantity of the current loop is calculated in the current loop;

[0052] In the position loop, calculate the difference between the command position and the actual position obtained through the position feedback module, which is the position following error. The position following error passes through the position PID control to output a voltage to the dynamic bias torque controller, and the dynamic bias torque controller calculates the input quantity of the current loop; the position feedback module realizes position feedback;

[0053] In the current loop, calculate the difference between the input quantity of the current loop and the torque obtained through the current feedback module, which is the torque following error. The torque following error passes through the current PID adjustment and is converted into a signal that can be accepted by the drive chip. The drive chip converts it into a current and sends it to the motor to control the operation of the motor. The current feedback module realizes current feedback.

[0054] The actual position obtained by the position feedback module is measured by the position encoder of the joint position.

[0055] The dynamic bias torque controller is arranged on the control board 6, and the control board 6 is installed on the bottom cover 3 of the housing.

[0056] Based on the above multi-motor double-loop control method, the adaptability of the number of motors and the dynamic bias torque control based on the position-current double-loop are realized. The position PID-current PID double-loop control is adopted, omitting the speed closed-loop, which can improve the control bandwidth and achieve better position response performance. At the same time, in a robot joint driven by multiple motors, multiple motors need to work in coordination to ensure the smooth and precise movement of the joint. Due to complex factors such as mechanical errors, uneven loads, friction, and elastic deformation in the multi-motor system, traditional control methods cannot completely eliminate these influences, while the dynamic bias torque control compensates for the dynamic errors, external disturbances, or uncertainties of the system by calculating the bias torque of each motor in real time, thereby maintaining the motion stability and accuracy of the robot.

[0057] Based on the above solution, an embodiment of a six-degree-of-freedom robotic arm composed of the robot joints of the present application is provided: Connecting six robot joints to the corresponding robotic arm rods to achieve six-joint series connection can form a small desktop robotic arm.

[0058] Among them, the two joints close to the base are driven by six motors to provide the maximum output torque; the two middle joints are driven by four motors, which can reduce a certain mass and also meet the motion requirements; the two end joints are driven by two motors, further reducing the end mass and retaining the backlash elimination ability of the two-motor drive, ensuring the output torque and control accuracy.

[0059] The present application has been disclosed above with preferred embodiments. However, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, can make some modifications or decorations to equivalent changes using the disclosed structure and technical content, and they are still within the scope of the technical solution of the present application.

Claims

1. A customized multi-motor-driven robot joint, characterized in that: Comprising: A housing (1) for accommodating a drive assembly; The drive assembly includes N gears (4) and N motors (5), where N ≥ 2, and a gear (4) is mounted on the output end of each motor (5); A hollow shaft (9) rotatably disposed within the housing (1), and internal teeth meshing with the gears (4) are provided on the inner wall of the hollow shaft (9); An output disk (7) connected to the hollow shaft (9) for configuring robots with different configurations.

2. The customized multi-motor driven robot joint according to claim 1, wherein: The reduction ratio of the internal teeth to the gears (4) is 1:

4.

3. The customized multi-motor driven robot joint according to claim 1, characterized in that: The number N of the gears (4) or motors (5) is three, four, five, or six.

4. The customized multi-motor driven robot joint according to claim 1, wherein: The housing (1) is a cylindrical housing, and an upper end cover (2) and a bottom end cover (3) are provided at opposite axial ends of the housing (1), and relative rotation between the upper end cover (2) and the hollow shaft (9) is achieved through a bearing (8).

5. The customized multi-motor driven robot joint according to claim 4, wherein: Mounting holes for assembling into a robot are distributed on the upper end cover (2) and the bottom end cover (3).

6. A dual-loop control method for a motor, characterized in that: For controlling the robot joint according to any one of claims 1 - 3, the method includes the following steps: system initialization, identifying the number of motors and ports, automatically switching the multi-motor control mode, the dynamic bias torque controller receiving the command position, dynamically calculating the bias current for each path, and controlling the rotation of each motor.

7. The method for dual-loop control of a motor according to claim 6, wherein: The input quantity of the current loop is calculated in the position loop, and the output quantity of the current loop is calculated in the current loop; In the position loop, the difference between the command position and the actual position obtained through the position feedback module is calculated, which is the position following error. The position following error passes through position PID control to output a voltage to the dynamic bias torque controller, and the dynamic bias torque controller calculates the input quantity of the current loop; In the current loop, the difference between the input quantity of the current loop and the torque obtained through the current feedback module is calculated, which is the torque following error. The torque following error passes through current PID regulation and is converted into a signal acceptable to the drive chip, and is converted into a current by the drive chip and sent to the motor to control the operation of the motor.

8. The method for dual-loop control of an electric machine according to claim 7, characterized in that: The actual position obtained by position feedback is measured by a position encoder of the joint position.

9. The method for dual-loop control of an electric machine according to claim 7, characterized in that: The dynamic bias torque controller is arranged on a control board (6), and the control board (6) is mounted on the bottom end cover (3) of the housing.

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