A structure and method for suppressing radial shaking of motor joints of a robotic arm

Abstract

The present invention discloses a structure and method for suppressing radial shaking of a motor joint of a robot arm. The present invention can effectively suppress shaking of the end of the robot arm caused by radial shaking of the output end of the motor itself. For a robot arm whose integrated motor reducer section adopts a gear reducer and cooperates with a non-crossed roller bearing output, the output shaft of the integrated motor has a large radial shaking due to the influence of the radial clearance of the gear system and the radial clearance of the bearing. For a robot arm directly driven by a motor, the radial shaking of the output shaft will be amplified at the end of the robot arm, seriously affecting the trajectory accuracy of the end of the robot arm. The present invention designs a shaking suppression structure outside the output shaft of the integrated motor, provides a configuration strategy for the entire robot arm and a design method for core parts, and increases radial support for the output shaft, so that the radial shaking of the end of the robot arm is suppressed and the trajectory accuracy of the end is improved.

Description

Technical Field

[0001] The present invention belongs to the field of robotic arm structure design, and particularly relates to a structure and method for suppressing radial wobbling of the electric joints of a robotic arm. Background Art

[0002] The usage scenarios of robotic arms are becoming increasingly diverse. With the gradual advancement of industrialization, the lightweighting and cost control of robotic arms have always been important focuses. For robotic arms using integrated motors, it is a common low-cost and lightweight solution to use a gear train for speed reduction in the reducer part and output with a non-crossed roller bearing. However, for the output with a non-crossed roller bearing, such as using a deep groove ball bearing, due to the existence of the radial clearance of the bearing itself and the radial clearance of the gear train, there will be a certain radial wobbling of the output shaft; as Figure 1 shown, the wobbling in the rotational directions of the joint around the Y-axis and Z-axis is the radial wobbling. When this wobbling of the output shaft of the integrated motor is transmitted to the end of the robotic arm, this radial wobbling will be amplified, and the farther the output shaft of the motor is from the arm end, the greater the amplification degree of this wobbling. For usage scenarios with high requirements for the trajectory accuracy of the robotic arm end, such as piano playing, etc., measures need to be taken to suppress the radial wobbling of the robotic arm.

[0003] In the prior art, a robotic arm and a robotic arm joint assembly disclosed in Chinese Patent CN 211842071 U add an annular elastic member between two parallel planes that move relatively up and down in the joint, and the upper and lower parallel planes are normally pressed against the annular elastic member. When the upper and lower parallel planes rotate relatively parallel, the annular elastic member is tangentially rubbed to generate damping, thereby achieving the effect of improving the wobbling of the joint with gravity. What this patent improves is Figure 1 the wobbling around the X-axis, and at the same time, the root cause of this wobbling is the circumferential backlash existing in the motor reducer. This patent only makes this wobbling less noticeable by increasing damping, but does not fundamentally eliminate the cause of the wobbling. Summary of the Invention

[0004] In view of the deficiency in the prior art that there is no method for improving the radial wobbling of a robotic arm under a low-cost motor solution, the present invention provides a structure and method for suppressing the radial wobbling of the electric joints of a robotic arm.

[0005] The object of the present invention is achieved through the following technical solutions: A structure for suppressing the radial wobbling of the electric joints of a robotic arm includes an auxiliary bearing, an extension shaft, and an extension housing; wherein, the extension shaft is fixedly connected to the motor output shaft; the auxiliary bearing is installed on the extension shaft; the extension housing is sleeved outside the auxiliary bearing and fixedly connected to the motor main body; a shoulder is provided on the extension shaft in the circumferential direction for axially positioning one side of the auxiliary bearing; and a circle of ribs is provided on the inner circumference of the extension housing for axially positioning the other side of the auxiliary bearing.

[0006] Furthermore, it also includes a first structural member; the extension shell is fixedly connected to the motor body through the first structural member.

[0007] Furthermore, it also includes a second structural member; the second structural member is used to transmit the output torque and is fixedly connected to the extension shaft.

[0008] Furthermore, round bosses are provided at both ends of the extension shaft, one end is used for centering and positioning assembly with the motor output shaft, and the other end is used for centering and positioning assembly with the second structural member.

[0009] Furthermore, a circular hole is provided on the second structural member for centering and positioning with the circular boss at one end of the extension shaft.

[0010] Furthermore, the second structural member is provided with a boss, which is used to just butt against the inner ring of the auxiliary bearing when assembled with the extension shaft.

[0011] A method for suppressing radial shaking of the end of a robot arm comprises configuring a structure for suppressing radial shaking of the joint of the motor of the robot arm for each joint motor of the robot arm; setting the length of the extension shaft according to the distance between the joint and the end of the robot arm, the clearance of the bearing of the motor output shaft, the clearance of the auxiliary bearing, and the trajectory accuracy requirement of the end of the robot arm.

[0012] Furthermore, the length L of the extension axis is set ext , specifically:

[0013]

[0014] Among them, L out is the length of the motor output shaft, Cr1 is the radial clearance of the motor output shaft bearing, Cr2 is the radial clearance of the auxiliary bearing; n is the number of motor joints; L i W is the arm length between motor i and motor i+1 or the end of the robot arm; i W is the offset caused by the radial shake output at motor i at motor i+1 or at the end of the robot arm; d It is the allowable total offset caused by the superposition of the radial shakes output by all motors at the end of the robot arm; || represents the modulus.

[0015] Furthermore, if the extension axes of the joints of the same robot arm can be shared, that is, the lengths of the extension axes are the same, then W i With L i The numerical relationship is directly proportional; each L i The value can be measured to obtain the offset W of each joint i , find the length of the extended axis:

[0016]

[0017] Where C is a constant.

[0018] Further, if the common extension axes of each joint are not considered, the offset W of each joint i and L i Numerically, it is calculated according to a directly proportional relationship, or W is given separately by any segmentation method i , as long as it satisfies: |W1| + |W2| + … + |W n | ≤ |W d |.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The present invention can effectively reduce the sway at the end of the robotic arm caused by the integrated motor itself, improve the trajectory accuracy at the end of the robotic arm, and enable the robotic arm to be applicable to more application scenarios with high precision requirements;

[0021] (2) The present invention can achieve the effect of suppressing the sway of the robotic arm by increasing a relatively small cost, providing a practical method for robotic arms with high cost limitations;

[0022] (3) The present invention is a method for suppressing radial sway that is generally applicable to single-degree-of-freedom and multi-degree-of-freedom robotic arms, with a simple supporting structure and good stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of the sway degrees of freedom in each direction of the joints of the integrated motor of the robotic arm;

[0024] Figure 2 is a schematic diagram of the structure for suppressing radial sway designed at the output shaft of the integrated motor;

[0025] Figure 3 is a schematic diagram of the layout of the integrated motor of the robotic arm and the corresponding arm lengths;

[0026] Figure 4 is an exploded view of the structure for suppressing radial sway in an embodiment;

[0027] Figure 5 is a structural configuration diagram of the entire arm for suppressing radial sway in an embodiment;

[0028] In the figure: integrated motor 1-1, radial shaking suppression structure 1-2, integrated motor fixed body 2-1, motor output shaft bearing 2-2, auxiliary bearing 2-3, second structural member 2-4, motor output shaft 2-5, extension shaft 2-6, extension shell 2-7, first structural member 2-8, motor No. i 3-1, robot arm end 3-2, circular boss 4-1, shaft shoulder 4-2, rib 4-3, circular hole 4-4, boss 4-5, first motor 5-1, second motor 5-2, third motor 5-3, third motor output end 5-4, second motor output end 5-5, first motor output end 5-6. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 As shown, for the joint in which the integrated motor 1-1 is arranged along the X-axis direction of the robot arm, that is, the axis of the integrated motor 1-1 coincides with the axis of the robot arm (X-axis), a radial shaking suppression structure 1-2 is designed at the output shaft of the integrated motor 1-1 to increase the radial support of the output shaft, so that the radial shaking of the robot arm is suppressed and the end trajectory accuracy is improved.

[0031] The present invention provides a structure for suppressing radial shaking of a motor joint of a mechanical arm, such as Figure 2 As shown, the radial shaking suppression structure 1-2 includes an auxiliary bearing 2-3, an extension shaft 2-6, and an extension housing 2-7. The robot arm is provided with a first structural member 2-8 and a second structural member 2-4. Among them, the extension shaft 2-6 is fixedly connected to the motor output shaft 2-5 by screws; the auxiliary bearing 2-3 is installed on the extension shaft 2-6; the extension housing 2-7 is sleeved outside the auxiliary bearing 2-3, and is fixedly connected to the first structural member 2-8 for installing the integrated motor fixed body 2-1 by screws; the second structural member 2-4 for transmitting the output torque is fixedly connected to the extension shaft 2-6 by screws. In this way, the motor output shaft 2-5 and the extension shaft 2-6 are connected by screws to form an integrated shaft, and the integrated shaft has two bearings, the motor output shaft bearing 2-2 and the auxiliary bearing 2-3.

[0032] like Figure 4As shown, a circular boss 4-1 structure is designed at both ends of the extension shaft 2-6, one end is used for centering and positioning assembly with the motor output shaft 2-5, and the other end is used for centering and positioning assembly with the second structural member 2-4. The extension shaft 2-6 is provided with a shoulder 4-2 protrusion in the circumference, which is used for axial positioning of one side of the auxiliary bearing 2-3. A circle of raised ribs 4-3 is provided in the inner circumference of the extension housing 2-7, which is used for axial positioning of the other side of the auxiliary bearing 2-3. A circular hole 4-4 is provided on the second structural member 2-4, which is used to match the circular boss 4-1 at one end of the extension shaft 2-6 for centering and positioning. The second structural member 2-4 is provided with a boss 4-5, which can just press the inner ring of the auxiliary bearing 2-3 when assembled with the extension shaft 2-6.

[0033] The present invention provides a method for suppressing radial shaking of the end of a mechanical arm. For the entire mechanical arm, each joint motor that coincides with the axial direction of the mechanical arm can be configured with a radial shaking suppression structure 1-2. The mechanical arm can be single-degree-of-freedom or multi-degree-of-freedom.

[0034] like Figure 3 As shown, according to the distance between the joint and the end 3-2 of the robot arm, the clearance of the bearing 2-2 of the motor output shaft, the clearance of the auxiliary bearing 2-3, the trajectory accuracy requirements of the end 3-2 of the robot arm, etc., the length of the extension shaft 2-6 is set, specifically:

[0035]

[0036] Among them, L ext The length of the extended axis 2-6, L out is the length of the motor output shaft 2-5, Cr1 is the radial clearance of the motor output shaft bearing 2-2, and Cr2 is the radial clearance of the auxiliary bearing 2-3; n is the number of integrated motor joints arranged in the axial direction of the robot arm; L i W is the arm length between motor i and motor i+1 (or the end 3-2 of the robot arm); i W is the offset caused by the radial shake output at motor i at motor i+1 (or at the end of the robot arm 3-2); d It is the allowable value of the total offset caused by the superposition of the radial shaking output by all motors at the end 3-2 of the robot arm; || represents the modulus.

[0037] If it is considered that the extension axes 2-6 of the joints of the same robot arm can be shared, that is, the lengths of the extension axes 2-6 are the same, then W i With L i The numerical relationship is proportional. According to the mechanical arm, each L i Value, so that the offset W of each joint can be obtained i , thus the length of the extended axis 2-6 can be calculated.

[0038]

[0039] Where C is a constant.

[0040] If the shared extension axis of each joint is not considered in engineering, the offset of each joint W i With L i The numerical value can still be calculated in direct proportion, or W can be given by any division method. i , as long as the following relationship is satisfied, the applicability of the method of the present invention will not be affected:

[0041] |W1|+|W2|+…+|W n |≤|W d |.

[0042] like Figure 5 As shown, an embodiment of calculating the length of the extension shaft 2-6. The axial distance (measured from output shaft to output shaft) of the straightened joint between the first motor 5-1 and the second motor 5-2 is L1=175mm; the axial distance (measured from output shaft to output shaft) of the straightened joint between the second motor 5-2 and the third motor 5-3 is L2=225mm; the axial distance (measured from output shaft to output shaft) of the straightened joint between the third motor 5-3 and the end 3-2 of the robotic arm is L3=350mm. The radial clearance Cr1 of the motor output shaft bearing 2-2 is 0.064mm, and the radial clearance Cr2 of the auxiliary bearing 2-3 is 0.064mm. The length L of the motor output shaft 2-5 out =10mm.

[0043] Under the specific working conditions of this embodiment, the total offset allowable value W generated by the superposition at the end 3-2 of the robot arm is d =3mm. In order to facilitate the reuse of parts in engineering, the lengths of the extension shafts 2-6 are designed to be the same, that is, L1 / L2 / L3=7 / 9 / 14, then W1 / W2 / W3=7 / 9 / 14, and W1≤0.7mm, W2≤0.9mm, W3≤1.4mm are obtained; finally, L is calculated. ext ≥6mm.

[0044] Since the axes of the first motor 5-1, the second motor 5-2, and the third motor 5-3 all coincide with the X-axis of the robot arm, three sets of radial shaking suppression structures 1-2 need to be designed respectively, which are respectively arranged at Figure 5 The first motor output terminal 5-6, the second motor output terminal 5-5, and the third motor output terminal 5-4 are located in the three positions. At the same time, the length of the extension shaft 2-6 in the designed radial shaking suppression structure 1-2 must be no less than 6mm. Therefore, the total radial offset of the robot end 3-2 caused by the integrated motor 1-1 itself can be controlled within 3mm.

Claims

1. A structure for suppressing the radial sway of the electric motor joint of a robotic arm, characterized in that, It includes an auxiliary bearing, an extension shaft, and an extension housing; wherein the extension shaft is fixedly connected to the motor output shaft; the auxiliary bearing is mounted on the extension shaft; the extension housing is sleeved outside the auxiliary bearing and fixedly connected to the motor body; a shoulder is provided in the circumferential direction of the extension shaft for axial positioning of one side of the auxiliary bearing; a circle of ribs is provided in the inner circumferential direction of the extension housing for axial positioning of the other side of the auxiliary bearing; The configuration method of the structure is as follows: the length of the extension shaft is set according to the distance between the joint and the end of the robot arm, the clearance of the bearing of the motor output shaft, the clearance of the auxiliary bearing, and the trajectory accuracy requirements of the end of the robot arm; Set the length L of the extension axis ext , specifically: Among them, L out is the length of the motor output shaft, Cr1 is the radial clearance of the motor output shaft bearing, Cr2 is the radial clearance of the auxiliary bearing; n is the number of motor joints; L i W is the arm length between motor i and motor i+1 or the end of the robot arm; i W is the offset caused by the radial shake output at motor i at motor i+1 or at the end of the robot arm; d It is the allowable total offset caused by the superposition of the radial shakes output by all motors at the end of the robot arm; || represents the modulus.

2. The structure for suppressing the radial sway of the robotic arm motor joint according to claim 1, wherein It also includes a first structural member; the extension shell is fixedly connected to the motor body through the first structural member.

3. The structure for suppressing the radial sway of the robotic arm motor joint according to claim 1, wherein It also includes a second structural member; the second structural member is used for transmitting output torque and is fixedly connected to the extension shaft.

4. The structure for suppressing the radial sway of the robotic arm motor joint according to claim 3, wherein, Round bosses are provided at both ends of the extension shaft, one end is used for centering and positioning assembly with the motor output shaft, and the other end is used for centering and positioning assembly with the second structural member.

5. The structure for suppressing the radial wobbling of the robotic arm motor joint according to claim 4, wherein The second structural member is provided with a circular hole for centering and positioning with the circular boss at one end of the extension shaft.

6. The structure for suppressing the radial wobbling of the robotic arm motor joint according to claim 3, wherein The second structural member is provided with a boss, which is used to just butt against the inner ring of the auxiliary bearing when assembled with the extension shaft.

7. A method for suppressing the radial sway at the end of a robotic arm, characterized in that, For each joint motor of the robot arm, the structure described in any one of claims 1 to 6 is configured; the length of the extension shaft is set according to the distance between the joint and the end of the robot arm, the clearance of the bearing of the motor output shaft, the clearance of the auxiliary bearing, and the trajectory accuracy requirements of the end of the robot arm; Set the length L of the extension axis ext , specifically: Among them, L out is the length of the motor output shaft, Cr1 is the radial clearance of the motor output shaft bearing, Cr2 is the radial clearance of the auxiliary bearing; n is the number of motor joints; L i W is the arm length between motor i and motor i+1 or the end of the robot arm; i W is the offset caused by the radial shake output at motor i at motor i+1 or at the end of the robot arm; d It is the allowable total offset caused by the superposition of the radial shakes output by all motors at the end of the robot arm; || represents the modulus.

8. The method for suppressing the radial sway at the end of the robotic arm according to claim 7, wherein If the extension axes of the joints of the same robotic arm can be shared, that is, the lengths of the extension axes are the same, then W i is numerically proportional to L i ; each L i value can be measured, so as to obtain the offset W i of each joint, and calculate the length of the extension axis: Where C is a constant.

9. The method for suppressing the radial sway at the end of the robotic arm according to claim 7, wherein If the common extension axes of each joint are not considered, the offset W of each joint i and L i Numerically, it is calculated according to a directly proportional relationship, or W is given separately by any segmentation method i , as long as it satisfies: |W1| + |W2| + … + |W n | ≤ |W d |.

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