CN113276141A

CN113276141A - End effector

Info

Publication number: CN113276141A
Application number: CN202110583386.3A
Authority: CN
Inventors: 王锋辉; 冯蓬勃
Original assignee: Beihang Gol Weifang Intelligent Robot Co ltd
Current assignee: Beihang Gol Weifang Intelligent Robot Co ltd
Priority date: 2021-05-27
Filing date: 2021-05-27
Publication date: 2021-08-20

Abstract

The invention provides an end effector, which comprises a shell, a moving shaft arranged in the shell, a first elastic disc, a second elastic disc and a prestress adjusting screw, wherein the first elastic disc, the second elastic disc and the prestress adjusting screw are sleeved on the moving shaft; wherein, the prestress of the first elastic disc is adjusted by the prestress adjusting screw; the first elastic disc and the second elastic disc are of central symmetry structures, one ends of the first elastic disc and the second elastic disc are respectively fixed on the moving shaft, the other ends of the first elastic disc and the second elastic disc are respectively fixed on the inner wall of the shell, and the first elastic disc and the second elastic disc move under the driving of the moving shaft. The invention can solve the problems of poor control precision and real-time performance, high cost and the like of the existing robot end effector.

Description

End effector

Technical Field

The invention relates to the technical field of robots, in particular to an end effector of a robot.

Background

At present, the robot mainly adopts a pneumatic device as an end effector, and an electrically driven end effector is also adopted in some occasions. The current pneumatic and electric end effectors only achieve simple opening and closing or displacement during the action. In the fields of precise electronic device plugging, fine grinding, space station equipment maintenance and the like, a robot end effector needs to keep constant acting force in the action process; when the end effector adopts a contact force sensor to perform force control or force position hybrid control on a ring, the sensor is difficult to process acquired signals under vibration or severe environment, so that the control precision and the real-time performance are poor.

In addition, in the multi-joint robot, since each joint has a gap, a delay in operation, and a certain degree of flexibility, even if an accurate value of the amount of deviation of the end load is obtained, it is difficult to compensate in real time. In addition, the multi-dimensional force sensor used in cooperation with the end effector is expensive, even close to the price of the robot body, and thus is difficult to be widely used.

In order to solve the above problems, the present invention is directed to a new end effector.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide an end effector to solve the problems of poor control accuracy and real-time performance and high cost of the existing robot end effector.

The invention provides an end effector, which comprises a shell, a moving shaft arranged in the shell, a first elastic disc, a second elastic disc and a prestress adjusting screw, wherein the first elastic disc, the second elastic disc and the prestress adjusting screw are sleeved on the moving shaft,

an end cover is arranged at the top end of the shell and is connected with the prestress adjusting screw; adjusting the prestress of the first elastic disc by the prestress adjusting screw;

the first elastic disc sheet and the second elastic disc sheet are of a central symmetrical structure, one end of the first elastic disc sheet and one end of the second elastic disc sheet are fixed on the movement shaft respectively, the other end of the first elastic disc sheet and the other end of the second elastic disc sheet are fixed on the inner wall of the shell respectively, and the first elastic disc sheet and the second elastic disc sheet move under the driving of the movement shaft.

In addition, it is preferable that the second elastic disk is a bistable elastic disk, wherein,

when the bistable elastic disc is in a first stable position, the fixing point of the bistable elastic disc fixed on the moving shaft is higher than the fixing point of the bistable elastic disc fixed on the inner wall of the shell;

when the bistable elastic disc is in the second stable position, the fixing point of the bistable elastic disc on the moving shaft is lower than the fixing point of the bistable elastic disc on the inner wall of the shell.

Further, it is preferable that the first elastic disk and the second elastic disk are connected in parallel by the moving shaft, and the rigidity of the moving shaft with respect to the housing is a sum of elastic coefficients of the two elastic disks.

Further, it is preferable that the load along the moving shaft is constant when the rigidity of the moving shaft with respect to the housing is zero.

In addition, the preferable structure is that the device also comprises a spring sleeved on the moving shaft, wherein,

the spring is a ripple spring, the ripple spring is limited between the prestress adjusting screw and the first elastic disc, wherein,

the wave spring is compressed by rotating the prestress adjusting screw to adjust the prestress of the first elastic disk.

In addition, it is preferable that the end cap is connected to the prestress adjusting screw by a screw thread.

Further, it is preferable that three bushings are provided inside the housing, wherein,

the two elastic disks fixed on the inner wall of the shell are separated by the three bushings.

In addition, it is preferable that a limit shoulder is provided below the moving shaft, and a flange adapted to the limit shoulder is provided at a central position of a lower end of the housing, wherein,

the limiting shaft shoulder is used for limiting the motion range of the motion shaft and preventing the structure of the end effector from being damaged by overlarge load of the motion shaft;

the flange is used for guiding the moving shaft.

In addition, it is preferable that a mounting hole is provided at a lower end edge position of the housing, and the housing is mounted and fixed to other components through the mounting hole.

According to the technical scheme, the end effector is of a revolving body structure, a moving shaft is arranged in a shell and sleeved on the moving shaft, two elastic discs, a spring and a prestress adjusting screw, wherein the spring is limited between the prestress adjusting screw and the elastic discs, and the prestress of the elastic discs is adjusted by compressing the spring through rotating the prestress adjusting screw; the two elastic disks are of a central symmetrical structure, one ends of the two elastic disks are fixed on the moving shaft, the other ends of the two elastic disks are fixed on the inner wall of the shell, and the two elastic disks move under the driving of the moving shaft. The constant force of the end effector of the invention is kept unchanged, and links and equipment such as a sensor, data acquisition and processing, calculation, feedback control and the like are not included, so the structure is simple and the cost is low.

To the accomplishment of the foregoing and related ends, one or more aspects of the invention comprise the features hereinafter fully described. The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Further, the present invention is intended to include all such aspects and their equivalents.

Drawings

Other objects and results of the present invention will become more apparent and more readily appreciated as the same becomes better understood by reference to the following description and appended claims, taken in conjunction with the accompanying drawings. In the drawings:

FIG. 1 is a schematic cross-sectional view of an end effector according to an embodiment of the present invention;

FIG. 2 is a schematic representation of the displacement of a moving axis versus the load at A, according to an embodiment of the present invention;

FIG. 3 is a diagram illustrating a second stable position of a bistable disk according to an embodiment of the present invention;

FIG. 4 is a schematic representation of the displacement of the moving axis versus the load at B in accordance with an embodiment of the present invention;

FIG. 5 is a schematic diagram of the displacement of a motion axis and its load relationship according to an embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating a principle of changing a constant force by adjusting a pre-tightening force according to an embodiment of the present invention;

FIG. 7 is a schematic view of the installation and operation of an end effector according to an embodiment of the present invention;

FIG. 8 is a perspective view of an end effector according to an embodiment of the present invention;

fig. 9 is a partially cut-away schematic view of an end effector according to an embodiment of the present invention.

Wherein the reference numerals include: 1. the device comprises a shell, 2, a moving shaft, 3, a prestress adjusting screw, 4, an end cover, 5, a spring, 6, a first bushing, 7, a first elastic disc, 8, a second bushing, 9, a second elastic disc, 10, a limiting shaft shoulder, 11, a third bushing, 12, a mounting hole, 13, a flange, 14, an end effector, 15, a robot, 16 and a workpiece.

The same reference numbers in all figures indicate similar or corresponding features or functions.

Detailed Description

Aiming at solving the problems of poor control precision and real-time performance, high cost and the like of the existing robot end effector, the invention provides the end effector.

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In order to illustrate the structure of the end effector provided by the present invention, fig. 1, 7 to 9 schematically indicate the structure of the end effector from different angles. Specifically, fig. 1 shows an end effector cross-sectional structure according to an embodiment of the present invention; FIG. 7 illustrates the installation and operation of an end effector in accordance with an embodiment of the present invention; FIG. 8 illustrates an end effector perspective structure according to an embodiment of the present invention; FIG. 9 illustrates a partial cutaway configuration of an end effector according to an embodiment of the present invention.

As shown collectively in fig. 1, 7 to 9, the present invention provides an end effector comprising: the device comprises a shell 1, a moving shaft 2 arranged in the shell 1, two elastic discs (a first elastic disc 7 and a second elastic disc 9), a spring 5 and a prestress adjusting screw 3, wherein the two elastic discs are sleeved on the moving shaft 2, the top end of the shell 1 is provided with an end cover 4, and the end cover 4 is connected with the prestress adjusting screw 3 through threads; the spring 5 is limited between the prestress adjusting screw 3 and the two elastic discs, and the prestress of the two elastic discs is adjusted by rotating the prestress adjusting screw 3 to compress the spring 5; two elastic disc pieces are of a central symmetrical structure, one end of each elastic disc piece is fixed on the moving shaft 2, the other end of each elastic disc piece is fixed on the inner wall of the shell 1, and the two elastic disc pieces move under the driving of the moving shaft 2.

The two elastic disks comprise a first elastic disk 7 and a second elastic disk 9, and the second elastic disk 9 is a bistable elastic disk; when the bistable elastic disc is at the first stable position, the fixing point of the bistable elastic disc fixed on the moving shaft 2 is higher than the fixing point of the bistable elastic disc fixed on the inner wall of the shell 1; when the bistable elastic disc is in the second stable position, the fixed point of the bistable elastic disc on the moving shaft 2 is lower than the fixed point of the bistable elastic disc on the inner wall of the shell 1.

The first elastic disk 7 and the second elastic disk 9 are connected in parallel through the moving shaft 2, the rigidity of the moving shaft 2 relative to the shell 1 is the sum of the elastic coefficients of the two elastic disks, wherein the elastic coefficient of the first elastic disk 7 is a positive value, the elastic coefficient of the second elastic disk 9 is a negative value, and when the rigidity of the moving shaft 2 relative to the shell 1 is zero, the load along the moving shaft 2 is unchanged.

Wherein the spring 5 is a ripple spring which is limited between the prestress adjusting screw 3 and the first elastic disk 7, wherein the ripple spring is compressed by rotating the prestress adjusting screw 3 to adjust the prestress of the first elastic disk 7.

Wherein three bushings are provided at the inner side of the housing 1, wherein two elastic discs fixed on the inner wall of the housing 1 are spaced by the three bushings. In the embodiment shown in fig. 1, the three bushings are a first bushing 6, a second bushing 8 and a third bushing 11, respectively, wherein the other end D of the first elastic disc 7 is fixed between the first bushing 6 and the second bushing 8, and the other end E of the second elastic disc 9 is fixed between the second bushing 8 and the third bushing 11. In the embodiment shown in fig. 1, one end a of the first elastic disk 7 and one end B of the second elastic disk 9 are both fixed on the moving shaft 2.

Wherein, be provided with spacing shoulder 10 below moving shaft 2, be provided with the flange 13 with spacing shoulder 10 looks adaptation in the central point of casing 1 lower extreme position, wherein, spacing shoulder 10 is used for spacing moving shaft 2's motion range, prevents that moving shaft 2 load from too big destroying end effector's structure. Wherein, the flange 13 is used for guiding the moving shaft 2; the edge position of the lower end of the shell 1 is provided with a mounting hole 12, and the shell 1 is fixedly mounted with other components through the mounting hole 12.

In an embodiment of the invention, the working principle of the end effector is as follows: the stiffness of the first elastic disc is positive, that is, when the moving shaft moves downward within a certain range, the larger the axial displacement, the larger the force acting on the joint (a) of the moving shaft and the first elastic disc, and the relationship between the displacement of the moving shaft and the load at a is illustrated in the relationship diagram of fig. 2.

The second elastic disc is a bistable elastic disc which has two stable positions. When the moving shaft moves downwards under load, the bistable elastic disc reaches a second stable position, which is shown in fig. 3. As shown in fig. 4, in the process that the bistable elastic disc reaches the second stable position, the larger the axial displacement is in a certain displacement range, the smaller the force acting on the joint (B) of the moving shaft and the bistable elastic disc is, that is, the bistable elastic disc has negative stiffness in the region.

In the embodiment of the present invention, the first elastic disk and the bistable elastic disk of fig. 1 are simplified into a spring model, and then the two springs are connected in parallel through a moving shaft, and the moving shaft has the rigidity relative to the shell which is the sum of the elastic coefficients of the two springs. Let the elastic coefficient of the first elastic disk be K1, and the elastic coefficient of the bistable elastic disk be K2. In a certain displacement range (such as the region between X1 and X2 in fig. 2, 4 and 5), K1 is a positive value, and K2 is a negative value, the rigidity of the moving shaft relative to the housing is K1+ K2, and K is equal to 0, as shown in fig. 5. When the rigidity K is equal to 0, namely in an approximately zero rigidity area, the load along the axial direction is kept unchanged in the process that the moving shaft moves up and down, so that the end effector can keep constant force. In order to ensure that the approximately zero stiffness region corresponds to a larger displacement range, the material, the variable cross section and the like of the bistable elastic disc are selected according to the specific design of the first elastic disc. In the embodiment of the present invention, to achieve the constant force holding of the end effector adjustable, the prestress acting on the first elastic disk 7 can be adjusted by rotating the prestress adjusting screw 3 on the end cap 4 to press or release the spring 5, so as to change the region of approximately zero stiffness and the corresponding constant load, and the specific relationship diagram is shown in the regions X3 to X4 in fig. 6.

In one embodiment of the invention, the stiffness of the moving shaft 2 with respect to the casing 1 is the sum of the elastic coefficients of the two elastic discs, namely: in the embodiment of the invention, the prestress of the first elastic disk is adjusted by rotating the prestress adjusting screw on the end cover, pressing or releasing the spring, so that the sum of the elastic coefficients is zero, and the constant force kept by the end effector is realized.

In the embodiment shown in fig. 7, the housing of the end effector 14 is positioned and fixed with the end flange of the robot 15 through the mounting hole, and the movement axis in the end effector 14 acts on the surface of the workpiece 16. Because the first elastic disc and the bistable elastic disc are both in a central symmetry structure, when the end effector 14 works, the tangential force in any direction in a certain range in the tangent plane of the contact surface can be balanced, and the tail end of the robot 15 can be ensured to move on the surface of the workpiece 16 according to a preset track.

According to the embodiment, the end effector provided by the invention is of a revolving body structure, the moving shaft is arranged in the shell and sleeved on the moving shaft, the two elastic discs, the spring and the prestress adjusting screw, wherein the spring is limited between the prestress adjusting screw and the elastic discs, and the prestress of the elastic discs is adjusted by compressing the spring through rotating the prestress adjusting screw; the two elastic disks are of a central symmetrical structure, one ends of the two elastic disks are fixed on the moving shaft, the other ends of the two elastic disks are fixed on the inner wall of the shell, and the two elastic disks move under the driving of the moving shaft. The constant force of the end effector of the invention is kept unchanged, and links and equipment such as a sensor, data acquisition and processing, calculation, feedback control and the like are not included, so the structure is simple and the cost is low.

The proposed end effector according to the present invention is described above by way of example with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that various modifications may be made to the end effector described above without departing from the scope of the invention. Therefore, the scope of the present invention should be determined by the contents of the appended claims.

Claims

1. An end effector is characterized by comprising a shell, a moving shaft arranged in the shell, a first elastic disc, a second elastic disc and a prestress adjusting screw, wherein the first elastic disc, the second elastic disc and the prestress adjusting screw are sleeved on the moving shaft,

2. The end effector as claimed in claim 1,

the second elastic disc is a bistable elastic disc, wherein,

3. The end effector as claimed in claim 1,

the first elastic disc and the second elastic disc are connected in parallel through the moving shaft, and the rigidity of the moving shaft relative to the shell is the sum of the elastic coefficients of the two elastic discs.

4. The end effector as claimed in claim 3,

when the stiffness of the moving shaft relative to the housing is zero, the load along the moving shaft is constant.

5. The end effector as claimed in claim 1,

also comprises a spring sleeved on the moving shaft, wherein,

6. The end effector as claimed in claim 1,

the end cover is connected with the prestress adjusting screw through threads.

7. The end effector as claimed in claim 1,

three bushings are provided inside the housing, wherein,

8. The end effector as claimed in claim 1,

a limiting shaft shoulder is arranged below the moving shaft, a flange matched with the limiting shaft shoulder is arranged at the center of the lower end of the shell, wherein,

the flange is used for guiding the moving shaft.

9. The end effector as claimed in claim 1,

and the lower end edge of the shell is provided with a mounting hole, and the shell is fixedly mounted with other components through the mounting hole.