Method and system for automatic assembly of curved surface part

Patent metadata

Field	Value
Publication number	US-11052497-B2
Application number	US-201716096088-A
Country	US
Kind code	B2
Filing date	Dec 4, 2017
Priority date	Sep 5, 2017
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A method and system for automatic assembly of a curved surface part are provided. First, a space coordinate system is established, and a first unit normal vector of the space coordinate system is determined. Then, coordinates of three measurement points on the surface of a curved surface part in the space coordinate system are acquired; and a second unit normal vector to the surface of the curved surface part are determined according to the coordinates of the measurement points. Finally, a rotation angle of the end effector is calculated according to the first unit normal vector and the second unit normal vector; and the end effector is adjusted according to the rotation angle, such that a third unit normal vector of the end effector after adjustment coincides with the second unit normal vector. The method and system enhance the automatic assembly quality of the curved surface part.

First claim

What is claimed is:

1. A method for automatic assembly of a curved surface part, comprising:
acquiring a central point of an execution end surface of an end effector;
acquiring a sensor plane formed by at least three sensors distributed on the end effector;
establishing a space coordinate system according to the central point and the sensor plane, wherein an origin of the space coordinate system is the central point, an x-y plane of the space coordinate system is the sensor plane, an axis z of the space coordinate system is a straight line on which a first unit normal vector is, the first unit normal vector being perpendicular to the x-y plane at the origin;
acquiring coordinates of three measurement points on the surface of a curved surface part in the space coordinate system, wherein the measurement points are intersections of the sensors and the surface of the curved surface part when the sensors collect information along a z-axis direction;
determining a curved surface expression of the surface of the curved surface part in the space coordinate system according to the coordinates of the measurement points;
calculating a second unit normal vector to the surface of the curved surface part according to the curved surface expression;
calculating a rotation angle of the end effector according to the first unit normal vector and the second unit normal vector; and
adjusting the end effector according to the rotation angle, such that a third unit normal vector of the end effector coincides with the second unit normal vector.

2. The method according to claim 1 , wherein the step of acquiring coordinates of three measurement points on the surface of a curved surface part in the space coordinate system comprises:
acquiring right-angle sides L 1 and L 2 of a first right triangle, wherein the first right triangle is the sensor plane of which three vertexes are formed by the three sensors respectively, the central point is a middle point on a hypotenuse of the first right triangle, and the three sensors are a first sensor, a second sensor, and a third sensor respectively;
acquiring coordinates of the sensors according to the space coordinate system, wherein the coordinates of the first sensor are

(

L
1

2

,

L
2

2

,
0

)

,

the coordinates of the second sensor are

(

L
1

2

,

-

L
2

2

,
0

)

,

and the coordinates of the third sensor are

(

-

L
1

2

,

-

L
2

2

,
0

)

;

acquiring coordinates of a fourth sensing point according to the coordinates of the first sensor, the second sensor, and the third sensor, wherein the coordinates of the fourth sensing point are

(

-

L
1

2

,

L
2

2

,
0

)

,

and the fourth sensing point is located at a right-angled vertex of a second right triangle; and the second right triangle and the first right triangle are identical in shape and their hypotenuses coincide, and the second right triangle and the first right triangle are combined into a rectangle;
acquiring distances from the first sensor, the second sensor, and the third sensor to the measurement points respectively, wherein the measurement points comprise a first measurement point, a second measurement point, and a third measurement point; the distance from the first sensor to the first measurement point is l a , the distance from the second sensor to the second measurement point is l b , and the distance from the third sensor to the third measurement point is l c ; and
calculating coordinates of the first measurement point, coordinates of the second measurement point, and coordinates of the third measurement point according to the space coordinate system and the distances l a , l b , l c , wherein the coordinates of the first measurement point, coordinates of the second measurement point, and coordinates of the third measurement point are

(

L
1

2

,

L
2

2

,

l
a

)

,

(

L
1

2

,

-

L
2

2

,

l
b

)

,

and
⁢

⁢

(

-

Assignees

• Univ Northwestern Polytechnical

Inventors

• Zhang Kaifu
• Cheng Yi
• Cheng Hui
• Luo Bin
• Li Yuan

Classifications

• B25J9/1694

  characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion · CPC title

• B23P19/105 Primary

  using sensing means · CPC title

• Y10T29/49769

  Using optical instrument [excludes mere human eyeballing] · CPC title

• Y10T29/4978

  Assisting assembly or disassembly · CPC title

• B25J9/0084

  comprising a plurality of manipulators · CPC title