# US 10,481,577 B2 · System and method for object distance detection and positioning

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- Number: US 10,481,577 B2
- Document ID: US10481577B2
- Status: Granted
- Kind: B2
- Application number: 15/440,616
- Filed: 2017-02-23
- Published: 2018-08-23
- Granted: 2019-11-19
- Earliest claimed: 2017-02-23
- Assignees: GM Global Technology Operations LLC
- Applicants: GM Global Technology Operations LLC
- Inventors: John Forrest; Joshua Solomon; Michael Poss
- Web page: https://patentgrep.com/patent/US10481577B2

## CPC

- G05B 19/402: characterised by control arrangements for positioning, e.g. centring a tool relative to a hole in the workpiece, additional detection means to correct position (G05B19/19 takes precedence)
- B23K 1/0056: {soldering by means of beams, e.g. lasers, electron beams [EB]}
- B23K 26/032: {using optical means}
- B23K 26/048: {by controlling the distance between laser head and workpiece}
- B23K 26/1464: {Supply to, or discharge from, nozzles of media, e.g. gas, powder, wire}
- G05B 19/182: {characterised by the machine tool function, e.g. thread cutting, cam making, tool direction control (G05B19/21 - G05B19/40 take precedence)}
- B23K 2101/006: {Vehicles}
- G05B 2219/36414: Compare image detected path with stored reference, difference corrects position
- G05B 2219/45138: Laser welding
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM

## Abstract

A method for object distance detection and focal positioning in relation thereto. The method comprising the steps of: (a) identifying (via a computing device) a desired distance among a plurality of designated sites on an object; (b) adjusting a focus (via an autofocus device) onto the plurality of designated sites; (c) calculating (via an image recognition module) the actual distance among the plurality of designated sites; (d) determining (via the image recognition module) if error exist between the actual distance and the desired distance; and (e) wherein (in no particular order) repeating the steps of (b), (c), and (d) until no substantial error exists between the actual distance and the desired distance.

## Claims

### Claim 1

A method for object distance detection and focal positioning in relation thereto, for improved first-time quality and accuracy in laser brazing applications, the method comprising:
(a) identifying, via a computing device, a desired distance among a plurality of designated sites on an object;
(b) adjusting a focus, via an autofocus device, onto the plurality of designated sites;
(c) calculating, via an image recognition module, the actual distance among the plurality of designated sites, wherein the image recognition module will conduct at least the following steps to calculate the actual distance among the plurality of designated sites:
(i) positioning regions of interest around each of the plurality of designated sites;
(ii) determining a pixel intensity within each region of interest;
(iii) for each pixel intensity:
determining an X-axis coordinate value relative to the center of the pixel intensity, wherein the X-axis coordinate value is defined by the following equation:
x
cm
=
∑
i
N
⁢
⁢
x
i
⁢
I
i
∑
i
N
⁢
I
i
and wherein xcm is an X-axis location of intensity center of mass, x is an X-axis pixel value, and/is an X-axis pixel intensity;
determining a Y-axis coordinate value relative to the center of the pixel intensity, wherein the Y-axis coordinate value is defined by the following equation:
x
cm
=
∑
i
N
⁢
⁢
x
i
⁢
I
i
∑
i
N
⁢
I
i
and wherein ycm is a Y-axis location of intensity center of mass, y is a Y-axis pixel value, and/is a Y-axis pixel intensity; and
wherein the X-axis and Y-axis coordinate values represent a center coordinate value; and
(iv) determining the distance between the center coordinate values of each pixel intensity;
(d) determining, via the image recognition module, if error exist between the actual distance and the desired distance; and
(e) wherein, in no particular order, repeating each of (b), (c), and (d) until no substantial error exists between the actual distance and the desired distance.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
(f) providing the existing error value to a feedback control loop; and
(g) producing, via the feedback control loop, a focus correction value.

### Claim 3 (depends on 1)

The method of claim 1, further comprising an industrial robot acting as a pass through system between the computing device and the brazing-welding device.

### Claim 4 (depends on 1)

The method of claim 1, wherein the feedback control loop is a PID controller located in the computing device.

### Claim 5 (depends on 1)

The method of claim 1, wherein the autofocus device is located in a brazing-welding device.

### Claim 6 (depends on 1)

The method of claim 1, wherein the image recognition module is located in the computing device.

### Claim 7

A system to detect the distance of an object and position a motorized autofocus device in relation thereto, for improved first-time quality and accuracy in laser brazing applications, the system comprising:
a computing device configured to establish a desired distance among a plurality of designated sites on the object, the computing device further comprising an image recognition module configured to calculate the actual distance among the plurality of designated sites, wherein the image recognition module will conduct at least the following steps to calculate the actual distance among the plurality of designated sites:
(i) positioning regions of interest around each of the plurality of designated sites;
(ii) determining a pixel intensity within each region of interest;
(iii) for each pixel intensity:
determining an X-axis coordinate value relative to the center of the pixel intensity, wherein the X-axis coordinate value is defined by the following equation:
x
cm
=
∑
i
N
⁢
⁢
x
i
⁢
I
i
∑
i
N
⁢
I
i
and wherein xcm is an X-axis location of intensity center of mass, x is an X-axis pixel value, and I is an X-axis pixel intensity;
determining a Y-axis coordinate value relative to the center of the pixel intensity, wherein the Y-axis coordinate value is defined by the following equation:
x
cm
=
∑
i
N
⁢
⁢
x
i
⁢
I
i
∑
i
N
⁢
I
i
and wherein ycm is a Y-axis location of intensity center of mass, y is a Y-axis pixel value, and/is a Y-axis pixel intensity; and
wherein the X-axis and Y-axis coordinate values represent a center coordinate value; and
(iv) determining the distance between the center coordinate values of each pixel intensity,
the image recognition module further configured to determine if error exists between the actual distance and desired distance of the plurality of designated sites;
the autofocus device configured to adjustably focus onto the plurality of designated sites;
wherein, the autofocus device will adjust the focus when error is determined to exist between the actual distance and desired distance of the plurality of designated sites.

### Claim 8 (depends on 7)

The system of claim 7, further comprising:
a feedback control loop located in the computing device, the feedback control loop configured to produce a focus correction value; and
wherein the focus correction value is configured to be sent to the autofocus device to adjust the focus to reduce error that exists between the actual distance and desired distance of the plurality of designated sites.

### Claim 9 (depends on 7)

The system of claim 7, further comprising an industrial robot configured to be a pass through system between the computing device and the brazing-welding device.

### Claim 10 (depends on 7)

The system of claim 7, wherein the feedback control loop is a PID controller.

### Claim 11 (depends on 7)

The system of claim 7, wherein the autofocus device is located in a brazing-welding device having a multifocal module.

### Claim 12

A method for detecting the distance among a plurality of designated sites on an object and positioning an autofocus device in relation to those designated sites, for improved first-time quality and accuracy in laser brazing applications, the method comprising:
(a) identifying, via a computing device, a desired distance among the plurality of designated sites on an object;
(b) adjusting a focus, via a motorized autofocus device of a brazing-welding device, to a focal distance that can monitor the plurality of designated sites, by moving the autofocus device closer to the object so as to decrease the focal distance or moving the autofocus device farther from the object so as to increase the focal distance;
(c) calculating, via an image recognition module, the actual distance among the plurality of designated sites, wherein the image recognition module will conduct at least the following steps to calculate the actual distance among the plurality of designated sites:
(i) positioning regions of interest around each of the plurality of designated sites;
(ii) determining a pixel intensity within each region of interest;
(iii) for each pixel intensity:
determining an X-axis coordinate value relative to the center of the pixel intensity, wherein the X-axis coordinate value is defined by the following equation:
x
cm
=
∑
i
N
⁢
⁢
x
i
⁢
I
i
∑
i
N
⁢
I
i
and wherein xcm is an X-axis location of intensity center of mass, x is an X-axis pixel value, and I is an X-axis pixel intensity;
determining a Y-axis coordinate value relative to the center of the pixel intensity, wherein the Y-axis coordinate value is defined by the following equation:
x
cm
=
∑
i
N
⁢
⁢
x
i
⁢
I
i
∑
i
N
⁢
I
i
and wherein ycm is a Y-axis location of intensity center of mass, y is a Y-axis pixel value, and/is a Y-axis pixel intensity; and
wherein the X-axis and Y-axis coordinate values represent a center coordinate value; and
(iv) determining the distance between the center coordinate values of each pixel intensity;
(d) calculating, via the image recognition module, an error value which corresponds to a discrepancy between the actual distance and the desired distance;
(e) calculating, via a feedback control loop, a focus correction value based on the error value, the focus correction value configured to reduce the error value to zero; and
(f) readjusting the focus, via the autofocus device, to a distance which corresponds to the focus correction value.

### Claim 13 (depends on 12)

The method of claim 12, further comprising an industrial robot acting as a pass through system between the computing device and the brazing-welding device.

### Claim 14 (depends on 12)

The method of claim 12, wherein the feedback control loop is a PID controller located in the computing device.

### Claim 15 (depends on 12)

The method of claim 12, wherein the brazing-welding device comprises a multifocal module.

### Claim 16 (depends on 12)

The method of claim 12, wherein the image recognition module is located in the computing device.