Laser welding system, laser welding method, and emitting device

• US 20070075055A1
• Filed: 09/05/2006
• Published: 04/05/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Komatsu, Gakushi
• Granted Patent: US 8,412,371 B2
• Time in Patent Office: Days
• US Class Current: 219/121.630
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/042 Automatically aligning the laser beam
• CPC Class Codes: B23K 26/0884 in at least in three axial directions, e.g. manipulators, robots
• CPC Class Codes: B23K 26/22 Spot welding

Abstract

A laser welding system includes a robot control unit that acquires movement amount measurement values from encoders provided on axes of the robot and calculates the current position of a laser processing head based on the measurement values. Based on the calculated current position of the laser processing head, the robot control unit calculates a laser beam emission direction specifying the direction in which the laser beam should be aimed in order to strike a predetermined laser irradiation position. The robot control unit sends a command indicative of the laser beam emission direction to a processing head control unit which changes the direction of a reflecting mirror provided inside the laser processing head such that the laser beam is emitted in the specified direction.

Claims

1. A laser welding system comprising:

a robot configured and arranged to move in accordance with predetermined movement data;

a laser beam emitting section mounted to the robot and configured and arranged to emit a laser beam;

a measuring section configured and arranged to measure a current movement position of the robot with respect to a movement position specified in the predetermined movement data; and

a control unit configured to adjust a laser emission direction in which the laser beam is emitted from the laser beam emitting section based on the current movement position of the robot measured by the measuring section such that the laser beam strikes a predetermined irradiation position.

2. The laser welding system as recited in claim 1, wherein

the laser beam emitting section includes an emission direction changing section configured and arranged to redirect the laser beam emitted from the laser beam emitting section, and

the control unit is configured to change the laser emission direction by moving a direction of the emission direction changing section in accordance with the current movement position of the robot.

3. The laser welding system as recited in claim 1, wherein

the robot has at least one moveable axis,

the measuring section is further configured and arranged to measure an actual movement amount of the at least one axis of the robot, and

the control unit is configured to calculate the current movement position of the robot based on the actual movement amount of the at least one axis of the robot as measured by the measuring section.

4. The laser welding system as recited in claim 1, wherein

the control unit is further configured to determine a current position of the laser beam emitting section based on the current movement position of the robot, and to adjust the laser emission direction based on the current position of the laser beam emitting section such that the laser beam strikes the predetermined irradiation position.

5. The laser welding system as recited in claim 1, further comprising

an estimating section configured to estimate a virtual robot movement position using a numerical model of a movement of the robot based on the predetermined movement data, and to obtain an estimated position of the laser beam emitting section with respect to the virtual robot movement position, and

the control unit being further configured to compare the estimated position of the laser beam emitting section obtained from the estimating section to a current position of the laser beam emitting section obtained based on the current movement position of the robot measured by the measuring section, and to adjust the laser emission direction to compensate for a deviation from the predetermined irradiation position based on a difference between the estimated position and the current position of the laser beam emitting section.

6. The laser welding system as recited in claim 1, wherein

the measuring section is provided externally with respect to the robot, and configured and arranged to externally measure a current position of the laser beam emitting section, and

the control unit is configured to adjust the laser emission direction based on the current position of the laser beam emitting section measured by the measuring section such that the laser beam strikes the predetermined irradiation position.

7. The laser welding system as recited in claim 1, wherein

the laser beam emitting section further includes a focal distance changing section configured and arranged to change a focal distance of the laser beam emitted from the laser beam emitting section, and

the control unit is further configured to control the focal distance changing section to compensate for a deviation of a revised focal distance calculated based on the current movement position of the robot from a focal distance specified in the predetermined movement data.

8. The laser welding system as recited in claim 1, wherein

the control unit is further configured to control output of the laser beam in accordance with a distance from the laser beam emitting section to the predetermined irradiation position.

9. A laser welding method comprising:

operating a robot having a laser beam emitting section in accordance with predetermined movement data;

controlling the laser beam emitting section to emit a laser beam onto a predetermined irradiation position of a workpiece to conduct welding;

measuring a current movement position of the robot with respect to a movement position specified in the predetermined movement data; and

adjusting a laser emission direction based on the current movement position such that the laser beam strikes the predetermined irradiation position.

10. The laser welding method as recited in claim 9, wherein

the controlling of the laser beam emitting section includes changing a direction of the laser beam of the laser beam emitting section, and

the adjusting of the laser emission direction includes moving the direction of the laser beam that has been directed to the laser beam emitting section such that the laser beam strikes the predetermined irradiation position.

11. The laser welding method as recited in claim 9, wherein

the operating of the robot includes moving at least one movable axis of the robot, and

the measuring of the current movement position of the robot includes measuring an movement amount of the at least one axis of the robot.

12. The laser welding method as recited in claim 9, further comprising

determining a current position of the laser beam emitting section based on the current movement position of the robot, and

the adjusting of the laser emission direction including adjusting the laser emission direction based on the current position of the laser beam emitting section such that the laser beam strikes the predetermined irradiation position.

13. The laser welding method as recited in claim 9, further comprising

estimating a virtual robot movement position using a numerical model of a movement of the robot based on the predetermined movement data to obtain an estimated position of the laser beam emitting section with respect to the virtual robot movement position, and

the adjusting of the laser emission direction including comparing the estimated position of the laser beam emitting section to a current position of the laser beam emitting section obtained based on the current movement position of the robot and adjusting the laser emission direction to compensate for a deviation from the predetermined irradiation position based on a difference between the estimated position and the current position of the laser beam emitting section.

14. The laser welding method as recited in claim 9, wherein

the measuring of the current movement position of the robot includes externally measuring a current position of the laser beam emitting section, and

the adjusting of the laser emission direction including controlling the laser emission direction based on the current position of the laser beam emitting section such that the laser beam strikes the predetermined irradiation position.

15. The laser welding method as recited in claim 9, further comprising

controlling a focal distance of the laser beam to compensate for a deviation of a revised focal distance calculated based on the current movement position of the robot from a focal distance specified in the predetermined movement data.

16. The laser welding method as recited in claim 9, further comprising

controlling an output of the laser beam in accordance with a distance from the laser beam emitting section to the laser irradiation position.

17. An emitting device comprising:

an emitting section configured and arranged to emit an emitted entity;

a moving device configured and arranged to move the emitting section in accordance with predetermined movement data;

a measuring section configured and arranged to measure a current movement position of the moving device with respect to a movement position specified in the predetermined movement data; and

a control unit configured to control an emission direction in which the emitted entity is emitted from the emitting section based on the current movement position measured by the measuring section such that the emitted entity strikes a predetermined position.

18. The emitting device as recited in claim 17, wherein

the emitting section includes an emission direction changing section configured and arranged to change the emission direction of the emitted entity, and

the control unit is configured to change a direction of the emission direction changing section based on the current movement position such that the emitted entity emitted from the emitting section strikes the predetermined position.

19. The emitting section as recited in claim 18, wherein

the emission direction changing section is configured and arranged to change the emission direction of the emitted entity by at least one of reflecting the emitted entity and refracting the emitted entity.