Laser welding system, laser welding method, and emitting device

• US 8,412,371 B2
• Filed: 09/05/2006
• Issued: 04/02/2013
• Est. Priority Date: 09/30/2005
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Komatsu, Gakushi
• Primary Examiner(s): Heinrich, Samuel M
• Application Number:
  US11/514,978
• Publication Number:
  US 20070075055A1
• Time in Patent Office: 2,401 Days
• Field of Search: 21912161-12164, 219/121.78, 219/121.79, 219/121.81, 219/121.83, 700/245, 700/250, 700/166, 700/253, 318/568.11
• US Class Current: 700/166
• 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, the laser beam emitting section including an emission direction changing section configured and arranged to redirect the laser beam emitted from the laser beam emitting section;

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 move a movement position of the robot to a prescribed position based on the predetermined movement data, and to control the emission direction changing section 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 and the predetermined movement data such that the laser beam strikes a predetermined irradiation position.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

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

the robot includes an arm;

and

the laser beam emitting section further includes a laser processing head that is mounted to a tip of the arm and further accommodates a reflecting mirror to redirect the laser beam transmitted via an optical fiber cable extending along the arm as controlled by the emission direction changing section in order to compensate for a deviation of the current movement position of the robot from the prescribed position.