Welding robot control system

• US 6,040,554 A
• Filed: 03/19/1998
• Issued: 03/21/2000
• Est. Priority Date: 07/19/1996
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Okuda, Mitsuhiro, Terada, Akihiro
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US09/043,487
• Time in Patent Office: 733 Days
• Field of Search: 219/124.34, 219/125.1, 219/125.11, 901/42, 364/571.01
• US Class Current: 219/124.34
• CPC Class Codes: B23K 9/1274 Using non-contact, optical means, e.g. laser means

Abstract

A control system of a welding robot for performing realtime tracking using a laser sensor in which a welding operation in passing a tack welded portion is rationally coped with. An arc welding torch and a laser sensor LS are mounted on a robot hand. A tool center point is set to coincide with an aimed position of a distal end of a welding wire. The tool center point is positioned at an advancing end of a formed bead B and immediately before a tack welded portion A1. The tool center point 4 is also positioned on a welding reference line (P₁ → . . . →P₆). A bright line 5 is formed between points 51 and 52 by a laser beam emitted from the laser sensor LS with a deflection range SC. A detected point SA is positioned at an edge of the tack welded portion A1 on the bright line 5 (there may be found no detected point). A deviation of the detected point SA from the proper welding reference line is determined based on a direction of a robot path immediately before the detected point. In such case, a detection substitutive point Q is determined based on the robot path immediately before the detected point and the TCP is moved toward the determined point. Detection substitutive points following the point Q are successively determined until the tack welded portion A1 has been passed, and the robot follows a path along a series of the detection substitutive points.

Claims

1. A control system for controlling a welding robot for performing arc welding by moving a welding torch mounted on a robot hand along a welding reference line, said system comprising:

a laser sensor mounted on said robot hand, for repeatedly detecting a characteristic point of a joint shape of workpieces by scanning a region in an advancing directions of said welding robot with a laser beam;

properness determining means for determining whether the detected characteristic point is proper or improper as a point representing a position of said welding reference line, when the characterizing point is detected by said laser sensor;

first storing means for storing data representing the position of the detected point as data of a welding reference line representative point when the detected characteristic point is determined to be proper by said properness determining means;

detection substitutive point determining means for determining a detection substitutive point to be substituted for the detected characteristic point when it is determined that the detected characteristic point is improper by said properness determining means or when the characteristic point is not detected by said laser sensor;

second storing means for storing data representing a position of the detection substitutive point as data of the welding reference line representative point; and

means for successively determining a target point of movement of said welding robot, based on the data of the welding reference line representative point stored in said first storing means and the data of the welding reference line representative point stored in said second storing means.

2. A welding robot control system according to claim 1, said properness determining means comprising:

means for obtaining a deviation index value which represents a magnitude of deviation of the detected characteristic point from the position of the welding reference line based on the data of the welding reference line representative points stored in near past in said first and second storing means and the data representing the position of the detected characteristic point; and

means for comparing the deviation index value with a reference value.

3. A welding robot control system according to claim 1, said detection substitutive point determining means including means for determining said detection substitutive point on an extended line of a straight welding reference line represented by the data of the welding reference line representative points stored in near past, when a taught path extends in a straight line.

4. A welding robot control system according to claim 1, said detection substitutive point setting means including means for determining said detection substitutive point on an extended arcuate line of an arcuate welding reference line represented by the data of the welding reference line representative points stored in near past, when a taught path is of a circular arc.

5. A control system for controlling a welding robot for performing arc welding along a welding reference line, said system comprising:

a welding torch to weld along the welding reference line;

a memory storing a taught path for the robot to follow during motion;

a laser sensor to repeatedly detect points of a joint shape of a workpiece by scanning with a laser beam; and

a control section to control motion of the welding torch by adding a detected point as a target point for movement of the welding reference line if the detected point is within a predetermined deviation index value and by adding a substitute point as a target point for movement of the welding reference line if the detected point is not within the predetermined reference value,

wherein said control section uses a predetermined number of previous target points for the determination of the substitute point.

6. A control system for controlling a welding robot for performing arc welding along a welding reference line, said system comprising:

means for welding along the welding reference line;

means for storing a taught path for the robot to follow during motion;

means for repeatedly detecting points of a joint shape of a workpiece by scanning with a laser beam; and

means for controlling motion of the welding torch by adding a detected point as a target point for movement of the welding reference line if the detected point is within a predetermined deviation index value and by adding a substitute point as a target point for movement of the welding reference line if the detected point is not within the predetermined reference value,

wherein said motion controlling means uses a predetermined number of previous target points for the determination of the substitute point.