Method for compensating position of robot using laser measuring instrument

• US 6,509,576 B2
• Filed: 07/13/2001
• Issued: 01/21/2003
• Est. Priority Date: 09/29/2000
• Status: Expired due to Term

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: Woo-Dong, Hwang
• Primary Examiner(s): Pyo, Kevin
• Assistant Examiner(s): Meyer, David C.
• Application Number:
  US09/905,797
• Publication Number:
  US 20020038855A1
• Time in Patent Office: 557 Days
• Field of Search: 901/3, 901/16, 901/42, 901/47, 250/559.3, 250/559.33, 250/222.1, 356/614, 356/622, 700/251, 700/259, 700/559.21, 219/121.6
• US Class Current: 250/559.33
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G05B 2219/39022 Transform between measuring and manipulator coordinate system
• CPC Class Codes: G05B 2219/39033 Laser tracking of end effector, measure orientation of rotatable mirror

Abstract

Disclosed is a method for compensating the position of a robot using a laser measuring instrument by establishing an origin coordinate system; irradiating laser beams onto reflectors and calculating distances to the reflectors; converting the origin coordinate system to an established coordinate system; generating coordinates of an end of a lower tip of a welding gun; calculating a position and posture of the robot; teaching the robot four or more postures; uploading position coordinates of the robot and robot teaching program data to a main computer; determining if an error between CAD data and data modeled through simulation is less than a predetermined value, revising the data if it is not or completing compensation of positions of the welding gun, the robot and the jigs if it is; and downloading the robot teaching program to a robot controller.

Claims

1. A method for compensating a position of a robot using a laser measuring instrument, the method comprising the steps of:

(a) establishing an origin coordinate system by installing a reflector in each of a plurality of jig NC holes of a jig table, precise locations of which are known based on a car assembly line coordinate system, irradiating laser beams onto the reflectors by the laser measuring instrument and calculating distances to the reflectors based on properties of the laser beams reflected back to a sensor head of the laser measuring instrument, setting one of the NC holes of the jig table as an origin, with lines extending from the origin to two other NC holes as X and Y axes, and with a line normal to the plane formed by the three NC holes as a Z axis;

(b) converting, in a controller of the laser measuring instrument, the origin coordinate system to an established coordinate system to enable the laser measuring instrument to recognize the origin coordinate system as a car assembly line coordinate system;

(c) generating coordinates of an end of a lower tip of a welding gun by irradiating a laser beam onto a reflector installed on the end of the lower tip of the welding gun and calculating a distance to the reflector based on the properties of the laser beam reflected back to the sensor head of the laser measuring instrument;

(d) calculating absolute coordinates of the end of the lower tip of the welding gun by using the coordinates determined in steps (a) and (c) to calculate a distance between the NC holes and the end of the lower tip of the welding gun, and calculating a position and posture of the robot using the absolute coordinates;

(e) teaching the robot four or more postures by setting the end of the lower tip of the welding gun as a reference point;

(f) uploading position coordinates of the robot calculated in step (d) and robot teaching program data of step (e) to a main computer;

(g) performing error compensation by the main computer in which the main computer runs the uploaded robot teaching program and compensates the four or more points not converging at a single point so that the points merge at the reference point, which is at the end of lower tip of the welding gun, and compares the points with data modeled through simulation in consideration of the plurality of points of the jig so that the points are made to correspond to an actual position standard;

(h) determining if an error between CAD data corresponding to the distance to the end of the lower tip of the welding gun and data modeled through simulation is less than a predetermined value; and

(i) completing compensation, if the error between the CAD data of the distance to the end of the lower tip of the welding gun and the data modeled through simulation is less than the predetermined value, of positions of the welding gun, the robot and the jigs, and downloading the robot teaching program to a robot controller.

2. The method of claim 1 wherein in step (h), if the error between the CAD data of the distance to the end of the lower tip of the welding gun and the data modeled through simulation is greater than or equal to the predetermined value, welding gun data modeled through simulation is revised, then step (i) of claim 1 is performed.