Method for work piece calibration and robot system using the same
A method for calibration of work piece mounted in a predetermined manner to a work object and a robot system using the same. The work object has a first surface, a second surface and a third surface, and wherein the work object frame of reference is defined by a first coordinate line, a second coordinate line, and a third coordinate line at intersections of the first surface, the second surface and the third surface converging on a point. The method includes: touching a first number of locations on the first surface of the work object positioned by the robot touch probe to measure their actual locations on the first surface in the robot frame of reference, and storing the measured first coordinates for the measured locations; touching a second number of locations on the second surface of the work object positioned by the robot touch probe to measure their actual locations on the second surface in the robot frame of reference, and storing the measured second coordinates for the measured locations; touching a third number of locations on the third surface of the work object positioned by the robot touch probe to measure their actual locations on the third surface in the robot frame of reference, and storing the measured third coordinates for the measured locations; calculating orientation and origin of the work object frame of reference from the robot frame of reference based on the measured first, second and third coordinates for the measured locations, where the work object is positioned in the robot cell. The method provides all the necessary data to determine orientation and origin of the actual work object frame of reference relative to the robot frame of reference. The method also enables the robot to perform machine operations accurately at locations on a work object.
1. A method for calibration of a work piece mounted in a predetermined manner to a work object in a robot system, wherein the work object has a first surface, a second surface and a third surface, and wherein the work object frame of reference is defined by a first coordinate line, a second coordinate line, and a third coordinate line at intersections of the first surface, the second surface and the third surface converging on a point, the method comprising:
touching a first number of locations on the first surface of the work object positioned by the robot touch probe to measure their actual locations on the first surface in the robot frame of reference, and storing the measured first coordinates for the measured locations;
touching a second number of locations on the second surface of the work object positioned by the robot touch probe to measure their actual locations on the second surface in the robot frame of reference, and storing the measured second coordinates for the measured locations;
touching a third number of locations on the third surface of the work object positioned by the robot touch probe to measure their actual locations on the third surface in the robot frame of reference, and storing the measured third coordinates for the measured locations;
calculating orientation and origin of the work object frame of reference from the robot frame of reference based on the measured first, second and third coordinates for the measured locations, where the work object is positioned in the robot cell;
wherein:
the first number amounts equal to or above three;
the second number amounts equal to or above three; and
the third number amounts equal to or above three; and
determining coordinates in the robot frame of reference for multiple points on the work piece, based on off-line data specifying coordinates in the work object frame of reference for the multiple points on the work piece and in consideration of the calculated orientation and origin of the work object frame of reference; and
applying to the work piece a coordinate transformation indicative of the off-line data specifying the workpiece coordinates in the work object frame of reference.
2. The method according to claim 1 , wherein:
determining orientation of the work object frame of reference relative to the robot frame of reference based on orientations of the first coordinate line, the second coordinate and the third coordinate line which are calculated by applying algorithm of square fitting respectively to the measured first, second and third coordinates for the measured locations; and
determining the origins between of the work object frame of reference and the robot frame reference based on coordinate in the robot frame of reference for the converging point of the first, second and third coordinate line which is calculated by applying algorithm of square fitting respectively to the measured first, second and third coordinates for the measured locations.
3. The method according to claim 2 , further comprising:
regulating orientations of the second and third coordination lines of the fixture frame of reference to be normal to that of the first coordination line of the fixture frame of reference in the robot frame of reference.
4. The method according to claim 1 , wherein:
the first, second and third surface are arranged substantially perpendicular to each other.
5. A robot system, including:
a work object, having a first surface, a second surface and a third surface, wherein the work object frame of reference is defined by a first coordinate line, a second coordinate line, and a third coordinate line at intersections of the first surface, the second surface and the third surface converging on a point, and being configured for having a work piece mounted thereto in a predetermined manner;
a manipulator holding a touch probe; and
a robot controller having a motion control module, a calculation module and a memory module;
wherein:
the motion control module is adapted for controlling the manipulator to touch a first number of locations on the first surface of the work object positioned by the robot touch probe to measure their actual locations on the first surface in the robot frame of reference, touch a second number of locations on the second surface of the work object positioned by the robot touch probe to measure their actual locations on the second surface in the robot frame of reference, and touch a third number of locations on the third surface of the work object positioned by the robot touch probe to measure their actual locations on the third surface in the robot frame of reference;
the memory module is adapted for storing the measured first coordinates for the measured locations, storing the measured second coordinates for the measured locations, and storing the measured third coordinates for the measured locations; and
the calculation module is adapted for calculating orientation and origin of the work object frame of reference from the robot frame of reference based on the measured first, second and third coordinates for the measured locations, where the work object is positioned in the robot cell;
wherein:
the first number amounts equal to or above three;
the second number amounts equal to or above three; and
the third number amounts equal to or above three; and
wherein the robot system is further adapted to determine coordinates in the robot frame of reference for multiple points on the work piece, based on off-line data specifying coordinates in the work object frame of reference for the multiple points on the work piece and in consideration of the calculated orientation and origin of the work object frame of reference; and
wherein the robot system is further adapted to apply to the work piece coordinates a coordinate transformation indicative of the off-line data specifying the workpiece coordinates in the work object frame of reference.
6. The robot system according to claim 5 , wherein:
the calculation of the first coordinate transformation includes:
determining orientation of the work object frame of reference relative to the robot frame of reference based on orientations of the first coordinate line, the second coordinate line and the third coordinate line which are calculated by applying algorithm of square fitting respectively to the measured first, second and third coordinates for the measured locations; and
determining the origins between of the work object frame of reference and the robot frame of reference based on coordinate in the robot frame of reference for the converging point of the first, second and third coordinate line which is calculated by applying algorithm of square fitting respectively to the measured first, second and third coordinates for the measured locations.
7. The robot system according to claim 6 , wherein:
orientations of the second and third coordination lines of the fixture frame of reference may be regulated to be normal to that of the first coordination line of the fixture frame of reference in the robot frame of reference.
8. The robot system according to claim 5 , wherein:
the first, second and third surface are arranged substantially perpendicular to each other.
9. The method according to claim 2 , wherein the first, second and third surface are arranged substantially perpendicular to each other.
10. The method according to claim 3 , wherein:
the first, second and third surface are arranged substantially perpendicular to each other.
11. The robot system according to claim 6 , wherein:
the first, second and third surface are arranged substantially perpendicular to each other.
12. The robot system according to claim 7 , wherein:
the first, second and third surface are arranged substantially perpendicular to each other.
13. The method according to claim 1 , wherein:
the first number amounts equal to four.
14. The robot system according to claim 5 , wherein:
the first number amounts equal to four.
15. The method according to claim 1 , wherein:
the work piece is defined by a shape without touchable features;
the work piece is mounted to the work object such that the work object and the work piece are transferred from location to location together without relative movement therebetween; and
determining coordinates in the robot frame of reference for points on the work piece based on the calculated orientation and origin of the work object frame of reference.
16. The robot system according to claim 5 , wherein:
the work piece is defined by a shape without touchable features;
the work piece is mounted to the work object such that the work object and the work piece are transferred from location to location together without relative movement therebetween; and
determining coordinates in the robot frame of reference for points on the work piece based on the calculated orientation and origin of the work object frame of reference.