Method for work piece calibration and robot system using the same

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.