Patent ID: 8457786

Claim:
A method for calibration of an industrial robot system comprising: at least one robot ( 1 ; 1 a - c ) having a first robot coordinate system (x r1 , y r1 , z r1 ) and configured to process a workpiece, a robot controller ( 3 ) including a processor ( 20 ) and a data storage ( 22 ), and a positioner ( 2 ; 30 ) adapted to hold the workpiece and to change an orientation of the workpiece by rotating it about a rotational axis while the robot processes the workpiece, and target points for a robot are programmed with respect to a first object coordinate system (x o1 , y o1 , z o1 ), wherein the method comprises: defining a positioner coordinate system (x p , y p , z p ) for the positioner in which said rotational axis is an axis of the positioner coordinate system, providing the positioner with at least three calibration objects ( 24 a - e ; 36 a - e ) which positions are known in the first object coordinate system, providing the robot with a calibration tool ( 26 ), determining the positions of at least three of calibration objects with respect to the first robot coordinate system by means of the robot and the calibration tool, rotating the positioner about its rotational axis, determining the positions of a first calibration object ( 24 a ) for at least three different angles of the rotational axis by means of the robot and the calibration tool, determining the positions of a second of said calibration objects ( 24 b ), located at a distance from the first calibration object along the rotational axis of the positioner, for at least three different angles of the axis, determining a direction of the rotational axis of the positioner in the first robot coordinate system based on the determined positions of the first and second calibration objects for the at least three different angles of the axis, converting the positions of the at least three calibration objects determined with respect to the first robot coordinate system and the positions of the at least three calibration objects known with respect to the first object coordinate system into a common coordinate system, and determining a relation between the first object coordinate system and the positioner coordinate system by performing a best fit between the known and the determined positions of the at least three calibration objects in the common coordinate system.