Method and system for determining the relation between a robot coordinate system and a local coordinate system located in the working range of the robot

A method for determining the relation between a local coordinate system located in the working range of an industrial robot and a robot coordinate system, wherein the method comprises:

• attaching a first calibration object in a fixed relation to the robot,
• determining the position of the first calibration object in relation to the robot,
• locating at least three second calibration objects in the working range of the robot, wherein at least one of the calibration objects is a male calibration object having a protruding part shaped as a sphere, and at least one of the calibration objects is a female calibration object comprising at least two nonparallel, inclining surfaces arranged to receive the sphere so that the sphere is in contact with the surfaces in at least one reference position, wherein the inclination of the surfaces is in the interval of 20-80°,
• determining at least one reference position for each of the second calibration objects in the local coordinate system,
• A) moving the robot in a compliant way until the sphere is in mechanical contact with said surfaces of the female calibration object,
• B) reading the position of the robot when the sphere is in mechanical contact with said surfaces,
• repeating the steps A-B for the other second calibration objects, and
• calculating the relation between the local coordinate system and the robot coordinate system based on the position of the first calibration object in relation to the robot, the reference positions of the second calibration objects in the local coordinate system, and the positions of the robot when the sphere is in mechanical contact with the surfaces of the second calibration objects.