Method and device for calibration of movement axes of an industrial robot

A method for calibration of an industrial robot which has a plurality of movement axes (A1-A6) with a position transducer for each of said axes adapted to supply an output signal which defines the current position of the axis, a robot hand for supporting a tool, and a control system for controlling the position and orientation of the robot hand in accordance with a program, wherein a number of calibration parameters for the robot are determined by the following steps:

• a) providing the robot with a calibration tool, supported by the robot hand, comprising a sphere with a known radius (r),
• b) providing a member adapted to transmit a calibration beam within the working range of the robot, and a member connected to the control system which detects an interruption in the calibration beam,
• c) running the calibration tool towards the calibration beam,
• d) reading and storing the output signals from the position transducers of the robot when an interruption in the calibration beam is detected,
• e) repeating steps c) and d) a number of times at least equal to the number of calibration parameters plus two and with different configurations of the robot,
• f) calculating the calibration parameters based on:
• 1) the kinematic equations of the robot,
• 2) a model of the relationship between axial position and position transducer signal,
• 3) the read and stored position transducer signals, and 4) the known radius.