Method and device for calibration of movement axes of an industrial robot
AssigneeAsea Brown Boveri AG
InventorJohn-Erik Snell
Life of this patent
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Abstract
In a calibration method for an industrial robot (2-6), a calibration tool (8) supported by the robot hand (6) is brought into contact a spherical calibration body (7) with a known radius. Thereafter, the output signals from the position transducers of the robot axes are read and stored. This method is repeated a plurality of times with different robot configurations. Thereafter, the calibration parameters of the robot are calculated starting from the kinematic equations of the robot, a model of the relationship between axial position and position transducer signal, the known radius of the calibration body, and the read and stored position transducer signals.
Claims7
A method for calibration of an industrial robot comprising a plurality of movement axes with a position transducer for each of said axes for supplying an output signal which defines the current position of the axis, and a robot hand for supporting a tool,
- wherein a number of calibration parameters for the robot are determined by:
- a) providing the robot with a calibration tool supported by the robot hand, b) running the calibrating tool into contact with a spherical calibration body which has at least one accurately known radius dimension,
- c) reading and storing, in contact positions, the output signals from the position transducers of the robot,
- d) repeating steps b) and c) a number of times at least equal to the number of calibration parameters plus three,
- and wherein, initial conditions for determining the calibration parameters, include:
- 1) kinematic equations of the robot,
- 2) a model of the relationship between axial position and a position transducer signal,
- 3) the radius of the calibration body, and
- 4) the read and stored output signals from the position transducers.
An industrial robot system operable in accordance with calibration parameters comprising:
- a plurality of movement axes with a position transducer for each one of said axes for supplying an output signal which defines the current position of an axis,
- a robot hand for supporting a tool,
- a control system for controlling the position and an orientation of the robot hand in accordance with a program for receiving the output signals of the position transducers,
- a calibration tool supported by the robot hand,
- a calibration body which has at least one accurately known dimension,
- wherein said calibration body has a spherical shape and an accurately known radius,
- and wherein a calculating means calculates the calibration parameters based upon:
- 1) kinematic equations of the robot,
- 2) a model of the relationship between an axial position and a position transducer signal,
- 3) the radius of the calibration body and
- 4) the read and stored output signals from the position transducers.
Dependencies are inferred from the claim text.