Method for in-line calibration of an industrial robot, calibration system for performing such a method and industrial robot comprising such a calibration system

Abstract

The invention refers to a method for in-line calibration of an industrial robot (1). The robot (1) comprises a fixed base section (2) and a multi chain link robot arm (3). The chain links (4) are interconnected and connected to the base section (2) of the robot (1), respectively, by means of articulated joints (5). An end effector (6) of the robot arm (3) can be moved in respect to the base section (2) within a three-dimensional workspace into any desired location. The idea is to move the end effector (6) into a predefined calibration location and to determine characteristic parameters of the robot (1) for that location. The characteristic parameters are compared to previously acquired values of the corresponding parameters for that calibration location. The differences between the characteristic parameters of the current location and the previously acquired parameters are used for correcting the kinematic model of the robot (1) and during normal operation of the robot (1) to enhance the accuracy of movement of the distal end (6). The end effector (6) is moved exactly into the calibration location by means of an iterative closed loop control process, in which light sources (7) fixedly connected to the end effector (6) emit light rays which impact on at least one optical position sensor (12) fixedly positioned in respect to the robot base (2). The end effector (6) is moved such that the actual ray positions (20) on the sensors (12) are moved to a predefined position (20') corresponding to the predefined calibration location by means of the iterative process.

Description

technical field [0001] The present invention relates to a method for on-line calibration of industrial robots, to a calibration system for on-line calibration of industrial robots and to industrial robots. The robot consists of a fixed base section and a multi-link robot arm. Via articulated joints, the chain links are respectively connected to each other and to the base part of the robot. The distal end of the robotic arm can be moved in three dimensions relative to the base portion to a desired position and orientation hereinafter referred to as orientation. Background technique [0002] In general, robot calibration is the process of using software to enhance the positional accuracy of a robot. Its purpose is to identify the exact kinematic properties of the robot, which will establish a mapping between joint angles and positions of end effectors at the distal end of the robot arm in Cartesian space. There can be many sources of error that lead to inaccuracies in the r...

AI Technical Summary

Problems solved by technology

While it is not necessary to estimate the full orientation of the end effector to perform the calibration, a measurement system that extracts the 6D orientation (position and orientation) of the end effector enables the calibration method to use a smaller number of calibration orientations (since more constraints are applied to each measuring)

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