An approach for the automated self-calibration of robot-based inspection systems

Robot-based inspection systems have the potential for being an alternative to coordinate measuring machines. Such systems, which are based on standard industrial robots, show advantages according to costs, flexibility and measuring speed. However, the use of these systems is currently limited by the pose accuracy of the robot. A possibility for an enhancement of the pose accuracy is provided by the calibration of the robot. Most of these methods are based on calibration data from external measurement systems which are expensive and complex. The presented approach uses the components of the system itself to generate calibration data. For this purpose, the 3D sensor of the system is aligned to a feature of the measurement object and rotated stepwise around its scan axis by a robot movement. For each rotational step the relative shift between the sensor and the feature is measured. On the basis of this data, conclusions on the kinematics of the robot can be made. Furthermore, a measurable indicator for the validity of the calibration is identified. Consequently, an automated calibration method for robot-based inspection systems without use of external components can be implemented.