Automated three-dimensional object detection using a robot-guided optical 3D scanning system
Industrial robots are gaining interest in many areas of industry as well as in metrology due to their versatile applicability. In combination with an optical measuring system, it enables new, highly accurate and tailored 3D recording processes. The aim of this project is to record complex measurement objects and to make information from the existing robot available for any measurement tasks.
Industrial robots are gaining interest in many areas of industry as well as in metrology due to their versatile applicability. In combination with an optical measuring system, it enables new, highly accurate and tailored 3D recording methods. Fundamental investigations have already been carried out for this connection in past project and master’s theses. The existing concepts will be taken up and expanded here. On the one hand, communication and control will be revised and expanded. On the other hand, the automated three-dimensional object acquisition is to be further developed. In general, reference points are needed to link point clouds. The relationship between two point clouds can be established via these reference points. However, this also involves a loss of information, since the object cannot be captured at the location of the reference points. For this reason, among others, a linkability for point clouds of objects without reference points is sought. In addition, a measurement without reference points opens up the possibility of recording, for example, antique objects for which it is inconceivable to attach reference points. This is realised via the relationship between the coordinate system of the industrial robot arm and that of the optical measuring system. This relationship enables a transformation with subsequent linking of the point clouds into a higher-level coordinate system. The developed relationship offers an automated measurement that saves both time and money.
Since 2016, the Mainz University of Applied Sciences and the i3mainz have been in possession of a mobile robot (MM-800 from Neobotix GmbH consisting of the mobile platform Neobotix MP-800 and the industrial robot arm KR16 from the company Kuka AG) due to the opening of the laboratory for applied robotics ROBOLAB funded by the Carl Zeiss Foundation “Invest”. This basically allows new, highly accurate and tailored 3D recording methods in metrology to create three-dimensional models. The aim is to combine the robot with a fringe light projection scanner (GOM ATOS Core 500) in order to automatically record archaeological objects, among other things. The aim is to record complex measuring objects and to make further information from the existing robot available for possible measuring tasks. In concrete terms, this means the realisation of a reference point-free measurement in which the positioning and orientation of the robot arm provides the basis for linking the individual scans to the object.
Development, implementation and verification of a calibration process to transfer the 3D measurement data of the optical close-range scanner into the robot’s own coordinate system (Fig. 2 shows the relationship between the individual coordinate systems). By specifying different robot positions and orientations (tool centre point), the close-range scanner could be oriented absolutely and capture the surface of an object three-dimensionally without photogrammetric reference marks. A spatial comparison of two individual scans is shown in Fig. 3, whereby no best-fit adjustment of both individual scans took place.