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Using Image Processing as a Metrological Solution (IPROMES)

Final Report Summary - IPROMES (Using Image Processing as a Metrological Solution)

The dimensional control plays an important role within the manufacturing industry. In the aeronautics sector, the metrology reaches a highly critical level, due to the high measurement precision required on large parts. The metrology operation is required not only during the final inspection, but above all in the scope of the assembly process.

Facing drastic requirements, and in order to take into account the size of the aircraft parts from the early beginning of aircrafts manufacturing, the industrial actors use complex frames which support both the parts to be controlled and the manual measurement tool. This solution is both time and cost consuming due to the characteristics of the frame which guarantees the accuracy of the measure. The IPROMES project aimed at developing relevant photogrammetry and image processing techniques to perform the 'in-process' positioning (during the assembly phase) and 'afterwards', to complete the final dimensional control in the aeronautics sector. The development of these innovating optical solutions will enable end-users to get direct measurements without specific instrumentation (particularly without targets). Consequently, the use of the sensors leads to a new concept of frame that will support only the parts to be controlled and the cameras.

The image-based measurement processes extend the state of the art in the field of optical three-dimensional (3D) measurement with innovative algorithms that target at measurements of highly reflecting surfaces, of curved edges, of chamfered edges, taking into account the required level of automation, accuracy and robustness. The different experiments showed that due to the properties of the aeronautic parts (specular material, shape of edges), each type of feature requires specific investigation in terms of image processing and photogrammetric techniques. For the automation, the partners have proposed original solutions in order to make the process fully automated. Concerning the accuracy and the robustness, the experimental results show that the proposed approaches have a promising potential in automatic 3D control of industrial parts.

ActiCM developed a sensor that extends the state of the art in the field of optical 3D measurements using innovative algorithms specially tailored for the requirements of the aeronautic end user in terms of accuracy and illumination robustness. ActiCM's AdventCR system with this new sensor measures geometrical feature coordinates using images taken from parts and estimates point coordinates on parametric surfaces using structured light patterns projected onto aeronautic part. This sensor is particularly tailored to perform following medium-range measurement of geometrical features (circular holes, square holes, slot holes) and medium-range measurement of surface points and edges.

The sensor development is closely linked to the development of image processing algorithms. For the highly accurate measurement of surface points, a new structured light pattern was developed and filed as a patent by ActiCM. The new design of the sensor allows handling of difficult surface properties as encountered on aeronautic parts, such as high reflectivity of the surface patches. Furthermore, the scientific progress in sensor design improved the accuracy requirements and the robustness to ambient illumination. The proposed sensor provides a basis for a wide range of different optical 3D measurement systems and methods. ActiCM intends to exploit the sensor design for automotive industry QC and for QC and assembly process in aeronautic industry.

Aeronautics has high accuracy requirements on the step and gap measurements. Coord3 and Metrostaff optimised the MAGAM sensor by a software solution that increases the accuracy of the sensor. The patent of the MAGAM sensor is owned by COORD3 / ESICSN / Logitest Westinghouse. Current MAGAM system allows to measure flush and gaps with an automated procedure, developed for car bodies and tuned on these particular shapes made of sheet metal. The new sensor provides to the user the possibility to align the measured shape and to define his / her own frame of reference based on measured data. This enables the operator to measure any arbitrary shape without any restriction. Moreover, the operator will be able to perform as many measurements as needed on each single profile. In particular, this extends the range of application to many common shapes such as aircraft parts or panels, which are presently unfeasible.

Aeronautics needs high accuracy as well as flexibility in the measurement of flush and gaps. The development of this new interface extends the possibilities of MAGAM system towards precise measurement of any shape. This option in the software will be released under a new licence. Future activities include the enhancement of the resolution of the sensor, in order to achieve a better sampling of high curvature corners, and a wireless connection to the host PC, to overcome restrictions related to the presence of a cable.