Multisensor data processing in dimensional metrology for collaborative measurement of a laser plane sensor combined to a touch probe

Abstract

Dimensional inspection, which consists in verifying the geometric conformity of parts in terms of ISO specifications, is an essential step in the product life cycle. In recent years, new optical measurement technologies, such as laser sensors or structured light sensors, have become increasingly important. However, the quality of the data limits their expansive use for metrology applications and touch probes with CMM (Coordinate Measurement Machine) remain the reference in terms of measurement quality. On the other hand, the cooperative use of an optical system and a contact sensor presents a good solution which takes advantage of the characteristics of both systems while maintaining a quality level satisfying the requirements of metrology. However, measurement with a laser sensor and a touch probe mounted on a CMM results in two heterogeneous point clouds that must be processed before the final evaluation of specifications. This paper presents a methodology that addresses the processing of measurement data in this scenario. The proposed approach consists of four phases. In the first phase, the measurement data resulting from the laser sensor is processed to remove outliers, reduce noise and partition the point cloud. In the second phase, the point cloud resulting from both sensors are unified in a unique coordinate system. In the third phase, a fusion method is proposed to fuse the point clouds. The specifications are finally evaluated based on the fused point clouds in the fourth phase. A case study is conducted to illustrate the proposed approach with the measurement data of a test part defined by its CAD model and specifications. The results are compared with a reference inspection report obtained by a touch probe measurement system.