Application of a reflectance model to the sensor planning system

conference paper

English

This study describes a new sensor planning system for the automatic generation of scanning positions based on a computer model of the part for digitization of sheet metal parts. The focus of this paper is in the application of a reflectance model into this sensor planning system. Optical 3D scanners and industrial robots are used more often for inspection of sheet metal parts in serial-line production. Measuring positions for accurate and fast digitization of a part need to be prepared as the manufacturing of the new part begins. Planning of such positions is usually done manually by positioning of the industrial robot and saving the positions. The planning of positions proposed by this system is done automatically. A methodology of sensor planning consists of positions planning, their simulation for true visibility of the part elements using a reflectance model, and a simulation of the positions for robot reachability. The entire methodology is implemented as a plug-in for the Rhinoceros software. This study is focused on digitization of sheet metal parts that are characterized by specular surfaces. The system is designed for and tested with a stereo camera fringe projection 3D scanner, ATOS Triple Scan (GOM GmbH). Compared to previous studies in the field of automated sensor planning, this study adds in the simulation phase the use of a reflectance model. The Nayar model is used as a reflectance model. This model uses three components of reflection: diffuse, specular lobe and specular spike. This paper describes the experimental determination of the Nayar model parameters and also determination of limit gray values (from scanner camera images) for correct decoding of fringes and thus correct scanning of a sheet metal (steel) part. For each sensor position an exposure time for scanning is determined based on simulation. Results of the scanning that were obtained using an ATOS Triple Scan 3D scanner and a KUKA KR 60 HA industrial robot were compared to the simulation. The comparison based on the correspondence of the polygons area acquired in each sensor position (in simulation and in scanning) shows that in the performed measurements the median of differences between simulation and scanning is around 16%.

sensor planning, 3D scanning, automation, reflectance model, sheet metal parts, automotive industry, fringe projection, industrial robot

KOUTECKÝ, T.; PALOUŠEK, D.; BRANDEJS, J.

2015

24. 6. 2015

SPIE

Munich, Germany

9781628416909

PROCEEDINGS OF SPIE - Automated Visual Inspection and Machine Vision

0277-786X

Proceedings of SPIE

9530

United States of America

953005-1

953005-13

13

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2345451