Mohamed R. Rahayem

Abstract: Industrial applications like robot-aided welding, automated inspection, and 3D measurements require 3D points to be captured from the surfaces of objects and processed to calculate the information-of-interest. The lack of research focused on fitting ellipses to 3D laser profile data, and the intrinsic features that distinguish it from 2D digital images, motivated us to conduct a comparative study involving the most popular ellipse-fitting methods. After describing our laser profile scanning system, and a survey of ellipse-fitting methods, we compare, using extensive experiments performed with synthetic and real data, the fitting algorithms in terms of stability and accuracy with respect to a variety of factors. The estimate obtained with the best method is used to initialize a robust non-linear iterative ellipse fitting method. Finally, we describe a novel method for the construction of cylindrical surfaces from estimated elliptical sections.

Abstract: Applications like geometric reverse engineering, robot vision and automatic inspection require sets of points to be measured from the surfaces of objects and then processed by segmentation and fitting algorithms to establish shape parameters of interest. In industrial applications where speed, reliability and automatic operation is of interest a measuring system based on a laser profile scanner mounted on an industrial robot can be of interest. In earlier publications we have presented such a system and also a segmentation algorithm for planar surfaces using 2D profile data in combination with robot poses. Due to the data reduction offered by this approach the segmentation algorithm computes faster than algorithms based on 3D point sets alone. Encouraged by the results we have now developed a segmentation algorithm for two different quadric surfaces also based on 2D profiles in combination with robot poses. This paper presents the new algorithm together with test results and also an interesting observation that points to future work.

Abstract: In industrial applications like rapid prototyping, robot vision, and geometric reverse engineering, where speed and automatic operation are important, an industrial robot and a laser profile scanner can be used as a 3D measurement system. This paper is concerned with the problem of segmenting the data from such a system into regions that can be fitted with planar surfaces. We have developed a new algorithm for planar segmentation based on laser scan profiles and robot poses. Compared to a traditional algorithm that operates on a point cloud, the new algorithm is shown to be more effective and faster.

Abstract: Geometric Reverse Engineering (GRE) can be described as the process of fitting surfaces to point data and connecting them to topologically well defined CAD models. We have mounted a laser profile scanner on an industrial robot with a turntable and interfaced them to an Open Source CAD platform. With this tool we have developed an integrated system that can automatically plan and control the robot movements needed to measure an object of unknown shape. Details of this work have been published earlier but we have not described the platform used to integrate the hardware with the GRE software. This paper illustrates the multi disciplinary nature of that problem and investigates what the requirements are for a suitable CAD tool.

Abstract:

Abstract: Laser scanners in combination with accurate orientation devices are often used in Geometric Reverse Engineering (GRE) to measure point data. The industrial robot as a device for orientation has relatively low accuracy but the advantage of being numerically controlled, fast, and flexible and it is therefore of interest to investigate if it can be used in this application. We have built a measuring system based on a laser profile scanner mounted on an industrial robot. In this paper we present results from practical tests based on point data. We also show how data from laser profiles can be used to increase accuracy in some cases. Finally we propose a new method for plane segmentation using laser profiles.

Abstract: High accuracy 3D laser measurment systems are used in applications like inspection and Reverse Engineering (RE). With automatic RE in mind, we have designed and built a system that is based on a laser profile scanner mounted on a standard industrial robot with a turntable. This paper is concerned with the relatively complex accuracy issues of such a system. The different parts of the system are analyzed individually and a brief discussion of how thew interact is given. Finally a detailed analysis of the scanner head along with experimental results is presented.

Abstract: Geometric Reverse Engineering (GRE) is the problem of creating CAD models of real objects by measuring point data from their surfaces. The GRE process is usually divided into four sub processes, data capturing, preprocessing, segmentation, fitting and finally CAD model creation. To automate the GRE process the sub processes need to be integrated. The work presented in this thesis concerns the integration of the sub processes and shows how to implement GRE using a system consisting of a laser profile scanner mounted on an industrial robot equipped with a turntable.The first paper is concerned with the relatively complex accuracy issues of the system and the sources of errors of the system are identified.The second paper continues the work with accuracy issues to investigate the 2D accuracy of the scanner head. Moreover it presents an implementation of planar segmentation and fitting based on point clouds. A new method for planar segmentation based on a laser profiles and robot poses is proposed.The Third paper presents a comprehensive review of the recent development of the measurement system and discusses the integrated GRE process and the requirements for integrating the GRE sub processes using an open source CAD tool which is maintained and developed at Örebro University.The fourth paper addresses the problem of segmentation of the measured data into planar regions by implementing and comparing two different algorithms. The first algorithm is well known and based on point clouds. The second algorithm is new and based on laser profiles and robot poses. Experimental results indicate that the second algorithm is faster and more accurate.The final paper continues the work on segmentation and fitting. A new algorithm to solve the complex problem of quadric segmentation and fitting is presented.Finally, the thesis points out interesting directions of future work.

Abstract: Laser scanners in combination with devices for accurate orientation like Coordinate Measuring Machines (CMM) are often used in Geometric Reverse Engineering (GRE) to measure point data. The industrial robot as a device for orientation has relatively low accuracy but the advantage of being numerically controlled, fast, flexible, rather cheap and compatible with industrial environments. It is therefore of interest to investigate if it can be used in this application. This thesis will describe a measuring system consisting of a laser profile scanner mounted on an industrial robot with a turntable. It will also give an introduction to Geometric Reverse Engineering (GRE) and describe an automatic GRE process using this measuring system. The thesis also presents a detailed accuracy analysis supported by experiments that show how 2D profile data can be used to achieve a higher accuracy than the basic accuracy of the robot. The core topic of the thesis is the investigation of a new technique for planar segmentation. The new method is implemented in the GRE system and compared with an implementation of a more traditional method. Results from practical experiments show that the new method is much faster while equally accurate or better.