Obstacle detection for robot navigation using structured light

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 84-85).Obstacle detection is an essential function for autonomous mobile robots. Current autonomous systems are generally heavy, high-powered devices. Additionally, obstacle detection systems often employ active ranging sensors that exhibit poor angular resolution, thereby preventing vehicles from navigating through narrow spaces. Other systems require considerable processing to resolve objects. The work in this thesis attempts to design a small, lightweight, low-cost, and low-power system to detect obstacles in the direct field of view of a small robotic vehicle. In particular, the range to the obstacle as well as shape estimation is key data that would aid in robot navigation as well as data gathering. Rather than using conventional active or passive ranging techniques, this thesis examines projections of structured light to determine range to the obstacle and surface information of the obstruction. A physical model was developed and tested through simulation, and verified in hardware.by Deborah L. Tran.M.Eng

A non-contact geomatics technique for monitoring membrane roof structures

This thesis presents research carried out to monitor the behaviour of membrane structures, using the non-contact geornatics techniques of terrestrial laser scanning and videogrammetry. Membrane structures are covers or enclosures in which fabric surface is pre-tensioned to provide a stable shape under environmental loads. It is most often adopted by structural engineers as the solution to the roof of a building. Membrane structures resist extemally-imposed loads by a combination of curvature and tension of the highly flexible fabric membrane. However, collapse may occur if the real deflections exceed the designed tolerances. In order to avoid such failures in the future, a generic monitoring system, incorporating in-house software for observing and analysing the behaviour of existing membrane structures, was developed. This system has been applied to observe three different types of as-built membrane structures, with two primary issues investigated and resolved. The first aspect of the research was devoted to determining differences which exist between the designed model and the finished structure. To address this issue, terrestrial laser scanning was applied to generate the as-built model of the membrane structure. Statistical comparisons were then performed between the resultant scanned model and the designed mathematical model. The disparities were determined, allowing the factors causing these differences to be further explored. The second research issue investigated the effects of loading on the displacement of the membrane roof. A videogrammetric monitoring system employing stereo CCD video cameras was used to observe the movements of the membrane roofs. In order to accommodate constraints at the test site, a non-contact control method and structured light targeting were adopted in the monitoring scheme. Once the processing was completed, displacements occurring over time were determined. Investigations on the three types of finished membrane structures have been successfully achieved, proving the system to be a viable metrology tool for structural engineers involved in monitoring real-world membrane structures. The system effectively fulfilled the requirements for understanding the interaction of membrane surface geometry, applied loads and structural response. The information acquired by the system offers great potential to collaborating engineers who are involved in the design and refinement of such structures.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

3D human body modelling from range data

This thesis describes the design, implementation and application of an integrated and fully automated system for interpreting whole-body range data. The system is shown to be capable of generating complete surface models of human bodies, and robustly extracting anatomical features for anthropometry, with minimal intrusion on the subject. The ability to automate this process has enormous potential for personalised digital models in medicine, ergonomics, design and manufacture and for populating virtual environments. The techniques developed within this thesis now form the basis of a commercial product. However, the technical difficulties are considerable. Human bodies are highly varied and many of the features of interest are extremely subtle. The underlying range data is typically noisy and is sparse at occluded areas. In addressing these problems this thesis makes five main research contributions. Firstly, the thesis describes the design, implementation and testing of the whole integrated and automated system from scratch, starting at the image capture hardware. At each stage the tradeoffs between performance criteria are discussed, and experiments are described to test the processes developed. Secondly, a combined data-driven and model-based approach is described and implemented, for surface reconstruction from the raw data. This method addresses the whole body surface, including areas where body segments touch, and other occluded areas. The third contribution is a library of operators, designed specifically for shape description and measurement of the human body. The library provides high-level relational attributes, an "electronic tape measure" to extract linear and curvilinear measurements,as well as low-level shape information, such as curvature. Application of the library is demonstrated by building a large set of detectors to find anthropometric features, based on the ISO 8559 specification. Output is compared against traditional manual measurements and a detailed analysis is presented. The discrepancy between these sets of data is only a few per cent on most dimensions, and the system's reproducibility is shown to be similar to that of skilled manual measurers. The final contribution is that the mesh models and anthropometric features, produced by the system, have been used as a starting point to facilitate other research, Such as registration of multiple body images,draping clothing and advanced surface modelling techniques