ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / This paper describes the design and implementation of an autonomous robot to navigate indoors to a specified target using an inexpensive commercial off the shelf USB camera and processor running an imbedded Linux system. The robot identifies waypoints to aid in navigation, which in our case consists of a series of quick response (QR) codes. Using a 1080p USB camera, the robot could successfully identify waypoints at a distance of over 4 meters, and navigate at a rate of 50 cm/sec.

A radiolocation/navigation system is considered in which mobile nodes use ultra-wideband (UWB) radios to obtain inter-node ranges via round-trip travel time (RTT). Each node is also assumed to contain an inertial measurement unit (IMU) which generates 2D position estimates subject to Gaussian drift and additive noise errors. The key problem in such a system is obtaining 2 or 3-D position estimates from the nonlinear UWB range measurements and fusing the resulting UWB and IMU estimates. The system presented uses a Steepest Descent Random Start (SDRS) algorithm to solve the nonlinear positioning problem. It is shown that SDRS is a stable algorithim under a realistic communications reciprocity assumption. The SDRS estimates are then treated as measurements by the navigation Kalman filter. The navigation filter also processes separate IMU-derived position estimates to update node position/velocity. Simulation results for an urban corridor are given showing < 6 m. rms position errors.

In this work we focus on building local maps to enable wheeled mobile robots to navigate safely and autonomously in urban environments. Urban environments present a variety of hazards that mobile robots have to detect and represent in their maps to navigate safely. Examples of hazards include obstacles such as furniture, drop-offs such as at downward stairs, and inclined surfaces such as wheelchair ramps. We address two shortcomings perceived in the literature on mapping. The first is the extensive use of expensive laser-based sensors for mapping, and the second is the focus on only detecting obstacles when clearly other hazards such as drop-offs need to be detected to ensure safety. Therefore, in this work we develop algorithms for building maps using only relatively inexpensive stereo cameras, that allow safe local navigation by detecting and modeling hazards such as overhangs, drop-offs, and ramps in addition to static obstacles. The hazards are represented using 2D annotated grid maps called local safety maps. Each cell in the map is annotated with one of several labels: Level, Inclined, Non-ground, or, Unknown. Level cells are safe for travel whereas Inclined cells require caution. Non-ground cells are unsafe for travel and represent obstacles, overhangs, or regions lower than safe ground. Level and Inclined cells can be further annotated as being Drop-off Edges. The process of building safety maps consists of three main steps: (i) computing a stereo depth map; (ii) building a 3D model using the stereo depths; and, (iii) analyzing the 3D model for safety to construct the safety map. We make significant contributions to each of the three steps: we develop global stereo methods for computing disparity maps that use edge and color information; we introduce a probabilistic data association method for building 3D models using stereo range points; and we devise a novel method for segmenting and fitting planes to 3D models allowing for a precise safety analysis. In addition, we also develop a stand-alone method for detecting drop-offs in front of the robot that uses motion and occlusion cues and only relies on monocular images. We introduce an evaluation framework for evaluating (and comparing) our algorithms on real world data sets, collected by driving a robot in various environments. Accuracy is measured by comparing the constructed safety maps against ground truth safety maps and computing error rates. The ground truth maps are obtained by manually annotating maps built using laser data. As part of the framework we also estimate latencies introduced by our algorithms and the accuracy of the plane fitting process. We believe this framework can be used for comparing the performance of a variety of vision-based mapping systems and for this purpose we make our datasets, ground truth maps, and evaluation code publicly available. We also implement a real-time version of one of the safety map algorithms on a wheelchair robot and demonstrate it working in various environments. The constructed safety maps allow safe local motion planning and also support the extraction of local topological structures that can be used to build global maps. / text

A guidance, navigation, and control (GN&C) module is being designed and fabricated as part of a series of CubeSats being built by the Satellite Design Laboratory at the University of Texas. A spacecraft attitude control simulation environment called StarBox was created in order to perform trade studies and conduct performance analysis for the GN&C module. Navigation and control algorithms were tested using StarBox and then implemented onto an embedded flight computer. These algorithms were then tested in a hardware-in-the-loop simulation. In addition, the feasibility of utilizing advanced constrained attitude control algorithms was investigated by focusing on implementation in flight software. A mechanical and electrical design for the GN&C module was completed. A prototype system was set up on a bench-top for integrated testing. The analysis indicates that the system will satisfy the requirements of several CubeSat missions, including the current missions at the University of Texas known as Bevo2 and ARMADILLO. / text

published_or_final_version / Geography and Geology / Master / Master of Philosophy

No description available.

Recent studies have demonstrated that images constructed from lidar reflectance information exhibit superior robustness to lighting changes. However, due to the scanning nature of the lidar and assumptions made in previous implementations, data acquired during continuous vehicle motion suffer from geometric motion distortion and can subsequently result in poor metric visual odometry (VO) estimates, even over short distances (e.g., 5-10 m). The first part of this thesis revisits the measurement timing assumption made in previous systems, and proposes a frame-to-frame VO estimation framework based on a pose-interpolation scheme that explicitly accounts for the exact acquisition time of each intrinsic, geometric feature measurement. The second part of this thesis investigates a novel method of lidar calibration that can be applied without consideration of the internal structure of the sensor. Both methods are validated using experimental data collected from a planetary analogue environment with a real scanning laser rangefinder.

No description available.

Navigation by satellite---GNSS---is a local technology with global repercussions. Although operation and control rest in government hands, the consequences of satellite use, most often beneficial, have a worldwide effect. Controversy arises when this free-of-direct-charge technology, on which the International Community relies, fails, thus causing damage to third parties. / It was the intention of the drafters and negotiators of the international space law regime to establish a victim-oriented liability framework, in order to guarantee adequate compensation for damage caused by space activities. Unfortunately, it seems that the present regime has only partially met these goals. / The surest means of obtaining compensation is through domestic legal regimes, but these regimes are naturally subject to the ebb and flow of government policy and judicial discretion. / The present thesis will analyse the established liability regimes for which a damaged GNSS final user may seek compensation, and will finally consider whether the drafting of a GNSS Convention is opportune.

The Global Satellite Navigation System (GNSS), the core of the International Civil Aviation Organization (ICAO) Communication, Navigation, Surveillance/Air Traffic Management concept is capable of supporting future aviation needs. The implementation of this revolutionary technology however remains overshadowed by a series of complex institutional and legal issues. The extraterritorial control and ownership of existing GNSS systems coupled with the dual character of this technology poses a serious threat to the concept of national sovereignty as traditionally understood. This is further aggravated by the fact that there exists only one de facto GNSS signal provider, thus placed in a position to impose its own conditions without reference to the requirements of the rest of the world. / In an attempt to secure both European political independence and a fair share in the global GNSS market Europe has decided to play an active role by launching Galileo, an autonomous global constellation under the control of civil authorities scheduled to be operational by 2008. / The present thesis analyses the desirability of a suitable legal and institutional GNSS framework to achieve universal acceptance of the GNSS. However, in the context of the present status quo it is unrealistic to expect that the only GNSS signal provider surrender its nationally procured system under the umbrella of an international instrument. National security concerns and industrial policy goals underlie this tendency. The present situation may turn different when the incumbent GPS faces the competition of Galileo, an alternative civil system willing to offer firm legal guarantees of service performance albeit in exchange for a fee. The entire viability of this theory remains however dependent upon the European capability of defining a successful business case for Galileo.