Browsing by Author "Xing, Zhiqiang"
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Item Analysis of Unmanned Aerial Vehicles Concept of Operations in ITS Applications(Center for Transportation Studies, 2011-03) Gebre-Egziabher, Demoz; Xing, ZhiqiangThe work described in this report is about developing a framework for the design of concept of operations (CONOP), which use small uninhabited aerial systems (SUAS) to support of intelligent transportation system (ITS) application of highway and transportation infrastructure monitoring. In these envisioned applications, these vehicles will be used for tasks such as remote collection of traffic data or inspection of roads and bridges. As such, a risk that has to be managed for these applications is that of vehicle-infrastructure collision. Various solutions to ensure safe separation between the unmanned aerial vehicle (UAV) and the object being inspected have been proposed. However, most, if not all, of these solutions rely on a multi-sensor approach, which combines digital maps of the infrastructure being inspected with an integrated GPS/Inertial navigator. While "turn key" solutions for such multi-sensor systems exist, the performance specifications provided by their manufactures does not provide sufficient information to allow precisely quantifying or bounding the collision risk. Furthermore, size, weight and power (or SWAP) constraints posed by these small aerial vehicles limits the use of redundant hardware and/or software as a risk mitigation strategy. The purpose of the work reported here was to develop a framework for the design of CONOPs, which take these SUAS limitations into account. The method outlined shows, in part, how these vehicle/infrastructure collision risks can be estimated or conservatively bounded.Item Over-bounding integrated INS/GNSS output errors.(2010-10) Xing, ZhiqiangThis thesis examines issues associated with the integrity risk over-bounding in INS/GNSS integration. The integrity risk over-bounding requires three issues to be considered: Modeling and over-bounding of inertial sensor output errors; modeling and over-bounding of GNSS signal errors; and the over-bounding of the output of nonlinear transformations of random variables. While considerable amaount of work has been done in modeling and over-bounding GNSS errors, this thesis explored the other two relatively new issues. This thesis develops a methodology for doing this whereby the varying and higher order process in the actual navigation solution are over-bounded using a lower-order, stationary time-domain model that is a conservative approximation of the actual noise process. This requires developing and validating unified mathematical models for over-bounding the behavior of the post calibration residual errors of inertial sensors. The mathematical models of the INS are a set of nonlinear stochastic differential equations. The nonlinearities of the system come from two parts which need to be handled in the over-bounding: the nonlinear transformation of the sensor errors, and the nonlinear transformation of the previous navigation states. A methodology for analyzing and over-bounding nonlinear transformations of random variables which occur in INS systems is developed. It is shown that the INS system output errors can be over-bounded by Gaussian distributions with an inflated variance. How this approach can be used to over-bound errors in simple vehicle navigation and guidance applications is shown by examples.