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Tsiotras, Panagiotis

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Publication Search Results

Now showing 1 - 7 of 7
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    Optimal Motion Planning with the Half-Car Dynamical Model for Autonomous High-Speed Driving
    (Georgia Institute of Technology, 2013-06) Cowlagi, Raghvendra V. ; Peters, Steven C. ; Karaman, Sertac ; Frazzoli, Emilio ; Tsiotras, Panagiotis ; Iagnemma, Karl ; Jeong Hwan, Jeon
    We discuss an implementation of the RRT* optimal motion planning algorithm for the half-car dynamical model to enable autonomous high-speed driving. To develop fast solutions of the associated local steering problem, we observe that the motion of a special point (namely, the front center of oscillation) can be modeled as a double integrator augmented with fictitious inputs. We first map the constraints on tire friction forces to constraints on these augmented inputs, which provides instantaneous, state-dependent bounds on the curvature of geometric paths feasibly traversable by the front center of oscillation. Next, we map the vehicle’s actual inputs to the augmented inputs. The local steering problem for the half- car dynamical model can then be transformed to a simpler steering problem for the front center of oscillation, which we solve efficiently by first constructing a curvature-bounded geometric path and then imposing a suitable speed profile on this geometric path. Finally, we demonstrate the efficacy of the proposed motion planner via numerical simulation results.
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    Hierarchical motion planning with kinodynamic feasibility guarantees: Local trajectory planning via model predictive control
    (Georgia Institute of Technology, 2012-05) Cowlagi, Raghvendra V. ; Tsiotras, Panagiotis
    Motion planners for autonomous vehicles often involve a two-level hierarchical structure consisting of a high-level, discrete planner and a low-level trajectory generation scheme. To ensure compatibility between these two levels of planning, we previously introduced a motion planning framework based on multiple-edge transition costs in the graph used by the discrete planner. This framework is enabled by a special local trajectory generation problem, which we address in this paper. In particular, we discuss a trajectory planner based on model predictive control for complex vehicle dynamical models. We demonstrate the efficacy of our overall motion planning approach via examples involving non-trivial vehicle models and complex environments, and we offer comparisons of our motion planner with state-of-the-art randomized sampling-based motion planners.
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    Multi-resolution Path Planning: Theoretical Analysis, Efficient Implementation, and Extensions to Dynamic Environments
    (Georgia Institute of Technology, 2010-12) Cowlagi, Raghvendra V. ; Tsiotras, Panagiotis
    A multi-resolution path planning algorithm based on the wavelet transform of the environment has been reported previously in the literature. In this paper, we provide a proof of completeness of this algorithm. In addition, we present an implementation of this algorithm that reuses information obtained in previous iterations to perform subsequent iterations more efficiently. Finally, we extend this path planning algorithm to dynamic environments by presenting a simple scheme for updating the wavelet transform coefficients to reflect changes in the environment.
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    Kinematic Feasibility Guarantees in Geometric Path Planning Using History-based Transition Costs over Cell Decompositions
    (Georgia Institute of Technology, 2010-06) Cowlagi, Raghvendra V. ; Tsiotras, Panagiotis
    The hierarchical decomposition of motion planning tasks into geometric path planning, followed by kinodynamic motion planning is useful for designing efficient algorithms, but it entails the possibility of inconsistency between the two layers of planning. In an earlier paper, we proposed a general framework, based on rectangular cell decompositions, for incorporating information about the kinodynamic behavior of the vehicle in the geometric planning layer itself. In this paper, we use this framework to design a geometric path planning scheme which simultaneously finds an obstacle-free channel of cells from the initial point to the goal, as well as a vehicle state trajectory lying within that channel.
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    On the Existence and Synthesis of Curvature-Bounded Paths Inside Nonuniform Rectangular Channels
    (Georgia Institute of Technology, 2010) Cowlagi, Raghvendra V. ; Tsiotras, Panagiotis
    Motion planners for autonomous mobile vehicles that are based on rectangular cell decompositions are often required to construct kinematically feasible path – typically curvature-bounded paths – traversing rectangular channels. In this paper, we present a numerical algorithm for determining the existence of a curvature-bounded path contained within a rectangular channel. The rectangular cells comprising the channel are assumed to be of arbitrary, non-uniform dimensions and the bounds on curvature are allowed to be different for different cells. The proposed algorithm is based on the explicit construction of the cone of feasible directions for a bounded-curvature path at the cell exit edge, given the entry point for each cell in the channel. Based on this analysis, we devise a path construction scheme that retains the convenience of cell-by-cell path synthesis but eliminates the guesswork involved in choosing terminal conditions within each cell.
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    Multiresolution Path Planning with Wavelets: A Local Replanning Approach
    (Georgia Institute of Technology, 2008) Cowlagi, Raghvendra V. ; Tsiotras, Panagiotis
    A path planning algorithm based on multiresolution cell decomposition of the environment using wavelets is proposed. The environment is assumed to be given by an occupancy grid at fine resolution. The algorithm constructs a cell decomposition at several levels of resolution (cell sizes) and constructs an optimal path to the destination from the current location of the agent. At each step the algorithm iteratively refines a coarse approximation to the path through local replanning. The replanning process uses previous information to refine the original cell channel in the immediate area of the path. This is done efficiently using the wavelet coefficients. Numerical tests show a speed-up of an order of magnitude over the baseline algorithm with minimal impact on the overall optimality of the resulting path. A comparative study with the well-known D* algorithm is also provided.
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    Beyond Quadtrees: Cell Decomposition for Path Planning using the Wavelet Transform
    (Georgia Institute of Technology, 2007-12) Cowlagi, Raghvendra V. ; Tsiotras, Panagiotis
    Path planning techniques based on hierarchical multiresolution cell decompositions are suitable for online implementation due to their simplicity and speed of implementation. We present an efficient multiresolution cell decomposition scheme based on the Haar wavelet transform. The decomposition approximates the environment using high resolution close to the agent and coarse resolution elsewhere. We demonstrate an algorithm to extract the adjacency and transition cost relations of the cells directly from the wavelet transform coefficients.