Taylor, Camillo J
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Publication Reconstruction of Linearly Parameterized Models from Single Images with a Camera of Unknown Focal Length(2001-07-01) Jelinek, David; Taylor, Camillo JThis paper deals with the problem of recovering the dimensions of an object and its pose from a single image acquired with a camera of unknown focal length. It is assumed that the object in question can be modeled as a polyhedron where the coordinates of the vertices can be expressed as a linear function of a dimension vector, λ. The reconstruction program takes as input, a set of correspondences between features in the model and features in the image. From this information, the program determines an appropriate projection model for the camera (scaled orthographic or perspective), the dimensions of the object, its pose relative to the camera and, in the case of perspective projection, the focal length of the camera. This paper describes how the reconstruction problem can be framed as an optimization over a compact set with low dimension - no more than four. This optimization problem can be solved efficiently by coupling standard nonlinear optimization techniques with a multistart method which generates multiple starting points for the optimizer by sampling the parameter space uniformly. The result is an efficient, reliable solution system that does not require initial estimates for any of the parameters being estimated.Publication Using Smart Cameras to Localize Self-Assembling Modular Robots(2007-09-25) Shirmohammadi, Babak; Taylor, Camillo J; Yim, Mark; Sastra, Jimmy; Park, MikeIn order to realize the goal of self assembling or self reconfiguring modular robots the constituent modules in the system need to be able to gauge their position and orientation with respect to each other. This paper describes an approach to solving this localization problem by equipping each of the modules in the ensemble with a smart camera system. The paper describes one implementation of this scheme on a modular robotic system and discusses the results of a self assembly experiment.Publication Reconstruction of Articulated Objects from Point Correspondences in a Single Uncalibrated Image(2000-12-01) Taylor, Camillo JThis paper investigates the problem of recovering information about the configuration of an articulated object, such as a human figure, from point correspondences in a single image. Unlike previous approaches, the proposed reconstruction method does not assume that the imagery was acquired with a calibrated camera. An analysis is presented which demonstrates that there are a family of solutions to this reconstruction problem parameterized by a single variable. A simple and effective algorithm is proposed for recovering the entire set of solutions by considering the foreshortening of the segments of the model in the image. Results obtained by applying this algorithm to real images are presented.Publication Camera Trajectory Estimation using Inertial Sensor Measurements and Structure fom Motion Results(2001-12-08) Jung, Sang-Hack; Taylor, Camillo JThis paper describes an approach to estimating the trajectory of a moving camera based on the measurements acquired with an inertial sensor and estimates obtained by applying a structure from motion algorithm to a small set of keyframes in the video sequence. The problem is formulated as an offline trajectory fitting task rather than an online integration problem. This approach avoids many of the issues usually associated with inertial estimation schemes. One of the main advantages of the proposed technique is that it can be applied in situations where approaches based on feature tracking would have significant difficulties. Results obtained by applying the procedure to extended sequences acquired with both conventional and omnidirectional cameras are presented.Publication A Vision-Based Formation Control Framework(2002-10-01) Das, Aveek K.; Kumar, R. Vijay; Fierro, Rafael; Ostrowski, James P.; Taylor, Camillo J; Spletzer, JohnWe describe a framework for cooperative control of a group of nonholonomic mobile robots that allows us to build complex systems from simple controllers and estimators. The resultant modular approach is attractive because of the potential for reusability. Our approach to composition also guarantees stability and convergence in a wide range of tasks. There are two key features in our approach: 1) a paradigm for switching between simple decentralized controllers that allows for changes in formation; 2) the use of information from a single type of sensor, an omnidirectional camera, for all our controllers. We describe estimators that abstract the sensory information at different levels, enabling both decentralized and centralized cooperative control. Our results include numerical simulations and experiments using a testbed consisting of three nonholonomic robots.Publication A Framework and Architecture for Multi-Robot Coordination(2002-10-01) Alur, Rajeev; Das, Aveek J; Kumar, R. Vijay; Esposito, Joel; Lee, Insup; Fierro, Rafael; Grudic, Gregory; Pappas, George J; Hur, Yerang; Taylor, Camillo J; Ostrowski, James; Southall, B.; Spletzer, John RIn this paper, we present a framework and the software architecture for the deployment of multiple autonomous robots in an unstructured and unknown environment with applications ranging from scouting and reconnaissance, to search and rescue and manipulation tasks. Our software framework provides the methodology and the tools that enable robots to exhibit deliberative and reactive behaviors in autonomous operation, to be reprogrammed by a human operator at run-time, and to learn and adapt to unstructured, dynamic environments and new tasks, while providing performance guarantees. We demonstrate the algorithms and software on an experimental testbed that involves a team of car-like robots using a single omnidirectional camera as a sensor without explicit use of odometry.Publication Maintaining network connectivity and performance in robot teams(2008-01-01) Hsieh, M. Ani; Kumar, R. Vijay; Cowley, Anthony; Taylor, Camillo JIn this paper, we present an experimental study of strategies for maintaining end-to-end communication links for tasks such as surveillance, reconnaissance, and target search and identification, where team connectivity is required for situational awareness. Our main contributions are three fold: (a) We present the construction of a radio signal strength map that can be used to plan multi-robot tasks and also serve as useful perceptual information. We show how a nominal model of an urban environment obtained by aerial surveillance is used to generate strategies for exploration. (b) We present reactive controllers for communication link maintenance; and (c) we consider the differences between monitoring signal strength versus data throughput. Experimental results, obtained using our multi-robot testbed in three representative urban environments, are presented with each of our main contributions.Publication Calibrating an Air-Ground Control System from Motion Correspondences(2004-06-27) Rao, Rahul; Taylor, Camillo J; Kumar, R. VijayIn this paper we consider the problem of controlling the motion of a vehicle moving on a ground plane based on aerial imagery. In the course of this work we propose a novel analysis of the relationship between the velocity of the vehicle on the ground plane and the velocity of its projection in the image. We show that this relationship provides information about a subset of the parameters of the homography relating the ground plane to the aerial image plane and describe how we can recover this relationship from available measurements.Publication Human Robot Interaction: Application to Smart Wheelchairs(2002-05-01) Rao, Rahul; Conn, K.; Jung, Sang-Hack; Katupitiya, J.; Kumar, R. Vijay; Kientz, Terry L; Ostrowski, James P.; Taylor, Camillo J; Patel, SarangiThis paper addresses the problem of human robot interaction with application to the design of assistive devices. We describe the design and development of a prototype of a smart wheelchair that can be commanded by a rider. Specifically, we focus on (a) the vision-based human interaction interface; (b) the suite of sensors on the chair; and (c) the software architecture and the control algorithms used to control the chair.Publication Planning and Control of Mobile Robots in Image Space from Overhead Cameras(2005-04-01) Rao, Rahul S; Kumar, Vijay; Taylor, Camillo JIn this work, we present a framework for the development of a planar mobile robot controller based on image plane feedback. We show that the design of such a motion controller can be accomplished in the image plane by making use of a subset of the parameters that relate the image plane to the ground plane, while still leveraging the simplifications offered by modeling the system as a differentially flat system. Our method relies on a waypoint-based trajectory generator, with all the waypoints specified in the image, as seen by an overhead observer. We present some results from simulation as well as from experiments that validate the ideas presented in this work and discuss some ideas for future work