Rajeev Sharma

Bio: Rajeev Sharma is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Gesture & Gesture recognition. The author has an hindex of 34, co-authored 107 publications receiving 5446 citations. Previous affiliations of Rajeev Sharma include University of Illinois at Urbana–Champaign.

Execution of saccades for active vision using a neurocontroller

Abstract: An important mechanism in active vision is that of fixating to different targets of interest in a scene. We present a two-stage design of a neurocontroller for the execution of saccades. The first stage is an "open loop" mode based on a learned spatial representation while the second stage is a closed-loop "visual servoing" mode. Explicit calibration of the kinematic and imaging parameters of the system is replaced with a self-organized learning scheme, thereby providing a flexible and efficient saccade control strategy. Experiments on the University of Illinois Active Vision System (UIAVS) are used to establish the feasibility of this approach.

Real-time tracking of multiple objects using fiducials for augmented reality

Abstract: Augmented reality requires understanding of the scene to know when, where and what to display as a response to changes in the surrounding world. This understanding often involves tracking and recognition of multiple objects and locations in real-time. Technologies frequently used for multiple object tracking, such as electromagnetic trackers are very limited in range, as well as constraining. The use of Computer Vision to identify and track multiple objects is very promising. However, the requirements for traditional object recognition using appearance-based or model-based vision are very complex and their performance is far from real-time. An alternative is to use a set of markers or fiducials for object tracking and recognition. In this paper we present a system of marker coding that, together with an efficient image processing technique, provides a practical method for tracking the marked objects in real-time. The technique is based on clustering of candidate regions in space using a minimum spanning tree. The markers in the codes also allow the estimation of the three dimensional pose of the objects. We demonstrate the utility of the marker-based tracking technique in an Augmented Reality application. The application involves superimposing graphics over real industrial parts that are tracked using fiducials and manipulated by a human in order to complete an assembly. The system aids in the evaluation of the different assembly sequence possibilities.

A framework for motion planning in stochastic environments: applications and computational issues

Abstract: The authors (1995) have previously presented a framework for analyzing motion plans for a robot that operates in an environment that changes over time in an uncertain manner. In this paper, the authors demonstrate the utility of their framework by applying it to a variety of motion planning problems. Examples are computed for problems that involve a changing configuration space, hazardous regions and shelters, and processing of random service requests. To achieve this, the authors have exploited the powerful principle of optimality, which leads to a dynamic programming-based algorithm for determining optimal strategies. Several computed examples are presented and discussed.

Map-Mediated geocollaborative crisis management

Abstract: Managing crises requires collecting geographical intelligence and making spatial decisions through collaborative efforts among multiple, distributed agencies and task groups. Crisis management also requires close coordination among individuals and groups of individuals who need to collaboratively derive information from geospatial data and use that information in coordinated ways. However, geospatial information systems do not currently support group work and can not meet the information needs of crisis managers. This paper describes a group interface for geographical information system, featuring multimodal human input, conversational dialogues, and same-time, different place communications among teams.

A survey of augmented reality

Abstract: This paper surveys the field of augmented reality AR, in which 3D virtual objects are integrated into a 3D real environment in real time. It describes the medical, manufacturing, visualization, path planning, entertainment, and military applications that have been explored. This paper describes the characteristics of augmented reality systems, including a detailed discussion of the tradeoffs between optical and video blending approaches. Registration and sensing errors are two of the biggest problems in building effective augmented reality systems, so this paper summarizes current efforts to overcome these problems. Future directions and areas requiring further research are discussed. This survey provides a starting point for anyone interested in researching or using augmented reality.

Planning Algorithms: Introductory Material

Abstract: Planning algorithms are impacting technical disciplines and industries around the world, including robotics, computer-aided design, manufacturing, computer graphics, aerospace applications, drug design, and protein folding. This coherent and comprehensive book unifies material from several sources, including robotics, control theory, artificial intelligence, and algorithms. The treatment is centered on robot motion planning but integrates material on planning in discrete spaces. A major part of the book is devoted to planning under uncertainty, including decision theory, Markov decision processes, and information spaces, which are the “configuration spaces” of all sensor-based planning problems. The last part of the book delves into planning under differential constraints that arise when automating the motions of virtually any mechanical system. Developed from courses taught by the author, the book is intended for students, engineers, and researchers in robotics, artificial intelligence, and control theory as well as computer graphics, algorithms, and computational biology.

A tutorial on visual servo control

Abstract: This article provides a tutorial introduction to visual servo control of robotic manipulators. Since the topic spans many disciplines our goal is limited to providing a basic conceptual framework. We begin by reviewing the prerequisite topics from robotics and computer vision, including a brief review of coordinate transformations, velocity representation, and a description of the geometric aspects of the image formation process. We then present a taxonomy of visual servo control systems. The two major classes of systems, position-based and image-based systems, are then discussed in detail. Since any visual servo system must be capable of tracking image features in a sequence of images, we also include an overview of feature-based and correlation-based methods for tracking. We conclude the tutorial with a number of observations on the current directions of the research field of visual servo control.

Robot Modeling and Control

Abstract: Preface. 1. Introduction. 2. Rigid Motions and Homogeneous Transformations. 3. Forward and Inverse Kinematics. 4. Velocity Kinematics-The Jacobian. 5. Path and Trajectory Planning. 6. Independent Joint Control. 7. Dynamics. 8. Multivariable Control. 9. Force Control. 10. Geometric Nonlinear Control. 11. Computer Vision. 12. Vision-Based Control. Appendix A: Trigonometry. Appendix B: Linear Algebra. Appendix C: Dynamical Systems. Appendix D: Lyapunov Stability. Index.