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.

Towards a unified framework for tracking and analysis of human motion

Abstract: We propose a framework for detecting, tracking and analyzing non-rigid motion based on learned motion patterns. The framework features an appearance based approach to represent the spatial information and hidden Markov models (HMM) to encode the temporal dynamics of the time varying visual patterns. The low level spatial feature extraction is fused with the temporal analysis, providing a unified spatio-temporal approach to common detection, tracking and classification problems. This is a promising approach for many classes of human motion patterns. Visual tracking is achieved by extracting the most probable sequence of target locations from a video stream using a combination of random sampling and the forward procedure from HMM theory. The method allows us to perform a set of important tasks such as activity recognition, gait-analysis and keyframe extraction. The efficacy of the method is shown on both natural and synthetic test sequences.

GeoCollaborative crisis management: designing technologies to meet real-world needs

Abstract: Preventing, preparing for, responding to, and recovering from natural and human-induced disasters all require access to geographically referenced information and tools for making available information relevant to the tasks at hand. Goals of the research summarized here are to advance our scientific understanding of how groups (or groups of groups) work with geospatial information and technologies in crisis management and to use that understanding to guide development of tools that are intuitive for non-specialist users and that enable coordination within and across crisis management teams. This overview highlights progress on: understanding work in crisis management, enabling distributed information access through context-mediated geo-semantic interoperability, extension of natural, multimodal interface methods to mobile devices, development of a collaborative map-based web portal to support international humanitarian relief logistics, and technology transition into real-world practice. We also introduce our new DHS-supported Regional Visualization & Analytics Center, which builds directly upon our GCCM work.

Analysis of uncertainty bounds due to quantization for three-dimensional position estimation using multiple cameras

Abstract: An important source of error when estimating the 3-D position of a point from two (stereo), three (trinocular), or more cameras is that of quantization error on the image planes. In this paper, we are concerned with bounding the quantization errors when using multiple cameras defined in terms of uncertainty regions in 3-D. We use a geometric error analysis method that models the quantization error as projected pyramids and the uncertainty region as an ellipsoid around the polyhedron intersection of the pyramids. We present a computational technique for determining the uncertainty ellipsoid for an arbitrary number of cameras. A numerical measure of uncertainty bound such as the volume of the ellipsoid can then be computed for aiding camera placement, trajectory planning, and various other multiple camera applications.

Exploiting speech/gesture co-occurrence for improving continuous gesture recognition in weather narration

Abstract: In order to incorporate naturalness in the design of human computer interfaces (HCI), it is desirable to develop recognition techniques capable of handling continuous natural gesture and speech inputs. Though many different researchers have reported high recognition rates for gesture recognition using hidden Markov models (HMM), the gestures used are mostly pre-defined and are bound with syntactical and grammatical constraints. But natural gestures do not string together in syntactical bindings. Moreover, strict classification of natural gestures is not feasible. We have examined hand gestures made in a very natural domain, that of a weather person narrating in front of a weather map. The gestures made by the weather person are embedded in a narration. This provides us with abundant data from an uncontrolled environment to study the interaction between speech and gesture in the context of a display. We hypothesize that this domain is very similar to that of a natural human-computer interface. We present an HMM architecture for continuous gesture recognition framework and keyword spotting. To explore the relation between gesture and speech, we conducted a statistical co-occurrence analysis of different gestures with a selected set of spoken keywords. We then demonstrate how this co-occurrence analysis can be exploited to improve the performance of continuous gesture recognition.

Prosody based co-analysis for continuous recognition of coverbal gestures

Abstract: Although recognition of natural speech and gestures have been studied extensively, previous attempts at combining them in a unified framework to boost classification were mostly semantically motivated, e.g., keyword-gesture co-occurrence. Such formulations inherit the complexity of natural language processing. This paper presents a Bayesian formulation that uses a phenomenon of gesture and speech articulation for improving accuracy of automatic recognition of continuous coverbal gestures. The prosodic features from the speech signal were co-analyzed with the visual signal to learn the prior probability of co-occurrence of the prominent spoken segments with the particular kinematical phases of gestures. It was found that the above co-analysis helps in detecting and disambiguating small hand movements, which subsequently improves the rate of continuous gesture recognition. The efficacy of the proposed approach was demonstrated on a large database collected front the weather channel broadcast. This formulation opens new avenues for bottom-up frameworks of multimodal integration.

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.