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Now showing 1 - 10 of 108
  • Publication
    A Framework for Scalable Cooperative Navigation of Autonomous Vehicles
    (2001-01-01) Fierro, Rafael; Song, Peng; Das, Aveek K; Kumar, R. Vijay
    We describe a general framework for controlling and coordinating a group of non-holonomic mobile robots equipped with range sensors, with applications ranging from scouting and reconnaissance, to search and rescue and manipulation tasks. We first describe a set of control laws that allows each robot to control its position and orientation with respect to neighboring robots or obstacles in the environment. We then develop a coordination protocol that allows the robots to automatically switch between the control laws to follow a specified trajectory. Finally, we describe two simple trajectory generators that are derived from potential field theory. The first allows each robot to plan its reference trajectory based on the information available to it. The second scheme requires sharing of information and results in a trajectory for the designated leader. Numerical simulations illustrate the application of these ideas and demonstrate the scalability of the proposed framework for a large group of robots.
  • Publication
    Simulation of Mechanical Systems With Multiple Frictional Contacts
    (1992-03-01) Wang, Yin-Tien; Kumar, R. Vijay
    There are several applications in robotics and manufacturing in which nominally rigid objects are subject to multiple frictional contacts with other objects. In most previous work, rigid body models have been used to analyze such systems. There are two fundamental problems with such an approach. Firstly, the use of frictional laws, such as Coulomb's law, introduce inconsistencies and ambiguities when used in conjunction with the principles of rigid body dynamics. Secondly, hypotheses traditionally used to model frictional impacts can lead to solutions which violate principles of energy conservation. In this paper these problems are explained with the help of examples. A new approach to the simulation of mechanical systems with multiple, frictional constraints is proposed which is free of inconsistencies.
  • Publication
    Control of Rolling Contacts in Multi-Arm Manipulation
    (1992-08-01) Paljug, Eric; Yun, Xiaoping; Kumar, R. Vijay
    When multiple arms are used to manipulate a large object, it is beneficial and sometimes necessary to maintain and control contacts between the object and the effector (the contacting surface of an arm) through force closure. Rolling and/or sliding can occur at these contacts, and the system is characterized by holonomic as well as nonholonomic (including unilateral) constraints. In this paper, the control of planar rolling contacts is investigated. Multi-arm manipulation systems are typically redundant. In our approach, a minimal set of inputs is employed to control the trajectory of the system while the surplus inputs control the contact condition. The trajectory includes the gross motion of the object as well as the rolling motion at the contacts. A nonlinear feedback scheme for simultaneous control of motion as well as contact conditions is presented. A new algorithm which adapts a two-effector grasp with rolling contacts to external loads and the trajectory is developed. Simulations and experimental results are used to illustrate the salient features in control and planning.
  • Publication
    A Hand-Eye-Arm Coordinated System
    (1991-01-14) Agrawal, Sanjay; Bajcsy, Ruzena; Kumar, R. Vijay
    In this paper we present the description and experiments with a tightly coupled Hand-Eye-Arm manipulatory system. We explain the philosophy and the motivation for building a tightly coupled system that actually consists of very autonomous modules that communicate with each other via a central coordinator. We describe each of the modules in the system and their interactions with each other. We highlight the need for sensory driven manipulation, and explain how the above system, where the hand is equipped with multiple tactile sensors, is capable of both manipulating unknown objects, but also detecting and complying in the case of collisions. We explain the partition of the control of the system into various closed loops, representing coordination both at the level of gross manipulator motions as well as fine motions. We describe the various modes that the system can work in, as well as some of the experiments that are being currently performed using this system.
  • Publication
    A Multiagent System for Intelligent Material Handling
    (1991-10-01) Bajcsy, Ruzena; Paul, Richard P; Yun, Xiaoping; Kumar, R. Vijay
    The goal of our research is to investigate manipulation, mobility, sensing, control and coordination for a multiagent robotic system employed in the task of material handling, in an unstructured, indoor environment. In this research, manipulators, observers, vehicles, sensors, and human operator(s) are considered to be agents. Alternatively, an agent can be a general-purpose agent (for example, a six degree of freedom manipulator on a mobile platform with visual force, touch and position sensors). Possible applications for such a system includes handling of waste and hazardous materials, decontamination of nuclear plants, and interfacing between special purpose material handling devices in warehouses. The fundamental research problems that will be studied are organization, or the decomposition of the task into subtasks and configuring the multiple agents with appropriate human interaction, exploration, or the process of exploring geometric, material and other properties about the environment and other agents, and coordination, or the dynamic control of multiple agents for manipulation and transportation of objects to a desired destination.
  • Publication
    Motion Planning in Humans and Robots
    (1997-10-01) Kumar, R. Vijay; Ostrowski, James P.; Zefran, Milos
    We present a general framework for generating trajectories and actuator forces that will take a robot system from an initial configuration to a goal configuration in the presence of obstacles observed with noisy sensors. The central idea is to find the motion plan that optimizes a performance criterion dictated by specific task requirements. The approach is motivated by studies of human voluntary manipulation tasks that suggest that human motions can be described as solutions of certain optimization problems.
  • Publication
    Cooperative Material Handling by Human and Robotic Agents:Module Development and System Synthesis
    (1994-12-15) Adams, Julie A; Bajcsy, Ruzena; Kumar, R. Vijay; Košecká, Jana; Mintz, Max L; Mandelbaum, Robert; Paul, Richard P; Wang, C.; Yamamoto, Yoshio; Yun, Xiaoping
    In this paper we present the results of a collaborative effort to design and implement a system for cooperative material handling by a small team of human and robotic agents in an unstructured indoor environment. Our approach makes fundamental use of human agents' expertise for aspects of task planning, task monitoring, and error recovery. Our system is neither fully autonomous nor fully teleoperated. It is designed to make effective use of human abilities within the present state of the art of autonomous systems. It is designed to allow for and promote cooperative interaction between distributed agents with various capabilities and resources. Our robotic agents refer to systems which are each equipped with at least one sensing modality and which possess some capability for self-orientation and/or mobility. Our robotic agents are not required to be homogeneous with respect to either capabilities or function. Our research stresses both paradigms and testbed experimentation. Theory issues include the requisite coordination principles and techniques which are fundamental to the basic functioning of such a cooperative multi-agent system. We have constructed a testbed facility for experimenting with distributed multi-agent architectures. The required modular components of this testbed are currently operational and have been tested individually. Our current research focuses on the integration of agents in a scenario for cooperative material handling.
  • Publication
    Control of Multiple Arm Systems With Rolling Constraints
    (1991-10-01) Yun, Xiaoping; Kumar, R. Vijay; Sarkar, Nilanjan; Paljug, Eric
    When multiple arms are used to manipulate a large object, it is necessary to maintain and control contacts between the object and effector(s) on one or more arms. The contacts are characterized by holonomic as well as nonholonomic constraints. This paper addresses the control of mechanical systems subject to nonholonomic constraints, rolling constraints in particular. It has been shown that such a system is always controllable, but cannot be stabilized to a single equilibrium by smooth feedback [l, 2]. In this paper, we show that the system is not input-state linearizable though input-output linearization is possible with appropriate output equations. Further, if the system is position-controlled (i.e., the output equation is a functions of position variables only), it has a zero dynamics which is Lagrange stable but not asymptotically stable. We discuss the analysis and controller design for planar as well as spatial multi-arm systems and present results from computer simulations to demonstrate the theoretical results.
  • Publication
    A Two-Arm Exploratory System for Identifying Moving and Removable Parts
    (1989-11-01) Yan, Xiaoping; Lee, Insup; King, Robert; Kumar, R. Vijay
    When working in an unstructurcd environment, a robot has partial or no a priori knowledge of the environment. The purpose of exploratory robotics is to provide robots with the ability to learn and automatically construct models of the environment by exploring and interacting with the environment. This paper describes a two-arm exploratory system whose purpose is to identify movable and removable parts of an object, and the mobility of the parts. The system is implemented by integrating RCI (Robot Control Interface) with Timix (a real-time kernel). The identification is accomplished through exp1oratory procedures which are generated from a numbcr of robust motion primitives.
  • Publication
    Important Considerations in Force Control With Applications to Multi-Arm Manipulation
    (1991-10-01) Paljug, Eric; Sugar, Thomas G; Kumar, R. Vijay; Yun, Xiaoping
    This paper addresses force control in overconstrained dynamic systems with special emphasis on robot control and multiarm coordination. Previous approaches to force control are studied and many of these are shown to be unsuitable for dynamic force control. Practical and theoretical considerations for designing force control algorithms are discussed. Experimental and simulation results that validate the theoretical findings are presented for a single-degree-of-freedom pneumatic force controller. Finally the theoretical development of a two-arm manipulation system with an extended statespace formulation and a computer simulation of the system are presented to illustrate the application of the basic ideas to a more complicated system.