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Articles 1 - 30 of 34
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Dynamic Role Assignment For Cooperative Robots, Luiz Chaimowicz, Mario F. M. Campos, R. Vijay Kumar
Dynamic Role Assignment For Cooperative Robots, Luiz Chaimowicz, Mario F. M. Campos, R. Vijay Kumar
R. Vijay Kumar
This paper proposes a new methodology for coordinating multi-robot teams in the execution of cooperative tasks. It is based on a dynamic role assignment mechanism, in which the robots assume and exchange roles during cooperation. We model the role assignment under a hybrid systems framework, using a hybrid automaton to represent roles, transitions and controllers. Using a multi-robot simulator, the methodology is demonstrated in a cooperative transportation task, in which a group of robots must find and cooperatively transport several objects scattered in the environment.
Input-To-State Stability On Formation Graphs, Herbert G. Tanner, George J. Pappas, R. Vijay Kumar
Input-To-State Stability On Formation Graphs, Herbert G. Tanner, George J. Pappas, R. Vijay Kumar
R. Vijay Kumar
Formation stability is now analyzed under a new prism using input-to-state stability. Formation ISS relates leader input to internal state of the formation and characterizes the way this input affects stability performance. Compared to other notions of stability for interconnected systems, formation ISS does not require attenuation of errors as they propagate, but instead quantifies the amplification and provides worst case bounds. The control interconnections that give rise to the formation are represented by a graph. The formation graphs considered are built from a small number of primitive graphs, the stability properties of which are used to reason about the …
The Effect Of Feedback And Feedforward On Formation Iss, Herbert G. Tanner, R. Vijay Kumar, George J. Pappas
The Effect Of Feedback And Feedforward On Formation Iss, Herbert G. Tanner, R. Vijay Kumar, George J. Pappas
R. Vijay Kumar
A new type of stability of leader follower formations is defined, based on input-to-state stability (ISS) properties of cascade interconnections. Formation ISS links leader input to internal state of the formation and characterizes the way this input affects performance. The effect of feedforward and feedback inter-agent communication is then investigated in this framework and it is indicated how the structure of interconnections and the amount of available information can affect stability performance.
Workspace Delineation Of Cable-Actuated Parallel Manipulators, Ethan Stump, R. Vijay Kumar
Workspace Delineation Of Cable-Actuated Parallel Manipulators, Ethan Stump, R. Vijay Kumar
R. Vijay Kumar
While there is extensive literature available on parallel manipulators in general, there has been much less attention given to cable-driven parallel manipulators. In this paper, we address the problem of analyzing the reachable workspace using the tools of semi-definite programming. We build on earlier work [1,2] done using similar techniques by deriving limiting conditions that allow us to compute analytic expressions for the boundary of the reachable workspace. We illustrate this computation for a planar parallel manipulator with four actuators.
A Two-Arm Exploratory System For Identifying Moving And Removable Parts, Xiaoping Yan, Robert King, Insup Lee, R. Vijay Kumar
A Two-Arm Exploratory System For Identifying Moving And Removable Parts, Xiaoping Yan, Robert King, Insup Lee, R. Vijay Kumar
R. Vijay Kumar
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 …
Experiments In Multirobot Air-Ground Coordination, Luiz Chaimowicz, Ben Grocholsky, James F. Keller, R. Vijay Kumar, Camillo J. Taylor
Experiments In Multirobot Air-Ground Coordination, Luiz Chaimowicz, Ben Grocholsky, James F. Keller, R. Vijay Kumar, Camillo J. Taylor
R. Vijay Kumar
This paper addresses the problem of coordinating aerial and ground vehicles in tasks that involve exploration, identification of targets and maintaining a connected communication network. We focus on the problem of localizing vehicles in urban environments where GPS signals are often unreliable or unavailable. We first describe our multi-robot tesbed and control software used to coordinate ground and aerial vehicles. We present the results of experiments in air-ground localization analyzing three complementary approaches to determining the positions of vehicles on the ground. We show that the coordination of aerial vehicles with ground vehicles is necessary to get accurate estimates of …
Incorporating User Inputs In Motion Planning For A Smart Wheelchair, Sarangi P. Parikh, Valdir Grassi Jr., R. Vijay Kumar, Jun Okamoto Jr.
Incorporating User Inputs In Motion Planning For A Smart Wheelchair, Sarangi P. Parikh, Valdir Grassi Jr., R. Vijay Kumar, Jun Okamoto Jr.
R. Vijay Kumar
We describe the development and assessment of a computer controlled wheelchair equipped with a suite of sensors and a novel interface, called the SMARTCHAIR. The main focus of this paper is a shared control framework which allows the human operator to interact with the chair while it is performing an autonomous task. At the highest level, the autonomous system is able to plan paths using high level deliberative navigation behaviors depending on destinations or waypoints commanded by the user. The user is able to locally modify or override previously commanded autonomous behaviors or plans. This is possible because of our …
Analysis And Simulation Of Mechanical Systems With Multiple Frictional Contacts, Yin Tien Wang, R. Vijay Kumar
Analysis And Simulation Of Mechanical Systems With Multiple Frictional Contacts, Yin Tien Wang, R. Vijay Kumar
R. Vijay Kumar
In many engineering applications such as assembly of mechanical components, robot manipulation, gripping, fixturing and part feeding, there are situations in which a rigid body is subject to multiple frictional contacts with other bodies. It is proposed to develop a systematic method for the analysis and simulation of such systems. A detailed study is presented on rigid body impact laws, and the assumption of contact compliance is investigated.
Multi-Agent Hybrid System Simulation, Joel Esposito, R. Vijay Kumar, George J. Pappas
Multi-Agent Hybrid System Simulation, Joel Esposito, R. Vijay Kumar, George J. Pappas
R. Vijay Kumar
In this paper a technique is presented for simulating a set of hybrid systems (agents) whose continuous dynamics are decoupled; however coupling is introduced in the form of constraints (inequalities whose violation signifies the occurrence of a discrete event). We introduce a step size selection algorithm, motivated by the control theoretic concept of Input/Output linearization, which allows two or more agents to be integrated asynchronously using different step sizes when the state is away from the constraint. When the state approaches a constriant, the algorithm is able to bring the two local time clocks into synchronization and localize …
Modeling And Control Of Formations Of Nonholonomic Mobile Robots, Jaydev P. Desai, James P. Ostrowski, R. Vijay Kumar
Modeling And Control Of Formations Of Nonholonomic Mobile Robots, Jaydev P. Desai, James P. Ostrowski, R. Vijay Kumar
R. Vijay Kumar
This paper addresses the control of a team of nonholonomic mobile robots navigating in a terrain with obstacles while maintaining a desired formation and changing formations when required, using graph theory.We model the team as a triple, (g, r, H), consisting of a group element g that describes the gross position of the lead robot, a set of shape variables r that describe the relative positions of robots, and a control graph H that describes the behaviors of the robots in the formation. Our framework enables the representation and enumeration of possible control graphs and the coordination of transitions between …
Efficient Dynamic Simulation Of Robotic Systems With Hierarchy, Joel M. Esposito, R. Vijay Kumar
Efficient Dynamic Simulation Of Robotic Systems With Hierarchy, Joel M. Esposito, R. Vijay Kumar
R. Vijay Kumar
In this paper multirate numerical integration techniques are introduced as a tool for simulating robotic systems. In contrast with traditional simulation techniques where a single global time step is used, multirate methods seek a gain in efficiency by using larger step sizes for the slow varying components and smaller step sizes for components with rapidly changing solutions. We argue that many robotic systems inherently posses different time scales, and therefore can benefit from multirate techniques. We have developed a multirate version of the popular Adams Predictor Corrector methods, which has a variety of modern features. We present results on the …
A Hand-Eye-Arm Coordinated System, Sanjay Agrawal, Ruzena Bajcsy, R. Vijay Kumar
A Hand-Eye-Arm Coordinated System, Sanjay Agrawal, Ruzena Bajcsy, R. Vijay Kumar
R. Vijay Kumar
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. …
Simulation Of Mechanical Systems With Multiple Frictional Contacts, Yin-Tien Wang, R. Vijay Kumar
Simulation Of Mechanical Systems With Multiple Frictional Contacts, Yin-Tien Wang, R. Vijay Kumar
R. Vijay Kumar
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. …
Modeling And Analyzing Biomolecular Networks, Rajeev Alur, Calin Belta, R. Vijay Kumar, Max L. Mintz, George J. Pappas, Harvey Rubin, Jonathan Schug
Modeling And Analyzing Biomolecular Networks, Rajeev Alur, Calin Belta, R. Vijay Kumar, Max L. Mintz, George J. Pappas, Harvey Rubin, Jonathan Schug
R. Vijay Kumar
The authors argue for the need to model and analyze biological networks at molecular and cellular levels. They propose a computational toolbox for biologists. Central to their approach is the paradigm of hybrid models in which discrete events are combined with continuous differential equations to capture switching behavior.
Control Of Multi-Affine Systems On Rectangles With Applications To Hybrid Biomolecular Networks, Calin Belta, Luc C.G.J.M. Habets, R. Vijay Kumar
Control Of Multi-Affine Systems On Rectangles With Applications To Hybrid Biomolecular Networks, Calin Belta, Luc C.G.J.M. Habets, R. Vijay Kumar
R. Vijay Kumar
Given a multi-affine system on an N-dimensional rectangle, the problem of reaching a particular facet, using multi-affine state feedback is studied. Necessary conditions and sufficient conditions for the existence of a solution are derived in terms of linear inequalities on the input vectors at the vertices of the rectangle, and a method for constructing a multi-affine state feedback solution is presented. The technique is applied to the control of hybrid models of bioregulatory networks.
Leader-To-Formation Stability, Herbert G. Tanner, George J. Pappas, R. Vijay Kumar
Leader-To-Formation Stability, Herbert G. Tanner, George J. Pappas, R. Vijay Kumar
R. Vijay Kumar
The paper investigates the stability properties of mobile agent formations which are based on leader following. We derive nonlinear gain estimates that capture how leader behavior affects the interconnection errors observed in the formation. Leader-to-formation stability (LFS) gains quantify error amplification, relate interconnection topology to stability and performance, and offer safety bounds for different formation topologies. Analysis based on the LFS gains provides insight to error propagation and suggests ways to improve the safety, robustness, and performance characteristics of a formation.
A Vision-Based Formation Control Framework, Aveek K. Das, Rafael Fierro, R. Vijay Kumar, James P. Ostrowski, John Spletzer, Camillo J. Taylor
A Vision-Based Formation Control Framework, Aveek K. Das, Rafael Fierro, R. Vijay Kumar, James P. Ostrowski, John Spletzer, Camillo J. Taylor
R. Vijay Kumar
We 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 …
Decentralized Motion Planning For Multiple Robots Subject To Sensing And Communication Constraints, Guilherme A. S. Pereira, Aveek K. Das, R. Vijay Kumar, Mario F. M. Campos
Decentralized Motion Planning For Multiple Robots Subject To Sensing And Communication Constraints, Guilherme A. S. Pereira, Aveek K. Das, R. Vijay Kumar, Mario F. M. Campos
R. Vijay Kumar
We address the problem of planning the motion of a team of mobile robots subject to constraints imposed by sensors and the communication network. Our goal is to develop a decentralized motion control system that leads each robot to their individual goals while keeping connectivity with the neighbors. We present experimental results with a group of car-like robots equipped with omnidirectional vision systems.
Cooperative Control For Localization Of Mobile Sensor Networks, Fan Zhang, Ben Grocholsky, R. Vijay Kumar, Max L. Mintz
Cooperative Control For Localization Of Mobile Sensor Networks, Fan Zhang, Ben Grocholsky, R. Vijay Kumar, Max L. Mintz
R. Vijay Kumar
In this paper, we consider the problem of cooperatively control a formation of networked mobile robots/vehicles to optimize the relative and absolute localization performance in 1D and 2D space. A framework for active perception is presented utilizing a graphical representation of sensory information obtained from the robot network. Performance measures are proposed that capture the estimate quality of team localization. We show that these measures directly depend on the sensing graph and shape of the formation. This dependence motivates implementation of a gradient based control scheme to adapt the formation geometry in order to optimize team localization performance. This approach …
Calibrating An Air-Ground Control System From Motion Correspondences, Rahul Rao, Camillo J. Taylor, R. Vijay Kumar
Calibrating An Air-Ground Control System From Motion Correspondences, Rahul Rao, Camillo J. Taylor, R. Vijay Kumar
R. Vijay Kumar
In 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.
Using Policy Gradient Reinforcement Learning On Autonomous Robot Controllers, Gregory Z. Grudic, R. Vijay Kumar, Lyle H. Ungar
Using Policy Gradient Reinforcement Learning On Autonomous Robot Controllers, Gregory Z. Grudic, R. Vijay Kumar, Lyle H. Ungar
R. Vijay Kumar
Robot programmers can often quickly program a robot to approximately execute a task under specific environment conditions. However, achieving robust performance under more general conditions is significantly more difficult. We propose a framework that starts with an existing control system and uses reinforcement feedback from the environment to autonomously improve the controller’s performance. We use the Policy Gradient Reinforcement Learning (PGRL) framework, which estimates a gradient (in controller space) of improved reward, allowing the controller parameters to be incrementally updated to autonomously achieve locally optimal performance. Our approach is experimentally verified on a Cye robot executing a room entry and …
Important Considerations In Force Control With Applications To Multi-Arm Manipulation, Eric Paljug, Thomas G. Sugar, R. Vijay Kumar, Xiaoping Yun
Important Considerations In Force Control With Applications To Multi-Arm Manipulation, Eric Paljug, Thomas G. Sugar, R. Vijay Kumar, Xiaoping Yun
R. Vijay Kumar
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 …
Motion Planning In Humans And Robots, R. Vijay Kumar, Milos Zefran, James P. Ostrowski
Motion Planning In Humans And Robots, R. Vijay Kumar, Milos Zefran, James P. Ostrowski
R. Vijay Kumar
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.
Design And Control Of A Compliant Parallel Manipulator, Thomas G. Sugar, R. Vijay Kumar
Design And Control Of A Compliant Parallel Manipulator, Thomas G. Sugar, R. Vijay Kumar
R. Vijay Kumar
We describe a novel design for a compliant arm that can be mounted on a mobile robot. Because the arm is compliant, a mobile robot can manipulate or interact with objects that are not precisely positioned in the environment. The main features of the arm are the in-parallel architecture and a novel control scheme that allows us to easily control the Cartesian stiffness or impedance in the plane. Springs are added in series to the limbs of the parallel manipulator. We analyze one limb and the manipulator to determine its performance when either controlling the force applied to an object …
Dynamics And Control Of Whole Arm Grasps, Peng Song, Masahito Yashima, R. Vijay Kumar
Dynamics And Control Of Whole Arm Grasps, Peng Song, Masahito Yashima, R. Vijay Kumar
R. Vijay Kumar
In this paper we consider the dynamics and control of whole arm grasping systems. We develop a control scheme that employs a minimal set of inputs to control the trajectory of the system while using the surplus inputs to control the interaction forces in order to maintain the unilateral constraints at both rolling and sliding contacts. Since the number of surplus inputs is less than the number of output force variables, we propose a controller that controls the critical contact force components. We emphasize the dynamic models and algorithms for computing contact forces, which are crucial to the development of …
Hybrid Control Of Formations Of Robots, Rafael Fierro, Aveek K. Das, R. Vijay Kumar, James P. Ostrowski
Hybrid Control Of Formations Of Robots, Rafael Fierro, Aveek K. Das, R. Vijay Kumar, James P. Ostrowski
R. Vijay Kumar
We describe a framework for controlling a group of nonholonomic mobile robots equipped with range sensors. The vehicles are required to follow a prescribed trajectory while maintaining a desired formation. By using the leader-following approach, we formulate the formation control problem as a hybrid (mode switching) control system. We then develop a decision module that allows the robots to automatically switch between continuous-state control laws to achieve a desired formation shape. The stability properties of the closed-loop hybrid system are studied using Lyapunov theory. We do not use explicit communication between robots; instead we integrate optimal estimation techniques with nonlinear …
Human Robot Interaction And Usability Studies For A Smart Wheelchair, Sarangi P. Parikh, Rahul Rao, Sang-Hack Jung, R. Vijay Kumar, James P. Ostrowski, Camillo J. Taylor
Human Robot Interaction And Usability Studies For A Smart Wheelchair, Sarangi P. Parikh, Rahul Rao, Sang-Hack Jung, R. Vijay Kumar, James P. Ostrowski, Camillo J. Taylor
R. Vijay Kumar
We build on previous work [12], [14] on the development of a computer controlled wheelchair equipped with a suite of sensors and a novel interface for human-robot interaction. In this paper, we present experimental results and usability studies for the wheelchair. The architecture for human-robot interaction is hierarchical, with the lowest level corresponding to trajectory control, the intermediate level being behavioral and the highest level involving the composition of behaviors and navigation. Our experimental results illustrate the benefits of a shared-control paradigm where the human operator selects the appropriate hehavior(s) or goals while the software is responsible for executing behaviors …
Mobile Robot For Uneven Terrain, Kenneth Chin, Robert Breslawski, Terry Kientz, R. Vijay Kumar
Mobile Robot For Uneven Terrain, Kenneth Chin, Robert Breslawski, Terry Kientz, R. Vijay Kumar
R. Vijay Kumar
This paper outlines the details of the development of a mobile robot than can navigate uneven terrain. The robot incorporates a combination of wheels and legs. The legs are based on a parallel-drive 2-R linkage that allows the motors to be located on the robot frame. The legs are driven through servo motors while the wheels are powered through DC motors. A PIC microcontroller is used to control the system, while a novel IR-based communication module allows the user to remotely control the device. In the proof-of-concept prototype, a human operator can control the approximately 6x9x4 inches (15.24x22.86x10.16 cm) and …
Control Of Mechanical Systems With Rolling Constraints: Application To Dynamic Control Of Mobile Robots, Nilanjan Sarkar, Xiaoping Yun, R. Vijay Kumar
Control Of Mechanical Systems With Rolling Constraints: Application To Dynamic Control Of Mobile Robots, Nilanjan Sarkar, Xiaoping Yun, R. Vijay Kumar
R. Vijay Kumar
There are many examples of mechanical systems which require rolling contacts between two or more rigid bodies. Rolling contacts engender nonholonomic constraints in an otherwise holonomic system. In this paper, we develop a unified approach to the control of mechanical systems subject to both holonomic and nonholonomic constraints. We first present a state space realization of a constrained system and show that it is not input-state linearizable. We then discuss the input-output linearization and zero dynamics of the system. This approach is applied to the dynamic control of mobile robots. Two types of control algorithms for mobile robots are investigated: …
On Controlling Aircraft Formations, Rafael Fierro, Calin Belta, Jaydev P. Desai, R. Vijay Kumar
On Controlling Aircraft Formations, Rafael Fierro, Calin Belta, Jaydev P. Desai, R. Vijay Kumar
R. Vijay Kumar
We describe a framework for controlling a group of unmanned aerial vehicles (UAVs) flying in close formation. We first present a nonlinear dynamical model which includes the induced rolling moment by the lead aircraft on the wing of the following aircraft. Then, we outline two methods for trajectory generation of the leading aircraft, based on interpolation techniques on the Euclidean group, SE(3). Two formation controllers that allow each aircraft to maintain its position and orientation with respect to neighboring UAVs are derived using input-output feedback linearization. Numerical simulations illustrate the application of these ideas and demonstrate the validity of the …