1842716
Dynamic control of 3-D rolling contacts in two-arm manipulation
When two or more 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 dynamic control of two arms manipulating a large object with rolling contacts is addressed. In the framework presented, the motion of the object as well as the loci of the contact points on the surface of the effectors and on the object can be directly controlled. The velocity and acceleration equations for three-dimensional rolling contacts are derived in order to obtain a dynamical model of the system. A nonlinear feedback algorithm that decouples and linearizes the system is used to demonstrate the control of rolling motion along each arm and the adaption of grasps to varying loads.<<ETX>>
7023425
A Paradigm for Dynamic Coordination of Multiple Robots
In this paper, we present a paradigm for coordinating multiple robots in the execution of cooperative tasks. The basic idea in the paper is to assign to each robot in the team, a role that determines its actions during the cooperation. The robots dynamically assume and exchange roles in a synchronized manner in order to perform the task successfully, adapting to unexpected events in the environment. We model this mechanism using a hybrid systems framework and apply it in different cooperative tasks: cooperative manipulation and cooperative search and transportation. Simulations and real experiments demonstrating the effectiveness of the proposed paradigm are presented.
15738427
A potential field based approach to multi-robot manipulation
We describe a framework for controlling and coordinating a group of robots for cooperative manipulation tasks. The framework enables a decentralized approach to planning and control. It allows the robots to approach the object, organize themselves into a formation that will trap the object, and then transport the object to the desired destination. Our controllers and planners are derived from simple potential fields and the hierarchical composition of potential fields. We show how these potential field based controllers and planners benefit complex group interactions, specifically for manipulating and transporting objects in the plane. Theoretically, we show how we can derive results on formation stability with potential field based controllers in many cases. Simulation results demonstrate successful application to a wide range of examples without showing sensitivity to parameters. Because the framework is decentralized at both trajectory generation level and the estimation and control agent level, our framework can potentially scale to groups of tens and hundreds of robots.
5542960
Metrics for analysis and optimization of grasps and fixtures
We develop two quality measures for the analysis and optimization of grasps and fixtures. The first metric is a measure of stability and is obtained by analyzing the effect of small perturbations in the position of the grasped object or small disturbance forces on the grasped object The second metric is a measure of robustness to errors in the positions of the fixture elements. In addition, we explore the effect that the stiffness of the fixture elements has on these two quality measures and propose a design optimization approach to maximize stability and robustness to errors.
29516211
Control of Contact Interactions with Acatastatic Nonholonomic Constraints
A robot arm performs many tasks by interacting with objects or other robots in the environment. It is important for the robot arm to be able to exhibit controlled interactions with the objects and other robots. The contact motion between the robot arm and an object can be rolling, sliding, or separation. In this article, we address the problem of maintaining rolling contact between the robot arm and an external moving object. We assume that a nominal model of the motion of the moving object is available. The dynamic system that characterizes the motion of the robot arm and the moving object in this case is acatastatic and nonholonomic. We have designed a nonlinear feedback for the control of such a system that successfully maintains rolling contact. Simulation results are presented to demonstrate the effectiveness of the system.
6879835
Calibrating an air-ground control system from motion correspondences
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.
33425730
A Superior Algorithm for Mutual Exclusion in Computer Networks - VISHNU
37917309
Management of Concurrency in Interpolation Based Grid File Organization and its Performance
The mathematical structure of the interpolation based grid file organization provides a suitable platform for supporting a high degree of concurrency under a concurrency control mechanism. To demonstrate this capability, we first identified its useful properties for designing a concurrency control mechanism and then developed a deadlock-free two-phase locking based mechanism using dynamic attributes of transactions. To establish the usefulness of our system (concurrency control and the file organization), we measured its performance through simulation modeling. We show that our system handles a number of different types of workloads efficiently and the directory overhead does not strictly depend on the type of workload.
8261257
TCOT-A Timeout-Based Mobile Transaction Commitment Protocol
We present a transaction commit protocol, "Transaction Commit On Timeout (TCOT)," based on a "timeout" approach for Mobile Database Systems (MDS), which can be universally used to reach a final transaction termination decision (e.g., commit, abort, etc.) in any message-oriented system. Particularly suited for a wireless environment, a timeout mechanism is the only way to minimize the impact of the slow and unreliable wireless link. We compare TCOT to a modified version of 2PC to show its superiority based on commit time.
45908534
KRISHNA - Concurrency Control Algorithms based on Dynamic Attributes
Three new concurrency control mechanisms that utilizes the dynamic attribute of concurrent transactions for resolving conflicts are presented. Our study shows that their performance is superior to all well-known two-phase concurrency control mechanisms. There are a large number of such algorithms but we report our findings since our approach has some unique features worth exploring.
35078097
An adaptive location management algorithm for mobile computing
In mobile computing mobile hosts or mobile units move randomly from one place to another within a well-defined geographical area. This requires some mechanism for identifying the exact location of a mobile host. Such mechanisms are usually referred to as location management and is one of the essential components for supporting mobility. In the past a number of efficient location management schemes have been suggested but they lack adaptability. We believe that an adaptable location management scheme is more desirable because of frequent change in the location of mobile hosts. In this paper, we report a location management algorithm, which adapts to the constant changing scenario. Our algorithm makes use of some of the concepts of location management schemes proposed in the past.