251 research outputs found
Robust MADER: Decentralized Multiagent Trajectory Planner Robust to Communication Delay in Dynamic Environments
Communication delays can be catastrophic for multiagent systems. However,
most existing state-of-the-art multiagent trajectory planners assume perfect
communication and therefore lack a strategy to rectify this issue in real-world
environments. To address this challenge, we propose Robust MADER (RMADER), a
decentralized, asynchronous multiagent trajectory planner robust to
communication delay. By always keeping a guaranteed collision-free trajectory
and performing a delay check step, RMADER is able to guarantee safety even
under communication delay. We perform an in-depth analysis of trajectory
deconfliction among agents, extensive benchmark studies, and hardware flight
experiments with multiple dynamic obstacles. We show that RMADER outperforms
existing approaches by achieving a 100% success rate of collision-free
trajectory generation, whereas the next best asynchronous decentralized method
only achieves 83% success.Comment: 8 pagers, 13 figures,. arXiv admin note: substantial text overlap
with arXiv:2209.1366
Collision-aware Task Assignment for Multi-Robot Systems
We propose a novel formulation of the collision-aware task assignment (CATA)
problem and a decentralized auction-based algorithm to solve the problem with
optimality bound. Using a collision cone, we predict potential collisions and
introduce a binary decision variable into the local reward function for task
bidding. We further improve CATA by implementing a receding collision horizon
to address the stopping robot scenario, i.e. when robots are confined to their
task location and become static obstacles to other moving robots. The
auction-based algorithm encourages the robots to bid for tasks with collision
mitigation considerations. We validate the improved task assignment solution
with both simulation and experimental results, which show significant reduction
of overlapping paths as well as deadlocks
Asynchronous Decentralized Task Allocation for Dynamic Environments
This work builds on a decentralized task allocation algorithm for networked agents communicating through an asynchronous channel, by extending the Asynchronous Consensus-Based Bundle Algorithm (ACBBA) to account for more real time implementation issues resulting from a decentralized planner. This paper specfically talks to the comparisons between global and local convergence in asynchronous consensus algorithms. Also a feature called asynchronous replan is introduced to ACBBA's functionality that enables e ffcient updates to large changes in local situational awareness. A real-time software implementation using multiple agents communicating through the user datagram protocol (UDP) validates the proposed algorithm.United States. Air Force (grant FA9550-08-1-0086)United States. Air Force Office of Scientific Research (grant FA9550-08-1-0086)Aurora Flight Sciences Corp. (SBIR - FA8750-10-C-0107
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The Zodiac Policy Subsystem: A Policy-Based Management System for a High-Security MANET
Zodiac (Zero Outage Dynamic Intrinsically Assurable Communities) is an implementation of a high-security MANET, resistant to multiple types of attacks, including Byzantine faults. The Zodiac architecture poses a set of unique system security, performance, and usability requirements to its policy-based management system (PBMS). In this paper, we identify theses requirements, and present the design and implementation of the Zodiac Policy Subsystem (ZPS), which allows administrators to securely specify, distribute and evaluate network control and system security policies to customize ZODIAC behaviors. ZPS uses the Keynote language for specifying all authorization policies. We also present a simple extension of the Keynote language to support obligation policies
Flexible Virtual Structure Consideration in Dynamic Modeling of Mobile Robots Formation
International audienceIn cooperative mobile robotics, we look for formation keeping and maintenance of a geometric configuration during movement. As a solution to these problems, the concept of a virtual structure is considered. Based on this idea, we have developed an efficient flexible virtual structure, describing the dynamic model of n vehicles in formation and where the whole formation is kept dependant. Notes that, for 2D and 3D space navigation, only a rigid virtual structure was proposed in the literature. Further, the problem was limited to a kinematic behavior of the structure. Hence, the flexible virtual structure in dynamic modeling of mobile robots formation presented in this paper, gives more capabilities to the formation to avoid obstacles in hostile environment while keeping formation and avoiding inter‐agent collision
Online Control Barrier Functions for Decentralized Multi-Agent Navigation
Control barrier functions (CBFs) enable guaranteed safe multi-agent
navigation in the continuous domain. The resulting navigation performance,
however, is highly sensitive to the underlying hyperparameters. Traditional
approaches consider fixed CBFs (where parameters are tuned apriori), and hence,
typically do not perform well in cluttered and highly dynamic environments:
conservative parameter values can lead to inefficient agent trajectories, or
even failure to reach goal positions, whereas aggressive parameter values can
lead to infeasible controls. To overcome these issues, in this paper, we
propose online CBFs, whereby hyperparameters are tuned in real-time, as a
function of what agents perceive in their immediate neighborhood. Since the
explicit relationship between CBFs and navigation performance is hard to model,
we leverage reinforcement learning to learn CBF-tuning policies in a model-free
manner. Because we parameterize the policies with graph neural networks (GNNs),
we are able to synthesize decentralized agent controllers that adjust parameter
values locally, varying the degree of conservative and aggressive behaviors
across agents. Simulations as well as real-world experiments show that (i)
online CBFs are capable of solving navigation scenarios that are infeasible for
fixed CBFs, and (ii), that they improve navigation performance by adapting to
other agents and changes in the environment
Space Traffic Management with a NASA UAS Traffic Management (UTM) Inspired Architecture
Space is becoming increasingly congested as the number of on-orbit satellites and debris objects continues to grow. Space traffic management (STM) is critical for ensuring that the expanding orbital population operates safely and efficiently, avoiding collisions and radio-frequency interference while still facilitating widespread space operations. Recent events such as the FCC approval of SpaceXs ~12,000 satellite constellation, the signing of Space Policy Directive 3 (which moves Space Situational Awareness responsibilities away from the Department of Defense and to a civil agency), and the growth in rideshare and small launch vehicles illustrate the rapidly changing nature of this domain. This paper will describe the concept of operations (ConOps) for a civilian STM research initiative, which has been developed from previous NASA work to enable safe operation of small unmanned aircraft systems. The STM ConOps proposes an architecture to enable efficient data sharing and coordination between participants to facilitate safe spaceflight operations. It is designed to utilize and promote the emerging field of commercial STM services, as a complement to existing government-provided STM services. The concept envisions a phased evolution that would gradually integrate additional capabilities, proposing a first phase architecture and tentative plans for a broader system. Work towards developing an STM research and prototyping platform is also discussed
Global Title X Series \u2713: Game Report
The Chief of Naval Operations’ (CNO’s) annual Title 10 War Game (also known as Global) conducted at the Naval War College (NWC) has become a primary venue for exploring emerging concepts. This year’s effort is a continuation of the NWC War Gaming Department’s examination of the Air-Sea Battle (ASB) concept. The 2012 Global War Game concluded that current command and control (C2) structures at the operational level of war may be inadequate to effectively execute cross-domain operations as envisioned by the concept. While the ASB concept outlines the need to command and control ‘cross-domain operations’ which are joint, networked and integrated, no organizational structure is proposed. The concept only suggests that any suitable structure must be capable of tight, real-time coordination
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