118 research outputs found
Lifelong Path Planning with Kinematic Constraints for Multi-Agent Pickup and Delivery
The Multi-Agent Pickup and Delivery (MAPD) problem models applications where
a large number of agents attend to a stream of incoming pickup-and-delivery
tasks. Token Passing (TP) is a recent MAPD algorithm that is efficient and
effective. We make TP even more efficient and effective by using a novel
combinatorial search algorithm, called Safe Interval Path Planning with
Reservation Table (SIPPwRT), for single-agent path planning. SIPPwRT uses an
advanced data structure that allows for fast updates and lookups of the current
paths of all agents in an online setting. The resulting MAPD algorithm
TP-SIPPwRT takes kinematic constraints of real robots into account directly
during planning, computes continuous agent movements with given velocities that
work on non-holonomic robots rather than discrete agent movements with uniform
velocity, and is complete for well-formed MAPD instances. We demonstrate its
benefits for automated warehouses using both an agent simulator and a standard
robot simulator. For example, we demonstrate that it can compute paths for
hundreds of agents and thousands of tasks in seconds and is more efficient and
effective than existing MAPD algorithms that use a post-processing step to
adapt their paths to continuous agent movements with given velocities.Comment: AAAI 201
Idle Time Optimization for Target Assignment and Path Finding in Sortation Centers
In this paper, we study the one-shot and lifelong versions of the Target
Assignment and Path Finding problem in automated sortation centers, where each
agent needs to constantly assign itself a sorting station, move to its assigned
station without colliding with obstacles or other agents, wait in the queue of
that station to obtain a parcel for delivery, and then deliver the parcel to a
sorting bin. The throughput of such centers is largely determined by the total
idle time of all stations since their queues can frequently become empty. To
address this problem, we first formalize and study the one-shot version that
assigns stations to a set of agents and finds collision-free paths for the
agents to their assigned stations. We present efficient algorithms for this
task based on a novel min-cost max-flow formulation that minimizes the total
idle time of all stations in a fixed time window. We then demonstrate how our
algorithms for solving the one-shot problem can be applied to solving the
lifelong problem as well. Experimentally, we believe to be the first
researchers to consider real-world automated sortation centers using an
industrial simulator with realistic data and a kinodynamic model of real
robots. On this simulator, we showcase the benefits of our algorithms by
demonstrating their efficiency and effectiveness for up to 350 agents.Comment: AAAI 2020, to appea
Distributed Fleet Management in Noisy Environments via Model-Predictive Control
This object is the reproducibility package for the paper Distributed Fleet Management in Noisy Environments via Model-Predictive Control accepted for publication at ICAPS '22.
The package contains the software for executing the experiments, the data presented in the paper, examples of Uppaal models, and scripts for redoing the experiments presented in the paper
Prioritized Multi-agent Path Finding for Differential Drive Robots
Methods for centralized planning of the collision-free trajectories for a
fleet of mobile robots typically solve the discretized version of the problem
and rely on numerous simplifying assumptions, e.g. moves of uniform duration,
cardinal only translations, equal speed and size of the robots etc., thus the
resultant plans can not always be directly executed by the real robotic
systems. To mitigate this issue we suggest a set of modifications to the
prominent prioritized planner -- AA-SIPP(m) -- aimed at lifting the most
restrictive assumptions (syncronized translation only moves, equal size and
speed of the robots) and at providing robustness to the solutions. We evaluate
the suggested algorithm in simulation and on differential drive robots in
typical lab environment (indoor polygon with external video-based navigation
system). The results of the evaluation provide a clear evidence that the
algorithm scales well to large number of robots (up to hundreds in simulation)
and is able to produce solutions that are safely executed by the robots prone
to imperfect trajectory following. The video of the experiments can be found at
https://youtu.be/Fer_irn4BG0.Comment: This is a pre-print version of the paper accepted to ECMR 2019
(https://ieeexplore.ieee.org/document/8870957
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