9 research outputs found
A Hierarchical Approach to Optimal Flow-Based Routing and Coordination of Connected and Automated Vehicles
This paper addresses the challenge of generating optimal vehicle flow at the
macroscopic level. Although several studies have focused on optimizing vehicle
flow, little attention has been given to ensuring it can be practically
achieved. To overcome this issue, we propose a route-recovery and eco-driving
strategy for connected and automated vehicles (CAVs) that guarantees optimal
flow generation. Our approach involves identifying the optimal vehicle flow
that minimizes total travel time, given the constant travel demands in urban
areas. We then develop a heuristic route-recovery algorithm to assign routes to
CAVs that satisfy all travel demands while maintaining the optimal flow. Our
method lets CAVs arrive at each road segment at their desired arrival time
based on their assigned route and desired flow. In addition, we present an
efficient coordination framework to minimize the energy consumption of CAVs and
prevent collisions while crossing intersections. The proposed method can
effectively generate optimal vehicle flow and potentially reduce travel time
and energy consumption in urban areas.Comment: 7 pages, 7 figure
Routing in Mixed Transportation Systems for Mobility Equity
This letter proposes a routing framework in mixed transportation systems for
improving mobility equity. We present a strategic routing game that governs
interactions between compliant and noncompliant vehicles, where noncompliant
vehicles are modeled with cognitive hierarchy theory. Then, we introduce a
mobility equity metric (MEM) to quantify the accessibility and fairness in the
transportation network. We integrate the MEM into the routing framework to
optimize it with adjustable weights for different transportation modes. The
proposed approach bridges the gap between technological advancements and
societal goals in mixed transportation systems to enhance efficiency and
equity. We provide numerical examples and analysis of the results.Comment: 6 pages, 5 figure
Modeling Travel Behavior in Mobility Systems with an Atomic Routing Game and Prospect Theory
In this paper, we present a game-theoretic modeling framework for studying
the travel behavior in mobility systems, by incorporating prospect theory. As
part of our motivation, we conducted an experiment in a scaled smart city to
investigate the frequency of errors in actual and perceived probabilities of a
highway route under free flow conditions. Based on these findings, we provide a
game that captures how travelers distribute their traffic flows in a
transportation network with splittable traffic, utilizing the Bureau of Public
Roads function to establish the relationship between traffic flow and travel
time cost. Given the inherent non-linearities, we propose a smooth
approximation function that helps us estimate the prospect-theoretic cost
functions. As part of our analysis, we characterize the best-fit parameters and
derive an upper bound for the error. We then show a Nash Equilibrium existence.
Finally, we present a numerical example and simulations to verify the
theoretical results and demonstrate the effectiveness of our approximation.Comment: arXiv admin note: text overlap with arXiv:2202.0769
Congestion-Aware Routing, Rebalancing, and Charging Scheduling for Electric Autonomous Mobility-on-Demand System
In this paper, we investigate the problem of routing, rebalancing, and
charging for electric autonomous mobility-on-demand systems concerning traffic
congestion. We analyze the problem at the macroscopical level and use a
volume-delay function to capture traffic congestion. To address this problem,
we first formulate an optimization problem for routing and rebalancing. Then,
we present heuristic algorithms to find the loop of the traffic flow and
examine the energy constraints within the resulting loop. We impose charging
constraints on the re-routing problem so that the new solution satisfies the
energy constraint. Finally, we verify the effectiveness of our method through
simulation.Comment: 6 pages, 2 figure
Combined Optimal Routing and Coordination of Connected and Automated Vehicles
In this letter, we consider a transportation network with a 100\% penetration
rate of connected and automated vehicles (CAVs) and present an optimal routing
approach that takes into account the efficiency achieved in the network by
coordinating the CAVs at specific traffic scenarios, e.g., intersections,
merging roadways, and roundabouts. To derive the optimal route of a travel
request, we use the information of the CAVs that have already received a
routing solution. This enables each CAV to consider the traffic conditions on
the roads. The solution of any new travel request determines the optimal travel
time at each traffic scenario while satisfying all state, control, and safety
constraints. We validate the performance of our framework through numerical
simulations. To the best of our knowledge, this is the first attempt to
consider the coordination of CAVs in a routing problem.Comment: 6 pages, 5 figure
Energy-Optimal Goal Assignment of Multi-Agent System with Goal Trajectories in Polynomials
In this paper, we propose an approach for solving an energy-optimal goal
assignment problem to generate the desired formation in multi-agent systems.
Each agent solves a decentralized optimization problem with only local
information about its neighboring agents and the goals. The optimization
problem consists of two sub-problems. The first problem seeks to minimize the
energy for each agent to reach certain goals, while the second problem entreats
an optimal combination of goal and agent pairs that minimizes the energy cost.
By assuming the goal trajectories are given in a polynomial form, we prove the
solution to the formulated problem exists globally. Finally, the effectiveness
of the proposed approach is validated through the simulation.Comment: 7 pages, 4 figure
Effects of Forest Therapy on Depressive Symptoms among Adults: A Systematic Review
This study systematically reviewed forest therapy programs designed to decrease the level of depression among adults and assessed the methodological rigor and scientific evidence quality of existing research studies to guide future studies. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The authors independently screened full-text articles from various databases using the following criteria: (1) intervention studies assessing the effects of forest therapy on depressive symptoms in adults aged 18 years and older; (2) studies including at least one control group or condition; (3) peer-reviewed studies; and (4) been published either in English or Korean before July 2016. The Scottish Intercollegiate Guideline Network measurement tool was used to assess the risk of bias in each trial. In the final sample, 28 articles (English: 13, Korean: 15) were included in the systematic review. We concluded that forest therapy is an emerging and effective intervention for decreasing adults’ depression levels. However, the included studies lacked methodological rigor. Future studies assessing the long-term effect of forest therapy on depression using rigorous study designs are needed