Re-Routing Strategy of Connected and Automated Vehicles Considering Coordination at Intersections Heeseung Bang Student Member IEEE Andreas A. Malikopoulos Senior Member IEEE

2025-04-29 0 0 508.65KB 6 页 10玖币
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Re-Routing Strategy of Connected and Automated Vehicles
Considering Coordination at Intersections
Heeseung Bang, Student Member, IEEE, Andreas A. Malikopoulos, Senior Member, IEEE
Abstract In this paper, we propose a re-routing strategy
for connected and automated vehicles (CAVs), considering
coordination and control of all the CAVs in the network. The
objective for each CAV is to find the route that minimizes
the total travel time of all CAVs. We coordinate CAVs at
signal-free intersections to accurately predict the travel time
for the routing problem. While it is possible to find a system-
optimal solution by comparing all the possible combinations
of the routes, this may impose a computational burden. Thus,
we instead find a person-by-person optimal solution to reduce
computational time while still deriving a better solution than
selfish routing. We validate our framework through simulations
in a grid network.
I. INTRODUCTION
OVER the last two decades, connected and automated
vehicles (CAVs) have attracted considerable attention
since they can improve safety, fuel economy, and other
traffic conditions. To reduce fuel consumption and travel
time, several research efforts have focused on efficient
coordination and control of CAVs at different traffic
scenarios such as merging roadways [1]–[3], signal-free
intersections [4]–[7], and corridors [8]–[10]. These efforts
have developed different coordination methods to reduce
stop-and-go driving, which has resulted in shorter travel time
with less energy use.
As another way to alleviate traffic issues, a significant
number of research efforts have considered the routing
problem of CAVs, which derived a solution for a single CAV
and applied it to multiple vehicles. Chen and Cassandras
[11] considered the dynamic vehicle assignment problem
in a shared mobility system to optimizes the travel times
of CAVs and the waiting times of passengers. Tsao et al.
[12] presented a similar approach for ride-sharing using
model predictive control with fixed traffic conditions. While
these methods find the efficient route for a single CAV,
they are not verified for multiple CAVs applications. Some
other approaches proposed in the literature include graph
search algorithms [13], reinforcement learning techniques
[14]–[16], and mixed-integer linear programs [17]–[19].
Furthermore, other research efforts considered variation of
basic formulations by including different types of vehicles
[19], [20], adding battery constraints [21], and considering
interaction with infrastructures [22], [23].
This work was supported by NSF under Grants CNS-2149520 and
CMMI-2219761.
The authors are with the Department of Mechanical Engineering,
University of Delaware, Newark, DE 19716, USA. (emails:
heeseung@udel.edu; andreas@udel.edu.)
In addition to a single CAV, many studies have also
focused on larger-scale interactions between multiple CAVs.
In the majority of these studies, a travel latency function
was used to estimate travel delay caused by other CAVs
[24]–[26]. Recent research efforts have developed a method
for routing and relocating CAVs in more complex networks
[27] and considered situations where charging scheduling of
electric CAVs is required [28]. However, none of these efforts
considered the impact of microscopic phenomena such as
coordination and control of CAVs on traffic conditions.
To the best of our knowledge, there have been only a few
studies focusing on the routing problem with consideration
of interactions between CAVs and their actual movements.
Chu et al. [29] solved the routing problem for each CAV
considering traffic by employing a dynamic lane reversal
approach. However, they simply approximated the travel
time of CAVs proportional to the number of CAVs on each
road segment. Likewise, Mostafizi et al. [30] developed a
decentralized routing framework with a heuristic algorithm,
but they estimated travel speeds inversely proportional to
the number of CAVs on the roads. In our previous work
[31], we introduced a new routing framework combined
with the coordination of CAVs. the framework predicts
traffic conditions from coordination information and finds
the optimal route for each new travel request. However, we
have imposed an assumption that a new CAV does not affect
previously planned trajectories. This assumption sometimes
causes the situation where a CAV entering the network has
no solution because it yields all the roads that it can travel
through. In addition, all CAVs only find their route at the
beginning of the trip because, once the trajectory is fixed, it
does not get affected by any other CAVs’ decisions, which
is quite a strong assumption to apply in reality.
In this paper, we propose a re-routing framework for CAVs
with consideration of traffic conditions resulting from each
CAV’s decision. The framework is built upon our previous
work [31], which consists of two parts: (i) at an intersection
level, we formulate a coordination problem to predict travel
time and acquire an exact trajectory, and (ii) we formulate a
routing problem using the predicted travel time at a network
level. To avoid computational challenge, we generate some
candidate routes for each CAV and find the best combination
of the routes to reduce the complexity of the problem and
make it possible to apply this framework to more extensive
networks. The main contribution of this work is to advance
the state-of-the-art congestion-aware routing problem in a
way that makes the problem more realistic by relaxing
those assumptions. Another contribution is that we provide
arXiv:2210.00396v2 [eess.SY] 19 Feb 2023
RouterCoordinators
CAVs
Candidate Route
Predicted
Travel Time
Entry/Trajectory Information
Other CAVs
Information
Fig. 1: The concept diagram of the routing process.
a method that always yields a person-by-person optimal
solution, which is a series of the best choice for each CAV.
The remainder of this paper is structured as follows.
In Section II, we formulate the routing problem and
coordination problem. In Section III, we present algorithms
to solve the problems and discuss the optimality of the
solution. We validate our method through the simulations
results in Section IV. Finally, in Section V, we conclude
and discuss some directions for future work.
II. PROBLEM STATEMENT
In this paper, we develop a framework that consists
of multiple optimization problems at two different levels.
The upper level contains a routing framework for a road
network. We consider having a finite number of candidate
routes and formulate optimization problems to find the best
combination of those routes. At the low level, we coordinate
CAVs to cross intersections fast without violating any safety
constraints, and a travel time computed from coordination
is directly involved in the upper-level optimization as a cost
function. The detailed problem formulation will be explained
next.
A. Trips and Routing on Road Network
We consider a road network given by a directed graph
G= (V,E), where Vis a set of nodes and Eis a set of
edges (roads). Each node is a junction point of two different
intersections (exiting from one intersection and entering
another one), and each node can simultaneously function
as the origin for one trip and the destination for another
trip. In the network, there exists a router that communicates
with CAVs and selects the best combination of routes and a
coordinator for each intersection which shares the geometry
of intersections and trajectories of other CAVs (Fig. 1).
Our framework considers a 100% penetration rate of CAVs
in the road network. Let N(t) = {1, . . . , N(t)}be a set
of CAVs traveling in the network at time tR0, where
N(t)Nis the total number of CAVs at moment. For each
CAV i N (t), we have trip information Ii= (oi, di, ts
i)
which consists of origin oi∈ V, destination di∈ V, and the
starting time of travel ts
it. This implies that we receive
trip information only when a new CAV starts a trip and do
not have any information about trips departing in the near
future. We assume that each CAV joins the network and
departs from oiat time ts
iand that there are enough CAVs at
the origin nodes. To relax this assumption, one can consider
a whole trip of CAVs departing from and returning to stations
[31] or relocation of empty CAVs [28].
In our previous work [31], we assumed that a newly
introduced CAV does not affect previous CAVs’ trajectories.
This assumption made it possible to solve a substantial
centralized problem in a computationally distributed manner.
However, this is a strong assumption in reality and also
yields cases where no solution exists when a new CAV is
introduced. To relax this assumption, we let the router to
re-route all the CAVs in the network within new candidate
routes whenever a new CAV joins the network and finds a
system-optimal solution.
At every time t, when a new CAV joins the network, we
generate MNdifferent candidate routes for each CAV
i N (t), which connect the current location of CAV ito the
destination di. We denote M={1, . . . , M}to be an index
set of those routes and let Pi={Pi,1,...,Pi,M }denote a
set of all candidate routes for the CAV i, where Pi,m ⊂ E
is a m-th candidate route of the CAV i. This paper assumes
that a finite number of candidate routes are determined by a
high-level decision maker and given to the router. Next, we
define an assignment matrix to match the CAVs to one of
their candidate routes.
Definition 1. Let assignment matrix A(t)be a binary matrix
that maps all CAVs i N (t)to a unique route Pi,m for
m∈ M.
Note that A(t)=[A1,...,AN(t)], where Ai=
[ai,1, . . . , ai,M ]Tis an assignment vector for CAV i N (t).
The assignment matrix can be determined by solving an
optimization problem, which we define next.
Problem 1 (Optimal Routing).We find a system-optimal
combination of the routes by solving the following problem
min
AnX
i∈N (t)X
m∈M
ai,mTi(A(t), m)o(1)
subject to: X
m∈M
ai,m = 1,i N (t),
ai,m ∈ {0,1},i N (t), m ∈ M,
where Ti(A(t), m)is the travel time of CAV ifollowing the
m-th candidate route. The constraints ensure each CAV to
be assigned to a unique route.
The travel time Ti(A(t), m)can be computed using the
coordination framework, which will be presented later in this
section.
B. Coordination at Intersections
Given the routes of all the trips, we now model
intersections and coordinate CAVs to travel without any
collision. Let L={1, . . . , L}denote a set of signal-
free intersections, where LNis the total number of
intersections. We let Nl(t) N (t)denote a set, which
includes all the CAVs in the intersection l∈ L. Each
intersection consists of four entry nodes, four exit nodes,
and twelve edges connecting each entry node to the exit
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Re-RoutingStrategyofConnectedandAutomatedVehiclesConsideringCoordinationatIntersectionsHeeseungBang,StudentMember,IEEE,AndreasA.Malikopoulos,SeniorMember,IEEEAbstract—Inthispaper,weproposeare-routingstrategyforconnectedandautomatedvehicles(CAVs),consideringcoordinationandcontrolofalltheCAVsinthenetw...

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