Data-Driven Distributionally Robust Electric Vehicle Balancing for Mobility-on-Demand Systems under Demand and Supply Uncertainties Sihong He Lynn Pepin Guang Wang Desheng Zhang Fei Miao

2025-05-06 0 0 1.06MB 8 页 10玖币
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Data-Driven Distributionally Robust Electric Vehicle Balancing for
Mobility-on-Demand Systems under Demand and Supply Uncertainties
Sihong He Lynn Pepin Guang Wang Desheng Zhang Fei Miao
Abstract As electric vehicle (EV) technologies become
mature, EV has been rapidly adopted in modern trans-
portation systems, and is expected to provide future au-
tonomous mobility-on-demand (AMoD) service with eco-
nomic and societal benefits. However, EVs require frequent
recharges due to their limited and unpredictable cruising
ranges, and they have to be managed efficiently given the
dynamic charging process. It is urgent and challenging
to investigate a computationally efficient algorithm that
provide EV AMoD system performance guarantees under
model uncertainties, instead of using heuristic demand
or charging models. To accomplish this goal, this work
designs a data-driven distributionally robust optimization
approach for vehicle supply-demand ratio and charging
station utilization balancing, while minimizing the worst-
case expected cost considering both passenger mobility
demand uncertainties and EV supply uncertainties. We
then derive an equivalent computationally tractable form
for solving the distributionally robust problem in a com-
putationally efficient way under ellipsoid uncertainty sets
constructed from data. Based on E-taxi system data of
Shenzhen city, we show that the average total balancing
cost is reduced by 14.49%, the average unfairness of
supply-demand ratio and utilization is reduced by 15.78%
and 34.51% respectively with the distributionally robust
vehicle balancing method, compared with solutions which
do not consider model uncertainties.
I. INTRODUCTION
There are over 5 million EVs by December 2018
globally, and this figure is predicted to increase to 100-
125 million by 2030 [3]. Compared to conventional gas
vehicles, EV fleets have prolonged charging time and
concentrated mobility patterns due to current charging
technologies and limited charging infrastructures, espe-
cially for commercial EV fleets, e.g., e-taxi, future au-
tonomous mobility-on-demand (AMoD) systems, given
their long daily travel distances [14].
Researchers have been focusing on models and algo-
rithms to study EVs [16], [14]. There have also been
This work has been published in International Conference on
Intelligent Robots and Systems (IROS 2020). Sihong He, Lynn Pepin,
and Fei Miao are with the Department of Computer Science and
Engineering, University of Connecticut, Storrs Mansfield, CT, USA
06268. Email: {sihong.he, lynn.pepin, fei.miao}@uconn.edu. This
work is also partially supported by NSF SAS-1849238 and CPS-
1932223. Guang Wang and Desheng Zhang are with the Department
of Computer Science, Rutgers University, Piscataway, NJ, USA 08901.
Email: {gw255, desheng.zhang}@cs.rutgers.edu.
focusing on how to choose the optimal locations for
charging stations and how to assign charging points
to EVs in each station to minimize the charging time
of EVs considering various constraints, e.g., demand,
costs, and charging compatibility [6], [15]. However,
high costs of charging infrastructures and land resources
make it impractical to deploy abundant charging stations
and points at the early promotion stage [15]. Even when
there is enough charging infrastructure for all EVs in
theory, the uncontrolled and decentralized charging and
mobility behaviors of some EV fleets, e.g., e-taxi, cause
long waiting times when the demand for charging points
greatly exceeds the availability [12].
The above mentioned EV management issues have
posed key optimization and scheduling algorithm chal-
lenges for world-wide EV adoption of AMoD. The
interaction between AMoD systems and power networks
through EVs based on the vehicles’ charging require-
ments, battery depreciation, and power transmission
constraints have been investigated, and the economic
and societal value of EV AMoD has been analyzed [11].
To improve the performance of general AMoD systems,
mobility demand based vehicle balancing methods have
been proposed with various system design objectives,
such as reducing the number of vehicles needed to serve
all passengers [19], [4], reducing customers’ waiting
time [13], or taxis’ total idle distance [8]. However, the
limited knowledge we have about charging patterns [14]
affect the performance of vehicle balancing strategies,
and make real-time decisions under demand model un-
certainties still a challenging and unsolved task.
The contributions of this work are as follows:
We are the first to consider both future demand
uncertainties and EV supply uncertainties predicted
based on charging activity data in designing a
system-level vehicle balancing algorithm. While
model predictive control algorithms [19], [4] have
been designed considering AMoD system demand
uncertainties in the literature, the supply side un-
certainties for EV AMoD is not well studied yet.
We design a distributionally robust optimization
approach to balance EVs across a city for min-
imum total idle distance and balanced charging
1
arXiv:2210.10887v1 [math.OC] 19 Oct 2022
station utilization with respect to the worst-case
expected cost. The approach considers probability
distribution uncertainties of the passenger mobility
demand and the EV supply caused by the challenge
of charging process prediction [15], [12].
We derive an equivalent form of convex opti-
mization problem for the proposed distributionally
robust optimization problem to provide system-
level performance guarantee in a computationally
tractable way under model uncertainties. Based
on real data of Shenzhen city, we show that the
average total balancing cost is reduced by 14.49%,
the average unfairness of supply-demand ratio and
utilization is reduced by 15.78% and 34.51%, re-
spectively, with the proposed method, compared
with solutions which do not consider model un-
certainties.
The rest of the paper is organized as follows. The dis-
tributionally robust EV balancing problem is presented
in Section II. An equivalent computationally tractable
form is derived in Section III. We show performance
improvement in experiments based on real data in Sec-
tion IV. Concluding remarks are provided in Section V.
II. PROBLEM FORMULATION
In this section, we formulate a distributionally robust
optimization problem to balance EVs across a city with
minimum total idle distance and balanced charging sta-
tion utilization. Both passenger mobility demand and EV
supply uncertainties are considered. The region every
empty EV will go is updated in a receding horizon
control process. At each time step, the EV status is up-
dated to the dispatch center first, then the dispatch center
calculates a vehicle balancing decision by solving the
proposed distributionally robust optimization problem,
and sent solutions to EVs. The goal is to dispatch vacant
EVs to different regions to pick up current and predicted
passengers if the EVs have enough energy, or to charging
stations if the EVs are short of energy, while minimize
the cost of dispatching for the following τtime steps.
Local dispatchers that match individual EV with one or
several passengers (for carpool) is out the scope of this
work.
A. EV States and Corresponding Actions
We assume there are three possible states for one EV:
vacant, occupied, and low-battery. Vacant means there
are no passengers in this EV, and it has enough energy to
finish the next trip. The controller dispatches vacant EVs
according to current and predicted passengers demand.
When a vacant EV picks up one or more passengers,
it turns to occupied, and the controller has no actions
for it until it becomes vacant again. An occupied EV
will be finishing current order in a time period and will
become a vacant EV once it drops off its passengers.
One occupied EV can only become a vacant EV when
it finishes the current order. When a vacant EV can
not finish the next trip with the remaining battery, this
EV becomes a low-battery EV and will go to regions
assigned by the controller where it can find a charging
station. Before a low-battery EV gets fully charged, it
stays in the low-battery status until it leaves the charging
station and becomes vacant. A low-battery can only
transfer to a vacant EV or stay in current state.
B. Problem Description
We assume that one day is divided into Ktime
intervals, and we use k= 1,2, ..., K to denote time
index. We assume the entire city is divided into N
regions and we use nto denote region index, where
n= 1,2, ..., N. At time k, the system-level controller
makes vacant and low-battery EVs to go to other regions
or stay in the same region for picking up passengers
or charging, respectively. After one EV arrives at its
dispatched region, a local-level controller assign the EV
to pick up passengers or to charge according to the EV’s
battery status.
During time k, there are rk
ipredicted total amount
of passengers demand and ck
ipredicted total number
of EVs finish charging (new supply of EVs) in re-
gion i, where i= 1,2, ..., N, k = 1,2, ..., K. Let
demand vector rk= [rk
1, rk
2, ..., rk
N]Tand supply vec-
tor ck= [ck
1, ck
2, ..., ck
N]TRNbe random vectors
instead of deterministic vectors. And assuming they
are independent. To model the spatial and temporal
relations of deman(supply) during every τconsecutive
time interval, we define concatenation of demand as
r= [r1, r2, ..., rτ], and concatenation of supply as
c= [c1, c2, ..., cτ]. We use F
rand F
cto denote the
unknown true probability distributions of r, c RNτ
respectively, i.e. rF
rand cF
c.
We use non-negative matrices Xkand Ykas the
decision matrices at time kwhere Xk, Y kRN×N
+and
xk
ij (yk
ij )is the total amount of vacant(low-battery) EVs
will be dispatched from region ito region jat the begin-
ning of time k. Minimizing the expected allocating cost
given true probability distributions of demand vector
and supply vector is defined as the following stochastic
programming problem:
min.
X1:τ,Y 1:τ
ErF
r,cF
cJ(X1:τ, Y 1:τ, r, c)
s.t. X1:τ, Y 1:τ∈ D,
(1)
2
摘要:

Data-DrivenDistributionallyRobustElectricVehicleBalancingforMobility-on-DemandSystemsunderDemandandSupplyUncertaintiesSihongHeLynnPepinGuangWangDeshengZhangFeiMiaoAbstract—Aselectricvehicle(EV)technologiesbecomemature,EVhasbeenrapidlyadoptedinmoderntrans-portationsystems,andisexpectedtoprovidefuture...

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