Optimal Scheduling for Flying Taxi Operation
Panwadee Tangpattanakul
1
and Ilhem Quenel
2
1
Capgemini Engineering, 4 avenue Didier Daurat, 31700 Blagnac, France
2
Capgemini Sophia Antipolis, 950 avenue de Roumanille, E. Golf-Park, BΓ’timent TECK, 06410 Biot, France
Keywords: Flying Taxi, Scheduling Problem, Metaheuristic, Genetic Algorithm, Simulated Annealing.
Abstract: According to the traffic congestion problem in big cities around the world, some sustainable transportation
technologies are researched and developed in these recent years. Flying taxi is a transportation mode, which
is being developed from several major brands. It can become an alternative transportation mode in the future.
In this work, a simplified optimization model of the flying taxi scheduling is proposed. Two algorithms, which
consists of genetic algorithm and simulated annealing, are used to solve the problem. The experiments are
conducted on 15 instances with different number of customer demands (between 10 and 200 demands) and
different number of available flying taxis in the system (from 2 to 10 taxis). The experimental results show
that both algorithms are efficient to solve the problem. The genetic algorithm obtains better quality solutions
for the small and medium size instances but it spends more computation time than the simulated annealing.
However, the simulated annealing can solve the large instances and obtain good solutions in reasonable time.
1 INTRODUCTION
Nowadays, there are not flying taxis in the daily life
yet, but the development of autonomous vehicles and
delivery drones is illustrated that the flying taxi
transportation mode will not be only the dream and
getting closer to reality. However, to reach the
success of the passenger transportation services,
several criteria, such as payload capacity, safety
constraint, noise pollution, and operation cost, must
be well-designed in the research process before it can
be launched in the real life.
This work will present a simplified scheduling
problem model for the future flying taxis by
mimicking the characteristics of parcel delivery
drones. It concerns two main subjects of literature
review, consisting of the delivery drone scheduling
and the taxi demand responsive scheduling. For the
drone delivery scheduling part, different
characteristics and constraints of parcel delivery
drones are studied. For the taxi demand responsive
scheduling part, the method to respond to the demand
is studied. We can see in details as follow:
1.1 Delivery Drone Scheduling
In this part, we want to understand the general
characteristics of drone and scheduling model of
delivery drones. We plan to mimic the delivery drone
model to obtain the simplified flying taxi model and
then combine this part with the taxi demand
scheduling to design the flying taxis scheduling
formula. The drone delivery concept was proposed by
Amazon Prime Air in 2013 (Amazon, 2013) and other
companies, such as Wing, UPS flight forward,
Flytrex, Wingcopter, Zipline also develop their own
commercial delivery drones later (Ueland, 2021).
In the research of parcel delivery, there are three
ways of delivery problem from depot center to
customers (Kuang, 2019). The first one is a traditional
method which delivers the packages by trucks only.
The second one is a drone delivery where the drones
bring the packages directly from the depot to
customers. The last one is a truck and drones
combination which brings the large number of
package by trucks from the depot to customer zone
and drones deliver package from the truck to the
customers. (Marray & Chu, 2015) proposed two
models of parcel delivery with drone, which are the
Flying Sidekick Traveling Salesman Problem
(FSTSP) and the Parallel Drone Scheduling Traveling
Salesman Problem (PDSTSP). In (Saleu et al., 2018),
they want to minimize the completion time for
PDSTSP by using an iterative two-step heuristic. In
(Ponza, 2016), the FSTSP is considered and the
simulated annealing is used to solve the problem.
There are several important drone constraints that
should be satisfied in the real operations such as the
Tangpattanakul, P. and Quenel, I.
Optimal Scheduling for Flying Taxi Operation.
DOI: 10.5220/0010677200003063
In Proceedings of the 13th International Joint Conference on Computational Intelligence (IJCCI 2021), pages 141-148
ISBN: 978-989-758-534-0; ISSN: 2184-3236
Copyright Β© 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
141
reliability of drone delivery network, battery
consumption, and delivery time windows. As in
(Torabbeigi et al., 2018), the reliability concerning
drone failure is considered. They assume the drone
failure follow an exponential distribution. In (Cheng
et al., 2020), the robust scheduling is proposed by
considering the wind condition uncertainty. In (Kim
et al, 2020), the drone operation planning model is
designed by considering the demands of each
destination and also the battery level of the drone.
Each drone is assigned to either deliver the parcels or
recharge the battery. In the operation planning of
(Torabbeigi et al., 2020), the battery consumption rate
of drones is modeled depending on the carrying
payload. The drones pick the parcels from the depot,
deliver to customers and then return to the depot.
(Dukkanci et al., 2020) studies the energy
consumption of drone according to its speed function.
For the delivery time window constraint, (Han et al.,
2020) considers a vehicle routing problem by
satisfying the time window. In (Huang et al., 2020),
the parcel delivery system which considers the
cooperation of public transport and drones is
considered. They model the system characteristic
including the delivery time, energy consumption and
battery recharging.
For the simplified model of flying taxi, we have
to select some constraints from drone operations to be
considered. We will concentrate to the battery
consumption function, battery recharging, and time
window of demands, but ignore other constraints in
this step.
1.2 Taxi Demand Scheduling
We study how to manage taxi demands efficiently in
this part. The passengers require the taxis to pick up
in the specific location and specific time window.
Then, the taxis bring them to the destination in the
limitation of tardiness.
A classical problem in the domain of operations
research, which concerns the taxi demand scheduling,
is the vehicle routing and scheduling problem with
time window constraints or VRSPTW. This problem
needs to find the minimum-cost vehicle routes to
serve a set of customers by satisfying the vehicle
capacity constraints. Moreover, each customer must
have a service in the specific available time window.
The VRSPTW is an NP-hard problem for which
heuristic algorithms are widely used. (Solomon,
1987).
We can also model the taxi demand scheduling
problem like the fleet management problems as in
(Bielli et al., 2011). It presents different mathematical
models for variant transportation modes and
characteristics. In (Glaschenko et al., 2009), it
considers a multi-agent approach to real-time
scheduling to be able to re-schedule and update
schedule in real time. The orders have to be matched
to drivers, vehicles, resources and work practices.
The schedule must ensure fair and proportional jobs
distribution for drivers. In (Shen et al. 2017), the
dispatching system to design a demand-responsive
schedule is considered. It consists of a planning of
travel path (routing) and customer pick-up and drop-
off times (scheduling) by considering certain
constraints such as vehicle capacity limitation and
available time windows.
The profit of taxi service is an important objective
for the business. The fare of general taxi services is
calculated from a base rate (for some first kilometers
as initial charge), a distance rate (multiply to the next
kilometer count), and a minute rate (multiply to the
minute count of the waiting time). However, the fare
of flying taxi will be calculated from only the base
rate and the distance rate. We ignore the congestion
on the low altitude air traffic in this step.
According to the related work, we design a
simplified model of flying taxi scheduling problem. It
is presented in Section 2. Some delivery drone
specifications such as the vertical take-off and
landing, operating hours, recharging time, battery
capacity, power consumption rate will be borrowed
from the literature for the experiments. We need to
maximize the working time that the flying taxis serve
the clients on the selected demands and it is used to
be the objective function in our work. In Section 3 and
4, two metaheuristics, which are a genetic algorithm
and a simulated annealing, are presented. We apply
these two algorithms to optimize the scheduling
problem. The computational results on fifteen
generated instances are illustrated in Section 5.
Lastly, the conclusion and the future work are
presented in Section 6 and 7, respectively.
2 FLYING TAXI SCHEDULING
OPTIMIZATION MODEL
In this section, an optimization model for the flying
taxi scheduling problem will be presented. The
simplified flying taxi characteristics are designed
from the commercial delivery drones in several
research works. We assume that the flying taxis
operate to serve the customers as same as the drone
service for transporting the parcel from an origin to a
destination. The main operating time of a task is to
ECTA 2021 - 13th International Conference on Evolutionary Computation Theory and Applications
142
move in horizontal axis between two geometric
points, which represent the origin and the destination
in x-y coordinate. The operating time is calculated by
using the Euclidean distance and the average speed of
the flying taxi. Moreover, we consider the fixed
additional time in the beginning of the task for
picking up the passenger and vertical takeoff, and in
the end of the task for vertical landing and dropping
the passenger as in Figure 1. Some unprofitable trips
(for changing the taxi location to pick up the next
passenger or to go to the center for battery recharging)
are also taken into account for the schedule
management.
Figure 1: Flying taxi passenger service in the considered
area.
For the flying taxi scheduling problem, we have
to find the optimal task schedule for all available
flying taxis in the system. The customers submit the
requests with the origin points, destination points, and
pick up time to the taxi center, and then the taxi center
will manage the demands to the flying taxis in order
to obtain the most advantage of the existing resources.
The assigned tasks can be a demand response for
passenger service or a battery recharging. The
location changes before starting tasks either for
moving to the next customer for preparing the
demand response or to the center for the battery
recharging are computed. The tasks are assigned to
the available flying taxis depending on the required
demands from the customers and the remaining
battery level of the flying taxis.
We propose a flying taxi scheduling model by
considering the above assumptions and borrowing
some drone characteristics from the literatures. The
objective of our work is to maximize the operational
time of the flying taxis to serve the customers and
gain the fare. The task assignment must satisfy the
flying taxi constraints that the taxi must be available
in required period and also has enough battery level
for finishing its task and return back to the center for
recharging, if it is necessary. The required parameters
and variables are shown as follow:
Indices
𝑖 demand index οˆΊπ‘–ξ΅Œ1,2,…,π‘›οˆ»
𝑗 flying taxi index οˆΊπ‘—ξ΅Œ1,2,…,π‘šοˆ»
π‘˜ flying taxi operation index
οˆΊπ‘˜ξ΅Œ1,2,…,𝐾
Parameters
𝑑

demand 𝑖
𝑒

pick-up time of demand 𝑖
𝑝_π‘œ

π‘₯_π‘œ

,𝑦_π‘œ

 origin point of demand 𝑖
𝑝_𝑒

π‘₯_𝑒

,𝑦_𝑒

 destination point of
demand 𝑖
𝑙

distance between origin and destination
points of demand 𝑖 (unit:metre)
𝑙


ξΆ₯
π‘₯_π‘œ

π‘₯_𝑒


ξ¬Ά
ξ΅…οˆΊπ‘¦_π‘œ

𝑦_𝑒


ξ¬Ά
𝑝_𝑐

π‘₯_𝑐,𝑦_𝑐

center point for battery
recharging
𝐡 battery consumption rate (unit:
%/minute)
𝑣 average speed in horizontal axis (unit:
m/minute)
𝑠 required time for vertical takeoff or
landing, including time to pick up and
drop passenger, if need (unit: minute)
𝑅 battery recharging time to full (unit:
minute)
𝑏

minimum remaining battery level to
prevent full discharge (unit: %)
𝑇 available time for flying taxi operations
in 24 hours (1440 minute)
Decision Variables
π‘₯

1 if flying taxi 𝑗 serves the customer of
demand 𝑖 as the π‘˜th operation, and 0
otherwise
𝑦

1 if flying taxi 𝑗 recharges its battery at
the center as the π‘˜th operation, and 0
otherwise
𝑏

battery level of flying taxi 𝑗 after flying
taxi 𝑗 finishes its π‘˜th operation (unit:
%)
The initial battery charge is set to
100%.
𝑑

time of flying taxi 𝑗 after flying taxi 𝑗
finishes its π‘˜th operation (unit: minute)
The initial time is set to 0 and it
increases as the operations are
performed.
𝑝

ξ΅«π‘₯_𝑝

,𝑦_𝑝

ξ΅― position in x-y
coordinate after flying taxi 𝑗 finishes
its π‘˜th operation
The initial position is set to center
position 𝑝_𝑐
𝑔

distance to change the location of
flying taxi 𝑗 to origin point of demand
𝑖 or to the recharging center as the π‘˜th
operation (unit: meter)
Optimal Scheduling for Flying Taxi Operation
143
The flying taxi scheduling problem is formulated as below:
max  
𝑙

𝑣
ξ΅…2𝑠π‘₯

ξ―„
ξ―žξ­€ξ¬΅
ξ― 

ξ―‘
ξ―œξ­€ξ¬΅
(1)
Subject to:
π‘₯

ξ΅‘
ξ―„
ξ―žξ­€ξ¬΅
1
ξ― 


,βˆ€π‘–
(2)
π‘₯

𝑦

ξ΅‘1,βˆ€
ξ―‘
ξ―œξ­€ξ¬΅
𝑗,π‘˜
(3)
𝑦

π‘₯

ξ―‘
ξ―œξ­€ξ¬΅
,βˆ€π‘—,π‘˜, π‘€β„Žπ‘’π‘Ÿπ‘’π‘˜ξ΅’2
(4)
𝑔

 π‘₯

ξΆ§
π‘₯_𝑝




π‘₯
_
π‘œ


ξ¬Ά
ξ΅…οˆΊπ‘¦
_
𝑝




𝑦
_
π‘œ


ξ¬Ά
𝑦

ξΆ§
π‘₯_𝑝




π‘₯
_
π‘οˆ»
ξ¬Ά
ξ΅…οˆΊπ‘¦
_
𝑝




𝑦
_
π‘οˆ»
ξ¬Ά
,βˆ€π‘—,π‘˜
(5)
𝑏




𝐡
𝑔

𝑣
ξ΅…2𝑠
𝑙

𝑣
ξ΅…2𝑠
ξ―‘
ξ―œξ­€ξ¬΅
ξ΅±π‘₯

ξ΅… 100%οˆ»π‘¦

ξ΅Œπ‘

,βˆ€π‘—,π‘˜
(6)
𝑏

𝐡
⎝
βŽ›
ξΆ§
ξ΅«π‘₯_𝑝

π‘₯
_
𝑐
ξ¬Ά
𝑦
_
𝑝

𝑦
_
𝑐
ξ¬Ά
𝑣
ξ΅…2𝑠
⎠
⎞
π‘₯

ξ―‘
ξ―œξ­€ξ¬΅
𝑏

,βˆ€π‘—,π‘˜
(7)
𝑑






𝑔

𝑣
ξ΅…2𝑠

ξ―‘
ξ―œξ­€ξ¬΅
π‘₯

𝑒

,βˆ€π‘—,π‘˜
(8)
𝑒

ξ΅…
𝑙

𝑣
ξ΅…2𝑠
ξ―‘
ξ―œξ­€ξ¬΅
π‘₯

ξ΅…

𝑑




ξ΅…
𝑔

𝑣
ξ΅…2𝑠𝑅

𝑦

ξ΅Œπ‘‘

,βˆ€π‘—,π‘˜
(9)
𝑑


𝑇,βˆ€π‘—,π‘˜
(10)
π‘₯



∈

0,1

,βˆ€π‘–,𝑗,π‘˜
(11)
𝑦


∈

0,1

,βˆ€π‘—,π‘˜
(12)
𝑏


,𝑑


ξ΅’0,βˆ€π‘—,π‘˜
(13)
𝑝


βˆˆβ„
ξ¬Ά
,βˆ€π‘—,π‘˜
(14)
The mathematic formula of the flying taxi scheduling
problem presents an objective function in Equation
(1) and the constraints in Equation (2) to (14) that
must be satisfied. In Equation (1), the objective
function of this problem is to maximize the
operational time that the flying taxi fleet can serve the
customers according to the selected and scheduled
demands in the solution sequences. This objective
value can represent the obtained profit from their
proportional relation. Equation (2) ensures that the
demand cannot be served more than once. Equation
(3) guarantees that the flying taxi can be assigned
only one task, demand response or battery recharging,
but it is not allowed to operate two tasks
simultaneously. Equation (4) ensures that only the
demand response task will be assigned to the flying
taxi if the previous task is the battery recharging.
Equation (5) calculates the unprofitable distance
when the flying taxi changes the position from the last
position of the previous task, to the origin position of
the next selected demand if the flying taxi is assigned
to serve the customer or to the recharging center if the
flying taxi is assigned to recharge the battery. This
unprofitable distance value will be used in the next
equations. Equation (6) calculates the remaining
battery level after the flying taxi finishes the assigned
task. If the assigned task is a demand response, the
battery consumption is calculated from the location
move to pick up the passenger and bring them to the
destination, and also including the vertical takeoff
and landing. If the assigned task is a battery
recharging, the battery level is always 100% after the
flying taxi finishes the tasks. Equation (7) guarantees
that the flying taxi has enough battery to finish the
passenger service task and also go back to the center
if the battery must be recharged. Equation (8) ensures
ECTA 2021 - 13th International Conference on Evolutionary Computation Theory and Applications
144
that the flying taxi has enough time to change the
location to the pick-up point of the next assigned
demand. Equation (9) calculates the finishing time
after the flying taxi operates the assigned demand
response task or the assigned battery recharging task
as in Figure 2. Equation (10) guarantees that the
finishing time of the last assigned task is in the
available operation time. Equations (11) and (12)
illustrate the binary decision variables of the demand
response and battery recharging tasks. Equation (13)
guarantees that the decision variables of battery level
and operating time of the flying taxis are nonnegative.
Finally, Equation (14) shows that the current position
of the flying taxi corresponds to real values in two
dimensions (x-y coordinate).
Figure 2: Operation time of possible assigned tasks:
demand response or battery recharging.
We do not have the real flying taxi characteristics
since the flying taxi service does not exist in real-life
yet. Therefore, we borrow some drone specifications
from Kim et al, 2020 and modify some specification
values for our experiments. We ignore the drone
failure reliability and weather uncertainty in this step.
The specifications for the experiments is shown as in
Table 1.
Table 1: Specifications for scheduling experiments.
Item Value
Battery consumption rate

𝐡

0.67%/minute (β‰ˆ 100% for
2.5 hours)
Average speed in
horizontal axis

𝑣

833 m/minute (β‰ˆ 50 km/h)
Required time to takeoff
or landing

𝑠

5 minutes
Battery recharging time to
full

𝑅

60 minutes
Minimum remaining
attery level

𝑏


5%
Available operating time
οˆΊπ‘‡οˆ»
1440 minutes/day (from
midnight to midnight of
the next day)
The algorithms, which are used to solve this
scheduling problem, will be explained in the next two
sections.
3 GENETIC ALGORITHM
The genetic algorithm is a popular metaheuristic
method, which is very efficient for solving complex
combinatorial optimization problems (Goldberg,
1989). It mimics the natural survival in life evolution.
The genetic algorithm will start with the first
generation, which generates an initial population. The
initial population is often generated randomly. The
population contains several chromosomes (solutions)
and each chromosome contains several genes. In this
work, we used a biased random key genetic
algorithm, which are proposed in (Gonçalves et al.,
2011), for solving the flying taxi scheduling problem.
The gene values are real values in the interval 0 and
1. The number of genes in each chromosome is equal
to number of demands multiply to number of flying
taxis. Each gene represents a demand, which is
responded by a flying taxi. In each iteration of the
genetic algorithm, a new population will be generated
from three sets of chromosomes: elite set from
selection process, crossover set from crossover
process and mutant set from mutation process. The
elite set copies the best chromosomes from the
previous population. The crossover set contains the
offspring chromosomes in which the gene values
come from two different parent chromosomes. The
first and the second parents are selected randomly
from the elite set and the non-elite set, respectively.
The mutant set is randomly generated as in the initial
population. This mutant set helps to escape local
optima. We use the number of iterations since the last
archive improvement as a stopping criterion. The
parameter values are tuned by the experiments and
they are set as in Table 2.
Table 2: Parameter values of GA.
Parameters Values
Population size 2 times of chromosome size
Elite set size 10% of population size
Crossover set size 70% of
p
o
p
ulation size
Crossover
p
robabilit
y
0.7
Sto
pp
in
g
criterion 30
A decoding method with ideal priority
combination are designed for obtaining the solution
from each chromosome.
Each gene of the GA chromosome represents a
demand, which is assigned to a flying taxi. We
borrow the decoding method from (Mendres et al.,
2009). The expression of the decoding with ideal
priority combination of the demand 𝑖 is presented as:
π‘ƒπ‘Ÿπ‘–π‘œπ‘Ÿπ‘–π‘‘π‘¦


𝑇𝑒

𝑇

1𝑔𝑒𝑛𝑒

2
ξ΅°
Optimal Scheduling for Flying Taxi Operation
145
where 𝑇 is the available operation time of the flying
taxi and 𝑒

is the pick-up time of the demand 𝑖. The
concept of the ideal priority is to give higher priority
to the demand, which has the earlier pick-up time.
In the decoding step, the demand and the specific
flying taxi, which has the highest priority, will be
considered firstly. If all necessary constraints are
satisfied, the demand will be assigned to the sequence
of the specific flying taxi. The gene concerning the
same demand of the assigned one will be removed
from the waiting list. Then, the next lower priority
demand will be considered until the all demands are
examined. Finally, we will obtain the sequence of the
selected demanded to be responded by the flying taxis
and their battery recharging tasks.
4 SIMULATED ANNEALING
The simulated annealing is a metaheuristic algorithm,
which is also efficient for solving combinatorial
optimization problems. It was proposed to solve the
traveling salesman problem in 1983 (Kirkpatrick,
1983). It mimics the heating and controlled cooling
down process of the material by decreasing the
probability to accept the worse solutions according
the temperature. The temperature is slowly
decreased from the initial value to zero. The
algorithm uses the perturbation strategies to
generate a new candidate close to the current
solution, measure its quality, and decide to move to
it according to the probability from the current
temperature.
In this work, we use the fast simulated annealing
from Brownlee, 2021. The temperature is calculated:
π‘‘π‘’π‘šπ‘ξ΅Œπ‘‘π‘’π‘šπ‘

/οˆΊπ‘–π‘‘π‘’π‘Ÿ
ξ―‘ξ―¨ξ― ξ―•ξ―˜ξ―₯
ξ΅…1
where π‘‘π‘’π‘šπ‘ is the current temperature, π‘‘π‘’π‘šπ‘

is
the initial temperature, and π‘–π‘‘π‘’π‘Ÿ
ξ―‘ξ―¨ξ― ξ―•ξ―˜ξ―₯
is the
iteration number. Since we consider the maximization
problem in this work, the acceptance probability of
the worse candidate is calculated from the difference
of the objective values between the candidate and
current solutions as follow:
π‘π‘Ÿπ‘œπ‘
ξ―”ξ―–ξ―–ξ―˜ξ―£ξ―§
exp
π‘œπ‘π‘—
ξ―ͺ
ξ΅†π‘œπ‘π‘—
ξ―–ξ―¨ξ―₯ξ―₯
π‘‘π‘’π‘šπ‘
ξ΅°
It shows that the algorithm can escape from basins of
attraction, since it allows accepting the candidate
solution even its quality is worse than the current
solution when the temperature parameter is still high.
The acceptance probability will decrease slowly
when the temperature parameter is lower. To generate
the candidate solution, the perturbations are designed
by changing one of the taxi to respond to the demand
and changing the order to assign the task to the
sequence. The initial temperature of the simulated
annealing process is set to 100. The number of
iterations that the best solution is not improved is
defined as a stopping criterion and it is set to 1000.
5 COMPUTATIONAL RESULTS
The genetic algorithm and the simulated annealing
are used to solve the flying taxi scheduling problem.
The experiments are done on fifteen generated
instances. They concern different number of demands
and different number of flying taxis in the 24 hours of
time duration. The day time demands are generated
randomly with higher probability than the demands in
the night time. The format of instance name is
β€œInstancexx_yy.txt”, where xx shows the number of
demands and yy shows the number of flying taxis in
this instance. As the example of β€œInstance10_2.txt”,
this instance concerns ten demands and two flying
taxis. The origin-destination points and the passenger
pick-up time of each demand are defined in the
instances. The algorithms are implemented in Python
3.8.8 and Conda 4.9.2 on a personal computer with an
Intel Corei5 1.6 GHz CPU and 8 GB RAM.
Figure 3 shows an example of the approximate
optimal schedule for β€œInstance100_5”, which
examines 100 customer demands and 5 available
flying taxis. The green bars represent the taxi services
to respond the customer demands and the orange bars
illustrate the battery recharging tasks. The obtained
schedule also satisfies all operational constraints such
as the necessary time to change the location for on
time picking up the next customer and the flying taxis
have enough remaining battery level after finishing
the mission and they can return to the center for
battery recharging, if they need.
Figure 3: A result example of the instance100_5.
The computational results of the genetic
algorithm and the simulated annealing are compared.
ECTA 2021 - 13th International Conference on Evolutionary Computation Theory and Applications
146
The boxplots of eleven runs of each instances are
shown in Figure 4. The results show that the genetic
algorithm with the ideal priority combination
decoding method obtains better solutions for the
small and medium instances. Since the genetic
algorithm is a population-based algorithm that
maintains and improves multiple solutions in each
iteration, it spends higher computation time than the
simulated annealing. On our parameter setting, the
genetic algorithm takes more than 24 hours to obtain
the approximate optimal solution for the large
instances and it is not reasonable for the dispatching
system of the flying taxi scheduling problem. So that
why, the genetic algorithm has not results for the
large instances. However, the simulated annealing,
which is a single solution approach, can solve the
large instances in acceptable time.
6 CONCLUSIONS
The simplified model of the flying scheduling
problem is presented in this work. Since there are not
the flying taxi in the daily life yet, the characteristics
of the flying taxi are mimicked from the parcel
delivery drone properties. The model concerns two
main subjects, consisting of the delivery drone
scheduling and the taxi demand responsive
scheduling. For the drone delivery scheduling part,
different characteristics and constraints of parcel
delivery drone are studied. The method to respond to
the demand is studied from the taxi demand
responsive scheduling part.
We assume that the flying taxis operate to serve
the customers as same as the drone service for
transporting the parcel from an origin to a destination.
The main operating time of a task is to move in
horizontal axis between two geometric points, which
represent the origin and the destination in x-y
coordinate. Moreover, we consider the fixed
additional time in the beginning of the task to pick up
the passenger and vertical takeoff and in the end of
the task to vertical landing and drop the passenger.
The objective of our work is to maximize the
operational time that the flying taxi fleet can serve the
customers according to the selected and scheduled
demands in the solution sequences. The task

Figure 4: Objective value and average computation time comparison between two algorithms: Genetic algorithm (GA) and
simulated annealing (SA).
Optimal Scheduling for Flying Taxi Operation
147
assignment must satisfy the flying taxi constraints
that the taxi must be available in specific period and
has enough battery level for finishing its task and
return back to the center for recharging, if it is
necessary. Two metaheurics are used to solve this
problem and the computational results are compared.
The results show that the genetic algorithm obtains
better solutions for the small and medium instances,
but it spends higher computation time than the
simulated annealing. However, the simulated
annealing can solve the large instances in reasonable
time.
7 FUTURE WORKS
For the future work, the characteristics of the flying
taxis and their scheduling model can be improved to
represent closer to the real operations in the future.
New technology of battery can be taken into account.
The air obstacles of the flying taxi trajectory can be
considered.
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