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  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>September</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>A Multi-Agent Based Framework for Controlling Self Managing Fleets of Autonomous Vehicles with a Transparent Reasoning Process</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Marcel Mauri</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Goethe University Frankfurt</institution>
          ,
          <addr-line>Robert-Mayer-Str. 10, 60325</addr-line>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2022</year>
      </pub-date>
      <volume>20</volume>
      <issue>2022</issue>
      <fpage>0000</fpage>
      <lpage>0002</lpage>
      <abstract>
        <p>This dissertation aims to research on multi agent systems to develop a base system to control a fleet of self-driving and self-organizing vehicles with a transparent reasoning process. The main focus for the application area is on the use in mobility as a service/ride hailing scenarios. Every vehicle will be controlled by a belief-desire-intention agent and will use utility functions to make its decisions. The agents will delegate unfavorable jobs to each other by using the contract net protocol for a decentralized decision making.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;BDI Agent</kwd>
        <kwd>Multi-agent system</kwd>
        <kwd>Mobility as a Service</kwd>
        <kwd>Simulation</kwd>
        <kwd>XAI</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Due to climate change growing scarcity of resources we have to reconsider parts of our way to
live. One of these is the mobility sector which ofers great potential for optimization. A new
and much more eficient way to move could be mobility as a service (MaaS) which means to
buy "mobility services as packages based on consumers’ needs instead of buying the means of
transport” [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. A specialization of MaaS where every passenger is served by a single autonomous
vehicle is called ride-hailing [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ].
      </p>
      <p>MaaS solutions based on a free floating model that are designed to cover the last few meters,
such as the bike and scooter sharing services that are widely used today, have some problems.
They tend an accumulation of vehicles in remote, inconvenient or dangerous places. To cover
this, additional employees are needed to permanently pick up the vehicles and place them at
locations with higher customer trafic.</p>
      <p>This dissertation is part of a project that uses a multi agent system (MAS) to develop a self
driving and self-organizing fleet of E-trikes which are intended to be used in a free float model.
This system is designed to be an improvement of the above described already available sharing
services. The vehicles will drive autonomously to the position of a calling customer, search
proactive for useful parking positions when not in use, drive to a charging station when needed
and communicate with each other to find the most suitable E-trike for every incoming job. Every
vehicle will be controlled by an BDI agent. Customer orders are first delegated to the nearest
vehicle. This vehicle will use a utility function to decide if the customer job can be handled by
itself. If not it will use the contract net protocol (CNP) to delegate it to a more suitable E-trike.
For this decision, the utility function will take into account, among other things, the already
accepted customer trips, the current battery level and expected arrival times. By using the BDI
architecture, each agent can think about the order and the way in which it performs its tasks,
which include customer, loading and parking trips.</p>
      <p>
        As trust is an important factor between interactions of humans and AI systems [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] we want
to achieve this for the framework. The reasoning process should be transparent and decisions
should be explainable to the user (e.g. why there is currently a waiting time). Also further
predictive explanations should be provided (e.g. user wants to know how much longer he has
to wait).
      </p>
      <p>In a first step the advantages of such a system will be examined in a simulation, later it is
planed to build two prototypes which will be tested in real life on the university campus. This
dissertation focuses on the development of the MAS and the evaluation by using a simulation.
The development of the hardware or software components, that does not belong the decision
making (like the obstacle detection as part of the autonomous driving), is not part of this thesis.
The MAS developed in this dissertation will be designed in such a way that it is suitable as a
basic framework for use in other scenarios with autonomous self-managing vehicles.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Motivation</title>
      <p>The individual technologies and methods in this dissertation are all well studied in their own
right. Their combined use for the upper described use case, especially in the context of XAI,
seems new and not much researched. An evaluation of the possibilities of such a combination
seems to be an interesting research gap.</p>
      <p>
        Multi-agent approaches in context of trafic scenarios are discussed in [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. BDI agents are well
known and have already been used for vehicles in projects that are to some kind comparable to
this [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] but mostly focused on the design of the agents and without an performance evaluation.
There are projects which researches similar problems but difer in the detail. So [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] uses neither
BDI agents nor the CNP. There are research projects in ride-hailing, but without the use of BDI
agents for the vehicles [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]. There are also highly scalable decentral approaches for decision
making but without the communication aspect of this project [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. Projects that use both, BDI
agents and a utility function, are not in the context of ride hailing [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ]. The decentralized
decision-making approach is also not widespread. In projects with an similar application
scenario centralized approaches seem to dominate. [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Research Question</title>
      <p>The goal of this dissertation is to develop a MAS framework with a transparent reasoning
process that can be used to control a fleet of cooperating autonomous self-organizing vehicles
usable for various application scenarios. Although this MAS framework is intended to be usable
for a variety of application scenarios, the focus is on ride-hailing with e-trikes as described
above.</p>
      <p>The aim is to find a reasonable balance between the achievability of the goals (in the case of the
ride-hailing scenario the waiting/driving times or customer losses) and the energy consumption
of the overall system.</p>
      <p>Research Question: How can a MAS framework for self-driving autonomous vehicles be
developed, to provide a transparent reasoning process for users across diferent application
domains?</p>
      <p>To date, the following sub questions have been found that should be answered:
• How does such a MAS compete with traditional/already existing solutions in terms of
the achievability of its goals?
• How does such a MAS compete with traditional/already existing solutions in terms of
the resources required?
• How does the diferent features of the MAS influence the results mentioned above?
• Can the user understand the decisions made by the agents’ reasoning process at any point
in time?</p>
    </sec>
    <sec id="sec-4">
      <title>4. Approach and first Results</title>
      <p>
        With the BDI architecture, a suitable agent architecture has already been identified for the
project. The list of tasks that an agent has to fulfil changes regularly. Therefore, it is necessary
for the agent to keep thinking about the best possible plans to fulfil them. For the communication
between the agents the contract net protocol have been identified as a possible solution. Initial
results have already been collected with a simplified prototype based on the JADE [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] agent
framework [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]. For the use in a cyber-physical system planned in a later project phase, a
separation between agent framework and simulation environment is aimed at. For this purpose it
is planned to connect BDI agents implemented in Jadex with the Matsim simulation environment
[13].
      </p>
    </sec>
    <sec id="sec-5">
      <title>5. Planned Evaluation</title>
      <p>The capability of the developed multi agent system will be evaluated by using simulations. One
part of the evaluation will take place in the former described ride-hailing scenario. Therefore it
is planned to use diferent configurations to compare the actual influence of the the special
abilities of the system (ability to communicate, to delegate trips, proactive charging and parking
trips) with diferent evaluation criteria. Criteria such as the energy consumption of the entire
lfeet, waiting and travel times, and the loss of customers due to delays can be used for the
evaluation. Corresponding tests are to be repeated with diferent scheduling strategies, parking
behavior and loading behavior. It is also planed to measure the benefits of the MAS compared to
a much simpler, already available ride-hailing system and an centralized optimization approach.</p>
      <p>It is considered to evaluate the capability of the MAS in an other application scenario to
show the universal applicability. This could for example be a garbage collection scenario. In
the process, the MAS will control autonomous trucks that must eficiently collect trash from
various locations. The details of the evaluation of this scenario and the XAI component are not
yet elaborated.
agents., in: Proceedings of the 14th International Conference on Agents and Artificial
Intelligence - Volume 1: ICAART„ INSTICC, SciTePress, 2022, pp. 425–432.
[13] L. Padgham, K. Nagel, D. Singh, Q. Chen, Integrating BDI Agents into a MATSim Simulation,
Proceedings of the Twenty-first European Conference on Artificial Intelligence (2014) 681
– 686.</p>
    </sec>
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