Abstract:
An autonomous system has been widely applied for various civil/military research
because of its versatile capability of understanding high-level intent and
direction of a surrounding environment and targets of interest. However, as autonomous
systems can be out of control to cause serious loss, injury, or death in
the worst case, the verification of their functionalities has got increasing attention.
For that reason, this study is focused on the verification of a heterogeneous
multi-agent autonomous system. The thesis first presents an overview of formal
methods, especially focuses on model checking for autonomous systems verification.
Then, six case studies are presented to verify the decision making behaviours
of multi-agent system using two basic scenarios: surveillance and convoy. The
initial system considered in the surveillance mission consists of a ground control
system and a micro aerial vehicle. Their decision-making behaviours are
represented by means of Kripke model and computational tree logic is used to
specify the properties of this system. For automatic verification, MCMAS (Model
Checker for Multi-Agent Systems) is adopted due to its novel capability to accommodate
the multi-agent system. After that, the initial system is extended
to include a substitute micro aerial vehicle. These initial case studies are then
further extended based on SEAS DTC exemplar 2 dealing with behaviours of
convoy protection. This case study includes now a ground control system, an
unmanned aerial vehicle, and an unmanned ground vehicle. The MCMAS successfully
verifies the targeting behaviours of the team-level unmanned systems.
Reversely, these verification results help retrospectively improve the design of
decision-making algorithms by considering additional agents and behaviours
during four steps of scenario modification. Consequently, the last scenario deals
with the system composed of a ground control system, two unmanned aerial
vehicles, and four unmanned ground vehicles with fault-tolerant and communications
relay capabilities. In conclusion, this study demonstrates the feasibility
of model checking algorithms as a verification tool of a multi-agent system in
an initial design stage. Moreover, this research can be an important first step of
the certification of multi-agent autonomous systems for the domains of robotics,
aerospace and aeronautics.
