Cooperative Localization and Control In Multi-Robot Systems With Event-Triggered Mechanism: Theory and Experiments
Creators: Kargar Tasooji, Tohid
Publisher: name: University of Alberta Library
Year: 2023

<p>With the rapid development of mobile robots in practical applications, single robots are generally unable to carry out complex tasks in a large-scale dynamic environment. Therefore, cooperative robotics has grown in recent years as a new research branch that focuses on the problem of coordinating mobile robot teams, such as the exploration of multi-robots and coordination of robotic networks. In a multi-robot system, the accurate localization of each robot in the team is essential for a successful operation. Existing cooperative localization approaches neglect some realistic<br>
limitations of mobile robots, such as battery capacity and communication bandwidth.<br>
Especially, this issue is important when the number of sensors, actuators, and robots in the team increases. To this end, event-triggered sampling, as an alternative to the time-triggered mechanism, has been employed. Using this framework,<br>
the energy consumption of sensors can be reduced and the average updating period of the actuators will be larger. In this aperiodic paradigm, the fundamental idea is that data is sent through the channel only when needed. Mathematically speaking, the system components do not exchange information unless a pre-set triggering condition is satisfied.<br>
The first part was motivated by these realistic limitations of mobile robots and it suggests a new approach for cooperative localization based on an event-triggered mechanism. Motivated by the aforementioned discussion, our objective is to design and implement the event-triggered cooperative localization for a group of e-puck2 robots. Our theoretical analysis and experimental results show that we achieve a<br>
tradeoff between localization accuracy and communication resources. The second part addresses the problem of decentralized event-triggered cooperative localization (DECL) for a group of mobile robots in the presence of time delays. We introduce a DECL algorithm for multi-robot systems under time delays. We consider two different scenarios (i) time-stamped (ii) non time-stamped which leads to different<br>
DECL algorithms. Then, we provide the stochastic boundedness of filtering error considering bounded random delays. We show that if the delay is due to multi-robot<br>
communication is sufficiently small, then by choosing proper event-triggering parameters, the filtering error and covariance remain bounded while reducing the transfer of information. In third part of thesis, we study the problem of a secure decentralized event-triggered cooperative localization (SDECL) for a team of mobile robots in an adversarial environment, where the objective is to perform localization in the presence of a malicious attacker. We consider a scenario in which the attacker is able to attack the communication channels between the exteroceptive sensors and filter of the robot and between two robots independently. In the fourth part of the thesis, we investigate the problem of event-triggered consensus control for a group of mobile robots based on cooperative localization (CL). In our framework, each robot employs the position estimates from CL to jointly achieve consensus. An event-triggered mechanism based on a mixed-type condition is adopted in order to reduce the frequency of control updates and unnecessary transmission of information between system components. Our goal is to design an event-triggered consensus controller based on CL such that the closed-loop system achieves the prescribed consensus<br>
in spite of inaccurate sensor measurements. We provide sufficient conditions that guarantee the desired consensus using eigenvalues and eigenvectors of the Laplacian<br>
matrix. In last part of thesis, we investigate the secure consensus control problem for multi-robot systems with event-triggered communication strategy under aperiodic<br>
energy-limited denial of-service (DoS) attacks, where DoS attacks prevent the transmission of information between robots. Based on the above discussion, our goal is to design a secure control scheme based on cooperative localization (CL) with an event-triggered mechanism and investigate under what conditions the N robots can move cooperatively to the desired consensus position despite the presence of DoS<br>
attacks.</p>