Nonlinear Dynamics Based Formation Control of Multiagent Systems

Abstract

In multiagent systems, agents work together based on their local interactions to achieve a common goal by following established rules. Compared to single agents, multiagent systems have grown in popularity because of their adaptability, scalability, reliability, robustness, and low cost. Consequently, these are being utilized in a variety of applications, such as intelligence, surveillance, and reconnaissance (ISR) missions, rescue and retrieval operations, precision agriculture, space and planetary exploration, cooperative transportation, etc. In order to effectively execute such applications, the agents must navigate in a certain pattern, which is achieved using formation tracking control algorithms. In the formation tracking problem, convergence time is of significant importance in situations where the execution time available for accomplishing a particular task is indispensable. This dissertation presents two novel decentralized formation tracking control strategies that guarantee a predefined convergence time for multiagent systems. In the first part, a decentralized predefined-time formation tracking controller is proposed for nonlinear multiagent systems by utilizing terminal sliding mode control (TSMC). The sigmoid functions are employed in the construction of the terminal sliding manifold, which eventually results in a predefined settling time. The switching control methodology is used to handle the inherent singularity that occurs in the case of terminal sliding modes. The efficacy of the proposed formation tracking controllers is established for the dynamics of multiple omnidirectional robots (ODRs) under modeling uncertainties and external disturbances. The second part of this dissertation addresses the problem of time-varying formation tracking of multiagent systems that are operating in hostile or challenging circumstances, such iv as disaster zones, where both the position constraints and execution time become crucial. A decentralized practical-predefined time formation tracking control scheme is proposed based on barrier Lyapunov functions in conjunction with linear sliding mode control. The proposed method is capable of handling both symmetric and asymmetric position constraints. The use of a linear sliding manifold ensures that there are no singularities in the controller; however, this merit is attained at the cost of tracking error accuracy. The effectiveness of the proposed method is examined using first the formation tracking of autonomous surface vessels (ASVs) under symmetric position constraints and then multi-missile formation tracking under asymmetric position constraints. The simulation results demonstrate the intended performance of the proposed formation tracking controller under modeling uncertainties and external disturbances.