Distributed Formation Control of Multi-Agent Systems: Theory and Applications

Abstract

Formation control of networked multi-agent systems has earned significant research interest over the past two decades due to its potential applications in multi-disciplinary engineering problems, such as precision agriculture, space and planetary exploration, multi-target surveillance, cooperative transportation, etc. In contrast to a single specialized agent, a multi-agent system offers flexibility, scalability, reliability, robustness to faults and cost-effectiveness in solving complex and challenging tasks. Firstly, two novel formation control techniques are proposed for linear multi-agent systems with directed communication topology. (i) A distributed adaptive group formation tracking protocol is proposed. In the proposed approach, the followers are distributed into several subgroups and each subgroup can track a desired sub-formation surrounding the respective leaders. When multiple leaders exist in a subgroup, the sub-formation attained by that subgroup keeps tracking a convex combination of the states of the leaders. Towards the end, a case study on multi-target surveillance operation is taken up to show an application of the proposed adaptive control technique. (ii) A two-layer fully distributed formation-containment control scheme is designed, where the states of the leaders attain a pre-specified time-varying/stationary formation and the states of the followers converge into the convex hull spanned by the states of the leaders. To achieve formation-containment, a set of fully distributed control protocols is developed utilizing the neighbouring state information, which enables the proposed scheme operate without using global information about the entire interaction topology. Simulation and experimental results are provided to demonstrate the feasibility and effectiveness of the proposed framework. Secondly, a hierarchical control system is proposed for a novel Unmanned Aerial Vehicle (UAV) platform based on a three-rotor configuration, where the three propellers can be tilted independently to obtain full force and torque vectoring authority. A robust feedback linearization controller is first developed to deal with this highly coupled and nonlinear dynamics of the proposed tri-rotor UAV, which linearizes the dynamics globally using geometric transformations. A distributed formation control tracking protocol and an optimal observer are then proposed to control a swarm of tri-rotor UAVs. The effectiveness of the designed control strategy is illustrated in a realistic virtual reality simulation environment based on real hardware parameters from a physical construction. Finally, an automatic cruise control scheme is developed to maintain the string stability of a heterogeneous and connected vehicle platoon moving with constant spacing policy. A feedback linearization tool is first applied to transform the nonlinear vehicle dynamics into a linear heterogeneous state-space model and then a distributed adaptive control protocol has been designed to keep equal inter-vehicular spacing between any consecutive vehicles while maintaining a desired longitudinal velocity of the entire platoon. The proposed scheme utilizes only the neighbouring state information. Simulation results demonstrated the effectiveness of the proposed platoon control scheme. Moreover, the practical feasibility of the scheme was validated by hardware experiments with real robots.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Zhengtao Ding (Supervisor) & Alexander Lanzon (Supervisor)