Event-Triggered and Affine Formation Control of Multiple Robotic Systems
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This thesis investigates the time-invariant and time-varying formation tracking control strategies for multi-agent systems (MASs). The time-invariant formation tracking control strategies are studied for multi-robotic systems with general linear agent dynamics under sampled-data-based event-triggered communication settings. Unlike traditional time-triggered communication strategies, event-triggered communication strategies (event generators) are designed in this thesis to adaptively regulate the inter-agent communication with the goal to reduce unnecessary communication while maintaining acceptable system performance. The formation tracking controllers are then designed based on the event-regulated information so that the formation control problem can be transformed into a stability analysis problem of the closed-loop formation error dynamics. Sufficient conditions in the form of linear matrix inequalities (LMIs) that ensure asymptotic convergence of the closed-loop formation error dynamics are derived for systems with an autonomous leader using Lyapunov-based stability analysis methods, and the event generator and controller gains are co-designed such that the derived conditions are feasible. Under a similar structure, a new event generator and a controller are then developed for systems with a non-autonomous leader to enable more general and practical formation maneuverings. A novel edge-based event-triggering strategy is further investigated to reduce communication resources while maintaining comparable system performance. Sufficient conditions that ensure an exponential convergence of the formation error dynamics are derived, where the convergence rate is explicitly expressed and can be tuned based on convergence speed requirements. The developed formation controllers and event generators are validated in simulations and experiments using a group of mobile robots with linearized dynamics. This thesis also studies the time-varying formation control problem for a group of quadcopters with experimentally identified dynamics using a two-layer affine formation control strategy, where a linear affine formation controller is designed based on the virtual translational dynamics in the formation layer and a nite-time controller is designed to track the virtual inputs in the local control layer.