Continuous Time Observers and Consensus Control for Heterogeneous Multi-Agent Space Structures

Multi-Agent Systems (MAS) are composed of multiple agents interacting to achieve specific goals, overcoming the typical limitations of single-agent approaches. This thesis investigates distributed attitude estimation and control strategies for a group of heterogeneous satellites. In particular, the agents cooperatively estimate and track the angular displacement and velocity of an uncooperative target, assuming that no angular rate measurements are available. The mathematical model of a satellite with flexible appendages is used to represent both the agents and the target as second-order dynamical systems. A minimal-order local observer is first presented to infer the angular velocity of the agents from their own attitude measurements. The observer formulation is transparently derived, and its existence condition is shown to be independent of quantitative changes in the satellite’s physical parameters. A distributed observer for the state estimation of continuous linear time-invariant systems is reviewed from the literature. A minimal order version is shown to exist for the second-order satellite model in consideration, with the key contribution of having a lower total order compared to other approaches found in the literature. A consensus control law derived from the standard proportional-derivative formulation is then coupled with the minimal order distributed observer previously discussed. The system is shown to reach consensus and accurately track the target states. Finally, numerical simulations are carried out to illustrate the theoretical results and compare the performance of the proposed method with a different approach based on a relative displacement feedback control law.