Adaptive Chain Observers for Controlling Cooperating Clusters of Nonlinear Delayed-Output Mechanical Systems

University Of Texas At Austin, Austin TX

Investigators

Abstract

Adaptive Chain Observers for Controlling Cooperating Clusters of Nonlinear Delayed-Output Mechanical Systems Abstract: This proposal combines basic research with hardware-in-the-loop experimentation to generate and validate new control methodologies for cooperating clusters of uncertain mechanical systems. Uniqueness of this study arises from our explicit consideration of time-delay characteristics that are integral within realistic low-bandwidth vehicle-to-vehicle communication networks. Theoretical part of the research plan focuses upon cooperating clusters of nonlinear dynamical systems that are commanded through a leader-follower hierarchy. The leader controller enforces absolute positioning and orientation of the fleet by tracking reference trajectories generated by a nonlinear reference model. The follower controllers rely upon time-delayed reference trajectory signals received from the leader to ensure that the desired "formation geometry" is maintained. Parameter uncertainty within the respective models of the followers necessitates the design of adaptive controllers that utilize currently available local state information. Duly taking the effects of communication delay into consideration, we propose the development of an innovative chain-observer structure onboard each follower whose objective would be to "estimate" in a closed-loop sense the undelayed instantaneous state of the nonlinear reference model of the leader. This chain structure would be further strengthened by new classes of adaptive control solutions that will be derived from nonlinear re-parameterization techniques recently given by the proposer. The adaptive control framework including the chain-observer avoids over-parameterization and provides certain unique manifold attractivity properties that significantly boost the closed-loop performance. The experimental component of this proposal will implement and evaluate all the theory within the distributed spacecraft formation flying testbed facility at the Goddard Space Flight Center.