  This paper is concerned with the problem of controlling a system of
constrained dynamic subsystems in a way that balances the performance
degradation of decentralized control with the practical cost of centralized
control. We propose a coalitional control scheme in which controllers of
subsystems may, as the need arises, group together into coalitions and operate
as a single entity. The scheme employs a robust form of distributed model
predictive control for which recursive feasibility and stability are
guaranteed, yet---uniquely---the reliance on robust invariant sets is merely
implicit, thus enabling applicability to higher-order systems. The robust
control algorithm is combined with an algorithm for coalition forming based on
consensus theory and potential games; we establish conditions under which
controllers reach a consensus on the sets of coalitions. The recursive
feasibility and closed-loop stability of the overall time-varying coalitional
control scheme are established under a sufficient dwell time, the existence of
which is guaranteed.
