Structured Optimal Feedback in Multi-Agent Systems: A Static Output   Feedback Perspective
  In this paper we demonstrate how certain structured feedback gains necessarily emerge as the optimal controller gains in two linear optimal control formulations for multi-agent systems. We consider the cases of linear optimal synchronization and linear optimal centroid stabilization. In the former problem, the considered cost functional integrates squared synchronization error and input, and in the latter, the considered cost functional integrates squared sum of the states and input. Our approach is to view the structures in the feedback gains in terms of a static output feedback with suitable output matrices and to relate this fact with the optimal control formulations. We show that the two considered problems are special cases of a more general case in which the optimal feedback to a linear quadratic regulator problem with cost functionals integrating squared outputs and inputs is a static output feedback. A treatment in this light leads to a very simple and general solution which significantly generalizes a recent result for the linear optimal synchronization problem. We illustrate the general problem in a geometric light. 
Shen Zeng, Frank Allg\"ower
math.OC