Controlling smart matter

We study the behavior of several organizations for distributed control of unstable physical systems and show how a hierarchical organization is a reasonable compromise between rapid local responses with simple communication and the use of global knowledge. This holds not only in ideal situations but also when imperfections and delays are present in the system. We also introduce a new control organization, the multihierarchy, and show it is better than a hierarchy in achieving stability. The multihierarchy also has a position invariant response that can control disturbances at the appropriate scale and location.