Nussbaum function–based universal cooperative output regulation design for uncertain nonlinear multiagent systems

This paper presents a Nussbaum function–based universal cooperative output regulation design for a class of nonlinear multiagent systems with both an unknown exosystem and nonidentical unknown control directions. The major challenges include the nonidentical unknown control directions in a directed communication graph and the concurrence of the unknown parameters in both the plant and the exosystem. To handle the nonidentical unknown control directions, we propose a dynamic compensator–based distributed controller such that the Nussbaum gain technique can be successfully implemented under directed communication graphs. Moreover, to deal with the unknown exosystem, we integrate the distributed controller with a novel internal model candidate. The resulting distributed controller is a universal regulator in the sense that it does not require the unknown parameters to be in known compact sets. Furthermore, the proposed controller is more flexible compared with those in the existing works as any existing Nussbaum gains can be adopted in the controller design and the adopted Nussbaum gains can be nonidentical for each agent.