Universal output feedback adaptive control with uncertain nonlinearity and unknown high‐frequency gain sign: A new design

Abstract

Summary In this paper, we propose a new universal output feedback adaptive controller to globally (or semiglobally) stabilize nonlinear output feedback systems, whose nonlinearities are bounded either by known functions with unknown parameters or by completely unknown functions. In addition, no a priori knowledge of the sign of high‐frequency gain is required. The new design focuses on properly arranging the control gains step by step in the filter backstepping design. Instead of Lyapunov‐based argument, an inductive contradiction argument is employed in the proof of stability, which is not common in literature.

Decentralized Control of Multiple Strict-Feedback Systems With Unknown Control Directions

“…Secondly, it is essentially an extension of the known control direction case. A stabilizer for a single system is firstly proposed in our previous work [41] in this way. To the best of our knowledge, it is the first time that this method is applied in a multi-agent system.…”