Automatica, Vol.44, No.3, 738-744, 2008
Explicit construction of H-infinity control law for a class of nonminimum phase nonlinear systems
This paper addresses a nonlinear H-infinity control problem for a class of nonminimum phase nonlinear systems. The given system is first transformed into a special coordinate basis, in which the system zero dynamics is divided into a stable part and an unstable part. A sufficient solvability condition is then established for solving the nonlinear H-infinity control problem. Moreover, based on the sufficient solvability condition, an upper bound of the best achievable L-2 gain from the system disturbance to the system controlled output is estimated for the nonlinear H-infinity control problem. The proofs of our results yield explicit algorithms for constructing required control laws for solving the nonlinear H-infinity control problem. In particular, the solution to the nonlinear H-infinity control problem does not require solving any Hamilton-Jacobi equations. Finally, the obtained results are utilized to solve a benchmark problem on a rotational/translational actuator (RTAC) system. (C) 2007 Elsevier Ltd. All rights reserved.