NONLINEAR CONTROLLERS FOR POSITIVE REAL SYSTEMS WITH ARBITRARY INPUT NONLINEARITIES

Input nonlinearities such as saturation can severely degrade closed-loop performance due to integrator windup and other effects. For positive real plants with positive real controllers, we propose a nonlinear controller modification that effectively counteracts the effects of arbitrary input nonlinearities. For this class of problems, we prove global asymptotic stability of the closed-loop system and demonstrate closed-loop performance by means of system simulation.