State Convergence of Passive Nonlinear Systems With an $L^{2}$ Input

We show that the state of a strictly output passive system with an L(2) input converges to zero. The result is applied to the disturbance rejection problem (with reference signal zero), where the disturbance can be decomposed into a finite superposition of sine waves of arbitrary but known frequencies and an L(2) signal. Using an LTI controller, constructed based on the internal model principle, the state trajectories of the plant (and hence also the error signal) converge to zero.