Convergence of the state of a passive nonlinear plant with an L2 input

In this paper, we consider a strictly output passive nonlinear plant P with storage function H. We assume that P is zero-state detectable. Under some mild conditions on H, we show that the state x of the plant converges to zero for any L² input. This implies the solvability for all t ≥ 0 of the system equations, for every input in L_loc². We define a stability notion called L² system-stable, a variant to the L²-stability concept, which has a nice interconnection properties.