An enhanced observer for nonlinear systems with time-varying measurement delays

In this paper we propose an observer for a classof Lipschitz nonlinear systems affected by time-varying andknown measurement delays which is an improvement of theone presented in [9]. Under the assumption that the delayfunction is piece-wise continuous and differentiable we prove thatexponential convergence to zero of the observation error can beachieved with any desired decay rate, by suitably tuning a gainvector. The delay bound achieved with the observer proposed hereis less conservative than the one obtained in [9], as confirmedby numerical tests. For the sake of brevity, in this paper onlyone-step observers are considered. However, a cascade observercan be arranged to cope with arbitrarily long delays.