Approximations to nonlinear observers

In this paper a criterion of observability for systems with analytic nonlinearities is used to derive finite dimensional approximations to nonlinear observers for this class of system. The observers and a second order filter are applied to stochastic velocity control of an asymmetrical rotating body. A configuration is considered which allows the observers to appear as useful devices in handling problems caused by discrete data transmission on a too slow rate. The results are illustrated by a digital computer simulation.