Role of Kalman filter in nonlinear dynamics
Kalman filters are useful if one is dealing with noisy systems, when one either has no knowledge about the source of the noise or the noise is created by a high-dimensional nonlinear system with many positive Lyapunov exponents.

Chaos synchronization is dealing with small low-dimensional systems which usually posses only one or two positive Lyapunov exponents. Applying a Kalman filter does not make much sense, since many better suited methods exist to deal with such systems, as one knows, that the system is not a stochastic one.