“…For instance, the problem of H ∞ filtering has been addressed for linear systems [9], linear systems with uncertain parameters [18], [22], delay systems [13], [23], and stochastic systems [16], [33]. It is noted that although H ∞ filtering offers robustness that is significantly better than Kalman filtering [1], [19] (also called H 2 filtering), H ∞ filtering is so conservative that it often leads to a large intolerable estimation error variance when the system is driven by white noise signals.…”