Interval functional observers design for time-delay systems under stealthy attacks

This study considers stealthy attacks in the design of interval functional observers for time-delay systems. We are interested in the case where a malicious agent compromises the sensors of the systems. We first design reduced-order observers to estimate bounds of the attack signals. Then by using the information on the bounds of the attack signals, we design novel interval functional observers for the systems. We derive conditions for the existence of the interval observers and formulate them in terms of linear programmings which are very efficient computational techniques. Two illustrative examples with extensive simulations are given to show correctness and effectiveness of the proposed method.