Secure PID Control For Cyber‐Physical Systems Against Joint Deception Attacks: An Unknown Input Observer Approach

ABSTRACT This article investigates secure proportional‐integral‐derivative (PID) control for cyber‐physical systems (CPSs) subject to joint deception attacks that randomly occur in both sensor‐observer (SO) and controller‐actuator (CA) channels. First, the attack model is established by two steps. The deception attack randomly occurring in the CA channel is treated as an additional unknown input (UI) and merged with the original UI to form a multiple UI. An output transformation technique is then applied to derive a new system output that can completely eliminate the deception attack in the SO channel. Next, an algebraic equation is developed to connect the system state with the multiple UI by using an interval observer. On this basis, an unknown input observer (UIO) is constructed to provide asymptotic estimates of both the system state and multiple UI. Subsequently, by employing the orthogonal decomposition approach, a compensation PID controller is developed, which can ensure the stability in the mean‐square sense of the considered CPS by defending against deception attacks in both channels. Finally, a practical quadruple‐tank system is used to demonstrate the effectiveness of the proposed approach.