LQ Secure Control for Cyber-Physical Systems Against Sparse Sensor and Actuator Attacks

This paper investigates the problem of secure control for cyber-physical systems (CPSs) under sensor and actuator attacks. The attacks are assumed to be sparse but arbitrary. The strong detectability under the sparse attacks is characterized by computing the rank of the so-called structural matrix pencil. An adaptive hybrid control strategy is proposed by automatically excluding the tampered measurement and input data. First, a hybrid system consisting of all possible combinations of models is implemented. Then, combining classical linear quadratic control theory, an adaptive switching logic is designed to online locate the proper system mode by observing the optimal performance index. As a result, the closed-loop system is ensured to be asymptotically stable in the presence of the attacks, while the performance loss can be mitigated. Also, the performance degradation under attacks is also analyzed quantificationally based on the quadratic cost function. Simulation results on an aircraft system are given to substantiate the proposed method.