Secure State Estimation Based on Unknown Input Filtering

This paper presents an attack-free time-distributed UIF approach to solve the secure state estimation (SSE) problem under malicious attacks. In this new approach, the malicious attacks are modeled as unknown inputs. This research investigates the SSE problem as the attack-resilient state estimation problem with sparse actuator and sensor attacks, and with both process and output noises. A sparse solution of the unknown inputs is sought to recast the SSE problem to a standard UIF problem. The existence and stability conditions of the optimal sparse solution are also provided to facilitate the design. An application of this new method to solve the chaotic synchronization problem is also addressed. Simulation results verify the usefulness of the proposed method.