Event-triggered interval estimation method for cyber-physical systems with unknown inputs.

The issue of secure estimation for cyber-physical systems subject to unknown inputs and stealthy deception attacks is addressed in this paper. First, the unknown inputs are treated as augmented state and on the basis of that, the original plant is transformed into a singular system, which is decoupled with the unknown inputs. Then, for the purpose of reducing communication burden and avoiding congestion in the network, the event-triggered mechanism is introduced. Two approaches are presented to accomplish state estimation. The former one is known as the monotone system method. In the latter method, an input-to-state stable robust observer is constructed and by using the set-membership method, approximated estimation error is obtained. Finally, the effectiveness of the proposed method is verified by two illustrative examples.