Stability analysis of networked control systems with unknown inputs

Unknown Input Observers (UIO) use the known plant´s inputs and outputs to generate state estimates for plants with unknown inputs. In many cases, the UIO´s inputs are transmitted through a communication network, which is a key component in modern Networked Control Systems (NCS). Most of the developed UIOs in the literature are designed for non-networked systems. In this paper, the objective is to study the effect of unknown inputs and network perturbations on state observation and stability using UIOs. Given an UIO design for any non-networked system, we derive the dynamics of the UIO-based NCS, also referred to as Networked Unknown Input Observer (N_etUIO). The stability of the N_etUIO is analyzed by deriving a stability-guaranteeing bound on the networked-induced perturbation. Numerical simulations are provided to highlight the applicability of the obtained bounds.