Robust control of observer-based sampled-data systems: Digital redesign approach

This study proposes the digital redesign (DR) method for an observer-based output-feedback control in the presence of parametric uncertainties. The term DR is to convert an existing analogue control into an equivalent digital one in the sense of state-matching. The DR problem can be reduced to find the digital gains minimising the norm distance between the closed-loop states of the analogue and digital control. The main feature of the proposed DR is that the state estimation error in the plant dynamics is considered for the state-matching condition. Also, by handling the parametric uncertainties in the concerned system, the robust stability is well guaranteed in the proposed DR procedure. Its constructive conditions are expressed as the linear matrix inequalities A numerical example has been demonstrated to visualise the feasibility of the proposed methodology.