Robust static output feedback control of a mixing unit

The paper deals with an application of the robust static output feedback control (RSOFC) to a mixing device, where sodium chloride (NaCl) water solution and water are mixed and the solution with required concentration of NaCl is prepared. The mixing unit is modelled as an uncertain polytopic system. Sufficient conditions for stabilization of an uncertain system via static output feedback are given at first and the problem of RSOF controller design is converted to the solution of linear matrix inequalities (LMIs). A simple non-iterative algorithm is used for calculating of LMIs and obtaining robust P, PI or PID controllers. The design procedure guarantees with sufficient conditions the robust quadratic stability and the guaranteed cost. Possibility to use robust static output feedback for control of real processes is demonstrated with results obtained by application of designed robust PI and PID controllers for control of a laboratory mixing device.