Robust Global Stabilisation of Stirred Tank Reactors by Saturated Output Feedback

Abstract

This paper is concerned with the robust stabilisation of a wide class of unstable processes operated in continuous stirred tank reactors, For non-isothermal reactors, the regulated output is the temperature. For isothermal reactors, the regulated output is the single concentration of either an initial reactant or a final product. In both cases the proposed control law is a dynamic output feedback which can be interpreted as a straightforward modification of a standard PI controller. In accordance with the engineering constraints, the control action is positive and saturated With this control law: it is shown that the output variable may be regulated at a prescribed set point despite a wide kinetic uncertainty. Furthermore, the controller achieves a global stabilisation of the process in its domain of physical existence. When the reactor is minimum phase, the closed loop has a single equilibrium which is globally asymptotically stable. When the reactor is non-minimum phase phase, a global practical output regulation with state boundedness is obtained with the same controller.