On the control of an uncertain water quality system

We consider a one-reach water quality system subject not only to bounded uncertain disturbances at the input and output levels but also to bounded uncertain variations of the rate coefficients. When the bounds of the time-varying uncertainties are known, two classes of robust controllers, based on the measured state, are proposed to assure some desired performance, including uniform boundedness and uniform ultimate boundedness. If only output rather than full state is available for the control, a class of estimated state-based control is proposed for the desired performance. When the bounds of the uncertainties are not known, we propose a class of controllers which, using the functional properties of the uncertainties, guarantees some desired system properties, one of which is the convergence to zero of all system responses.