Dual-mode control of a time-varying boiler model with parameter and state estimation

A time-varying mathematical model of an oil-fired boiler unit, with estimated parameters, is used to represent a poorly defined multivariable physical process subjected to input disturbances and measurement noise. The model is simulated in discrete form and is used to generate on-line control action related to a quadratic performance criterion. A parameter-estimation technique is included in the overall control logic, based on a time-domain sensitivity analysis of the system-transition and -driving matrixes, and is used for continuously updating the model to the process system which is subjected to continuous change and random input disturbances. A form of predictive on¿off and bounded linear control is included within the control programme to give suboptimal performance based on minimisation of a two-period and current-performance index, respectively. Relatively close model following and/or improved control can be obtained with inputs based on the model reference system, and some slight improvement in performance is possible using dual-mode control action.