Simultaneous adaptive decoupling and model matching control of a fluidized bed combustor for sewage sludge

The major difficulties in designing a controller for the fluidized bed combustor for sewage sludge result from the following reasons: 1) The dynamical behavior of the plant is highly unknown and the experimental data only render a coarse model; 2) the combustion process shows large time-delay; and 3) the plant model is a stiff differential equation because the parameter values among the subsystems differ severely. To circumvent these difficulties, this paper proposes to describe each channel of the multiple-input-multiple-output system by a first-order transfer function with variable coefficients and a fixed time delay. A model reference adaptive control scheme, which can simultaneously achieve adaptive decoupling and model matching, is proposed. The resulting adaptive control law guarantees closed-loop stability. The newly obtained controller has a structure that is similar to the well-known Smith predictor. This explains why the present scheme can cope with the time delay effects on the system performance. Due to its adaptation abilities, it can lower the limitations of the Smith scheme to accurate plant descriptions. The application study demonstrates that the proposed design can reach the desired performance requirements.