Multivariable control design in the frequency domain for an industrial electrical tubular oven

A major difficulty in the design of controllers for multivariable linear systems is the cross-coupling between inputs and outputs which obscures the effects of a specific loop controller on the system behavior. In the case of thermodynamic processes, the control problem is still more complex due to the time delay involved in the process itself. This paper considers the application of frequency domain techniques to the design of multivariable feedback controllers for a nonlinear, six-heating-zones electrical oven system. Multivariable frequency domain techniques are used to analyze the system, to improve the system decoupling and to validate a single-input single-output (SISO) linear design approach. Classical SISO techniques are applied to design a controller. Feasible temperatures profiles and their effects on the controller design are discussed. Simulation results are presented. Finally, a general procedure for control design is suggested.