Multivariable control of a distillation column by exact input-output linearization

Exact input-output linearization, which is one method of nonlinear control, was applied to multivariable control of a distillation column. First, a four-input four-output system was transformed to four SISO systems by input-output linearization based on a simplified model of the distillation column. For this purpose, an appropriate set of outputs must he selected. Second, a control sq-stem was designed for the linearized lour SISO systems, considering the influence of model mismatch, Finally, the performances of the control system mere evaluated with simulation of a methanol-water distillation column. The simulation model was much more rigorous than the simplified one used for controller design. From the various viewpoints, such as the speed of response, recovery of the materials, and energy efficiency, the control system by input-output linearization showed better performance than the conventional multiloop control system. These characteristics were clearly noticed under large scaled disturbances.