Controllability of SVD control structures for ill-conditioned plants

A conventional diagonal controller can be designed from very limited process information. In the SVD control structure, a diagonal controller is applied to orthogonal sums and differences of the inputs and outputs. In this work, the process knowledge needed for the design of an SVD controller is analyzed. In contrast to conventional decentralized controllers, the SVD controller can compensate for the process directionality of ill-conditioned processes. The dual composition control problem of distillation columns is of particular interest, since reliable models for these columns are quite hard to obtain.