Process controllability analysis based on passivity condition

A new input-output controllability measure for chemical processes is presented in this paper. This controllability measure indicates the achievable dynamic performance of a process using its open-loop model. The controllability measure proposed in this paper is derived from the passivity condition. Passivity is an input/output property of processes. Passive processes are stable and minimum phase and thus very easy to control. Therefore, for a given process, its shortage of passivity, which reflects destabilizing effects of factors such as time delays and Right-Half-Plane (RHP) zeros, can be used to indicate its controllability. The best achievable sensitivity function of the controlled process is used as the new controllability measure, which can be used to rank process designs in term of their controllability. A case study of input/output selection of a distillation column is presented to illustrate the use of the proposed approach.