Control structure selection for optimal disturbance rejection

Control structure selection is an important part of control system design which has a strong influence on the resulting plant performance. This paper presents a systematic procedure for choosing control structure by extending previous work based on steady-state optimization to include the dynamic performance in a consistent manner. To address the problem that the dynamic performance depends on the type and the parameterization of the controllers used when comparing control structures, NMPC controllers are assumed. For each structure, the performance weights of these controllers are optimized with respect to the economic performance to yield an optimal tuning. This gives the best performance that is attainable for each structure and the structures are compared on equal grounds. The approach is demonstrated for a distillation control problem.