Simultaneous control of safety constraint sets and process economics using economic model predictive control

Maintaining safe operation of chemical processes is of paramount importance in process systems and control engineering, and is ideally achieved while maximizing profit. It has long been argued that process safety is fundamentally a process control problem, yet few research efforts have attempted to integrate process safety and control. Economic model predictive control (EMPC) has attracted significant attention recently due to its ability to optimize process operation from an economic perspective. However, there is very limited work on the problem of integrating safety considerations with EMPC. Motivated by the above considerations, this work presents an EMPC methodology that adjusts in real-time the size of the safety sets in which the process state should reside in order to ensure safe process operation and feedback control of the process state while optimizing economics via time-varying process operation. Recursive feasibility and closed-loop stability are established for a sufficiently small EMPC sampling period. The proposed method is demonstrated with a chemical process example.