Control of Chemical Processes via Output Feedback Controller Networks

Many modern chemical plants are complex systems consisting of a large number of process units. The interactions between these units often intensify the complexity of large scale plantwide systems and cause significant difficulties in plantwide process control. This paper aims to address these issues by developing a networked control approach. The plantwide process is modeled as a network of process units connected via mass and energy flow. A network of output feedback distributed controllers are then designed to control the process network. Using the concept of dissipativity, plantwide stability and global performance requirement are translated into dissipativity conditions for which each output feedback control system has to satisfy. This allows controllers to be designed and implemented independently. In this framework, the plantwide connective stability is established to ensure the stability of the plant even when communications between controllers break down. This leads to improved reliability and fault tolerance. The effectiveness of the proposed linear control approach is demonstrated in a case study of a process network that consists of a reactor and two multistage distillation columns.