Control of a Polyethylene Reactor: Handling Sensor Faults

This work considers the problem of control of a gas phase polyethylene reactor subject to intermittent data losses. A fault-tolerant controller is designed that utilizes reconfiguration (switching to an alternate control configuration) in a way that accounts for the process nonlinearity, the presence of constraints and the occurrence of sensor faults. To this end, control configurations are first identified that can be utilized as backup configurations in the event that the primary control configuration is unable to stabilize the system (due to sensor faults). The stability properties of the control configurations, specifically, the set of initial conditions as well as the maximum allowable data loss rate that preserves stability, are explicitly characterized using Lyapunov-based tools. This characterization is utilized in identifying the occurrence of a destabilizing sensor fault in the polyethylene reactor and in preserving closed-loop stability via reconfiguration.