An Integrated Fault Detection and Isolation and Safe-Parking Framework for Networked Process Systems

This work considers the problem of fault detection and isolation (FDI) and fault-handling for networked process systems subject to actuator faults. Multiple units are interconnected in the context of a networked plant. It is assumed that the failed actuator reverts to its fail-safe position and precludes the possibility of nominal operation in the affected unit. First, a robust FDI design is presented, where relations between the prescribed inputs and state measurements in the absence of faults are constructed with the consideration of uncertainty by using the process model. A fault is detected and isolated when the corresponding relation is violated. Then, an algorithm is developed to generalize the safe-parking approach (maintaining the process at an appropriate temporary operating point, which is called a safe-park point, during fault rectification) for fault-tolerant control to account for complex interconnections such as parallel and recycle streams in networked process systems. In particular, it can determine the units that need to be safe-parked during fault rectification and generate possible safe-park points for these units. The efficacy of the integrated FDI and safe-parking framework is demonstrated on a chemical process example comprising three reactors and a separator.