Monitoring and handling of actuator faults in two-tier control systems for nonlinear processes

• Published in: Chemical engineering science Vol. 65; no. 10; pp. 3179 - 3190
• Main Authors: Liu, Jinfeng, Ohran, Benjamin J., Muñoz de la Peña, David, Christofides, Panagiotis D., Davis, James F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.05.2010; Elsevier
• Subjects: Actuation; Actuators; Applied sciences; Asynchronous measurements; Chemical engineering; Control systems; Exact sciences and technology; Fault detection and isolation; Fault tolerance; Fault-tolerant control; Faults; Mathematical analysis; Mathematical models; Nonlinear processes; Nonlinearity; Reactors; Safety; Two-tier control systems; Two-tier control systems; Fault detection and isolation; Asynchronous measurements; Nonlinear processes; Fault-tolerant control; Closed loop; Stability; Control system; Continuous stirred tank reactor; Non linear system; Design; Surveillance; Mathematical analysis; Failure detection; Continuous measurement; Separator; Actuator; Handling
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2010.02.001

This work focuses on the monitoring and reconfiguration of two-tier control systems applied to general nonlinear processes in the presence of control actuator faults. Specifically, a general class of nonlinear process systems is first considered and is controlled by a two-tier control system integrating a local control system using continuous sensing/actuation with a networked control system using asynchronous sensing/actuation. To deal with control actuator faults that may occur in the closed-loop system and eliminate the ability of the two-tier control system to stabilize the process, a fault detection and isolation (FDI) and fault-tolerant control (FTC) system is designed which detects and isolates actuator faults and determines how to reconfigure the two-tier control system to handle the actuator faults and ensure closed-loop stability. The FDI/FTC system uses continuous measurements of process variables like temperature and asynchronous measurements of variables like species concentrations. We develop reconfiguration-based FTC schemes that effectively deal with faults in the actuators of both the local and networked control systems. A detailed mathematical analysis is carried out to determine precise conditions for the stabilizability of the FDI/FTC system. The method is demonstrated using a reactor-separator process consisting of two continuously stirred tank reactors and a flash tank separator with recycle stream.