Managing Performance Degradation in Fault Tolerant Control Systems

A fault tolerant control system design technique has been proposed and analyzed for managing performance degradation in the presence of multiple faults in actuators. The method is based on a control structure with model reference reconfigurable control design in an inner loop and command input adjustment in an outer loop. The reduced dynamic performance requirements in the presence of different actuator faults are accounted for through different performance reduced (degraded) reference models. The degraded steady-state performance are governed by the reduced levels of command inputs. The reconfigurable controller is designed on-line and automatically in an explicit model reference control framework so that the dynamics of the closed-loop system follows that of the performance reduced reference model under each fault condition. The reduced command input level is determined to prevent potential actuator saturation. The proposed method has been evaluated and analyzied using an aircraft example against actuator faults subject to constraints on the magnitude and slew-rate of actuators. Copyright c °2005 IFAC