| dc.description.abstract | In the event of actuator faults in systems, standard control algorithms might not
be sufficient for stabilizing the system and keeping the performance at an accept-
able level. Because of this, fault-tolerant control methods have been an active area
during the last decade, and several significant contributions to the reliability of
safety-critical systems have been made.
Model predictive control (MPC) has shown to be a powerful control scheme for
multi-variable control problems, and provide a natural framework for integrating
receding-horizon optimization, while also achieving system reconfiguration in the
event of faults. However, almost all the efforts on incorporating fault-tolerance in
MPC are focused on reactive fault-tolerance, which aim to handle a fault after it
has occurred. In contrast, proactive fault-tolerant control seeks to utilize an es-
timated, conservative time window between the warning of an incipient fault and
the time at which the faulty component is rendered useless to steer the state inside
a recoverable region before the fault occurs. As such, a proactive approach circum-
vents the issues of possible infeasibilities and destabilization often encountered in
reactive approaches, while allowing the system to continue operation during the
subsequent system repair.
Furthermore, economic MPC (EMPC) has received increasing attention in the re-
cent years. Rather than separating real-time optimization and control, an economic
MPC scheme merges dynamic economic operations with the feedback properties of
conventional MPC. However, there has not been paid much attention to including
fault-tolerance and economic optimization in a unified framework.
This thesis proposes a proactive EMPC algorithm for handling incipient faults,
that also takes economic profits in to account. The scheme utilizes an exact penalty
function to steer the system inside an invariant set ensuring stability during the
loss of actuation in the system. Additionally, the scheme is extended to be robust
in terms of handling unknown disturbances to the system, while still achieving the
desired fault-tolerance. Stability for the proposed scheme is proven, both for sys-
tems with and without disturbances. The merits and shortcomings of the proposed
scheme is demonstrated through several numerical examples | |
