Control reconfiguration is an active approach in control theory to achieve fault-tolerant control for dynamic systems. It is used when severe faults, such as actuator or sensor outages, cause a break-up of the control loop, which must be restructured to prevent failure at the system level. In addition to loop restructuring, the controller parameters must be adjusted to accommodate changed plant dynamics. Control reconfiguration is a building block toward increasing the dependability of systems under feedback control.

The figure to the right shows a plant controlled by a controller in a standard control loop.

The nominal linear model of the plant is

${\displaystyle {\begin{cases}{\dot {\mathbf {x} }}&=\mathbf {A} \mathbf {x} +\mathbf {B} \mathbf {u} \\\mathbf {y} &=\mathbf {C} \mathbf {x} \end{cases}}}$

The plant subject to a fault (indicated by a red arrow in the figure) is modelled in general by

${\displaystyle {\begin{cases}{\dot {\mathbf {x} }}_{f}&=\mathbf {A} _{f}\mathbf {x} _{f}+\mathbf {B} _{f}\mathbf {u} \\\mathbf {y} _{f}&=\mathbf {C} _{f}\mathbf {x} _{f}\end{cases}}}$

where the subscript ${\displaystyle f}$ indicates that the system is faulty. This approach models multiplicative faults by modified system matrices. Specifically, actuator faults are represented by the new input matrix ${\displaystyle \mathbf {B} _{f}}$, sensor faults are represented by the output map ${\displaystyle \mathbf {C} _{f}}$, and internal plant faults are represented by the system matrix ${\displaystyle \mathbf {A} _{f}}$.

The upper part of the figure shows a supervisory loop consisting of fault detection and isolation (FDI) and reconfiguration which changes the loop by