Control reconfiguration: Difference between revisions

Revision as of 20:49, 11 February 2008

Revision as of 23:30, 30 April 2008

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[[Control]] reconfiguration is an active approach to achieve [[Fault-Tolerant Control|fault-tolerant control]] for [[Dynamic systems|dynamic systems]] {{Harv|Blanke|Kinnaert|Lunze|Staroswiecki|2006}}. It is used when severe [[Fault (technology)|faults]], such as actuator or sensor outages, cause a break-up of the [[Control loop|control loop]], which must be restructured to prevent [[Failure|failure]] at the system level. In addition to loop restructuring, the [[Controller (control theory)|controller]] parameters must be adjusted to accommodate changed plant dynamics. Control reconfiguration is a building block toward increasing the [[Dependability|dependability]] of systems under [[Feedback|feedback]] control {{Harv|Patton|1997}}.

== Reconfiguration Problem ==

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Usually a combination of goals is pursued in practice, such as the equilibrium recovery goal with stability.

The question whether or not these or similar goals can be reached for specific faults is addressed by [[Reconfigurability|reconfigurability]] analysis.

== Reconfiguration Approaches ==

=== Fault hiding ===

[[Image:FaultHiding with Goals.png|frame|Fault hiding principle. A reconfiguration block is placed between faulty plant and nominal controller. The reconfuigured plant behaviour must match the nominal behaviour. Furthermore, the reconfiguration goals are pointed out.]]

This paradigm aims at keeping the nominal controller in the loop. To this end, a reconfiguration block is placed between the faulty plant and the nominal controller. Together with the faulty plant, it forms the reconfigured plant. The reconfiguration block has to fulfill the requirement that the behaviour of the reconfigured plant matches the behaviour of the nominal, that is fault-free plant {{Harv|Steffen|2005}}.

=== Linear model following ===

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* [[Robust control]] techniques

== RelatedSee Topicsalso ==

Prior to control reconfiguration, it must be at least determined whether a fault has occurred ([[Fault Detection|fault detection]]) and if so, which components are affected ([[Fault Isolation|fault isolation]]). Preferably, a model of the faulty plant should be provided ([[Fault Identification|fault identification]]). These questions are addressed by [[Fault diagnosis|fault diagnosis]] methods.

[[Fault Accommodation|Fault accommodation]] is another common approach to achieve [[Fault Tolerance|fault tolerance]]. In contrast to control reconfiguration, accommodation is limited to internal controller changes. The sets of signals manipulated and measured by the controller are fixed, which means that the loop cannot be restructured {{Harv|Blanke|Kinnaert|Lunze|Staroswiecki|2006}}.