19 October, 2006

Control Mechanisms

Control Mechanisms define how a control works and its function within the Controls Hierarchy.

Detective - Detective controls identify when a defined action or series of actions take place.
• Only provide control functionality if combined with active control
• Typically feeds data to and active control at a different layer of the controls hierarchy
– Sense
– Notify
– Log
Active - Active controls directly modify system behavior
• Without Detective they have no feedback mechanism they just make things change blindly
• Typically guided by detective at a different level of the controls hierarchy
– Adjusts system
– Starts actions
– Stops actions
Reactive/Responsive - Reactive or Responsive controls modify the system based on identification of defined actions or series of actions
• Comprised of two parts - the detective portion and the action (active) portion
• Differentiated from detective and active controls in that both functions occur at the same level of the controls hierarchy
– Sense and Adjust
– Sense and Stop
Inherent - Inherent controls rely on fundamental principles of the system to prevent undesired action
• A control that is inherent at one level may not be at another
– It Just can’t happen (within certain assumptions)
– Settings
– Temperature Coefficient of Reactivity in a Nuclear core

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