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l6_ocsp_conf_ast

l6_ocsp_conf_ast - Optimal CSPs and Conflict-directed A...

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2/22/2005 copyright Brian Williams, 2002 1 courtesy of JPL Optimal CSPs and Conflict-directed A* Brian C. Williams 16.412J/6.834J February 22 nd , 2005 Brian C. Williams, copyright 2000
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2/22/2005 copyright Brian Williams, 2002 2 System Model Control Program RMPL Model-based Program Deductive Commands Observations Plant Titan Model-based Executive State goals State estimates Tracks likely plant states Tracks least cost goal states z Executes concurrently z Preempts z Queries (hidden) states z Asserts (hidden) state Closed Closed Valve Valve Open Open Stuck open Stuck Stuck closed closed Open Open Close Close 0. 01 0. 01 0.01 0.01 inflow = outflow = 0 Generates target goal states conditioned on state estimates Mode Reconfiguration: Select a least cost set of commandable component modes that entail the current goal, and are consistent Mode Estimation: Select a most likely set of component modes that are consistent with the model and observations arg min P t (Y| Obs) s.t. Ψ (X,Y) O(m’) is consistent arg max R t (Y) s.t. Ψ (X,Y) entails G(X,Y) s.t. Ψ (X,Y) is consistent
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2/22/2005 copyright Brian Williams, 2002 3 Outline Optimal CSPs Application to Model-based Execution Review of A* Conflict-directed A* Generating the Best Kernel Intelligent Tree Expansion Extending to Multiple Solutions Performance Comparison
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2/22/2005 copyright Brian Williams, 2002 4 Constraint Satisfaction Problem CSP = <X, D X ,C> variables X with domain D X Constraint C(X): D X {True,False} Find X in D X s.t. C(X) is True R , G, B G R , G Different-color constraint V 1 V 2 V 3
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2/22/2005 copyright Brian Williams, 2002 5 Optimal CSP OCSP= <Y, g , CSP> Decision variables Y with domain D Y Utility function g(Y): D Y → ℜ CSP is over variables <X,Y> Find Leading arg max g (Y) Y D y s.t. X D X s.t. C(X,Y) is True Î Frequently we encode C in propositional state logic Î g() is a multi-attribute utility function that is preferentially independent .
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2/22/2005 copyright Brian Williams, 2002 6 CSP Frequently in Propositional Logic (mode(E1) = ok implies (thrust(E1) = on if and only if flow(V1) = on and flow(V2) = on)) and (mode(E1) = ok or mode(E1) = unknown) and not (mode(E1) = ok and mode(E1) = unknown) V1 V2 E1
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