Guaranteed Stable Projection-Based Model Reduction for Indefinite and Unstable Linear Systems Brad Bond Luca Daniel MIT Speaker: Tuck, Fang Gong
Overview MotivationMotivation BackgroundBackground Extraction and Stability Stable Model Reduction Stabilizing ProjectionsStabilizing Projections Problem Formulation Stability Constraints Existence of Stabilizing Projections Computation of Stabilizing Projections ExamplesExamples ConclusionConclusion
Motivation Passive physical systems, described by Partial Derivatives Equations (PDEs) Field-solver PDEs Discretization Linear system -1,000,000 equations -Potentially unstable & unstructured Reduced order model -Stable Ideally
Overview MotivationMotivation BackgroundBackground Extraction and Stability Stable Model Reduction Stabilizing ProjectionsStabilizing Projections Problem Formulation Stability Constraints Existence of Stabilizing Projections Computation of Stabilizing Projections ExamplesExamples ConclusionConclusion
Background BUT we have little control over this stepBUT we have little control over this step Linear may be unstable / unstructuredLinear may be unstable / unstructured Field-solver PDEs Discretization Linear system Passive physical systems (describe by PDEs)
Stability L(x) : Lyapunov functionL(x) : Lyapunov function Characterize stability of linear systemCharacterize stability of linear system Stability constraints for a linear systemStability constraints for a linear system * M. Vidyagasar. Nonlinear Systems Analysis. Prentice Hall, New York,1978. S. Sastry. Nonlinear Systems: Analysis, Stability, and Control. Springer, New York, Lyapunov Function: P is a symmetric positive definite matrix
Stable Model Reduction Congruence transform (Galerkin Projection), PRIMACongruence transform (Galerkin Projection), PRIMA Construct V for accuracyConstruct V for accuracy However …However …
Stable model reduction Stabilizing Projections
Intro : Stabilizing Projections
Overview MotivationMotivation BackgroundBackground Extraction and Stability Stable Model Reduction Stabilizing ProjectionsStabilizing Projections Problem Formulation Stability Constraints Existence of Stabilizing Projections Computation of Stabilizing Projections ExamplesExamples ConclusionConclusion
Problem Formulation I
Problem Formulation II
Stabilizing Projections: Stability Constraints
Difficult to solve: Quadratic in U
Stabilizing Projections: Linear Constraints
Existence of Solutions
Existence of Solutions: Unstable Systems E > 0 A+A T < 0 Space of stabilizing U
Stabilizing Projections: Existence Summary
Computing Solutions: Efficient Solutions
Efficient Optimal Solutions
Stabilizing Projections Summary
Overview MotivationMotivation BackgroundBackground Extraction and Stability Stable Model Reduction Stabilizing ProjectionsStabilizing Projections Problem Formulation Stability Constraints Existence of Stabilizing Projections Computation of Stabilizing Projections ExamplesExamples ConclusionConclusion
Example: Interconnect
Example: Inductor
Example: Power Grid
Example: MEMS Linearization
Comparison to other Methods
Conclusion