construction of lyapunov functions with linear optimization
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Construction of Lyapunov functions with linear optimization. Sigurður F. Hafstein, Reykjavík University. What can we do to get information about the solution ?. Analytical solution ( almost never possible )

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construction of lyapunov functions with linear optimization
Construction of Lyapunov functionswith linear optimization

Sigurður F. Hafstein, Reykjavík University

slide2

Whatcanwedoto get informationaboutthesolution?

  • Analyticalsolution (almostneverpossible)
  • Numericalsolution (not applicable for thegeneralsolution, badapproximation for largetimes for specialsolutions)
  • Search for trapsinthephase-space ( trap = forwardinvariant set)
dynamical systems

Let be the solution to the idealized closed physical system

Dynamical systems

Then, by conservation of energy, we have

or equivalently

dynamical systems1

Let be the solution to the non-idealized closed physical system

Dynamical systems

Then, by dissipation of energy, we have

or equivalently

slide5

Energy vs. Lyapunov-functions

Real physical systems end up in a state where the energy of the system is at a local minimum.

Such a state is called a stable equilibrium

If we have a differential equation that does not possess an energy, can we do something similar?

Answer by Lyapunov 1892: if similar to energy Kurzweil/Massera 1950‘s: such an energy exists

YES !

slide6

Example:

where

Partition of the domain of V:

slide7

Example:

where

Grid :

slide8

Example:

where

Values for , that fulfill the constraints

slide9

Example:

where

Convex interpolation delivers a Lyapunov-function

slide10

Example:

where

Region of attraction:

arbitrary switched systems
Arbitrary switched systems

right-continuous and the discontinuity

points form a discrete set

common Lyapunov function

asymptotically stable under arbitrary switching

slide17

Variable structure system (sliding modes)

Weallowthesystemtoswitch

arbitiarybetweenthedynamicson a thinstripoverlappingtheboundaries

slide18

Variable structure system (sliding modes)

Weallowthesystemtoswitch

arbitiarybetweenthedynamicson a thinstripoverlappingtheboundaries

slide19

Triangle-Fan Lyapunov function

(with Peter Giesl Uni Sussex)

slide20

Extension of the region of attraction

alsowith

Peter

Wemakeadditionallinearconstraintsthatsecure

Thentheregion of attractionsecuredbythe

Lyapunovfunctionmustcontainthegreen box

slide21

Extension of the region of attraction

withoutoptimization

withoptimization

slide23

Differential inclusions and Filippov solutions

(with L. Grüne and R. Baier Uni Bayreuth)

is convex and compact

is a Filippov solution iff

a.e.

and

one allows evil right-hand sides, but demands

high regularity of the solutions

slide24

Differential inclusions and Filippov solutions

is convex and compact

for

where

is upper semicontinuous

slide25

Differential inclusions and Filippov solutions

Clarke, Ledyaev, Stern 1998

is strongly (everysolution) asymptoticallystable

possesses a smooth

Lyapunov function

The algorithm can generate a Lyapunov function for the differential inclusion, if one exists. One just has to demand LC4 for faces of the simplices if necessary

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