265 research outputs found
Numerical Construction of LISS Lyapunov Functions under a Small Gain Condition
In the stability analysis of large-scale interconnected systems it is
frequently desirable to be able to determine a decay point of the gain
operator, i.e., a point whose image under the monotone operator is strictly
smaller than the point itself. The set of such decay points plays a crucial
role in checking, in a semi-global fashion, the local input-to-state stability
of an interconnected system and in the numerical construction of a LISS
Lyapunov function. We provide a homotopy algorithm that computes a decay point
of a monotone op- erator. For this purpose we use a fixed point algorithm and
provide a function whose fixed points correspond to decay points of the
monotone operator. The advantage to an earlier algorithm is demonstrated.
Furthermore an example is given which shows how to analyze a given perturbed
interconnected system.Comment: 30 pages, 7 figures, 4 table
Existence of periodic solutions of the FitzHugh-Nagumo equations for an explicit range of the small parameter
The FitzHugh-Nagumo model describing propagation of nerve impulses in axon is
given by fast-slow reaction-diffusion equations, with dependence on a parameter
representing the ratio of time scales. It is well known that for all
sufficiently small the system possesses a periodic traveling wave.
With aid of computer-assisted rigorous computations, we prove the existence of
this periodic orbit in the traveling wave equation for an explicit range
. Our approach is based on a novel method of
combination of topological techniques of covering relations and isolating
segments, for which we provide a self-contained theory. We show that the range
of existence is wide enough, so the upper bound can be reached by standard
validated continuation procedures. In particular, for the range we perform a rigorous continuation based on
covering relations and not specifically tailored to the fast-slow setting.
Moreover, we confirm that for the classical interval
Newton-Moore method applied to a sequence of Poincar\'e maps already succeeds.
Techniques described in this paper can be adapted to other fast-slow systems of
similar structure
Continuation-Based Pull-In and Lift-Off Simulation Algorithms for Microelectromechanical Devices
The voltages at which microelectromechanical actuators and sensors become unstable, known as pull-in and lift-off voltages, are critical parameters in microelectromechanical systems (MEMS) design. The state-of-the-art MEMS simulators
compute these parameters by simply sweeping the voltage, leading to either excessively large computational cost or to convergence failure near the pull-in or lift-off points. This paper proposes to simulate the behavior at pull-in and lift-off employing
two continuation-based algorithms. The first algorithm appropriately adapts standard continuation methods, providing a complete set of static solutions. The second algorithm uses continuation to trace two kinds of curves and generates the sweep-up or sweep-down curves, which can provide more intuition for MEMS designers. The algorithms presented in this paper are robust and suitable for general-purpose industrial MEMS designs. Our algorithms have been implemented in a commercial MEMS/integrated circuits codesign tool, and their effectiveness is validated by comparisons against measurement data and the commercial finite-element/boundary-element (FEM/BEM) solver CoventorWare
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