ELFT HÍRADÓ

[Tamas Insperger <inspi AT mm.bme.hu>]

MEGHÍVÓ 

a BME Tartószerkezetek Mechanikája Tanszék és

a BME Műszaki Mechanikai Tanszék

által közösen szervezett Mechanika szeminárium következő előadására 

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Prof. Walter Wedig 

Institut für Technische Mechanik
Universität Karlsruhe 


Nonlinear Car Dynamics under Stochastic Road Excitations  


2004. március 11. csütörtök, 12.30 óra

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Az előadás helye:

BME Műszaki Mechanikai Tanszék

MM épület, könyvtár



Abstract:


To quantify comfort and safety of nonlinear vehicles riding
on rough road surfaces, the paper proposes to introduce dimensionless
time and normalized coordinates derived by the stationary analysis of
linear road-vehicle systems. This leads to equations of motion in
dimensionless forms independent on the intensities of the base
excitations. In a second step, initial perturbations are introduced into
the road-vehicle systems in order to derive variational equations which
determine the asymptotic stability of the perturbed equations of motion.

The variational equations are transformed by means of polar
coordinates in order to determine the top Lyapunov exponent and
associated rotation number. According to Oseledec s [1] multiplicative
ergodic theorem, both characteristic numbers are independent on the
initially introduced perturbations. They are only dependent on
frequency parameters and damping measures of the road-vehicle system of 
interest.
For increasing nonlinearity parameters or varying linear frequencies or
damping measures, the top Lyapunov exponent can become positive, i.e.
the stationary system behaviour becomes unstable bifurcating into
nonstationary attractors.
In a third part, numerical solutions of associated
Fokker-Planck equations are investigated applying central differeneces
schemes. To avoid negative density values in the density tales, the
derived linear equations are solved by means of large-scale quadratic
optimization programming. The method is demonstrated by one- and
two-dimensional problems with known closed-form density distributions
and then extended to more general non-symmetrical problems of nonlinear
dynamical systems.




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