Welcome to the pyvib documentation¶
Pyvib is a python program for analyzing nonlinear vibrations and estimating(and simulating) models from measured data.
The highlights are
- Analyzing (working on data):
Restoring force surface (RFS) to visualize the functional form of the nonlinearties.
Wavelet transform gives a frequency and time resolution plots from where the type of nonlinearity can be deducted.
Quantification of noise and nonlinear distortion using the best linear approximation (BLA).
- Modeling (working on data):
White box, using subspace identification and specified polynomials and splines to model the identified nonlinearities, known as frequency nonlinear system identification (FNSI).
Black box, using polynomial nonlinear state-space (PNLSS).
- Understanding (working on identified FE model):
Harmonic balance continuation to reveal bifurcations and jumps
Nonlinear normal modes to reveal internal resonances and energy transfer between modes [1].
See the references for description of the methods and the credits.
Usage¶
The User Guide provides a detailed description of the pnlss example, to show how pyvib works. See the examples directory for additional examples.
The Modules documentation provides API-level documentation. Contributing shows how to contribute to the program or report bugs.
Credits¶
The PNLSS functionality is a translation of a matlab program written by the staff at Vrije Universiteit Brussel (VUB) . The documentation is written by Koen Tiels and he have also written a short primer on pnlss
The FNSI method is developed by Jean-Philippe Noël. He also kindly provided a matlab implementation of the spline method during my thesis.
References¶
PNLSS: Identification of nonlinear systems using polynomial nonlinear state space models. PhD thesis. article
FNSI: Frequency-domain subspace identification for nonlinear mechanical systems. PhD thesis Not longer available online. I will ask if it can be uploaded. article
RFS and wavelet transform are described in the PhD thesis of J.P. Noël.
HBC: The harmonic balance method for bifurcation analysis of large-scale nonlinear mechanical systems. PhD thesis Not longer available online. article
NNM: Nonlinear normal modes, Part II: Toward a practical computation using numerical continuation techniques PhD thesis by Maxime Peeters no longer available. article
You can also read my master thesis which describe the methods and provides additional references.
The project is on GitHub and you are welcome to modify, comment or suggest changes to the code.
Written by Paw, PhD student at the University of Liege.