System identification of structural engineering systems
Project description
Python package for system identification of structural dynamic systems.
The identification methods are applicable to general linear systems, and the implementation may also be used in other domains.
Installation
Either download the repository to your computer and install, e.g. by pip
pip install .
or install directly from github.
pip install git+https://github.com/gunnstein/strid.git
Usage
The package provides funtionality to identify structural systems through subspace identification methodology. Utility functionality associated with characterizing modal properties and behaviour is also included.
The code example below shows how the modes of a combined deterministic-stochastic system can be obtained from measurements of the input u and the output y.
# ..
# Assume that the measured input u and output y and sampling rate is available
#
# First, import the strid module
import strid
# Then instanciate the appropriate subspace identification (SID) object
csid = strid.CombinedDeterministicStochasticSID(u, y, fs)
# If we know the model order we can now perform the SID and obtain the
# state space system matrices. For instance, we can 20 block rows and
# a model order of 100 as shown below
A, B, C, D = csid.perform(100, 20, estimate_B_and_D=True)
# Most often, we do not know the model order, and instead we overestimate
# model order and pick the physical modes with the help of a stabilization
# diagram. Strid also includes a stabilization diagram and functionality to
# pick modes directly from the plot.
# First, we must estimate modes for a range of different model orders
modes = dict()
for order in range(5, 150, 5):
A, C = csid.perform(order, 20)
modes[order] = strid.Mode.find_modes_from_ss(A, C, csid.fs)
# Then we can create and plot a stabilization diagram (see image below)
stabdiag = strid.StabilizationDiagram()
stabdiag.plot(modes)
# And we can use the mouse to pick the stable poles from
# the diagram and then access the picked modes with the
# `picked_modes` property of the StabilizationDiagram instance.
picked_modes = stabdiag.picked_modes
Additional examples are found in the examples folder.
Support
Please open an issue for support.
Contributing
Please contribute using Github Flow. Create a branch, add commits, and open a pull request.
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