Package Layout

This document will describe the layout of SDynPy to help users find the functions they are looking for.

SDynPy Subpackages

SDynPy is split up into several subpackages to help organize its content. While these subpackages are convenient to organize the content, they are not convenient to use, as typical function calls might require descending multiple package levels, resulting in inconveniently long code. Therefore, SDynPy heavily relies on aliases to commonly used functions and classes.

The following sections describe the major subpackages that exist in SDynPy.

SDynPy Core Objects

The sdynpy.core subpackage contains Python modules that define the core SDynPy objects and other core functionality. These are designed to represent common data used in structural dynamics, including degrees of freedom, geometry, data, or dynamic systems. Because of their ubiquitous nature, almost all of the modules, classes, and their corresponding helper functions are aliased to the top-level SDynPy namespace. The core modules are:

SDynPy Core Modules	Alias	Description
sdynpy.core.sdynpy_array	sdynpy.array	Definition of the parent SdynpyArray class.
sdynpy.core.sdynpy_colors	sdynpy.colors	Definition of the color map scheme used by | SDynPy.
sdynpy.core.sdynpy_coordinate	sdynpy.coordinate	Definition of the CoordinateArray class used to represent degrees of freedom.
sdynpy.core.sdynpy_data	sdynpy.data	Definition of the NDDataArray class and it’s subclasses. (TimeHistoryArray, SpectrumArray, etc.) used to represent data.
sdynpy.core.sdynpy_geometry	sdynpy.geometry	Definition of the Geometry class and its component classes (NodeArray, ElementArray, TracelineArray, CoordinateSystemArray) used to represent the locations and orientations of measurements.
sdynpy.core.sdynpy_matrix	sdynpy.matrix_mod	Definition of the Matrix class used to map degrees of freedom to rows and columns of a matrix.
sdynpy.core.sdynpy_shape	sdynpy.shape	Definition of the parent ShapeArray class used to represent mode or deflection shapes.
sdynpy.core.sdynpy_system	sdynpy.system	Definition of the parent System class used to represent dynamic systems (mass, stiffness, and damping).

In addition to the modules being aliased to the SDynPy namespace, many of the classes and functions from the core subpackage are also aliased to the top-level namespace, as these are the most often called functions and classes in SDynPy.

SDynPy Array Class	Alias	Description
sdynpy.core.sdynpy_array.SdynpyArray	sdynpy.SdynpyArray	Parent class of all SDynPy Arrays.

Coordinate Classes and Functions	Alias	Description
sdynpy.core.sdynpy_coordinate.CoordinateArray	sdynpy.CoordinateArray	Class to represent degrees of freedom.
sdynpy.core.sdynpy_coordinate.coordinate_array	sdynpy.coordinate_array	Helper function to create CoordinateArray objects.

Data Classes and Functions	Alias	Description
sdynpy.core.sdynpy_data.NDDataArray	sdynpy.NDDataArray	Parent class of all SDynPy Data Arrays.
sdynpy.core.sdynpy_data.TimeHistoryArray	sdynpy.TimeHistoryArray	Data class representing time histories.
sdynpy.core.sdynpy_data.TransferFunctionArray	sdynpy.TransferFunctionArray	Data class representing transfer functions or frequency response functions.
sdynpy.core.sdynpy_data.CoherenceArray	sdynpy.CoherenceArray	Data class representing coherence functions.
sdynpy.core.sdynpy_data.MultipleCoherenceArray	sdynpy.MultipleCoherenceArray	Data class representing multiple coherence functions.
sdynpy.core.sdynpy_data.PowerSpectralDensityArray	sdynpy.PowerSpectralDensityArray	Data class representing power spectral density functions.
sdynpy.core.sdynpy_data.SpectrumArray	sdynpy.SpectrumArray	Data class representing spectra (e.g. FFTs).
sdynpy.core.sdynpy_data.GUIPlot	sdynpy.GUIPlot	An interactive data plotter.
sdynpy.core.sdynpy_data.CPSDPlot	sdynpy.CPSDPlot	An interactive data plotter specifically for cross-power spectral density data.
sdynpy.core.sdynpy_data.data_array	sdynpy.data_array	Helper function to create NDDataArray (and subclasses) objects.
sdynpy.core.sdynpy_data.time_history_array	sdynpy.time_history_array	Helper function to create TimeHistoryArray objects.
sdynpy.core.sdynpy_data.transfer_function_array	sdynpy.transfer_function_array	Helper function to create TransferFunctionArray objects.
sdynpy.core.sdynpy_data.coherence_array	sdynpy.coherence_array	Helper function to create CoherenceArray objects.
sdynpy.core.sdynpy_data.multiple_coherence_array	sdynpy.multiple_coherence_array	Helper function to create MultipleCoherenceArray objects.
sdynpy.core.sdynpy_data.power_spectral_density_array	sdynpy.power_spectral_density_array	Helper function to create PowerSpectralDensityArray objects.
sdynpy.core.sdynpy_data.spectrum_array	sdynpy.spectrum_array	Helper function to create SpectrumArray objects.

Geometry Classes and Functions	Alias	Description
sdynpy.core.sdynpy_geometry.Geometry	sdynpy.Geometry	Class to represent a test or analysis geometry.
sdynpy.core.sdynpy_geometry.NodeArray	sdynpy.NodeArray	Class to represent node locations in a geometry.
sdynpy.core.sdynpy_geometry.CoordinateSystemArray	sdynpy.CoordinateSystemArray	Class to represent global and local coordinate systems in a geometry.
sdynpy.core.sdynpy_geometry.TracelineArray	sdynpy.TracelineArray	Class to represent lines connecting nodes for visualization.
sdynpy.core.sdynpy_geometry.ElementArray	sdynpy.ElementArray	Class to represent elements connecting nodes for visualization.
sdynpy.core.sdynpy_geometry.node_array	sdynpy.node_array	Helper function to create NodeArray objects.
sdynpy.core.sdynpy_geometry.coordinate_system_array	sdynpy.coordinate_system_array	Helper function to create CoordinateSystemArray objects.
sdynpy.core.sdynpy_geometry.traceline_array	sdynpy.traceline_array	Helper function to create TracelineArray objects.
sdynpy.core.sdynpy_geometry.element_array	sdynpy.element_array	Helper function to create ElementArray objects.
sdynpy.core.sdynpy_geometry.id_map	sdynpy.id_map	Class to represent identification number maps between two geometries.

Matrix Classes and Functions	Alias	Description
sdynpy.core.sdynpy_matrix.Matrix	sdynpy.Matrix	Class used to map degrees of freedom to rows and columns of a matrix.
sdynpy.core.sdynpy_matrix.matrix	sdynpy.matrix	Helper function to create Matrix objects.

Shape Classes and Functions	Alias	Description
sdynpy.core.sdynpy_shape.ShapeArray	sdynpy.ShapeArray	Class used to represent mode or deflection shapes.
sdynpy.core.sdynpy_shape.shape_array	sdynpy.shape_array	Helper function to create ShapeArray objects.

System Classes	Alias	Description
sdynpy.core.sdynpy_system.System	sdynpy.System	Class used to represent dynamic systems with mass, stiffness, and damping matrices.

File Input and Output

Structural dynamics data often comes from external sources, whether it is a modal, vibration, or shock test or an equivalent finite element simulation. Therefore, being able to quickly and easily bring external data into SDynPy is a priority. While users could strip data from their external files and manually construct SDynPy objects from that data, this risks bookkeeping and other translation errors. Therefore if a file type is commonly read into or written from SDynPy, it is useful to add a dedicated reader or writer into SDynPy to handle this translation correctly. The sdynpy.fileio subpackage contains much of the code to handle these conversions. For convenience, the modules are aliased to the top-level namespace. The fileio modules are:

File Input/Output Modules	Alias	Description
sdynpy.fileio.sdynpy_uff	sdynpy.uff or sdynpy.unv	Functionality for reading and writing the Universal File Format, a text-based file format common in structural dynamics.
sdynpy.fileio.sdynpy_rattlesnake	sdynpy.rattlesnake	Functionality for reading output from the open-source vibration controller and modal testing software Rattlesnake
sdynpy.fileio.sdynpy_vic	sdynpy.vic	Functionality for reading output from Correlated Solution’s VIC3D .mat file output.
sdynpy.fileio.sdynpy_pdf3D	sdynpy.pdf3D	Functionality for writing geometry and shape data to a format that can be embedded into an interactive PDF for test or analysis documentation.
sdynpy.fileio.sdynpy_tshaker	sdynpy.tshaker	Functionality for reading output data from T-Shaker, a vibration shaker controller.
sdynpy.fileio.sdynpy_escdf	sdynpy.escdf	Functionality for reading and writing the Engineering Sciences Common Data Format.

Finite Elements and Similar Numerical Functionality

SDynPy has a limited set of finite element and other numerical functionality in the sdynpy.fem subpackage. This includes simple beam finite elements, electrodynamic shaker models, and sensor optimization routines to select optimal sensors for a test from finite element results. For convenience, the modules are aliased to the top-level namespace. The fem modules are:

FEM Modules	Alias	Description
sdynpy.fem.sdynpy_beam	sdynpy.beam	Functionality for defining beam finite elements.
sdynpy.fem.sdynpy_shaker	sdynpy.shaker	Functionality for definining shaker electromechanical models per Lang and Snyder.
sdynpy.fem.sdynpy_dof	sdynpy.dof	Techniques such as effective independence used to select sensors for a test given finite element data
sdynpy.fem.sdynpy_exodus	See Below	Functionality for reading and writing the Exodus finite element model format.

Because the Exodus file format is used often at Sandia National Laboratories where SDynPy was originally developed, key classes from the sdynpy_exodus module are also aliased to the top-level namespace.

Exodus Classes	Alias	Description
sdynpy.fem.sdynpy_exodus.Exodus	sdynpy.Exodus	Class to represent an Exodus file as stored on the filesystem
sdynpy.fem.sdynpy_exodus.ExodusInMemory	sdynpy.ExodusInMemory	Class that represents an Exodus file in memory in a format similar to a Matlab Structure

Modal Analysis

SDynPy has capabilities for performing experimental modal analysis which entails fitting modes to frequency response functions measured on the test article. These and similar capabilities exist in the sdynpy.modal subpackage. Many of the modules in this subpackage provide both code-based and GUI-based tools to fit modes to data. In the case of the modal subpackage, much of the useful content boils down to a handful of classes. Therefore, instead of aliasing the modules in the subpackage to the top-level namespace, SDynPy aliases these classes to the top-level namespace.

Modal Classes	Alias	Description
sdynpy.modal.sdynpy_polypy.PolyPy	sdynpy.PolyPy	Code-based implementation of the PolyMax mode fitter.
sdynpy.modal.sdynpy_polypy.PolyPy_GUI	sdynpy.PolyPy_GUI	GUI-based implementation of the PolyMax mode fitter.
sdynpy.modal.sdynpy_smac.SMAC	sdynpy.SMAC	Code-based implemenation of the Synthesize Modes and Correlate mode fitter.
sdynpy.modal.sdynpy_smac.SMAC_GUI	sdynpy.SMAC_GUI	GUI-based implemenation of the Synthesize Modes and Correlate mode fitter.
sdynpy.modal.sdynpy_ccmif.ColoredCMIF	sdynpy.ColoredCMIF	GUI-based tool to interactively select and combine modes fit to multiple single-reference measurements.
sdynpy.modal.sdynpy_signal_processing_gui.SignalProcessingGUI	sdynpy.SignalProcessingGUI	GUI-based tool to compute spectral quantities from time histories.
sdynpy.modal.sdynpy_modal_test.ModalTest	sdynpy.ModalTest	A class to represent a typical modal test, intended to aid modal test practitioners in the data processing and documentation workflow.

Signal Processing

The sdynpy.signal_processing subpackage includes a wide variety of tools that are related to structural dynamics. Often, the code in this package is at a “lower level” than the rest of the SDynPy code, operating on raw data rather than SDynPy objects. Many times, SDynPy objects will often call these lower-level functions as part of their own operations. signal_processing functions can be faster in that they remove the bookkeeping overhead that a lot of SDynPy objects implement, but the user must then be aware that their data must be correctly sorted prior to using the techniques. Additionally, some of the content in signal_processing does not fit well within the existing SDynPy core objects, so the subpackage serves as a kind of catch-all for tools that can be used in structural dynamics, but perhaps are not commonly used. The modules of signal_processing are generally aliased to the top-level namespace.

Signal Processing Modules	Alias	Description
sdynpy.signal_processing.sdynpy_camera	sdynpy.camera	Various functions for dealing with data from cameras, including camera calibration.
sdynpy.signal_processing.sdynpy_complex	sdynpy.complex	Utility functions for working with complex numbers.
sdynpy.signal_processing.sdynpy_correlation	sdynpy.correlation	Functions like the modal assurance cirterion for comparing data.
sdynpy.signal_processing.sdynpy_cpsd	sdynpy.cpsd	Various functions for dealing with cross-power spectral density matrices.
sdynpy.signal_processing.sdynpy_frf	sdynpy.frf	Various functions computing frequency response functions.
sdynpy.signal_processing.sdynpy_frf_inverse	sdynpy.frf_inverse	Various functions for inverting frequency response functions, including regularization.
sdynpy.signal_processing.sdynpy_generator	sdynpy.generator	Various functions for generating common time signals, like pseudorandom or sine sweeps.
sdynpy.signal_processing.sdynpy_geometry_fitting	sdynpy.geometry_fitting	Various functions for dealing with geometry; for example, fitting a shape to a point cloud, or finding intersection points of lines.
sdynpy.signal_processing.sdynpy_harmonic	sdynpy.harmonic	Functions for fitting sine waves to data.
sdynpy.signal_processing.sdynpy_integration	sdynpy.integration	Various functions for generating and integrating state space systems.
sdynpy.signal_processing.sdynpy_lrm	sdynpy.lrm	Advanced FRF computation technique using local rational modeling.
sdynpy.signal_processing.sdynpy_rotation	sdynpy.rotation	Various functions for dealing with rotations; rotation matrices, Rodrigues parameters, rigid body transformations.
sdynpy.signal_processing.sdynpy_srs	sdynpy.srs	Various functions for working with shock response spectra.

Documentation

SDynPy has limited functionality to create documentation for test or analysis results. This functionality is currently a work-in-progress, but capability exists to dump common formats into PowerPoint or LaTeX documents.

Documentation Modules	Alias	Description
sdynpy.doc.sdynpy_ppt	sdynpy.doc.ppt	Various functions to document SDynPy results in a PowerPoint document.
sdynpy.doc.sdynpy_latex	sdynpy.doc.latex	Various functions to document SDynPy results in a LaTeX document.

Demonstration Objects

Sometimes when a user has a new idea that they would like to try out, they simply want to quickly create a somewhat “interesting” system (e.g. something more than a simple beam or spring-mass-damper system), and generate data to explore. The sdynpy.demo subpackage provides two demonstration objects: a flat plate and a simple airplane-like model made out of beam elements. Note that there is some overhead in creating these demonstration objects, therefore the sdynpy.demo subpackage is not imported automatically with SDynPy, it must be imported separately using import sdynpy.demo. Because these are imported separately, there is no aliasing of the modules to the top-level namespace.

Demonstration Modules	Alias	Description
sdynpy.demo.beam_airplane	None	Creates a system and geometry for a structure that looks like a V-tailed airplane.
sdynpy.demo.beam_plate	None	Creates a system and geometry for a structure that looks like a flat plate.