IMAT+Modal offers significant additional functionality that extends IMAT's capabilities for the modal test engineer. Several major areas of functionality are included, and are described below. These are useful for pre-test analysis to select optimal accelerometer locations for the modal test, to curve-fitting routines for extracting shapes from the test data.
All of the IMAT+Modal functionality ships with the IMAT toolbox, but requires a separate license to access. You can use either tokens or a perpetual license to access these useful features. Please contact us for more information.
The Genetic Algorithm (GA) for Accelerometer Placement will optimally select accelerometer locations for a modal vibration test. This iterative process replicates the way a new gene sequence is produced through direct reproduction, crossover, and mutation from an existing population. By this process a set of accelerometer locations can be efficiently selected to maximize the linear independence of test-measured mode shapes. The GA can also accommodate multiple FEM configurations, simultaneously selecting the best accelerometer locations for multi-configuration modal tests to minimize the test setup time. GA is directly compatible with NASTRAN; DMIG matrices are read in and final accelerometer DOF can be written to ASET cards.
The GA documentation is located
selectASET is another accelerometer selection capability available in IMAT. It uses a brute-force method to iteratively removed the least important DOF (or triax) to achieve a user-defined target error or number of DOF. Multiple FEM configurations can be processed simultaneously. The selectASET functionality is available both from a GUI and from the command line. The GUI helps guide the user through the process of setting up the relevant parameters and run options and automates the process of post processing the results, including the ability to select intermediate TAM results for visualization and post processing. Results summaries can be exported to Excel-compatible XML format and the final degrees of freedom can be exported to NASTRAN ASET cards.
The selectASET GUI documentation is located
TAMKIT provides procedures for selecting the instrumented DOF and for reducing the FEM matrices to these DOF. It is implemented as a set of NASTRAN DMAP alters, with some MATLAB functions used to read and interpret the NASTRAN data. It also includes procedures for comparing two similar models, and for comparing test and analysis modes on completion of the modal test. The documentation includes extensive discussion on the pros and cons of each DOF selection and matrix reduction method.
The TAMKIT documentation is located
Modal Test Kit, or MTK, contains routines that are useful when performing modal survey tests. These routines include methods for sensor and exciter placement, extracting modes from test data, verifying shape extractions through FRF synthesis comparisons, providing shape independence and completeness checks, and other useful routines. This documentation also covers steps for generating a Test Analysis Model (TAM) in NASTRAN without the use of a DMAP alter.
The MTK documentation is located
OPoly replaced AFPoly as the modal parameter estimation application in IMAT release v.7.3.0. While the AFPoly application had only a Laplace-domain orthogonal polynomial solver (also called AFPoly, for alias-free polyreference), OPoly (for orthogonal polyreference) provides an additional, complementary solver. This new z-domain orthogonal polynomial algorithm has been named ZDOP, and the AFPoly algorithm is now referred to as LDOP. The use of orthogonal polynomials in these methods allow for a wide frequency range containing many modes to be processed in one solution without hindrance of numerical ill-conditioning inherent in traditional frequency-domain methods.
AFPoly is protected in Korea under patent number 10-1194238 and in Japan under patent number 4994448.
The OPoly documentation is located
SDOFit is a single degree of freedom (SDOF) modal parameter estimation (or “curve-fitting”) application. The algorithm is a single-input, single-output, frequency domain, rational fraction polynomial model with generalized residuals. It will estimate the frequency and damping of modes in a narrow frequency band from a single frequency response function (FRF). The residuals are included in the model to account for the out-of-band modes. Although it is primarily intended as an SDOF method, it will allow more than one mode to be included in the model, as there are occasions that this approach will yield better results.
The SDOFit documentation is located
MIFODS stands for “Mode Indicator Function” and “Operating Deflection Shape,” a name chosen to indicate that the application’s purpose is to produce operating deflection shapes for peaks selected from mode indicator functions. The shapes can be saved with only the selected spectral line frequency, or the frequency and damping of the associated mode can be estimated from an enhanced frequency response function. In addition, the selected peaks can be evaluated with modal assurance criteria and mode tracking, and the results can be verified by overlaying test and synthesized functions.
The MIFODS documentation is located