The toolbox for spectrum analysis, statistics and more

ModalTools™ is the toolbox for experimental modal analysis and includes geometry creation, animation, modal parameter extraction etc. that you typically find in experimental modal analysis software. But it contains more; because of the excellent matrix capabilities of MATLAB, you can also use ModalTools to simulate mechanical systems using either mass, damping and stiffness matrices, or using a modal model with poles (resonance frequencies and damping factors) and residues (mode shapes).

Modal Analysis

If you are working with experimental modal analysis or mechanical simulation, you will find that ModalTools is an indispensable tool for your work. ModalTools contains functions for setting up your geometry, or to import it from a universal file. It then allows you to select a number of different modal parameter extraction methods to extract resonance frequencies, damping factors, and mode shapes. The methods range from several SDOF methods to a least squares time domain (polyreference) implementation allowing you to simultaneously extract modes from data taken with multiple references (that is, multiple shakers, or several accelerometers during an impact hammer test with roving hammer). After you have extracted your mode shapes, you can animate the results, and you can also produce Windows AVI files to send to colleagues who do not have ModalTools. In the AVI file, you can have the geometry rotate while animating a mode, so that the person viewing it can see the mode from all directions.

Structural Modification

With the functions for structural modification in ModalTools you can investigate how a change in mass, stiffness or damping would change the frequency response functions. The algorithms implemented are the so-called SMURF (Structural Modification Using Frequency Response functions) algorithm. Changes can be added mass, or stiffener/damper between a degree-of-freedom and ground, an added tuned damper etc. See the specification for details.

Mechanical Simulation

Computing the output response (displacement, velocity) of a mechanical system for a known force input is a common simulation task. Although for stationary signals (random or periodic) you can compute it easily in the frequency domain, in many cases it is preferable to compute the forced response in the time domain. For transient inputs, it is the only way. ModalTools includes a unique and state-of-the-art technology for doing this, which is hundred to several thousand times faster than alternative techniques, commonly used by for example finite element software. The approach we use is based on modal superposition, or knowing the poles and residues of the system. The unique feature of the algorithm we use is that an extremely fast digital filter is defined for each mode of the system. This makes our simulations run approximately 100 times faster than classical modal superposition algorithms based on convolution by the impulse response of the system, which is the most common approach in other software packages. As an example, using a laptop PC, computing the response for a 10-degree-of-freedom system, with 1 mega samples force inputs, takes approximately one second! In ModalTools there are functions to compute displacement or velocity output for systems described with mass, damping, and stiffness matrices, or with mass, stiffness matrices and modal damping, or with systems described by poles and residues. This means you can use models from an experimental modal analysis, or from normal mode results from a finite element model.

Mechanical Systems Synthesis

The software is capable of working with modal models or M, C, and K matrices. However, in ModalTools there are comprehensive sets of commands to synthesize frequency response functions from any formulation of your mechanical system, whether it is by mass, damping, and stiffness matrices, or by mass and stiffness matrices and modal damping, or by poles and residues.

Key Features

• Standard data storage format with header values for noise and vibration signals, such as measurement position, direction, etc.
• Import/export of modal data in universal file format
• Estimation of frequency response functions for single input/single-output and multiple-input/multiple output, including ordinary and multiple coherence
• Source identification by partial coherence and principal response analysis
• Synthesis of frequency response functions from M, C, and K matrices
• Unique time domain filtering functions for computation of forced response of experi-mentally or analytically defined mechanical systems

Requirements

• MATLAB 5.1 or higher from The MathWorks Inc.
• Signal Processing Toolbox from The MathWorks Inc.
• VibraTools

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